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Room temperature sensing characteristics of the polypyrrole (PPy) films modified with different weight percentages of ZnO nanowires (ZnO-NWs) have been studied for various oxidizing (NO2 and Cl2) as well as reducing (H2S, NH3, CH4, and CO) gases. We demonstrate that ZnO-NW (50 wt %):PPy composite films are highly selective to Cl2 along with high-sensitivity (40 at 10 ppm), fast-response (55 s), and highly reproducible response curves. It has been shown that negatively charged O2- surfaces of ZnO-NW transfer electrons to PPy, making it in a highly reduced form. A strong localization of charge carriers in the reduced PPy makes composite film highly resistive (>1010 Ω cm) as well insensitive to interaction with most of the gases except Cl2. Cl2 being highly oxidizing gas interacts with composite films and causes a sharp reduction in its resistivity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]