High sensitivity detection of H2O2 and glucose based on carbon quantum dots-catalyzed 3, 3′, 5, 5′-tetramethylbenzidine oxidation

Carbon quantum dots (CQDs) with fluorescence quantum yield of 15.8% were prepared from pig liver via hydrothermal method. These CQDs exhibited peroxidase-like activity and catalyzed the oxidation of 3,3',5,5' tetramethylbenzidine (TMB) by H2O2 to form oxidized TMB (ox-TMB) with an absorption peak at 652 nm. The influences of acidity, temperature and incubation time on the catalytic activity of CQDs were studied. Under the conditions of pH 3.5, temperature of 40 degrees C, CQDs of 200 mu L, TMB of 2.0 mM, and incubation time of 30 min, the increase of absorbance at 652 nm, induced by the CQD-catalyzed TMB oxidation, enabled the sensitive determination of H2O2 in the range of 5.0-60.0 mu M with a low detection limit of 0.86 mu M. Given that H2O2 was one of the products of glucose catalytic oxidation, a convenient colorimetric method for glucose determination was also developed. The experimental results showed that the absorbance response was strongly correlated with glucose concentration of 10.0-200.0 mu M. The detection limit of glucose was calculated to be 2.89 mu M. The method developed herein exhibited excellent selectivity with no interference from the matrix (such as lactose, fructose, sucrose, ascorbic acid and various amino acids). Moreover, this method was used for determining glucose in human serum with satisfactory results.