Sensing performance of Ti/TiO2 nanosheets/Au capacitive device: Implication of resonant frequency

Abstract

Frequency selective gas sensing performance of Ti/TiO2 nanosheets/Au sensor is presented in this communication. The device was tested over the frequency range of 0.05–225 kHz with peak to peak amplitude of 0.5 V at the temperature ranging from 50 to 225°C under the exposure of acetone, ethanol, and methanol. The optimum sensor response towards acetone, ethanol, and methanol was recorded to be at resonant frequencies of 0.7 kHz, 0.4 kHz, and 0.3 kHz, respectively. Resonant frequency shifts under gas exposure with respect to that in the air were correlated with the change in dielectric (εr) at the nanosheets surfaces and interfaces. Over the tested frequency range order of capacitive change was found to be methanol > ethanol > acetone. Such gas response has been correlated with the degree of polarization of the analytes at the nanosheets surfaces and edges. Equivalent circuit model correlating capacitive and resistive contribution of the nanosheets have been analysed with the help of impedance spectroscopy in complex plane. Optimum capacitive response magnitude (CRM) was found to be ∼ 199%, 252%, and 256% towards 50 ppm of acetone, ethanol, and methanol, respectively. The fastest response time and recovery time of ∼ 24/14 s, 10/3 s, and 17/11 s were recorded for acetone, ethanol, and methanol, respectively.