Nanoscale Photocatalytic Activity of Gold and Gold–Palladium Nanostructures Revealed by Tip-Enhanced Raman Spectroscopy
Zhandong Li, Rui Wang, Dmitry Kurouski
Abstract
The new paradigm of solid-state catalysis is that coupling of plasmonic and catalytic metals can be used to achieve much higher catalytic efficiency relative to their counterparts. Chemical reactions on such bimetallic nanostructures are light-driven, which essentially enables “green catalysis” in organic synthesis. The catalytic efficiency of bimetallic platforms directly depends on their nanoscale structures, which remain poorly understood. We used tip-enhanced Raman spectroscopy (TERS) to investigate nanoscale plasmonic and photocatalytic properties of novel gold–palladium microplates (Au@PdMPs), along with their monometallic counterparts. We found that 4-nitrobenzenethiol (4-NBT) can be catalyzed to p,p′-dimercaptoazobisbenzene (DMAB) and 4-aminothiophenol (4-ATP) on Au@PdMPs, whereas monometallic AuMPs produce exclusively DMAB as a result of such photocatalytic reduction of 4-NBT. Using 4-NBT as a molecular reporter, we found that the efficiency of these catalytic reactions has strong correlation with the nanoscale structure of microplates. Coupling TERS to GC-MS, we also found that Au@PdMPs were capable of catalyzing the Suzuki–Miyaura coupling reaction.