Facile colorimetric assay for trinitrotoluene based on the intrinsic peroxidase-like activity of MoS2 nanosheets

In this study, a facile colorimetric assay for 2,4,6-trinitrotoluene (TNT) in aqueous solution is developed based on the intrinsic peroxidase-like activity of cysteine protected molybdenum disulfide nanosheets (Cys-MoS2 NSs). The Cys-MoS2 NSs, obtained from sonication-assisted exfoliation of bulk MoS2 crystals, possess a great intrinsic peroxidase-like activity for the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to produce a blue-colored solution. Significantly, the oxidation of TMB was weakened or even prevented in the presence of TNT because of the formation of a Meisenheimer complex between TNT and TMB, which results in a marked decrease in the absorption and a color change of MoS2-TMB-H2O2 solution (TMB reaction system). The relative absorbance is proportional to the logarithm of concentration of TNT in the range of 0-50 mu M with a 3 sigma limit of detection of 10 nM. Moreover, this assay for TNT is also applicable to real water samples.