Probing Oxidation Mechanisms in Plasmonic Catalysis: Unraveling the Role of Reactive Oxygen Species

Abstract

Plasmon-induced oxidation has conventionally been attributed to the transfer of plasmonic hot holes. However, this theoretical framework encounters challenges in elucidating the latest experimental findings, such as enhanced catalytic efficiency under uncoupled irradiation conditions and superior oxidizability of silver nanoparticles. Herein, we employ liquid surface-enhanced Raman spectroscopy (SERS) as a real-time and in situ tool to explore the oxidation mechanisms in plasmonic catalysis, taking the decarboxylation of p-mercaptobenzoic acid (PMBA) as a case study. Our findings suggest that the plasmoninduced oxidation is driven by reactive oxygen species (ROS) rather than hot holes, holding true for both the Au and Ag nanoparticles. Subsequent investigations suggest that plasmon-induced ROS may arise from hot carriers or energy transfer mechanisms, exhibiting selectivity under different experimental conditions. The observations were substantiated by investigating the cleavage of the carbon−boron bonds. Furthermore, the underlying mechanisms were clarified by energy level theories, advancing our understanding of plasmonic catalysis.

Raman Monitoring of the Electro-Optical Synergy-Induced Enhancements in Carbon–Bromine Bond Cleavage, Reaction Rate, and Product Selectivity of p-Bromothiophenol

“…On the other hand, in situ Raman spectroscopy could be applied to continuously monitor catalytic reactions. ,, Especially, the Raman scattering signal of the molecules in the vicinity of plasmonic nanostructures could be largely enhanced, by up to 10 8 –10 12 -fold, which is referred to as surface-enhanced Raman scattering (SERS). This in situ SERS technique provides a convenient and sensitive way to continuously monitor the plasmon-mediated catalytic reactions, , helping us to deeply understand the mechanism of the catalytic reactions.…”

Mechanism Switch in Surface-Enhanced Raman Scattering: The Role of Nanoparticle Dimensions

“…Surface-enhanced Raman scattering (SERS) stands as a powerful spectroscopic method that notably amplifies the Raman signals of molecules on roughened noble metal substrates, providing significant insights into molecular structures and their interactions. − The remarkable sensitivity of SERS, which reaches the capability of detecting single molecules, is derived from two fundamental mechanisms: the electromagnetic mechanism (EM) and chemical mechanism (CM) . EM enhancement primarily emerges from the localized surface plasmon resonance (LSPR) in metallic nanostructures, significantly intensifying electromagnetic fields at the surface around the materials. , Conversely, CM enhancement is a consequence of charge transfer (CT) interactions between the adsorbed molecules and the substrate, which modifies the polarizability of the molecules, thereby affecting their Raman scattering cross sections. − …”