Silica (SiO2) nanoparticles have wide potential applications in many advanced areas. In this paper, we report an easy method for the synthesis of monodisperse SiO2 nanoparticles by a simple emulsion method. The novelty of this method lies in the synthesis of nanoparticles without the traditional use of any surfactants and toxic solvents. The phase purity of the synthesized SiO2 nanoparticles were determined by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). Morphology and nanoparticle size was determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the concentration of tetraethyl orthosilicate (TEOS), ammonia and water on the final size of the nanoparticles was observed. By precisely controlling the concentration of ammonia and water, SiO2 nanoparticles ranging between 30 and 90 nm were synthesized without the use of any surfactants. The results presented a simple, convenient and non-toxic method for the synthesis of SiO2 nanoparticles on a large-scale with precise control of the particle size. (C) 2016 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan. All rights reserved.