In this work, silica nanoparticles (SNPs), vinyl and acrylate modified SNPs were synthesized by a novel one-pot synthesis method using TEOS and the appropriate organosilanes as the modifier molecules including vinyltrimethoxysilane (VTMS) and 3-( methacryloyloxy) propyltrimethoxysilane (MPS). Although, spherical SNPs with average diameter ranging from 50 to 700 nm were synthesized, the reaction conditions were tuned to obtain the final modified silica nanoparticles with diameter smaller than 50 nm. Various experimental conditions including solvent, ammonia concentration, reaction time and temperature were optimized. Particles were characterized using FTIR TGA, SEM, TEM and water contact angle. It was found that the modifier silane, when used in one-pot method, can reduce the size of the silica nanoparticles due to the non-hydrolysable substitution in its chemical structure compared to TEOS. The one-pot method is a shortcut and versatile method for synchronized synthesis and modification of a wide range of customized silica nanoparticles using different modifier silanes. (C) 2012 Elsevier B.V. All rights reserved.