Synthesis of catalytically active carbon quantum dots and its application for colorimetric detection of glutathione

Carbon quantum dots (CQDs) were prepared from wood soot, and the CQDs could catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the presence of H2O2 to form oxidized TMB (ox-TMB) with an absorption peak at 652 nm. It was found that the introduction of glutathione (GSH) could cause the reduction of ox-TMB, resulting in a decrease of the absorbance at 652 nm. Based on this, a highly sensitive colorimetric sensor for detection of GSH was fabricated. The influences of various experimental variables, including pH, temperature, and the concentrations of H2O2, CQDs and TMB, on the analytical performance of the method were systematically investigated. Under the conditions of pH 3.5, temperature 35 degrees C, H2O2 1.0 mM, CQDs 2.5 mu g/mL and TMB 0.5 mM, the response was linearly proportional to the concentration of GSH within the range of 0.05 to 20 M with a low detect limit (3 sigma/k) of 0.016 M. The method was successfully applied to determination of GSH in human serum samples with the recovery of 95.7%-103.6%.