High-temperature treated TiO₂ modified with 3-aminopropyltriethoxysilane as photoactive nanomaterials

A series of titanium dioxide (TiO₂) modified with 3-aminopropyltriethoxysilane (APTES) was prepared by high-temperature calcination in an argon atmosphere in the temperature range from 800 to 1,000°C. The properties of the obtained samples were compared with those of pure TiO₂ annealed under the same conditions. Examining electron paramagnetic resonance (EPR) parameters at room temperature for APTES–TiO₂ showed an intense resonance line from defects related to conducting electrons with g_eff from 2.0028 to 2.0026 and 1.9052 for temperatures 800, 900, and 1,000°C, respectively, while for pure calcined TiO₂, these ERP lines were not observed. With the increase in the calcination temperature to 900°C for APTES–TiO₂ samples, the EPR increases linearly. This has been combined with a relatively high anatase content and small crystallites. The EPR line intensity at RT calculated for 1 g of sample showed an almost linear relationship with the photoactivity in removing ORANGE II dyes from water.