Nanoscale structures

The SFM images shown in Fig. 11 have proved that CNTs are promising for nanoscale structural investigation and are better than the normal silicon nitride probes [36]. 

Desai TA. Micro- and nanoscale structures for tissue engineering constructs [J]. Med Eng Phys, 2000, 22, 595-606. 

In any case, it is interesting to note that catalytic efficacy has been observed with nano- or mesoporous gold sponges [99-101, 145] suggesting that neither a discrete particle nor an oxide support is actually a fundamental requirement for catalysis. An alternative mechanism invokes the nanoscale structural effect noted in Section 7.2.2, and proposes that the catalytic effect of nanoscale gold structures is simply due to the presence of a large proportion of lowly-coordinated surface atoms, which would have their own, local electronic configurations suitable for the reaction to be catalyzed [34, 49,146] A recent and readily available study by Hvolbaek et al. [4] summarizes the support for this alternate view. 

Laser ablation of polymer films has been extensively investigated, both for application to their surface modification and thin-film deposition and for elucidation of the mechanism [15]. Dopant-induced laser ablation of polymer films has also been investigated [16]. In this technique ablation is induced by excitation not of the target polymer film itself but of a small amount of the photosensitizer doped in the polymer film. When dye molecules are doped site-selectively into the nanoscale microdomain structures of diblock copolymer films, dopant-induced laser ablation is expected to create a change in the morphology of nanoscale structures on the polymer surface. 

Recent developments of materials and devices with structures in nanometer length scales have created new opportunities and challenges in the science of thermal transport. Interfaces play a particularly important role in the properties of nanoscale structures and nanostructured materials [97-98], This is why a renewed interest for contact resistance arose in recent years with studies of nanocomposite, semicrystalline and polycrystalline materials where contact resistances has a controlling role to determine the bulk thermal conductivity of the material [99-100],... 

The study of principles relevant to building nanoscale structures of, for example, 1-100 nm in size has recently been referred to as nanoscience, and it is expected that methods for the fabrication of nanostructures will evolve into nanotechnologies. The present approach toward a nanochemistry is of more fundamental character since it is restricted to single molecules of a few nm in size or even smaller and focuses on the molecular pattern. 

Based on the specific requirements for the operation of fluorescence reporters, we have divided them into two broad categories [2]. One category comprises reporters that serve as labels and tags. Their only response is based on their presence in a particular medium or at a particular site, and the major parameters that have to be optimized are their brightness and photostability. Brightness and durability can be increased dramatically if, instead of single molecules, we use nanoscale structures containing hundreds or thousands of them, and if we incorporate... 

Figure 15.1 Ordered nanoscale structures of mesoporous materials such as FSM-16 and HMM-1 (Et-HMM-1) as the silica and organosilica templates for surface-mediated synthesis of metal/alloy nanowires and nanoparticles.

The weak physical forces that hold together self-assembled nanoparticles are, of course, susceptible to disruption under the influence of thermodynamic and/or mechanical stresses. Hence some workers have investigated ways to reinforce nanoscale structures via covalent bonding. For instance, improved stability of protein nanoparticles, in particular, casein micelles, can be achieved by enzymatic cross-linking with the enzyme transglutaminase, which forms bonds between protein-bound glutamine and lysine residues. By this means native casein micelles can be converted from semi-reversible association colloids into permanent nanogel particles (Huppertz and de Kruif, 2008). 

Table 6.2 Schematic representation of nanoscale structure and experimental data relating to self-assembly of sodium caseinate induced by interactions of the protein (1.0 % w/v) with micelles of food-grade surfactants (CITREM and SSL) in an aqueous medium (pH = 5.5, ionic strength = 0.05 M, 293 K) above the surfactant cmc. 

Hence, from the previously described light-scattering study of caseinate self-assembly in solution, we can postulate that heating/cooling not only alters the nature and strength of the physical (hydrophobic) interactions between emulsion droplets covered by caseinate. It most likely also transforms the nanoscale structural characteristics of the protein network in the bulk and at the interface, thereby affecting the viscoelastic and microstructural properties of the emulsions. 

An important nature-mimicking methodology involves the use of covalent synthesis followed by molecular self-assembly of the synthesized molecules. These molecules are generally small mono- or oligomers that interact with each other and with other kinds of mono- or oligomers to form thermodynamically stable, nanoscale structures. See also Molecular Recognition. 

Further reduction in feature size to achieve nanoscale structures by photolithography will necessitate the use of ever smaller wavelengths of light. 

The most recent approach to reductive nanofabrication that can indeed construct nanoscale structures and devices uses microscopic tools (local probes) that can build the structures atom by atom, or molecule by molecule. Optical methods using laser cooling (optical molasses) are also being developed to manipulate nanoscale structures. 

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