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Highly Oriented Pyrolytic Graphite (highly + oriented_pyrolytic_graphite)
Selected AbstractsOrientation and Arrangement of Octaruthenium Supramolecules with Alkyl Chains on GraphiteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2007Dong-Lin Shieh Abstract The self-assemblies of octaruthenium grid-type supramolecules, {[Ru2(CO)4(NH2C16H33)2](,-O2CCO2)}4, on highly oriented pyrolytic graphite (HOPG) in air and in 1-phenyloctane were studied by scanning tunneling microscopy (STM). The surface supramolecules are arranged into rows in which the metal cores are linearly packed and the alkyl chains are parallel to the surface. With the aid of theoretical calculations in the framework of density functional theory, the electronic origin of the tunneling in the measured STM images is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Deposition of Functionalized Cr7Ni Molecular Rings on Graphite from the Liquid PhaseADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Alberto Ghirri Abstract Graphite is a clean substrate and its nanostructures hold great potential for applications. Anchoring large molecules on graphite represents a challenge for several reasons that essentially rise from the planar bonds of the packed honeycomb structure of carbon. Here, a systematic investigation by AFM and XPS on different derivatives of molecular Cr7Ni rings deposited on highly oriented pyrolytic graphite (HOPG) is reported. Cr7Ni is emerging as a prototipical example of molecular antiferromagnet on which quantum phenomena and coherence have been demonstrated. For the deposition of Cr7Ni on HOPG, two strategies are adopted: 1) Cr7Ni rings are functionalized with extended alkyl/benzene terminations and 2) a self-assembled monolayer of alkyl chains with sulfonate terminations is deposited and then a cationic Cr7Ni derivative is used. In both cases the electronic bond with the carbon surface is soft, but the two-step procedure is efficient, albeit indirect, in sticking molecular Cr7Ni on HOPG. These strategies can be easily extended to deposit other complex molecular aggregates on graphite from the liquid phase. [source] Spontaneous Resolution of Racemic Hydrogen-Bonded Nanoassemblies on Graphite Revealed by Atomic Force Microscopy,ADVANCED MATERIALS, Issue 16 2004H. Schönherr An atomic force microscopy (AFM) investigation into the spontaneous resolution of a P/M racemic mixture of helical self-assembled tetrarosettes 13·(DEB)12 (see Figure) into enantiopure domains in 2D supramolecular assemblies on highly oriented pyrolytic graphite (HOPG) is reported. These results represent the first reported case of spontaneous resolution of a racemate of chiral nanostructures. [source] Nanocarbon materials: probing the curvature and topology effects using phonon spectraJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Sanju Gupta Abstract Much has been learned from the use of resonance Raman spectroscopy and high-resolution transmission electron microscopy techniques about the micro-/nanoscopic structure of various nanostructured carbons. However, they still possess some features that are not entirely understood particularly in terms of topological characteristics, which go beyond making a distinction with just the geometrical structure at nanoscale. To effectively utilize the potential of these materials for technological needs, understanding both the geometrical and topological structure and perhaps relating these attributes to physical (optical/electronic, lattice vibrational) properties become indispensable. Here, we make an attempt to describe the differences between various nanostructures and provide geometrical and topological property assessment semiquantitatively by monitoring the phonon spectra using resonance Raman spectroscopy thereby also capturing the electronic spectra. We elucidate the notion of global topology and curvature for a range of technologically important nanoscale carbons including tubular (single-, double- and multiwalled nanotubes, peapod), spherical (hypo- and hyperfullerenes, onion-like carbon) and complex (nanocones, nanohorns, nanodisks and nanorings) geometries. To demonstrate the proof-of-concept, we determined the variation in the prominent Raman bands of the respective materials, represented as D, G and D* (the overtone of D) bands, as a possible topological or curvature trend due to their sensitivity toward structural modification. The latter arises from local topological defects such as pentagons giving rise to curved nanocarbons. In this study, we provide systematics of their variation with respect to their geometric forms and compare with highly oriented pyrolytic graphite and