Shaping Nanostructure Using Molecules

Metallic nanoparticles are widely used for technological applications in catalysis, data storage and medicine. There are many experimental and theoretical investigations studying promising materials for new applications and understanding how they work. A number of strategies are also employed to improve performance for specific applications including doping, annealing and chemical processing. In this thesis we have investigated the influence of external factors (such as adsorbed molecules or substrate materials) on the structure and properties of four different nanoparticle systems. First, we have investigated the morphology of L10 ordered FePt nanoparticles supported on various Mg(1-x)TixO substrates. The adhesion energy between FePt and the MgTiO slabs is found to decrease with the increasing number of TiO layers due to Ti-Fe bond formation. In addition, the Fe-Ti interaction hinders the growth of the FePt nanoparticle in [001] direction and reduces the density of information storage. Next, we have studied the oxidation of Ti and TiPt nanoparticles. We find oxygen atoms should adsorb on the three-fold follow sites on Ti nanoparticles and linear O-Ti-O structures minimise the adsorption energy. Increasing oxygen coverage leads an increase of surface strain on the Ti nanoparticle. For each 1 % increase in surface strain the energy barrier for subsurface oxygen diffusion in the middle of the facets decreases by 0.1 eV. Oxidation of TiPt nanoparticles results in an atomic rearrangement of the bimetallic nanoparticle that can be controlled by the oxygen coverage. With increased oxygen adsorption, the atomic arrangement transforms from Pt atoms segregated to the vertices to a core-shell configuration. Finally, we have investigated Au nanoparticles supported on ZnO nanorods for CO oxidation. We demonstrate zinc interstitials in bulk ZnO can lead to the formation of a ZnO encapsulation layer around the Au nanoparticles under oxygen-rich conditions. Moreover, the ZnO encapsulation provides alternative adsorption sites for oxygen molecules and further increases the number of possible reaction pathways for CO oxidation, explaining the experimentally observed enhanced activity.