Photophysics of photothermal activation of plasmonic nanostructures

Abstract

This thesis primarily focuses on photophysics of charge and energy transfer in plasmonic structures. After an initial study of photothermal catalysis using silver bromide for methane activation which found the process to be unsuitable at 1 bar, the focus pivoted towards plasmonic nanostructures for photothermal applications. Charge transfer across a 4-mercaptobenzoic acid linker between silver nanocubes and cerium dioxide was examined using Raman spectroscopy, this found an increase in charge transfer with thicker shells and higher energy light. The photophysics of a similar system were then probed, using time-resolved spectroscopy and gold nanoparticles embedded in a cerium praseodymium mixed metal oxide. That study indicated that charge and energy transfer could occur and were influenced by the composition: with ballistic charge transfer dominating in cerium oxide, chemical interfacial damping being prevalent with low levels of praseodymium, and plasmon induced resonant energy transfer occurring with higher loadings of praseodymium. A final study is, at first glance, somewhat of a non-sequitur and examines the photophysics of hafnium nitride. In existing literature there was a discrepancy between theoretical and experimental work regarding the lifetime of photo-excited electrons in hafnium nitride, in this study this discrepancy is resolved and shows that the photo-excited electrons rapidly (<50 fs) couple to the lattice and generate heat. Final remarks suggest linking the work on hafnium nitride to the gold/mixed-metal-oxide work to examine the potential energy transfer