Abstract
The plasmon-driven oxidation of amine (-NH2) groups and the reduction of nitro (-NO2) groups on a nanostructured metal surface in an aqueous environment have been reported experimentally and theoretically. The question of which process occurs first in the aqueous environment is an interesting question in the field of plasmon-related photochemistry. Para-nitroaniline (PNA), with both nitro (-NO2) and amine (-NH2) groups, is the best candidate for studying the priority of the plasmon-driven oxidation and the reduction reactions in an aqueous environment. Using surface-enhanced Raman scattering (SERS) spectroscopy, our experimental results and theoretical simulations reveal that PNA is selectively catalyzed to 4,4'-diaminoazobenzene (DAAB) through the plasmon-assisted dimerization of the nitro (-NO2) group into an azo group in an aqueous environment. This indicates that the plasmon-driven reduction of the nitro (-NO2) group clearly occurs before the oxidation of the amine (-NH2) group in an aqueous environment. The plasmon-driven reduction of PNA to DAAB is a selective surface catalytic reduced reaction in aqueous environment.