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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
Professor, School of Mathematical and Physical Sciences, School of Mathematical and Physical Sciences
Member, Research Centre for Clean Energy Technology
Associate Member, GEVIC - Green Energy and Vehicle Innovations Centre
Core Member, CCET - Centre for Clean Energy Technology
BSc (Wits), ME (UP), PhD (Wits)
Member, Institution of Engineers, Australia
 
Phone
+61 2 9514 2208

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. A recent paper, for example, shows how 'dark mode' plasmon resonances can be excited using a specially tuned nano-antenna.  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 sixteen most recent scientific publications (as of July 2015) are (* indicates MBC was the 'corresponding author')

1.* S. Supansomboon, A. Dowd, A. Gentle, E. van der Lingen and M.B. Cortie, Thin films of PtAl2 and AuAl2 by solid-state reactive synthesis, Thin Solid Films, in press, doi:10.1016/j.tsf.2015.07.019

2. S. Zhu, M.B. Cortie and I. Blakey, Effect of multimodal plasmon resonances on the optical properties of five-pointed nanostars, Nanomaterials & Nanotechnology, vol.5, 2015, article 22, doi: 10.5772/60726

3.* M. Tai, A. Gentle, K.S.B. de Silva, M.D. Arnold, E. van der Lingen and M.B. Cortie, Thermal stability and catalytic efficacy of nanoporous Raney gold, Metals, vol.5, 2015, pp.1197-1211

4. V. J. Keast, J. Ewald, K.S.B. De Silva, M. B. Cortie, B. Monnier, D. Cuskelly and E. H. Kisi, Optical properties and electronic structure of the Cu-Zn brasses, J. Alloys Cmpd., vol.647, 2015, pp.129-135.

5.* G. Fletcher, M.D. Arnold, T. Pedersen, V.J. Keast and M.B. Cortie, Multipolar and dark mode plasmon resonances on drilled silver nano-triangles, Optics Express, vol.23(14), 2015, pp.18002-18013.

6. D.J.M. King, S.C. Middleburgh, A.C.Y. Liu, H.A. Tahini, G.R. Lumpkin, M.B. Cortie, Formation and structure of V–Zr amorphous alloy thin films, Acta Mater., vol. 83, 2015, pp.269-275.

7. Y. Chen, D. Zeng, M.B. Cortie, A. Dowd, H. Guo, J. Wang, D-L Peng, Seed-induced growth of flower-like Au-Ni-ZnO metal-semiconductor hybrid nanocrystals for photocatalytic applications, Small, vol.11(12), 2015, pp.1460-1469, DOI: 10.1002/smll.201401853

8.* K.S.B. De Silva, A. Gentle, M. Arnold, V.J. Keast, M.B. Cortie, Dielectric function and its predicted effect on localized plasmon resonances of equiatomic Au–Cu, J. Phys. D: Appl. Phys., 48 (2015) 215304.

9. S. Zhu, H-H Cheng, I. Blakey, N. Stokes, K. Ostrikov, and M.B. Cortie, Fabrication of arrays of plasmonic ‘top-hat’ structures using electron beam lithography, Microelectronic Engineering, vol.139, 2015, pp.13-18.

10.* 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

11.* 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, DOI 10.1007/s11051-014-2344-z

12. 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

13. 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.

14. 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.

15.* 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 Applied Materials & Interfaces, vol.6 (12),  2014, pp 9411–9417,  DOI:10.1021/am501794y

16. 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.

Can supervise: Yes

http://www.sciencedirect.com/science/article/pii/S0925838814001819Chemistry for Engineering students
Materials Engineering
Nanomaterials
Advanced Nanomaterials

Chapters

Ting, S.R.S., Min, E.H., Cortie, M.B., Nguyen, H.T. & Hutvagner, G. 2015, 'Non-Viral Nano-Vectors for Nucleic Acid Delivery' in Bondi, M.L., Botto, C. & Amore, E. (eds), Frontiers in Nanomedicine, Bentham Science, UAE, pp. 222-255.
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The development of therapeutic nucleic acids has led to new strategies for treating various diseases. Non-viral, synthetic nano-vectors in gene therapy have attracted increasing attention due to their low immunogenicity and low toxicity compared to viral counterparts. Due to the molecular structure of nucleic acids, they are very prone to degradation in pH sensitive biological environments. Therefore, synthetic nano-vehicles for therapeutic delivery, known as 'nano-vectors', need to be cleverly designed and engineered to protect and deliver appropriate therapeutic nucleic acids to the targeted sites for action. In this chapter, a brief overview of various types of therapeutic nucleic acids is first provided, followed by analysis of the synthetic nanomaterials under development as delivery systems to carry nucleic acids. The nucleic acid-encapsulated nano-vectors discussed here open a window for a new generation of nanomedicine.
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.
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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.M. 2009, 'Nanoscience of gold and gold surfaces' in Mohr, F. (ed), gold chemistry: applications and future directions in the life sciences, Wiley-VCH, Weinheim, pp. 321-355.
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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.
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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

