Dr Xiaoxue Xu is a Vice Chancellor’s Postdoctoral Research Fellow at the University of Technology Sydney working with Professor Dayong Jin in the Institute for Biomedical Materials & Devices. Her research focuses on inorganic luminescent nanocrystals for biomedical applications. Prior to joining UTS, she completed a Macquarie University Research Fellowship having completed her PhD and a postdoctoral position at the University of Western Australia.
Can supervise: YES
1, Luminescent nanocrystals for bioimaging and biolabeling applications;
2, Metal and metal oxides nanostructures for gas sensing;
3, Bulk metal materials for biomedical devices development.
1, Intro to Materials Science
2, Materials Science and Chemistry
3, Medical Imaging Physics
Xu, X, Zhou, Z, Liu, Y, Wen, S, Guo, Z, Gao, L & Wang, F 2019, 'Optimising passivation shell thickness of single upconversion nanoparticles using a time-resolved spectrometer', APL PHOTONICS, vol. 4, no. 2.View/Download from: Publisher's site
Clarke, C, Liu, D, Wang, F, Liu, Y, Chen, C, Ton-That, C, Xu, X & Jin, D 2018, 'Large-scale dewetting assembly of gold nanoparticles for plasmonic enhanced upconversion nanoparticles.', Nanoscale, vol. 10, no. 14, pp. 6270-6276.View/Download from: UTS OPUS or Publisher's site
Plasmonic nanostructures have been broadly investigated for enhancing many photophysical properties of luminescent nanomaterials. Precisely controlling the distance between the plasmonic nanostructure and the luminescent material is challenging particularly for the large-scale production of individual nanoparticles. Here we report an easy and reliable method for the large-scale dewetting of plasmonic gold nanoparticles onto core-shell (CS) upconversion nanoparticles (UCNPs). A commensurate NaYF4 shell with a thickness between 5 nm and 15 nm is used as a tunable spacer to control the distance between the UCNP and the plasmonic gold nanoparticles. The upconversion emission intensity of single gold decorated core-inert shell (Au-CS) UCNPs is quantitatively characterized using a scanning confocal microscope. The results demonstrate the highest feasible enhancement of upconversion emission and a record reduction in lifetime for UCNPs fabricated in this manner. The Au-CS UCNPs are further investigated by simulation and synchrotron near edge X-ray absorption fine structure (NEXAFS) analysis.
Sun, Y, Zhang, W, Wang, B, Xu, X, Chou, J, Shimoni, O, Ung, AT & Jin, D 2018, 'A supramolecular self-assembly strategy for upconversion nanoparticle bioconjugation.', Chemical communications (Cambridge, England), vol. 54, no. 31, pp. 3851-3854.View/Download from: UTS OPUS or Publisher's site
An efficient surface modification for upconversion nanoparticles (UCNPs) is reported via supramolecular host-guest self-assembly. Cucurbituril (CB) can provide a hydrophilic surface and cavities for most biomolecules. High biological efficiency, activity and versatility of the approach enable UCNPs to be significantly applied in bio-imaging, early disease detection, and bio-sensing.
Ma, C, Xu, X, Wang, F, Zhou, Z, Liu, D, Zhao, J, Guan, M, Lang, CI & Jin, D 2017, 'Optimal Sensitizer Concentration in Single Upconversion Nanocrystals.', Nano Letters, vol. 17, no. 5, pp. 2858-2864.View/Download from: UTS OPUS or Publisher's site
Each single upconversion nanocrystal (UCNC) usually contains thousands of photon sensitizers and hundreds of photon activators to up-convert near-infrared photons into visible and ultraviolet emissions. Though in principle further increasing the sensitizers' concentration will enhance the absorption efficiency to produce brighter nanocrystals, typically 20% of Yb3+ ions has been used to avoid the so-called "concentration quenching" effect. Here we report that the concentration quenching effect does not limit the sensitizer concentration and NaYbF4 is the most bright host matrix. Surface quenching and the large size of NaYbF4 nanocrystals are the only factors limiting this optimal concentration. Therefore, we further designed sandwich nanostructures of NaYbF4 between a small template core to allow an epitaxial growth of the size-tunable NaYbF4 shell enclosed by an inert shell to minimize surface quenching. As a result, the suspension containing 25.2 nm sandwich structure UCNCs is 1.85 times brighter than the homogeneously doped ones, and the brightness of each single 25.2 nm heterogeneous UCNC is enhanced by nearly 3 times compared to the NaYF4: 20% Yb3+, 4% Tm3+ UCNCs in similar sizes. Particularly, the blue emission intensities of the UCNCs with the sandwich structure in the size of 13.6 and 25.2 nm are 1.36 times and 3.78 times higher than that of the monolithic UCNCs in the similar sizes. Maximizing the sensitizer concentration will accelerate the development of brighter and smaller UCNCs as more efficient biomolecule probes or photon energy converters.
