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New developments in fluorofullerenes chemistry

Description: Flurofullerenes were among the first chemical derivatives prepared from new spherical forms of carbon, yet it took 3 years of research to isolate the first single compound, C{sub 60}F{sub 48}. Subsequent studies provided a better understanding of physical and chemical properties of this compound. Here we present new data concerning synthesis, reactions, and properties of C{sub 60}F{sub 48}.
Date: May 1, 1996
Creator: Gakh, A.A.; Sachleben, R.A.; Hagaman, E.W. & Tuinman, A.A.
Partner: UNT Libraries Government Documents Department

Final Technical Report [Polynuclear aromatic hydrocarbons with curved surfaces: Models and precursors for fullerenes]

Description: Highlights of selected achievements are briefly outlined. The bowl-to-bowl inversion barrier was measured for a hydrocarbon on the C{sub 60} surface larger than corannulene; {Delta}G was determined to be 27.8 kcal/mol. A new route to the preparation of tetraketone involving benzeneseleninic anhydride was developed that represents a significant improvement in the overall process making semibuckminsterfullerene more accessible. The first crystallographically characterized transition metal buckybowl compound was reported.
Date: February 23, 2001
Creator: Radideau, Peter W.
Partner: UNT Libraries Government Documents Department

Nano-composite Structures for OPV Devices

Description: Improved material for use in organic photovoltaics (OPV) devices, also called polymer-solar cells (PSC), has been developed. Increased ordering of the active layer of bulk heterojunction (BHJ) cells has been achieved by the use of inert silica spheres in conjunction with suitable fullerene derivatives. Silica spheres with average diameters between 10 and 15 nm, consistent with the exciton diffusion length in the active layer, have been added. The potential for significantly improved device performance due to a higher degree of photon absorption, enabled by increased light scattering, and a maximized interface between electron donor and acceptor, ensuring efficient exciton dissociation, has been demonstrated. A method allowing for the covalent attachment of fullerene derivatives to the silica sphere surface has been developed.
Date: November 23, 2010
Creator: Richter, Henning
Partner: UNT Libraries Government Documents Department

Optically detected magnetic resonance studies on {pi}-conjugate polymers and novel carbon allotropes

Description: This report describes the following: introduction to photoluminescence detected magnetic resonance (PLDMR); introduction to {pi}-conjugated systems; PLDMR measurements on poly(p-phenylene)-type ladder polymers; PLMDR measurements on poly(p-phenylene ethylene); and PLDMR measurements on C{sub 70}, polythiophene, poly(p-phenylene vinylene) and Dan-40. Appendices to this report describe: Operation of ODMR (optically detected magnetic resonance) spectrometer; ODMR system parameters; and Special purpose circuitry.
Date: February 12, 1999
Creator: Partee, J.
Partner: UNT Libraries Government Documents Department

Ultrafast and nonlinear optical characterization of optical limiting processes in fullerenes

Description: The authors present recent results of broadband femotosecond (fs) transient absorption (TA) and broadband nanosecond (ns) optical limiting (OL) studies of C{sub 60} and derivatized C{sub 60}. Improvements in measurement techniques for fs TA spectra provide sensitivity to 10{sup {minus}5} in differential transmission, allowing detailed comparison of excited-state spectra with established energy level diagrams, as well as comparison of the ratio of triplet to singlet excited-state absorption cross sections from TA spectra with those obtained by modeling time transients at different wavelengths. For derivatized fullerenes, which provide enhanced solubility and a ground-state absorption extended into the infrared compared with C{sub 60} there is no spectral region where the triplet absorption cross section dominates the singlet as strongly as demonstrating broadband limiting in all 6, 6 mono-adducts and neat C{sub 60}. The authors report new approaches to processing sol-gel encapsulated fullerenes to improve the OL performance of solid-state materials to approach the response of solution limiters.
Date: October 1, 1997
Creator: Kohlman, R.; Klimov, V. & Shi, X.
Partner: UNT Libraries Government Documents Department

