Engineering Cu/Co-NC dual-atom nanozyme with high oxidase-mimicking activity for colorimetric sensing of tannic acid

Enhancing the catalytic activity of traditional single-atom nanozymes via incorporating dual-metal atomic centers is a significant progress in catalysis field. In this work, we introduce a pyrolysis method to prepare Cu/Co-NC dual-atom nanozymes (Cu/Co-NC DANs) with different Cu 2+ : Co 2+ mass ratios. The optimized Cu/Co-NC DANs (with a Cu 2+ : Co 2+ mass ratio of 70:30) indicated remarkably higher catalytic activity compared to monometallic counterparts, which is due to the synergistic effect of bi-metallic sites. Mechanistic studies revealed that the DANs effectively catalyze the decomposition of O 2 , generating superoxide radical (O 2 • − ) and singlet oxygen ( 1 O 2 ). These reactive species subsequently oxidize TMB to ox-TMB, causing a color change from colorless to green-blue. Based on the inhibitory effect of tannic acid (TA) on the oxidation of TMB, we developed a colorimetric assay for TA with a limit of detection of 0.02 μM. This chromogenic system was also successfully integrated with a smartphone-based detection achieving an LOD as low as 0.14 μM. These findings offer a cost-effective and practical strategy for accurate quantification of TA in real samples.