Silver Ion-Facilitated Singular Poulos-Kraut Mechanism of O-O Heterolysis to Enhance the Light Activation of H 2 O 2 over Peroxidase-Mimicking Photonanozymes.

The Poulos-Kraut heterolytic O-O cleavage mechanism is essential for natural peroxidases to activate H 2 O 2 . 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 2 PNZs to boost the hot hole-driven O-O heterolysis for the expedited H 2 O 2 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 H 2 O 2 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 2 PNZs enables the construction of a rapid colorimetric sensing platform for Ag + determination. This work provides valuable insights into the mechanism of H 2 O 2 activation and exemplifies a novel photoregulation strategy for controlling reaction pathways in nanozymes.