Bilokur, M., Gentle, A., Arnold, M., Cortie, M.B. & Smith, G.B. 2015, 'Optical properties of refractory TiN, AlN and (Ti,Al)N coatings', MICRO+NANO MATERIALS, DEVICES, AND SYSTEMS.
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Shahcheraghi, N., Dowd, A., Arnold, M.D. & Cortie, M.B. 2015, 'Plasmon Resonances on Opto-capacitive Nanostructures', MICRO+NANO MATERIALS, DEVICES, AND SYSTEMS.
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Gali, M.A., Tai, M.C., Arnold, M.D., Cortie, M.B., Gentle, A.R. & Smith, G.B. 2015, 'Plasmonic response in nanoporous metal: dependence on network topology', MICRO+NANO MATERIALS, DEVICES, AND SYSTEMS.
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Zhu, S. & Cortie, M. 2015, 'Optical properties of arrays of five-pointed nanostars', Proceedings of SPIE - The International Society for Optical Engineering.
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© 2015 SPIE. The optical properties of nanostructures control the performance of applications that are based on localized surface plasmon resonances. Here we use finite-difference time-domain calculations to explore the effect of geometry and material-of-construction on the transmission and near-field optical intensity of arrays of closely-spaced five-pointed nano-star shapes. We compared isolated solid star shapes to star-shaped nano-gaps set within a surrounding square metal shape. The materials investigated were silver, gold, copper and aluminum. The study showed that both the geometry and material chosen had a significant effect on the resulting transmittance spectra. Transmittance spectra of arrays of solid five-pointed nano-stars did not show any strong absorption peaks in the visible region whereas, in contrast, the arrays of star-shaped nano-gaps set within the metal squares did show strong absorption peaks. However, on closer examination it became obvious that the enhanced electric field of the latter was mostly on the corners of the square metal domains and not actually in or on the star-shaped nano-gaps. Therefore we deduce that arrays of simple metal squares will be more suitable as substrates for surface enhanced Raman spectroscopy than arrays of stars or star-shaped nano-gaps. Gold, silver and copper were suitable choices for the latter type of array. Aluminum was unsuitable, at least for applications in the visible part of the spectrum, because it was associated with relatively weak electric fields.
Shahcheraghi, N., Dowd, A., McDonagh, A., Cortie, M.B. & Keast, V. 2014, 'Multimode plasmon resonances on double- and triple-decker stacks of silver nanotriangles', 2014 International Conference on Nanoscience and Nanotechnology, IEEE, pp. 57-60.
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Nanotriangles of silver may be readily synthesized by wet chemical techniques and exhibit a strong localized surface plasmon resonance with light. Here we examine the complex resonances of nanotriangles in double-and triple-decker sandwich configurations.
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, 141st TMS Annual Meeting & Exhibition, Wiley, Orlando, pp. 267-274.
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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, COMMAD, IEEE, Sydney, pp. 228-231.
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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.G., Dowd, A.R. & Cortie, M.B. 2008, 'Synthesis of hollow gold nanoparticles and rings using silver templates', International Conference on Nanoscience and Nanotechnology, ICONN 2008, IEEE International Conference on Nanoscience and Nanotechnology, IEEE, Melbourne, Australia, pp. 36-39.
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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.
Cortie, M. 2008, 'Rainbow's end: Gold-themed papers at the 2008 International Conference on Nanoscience and Nanotechnology', Gold Bulletin, pp. 209-210.
Gentle, A.R., Maaroof, A.I., Cortie, M.B. & Smith, G. 2007, 'Optical and electrical switching in nanostructured coatings of VO2', Nanocoatings. Proceedings of SPIE vol 6647, SPIE, SPIE, San Diego, California, USA, pp. 1-8.
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Vanadium dioxide udergoes a reversible metal-insulator phase transition at about 68 degrees C. Cooatings iof 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 methods for deposting films with nano-sized grains, which are then optically and electrically characterised. Emphasis in this study is the impact of aluminium doping and grain sturcture. The optical hysteresis is rpesnted and its switching range is not altered at different soping levels but he 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, in the drop in Tc and the electrica properties in the metal state. For grain sizes under about 180 nm the conductivity in the mtal phase is not linear in temperature but is thermally activated, with activation enegies delta E dependent on both grain size G and doping level.
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, Annual Condensed Matter and Materials Meeting, Australian Institute of Physics, Wagga Wagga, Australia, pp. 1-3.
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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.W. & Ford, M. 2007, 'Active control of the optical properties of nanoscale coatings using 'smart' nanoparticles', Nanocoatings. Proceedings of SPIE vol 6647, SPIE, SPIE, San Diego, USA, pp. 1-4.
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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 VO2, 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 - art. no. 66470D', Nanocoatings, pp. D6470-D6470.
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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, p. vii.
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Gentle, A.R., Maaroof, A.I., Smith, G. & Cortie, M.B. 2005, '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, Conference on Photonics - Design, Technology and Packaging II, SPIE, Brisbane, Australia, pp. 3816-3816.
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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.O., Ford, M. & Cortie, M.B. 2006, 'Local electromagnetic fields surrounding gold nano-cap particles', 2006 International Conference on Nanoscience and Nanotechnology, ICONN, IEEE Publishing Company, Brisbane, Australia, pp. 1-4.
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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 30000 times the applied field. The electric field contours surounding the particle are used to assign the order of the surface plasmon resonance.
Cortie, M.B., Maaroof, A.I., Mortari, A. & Wuhrer, R. 2006, 'Application of nano-and mesoporous gold in electrodes and electrochemical sensors', ICONN2006, Interantional Conference on nanoscience and Nanotechnology, IEEE, Brisbane, QLD Australia, pp. 524-527.
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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. & Cortie, M.B. 2006, 'Optimisation of absorption efficiency for varying dielectric spherical nanoparticles', ICONN2006, International Conference on Nanoscience and nanotehcnology, IEEE, Brisbane, QLD Australia, pp. 556-559.
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In this paper we compare tje 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 claculate the absorption efficiency for nanospheres varying in radii between 5nm and 100 nm in vacuum. We show that although gold is the most commonly used nanoparicle material, its absorption efficiency at the lasmon 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 peaporition shifts by 100 nm for spheres ranging from 5 nm to 65 nm, the shift is less than 10 nm for gold spheres.
Hoft, R.C., Ford, M. & Cortie, M.B. 2006, 'Effect of dipole moment on current-voltage characteristics of single molecules', ICONN2006, International Conference on Nanoscience and nanotechnology, IEEE, Brisbane, QLD Australia, pp. 395-398.
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We perform emperical calculations of the tunneling current through various small organic molecules sandwiched between gold electrodes by using the Wenzel-Kramers-Brillouin (WKB) approximation. The barrierto tunneling is taken to eb 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 exisiting first principles and experimental results. In this model the surface dipole moment, induced by the adsorbed molecule can have asignificant effect on the current and hence dipole moments may be an important property for prediction of the conductance chracteristics of a molecule.
Cortie, M.B. & Xu, X. 2006, 'Control of plasmon resonance in coatings of gold nanorods', ICONN2006, International Conference on Nanoscience and Nanotechnology, IEEE, Brisbane, QLD Australia, pp. 470-473.
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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. 2007, 'Self-organised materials: from organic molecules to genetically engineered gold-binding proteins', 2006 International Conference on Nanoscience and Nanotechnology, ICONN, IEEE, Brisbane, Australia, pp. 517-519.
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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. 2005, 'Electron tunneling through alkanedithiol molecules - art. no. 603603', Biomems And Nanotechnology Ii, Conference on BioMEMS and Nanotechnology II, Spie-Int Society Optical Engineering, Brisbane, AUSTRALIA, pp. 3603-3603.
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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 beta(n
Ford, M., Kirkup, L., Gentle, A.R., Zareie, H.M. & Cortie, M.B. 2005, 'How reliable are scanning tunneling microscopy measurements of electron transport in molecules? - art. no. 603604', Biomems And Nanotechnology Ii, Conference on BioMEMS and Nanotechnology II, Spie-Int Society Optical Engineering, Brisbane, AUSTRALIA, pp. 3604-3604.
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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
Hoft, R.C., Ford, M.J., Cortie, M.B. & IEEE 2006, 'Effect of dipole moment on current-voltage characteristics of single molecules', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, pp. 77-80.
