Exploitation of SnO₂/Polypyrrole Interface for Detection of Ammonia Vapors Using Conductometric and Optical...

This study describes the construction of a lab-built Surface Plasmon Resonance (SPR) system for gas sensing applications employing a highly sensitive and trustworthy optical approach. The nanocomposite thin film of tin oxide (SnO₂) and Polypyrrole (PPy) were prepared for sensing highly toxic gas, i.e., ammonia (NH₃) gas. The gas sensor was validated by both optical and conductometric techniques of gas sensing. The optical SPR gas sensor is based on the change in refractive index at the SnO₂/Polypyrrole (PPy) interface with gas adsorption (NH₃). The thickness of SnO₂ and Polypyrrole thin films was optimised using theoretical calculations for a sharp SPR reflectance curve. The manuscript also offers theoretical SPR curves for different PPy and SnO₂ layer thicknesses. To support the theoretical conclusions, the effects of NH₃ gas on the prism/Au/SnO₂/Polypyrrole system were also investigated experimentally. In comparison to other research described in the literature, it was observed that the constructed sensor's sensitivity was higher. The obtained results demonstrate the utility of the SPR setup in the investigation of the interactions of adhered gas molecules with dielectrics and gas sensing. For conductometric gas sensing studies, the film having optimised thicknesses for sharp SPR reflectance curves was separately prepared on Interdigitated Electrodes. At a low working temperature of roughly 150 °C, the sensing response of the constructed film was observed and found to be maximal (60).