Enhanced $NO2$ selectivity of hybrid poly(3-hexylthiophene): ZnO-nanowire thin films

Sensing characteristics of the drop-cast thin films of poly(3-hexylthiophene) (P3HT), ZnO nanowires, and P3HT:ZnO-nanowire hybrids with different compositions have been studied for various gases, namely, $NO2$⁠, $H2S$⁠, $NH3$⁠, $CH4$⁠, and CO. At room temperature, pure P3HT and ZnO-nanowire films were highly sensitive to $NO2$ and $H2S$⁠, moderately sensitive to CO, and nearly insensitive to $NH3$ and $CH4$⁠. P3HT:ZnO-nanowire hybrid films, with increasing ZnO-nanowire content, exhibited gradual enhancement in $NO2$ sensitivity, while reducing sensitivity for $H2S$⁠. P3HT:ZnO-nanowire (1:1 ratio by weight) films were found to be highly selective for $NO2$⁠. Plausible mechanisms explaining the enhanced $NO2$ selectivity by hybrid films are discussed.