Preparation of Monodispersed Mesoporous Silica Spheres with Controllable Particle Size Under an Alkaline Condition

Monodispersed mesoporous silica spheres ( MMSS s) with tunable particle size were successfully synthesized from tetraethyl orthosilicate ( TEOS ) and cetyltrimethylammonium bromide ( CTAB ) under an alkaline condition. The MMSS s synthesized under different reaction conditions, such as reaction temperature, co‐solvent amount, and TEOS and CTAB concentrations, have been investigated by scanning electron microscopy ( SEM ), transmission electron microscopy ( TEM ), small angle X ‐ray diffraction ( SAXRD ), and nitrogen adsorption–desorption. The average particle size increases with increase in the reaction temperature from 40°C to 90°C, and 80°C is the optimal temperature to synthesize MMSS s with narrow particle size of 75 ± 14 nm. Ethanol plays a role as co‐surfactant in low concentration, and then as co‐surfactant and co‐solvent in high concentration, which results in an increase in particle size from 75 ± 14 nm to 518 ± 30 nm and change of the mesoporous structure from paralleled array type to radially orientated type. The average particle size and yield of MMSS s increase with increase in the TEOS concentration when the TEOS concentration reaches saturated level ( C _s = 0.09 M ), but some small silica particles appear when the TEOS concentration is higher than the critical level ( C _s * = 0.134 M ). When the CTAB concentration increases, at the same TEOS concentration, the surface area, and pore volume increases, but the monodispersity becomes low.