Structural and morphological control of mesostructures: Vanadium based nanofibers

Mesostructured vanadium-magnesium oxides (V-Mg-O) with various morphologies were synthesized at room temperature using MgCl2 and V2O5 as source materials and a large number of surfactants as templates. It was found that, among the surfactants employed, the quaternary ammonium surfactants with long alkyl chains, such as cetyltrimethylammonium bromide (CTAB), or the nonionic surfactant Triton-X 100 could template V-Mg-O mesostructures. In the former case, the synthesized specimen had a lamellar structure and nanofibrous morphology. In the latter case, the specimen had a lamellar structure but a particulate morphology. Among the binary mixtures of cationic, anionic, or nonionic surfactants employed, only the combinations between a quaternary ammonium surfactant and hexadecylamine (HDA) were effective in templating a lamellar mesophase with nanofibrous morphology. The binary surfactants were more effective than the single surfactants in generating a higher regularity of the lamellar mesostructure. Mesostructured V-Mg-O could be synthesized even using binary mixtures consisting of HDA and a quaternary ammonium surfactant with a short alkyl chain, such as benzyltrimethyl (neither of the two was effective when used alone). The mesostructured V-Mg-O nanofibers synthesized with binary mixtures of surfactants were more stable during heating at high temperatures than those synthesized with a cationic surfactant alone.