Selective gas detection of titania nanoparticles via impedance spectroscopy and capacitive measurement

The present paper demonstrated the impedance analysis of Au/TiO₂nanoparticles/Si-Al capacitive sensor for selective detection of volatile organic compounds (VOCs) at different frequency regimes. TiO₂nanoparticles (NP) were synthesized through the solution process and characterized by field-emission scanning electron microscopy , x-ray diffraction analysis, photoluminescence spectroscopy, and atomic force microscopy. The gas sensitivity of Au/TiO₂-NP/Si-Al was investigated, with the effect of temperature modulation (25 °C-250 °C) and dielectric variation in the vicinity of nanoparticles. Impedance spectroscopy of TiO₂-NP was carried out to obtain resonant peaks over the frequency ranging from 0.05 to 225 kHz and fitted with a complex nonlinear least-squares method. The optimum sensor response of 136%, 63%, 152%, and 174% was found at resonant frequencies of 0.38 kHz, 0.22 kHz, 0.15 kHz, and 0.1 kHz for the exposure of 2-propanol, acetone, ethanol, and methanol, respectively. The fastest response time and recovery time were found to be 32/21 s, 31.2/8 s, 32.5/9 s, and 40/26 s for acetone, 2-propanol, ethanol, and methanol, respectively. Selective detection of different VOCs at various resonant frequencies has correlated with the dielectric variation of the NPs and their associated void region under gas exposure.