Size-controlled synthesis of monodispersed mesoporous silica nano-spheres under a neutral condition

Under a neutral condition, monodispersed mesoporous silica nano-spheres (MSNs) with controllable size were synthesized. The effects of temperature, structure-directing agent (SDA), co-surfactant/co-solvent propanetriol (PT) and multistep addition modes on particle size and the dispersivity of MSNs were studied. The results showed that MSNs became bigger and more uniform in size with the increase of the temperature. Compared with single surfactant, the use of cationic–nonionic composite surfactants of CTAB and Brij-56 as SDA resulted in the improved dispersivity and regularity of spherical shape, and the decreased particle size of MSNs. PT as additive effectively improved the monodispersivity of MSNs. With the gradual increase of the PT concentration, PT played a role of co-surfactant at first and then of co-solvent, resulting in an unusual dependence of the particle size of MSNs on the PT concentration. Multistep addition modes further contributed to the uniformity and bigger size of MSNs.