In Situ Monitoring of Catalytic Molecular Transformations on Noble Metal Nanocatalysts Using Surface-Enhanced Raman Spectroscopy

摘要

Noble metal nanoparticles have long been of tremendous interest in the nanophotonics and nanocatalysis communities owing to their intriguing size- and shape-dependent plasmonic and catalytic properties. The combination of tunable plasmon resonances with superior catalytic activities on the same noble metal nanoparticle, however, has long been challenging because the research on nanoplasmonics and nanocatalysis deals with nanoparticles in two drastically different size regimes. While tunable plasmon resonances are a unique feature of metallic nanoparticles in the sub-wavelength size regime, heterogeneous catalysis requires the use of substrate-supported sub-5 nm nanoparticulate catalysts. In this mini-review article, we share with the readers several approaches we recently developed toward the realization of plasmonic-catalytic dual-functionalities on a single noble metal nanoparticle. Our approaches involve judicious tailoring of the atomic-level surface structures of sub-wavelength plasmonic nanoparticles through either kinetically controlled seed-mediated nanocrystal growth or regioselective surface etching. These structurally tailored, dual-functional nanoparticles serve as both substrates for surface-enhanced Raman spectroscopy (SERS) and free-standing nanoparticulate catalysts. Using SERS as a molecular finger-printing spectroscopic tool, we have been able to track detailed structural evolution of molecular adsorbates in real time during catalytic reactions. The quantitative insights gained from the in situ SERS measurements shed light on the detailed relationships between interfacial molecule-transforming behaviors and the atomic-level surface structures of noble metal nanocatalysts.