A novel one step green chemistry approach utilizing trioctylmethyl ammonium hydrogen phthalate (TOMAHP), task specific ionic liquid has been attempted for synthesis of Ag and Pt nanoparticles supported on silica (Ag@mSiO(2) and Pt@mSiO(2)). Structure, size distribution and morphology of these nano composite particles were evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), small angle neutron scattering (SANS) as well as small angle X-ray scattering (SAXS) techniques. The XRD results show that Ag/Pt metal nanoparticles deposited on to SiO2 surface are face center cubic (fcc) in nature. The TEM and SAXS/SANS results show the morphology and size distributions of Ag and Pt nanoparticles loaded on to the surface of SiO2. It has been found that Ag nanoparticles are well dispersed on to the SiO2 surface and are quite monodisperse in size, whereas Pt nanoparticles are quite poly disperse in size and forms aggregate or chain like structure on SiO2 surface containing primary nano particles of typical size range 3-7 nm. The stability of nanoparticles, which controls its dispersion on SiO2 substrate, has been discussed. (C) 2016 Elsevier B.V. All rights reserved.