Enhancement of Ethanol Vapor Sensing of TiO2 Nanobelts by Surface Engineering

TiO2 nanobelts were prepared by a hydrothermal process, and the structures were manipulated by surface engineering, including surface coarsening by an acid-corrosion procedure and formation of Ag-TiO2 heterostuctures on TiO2 nanobelts surface by photoreduction. Their performance in the detection of ethanol vapor was then examined and compared by electrical conductivity measurements at varied temperatures. Of the sensors based on the four nanobelt samples (TiO2 nanobelts, Ag-TiO2 nanobelts, surface- coarsened TiO2 nanobelts, and surface-coarsened Ag-TiO2 nanobelts), they all displayed improved sensitivity, selectivity, and short response times for ethanol vapor detection, in comparison with sensors based on other oxide nanostructures. Importantly, the formation of Ag-TiO2 heterostuctures on TiO2 nanobelts surface and surface coarsening of TiO2 nanobelts were found to lead to apparent further enhancement of the sensors sensitivity, as well as a decrease of the optimal working temperature. That is, within the present experimental context, the vapor sensor based on surface-coarsened Ag-TiO2 composite nanobelts exhibited the best performance. The sensing mechanism was interpreted on the basis of the surface depletion model, and the improvement by oxide surface engineering was accounted for by the chemical sensitization mechanism. This work provided a practical approach to the enhancement of gas sensing performance by one-dimensional oxide nanomaterials.