Silver Ion-Facilitated Singular Poulos-Kraut Mechanism of O-O Heterolysis to Enhance the Light Activation of HO over Peroxidase-Mimicking Photonanozymes.

The Poulos-Kraut heterolytic O-O cleavage mechanism is essential for natural peroxidases to activate HO. Current existing peroxidase-mimicking nanozymes, including photonanozymes (PNZs), however, are generally believed to prefer the Fenton-type mechanism of O-O homolysis, which produces OH radicals. Here, Ag ions are introduced into TiO PNZs to boost the hot hole-driven O-O heterolysis for the expedited HO activation in the peroxidase-like photonanozymatic reaction while inhibiting the Fenton-type O-O homolysis. The Ag-facilitated Poulos-Kraut heterolytic O-O cleavage mechanism for HO activation is explicated in terms of the speedy capture and exhaustion of photogenerated electrons by Ag and the dissociation of the peroxo-oxygen bridge in Ti-O-OH promoted by accumulated hot holes. Moreover, the enhanced photonanozymatic activity of TiO PNZs enables the construction of a rapid colorimetric sensing platform for Ag determination. This work provides valuable insights into the mechanism of HO activation and exemplifies a novel photoregulation strategy for controlling reaction pathways in nanozymes.