Computational characterisation of gold nanocluster structures

Abstract

This thesis presents computational work on the structures, characterisation and optical properties of homogeneous gold nanoclusters, and gold-containing bimetallic nanoalloys. An introductory overview of nanoscience is followed by four results chapters in which various computational methods are applied to elucidate properties that are not fully understood; from these results areas for future development, and application, are identifed. Chapter 2 looks at structural motif preference as a function of composition and size for Au and Pd. Bimetallic (AuPd)\(_N\) particles are further studied, with thermodynamic preference found for Au\(_{shell}\)Pd\(_{core}\) configurations with a monolayer Au shell. Chapter 3 discusses the development and implementation of a genetic algorithm designed to aid the determination of the structures of small nanoclusters from images taken with a scanning transmission electron microscope. The implementation of a search method proves efficient at identifying high-symmetry test clusters, and shows promise for further application to the identification of cluster structure from experimental images. Chapter 4 contains a first-principles study of Au\(_{16}\) deposited on a graphite substrate. We introduce surface defects to see their influence on the nanocluster structure, as well as testing for potential catalytic applications. Finally, Chapter 5 looks at the optical response of monometallic and bimetallic nanoparticles. Surface plasmon resonance spectra are calculated for a variety of geometries, compositions and chemical ordering. The greatest influence on the extinction spectra is attributed to the particle shape and its environment.