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1

Probability of self-healing in damaged graphene bombarded by fullerene  

NASA Astrophysics Data System (ADS)

Using non-equilibrium molecular dynamics method, we study the self-healing behavior of graphene after bombarded by fullerene (C60) through controlling the environmental temperature and the incident velocity of C60. The self-healing probability depends on the size of graphene, the velocity of fullerene (C60), and the temperature of heat baths. It is suggested that the self-healing in damaged graphene originates from thermal fluctuation. Our results can offer additional insights for further understanding self-healing mechanisms and bombardment phenomena in low dimensional materials. Additionally, controlling the bombardment between the graphene and the fullerene (C60) may also lead to some potential applications in the surface cleaning of graphene and the production of nanopore.

Xu, Zhi-Cheng; Zhong, Wei-Rong

2014-06-01

2

The production and sputtering of S2 by keV ion bombardment  

NASA Technical Reports Server (NTRS)

The ion bombardment of S-containing molecules in comets is simulated experimentally. Mass-analyzed 30-keV beams of Ar(+) and He(+) are directed at solid S, H2S, and CS2 targets at temperatures 15 K, and the neutral molecular species produced are ionized and analyzed using a quadrupole mass spectrometer. The dominant species detected are S1 and S2 for the S target, H2S and S2 for the H2S target, and S, CS, S2, and CS2 for the CS2 target. In the latter case, it is found that after about 10 to the 14th He(+) ions/sq cm have struck the target, further sputtering is prevented by formation of a dark brown deposit which is stable at room temperature; the residue forms more slowly when Ar(+) ions are used. These results, indicating relatively efficient S2 production by ion bombardment, are applied to theoretical models of S2 production and/or ejection by solar-wind, solar-flare, or cosmic-ray ions striking comets. It is found that direct solar-wind production of S2 by sputtering is unlikely at realistic bombardment rates, but that H2S-S2 conversion by energetic ions could be significant, with less stringent ice-temperature and irradiation-flux constraints than in the case of S2 production by photons.

Boring, J. W.; Chrisey, D. B.; Oshaughnessy, D. J.; Phipps, J. A.; Zhao, N.

1986-01-01

3

L-shell x-ray-production cross sections in lead by proton bombardment (240--440 keV)  

SciTech Connect

The L-shell x-ray-production process in lead (Pb) by proton impact over the energy range 240--440 keV has been studied. The x rays emitted from a thin (44.4 +- 3.9 ..mu..g/cm/sup 2/) Pb target were detected using a high-purity Ge low-energy photon spectroscopy detector. The total x-ray cross sections and the x-ray cross sections for the Ll, L..cap alpha../sub 1,2/, L..beta..'s, L..gamma../sub 1/, and L..gamma../sub 2,3/ components were determined at 20-keV intervals over the bombarding energy range. The experimental x-ray cross sections were found to be in reasonable agreement with those predicted by perturbed stationary-state (PSS) theory with relativistic (R), energy-loss (E), and Coulomb-deflection (C) corrections (ECPSSR).

Moheb, H.; Bigaouette, R.; Inman, F.W.

1985-12-01

4

Sputtering of thin benzene and polystyrene overlayers by keV Ga and C 60 bombardment  

NASA Astrophysics Data System (ADS)

The mechanisms of ion-stimulated desorption of thin organic overlayers deposited on metal substrates by mono- and polyatomic projectiles are examined using molecular dynamics (MD) computer simulations. A monolayer of polystyrene tetramers (PS4) physisorbed on Ag{1 1 1} is irradiated by 15 keV Ga and C 60 projectiles at normal incidence. The results are compared with the data obtained for a benzene overlayer to investigate the differences in sputtering mechanisms of weakly and strongly bound organic molecules. The results indicate that the sputtering yield decreases with the increase of the binding energy and the average kinetic energy of parent molecules is shifted toward higher kinetic energy. Although the total sputtering yield of organic material is larger for 15 keV C 60, the impact of this projectile leads to a significant fragmentation of ejected species. As a result, the yield of the intact molecules is comparable for C 60 and Ga projectiles. Our data indicate that chemical analysis of the very thin organic films performed by detection of sputtered neutrals will not benefit from the use of C 60 projectiles.

Czerwi?ski, B.; Delcorte, A.; Garrison, B. J.; Samson, R.; Winograd, N.; Postawa, Z.

