A highly sensitive BTX sensor based on electrochemically derived wall connected TiO2 nanotubes

This paper concerns development of electrochemically synthesized titanium dioxide (TiO2) nanotube array for sensing the carcinogenic aromatic hydrocarbons like benzene, toluene, and xylene (BTX) with enhanced sensitivity achievable at relatively low temperature. Structural characterizations (XRD, FESEM), revealed that variation of the H2O concentrations (1%, 2%, 5%, 8%, 10%, and 100% by volume) in mixed electrolyte, comprising of ethylene glycol (EG) and ammonium fluoride (NH4F), resulted in the formation of six distinctly different TiO2 nanoforms. Photo luminescence spectra (PL spectra) analysis authenticated different stoichiometry of these six samples. Besides, the X-ray photoelectron spectroscopy (XPS) was carried out to investigate the defect states. The XPS study enables to correlate the oxygen vacancy concentration with the anodization parameters. Among the various nanoforms, the wall connected TiO2 nanotube array was found to be the most efficient one for BTX sensing in the concentration range 1-400 ppm at relatively lower operating temperatures (50-200 °C). Among the three target species, benzene was found to offer the highest response magnitude followed by that of toluene and xylene at all the concentrations. The concerned sensing mechanism was also discussed correlating the experimental findings.