Graphitic carbon nitride with Cu²⁺ and triazole group co-doping for enhanced peroxidase-like activity and its application for glutathione detection

Nanozymes have attracted great interest in the field of biotechnology, (bio)sensing, and environmental monitoring. Herein, a co-doping strategy is proposed to enhance the peroxidase-like activity of graphitic carbon nitride (g-C3N4). Cu2+ and triazole group co-doped graphitic carbon nitride (g-C3N5-Cu2+) was derived from thermal polymerization of 3-amino-1,2,4-triazole and then coordination with Cu2+. g-C3N5-Cu2+ nanosheets (NSs) could catalyze the oxidation reaction of 3,3 ',5,5 '-tetramethylbenzidine (TMB) by H2O2 under neutral conditions, yielding 10.9-fold better catalytic activity than g-C3N4 NSs. Reactive oxygen species scavenging experiments indicated that (OH)-O-center dot played a crucial role during the catalytic process. When glutathione (GSH) was introduced, the absorbance of the system decreased because of the reduction of the oxidation product of TMB by GSH. The colorimetric method demonstrated a sensitive response for GSH with a linear range of 0.8-33.3 mu mol L-1 and a limit of detection of 0.3 mu mol L-1. The sensitivity is higher than most other peroxidase mimetic-based colorimetric methods for GSH. Finally, the feasibility for the detection of GSH in HeLa cells was demonstrated.