ZIF-8-Derived Zn Single-Atom Nanozyme with High Oxidase Activities for Highly Sensitive Colorimetric Detection of Tannic Acid in Tea

This work demonstrates that Zn single atoms exhibit intrinsic oxidase-like activity. Zn single-atom nanozymes (Zn-SAs/NC) were synthesized via direct pyrolysis of ZIF-8 at 1000 °C under N 2 atmosphere, which retains a rhombic dodecahedral morphology with atomically dispersed Zn sites. Crucially, Zn-SAs/NC exhibited pronounced oxidase-like activity, efficiently catalyzing the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB without exogenous H 2 O 2 . Control experiments with metal-free NC confirmed that the catalytic activity originated specifically from the Zn single atoms, challenging the traditional view of Zn's catalytic inertness. The Zn-SAs/NC-catalyzed TMB oxidation system was exploited for colorimetric detection of tannic acid (TA) based on TA's inhibitory effect, achieving high sensitivity (LOD = 0.016 µM) and selectivity. Successful application in real tea samples validated the method's practicality, establishing Zn single atoms as a novel nanozyme platform. Graphical This work develops a Zn single-atom nanozyme (Zn-SAs/NC) derived from ZIF-8 pyrolysis, which exhibits robust intrinsic oxidase-like activity for highly sensitive and selective colorimetric detection of tannic acid with a low detection limit of 0.016 µM.