Rapid response and high-enhancement sensitivity formic acid gas sensor based on electrospun polyimide/polyvinylpyrrolidone composite nanofibers

Formic acid gas is a volatile compound that is widely used in various industrial processes and has the potential to cause health and environmental impacts when exposed to concentrations of more than 30 ppm. Therefore, the development of gas sensors that are sensitive, selective, and capable of operating at room temperature is an important requirement. In this study, a formic acid gas sensor based on quartz crystal microbalance (QCM) with an active layer of polyimide/polyvinylpyrrolidone (PI/PVP) composite nanofibers was developed. PI/PVP nanofibers were synthesized using the electrospinning method. Test results show that the addition of PVP to the PI matrix improves the sensor's performance in detecting formic acid gas, with a sensitivity reaching 0.389 Hz·ppm-1. Remarkably, the fabricated sensor demonstrated enhanced linearity with an exceptional coefficient of correlation (R2 = 0.986) within a wide range of 10 – 300 ppm. Furthermore, the fabricated sensor exhibited a rapid response time of 7 s, showcasing its efficiency compared to conventional polymer-based sensors. The fabricated sensor also shows repeatability and reversibility that do not change significantly after three cycles, as well as stability for 2 weeks. The decrease in frequency due to the response to formic acid was dominated by hydrogen bonding interactions between the carbonyl groups in PVP and formic acid gas molecules. With its fairly good detection capability, this PI/PVP nanofiber-coated QCM sensor shows promising potential for real-time formic acid gas monitoring applications in industrial and laboratory environments.