Gas-phase models of cluster-surface interactions
The electronic and geometric structures are key pieces of information that are necessary to gain understanding of any cluster-surface interaction.
For clusters where quantum effects dominate, the electronic structure can change significantly when a single metal atom is added or subtracted. Since the electronic structure is strongly linked to the geometric structure, changes in geometry can also be expected when the cluster size is altered.
However, this information is extremely difficult to extract by only investigating clusters deposited on surfaces.
By combining accurate laser-based photo-ionisation efficiency (PIE) spectroscopy with state-of-the-art computational methodology, we can determine the local geometric and electronic structures of metal clusters bound to model metal-oxide ‘surface’ clusters.
Our current and emerging work is focused on Au, Rh and Pt clusters bound to cerium-oxide and titanium-oxide clusters, which are all important surfaces for catalytic oxidation reactions. The measured spectrum for each 'bi-clusters' yields quantitative information about the electronic charge transfer between the cluster and metal-oxide support. The theoretical calculations are directly compared against the experimental values to provide valuable benchmarking data to enable more complicated calculations on bulk (real life) metal-oxide surfaces.
In this honours project, skills in operating high energy lasers, high vacuum pumps and high voltage power supplies will be developed as well as learning to undertake advanced quantum computational calculations and simulations. This work is done with collaborators at the University of Tokyo and could include student visits to work overseas.
Study in the Metal Cluster Laboratory
Professor Gregory Metha leads the Metal Cluster Laboratory which investigates how the properties of the metallic elements are affected by their size.
At the subnanometre size regime (< 1 nm), metal particles, called clusters, have chemical and physical properties that are markedly different from the bulk due to the dominance of quantum size effects.
Furthermore, each atom within the cluster is not 'locked' into place, allowing clusters to be able to move readily between various structural minima. Due to the size dependent variation of each cluster's electronic and geometric structure, the interaction of a specific sized metal cluster with a molecule (e.g. reactivity) is also unique.
Therefore, we consider cluster size to be the third dimension of the Periodic Table, which can be manipulated to produce new chemical species with novel chemical and physical properties that can explored and potentially exploited.
It has only been recently demonstrated that the size variable reactivity of metal clusters can be utilised to enhance catalytic activity. Metal clusters deposited onto surfaces, containing as few as several atoms, have been shown to induce catalysed activity at significantly lower temperatures compared with bulk metallic surfaces, and also demonstrate improved selectivity for particular reaction products.
This emerging field of research is known as nanocatalysis, where the properties depend on exactly how many atoms are in each cluster. The study and understanding of the underlying principles of these effects have the potential to provide a revolutionary methodology for developing next generation ultra-efficient catalysts.
Research within the Metal Cluster Laboratory involves the experimental and theoretical study of the chemical and physical properties of metal clusters, their deposition onto surfaces, and their chemical activity towards important molecules such as CO2, H2O and N2.
The research is broadly separated into 2 themes; (i) fundamental laser spectroscopic investigations of metal cluster systems isolated in the gas phase; and (ii) application of metal clusters as catalysts and photocatalysts.
Both themes are underpinned by computational studies to help explain the experimental data and provide insight into the strange nature of metal clusters.