UTS site search

Professor Michael Cortie

Biography

Mike Cortie is the Director of the Institute for Nanoscale Technology at the University of Technology, Sydney (UTS), in Australia. He was born and educated in South Africa and has a BSc(Eng) degree in Physical Metallurgy, a Masters degree on the corrosion of zirconium and a PhD degree, on metal fatigue and fracture mechanics. After a stint at South Africa's Atomic Energy Corporation and at Pylon Engineering, a gear-cutting and general works, Mike joined Mintek, a minerals and metals research organisation. Mike headed the Physical Metallurgy Division of Mintek between 1997 and 2002. The Division consulted widely to South African and international industry and generated the major portion of its funds from foreign contract research. He relocated to Australia and joined UTS in July 2002.

Mike's current research interest is nanotechnology, and in particular the applications of precious metals in nanotechnology. The synthesis or fabrication of precious metal nanostructures of various shapes and compositions, and their optical properties is a strong theme. Many of these activities fall into the field of ‘plasmonics’ and the study of the electric field distributions around these structures is an important dimension to the research at UTS.

Mike also does applied research for industrial clients. For example projects on the synthesis of zinc oxide, an important industrial chemical, and on sensors for measuring the concentration of hydrogen peroxide were completed in 2012.

Published work spans ferritic and nickel-substituted stainless steels, intermetallic compounds with the C1 (CF12) and B2/L21 crystal structures, X-ray diffraction and crystallographic texture of bcc and fcc alloys, cellular automata and the simulation of metal solidification, cracking and solid state transformations, explosive interactions between molten metal and water, phase transformations in and Au- and Pt-containing alloys and compounds, mathematical modelling, solid state chemistry of zinc hydroxide double salts, plasmonics and electromagnetic phenomena around nanoscale antennas, growth of gold nanorods, and targeting of gold nanoparticles to macrophage cells and protozoan parasites.

Professional

member:

Engineers Australia

Materials Australia

Australian Institute of Physics

Image of Michael Cortie
Director, Institute for Nanoscale Technology
Professor, School of Physics and Advanced Materials
Member, Research Centre for Clean Energy Technology
Director, Institute for Nanoscale Technology
Associate Member, GEVI Research Strength
BSc (Wits), ME (UP), PhD (Wits)
Member, Institution of Engineers, Australia
 
Phone
+61 2 9514 2208
Room
CB01.11.12

Research Interests

Michael Cortie’s research is directed at the use of metals in nanoscale technology and in nanomaterials in general. Oxidation and other surface phenomena become an important issue at the nanoscale. One solution to these problems  is to use noble elements such as gold or silver for nanodevices that need to be metallic, and in this way control the surface properties. In addition, the use of these elements opens up the possibility of exploiting novel optical functionalities, in particular plasmon resonances, and the study of these resonances is a second important theme in Mike’s research. Overall, the work is aimed at the synthesis and/or fabrication of various nanoscale devices, and their eventual exploitation for various technological purposes. One use might be in spectrally selective coatings for energy efficiency, another is in the design of nanoporous sponges for sensor applications.

See some of Cortie's YouTube videos for animations of the nanoscale electric field of of localized surface plasmon resonances:

Interesting multimodal plasmon resonance

Longitudinal plasmon resonance

Another theme of Cortie's research is the application of nanotechnology in medicine. In work with colleagues he has shown how gold nanoparticles can be selectively targeted to macrophage cells, for example. Other work has shown up the intriguing possibility that gold nanoparticles can be used to down-regulate (suppress) and inflammatory response in a obese mice (and by implication humans).

Mike also has an interest in intermetallic compounds, shape memory alloys, precious metal alloys, especially of gold and platinum, the stainless steels and the semi-conducting metal oxides. Many of the properties of these substances are controlled by phenomena that occur at the nanoscale. For example, while pure gold is relatively soft, its hardness can be greatly increased by reducing its grain size to several tens of nanometers.

An up to date list of Mike's scientific publications may be found on his Google Scholar profile.

Mike's fifteen most recent scientific publications (as of July 2014) are (* indicates MBC was the 'corresponding author'):

H. Chen, A. Dorrigan, S. Saad, D.J. Hare, M.B. Cortie, S. M. Valenzuela, In vivo study of spherical gold nanoparticles: inflammatory effects and distribution in mice, PLoS ONE, 2013, vol.8(2): e58208. doi:10.1371/journal.pone.0058208.

*A. Moezzi, M.B. Cortie and A.M. McDonagh, Formation of zinc hydroxy nitrate by H+-catalyzed dissolution-precipitation, Europ. J. Inorg. Chem., 2013, pp.1326–1335, DOI 10.1002/ejic.201201244
*M.B. Cortie, M.J. Coutts, C. Ton-That, A. Dowd, V.J. Keast, A.M. McDonagh, On the coalescence of nanoparticulate gold sinter ink, J. Phys. Chem. C, vol.117 (21), 2013, pp 11377-11384 DOI: 10.1021/jp401815b
V. J. Keast, B. Zwan, S. Supansomboon, M. B. Cortie and P. O. Å. Persson, AuAl2 and PtAl2 as potential plasmonic materials, J. Alloys & Compounds, vol.577, 2013, pp.581–586, DOI: 10.1016/j.jallcom.2013.06.161
M. Frederiksen, V. Bochenkov, M. Cortie and D.S. Sutherland, Plasmon hybridization and field confinement in multilayer metal-dielectric nanocups, J. Phys. Chem. C , 117 (30), 2013, pp 15782-15789, DOI: 10.1021/jp402613u
*A. Moezzi, M. B. Cortie and A. M. McDonagh, Zinc hydroxide sulphate and its transformation to crystalline zinc oxide, Dalton Trans., vol.42 (40), 2013, pp.4432 - 14437, DOI: C3DT51638E
*A. Moezzi, M. Cortie, R. Shimmon and A. McDonagh, On the reactivity of zinc hydroxide acetate dihydrate in ethanol, Europ J. Inorg. Chem., 2013, pp. 5133–5137, DOI: 10.1002/ejic.201300650
*M.B. Cortie, E.H. Nafea, H. Chen, S.M. Valenzuela, S.R.S. Ting, F. Sonvico, B. Milthorpe, Nanomedical research in Australia and New Zealand, Nanomedicine, vol.8(12), 2013, pp.1999-2006.
*D. McPherson, S. Supansomboon, B. Zwan, D.L. Cortie, V. Keast, A. Gentle, A. Dowd and M.B. Cortie, Strategies to control the spectral properties of Au-Ni thin films, Thin Solid Films, vol. 551, 2014, pp.200–204, DOI 10.1016/j.tsf.2013.11.115
*A. Moezzi, M.B. Cortie, A.Dowd and A. M. McDonagh, On the formation of active zinc oxide from zinc hydroxide carbonate, J. Nanoparticle Res, vol.16(4), 2014, article 2344
M.J. Coutts, H.M. Zareie, M.B. Cortie and A.M. McDonagh, SEM charging of gold - metal oxide - gold nanocapacitors in a scanning electron microscope, Nanotechnology, vol.25(15), 2014, article 155703, doi:10.1088/0957-4484/25/15/155703
H. Guo, Y. Chen, M.B. Cortie, X. Liu, Q. Xie, X. Wang, D-L Peng, Shape-selective formation of monodisperse copper nanospheres and nanocubes via disproportionation reaction route and their optical properties, J. Phys. Chem. C, vol.118 (18), 2014, pp 9801–9808.
S.C. Middleburgh, D.M. King, G.R. Lumpkin, M. Cortie, L. Edwards, Segregation and migration of chromium in the CrCoFeNi high entropy alloy, J. Alloys & Compounds, vol. 599, 2014, pp.179-182.
*S. Supansomboon, A. Porkovich, A. Dowd, M.D. Arnold, and M.B. Cortie, Effect of precursor stoichiometry on the morphology of nanoporous platinum sponges, ACS Materials & Interfaces,in press, May 2014, DOI:10.1021/am501794y
V J Keast, R L Barnett and M. B Cortie, First principles calculations of the optical and plasmonic response of Au alloys and intermetallic compounds, J. Phys. Cond. Mat., vol.26, (2014) article 305501.

Chemistry for Engineering students
Materials Engineering
Nanomaterials
Advanced Nanomaterials

Chapters

Cortie, M.B., Stokes, N.L., Heness, G.L. & Smith, G. 2014, 'Applications of Nanotechnology in the Building Industry' in David Rickerby (ed), Nanotechnology for Sustainable Manufacturing, CRC Press, USA.
Blaber, M.G., Ford, M. & Cortie, M.B. 2010, 'The Physics and Optical Properties of Gold' in Corti, C. & Holliday, R. (eds), Gold Science and Applications, CRC Press, Boca Raton, Florida, pp. 13-30.
Although gold is well down on the periodic table, at position 79, it was the first of the metals to be discovered and exploited by humans. This was almost certainly as a result of it possessing four unique attributes: a bright metallic yellow color, excellent resistance to corrosion, considerable malleability, and a high density (19.32 g/cm3). The high corrosion resistance and density facilitated the concentration of native gold nuggets and powders in the beds of streams, while the yellow color and malleability made it very suitable for the production of jewelry or religious artifacts. A few other metallic elements-such as silver, copper, or platinum-possess color and/or corrosion resistance and/or ductility and/or density, but none to the simultaneous degree exhibited by gold. What are the reasons for this unusual cluster of interesting properties in element 79?
Edgar, J.A. & Cortie, M.B. 2010, 'Nanotechnological Applications of Gold' in Corti, C. & Holliday, R. (eds), Gold Science and Applications, CRC Press, Boca Raton, Florida, pp. 369-397.
The scientific and technological properties of gold nanoparticles and nanoscale coatings have been the subject of much research in the last decade. There are several stand-alone reviews of these topics in the literature (see, for example, Daniel and Astruc [1] and Glomm [2]), while a whole issue of Chemical Society Reviews was recently targeted at these topics [3], and there is at least one other recent text devoted to gold. So why another review here?
Cortie, M.B. & McDonagh, A. 2009, 'Nanoscience of Gold and Gold Surfaces' in Gold Chemistry: Applications and Future Directions in the Life Sciences, John Wiley and Sons, pp. 321-356.
View/Download from: Publisher's site
Muir, J.G., Masens, C.D., Tomkin, D.F. & Cortie, M.B. 2004, 'The NanohouseTM - An Australian initiative for the future of energy efficient housing' in al, P.J.M.B.E. (ed), Nanotechnology in Construction, Royal Society of Chemistry, Cambridge, UK, pp. 291-304.
Nanotechnology encompasses an array of technologies, all sharing the common attribute of arising from the science of the scale of nanometres. At this scale many materials exhibit physical properties different from those observable in larger quantities of the same materials. This presents a vast number of opportWlities to develop new materials and systems leading to a corresponding array of new products and processes. There is great interest in exploring how these new materials can be applied in existing and new buildings. A multidisciplinary team led by The Institute for Nanoscale Technology at the University of Technology, Sydney (UTS), that includes people from a number other institutions within Australia such as the Commonwealth Scientific Industrial Research Organisation (CSlRO) are developing the Nanohouse The Nanohouse is at the time of writing a concept house, existing in the fonn of architectural drawings, mathematical models and as a 3D computer simulation. The Nanohouse is being designed to illustrate what uses various nanotechnologies (and other recent innovations) have to offer within the context of a domestic dwelling and also to note the wider applications of these technologies in commercial structures. It is naturally a dynamic project, with the design being modified as new technologies and materials become available. In this paper we describe the methodology used to create the Nanohouse, and evaluate some aspects of its perfonnance. The aspects that touched on include the architectural design and the Nanohouses overall energy efficiency.
Cortie, M.B. 2001, 'Stainless steels, ferritic' in al, K.H.J.B.E. (ed), Encyclopaedia of Materials: Science and Technology, Pergamon, UK, pp. 3037-3039.

