Cu-NC single-atom nanozymes with peroxidase-like activity for colorimetric detection of d-penicillamine

Most conventional nanozymes have poor specificity and low activity, and designing high-performance nanozymes remains a challenge. In contrast, single-atom nanozymes have high atom utilization and high reactivity. Here, we prepared Cu single-atom nanozymes (Cu-NC) with excellent peroxidase-like activity by high-temperature pyrolysis using Cu as a transition metal source. The introduction of Cu formed the Cu-N_x active site, which accelerated charge transfer between the reactants and the active site and was the key for improving the activity. With Cu-NC as a catalyst, H₂O₂ rapidly oxidized 3,3',5,5'-tetramethylbenzidine (TMB) to oxTMB, and the solution turned blue with strong absorption at 652 nm. Because d-penicillamine (D-PA) can reduce oxTMB or react with reactive oxygen species radicals to inhibit the color reaction, we built a colorimetric sensing platform around Cu-NC for the determination of D-PA and successfully used it for the determination of D-PA in urine samples. This work provides new ideas for the design of high-performance nanozymes and the detection of D-PA in real environments.