Polyaniline/CuO Nanoparticle Composites for Use in Selective H2S Sensors

For ambient use, flexible hydrogen sulfide (H2S) 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 H2S of 0–25 ppm concentration in ambient conditions. The P-2 sensor maintained high sensitivity (S = 7.25) and excellent responsiveness (ΔRe = 188%). The P-1 sensor had high responses (<30 s), linearity (R2 = 99.5%), and stability, while the CuO NP sensor was especially sensitive (S = 13.5) within 0–10 ppm of H2S concentration. In addition, the flexible/conformable composite sensors had excellent H2S 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 H2S 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.