Xu, X, Clarke, C, Ma, C, Casillas, G, Das, M, Guan, M, Liu, D, Wang, L, Tadich, A, Du, Y, Ton-That, C & Jin, D 2017, 'Depth-profiling of Yb3+ sensitizer ions in NaYF4 upconversion nanoparticles.', Nanoscale, vol. 9, no. 23, pp. 7719-7726.View/Download from: UTS OPUS or Publisher's site
Enhancing the efficiency of upconversion nanoparticles (UCNPs) and therefore their brightness is the critical goal for this emerging material to meet growing demands in many potential applications including sensing, imaging, solar energy conversion and photonics. The distribution of the photon sensitizer and activator ions that form a network of energy transfer systems within each single UCNP is vital for understanding and optimizing their optical properties. Here we employ synchrotron-based X-ray Photoelectron Spectroscopy (XPS) to characterize the depth distribution of Yb3+ sensitizer ions in host NaYF4 nanoparticles and systematically correlate the structure with the optical properties for a range of UCNPs with different sizes and doping concentrations. We find a radial gradient distribution of Yb3+ from the core to the surface of the NaYF4 nanoparticles, regardless of their size or the sensitizer's concentration. Energy dispersive X-ray Spectroscopy (EDX) was also used to further confirm the distribution of the sensitizer ions in the host matrix. These results have profound implications for the upconversion optical property variations.
Wang, L, Ren, L, Mitchell, D, Casillas-Garcia, G, Ren, W, Ma, C, Xu, XX, Wen, S, Wang, F, Zhou, J, Xu, X, Hao, W, Dou, SX & Du, Y 2017, 'Enhanced energy transfer in heterogeneous nanocrystals for near infrared upconversion photocurrent generation.', Nanoscale, vol. 9, no. 47, pp. 18661-18667.View/Download from: UTS OPUS or Publisher's site
The key to produce inorganic heterogeneous nanostructures, and to integrate multiple functionalities, is to enhance or at least retain the functionalities of different components of materials. However, this ideal scenario is often deteriorated at the interface of the heterogeneous nanostructures due to lattice mismatches, resulting in downgraded performance in most hybrid nanomaterials. Here, we report that there is a narrow window in controlling temperature in a Lewis acid-base reaction process to facilitate epitaxial alignment during the synthesis of hybrid nanomaterials. We demonstrate a perfectly fused NaYF4:Yb,Tm@ZnO heterogeneous nanostructure, in which the semiconductor ZnO shell can be epitaxially grown onto lanthanide-doped upconversion nanoparticles. By achieving a matched crystal lattice, the interface defects and crystalline grain boundaries are minimized to enable more efficient energy transfer from the upconversion nanoparticles to the semiconductor, resulting in both enhanced upconversion luminescence intensity and superior photoelectrochemical properties. This strategy provides an outstanding approach to endow lanthanide-doped upconversion nanoparticles with versatile properties.