Conferences

Lucey, T.J., Wuhrer, R., Huggett, P.G., Moran, K., Yeung, W.Y. & Cortie, M.B. 2012, 'Solidification phenomena during casting of steel/cast iron composites', Supplemental Proceedings: Materials Properties, Characterization, and Modeling, Volume 2, Wiley, Orlando Florida USA, pp. 267-274.
View/Download from: Publisher's site
A novel vacuum casting technique has previously been used to manufacture white cast iron/steel composites. This process allows the production of complex shaped products with significantly improved wear resistance and impact strength in order to achieve higher performance in mining applications.
Liu, J., Cankurtaran, B.O., Wuhrer, R. & Cortie, M.B. 2008, 'Fabrication of double nano-cup assemblies and their anomalous plasmon absorption', COMMAD '08 Proceedings of the 2008 Conference on Optoelectronic and Microelectronic Materials and Devices, IEEE, Sydney, pp. 228-231.
View/Download from: Publisher's site
Double-cup assemblies of nanoscale gold semi-shells have been synthesized using a combination of thermal evaporation and chemical etching. The optical extinction of these structures peaked at 740 nm, but there was also evidence of additional extinction maxima at 560, 940 and 1110 nm. Numerical simulations of the optical properties revealed that the extinction was due mainly to scattering rather than to absorption In contrast, the extinction in simple single-shell nanocups was strongly absorptive in nature. Multiple plasmon resonances were identified in the double-cup structures, including an interesting quadrupole resonance in which oscillations of the inner and outer shells should operate 180deg out-of-phase.
Edgar, J.A., Zareie, H.M., Blaber, M., Dowd, A. & Cortie, M.B. 2008, 'Synthesis of hollow gold nanoparticles and rings using silver templates', Proceedings of the 2008 International Conference on Nanoscience and Nanotechnology, ICONN 2008, pp. 36-39.
View/Download from: Publisher's site
Gold nanoshells have gained attention recently due to their versatile optical properties. In particular, their spectrally selective extinction has been exploited for experimental medical applications, functional coatings and contrast enhancement for analytical techniques. Here we discuss nanoshells and the formation of gold nanorings by the galvanic replacement of Ag nanosphere template particles. Hollow Au/Ag nanoshells can be converted to nanorings upon addition of excess HAuCl4. Nanorings present a distinct particle geometry, with optical properties exhibiting characteristics of both nanorods and nanoshells. 2008 IEEE.
Gentle, A.R., Maaroof, A.I., Cortie, M.B. & Smith, G.B. 2007, 'Optical and electrical switching in nanostructured coatings of VO 2', Proceedings of SPIE - The International Society for Optical Engineering.
View/Download from: Publisher's site
Vanadium dioxide undergoes a reversible metal-insulator phase transition at about 68C. Coatings of this compound are reflective in the infrared above this temperature, and transmissive or absorptive below it, while resistivity changes by several orders of magnitude. We present a convenient method for depositing films with nano-size grains, which are then optically and electrically characterised. Emphasis in this study is the impact of aluminum doping and grain structure. The optical hysteresis is presented and its switching range is not altered at different doping levels but the value of transition temperature Tc does shift. In contrast hysteresis in dc resistance does change with a strong correlation between the fall in resistance in the semiconductor state with doping, the drop in Tc and the electrical properties in the metal state. For grain sizes under about 180 nm the conductivity in the metal phase is not linear in temperature but is thermally activated, with activation energies AE dependent on both grain size G and doping level. Simple mathematical relationships are found connecting ?E with G and with carrier density in the semiconductor state. ?E ranges in our samples from 0.15 eV in the smallest grain sizes to around 0.06 eV. This anomalous low frequency metal response is linked to excitations that arise in the metal phase associated with transient singlet pairing on neighbouring sites. Such pairing is weakened by doping, and in large grains appears to be present but incoherent.
Bai, H., Berkahn, M.B. & Cortie, M.B. 2007, 'Characterization of nanometer-sized VO2 nanoparticles prepared by an aqueous route', Proceedings of the 31st Annual Condensed Matter and Materials Meeting, Australian Institute of Physics, Canberra, Australia, pp. 1-3.
We describe a convenient aqueous route to prepare VO2, based on the reductive precipitation of vanadium dioxide VO2 from a vanadate solution. The effect of the reaction conditions is systematically studied, and a protocol to optimize the production of VO2 while minimizing the appearance of other compounds is presented. The products were characterized using calorimetry, X-ray diffraction and high-resolution scanning electron microscopy.
Cortie, M.B., Barnett, M. & Ford, M.J. 2007, 'Active control of the optical properties of nanoscale coatings using 'smart' nanoparticles', Proceedings of SPIE - The International Society for Optical Engineering.
View/Download from: Publisher's site
Coatings that can self-modulate their optical properties as a function of an external stimulus are of significant technological interest. In this regard, the possibilities for thermo- or electrochromic materials such as VO2 and WO3 are already comparatively well-known. Here, however, we explore a new kind of 'smart' coating, based on the active control of a plasmon resonance in nanoparticles. One possible system is based on the modulation of the plasmon resonance of a precious metal nanorod or nanosphere by an active dielectric shell. The active dielectric undergoes an insulator-to-metal transition on increase of temperature which modulates the plasmon resonance of the underlying precious metal nanoparticle, thereby changing the wavelength at which its optical extinction is maximum. In the case of nanorods, the absorption maximum of the longitudinal plasmon is particularly sensitive to the aspect ratio of the nanoparticle and the dielectric properties of the environment, and may be readily tuned across the visible and near-infrared portions of the spectrum. In addition, nanoparticles of certain thermochromic dielectrics, such as VO 2, are expected to have a plasmon resonance of their own which can be switched on or off by control of the temperature. We consider some of the possibilities, using both the discrete dipole approximation and the exact analytical solution due to Mie to calculate the optical properties.
Maaroof, A.I., Gentle, A.R., Cortie, M.B. & Smith, G.B. 2007, 'Nanoporous plasmonic coatings', Proceedings of SPIE - The International Society for Optical Engineering.
View/Download from: Publisher's site
The electrical and optical properties of mesoporous gold are compared to those of thin porous gold films and a simulated thin film made by randomly distributing voids in gold, until the voids fill 76% of film volume. All layers are electrically conducting but in some cases the critical percolation thresholds are close to zero, so conduction is possible at very high void content. Significant qualitative differences are apparent between the properties of mesoporous gold, and very thin sputtered gold containing voids, in plasmonic responses at optical frequencies and in dc resistance, both as a function of fill factor. The mesoporous films have an effective plasma frequency determined by void fill factor and structure, but do not support surface plasmons. In contrast thin porous gold layers display optical features associated with localized and de-localized surface plasmons. Sputtered porous gold is 2-dimensional and its percolation threshold requires a "Swiss-cheese" rather than particle cluster model. Thicker mesoporous layers have critical parameters consistent with very high connectivity, or equivalently large hyper-dimensionality. Our meso-gold samples display various hyper- dimensionalities from 3 to above 10.
Smith, G.B. & Cortie, M.B. 2007, 'Proceedings of SPIE - The International Society of Optical Engineering: Introduction', Proceedings of SPIE - The International Society for Optical Engineering.
View/Download from: Publisher's site
Gentle, A.R., Maaroof, A.I., Smith, G. & Cortie, M.B. 2006, 'Optical properties and applications to production of plasmonic thin film nanostructures of self-ordered columnar alumina arrays on glass', Photonics: Design, Technology, And Packaging II, SPIE, Bellingham, USA, pp. 3816-3816.
View/Download from: Publisher's site
In this paper we report on new techniques for making self-ordered porous layers of alumina of varying aspect ratios on glass, without the use of lithographic or masking techniques. Use of RF etching in one of the hole forming steps and also when filling
Cankurtaran, B., Ford, M.J. & Cortie, M. 2006, 'Local electromagnetic fields surrounding gold nano-cap particles', Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, ICONN, pp. 478-481.
View/Download from: Publisher's site
Using the discrete dipole approximation (DDA) the local electromagnetic fields surrounding gold nano-cap particles are investigated. Suitable k-vectors and polarization vectors of the incident light are used to determine the largest local electric field enhancement. The largest enhancement can be found for the 864 nm dipole resonance; where the field enhancement is approximately 30 000 times the applied field. The electric field contours surrounding the particle are used to assign the order of the surface plasmon resonances. 2006 IEEE.
Cortie, M.B., Maaroof, A.I., Mortari, A. & Wuhrer, R. 2006, 'Application of nano-and mesoporous gold in electrodes and electrochemical sensors', ICONN2006, IEEE, USA, pp. 524-527.
View/Download from: Publisher's site
A nano- or- mesoporous sponge of Au is formed when the intermetallic compound AuAl2 is de-alloyed with NaOH. The large specific surface area of the sponge, and the unique surface chemical properties of Au indicate that this porous material might suefully serve as an electrode in capacitive sensors or other specialised electrochemical cells. Results for some prototype sensor and emergy storage systems are presented, and methods of controlling the nature of the porosity presented.
Blaber, M.G., Harris, N., Ford, M.J. & Cortie, M.B. 2006, 'Optimisation of absorption efficiency for varying dielectric spherical nanoparticles', Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, ICONN, pp. 556-559.
View/Download from: Publisher's site
In this paper we compare the optical absorption for nanospheres made from a range of transition and alkali metals from Li (A=3) to Au (A=79). Numerical solutions to Mie theory were used to calculate the absorption efficiency, Q abs, for nanospheres varying in radii between 5 nm and 100 nm in vacuum. We show that, although gold is the most commonly used nanoparticle material, its absorption efficiency at the plasmon resonance is not as strong as materials such as the alkali metals. Of all the materials tried, potassium spheres with a radius of 21 nm have an optimum absorption efficiency of 14.7. In addition we also show that, unlike gold, the wavelength of the plasmon peak in other materials is sensitive to the sphere radius. In potassium the peak position shifts by 100 nm for spheres ranging from 5 nm to 65 nm, the shift is less than 10 nm for gold spheres. 2006 IEEE.
Hoft, R.C., Ford, M.J. & Cortie, M.B. 2006, 'Effect of dipole moment on current-voltage characteristics of single molecules', Proceedings of the 2006 International Conference on Nanoscience and Nanotechnology, ICONN, pp. 395-398.
View/Download from: Publisher's site
We perform empirical calculations of the tunneling current through various small organic molecules sandwiched between gold electrodes by using the Wenzel-Kramers-Brillouin (WKB) approximation. The barrier to tunneling is taken to be the work function of gold and calculated from a first principles electronic structure code. The current-voltage characteristics of these molecules are compared in the context of existing first principles and experimental results. In this model the surface dipole moment, induced by the adsorbed molecule, can have a significant effect on the current and hence dipole moments may be an important property for prediction of the conductance characteristics of a molecule. 2006 IEEE.
Cortie, M.B. & Xu, X. 2006, 'Control of plasmon resonance in coatings of gold nanorods', ICONN2006, IEEE, USA, pp. 470-473.
Gold nanorods manifest a tunable plasmon resonance with light in the visible to near-infrared regions of the spectrum, and have been proposed for use in spectrally selective coatings on glass. however, details of shape and packing density have a significant effect onthe optical properties of these nanoparticle coatings. Here we show how these effects can be controlled and exploited to produce a flexible spectral response.
Zareie, H.M., Sarikaya, M., McDonagh, A.M., Barber, J., Cortie, M.B. & Phillips, M. 2006, 'Self-organised materials: from organic molecules to genetically engineered gold-binding proteins', 2006 International Conference on Nanoscience and Nanotechnology, IEEE, USA, pp. 517-519.
We present examples of ordered assemblies of organic and biological molecules on gold(111) surfaces. The first example shows how control over mono or multilayer assemblies of 1,4-phenylenedimethanthiol can be achieved and monitored. The second example shows how monolayers on gold can be prepared using amine groups to anchor aromatic molecules to the surface. A third example whos how ordered assemblies of genetically-engineered inorganic-binding polypeptides can be formed on gold surfaces using a 3-repeat, 14 amino acid gold-binding protein (GBP1).
Hoft, R.C., Liu, J., Cortie, M.B. & Ford, M.J. 2006, 'Electron tunneling through alkanedithiol molecules', Progress in Biomedical Optics and Imaging - Proceedings of SPIE.
View/Download from: Publisher's site
We report on first principles calculations of the tunneling current across n-alkanedithiol molecules (n = 4,6,8,10,12) sandwiched between two Au {111} electrodes. The conductance drops exponentially with increased chain length with decay parameter ?n= 0.9. The results are compared with scanning tunneling microscopy measurements on decanedithiol and with other n-alkanedithiol (n = 6,8,10) results in the literature. The theoretical results are found to be an order of magnitude larger than experimental values but follow the same trend. However, two additional, more realistic, geometries are modeled by changing the bond type and by combining the first-principles results with a Wentzel-Kramer-Brillouin (WKB) expression for tunneling across the air gap that is invariably present during scanning tunneling microscopy (STM) measurements. These results are more compatible with the experimental data.
Ford, M.J., Kirkup, L., Gentle, A., Zareie, H. & Cortie, M. 2006, 'How reliable are scanning tunneling microscopy measurements of electron transport in molecules ?', Progress in Biomedical Optics and Imaging - Proceedings of SPIE.
View/Download from: Publisher's site
Scanning tunneling microscopy measurements of tunneling through molecules adsorbed on a surface have been simulated using a standard empirical model based upon the Wentzel-Kramer-Brillouin method applied to tunneling through a barrier. The Gaussian noise inherent in these experiments has been added to the model data using a Monte Carlo technique. By generating multiple sets of current-voltage curves and fitting these to the model we have evaluated how reliably barrier height can be determined as a function of noise level. The results suggest that for constant percentage standard deviation in the noise greater than 5% the barrier height cannot be determined reliably. At this level, the standard deviation in the estimate of the barrier height is about 10%. Weighted fits give more reliable estimates of the barrier height. If the height of the tip above the molecule is known, so that the fit is only a single parameter the barrier height can be determined reliably even at percentage noise levels as high as 20%. However, in this case unweighted fits must be used otherwise the estimated value deviates by up to 15% from the true value. Data with constant absolute noise give similar results. The effects of experimental resolution have been evaluated in a similar manner and are shown to have a significant influence on the reliability. At a resolution of about 0.1% of full scale the standard deviation in the estimate of barrier height is only about 2% but increases rapidly to 10% for a resolution of about 1%.
Cortie, M.B., Zareie, H., Liu, J., Mller, K.-.H. & Ford, M.J. 2005, 'Modelling and verification of the electrical properties of organic dielectric monolayers in capacitive configurations', Proceedings of SPIE - The International Society for Optical Engineering, pp. 316-322.
View/Download from: Publisher's site
The possible role of self-assembled monolayers (SAMs) as the dielectric component of nanoscale capacitors is considered. SAMs of two rather different molecules, ?,?-p-xylyldithiol ('XYL') and dodecanedithiol ('C12') were produced on a gold {111} substrate, and characterized with respect to their conductivity. The data were fitted with a double tunnel barrier model, in which the two SAMs are primarily differentiated by barrier height and thickness with that of XYL having a thickness of 1.0 nm and a barrier height of 0.78 eV compared to 1.69 nm and 1.39 eV for C12. The remaining parameters of the model were determined by Monte Carlo optimization. Assuming perfect connection of top and bottom electrodes, the leakage current through the XYL at 1 volt is calculated to be 1.4105 A/cm2, compared to 2.7104 A/cm2 through C12. These values are not as low as can be obtained with SiO2 of the same thickness. However, SAMs are readily and precisely produced by simple, low temperature processes, a factor which may allow them a niche in the future.
Cortie, M.B., Xu, X., Chowdhury, H.A., Zareie, H.M. & Smith, G. 2005, 'Plasmonic heating of gold nanoparticles and its exploitation', Smart Structures, Devices, and Systems II: Proceedings Of The Society Of Photo-Optical Instrumentation Engineers (SPIE) Volume 5649, SPIE, Washington, USA, pp. 565-573.
View/Download from: Publisher's site
Nanoscale particles of metals such as gold can interact with light by means of a plasmon resonance, even. though they are much smaller than the wavelengths of visible light. The proportions of light that are absorbed and scattered vary with wavelength. A
Smith, G., Cortie, M.B. & Maaroof, A.I. 2005, 'The apparent optical indices of spongy nanoporous gold', Proceedings of the 16th National Congress of the Australian Institute of Physics, Australian Institute of Physics, Canberra, pp. 177-180.
Very thin spongy nanoporous gold films have a unique nanostructure and hence unusual properties. Our interest in these materials is also due to their wide range of potential application (1,2). An optical study for such nanostructured films is of fundamental interest for understanding how light interacts with such a spongy nanoporous structure. In general the gold either percolates or is very closely packed. This surface plasmons, and surface plasmon resonant effects, are expected to play a key role given the large surface area of metal and the metal backbone of the nanostructure. The ropological complexity of the nano-void network is also expected to be a major influence. The optical response has, for a metal system, quite unusual dispersion relations for the effective complex refractive index components n*, k*. Once these are better understood new optical engineering possibilities arise. We are not aware of any optical studies for spongy metal film nanostructures apart from a brief preliminary report of our own on one such film 93) whose nanstructure was different to the spongy nanoporous films presented here. We check the internal consistency and physical accpetability of the results with a Kramers-Kronig analysis of the spectrumn of n*, k* values, because of their unusual spectral character.
Maclurcan, D., Ford, M., Cortie, M.B. & Ghosh, D. 2004, 'Medical Nanotechnology and Developing Nations', Proceedings of the Asia Pacific Nanotechnology Forum 2003, World Scientific Publishing Co, Singapore, pp. 165-172.
Cortie, M.B., Van Der Lingen, E. & Patrick, G. 2004, 'Catalysis and capacitance on nano-structured gold particles and sponges', Proceedings of the Asia Pacific Nanotechnology Forum 2003, World Scientific, Singapore, pp. 79-82.
In the present paper we descrbe the catalytic properties and electrolytic double-layer capacitance of nano-structured, mesoporous gold sponges. These materials are effective catalysts for CO oxidation and for the selective catalytic conversion of NOx. The possible application of mesoporous gold in electric double layer capacitors is premised on its high durface area, corrosion resistance and excellent electrical conductivity. The niche, if any exists, would be in high-efficiency, and high-power density ultra-capacitors for top-end consumer appliances
Smith, G.B., Maaroof, A.I., Allan, R.S., Schelm, S., Anstis, G.R. & Cortie, M.B. 2004, 'Optical response of nanostructured metal/dielectric composites and multilayers', Proceedings of SPIE - The International Society for Optical Engineering, pp. 192-205.
View/Download from: Publisher's site
The homogeneous optical response in conducting nanostructured layers, and in insulating layers containing dense arrays of self assembled conducting nanoparticles separated by organic linkers, is examined experimentally through their effective complex indices (n*, k*). Classical effective medium models, modified to account for the 3-phase nanostructure, are shown to explain (n*, k*) in dense particulate systems but not inhomogeneous layers with macroscopic conductance for which a different approach to homogenisation is discussed, (n*, k*) data on thin granular metal films, thin mesoporous gold, and on thin metal layers containing ordered arrays of voids, is linked to properties of the surface plasmon states which span the nanostructured film. Coupling between evanescent waves at either surface counterbalanced by electron scattering losses must be considered. Virtual bound states for resonant photons result, with the associated transit delay leading to a large rise in n* in many nanostructures. Overcoating n-Ag with alumina is shown to alter (n*, k*) through its impact on the SP coupling. In contrast to classical optical homogenisation, effective indices depend on film thickness. Supporting high resolution SEM images are presented.
Tomkin, D.F., Muir, J.G. & Cortie, M.B. 2003, 'Customized Sustainable Housing', Sustainable Innovation 03.
Tomkin, D.F., Muir, J.G., Cortie, M.B., Masens, C. & Smith, G. 2003, 'The Nanohouse- Australian initiative to develop the home of the future', Nanotechnology, Nanotechnology, Scotland.
Conference presentation
Ekanayake, S.R., Rodanski, B., Cortie, M.B. & Ford, M. 2003, 'Quantum electrical characterisatic of nanocapacitors', 2003 Third IEEE Conference on Nanotechnology, IEEE-Nano 2003, IEEE, Pisacataway, USA, pp. 756-759.
View/Download from: Publisher's site
Current integrated circuit miniaturization will soon require device sizes at atomic scale. Recent work has proposed many Coulomb blockade, and tunneling devices as active devices. However, among passive components, capacitors are extremely critical circuit elements in all electronic circuits with wide range applications. In this work, we present the operational criteria that will govern the feasibility of nanocapacitors for future nanoelectronic circuits.
Cortie, M.B. 2003, 'Conference report: Nano tech + future 2003 Chiba, Japan, February '03', Gold Bulletin, pp. 59-62.

