Anatase TiO2 hierarchical microspheres consisting of truncated nanothorns and their structurally enhanced gas sensing performance

Anatase TiO2 hierarchical microspheres were synthesized by a facile hydrothermal method. Characterization results indicated that the microspheres were consisted of massively aggregative nanothorns with truncated tips, which had exposed {001} and (101) crystal facets, and there were abundant mesoporous structures in the microspheres. A possible growth model of the TiO2 hierarchical microspheres was put forward based on a series of experimental analysis. When used for gas sensing, it was found that the TiO2 hierarchical microspheres showed a distinct high sensitivity towards acetone, the optimal response to 100 ppm acetone was 14.6, which was much higher than that of other materials reported in previous works. Moreover, the TiO2 hierarchical microspheres exhibited a fast response/recovery speeds (<10 s), a low detection limit (the response still reaches 6.1 even at a low acetone concentration of 10 ppm) and an excellent selectivity. Through systematical analysis, it can be concluded that the enhancement of gas sensing performance of the TiO2 hierarchical microspheres was ascribed to its unique structural features (perfect hierarchical mesoporous structure as well as specific crystal facets exposing), which could be described as structurally enhanced gas sensing performance. The present results encourage us to further investigate crystal facets-dependent gas sensing properties of TiO2 for the designing of conductometric gas sensors with better sensing performance. (C) 2016 Elsevier B.V. All rights reserved.