Liu, D., Xu, X., Wang, F., Zhou, J., Mi, C., Zhang, L., Lu, Y., Ma, C., Goldys, E., Lin, J. & Jin, D. 2016, 'Emission stability and reversibility of upconversion nanocrystals', Journal of Materials Chemistry C, vol. 4, pp. 9227-9234.View/Download from: Publisher's site
Ma, C, Xu, X, Wang, F, Zhou, Z, Wen, S, Liu, D, Fang, J, Lang, CI & Jin, D 2016, 'Probing the Interior Crystal Quality in the Development of More Efficient and Smaller Upconversion Nanoparticles', Journal of Physical Chemistry Letters, vol. 7, pp. 3252-3258.View/Download from: UTS OPUS or Publisher's site
Optical biomedical imaging using luminescent nanoparticles as contrast agents prefers small size, as they can be used at high dosages and efficiently cleared from body. Reducing nanoparticle size is critical for the stability and specificity for the fluorescence nanoparticles probes for in vitro diagnostics and subcellular imaging. The development of smaller and brighter upconversion nanoparticles (UCNPs) is accordingly a goal for complex imaging in bioenvironments. At present, however, small UCNPs are reported to exhibit less emission intensity due to increased surface deactivation and decreased number of dopants. Here we show that smaller and more efficient UCNPs can be made by improving the interior crystal quality via controlling heating rate during synthesis. We further developed a unique quantitative method for optical characterizations on the single UCNPs with varied sizes and the corresponding shell passivated UCNPs, confirming that the internal crystal quality dominates the relative emission efficiency of the UCNPs.
Liu, D, Xu, X, Wang, F, Zhou, J, Mi, C, Zhang, L, Lu, Y, Ma, C, Goldys, E, Lin, J & Jin, D 2016, 'Emission stability and reversibility of upconversion nanocrystals', Journal of Materials Chemistry C, vol. 4, no. 39, pp. 9227-9234.View/Download from: UTS OPUS or Publisher's site
Rare-earth doped upconversion nanocrystals have emerged as a novel class of luminescent probes for biomedical applications. The knowledge about their optical stability in aqueous solution under different pH and temperature conditions has not been comprehensively explored. Here we conduct a systematic investigation and report the emission stability and reversibility of typical NaYF4:Yb3+,Er3+ nanocrystals and their core–shell nanostructures in aqueous solution at different temperatures and with different pH values. These nanocrystals show reversible luminescence response to temperature changes, while low pH permanently quenches their luminescence. With the addition of inert shells, with thicknesses ranging from 1.5 nm to 8 nm, the emission stability and reversibility change significantly. Thicker inert shells not only lead to a significant enhancement in the emission intensity but also stabilize its optical responses which become less affected by temperature variations and pH conditions. This study suggests that upconversion nanocrystal-based sensitive temperature and pH sensors do not generally benefit from the core–shell structure usually recommended for enhanced upconversion luminescence.
Liu, D, Xu, X, Du, Y, Qin, X, Zhang, Y, Ma, C, Wen, S, Ren, W, Goldys, EM, Piper, JA, Dou, S, Liu, X & Jin, D 2016, 'Three-dimensional controlled growth of monodisperse sub-50 nm heterogeneous nanocrystals', Nature Communications, vol. 7, pp. 1-8.View/Download from: UTS OPUS or Publisher's site
The ultimate frontier in nanomaterials engineering is to realize their composition control with atomic scale precision to enable fabrication of nanoparticles with desirable size, shape and surface properties. Such control becomes even more useful when growing hybrid nanocrystals designed to integrate multiple functionalities. Here we report achieving such degree of control in a family of rare-earth-doped nanomaterials. We experimentally verify the co-existence and different roles of oleate anions (OA) and molecules (OAH) in the crystal formation. We identify that the control over the ratio of OA to OAH can be used to directionally inhibit, promote or etch the crystallographic facets of the nanoparticles. This control enables selective grafting of shells with complex morphologies grown over nanocrystal cores, thus allowing the fabrication of a diverse library of monodisperse sub-50nm nanoparticles. With such programmable additive and subtractive engineering a variety of three-dimensional shapes can be implemented using a bottom–up scalable approach.
