Tom Arnold
Surfaces and Interfaces
Tom Arnold is the Beamline Scientist for the surface and interface diffraction beamline I07. Prior to joining Diamond he was briefly a post-doc with Dr. Stuart Clarke at Cambridge University (for 6 months) and before that as a DOE postdoc with Prof. John Z. Larese at Oak Ridge National Laboratory. During this period he spent time as a visitor to ISIS dealing mainly with the molecular spectroscopy group instruments, TOSCA, OSIRIS and IRIS. His main research interests are the physical chemistry of molecular adsorption at solid surfaces using a wide range of thermodynamics and X-ray and neutron scattering techniques.
Email: Tom Arnold
Tel: +44 (0) 1235 778543
Beamline I07: Surfaces and Interfaces
Key Research Areas
Molecular adsorption using X-ray (GIXD, GISAXS, XRR, 2D Powder Diffraction) and Neutron (2D Powder Diffraction, Reflection, INS, QENS, Vibrational Spectroscopy) Scattering and Thermodynamics techniques.
Current Research Interests
The adsorption of molecules from liquids and solutions to solid surfaces is central to many areas of academic and industrial importance, such as catalysis and lubrication. My post-doc research has used a combination of experimental techniques to provide detailed information on the thermodynamics, crystallographic structure and dynamic processes of surface layers adsorbed under real-world conditions. This work remains of interest and below I describe some of the recent results of these well established collaborations.
The research has included detailed studies of the properties of hydrocarbon films adsorbed on well characterised and technologically relevant surfaces, such as graphite or magnesium oxide from the gas or liquid phase, and including studies of competitive adsorption from solution. In particular, we were interested in the subtle interplay between the intermolecular and molecule-substrate interactions that define the structural and phase behaviour in adsorbed films, growth from two to three dimensions, the melting and wetting behaviour and adsorption thermodynamics.
Many industrially important materials consist of complicated multi-component mixtures, either because mixtures are cheaper than pure components or because the simultaneous adsorption of more than one component may lead to enhancement of performance relative to the pure components. Understanding what influences the preferential adsorption of one component over others therefore has wide reaching implications. Much of my research has been on making direct measurements of the preferential adsorption and the subsequent phase-behaviour in two dimensions including whether, for example, two adsorbed components phase separate or form molecular compounds on the surface.
Understanding the trapping and release of hydrogen from surfaces is key to developing new compounds for storage and catalytic applications. We used a combination of diffraction and inelastic neutron scattering and high-resolution adsorption isotherms to help facilitate a microscopic understanding of the interaction of thin hydrogen films adsorbed on the surface of magnesium oxide nanocubes. Variation of temperature and film thickness was used to correlate changes in the film structure with the dynamical response, and to establish that an extremely sharp signal in the inelastic neutron scattering data (at ~11.3meV) corresponds to the hindered para-ortho transition in hydrogen molecules adsorbed directly above the Mg2+ ions in the rock-salt structured (100) surface.
My future research interests will mainly focus on the application of x-ray scattering methods to the sorts of problems described above. I am particularly interested in using these techniques to access novel thin films and adsorbed molecular species under technologically realistic conditions.
Selected Publications
- Arnold, T.; Chanaa, S.; Larese, J. Z.; Cook, R. E.; Clarke, S. M., Structure of an n-butane monolayer adsorbed on magnesium oxide (100). Physical Review B 2006, 74, 085421.
- Arnold, T.; Clarke, S. M., Thermodynamic Investigation of the Adsorption of Amides on Graphite from Their Liquids and Binary Mixtures. Langmuir 2008, 24, (7), 3325-3335.
- Larese, J. Z.; Arnold, T.; Frazier, L.; Hinde, R. J.; Ramirez-Cuesta, A. J., Direct Observation of H2 Binding to a Metal Oxide Surface. Physical Review Letters 2008, 101, 165302.
- Larese, J. Z.; Arnold, T.; Barbour, A.; Frazier, L. R., Neutron Investigations of Rotational Motions in Monolayer and Multilayer Films at the Interface of MgO and Graphite Surfaces. Langmuir 2009, 25, (7), 4078–4083.
- Bhinde, T.; Clarke, S. M.; Phillips, T. K.; Arnold, T.; Parker, J. E., Crystalline Structures of Alkylamide Monolayers Adsorbed on the Surface of Graphite. Langmuir 2010, 26, 8201-8206.