Formaldehyde Gas Sensor Based on Quartz Crystal Microbalance Modified with Aniline-Doped Polyvinyl Acetate Nanofibers

Real-time monitoring of airborne formaldehyde continues to be difficult because existing gas-phase formaldehyde detection approaches lack adequate sensitivity, selectivity, and robustness. This work presents a quartz crystal microbalance (QCM) platform designed for selective formaldehyde detection in air. The QCM electrode surface was functionalized with electrospun polyvinyl acetate (PVAc) nanofibers doped with aniline at 2, 4, and 6 wt% to enhance sensitivity and selectivity. Chemical composition and fiber morphology of the aniline-doped PVAc nanofibers were verified using Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDX) spectroscopy, and scanning electron microscopy (SEM). The best-performing modified sensor reached a sensitivity of 0.056 Hz·ppm⁻¹, with response and recovery times of 200 s and 90 s, respectively, and limits of detection (LOD) and quantitation (LOQ) of 28 ppm and 96 ppm for formaldehyde. The modified QCM also demonstrated selectivity for formaldehyde relative to other common gases and vapors. Since the occupational workplace exposure limit (WEL) for formaldehyde is 2 ppm as an 8-hour time-weighted average, further development is required to push the LOD of this sensor down to levels relevant for environmental and industrial monitoring; this is identified as a direction for future work.