Influence of morphology and structure geometry on NO₂ gas-sensing characteristics of SnO₂ nanostructures synthesized via a thermal evaporation method

SnO₂ microwires, nanowires and rice-shaped nanoparticles were synthesized by a thermal evaporation method. The diameters of microwire and nanowire were 2 μm and 50-100 nm, respectively, with approximately the same length (∼20 μm). The size of nanoparticles was about 100 nm. It was confirmed that the as-synthesized products have SnO₂ crystalline rutile structure. The sensing ability of SnO₂ particle and wire-like structure configured as gas sensors was measured. A comparison between the particle and wire-like structure sensors revealed that the latter have numerous advantages in terms of reliability and high sensitivity. Although its high surface-to-volume ratio, the nanoparticle sensor exhibited the lowest sensitivity. The high surface-to-volume ratio and low density of grain boundaries is the best way to improve the sensitivity of SnO₂ gas sensors, as in case of nanowire sensor which exhibited a dramatic improvement in sensitivity to NO₂ gas.