N-doped graphene quantum dot-modified polyaniline for room-temperature sensing of alcohol vapors

Uniformly distributed nitrogen-doped graphene quantum dots (NGQDs) were obtained using a facile microwave-assisted hydrothermal technique. A composite of NGQDs and polyaniline (Pani) was prepared via an in situ chemical oxidative polymerization method and characterized using transmission electron microscope (TEM), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), and ultraviolet–visible (UV–vis) spectra. Room temperature operable gas sensors were prepared using bare Pani and NGQDs/Pani films deposited separately onto gold-plated interdigitated electrodes (IDEs) embedded on printed-circuit board (PCB) substrates. The prepared sensors showed a good response towards 50–150 ppm ethanol vapors at room temperatures and relative humidity of 45%. The incorporation of NGQDs in Pani promoted a better response signal and sensitivity, and improved the baseline resistance of the composites, which was attributed to the enhanced conductive pathways between Pani and NGQDs. The composite sensor reached the lowest response and recovery times of 85 s and 62 s towards 100 ppm of ethanol respectively. Both sensors exhibited a good reproducibility of the response signal towards 100 ppm of ethanol vapor.