Energy Flow during the Plasmon Resonance-Driven Photocatalytic Reactions on Single Nanoparticles
Jun Zhou, He Wei, Hui Liu, Cheng Zhi Huang
Abstract
Understanding the mechanisms that control the flow of energy and charge carriers in plasmonic nanostructures is essential to improve the efficiency of light energy conversion in plasmon resonance-mediated photocatalytic chemical reactions. For this, here, we demonstrate the plasmon energy distributed in time by dark-field microscopy (DFM) through monitoring the resonance photocatalysis of p-aminothiophenol (p-ATP) oxidized to 4,4′-dimercaptoazobenzene on Au nanoparticles (AuNPs). The spectral red shift of the scattered light under localized surface plasmon resonance excitation reveals that dissolved oxygen molecules in solution are activated by accepting the electrons from AuNPs. This allows us to study the nanoscopic energy flow and excited charge carriers in plasmonic nanoparticle–adsorbate systems. With the aid of DFM imaging and color-coding, the number of energetic charges in plasmonic nanoparticles flowing into the adsorbed p-ATP molecules could be accurately quantified, showing that dissolved oxygen molecules in solution and energy flow in the plasmonic nanoparticle–adsorbate systems are critical to the activation of the oxidation reaction of p-ATP. This visualized energetic charge distributed in time can provide a simple and effective method for studying the microscopic mechanism of energy flow.