Elucidation of Photocatalytic Properties of Gold–Platinum Bimetallic Nanoplates Using Tip-Enhanced Raman Spectroscopy

Plasmonic catalysis is based on a unique property of noble metal nanostructures to harvest electromagnetic radiation converting it into hot carriers. These high energy species can catalyze chemical reactions in molecules located in the vicinity to surfaces of the plasmonic nanostructures. However, traditional plasmonic metals such as gold (Au) are useful only for a limited number of chemical reactions. The spectrum of chemical reactions can be broadened up by coupling plasmonic and catalytic metals, such as platinum (Pt), in one nanostructure. In this study, we use tip-enhanced Raman spectroscopy (TERS) to probe photocatalytic properties of gold–platinum nanoplates (Au@PtNPs). We found that Au@PtNPs highly efficiently proto-reduced 4-nitrobenzenethiol (4-NBT) to p, p ′-dimercaptoazobisbenzene (DMAB) with the yield similar to the one observed for gold nanoplates (AuNPs). These Au@PtNPs could be used to proto-oxidize 4-aminothiophenol (4-ATP) first to 4-NBT and then 4-NBT to DMAB, whereas photo-oxidation of 4-ATP on the surface of AuNPs directly proceeds to DMAB.