Fabrication of TiO₂/polyelectrolyte thin film for a methyl mercaptan gas sensor

Abstract

Quartz crystal microbalance (QCM) gas sensor to detect methyl mercaptan (CH 3 SH) gas was fabricated by depositing TiO 2 nanoparticles and polyelectrolyte on the electrode of QCM. The TiO 2 /poly(sodium 4-styrenesulfonate) (PSS) thin film fabricated by a layer-by-layer self-assembly (LBL-SA) method showed a high surface area and increased the sensitivity of gas sensor. When the QCM sensors coated with triethanolamine (TEA) or (TiO 2 /PSS) were exposed to methyl mercaptan gas (1.0 ppm), the frequency shifts of QCM with TEA casting film and TiO 2 /PSS thin film were ca. 9 Hz and ca. 24 Hz, respectively. As the bilayer number of (TiO 2 /PSS) increased, the frequency shift of QCM sensor with (TiO 2 /PSS) thin film was gradually increased. In addition, the frequency shift of QCM sensor was gradually increased as the concentration of methyl mercaptan gas increased from 0.5 ppm to 2.0 ppm. In this study, the surface morphology and sensor property of QCM sensor coated with (TiO 2 /PSS) thin film were measured.