Fabrication and gas sensitivity in heterostructures of ortho-chloropolyaniline-ZnO nanocomposites

Recently, the gas-sensing properties of conducting polymer nanocomposites have been widely investigated. In this paper, we report the fabrication of heterojunctions based on conducting ortho-chloropolyaniline-zinc-oxide nanocomposites by in situ polymerization using sodium dodecylbenzene sulphonic acid and their potential toward gas-sensing applications. The prominent peaks in FTIR spectra confirm the formation of nanocomposites. One-dimensional growth of polymer fiber is observed through SEM and TEM with ZnO nanoparticles homogeneously distributed within the fiber matrix. The temperature-dependent conductivity of the nanocomposites increases with increasing temperature, as well as with the concentration of ZnO nanoparticles within the polymer matrix. This increase in conductivity is because of the hopping of charge carriers between the favorable sites. The synthesized nanocomposites were used to fabricate the sensor device on a glass substrate with aluminium-top electrodes. Gas-sensing studies were carried out using a two-probe method in a laboratory-made sensor setup; it is observed that 50 wt% of nanocomposites show high sensitivity of 93% at 400 ppm with a rapid response and small recovery time of 56.76 and 37.59 s, respectively. A reproducibility and stability study shows that these nanocomposites are highly stable. A selectivity study was carried out by passing different test gases and determined that these composites show high sensitivity towards LPG.