Synthesis of highly crystalline titania nanocrystals through solvothermal technique

Highly crystalline rhombic TiO2 nanocrystals (NCs) were fabricated through a solvothermal technique in anhydrous ethanol. A Teflon cup with reaction agents including titanium (IV) isopropoxide, oleic acid (OA), oleylamine (OM), and anhydrous ethanol was put into a Teflon-lined stainless steel autoclave with ethanol and water for the purpose of controlling the hydrolytic reaction of Ti precursors. Water vapor generated from the mixture of water and ethanol was as a hydrolysis agent and oleic acid and oleylamine were as two distinct capping surfactants which have different binding strengths to control the growth of the TiO2 NCs. The molar ratios of oleic acid/oleylamine play a crucial role for the size and morphology of TiO2 NCs created through hydrolytic and nonhydrolytic processes. Highly crystalline rhombic TiO2 NCs were fabricated by combining hydrolytic and nonhydrolytic sol-gel reactions of titanium (IV) isopropoxide using a molar ratio of Ti precursors/OA/OM of 1/2/3 at 180 degrees C for 22 h. The transmission electron microscopic observations indicated that the rhombic TiO2 NCs have a uniform size distribution under optimal preparation conditions. The size and size distribution of the rhombic TiO2 NCs were adjusted by adding OM to the reaction mixture as a cosurfactant together with OA.