Cobalt single-atom nanozymes with peroxidase-like activity for the development of electrochemical and colorimetric dual-mode sensors for catechol detection

The advancement of rapid phenolic contaminant identification systems holds vital significance in maintaining ecological security while strengthening health protection frameworks. Currently, cobalt-based nanozymes suffer from a significant catalytic activity decline due to active site aggregation, which limits their application in phenol detection. To address this challenge, in this study, highly dispersed cobalt single-atom nanocomposites (CuCo-NPC) were prepared by a cascade anchoring strategy using copper-based metal–organic frameworks (Cu-MOFs) as templates. Based on its excellent electrocatalytic and peroxidase-like activities, an electrochemical-colorimetric dual-mode sensor was constructed to simultaneously monitor the electrochemical signals of phenolics at the modified electrode and the colorimetric signals generated by the reduction of the oxidized 3,3′,5,5′-tetramethylbenzidine (oxTMB) by phenolics. Under optimized experimental parameters, the dual-mode sensing platform demonstrated excellent sensing performance with remarkable sensitivity and selectivity for catechol (CC) determination. The detection limits were determined to be 0.82 μM and 0.34 μM when employing electrochemical and colorimetric analytical approaches, respectively. In the actual water sample spiking experiments, the recoveries of CC ranged from 97.6 % to 100.8 %. To some extent, the single-atom dispersion strategy has overcome the activity limitation of cobalt-based materials and provided a scalable dual-mode sensing method for the on-site detection of phenolic pollutants.