Yan, L, Zhao, B, Liu, X, Li, X, Zeng, C, Shi, H, Xu, X, Lin, T, Dai, L & Liu, Y 2016, 'Aligned Nanofibers from Polypyrrole/Graphene as Electrodes for Regeneration of Optic Nerve via Electrical Stimulation', ACS Applied Materials and Interfaces, vol. 8, pp. 6834-6840.View/Download from: UTS OPUS or Publisher's site
Wang, R, Xu, X, Zhang, Y, Chang, Z, Sun, Z & Dong, W-F 2015, 'Functionalized ZnO@TiO2 nanorod array film loaded with ZnIn0.25Cu0.02S1.395 solid-solution: synthesis, characterization and enhanced visible light driven water splitting', Nanoscale, vol. 7, pp. 11082-11092.View/Download from: Publisher's site
Sercombe, TB, Xu, X, Challis, VJ, Green, R, Yue, S, Zhang, Z & Lee, PD 2015, 'Failure modes in high strength and stiffness to weight scaffolds produced by Selective Laser Melting', Materials and Design, vol. 67, pp. 501-508.View/Download from: Publisher's site
Challis, VJ, Xu, X, Zhang, LC, Roberts, AP, Grotowski, JF & Sercombe, TB 2014, 'High specific strength and stiffness structures produced using selective laser melting', Materials and Design, vol. 63, pp. 783-788.View/Download from: Publisher's site
Li, J, Mei, H, Zheng, W, Pan, P, Sun, XJ, Li, F, Guo, F, Zhou, HM, Ma, JY, Xu, XX & Zheng, YF 2014, 'A novel hydrogen peroxide biosensor based on hemoglobin-collagen-CNTs composite nanofibers', COLLOIDS AND SURFACES B-BIOINTERFACES, vol. 118, pp. 77-82.View/Download from: UTS OPUS or Publisher's site
Xu, XX, Ding, MH, Zhang, JX, Zheng, W, Li, L & Zheng, YF 2013, 'A novel copper/polydimethiylsiloxane nanocomposite for copper-containing intrauterine contraceptive devices', Journal of Biomedical Materials Research Part B: Applied Biomaterials, vol. 101, pp. 1428-1436.View/Download from: UTS OPUS or Publisher's site
Li, A, Sun, ZZ, Zhou, M, Xu, XX, Ma, JY, Zheng, W, Zhou, HM, Li, L & Zheng, YF 2013, 'Electrospun Chitosan-graft-PLGA nanofibres with significantly enhanced hydrophilicity and improved mechanical property', Colloids and Surfaces B: Biointerfaces, vol. 102, pp. 674-681.View/Download from: UTS OPUS or Publisher's site
Xu, X, Yang, H & Liu, Y 2012, 'Self-assembled structures of CuO primary crystals synthesized from Cu(CH 3COO) 2-NaOH aqueous systems', CrystEngComm, vol. 14, pp. 5289-5298.View/Download from: UTS OPUS or Publisher's site
Meng, ZX, Zeng, QT, Sun, ZZ, Xu, XX, Wang, YS, Zheng, W & Zheng, YF 2012, 'Immobilizing natural macromolecule on PLGA electrospun nanofiber with surface entrapment and entrapment-graft techniques', Colloids and Surfaces B: Biointerfaces, vol. 94, pp. 44-50.View/Download from: UTS OPUS or Publisher's site
Xu, XX, Nie, FL, Wang, YB, Zhang, JX, Zheng, W, Li, L & Zheng, YF 2012, 'Effective inhibition of the early copper ion burst release with ultra-fine grained copper and single crystal copper for intrauterine device application', Acta Biomaterialia, vol. 8, pp. 886-896.View/Download from: UTS OPUS or Publisher's site
Guo, F, Xu, XX, Sun, ZZ, Zhang, JX, Meng, ZX, Zheng, W, Zhou, HM, Wang, BL & Zheng, YF 2011, 'A novel amperometric hydrogen peroxide biosensor based on electrospun Hb-collagen composite', Colloids and Surfaces B: Biointerfaces, vol. 86, pp. 140-145.View/Download from: UTS OPUS or Publisher's site
