Super lattice

In order to make practical use of the physical properties of nanoparticles, whether individual or collective, one has to find a way to address them. If we leave out the near field techniques, this in turn requires that the particles be monodisperse and organized in two or three dimensions. It is therefore necessary to imagine techniques allowing the self-organization and even, ideally, the crystallization of nanoparticles into super-lattices. 

One of the main challenges in the field is the controlled crystalhzation of the nanoparticles into 3D super-lattices, similar to artificial opals but including much smaller individual particles. For this we have used electrically charged stabihzers (ligands and surfactants). For example, the photochemical decomposition of the precursor [Sn(NMe2)2]2 in the presence of HDA... 

Fig. 11 Formation of crystalline 3D super-lattices of tin nanoparticles a TEM view of a facetted super-crystal b SEM image showing particles included into a super-crystal as well as the organic surrounding c High resolution micrograph showing the alignment of the tin atomic planes inside the super-structure...

This process of crystalHzation using charges was extended to other systems using as an alternative mixtures of amines and long chain carboxylic acids. In this way, super-lattices of nanorods of cobalt and of nanocubes of iron were prepared (vide infra). 

In summary, super-lattices may be obtained using the estabUshed techniques of self-organization but also a technique derived from molecular chemistry, the creation of hydrogen bond networks, hi addition, the crystallization of nanoparticles inside 3D super-crystals may be achieved using ionic stabilizers. 

Fig. 13 Super-lattice of cobalt nanorods a Top view hexagonal b vue de cote c image k haute resolution...

Fig. 15 Super-lattices of iron nanocubes a SEM micrograph of a super-cube b TEM micrograph of a super lattice c TEM micrograph after ultramicrotomy...

The unit cell of cellulose from Chaetomorpha melagonium is monoclinic, with a = 16.43 A (1.643 nm), b(fiber axis) = 10.33 A (1.033 nm), c = 15.70 A (1.570 nm), and /3 = 96.97°. In base-plane projection, each of the Meyer-Misch subcells that make up the super-lattice are identical. All equatorial reflections can be indexed by using a one-chain unit-cell, meaning that every single chain has... 

A number of publications have appeared recently on super-lattice complexes which have enhanced conductivity, eg. "nazirpsio NaaPOif 2Zr02 2Si02 whose conductivity at room temperature is of the same order as that of an aqueous salt solution. Most of the super-lattices are unstable thermodynamically, and can be expected to collapse under chemical attack by the anodic and cathodic reactants. However, there may exist some thermodynamically stable structures, and the search should concentrate on the complicated phase-diagram studies of selected quatemarys. 

In the majority of cases where adsorbates form ordered surface structures, the unit cells of those structures are larger than the unit cell of the substrate the surface lattice is then called a super lattice. The surface unit cell is the basic quantity in the description of the ordering of surfaces. It is necessary therefore to have a notation that allows the unique characterization of superlattices relative to the substrate lattice. 

In zone II, that of normal mixed layered dioctahedral minerals, there are few characteristic mineral reactions. However, the change of the interstratified material as it becomes "allevardite-type" mineral, i.e., showing a discrete super-lattice reflection, is undoubtedly complex. 

The 13 mode polyiodines form a super lattice with a spacing of 900 pm within a crystal, demonstrated directly by X-ray diffraction in the specimens soaked at high iodine concentrations, as will be shown in next section. In this case, however, no evidence is obtained for the existence of any super lattice of these polyiodines. Thus the result on the breadth of the profile indicates that the polyiodines coagulate to make an apparent linear lattice in which iodine atoms keep nearly the same distance to their neighbors. 

In 1993, following the experimental evidence of nanoscale striped lattice fluctuations in cuprates shown in Fig. 2, we have proposed to increase Tc via a Feshbach shape resonance in a different class of systems super lattices of superconducting units as shown in Fig. 3 [75,76,80,81,87-89,93-97,102,109,110],... 

If h > k and k 0 then the super-lattice is unsymmetrically disposed with respect to the original lattice. If the lattice is turned over and superimposed on itself so that the super-lattice points coincide, then we have a coincidence site lattice (in which a fraction 1 /(h2 + hk + k2) of the original lattice points coincide). Coincidence site lattices can also be found in three dimensions, particularly for cubic lattices. 

Stabilization of Super lattices by Friedel Oscillations in Surface States... 

Toth, R.S., Sato, H. (1962) Long period super lattice Cu3AuII, J. Appl. Phys, 33(11), 3250-3256. 

John S. (1987) Strong localization of photons in certain disordered dielectric super lattices. Phys Rev Lett 58 2486-2488. 

In the SC and SS structures, the nodes of the component lattices of A and B coincide at multiples of the basic vector(s) and there is a coincidence ( super -) lattice, and its coincidence unit cell. The former represents a set of coinciding nodes of the true component lattices, and in the ideal case - with structurally-independent layer sets - it is not connected with common structural changes (modulation) in them. For growth considerations it is important that the SC and SS (as well as CC) structures have a coincidence mesh (coincidence net) parallel to the layers, whereas the IS structures have only a coincidence row in the layer plane. 

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