Electron transport in surface modified TiO2 nanoparticles

Surface modified nanoparticles of P25 Evonik Degussa TiO2 with silane coupling agent 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTMS) were prepared at low temperature conditions. The samples were characterized using the BET technique. Their temperature dependent dc electrical conductivity was investigated in the temperature range 195-440 K. In order to investigate the influence of the environment, measurements were conducted in vacuum and in air. A change of conductivity with the molar ratio of AAPTMS/P25 is shown. Moreover, a decrease of conductivity is exhibited when compared to that of P25 nanopowder, attributed to the presence of silica in AAPTMS. The modified samples show a significant decrease of conductivity in air. In addition, the conductivity dependence on temperature differs from that in vacuum, suggesting the competition between the adsorption of oxygen and water from the surrounding atmosphere. It was demonstrated that the electrical conduction was controlled by the grain boundaries and the small polaron hopping at the high and intermediate temperatures whereas Mott's variable range hopping was the main conduction mechanism at the lower temperature regime.