Blaber, M.G., Harris, N., Ford, M.J., Cortie, M.B. & IEEE 2006, 'Optimisation of absorption efficiency for varying dielectric spherical nanoparticles', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, pp. 61-64.
Cankurtaran, B., Ford, M.J., Cortie, M. & IEEE 2006, 'Local electromagnetic fields surrounding gold nano-cap particles', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, pp. 15-18.
Smith, G.B., Maaroof, A., Dowd, A., Gentle, A. & Cortie, M. 2006, 'Tuning plasma frequency for improved solar control glazing using mesoporous nanostructures - art. no. 61970T', Photonics for Solar Energy Systems, pp. T1970-T1970.
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Cortie, M., Maaroof, A. & Smith, G.B. 2006, 'Functional metamaterials based on mesoscale gold sponges, particulate aggregates, and their composites with dielectric materials', Materials Research Society Symposium Proceedings, pp. 25-30.
The optical properties of some nanoscale composites may deviate from that expected from a simple law of mixture of their individual components. In these cases the resulting structure can be considered to be a type of 'metamateriar. Here we explore some of the possibilities for nanoscale composite structures comprised of gold and VO2 - the latter being a functional material that undergoes a reversible insulator to metallic phase transition at 68°C. Two microstructures are examined: aggregates of gold nanoparticles surrounded by VO2 as the continuous phase, and its geometric inverse, mesoporous gold sponge with discontinuous VO2 inclusions. A composite, right-angled parallelepiped measuring 40100100 nm is taken as representative of the mixture, and calculations of the optical properties performed using the discrete dipóle approximation code of Draine and Flatau. The VO2 matrix strongly attenuates the dipole-dipole plasmon resonance of the gold structure, and thermochromic switching of the remaining plasmon resonance occurs. © 2007 Materials Research Society.
Cortie, M., Maaroof, A., Mortari, A., Wuhrer, R. & IEEE 2006, 'Applications of nano- and mesoporous gold in electrodes and electrochemical sensors', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, pp. 95-98.
Cortie, M., Xu, X. & IEEE 2006, 'Control of plasmon resonance in coatings of gold nanorods', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, pp. 81-84.
Zareie, H., Sarikaya, M., McDonagh, A.M., Barber, J., Cortie, M., Phillips, M. & IEEE 2006, 'Self-organized materials: From organic molecules to genetically engineered gold-binding proteins', 2006 INTERNATIONAL CONFERENCE ON NANOSCIENCE AND NANOTECHNOLOGY, VOLS 1 AND 2, pp. 530-532.
Cortie, M., Laguna, A. & Thompson, D. 2006, 'Gold 2006. Highlights of 4th International Conference on the Science, Technology and Industrial Applications of Gold: Limerick, Ireland 3-6 September 2006', Gold Bulletin, pp. 226-235.
Cortie, M.B., Zareie, H.M., Liu, J., Muller, K.H. & Ford, M. 2004, 'Modelling and verification of the electrical properties of organic dielectric monolayers in capacitive configurations', Proceedings Of The Society Of Photo-Optical Instrumentation Engineers (SPIE) Vol 5649, Conference on Smart Structures, Devices, and Systems II, International Society for Optical Engineering (SPIE), Sydney, Australia, pp. 316-322.
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The possible role of self-assembled monolayers (SAMs) as the dielectric component of nanoscale capacitors is considered. SAMs of two rather different molecules, á,á′-p-xylyldithiol (′ XYL′) and dodecanedithiol (′ C12&P
Cortie, M.B., Xu, X., Chowdhury, H.A., Zareie, H.M. & Smith, G. 2004, '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, Conference on Smart Structures, Devices, and Systems II, SPIE, Sydney, Australia, pp. 565-573.
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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, National Congress of the AIP, Australian Institute of Physics, Canberra, pp. 177-180.
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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. 2003, 'Medical Nanotechnology and Developing Nations', Proceedings of the Asia Pacific Nanotechnology Forum 2003, Oz Nano, World Scientific Publishing Co, Cairns, Australia, pp. 165-172.
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Cortie, M.B., Van Der Lingen, E. & Patrick, G. 2003, 'Catalysis and capacitance on nano-structured gold particles and sponges', Proceedings of the Asia Pacific Nanotechnology Forum 2003, Asia Pacific Nanotechnology Forum, World Scientific, Cairns, Australia, pp. 79-82.
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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., Maaroof, A.I., Schelm, S., Allan, R.S., Anstis, G. & Cortie, M.B. 2004, 'Optical response of nanostructured metal/dielectric composites and multilayers', Complex Mediums V: Light and Complexity: Proceedings of SPIE Vol 5508, Complex Mediums V: Light & Complexity, International Society for Optical Engneering, Colorado, USA, pp. 192-205.
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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.
Cortie, M., Holliday, R., Laguna, A., Nieuwenhuys, B. & Thompson, D. 2004, 'Newsbrief: Gold2003: Highlights of this International Conference on the Science, Technology and Industrial Applications of Gold, Vancouver 28 September - 1 October 2003', Applied Catalysis A: General, pp. N2-N10.
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A report on "Gold2003: Highlights of this International Conference on the Science, Technology, and Industrial Applications of Gold" held on 9/28/2003-10/1/2003 in Vancouver, Canada, introducing the four principal themes of the conference, i.e., gold catalysis, chemistry, materials, and nanotechnology, covers papers on commercial aspects of gold applications, including fuel cell systems, pollution and emission control, chemical processing, and development of new coatings; gold as a novel catalyst in the 21st century, including applications in pollutant emission control, production of hydrogen for energy applications, e.g., fuel cells, and conversion of propylene to propylene oxide; gold as an active catalyst in CO oxidation, selective hydrogenation of acrolein to allyl alcohol and of crotonaldehyde to crotyl alcohol; photocatalytic hydrogen production from methanol; NH3 oxidation; and development of fuel systems, including use of gold in the generation and purification of hydrogen as well as in the fuel cell itself, with potential applications on generators, cars and buses, industrial vehicles, and small portable power suppliers.
Tomkin, D.F., Muir, J.G. & Cortie, M.B. 2003, 'Customized Sustainable Housing', Sustainable Innovation 03, Sustainable Innovation 03, Stockholm, Sweden.
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, 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 Conference on Nanotechnology, IEEE, San Franscisco, USA, pp. 756-759.
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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.
Biggs, T., Cornish, L.A., Witcomb, M.J. & Cortie, M.B. 2001, 'The effect of nickel on the martensitic-type transformations of Pt3Al and TiPt', Journal De Physique. IV : JP, pp. Pr8493-Pr8498.
The effect of nickel on two classes of martensitic-type transformations in platinum systems has been studied. The first transformation is L12 to DOc' in the Pt3Al system and the second is B2 to B19 in the TiPt system. The microstructures after transformation in the two systems are very different. The product of the Pt3Al transformation has a twinned microstructure, typical of cubic-to-tetragonal transformations. The product of the TiPt transformation is lath-like, although the morphology can he altered using heat treatments. The parent phase in the TiPt system is not retained at room temperature, whereas the parent phase in the Pt3Al transformation can he 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 Pt3Al transformation temperature has been reported to range from around room temperature to 1000°C. The TiPt transformation temperature can range from 1000 to 1080°C. 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 Pt3Al phase is complex, as nickel appears to stabilise the parent phase. The hardness varied in the region of 350 to 500 HV10. For the TiPt phase, the hardness values were generally found to increase with the nickel additions increasing from 250 to about 600 HV10. The addition of 20 at.% nickel decreases the transformation temperature from around 1000°C to about 600°C.
Levey, F.C. & Cortie, M.B. 1999, 'Ordering and quasi-martensitic transformations in Au-Cu-Al alloys', JAPAN INSTITUTE OF METALS, PROCEEDINGS, VOL 12, (JIMIC-3), PTS 1 AND 2, pp. 1116-1119.
Levey, F.C., Cortie, M.B., Barker, I.J. & SOC, I.S. 1997, 'The blobulator - A new technology to convert liquid metal into solid lumps', 54TH ELECTRIC FURNACE CONFERENCE PROCEEDINGS, pp. 243-248.
Nkosibomvu, Z.L., Pollak, H., Witcomb, M.J. & Cortie, M.B. 1996, 'Effect of alloy composition on aging of the ferrite phase in Fe-Cr alloys.', INTERNATIONAL CONFERENCE ON THE APPLICATIONS OF THE MOSSBAUER EFFECT - ICAME-95, pp. 173-176.
Cortie, M.B. 1995, 'Modelling the surface bumps and spikes of molluscan shells', PROCEEDINGS OF THE FIRST INTERNATIONAL CONCHOLOGY CONFERENCE, pp. 46-65.
CORTIE, M. 1994, 'COPPER AS AN AUSTENITIZING ADDITION TO STAINLESS STEELS', PROCEEDINGS XVTH CMMI CONGRESS, VOL 2, pp. 165-172.
Cortie, M.B., Boothroyd, C.A. & Garrett, G.G. 1985, 'CREEP-INDUCED FAILURE OF AUSTENITIC STAINLESS STEEL PIPELINES.', pp. 247-254.
Cracking was observed in certain highly stressed weld joints in a pipeline of a petrochemical plant operating at 530 degree C with an internal pressure of 3MPa. An attempt was made to repair the pipeline by grinding out the cracks and rewelding but this action resulted in further cracking. This paper describes the subsequent investigation, and details some of the findings. The cracking observed after welding appears to have been the result of extensive creep damage localized at the grain boundaries. Unable to sustain the stresses induced by welding, intragranular cracking occurred at the weakened grain boundaries.