Journal articles

King, D.J.M., Middleburgh, S.C., Liu, A.C.Y., Tahini, H.A., Lumpkin, G.R. & Cortie, M.B. 2015, 'Formation and structure of V-Zr amorphous alloy thin films', Acta Materialia, vol. 83, pp. 269-275.
View/Download from: Publisher's site
Although the equilibrium phase diagram predicts that alloys in the central part of the V-Zr system should consist of V2Zr Laves phase with partial segregation of one element, it is known that under non-equilibrium conditions these materials can form amorphous structures. Here we examine the structures and stabilities of thin film V-Zr alloys deposited at room temperature by magnetron sputtering. The films were characterized by X-ray diffraction, transmission electron microscopy and computational methods. Atomic-scale modelling was used to investigate the enthalpies of formation of the various competing structures. The calculations confirmed that an amorphous solid solution would be significantly more stable than a random body-centred solid solution of the elements, in agreement with the experimental results. In addition, the modelling effort provided insight into the probable atomic configurations of the amorphous structures allowing predictions of the average distance to the first and second nearest neighbours in the system.
Coutts, M.J., Zareie, H.M., Cortie, M.B. & McDonagh, A.M. 2014, 'Charging of gold/metal oxide/gold nanocapacitors in a scanning electron microscope', Nanotechnology, vol. 25, no. 15.
View/Download from: Publisher's site
Triangular parallel-plate nanocapacitors were fabricated by a combination of microsphere lithography and physical vapor deposition. The devices were comprised of a 20 nm layer of dielectric material sandwiched between two 20 nm layers of gold. Dielectric materials with a range of relative permittivities were investigated. Charging of the capacitors was probed in a scanning electron microscope (SEM) by monitoring the change in brightness of the images of the devices as a function of time. The time constants, RC, associated with the charging of the capacitors, were extracted from the SEM grayscale data. The resulting average RC values were 248 27 s for SiO2, 70 8 s for Al2O3, 113 80 s for ZnO and 125 13 s for HfO2. These values are consistent with the anticipated RC values based on the resistivities and permittivities of the materials used in the devices and importantly, were measured without the need to attach any wires or leads. 2014 IOP Publishing Ltd.
Guo, H., Chen, Y., Cortie, M.B., Liu, X., Xie, Q., Wang, X. & Peng, D.-.L. 2014, 'Shape-selective formation of monodisperse copper nanospheres and nanocubes via disproportionation reaction route and their optical properties', Journal of Physical Chemistry C, vol. 118, no. 18, pp. 9801-9808.
View/Download from: Publisher's site
Synthesis of stable and monodisperse Cu nanocrystals of controlled morphology has been a long-standing challenge. In this Article, we report a facile disproportionation reaction approach for the synthesis of such nanocrystals in organic solvents. Either spherical or cubic shapes can be produced, depending on conditions. The typical Cu nanospheres are single crystals with a size of 23.4 1.5 nm, and can self-assemble into three-dimensional (3D) nanocrystal superlattices with a large scale. By manipulating the chemical additives, monodisperse Cu nanocubes with tailorable sizes have also been obtained. The probable formation mechanism of these Cu nanocrystals is discussed. The narrow size distribution results in strong surface plasmon resonance (SPR) peaks even though the resonance is located in the interband transition region. Double SPR peaks are observed in the extinction spectra for the Cu nanocubes with relative large sizes. Theoretical simulation of the extinction spectra indicates that the SPR band located at longer wavelengths is caused by assembly of Cu nanocubes into more complex structures. The synthesis procedure that we report here is expected to foster systematic investigations on the physical properties and self-assembly of Cu nanocrystals with shape and size singularity for their potential applications in photonic and nanoelectronic devices. 2014 American Chemical Society.
Dowd, A., Pissuwan, D. & Cortie, M.B. 2014, 'Optical readout of the intracellular environment using nanoparticle transducers', Trends in Biotechnology, vol. 32, no. 11, pp. 571-577.
View/Download from: Publisher's site
There is rapid growth in the use of multi-functional nanoparticles as transducers to probe the intracellular environment. New designs of nanoparticles can provide quantitative information at sub-cellular resolution on parameters such as pH, temperature and concentration of nicotinamide adenine dinucleotide (NADH) or selected metal ions. This new work builds on the existing practice of using nanoparticles and fluorescent dyes to provide enhanced microscopic images of cells, but goes beyond it by adding new functionalities and analytical capabilities. In this review, we discuss the recent literature on the development of such nanoparticles for simultaneous biosensing and imaging. We explore and examine the different measurements that will be possible, and analyze the likely accuracy and resolution that could be achieved.
Supansomboon, S., Porkovich, A., Dowd, A., Arnold, M.D. & Cortie, M.B. 2014, 'Effect of precursor stoichiometry on the morphology of nanoporous platinum sponges', ACS Applied Materials and Interfaces, vol. 6, no. 12, pp. 9411-9417.
View/Download from: Publisher's site
Nanoscale sponges formed by de-alloying suitable metallic alloys have a wide variety of potential applications due to their enhanced catalytic, optical, and electrochemical properties. In general, these materials have a bi-continuous, vermicular morphology of pores and ligaments with a fibrous appearance; however, other morphologies are sometimes reported. Here, we investigate how stoichiometry and process parameters control the characteristics of sponges formed from thin film precursors of AlxPt. Materials deposited at elevated temperatures and with mole fraction of Al between 0.65 and 0.90 produce the classic isotropic fibrous sponges with a morphology that varies systematically with precursor stoichiometry; however, de-alloying of material deposited at room temperature produced unusual isotropic foamy sponges. The evidence suggests that formation of a conventional fibrous sponge requires an equilibrated precursor whereas foamy morphologies will result if the precursor is metastable. Modeling was used to investigate the range of possible morphologies. As stoichiometry changed in the model system, the average mean and Gaussian curvature of the sponges systematically changed, too. The evolution of these shapes passed through certain special morphologies; for example, modelled structures with 0.80 Al had a zero average Gaussian curvature and might represent a structural optimum for some applications. These observations provide a means to control sponge morphology at the nanoscale. 2014 American Chemical Society.
Elcombe, M.M., Kealley, C.S., Bhatia, V.K., Thorogood, G.J., Carter, D.J., Avdeev, M. & Cortie, M.B. 2014, 'Determination of martensite structures of the Au7Cu 5Al4 and Au7Cu5.7Al3.3 shape-memory alloys', Acta Materialia, vol. 79, pp. 234-240.
View/Download from: Publisher's site
The ?-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au7Cu 5Al4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn, a = 4.4841 , b = 5.8996 , c = 17.8130 ); however, when this composition is cooled to only ?260 K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P21/m, a = 4.4742 , b = 5.9265 , c = 13.3370 , ? = 91.425). In contrast, a sample with decreased Al content (Au7Cu5.7Al3.3) transforms fully to monoclinic phase if cooled to ?260 K. 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Lu, A., Chen, Y., Li, H., Dowd, A., Cortie, M.B., Xie, Q., Guo, H., Qi, Q. & Peng, D.-.L. 2014, 'Magnetic metal phosphide nanorods as effective hydrogen-evolution electrocatalysts', International Journal of Hydrogen Energy, vol. 39, no. 33, pp. 18919-18928.
View/Download from: Publisher's site
Efficient and economical hydrogen evolution reaction (HER) from water splitting holds a bright prospect for clean energy. Replacement of expensive Pt-based catalysts with earth-abundant catalysts is beneficial for this field. In this study, nanoscale magnetic metal phosphides including Co2P, Co1.33Ni0.67P and Ni2P nanorods are synthesized by a facile solution method. Their HER activities and stabilities on glassy carbon and Ti electrodes are investigated. The Co2P nanorods deposited on glassy carbon electrodes are found to show higher activity and better reversibility than the Co1.33Ni0.67P and Ni2P counterparts. Nevertheless, the Co1.33Ni0.67P and Ni2P samples on Ti electrodes gain a significant activity promotion after annealing in H2/Ar atmosphere. Investigation of the Tafel curves shows that the Co2P nanorods on glassy carbon have the lowest Tafel slope while their exchange current density on Ti electrode exhibits a high value which is comparable to that of Pt electrode. Furthermore, the cyclic voltammetric tests show that the reversibility of annealed Co2P on Ti electrode is the best, which emphasizes the superiority of Co species in catalyzing HER reaction. Finally, the three magnetic metal phosphide catalysts are found to exhibit good stabilities in acidic conditions according to the galvanostatic testing results.
Chen, Y., Zeng, D., Cortie, M.B., Dowd, A., Guo, H., Wang, J. & Peng, D.L. 2014, 'Seed-Induced Growth of Flower-Like Au-Ni-ZnO Metal-Semiconductor Hybrid Nanocrystals for Photocatalytic Applications.', Small.
View/Download from: Publisher's site
The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au-Ni-ZnO metal-semiconductor hybrid nanocrystals with a flower-like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room-temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as-prepared Au-Ni-ZnO nanocrystals are strongly photocatalytic and can be separated and re-cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications.
McPherson, D.J., Supansomboon, S., Zwan, B., Keast, V.J., Cortie, D.L., Gentle, A., Dowd, A. & Cortie, M.B. 2014, 'Strategies to control the spectral properties of Au-Ni thin films', Thin Solid Films, vol. 551, pp. 200-204.
View/Download from: Publisher's site
Gold and nickel have quite different dielectric functions. Here we use a combination of calculation and sample manufacture to assess two strategies by which thin films of these elements can be produced with a controlled range of far-field optical properties. In the first approach, control can be achieved by manipulating the density of states of metastable solid solutions, which in turn controls the dielectric function. In the second approach the optical properties of the films are controlled by varying the geometry of stacks fabricated from the constituent elements. We show that the two approaches can produce equivalent results so both are viable options in practice. Modeling is used to reveal how the structure controls the optical properties and to map out the possible color gamut. Predictions are tested with thin film samples fabricated by magnetron sputtering. 2013 Elsevier B.V.
Keast, V.J., Barnett, R.L. & Cortie, M.B. 2014, 'First principles calculations of the optical and plasmonic response of Au alloys and intermetallic compounds', Journal of Physics Condensed Matter, vol. 26, no. 30.
View/Download from: Publisher's site
Pure Au is widely used in plasmonic applications even though its use is compromised by significant losses due to damping. There are some elements that are less lossy than Au (e.g. Ag or Al) but they will normally oxidize or corrode under ambient conditions. Here we examine whether alloying Au with a second element would be beneficial for plasmonic applications. In order to evaluate potential alternatives to pure Au, the density of states (DOS), dielectric function and plasmon quality factor have been calculated for alloys and compounds of Au with Al, Cd, Mg, Pd, Pt, Sn, Ti, Zn and Zr. Substitutional alloying of Au with Al, Cd, Mg and Zn was found to slightly improve the plasmonic response. Of the large number of intermetallic compounds studied, only AuAl2, Au3Cd, AuMg, AuCd and AuZn were found to be suitable for plasmonic applications. 2014 IOP Publishing Ltd.
Cortie, M.B., Coutts, M.J., Ton-That, C., Dowd, A., Keast, V.J. & McDonagh, A.M. 2013, 'On the coalescence of nanoparticulate gold sinter ink', Journal of Physical Chemistry C, vol. 117, no. 21, pp. 11377-11384.
View/Download from: Publisher's site
We examine the mechanism by which thiol-protected gold nanoparticle inks can sinter at surprisingly low temperatures. At room temperature the sample is comprised of randomly close-packed gold nanoparticles of about 2.3 nm diameter with a ligand shell of about 0.2 nm effective thickness. As the particles are heated through 80 C they begin to coarsen, reaching about 10 nm diameter at 180 C. Upon further heating, rapid sintering and grain growth occurs at a temperature that depends on environment and heating rate. Sintering in vacuum requires a higher temperature than in oxidizing environments. Mass spectrometry in the former case is consistent with volatile species such as C 4H9, C2SH, and C2H4 being displaced, whereas XPS shows that the exposed surface of the Au is rich in C and S. However, when sintering is performed in the presence of even trace O 2, it is the Au-S bond that is cleaved, and the sintering temperature is lowered by up to 50 C. In this case mass spectrometry shows the generation of alkane and thiol fragments, some S2 and H2S, and oxidized sulfur-containing species, whereas XPS shows that C and S on the Au surface is much reduced. 2013 American Chemical Society.
Frederiksen, M., Bochenkov, V.E., Cortie, M.B. & Sutherland, D.S. 2013, 'Plasmon hybridization and field confinement in multilayer metal-dielectric nanocups', Journal of Physical Chemistry C, vol. 117, no. 30, pp. 15782-15789.
View/Download from: Publisher's site
Large-area arrays of dispersed multilayer gold-dielectric nanocups were fabricated by colloidal lithography and studied by extinction spectroscopy. Hybridization of the elemental plasmons of the individual nanocups gave rise to new resonance peaks in the visible and near-infrared regions of the extinction spectrum. Transmission electron microscopy was used to confirm the fabricated structure geometry, and the optical properties of the arrays were studied by UV-vis-NIR spectroscopy and finite-difference time-domain (FDTD) simulations. The nature of the resonances was elucidated from E-field plots and charge plots showing clear hybridized modes. We observe a dominant hybridized dipolar mode combining a bonding and antibonding mode at the two caps. A high-energy antibonding (antisymmetric) quadrupolar mode of an individual nanocup is revealed through hybridization with an elemental mode on the second nanocup. A low-energy tunable cavity mode with a very small mode volume is observed in the near-IR range. 2013 American Chemical Society.
Chen, H., Dorrigan, A., Saad, S., Hare, D.J., Cortie, M.B. & Valenzuela, S.M. 2013, 'In Vivo Study of Spherical Gold Nanoparticles: Inflammatory Effects and Distribution in Mice', PLoS ONE, vol. 8, no. 2.
View/Download from: Publisher's site
Objectives: Gold nanoparticles (AuNPs) of 21 nm have been previously well characterized in vitro for their capacity to target macrophages via active uptake. However, the short-term impact of such AuNPs on physiological systems, in particular resident macrophages located in fat tissue in vivo, is largely unknown. This project investigated the distribution, organ toxicity and changes in inflammatory cytokines within the adipose tissue after mice were exposed to AuNPs. Methods: Male C57BL/6 mice were injected intraperitoneally (IP) with a single dose of AuNPs (7.85 ?g AuNPs/g). Body weight and energy intake were recorded daily. Tissues were collected at 1 h, 24 h and 72 h post-injection to test for organ toxicity. AuNP distribution was examined using electron microscopy. Proinflammatory cytokine expression and macrophage number within the abdominal fat pad were determined using real-time PCR. Results: At 72 hours post AuNP injection, daily energy intake and body weight were found to be similar between Control and AuNP treated mice. However, fat mass was significantly smaller in AuNP-treated mice. Following IP injection, AuNPs rapidly accumulated within the abdominal fat tissue and some were seen in the liver. A reduction in TNF? and IL-6 mRNA levels in the fat were observed from 1 h to 72 h post AuNP injection, with no observable changes in macrophage number. There was no detectable toxicity to vital organs (liver and kidney). Conclusion: Our 21 nm spherical AuNPs caused no measurable organ or cell toxicity in mice, but were correlated with significant fat loss and inhibition of inflammatory effects. With the growing incidence of obesity and obesity-related diseases, our findings offer a new avenue for the potential development of gold nanoparticles as a therapeutic agent in the treatment of such disorders. 2013 Chen et al.
Moezzi, A., Cortie, M. & McDonagh, A.M. 2013, 'Formation of Zinc Hydroxide Nitrate by H+-Catalyzed Dissolution-Precipitation', EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, no. 8, pp. 1326-1335.
View/Download from: Publisher's site
Moezzi, A., McDonagh, A., Dowd, A. & Cortie, M. 2013, 'Zinc Hydroxyacetate and Its Transformation to Nanocrystalline Zinc Oxide', INORGANIC CHEMISTRY, vol. 52, no. 1, pp. 95-102.
View/Download from: Publisher's site
Cortie, M.B., Nafea, E.H., Chen, H., Valenzuela, S.M., Ting, S.S., Sonvico, F. & Milthorpe, B. 2013, 'Nanomedical research in Australia and New Zealand', Nanomedicine, vol. 8, no. 12, pp. 1999-2006.
View/Download from: Publisher's site
Although Australia and New Zealand have a combined population of less than 30 million, they have an active and interlinked community of nanomedical researchers. This report provides a synopsis and update on this network with a view to identifying the main topics of interest and their likely future trajectories. In addition, our report may also serve to alert others to opportunities for joint projects. Australian and New Zealand researchers are engaged in most of the possible nanomedical topics, but the majority of interest is focused on drug and nucleic acid delivery using nanoparticles or nanoporous constructs. There are, however, smaller programs directed at hyperthermal therapy and radiotherapy, various kinds of diagnostic tests and regenerative technologies. 2013 Future Medicine Ltd.
Keast, V.J., Zwan, B., Supansomboon, S., Cortie, M.B. & Persson, P.O.. 2013, 'AuAl2 and PtAl2 as potential plasmonic materials', Journal of Alloys and Compounds, vol. 577, pp. 581-586.
View/Download from: Publisher's site
The dielectric functions of PtAl2, AuAl2 and hypothetical intermediate alloys of the two in the form of Aux- Pt1-xAl 2 were calculated from first principles using density functional theory (DFT) and the random phase approximation (RPA). From these, the reflectivity, electron energy-loss spectra (EELS) and small sphere extinction spectra are predicted. The experimental reflectivity and EELS were measured for PtAl2 and showed good agreement with the theoretical spectra. The yellow color of PtAl2 is associated with a bulk plasmon at 3 eV. We predict that the optical properties of hypothetical intermediate alloys would show a smooth evolution with composition. The details of this change can be understood by examination of the underlying density of states (DOS). The predicted small sphere extinction spectra and quality factors show a strong surface plasmon resonance for these materials, with PtAl2 having the optimum performance. The results indicate that these materials are good candidates for applications in plasmonics. 2013 Elsevier B.V. All rights reserved.
Moezzi, A., Cortie, M.B., Shimmon, R. & McDonagh, A.M. 2013, 'On the reactivity of zinc hydroxide acetate dihydrate in ethanol', European Journal of Inorganic Chemistry, no. 29, pp. 5133-5137.
View/Download from: Publisher's site
Zinc hydroxide acetate dihydrate, Zn5(OH)8(CH 3CO2)22H2O, reacts in ethanol at room temperature to yield a mixture of zinc oxide and anhydrous zinc acetate. The process is driven by dehydration of the starting salt. Dehydration of Zn5(OH)8(CH3CO2) 22H2O also occurs when it is heated in air, but the product obtained in that case depends on the heating rate, environment and temperature. For example, when it is kept in a sealed silica capillary at 100 C, Zn5(OH)8(CH3CO2) 21.5H2O is formed after 15 min, whereas treatment in the range 90-100C in an open environment results in the formation of anhydrous zinc hydroxide acetate. Heating of any of these products further causes their decomposition to Zn(CH3CO2)2 and ZnO. The coordination bonding mode of the acetate groups in the anhydrous layered zinc hydroxide acetate prepared by reaction with ethanol was studied by using solid-state NMR spectroscopy. The presence of chelating, unidentate and bidentate bridging modes for the carbonyl carbon atom was revealed, but there was no evidence for the inclusion of ethanol in the resultant structure. Therefore, the reaction in ethanol offers a convenient strategy to prepare anhydrous zinc hydroxide acetate and/or zinc oxide, because it avoids the sensitivity of the thermally induced dehydroxlation process to time, temperature and environment. Decomposition of zinc hydroxide acetate dihydrate in ethanol can be exploited to generate ZnO nanoparticles at room temperature. The mechanism involves the removal of waters of hydration and the formation of Zn5(OH)8(CH3CO2)2 followed by the generation of Zn(CH3CO)2 and ZnO. Copyright 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Moezzi, A., Cortie, M.B. & McDonagh, A.M. 2013, 'Zinc hydroxide sulphate and its transformation to crystalline zinc oxide', Dalton Transactions, vol. 42, no. 40, pp. 14432-14437.
View/Download from: Publisher's site
The thermal transformation of zinc hydroxide sulphate hydrate to zinc oxide has been examined using synchrotron X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and surface area measurements. By collecting X-ray diffraction data in situ, we found that the dehydration of zinc hydroxide sulphate pentahydrate proceeded in discrete steps to form anhydrous zinc hydroxide sulphate. This compound then decomposed to a mixture of zinc oxide and a compound tentatively identified as Zn3(OH) 2(SO4)2 at ?235 C. At ?360 C, the final dehydroxylation occurred with the formation of zinc oxy-sulphate, Zn3O(SO4)2, which then decomposed to ZnO at about ?800 C. Interruption of the dehydration process can be used to synthesize the intermediate compounds. 2013 The Royal Society of Chemistry.
Bosman, M., Anstis, G.R., Keast, V.J., Clarke, J.D. & Cortie, M.B. 2012, 'Light splitting in nanoporous gold and silver', ACS Nano, vol. 6, no. 1, pp. 319-326.
View/Download from: Publisher's site
Figure Persented: Nanoporous gold and silver exhibit strong, omnidirectional broad-band absorption in the far-field. Even though they consist entirely of gold or silver atoms, these materials appear black and dull, in great contrast with the familiar luster of continuous gold and silver. The nature of these anomalous optical characteristics is revealed here by combining nanoscale electron energy loss spectroscopy with discrete dipole and boundary element simulations. It is established that the strong broad-band absorption finds its origin in nanoscale splitting of light, with great local variations in the absorbed color. This nanoscale polychromaticity results from the excitation of localized surface plasmon resonances, which are imaged and analyzed here with deep sub-wavelength, nanometer spatial resolution. We demonstrate that, with this insight, it is possible to customize the absorbance and reflectance wavelength bands of thin nanoporous films by only tuning their morphology. 2011 American Chemical Society.
Porkovich, A.J., Arnold, M.D., Kouzmina, G., Hingley, B. & Cortie, M.B. 2012, 'Calorimetric sensor for H 2O 2/H 2O mist streams', IEEE Sensors Journal, vol. 12, no. 7, pp. 2392-2398.
View/Download from: Publisher's site
Mist streams comprised of H 2O 2/H 2O droplets are a recent innovation for disinfecting medical equipment, but the availability of a sensor that could monitor the concentration of H 2O 2 applied during the treatment would be desirable. Here we describe a means to obtain a rapid estimation of H 2O 2 concentration in this environment. The proposed sensor is based on a platinum resistance thermometer coated with a layer of MnO 2 catalyst. It may be calibrated to operate either during the mist delivery step of a disinfection cycle, or during the evacuation (drying) phase. Cooling of the sensor surface due to evaporation of H 2O} and effervescence of decomposing H 2O 2 operates against heat generated by the decomposition reaction to produce a well-defined minimum in the temperature. The time and temperature at which this minimum occurs are well correlated, with the H 2O 2 content of the solution used to produce the mist droplets. 2012 IEEE.
Stokes, N., Cortie, M.B., Davis, T.J. & McDonagh, A.M. 2012, 'Plasmon Resonances in V-Shaped Gold Nanostructures', Plasmonics, vol. 7, no. 2, pp. 235-243.
View/Download from: Publisher's site
