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

Abstract

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 μM with a 3σ limit of detection of 10 nM. Moreover, this assay for TNT is also applicable to real water samples.