Creation and destruction of C{sub 60} and other fullerene solids. Final report

Description: The 1990 announcement of the Huffman-Kratschmer fullerene-production technique set off a world-wide explosion of research into the properties and potential applications of C{sub 60} and C{sub 70}. In the last five years, 4,000+ fullerene articles have appeared in the scientific literature dealing with these fascinating molecules and their condensed phases. They possess a complex chemistry reminiscent of the alkenes, and this has led to the syntheses of numerous new compounds and fullerene-based materials, with suggested applications ranging from medicine to photo-conducting polymers to rocket fuel. The work summarized in this report focused on the creation and destruction of fullerene-based materials, for the purpose of producing new materials of interest. This three year project was supported by a grant from the Advanced Energy Projects Division, Office of Basic Energy Sciences, U.S. Department of Energy (DE-FG03-93ER12133). Following are outlines of the work completed in each of the three years, a section devoted to the professional and educational development of those involved, a brief section on the outlook for fullerene-based materials, and an appendix listing the publications resulting from this project.
Date: June 5, 1996
Creator: Huffman, D. R.
Partner: UNT Libraries Government Documents Department

TEM study of diamond films grown from fullerene precursors

Description: Transmission Electron Microscope (TEM) techniques are applied to study the microstructure of diamond films grown from fullerene precursors. Electron diffraction and electron energy loss spectra (EELS) collected from the diamond films correspond to that of bulk diamond. Microdiffraction, high resolution images and EELS help determine that the first diamond grains that nucleate from fullerene precursors generally form on a thin amorphous carbon interlayer and seldom directly on the silicon substrate. Grain size measurements reveal nanocrystalline diamond grains. Cross section TEM images show that the nanocrystalline diamond grains are equiaxed and not columnar nor dendritic. The microstructure of small equiaxed grains throughout the film thickness is believed responsible for the very smooth surfaces of diamond films grown from fullerene precursors.
Date: November 1, 1995
Creator: Csencsits, R.; Gruen, D.M.; Krauss, A.R. & Zuiker, C.
Partner: UNT Libraries Government Documents Department

Semiempirical study of hydrogen addition to single-walled carbon nanotubes

Description: Single-walled carbon nanotube models have been constructed by insertion of 10-carbon bracelets into C{sub 70} to form C{sub 90} and C{sub 120}. Semiempirical heats of vicinal hydrogenation along the sides of the tubes are {approximately}40 kcal/mol more endothermic (less stable) than addition to the endcaps. Based on the similarity of the endcaps to C{sub 60}, hydrogenation of nanotubes is estimated to be approximately thermoneutral; therefore, only relatively high energy dienes or other species are likely to yield stable addended products.
Date: July 1, 1995
Creator: Cahill, P.A.
Partner: UNT Libraries Government Documents Department

CARBON NANOMATERIALS AS CATALYSTS FOR HYDROGEN UPTAKE AND RELEASE IN NAALH4

Description: A synergistic approach involving experiment and first-principles theory not only shows that carbon nanostructures can be used as catalysts for hydrogen uptake and release in complex metal hydrides such as sodium alanate, NaAlH{sub 4}, but also provides an unambiguous understanding of how the catalysts work. The stability of NaAlH{sub 4} originates from the charge transfer from Na to the AlH{sub 4} moiety, resulting in an ionic bond between Na{sup +} and AlH{sub 4}{sup -} and a covalent bond between Al and H. Interaction of NaAlH{sub 4} with an electro-negative substrate such as carbon fullerene or nanotube affects the ability of Na to donate its charge to AlH{sub 4}, consequently weakening the Al-H bond and causing hydrogen to desorb at lower temperatures as well as facilitating the absorption of H{sub 2} to reverse the dehydrogenation reaction. Ab initio molecular dynamics simulation further reveals the time evolution of the charge transfer process with hydrogen desorption occurring when the charge transfer is complete.
Date: June 19, 2008
Creator: Berseth, P; Ragaiy Zidan, R & Andrew Harter, A
Partner: UNT Libraries Government Documents Department

Lithium-endohedral C{sub 60} complexes.

Description: High capacity, reversible, lithium intercalated carbon anodes have been prepared, 855 m.Ah/g, which exceed the capacity for stage 1 lithium intercalated carbon anodes, 372 mAh/g. Since there is very little hydrogen content in the high capacity anode, the fullerene C{sub 60} lattice is used to investigate the nature of lithium ion bonding and spacing between lithiums in endohedral lithium complexes of C{sub 60}. Three lithium-endohedral complexes have been investigated using ab initio molecular orbital calculations involving 2,3 and 5 lithium. The calculated results suggest that lithium cluster formation may be important for achieving the high capacity lithium carbon anodes.
Date: May 4, 1998
Creator: Scanlon, L. G.
Partner: UNT Libraries Government Documents Department

