Prof. P. P. Edwards FRS

Inorganic Chemistry Laboratory

Email Address: peter.edwards@chem.ox.ac.uk

Telephone: 44 (0) 1865 272 646

Our current research topics cover a broad range of interests and activities, these include:

1. Turning Insulators into Metals
There are numerous systems and materials for which small changes in temperature, pressure or composition can transform a non-metallic (insulating) material into a highly conducting metallic state. C.N.R. Rao of Bangalore has drawn a graphic analogy, noting this process is akin to "Turning Wood into Copper". A detailed understanding of this remarkable electronic phase transition is one of our major interests.

2. The Challenge of High-Temperature Superconductivity
The observation, in 1987, of high-temperature superconductivity by J.G. Bednorz and K.A. Mller represents one of the greatest experimental discoveries of the last century. The phenomenon is simply not yet understood. Our project has the ultimate goal of a deep understanding of this fascinating natural phenomenon. We try to synthesize materials which we believe might be new superconductors. One recent example is a collaboration with Wojciech Grochala (Warsaw) and centres on fluoroargenates.

3. Chemical and Physical Properties of Colloidal or Nanoscale Metals
Here we are interested in how the fundamental properties of a material change as we vary the characteristic size of individual particles. The picture (left) shows colloidal (nanoscale) gold... Finely divided (left) through to tiny particles (right) of diameter around 50.

Novel synthesis of metal nano-particles.
Measuring the electrical conductivity and microwave absorption of individual particles with new microwave techniques.

4. Hydrogen Storage in Solids
Hydrogen is widely regarded as the most promising alternative to carbon-based fuels since it will help alleviate the inevitable environmental and energy supply concerns when fossil fuels become scarce and/or unsustainable because of ecological and energy/security reasons. Hydrogen is ideal as a synthetic fuel; it is light weight, highly abundant -recall, hydrogen is the most abundant element in the universe- and when used as an energy carrier it generated no emissions other than normally benign water molecules.

This research theme encompasses Carbon, Light-Metal Hydrides and New Materials for Hydrogen Storage. At the heart of the activity is an attempt to understand -and hence control- the micro-, meso-, and nano-structure of low atomic number hydrogen storage materials. To achieve a breakthrough requires a suitable storage material of 6-7 weight percent hydrogen.

5. Transparent Conducting Metals
Transparent conductors (TC) are extremely important functional materials, with applications in many industries. The most important TC is indium tin oxide (ITO), as it possesses the ideal combination of optical transparency and high conductivity. However, indium is extremely costly and thus it would be beneficial if indium free or reduced-indium TCs, with similar or better electrical properties, could be produced. To that end our research encapsulates;

Increased electron mobility, and hence conductivity of ITO materials. Enhanced conductivity would lead to reduced film thickness, and thus reduced indium usage.
Increased number of charge carriers (electrons). Similarly, increasing the number of charge carriers in ITO enhances conductivity.
Synthesis and processing of new transparent conductor materials.

6. Thin Film Materials
In collaboration with the University of Birmingham. Many advanced materials show enhanced properties in thin film form or are required to be in thin film form for industrial applications. We produce functional thin film materials using the technique of pulsed laser deposition. Some of our areas of research are;

Use of pulsed laser deposition as a chemical synthesis tool.
Deposition of so-called 'precursor films' for treatment external (ex-situ) to the laser chamber to induce interesting electronic and magnetic behaviour.
Production of superconductor, transparent conductor and other functional material thin films.

7. Microwave Synthesis, Processing and Characterization
Microwave frequency radiation may be used as an efficient and environmentally-friendly alternative to traditional synthesis energy sources for solid state synthesis. Furthermore, microwave radiation can be used as a processing tool for functional materials and a method for determining their electronic properties. We investigate;

Quick and energy efficient synthesis routes for industrially important functional materials.
New synthesis techniques involving either microwave-only initiated reactions or hybrid methods combining existing techniques with microwave radiation.
Developmental synthesis techniques whereby the reaction products are controlled by the precise chemical and physical nature of the reactants.
Microwave plasma processing of materials to induce desired functional properties.
Development of new microwave frequency sensors to investigate electronic properties.

