A MoS2 quantum dot functionalized TiO2 nanotube array for selective detection of xylene at low temperature

Xylene is among the most complex volatile organic compounds (VOCs) and is significant in many applications. Xylene as an efficient breath marker of lung cancer raises the concern of discrimination between compounds having chemically similar nature like benzene, toluene, etc. For highly stable and selective detection of xylene, in this study, we report a 0D–1D nanocomposite, i.e. a MoS₂ quantum dot (QD) functionalized TiO₂ nanotube array. The nanocomposite synthesis involves a hydrothermal reaction between MoS₂ QDs and the 1D TiO₂ nanotube array which is synthesized by anodic oxidation of titanium foil. The Au/MoS₂–TiO₂ nanotube/Ti structured sandwich type sensor exhibited selective xylene detection with a high response magnitude of 188% (50 ppm xylene) which is many times higher than those of the pure MoS₂ QD and TiO₂ nanotube sensors at a relatively low operating temperature, i.e. 75 °C. It also displayed a fast response time (35 s) and maximum recoverability, with a lower detection limit (LOD) of 33 ppb. Notably, the highest selectivity of detection towards xylene over benzene and toluene makes the sensor potential for environmental and breath VOC monitoring. Additionally, the long-term stability of the sensor was apparent from the stable sensing behavior even after 1 month.