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.

中文翻译：

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基于 WS2 纳米片的内在过氧化物酶模拟活性，用于超灵敏和选择性检测环境和生物样品中的铅 (II) 的简便比色传感器

具有丰富活性边缘的二维层状 WS2 纳米片表现出内在的过氧化物酶模拟活性，这使其成为传感器设计的理想材料。然而，对于层状WS2纳米片的催化和调控机制及其在有害物质检测中的应用仍缺乏研究。在此，首次研究了 Pb(II) 对层状 WS2 纳米片的过氧化物酶模拟活性的调节作用，这使我们能够构建一种新颖且简便的比色传感器，用于超灵敏和选择性检测 Pb(II)。为了提高比色传感器的性能，研究了一些重要的参数，如缓冲条件、底物和温度。在最佳条件下，广泛研究了层状 WS2 纳米片的催化动力学。过氧化物酶模拟催化反应被证明是“乒乓”机制，并且 Pb(II) 对层状 WS2 纳米片的调节作用与非竞争性抑制一致。比色传感器的吸光度变化与重金属浓度成正比，这使我们能够在不到 20 分钟的时间内轻松辨别 Pb(II) 是否超过允许水平，即使是肉眼也能做到。所提出的 Pb(II) 比色传感器的检测限 (LOD) 和定量限 (LOQ) 低至 4 μg L-1 和 13.3 μg L-1，并且对其他竞争性金属显示出出色的选择性离子。此外，进一步的研究还验证了比色传感器在几个实际样品中的适用性，