Temperature Dependent Sensitivity Inversion in SnO_(1.8):Pd Mixed Nanoparticle Layer Based CO Sensors

摘要

This study reports a novel observation of the temperature dependent inversion in the CO sensitivity of the nanoparticle layers consisting of homogeneously mixed monodispersed Pd and SnO_(1.8) nanoparticles synthesized via aerosol route. Ability of sensing CO as low as 10 ppb in dry synthetic air has been observed with decrease in nanoparticle size (to 5 nm) in the samples mixed with Pd nanoparticles, as compared to samples without Pd nanoparticles which show no sensitivity to CO in ppb levels. In contrast to the conductivity increase in SnO_(1.8) in response to CO exposure in the absence of Pd, the mixed nanoparticle layers exhibit decrease in conductivity. With increase in the operating temperature (523 to 673 K) reversal in the sensitivity has been observed at higher CO concentrations. The observed behavior can be understood in terms of the physiochemical and electronic processes.