Superstructures-Multilayers

Stoichiometric modulations through the superlattice period all have substantial effects on these properties. 

This pulse plating technique has the advantage of simplicity, i.e., application of a simple waveform in current or potential in a single solution. Problems arise, however, because at the more positive potential a pure element or compound is deposited, while during the pulse the second element or compound formed is inevitably contaminated with the first. Switzer et al. [73] reported a variation on 

Well-defined CdS/CdSe superlattices have been formed by means of ECALE [74]. In these structures the CdS component - and not CdSe - suffered from substantial crystallographic strain as was evidenced by surface-enhanced Raman spectroscopy (SERS) - a valuable tool for characterizing the superlattice phonons in electrochemical or other ambient environments. Torimoto et al. reported quantum confinement in superlattices of ZnS/CdS grown by ECALE [75]. 

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Fig. 4.5 Superlattices (superstructures) and multilayers are systems composed of alternating layers of, say, phases A and B with a specified AB bdayer thickness, which is called the modulation wavelength (A), or period...

Certain azacrown-appended cholesterol derivatives can form unique vesicular or lamellar structures in the absence and the presence of metal salts in aqueous solution.187-190 These superstructures created from the azacrown-appended cholesterol derivatives are useful as a template for the transcription into the silica structure. Azacrown-appended cholesterol gelator creates the novel multilayered spherical structure in acetic acid, whereas this gelator results in the fluffy globular aggregates in the presence of Pd(N03)2.191... 

Synthesis of DNA-Au hybrid nanocomposites holds promise for applications in nanotechnology. Following the pioneering work of Mirkin et al., these modified Au nanopartides can act as useful building blocks to form spatially well-defined superstructures, including nanocrystals [108], binary and multilayered nanoparticle assemblies [109,110] and also well-ordered 3D nanoclusters [111]. 

Moving from discrete interactions between molecules to larger superstructures, Kuhn and coworkers used Langmuir-Blodgett techniques to construct surfaces modified by monolayers of D and A which were separated by non-fluores-cent spacer molecules in a multilayer sandwich arrangement [30]. The measured fluorescence intensity depended on the inverse fourth power of the separation between D and A, obeying the following ... 

The other self-assembly method is layer-by-layer deposition. This method is also potentially interesting for complex superstructures creation. This method uses the oppositely charged polyelectrolytes to build multilayer stmctures from nanoparticles of various types. For instance, this method permits to fabricate the nanocomposites with magnetic luminescence. The Fc304 magnetic particles of 8.5 nm size were used as templates for the deposition of CdTe (QDs) quantum dots in polyelectrolyte during multilayers manufacturing [346],... 

Kang SJ, Kocabas C, Kim HS, Cao Q, Meitl MA, Khang DY, et al. Printed multilayer superstructures of aligned single-walled carbon nanombes for electronic applications. Nano Lett 2007 7 3343-8. 

Phase separation on one hand, and formation of a superstructure of the diyne compound on the other hand, have been explained by assuming strong interactions between the parafBn chains of the otherwise immiscible compounds. Such interactions could originate from similarities in the packing geometry of the paraffinic portions of the hydrophobic chains, as it was indicated by electron diffraction studies of the mixed multilayers... 

Interestingly, the second and third monolayers of some unsubstituted Pcs still show very good submolecular resolution when observed with low-temperature STM, suggesting a very good orbital overlap between aromatic macrocycles in adjacent layers. In the case of FePc, the unit cell of the formed molecular superstructure of the second layer shifts compared to the unit cell of the first layer. The Fe atoms in the top layer are shifted with respect to the ones underneath, and the plane of the Pc in the second layer was found to be tilted with respect to the plane of the substrate. Multilayers of CoPc (up to three layers) were also studied and it was shown that in this case the positions of both the unit cell and the metal atom are retained from one layer to the next. Nevertheless, the plane of the Pc starts to tilt from the second layer on, being even more tilted in the third monolayer. To date, there is no explanation for this... 

Fig. 2 Top-view SEM images of monolayer (left) en multilayer (right) silica sphere arrays after PFDTS assembly. The silica sphere diameters amount to 140 nm (top), 440 nm (middle) and 830 nm (bottom). The insets show side-view images of cleaved samples, as well as the large static contact angles (8/tl droplets) revealing the (super) hydrophobicity of the superstructures...

LB films of these CT complexes indicate a dense packing of the columnar aggregates lying parallel to the surface in a multilayer superstructure virtually identical to that in the bulk Colho phase, quite different to the double layer structure observed for LB fi 1 ms of the neat monomeric and polymeric triphenylene centered mesogens [41 f]. 

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