Quartz Crystal Microbalances Functionalized with Citric Acid-Doped Polyvinyl Acetate Nanofibers for Ammonia Sensing

We fabricated highly sensitive and selective ammonia gas sensors based on quartz crystal microbalance (QCM) platforms that were functionalized with electrospun polyvinyl acetate (PVAc) nanofibers and doped with various organic acids (i.e., oxalic, tartaric, and citric acids). The structural and chemical surface conditions of the nanofiber-based active layers on top of the QCMs were confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared (FTIR) spectroscopy. The sensitivity of the PVAc nanofiber-based QCM sensor doped with citric acid was found to be the highest (2.95 Hz/ppm) among others with a limit of detection (LOD) of down to the sub-ppm level (550 ppb). It also exhibited good selectivity, rapid response, short recovery time, and decent repeatability. This simple yet low-cost alternative solution based on chemical modification of nanofibers could improve the performance of QCM-based ammonia gas sensors in many areas including for smart electronic nose applications.