Chemical Nanoimaging and Characterizing Kinetics of Bimetallic Nanostructure-Plasmon-Driven Dimerization Reactions by Tip-Enhanced Raman Spectroscopy

High synthetic costs of noble metal nanostructures, which are broadly used for plasmonic catalysis, triggered an interest in the use of less expensive metals such as copper for their fabrication. Catalytic properties of copper nanoparticles can be expanded by their doping with catalytic metals such as ruthenium or palladium. However, the catalytic properties of these novel bimetallic catalysts remain poorly understood. In this study, we used tip-enhanced Raman spectroscopy to investigate plasmon-driven transformation of 4-nitrobenzenethiol (4-NBT) to 4,4 '-dimercaptoazobenzene (DMAB) on copper@ruthenium nanoparticles (Cu@RuNPs). We found that the presence of RuNPs on Cu nanoplate (CuNPt) surfaces drastically enhances catalytic reactivity of Cu@RuNPs compared to their monometallic analogues. The kinetics of the catalytic reaction have been studied, and the reaction rate constant for Cu@RuNPs is higher than that of CuNPts for hot-carrier-driven reduction of 4-NBT to DMAB. Our findings can be used to design novel bimetallic nanostructures with the desired catalytic properties.