Ultrasensitive and selective sensing material of ultrafine WO3 nanoparticles for the detection of ppb-level NO2

Abstract

WO3 nanoparticles were successfully deposited onto SiO2/Si substrates equipped with a pair of interdigitated Pt electrodes by heating tungsten filaments in a vacuum chamber. The morphology and structure of the obtained WO3 nanoparticles were characterized by means of field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD). The results revealed that these nanoparticles show a sphere-like structure and their sizes depend on deposing pressure. Furthermore, the NO2 sensing properties of WO3 nanoparticles were studied. The intrinsic WO3 nanoparticles with small size exhibit surprisingly high response to ppb-level NO2, low detection limit, excellent selectivity, and good stability at a very low operating temperature, demonstrating their potential in monitoring ppb-level NO2 at low power consumption. In addition, an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurement was carried out to propose the NO2 sensing mechanism, which demonstrates that adsorbed nitrate and nitrite species are the main species on WO3 surface. Furthermore, the intensity and the sensing response show the same trend with respect to the temperature, indicating that nitrate and nitrite species play a joint role in NO2 sensing behavior on WO3 surface.