Thermal management technology for hydrogen storage: Fullerene option

Description: Fullerenes were picked as first option for H storage because of potentially high volumetric and gravimetric densities. Results indicate that about 6 wt% H (corresponding to C{sub 60}H{sub 48}) can be added to and taken out of fullerenes. A model with thermally activated hydrogenation/dehydrogenation was developed. Activation energies were estimated to be 100 and 160 kJ/mole (1.0 and 1.6 eV/H{sub 2}) for hydrogenation and dehydrogenation, respectively; difference is interpreted as heat release during hydrogenation. The activation energies and hydrogenation heat may be modifiable by catalysts. Preliminary H storage simulations for a conceptually simple device were performed (a 1-m long hollow metal cylinder with inner dia 0.02 m filled with fullerene powders). Results indicate that the thermal diffusivity of the fullerenes controls the hydrogenation and dehydrogenation rates. Rates can be significantly modified by changing the thermal diffusivity, eg, by incorporating a metal mesh. The simulation suggest that thermal management is essential for efficient H storage devices using fullerenes. More controlled experiments, model development, and physical property determinations are needed; catalyst use also needs to be pursued. Future ORNL/MER cooperative work is planned.
Date: May 28, 1996
Creator: Wang, J.C.; Chen, F.C. & Murphy, R.W.
Partner: UNT Libraries Government Documents Department

The interactions of high-energy, highly-charged ions with fullerenes

Description: In 1985, Robert Curl and Richard Smalley discovered a new form of carbon, the fullerene, C{sub 60}, which consists of 60 carbon atoms in a closed cage resembling a soccer ball. In 1990, Kritschmer et al. were able to make macroscopic quantities of fullerenes. This has generated intense activity to study the properties of fullerenes. One area of research involves collisions between fullerenes and atoms, ions or electrons. In this paper we describe experiments involving interactions between fullerenes and highly charged ions in which the center-of-mass energies exceed those used in other work by several orders of magnitude. The high values of projectile velocity and charge state result in excitation and decay processes differing significantly from those seen in studies 3 at lower energies. Our results are discussed in terms of theoretical models analogous to those used in nuclear physics and this provides an interesting demonstration of the unity of physics.
Date: March 1, 1996
Creator: Ali, R.; Berry, H.G. & Cheng, S.
Partner: UNT Libraries Government Documents Department

The discovery of fullerenes in the 1.85 billion-year-old Sudbury meteorite crater

Description: Fullerenes (C{sub 60}, C{sub 70}) have been identified by laser time-of-flight and electron-ionization mass spectroscopy in rock samples (black tuff in the Onaping formation) from the crater. They were likely synthesized within the impact plume from carbon contained in the meteorite. The isotopic ratios suggest {sup 13}C enrichment. They are associated with sulfur which may have protected them. This is the largest known deposit of naturally occurring fullerenes.
Date: February 1, 1996
Creator: Becker, L.; Bada, J.L.; Winans, R.E.; Hunt, J.E.; Bunch, T.E. & French, B.M.
Partner: UNT Libraries Government Documents Department

Diamond films grown from fullerene precursors

Description: Fullerene precursors have been shown to result in the growth of diamond films from argon microwave plasmas. In contradistinction to most diamond films grown using conventional methane-hydrogen mixtures, the fullerene-generated films are nanocrystalline and smooth on the nanometer scale. They have recently been shown to have friction coefficients approaching the values of natural diamond. It is clearly important to understand the development of surface morphology during film growth from fullerene precursors and to elucidate the factors leading to surface roughness when hydrogen is present in the chemical vapor deposition (CVD) gas mixtures. To achieve these goals, we are measuring surface reflectivity of diamond films growing on silicon substrates over a wide range of plasma processing conditions. A model for the interpretation of the laser interferometric data has been developed, which allows one to determine film growth rate, rms surface roughness, and bulk losses due to scattering and absorption. The rms roughness values determined by reflectivity are in good agreement with atomic force microscope (AFM) measurements. A number of techniques, including high-resolution transmission electron microscopy (HRTEM) and near-edge x-ray absorption find structure (NEXAFS) measurements, have been used to characterize the films. A mechanism for diamond-film growth involving the C{sub 2} molecule as a growth species will be presented. The mechanism is based on (1) the observation that the optical emission spectra of the fullerene- containing plasmas are dominated by the Swan bands of C{sub 2} and (2) the ability of C{sub 2} to insert directly into C-H and C-C bonds with low activation barriers, as shown by recent theoretical calculations of reactions of C{sub 2} with carbon clusters.
Date: July 1, 1995
Creator: Gruen, D.M.; Zuiker, C.D. & Krauss, A.R.
Partner: UNT Libraries Government Documents Department

