Surfactant Controlled Growth of Niobium Oxide Nanorods

his paper describes a solution-phase hydrothermal synthesis of crystalline niobium pentoxide (Nb2O5) nanorods. The methods reported herein yield uniform Nb2O5 nanorods with average diameters of 6 nm and lengths of 38 nm, which are directly synthesized from niobic acid by a hydrothermal process. The formation of Nb2O5 nanorods from niobic acid was studied in the presence of surfactants that stabilize the nanostructures. The crystalline Nb2O5 nanorods were relatively uniform in size and shape. The size of the Nb2O5 nanorods could be tuned through the choice of surfactant even in the absence of a worm-like micellar morphology. Amine, amide, ammonium, carboxylate, sulfonate, and sulfate containing surfactants were systematically evaluated for their influence on the ability to form uniform Nb2O5 nanorods. The surfactants in this study had hydrophobic tails that were either straight or branched, such as a polymer, and contained either a single or multiple head groups. The nanorods grew by a process of oriented attachment of nanoparticles that was regulated by the surfactants added into the reaction mixture. The results of these studies indicate that this synthetic approach serves as a tunable platform to prepare single crystalline niobium oxide based nanostructures with well-defined morphologies and dimensions. This surfactant assisted formation of crystalline Nb2O5 nanorods could also have important implications in the design of other transition metal oxide based nanomaterials.