Single-precursor-derived carbon and nitrogen co-doped CuO nanozymes for colorimetric detection of tetracycline

Herein, carbon and nitrogen co-doped CuO nanozymes (C-N/CuO) were constructed via direct pyrolysis of copper(II) phthalocyanine (CuPc) as a single-source precursor. This approach enables the simultaneous incorporation of Cu, C, and N without additional dopants, offering a simple route to tune the electronic structure of CuO. The sample obtained at 400 °C (C-N/CuO-400) exhibits enhanced peroxidase-like activity, which is attributed to C-N incorporation and reduced particle size. In the presence of H₂O₂, C-N/CuO-400 catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by reactive oxygen species (˙OH and ¹O₂). Tetracycline (TC) suppresses this process, resulting in a decreased color signal. Based on this effect, a colorimetric and smartphone-assisted method was developed for TC detection, showing a linear range of 1-40 µM with detection limits of 0.15 µM and 0.38 µM. This work provides a simple and effective strategy for nanozyme-based sensing.