Direct observation of the plasmon-enhanced palladium catalysis with single-molecule fluorescence microscopy

Plasmonic nanostructures have been proved effective not only in catalyzing chemical reactions, but also in improving the activity of non-plasmonic photocatalysts. It is essential to reveal the synergy between the plasmonic structure and the non-plasmonic metal photocatalyst for expounding the underlying mechanism of plasmon-enhanced catalysis. Herein, the enhancement of resazurin reduction at the heterostructure of silver nanowire (AgNW) and palladium nanoparticles (PdNPs) is observed in situ by single-molecule fluorescence microscopy. The catalysis mapping results around single AgNW suggest that the catalytic activity of PdNPs is enhanced for ~ 20 times due to the excitation of localized surface plasmon resonance (LSPR) in the vicinity of the AgNW. This catalysis enhancement is also highly related to the wavelength and polarization of the excitation light. In addition, the palladium catalysis is further enhanced by ~ 10 times in the vicinity of a roughened AgNW or a AgNW–AgNW nanogap because of the improvement of catalytic hotspots. These findings clarify the contribution of plasmon excitation in palladium catalysis at microscopic scale, which will help to deepen the understanding of the plasmon-enhanced photocatalysis and provide a guideline for developing highly efficient plasmon-based photocatalysts.