Novel R-SiO1.5/TiO2 hybrid nanoparticles were synthesized by hydrolytic co-conclensation of titanium alkoxides; (Ti(OR')(4), R'= ethyl, isopropyl, and butyl) with a triethoxysilane precursor, R-Si(OCH2CH3)(3), R = -CH2CH2CH2 N(CH2CH2 COOCH2CH2OH)(2), derived from 2-hydroxyethyl acrylate. Co-condensation of a titanium alkoxide with the triethoxysilane precursor was investigated at different feed ratios, suggesting that water-soluble nanoparticles; were obtained only at less than 30% ofTi(OEt)(4) molar ratio in the feed. In contrast, the co-condensation of titaniurn tetraisopropoxicle, Ti((OPr)-Pr-i)(4), with the triethoxysilane precursor in the presence of acetylacetone proceeded as a homogeneous system until 70% of Ti((OPr)-Pr-i)(4) molar ratio to afford water-soluble organic-inorganic hybrid nanoparticles containing titania-silica mixed oxides, as confirmed by NMR, FT-IR, elemental and ICP analyses. Scanning force microscopy (SFM) measurements of the product prepared at Ti((OPr)-Pr-i)(4)/triethoxysi lane = 50/50 mol% with acetylacetone indicated the formation of the nanoparticles having relatively narrow size distribution with average particle diameter less than 2.0 nm without aggregation. The refractive index of the hybrid nanoparticle was 1.571. The isolated nanoparticles distributed homogeneously were visualized by transmission electron microscopy (TEM), and the size of the hybrid nanoparticle (1.9 nm) was determined by X-ray diffraction (XRD). (C) 2008 Elsevier B.V. All rights reserved.