Probing Plasmon-Molecules Interactions with Surface-enhanced Raman Spectroscopy: Towards the Guided Design of Plasmonic Photocatalysts

Abstract

Plasmonic materials have proven their strong candidacy as photocatalysts with their unique optical properties and strong interactions with light. The possibility of driving chemical reactions with sunlight to achieve high efficiency and selectivity has driven a lot of research exploring plasmonic photocatalysts. However, the progress has been slow due to a lack of mechanistic understanding. My thesis work aims to provide guidelines for plasmonic catalysts design through investigating plasmon-molecules interaction with various spectroscopic techniques.In this thesis, I will discuss my investigation of the energy transfer processes in the plasmonic-molecules systems on the ultrafast and steady state timescales with surface-enhanced Raman thermometry. Our results reveal that following the initial transient energy deposition, there is a quick energy dissipation between the molecules through intermolecular interactions on the ultrafast timescale (within 30 ps). On the steady state, surprisingly, we observed a “plasmon refrigerator” where the molecules are cooled below room temperature. In later work, I will discuss our work on developing surface-enhanced Raman optical activity spectroscopy and our investigation of the chiral interactions between molecules and plasmons. Our initial results suggest chirality transfer in the plasmonic-molecules systems. Lastly, I will propose a series of future directions to further the study of plasmon-molecules interactions. Herein, I show that surface-enhanced Raman spectroscopy (SERS) is a powerful technique, especially when coupled with other techniques such as Raman thermometry and Raman optical activity. Our studies on plasmon-molecules interactions will help with the development of plasmonic catalysis by providing guidelines for the design and optimization of plasmonic catalysts.