Structure formation nanorods

Self-assembled nanorods of vanadium oxide bundles were synthesized by treating bulk V2O5 with high intensity ultrasound [34]. By prolonging the duration of ultrasound irradiation, uniform, well defined shapes and surface structures and smaller size of nanorod vanadium oxide bundles were obtained. Three steps which occur in sequence have been proposed for the self-assembly of nanorods into bundles (1) Formation of V2O5 nuclei due to the ultrasound induced dissolution and a further oriented attachment causes the formation of nanorods (2) Side-by-side attachment of individual nanorods to assemble into nanorods (3) Instability of the self-assembled V2O5 nanorod bundles lead to the formation of V2O5 primary nanoparticles. It is also believed that such nanorods are more active for n-butane oxidation. 

Figure 15.18 Proposed structures of (a) Pt nanorod wires in silica FSM-16 and (b) Pt nanonecklace wires in organosilica such as HMM-1 (Et-HMM) and HMM-p (Ph-HMM), which are used as the mesoporous templates for nanowire formation.

In 2003, Sugimoto and Kanie published what appears to be the first claim on the formation of nematic-like one-dimensional ordering in liquid crystal-nanoparticle hybrid materials. Different shapes of Ti02 nanoparticles were hybridized with two structurally different rod-like liquid crystal amines (one based on a cyanobiphenyl and a second with a fluorinated cyclohexylbiphenyl core), but only the combination of spindle-like Ti02 nanorods (with an aspect ratio greater than 10) with the... 

By oriented attachment, Yu et al. [8] could obtain ZnS nanorods with cubic blend structure, in which the (11 1) planes of the component ZnS nanocrystals are nearly perfectly aligned. Pradhan et al. [9] have reported the formation of colloidal CdSe quantum wires by the oriented attachment of magic-sized clusters of CdSe. 

Various compounds have been prepared by solvothermal reactions metals, metal oxides, chalcogenides, - ° nitrides, - -" phosphides, open-framework structures, - oxometalate clusters, - organic-inorganic hybrid materials, - - and even carbon nanotnbes. - Most of the solvothermal products are nano- or microparticles with well-defined morphologies. The distribution of the particle size of the prodnct is nsnally qnite narrow, and formation of monodispersed particles is freqnently reported. - When the solvent molecules or additives are preferentially adsorbed on (or have a specific interaction with) a certain surface of the products, growth of the surface is prohibited and therefore products with unique morphologies may be formed by the solvothermal reaction. - - Thus nanorods, wires, tnbes, and sheets of various types of products have been obtained solvothermally. 

Mesophase structures self-assembled from surfactants (Figure 8.35) provide another class of useful and versatile templates for generating ID nanostructures in relatively large quantities. It is well known that at critical micellar concentration (CMC) surfactant molecules spontaneously organize into rod-shaped micelles [315c]. These anisotropic structures can be used immediately as soft templates to promote the formation of nanorods when coupled with appropriate chemical or electrochemical reaction. The surfactant needs to be selectively removed to collect the nanorods/nanowires as a relatively pure sample. Based on this principle, nanowires of CuS, CuSe, CdS, CdSe, ZnS and ZnSe have been grown selectively by using surfactants such as Na-AOT or Triton X of known concentrations [238, 246]. 

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