Synthesis and characterization of polythiophene/zinc oxide nanocomposites for chemiresistor organic vapor-sensing application

In this article, polythiophene (PTh) and a sequence of PTh/(1, 5, 10 wt.%) ZnO composites were prepared by in situ chemical oxidative polymerization method. The successful formation of PTh, ZnO, and interaction between PTh and ZnO were confirmed by various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry, UV–vis spectroscopy, fluorescence studies, followed by DC electrical conductivity. The XRD spectra showed crystallinity modification for PTh with ZnO wt.%, demonstrating the crystal structure of the sulfur modification. The SEM micrographs showed the existence of randomly linked ZnO nanoparticles, confirming the interaction of ZnO nanoparticles with the polymer matrix. A good agreement was observed in comparison to spectral studies. From the Tauc plot, it was found that the pure PTh bandgap was 2.0 eV and eventually decreased on decreasing the (wt.%) of doping. PTh/10(wt.%) ZnO showed enhanced conductivity (i.e., 0.00982 S cm−1) compared to pure PTh (0.000472 Scm−1). At room temperature (30 °C), the sensing performance was evaluated in terms of percent sensing and response/recovery time. It was noticed that the prepared composites were suitable for acetone sensing. Pure PTh showed 48.40% sensitivity, and sensitivity response for PTh/1(wt.%) ZnO, PTh/5(wt.%) ZnO, and PTh/10(wt.%) ZnO was 55.35%, 58.08%, and 75.11%, respectively. Sensitivity of the PTh/10(wt.%) ZnO composites–based sensors increased more than that of PTh. PTh/10(wt.%) ZnO showed a 122 s response time compared to another fabricated sensor. In reversibility test for PTh/10(wt.%) ZnO, an oscillating trend in sensitivity for four cycles was observed. The sensor’s operating stability was checked over a 16-day period and a fluctuating trend was observed in percentage sensitivity, reversibility, and response/recovery time.