Mesoporous silicas of hierarchical structure by hydrothermal surfactant-templating under mild alkali conditions

Mesoporous silicas with hierarchical structures were synthesized under a mild alkali condition by cationic or mixed cationic-nonionic surfactant templating. When cetylpyridium bromide was used, a novel morphology of mesoporous silica of type MCM-41 was formed. It was obsearved. that single nanotubes with diameter of about 5 nm and bundles of nanotubes grew from the (001) surface of the mesoporous silica particles, forming a paintbrush-like morphology. The synthesis process was investigated and the formation mechanism of such a surface nanotube patterning is discussed. When mixed surfactant of cetylpyridium chloride and Triton X-100 was used, a mixed ordered-disordered hierarchical mesostructure with arc rings of submicrometer scales was observed in the synthesized mesoporous silica which exhibits a narrow pore size distribution, high surface area and a large pore volume. Are ropes consisting of ordered mesopores, as well as many spheres of submicrometer in diameter with shells of about 40 nm in thickness consisting of ordered arrays of mesopores, were observed, though the majority of the particles contained disordered mesoporous microdomains. This material lacks overall long-range ordering whereas local ordering of mesopores exists.