Biomass-based Carbon Dots as Peroxidase Mimics for Colorimetric Detection of Glutathione and L-Cysteine

Biomass-carbon dots(named as B-CDs) have been successfully prepared via facile one-step hydrothermal reflux treatment at a low temperature from passion fruit peel. The as-prepared B-CDs had a uniform sphere morphology and size of 1–3 nm, which possessed rich nitrogen/oxygen-containing functional groups. B-CDs could imitate peroxidase and accelerate the reaction process of HO oxidizing the substrate 3,3’,5,5’-tetramethylbenzidine(TMB), which caused an obvious color change in the solution due to the oxidization of achromic TMB into blue oxidation product(ox-TMB) with an absorption peak at 652 nm. Furthermore, the product could be further reduced to native colorless TMB by the reducing agent glutathione or L-Cysteine. Thus, depending on the peroxidase-like properties of B-CDs, we developed a colorimetric approach to detecting both glutathione and L-Cysteine, which showed superior selective and sensitive detection towards glutathione and L-Cysteine in a linear range of 0–20 µmol/L. The limits of detection were 0.62 and 0.58 µmol/L, respectively.