8. Metals in Zeolites
Here we study the chemistry of zeolite ion exchange and salt occlusion compounds and the products obtained from their decomposition, reduction and/or oxidation at high temperature (providing fine coloured dispersions).

Incorporation or dispersion of nanoscale alkali and coinage metals within highly porous zeolitic host materials.
The production of complex metal oxides by salt occlusion and the decomposition of ion-exchanged and salt-occluded zeolite precursors.
The production of metal and metal alloy nano-sized particles in zeolite host materials.

9. Metals in Ammonia
Here we study the chemistry of alkali metals as solutes in ammonia and the primary amines and associated systems.

Detailed investigations of the nature of the solvated electron in alkali metal ammonia solutions using both ESR and NMR spetroscopies.
The study of metal mixed solvent systems by ESR and NMR spetroscopies.
The close examination of the phase separation boundary region of the sodium ammonia solution using various spectroscopic techniques.

Selected Recent Publications

"Synthesis, Structure and Magnetic Characterisation of Pulsed Laser-Ablated Superconducting La₂CuO₄F_x Thin Films", S.T. Lees, I. Gameson, M.O. Jones, P.P. Edwards and M. Slaski, Chem. Mater., Special Issue: 'Frontiers in Inorganic Materials Chemistry', 10, 3146-3155 (1998)
"A Perspective on the Metal-Nonmetal Transition", P.P. Edwards, R.L. Johnston, F. Hensel, C.N.R. Rao, D.P. Tunstall, Solid State Physics - Advances in Research and Applications, 52, 229-338 (1999).
"On the Size-Induced Metal-Nonmetal Transition in Particles and Clusters", P.P. Edwards, R.L. Johnston and C.N.R. Rao, in 'Metal Clusters in Chemistry', eds. P.R. Raithby and P. Braunstein, Wiley-V.C.H., pp 1454-1481 (1999).
"Metal Nanoparticles and Their Assemblies", C.N.R. Rao, G.U. Kulkarni, P.J. Thomas and P.P. Edwards, Chem. Soc. Rev., 29, 27-35 (2000).
"What Why and When is a Metal?", P.P. Edwards in "The New Chemistry", ed. N. Hall, Cambridge University Press, pp. 85-114 (2000).
"High-T_c Cuprates: A New Electronic State of Matter?", A.S. Alexandrov and P.P. Edwards, Physica C, 331, 97-112 (2000).
"Polarons, Bipolarons, and Possible High-T_c Superconductivity in Metal-Ammonia Solutions", P.P. Edwards, Lecture presented at MTSC 2000, Conference on "Major Trends in Superconductivity in the New Millennium," in Kolsters, Switzerland (2000)
Journal of Superconductivity: Incorporating Novel Magnetism, 13(6), 933-946 (2000).
"Alkali Metal Loaded Zeolite LiA: Evidence for Highly Symmetrical Rb^- and K^-", V.V. Terskikh, I.L. Moudrakovski, C.I. Ratcliffe, J.A. Ripmeester, C.J. Reinhold, P.A. Anderson and P.P. Edwards, J. Am. Chem. Soc., 123, 2891-2892 (2001).
"Electron Beam Induced Growth of Bare Silver Nanowires from Zelolite Crystallites", P.P. Edwards, M.J. Edmondson, W. Zhou and S.A. Sieber, Advanced Materials, 13, 1608 (2001)
"Size-Dependent Chemistry: Properties of Nanocrystals", P.P. Edwards, C.N.R. Rao, G.U. Kulkarni, P.J. Thomas, Chem. Eur. J., 8, 29-35 (2002).
"Metallic Oxygen", P.P. Edwards and F. Hensel, ChemPhysChem., 3, 53-56 (2002)
"Chemistry of Vibronic Coupling in Molecules and in Superconductors", W. Grochala, R. Hoffman and P.P. Edwards, Chemistry; a European Journal, 2, 575-587, (2003)