Extraction of biomass carbon dots with peroxidase activity from peanut shells for visual sensing of edible cysteine

With the increase of agricultural production, the utilization of biomass waste has become the focus of current research. In this study, Si-containing carbon dots (Si-CDs) were prepared from peanut shells by one-pot hydrothermal method. These Si-CDs exhibit peroxidase-like activity and can catalyze H 2 O 2 oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce a chromogenic reaction, while cysteine (Cys) can reduce the oxidation product of TMB (ox-TMB) to discolor it. A method for the determination of Cys using Si-CDs as peroxidase was developed. In addition, the effect of environmental factors on the enzyme-like reaction was investigated. The experimental results showed that the best catalytic effect was achieved at pH = 2.5, reaction temperature of 60 °C, and reaction time of 55 min when the concentrations of TMB and H 2 O 2 were 5 mmol·L −1 and 2.75 mmol·L −1 , indicating that Si-CDs still have the potential for enzymatic activity in extreme environments. The decrease in absorbance of the system (ΔA) showed a good linear relationship with Cys in the range of 5–100 μmol·L −1 , and the limit of detection was 0.037 μmol·L −1 . This sensor was successfully used for the determination of edible Cys content.