Synthesis and characterization of spherical silica nanoparticles by modified Stober process assisted by slow-hydrolysis catalyst

We demonstrate the synthesis of spherical silica nanoparticles via a facile method based on the modified Stober process for reacting tetraethyl orthosilicate with a slow hydrolysis catalyst in water. Analyses by Fourier-transform infrared spectroscopy and energy dispersive X-ray spectroscopy indicated that the products were pure silica after calcination at 800 A degrees C for 10 h. The amorphous natures of the products were verified by X-ray and electron diffraction. Transmission electron microscopy observations revealed that the amorphous silica nanoparticles were dispersed and fine in size. The average particle sizes and particle size distributions of the amorphous silica nanoparticles could be controlled by adjusting the type of the slow hydrolysis catalyst. Dispersed spherical silica nanoparticles with average particle sizes ranging from 13 to 32 nm were synthesized successfully.