Using numerical simulations, we examine the change in plasmon resonance behavior in gold nanorod structures that have a V shape. The reduction in symmetry compared to linear rods causes two different longitudinal-type resonances to appear in a single structure, and the relative intensity and hybridization of these can be controlled by varying the angle of the arms of the "V." The resonances may also be selectively excited by controlling the polarization of the incident light, thereby providing a convenient way to control a nanoscale optical electric field using far-field parameters. For example, the wavelength at which a strong resonance occurs in the V-shaped structures studied can be switched between 630 and 900 nm by a 90 rotation of the polarization of the incident light. Due to the symmetry of the targets, there will be three types of special near-field location; a location at which the electric field intensity is enhanced by either resonance, a location at which the electric field intensity is enhanced by the 630 nm resonance but not by the 890 nm resonance, and a location at which the electric field intensity is enhanced by the 890 nm resonance but not by the 630 nm one. 2011 Springer Science+Business Media, LLC.
Cortie, M.B., Liu, F., Arnold, M.D. & Niidome, Y. 2012, 'Multimode resonances in silver nanocuboids', Langmuir, vol. 28, no. 24, pp. 9103-9112.
View/Download from: Publisher's site
A rich variety of dipolar and higher order plasmon resonances have been predicted for nanoscale cubes and parallopipeds of silver, in contrast to the simple dipolar modes found on silver nanospheres or nanorods. However, in general, these multimode resonances are not readily detected in experimental colloidal ensembles, due primarily to the usual variation of size and shape of the particles obscuring or blending the individual extinction peaks. Recently, methods have been found to prepare silver parallopipeds with unprecedented shape control by nucleating the silver onto a tightly controlled suspension of gold nanorods (Okuno, Y.; Nishioka, K.; Kiya, A.; Nakashima, N.; Ishibashi, A.; Niidome, Y. Uniform and Controllable Preparation of Au-Ag Core-Shell Nanorods Using Anisotropic Silver Shell Formation on Gold Nanorods. Nanoscale2010, 2, 1489-1493). The optical extinction spectra of suspensions of such monodisperse particles are found to contain multiple extinction peaks, which we show here to be due to the multimode resonances predicted by theoretical studies. Control of the radius of the nanoparticle edges is found to be an effective way to turn some of these modes on or off. These nanoparticles provide a flexible platform for the excitation, manipulation, and exploration of higher order plasmon resonances. 2012 American Chemical Society.
Edgar, J.A., McDonagh, A.M. & Cortie, M.B. 2012, 'Formation of gold nanorods by a stochastic "popcorn" mechanism', ACS Nano, vol. 6, no. 2, pp. 1116-1125.
View/Download from: Publisher's site
Gold nanorods have significant technological potential and are of broad interest to the nanotechnology community. The discovery of the seeded, wet-chemical synthetic process to produce them may be regarded as a landmark in the control of metal nanoparticle shape. However, the mechanism by which the initial spherical gold seeds acquire anisotropy is a critical, yet poorly understood, factor. Here we examine the very early stages of rod growth using a combination of techniques including cryogenic transmission electron microscopy, optical spectroscopy, and computational modeling. Reconciliation of the available experimental observations can only be achieved by invoking a stochastic, "popcorn"-like mechanism of growth, in which individual seeds lie quiescent for some time before suddenly and rapidly growing into rods. This is quite different from the steady, concurrent growth of nanorods that has been previously generally assumed. Furthermore we propose that the shape is controlled by the ratio of surface energy of rod sides to rod ends, with values of this quantity in the range of 0.3-0.8 indicated for typical growth solutions. 2012 American Chemical Society.
Moezzi, A., McDonagh, A.M. & Cortie, M.B. 2012, 'Zinc oxide particles: Synthesis, properties and applications', Chemical Engineering Journal, vol. 185-186, pp. 1-22.
View/Download from: Publisher's site
Zinc oxide powder has traditionally been used as a white pigment and as an additive to rubber. While it has largely been displaced as a pigment in paints, its usage in rubber remains very important. However, the myriad of other practical uses of ZnO are sometimes overlooked, and reviews in the recent scientific literature tend to emphasize high technology applications that do not yet have any commercial reality. Similarly, while some of the low-volume processes used to manufacture ZnO nanostructures have been well covered in the literature, there has been far less reported on the tonnage chemical engineering processes by which most ZnO is actually made. The multiplicity of processes by which ZnO can be produced is a potential source of confusion, however, the process used has a large influence on the properties of the oxide, and hence on its suitability for various applications. Here we provide a contemporary review and analysis of the manufacture of ZnO, and its properties, applications, and future prospects. 2012 Elsevier B.V.
Lucey, T.J., Wuhrer, R., Moran, K., Reid, M., Huggett, P.G. & Cortie, M.B. 2012, 'Interfacial Reactions In White Iron/steel Composites', Journal of Materials Processing Technology, vol. 212, no. 11, pp. 2349-2357.
View/Download from: Publisher's site
The interfacial phenomena occurring when a white iron of low melting point is cast onto a steel substrate are considered. Such layered composites offer the prospect of combining the toughness of steel and the wear-resistance of a white cast iron into a s
Lin, Z.W., Li, Y.J., Zhu, J.G., Wang, X.L., Dou, S.X., Guo, Y.G., Lei, G., Wang, Y., Philips, M., Cortie, M., Li, Y.C., Choi, K.-.Y. & Shi, X. 2011, 'Visualization of vortex motion in FeAs-based BaFe1.9Ni 0.1As2 single crystal by means of magneto-optical imaging', Journal of Applied Physics, vol. 109, no. 7.
View/Download from: Publisher's site
Superconductivity has been found in newly discovered iron-based compounds. This paper studies the motion of magnetic vortices in BaFe1.9Ni 0.1As2 single crystal by means of the magneto-optical imaging technique. A series of magneto-optical images reflecting magnetic flux distribution at the crystal surface were taken when the crystal was zero-field cooled to 10 K. The behavior of the vortices, including penetration into and expulsion from the single crystal with increasing and decreasing external fields, respectively, is discussed. The motion behavior is similar to that observed in high-Tc superconducting cuprates with strong vortex pinning; however, the flux-front is irregular due to randomly distributed defects in the crystal. 2011 American Institute of Physics.
Bhatia, V.K., Kealley, C.S., Prior, M.J. & Cortie, M.B. 2011, 'Martensite destabilization in Au7Cu5Al4 shape-memory alloy', Acta Materialia, vol. 59, no. 5, pp. 2193-2200.
View/Download from: Publisher's site
Aging-induced changes in the austenite peak (AP) temperature of Au7Cu5Al4 shape-memory alloy are investigated. Whereas heat treating the parent phase at temperatures >140 C or aging the martensite for long times at room temperature both stabilized the A P to ?80 C, low-temperature excursions into the parent phase caused the subsequent AP to drop to ?60 C and the transformation hysteresis to decrease. The evidence indicates that this destabilization of the martensite is caused by time-dependent relaxation of elastic constraint due to parent-phase lath migration during the preceding low-temperature austenitizing treatment. This mechanism of aging is different from that of the better-known symmetry-conforming short-range order phenomenon. 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Cortie, M.B., Kealley, C.S., Bhatia, V., Thorogood, G.J., Elcombe, M.M. & Avdeev, M. 2011, 'High temperature transformations of the Au7Cu5Al 4 shape-memory alloy', Journal of Alloys and Compounds, vol. 509, no. 8, pp. 3502-3508.
View/Download from: Publisher's site
The ?-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation, however there has been some uncertainty regarding the crystal structure or structures of the parent phase. Here we show that, under equilibrium conditions, the parent phase possesses the L21 structure between its Ap (about 79 C) and ?630 C, and the B2 primitive cubic structure between ?630 C and its melting point. It melts directly from B2 into the liquid state and hence never achieves the random bcc A2 structure that has been previously mooted. Splat-cast samples of the alloy are martensitic, proving that development of equilibrium order and defect concentration are not pre-requisites for the A ? M transformation to occur. 2010 Elsevier B.V. All rights reserved.
Porkovich, A.J., Arnold, M.D., Kouzmina, G., Hingley, B., Dowd, A. & Cortie, M.B. 2011, 'Calorimetrie sensor for use in hydrogen peroxide aqueous solutions', Sensor Letters, vol. 9, no. 2, pp. 695-697.
View/Download from: Publisher's site
A sensor for characterising aqueous solutions of hydrogen peroxide is described. The sensor is based on the calorimetrie signal obtained when catalysing the decomposition of H 2O 2. The system is quick and simple, and is suitable for determinations of H 2O 2 concentration between 0% and at least 50% (w/w). Copyright 2011 American Scientific Publishers. All rights reserved.
Bhatia, V., Thorogood, G., Annette, D. & Cortie, M.B. 2011, 'Thin films of AuCuAl shape memory alloy for use in plasmonic nano-actuators', Materials Research Society Symposium Proceedings, vol. 1295, pp. 33-38.
View/Download from: Publisher's site
We describe the fabrication and structure of nanoscale thin films of ? phase shape memory alloys with the nominal atomic stoichiometry Au 7Cu5Al4 (corresponding to 5.8 wt% Al). These alloys possess properties that suggest they could be used in nanoscale actuators. The films described here are between 20 and 50 nm thick which is below the thickness at which some other shape memory alloys cease to transform. However, microstructural and X-ray studies confirm that the coatings still exhibit the displacive transformations that are a prerequisite for the shape memory effect. 2011 Materials Research Society.
Cortie, M.B. & McDonagh, A.M. 2011, 'Synthesis and optical properties of hybrid and alloy plasmonic nanoparticles', Chemical Reviews, vol. 111, no. 6, pp. 3713-3735.
View/Download from: Publisher's site
Synthesis and optical properties of hybrid and alloy plasmonic nanoparticles hybrid systems that display a plasmon resonance in the visible or near-visible regions of the spectrum are studied. In the hybrid system, also called passive metallo-dielectric hybrids, the functionalities of the parts remain reasonably independent. The optical properties of these structures are explained by the properties of the individual parts, except for some bathochromic shifting of the plasmon resonance of the metallic component due to the increase in local dielectric constant due to the other component. Metal-metal hybrids and their closely related alloyed nanoparticles exhibit more complex behavior. The plasmon resonance or resonances of the parts can be enhanced, shifted, or suppressed. In the case of core-shell particles, the dielectric properties of the shell material will dominate above some modest thickness, and in the limit, the result is as if the hybrid was composed throughout of the shell material.
Cortie, M.B., Xiao, L., Erdei, L., Kealley, C.S., Dowd, A.R., Kimpton, J.A. & McDonagh, A.M. 2011, 'Thermal stability of (KxNayH1-x-y) 2Ti6O13 nanofibers', European Journal of Inorganic Chemistry, no. 33, pp. 5087-5095.
View/Download from: Publisher's site
Potassium-rich titanate nanofibers were produced by digesting TiO 2 in concentrated KOH solutions under hydrothermal conditions. The nanofibers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and thermogravimetric analysis. A hexatitanate structure was assigned, in contrast to the trititanate structure usually resulting from NaOH treatment of TiO2. The potassium cations could be exchanged with others, such as sodium, hydrogen, and ammonium. The potassium-rich hexatitanate was found to be photocatalytic in its as-synthesized condition. The thermal stability of the fibers during calcination was followed in situ using X-ray diffraction and was found to be strongly dependent on the chemical composition. The potassium-rich titanate converted to anatase at only 480 C, whereas the hydrogen- and ammonium-rich materials had to be heated to over 600 C before conversion took place. Conversion was notably slowest in the ammonium-rich material. Surprisingly, the sodium-rich hexatitanate did not form anatase at temperatures up to 800 C and instead recrystallized. Copyright 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Pissuwan, D., Niidome, T. & Cortie, M.B. 2011, 'The forthcoming applications of gold nanoparticles in drug and gene delivery systems', Journal of Controlled Release, vol. 149, no. 1, pp. 65-71.
View/Download from: Publisher's site
The unique optical, chemical, and biological properties of gold nanoparticles have resulted in them becoming of clinical interest in several applications including drug and gene delivery. The attractive features of gold nanoparticles include their surface plasmon resonance, the controlled manner in which they interact with thiol groups, and their non-toxic nature. These attributes can be exploited to provide an effective and selective platform to obtain a targeted intracellular release of some substance. The use of gold nanoparticles can also increase the stability of the payload. Here we review recent advances in the use of gold nanoparticles in drug and gene delivery systems. The topics of surface modification, site-specificity and drugs and gene and gene delivery are discussed. 2009 Elsevier B.V. All rights reserved.
Moezzi, A., Cortie, M. & McDonagh, A. 2011, 'Aqueous pathways for the formation of zinc oxide nanoparticles', DALTON TRANSACTIONS, vol. 40, no. 18, pp. 4871-4878.
View/Download from: Publisher's site
Keast, V.J., Birt, K., Koch, C.T., Supansomboon, S. & Cortie, M.B. 2011, 'The role of plasmons and interband transitions in the color of AuAl 2, AuIn2, and AuGa2', Applied Physics Letters, vol. 99, no. 11.
View/Download from: Publisher's site
First principles calculations of the optical properties of the intermetallic compounds AuAl2, AuIn2, and AuGa2 have been performed. Analysis of the dielectric functions showed that AuAl 2 is unique because a bulk plasmon is seen in the optical region and contributes to the purple color of this material. An experimental electron energy-loss spectrum showed excellent agreement with the theoretical prediction and confirmed the presence of the bulk plasmon. 2011 American Institute of Physics.
Kealley, C.S., Arnold, M.D., Porkovich, A. & Cortie, M.B. 2010, 'Sensors based on monochromatic interrogation of a localised surface plasmon resonance', Sensors and Actuators, B: Chemical, vol. 148, no. 1, pp. 34-40.
View/Download from: Publisher's site
The localised surface plasmon resonance in gold nanoparticles can be used as the basis of a refractometric sensor. Usually, this is accomplished by monitoring a shift in wavelength of the resonance peak, a task which requires measurements over a range of wavelengths. Here we investigate a different scheme, in which interrogation of the sensor is carried out at a single wavelength. We have used numerical simulations to estimate the effect that the shape of gold nanoparticles would have on the performance on such sensors. A variety of geometries of gold nanoparticles were investigated, including nano-spheres, nano-rods, nano-triangles, and nano-bowties. The performance of a sensor that operates at a single wavelength is controlled by dT/dn, the change in transmittance T with refractive index n, determined at the interrogation wavelength. In turn, dT/dn depends upon the extinction cross-section of the nanoparticles at the chosen wavelength, and on the density of the nanoparticles in the light path. Contributions to the sensor efficiency also include the shift in wavelength of the plasmon resonance and, importantly, the peak sharpness. Of the particles examined, gold nano-rods will provide the most sensitive sensors by a large margin. 2010 Elsevier B.V. All rights reserved.
Coutts, M.J., Zareie, H.M., Cortie, M.B., Phillips, M.R., Wuhrer, R. & McDonagh, A.M. 2010, 'Exploiting zinc oxide re-emission to fabricate periodic arrays', ACS Applied Materials and Interfaces, vol. 2, no. 6, pp. 1774-1779.
View/Download from: Publisher's site
The synthesis of hexagonal ring-shaped structures of zinc oxide using nanosphere lithography and metal/metal oxide sputtering is demonstrated. This synthesis exploits the surface re-emission of zinc oxide to deposit material in regions lying out of the line-of-sight of the sputtering source. These rings can nucleate the hydrothermal growth of zinc oxide crystals. Control over the growth could be exercised by varying growth solution concentration or temperature or by applying an external potential. 2010 American Chemical Society.
Cortie, M.B., Giddings, J.A. & Dowd, A.R. 2010, 'Optical Properties And Plasmon Resonances Of Titanium Nitride Nanostructures', Nanotechnology, vol. 21, no. 11, pp. 1-8.
View/Download from: Publisher's site
We examine the optical properties of nanostructures comprised of titanium nitride, TiN, an electrically conducting intermetallic-like compound. This material can be deposited in the form of durable films by physical vapor deposition. Use of nanosphere te
Kealley, C.S. & Cortie, M.B. 2010, 'A computational exploration of the color gamut of nanoscale hollow scalene ellipsoids of Ag and Au', Plasmonics, vol. 5, no. 1, pp. 37-43.
View/Download from: Publisher's site
Hollow, nanoscale, scalene ellipsoids of Ag or Au provide an exceedingly tunable localized surface plasmon resonance. Here, we use numerical simulations to determine the limits of the color space that would be possible from colloidal suspensions of these particles and show that their color gamut will exceed that possible with nanorods, nanoshells, or nanorice. The important parameters are composition, thickness of the shell, and shape of the particle, in that order. The sensitivity of colors to geometry is optimized for an aspect ratio of between 0.3 and 0.5 and was reduced for thinner shells. Shells of Ag will have much wider and more vibrant gamut than those of Au. These findings indicate that hollow scalene ellipsoids could be used as versatile pigments in materials or display systems that exploit plasmon resonance to produce color. Springer Science+Business Media, LLC 2009.
Stokes, N.L., Edgar, J.A., McDonagh, A.M. & Cortie, M.B. 2010, 'Spectrally selective coatings of gold nanorods on architectural glass', Journal of Nanoparticle Research, vol. 12, no. 8, pp. 2821-2830.
View/Download from: Publisher's site
Infrared-blocking coatings on window glass can be produced by dispersing gold nanorods into a polymer coating. The spectral selectivity of the coating is controlled by the shape and aspect ratio of the nanoparticles, which are in turn determined by the conditions applied during their synthesis. Coatings of nanorods in polyvinyl alcohol were deposited onto glass and characterized in both laboratory and sun-lit conditions. Selective attenuation of the near-infrared was demonstrated with the test panels transmitting approximately one-third of the incident solar radiation and absorbing nearly two-thirds. The high absorptive cross sections of the gold nanorods suggest that they can be applied in efficacious coatings at relatively low volume fractions. 2010 Springer Science+Business Media B.V.
Pissuwan, D., Cortie, C.H., Valenzuela, S.M. & Cortie, M.B. 2010, 'Functionalised gold nanoparticles for controlling pathogenic bacteria', Trends in Biotechnology, vol. 28, no. 4, pp. 207-213.
View/Download from: Publisher's site
The increasing number of bacterial strains that are resistant to available pharmaceutical compounds is a vital issue for public health. Innovative approaches will be required to improve the methods for both diagnosis and destruction of these organisms. Here, we consider the possible role that can be played by technologies based on gold nanoparticles. Gold nanoparticles generally are considered to be biologically inert but can be engineered to possess chemical or photothermal functionality. A growing body of research is devoted to the potential use of these nanoparticles in the diagnosis and treatment of bacterial infections. The results are both promising and intriguing, and suggest a range of new strategies to identify, target or destroy pathogenic organisms. 2009 Elsevier Ltd.
Cortie, M.B., Giddings, J. & Dowd, A. 2010, 'Optical properties and plasmon resonances of titanium nitride nanostructures', Nanotechnology, vol. 21, no. 11.
View/Download from: Publisher's site
We examine the optical properties of nanostructures comprised of titanium nitride, TiN, an electrically conducting intermetallic-like compound. This material can be deposited in the form of durable films by physical vapor deposition. Use of nanosphere templating techniques extends the range of nanostructures that can be produced to include the versatile semi-shell motif. The dielectric properties of TiN1 - x depend upon stoichiometry and are favorable for plasmon resonance phenomena in the mid-visible to near-infrared range of the spectrum and for x?0. We analyze the optical phenomena operating in such structures using a combination of experiment and simulation and show that semi-shells of TiN exhibit a tunable localized plasmon resonance with light. The material is, however, unsuitable for applications in which a long-distance surface plasmon polariton is desired. 2010 IOP Publishing Ltd.
Kealley, C.S., Cortie, M.B., Maaroof, A.I. & Xu, X. 2010, 'Erratum: The versatile colour gamut of coatings of plasmonic metal nanoparticles (Physical Chemistry Chemical Physics (2009) 11 (5897-5902) DOI: 10.1039/b903318a)', Physical Chemistry Chemical Physics, vol. 12, no. 45, pp. 15141-15143.
View/Download from: Publisher's site
Cortie, M.B., Stokes, N. & McDonagh, A. 2009, 'Plasmon resonance and electric field amplification of crossed gold nanorods', Photonics and Nanostructures - Fundamentals and Applications, vol. 7, no. 3, pp. 143-152.
View/Download from: Publisher's site
Here we explore the unusual plasmon resonances of crossed gold nanorod structures of varying geometries. Using numerical simulations, we show that the resonances of simple rods are hybridized and blue-shifted in the composite structures and that these structures are surrounded by spatially extended and high intensity electric fields. This attribute suggests several potential uses for these shapes, for example as a nano-antenna for the generation of two-photon fluorescence. 2009 Elsevier B.V. All rights reserved.
Bhatia, V.K., Levey, F.C., Kealley, C.S., Dowd, A. & Cortie, M.B. 2009, 'The aluminium-copper-gold ternary system', Gold Bulletin, vol. 42, no. 3, pp. 201-208.
Despite Au, Al and Cu being individually very well-known elements, their ternary phase diagram has not been studied in as much detail as those of many other Au-containing ternaries. Here we review what is known, and consider the prospects for technological exploitation of some of the ternary compositions. The components of greatest interest in Al-Au-Cu may be the ?-phases, at least two of which have shape memory properties. Of these, 'Spangold', which has the nominal stoichiometry Au7Cu5Al4, has received some attention for jewellery applications, while the edge compound Cu3Al is a well-known shape memory composition with corresponding specialised industrial uses. The properties of other ?-phase compositions in the system have been scarcely investigated. The system also contains an extensive ?-phase, Al4AuxCu9-x, where x ranges from 0 to ~6.5, and the purple gold phase AuAl2.
Coutts, M.J., Cortie, M.B., Ford, M.J. & McDonagh, A.M. 2009, 'Rapid and controllable sintering of gold nanoparticle inks at room temperature using a chemical agent', Journal of Physical Chemistry C, vol. 113, no. 4, pp. 1325-1328.
View/Download from: Publisher's site
We show that oxidation of protective thiol ligands and the exothermic reduction of surface area are important factors in the sintering of thiol-stabilized gold nanoparticle films. We also present a chemical treatment to achieve sintering of gold nanoparticles at room temperature. The process is facilitated by the remarkable enthalpy of reaction arising from the reduction of the surface area of the nanoparticles. 2009 American Chemical Society.
Bhatia, V.K., Kealley, C.S., Wuhrer, R., Wallwork, K.S. & Cortie, M.B. 2009, 'Ternary ? and ? phases in the Al-Au-Cu system at 750 C', Journal of Alloys and Compounds, vol. 488, no. 1, pp. 100-107.
View/Download from: Publisher's site
There are many aspects of the phases and phase boundaries of the Al-Au-Cu ternary system that are still unknown. Although a 500 C isothermal section and an 18 karat pseudobinary have been reported, many of the other constitutive relationships within the ternary are uncertain. Another unresolved issue is the range of compositions that can possibly serve as shape-memory alloys. Here we investigate the constitutive relationships in this system at 750 C. We confirm that the ? and ? phases extend deep into the ternary but that the other known compounds are largely confined to the binary edges. The suitability of ?-phase compositions of lower Au content for shape memory service is established. 2009 Elsevier B.V. All rights reserved.
