Ammonia Sensing by Sn_1–xV_xO₂ Mesoporous Nanoparticles

Chemiresistive gas sensing by metal oxide based materials has been usually explained in terms of surface chemistry and band structure modifications due to factors such as chemical composition, particle surface to volume ratio, material morphology, temperature, and surface oxygen vacancy. In this work, keeping parameters such as particle size, morphology, surface area, temperature, and surface oxygen vacancy fixed, we have for the first time attempted to delineate quantitatively the role of crystal structure and surface electronic states in improving gas sensing responses of doped nanosized metal oxide samples. While vanadium-doped tin oxide samples show a nearly 4-fold increase in 10 ppm ammonia sensing responses, the Sn0.696V0.304O2 sample shows ∼1.2 times more sensing response as compared to Sn0.657V0.343O2. The ammonia sensing behavior has been found to be directly correlated to crystal structures and concentrations of various oxidation states of vanadium dopants present in the studied samples. Detailed comparative analysis of crystal and electronic structures of the samples has revealed the mechanism of enhancement in the ammonia sensing behavior of vanadium-doped tin oxides. It is expected that similar mechanisms might be responsible for enhancement in gas sensing properties of other metal oxide based systems.