Abstract: Surfacemodified titanium dioxide nanoparticles are synthesized in organic media via solgel method. The chemical structure of nanoparticles as well as its formation mechanism are discussed on the basis of Fouriertransform infrared spectroscopy (FTIR), Xray photoelectron spectroscopy (XPS), transmission electron microscopy(TEM), and Xray diffraction (XRD). The results confirm the existence of organic layer, which was connected with the inorganic nuclei by bidentate coordination.The average diameter of nanoparticles is about 68 nm. Although poor crystallinity obtained, the anatase phase of TiO2 could be inferred.The existence of organic ligands would greatly impact the nucleation and surface coordination of nanoparticles. The formation mechanism is postulated as a competitive reaction between polymerization and inhibition processes. Finally, the structural model for organo capped TiO2 nanoparticles is proposed.

Key words: Titanium dioxide, Surface modification, Nanoparticles, Sol-gel, 　Competitive reaction