Plasmon-Induced Nanolocalized Reduction of Diazonium Salts

Surface grafting from diazonium solutions triggered by localized surface plasmon has been investigated. An organic layer that is 20-30 nm thick is easily grafted onto gold nanoparticles (AuNPs) by visible-light illumination in a few minutes without any reducing agent or molecular photocatalyst. Grafting depends on the wavelength and polarization of the incident light. As a consequence, the orientation of the growth of the layer deposited on the AuNPs can be controlled by polarized light. Grafting is also highly enhanced between adjacent AuNPs or at the corners of triangular AuNPs, that is, in plasmonic hot spots. These results clearly demonstrate plasmon enhancement and strongly suggest that the transfer of hot electrons from the excited plasmonic NPs to the diazonium is the main mechanism. They also confirm that localized surface plasmon resonance can induce nanolocalized electrochemical reactions, thus contributing to the field of "plasmonic electrochemistry".