Meng, ZX, Xu, XX, Zheng, W, Zhou, HM, Li, L, Zheng, YF & Lou, X 2011, 'Preparation and characterization of electrospun PLGA/gelatin nanofibers as a potential drug delivery system', Colloids and Surfaces B: Biointerfaces, vol. 84, pp. 97-102.View/Download from: UTS OPUS or Publisher's site
Xu, XX, Zhang, JX, Guo, F, Zheng, W, Zhou, HM, Wang, BL, Zheng, YF, Wang, YB, Cheng, Y, Lou, X & Jang, BZ 2011, 'A novel amperometric hydrogen peroxide biosensor based on immobilized Hb in Pluronic P123-nanographene platelets composite', Colloids and Surfaces B: Biointerfaces, vol. 84, pp. 427-432.View/Download from: UTS OPUS or Publisher's site
Xu, X, Yang, H, Liu, Y, Zheng, Y, Li, L, Ji, Y & Han, X 2011, 'Formation mechanism of novel two-dimensional single crystalline dendritic copper plates in an aqueous environment', Acta Materialia, vol. 59, pp. 7177-7188.View/Download from: UTS OPUS or Publisher's site
Zheng, W, Zhao, HY, Zhou, HM, Xu, XX, Ding, MH & Zheng, YF 2010, 'Electrochemistry of bilirubin oxidase at carbon nanotubes', Journal of Solid State Electrochemistry, vol. 14, pp. 249-254.View/Download from: Publisher's site
Zhao, HY, Xu, XX, Zhang, JX, Zheng, W & Zheng, YF 2010, 'Carbon nanotube-hydroxyapatite-hemoglobin nanocomposites with high bioelectrocatalytic activity', Bioelectrochemistry, vol. 78, pp. 124-129.View/Download from: Publisher's site
Zheng, W, Zhao, HY, Zhang, JX, Zhou, HM, Xu, XX, Zheng, YF, Wang, YB, Cheng, Y & Jang, BZ 2010, 'A glucose/O2 biofuel cell base on nanographene platelet-modified electrodes', Electrochemistry Communications, vol. 12, pp. 869-871.View/Download from: Publisher's site
Guo, X, Lu, X, Fang, X, Mao, Y, Wang, Z, Chen, L, Xu, X, Yang, H & Liu, Y 2010, 'Lithium storage in hollow spherical ZnFe2O4 as anode materials for lithium ion batteries', Electrochemistry Communications, vol. 12, pp. 847-850.View/Download from: Publisher's site
Xu, XX, Nie, FL, Zhang, JX, Zheng, W, Zheng, YF, Hu, C & Yang, G 2010, 'Corrosion and ion release behavior of ultra-fine grained bulk pure copper fabricated by ECAP in Hanks solution as potential biomaterial for contraception', Materials Letters, vol. 64, pp. 524-527.View/Download from: Publisher's site
Sabir, MI, Xu, X & Li, L 2009, 'A review on biodegradable polymeric materials for bone tissue engineering applications', Journal of Materials Science, vol. 44, pp. 5713-5724.View/Download from: Publisher's site
Zhao, HY, Zheng, W, Meng, ZX, Zhou, HM, Xu, XX, Li, Z & Zheng, YF 2009, 'Bioelectrochemistry of hemoglobin immobilized on a sodium alginate-multiwall carbon nanotubes composite film', Biosensors and Bioelectronics, vol. 24, pp. 2352-2357.View/Download from: Publisher's site
Yang, Z, Ding, G, Cai, H, Xu, X, Wang, H & Zhao, X 2009, 'Analysis and elimination of the 'skip contact' phenomenon in an inertial micro-switch for prolonging its contact time', JOURNAL OF MICROMECHANICS AND MICROENGINEERING, vol. 19, no. 4.View/Download from: Publisher's site
Xu, X-X, Li, L & Zheng, Y-F 2008, 'Preparation and surface modification of magnetic nanoparticles for biomedical applications', Cailiao Kexue yu Gongyi/Material Science and Technology, vol. 16, pp. 562-568.
Li, Q-F, Li, L, Liu, E-B, Wang, J, Xu, X-X & Wang, Y-B 2004, 'Study of reverse temper embrittlement NGS mechanism in steel 12CrlMoV', Harbin Gongcheng Daxue Xuebao/Journal of Harbin Engineering University, vol. 25, pp. 451-456.
