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.