Multi-Layered TiO2 Nanotubes Array-Based Highly Sensitive Room-Temperature Vapor Sensors

Single-, double-, and triple-layered TiO
₂
nanotubes (NTs) array were synthesized by using a voltage pulse-assisted anodic oxidation technique. Morphological and structural evolution of different NTs have been studied by field-emission scanning electron microscopy and X-ray diffraction spectroscopy. “Au/TiO
₂
NT layer(s)/Ti” types vertical structured sensors were fabricated and characterized at room temperature (300 K) toward multiple volatile organic compounds (VOCs) and high sensitivity was observed at low concentration (40-160 ppm) of VOCs. Response magnitude was increased with increase of number of layer(s) and found maximum of ~96% at 160 ppm of ethanol for triple-layered NTs. Efficient sensing was achieved for multi-layered TiO
₂
NTs due to the benefits of 1) incremental effective surface area and 2) Schottky barrier effect at interlayer junctions.