Zhao, M, Yang, Z, Sun, B, Dai, B, Liu, H, Yao, J, Xu, X, Ding, G & Zhao, X 2018, 'A micro electromagnetically-driven scanner by 2-DOF second-order resonance to extend scanning scale for ultra-thin single-fiber endoscope application', Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS), pp. 575-578.View/Download from: Publisher's site
© 2018 IEEE. This paper presents an electromagnetically-driven single-fiber scanner utilizing 2 degree-of-freedom (DOF) second-order resonance to realize a larger field scanning scale in narrow space of the human body. We design a reasonable 2-DOF system structure including fiber, magnet and weight, which can conveniently execute high-order resonance modal to extend the scanning angle in the limited dimensional tube of the ultra-thin endoscope. A low-cost flexible microcoil embedded in polyimide film is also fabricated to drive the fiber-magnet-weight 2-DOF system to vibrate. The magnetic field distributions of the microcoil with different structural parameters are simulated. The test result shows that the scanner with the second-order resonance model successfully realizes 9.47° scanning scale, which is much larger than that (2.98°) obtained at the traditional first-order resonance model. Finally, the scanning locus of fiber tip in the scanner probe has been measured in xoy-plane by standard position sensitive detector (PSD).
Wen, S, Li, D, Liu, D, Xu, X, Du, Y, Mitchell, DRG, Shi, B, Shi, X & Jin, D 2016, 'Seed mediated one-pot growth of versatile heterogeneous upconversion nanocrystals for multimodal bioimaging', Proceedings of SPIE - The International Society for Optical Engineering, International Society for Optical Engineering, SPIE Digital Library, Adelaide, South Australia, Australia.View/Download from: UTS OPUS or Publisher's site
© 2016 SPIE.The rapid development of a variety of molecular contrast agents makes the multimodality bioimaging highly attractive towards higher resolution, more sensitive, informative diagnosis. The key lies in the development of facile material synthesis that allows the integration of multiple contrast agents, ideally in a way that each of the components should be logically assembled to maximize their performances. Here, we report the one-pot programmable growth of multifunctional heterogeneous nanocrystal with tunable size, shape, composition, and properties. We demonstrated a facile one-pot hot-injection method to enable the highly selectively controlled growth of different sodium lanthanide fluoride nanomaterials in either longitudinal or transversal directions with atomic scale precision. This technique allows the upconversion luminescence signal, MRI signal and x-ray signal logically integrated and optimized within one single versatile nanoplatform for multimode bioimaging. These findings suggest that the facile strategy developed here have the promising to get the desired heterogeneous nanocrystals as an all-in-one contrast agent for integrated and self-correlative multimodal bioimaging.
Zheng, W, Ma, JY, Guo, F, Li, J, Zhou, HM, Xu, XX, Li, L & Zheng, YF 2013, 'A novel biofuel cell based on electrospun collagen-carbon nanotube nanofibres', Bio-Medical Materials and Engineering, International Conference on Biomedical Engineering and Biotechnology (iCBEB), IOS Press, Wuhan, China, pp. 229-235.View/Download from: UTS OPUS or Publisher's site
The paper demonstrates a novel glucose/O2 biofuel cell (BFC) based on the electrospun collagen-SWNTs nanofibres with the glucose oxidase (GOD) as the anodic biocatalysts and the laccase as the cathodic biocatalysts. With an average diameter of about (260±95) nm, the electrospun collagen-SWNTs nanofibres exhibited smooth surfaces. The collagen-SWNTs nanofibres modified electrode showed good electron transfer behavior, because of the properties of SWNTs and the three-dimensional reticular structure of the electrospun nanofibers. The GOD and laccase, immobilized in the collagen-SWNTs nanofibres, exhibited good catalytic activity towards glucose oxidation and oxygen reduction through mediators of ferrocene monocarboxylic acid (FMCA) and 2,2'-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), respectively. The maximum power density of the assembled glucose/O2 BFC based on the electrospun collagen-SWNTs nanofibres was ca. 14.3 W/cm2. Moreover, more than 50% of the initial value remained after continuous operation of 100 h. The results indicated the potential to apply the electrospun collagen-SWNTs nanofibres for novel BFC device.
Xu, XX & Zheng, YF 2006, 'Synthesis and characterization of magnetic nanoparticles and their reinforcement in polyurethane film', Key Engineering Materials, pp. 659-662.
Li, L, Li, Q-F, Guo, E, Liu, E, Cui, X & Xu, X 2005, 'Study on temper embrittlement of phosphorus in steel 12Cr1MoV', Key Engineering Materials, pp. 1183-1188.
1, Peking University and Harbin Engineering Unviersity in China;
2, Case Western Reserve University in USA;
1, The University of Western Australia;
2, University of Wollongong;
3, The Western Sydney University;
4, Macquarie University;