Response and selectivity of conductive polymer/metal oxide gas sensors in presence of binary mixtures of ammonia with alcohols and acetone

Abstract

In this study, nanocomposites of conductive polymers (polyaniline and polypyrrole) with metal oxide nanoparticles (SnO₂ and ZnO) were synthesized and evaluated as ammonia sensors exposed to single-gas or binary-gas mixtures (ammonia with methanol, ethanol, or acetone) at room temperature. Sensor composites were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), and atomic force microscopy (AFM), that revealed the microstructural features influencing sensor performance. Taguchi experimental design was, first used to quantify the effects of polymer type, nanoparticle type, and nanoparticle loading on gas sensor response and selectivity when exposed to ammonia as single gas. The second experimental design was used to study the effect of these factors in presence of an interfere gas showing that the conductive polymer type dominated sensor behavior, while nanoparticles provided synergistic, polymer-dependent enhancements in charge transfer and active-site availability. Coexisting vapors affected ammonia detection, with acetone producing the least interference. The PAni/SnO₂ (20 wt%) composite was identified as optimal, delivering high ammonia response and selectivity. Long-term stability tests after 18 month, demonstrated a retention of over 86 % of the initial response, and cycling experiments confirmed repeatable operation. In addition, it we found that the moderate relative humidity (RH) enhances protonic conduction, while high RH partially reduces response due to polymer swelling. This work establishes a rationally engineered polymer–metal oxide nanocomposite platform for selective, durable ammonia sensing under realistic mixed-gas and humidity conditions. © 2025 Elsevier B.V.