Spontaneous water release inducing nucleation during the nonaqueous synthesis of TiO2 nanoparticles

Abstract

The formation of anatase nanoparticles by reaction of titanium(IV) isopropoxide in benzyl alcohol was studied. In contrast to previous reports on the nonaqueous synthesis, in this system the particle formation occurs within a very limited time span in the course of the synthesis, concurrently to a fast step-type pressure increase within the closed reaction system. By Karl Fischer titration and ¹H NMR spectroscopy of both the liquid and the gaseous phase at different stages of the reaction, it is shown that water formation occurs during the pressure increase due to catalytic ether formation from benzyl alcohol. The generated water leads to instant nucleation and fast growth of crystalline nanoparticles, which is traced by powder X-ray diffraction as well as small-angle X-ray scattering and thereby shown to play a crucial role in the particle formation process.