Spectroscopic determination of the role of vanadyl oxygen in room temperature NH sensing by VO nanoparticles.

In the present study, a multi-modal approach consisting of in-situ photoluminescence, Raman, and UV-Vis absorption spectroscopic studies is carried out along with chemiresistive sensing to unveil the mechanism of NH gas sensing by VO nanoparticles in ambient air. VO nanoparticles with an average size of 49 nm show a superior sensor response of 17 ± 1.5 % towards 1 ppm of NH gas with a response and recovery time of 96 s and 45 s, respectively. The photoluminescence and UV-Vis absorption studies in the presence of NH reveal electron doping to a new energy level at 1.84 eV, resulting in conduction band filling and increase in the optical band gap. The intensity of the photoluminescence spectrum shows an increase in the presence of NH gas as a result of this electron doping. The sensor response from the optical sensing carried out by in-situ photoluminescence study is 43 % for 40 ppm of NH gas. The vanadyl oxygen site is the most active in the sensing process, as evident by a selective enhancement in the intensity of V-O (vanadyl) bond vibration. This study gives an experimental evidence for the changes in optical and electronic properties of VO on the adsorption of NH gas molecules.