Light-switchable dual-functional enzyme-like activity of ultrasmall Pt nanoclusters

Dual-functional nanozymes, which are capable of mimicking two distinct enzymatic activities, have recently attracted considerable attention due to their promising application potential across various fields. However, research on advanced dual-functional nanozymes-particularly those with light-modulation capabilities-remains at an early stage. In this study, we successfully synthesized an ultrasmall platinum-based nanozyme using 6-aza-2-thiothymine (ATT) and L-arginine (L-Arg) as protective ligands, denoted as L-Arg/ATT-Pt NCs. Systematic steady-state optical and kinetic analyses revealed their excellent dual-functional catalytic performance toward the oxidation of classic substrate 3,3',5,5'-tetramethylbenzidine (TMB). In the presence of H₂O₂, L-Arg/ATT-Pt NCs exhibited superior peroxidase (POD)-like activity, with a low Michaelis-Menten constant (Kₘ) of 0.098 mM. Under light irradiation, the catalytic behavior switched to oxidase (OXD)-like activity, where photogenerated electron-hole pairs and subsequent reactive oxygen species (ROS) drove the efficient oxidation reaction. Transient absorption spectroscopy further indicated that the light-triggered TMB oxidation initiates on an ultrafast timescale, suggesting an efficient and green catalytic pathway. Therefore, the complementary functionalities of L-Arg/ATT-Pt NCs enhance their catalytic versatility under different conditions. Additionally, the successful application of L-Arg/ATT-Pt NCs in accelerating the oxidation of L-dopa, o-phenylenediamine (OPD) and methylene blue (MB) highlights their potential for catalyzing a wide range of substrates and their applicability in diverse fields.