Organic superlattice

Apart from these few examples, most nanostruc-tured materials are synthetic. Empirical methods for the manufacture of stained glasses have been known for centuries. It is now well established that these methods make use of the diffusion-controlled growth of metal nanoparticles. The geometrical constraints on the electron motion and the electromagnetic field distribution in noble-metal nanoparticles lead to the existence of a particular collective oscillation mode, called the plasmon oscillation, which is responsible for the coloration of the material. It has been noticed recently that the beautiful tone of Maya blue, a paint often used in Mesoamer-ica, involves simultaneously metal nanoparticles and a superlattice organization [3.1]. 

Generation of nanoparticles under Langmuir monolayers and within LB films arose from earlier efforts to form nanoparticles within reverse micelles, microemulsions, and vesicles [89]. Semiconductor nanoparticles formed in surfactant media have been explored as photocatalytic systems [90]. One motivation for placing nanoparticles within the organic matrix of a LB film is to construct a superlattice of nanoparticles such that the optical properties of the nanoparticles associated with quantum confinement are preserved. If mono-layers of capped nanoparticles are transferred, a nanoparticle superlattice can be con-... 

In this review, we describe collective physical properties due to self-organization of nanocrystals in 2D and 3D superlattices. 

V. COLLECTIVE PROPERTIES OF NANOCRYSTALS SELF-ORGANIZED IN 2D AND 3D SUPERLATTICES... 

When the silver nanocrystals are organized in a 2D superlattice, the plasmon peak is shifted toward an energy lower than that obtained in solution (Fig. 6). The covered support is washed with hexane, and the nanoparticles are dispersed again in the solvent. The absorption spectrum of the latter solution is similar to that used to cover the support (free particles in hexane). This clearly indicates that the shift in the absorption spectrum of nanosized silver particles is due to their self-organization on the support. The bandwidth of the plasmon peak (1.3 eV) obtained after deposition is larger than that in solution (0.9 eV). This can be attributed to a change in the dielectric constant of the composite medium. Similar behavior is observed for various nanocrystal sizes (from 3 to 8 nm). 

When silver particles are self-organized in a 2D superlattice on Au(lll) substrate (Fig. IB), the recorded I(V) curve is that given in Figure 9B. For large biases, the detected current is reduced by more than one order of magnitude compared to that observed for isolated particles. This indicates an increase in the ohmic contribution to the current. The... 

Chapter 8 presents evidence on how the physical properties of colloidal crystals organized by self-assembly in two-dimensional and three-dimensional superlattices differ from those of the free nanoparticles in dispersion. 

Murray, C. B. Kagan, C. R. Bawendi, M. G. 1995. Self-organization of CdSe nanocrystallites into three-dimensional quantum dot superlattices. Science 270 1335-1338. 

Superionic conducting glass systems, 12 586 Superior vena cava, 5 80 Super iron cells, 3 431t Superlattice(s), 13 499, 19 166 via MOCVD, 22 158-160 Superleaks, 17 354 Super Lewis acids, 12 191 Superluminscent LEDs, 22 176 Supermilling acid dyes, 26 396 Super milling dyes, 9 184, 185 Super-moire pattern, 17 428 Supermolecular organization, of polyamide fibers, 19 740... 

LB films also form well-defined engineered organic/inorganic superlattices. There are many examples in the literature and we just recall here some of them ... 

These experimental facts indicate that this system can be an excellent model of band-filling control, and will be a good candidate for making a superlattice composed of Mott insulator/superconductor hetero-junctions. It should be emphasized that their lattice parameters are nearly kept constant through such an anion modification, which is the most essential feature for achieving the successful tuning of Tc in an organic superconductor. 

Self assembly of non-centrosymmetric hybrid superlattices containing metal ions and unidirectionally aligned dipolar organic chromophores as intercalated... 

Monolayers of alkyl chains on silicon are a significant addition to the family of SAMs. An ability to directly connect organic materials to silicon allows a direct coupling between organic materials and semiconductors. The fine control of superlattice structures provided by the self-assembly technique offers a route for building organic thin films with, for example, electrooptic properties on silicon. 

Fig. 10. The leh-hand diagram shows an organic superlattice with a unique polar axis. The two types of molecule involved could be a fatty acid and a fatty amine. The insert is designed to show that these two materials have dipole moments in opposite senses with respect lo the hydrophobic chain. Thus, the V-lype film has a resultant dipole moment...

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