monolayer graphene since the nanocarbons discussed are their derivatives. Once established, this knowledge will provide a powerful machinery to understand newer nanocarbons and indeed point to an unprecedented emergent paradigm of global topology/curvature , property , functionality relationship. We emphasize that these concepts are applicable to other topologically distinct nanomaterials, which include boron-nitride (BN) nanotubes and nanotori, helical gold nanotubes and Möbius conjugated organics. Copyright © 2009 John Wiley & Sons, Ltd. [source] Extension of a tuned log spiral of revolution fluorescence XAFS detector, designed for optimal detection of a particular element Z, to XAFS of elements other than ZJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001D. M. Pease Recently, it has been demonstrated that an x-ray detector in the form of a log spiral of revolution, covered with highly oriented pyrolytic graphite, is an excellent device for obtaining the fluorescence XAFS of an element of interest in the presence of competing fluorescence from other elements. In the present work we investigate the capabilities of a log spiral of revolution (LSR) detector, with a geometry optimized for one element (in this case Cr), if used for XAFS of other elements. [source] Development of graphene layers by reduction of graphite fluoride C2F surfacePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009A. V. Okotrub Abstract We studied a possibility of reduction of the surface of graphite fluoride obtained by fluorination of highly oriented pyrolytic graphite (HOPG) by a gaseous mixture of BrF3 and Br2. X-ray diffraction (XRD) revealed a layered structure of the fluorinated product being a second-stage intercalate due to a presence of bromine molecules between the fluorinated graphite layers. Scanning tunneling microscopy and spectroscopy showed that the "old" surface of graphite fluoride (exposed to the ambient air) has the graphite-like structure, while the fresh cleaved surface is non-conductive. Therefore, the outer layers of graphite fluoride can be reduced by water present in the laboratory atmosphere. The sample was treated by H2O vapor to confirm that. The reduction was controlled by Raman spectroscopy using intensity of the 1360 and 1580,cm,1 bands. The energy dependent photoelectron spectroscopy was used for estimation of thickness of the reduction layer, which was found, does not exceed 2,3 graphite layers. The obtained results indicate the possibility of synthesis of graphene layers on dielectric fluorinated graphite matrix. [source] Graphite under the magnetic force microscopePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007T. L. Makarova Abstract In search for magnetically active carbon structures, we have undertaken the magnetic force microscopy study of intrinsic defects at the surface of highly oriented pyrolytic graphite. Most of the observed defects, such as ridges and cleavage edges, are found magnetically inert. However, some of the observed sharp cleavage edges do show magnetic activity , a built-in surface magnetization, which reveals itself as the magnetic force gradient signal sensitive to the polarity of the tip magnetization. These results indicate the existence of a defect related magnetism at room temperature on graphite surface. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two-Dimensional Self-Assembly of a Porphyrin,Polypyridyl Ruthenium(II) Hybrid on HOPG Surface through Metal,Ligand InteractionsCHEMPHYSCHEM, Issue 9 2010Aimei Gao Dr. Abstract The synthesis and self-assembly behavior of porphyrin,polypyridyl ruthenium(II) hybrid, which consists of a flexible alkyl chain attached with two conjugated moieties is described. The electronic absorption spectrum and emission spectra show that the [C8 -TPP-(ip)Ru(phen)2](ClO4)2, abbreviated as (C8ip)TPPC has optical properties. Scanning tunneling microscopy (STM) studies found that the ,,, interaction and metal,ligand interaction allow (C8ip)TPPC to form self-assembled structure and have an edge-on orientation on the highly oriented pyrolytic graphite (HOPG) surface. The multidentate structure in (C8ip)TPPC molecules act as linkers between the molecules and form metal,ligand coordination, which forces the assembly process in the direction of stable columnar arrays. In addition, although the sample was stored for two months in ambient conditions, STM experiments showed that the order of (C8ip)TPPC self-assembly only slightly decreased which indicates that the self-assembled monolayer is stable. This work demonstrates that introducing a metal-ligand in the porphyrin-polypyridyl compound is a useful strategy to obtain novel surface assemblies. [source] | |||||||||||||