Quartz Crystal Microbalance Sensor Based on ZnO–Graphene Thin Film for Gas Detection

Abstract

Gas detection is vital for safety in important industrial and private sectors. Its major significance lies in its proactive risk mitigation, safeguarding lives and resources. In this paper, the focus is on the development of a gas sensor based on quartz crystal microbalance coated with a sensitive layer of zinc oxide (ZnO)–graphene nanocomposite for the detection of volatile organic compounds at room temperature. The incorporation of graphene or reduced graphene oxide is preferred in such applications due to their excellent electrical conductivity, chemical stability, and high surface area. These nanocomposites were synthesized using a chemical method via spray pyrolysis. Various techniques were employed to analyze the coated QCM electrode: contact angle measurements to assess surface wettability, Fourier transform infrared and energy-dispersive X-ray spectroscopy to investigate the composition of the coated electrode, and scanning electron and atomic force microscopies were used to study its surface morphology. These analyses provided valuable insights into the nanocomposite's interaction with the environment, composition, structure, and topography of the sensor's sensitive layer. To evaluate the sensor's sensitivity, the frequency shift ( Δf ) of the coated QCM electrode is monitored when exposed to different  gas  concentrations  of ethanol,  toluene,  chloroform,  humidity,  and formamide, ranging from 47 to 142 ppm. The frequency shift indicated the detected gas concentration. The results demonstrate good repeatability and reversibility, which are crucial indicators of a sensor's reliability. This reliability is essential for applications in environmental monitoring or industrial safety, where accurate gas detection is critical.