Transition metal oxides
Transition metal oxides display exciting and important physical properties such as high temperature superconductivity, colossal magnetoresistance and ferroelectricity. We are developing new chemistry of the transition metal oxides, addressing targets such as lead-free replacements for the widely used ferroelectric lead zirconate titanate and new multiferroic materials where properties such as ferroelectricity and ferromagnetism are coupled in the same material. In addition to conventional ceramic synthesis methods we are developing low-temperature synthesis routes, synthesis of complex oxide materials in nanoparticle form, and the application of high pressure synthesis routes to new transition metal oxides.
Li, M.-R., U. Adem, et al. (2012). "A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature." Journal of the American Chemical Society 134(8): 3737-3747.
Evans, G., G. V. Duong, et al. (2010). "Chemical Bonding Assembly of Multifunctional Oxide Nanocomposites." Advanced Functional Materials 20(2): 231-238.
Claridge, J. B., H. Hughes, et al. (2009). "Frustration of Magnetic and Ferroelectric Long-Range Order in Bi2Mn4/3Ni2/3O6." Journal of the American Chemical Society 131(39): 14000-14017.
Materials for solid oxide fuel cells and ceramic gas separation and catalytic membranes
Solid oxide fuel cells require electrodes which conduct both oxide ions and electrons (mixed conductors) and catalyse the reactions at the anode and cathode of the cell, and electrolytes which conduct only oxide ions. Related systems operate with proton conducting electrolytes. Our role is to identify new candidate materials for these properties and understand the chemical and structural factors which contribute to the properties. We have identified new mixed conducting oxides and are now evaluating them in fuel cell assemblies, and have recently reported new highly conducting oxide ion conductors based on interstitial excess oxide ions. This work involves new materials synthesis, characterisation of structures to identify key property-controlling features and evaluation of the electron and ion transport properties.
Demont, A., M. S. Dyer, et al. (2010). "Stabilization of a Complex Perovskite Superstructure under Ambient Conditions: Influence of Cation Composition and Ordering, and Evaluation as an SOFC Cathode." Chemistry of Materials 22(24): 6598-6615.
Deng, Z. Q., J. P. Smit, et al. (2009). "B Cation Ordered Double Perovskite Ba2CoMo0.5Nb0.5O6-delta As a Potential SOFC Cathode." Chemistry of Materials 21(21): 5154-5162.
Kuang, X., M. A. Green, et al. (2008). "Interstitial oxide ion conductivity in the layered tetrahedral network melilite structure." Nature Materials 7(6): 498-504.
New materials in thin film form
We are using pulsed laser deposition to assemble new oxide materials from structural sub-components identified from the structure of the target material – the in-situ RHEED monitoring of the deposition of individual layers permits switching between rock salt and perovskite components of the Ruddlesden-Popper structure.
R. Palgrave et al. (2012). “Artificial Construction of the Layered Ruddlesden-Popper Manganite La2Sr2Mn3O10 by Reflection High Energy Electron Diffraction Monitored Pulsed Laser Deposition” Journal of the American Chemical Society 134, 7700-7714.
L. Yan, M. J. Rosseinsky et al. (2007) “Unit-cell-level assembly of metastable transition-metal oxides by pulsed-laser deposition”, Angewandte Chemie International Edition 46, 4539.
L. Yan, G. Van Tendeloo, M. J. Rosseinsky et al. (2011). “Cation ordering within the perovskite block of a six-layer Ruddlesden-Popper oxide from layer-by-layer growth - artificial interfaces in complex unit cells”, Chemical Science 2, 261.
C. Grygiel, S. R. C. McMitchell, M. J. Rosseinsky et al. (2010). “A-Site Order Control in Mixed Conductor NdBaCo2O5+delta Films through Manipulation of Growth Kinetics”, Chemistry of Materials 22, 1955.
