Interface modification of titanium dioxide nanoparticles by titanium-substituted polyoxometalate doping for improvement of photoconductivity and gas sensing applications

TiO2 nanoparticles are commonly used as versatile precursors to make functional nanocomposite materials. However, the surface defects at grain boundaries of TiO2 nanoparticles significantly affect the photoelectric properties of TiO2 nanomaterials. In this work, we firstly prepared nanocomposites of TiO2 and polyoxometalates (POMs) in which different POMs, including titanium-substituted POMs K-5 [PW11TiO40 ] and K-7 [PW10Ti2O40], are incorporated with TiO2 nanoparticles so as to make an interface modification on grain boundaries of TiO2 nanoparticles. Then the photoconductivities of the TiO2/POM nanocomposites were investigated through measurement of photocurrent responses, current-voltage curves, Mott-Schottky plots and surface photocurrent spectra. Compared with pure TiO2 nanoparticles, TiO2/POM nanocomposites exhibit superior photoelectric properties, benefitting from the interface modification from different POMs. The gas sensing performance for acetone was also explored by use of the as-prepared photoconductive devices, and TiO2/PW11Ti exhibited a high gas sensing performance.