Bulk composite nanostructures

Arrays of concentric composite nanowires of Zr02 with Co cores were made in an alumina template by the sol-gel method from Zr02 sol [48]. The sol was made from Zr0Cl2 8H20, ethanol, HNO3 and acetylacetone. The alumina membrane was dipped in the sol for 0.5-1 h and after drying was aimealed at around 500 °C. The Zr02 template was then filled with Co metal by electrodeposition. This composite nanostructure had an enhanced coercivity compared to that of bulk Co. 

Bulk semiconductor nanostructured networks of CdS have been prepared in L and Hi phases [33,34]. The L phase was formed by a polyol amphiphile shown in Fig. 6. This LLC phase was doped with Cd2+ ions and then CdS was precipitated by diffusion of H2S into the gel. This nanocomposite was found to incorporate the amphiphile and metal in alternating layers (Fig. 6), closely resembling the structure of biominerals (e.g., mother of pearl). Similarly, Hi phases were prepared from an oligo(ethylene oxide) oleyl ether amphiphile (Fig. 7) mixed with a solution of Cd2+. Again, H2S was added to precipitate CdS and the resulting composite preserved the hexagonal symmetry (Fig. 7). 

Optimization of Bulk Heterojunction Composite Nanostructures 175 Pressure... 

Yang and coworkers reported an electrochemical method to control the surface and bulk compositions, size, and morphology of Ag-Pt heterogeneous nanostructures by potential cycle in perchloric acid (HCIO ) aqueous solution (Fig. 2.14) [61]. When the PtigAg nanoparticles were treated at 0.6V or lower, which is below the... 

Due to unsaturation or strain, equilibrium of the interatomic forces on a sur ce is reached by adsorption of surrounding molecules. Therefore, the chemical composition of the fost atomic layer may be different from that of the bulk. The importance of the sur ce with respect to the bulk in nanostructured powders makes the exact knowledge of the sur ce composition critical. Fourier transform infrared (FT-IR) spectrometry is a powerful tool to determine the nature of the chemical sur ce species as well as the reactive sites. As an example of an FT-IR sur ce study, a nanostructured aluminum nitride powder was analyzed and its sur ce was coiiq)ared with the y-alumina sur ce. 

These results are quite interesting. The initial stages of Al deposition result in nanosized deposits. Indeed, from the STM studies we recently succeeded in making bulk deposits of nanosized Al with special bath compositions and special electrochemical techniques [10]. Moreover, the preliminary results on tip-induced nanostructuring show that nanosized modifications of electrodes by less noble elements are possible in ionic liquids, thus opening access to new structures that cannot be made in aqueous media. 

Answer. There has been little effective interplay between experimental results obtained on single nanostructures grown as quantum-wells and studied by optical-pumping methods and those obtained on bulk nanoscale semiconductors by more conventional NMR approaches. However, this situation may change, since the former studies can provide information about the effects of, e.g., charge carriers or strain or compositional interfaces upon NMR parameters such as chemical and Knight shifts and EFGs in reasonably well-defined systems. 

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... 

The disulfide nanotubes have been characterized by Raman spectroscopy. The Raman bands for the MoS2 nanotubes are similar to those of the bulk 2H-phase, except that the bands of the nanostructures show slight broadening. The composite nanotubes like those of Ti-Mo-S and Nb-W-S were also characterized by Raman spectroscopy.41 45 The bands were similar to those of the undoped nanotubes, except for the appearance of a new band at 313 cm 1 which has been assigned to the increase in disorder owing to the presence of Nb.41... 

The physical and chemical properties of nanostructures differ significantly from that of bulk materials of the same composition. For example, a decrease in the crystal size results in an increase in the surfaceNolume ratio, which is becoming exceptionally high when entering the lower nanometer range. As a result, properties are primarily determined by the shape of the crystals and their surfaces. Therefore, controlling both the size of nanostructures as well as their surface chemistry appears to be cmcial. 

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