Surface functionalization of PANI and PANI/ZnO hybrid nanofibers with metallic catalysts for ammonia sensing at room temperature

Four different sensor devices were fabricated using the deposition of gold and nickel on top of polyaniline and polyaniline/zinc oxide composite thin films on glass substrates. Prepared samples were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and UV-Visible spectroscopy. FESEM images confirmed the formation of interwoven nanofibers for all samples with the mean diameter of about 90 nm for PANI. The responses of the prepared samples toward various concentrations of ammonia gas were investigated by conductometric measurements at room temperature. The responses of the fabricated sensors toward 100 ppm of NH3 were obtained to be 112%, 3%, 177% and 148% for PANI/Au, PANI/Ni, PANI/ZnO/Au and PANI/ZnO/Ni samples, respectively. Results show both Ni and Au thin films as a metallic catalyst on top of PANI/ZnO nanocomposite can greatly improve the sensing characteristics toward NH3 at room temperature. However, PANI/ZnO/Au has the highest response with the lowest response time (4 s). The mechanism for the sensitivity enhancement of the fabricated devices was discussed.