Superconducting and normal-state properties of novel materials

Description: Interest in solid state physics naturally gravitates towards novel systems such as the copper oxide superconductors or the alkali-doped fullerenes. This paper tackles high temperature superconductivity by extension of the BCS theory for ordinary superconductors, in particular, incorporation of anharmonicity in phonon dynamics and anisotropy in electron-phonon coupling. These refinements can account for many anomalous properties of the cuprates. Phonon anharmonicity is consistent with a small isotope effect at optimal doping and a larger isotope effect in suboptimal systems. Anisotropy in the interaction, a plausible consequence of certain anharmonic models, can circumvent objections to electron-phonon coupling based on transport measurements. Such anisotropy is consistent with gap anisotropy and strong temperature dependence of Hall coefficient. In contrast to cuprates, the doped fullerenes appear understandable within the standard model of single electron band theory and BCS theory. Microscopic parameters derivable from transport and critical field measurements yield a self-consistent picture of a disordered Type-2 BCS superconductor. Isotope effects imply that superconductivity is mediated by carbon phonons opposed to alkali atom vibrations. The novel properties of the fullerenes are generally traceable to their microscopic heterogeneity, being a collection of tightly bound but weakly overlapping molecules. Separation of electronic regimes into weak intermolecular overlap and strong carbon-carbon on-ball bonds yields a superconductor with both a large density of states and a high phonon frequency, properties consistent with a relatively high {Tc}. Disordered nature of intermolecular overlap produces a large residual resistivity and a universal dependence to the Hall coefficient. This disorder is also consistent with the anomalously large carbon isotope effect for heterogeneous isotopic substitution.
Date: September 1, 1994
Creator: Crespi, V.H.
Partner: UNT Libraries Government Documents Department

Characterization of fullerenes and fullerene derivatives by small-angle neutron scattering and transmission measurements

Description: Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes (1) in solvents with strong SANS contrast (e.g. CS{sub 2}) and we have extended initial studies of C{sub 60} (1) to include C{sub 70} and C{sub 84} moieties. Deuterated solvents (e.g. toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60}, so there is virtually no SANS contrast with the solvent. Hence, these particles are practically {open_quotes}invisible{close_quotes} in such media, though the negative scattering length of hydrogen means that SLD of H{sup 1}-containing materials is much lower, so they have strong contrast with toluene-d{sub 8}. Thus, SANS makes it possible to study the size and shapes of modified buckyballs and this paper describes the first results on cyclohexane-substituted fullerenes.
Date: January 1, 1997
Creator: Melnichenko, Y.B.; Wignall, G.D. & Affholter, K.A.
Partner: UNT Libraries Government Documents Department

A New Class of Macrocyclic Chiral Selectors for Stereochemical Analysis

Description: This report summarizes the work accomplished in the authors laboratories over the previous three years. During the funding period they have had 23 monographs published or in press, 1 book chapter, 1 patent issued and have delivered 28 invited seminars or plenary lectures on DOE sponsored research. This report covers the work that has been published (or accepted). The most notable aspect of this work involves the successful development and understanding of a new class of fused macrocyclic compounds as pseudophases and selectors in high performance separations (including high performance liquid chromatography, HPLC; capillary electrophoresis, CE; and thin layer chromatography, TLC). They have considerably extended their chiral biomarker work from amber to crude oil and coal. In the process of doing this we've developed several novel separation approaches. They finished their work on the new GSC-PLOT column which is now being used by researchers world-wide for the analysis of gases, light hydrocarbons and halocarbons. Finally, we completed basic studies on immobilizing a cyclodextrin/oligosiloxane hybrid on the wall of fused silica, as well as a basic study on the separation behavior of buckminster fullerene and higher fullerenes.
Date: March 11, 1999
Partner: UNT Libraries Government Documents Department

