Colorimetric evaluation of total antioxidant capacity based on peroxidase-like nonstoichiometric Cu_2-xSe nanoparticles

Antioxidants can help trap and neutralize free reactive oxygen species to reduce their damage. Thus, it is important to evaluate the content of antioxidants in foods and drugs. In this paper, a simple and sensitive colorimetric sensing platform for total antioxidant capacity (TAC) detection was developed based on the peroxidase-like nanozyme of nonstoichiometric copper selenide nanoparticles (Cu2-xSe NPs). The Cu2-xSe NPs with copper vacancy structures can accelerate intramolecular charge transfer and effectively catalyze the oxidation of chromogenic substrate colorless 3,3 ' 5,5 '-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB), exhibiting that they had good peroxidase-like activity. Base on the good activity of Cu2-xSe NPs peroxidase mimics, a colorimetric sensing array combining UV-vis spectrometer, naked eye and smartphone-based digital image analysis for three typical antioxidant acids (ascorbic acid (AA), gallic acid (GA) and citric acid (CA)) were realized and the platform was successfully used for evaluating the TAC in the medical tablets, beverages and fruit juices.