Pissuwan, D., Valenzuela, S.M., Miller, C.M., Killingsworth, M.C. & Cortie, M.B. 2009, 'Destruction and control of Toxoplasma gondii tachyzoites using gold nanosphere/antibody conjugates', Small, vol. 5, no. 9, pp. 1030-1034.
View/Download from: Publisher's site
The targeting and destruction of Toxoplasma gondii (T.gondii) tachyzoites was studied to be achieved with simple antibody-functionalized gold nanospheres. The nanospheres of approximately 20-nm diameter were conjugated to an antibody specified to T.gondii to produce a gold/antibody conjugate. Microscopic imaging and optical properties indicate the presence of 3000 to 3500 gold nanospheres per tachyzoite. There is no significant photothermal destruction of tachyzoites observed in the absence of Au/anti-T.g. and in this case the number of dead tachyzoites did not increase when the laser dose is increased from 900 to 2100J cm-3. The results also show that an irradiation of 1800J cm -3 caused a cell death rate of 13.5%?3.6%. The percentage of CHO-K1 cells infected by tachyzoites is inhibited when they are incubated with anti-T.G. alone.
Bai, H., Cortie, M.B., Maaroof, A.I., Dowd, A., Kealley, C. & Smith, G.B. 2009, 'The preparation of a plasmonically resonant VO2 thermochromic pigment', Nanotechnology, vol. 20, no. 8.
View/Download from: Publisher's site
Vanadium dioxide (VO2) undergoes a reversible metal-insulator transition, normally at ?68 C. While the properties of continuous semi-transparent coatings of VO2 are well known, there is far less information available concerning the potential use of discrete VO2 nanoparticles as a thermochromic pigment in opaque coatings. Individual VO 2 nanoparticles undergo a localized plasmon resonance with near-infrared light at about 1100 nm and this resonance can be switched on and off by simply varying the temperature of the system. Therefore, incorporation of VO2 nanoparticles into a coating system imbues the coating with the ability to self-adaptively modulate its own absorptive efficiency in the near-infrared. Here we examine the magnitude and control of this phenomenon. Prototype coatings are described, made using VO2 powder produced by an improved process. The materials are characterized using calorimetry, x-ray diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, and by measurement of optical properties. 2009 IOP Publishing Ltd.
Kealley, C.S., Cortie, M.B., Maaroof, A.I. & Xu, X. 2009, 'The versatile colour gamut of coatings of plasmonic metal nanoparticles', Physical Chemistry Chemical Physics, vol. 11, no. 28, pp. 5897-5902.
View/Download from: Publisher's site
We have investigated the colour gamut of coatings produced by the growth of plasmonically-active coatings of cap-shaped Au or Ag nanoparticles on a transparent substrate. The control of colour and spectral selectivity that can be obtained by the manipulation of the rates of nucleation and growth were explored using a combination of experiment and calculation. In our experimental work the Au nanoparticles were grown in situ using a wet chemical electroless plating technique while the Ag nanoparticles were produced by physical vapour deposition. The optical properties were numerically simulated using the discrete dipole approximation. The resulting measured or calculated transmission spectra were mapped to the CIE L-a*-b* colour space. The aspect ratio of the nanoparticles was the primary factor in determining the colours in both cases. However, increasing the nucleation rate of the particles resulted in them becoming more closely packed, which also red-shifted the optical extinction peak of the structure due to interactions of their near-fields. This caused an enhancement in the blue component of the transmitted light. Coatings of Ag particles had a significantly wider and brighter colour gamut than those of Au. 2009 the Owner Societies.
Pissuwan, D., Valenzuela, S.M. & Cortie, M.B. 2008, 'Prospects for gold nanorod particles in diagnostic and therapeutic applications', Biotechnology and Genetic Engineering Reviews, vol. 25, pp. 93-112.
Rod-shaped gold nanoparticles ('nanorods') have recently attracted widespread attention due to their unique optical properties and facile synthesis. In particular, they can support a longitudinal surface plasmon, which results in suspensions of them having a strong extinction peak in the upper visible or near-infrared parts of the spectrum. The position of this peak can be readily tuned by controlling the shape of the rods. In addition, the surface of the nanorods can be functionalized by a very wide variety of molecules. This has led to interest in their use as selective biomarkers in biodiagnostics or for selective targeting in photothermal thearapeutics. Here, we review the recent advances in the use of gold nanorods in these applications. Additionally, the information available regarding their biocompatibility is discussed.
Hoft, R.C., Ford, M.J., Garca-Surez, V.M., Lambert, C.J. & Cortie, M.B. 2008, 'The effect of stretching thiyl- and ethynyl-Au molecular junctions', Journal of Physics Condensed Matter, vol. 20, no. 2.
View/Download from: Publisher's site
We perform density functional theory (DFT) calculations of the stretching of Au(111)-X-Au(111) molecular junctions where X is either a thiyl or ethynyl biradical. The equilibrium geometries for the radicals adsorbing on the surface are first calculated and the radicals then placed in the junction geometry. The unit cell is stepwise increased in length and the geometry relaxed at each step. When stretching the ethynyl junction, a single gold atom is detached from the rest of the surface and the gold-carbon bond does not break. In contrast, the gold-sulfur bond in the thiyl junction breaks without detaching any gold atoms. This behaviour can be attributed to the enhanced strength of the Au-C interaction over the Au-S interaction. In both junctions the conductance calculated using the non-equilibrium Green's function formalism (NEGF) decreases as the junction is stretched. After breakage of the Au-S bond, the thiyl radical contains an unpaired electron on the sulfur atom and the system is in a spin doublet state. Transmission spectra were calculated for the spin-unpolarized case only; evaluation of the spin-polarized density of states suggests that an enhanced conductance for electrons of one spin type may be observed after the Au-S bond is broken. 2008 IOP Publishing Ltd.
Ford, M., Hoft, R.C., McDonagh, A.M. & Cortie, M.B. 2008, 'Rectification in Donor-Acceptor Molecular Junctions', Journal Of Physics: Condensed Matter, vol. 20, no. 37, pp. 1-8.
View/Download from: Publisher's site
We perform density functional theory (DFT) calculations on molecular junctions consisting of a single molecule between two Au(111) electrodes. The molecules consist of an alkane or aryl bridge connecting acceptor, donor or thiol endgroups in various combinations. The molecular geometries are optimized and wavefunctions and eigenstates of the junction calculated using the DFT method, and then the electron transport properties for the junction are calculated within the non-equilibrium Green's function (NEGF) formalism. The currentvoltage or i(V) characteristics for the various molecules are then compared. Rectification is observed for these molecules, particularly for the donorbridgeacceptor case where the bridge is an alkane, with rectification being in the same direction as the original findings of Aviram and Ratner (1974 Chem. Phys. Lett. 29 27783), at least for relatively large negative and positive applied bias. However, at smaller bias rectification is in the opposite direction and is attributed to the lowest unoccupied orbital associated with the acceptor group.
Zareie, H.M., Morgan, S.W., Moghaddam, M., Maaroof, A.I., Cortie, M.B. & Phillips, M.R. 2008, 'Nanocapacitive circuit elements', ACS Nano, vol. 2, no. 8, pp. 1615-1619.
View/Download from: Publisher's site
"Natural" lithography was used to prepare arrays of nanoscale capacitors on silicon. The capacitance was verified by a novel technique based on the interaction of a charged substrate with the electron beam of a scanning electron microscope. The "nanocapacitors" possessed a capacitance of ?1 10-16F and were observed to hold charge for over an hour. Our results indicate that fabricating nanostructures using natural lithography may provide a viable alternative for future nanoelectronic devices. 2008 American Chemical Society.
Harris, N., Ford, M.J., Mulvaney, P. & Cortie, M.B. 2008, 'Tunable infrared absorption by metal nanoparticles: The case for gold rods and shells', Gold Bulletin, vol. 41, no. 1, pp. 5-14.
Nanoparticles of elements such as Au, Al or Ag have optical extinction cross-section that considerably surpass their geometric cross-sections at certain wavelengths of light. While the absorption and scattering maxima for nanospheres of these elements are relatively insensitive to particle diameter, the surface plasmon resonance of Au nanoshells and nanorods can be readily tuned from the visible into the infrared by changing the shape of the particle. Here we compare nanoshells and nanorods in terms of their ease of synthesis, their optical properties, and their longer term technological prospects as tunable "plasmonic absorbers". While both particle types are now routinely prepared by wet chemistry, we submit that it is more convenient to prepare rods. Furthermore, the plasmon resonance and peak absorption efficiency in nanorods may be readily tuned into the infrared by an increase of their aspect ratio, whereas in nanoshells such tuning may require a decrease in shell thickness to problematic dimensions.
Supansomboona, S., Maaroof, A. & Cortie, M.B. 2008, '"Purple glory": The optical properties and technology of AuAl2 coatings', Gold Bulletin, vol. 41, no. 4, pp. 296-304.
The application of thin coatings of the purple gold intermetallic compound AuAl2 provides a possible alternative to the use of this material in the bulk form. Here we explore the properties of AuAl2 coatings prepared by vacuum deposition onto heated substrates. Control of the thickness and microstructure of the deposit allowed the optical properties of the film to be tuned over a wide range. The properties were characterised using CIE LAB colour coordinates, and by measurement and calculation of reflection and transmission spectra. Reflection colours could be varied at will between dark-silver through to light purple, and were largely a function of the degree of crystallization of the deposit. Transmission colours could be varied from light to dark greenish-brown, and were a function of both microstructure and film thickness. The complex refractive indices, n(?) +i.k(?), and ? 1(?)+?2(?), of AuAl2 were determined from the experimental measurements and are provided in tabular form. Proof-of-concept jewellery items were successfully produced to showcase the decorative aspects of this technology. Finally the possibility of using AuAl2 as a spectrally selective coating on architectural glass was considered. Use of it would certainly provide a degree of solar screening with a somewhat more neutral colour than elemental Au coatings, but the figure-of-merit, Tvis/Tsol, for the pure Au film is always better when compared at the same luminance.
Stokes, N., McDonagh, A.M. & Cortie, M.B. 2008, 'Preparation of nanoscale gold structures by nanolithography', Gold Bulletin, vol. 40, no. 4, pp. 310-320.
Gold is the material of first choice for the realisation of a large number of interesting nanoscale devices and structures due to its unique chemical and optical properties. However, conventional photolithographic processes cannot be used to manufacture such tiny structures in gold (or any other material) due to limitations imposed by the diffraction of light. New methods of lithography have been developed to overcome this limitation. In this article we review these new nanolithographic techniques, describe how they have been used to produce nanoscale precious metal artefacts, and briefly survey some of the existing and potential applications for these structures.
Maaroof, A.I., Cortie, M.B., Harris, N. & Wieczorek, L. 2008, 'Mie and bragg plasmons in subwavelength silver semi-shells', Small, vol. 4, no. 12, pp. 2292-2299.
View/Download from: Publisher's site
2D arrays of silver semi-shells of 100 and 200 nm diameter display complex reflection and transmission spectra in the visible and near-IR. Here these spectral features are deconstructed and it is demonstrated that they result from the coupling of incident light into a delocalized Bragg plasmon, and the latter's induction of localized Mie plasmons in the arrays. These phenomena permit the excitation of transverse dipolar plasmon resonances in the semi-shells despite an ostensibly unfavorable orientation with respect to normally incident light. The resulting spectral feature in the mid-visible is strong and tunable. 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
Smith, G.B., Maaroof, A.I. & Cortie, M.B. 2008, 'Percolation in nanoporous gold and the principle of universality for two-dimensional to hyperdimensional networks', Physical Review B - Condensed Matter and Materials Physics, vol. 78, no. 16.
View/Download from: Publisher's site
Percolation in nanoporous gold can be achieved with as little as 8% by volume of gold. Samples of nanoporous gold of various morphologies are analyzed with a combination of electrical and optical data. Growing thin films and complex multiply connected three-dimensional networks both display nonuniversal character. Growing films have two-dimensional morphology but a three-dimensional percolation threshold and nonuniversal critical coefficients, yet similar silver films percolate as expected with universal coefficients. Growing gold however regresses to two-dimensional resistive behavior between 65% to 100% gold, and this regime lies along a single power-law curve shared by the hyperdimensional networks of gold, suggesting underlying symmetry governed by diffusion-limited aggregation. Models of data imply either hyperdimensionality or major internal property changes as density shifts. The distinctive flat spectral signature found near the percolation threshold is common to all highly porous samples and is explained quantitatively in terms of effective plasmonic response. Parameters from fits of effective medium models to optical and resistivity data are in close agreement, especially at the highest porosities. They imply an effective dimension which increases continuously as porosity grows via the increased branching needed for structural integrity. 2008 The American Physical Society.
Ford, M.J., Hoft, R.C., McDonagh, A.M. & Cortie, M.B. 2008, 'Rectification in donor-acceptor molecular junctions', Journal of Physics Condensed Matter, vol. 20, no. 37.
View/Download from: Publisher's site
We perform density functional theory (DFT) calculations on molecular junctions consisting of a single molecule between two Au(111) electrodes. The molecules consist of an alkane or aryl bridge connecting acceptor, donor or thiol endgroups in various combinations. The molecular geometries are optimized and wavefunctions and eigenstates of the junction calculated using the DFT method, and then the electron transport properties for the junction are calculated within the non-equilibrium Green's function (NEGF) formalism. The current-voltage or i(V) characteristics for the various molecules are then compared. Rectification is observed for these molecules, particularly for the donor-bridge-acceptor case where the bridge is an alkane, with rectification being in the same direction as the original findings of Aviram and Ratner (1974 Chem. Phys. Lett. 29 277-83), at least for relatively large negative and positive applied bias. However, at smaller bias rectification is in the opposite direction and is attributed to the lowest unoccupied orbital associated with the acceptor group. 2008 IOP Publishing Ltd.
Pissuwan, D., Valenzuela, S.M., Killingsworth, M.C., Xu, X. & Cortie, M.B. 2007, 'Targeted destruction of murine macrophage cells with bioconjugated gold nanorods', Journal of Nanoparticle Research, vol. 9, no. 6, pp. 1109-1124.
View/Download from: Publisher's site
Gold nanorods manifest a readily tunable longitudinal plasmon resonance with light and consequently have potential for use in photothermal therapeutics. Recent work by others has shown how gold nanoshells and rods can be used to target cancer cells, which can then be destroyed using relatively high power laser radiation (?1105 to 11010 W/m 2). Here we extend this concept to demonstrate how gold nanorods can be modified to bind to target macrophage cells, and show that high intensity laser radiation is not necessary, with even 5102 W/m 2 being sufficient, provided that a total fluence of ?30 J/cm2 is delivered. We used the murine cell line RAW 264.7 and the monoclonal antibody CD11b, raised against murine macrophages, as our model system and a 5 mW solid state diode laser as our energy source. Exposure of the cells labeled with gold nanorods to a laser fluence of 30 J/cm2 resulted in 81% cell death compared to only 0.9% in the control, non-labeled cells. 2007 Springer Science+Business Media, Inc.
Pissuwan, D., Cortie, C.H., Valenzuela, S.M. & Cortie, M.B. 2007, 'Gold nanosphere-antibody conjugates for hyperthermal therapeutic applications', Gold Bulletin, vol. 40, no. 2, pp. 121-129.
Gold nanoparticles can be conjugated with antibodies or other proteins, and the resulting composite particles will selectively attach to various kinds of biological material. Although exploitation of this for staining microscopy specimens is well known, there has recently been interest in attaching gold nanoparticles to live cells for therapeutic reasons. One motivation is that gold nanoparticles display a strong plasmon resonance with light, which can be exploited in principle for an 'in vivo' photothermal therapy. The treatment of cancer by this technique has recently received attention by others, but here we show how gold nanoparticle-based therapies can be developed to target live macrophage cells. We have employed 'active targeting', a scheme in which gold nanoparticles are functionalised with an antibody specific to the target macrophage cell. We describe how to prepare the conjugated particles, demonstrate that they will selectively attach 'in vitro' to their target macrophage cell but not to a non-target cell type and show that their presence renders the target cell susceptible to destruction by a low power laser.
Yuan, L., Liu, H., Maaroof, A.I., Konstantinov, K., Liu, J. & Cortie, M.B. 2007, 'Mesoporous gold as anode material for lithium-ion cells', Journal Of New Materials For Electrochemical Systems, vol. 10, no. 2, pp. 95-99.
Mesoporous goldsponges were prepared by chemical removal of Al from thin films of an AuAl2 precursor that had been deposited on Cu sheet. The morphology of the An was characterised by interconnected pores and channel,v of between 5 and 20 nm in diameter.
Cortie, M.B., Harris, N. & Ford, M.J. 2007, 'Plasmonic heating and its possible exploitation in nanolithography', Physica B: Condensed Matter, vol. 394, no. 2, pp. 188-192.
View/Download from: Publisher's site
Gold nanoparticles manifest one or more plasmon resonances, resulting in enhanced absorption and scattering of light at the resonant frequencies. The absorbed light is converted to heat. Here we analyze how the resulting localized heat generation might be exploited to generate nanoscale polymer arteifacts. 2007 Elsevier B.V. All rights reserved.
Maaroof, A.I., Gentle, A., Smith, G.B. & Cortie, M.B. 2007, 'Bulk and surface plasmons in highly nanoporous gold films', Journal of Physics D: Applied Physics, vol. 40, no. 18, pp. 5675-5682.
View/Download from: Publisher's site
The far field plasmonic behaviour of nanoporous gold films with void densities ranging from 60% to 90% has been investigated and modelled. These layers have good dc conductivity and quite different nanostructure to traditional porous layers in which the metal percolates. Our gold films with void density f above 70% have high thermal emittance for a conductor at their thicknesses and their flat spectral response at visible and near infrared wavelengths is not metal like. We derive effective optical constants which become plasmonic at wavelengths between 1.8 and 4 ?m for f from 72 to 87%. This onset is much longer than that in bulk gold. For void densities below 70% the onset of plasmonic behaviour is much closer to the dense material. A simple test is implemented to test for surface plasmon polaritons (SPPs) under illumination. The more porous films show no evidence of SPP, while the less porous films display weak evidence. Thus by tailoring void content in these nanostructures we can tailor the onset of effective plasmonic response across a wide range from 0.8 to 4 ?m and emittance from around 0.9 down to low values. An effective uniform metal response is thus found in the presence of surface nanostructure without the interface absorption found in dense gold layers with structured surfaces. 2007 IOP Publishing Ltd.
Cortie, M.B., Maaroof, A.I., Stokes, N. & Mortari, A. 2007, 'Mesoporous gold sponge', Australian Journal of Chemistry, vol. 60, no. 7, pp. 524-527.
View/Download from: Publisher's site
Mesoporous gold sponge may be prepared by the removal of aluminium from AuAl2 by an alkaline leach. The resulting material has nanoscale pores and channels, with a high specific surface area that can be exploited in electrochemical applications. For example, the material may serve as the basis of a more sensitive capacitive sensor or biosensor, as an electrode material for a high efficiency ultracapacitor, as the semi-transparent current collector in a dye sensitized photovoltaic cell, or as the lithium storage electrode in a lithium ion cell. The properties of the sponge may be controlled by varying its density, pore size, and pore size distribution, factors which are in turn controlled by the microstructure of the precursor compound and the conditions of deposition. CSIRO 2007.
Maaroof, A.I., Cortie, M.B., Gentle, A. & Smith, G.B. 2007, 'Mesoporous gold sponge as a prototype 'metamaterial'', Physica B: Condensed Matter, vol. 394, no. 2, pp. 167-170.
View/Download from: Publisher's site
Mesoporous gold sponge has optical properties that can be intermediate between those of metals and insulators, with a flat spectral response that is unlike that of bulk gold. Films of different thicknesses were produced and an extension of the Lorentz-Drude (LD) model used to model their spectral behavior. We found that it was necessary to include an additional special oscillator centered at 1.4 eV in order to model the unusual spectral response. This is quite unlike bulk gold, which can be modeled using a standard two-oscillator LD model. 2007 Elsevier B.V. All rights reserved.
Armstrong, N., Hoft, R.C., McDonagh, A., Cortie, M.B. & Ford, M.J. 2007, 'Exploring the performance of molecular rectifiers: Limitations and factors affecting molecular rectification', Nano Letters, vol. 7, no. 10, pp. 3018-3022.
View/Download from: Publisher's site
There has been significant work investigating the use of molecules as nanoscale rectifiers in so-called "molecular electronics". However, less attention has been paid to optimizing the design parameters of molecular rectifiers or to their inherent limitations. Here we use a barrier tunneling model to examine the degree of rectification that can be achieved and to provide insight for the design and development of molecules with optimum rectification responses. 2007 American Chemical Society.
Cortie, M.B. 2007, 'Gold 2006 - Welcome And Introduction', Materials Science And Engineering B-solid State Materials For Advanced Technology, vol. 140, no. 3, pp. 137-137.
NA
Cortie, M. & Ford, M. 2007, 'A plasmon-induced current loop in gold semi-shells', Nanotechnology, vol. 18, no. 23.
View/Download from: Publisher's site
We perform a computational investigation of the optical properties of nanoscale gold 'semi-shells' and show how additional plasmon resonances develop as the shape is successively mutated from 'nanoshell' to 'nano-cup', 'half-shell' and finally to 'nano-cap'. The effects of aspect ratio, surface roughness and cut-off height are explored. Of special interest is a new longitudinal resonance that generates an electric current loop. We predict that this will induce an orthogonal magnetic component that will sum with the magnetic component of incident light at certain orientations. Exploitation of this phenomenon in an ordered array of semi-shells may produce anomalous optical effects due to an altered magnetic permeability. IOP Publishing Ltd.
Chowdhury, H. & Cortie, M.B. 2007, 'Thermal stresses and cracking in absorptive solar glazing', Construction and Building Materials, vol. 21, no. 2, pp. 464-468.
View/Download from: Publisher's site
The emerging popularity of absorptive, as opposed to reflective, solar glazing coatings on windows has generated renewed interest in thermally induced cracking of glass structures. Here we analyse the stresses on glass coated with absorptive solar glazing films caused by uneven solar illumination. It is shown that the occasionally reported brittle fracture of such structures can be readily explained as being the result of differential thermal expansion of the glass. The magnitude of the effect is linearly proportional to the shading coefficient of the glass and is also influenced by the manner in which the glass is supported. 2005 Elsevier Ltd. All rights reserved.
