Nanostructural orientation

Fig. 7 2D thickness-surface energy gradient library for mapping the effects of these parameters on the self-assembly of PS-b-PMMA block copolymer thin films. See text for a fuU description. Lq is the equilibrium self-assembly period and h is the film thickness. Dashed white lines delineate the neutral surface energy region, which exhibits nanostructures oriented perpendicular to the substrate plane. (Derived from [18] with permission)... 

On the basis of these observations, an interesting formation of nanostructures consisting of SWNTs was probably achieved by magnetic force, magnetic orientation, interaction of induced magnetic moment of SWNTs due to strong magnetic fields, and self-assembly of SWNTs due to hydrophobic interaction in aqueous solution and so on [46, 48]. 

Opportunities and Limits. If we intend to obtain a clearer look on nanostructure than the one the CLD is able to offer, we can try to get rid of the orientation smearing - either by considering materials with a special topology (layer stacks), or by studying anisotropic materials. 

Special care has to be taken concerning data pre-evaluation if the scattering of highly oriented nanostructures are investigated in symmetrical reflection or at grazing incidence. Absorption correction is delicate (cf. Sect. 7.6.3). Even a refraction correction (Sect. 7.6.5) may be necessary118. 

Let us consider a nanostructured thin film built from lamellar particles [84], If the principal axis of layer stacks is oriented normal to the film surface, the scattered intensity measured in symmetrical-reflection geometry (SRSAXS) is... 

Various works has pointed out the role of the nanostructure of the catalysts in their design.18-26 There is a general agreement that the nanostructure of the oxide particles is a key to control the reactivity and selectivity. Several papers have discussed the features and properties of nanostructured catalysts and oxides,27-41 but often the concept of nanostructure is not clearly defined. A heterogeneous catalyst should be optimized on a multiscale level, e.g. from the molecular level to the nano, micro- and meso-scale level.42 Therefore, not only the active site itself (molecular level) is relevant, but also the environment around the active site which orients or assist the coordination of the reactants, may induce sterical constrains on the transition state, and affect the short-range transport effects (nano-scale level).42 The catalytic surface process is in series with the transport of the reactants and the back-diffusion of the products which should be concerted with the catalytic transformation. Heat... 

P. Kumar, A. Mehta, S.M. Mahurin, S. Dai, M.D. Dadmun, B.G. Sumpter, and M.D. Barnes, Formation of oriented nanostructures from single molecules of conjugated polymers in microdroplets of solution the role of solvent, Macromolecules, 37 6132-6140, 2004. 

Abstract This article is a review of the chemical and physical nature of patternable block copolymers and their use as templates for functional nanostructures. The patternability of block copolymers, that is, the ability to make complex, arbitrarily shaped submicron structures in block copolymer films, results from both their ability to self-assemble into microdomains, the bottom-up approach, and the manipulation of these patterns by a variety of physical and chemical means including top-down lithographic techniques. Procedures for achieving long-range control of microdomain pattern orientation as well... 

The self-assembly of block polymers, in the bulk, thin film and solution states, produces uniformly sized nanostructured patterns that are very useful for nanofabrication. Optimal utilization of these nanoscopic patterns requires complete spatial and orientational control of the microdomains. However, the microdomains in the bulk state normally have grain sizes in the submicron range and have random orientations. In block copolymer thin films, the natural domain orientations are generally not desirable for nanofabrication. In particular, for composition-asymmetric cylindrical thin films, experimental... 

By modifying the surface/interface energies in a periodic manner, chemically patterned surfaces have also been widely used to control the orientation of nanostructures over large areas (Fig. 6). Theoretical [138-145] and experimental [73-76,88,89,146] results have indicated that with the appropriate surface grating and boundary conditions, lateral control over nanostructures propagates microns away from the surface (deep into the film), thus providing true 3D control of the self-assembly process. Russell and coworkers [73,74]... 

The nanoreplication of functional nanostructures has also been achieved through other block copolymer-templated structures. De Boer et al. [35] applied honeycomb-structured films of rod-coil block copolymer as patterned templates to replicate hexagonally packed arrays of aluminum cups on the substrate surfaces (Fig. 10b). Nguyen et al. [237] embedded semiconducting polymers in the channels of oriented hexagonal nanoporous silica and used this nanoscale architecture to control the energy transfer for potential optoelectronic applications. 

It is necessary to disperse the nanomaterials in the best possible manner, especially those layered structures such as graphite, graphene or clays. It is important to obtain very thin (ca. one nanometer) and very wide (ca. 500 nanometers) nanostructures dispersed in the polymer matrices to achieve optimal gas permeability and to improve their mechanical properties without affecting structural quality, using a small amount of the nanomaterial. The particle orientation also has an important effect on the properties of the nanocomposite. Nanoparticles need to be dispersed within the polymer so that are parallel to the material s surface. This condition ensures a maximum tor-... 

The nanostructured thin-film electrode was first developed at 3M Company by Debe et al. [40] and Debe [41], who prepared thin films of oriented crystalline organic whiskers on which Ft had been deposited. The film was then transferred to the membrane surface using a decal method, and a nanostructured thin-film catalyst-coated membrane was formed as shown in Figure 2.10. Interestingly, both the nanostructured thin-film (NSTF) catalyst and the CL are nonconventional. The latter contains no carbon or additional ionomer and is 20-30 times thinner than the conventional dispersed Pt/ carbon-based CL. In addition, the CL was more durable than conventional CCMs made from Pt/C and Nation ionomer [40]. 

The correct orientation and rigidity of the anthracene is also related to the second important idea in the nanostructuring of the electrode interface used by... 

Preparation of a new type of nanostructured composite thin film in which one component possesses unidirectional order while the other component is randomly oriented. 

Makinen R, Ruokolainen J, Ikkala O, De Moel K, ten Brinke G, De Odorico W, Stamm M. Orientation of supramolecular self-organized polymeric nanostructures by oscillatory shear flow. Macromolecules 2000 33 3441-3446. 

A key aspect of metal oxides is that they possess multiple functional properties acid-base, electron transfer and transport, chemisorption by a and 7i-bonding of hydrocarbons, O-insertion and H-abstraction, etc. This multi-functionality allows them to catalyze complex selective multistep transformations of hydrocarbons, as well as other catalytic reactions (NO,c conversion, for example). The control of the catalyst multi-functionality requires the ability to control not only the nanostructure, e.g. the nano-scale environment around the active site, " but also the nano-architecture, e.g. the 3D spatial organization of nano-entities. The active site is not the only relevant aspect for catalysis. The local area around the active site orients or assists the coordination of the reactants, and may induce sterical constrains on the transition state, and influences short-range transport (nano-scale level). Therefore, it plays a critical role in determining the reactivity and selectivity in multiple pathways of transformation. In addition, there are indications pointing out that the dynamics of adsorbed species, e.g. their mobility during the catalytic processes which is also an important factor determining the catalytic performances in complex surface reaction, " is influenced by the nanoarchitecture. 

As pointed out in part 1, ° ID oxide nanostructures do not represent only particles with high elongation ratio, but possess different spedfie eharaeteristics related to the nanostructure. For example, O2 adsorption is different from that observed for Ti02 single erystals and this has consequenees on the catalytic behaviour. In order to exploit the properties of ID oxide nanostructure, however, it is essential to orient nanotubes on substrates and to create ordered arrays. 

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