Journal articles

Keast, V.J., Walhout, C.J., Pedersen, T., Shahcheraghi, N., Cortie, M.B. & Mitchell, D.R.G. 2016, 'Higher Order Plasmonic Modes Excited in Ag Triangular Nanoplates by an Electron Beam', Plasmonics, pp. 1-6.
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© 2015 Springer Science+Business Media New York Ag triangular nanoplates are known to generate strong plasmonic resonances when excited by both light and electron beams. Experimental electron energy-loss spectra (EELS) and maps were acquired using an aberration-corrected JEOL-ARM microscope. The corner, edge and centre modes that are often observed in such structures were also observed in these measurements. In addition, novel higher order internal modes were observed and were found to be well reproduced by theoretical calculations using boundary element method (BEM). These modes are 'dark modes so are not observed in the optical extinction spectra. They are confined surface propagating modes and are analogous to laser cavity modes.
King, D.J.M., Middleburgh, S.C., McGregor, A.G. & Cortie, M.B. 2016, 'Predicting the formation and stability of single phase high-entropy alloys', Acta Materialia, vol. 104, pp. 172-179.
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Crown Copyright © 2015 Published by Elsevier Ltd on behalf of Acta Materialia Inc. A method for rapidly predicting the formation and stability of undiscovered single phase high-entropy alloys (SPHEAs) is provided. Our software implementation of the algorithm uses data for 73 metallic elements and rapidly combines them - 4, 5 or 6 elements at a time - using the Miedema semi-empirical methodology to yield estimates of formation enthalpy. Approximately 186,000,000 compositions of 4, 5 and 6 element alloys were screened, and 1900 new equimolar SPHEAs predicted. Of the 185 experimentally reported HEA systems currently known, the model correctly predicted the stability of the SPHEA structure in 177. The other sixteen are suggested to actually form a partially ordered solid solution - a finding supported by other recent experimental and theoretical work. The stability of each alloy at a specific temperature can also be predicted, allowing precipitation temperatures (and the likely precipitate) to be forecast. This combinatorial algorithm is described in detail, and its software implementation is freely accessible through a web-service allowing rapid advances in the design, development and discovery of new technologically important alloys.
Keast, V.J., Myles, T.A., Shahcheraghi, N. & Cortie, M.B. 2016, 'Corrosion processes of triangular silver nanoparticles compared to bulk silver', Journal of Nanoparticle Research, vol. 18, no. 2, pp. 1-11.
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© 2016, Springer Science+Business Media Dordrecht. Excessive corrosion of silver nanoparticles is a significant impediment to their use in a variety of potential applications in the biosensing, plasmonic and antimicrobial fields. Here we examine the environmental degradation of triangular silver nanoparticles (AgNP) in laboratory air. In the early stages of corrosion, transmission electron microscopy shows that dissolution of the single-crystal, triangular, AgNP (side lengths 50–120 nm) is observed with the accompanying formation of smaller, polycrystalline Ag particles nearby. The new particles are then observed to corrode to Ag2S and after 21 days nearly full corrosion has occurred, but some with minor Ag inclusions remaining. In contrast, a bulk Ag sheet, studied in cross section, showed an adherent corrosion layer of only around 20–50 nm in thickness after over a decade of being exposed to ambient air. The results have implications for antibacterial properties and ecotoxicology of AgNP during corrosion as the dissolution and reformation of Ag particles during corrosion will likely be accompanied by the release of Ag+ ions.
Moezzi, A., Cortie, M. & McDonagh, A. 2016, 'Transformation of zinc hydroxide chloride monohydrate to crystalline zinc oxide.', Dalton transactions (Cambridge, England : 2003), vol. 45, no. 17, pp. 7385-7390.
Thermal decomposition of layered zinc hydroxide double salts provides an interesting alternative synthesis for particles of zinc oxide. Here, we examine the sequence of changes occurring as zinc hydroxide chloride monohydrate (Zn5(OH)8Cl2H2O) is converted to crystalline ZnO by thermal decomposition. The specific surface area of the resultant ZnO measured by BET was 1.3 m(2) g(-1). A complicating and important factor in this process is that the thermal decomposition of zinc hydroxide chloride is also accompanied by the formation of volatile zinc-containing species under certain conditions. We show that this volatile compound is anhydrous ZnCl2 and its formation is moisture dependent. Therefore, control of atmospheric moisture is an important consideration that affects the overall efficiency of ZnO production by this process.
De Silva, K.S.B., Keast, V.J. & Cortie, M.B. 2016, 'Effect of Al additions on the optical properties of Au -phase', Journal of Alloys and Compounds, vol. 679, pp. 225-230.
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&copy; 2016 Elsevier B.V. All rights reserved. The effect of aluminium on the optical properties of AlxAu1-x (0 < x < 0.12) substitutional solid solutions is determined. Reflectance spectra and ellipsometric data of a range of compositions are measured and the dielectric functions extracted. Al additions flatten the reflection edge and increase optical loss in the Drude region. The implications of these changes for selected technological applications are investigated. Aluminium is found to be a very effective bleaching agent for Au and could have application for the formulation of improved 'white gold' jewellery alloys. However, due to its limited solubility in Au -phase, other alloying additions would still be required to make a commercially acceptable 'white gold'. In contrast, the increased optical loss brought by the Al makes the alloys less suitable than pure Au for plasmonic applications or for spectrally selective coatings.
Zhu, S., Xiao, L. & Cortie, M.B. 2016, 'Surface enhanced Raman spectroscopy on metal nitride thin films', Vibrational Spectroscopy, vol. 85, pp. 146-148.
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&copy; 2016 Elsevier B.V. All rights reserved. Some metal nitride thin films can exhibit resonant plasmonic characteristics that can be exploited in surface enhanced Raman spectroscopy (SERS). In this paper, we explored SERS on titanium nitride (TiN), aluminium nitride (AlN) and titanium-aluminium nitride (TiAlN) thin films produced by physical vapour deposition under vacuum. The films were compared at the same thickness (30 nm). Rhodamine 6 G (R6G) was used as the Raman probe molecule. The Raman spectra of these three samples showed that the SERS signal could be enhanced by 95% compared to the bare glass substrate. Oxidation of the AlN film destroyed the enhancement effect suggesting that, in these films, the enhancement was probably due to the presence of plasmon resonances on some metallic constituent.
Smith, G., Gentle, A., Arnold, M. & Cortie, M. 2016, 'Nanophotonics-enabled smart windows, buildings and wearables', Nanophotonics, vol. 5, no. 1, pp. 55-73.
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&copy; 2016 Geoff Smith et al., published by De Gruyter Open.Design and production of spectrally smart windows, walls, roofs and fabrics has a long history, which includes early examples of applied nanophotonics. Evolving nanoscience has a special role to play as it provides the means to improve the functionality of these everyday materials. Improvement in the quality of human experience in any location at any time of year is the goal. Energy savings, thermal and visual comfort indoors and outdoors, visual experience, air quality and better health are all made possible by materials, whose "smartness" is aimed at designed responses to environmental energy flows. The spectral and angle of incidence responses of these nanomaterials must thus take account of the spectral and directional aspects of solar energy and of atmospheric thermal radiation plus the visible and color sensitivity of the human eye. The structures required may use resonant absorption, multilayer stacks, optical anisotropy and scattering to achieve their functionality. These structures are, in turn, constructed out of particles, columns, ultrathin layers, voids, wires, pure and doped oxides, metals, polymers or transparent conductors (TCs). The need to cater for wavelengths stretching from 0.3 to 35 m including ultraviolet-visible, near-infrared (IR) and thermal or Planck radiation, with a spectrally and directionally complex atmosphere, and both being dynamic, means that hierarchical and graded nanostructures often feature. Nature has evolved to deal with the same energy flows, so biomimicry is sometimes a useful guide.
Shahcheraghi, N., Keast, V.J., Gentle, A.R., Arnold, M.D. & Cortie, M.B. 2016, 'Anomalously strong plasmon resonances in aluminium bronze by modification of the electronic density-of-states.', Journal of physics. Condensed matter : an Institute of Physics journal, vol. 28, no. 40, p. 405501.
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We use a combination of experimental measurements and density functional theory calculations to show that modification of the band structure of Cu by additions of Al causes an unexpected enhancement of the dielectric properties. The effect is optimized in alloys with Al contents between 10 and 15 at.% and would result in strong localized surface plasmon resonances at suitable wavelengths of light. This result is surprising as, in general, alloying of Cu increases its DC resistivity and would be expected to increase optical loss. The wavelengths for the plasmon resonances in the optimized alloy are significantly blue-shifted relative to those of pure Cu and provide a new material selection option for the range 2.2-2.8eV.
Chen, Y., Zeng, D., Cortie, M.B., Dowd, A., Guo, H., Wang, J. & Peng, D.L. 2015, 'Seed-induced growth of flower-like Au-Ni-ZnO metal-semiconductor hybrid nanocrystals for photocatalytic applications.', Small (Weinheim an der Bergstrasse, Germany), vol. 11, no. 12, pp. 1460-1469.
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.
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.
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&copy; 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved. 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.
Zhu, S., Cheng, H.H., Blakey, I., Stokes, N., Ostrikov, K. & Cortie, M. 2015, 'Plasmonic 'top-hat' nano-star arrays by electron beam lithography', Microelectronic Engineering, vol. 139, pp. 13-18.
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&copy; 2015 Published by Elsevier B.V.. Lithography techniques play an important role in the fabrication of nanoscale functional devices. In electron beam lithography (EBL) the optimum dose of electron irradiation is a critical parameter. In this paper, we first identify suitable EBL fabrication parameters by writing patterns with different sizes, periods and electron radiation doses. After finding suitable fabrication parameters, we show how five-pointed gold nanostructures with electric field-enhancing 'top hats' can be fabricated using EBL. Reflectance data of these arrays is measured in order to assess their potential applications in biosensing arrays
De Silva, K.S.B., Gentle, A., Arnold, M., Keast, V.J. & Cortie, M.B. 2015, 'Dielectric function and its predicted effect on localized plasmon resonances of equiatomic Au-Cu', Journal of Physics D: Applied Physics, vol. 48, no. 21.
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Equiatomic (Au,Cu) solid solution orders below 658 K to form a tetragonal AuCu (I) phase with significant changes in physical properties and the crystal structure. The effect of ordering on the dielectric function of the material is controversial however, with inconsistent results reported in the literature. Since the nature of any localized surface plasmon resonance (LSPR) in the nanostructures is very sensitive to the dielectric function, this uncertainty hinders the use of AuCu in plasmonic devices or structures. Therefore, we re-examine the question using a combination of measurements and computations. We find that no significant change in the dielectric function occurs when this material becomes ordered, at least over the range of photon energies relevant to LSPRs. The likely properties of LSPRs in plasmonic devices made of AuCu are analyzed. Use of the alloy offers some advantages over pure Cu, however pure Au would still be the superior option in most situations.
King, D.M., Middleburgh, S.C., Edwards, L., Lumpkin, G.R. & Cortie, M. 2015, 'Predicting the Crystal Structure and Phase Transitions in High-Entropy Alloys', JOM, vol. 67, no. 10, pp. 2375-2380.
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Keast, V.J., Ewald, J., De Silva, K.S.B., Cortie, M.B., Monnier, B., Cuskelly, D. & Kisi, E.H. 2015, 'Optical properties and electronic structure of the Cu-Zn brasses', JOURNAL OF ALLOYS AND COMPOUNDS, vol. 647, pp. 129-135.
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Fletcher, G., Arnold, M.D., Pedersen, T., Keast, V.J. & Cortie, M.B. 2015, 'Multipolar and dark-mode plasmon resonances on drilled silver nano-triangles', Opt. Express, vol. 23, pp. 18002-18013.
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Dark-mode plasmon resonances can be excited by positioning a suitable nano-antenna above a nanostructure to couple a planar incident wave-front into a virtual point source. We explore this phenomenon using a prototypical nanostructure consisting of a silver nanotriangle into which a hole has been drilled and a rod-like nano-antenna of variable aspect ratio. Using numerical simulations, we establish the behavior of the basic drilled nanotriangle under plane wave illumination and electron beam irradiation to provide a baseline, and then add the nano-antenna to investigate the stimulation of additional dark-mode plasmon resonances. The introduction of a suitably tuned nano-antenna provides a new and general means of exciting dark-mode resonances using plane wave light. The resulting system exhibits a very rich variety of radiant and sub-radiant resonance modes.
