Metal clusters activated SnO2 thin film for low level detection of NH3 gas

In this communication, the fabrication of NH3 gas sensor based on SnO2 thin films modified with metallic clusters (MCs) has been reported. Amongst all the MCs (Pt, Pd, Cr, Au, Cu and In), the integration of Pt MCs of thickness ∼8 nm and 200 μm diameter onto surface of SnO2 thin film exhibit a high sensing response (∼25.7) with a fast response time (∼1 s) towards 450 ppm NH3 at an operating temperature of 230 °C. Pt MCs activate the spill over mechanism for NH3 gas molecules and enhance its interaction with uncovered SnO2 surface. The structural and surface morphology of SnO2 film have been studied and a correlation between the high degree of response behaviour of sensor and highly nanoporous active sensing element is identified. Sensor operation was also tested and showed a good selectivity towards ammonia over acetone, LPG, methane, TCE, NOx, IPA, chloroform and CO2. The Pt/SnO2 sensor was tested for repeated cycles and no significant deterioration in the sensing response was observed and sensor was found to be completely reversible operation for a long span of time. The simple and low-cost sensor structure shows the promising results for the practical realization in NH3 sensing.