Cu-Mo dual-doped carbon nitride with excellent peroxidase-like activity for portable colorimetric quantifying D-penicillamine

A low-cost Cu-Mo dual-doped carbon nitride nanozyme was synthesized. • It shows excellent peroxidase-like activity via superoxide radical pathway. • A smartphone-based platform enables portable and visual D-PA detection. D-Penicillamine (D-PA), a sulfur-containing amino acid, is used to treat various diseases such as Wilson's disease, fibrotic lung disease, and cystinuria. However, excessive intake of D-PA can cause adverse effects, necessitating the development of accurate quantitative detection methods. This study aimed to establish a visual colorimetric method for D-PA detection using a synthesized Cu-Mo dual-doped carbon nitride nanomaterial ( Cu - Mo - VC - CN ). The synthesis capitalizes on the simplicity and cost-effectiveness of a one-pot thermal polymerization reaction, utilizing only inexpensive and commercially available precursors, namely copper chloride, ammonium molybdate, urea, and vitamin C. The material exhibited exceptional peroxidase-like activity, catalyzing the oxidation of TMB by H 2 O 2 via a superoxide radical pathway. The optimal reaction conditions were: temperature 30 °C, time 30 min, pH 5.5, TMB concentration 0.2 mM, and H₂O₂ concentration 0.2 mM. Steady-state kinetic analysis revealed that the Cu - Mo - VC - CN nanozyme had Michaelis-Menten constants ( K ₘ) of 0.083 mM for TMB and 0.603 mM for H 2 O 2 . Under optimal conditions, the system enabled highly sensitive D-PA quantification with a linear range of 0.5–100 μM and a detection limit of 0.45 μM. The nanozyme was successfully applied to determine D-PA content in pharmaceutical tablets with satisfactory recovery (from 97.73 to 98.27%). Furthermore, a smartphone-based testing platform was established to provide a portable and practical solution for the real-time monitoring of D-PA. This work provides both an efficient strategy for developing multi-metal-doped nanozymes and a reliable colorimetric platform for D-PA monitoring. Download: Download high-res image (279KB) Download: Download full-size image