Flexible open-framework materials for chiral and gas separation applications
Porous materials with nanometre size openings have applications in the storage of energy gases such as methane and hydrogen, gas separation and purification, delivery of drugs and medical gases, and as catalysts and separation materials. The best-established systems are the aluminosilicate zeolites. We have been involved in developing open-framework materials based on the coordination of organic ligands to metal centres – this has allowed us to show how these molecule-based materials can have a flexible response to guests, opening up to accommodate guests that appear too large based on a static view of the structure. This has produced new modes of hydrogen storage, discovered in work with Professor Mark Thomas at Newcastle, and allowed us to study the course of a chemical reaction that takes place within the pores of a nanoporous material. We have also developed chiral open framework materials and open-frameworks based on amino acid ligands.
Perkins, C. G., J. E. Warren, et al. (2012). "A porous layered metal-organic framework from pi-pi-stacking of layers based on a Co-6 building unit." Microporous and Mesoporous Materials 157, 24-32.
Rabone, J., Y. F. Yue, et al. (2010). "An Adaptable Peptide-Based Porous Material." Science 329(5995), 1053-1057.
Stylianou, K. C., R. Heck, et al. (2010). "A Guest-Responsive Fluorescent 3D Microporous Metal-Organic Framework Derived from a Long-Lifetime Pyrene Core." Journal of the American Chemical Society 132(12), 4119-4130.
Stylianou, K. C., J. E. Warren, et al. (2011). "CO2 selectivity of a 1D microporous adenine-based metal-organic framework synthesised in water." Chemical Communications 47(12), 3389-3391.
Swamy, S. I., J. Bacsa, et al. (2010). "A Metal-Organic Framework with a Covalently Prefabricated Porous Organic Linker." Journal of the American Chemical Society 132(37): 12773-12775.
New superconducting materials
Superconducting materials carry electrical current without resistance below their superconducting transition temperature Tc. Our role is to identify new classes of complex systems which are superconducting and understand the chemical and structural basis for this behaviour. The superconducting state is vey demanding to access in a material, and understanding the electronic properties of systems related to the superconductors but with different electronic ground states plays an important part of this work.
We have recently discovered the highest transition temperature molecule-based superconductor (38K Cs3C60) working with the group of Professor Kosmas Prassides at Durham.
Ganin, A. Y., Y. Takabayashi, et al. (2010). "Polymorphism control of superconductivity and magnetism in Cs3C60 close to the Mott transition." Nature 466(7303), 221-U293.
Klupp, G., P. Matus, et al. (2012). "Dynamic Jahn-Teller effect in the parent insulating state of the molecular superconductor Cs3C60." Nature Communications 3.
Rosseinsky, M. J. and K. Prassides (2010). "MATERIALS SCIENCE Hydrocarbon superconductors." Nature 464(7285), 39-41.
Tamai, A., A. Y. Ganin, et al. (2010). "Strong Electron Correlations in the Normal State of the Iron-Based FeSe0.42Te0.58 Superconductor Observed by Angle-Resolved Photoemission Spectroscopy." Physical Review Letters 104(9).
In addition to the deposition of thin oxide films, we are working on the preparation of materials with multiple properties based on functional transition metal oxide nanoparticles.
Chalker, P. R., S. Romani, et al. (2010). "Liquid injection atomic layer deposition of silver nanoparticles." Nanotechnology 21(40): 405602-405602.
Peacock, A. K., S. I. Cauet, et al. (2012). "Poly 2-(methacryloyloxy)ethylphosphorylcholine -coated iron oxide nanoparticles: synthesis, colloidal stability and evaluation for stem cell labelling." Chemical Communications 48(75): 9373-9375.
Woodward, R. T., C. I. Olariu, et al. (2011). "Multi-responsive polymer-stabilized magnetic engineered emulsions as liquid-based switchable magneto-responsive actuators." Soft Matter 7(9): 4335-4340.
Yiu, H. H. P., H.-j. Niu, et al. (2010). "Designed Multifunctional Nanocomposites for Biomedical Applications." Advanced Functional Materials 20(10): 1599-1609.
Yiu, H. H. P., M. R. Pickard, et al. (2012). "Fe3O4-PEI-RITC Magnetic Nanoparticles with Imaging and Gene Transfer Capability: Development of a Tool for Neural Cell Transplantation Therapies." Pharmaceutical Research 29(5): 1328-1343.