Highly Uniform Nano and Mesostructures of Silica Obtained by Reverse Micellar and Hydrothermal Methods

Silica nanoparticles with controlled size and morphology and a high degree of monodispersity have been synthesized using single and double microemulsion systems employing a cationic surfactant (CTAB) and a non-ionic surfactant (Tergitol). Depending on the type of surfactant aggregate acting as templates, very different morphologies were formed. Nanospindles of silica of similar to 200-300 nm in length and nanofibres could be obtained by suitably controlling the reverse micellar methodology. The hydrothermal method resulted in highly porous and uniform spheres of diameter similar to 300 nm which appears to be formed from aggregates of small silica nanoparticles of size similar to 10 nm. The surface area of the nanoparticles (119 m(2)/g) was found to be much higher than the corresponding bulk SiO2 (500-600 nm) which had a surface area of 22 m(2)/g. The hydrothermally obtained spheres of size similar to 300 nm show a surface area of 35 m(2)/g.