Selectivity towards acetylene gas of flame-spray-made Nb-substituted SnO<inf>2</inf> particulate thick films

Abstract

0.1–2 wt% Nb-doped SnO2 nanoparticles were produced via flame spray pyrolysis (FSP) in a single step for the first time. The structural characterizations including X-ray diffraction, nitrogen sorption analysis, electron microscopy, energy dispersive and photoelectron X-ray spectroscopy revealed that Nb5+ species were substitutionally doped into the lattice of nanocrystalline tetragonal SnO2 nanoparticles (5–15 nm). The sensing layers produced by spin coating were tested towards 0.05–1 vol% C2H2 at 200–400 °C in air. Gas-sensing results indicated that the optimal Nb content of 0.5 wt% provided the best sensor response of ~776 with an excellent response time of 1.1 s to 1 vol% C2H2 at the optimal sensing temperature of 350 °C. Additionally, the optimal Nb-doped SnO2 sensor exhibited low humidity dependence, good long-term stability and high C2H2 selectivity relative to HCHO, CH3OH, C2H5OH, C3H6O, CH4, C2H4, C6H6, C7H8, C8H10, H2, NO2, NO and NH3. Moreover, low direct cross interferences were demonstrated against CH3OH and C8H10. The results were explained by the catalytic and electronic roles of n-type Nb dopants on C2H2 interaction. Thus, the Nb-doped SnO2 sensor is an attractive candidate for selective C2H2-sensing applications.