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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]

SnO2-WOX nanowire heterostructure were grown by physical deposition method. Characterization by XRD, UV-Vis and TEM shows that both the nanowire systems do not interact with each other, and retain their individual characteristic. Sensors fabricated from both, mat films and single isolated nanowire shows response to chlorine as well as H2S gas at room temperature. Single nanowire sensors are found to be better sensitive as well as selective Cl2 sensor. [ABSTRACT FROM AUTHOR]