Thin films of TiO2(B) nanowires are known to have sensitive and fast response to vapors of nitro-explosives under ambient conditions. The sensing response is believed to be affected by the humidity of ambient air that changes the density of hydroxyl groups on the TiO2(B) surfaces. To verify this mechanism, the role of surface hydroxyl groups on TiO2(B) nanowires was investigated via various surface modifications. It was found that a higher density of surface hydroxyl groups will constantly enhance the chemiresistive response of TiO2(B) nanowires to the nitro-explosives vapors. These surface hydroxyl groups serve as a pathway for effective charge transfer between the nitro groups on the explosive molecules and the TiO2(B). The evidence of charge transfer complex formation between nitro groups and titanium dioxide is also confirmed by Fourier transform infrared spectroscopy.
