Silica nanoparticles have been prepared from tetraethylorthosilicate dissolved in ethanol followed by base-catalyzed condensation. Earlier works reported that at least four parameters, namely concentration of tetraethylorthosilicate, ethanol, water and ammonia solution are needed to be optimized for the size tuning of silica nanoparticles. In this work size tuning of 5 nm-250 nm has been achieved by varying a single synthesis parameter i.e., the concentration of ammonia solution. Oxygen plasma was found to be successful for generating pores on silica nanoparticles without using any structure directing agents. The properties and morphology of nanoparticles were investigated by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transformed infrared spectroscopy. Silica nanoparticles have been prepared from tetraethylorthosilicate dissolved in ethanol followed by base-catalyzed condensation. Earlier works reported that at least four parameters, namely concentration of tetraethylorthosilicate, ethanol, water and ammonia solution are needed to be optimized for the size tuning of silica nanoparticles. In this work size tuning of 5 nm-250 nm has been achieved by varying a single synthesis parameter ie, the concentration of ammonia solution. Oxygen plasma was found to be successful for generating pores on silica nanoparticles without using any structure directing agents. The properties and morphology of nanoparticles were investigated by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transformed infrared spectroscopy.