Detecting Benzene Vapor via a Low-Cost Nanostructured TiO₂ Sensor

Cost-effectively detecting benzene, a human carcinogen, at occupationally and atmospherically relevant concentrations would benefit individuals at risk of exposure. This paper presents the development of a titania (TiO
₂
) nanotube-based sensor array that has a high surface area, is highly sensitive, and operates at room temperature using simple, portable instrumentation. An n-type TiO
₂
nanotube was synthesized through electrochemical anodization in an electrolytic solution of ammonium fluoride-ethylene glycol and oxygen annealed at 500 °C for up to 8 hours. The nanotube sensor had a bandgap (Eg) of ~2.6 eV, and it was operated at a bias voltage of +1.5 V. The response of the sensor to benzene vapor was measured using an amperometric technique at room temperature, and when exposed to benzene, the sensor exhibited a decrease in current, as expected for an n-type metal oxide semiconductor. The sensor response was proportional to benzene concentration over a range of 100-400 ppb. A sensing mechanism based on Fermi level changes caused by band bending has been explained for this benzene sensor.