Gas sensor using noble metal-loaded TiO₂ nanotubes for detection of large-sized volatile organic compounds

Detection of volatile organic compounds (VOCs) has attracted considerable attention for indoor air quality and human breath analysis. Here, resistive-type gas sensors with porous films made of Au-loaded TiO₂ nanotubes were developed for the detection of large-sized VOCs. Well-dispersed Au nanoparticles (10 to 20 nm) were photo-chemically deposited on TiO₂ nanotubes (80nm in diameter, 700nm in length) prepared by a hydrothermal method. The device using the Au-loaded TiO₂ nanotubes showed improved sensor responses to ethanol and toluene (50 ppm) in air at 500°C. This suggested that Au nanoparticles deposited on the surface of TiO₂ nanotubules without aggregation. We also demonstrated that the device could be used for the detection of largesized VOC molecule, i.e., 2,6-diisopropylphenol (propofol), an intravenously administered hypnotic drug for induction and maintenance of anesthesia. The Au-loaded TiO₂ nanotubes would offer a way to continuously monitor a change in the concentration of VOCs in exhaled air for medical diagnostics.