Organic Solvent Dispersed TiO2 Nanocrystal Sol: Synthesis and Characterization
Y.Q. Rao, B. Antalek, J. Minter, T. Mourey, T. Blanton, G. Slater, L. Slater, J. Fornalik
Eastman Kodak Company, US
Keywords: TiO2, nanocrystal, synthesis, characterization
Abstract:Anatase TiO2 nanocrystals with a mean diameter of about 10 nm were successfully synthesized through a non-aqueous sol gel route without the use of air free equipments. The nanocrystals were well dispersed in organic solvents in the form of primary particles. A monolayer siloxane layer stabilizes the dispersion. The average particle size measured by X-ray diffraction, TEM, AFM, dynamic light scattering, nuclear magnetic spectroscopy and size exclusion chromatography are in excellent agreement. Moreover, NMR and SEC are able to detect the presence of the second population of particles, with a much smaller diameter of 2 nm. These particles are identified as the dimer and trimer of the acrylate siloxide used to stabilize the TiO2. Because of the similar chemical nature, these small particles can not be removed using selective precipitation. Rather, a high speed centrifugation successfully removes the smaller particles rendering a pure TiO2 nanocrystal colloid to make high refractive index coating. The use of NMR and SEC to characterize the nanoparticle colloid overcome the shortcoming of heavy weighing of bigger particles in any diffusion related measurement and allow the characterization of chemical group and its interaction with the particle. These characterization tools will provide essential information to understand the organic-inorganic interface and control the nanoparticle synthesis.