XUV postionization of fragments of photodissociated C{sub 60}

Description: We report experimental evidence for the loss of neutral C, C{sub 2}, C{sub 3}, and C{sub 4} from photoexcited C{sub 60} and C{sub 70}. These species are detected by postionization with XUV radiation formed by four-wave mixing in Kr vapor. The fragments have been detected in the nascent distribution (i.e., before total disintegration of the fullerene-size molecular entities). A resonant autoionization transition in C atom has yielded an upper limit to the translational energy release for dissociation into C atoms. The detection of these products gives new insight into the fragmentation mechanism of fullerenes.
Date: June 1, 1995
Creator: Lykke, K.R.
Partner: UNT Libraries Government Documents Department

New fullerene-based mixed materials: Synthesis and characterization

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors present results of broadband femtosecond transient absorption and broadband nanosecond optical limiting studies of C{sub 60} and derivatized C{sub 60}. They have investigated both solutions and solid-state mixed materials (sol-gel glass hosts doped with fullerene guests). They show that derivatized fullerenes provide enhanced solubility and processability, with a ground-state absorption extended into the infrared compared with C{sub 60}. They have extensively studied both the dynamic optical response and the excited-state absorption cross sections of solutions and solids for multiple wavelengths in the visible to near infrared. Wavelength-dependent studies show that the optical limiting response improves monotonically at longer wavelengths, demonstrating broadband limiting in all 6,6 mono-adducts and neat C{sub 60}. The authors report new approaches to processing sol-gel glass/fullerene composites to improve the optical limiting performance of solid-state materials to approach the response of solution limiters.
Date: November 1, 1998
Creator: McBranch, D.; Kohlman, R.; Klimov, V.; Grigorova, M.; Shi, X.; Smilowitz, L. et al.
Partner: UNT Libraries Government Documents Department

Capillary electrokinetic separations with optical detection. Technical progress report, February 1, 1994--January 31, 1995

Description: This multifarious research program is dedicated to the development of capillary electrokinetic separation techniques and associated optical methods of detection. Currently, research is directed at three general objectives. First, fundamental studies of pertinent separation and band broadening mechanisms are being conducted, with the emphasis on achieving rapid separations and understanding separation systems that include highly-ordered assemblies as running buffer additives. Second, instrumentation and methodologies associated with these capillary separation techniques are being advanced. Third, applications of these separation and detection systems should fill current voids in the capabilities of capillary separation techniques. In particular, it should be possible to perform rapid, highly efficient, and selective separations of hydrophobic compounds (e.g., higher MW polycyclic aromatic hydrocarbons (PAHs) and fullerenes), certain optical isomers, DNA fragments, and various pollutants including certain heavy metals.
Date: May 1, 1995
Creator: Sepaniak, M. J.
Partner: UNT Libraries Government Documents Department

Field emission and growth of fullerene nanotubes

Description: Efforts to control the growth of individual carbon nanotubes from nanotube seed crystals have led to a characterization of their field-induced electron emission behavior. The application of a bias voltage in the growth apparatus was motivated by the prolific formation of nanotubes in the carbon are growth method, in which the electric field appears to play a central role. The authors report here the ability to achieve various tube tip configurations by the controlled application of voltage, heat and chemicals to an individual nanotube, and that these states are well characterized by the emission currents they induce.
Date: November 1994
Creator: Rinzler, A. G.; Hafner, J. H.; Nilolaev, P.; Colbert, D. T. & Smalley, R. E.
Partner: UNT Libraries Government Documents Department

Hydrogen storage in fullerenes and in an organic hydride

Description: While the authors have demonstrated the importance and usefulness of thermal management to the hydrogen storage in fullerenes, their recent effort has concentrated on materials improvement and physical model development. In this paper, they report the results of this effort as follows: (1) Liquid phase hydrogenation of fullerenes indicated that more than 6 wt% capacity can be obtained at 180 C, 350--400 psi; (2) Dehydrogenation of fullerenes hydrides below 225 C was demonstrated using an Ir-based P-C-P pincer complex catalyst; (3) Cyclic hydrogenation and dehydrogenation tests of an organic hydride at 7 wt% capacity were conducted at 180--260 C; and (4) Physical models developed for fullerenes were determined to be applicable to this organic hydride (with much smaller activation energies).
Date: May 29, 1998
Creator: Wang, J.C.; Murphy, R.W.; Chen, F.C.; Loutfy, R.O.; Veksler, E. & Li, W.
Partner: UNT Libraries Government Documents Department