Ti/TiO2 Nanotube Array/Ti Capacitive Device for Non-polar Aromatic Hydrocarbon Detection

In this paper, highly repeatable aromatic hydrocarbon [such as benzene (B), toluene (T) and xylene (X) (BTX)] sensing performance of Ti/TiO2 nanotube (NT) array/Ti sandwiched device structure, in the capacitive mode, is reported. The sensing layer was synthesized via electrochemical route and the capacitive performance of the device, toward organic vapors having low dielectric constant (e.g. BTX), was investigated. For a detection range of 10-200 ppm (at 150 °C), the sensor offered a highly promising performance. TiO2 NT array, being a highly oriented and freestanding nanostructure, offered sufficient intertubular and intratubular free space, which can be easily filled up by the target gas/vapor species, causing a significant change in the effective dielectric constant and therefore in the resultant capacitance of the sensor device. An equivalent circuit model was developed to demonstrate the underlying mechanistic framework of the capacitive type gas/vapor sensor considering the effects of the external factors, viz., temperature and target vapor concentrations.

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