2006-07-01

5

Irradiation resistance of grains near {0?0?1} on polycrystalline tungsten under 30 keV He+ bombardment at 1173 K  

NASA Astrophysics Data System (ADS)

Samples of polycrystalline tungsten were irradiated at normal incidence by 30 keV 4He+ at 1173 K from fluences of 6 × 1021 to 6 × 1022 He m-2. Zones on each sample were marked using a focused ion beam so they could be easily found after irradiation. Electron backscatter diffraction was used to analyze the orientation of the grains in the marked zones before and after irradiation. Grains with orientations ˜4° to ˜8° tilt from {0 0 1} remained smoother after irradiation and were less eroded. Grains with all other orientations farther from {0 0 1} experienced complete morphology change and severe erosion due to the ion bombardment. A grain with orientation (0 0 1) was also highly eroded. Mass loss of each sample was measured and the sample at the highest fluence had 12 g m-2 mass loss normalized to irradiated area.

Garrison, L. M.; Kulcinski, G. L.

2014-04-01

6

Sputtering yields, range and range straggling in Al following Kr + ions bombardment in the energy range (20-160) keV  

NASA Astrophysics Data System (ADS)

The sputtering of Al metallic films by 84Kr + ions has been studied over the energy range (20-160) keV. Sputtering yield data have been extracted by means of the Rutherford backscattering technique (RBS) using a 2 MeV beam of 4He + ions. They have been compared to values derived by Sigmund's linear cascade theory, Yamamura's semi-empirical formula or by Monte Carlo computer simulation using the TRIM code. A fair agreement was observed between the measured sputtering yields and the predicted ones. The depth profiles of the implanted Kr + ions into Al have also been measured, and then fitted assuming Gaussian shape distributions, which allowed us to extract the projected range, Rp, and the associated range straggling, ? Rp. For the former stopping parameter, a very good agreement is obtained between experiment and the LSS theory predictions while the MC simulation also accounts satisfactorily for the measured data over the whole explored energy range, reflecting an adequate description of the projectile-target interaction by the universal potential of the Thomas-Fermi type assumed in the LSS formalism. In contrast, the ? Rp measured data show to be consistent with the predicted values only at E ? 60 keV but lie to ˜30% above them at lower energies. This discrepancy not caused by the sputtering effect relates to an incomplete evaluation of the range straggling by theory at low bombarding energies.

Mammeri, S.; Ouichaoui, S.; Zemih, R.; Ammi, H.; Abdesselam, M.; Chami, A. C.

2005-10-01

7

Spectral reflectance change and luminescence of selected salts during 2-10 KeV proton bombardment - Implications for Io  

NASA Technical Reports Server (NTRS)

Radiation damage and luminescence caused by magnetospheric charged particles have been suggested by several investigators as mechanisms that are capable of explaining some of the peculiar spectral/albedo features of Io. In the present paper, this possibility is pursued by measuring the UV-visual spectral reflectance and luminescent efficiency of several proposed Io surface constituents during 2 to 10 keV proton irradiation at room and low temperatures. The luminescence efficiencies of pure samples, studied in the laboratory, suggest that charged-particle induced luminescence from Io's surface might be observable by spacecraft such as Voyager when viewing Io's dark side.

Nelson, R. M.; Nash, D. B.

1979-01-01

8

Dose dependence of the production yield of endohedral 133Xe-fullerene by ion implantation  

NASA Astrophysics Data System (ADS)

The production yield of endohedral 133Xe-fullerene by ion implantation has been studied by taking advantage of the radioactivity of 133Xe. Fullerene targets, which were produced by vacuum evaporation of C 60 or C 70 on a Ni backing, were bombarded with 30-38 keV 133Xe ions by using an isotope separator at doses ranging from 1 × 10 12 to 1 × 10 14 cm -2. The production yield of endohedral 133Xe-fullerene was determined by an high performance liquid chromatography analysis following the dissolution of the targets in o-dichlorobenzene. It was found that the production yield decreased with increasing dose and incident energy, and the production yield of 133Xe@C 70 was higher than that of 133Xe@C 60 for the same dose and incident energy. Those production yields are discussed in connection with amorphization of fullerene molecules in collisions with 133Xe ions.

Watanabe, S.; Ishioka, N. S.; Shimomura, H.; Muramatsu, H.; Sekine, T.

