Synthesis of anatase TiO$_{2}$ nanocrystals by low temperature sol-gel method modified with a hydrophobic ionic liquid

Anatase TiO$_{2}$ nanocrystals of uniform sizes were synthesized via low temperature sol-gel reaction of titanium tetraisopropoxide (TIP) with water in the presence of small amount of hydrophobic ionic liquid (IL) molecules. It was found that the IL molecules did not actively participate in precursor hydrolysis and TiO$_{2}$ nucleation. However, the IL molecules strongly screened the abundant remaining hydroxylic bonds on the surfaces of the primordial TiO$_{2}$ particles, giving rise to low temperature transition to anatase phase at 100 ${^\circ}$C and impeded inter-particle sintering. The former was believably induced by self-organization of the IL molecules that adsorbed on the hydroxylic bonds. This IL-modified sol-gel reaction resulted in uniform sized ($\sim $ 10 nm) anatase TiO$_{2}$ nanocrystalline particles, useful for high efficiency photo-catalytic applications.