Tai, M.C., Gentle, A., de Silva, K.S.B., Arnold, M.D., van der Lingen, E. & Cortie, M.B. 2015, 'Thermal Stability of Nanoporous Raney Gold Catalyst', METALS, vol. 5, no. 3, pp. 1197-1211.
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Supansomboon, S., Dowd, A., Gentle, A., Van Der Lingen, E. & Cortie, M.B. 2015, 'Thin films of PtAl2 and AuAl2 by solid-state reactive synthesis', Thin Solid Films, vol. 589, pp. 805-812.
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&copy; 2015 Elsevier B.V. The intermetallic compounds AuAl<inf>2</inf> and PtAl<inf>2</inf> are colored purple and yellow respectively. In the past they have been prepared by bulk melting techniques or by co-deposition in a magnetron sputterer. Here, however, we investigate films of AuAl<inf>2</inf>, PtAl<inf>2</inf> and (Au,Pt)Al<inf>2</inf> prepared by sequential physical vapor deposition of the elements, followed by in situ solid-state reaction. The microstructure, dielectric functions, optical properties and thermal stability of the resulting films are characterized and compared to those prepared by bulk melting or co-deposition. The (Au,Pt)Al<inf>2</inf> films show a color gamut that stretches from purple to brassy yellow depending on composition and microstructure. High temperature synchrotron X-ray diffraction experiments show that the (Au,Pt)Al<inf>2</inf> phase is metastable, decomposing when heated above 420 &deg;C. In contrast, the pure AuAl<inf>2</inf> or PtAl<inf>2</inf> phases are stable to about 580 &deg;C before they oxidize or decompose. The alternative possibility of producing the purple-to-yellow color gamut by depositing optical stacks of very thin films of AuAl<inf>2</inf> and PtAl<inf>2</inf> is also assessed. Either scheme will provide a range of colors lying between those of the binary compound endpoints. Calculations predict that deposition of AuAl<inf>2</inf> onto PtAl<inf>2</inf> will produce more intense colors than vice versa, an unexpected finding that is worth further investigation.
Keast, V.J., Wallace, J.W., Wrightson, C.J., Tai, M., Gentle, A., Arnold, M.D. & Cortie, M.B. 2015, 'The effect of vacancies on the optical properties of AuAl2', JOURNAL OF PHYSICS-CONDENSED MATTER, vol. 27, no. 50.
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Zhu, S., Cortie, M. & Blakey, I. 2015, 'Effect of Multimodal Plasmon Resonances on the Optical Properties of Five-pointed Nanostars', Nanomaterials and Nanotechnology, vol. 5, no. 1, pp. 1-7.
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The optical transmission and electric field distribution of plasmonic nanostructures dictate their performance in nano-optics and nano-biosensors. Here, we consider the use of hollow, five-pointed, star-shaped nanostructures made of Al, Ag, Au or Cu. We use simulations based on finite-difference time-domain and the discrete dipole approximation to identify the strongest plasmon resonan ces in these structures. In particular, we were seeking plasmon resonances within the visible part of the spec trum. The silver pentagrams exhibited the strongest such resonance, at a wavelength of about 530 nm. The visiblelight resonances of Au and Cu pentagrams were relative ly weaker and red-shifted by about 50 nm. The main resonances of the Al pentagrams were in the ultra-violet. All the nanostars also showed a broad, dipolar-like resonance at about 1000 nm. Surprisingly, the maximum field intensities for the visible light modes were greatest along the flanks of the stars ratherthan at theirtips, whereas those of the dipolar-like modes in the near-infrared were greatest at the tips of the star. These findings have practical implications for sensor design. The inclusion of a confor mally hollow interior is beneficial because it provides additional 'hot spots'.
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.
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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.
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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.
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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 & INTERFACES, vol. 6, no. 12, pp. 9411-9417.
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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 Au7Cu5Al4 and Au7Cu5.7Al3.3 shape-memory alloys', ACTA MATERIALIA, vol. 79, pp. 234-240.
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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.
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Moezzi, A., Cortie, M., Dowd, A. & McDonagh, A. 2014, 'On the formation of nanocrystalline active zinc oxide from zinc hydroxide carbonate', JOURNAL OF NANOPARTICLE RESEARCH, vol. 16, no. 4.
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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.
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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.
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Middleburgh, S.C., King, D.M., Lumpkin, G.R., Cortie, M. & Edwards, L. 2014, 'Segregation and migration of species in the CrCoFeNi high entropy alloy', Journal of Alloys and Compounds, vol. 599, pp. 179-182.
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Cortie, M.B., Coutts, M.J., Ton-That, C., Dowd, A.R., Keast, V. & McDonagh, A.M. 2013, 'On The Coalescence Of Nanoparticulate Gold Sinter Ink', Journal Of Physical Chemistry C, vol. 117, no. 21, pp. 11377-11384.
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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
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.
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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 Efield 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 lowenergy tunable cavity mode with a very small mode volume is observed in the near-IR range.
Chen, H., Dorrigan, A., Saad, S., Hare, D.J., Cortie, M.B. & Valenzuela, S. 2013, 'In Vivo Study of Spherical Gold Nanoparticles: Inflammatory Effects and Distribution in Mice', PLoS One, vol. 8, no. 2, pp. 1-8.
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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 &micro;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.
Moezzi, A., Cortie, M.B. & McDonagh, A.M. 2013, 'Formation Of Zinc Hydroxide Nitrate By H+-catalyzed Dissolution-precipitation', European Journal Of Inorganic Chemistry, vol. 8, no. 8, pp. 1326-1335.
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The formation of zinc hydroxide nitrate, Zn5(OH)8(NO3)22H2O, by reaction between zinc oxide and aqueous zinc nitrate solution was examined. Scanning electron microscopy, X-ray diffraction and thermogravimetric analysis were used to analyze the conversion of nanoscale ZnO particles into much larger crystals of the hydroxide nitrate. The rate of the reaction displayed sigmoidal behavior with the maximum conversion rate at ca. 75 min. The reaction stoichiometry involves a 1:1 ZnO/Zn(NO3)2 molar ratio. The data indicate that an amorphous zinc-containing intermediate phase is formed during the transition, and that the zinc hydroxide nitrate crystals nucleate and grow from this phase. The crystals of zinc hydroxide nitrate are several &micro;m in size, but are formed from zinc oxide crystals of only a few hundred nanometers in size, indicating that mass transfer in the aqueous phase plays an important role. We propose that H+-catalyzed dissolution/precipitation is the key process in the mechanism of the reaction. The zinc hydroxide nitrate is stable to about 110 &deg;C, but decomposes above that temperature to a series of less hydrated phases, with associated loss of mass, until zinc oxide is formed at about 190 &deg;C. The solubility product, Ksp, of Zn5(OH)8(NO3)22H2O in water was measured by two independent techniques and found to be in the range of 7.48.5??1011
Moezzi, A., McDonagh, A.M., Dowd, A.R. & Cortie, M.B. 2013, 'Zinc Hydroxyacetate And Its Transformation To Nanocrystalline Zinc Oxide', Inorganic Chemistry, vol. 52, no. 1, pp. 95-102.
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The synthesis of nanocrystalline ZnO by thermal decomposition of zinc hydroxyacetate, Zn-5(OH)(8)(CH3CO2)(2)center dot nH(2)O, was investigated. The decomposition process was examined using X-ray diffraction, thermogravimetric analysis, mass spectrometry
Cortie, M.B., Al Hafed, E., Chen, H., Valenzuela, S., Ting, S., Sonvico, F. & Milthorpe, B.K. 2013, 'Nanomedical research in Australia and New Zealand', Nanomedicine, vol. 8, no. 12, pp. 1999-2006.
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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.
Keast, V.J., Zwan, B., Supansomboon, S., Cortie, M.B. & Persson, P. 2013, 'AuAl2 and PtAl2 as potential plasmonic materials', Journal Of Alloys And Compounds, vol. 577, no. 1, pp. 581-586.
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The dielectric functions of PtAl2, AuAl2 and hypothetical intermediate alloys of the two in the form of AuxPt1-xAl2 were calculated from first principles using density functional theory (DFT) and the random phase approximation (RPA). From these, the refl
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, vol. 2013, no. 29, pp. 5133-5137.
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Zinc hydroxide acetate dihydrate, Zn-5(OH)(8)(CH3CO2)(2)2H(2)O, 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 Zn-5(OH)(8)(CH3CO
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.
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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 da
Bosman, M., Anstis, G., Keast, V.J., Clarke, J. & Cortie, M.B. 2012, 'Light Splitting In Nanoporous Gold And Silver', Acs Nano, vol. 6, no. 1, pp. 319-326.
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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
Porkovich, A., Arnold, M.D., Kouzmina, G., Hingley, B. & Cortie, M.B. 2012, 'Calorimetric Sensor For H2O2/H2O Mist Streams', Ieee Sensors Journal, vol. 12, no. 7, pp. 2392-2398.
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Mist streams comprised of H2O2/H2O droplets are a recent innovation for disinfecting medical equipment, but the availability of a sensor that could monitor the concentration of H2O2 applied during the treatment would be desirable. Here we describe a means to obtain a rapid estimation of H2O2 concentration in this environment. The proposed sensor is based on a platinum resistance thermometer coated with a layer of MnO2 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 H2O and effervescence of decomposing H2O2 operates against heat generated by the decomposition reaction to produce a wellde?ned minimum in the temperature. The time and temperature at which this minimum occurs are well correlated, with the H2O2 content of the solution used to produce the mist droplets.
Stokes, N.L., Cortie, M.B., Davis, T. & McDonagh, A.M. 2012, 'Plasmon Resonances In V-Shaped Gold Nanostructures', Plasmonics, vol. 7, no. 2, pp. 235-243.
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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 str
Cortie, M.B., Liu, F., Arnold, M.D. & Niidome, Y. 2012, 'Multimode Resonances In Silver Nanocuboids', Langmuir, vol. 28, no. 24, pp. 9103-9112.
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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 reson
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.
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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 nanopartic
Moezzi, A., McDonagh, A.M. & Cortie, M.B. 2012, 'Zinc Oxide Particles: Synthesis, Properties And Applications', Chemical Engineering Journal, vol. 185, pp. 1-22.
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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
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.
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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., Li, Y., Zhu, J., Wang, X., Dou, S.X., Guo, Y., Lei, G., Wang, Y., Phillips, M., Cortie, M.B., Li, Y., Choi, K. & Shi, X. 2011, 'Visualization Of Vortex Motion In Feas-Based Bafe(1.9)Ni(0.1)As(2) Single Crystal By Means Of Magneto-Optical Imaging', Journal Of Applied Physics, vol. 109, no. 7, pp. 0-0.
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Superconductivity has been found in newly discovered iron-based compounds. This paper studies the motion of magnetic vortices in BaFe(1.9)Ni(0.1)As(2) single crystal by means of the magneto-optical imaging technique. A series of magneto-optical images re
Bhatia, V.K., Kealley, C.S., Prior, M.J. & Cortie, M.B. 2011, 'Martensite Destabilization In Au(7)Cu(5)Al(4) Shape-Memory Alloy', Acta Materialia, vol. 59, no. 5, pp. 2193-2200.
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Aging-induced changes in the austenite peak (A(P)) temperature of Au(7)Cu(5)Al(4) shape-memory alloy are investigated. Whereas heat treating the parent phase at temperatures >140 degrees C or aging the martensite for long times at room temperature both s
Cortie, M.B., Kealley, C.S., Bhatia, V.K., Thorogood, G., Elcombe, M. & Avdeev, M. 2011, 'High Temperature Transformations Of The Au(7)Cu(5)Al(4) Shape-Memory Alloy', Journal Of Alloys And Compounds, vol. 509, no. 8, pp. 3502-3508.
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The beta-phase of Au(7)Cu(5)Al(4) 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 pa
Porkovich, A., Arnold, M.D., Kouzmina, G., Hingley, B., Dowd, A.R. & Cortie, M.B. 2011, 'Calorimetric sensor for use in hydrogen peroxide aqueous solutions', Sensor Letters, vol. 9, no. 2, pp. 695-697.
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A sensor for characterising aqueous solutions of hydrogen peroxide is described. The sensor is based on the calorimetric signal obtained when catalysing the decomposition of H(2)O(2). The system is quick and simple, and is suitable for determinations of H(2)O(2) concentration between 0% and at least 50% (w/w).
Cortie, M.B. 2011, 'Thin films of AuCuAl shape memory alloy for use in plasmonic nano-actuators', Proceedings MRS Fall Meeting, Materials Research Society, vol. 1295, pp. 1-6.
