Synthesis of Vanadium Oxide Nanostructures for Functional Applications By Haitao Fu A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy School of Materials Science and Engineering Faculty of Science The University of New South Wales August 2013 ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed ……………………………………………...... Date …………………………………………….............. i List of Publications Peer-Reviewed Journals 1. Fu, H.; Yang, X.; Jiang, X.; Yu, A., Bimetallic Ag–Au Nanowires: Synthesis, Growth Mechanism, and Catalytic Properties. Langmuir 2013, 29, (23), 7134-7142. 2. Fu, H.; Yang, X.; Yu, A.; Jiang, X., Rapid synthesis and growth of silver nanowires induced by vanadium trioxide particles. Particuology 2013, 11, (4), 428-440. 3. Su, D.; Fu, H.; Jiang, X.; Wang, G., ZnO nanocrystals with a high percentage of exposed reactive facets for enhanced gas sensing performance. Sensors and Actuators B: Chemical, 2013, 186, (0), 286-292. 4. Fu, H.; Jiang, X.; Yang, X.; Yu, A.; Su, D.; Wang, G., Glycothermal synthesis of assembled vanadium oxide nanostructures for gas sensing. J. Nanopart. Res. 2012, 14, (6), 1-14. 5. Yang, X.; Fu, H.; Yu, A.; Jiang, X., Large-surface mesoporous TiO2 nanoparticles: Synthesis, growth and photocatalytic performance. Journal of Colloid and Interface Science 2012, 387, (1), 74-83. 6. Yang, X.; Fu, H.; Yu, A.; Jiang, X., Hybrid Ag@TiO2 core-shell nanostructures with highly enhanced photocatalytic performance. Nanotechnology, 2013, accepted. Book Chapter 7. Yang, X.; Fu, H.; Jiang, X.; Yu, A., (2013) Silver Nanoparticles: Synthesis, Growth Mechanism and Bioapplication, Silver Nanoparticles: Synthesis, Uses and Health Concerns, Chapter ID: 17048, ISBN: 978-1-62808-407-8, NOVA Science. Conference Proceedings 8. Fu, H.; Yang, X.; Jiang, X.; Yu, A., Glycothermal Synthesis of Urchin-Like Vanadium Pentoxide Nanostructure for Gas Sensing, the 13th IEEE International Conference on Nanotechnology (IEEE-NANO 2013), August 5-8, 2013, Shangri-La Hotel, Beijing, China. ii Abstract Vanadium oxide nanoparticles have displayed excellent properties in the field of clean energy, environment, and catalysis. Nowadays, the applications of vanadium oxides in catalysts, lithium ion batteries (LIB), gas sensors, smart windows, and temperature switches attract increasing more attention. Therefore, the studies of the synthesis and properties of these materials are important for scaling up production and understanding the formation and growth mechanism, and surface behaviours for functional properties and potential applications. In this thesis, a brief introduction of the relative research and a literature review on the vanadium oxides and their nanocomposites were presented in Chapters 1 and 2, respectively. Chapter 3 systematically described the preparation of various vanadium oxides (V2O5 and V2O3) with different shapes (microspheres, microurchins and nanorods) by a polythermal method, the growth mechanism, and the sensing performance of V2O5 nanoparticles. To enhance the function properties of gas sensing, the nanocomposites of silver vanadium oxides (SVO) and vanadium oxides with Ag nanocomposites (VOx@Ag) were investigated in Chapter 4, in which Ag2V4O11 nanobelts were found to exhibit high sensitivity and selectivity to amines. To enrich the application of V2O3 particles, Chapters 5 and 6 respectively demonstrated wet-chemical methods for induced synthesis of Ag nanowires and Ag-Au bimetallic nanowires by V2O3 particles. In these chapters, the formation mechanisms and catalytic performance for reduction of 4-nitrophenol were discussed. Finally, the conclusions were summarised in Chapter 7. iii Table of Contents List of Publications ................................................................................................................ ii Abstract ................................................................................................................................. iii Acknowledgements ................................................................................................................ x Abbreviations and Symbols .................................................................................................. xi Captions of Figures ............................................................................................................. xiv List of Tables..................................................................................................................... xxiii Chapter 1. Introduction ...................................................................................................... 1 1.1 Background ............................................................................................................. 1 1.2 Scope of Research ................................................................................................... 2 Chapter 2. Literature review .............................................................................................. 5 2.1 Vanadium oxides ..................................................................................................... 5 2.1.1 Vanadium pentoxide ........................................................................................ 5 2.1.2 Vanadium dioxide ............................................................................................ 6 2.1.3 Vanadium trioxide ............................................................................................ 7 2.1.4 Transformation among three oxides................................................................. 8 2.2 Synthesis Methods ................................................................................................... 9 2.2.1 Physical methods of vanadium oxides ............................................................. 9 2.2.2 Chemical methods of vanadium oxides ......................................................... 13 iv 2.2.3. Shape controlled synthesis of Ag nanoparticles............................................. 31 2.2.4 Shape controlled synthesis of Au nanoparticles............................................. 33 2.3 Surface modifications ............................................................................................ 34 2.3.1 Polymers ......................................................................................................... 35 2.3.2 Metal dopants ................................................................................................. 37 2.3.3 Metal Oxide dopants ...................................................................................... 38 2.3.4 Silica modifier(s) ............................................................................................ 39 2.4 Properties of vanadium oxide nanoparticles and composites ................................ 40 2.4.1 Redox properties ............................................................................................ 40 2.4.2 Metal insulator transition ............................................................................... 41 2.4.3 Electrical properties ....................................................................................... 42 2.4.4 Magnetic properties ........................................................................................ 44 2.5 Functional applications .......................................................................................... 46 2.5.1 Gas sensing materials ..................................................................................... 46 2.5.2 Catalysts ......................................................................................................... 49 2.5.3 Actuators ........................................................................................................ 49 2.5.4 Optical switches and smart windows ............................................................. 50 2.5.5 Electrode in LIBs ........................................................................................... 51 2.6 Summary ................................................................................................................... 51 v Chapter 3. Glycothermal synthesis of assembled vanadium oxide nanostructures for gas sensing…………………………………………………………………………...…………53 3.1 Abstract ................................................................................................................. 53 3.2 Introduction ........................................................................................................... 53 3.3. Experimental work ................................................................................................ 55 3.3.1 Materials ............................................................................................................ 55 3.3.2 Synthesis ...........................................................................................................