Room temperature synthesis of nanoporous silica spheres and their formation mechanism

We describe a robust process for the synthesis of micrometer-sized nanoporous (mesoporous) silica spheres using disodium trioxosilicate as an economical silica source and cetyltrimethylammonium chloride as the structure directing agent by the self-assembly process in the presence of formamide under alkaline condition at room temperature. The surface area of the spheres is 600 m2/g, whereas the pore diameter and pore volume are 3.3 nm, and 0.3 cm3/g, respectively. The formation mechanism of the spheres is studied with dynamic light scattering (DLS) and atomic force microscopy (AFM) techniques. We found that the formation involved two steps. In the first step 20–30 nm size primary particles are formed which then fuse together in the second step to form micron-sized mesoporous spheres.