Plasmonic nanostructures acting as a light-driven O₂-sensitive nitroreductase mimic for enhanced photochemical oxidation of para-aminothiophenol

Nanozymes, as a novel form of enzyme mimics, have garnered considerable interest. Despite overcoming the main disadvantages of their natural analogs, they still face challenges such as restricted mimic types and low substrate specificity. Herein, we introduce a reactive ligand modification strategy to diversify enzyme mimic types. Specifically, we have utilized helical plasmonic nanorods (HPNRs) modified with para-nitrothiophenol (4-NTP) to create an oxygen-sensitive nitroreductase (NTR) with light-controllability. HPNRs act as a light-adjustable source of nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NAD(P)H), providing photon-generated energetic electrons to adsorbed 4-NTP molecules. In the presence of O₂, the activated 4-NTP transfers the captured electron to the adsorbed O₂, mimicking the electron transfer process in its natural counterpart. This enhanced O₂ activation notably boosts the oxidative coupling of para-aminothiophenol (4-ATP). Density functional theory (DFT) calculations reveal that hot electrons injected into the lowest unoccupied molecular orbital (LUMO) energy level of 4-NTP can be transferred to that of molecular oxygen. In conclusion, our findings underline the potential of the reactive ligand modification strategy in developing new types of enzyme reactions, which opens up promising avenues for the enhancement and diversification of nanozyme functionalities.