Plasmonic monitoring of catalytic hydrogen generation by a single nanoparticle probe

Plasmonic nanostructures such as gold nanoparticles are very useful for monitoring chemical reactions because their optical properties are highly dependent upon the environment surrounding the particle surface. Here, we designed the catalytic structure composed of platinized cadmium sulfide with gold domains as a sensitive probe, and we monitored the photocatalytic decomposition of lactic acid to generate hydrogen gas in situ by single-particle dark-field spectroscopy. The plasmon band shift of the gold probe throughout the reaction exhibits significant particle-to-particle variation, and by simulating the reaction kinetics, the rate constant and structural information (including the diffusion coefficient through the shell and the relative arrangement of the active sites) can be estimated for individual catalyst particles. This approach is versatile for the monitoring of various heterogeneous reactions with distinct components at a single-particle level.