The Delivery of 4-Aminothiophenol to Reactive Sites by Plasmon-Activated Adsorbed Oxygen Species Significantly Enhances Its Azo-Dimerization

Capitalizing on the spatiotemporal controllability of localized plasmons, plasmonic nanostructures show great promise in photocatalysis. Herein, using plasmon-mediated azo-dimerization of 4-aminothiophenol (4-ATP) on helical plasmonic nanorods (HPNRs), we demonstrate a unique route to modulate catalytic activity. This approach leverages plasmon-mediated activation of adsorbed oxygen species (one reactant) to control the delivery of free 4-ATP (the other reactant) in the liquid phase to reactive sites, thereby significantly enhancing the formation of azo-coupling product 4,4'-dimercaptoazobenzene (DMAB). Upon plasmon excitation, adsorbed oxygen species on the HPNR surface capture hot electrons and become activated. These photoactivated oxygen species facilitate the transport of free 4-ATP molecules, shuttled outside the surface-stabilizing ligand shell of the HPNR, to surface-active sites and participate in the coupling reaction. Considering tunability of local plasmons, surface ligand design (e.g., bromide ions scavenging holes), and plasmonic nanostructure morphology, this strategy, regulating one reactant's activation to control another's, offers distinct advantages for on-demand and site-specific reactions with high selectivity. Our findings highlight a versatile means of modulating reaction activity with potential applications in spatially and temporally controlled catalysis.