Highly sensitive BTEX sensors based on hexagonal WO3 nanosheets

Hexagonal WO3 (h-WO3) nanosheets (NSs), nanoparticles (NPs) and nanorods (NRs) were synthesized by a facile, low-cost and environmentally friendly hydrothermal and sol-hydrothermal methods. The structure and morphology of the products were characterized by several techniques, such as XRD, FESEM, TEM, and HRTEM. These results showed that the as-prepared WO3 were hexagonal nanosheets and the diameter was about 400 nm. Gas sensing tests of side-heating sensors indicated that the h-WO3 NSs had the superior selectivity and sensitivity for BTEX vapors (benzene, toluene, ethylbenzene, and p-xylol), which was 9 times more than h-WO3 NPs and NRs. M the optimal working temperature of 320 degrees C, the values of response based on the h-WO3 NSs sensor to 50 ppm BTEX vapors were 12.33, 27.73, 43.17, 36.27, respectively. The gas sensing mechanism of h-WO3 NSs was discussed in terms of DFT calculation, together with the XRD patterns. The results revealed that the adsorption energy of (100) facet to chemically adsorbed O-2 molecules was more than that of (200) facet, which demonstrated strongly dependence on its exposed crystal facets to enhance gas sensing performance.