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We describe the fabrication and structure of nanoscale thin films of ? phase shape memory alloys with the nominal atomic stoichiometry Au 7Cu 5Al 4 (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
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.
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The plasmon resonances and other optical properties of elemental noble and alkali metal nanoparticles have generated enormous scienti?c interest. 1-11 There are numerous applications for plasmon-active nanoparticles, especially in areas such as biological microscopy, medicine, and sensors. 12-18 The various applications exploit some aspect of the plasmon resonance, which include particle-particle plasmon interactions, 19 the unusual coloring or dichroic e?ects in isolated particles, 20,21 light-induced plasmonic heating, 22 light scattering, 23 or twophoton phenomena. 24 Hybrid or multifunctional nanoparticles constructed from more than one component phase have also been attracting increasing interest due to their additional functionalities. 25-30 In this review, we consider speci?cally the optical properties of solid nanoparticles composed of more than one phase or compound. Alloyed nanoparticles (solid solutions or intermetallic compounds of the metallic elements) are also included because these intergrade with the two-phase hybrids
Cortie, M.B., Xiao, L.H., 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, vol. 2011, no. 33, pp. 5087-5095.
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Potassium-rich titanate nanofibers were produced by digesting TiO2 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 &deg;C, whereas the hydrogen- and ammonium-rich materials had to be heated to over 600 &deg;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 &deg;C and instead recrystallized.
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 Special Issue, pp. 65-71.
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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.
Moezzi, A., Cortie, M.B. & McDonagh, A.M. 2011, 'Aqueous pathways for the formation of zinc oxide nanoparticles', Dalton Transactions, vol. 40, no. 18, pp. 4871-4878.
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We examine the effect of reactant concentrations, temperatures and feeding methods on the morphology of ZnO formed when reacting solutions of ZnSO4 and NaOH. The catalytic effect of hydroxide in excess relative to the stoichiometric ratio is considered. It is shown that, having fixed other reaction conditions, the end-products, particle structures and size strongly depend on the mole ratio of the precursors. The presence of zinc salt hydroxide species was confirmed at sub-stoichiometric ratios in slightly acidic conditions. At the stoichiometric ratio both zinc hydroxide and zinc oxide are formed, while only zinc oxide forms in an excess of hydroxide. The method of feeding the reactants into the reaction vessel also has a strong influence on the end-product properties, as does the reaction temperature. By control of these parameters the specific surface area could be varied from 10 to 33 m2 g-1, the particle shape could be varied from equiaxed, through to star-like and needle-like, and the particle size may be varied from 50 to over 300 nm.
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 BaFe(1.9)Ni(0.1)As(2) single crystal by means of magneto-optical imaging (vol 109, 07E142, 2011)', JOURNAL OF APPLIED PHYSICS, vol. 109, no. 10.
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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 AuAl2, AuIn2, and AuGa2', APPLIED PHYSICS LETTERS, vol. 99, no. 11.
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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.
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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.
Coutts, M.J., Zareie, H.M., Cortie, M.B., Phillips, M., Wuhrer, R. & McDonagh, A.M. 2010, 'Exploiting Zinc Oxide Re-Emission To Fabricate Periodic Arrays', ACS Applied Materials & Interfaces, vol. 2, no. 6, pp. 1774-1779.
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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 l
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.
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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.
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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
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.
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Infrared-blocking coatins n 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 ration 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 characterised 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 radiatyion and absorbing nearly two-thirds. The high absoprtive cross sections of the gold nanorods suggest that they can be applied in efficacious coatings at relatively low volume fractions.
Pissuwan, D., Cortie, C.H., Valenzuela, S. & Cortie, M.B. 2010, 'Functionalised gold nanoparticles for controlling pathogenic bacteria', Trends In Biotechnology, vol. 28, no. 4, pp. 207-213.
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The incereasing 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 methids for both diagnosis and destruction of these organisms. Here we consider the possible role that can be plaued 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 io identiofy target or destrpy pathogenic organisms.
Cortie, M.B., Giddings, J. & Dowd, A. 2010, 'Optical properties and plasmon resonances of titanium nitride nanostructures', NANOTECHNOLOGY, vol. 21, no. 11.
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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.
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Kealley, C.S., Cortie, M.B., Maaroof, A.I. & Xu, X. 2010, 'The versatile colour gamut of coatings of plasmonic metal nanoparticles (vol 11, pg 5897, 2009)', PHYSICAL CHEMISTRY CHEMICAL PHYSICS, vol. 12, no. 45, pp. 15141-15143.
Pissuwan, D., Valenzuela, S. & Cortie, M.B. 2009, 'Prospects for Gold Nanorod Particles in Diagnostic and Therapeutic Applications', Biotechnology & Genetic Engineering Reviews, vol. 25, pp. 93-112.
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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 longtudinal surface plasmon, which results in suspensions of themhaving 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 functionalised by a very wide variety of molecules. This has led to interest in their use as selctive biomarkers in biodiagnostics or for selective targeting in photothermal therapeutics. Here we review the recent advances in the use of gold nanoparticles in these applications. additionally the information available regarding their biocompatibility in discussed.
Cortie, M.B., Stokes, N.L. & McDonagh, A.M. 2009, 'Plasmon resonance and electric field amplification of crossed gold nanorods', Photonics and Nanostructures: Fundamentals and Applications, vol. 7, no. 3, pp. 143-152.
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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.
Bhatia, V.K., Levey, F.C., Kealley, C.S., Dowd, A.R. & Cortie, M.B. 2009, 'The aluminium-copper-gold ternary system', Gold Bulletin, vol. 42, no. 3, pp. 201-208.
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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 P-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 beta-phase compositions in the system have been scarcely investigated. The system also contains an extensive gamma-phase, Al4AuxCu9-x, where x ranges from 0 to similar to 6.5, and the purple gold phase AuAl2.
Coutts, M.J., Cortie, M.B., Ford, M. & 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.
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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.
Bhatia, V.K., Kealley, C.S., Wuhrer, R., Wallwork, K. & Cortie, M.B. 2009, 'Ternary Beta And Gamma Phases In The Al-Au-Cu System At 750 Degrees C', Journal Of Alloys And Compounds, vol. 488, no. 1, pp. 100-107.
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There are many aspects of the phases and phase boundaries of the Al-Au-Cu ternary system that are still unknown. Although a 500 degrees C isothermal section and an 18 karat pseudobinary have been reported, many of the other constitutive relationships wit
Pissuwan, D., Valenzuela, S., 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.
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The protozoan parasiteToxoplasma gondii can be selectively targeted and photothermally destroyed by gold nanosphere/antibody conjugates (see image). The optical response of the nanospheres within the tissue window is shifted and enhanced by aggregation. Attachment of the conjugates alone, even without plasmonic heating, lowers the infectivity of the organism.
Maaroof, A.I., Cortie, M.B., Harris, N. & Wieczorek, L. 2009, 'Mie and Bragg plasmons in subwavelength silver semi-shells', Small, vol. 4, no. 12, pp. 2292-2299.
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Bai, H., Cortie, M.B., Maaroof, A.I., Dowd, A.R., Kealley, C.S. & Smith, G. 2009, 'The preparation of a plasmonically resonant VO2 thermochromic pigment', Nanotechnology, vol. 20, no. 8, pp. 1-9.
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Vanadium dioxide (VO2) undergoes a reversible metal-insulator transition, normally at similar to 68 degrees 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 VO2 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.
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.
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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.
Cortie, M. & Rahmani, A. 2009, 'Plasmonics' demystified', Australian Physics, vol. 46, no. 2, pp. 42-45.
Hoft, R.C., Ford, M., Garcia-Suarez, 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, pp. 1-9.
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We perform density functional theory (DFT) calculations of the stretching of Au(111)XAu(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 goldcarbon bond does not break. In contrast, the goldsulfur bond in the thiyl junction breaks without detaching any gold atoms. This behaviour can be attributed to the enhanced strength of the AuC interaction over the AuS 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 AuS 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 AuS bond is broken.
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.
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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. 2008, 'Nanocapacitive circuit elements', ACS Nano, vol. 2, no. 8, pp. 1615-1619.
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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 nanocapacit
Harris, N., Ford, M., 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.
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Nanoparticles of elements such as Au, Al or Ag have optical extinction cross-sections 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.
Supansomboon, S., Maaroof, A.I. & Cortie, M.B. 2008, '"Purple glory": The optical properties and technology of AuAl2 coatings', Gold Bulletin, vol. 41, no. 4, pp. 296-304.
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"Purple glory": the optical properties and technology of AuAi2 coatings
Stokes, N.L., McDonagh, A.M. & Cortie, M.B. 2008, 'Preparation of Nanoscale Gold Structures by Nanolithography', Gold Bulletin, vol. 40, no. 4, pp. 310-320.
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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.
Smith, G., 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, vol. 78, no. 16, pp. 1-1.
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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 th
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.
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Pissuwan, D., Valenzuela, S., 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.
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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 (similar to 1x10(5) to 1x10(10) 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 5x10(2) W/m(2) being sufficient, provided that a total fluence of similar to 30 J/cm(2) 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/cm(2) resulted in 81% cell death compared to only 0.9% in the control, non-labeled cells.
Pissuwan, D., Cortie, C.H., Valenzuela, S. & Cortie, M.B. 2007, 'Gold Nanosphere-Antibody Conjugates for Hyperthermal Therapeutic Applications', Gold Bulletin, vol. 40, no. 2, pp. 121-129.
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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 motication is that gold nanoparticles display a strong plasmon resonance with light, which can be exploted 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.
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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. 2007, 'Plasmonic heating and its possible exploitation in nanolithography', Physica B: Condensed Matter, vol. 394, no. 2, pp. 188-192.
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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 artifacts
Maaroof, A.I., Gentle, A.R., Smith, G. & 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.
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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 fora conductor at their thickness 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 4um 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 taolor the onset of efefctive plasmonic response across a wide range from 0.8 to 4 um and emittance from around0.9 down to low values. An effective uniform metal response is this found in the presence o fsurface nanostructure without the interface absorption found in dense gold layers with sturctured surfaces.
Cortie, M.B., Maaroof, A.I., Stokes, N.L. & Mortari, A. 2007, 'Mesoporous Gold Sponge', Australian Journal Of Chemistry, vol. 60, no. 7, pp. 524-527.
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Mesoporous gold sponge may be prepared by the removal of aluminium from AuAl2 by an alkaline leach. The resulting material has nanosclae 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 suze distribution fctors which are in turn controlled by the microstructure of the precursor compound and the conditions of deposition.
