Polyaniline/CuO Nanoparticle Composites for Use in Selective H₂S Sensors

For ambient use, flexible hydrogen sulfide (H 2 S) gas sensors based on polyaniline (PANI) and copper oxide nanoparticles (CuO NPs) were investigated. PANI/CuO nanocomposites made by in situ (P-1) and bilayer (P-2) methods have shown high performances when sensing H 2 S of 0–25 ppm concentration in ambient conditions. The P-2 sensor maintained high sensitivity ( S = 7.25) and excellent responsiveness (Δ R e = 188%). The P-1 sensor had high responses (<30 s), linearity ( R 2 = 99.5%), and stability, while the CuO NP sensor was especially sensitive ( S = 13.5) within 0–10 ppm of H 2 S concentration. In addition, the flexible/conformable composite sensors had excellent H 2 S selectivity and bending stability. The enhancements of the composite sensors are mainly attributed to the PANI/CuO heterojunction formation that effectively reduced the PANI band gap from 2.51 eV (PANI) to 2.48 eV (P-1) and further down to 2.43 eV (P-2) for improved conductivity and charge-transport efficiency in the semiconductor network. The X-ray photoelectron spectroscopy analyses identified elements and valence band energy changes before and after H 2 S exposure. This study used facile methods for preparing nanocomposite-based gas sensors for the development of cost-effective, sensitive, conformable, durable, and ambient workable devices for monitoring fresh food quality in the food supply chain and environment safety for mining and petrochemical industry.