Synergistic modulation of oxidation state of Pt nanozymes via Pd doping and ZIF-67 support enhances the catalytic efficiency for immunoassay detection.

Modulating the oxidation state of active sites presents a promising strategy for enhancing catalytic performance. However, the intrinsic electronic properties of a single regulatory strategy make it difficult to accurately control the oxidation state of nanozymes. Herein, we design high-efficiency PtPd@ZIF-67 nanozymes by integrating two modulation strategies (Pd doping and ZIF-67 support) to effectively regulate the oxidation state of the Pt active center. The results demonstrate that PtPd@ZIF-67 nanozyme with a moderate oxidation state exhibits the best catalytic activity, which is 1.97- and 3.87-fold higher than that of Pt@ZIF-67 and Pt@ZIF-67-S (S represents the removal of ZIF-67 support), respectively. Theoretical calculations indicate that the moderate oxidation state of Pt enhances the adsorption of OH, thereby reducing the energy barrier of the key reaction step (2∗OH → ∗O + HO) and ultimately improving the catalytic activity of nanozyme. Crucially, PtPd@ZIF-67 nanozyme was successfully employed to develop a novel indirect competitive immunoassay for the detection of zearalenone, with a limit of detection of 0.534 ng L. This work provides a potential strategy for the rational design of high catalytic performance nanozymes for immunoassay detection.