A facile colorimetric sensor for ultrasensitive and selective detection of Lead(II) in environmental and biological samples based on intrinsic peroxidase-mimic activity of WS2 nanosheets.

Two-dimentional layered WS2 nanosheets with rich active edge exhibit intrinsic peroxidase-mimic activity, which make them an ideal material for sensor design. However, there is still lack of research on the catalysis and regulation mechanisms of the layered WS2 nanosheets as well as their application in the detection of hazardous substances. Herein, the regulatory effect of Pb(II) on the peroxidase-mimic activity of the layered WS2 nanosheets was firstly investigated, which enable us to construct a novel and facile colorimetric sensor for ultrasensitive and selective detection of Pb(II). To improve the performance of colorimetric sensor, some important parameters like buffer conditions, substrates and temperature have been investigated. Under the optimal conditions, the catalytic kinetics of layered WS2 nanosheets were extensively investigated. The peroxidase-mimic catalytic reaction was proved to be the "ping pong" mechanism, and the regulatory effect of Pb(II) on layered WS2 nanosheets was agreed with noncompetitive inhibition. The absorbance variation of colorimetric sensor is proportionally related to the concentration of heavy metals, which enable us to easily distinguish whether Pb(II) exceeds the permissible level in less than 20 min even by the naked eyes. The limit of detection (LOD) and the limit of quantification (LOQ) of the proposed colorimetric sensor for Pb(II) were determined as low as 4 μg L-1 and 13.3 μg L-1, and displays excellent selectivity against other competitive metal ions. Moreover, the further studies also validate the applicability of colorimetric sensor in several actual samples, indicating that our strategy may has prospective applications for Pb(II) detection in environment and biological samples.