Molecularly imprinted polyvinyl acetate doped with boric acid for sensitivity and selectivity of ammonia sensing by QCM

A reliable ammonia gas detection method is essential for various applications, so improving the sensitivity and selectivity of ammonia sensors is still challenging. In this study, we develop an ammonia sensor based on quartz crystal microbalance (QCM) using a simple preparation of molecularly imprinting polymer (MIP) active layer of polyvinyl acetate (PVAc) and boric acid (BA) as additional doping. The active layer materials are then characterized by a scanning electron microscope (SEM) equipped with dispersive x-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) to examine the morphology and the functional groups. The sensitivity of the ammonia sensor developed using the MIP-doped BA method resulted in 0.243 Hz/ppm, which is three times greater than the sensor developed without the MIP method. Apart from the significantly enhanced sensitivity, high selectivity to ammonia was also observed. The response increased significantly when the QCM-PVAc MIP 6BA sensor was exposed simultaneously to several analytes, such as ammonia, trimethylamine (TMA), and methylamine (MA). A decreased response was observed when the developed sensor was exposed simultaneously without ammonia. The sensor also showed good selectivity towards other analytes and was proven to have good long-term stability during a month of testing. This result suggests that the ammonia imprinting PVAc-doped BA is a promising new method for obtaining high sensitivity and selectivity sensors.