Xu, X. & Cortie, M.B. 2007, 'Precious metal core-shell spindles', Journal of Physical Chemistry C, vol. 111, no. 49, pp. 18135-18142.
View/Download from: Publisher's site
A simplified method to produce spindle-shaped particles with a hematite core and a silica shell is described. The silica shell can, in turn, serve as the substrate for an outer coating of Ag or Au nanoparticles. The resulting multilayer core-shell particles display a flexible optical extinction spectrum, due primarily to the sensitivity of their plasmon resonance to the morphology of the precious metal outer coating. 2007 American Chemical Society.
Hoft, R.C., Ford, M.J. & Cortie, M.B. 2007, 'Electron tunneling in the presence of adsorbed molecules', Surface Science, vol. 601, no. 24, pp. 5715-5720.
View/Download from: Publisher's site
We perform ab initio density functional theory calculations of the tunneling current through an electrode-molecule-electrode system with four different small organic molecules, benzenedithiol (BDT), benzenedimethanethiol (XYL), diethynylbenzene (DEB) and dodecanethiol (C12), sandwiched between two gold (1 1 1) electrodes. For the XYL molecule, we test the effect of alternate bonding types and sites. Although this reduces the current considerably, it does not account for the orders of magnitude differences between experimental and theoretical results in the literature. We also model a typical STM experimental setup with a gold nanoparticle absorbed on a self-assembled monolayer (SAM) of the molecule with a gap between the nanoparticle and probing tip and show that such a gap could account for these differences. Finally, we describe the effect that the gap has on the ability of STS measurements to distinguish between the i(V) characteristics and thicknesses of self-assembled monolayers of different molecules. 2007 Elsevier B.V. All rights reserved.
Hoft, R.C., Ford, M.J. & Cortie, M.B. 2007, 'The effect of reciprocal-space sampling and basis set quality on the calculated conductance of a molecular junction', Molecular Simulation, vol. 33, no. 11, pp. 897-904.
View/Download from: Publisher's site
We perform density functional theory and non-equilibrium Green's function calculations of the conductance of a gold wire and a 1,4-phenylenedimethanethiol (XYL) molecule adsorbed between Au(111) electrodes using the TranSIESTA software package. The effect of varying different computational parameters is investigated. We find that the conductance is more sensitive to the reciprocal-space sampling grid than the quality of the basis set employed. The conductance can vary up to a factor of five as a result of the choice of computational parameters. We report a set of computational parameters that yields a well-converged conductance value.
Pissuwan, D., Valenzuela, S., Miller, C.M. & Cortie, M.B. 2007, 'A Golden bullet? Selective targeting of Toxoplasma gondii Tachyzoites using antibody-functionalised gold nanorods', Nano Letters, vol. 7, no. 12, pp. 3808-3812.
View/Download from: Publisher's site
Conjugates of gold nanoparticles and antibodies have useful functionalities. Here we show how they can be used to selectively target and destroy parasitic protozoans. Gold nanorods were conjugated with an anti-Toxoplasma gondii antibody and used to target the extracellular tachyzoite which is an infectious from on an obligate parasite Toxoplasma gondii. Subsequent laser irradiation was used to kill the targeted protozoans. This concept provides a new paradigm for the treatment of parasitic protozoans.
Ford, M.J., Soul de Bas, B. & Cortie, M.B. 2007, 'Stability of the tetrahedral motif for small gold clusters in the size range 16-24 atoms', Materials Science and Engineering B: Solid-State Materials for Advanced Technology, vol. 140, no. 3, pp. 177-181.
View/Download from: Publisher's site
A 20-atom tetrahedral cluster of gold atoms is known to be anomalously stable, relative to more disordered structures. Here, we systematically investigate the nature of this stability and the extent to which it also applies to clusters derived from the tetrahedron by adding or removing Au atoms. 2007 Elsevier B.V. All rights reserved.
Bhargava, A. & Cortie, M.B. 2007, 'Prospects for light-activated nano-devices based on shape-memory polymers', Journal of Nanophotonics, vol. 1, no. 1.
View/Download from: Publisher's site
The recent development of new types of light-activated, conformation-changing polymers has stimulated much interest. These 'smart' materials offer new functionalities and may enable diverse novel devices. One possible application of these substances may be in optically-driven nanoscale actuators, especially in the case of devices in which a plasmon resonance in a precious-metal nanostructure is actively modulated. A one-way or two-way shape memory effect is possible, however, application at the nanoscale will necessitate certain design changes. Nanoscale devices based on these materials could conceivably be used for drug-release or to switch the spectral selectivity of a coating. 2007 Society of Photo-Optical Instrumentation Engineers.
Yeung, W.Y., Wuhrer, R., Cortie, M.B. & Ferry, M. 2007, 'Equal channel angular extrusion of high purity gold', Materials forum, vol. 31, pp. 31-35.
Mortari, A., Maaroof, A., Martin, D. & Cortie, M.B. 2007, 'Mesoporous gold electrodes for sensors based on electrochemical double layer capacitance', Sensors and Actuators, B: Chemical, vol. 123, no. 1, pp. 262-268.
View/Download from: Publisher's site
The use of mesoporous gold as electrode material for measurement of electrochemical capacitance is investigated. The electrodes possess a pore size in the range of 10-30 nm and are prepared by de-alloying films of AuAlx, where x ? 2. Analyses conducted with X-ray photoelectron spectra (XPS) show that their surfaces are essentially pure gold, with only traces of aluminium remaining. The electrodes show near-ideal capacitor behaviour under both cyclic voltammetry and potential-step conditions. The higher capacitance of the mesoporous electrodes leads to a better dynamic range in potential-step experiments, resulting in improved accuracy of measurement. The sensitivity of the new material as a capacitive sensor is demonstrated in a milk fouling experiment, and is improved by up to 30 times compared to the control sample of ordinary planar gold. We propose that the use of mesoporous gold electrodes offers a convenient way to sensitively and accurately amplify the capacitance signal of an electrochemical sensor. 2006 Elsevier B.V. All rights reserved.
Bosman, M., Keast, V.J., Watanabe, M., Maaroof, A.I. & Cortie, M.B. 2007, 'Mapping surface plasmons at the nanometre scale with an electron beam', Nanotechnology, vol. 18, no. 16.
View/Download from: Publisher's site
The optical response from metal nanoparticles and nanostructures is dominated by surface plasmon generation and is critically dependent on the local structure and geometry. Electron energy-loss spectroscopy (EELS), combined with recent developments in spectrum imaging and data processing, has been used to observe the energy and distribution of surface plasmons excited by fast electrons. The energy of the plasmon responses is consistent with the optical response and with calculations. For gold and silver rods and ellipsoids, longitudinal, transverse and distinct cluster modes were readily identified and mapped. The spatial resolution of the presented maps is one order of magnitude better than that achievable with scanning near-field optical microscopy (SNOM)-based techniques. IOP Publishing Ltd.
Zareie, M.H., Xu, X. & Cortie, M.B. 2007, 'In situ organization of gold nanorods on mixed self-assembled-monolayer substrates', Small, vol. 3, no. 1, pp. 139-145.
View/Download from: Publisher's site
A method is described for assembling gold nanorods, end-to-end, into long chains attached on top of a mixed self-assembled monolayer that has been functionalized with streptavidin. Methods to prepare chains of nanorods in colloidal suspension have been reported by others, but our protocol offers a way to directly form such structures on a substrate. The rods are spaced ?5 nm apart in the resulting chains, which extend for over a micrometer in length. The assembly and morphology of the nanorod structures were characterized by surface plasmon resonance spectroscopy, as well as by scanning electron microscopy and scanning probe microscopy. Structures of this type could conceivably serve as plasmonic waveguides in future nanodevices. 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
Harris, N., Ford, M.J., Cortie, M.B. & McDonagh, A.M. 2007, 'Laser-induced assembly of gold nanoparticles into colloidal crystals', Nanotechnology, vol. 18, no. 36.
View/Download from: Publisher's site
Micron-sized colloidal crystals comprised of gold nanospheres have been synthesized directly from a gold nanoparticle/methyl methacrylate colloid by application of a 514 nm laser at 500 mW. An array of colloidal crystals can be created by translation of the glass substrate under the laser beam, after 2 min of irradiation at each site. We demonstrate through a series of control experiments and calculations that plasmon-induced, localized heating of the gold nanoparticles contributes to the mechanism responsible for the formation of these colloidal crystals. IOP Publishing Ltd.
Hoft, R.C., Armstrong, N., Ford, M.J. & Cortie, M.B. 2007, 'Ab initio and empirical studies on the asymmetry of molecular current-voltage characteristics', Journal of Physics Condensed Matter, vol. 19, no. 21.
View/Download from: Publisher's site
We perform theoretical calculations of the tunnelling current through various small organic molecules sandwiched between gold electrodes by using both a tunnel barrier model and an ab initio transport code. The height of the tunnelling barrier is taken to be the work function of gold as modified by the adsorbed molecule and calculated from an ab initio electronic structure code. The current-voltage characteristics of these molecules are compared. Asymmetry is introduced into the system in two ways: an asymmetric molecule and a gap between the molecule and the right electrode. The latter is a realistic situation in scanning probe experiments. The asymmetry is also realized in the tunnel barrier model by two distinct work functions on the left and right electrodes. Significant asymmetry is observed in the ab initioi(V) curves. The tunnel barrier i(V) curves show much less pronounced asymmetry. The relative sizes of the currents through the molecules are compared. In addition, the performance of the WKB approximation is compared to the results obtained from the exact Schrdinger solution to the tunnelling barrier problem. IOP Publishing Ltd.
Hoft, R.C., Ford, M.J., McDonagh, A.M. & Cortie, M.B. 2007, 'Adsorption of amine compounds on the Au(111) surface: A density functional study', Journal of Physical Chemistry C, vol. 111, no. 37, pp. 13886-13891.
View/Download from: Publisher's site
A Density Functional Theory study of the adsorption energetics of various amine compounds on the gold-(111) surface revealed that preferential binding occurs in under-coordinated sites. The largest binding energy is obtained when a gold adatom is placed in the fee position and the amine positioned with the nitrogen above the adatom. The results are compared with previous calculations for thiols, phosphines, and ethynylbenzene molecules to provide a meaningful comparison within a consistent computational framework. The systematic increase in binding energy with methyl group substitution previously observed for phosphine compounds is not observed for the amine analogues. The binding energy of the amines is considerably lower than that for thiols and binding is indicated for only the adatom geometry-a result consistent with experimental data. 2007 American Chemical Society.
Blaber, M.G., Arnold, M.D., Harris, N., Ford, M.J. & Cortie, M.B. 2007, 'Plasmon absorption in nanospheres: A comparison of sodium, potassium, aluminium, silver and gold', Physica B: Condensed Matter, vol. 394, no. 2, pp. 184-187.
View/Download from: Publisher's site
The optical absorption for nanospheres made from Na, K, Al, Ag and Au are compared as a precursor to choosing the ideal metal for use in a negative permittivity (NP) near-field superlens. The relationship between optical absorption of the metal nanosphere and the ability of the NP lens to reconstruct the near field is one to one. Metals with low dielectric losses have large plasmon absorption cross-sections and absorb over a very narrow wavelength range; they are consequently excellent materials for superlenses. Numerical solutions to Mie theory were used to calculate the absorption efficiency, Qabs, for nanospheres varying in radius between 5 and 100 nm in vacuum. We show that, although silver is the most commonly used material for superlensing, its absorption efficiency, as a nanosphere, at the plasmon resonance is not as strong as materials such as the alkali metals. Of all these materials, potassium spheres with a radius of 21 nm have an optimum absorption efficiency of 14.7, resulting in the ability of a film with thickness of 40 nm to reconstruct a grating with a period of 57 nm. 2007 Elsevier B.V. All rights reserved.
Liu, J., McBean, K.E., Harris, N. & Cortie, M.B. 2007, 'Optical properties of suspensions of gold half-shells', Materials Science and Engineering B: Solid-State Materials for Advanced Technology, vol. 140, no. 3, pp. 195-198.
View/Download from: Publisher's site
Suspensions of mesoscale gold half-shells of controlled size were produced by microsphere-templated vapour deposition and their optical properties were studied. The transmission spectra of the particles exhibited an extinction peak that could be tuned from 530 to over 2000 nm by variation of the diameter of the template used. In this respect the optical properties of these reduced-symmetry particles are similar to those of full nanoshells, however they may be more convenient to prepare. 2007 Elsevier B.V. All rights reserved.
Cortie, M.B., Dowd, A., Harris, N. & Ford, M.J. 2007, 'Core-shell nanoparticles with self-regulating plasmonic functionality', Physical Review B - Condensed Matter and Materials Physics, vol. 75, no. 11.
View/Download from: Publisher's site
We propose a smart nanoparticle, a "regulatron," that exploits a cycle of dynamic plasmonic feedback to self-regulate its temperature to a fixed range. One kind of regulatron can be conceived from V O2 and Au; the temperature of this particle when illuminated by laser irradiation of suitable intensities and wavelengths is ?340 K. We expect that regulatrons of this and other compositions will be useful in applications such as photothermal medical therapeutics. 2007 The American Physical Society.
Pissuwan, D., Valenzuela, S.M., Miller, C.M. & Cortie, M.B. 2007, 'A golden bullet? Selective targeting of toxoplasma gondii tachyzoites using antibody-functionalized gold nanorods', Nano Letters, vol. 7, no. 12, pp. 3808-3812.
View/Download from: Publisher's site
Conjugates of gold nanoparticles and antibodies have useful functionalities. Here, we show how they can be used to selectively target and destroy parasitic protozoans. Gold nanorods were conjugated with an anti-Toxop/asma gondii antibody and used to target the extracellular tachyzoite which is an infectious form of an obligate parasite Toxoplasma gondii. Subsequent laser irradiation was used to kill the targeted protozoans. This concept provides a new paradigm for the treatment of parasitic protozoans. 2007 American Chemical Society.
Zareie, H.M., McDonagh, A.M., Edgar, J., Ford, M.J., Cortie, M.B. & Phillips, M.R. 2006, 'Controlled assembly of 1,4-phenylenedimethanethiol molecular nanostructures', Chemistry of Materials, vol. 18, no. 9, pp. 2376-2380.
View/Download from: Publisher's site
We present here the first high-resolution scanning tunneling microscope images showing that 1,4-phenylenedimethanethiol forms mono- and multilayers on gold(111) substrates under particular solution-deposition conditions. The high-resolution images show that the deposition conditions strongly influence the type of surface structure formed. The molecular structures were also probed using molecular-etching techniques and through deposition and imaging of gold nanoparticles. The current-voltage (I-V) characteristics of the multilayer structures are significantly different from those of monolayers. For the first time, scanning electron microscopy experiments were used to investigate the homogeneity of larger surface areas of the surface structures. 2006 American Chemical Society.
Harris, N., Ford, M.J. & Cortie, M.B. 2006, 'Optimization of plasmonic heating by gold nanospheres and nanoshells', Journal of Physical Chemistry B, vol. 110, no. 22, pp. 10701-10707.
View/Download from: Publisher's site
Gold nanoparticles have strong and tunable absorption peaks in their optical extinction spectra, a phenomenon that has recently been exploited to generate localized heating in the vicinity of these particles. However the optimum particle geometry and illumination regime to maximize these effects appears not to have been previously examined in any detail. Here we show that the interplay between the particles' absorption cross-sections, volume, and surface area lead to there being specific conditions that can maximize particle temperature and surface heat flux. Optical absorption efficiencies were calculated from the formulation of Mie, and radiative, convective, and conductive heat transfer models were used to model the thermal performance of particles in different situations. Two technologically relevant scenarios for illumination, namely, irradiation by sunlight at 800 W/m2 and by a monochromatic laser source of 50 kW/m2 tuned to the peak absorption wavelength, were considered. For irradiation by sunlight, the resultant heat flux is optimized for an 80 nm diameter nanoshell with an aspect ratio of 0.8, while for irradiation by laser the maximum heat flux is found for 50 nm nanoshells, with an aspect ratio of 0.9. 2006 American Chemical Society.
Cortie, M.B., Xu, X. & Ford, M.J. 2006, 'Effect of composition and packing configuration on the dichroic optical properties of coinage metal nanorods', Physical Chemistry Chemical Physics, vol. 8, no. 30, pp. 3520-3527.
View/Download from: Publisher's site
When nanorods of Au, Ag and some other elements are aligned with a preferred orientation with respect to light, their optical extinction characteristics become dependent on the polarization and angle of incidence of the light. This effect is explored here and it is shown that it could potentially be exploited to produce a 'colour-change coating'. However, particle-particle interactions are also likely to occur in such coatings, with red shifting of extinction spectra occurring for end-on-end configurations of monodisperse rods, and blue shifting for side-by-side configurations. Surprisingly, the particle-particle interactions are attenuated if they are between rods of differing aspect ratios, and this offers a useful new means of control of the optical properties of coatings of nanorods. the Owner Societies 2006.
Xu, X., Gibbons, T.H. & Cortie, M.B. 2006, 'Spectrally-selective gold nanorod coatings for window glass', Gold Bulletin, vol. 39, no. 4, pp. 156-165.
The unique optical properties of gold nanorods, which exhibit tuneable absorption as a function of their aspect ratio, suggest that they might have potential applications in coatings for solar control on windows. Here we explore the properties of coatings produced by attaching gold nanorods to the surface of glass. Such coatings can attenuate solar radiation effectively, even at very low gold contents, but the figure-of-merit, Tvis/Tsol, of our experimental coatings was close to unity, indicating that they are not spectrally selective, However, calculations are presented to show how coatings comprised of a blend of rods with aspect ratios of greater than 3 can produce coatings with Tvis/Tsol of up to at least 1.4. The maximum value possible for perfectly spectrally-selective coating in sunlight is 2.08. Unfortunately, the practical realization of such coatings requires the further development of reliable methods to scale up the production of gold nanorods of longer aspect ratios.
Ford, M., Masens, C.D. & Cortie, M.B. 2006, 'The application of gold surfaces and particles in nanotechnology', Surface Review Letters, vol. 12, no. 2-3, pp. 297-307.
Gold is widely used in nanotechnology, for example as a substrate in forming self-assembled monolayers or as nanoparticles for their unique optical and chemical properties. In this paper we give an overview of the properties of gold relevant to its potential application in molecular-scale devices and present some of our recent computational predictions. Density functional calculations of molecular adsorption onto gold surfaces were used to investigate the effect of surface symmetry and identify new linking schemes for self-assembled monolayers. Adsorption energies of methythiolate (SCH3) onto the (111), 9100) and (110) surfaces of gold are predicted to be 39.3, 48.4 and 51.1 kcal/mol respectively and demonstrate that selective functionalisation of the surfaces is possible. Phosphine molecules with at least two hydrogen atoms substituted for methyl groups are predicted to form Au-P surface bonds with energies of about 13-20 kcal/mol.
Soul De Bas, B., Ford, M.J. & Cortie, M.B. 2006, 'Melting in small gold clusters: A density functional molecular dynamics study', Journal of Physics Condensed Matter, vol. 18, no. 1, pp. 55-74.
View/Download from: Publisher's site
Molecular dynamics simulations of the thermal behaviour of gold clusters containing 7, 13 and 20 atoms have been performed. Total energies and forces at each step of the simulation are calculated from first principles using density functional theory. Ion trajectories are then calculated classically from these forces. In each case the global minimum energy structure and a low-lying isomer are used as the starting structures. In most cases, the clusters do not exhibit a sharp transition from a solid-like phase to a liquid-like phase, but rather pass through a region of transformations between structural isomers that extends over a considerable temperature range. Solid-like behaviour is observed in the atomic trajectories of the simulation at temperatures up to, or above, the bulk melting point. The 20-atom tetrahedral structure is the one exception, showing a sharp transition between solid-like and liquid-like phases at about 1200 K. The starting structure used in the simulation is shown to have a considerable effect upon the subsequent thermal behaviour.
Pissuwan, D., Valenzuela, S.M. & Cortie, M.B. 2006, 'Therapeutic possibilities of plasmonically heated gold nanoparticles', Trends in Biotechnology, vol. 24, no. 2, pp. 62-67.
View/Download from: Publisher's site
Nanoparticles of gold, which are in the size range 10-100 nm, undergo a plasmon resonance with light. This is a process whereby the electrons of the gold resonate in response to incoming radiation causing them to both absorb and scatter light. This effect can be harnessed to either destroy tissue by local heating or release payload molecules of therapeutic importance. Gold nanoparticles can also be conjugated to biologically active moieties, providing possibilities for targeting to particular tissues. Here, we review the progress made in the exploitation of the plasmon resonance of gold nanoparticles in photo-thermal therapeutic medicine. 2005 Elsevier Ltd. All rights reserved.
Cortie, M.B., Maaroof, A., Smith, G.B. & Ngoepe, P. 2006, 'Nanoscale coatings of AuAlx and PtAlx and their mesoporous elemental derivatives', Current Applied Physics, vol. 6, no. 3, pp. 440-443.
View/Download from: Publisher's site
A method to produce nanoscale films of AuAlx and PtAlx, and their mesoporous elemental derivatives is described, and the morphology and optical properties of these coatings explored. The color of the AuAlx film is bright purple, in agreement with ab initio calculations and experimental observations for the compound AuAl2, but becomes black after de-alloying with NaOH. The film of PtAlx is silver-grey and changes to grey after being converted to mesoporous Pt by de-alloying. Both mesoporous coatings exhibit a very rough surface, with pores of between 2 and 20 nm in diameter, and display a significantly more absorptive optical characteristic compared to their ordinary elemental counterparts. 2005 Elsevier B.V. All rights reserved.
Liu, J., Cankurtaran, B., Wieczorek, L., Ford, M.J. & Cortie, M. 2006, 'Anisotropic optical properties of semitransparent coatings of gold nanocaps', Advanced Functional Materials, vol. 16, no. 11, pp. 1457-1461.
View/Download from: Publisher's site
