Dendritic growth of cubically ordered nanoporous materials through self-assembly

Self-assembled nanoporous materials have potential for many applications. Here we report unusual dendritic crystals from self-assembled nanoporous silicates and continuous morphological change of such materials through chemical means. We used hybrid organic silane and quaternary ammonium surfactants to prepare large dendritic nanoporous crystals. These self-assembled crystals have a cubic structure (Pm3m), 4-fold symmetry, and are oriented with the [100] direction perpendicular to the surface. Remarkably, the morphology of the crystals can change from highly branched, square-shaped dendrites to less branched structures, to nonbranched crosses, and finally to regular compact crystals when the Cl- counterions on the surfactant were gradually replaced by Br- while keeping the total surfactant concentration constant. The unusual dendritic crystals and their continuous morphology change suggest the importance to control diffusion and surface reactivity for self-assembled crystal growth under nonequilibrium conditions. The open dendritic nanoporous structures may be useful for sensing and other applications.