Facile synthesis of Co3O4/g-C3N4 with enhanced peroxidase-like activity for the colorimetric detection of glutathione and l-cysteine

Abstract

Biothiols, such as glutathione (GSH) and L-cysteine (L-Cys), are essential for maintaining human physiological homeostasis, and their abnormal levels are closely associated with various diseases. Herein, a composite nanozyme, Co₃O₄/g-C₃N₄, with a significantly enhanced peroxidase-like activity was successfully synthesized by combining ZIF-67-derived Co₃O₄ with graphitic carbon nitride (g-C₃N₄). 3,3′,5,5′-Tetramethylbenzidine (TMB) could be efficiently oxidized to blue TMB (oxTMB) by Co₃O₄/g-C₃N₄ in the presence of H₂O₂, while biothiols (GSH and L-Cys) inhibited this catalytic reaction due to their antioxidant properties, leading to a visible color change. Based on this mechanism, a colorimetric detection method was established for the quantitative analysis of GSH and L-Cys with linear ranges of 0–30 µM for GSH and 1–30 µM for L-Cys. Moreover, a convenient smartphone-assisted sensing platform was established for the detection of GSH and L-Cys, benefiting from the Co₃O₄/g-C₃N₄-based colorimetric strategy. These established methods could be applied to detect GSH and L-Cys in human urine, demonstrating great potential for self-health monitoring.