Co-ITO granular magnetoresistance films fabricated by precipitation of magnetic nanoparticles from amorphous oxide J.A nanometer-scale hybrid film of Co particle/Co-C 60 compound was prepared by alternate deposition of Co and C 60 under UHV condition. All of Raman spectra, magnetization curves, and tunnel conductivity concluded that the hybrid system has a granular structure consisting of Co nanoparticles embedded in a Co-C 60 compound matrix. The magnetoresistance ratio of 26% was obtained at 2 K and 10 kOe for the electron tunneling across the Co-C 60 compound barrier. In addition, anomalously large bias voltage dependence was found in the magnetotransport properties.
One-dimensional structures such as nanowires, nanofibers, and nanoribbons with high aspect ratios have attracted much attention lately due to their high potential for applications in fabricating electronic devices, sensors, etc. These structures are expected to have their unusual characteristics amplified through quantum size effects, and marked shape-specific effects.[1±3] To obtain one-dimensional materials, organic molecules are often used as a medium or template. The use of sodium bis(2-ethylhexyl)sulfosuccinate (NaAOT) represents an especially powerful tool to synthesize nanowires of materials such as CaSO 4 , [4] BaSO 4 , [5] Cu, [6] BaCrO 4 , [7] BaWO 4 , [8] and CdS. [9] Less-ordered hexagonal mesostructured SnO 2 , templated by NaAOT has also been reported. [10] Ceria (CeO 2 ) and ceria-based materials have been extensively used as solid electrolytes in solid oxide fuel cells; as automotive catalysts, utilizing their oxygen storage capacity; as absorbents for fluoride ion or arsenic-based compounds; and as substances to filter out ultraviolet rays. Ceria and ceria-based compounds obtained in nanostructured forms are thus expected to be promising as materials that show interesting properties through shape-specific and/or quantum size effects. Nanostructured ceria, synthesized using organic molecules, has been previously reported in the literature. Masui et al. reported the synthesis of monodisperse ceria nanoparticles with diameters of 2.6 nm in reverse micelles composed of AOT (bis(2-ethylhexyl)sulfosuccinate) anions.[11] Less-ordered mesoporous ceria was synthesized using alkyltrimethylammonium bromide as a template.[12] Ordered mesoporous ceria templated by hexadecylamine has also been reported.[13]Macroporous ceria was obtained by a nanotectonic approach based on the template-directed assembly of organically functionalized ceria crystalline particles by poly(c-benzyl-L-glutamate). [14] In this paper, we report for the first time the synthesis of cerium compound nanowires and nanorings templated by AOT anions and alkyl alcohols. We also demonstrate nanostructural control of the cerium compound nanostructures by the carbon number of the incorporated alkyl alcohol. Figure 1a shows the transmission electron microscopy (TEM) image of a solid synthesized in the presence of NaAOT after a reaction time of 5 h. Nanowires were obtained with widths of several tens of nanometers and lengths of the order of micrometers. The sulfur to cerium, or AOT to cerium molar ratio, determined by energy dispersive X-ray (EDX) analysis was 0.37, indicating that AOT molecules were incorporated in the solid. Figure 1b is an enlarged image of the nanowire and shows stripes, suggesting the formation of a layered structure composed of a cationic cerium-based inorganic sheet with a thickness of 2.0 nm, and an anionic AOT bilayer with a thickness of 1.0 nm, as shown in the schematic representation of Figure 2. When the synthesis was performed in the presence of both butyl alcohol and NaAOT, instead of only NaAOT, similar but more ...
The atomic and electronic structure of narrow zigzag nanoribbons with finite length, consisting of graphene terminated by fluorine on one side, hexagonal (h) h-BN, and h-SiC were studied with density functional theory. It is found that the asymmetry of nanoribbon edges causes a uniform curvature of the ribbons due to structural stress in the aromatic ring plane. Narrow graphene nanoribbons terminated with fluorine on one side demonstrate a considerable out-of-plane bend, suggesting that the nanoribbon is a fraction of a conical surface. It is shown that the intrinsic curvature of the narrow nanoribbons destroys the periodicity and results in a systematic cancellation of the dipole moment. The in- and out-of-plane curvature of thin arcs allows their closure in nanorings or cone fragments of giant diameter. Using the fragment molecular orbital method, we optimized the structure of a planar giant arc and a closed ring of h-BN with a diameter of 105 nm.
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