Investigation of Gas-Sensing Performance of ${\rm SnO}_{\rm 2}$ Nanoparticles With Different Morphologies

Two forms of tin oxide (SnO
₂
) nanoparticles (NPs) with different morphologies (small dispersed NPs and big clusters aggregated from small NPs) were synthesized via chemical solution methods and assembled into films on Si/SiO
₂
substrate for a comparative sensing study, which were tested for the responses to H
₂
S reducing gas and NO
₂
oxidizing gas, respectively. Similar detection limits to part per million levels H
₂
S reducing gas and part per billion (ppb) levels NO
₂
oxidizing gas were observed for both films with different morphologies at room temperature. It was found, however, that the small NP film showed higher sensitivity and detection limit to H
₂
S down to ppb levels after surface modification by depositing Au nanocatalysts, while SnO
₂
big cluster film presented better sensitivity to NO
₂
detection down to ppb levels with/without the nanocatalyst modification, much determined by the morphology of these two forms of NPs. The sensing mechanism is also discussed.