Bidirectional photo-induced and phosphate-mediated nanozyme-based sensing platform via metal valence switching for screening multiple antioxidants.

Precise regulation of nanozyme activity is crucial for expanding their practical applications in complex multi-domain environments, yet designing a bidirectional precision regulation strategy remains a significant challenge. Herein, this study developed a novel strategy based on photoinduced and phosphate-mediated of nanozymes, enabling bidirectional and dynamic regulation of enzymatic activity. Specifically, UV-responsive nitrogen-doped carbon quantum dots (NCDs) served as photosensitive materials were introduced with 2D nanosheets copper-iron layered double hydroxide (CuFe-LDH) to form a composite structure (NCDs/LDH, NL). Photo-induced method could enhance peroxidase-like (POD) activity by facilitating interfacial electron transfer, which accelerates the valence state cycling of copper and iron centers. In addition, phosphate-mediated coordination suppressed the catalytic reaction by forming metal-oxygen-phosphorus coordination bonds that alter the electron density of the active sites. Both regulatory modalities operate by modulating the electron transfer and valence transition processes at the copper and iron active centers. Based on this mechanism, the constructed nanozyme-based sensor platform demonstrates effective performance in the accurate screening of multiple antioxidants. Principal component analysis of the response dataset revealed well-defined clustering of all six antioxidants, with 95% confidence ellipses being sharply separated, demonstrating its high discrimination capability. This work not only elucidates the regulatory principles of photo-induced method and phosphate-mediated coordination in the bidirectional control of nanozyme activity, but also provides a new design pathway for developing intelligent nanozymes applicable to complex biological and environmental systems.