Portable High Surface Area TiO₂ Nanotube Array Sensor for the Detection of Benzene at Room Temperature

Abstract

Benzene is one of the few known human carcinogens as identified by the International Agency for Research on Cancer. It is a common indoor and outdoor pollutant, with sources ranging from cigarette smoke to traffic. Hence, there is an increasing need to detect low concentrations of benzene. Metal-oxide based nano-sensors, with their simple sensing mechanisms make for a good choice. Thin films based on titanium dioxide (TiO2) have previously been shown to respond to benzene (1), however these sensors are run at high temperatures (160-200°C), require a complex setup for operation, and have low surface area for sensing. This paper presents the development of TiO2 nanotube based sensor array (Figure 1) that has high surface area, is highly sensitive, and operates at room temperature using portable and simple instrumentation. TiO2 nanotubes were synthesized through anodization in electrolytic solution of ammonium fluoride (NH4F)-ethylene glycol (EG) and oxygen annealed for up to 500°C. The response of the synthesized hollow nanotubes was studied at room temperature for different concentrations of benzene vapor (100-500ppm). The response of the sensor coupons to benzene vapor was measured using an amperometric technique. The results showed an increase in current that was directly proportional to the concentration of benzene in the sample which indicates a quantitative nature of the sensor (Figure 2). The sensor was placed in a portable system which can be deployed to potential contamination sites for real-time monitoring applications. Results on sensing mechanism, stability of the sensor over time, sensor reusability, and detection limit will be presented. (1) Mabrook M., Hawkins P. (2001) Sensors and Actuators, B: Chemical 75, 197-202. Figure 1