WS2 nanosheets as a potential candidate towards sensing heavy metal ions: A new dimension of 2D materials

Here we present unique features of metal ion treated tungsten disulphide (WS2) nanosheets. Through chemical exfoliation of bulk WS2, multilayered WS2 nanosheets were prepared and drop casted on finger like Cu (Copper) electrodes, thereby fabricating 2D material-based sensor units. Later, I-V characteristics of the units were investigated with and without heavy metal ion treatment. In case of Zn2+ ions, the sensor unit shows prominent negative resistance in the positive potential region of the I-V characteristics., which was further quantified by taking the difference between the peak and valley point of the negative resistance region to selectively detect Zn2+ ions. Accordingly, the response of the novel scheme was visualized by plotting calibration curve for Zn2+ ions, accompanied by analysis of the influence from other interfering ions through I-V characteristics. Excellent selectivity towards Zn2+ ions, with limit of detection 0.94 +/- 0.05 ppb was found. Sensitivity of 0.63 +/- 0.05 mu A per ppb was achieved, accompanied by a rapid response.