Maaroof, A.I., Cortie, M.B., Gentle, A.R. & Smith, G. 2007, 'Mesoporous gold sponge as a prototype 'metamaterial'', Physica B: Condensed Matter, vol. 394, no. 2, pp. 167-170.
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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 behaviour. We found that it was necessary to include an additional special oscillator centered at 1.4eV in order to model the unusual spectral response. This is quite unlike bulk gold, which can be mideled using a standard two-oscillator LD model.
Armstrong, N.G., Hoft, R.C., McDonagh, A.M., Cortie, M.B. & Ford, M. 2007, 'Exploring The Performance Of Molecular Rectifiers Limitations And Factors Affecting Molecular Rectification', Nano Letters, vol. 7, no. 10, pp. 3018-3022.
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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 limitati
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.
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Cortie, M.B. & Ford, M. 2007, 'A Plasmon-induced Current Loop In Gold Semi-shells', Nanotechnology, vol. 18, no. 23, pp. 1-6.
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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 e
Chowdhury, H.A. & Cortie, M.B. 2007, 'Thermal Stresses And Cracking In Absorptive Solar Glazing', Construction And Building Materials, vol. 21, no. 2, pp. 464-468.
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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 glazin
Xu, X. & Cortie, M.B. 2007, 'Precious metal core-shell spindles', Journal Of Physical Chemistry C, vol. 111, no. 49, pp. 18135-18142.
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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
Hoft, R.C., Ford, M. & Cortie, M.B. 2007, 'Electron tunneling in the presence of adsorbed molecules', Surface Science, vol. 601, no. 24, pp. 5715-5720.
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We perform ab initio density functional theory calculations of the tunneling current through an electrodemoleculeelectrode system with four different small organic molecules, benzenedithiol (BDT), benzenedimethanethiol (XYL), diethynylbenzene (DEB) and dodecanethiol (C12), sandwiched between two gold (111) 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 selfassembled 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.
Hoft, R.C., Ford, M. & 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.
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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.
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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., Soule, D.B.B.J. & 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.
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The tetrahedral 20-atom gold cluster is surprisingly stable, and is believed to be the ground state structure as evidenced both by ab initio calculations [1-3] and experiment [3]. This sturcture is very orderd, has no internal atoms and is essentially a small section of fcc-bulk gold cut along four intersecting close-packed (111) planes. We have previously shown that it is at least 0.5eV more stable than the tetrahedral structure represents a deep minimum in the potential energy surface that is isolated from its isomers, gives rise to a well-defined melting point with a melting temperature comparable to bulk gold [4].
Bhargava, A. & Cortie, M.B. 2007, 'Prospects for light-activated nano-devices based on shape-memory polymers', Journal of Nanophotonics, vol. 1, pp. 1-13.
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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.
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.
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Mortari, A., Maaroof, A.I., Martin, D.K. & 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.
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he use of mesoporous gold as electrode material for measurement of electrochemical capacitance is investigated. The electrodes possess a pore size in the range of 10-30nm and are prepared by de-alloying films of AuAl"x, where x>=2....
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, pp. 1-5.
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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 (EELS0, combined with recent developments in spectrum imaging and data processing, has been used obserne 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 presneted maps is one order of magnitude better than that achievable with scanning near-field optical microscopy (SNOM)-based techniques.
Zareie, H.M., 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.
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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 i the resulting chains, which extend for over a micrometer in length. The assembly and morphology of the nanorods structures were characterised by surface plasmon resonance spectroscopy as well as by scanning electron microscopy and scanning probe microscopy. Strcutures of this type could concievably serve as plasmonic waveguides in future nanodevices.
Harris, N., Ford, M., Cortie, M.B. & McDonagh, A.M. 2007, 'Laser-induced Assembly Of Gold Nanoparticles Into Colloidal Crystals', Nanotechnology, vol. 18, no. 36, pp. 1-4.
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Micron-sized colloidal crystals comprised of gold nanospheres have been synthesized directly from a gold nanoparticlepermethyl methacrylate colloid by application of a 514 nm laser at 500 mW. An array of colloidal crystals can be created by translation o
Hoft, R.C., Armstrong, N.G., Ford, M. & 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, pp. 1-14.
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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 t
Hoft, R.C., Ford, M., 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.
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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 i
Blaber, M.G., Arnold, M.D., Harris, N., Ford, M. & 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.
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The optical absorption for nanospheres made from Na, K, At, Ag and An 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 nanospher
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.
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Suspensions of mesoscale gold half-shells of controlled size were produced by microsphere-templated vapour deposition and their optical proper-ties were studied. The transmission spectra of the particles exhibited an extinction peak that could be tuned f
Cortie, M.B., Dowd, A., Harris, N. & Ford, M.J. 2007, 'Core-shell nanoparticles with self-regulating plasmonic functionality', PHYSICAL REVIEW B, vol. 75, no. 11.
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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.
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 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.
Zareie, H.M., McDonagh, A.M., Edgar, J.A., Ford, M., Cortie, M.B. & Phillips, M. 2006, 'Controlled assembly of 1,4-phenylenedimethanethiol molecular nanostructures', Chemistry Of Materials, vol. 18, no. 9, pp. 2376-2380.
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We present here the first high-resolution scanning tunneling microscope images showing that 1,4phenylenedimethanethiol forms mono- and multilayers on gold(1 11) substrates under particular solution-deposition conditions. The high-resolution images show t
Harris, N., Ford, M. & 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.
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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 ill
Cortie, M.B., Xu, X. & Ford, M. 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.
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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 her
Xu, X., Gibbons, T. & Cortie, M.B. 2006, 'Spectrally-selective gold nanorod coatings for window glass', Gold Bulletin, vol. 39, no. 4, pp. 156-165.
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The unique optical properties of gold nanorods, which exhibit tuneable absorption asa 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 of our experimental coatings was close to unit, indicating that theyr 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 of up to 1.4. The maximum avlue possible for perfectly spectrally-selective coating in sunlight is 2.08. Unfortunately, the practical realisation 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.
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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.
Soule, D.B.B.J., Ford, M. & 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.
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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 transformation between structural isomers that extends over a considerable temperature range. Solid-like behaviour is observed in the atomic trajectories of ther simulation at temperatures up to, or above, the bulk melting point. The 20-atom tetrahedral structure is the one exception, showing a sharo transition between solid-like and liquid-like phases at about 1200 K. The starting sturcture used in the simulation is shown to have a considerable effect upon the subsequent thermal behaviour.
Pissuwan, D., Valenzuela, S. & Cortie, M.B. 2006, 'Therapeutic possibilities of plasmonically heated gold nanoparticles', Trends In Biotechnology, vol. 24, no. 2, pp. 62-67.
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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 effec
Cortie, M.B., Maaroof, A.I., Smith, G. & Ngoepe, P. 2006, 'Nanoscale coatings of AuAlx and PtAlx and their mesoporous elemental derivatives', Current Applied Physics, vol. 6, no. 3, pp. 440-443.
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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 init
Liu, J., Cankurtaran, B.O., Wieczorek, L., Ford, M. & Cortie, M.B. 2006, 'Anisotropic optical properties of semitransparent coatings of gold nanocaps', Advanced Functional Materials, vol. 16, no. 11, pp. 1457-1461.
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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 o
Hoft, R.C., Ford, M. & 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.
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We use ab initio calculations of the tunneling current through a 1,4-phenylenedimethanethiol (XYL) molecule adsorbed between Au(111) electrodes to show that there are circumstances under which tunneling currents can be increased by bond stretching. The e
Cortie, M.B., McBean, K.E. & Elcombe, M. 2006, 'Fracture Mechanics Of Mollusc Shells', Physica B: Condensed Matter, vol. 385, no. 1, pp. 545-547.
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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
Cortie, M.B. 2006, 'Antipodean Gold', Gold Bulletin, vol. 39, no. 3, pp. 92-92.
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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.
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It is shown here that deviations from a prolate ellipsoidal shape have a significant effect on the optical properties of gold nanorods. Transitions from rods to 'dumbbell'- or 'phi'-shaped particles lead to a shift in the longitudinal plasmon peak in the
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.
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Cortie, M.B., Zareie, H.M., Ekanayake, S.R. & Ford, M. 2005, 'Conduction, storage, and leakage in particle-on-SAM nanocapacitors', IEEE Transactions On Nanotechnology, vol. 4, no. 4, pp. 406-414.
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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 b
Maaroof, A.I., Cortie, M.B. & Smith, G. 2005, 'Optical properties of mesoporous gold films', Journal Of Optics A-Pure And Applied Optics, vol. 7, no. 7, pp. 303-309.
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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
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.
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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
Chowdhury, H.A., 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.
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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 ass
Liu, J., McCredie, G., Ford, M., Wieczorek, L. & Cortie, M.B. 2005, 'Investigation of the optical properties of hollow aluminium 'nano-caps'', Nanotechnology, vol. 16, no. 12, pp. 3023-3028.
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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 applciations requiring absorption in the near infrared.
Cortie, M.B., Maaroof, A.I. & Smith, G. 2005, 'Electrochemical capacitance of mesoporous gold', Gold Bulletin, vol. 38, no. 1, pp. 14-22.
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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.
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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.D., Ford, M. & Cortie, M.B. 2005, 'The effect of surface symmetry on the adsorption energetics of SCH3 on gold surfaces studied using Density Functional Theory', Surface Science, vol. 580, no. 1-3, pp. 19-29.
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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
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. 1276-1282.
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Cap-shaped metal nanoparticles (see Figure) have optical spectra with significant absorption in the infrared. Such shapes, produced by physical vapor deposition onto a polymer-particle template, can be readily separated from one another provided that dep
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 900&deg;C. 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. &copy; Institute of Materials Engineering Australasia Ltd.
Xu, X.D., 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.