An ordered array of cap-shaped gold nanoparticles has been prepared by vapor deposition onto polystyrene nanospheres supported on a glass substrate. The method of fabrication used imparts a significant anisotropy to the geometric and optical properties of the coating. The optical-absorption properties of these deposits have been measured using UV-vis spectrometry and simulated using a code based on the discrete dipole approximation. Because the nanocaps are not interconnected, they interact with incident light as individual particles with a plasmon resonance that depends upon wavelength and the polarization vector of the light. The resulting extinction peaks manifest in the upper visible and near-infrared regions of the electromagnetic spectrum. Surprisingly, varying the angle of incidence of the light (for a fixed polarization) has no effect on the optical properties of individual nanocaps. Calculations show that these phenomena may be readily interpreted in terms of dipole resonances excited across the longitudinal, transverse, and short-transverse directions of the nanocaps. Coatings comprised of arrays of these particles have the potential to serve as angularly and spectrally selective filters. 2006 WILEY-VCH Verlag GmbH & Co. KGaA.
Hoft, R.C., Ford, M.J. & Cortie, M.B. 2006, 'Prediction of increased tunneling current by bond length stretch in molecular break junctions', Chemical Physics Letters, vol. 429, no. 4-6, pp. 503-506.
View/Download from: Publisher's site
We use ab initio calculations of the tunneling current through a 1,4-phenylenedimethanethiol (XYL) molecule adsorbed between Au(1 1 1) electrodes to show that there are circumstances under which tunneling currents can be increased by bond stretching. The effect is dependent upon the geometry of the gold-sulfur bond and does not occur for the physisorbed thiol, that is, a thiol with the hydrogen atom still in place. However, we predict that when the hydrogen atom is removed, causing the sulfur atom to be strongly bound to the gold surface, stretching this bond away from equilibrium will actually increase the tunneling current. 2006 Elsevier B.V. All rights reserved.
Cortie, M.B., McBean, K.E. & Elcombe, M.M. 2006, 'Fracture mechanics of mollusc shells', Physica B: Condensed Matter, vol. 385-386 I, pp. 545-547.
View/Download from: Publisher's site
The shape and structure of the shells of molluscs has attracted considerable attention. One aspect of interest is the comparatively high resistance to fracture of these shells. It is known that they are composite structures of aragonite, other calcereous materials, and up to 5% by volume of protein 'glue'. A large component of their toughening derives from crack tip blunting, deflection and closure, concepts well-known from the field of fracture mechanics. However, the possibility that they might also derive a measure of toughening from a residual stress distribution has been generally overlooked, although Illert first raised this over a decade ago. The optimum situation would be when the inner surface of the shell is maintained in a state of tensile stress, while the outer layers are in the necessarily counter-balancing compressive state. We have examined this hypothesis using a combination of neutron diffraction and scanning electron microscopy and find that it is certainly feasible. However, a definitive proof will require a diffraction study at higher resolution. 2006 Elsevier B.V. All rights reserved.
Cortie, M.B. 2006, 'Antipodean Gold', Gold Bulletin, vol. 39, no. 3, pp. 92-92.
NA
Ford, M., Cortie, M.B., Maclurcan, D. & Martin, D.K. 2006, 'Real world nanotechnology', Materials Australia, vol. 39, no. 3, pp. 10-12.
There is a degree of uncertainty in the public mind concerning the exact subject matter of nanotechnology. Novels such as Michael Crichtons Prey and the movie Agent Codie Banks have primed many to believe that nanotechnology is about tiny (and rather dangerous) nano-robots. Of course, most technically savvy individuals know better, but because this misconception exists there is an obligation on researchers in this field to communicate a more accurate understanding of the topic to the wider community. The Institute for Nanoscale Technology at the University of Technology, Sydney (UTS) has sought to bridge this gap in understanding.
Xu, X. & Cortie, M.B. 2006, 'Shape change and color gamut in gold nanorods, dumbbells, and dog bones', Advanced Functional Materials, vol. 16, no. 16, pp. 2170-2176.
View/Download from: Publisher's site
It is shown here that deviations from a prolate ellipsoidal shape have a significant effect on the optical properties of gold nano-rods. Transitions from rods to 'dumbbell'- or 'phi'-shaped particles lead to a shift in the longitudinal plasmon peak in the blue and red directions, respectively. Development of 'dog-bone' shapes leads to a red-shift and to the development of a third peak. A broad and flexible color gamut can be obtained. 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Ford, M.J., Masens, C. & Cortie, M.B. 2006, 'The application of gold surfaces and particles in nanotechnology', Surface Review and Letters, vol. 13, no. 2-3, pp. 297-307.
Gold is widely used in nanotechnology, for example as a substrate in forming self-assembled monolayers or as nanoparticles for their unique optical and chemical properties. In this paper we give an overview of the properties of gold relevant to its potential application in molecular-scale devices and present some of our recent computational predictions. Density functional calculations of molecular adsorption onto gold surfaces were used to investigate the effect of surface symmetry and identify new linking schemes for self-assembled monolayers. Adsorption energies of methylthiolate (SCH 3) onto the (111), (100) and (110) surfaces of gold are predicted to be 39.3, 48.4 and 51.1 kcal/mol respectively and demonstrate that selective functionalization of the surfaces is possible. Phosphine molecules with at least two hydrogen atoms substituted for methyl groups are predicted to form Au-P surface bonds with energies of about 13-20 kcal/mol. World Scientific Publishing Company.
Cortie, M.B., Zareie, M.H., Ekanayake, S.R. & Ford, M.J. 2005, 'Conduction, storage, and leakage in particle-on-SAM nanocapacitors', IEEE Transactions on Nanotechnology, vol. 4, no. 4, pp. 406-413.
View/Download from: Publisher's site
Individual gold nanoparticles exhibit discrete capacitances of the order of 1 aF, and they can be tethered to a conductive substrate using a bi-functional monolayer of a suitable organic molecule. However the conduction, retention and leakage of charge by such an attached "nanocapacitor" will be an important issue in any practical application of this concept. Here we investigate the electrical properties of the particles using a combination of scanning tunneling spectroscopy and numerical modeling based on equalizing Wentzel-Kramers-Brillouin style tunneling currents. Application of the model provides the voltage division across the structure, and, together, with an estimate of the capacitance of the particle, provides an indication of likely stored charge and energy and its decay. The methodology was tested with I-V data measured for an Au{111}-?, ?'-p-xylyldithiol-Au nanoparticle system in air. About 25 eV can be stored on the nanoparticles using a charging voltage of 3 V, corresponding to up to twenty electrons. However, leakage of the charge will occur by tunneling in approximately 610-9 s. Therefore, these nanocapacitors would discharge completely in any electric circuit slower than about 1.5 GHz. 2005 IEEE.
Maaroof, A.I., Cortie, M.B. & Smith, G.B. 2005, 'Optical properties of mesoporous gold films', Journal of Optics A: Pure and Applied Optics, vol. 7, no. 7, pp. 303-309.
View/Download from: Publisher's site
Mesoporous gold thin films on glass substrates were fabricated by sputtering of AuAl2 precursor films followed by a de-alloying etch. The resulting sponge-like Au films have very high internal surface area due to nanoscale pores and channels. Scattering is not significant and the optical properties for such nanostructured films were examined using ellipsometry and spectrophotometry. The complex refractive indices of the optically equivalent uniform smooth layer satisfy Kramers-Kronig (KK) self-consistency but have unusual dispersion relations and magnitudes for a film containing the amount of noble metal present. The reflectance at infrared wavelengths is neither metal-nor insulator-like, and the indices have unique dispersion curves. 2005 IOP Publishing Ltd.
Peceros, K.E., Xu, X., Bulcock, S.R. & Cortie, M.B. 2005, 'Dipole - Dipole plasmon interactions in gold-on-polystyrene composites', Journal of Physical Chemistry B, vol. 109, no. 46, pp. 21516-21520.
View/Download from: Publisher's site
Red-shifting of the optical absorption spectra of aggregates of gold nanoparticles by dipole - dipole interactions is of considerable interest, both for theoretical reasons and because the phenomenon can be potentially exploited in various applications. A convenient and practical way to control the effect is to assemble the aggregated ensemble of n gold nanoparticles on the outer surface of larger dielectric spheres. Here, we show by experiment and calculation how the spectra of these structures can be systematically morphed from that of isolated gold particles, through the regime of broad absorption dominated by particle - particle interactions, and finally to the limiting case of a continuous nanoshell. The experimental data were produced using the process of deposition-precipitation, which provides a facile method to decorate polystyrene microspheres with gold nanoparticles. There is no need for prior functionalization of the microsphere surface in our method of deposition-precipitation. Calculations were carried out using a code based on the discrete dipole approximation (DDA). The spectra were dominated by three effects. These were a peak absorption at about 540 nm produced by the conventional plasmon resonance of spherical gold nanoparticles, a broad absorption in the range 600-900 nm caused by diverse dipole - dipole interactions between particles, which strengthened as the number of attached gold particles increased and finally, when n was large, an absorption peak due to the onset of nanoshelllike resonances. The experimental spectra could be successfully fitted by spectra calculated using combinations of these effects. 2005 American Chemical Society.
Chowdhury, H., Xu, X., Huynh, P. & Cortie, M.B. 2005, 'Radiative heat transfer across glass coated with gold nano-particles', Journal of Solar Energy Engineering, Transactions of the ASME, vol. 127, no. 1, pp. 70-75.
View/Download from: Publisher's site
Solar glazing based on reflective or absorptive coatings of noble metals or dielectric compounds respectively is well-known. However, the use of gold nano-particles in an absorptive role has hardly been considered. The performance of such coatings was assessed using an array of incandescent lamps as radiation source, and the results ranked against commercial glazing systems. The nanoparticle coatings attenuated the radiation by 40%. An additional 15% of the incoming energy was convected off the inside surface of the glass. The neutral color and simple manufacture of the coatings suggests that they might have applications on architectural glass. Copyright 2005 by ASME.
Liu, J., Cankurtaran, B., McCredie, G., Ford, M.J., Wieczorek, L. & Cortie, M.B. 2005, 'Investigation of the optical properties of hollow aluminium 'nano-caps'', Nanotechnology, vol. 16, no. 12, pp. 3023-3028.
View/Download from: Publisher's site
A colloidal suspension of hollow aluminium, cap-shaped nanoparticles ('nano-caps') can be conveniently produced by evaporation of aluminium onto a spin-coated layer of polystyrene nanoparticles (PSNPs), followed by sonication and dissolution of the polymer template. Although ordinary spherical aluminium nanoparticles have a plasmon resonance in the ultra-violet, the 'nano-caps' show plasmon absorption between 700 and 1200 nm due to their geometry. The position of their extinction peaks can be tuned by varying the thickness of the aluminium and the shape of the nano-cap. The optical properties of these shapes were modelled using the discrete dipole approximation method, which confirmed that the 'caps' have very significantly red-shifted absorbance and scattering compared to spheres. This finding suggests that aluminium nano-caps might compete with gold and silver nanoparticles in applications requiring absorption in the near infrared. 2005 IOP Publishing Ltd.
Cortie, M.B., Maaroof, A.I. & Smith, G.B. 2005, 'Electrochemical capacitance of mesoporous gold', Gold Bulletin, vol. 38, no. 1, pp. 14-22.
The surfaces of nanoscale gold particles and components are oxide-free under normal ambient conditions. This unusual attribute permits the exploration of microstructures and functionalities that would not be feasible for less noble metals. Here we consider the electrochemical properties of mesoporous gold sponges, prepared by de-alloying an AuAl2 precursor. The sponges have a high specific surface area, with an average pore diameter of 12 nm, but are prone to sinter. They may be prepared in bulk, or, more usefully, as coatings. Their electrochemical capacitance divided by their nominal surface area is high and, at a cell voltage of 0.6 V, reaches 100 mF/cm2 for bulk samples and 2 mF/cm2 for coatings. This is up to a thousand times greater than the 50 to 100 ?F/cm2 exhibited by a planar gold surface.
Xu, X., Cortie, M.B. & Stevens, M.G. 2005, 'Effect of glass pre-treatment on the nucleation of semi-transparent gold coatings', Materials Chemistry And Physics, vol. 94, no. 38778, pp. 266-274.
Coatings of gold nanoparticles with a uniform film texture and a neutral blue hue may be applied to glass by an aqueous process and such coatings have recently been proposed for architectural applications. Here, we show that the optical transmission spec
Masens, C., Ford, M.J. & Cortie, M.B. 2005, 'The effect of surface symmetry on the adsorption energetics of SCH 3 on gold surfaces studied using Density Functional Theory', Surface Science, vol. 580, no. 1-3, pp. 19-29.
View/Download from: Publisher's site
Adsorption of methanethiol onto the three, high symmetry gold surfaces has been studied at the density functional level using a linear combination of atomic orbitals approach. In all three cases the bond energy between the thiolate radical and surface is typical of a covalent bond, and is of the order of 40 kcal mol-1. For the (1 1 1) surface the fcc hollow site is slightly more stable than the bridge site. For the (1 0 0) surfaces the four-fold hollow is clearly the most stable, and for the reconstructed (1 1 0) surface the bridge/edge sites either side of the first layer atoms are preferred. The calculated differences in binding energy between the three surfaces indicate that the thiolate will preferentially bind to the Au(1 1 0) or (1 0 0) before (1 1 1) surface, by about 10 kcal mol-1. The (1 1 0) surface is slightly more favourable than the (1 0 0), although the energy difference is only 3 kcal mol-1. The results suggest the possibility of selectively functionalising the different facets offered by a gold nanoparticle. 2005 Elsevier B.V. All rights reserved.
Liu, J., Maaroof, A.I., Wieczorek, L. & Cortie, M.B. 2005, 'Fabrication of hollow metal "nanocaps" and their red-shifted optical absorption spectra', Advanced Materials, vol. 17, no. 10, pp. 1276-1281.
View/Download from: Publisher's site
The optical and infrared radiation (IR) absorption spectra of randomly oriented suspensions of discrete cap-shaped metal nanoparticles were discussed. Nanocaps of gold, silver, aluminum, copper, and chromium were produced and the effect of variations in deposition angle and thickness were analyzed. The nanocaps were fabricated with the application of 200 nm diameter PSPs onto a glass substrates by spin-coating. The results show that the absorption peaks of these nanocaps are strongly red shifted relative to those of solid nanospheres.
Cortie, M.B., Kerr, J., Nana, S. & Knight, D.S. 2005, 'Experimental processing of FeCr sigma-phase powders', Materials Forum, vol. 29, pp. 262-267.
Ultra-ferritic Fe-35 to 40%Cr stainless steel may be completely converted to sigma phase by thermo-mechanical processing at temperatures in the range 600 to 900C. The resultant intermetallic compound is brittle and readily milled to powder by conventional techniques. In this form it can be processed and shaped like a ceramic powder. The green component can then be converted back into metallic form by an appropriate heat treatment that raises the temperature above that at which sigma phase is stable, causing the material to revert to the ferritic structure. Under appropriate conditions, sintering and consolidation of the compact can be arranged to occur at this time. The sintering treatment must be followed by a fast cool to room temperature in order to prevent reversion to sigma phase. Prototype components have been produced by powder metallurgy and thermal spraying, and the concept has been extended to the production of simple shapes by laser-based rapid-prototyping. Institute of Materials Engineering Australasia Ltd.
Xu, X., Cortie, M.B. & Stevens, M. 2005, 'Effect of glass pre-treatment on the nucleation of semi-transparent gold coatings', Materials Chemistry and Physics, vol. 94, no. 2-3, pp. 266-274.
View/Download from: Publisher's site
Coatings of gold nanoparticles with a uniform film texture and a neutral blue hue may be applied to glass by an aqueous process and such coatings have recently been proposed for architectural applications. Here, we show that the optical transmission spectrum of these coatings is directly related to the interplay between the nucleation, growth and aggregation of the particles. In particular, prior treatments of the glass substrate in 1:1 sulfuric acid (H 2SO4), 98% H2SO4 and buffered hydrofluoric acid (HF) exerted a strong influence on the subsequent particle size and coverage, which is explained here in terms of contact angle and its effect on rates of nucleation. The rate of nucleation on the surface treated with HF is estimated to be twice that of the surface treated with 98% H 2SO4. The color of the coatings is the result of inter-particle plasmonic interactions and is, therefore, also controlled by the nature of nucleation and growth process. 2005 Elsevier B.V. All rights reserved.
Maclurcan, D., Ford, M. & Cortie, M.B. 2004, 'The confusion surrounding nanotechnology', Materials Australia, vol. 37, no. 2, pp. 24-25.
Maclurcan, D., Ford, M. & Cortie, M. 2004, 'Rectifying nanotechnology confusion and redirecting focus', Physicist, vol. 41, no. 3, pp. 84-85.
Ekanayake, S.R., Ford, M. & Cortie, M. 2004, 'Metal-insulator-metal (MIM) nanocapacitors and effects of material properties on their operation', Materials Forum, vol. 27, pp. 15-20.
Metal-insulator-metal (MIM) capacitors play an important part in many integrated electronic circuits in the areas of analog, microwave, and radio frequency systems. However the transverse dimensions of current MIM capacitors are in the micrometer scale. If integrated circuits continue to be miniaturized, the capacitor, alongside other components, must also be miniaturized to realize nanoelectronic circuits and systems. This article presents a novel device, the nanocapacitor, of which the dimensions are constrained to nanoscale in longitudinal and transverse directions, and discusses the effects of material properties on their operation. In particular, this work discusses the effects of dielectric constant, dielectric strength, and quantum electrical phenomena on achieving relatively high capacitances and capacitance densities in nanocapacitors. Institute of Materials Engineering Australasia Ltd - Materials Forum Volume 27 - Published 2004.
Biggs, T., Cornish, L.A., Witcomb, M.J. & Cortie, M.B. 2004, 'Revised phase diagram for the Pt-Ti system from 30 to 60 at.% platinum', Journal of Alloys and Compounds, vol. 375, no. 1-2, pp. 120-127.
View/Download from: Publisher's site
Alloys of the Ti-Pt system between 30 and 61 at.% Pt were studied using metallography with optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential thermal analysis (DTA). A phase of nominal composition Ti4Pt3, in the range 41.7-43.4 at.% Pt was found in samples containing between 30 and 47 at.% Pt, and was apparently formed by a peritectoid reaction between ?-TiPt and Ti3Pt at 120510C. The eutectic reaction between Ti3Pt and ?-TiPt was found to be at ?35 at.% Pt and 142410C, and the Ti3Pt phase melted at circa 1500C. The other phase boundaries agreed with the published literature, except that a slightly wider range was found at 1200C for ?-TiPt. 2004 Elsevier B.V. All rights reserved.
Xu, X., Stevens, M. & Cortie, M.B. 2004, 'In situ precipitation of gold nanoparticles onto glass for potential architectural applications', Chemistry of Materials, vol. 16, no. 11, pp. 2259-2266.
View/Download from: Publisher's site
The optical properties of in situ deposited gold nanoparticle coatings are investigated for potential application in architectural glass. It is found that the optical properties of the coating can be controlled by the pH of the deposition solution. At a pH of 5.1, the color of the coatings develops from pink, through violet, to blue in transmission. This is due to a plasmon resonance peak at 520 nm from isolated particles, and one at about 700 nm due to near-field dipole interactions, with an intermediate zone of the coexistence of the two, which produces the violet color. However, the two peaks do not coexist in the spectra of coatings produced at pH 8.0 or 10.0, with the peak due to the 520 nm resonance being swamped by the development of the resonance due to particle-particle interactions. In all cases the 700 nm peak could be broadened and red-shifted by increasing the deposition time. The reasons for these differences are explored and are shown to be attributable to the smaller, more aggregated morphology of nanoparticles precipitated at the higher pHs. The wavelength of maximum plasmon resonance is examined as a function of the volume fraction of nanoparticles. Significant deviations from the well-known Genzel-Martin analytical model are observed. The reasons for deviation of the model are discussed. Finally, it is shown how coatings that are blue or blue-gray in transmission can be obtained by exploiting this deviation. Such coatings may be more suitable for architectural application than the conventional pink-hued coatings obtained with colloidal gold nanoparticles.
Cortie, M.B. 2004, 'The Weird World of Nanoscale Gold', Gold Bulletin, vol. 37, no. 1 & 2, pp. 12-19.
View/Download from: Publisher's site
Ford, M. & Cortie, M.B. 2004, 'Nanotechnology, nanoscience and nanohype', Chemistry in Australia, vol. 73, no. 3, p. 2.
Ekanayake, S.R., Cortie, M.B. & Ford, M.J. 2004, 'Design of nanocapacitors and associated materials challenges', Current Applied Physics, vol. 4, no. 2-4, pp. 250-254.
View/Download from: Publisher's site
The International Technology Roadmap for Semiconductors (ITRS) projects that the spatial resolution of feature sizes in integrated circuits is rapidly approaching nanoscopic dimensions. Consequently, there is an active interest in the design of nanoscale circuit elements such as transistors, resistors, and capacitors. The properties of materials used to fabricate capacitors pose an important design factor, as with all circuit elements. We analyze the critical materials properties that would influence engineering nanocapacitors (nanoscopic capacitors), and show that at nanoscale, dielectric properties (dielectric constant, dielectric strength, and dielectric relaxation) determine the practicality of such capacitors. 2003 Elsevier B.V. All rights reserved.
De Bas, B.S., Ford, M.J. & Cortie, M.B. 2004, 'Low energy structures of gold nanoclusters in the size range 3-38 atoms', Journal of Molecular Structure: THEOCHEM, vol. 686, no. 1-3, pp. 193-205.
View/Download from: Publisher's site
Using a combination of first principles calculations and empirical potentials we have undertaken a systematic study of the low energy structures of gold nanoclusters containing from 3 to 38 atoms. A Lennard-Jones and many-body potential have been used in the empirical calculations, while the first principles calculations employ an atomic orbital, density functional technique. For the smaller clusters (n=3-5) the potential energy surface has been mapped at the ab initio level and for larger clusters an empirical potential was first used to identify low energy candidates which were then optimised with full ab initio calculations. At the DFT-LDA level, planar structures persist up to six atoms and are considerably more stable than the cage structures by more than 0.1 eV/atom. The difference in ab initio energy between the most stable planar and cage structures for seven atoms is only 0.04 eV/atom. For larger clusters there are generally a number of minima in the potential energy surface lying very close in energy. Furthermore our calculations do not predict ordered structures for the magic numbers n=13 and 38. They do predict the ordered tetrahedral structure for n=20. The results of the calculations show that gold nanoclusters in this size range are mainly disordered and will likely exist in a range of structures at room temperature. 2004 Elsevier B.V. All rights reserved.
Cortie, M.B. 2004, 'The weird world of nanoscale gold', Gold Bulletin, vol. 37, no. 1-2, pp. 12-19.
