Investigations on MWO4 (M = Cu, Zn, Cd and Sn) nanostructures for detecting toluene gas at room temperature

Constructing the room temperature (RT) based semiconductor gas sensors is pivotal for its commercialization. In this investigation, four well-known tungstate based CuWO4, ZnWO4, CdWO4 and SnWO4 nanomaterials were prepared by the hydrothermal method. These materials were characterized by XRD, FESEM, TEM, EDX, DFT, BET surface area, XPS, FTIR and UV-Vis DRS. The selectivity alongside the response of these compounds were tested by sensing gases like 1-butanol (C4H10O), acetone (C3H6O), ethanol (C2H6O), benzene (C6H6), toluene (C6H5CH3) and xylene (C8H10). The gas sensing studies performed on these compounds conclusively disclose that these sensors have adequate sensitivity and response to detect the tested gases at RT. Among these compounds, owing to unique crystal structure α-SnWO4 sensor exhibits an enormous selectivity with a response of 12.32 towards the detection of toluene and the detection limit is 5 ppm. Compared to the other compounds, SnWO4 offers the shortest conducting pathways viz. O-Sn-O-Sn/O-W-O-W-O which facilitated the effective charge transport for sensing toluene gas at RT.