Abstract
We have synthesized highly ordered mesoporous MCM-41 silica nanoparticles with controlled particle sizes by tuning the concentrations of the reactants. In addition, by mixing non-ionic surfactants with the cationic surfactant cetyltrimethylammoium bromide, the structure of the resulting mesoporous silicas can be tailored. Interestingly, we have successfully prepared mesoporous silica nanoparticles with a novel two-dimensional rectangular c2mm structure and elliptical pore section. In-situ small angle X-ray scattering/diffraction measurements have been applied to follow the structural evolution during the synthesis of the material, and the c2mm structure of the final product has been confirmed by powder X-ray diffraction and transmission electron microscopy. Furthermore, the scanning electron microscopic studies have shown that most of the c2mm mesoporous silica nanoparticles are spherical in shape and uniform in size, and only few particles with rod shape have been observed. We have also infiltrated platinum into the c2mm mesoporous silica nanoparticles, which clearly show that while the mesopore channels in the spherical nanoparticles are circular around the center axis, those in the rod-like nanoparticles have a chiral morphology.