Improved selectivity of SnO2:C alloy nanoparticles towards H2 and ethanol reducing gases; role of SnO2:C electronic interaction

Abstract In the present study, changes in the sensing properties of SnO 2 on Carbon incorporation have been investigated in detail. The gas sensing response of size-selected SnO 2 and SnO 2 :C alloy nanoparticles prepared by gas phase deposition method have been investigated for H 2 and ethanol over a varied temperature range (50 °C–200 °C). The incorporation of carbon into SnO 2 lattice results in a large change in the sensing behaviour towards the two gases both having reducing nature. SnO 2 :C nanoparticles show positive sensing response for H 2 and negative sensing response for ethanol, whereas SnO 2 nanoparticles show a normal sensing response of an n-type semiconductor towards both the reducing gases. Observed values of activation energy of sensing and energy levels of O-vacancies observed in the PL spectra of SnO 2 and SnO 2 :C are consistent with these results. (i) Catalytic C–H interaction and (ii) modified work function of SnO 2 and C on hydrogenation resulting in alteration of electronic exchange between SnO 2 and C, and (iii) passivation effect of carbon during SnO 2 -ethanol interaction along with a possibility of reduction in SnO 2 sites in SnO 2 :C nanoparticles, are responsible for the observed behaviour. The present study shows that the incorporation of C in SnO 2 nanoparticles results in excellent selectivity towards H 2 and ethanol (both having reducing nature) in the low temperature range, normally not observed in oxide based resistive sensors.