Morphology nanorods

Of the various semiconductors tested to date, Ti02 is the most promising photocatalyst because of its appropriate electronic band structure, photostability, chemical inertness and commercial availability. But currently, a variety of nanostmctured Ti02 with different morphologies including nanorods, nanowires, nanostmctured films or coatings, nanotubes, and mesoporous/nanoporous structures have attracted much attention. 

The alternation of temperature in a hydrothermal reaction was demonstrated to be crucial in changing the crystal phases or morphologies of nanomaterials. In the case of K2Cr207, when the reaction temperature was increased to 180 °C, K-OMS-2 microspheres consisting of nanoneedles were synthesized in contrast to the nanoduster arrays composed of tetragonal prism nanorods synthesized at 120 °C (Figure 8.1a-c). In the case of Na2Cr207, when the reaction temperature was 100 °C, Na-OMS-2 phase was formed. However, when the reaction temperature was... 

Liu, Q., Mao, D., Chang, C. and Huang, F. (2007) Phase conversion and morphology evolution during hydrothermal preparation of orthorhombic I iMiiO, nanorods for lithium ion battery application, journui of Power Sources, 173, 538-544. 

The reaction yielding W02(0H)2 is necessary to provide a volatile species to form the nanorod morphology. Without it, mass transport would be exceedingly slow and the nanorod morphology impossible. 

Readers interested in more specific details about synthesis strategies, mechanisms of nanorod formation, characterization, or factors influencing the morphology of noble metal nanorods are referred to a comprehensive review by Sau and Rogach [185]. Reviews by Kijima and Zhang et al. will provide additional, detailed information on the synthesis of other one-dimensional metal nanostructures (including nanowires and nanotubes) [186, 187]. 

Numerous nanostructures such as nanorods, nanotubes, or nanorings have been obtained by this approach. In particular, the use of organoge-lators as directors to control the morphologies of the aggregates has been explored recently. Cholesterol- and phospholipid-thethered trans-styl-benes are able to gelate different organic solvents in which the steroid and the lipid units serve as templates to form one-dimensional stacks. 

Colloidal boehmite nanorods have been included in a PA-6 matrix to yield a homogeneous dispersion by in situ polymerization.91 At weight fractions up to 9%, improvements in the Young s modulus of the composite and changes in the crystalline morphology of the PA-6 matrix were observed, although fire properties were not reported. 

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