Organic-inorganic hybrid core-shell nanoparticles with diameters ranging from 100 to 1000 nm were prepared by a one-pot synthesis based on base catalyzed sol-gel reactions using tetraethoxysilane and a triethoxysilane-terminated polyethylene-b-poly(ethylene glycol) as reactants. Data from TEM, TGA, and solid-state NMR analysis are in agreement with the formation of core-shell nanoparticles with an inorganic-rich core and an external shell consisting of an amphiphilic block copolymer monolayer. The influence of the organic-inorganic ratio, solution concentration, and postcuring temperature on core and shell dimensions of the nanospheres were investigated by TEM microscopy. (c) 2008 Wiley Periodicals, Inc.