A polyaniline-enhanced quartz crystal microbalance sensor for room-temperature camphor detection

Abstract

A method to detect camphor gas is considered indispensable in the pharmaceutical industry. Unfortunately, the available sensors to detect the presence of camphor in the air are very limited and still on a laboratory scale, such as using chromatography-mass spectroscopy (GC-MS). The research's main focus is to obtain a portable sensing system with excellent sensitivity and selectivity. This study explored polyaniline (PANi) concentrations cast over PVAc nanofiber as a matrix to detect camphor gas using a quartz crystal microbalance (QCM) system to measure camphor exposure. Scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) were used to analyze the morphology and chemical composition of the fabricated active layer (i.e., nanofiber with PANi thin film). Increasing the PANi concentration provides more PANi on the sensor surface, thus amassing the active groups to interact with camphor gas molecules. It shows that a sensor with a 0.08% PANi thin film (Nano-PANi8) has a sensitivity of 2.594 Hz ppm⁻¹, much greater than the sensor without PANi, which is only 0.305 Hz ppm⁻¹. In addition, the sensor also has good repeatability and rapid response and recovery time of 47 s and 133 s, respectively. Compared to other gaseous compounds, the sensor also has excellent selectivity for camphor and robust long-term stability over three weeks of testing. The produced QCM sensor employing PANi thin film can give a camphor sensor superior performance, including excellent sensitivity, selectivity, and long-term stability. Furthermore, the use of QCM as a base sensor also makes the fabricated sensor portable.