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Liu, J.Q., 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-+.
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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.B. 2004, 'Rectifying Nanotechnology Confusion and Redirecting Focus', The Physicist, vol. 41, no. 3, pp. 84-85.
Ekanayake, S.R., Ford, M. & Cortie, M.B. 2004, 'Metal-insulator-metal (MIM) nanocapacitors and effects of material properties on their operation', Materials Forum, vol. 27, pp. 15-20.
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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, pp. 120-127.
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Xu, X., Stevens, M.G. & Cortie, M.B. 2004, 'In situ precipitation of gold nanoparticles onto glass for potential architectural applications', Chemistry of Materials, vol. 16, no. 1, pp. 2259-2266.
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The optical properties of in situ depositied gold nanoparticle coatings are investigated for potential application in architectural glass. It is found that the optical properties of the coating canbe 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 700nm 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 520nm 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 smalle, 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 wellpknown Genzel-Martin analytical model are observed. The reasons for deviation of themodel are discussed. FInally, it is shown how coatings that are blue or blue-gray in transmission canve obtained by exploiting this deviation. Such coatings may be more suitable for architectural application than the conventional pink-hued coatings obtained with aolloidal gold nanoparticles.
Cortie, M.B. 2004, 'The Weird World of Nanoscale Gold', Gold Bulletin, vol. 37, no. 1 & 2, pp. 12-19.
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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. 2004, 'Design of nanocapacitors and associated materials challenges', Current Applied Physics, vol. 4, no. 2-4, pp. 250-254.
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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.
Soule, D.B.B.J., Ford, M. & Cortie, M.B. 2004, 'Low energy structured of gold nanoclusters in the size range 3-38 atoms', Journal of Molecular Structure, vol. 686, no. 1-3, pp. 193-205.
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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=35) 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.
Cortie, M.B. 2004, 'The weird world of nanoscale gold', GOLD BULLETIN, vol. 37, no. 1-2, pp. 12-19.
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.
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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.
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.
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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 Pt3Al 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 1000&deg;C, 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.
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Cortie, M.B. & Van Der Lingen, E. 2002, 'Catalytic gold nano-particles', Materials forum, vol. 26, pp. 1-14.
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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.
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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 Image 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 Image stacking sequence is deduced, which for reasons of the L21 ordering inherited from the parent phase, must be doubled to produce a notional Image 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.
Levey, F.C., Cortie, M.B. & Cornish, L.A. 2002, 'Hardness and colour trends across the 76 weight % Au section of the Au-Cu-Al system', Scripta Materialia, vol. 47, pp. 95-100.
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Colour and hardness were measured on a series of alloys along the 76 wt.% Au line of the AuCuAl 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.
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.
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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.
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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 1000&deg;C. The TiPt transformation temperature can range from 1000 to 1080&deg;C. 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 1000&deg;C to about 600&deg;C.
Levey, F.C., Cortie, M.B. & Cornish, L.A. 2001, 'A 500°C isothermal section for the Al-Au-Cu system', Metallurgical and Materials Transactions A, vol. 33, no. 4, pp. 987-994.
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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 &deg;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 &deg;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 &deg;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-x Cu1-x (0?x?1) was confirmed, and its phase field at 500 &deg;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. 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.
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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.
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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.
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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.
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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.
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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.
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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.
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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. & Boniface, T.D. 1996, 'Synthesis and processing of Ruthenium Aluminide', Journal of Materials Synthesis and Processing, vol. 4, no. 6, pp. 413-428.
Ruthenium aluminide (RuAl) is significantly tougher than most other intermetallic compounds and, also, possesses good oxidation resistance, excellent resistance to corrosion, and a high strength at elevated temperatures. Unfortunately, the application of intermetallic compounds in structural applications has been generally hampered by difficulties encountered in manufacturing. Methods for producing engineering components out of RuAl are described, and it is shown that these are compatible with processing technologies already available and in use industrially. In particular, production of near-net-shape artifacts by a modified reactive hot isostatic pressing (RHIP) technique is feasible with equipment currently used to manufacture tungsten carbide-cobalt composites. Machining by spark erosion or grinding may be successfully used to finish components. The material can also be machined conventionally, with some limitations. &copy; 1996 Plenum Publishing Corporation.
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.
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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.
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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.
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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.
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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.
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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., Paton, R. & Enright, D. 1994, 'Environmentally assisted cracking of martensitic stainless steels in goldmining environments', British Corrosion Journal, vol. 29, no. 4, pp. 271-274.
The environmentally assisted cracking of martensitic stainless steels in gold mine environments has been investigated. The experimental work was focused on the possibility of cracking in type 431 stainless steel and in an experimental material similar to type 420. Four types of mine water were studied, ranging from neutral to acidic, with various chloride contents. Stagnant, anaerobic conditions in two of the waters were simulated in the laboratory by the addition of 25 ppm sulphide ions. Specimen geometries examined included C ring specimens, compact tension specimens, and tensile specimens (type 431); and a notched tension specimen (experimental alloy). C ring specimens of type 431 were inserted into flow loops at two gold mines. Cracking under aerated or flowing conditions at the mines was slow or absent. However, all the alloys examined were susceptible to cracking under the stagnant conditions simulated in the laboratory.
Wolff, I.M. & Cortie, M.B. 1994, 'The development of Spangold', Gold Bulletin, vol. 27, no. 2, pp. 44-54.
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The underlying mechanisms of martensitic phase transformations in gold alloys have attracted a great deal of study. Whereas their technological exploitation in shape-memory devices has found only limited application, the Spangold concept introduces a novel application - that of using the transformation to decorate gold ornaments. This article examines the attributes of suitable alloys and the development of a prototype alloy for use in jewellery. &copy; 1994 World Gold Council.
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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
Cortie, M.B. 1991, 'Occurrence, recognition, and prevention of hot cracking', Forensic engineering, vol. 3, no. 1, pp. 23-35.
Hot cracking of metallic materials can occur under a wide variety of conditions, including casting, forging, rolling, and service. A variety of mechanisms are responsible for hot cracking including grain-boundary weakness due to low melting point compounds, grain boundary embrittlement due to precipitate formation, the growth of creep and fatigue cracks, and intergranular oxidation. Case studies are presented in which hot cracking has occurred in an industrial component or product. The factors influencing hot cracking in each of the case studies are discussed and evaluated.
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.
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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.
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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.
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Tullmin, M.A.A., Witcomb, M.J., Cortie, M.B. & Robinson, F.P.A. 1990, 'Intergranular corrosion in low interstitial 40% Cr ferritic stainless steels.', BRITISH CORROSION J., vol. 25, no. 3, pp. 191-196.
The intergranular corrosion resistance of a range of experimental ferritic stainless steels containing 40%Cr and low levels of the interstitial elements carbon and nitrogen was assessed by means of total immersion and electrochemical potentiokinetic reactivation testing. Despite the low interstitial element levels, these alloys can be susceptible to severe intergranular corrosion in the solution annealed condition. Sensitisation was mainly related to grain boundary precipitation of chromium rich M "SUB 23" *C,N "SUB 6" with associated chromium depleted zones. This undesirable precipitation is the result of the low carbon and nitrogen solubility at a level of 40%Cr. Total immunity to intergrannular attack in solution annealed Fe-40Cr alloys was only observed at stabiliser (C+N) ratios over 20. A 4 hour isothermal annealing heat treatment at 621 degreesC restores the intergranular corrosion resistance, similarly to the behaviour of lower chromium alloys. (A)
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.
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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.
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Cortie, M.B. 1989, 'Models For Mollusk Shell Shape', South African Journal Of Science, vol. 85, no. 7, pp. 454-460.
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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.
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Cortie, M.B. 1989, 'Progress And Trends In The Substitution For Chromium In Steels', Materials And Society, vol. 13, no. 1, pp. 13-31.
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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.
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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 &deg; C, and Fe-1%Cr-0.5%Mo and Fe-0.5%Cr-0.5%Mo-0.25%V at 550 &deg; 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.
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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.
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Cortie, M. & Wedepohl, P. 1988, 'INTERMETALLIC STRUCTURAL MATERIALS-DREAM OR REALITY.', South African mechanical engineer, vol. 38, no. 8, pp. 474-479.
The paper discusses the use of intermetallic compounds as engineering materials. Intermetallics are compared to ceramics and metal alloys and four of the most widely studied intermetallic phases are discussed: the titanium aluminides Ti//3Al and TiAl, the zirconium aluminide Zr//3Al, and the nickel aluminide Ni//3Al. Potential applications for these materials are considered, as well a the processing routes by which they can be produced. A novel processing route is described as well as its application to titanium aluminides. 20 Refs.
Cortie, M.B. & Garrett, G.G. 1988, 'Thermal activation energy for fatigue of Fe-1 Pct Cr-0.5 Pct Mo', Metallurgical transactions. A, Physical metallurgy and materials science, vol. 19 A, no. 12, pp. 2979-2987.
The temperature dependence of fatigue crack propagation is considered in an Fe-1 pct Cr-0.5 pct Mo alloy steel. This material was tested at temperatures between 425 and 550&deg;C, a frequency of 1 Hz, and an R-ratio of 0.1. It is shown that the effect of temperature can be explained in terms of a thermal activation energy for fatigue. The magnitude of this activation energy is a function of K and varies from more than 150 kJ/mole at 15 MPam to 30 kJ/mole above 30 MPam. The magnitude of these activation energies supports the idea that oxidation, and not creep, is the rate-controlling time-dependent process for the test conditions studied.