Hydrophilic and hydrophobic silica nanoparticles were synthesized by a cheap, simple and low temperature one-step method. The method involves a catalytic reaction between ammonium hydroxide, tetraethyl orthosilicate (TEOS) and dichlorodimethylsilane (DDS) in an ethanol solvent. The effects of different parameters such as chemical concentration and reaction temperature were investigated on size of the synthesized silica particles. Characterizations of hydrophilic and hydrophobic particles were performed using dynamic light scattering (DLS), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). According to the results, by reducing the amount of ammonium hydroxide, ethanol and temperature, the size of hydrophilic silica particles can be reduced to 129 +/- 10.4 nm. Other sides, addition of DDS agent caused to silica particles found hydrophobic property and size of the particles reduced to about 65 +/- 6.5 nm. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.