A facile and finely-controlled synthesis of versatile porous silica nanomaterials: Nanopods, helical nanorods and nanovesicles

A variety of mesoporous silica nanomaterials with different morphologies and pore structures have been successfully synthesized by only adjusting a single parameter in an identical approach through a basic-catalyzed silica sol–gel process with tetradecyltrimethylammonium bromide (C14TAB) and sodium perfluorooctanoate (PFONa) as co-templates. By simply increasing the amount of PFONa, the porous structure changes from ordered hexagonal mesostructure with short cylindrical shape to helical mesostructure with straight rod-like morphology, then to hollow particles with porous wall, and finally to nanovesicles. More importantly, it is found that the structural transition occurs in the middle of helical rods where the strongest micelle tension strength exists and is considered to be the most unstable area of the particle. We propose that the surface free energy and hydrophilic/hydrophobic ratio are the driving forces to induce the morphological and structural transformation. Our research provides a facile preparation method to obtain various porous silicas which opens new opportunities for the exploration of versatile practical applications for novel porous materials in future. We report a finely-controlled synthesis of various nanoporous silicas such as ordered mesoporous nanopods, helical nanorods, hollow particles with porous wall, and nanovesicles in an identical approach by simply adjusting the weight ratio of tetradecyltrimethylammonium bromide (C14TAB) and sodium perfluorooctanoate (PFONa) co-templates. Such morphological and structural transformation is proposed to be induced by the reduction of surface free energy and hydrophilic/ hydrophobic ratio. More importantly, we explore the interaction between perfluorinated molecules and ionic surfactant with shorter alkyl chain and reveal the effect of the chain stiffness of surfactants on the self-assemble behavior. [Display omitted] •A variety of porous silicas has been synthesized by simply tuning the weight ratio of co-templates.•The structural transition occurs in the middle of helical rods where is the most unstable area.•The surface free energy and hydrophilic/hydrophobic ratio are responsible for the transition.