Oxygen Plasma-Treated Graphene Oxide Surface Functionalization for Sensitivity Enhancement of Thin-Film Piezoelectric Acoustic Gas Sensors

In this work, we presented a thin-film piezoelectric acoustic gas sensor with enhanced sensitivity by a surface modification strategy of oxygen plasma treated graphene oxide (GO) functionalization. By exposing to ammonia vapor (NH3) of various concentrations at controlled temperature and humidity, the characteristics of the GO-coated acoustic sensor were investigated, that is, sensitivity, linearity, response, and recovery time. Oxygen plasma treatment of the GO-coated sensor further enhanced the sensitivity compared with the freshly prepared GO-coated sensor. The mechanism of oxygen plasma treatment effect on the GO-coated sensor was discussed based on characterizations of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscope (SEM), and precise weighing of the acoustic sensor. It was found that the oxygen plasma treatment introduces numerous defects to GO flakes, which are uniformly distributed across the GO surface, providing more gas molecule binding sites.