Protagonists in the emerging field of nanotechnology have as their objective the design, construction and study of useful devices based on nanoscale materials and objects. Objects or structures that have at least one important dimension in the range 0.5 to perhaps 50 nm may be considered to be in the nanoscale domain. These sizes lie far below the 200 nm or so that can be resolved with an optical microscope, and are closer in size to the 0.3 nm diameter of individual atoms. The field of nanotechnology is attracting keen interest at present. The excitement is motivated by the observation that control of matter at the nanoscale holds the promise of, amongst others, faster computing, better medicines, and more useful materials. In this paper, the physical phenomena on which this optimism is based are broadly discussed and explained. Where appropriate, examples of the rather different and curious properties of gold at the nanoscale are used to illustrate the points covered.
Levey, F.C., Cortie, M.B. & Cornish, L.A. 2003, 'Determination of the 76 wt.% Au section of the Al-Au-Cu phase diagram', Journal of Alloys and Compounds, vol. 354, no. 1-2, pp. 171-180.
View/Download from: Publisher's site
The substitution of Al for Cu along the 76 wt.% Au section of the Al-Au-Cu system causes the ? phase of the Au-Cu edge to be successively replaced by a ternary ? electron compound, a ternary extension of the Cu-Al ? electron compound, designated here as ??, and finally the compound AuAl2. A vertical section of this part of the phase diagram has been determined and is presented here, and the relationships between the phases explored. It is considered likely that the section contains the peritectic reactions L+??? and L+????. Both the ? and the ? phases form ordered phases at lower temperatures. 2003 Elsevier Science B.V. All rights reserved.
Biggs, T., Cortie, M.B., Witcomb, M.J. & Cornish, L.A. 2003, 'Platinum Alloys for Shape Memory Applications', Platinum Metals Review, vol. 47, no. 4, pp. 142-156.
Shape memory alloys (SMAs) are materials that can change their shape at a specific temperature and are used in applications as diverse as sensors, temperature sensitive switches, force actuators, fire-safety valves, orthodontic wires, fasteners, and couplers. The possible advantages offered by platinum-based SMAs involving the metals: iron, aluminium, gallium, titanium, chromium, and vanadium, are considered here and the likely systems upon which such alloys might be based are assessed. It is suggested that the most promising candidate systems are ternary-alloyed variations of the Pt 3Al and PtTi phases, although SMAs based on PtFe3 have potential for low temperature applications. It appears possible to engineer a shape memory transition in the (Pt, Ni)Ti system anywhere between room temperature and 1000C, a versatility which is probably unique among all known SMAs.
Cortie, M.B. 2003, 'New Uses For Gold In The Emerging Field Of Nanotechnology', Gold Bulletin, vol. 36, no. 3, pp. 74-74.
NA
Cortie, M.B. & Van Der Lingen, E. 2002, 'Catalytic gold nano-particles', Materials Forum, vol. 26, pp. 1-14.
Although gold is the most inert of all metallic elements, it has interesting properties as a heterogeneous catalyst. There are a number of curious aspects to catalysis by gold that are currently attracting academic investigation, while the observation that gold-based catalysts are active at room temperature and below is driving considerable industrial interest. However, much is still not understood about these catalysts and, for example, apparently similar preparation techniques result in activities of hugely varying magnitude. In the present paper we assess the known phenomenology of heterogeneous catalysis by gold, with particular reference to the material properties of the individual nano-particles of catalyst and the many disagreements in the literature. Even the structure of the nano-particles is uncertain, with claims being made for truncated octahedra, cub-octahedra, icosahedra, various kinds of decahedra, and amorphous structures. As far as uncertainty concerning the mechanism of catalysis is concerned, we show that the situation has not yet been resolved, with evidence that catalysis can proceed even in the absence of either a discrete particulate morphology or an oxide support. One possibility is that more than one mechanism applies. Alternatively, the explanation may be that the activity of gold as a catalyst is determined only by the availability of surface gold atoms with low coordination numbers and an associated electron density suitable for whatever reaction is being catalysed. In this case, the role of the oxide support and of gold particle size and structure is indirect, and they would serve mainly to modulate the specific surface area of the gold, and the electronic configuration of its surface atoms.
Cortie, M.B. & Levey, F.C. 2002, 'Formation, modulation and adaptive twinning of martensite in the Au7Cu5Al4 shape memory system', Intermetallics, vol. 10, no. 1, pp. 23-31.
View/Download from: Publisher's site
The Au7Cu5Al4 ? electron phase transforms displacively from an L21 parent to a nominally body-centred tetragonal martensite with c/a<1. The compound is of interest because it has the potential to serve as an 18 carat shape memory alloy in jewellery. Analysis of its X-ray diffraction spectra indicates that the martensite is modulated by a [110]/[[110][1?10]]transverse shear wave, showing that it belongs, strictly speaking, to the generic B19 structure type. The martensite is also twinned, and the probable twinning structure is explored. A 15R(9,6?) stacking sequence is deduced, which for reasons of the L21 ordering inherited from the parent phase, must be doubled to produce a notional 30R(9,6?,9,6?) martensite that properly repeats. However, although the measured X-ray diffraction spectra can be substantially explained by the structures derived, the martensite probably also has additional, higher-order lattice modulations. 2002 Elsevier Science Ltd. All rights reserved.
Levey, F.C., Cortie, M.B. & Cornish, L.A. 2002, 'A 500 C isothermal section for the Al-Au-Cu system', Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, vol. 33, no. 4, pp. 987-993.
The Al-Au-Cu system and its associated ternary alloys and intermetallic compounds is surprisingly poorly known, and the authors could find no phase diagram for it in the literature. This article addresses this omission by presenting an isothermal section at 500 C, derived with the aid of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), metallography, and hardness measurements. The samples studied had generally received an anneal of 2 hours at 500 C, primarily in order to complete any transformations that occurred during solidification and cooling of the castings. The possibility of further changes on protracted annealing at 500 C is not ruled out, and the diagram presented is, therefore, applicable only to material prepared by thermal processing of an industrial nature. The presence of a ternary ? phase with a nominal stoichiometry of AlAu2-xCu1+x (0 ? x ? 1) was confirmed, and its phase field at 500 C was determined. A number of the binary intermetallic phases were found to exhibit some solid solubility of the ternary element. In particular, the ?-Al4Cu9 phase extends deep into the ternary and, in the vicinity of the commercially interesting 18-carat line, appears to exist in a ternary ordered form, designated here as ?2.
Levey, F.C., Cortie, M.B. & Cornish, L.A. 2002, 'Hardness and colour trends along the 76 wt.% Au (18.2 carat) line of the Au-Cu-Al system', Scripta Materialia, vol. 47, no. 2, pp. 95-100.
View/Download from: Publisher's site
Colour and hardness were measured on a series of alloys along the 76 wt.% Au line of the Au-Cu-Al system. Complex, non-monotonic behaviour was observed, which is shown to be correlated with microstructural changes. The available colours include reddish, yellow, 'apricot', white and purple. The hardness of as-cast material varies from 150 to 500 Vickers. 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
Cortie, M.B. 2001, 'Body-centred tetragonal martensite formed from the Au7Cu5Al4 beta phase', Materials Science and Engineering A, vol. 303, pp. 1-10.
Cortie, M.B. 2001, 'Martensitic transformations, microstructure and mechanical workability of TiPt', Metallurgical and Materials Transactions A, vol. 32, no. 8, pp. 1881-1886.
View/Download from: Publisher's site
Biggs, T., Cornish, L.A., Witcomb, M.J. & Cortie, M.B. 2001, 'The effect of nickel on the martensitic-type transformations of Pt3Al and PtTi', Journal de Physique IV France, vol. 11, no. Pr8, pp. 493-498.
View/Download from: Publisher's site
The effect of nickel on two classes of martensitic-type transformations in platinum systems has been studied. The first transformation is Ll[2] to DO[c]' in the Pt3Al system and the second is B2 to B 19 in the TiPt system. The microstructures after transformation in the two systems are very different. The product of the Pt[3]Al transformation has a twinned microstructure, typical of cubic-to-tetragonal transformations. The product of the TiPt transformation is lath-like, although the morphology can be altered using heat treatments. The parent phase in the TiPt system is not retained at room temperature, whereas the parent phase in the Pt[3]Al transformation can be stabilised to room temperature. A great variation in hardness and transformation temperature is seen in each system as the composition is varied about the stoichiometric ratio, which has the lowest hardness. The Pt[3]Al transformation temperature has been reported to range from around room temperature to 1000C. The TiPt transformation temperature can range from 1000 to 1080C. The effect of nickel additions on these alloys also has a marked effect on the parent and product phase stability, and hence the microstructure and resulting hardness. The effect on the Pt[3]Al phase is complex, as nickel appears to stabilise the parent phase. The hardness varied in the region of 350 to 500 HV[10]. For the TiPt phase, the hardness values were generally found to increase with the nickel additions increasing from 250 to about 600 HV[10]. The addition of 20 at.% nickel decreases the transformation temperature from around 1000C to about 600C.
Levey, F.C., Cortie, M.B. & Cornish, L.A. 2000, 'Displacive Transformations In Au-18 Wt Pct Cu-6 Wt Pct Al', Metallurgical And Materials Transactions A-physical Metallurgy And Materials Science, vol. 31, no. 8, pp. 1917-1923.
View/Download from: Publisher's site
A gold alloy with 18 wt pct Cu and 6 wt pet Al undergoes a reversible displacive phase transformation between an incompletely ordered L2(1) parent phase and a tetragonal product. The characteristics of these transformations were studied using acoustic em
Cortie, M.B. & Levey, F.C. 2000, 'Structure And Ordering Of The 18-carat Al-au-cu Beta-phase', Intermetallics, vol. 8, no. 7, pp. 793-804.
View/Download from: Publisher's site
Gold alloys with around 30 at% copper and 25 at% aluminium undergo a reversible displacive transformation with M-s and A(s) temperatures of about 30 and 75 degrees C respectively. However, the nature of the parent and product phases in this system has no
Horner, I., Hall, N., Cornish, L.A., Witcomb, M.J., Cortie, M.B. & Boniface, T. 1998, 'An Investigation Of The B2 Phase Between Alru And Alni In The Al-ni-ru Ternary System', Journal Of Alloys And Compounds, vol. 264, no. 1-2, pp. 173-179.
View/Download from: Publisher's site
An investigation was undertaken to ascertain the extension of the B2 phase fields from AlNi and AlRu in the Al-Ni-Ru ternary system. The samples were are-melted, annealed at 1500 or 1600 degrees C, and examined using optical microscopy, scanning electron
Levey, F.C., Cortie, M.B. & Cornish, L.A. 1998, 'A 23 Carat Alloy With A Colourful Sparkle', Gold Bulletin, vol. 31, no. 3, pp. 75-0.
View/Download from: Publisher's site
Lightly etched surfaces of specimens comprised of the Au-Al beta-phase exhibit a remarkable sparkling appearance and play of colour. An investigation of this phenomenon is described and explained here. The play of colour produced from individual grains a
Wong-kian, M., Cortie, M.B. & Cornish, L.A. 1998, 'Hot Isostatic Consolidation And Transformation Of Sigma Phase Powders', Materials Science And Technology, vol. 14, no. 12, pp. 1242-1248.
View/Download from: Publisher's site
Superferritic stainless steel compositions containing 38%Cr and at least 2% each of Ni and Mo carl be converted to sigma phase by heat treatment and then to powder by mechanical attrition. This powdered sigma phase has been experimentally processed by po
Cortie, M.B. & Cortie, L. 1997, 'Science, Technology And The Education Of The South African Child', South African Journal Of Science, vol. 93, no. 8, pp. 346-348.
The Department of Educations Curriculum 2005 discussion document describes the outcomes that are desired from the education to be offered to children at school in the years to come. It is debatable whether they will be achieved to the extent required in
Cortie, M.B. & Jackson, E. 1997, 'Simulation Of The Precipitation Of Sigma Phase In Duplex Stainless Steels', Metallurgical And Materials Transactions A-physical Metallurgy And Materials Science, vol. 28, no. 12, pp. 2477-2484.
View/Download from: Publisher's site
The precipitation of sigma phase within the ferrite component of a duplex stainless steel has been simulated using a two-dimensional computer model which takes into account the partitioning of alloy elements between ferrite and austenite. The model is ba
Cortie, M.B., Mcewan, J. & Enright, D. 1996, 'Materials Selection In The Mining Industry Old Issues And New Challenges', Journal Of The South African Institute Of Mining And Metallurgy, vol. 96, no. 4, pp. 145-157.
The historical development of materials engineering in the mining industry is briefly reviewed, and some of the factors currently influencing the industry in South Africa are discussed, Material usages in various parts of the mining operation are surveye
Nana, S. & Cortie, M.B. 1996, 'Retardation Of Intermetallic Phase Formation In Experimental Superferritic Stainless Steels', Metallurgical And Materials Transactions A-physical Metallurgy And Materials Science, vol. 27, no. 9, pp. 2436-2444.
View/Download from: Publisher's site
While superferritic stainless steels containing 29 pct chromium possess excellent resistance to corrosion, they may, under certain conditions, be embrittled by the precipitation of intermetallic phases. The extent to which the precipitation reactions can
Cortie, M.B. & Pollak, H. 1995, 'Embrittlement And Aging At 475-degrees-c In An Experimental Ferritic Stainless-steel Containing 38 Wt-percent Chromium', Materials Science And Engineering A-structural Materials Properties Microstructure And Processing, vol. 199, no. 2, pp. 153-163.
View/Download from: Publisher's site
The aging at 475 degrees C of an experimental ferritic stainless steel containing 38 wt.% chromium was studied. The physical changes occurring at this temperature were followed with the aid of Mossbauer spectroscopy, measurements of Charpy V-notch toughn
Levey, F.C., Cortie, M.B. & Cornish, L.A. 1995, 'Displacive Phase Transformations In Spangold 18 Carat Gold Alloys', Journal De Physique Iv, vol. 5, no. C8, pp. 1087-1092.
View/Download from: Publisher's site
The displacive phase transformations in an Au-32 at% Cu-22 at% Al gold alloy are discussed. This alloy, and others similar to it, is used to produce Spangold(TM) jewellery pieces. Complex textures of intersecting laths are produced on polished surfaces o
Cortie, M.B., Fletcher, C.J. & Louw, K. 1995, 'Fatigue Cracking Of Type-304 Sheet In Pasteurizer Water', International Journal Of Fatigue, vol. 17, no. 7, pp. 463-470.
View/Download from: Publisher's site
Cracking has been observed in the beams of pasteurizing machines made of type 304 stainless steel. In order to gain greater insight into the problem, samples of type 304 were fatigue tested in a simulated pasteurizer environment. The cracking produced in
Cortie, M.B. 1994, 'Life May Be A Cellular-automaton', South African Journal Of Science, vol. 90, no. 10, pp. 508-510.
NA
Iorio, L., Cortie, M.B. & Jones, R.K. 1994, 'Technical Note - Solubility Of Nitrogen In Experimental Low-nickel Austenitic Stainless-steels', Journal Of The South African Institute Of Mining And Metallurgy, vol. 94, no. 7, pp. 173-177.
The amount of nitrogen contained in an austenitic stainless steel affects its properties significantly. The maximum content of nitrogen feasible in a range of experimental low-nickel austenitic stainless steels containing significant additions of copper
Cortie, M.B. 1994, 'Effect Of Temperature On The Resistance To Tearing Of Type 430 Stainless-steel Sheet', Isij International, vol. 34, no. 5, pp. 443-450.
View/Download from: Publisher's site
The effect of temperature and specimen orientation on the tearing of type 430 stainless-steel sheet was examined. Tests were conducted at temperatures between -50 and +150-degrees-C (223 to 423 K) on compact tension and conventional tensile specimens man
Nana, S. & Cortie, M.B. 1993, 'Microstructure And Corrosion-resistance Of Experimental Low-nickel Duplex Stainless-steels', Journal Of The South African Institute Of Mining And Metallurgy, vol. 93, no. 11-12, pp. 307-315.
Duplex stainless steels containing high levels of manganese and copper and lower-than-normal levels of nickel were produced and evaluated. The experimental alloys containing 3 per cent copper by mass could not be successfully hot-rolled. Alloys contain
Cortie, M.B. 1993, 'Simulation Of Metal Solidification Using A Cellular-automaton', Metallurgical Transactions B-process Metallurgy, vol. 24, no. 6, pp. 1045-1053.
View/Download from: Publisher's site
The solidification of a hypothetical liquid was studied by means of simulations conducted using a cellular automaton. Construction and operation of the automaton are described. The effects of varying the temperatures of the liquid and solid phases, the f
Cortie, M.B. 1993, 'Digital Seashells', Computers & Graphics, vol. 17, no. 1, pp. 79-84.
View/Download from: Publisher's site
The spiral shells of molluscs may be simulated by suitable mathematical expressions. This paper reviews progress in this field, and describes techniques for the generation of synthetic shells. The method presented is fast enough for convenient interactiv
Cortie, M.B. 1993, 'History And Development Of Ferritic Stainless-steels', Journal Of The South African Institute Of Mining And Metallurgy, vol. 93, no. 7, pp. 165-176.
An account is given of the development of ferritic stainless steels since their discovery in the early years of this century. The alloys became very widely used in the 1950s, the market during that decade being driven strongly by a demand for automobile
Cortie, M.B. & Premachandra, K. 1992, 'Microstructural Development And Abrasion-resistance Of An Experimental Ferrite-sigma Alloy', Scripta Metallurgica Et Materialia, vol. 27, no. 12, pp. 1847-1852.
View/Download from: Publisher's site
NA
Premachandra, K., Cortie, M.B. & Eric, R. 1992, 'Effect Of Stabilizing Elements On Formation Of Sigma-phase In Experimental Ferritic Stainless-steels Containing 39-percent-cr', Materials Science And Technology, vol. 8, no. 5, pp. 437-442.
View/Download from: Publisher's site
The effect of additions of the stabilising elements aluminium, niobium, titanium, and zirconium on the formation of sigma-phase in the experimental ferritic stainless steel Fe-39Cr-2Mo-2Ni (wt-%) has been studied. It was found that additions of titanium
Cortie, M.B., Wolff, I. & Cornish, L.A. 1992, 'Intermetallic Compounds And Phenomenological Structure Maps', South African Journal Of Science, vol. 88, no. 3, pp. 141-143.
The JIMIS-6 conference on intermetallic compounds was held at Sendai in Japan from 17 to 20 June 1991. The conference was both timely and well attended by a large number of researchers in the field. Interest in these comparatively unusual substances is
Wolff, I., Premachandra, K. & Cortie, M.B. 1992, '2nd-phase Particles In Ferritic Stainless-steels Containing 40% Chromium', Materials Characterization, vol. 28, no. 2, pp. 139-148.
View/Download from: Publisher's site
The nature and occurrence of secondary phases in experimental ferritic stainless steels containing 40% chromium is reviewed. Phases discussed include oxides, carbides, nitrides, sulphides, and the intermetallic sigma phase. The influence of these particl
Wai, S., Cortie, M.B. & Robinson, F. 1992, 'A Study Of High-temperature Cracking In Ferritic Stainless-steels', Materials Science & Engineering A, vol. 158, no. 1, pp. 21-30.
The cracking that can occur in cast ferritic stainless steel ingots or slabs during cooling to room temperature is considered. The present work is focused particularly on the solid state cracking phenomenon sometimes called clinking. Examination of sampl
Cortie, M.B. 1991, 'The Irrepressible Relationship Between The Paris Law Parameters', Engineering Fracture Mechanics, vol. 40, no. 3, pp. 681-682.
View/Download from: Publisher's site
The high apparent correlation between the parameters C and m in the Paris law for Stage II fatigue-crack growth has been shown to be an artifact produced by the logarithmic and mathematical methods used to represent fatigue data. Although the correlation
Potgieter, J. & Cortie, M.B. 1991, 'Determination Of The Microstructure And Alloy Element Distribution In Experimental Duplex Stainless-steels', Materials Characterization, vol. 26, no. 3, pp. 155-165.
View/Download from: Publisher's site
An investigation was carried out on the microstructure and distribution of alloy elements in a series of experimental duplex stainless steels containing up to 35% chromium. It was found that the proportion of austenite and ferrite present could be accur
Cortie, M.B. & Mavrocordatos, C. 1991, 'The Decomposition Of The Beta Phase In The Copper-tin System', Metallurgical Transactions A-physical Metallurgy And Materials Science, vol. 22, no. 1, pp. 11-18.
The heat treatment of beta-phase alloys in the copper-tin system has been of technological significance for over 2000 years but has hardly been investigated by metallurgists. In this paper, the isothermal decomposition of the beta phase has been examine
Cortie, M.B. & Potgieter, J. 1991, 'The Effect Of Temperature And Nitrogen-content On The Partitioning Of Alloy Elements In Duplex Stainless-steels', Metallurgical Transactions A-physical Metallurgy And Materials Science, vol. 22, no. 10, pp. 2173-2179.
View/Download from: Publisher's site
The partitioning of the alloy elements chromium, nickel, and molybdenum that occurs in conventional duplex stainless steels has been measured for various nitrogen contents and annealing temperatures. The experimental results have been combined with data
Tullmin, M., Strydom, H., Cortie, M.B. & Robinson, F. 1990, 'Eds And Sims Analysis Of Grain-boundary Precipitates In Fe-40cr Alloys Responsible For Reduced Corrosion-resistance', South African Journal Of Science, vol. 86, no. 4, pp. 205-207.
NA
Potgieter, J. & Cortie, M.B. 1990, 'High-chromium, Low-nitrogen Duplex Stainless-steels', Journal Of The South African Institute Of Mining And Metallurgy, vol. 90, no. 5, pp. 111-118.
NA
Muller, B., Cortie, M.B. & Matthews, L. 1990, 'Simulating The Production Of Deep-drawable Aisi 430 Stainless-steel', Journal Of The South African Institute Of Mining And Metallurgy, vol. 90, no. 1, pp. 17-26.
NA
Cortie, M.B. 1989, 'The Effect Of Geometric Similarity On Gill Size In The Mollusca', South African Journal Of Science, vol. 85, no. 10, pp. 621-621.
NA
Cortie, M.B. & Garrett, G. 1989, 'A New Look At An Old Technique For The Measurement Of Fatigue Crack-growth Rates', Experimental Mechanics, vol. 29, no. 3, pp. 291-294.
View/Download from: Publisher's site
NA
Cortie, M.B. 1989, 'Models For Mollusk Shell Shape', South African Journal Of Science, vol. 85, no. 7, pp. 454-460.
NA
Boothroyd, C.A., Potgieter, J. & Cortie, M.B. 1989, 'Metallurgical Examination Of An Unidentified Fallen Object', South African Journal Of Science, vol. 85, no. 5, pp. 326-327.
NA
Cortie, M.B. 1989, 'Progress And Trends In The Substitution For Chromium In Steels', Materials And Society, vol. 13, no. 1, pp. 13-31.
NA
Cortie, M.B. & Garrett, G. 1989, 'A Comparison Of Fatigue Crack-growth Of Three Alloy-steels At Elevated-temperature', Theoretical And Applied Fracture Mechanics, vol. 11, no. 1, pp. 9-19.
View/Download from: Publisher's site
Fatigue cracks were grown in alloy steels by the use of a triangular loading waveform with a frequency of 1 Hz and an R-ratio of 0.1, and the crack growth rates were determined. The steel alloys Fe-1%Cr-0.5%Mo and Fe-1.5%Mn-0.8%Ni-0.5%Mo (SA508) were tested at 450 C, and Fe-1%Cr-0.5%Mo and Fe-0.5%Cr-0.5%Mo-0.25%V at 550 C. Statistical treatment of the results indicated that, over the range of alternating stress intensities applied, the fatigue crack growth rates were very similar for each pair of alloys tested. The use of the Paris Law to describe the rates of fatigue crack growth would have led to an erroneous conclusion in this regard, and a sigmoidal descriptive model is therefore proposed for the growth of fatigue cracks. With the use of a microcomputer, this model is not much more difficult to apply than the Paris Law, and gives a far better description of the results. Finally, a statistical method for the comparison of sets of data on fatigue crack growth is presented and demonstrated.
Cortie, M.B. & Garrett, G. 1988, 'The Thermal-activation Energy For Fatigue Of Fe-1 Pct Cr-0.5 Pct Mo', Metallurgical Transactions A-physical Metallurgy And Materials Science, vol. 19, no. 12, pp. 2979-2987.
View/Download from: Publisher's site
NA
Cortie, M.B. & Garrett, G. 1988, 'On The Correlation Between The C And M In The Paris Equation For Fatigue Crack-propagation', Engineering Fracture Mechanics, vol. 30, no. 1, pp. 49-58.
View/Download from: Publisher's site
NA