| Abstract
| - A formation mechanism for monodispersed mesoporous silica spheres was investigated from the viewpointof both particle growth and the progress of the condensation of the silica precursor. The particle growth ofmonodispersed mesoporous silica spheres was studied by TEM observation. The development of the mesoporeswas examined by in situ X-ray diffraction measurements. The condensation reaction of the silica precursorwas analyzed by silicic acid titration and pH−conductivity measurements during the synthesis. It was foundthat small particles emerged suddenly after the commencement of the synthesis, and then the residual silicaprecursors reacted preferentially with the surface silanols on these existing particles. This led to the formationof monodispersed mesoporous silica spheres. Conversely, new small particles emerge throughout the synthesisin the case of a heterogeneous system. To confirm the preferential reaction of the silica precursors with thesurface silanols, expansion of the existing particles was carried out by adding more silica precursor after thecompletion of the synthesis. It was found that the sizes of the particles were enlarged by the successiveaddition of more of the silica precursor. Surprisingly, the radial alignment of the hexagonal mesopores wasstill retained in the expanded particles. In addition, by the addition of a different silica precursor to the initialone, highly monodispersed core/shell mesoporous silica spheres possessing a hydrophilic core and a hydrophobicshell were successfully obtained for the first time.
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