Fabrication of surface functionalized QCM sensor for BTX detection at ambient conditions

Abstract

Developing optimized gas sensors for detecting low concentrations of Benzene, Toluene, and Xylene (BTX) in ambient conditions is advantageous for health and environment monitoring applications. This study reports on the feasibility of using Quartz Crystals Microbalance (QCM) coated by Tungsten Oxide (WO3) to detect BTX compounds. A WO3 layer was deposited on the QCM surface using DC magnetron sputtering. Optical Profilometry (OP), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) were employed to analyze sensor surface morphology and structure. Adsorption properties were studied through the Langmuir adsorption isotherm. Thermal stability was evaluated by thermogravimetric analysis. The response to BTX vapours was investigated using a laboratory-designed gas-sensing setup in ambient conditions. The optimized film thickness was 200.81 ± 0.39 nm for 540 s of sputtering. XRD pattern confirms the amorphous nature, and SEM images of WO3 show the granular microstructure with 200 nm diameter. The developed sensor shows the highest sensitivity for xylene (5.10 ± 0.08 Hz/ppm), followed by toluene (5.69 ± 0.22 Hz/ppm) and benzene (3.36 ± 0.24 Hz/ppm). The limit of detection for BTX was 1.48 ppm, 0.79 ppm, and 0.33 ppm, respectively. The sensor exhibited faster response times of 30 s, 32 s, and 43 s for BTX, respectively. Repeatability of 99 % and reproducibility of 98 % were observed for BTX vapours. The fabricated WO3-coated QCM sensor can detect BTX vapour at room temperature with high sensitivity and response time. Thus, it can play a significant role in detecting BTX in the workplace for health and environment monitoring systems.