2003-05-01

9

The temperature effect on the glycine decomposition induced by 2 keV electron bombardment in space analog conditions  

NASA Astrophysics Data System (ADS)

Glycine is the simplest proteinaceous amino acid that has been extensively detected in carbonaceous meteorites and was recently observed in the cometary samples returned to Earth by NASA's Stardust spacecraft. In space, such species is exposed to several radiation fields at different temperatures. In aqueous solutions, this species appears mainly as zwitterionic glycine (+NH3CH2COO-) however, in solid phase, it may be found in amorphous or crystalline forms. Here, we present an experimental study on the destruction of two zwitterionic glycine crystals ( ?- and ?-form) at two different temperatures (300 K and 14 K) by 2 keV electrons in an attempt to test the behavior and stability of this molecular species in different space environments. The samples were analyzed in situ by Fourier transform infrared spectrometry at electron fluences. The experiments were carried out under ultra-high vacuum conditions at the Molecular Physics Laboratory at the Open University at Milton Keynes, UK. The dissociation cross section of glycine is approximately 5 times higher for the 14 K samples when compared to the 300 K samples. In contrast, no significant differences emerged between the dissociation cross sections of ?- and ?-forms of glycine for fixed temperature experiments. We therefore conclude that the destruction cross section is more heavily dependent on temperature than the phase of the condensed glycine material. This may be associated with the opening of additional reaction routes in the frozen samples involving the trapped daughter species (e.g. CO2 and CO). The half-life of studied samples extrapolated to space conditions shows that glycine molecules on the surface of interstellar grains has less survivability and they are highly sensitive to ambient radiations, however, they can survive extended period of time in the solar system like environments. Survivability increases by a factor of 5 if the samples are at 300 K when compared to low temperature experiments at 14 K and is independent of the crystalline structure. In addition, this survival would increase if the molecular species were protected by several layers of other molecular species as trapped in comet mantles or embedded within regolith in asteroids/lunar surfaces. The understanding of the excitation and dissociation processes of organic compounds in space simulation is highly required to put constrains in the puzzle over the origin of life in the primitive Earth.

Pilling, Sergio; Nair, Binu G.; Escobar, Antonio; Fraser, Helen; Mason, Nigel

2014-03-01

10

Ranges and fragmentation behavior of fullerene molecules: A molecular-dynamics study of the dependence on impact energy and target material  

NASA Astrophysics Data System (ADS)

Using molecular-dynamics simulation, we study the impact of C 60 fullerene molecules with energies up to several tens of keV on various target materials: graphite, fullerite, Au and a condensed Ar solid. The analysis is based on single impact events. For all the target materials, fragmentation of the fullerene projectile sets in at around 1 keV impact energy; it starts the earliest in the heavy Au target. Full atomization of the projectile is observed at around 10 keV impact energy. The projectile ranges, on the other hand, depend strongly on the target material. The highest ranges are achieved in the weakly bonded Ar target. Also ranges in the fcc-C 60 solid are systematically larger than in the graphite target. Interestingly, at energies above 5 keV, the fullerene penetrates deeper into the Au target than into graphite, even though the Au has a considerably higher mass and efficiently reflects the fullerenes at lower bombarding energies; this indicates the dominant role of the cohesive energy of the target. The energy dependence of fullerene molecules is surprisingly flat and varies between E1/3 and E2/3 at smaller impact energies, E < 10 keV. At higher impact energies, where the projectile has been fully atomized, the energy dependence becomes more pronounced, ? E.

Anders, Christian; Kirihata, H.; Yamaguchi, Y.; Urbassek, Herbert M.

2007-02-01

11

Diagnostics of non-thermal processes in chromospheric flares. II. HOC and Call K line profiles for an atmosphere bombarded by 100 keV-1 MeV protons  

NASA Astrophysics Data System (ADS)

The effects on the H? line profile of non-thermal excitation and ionization of hydrogen by a 100 KeV- 1 MeV proton beam have been investigated. Non-LTE H? line profiles have been calculated for the temperature distributions of semi- empirical flares models F1 and F2 (Machado et al. 1980). For reasonable values of the beam energy flux and power index, the hydrogen lines are greatly strengthened. However, contrary to the case of an electron bombarded atmosphere, the line is not broadened, and no central reversal appears. These effects, alone or in conjunction with linear polarization measurements or Ly? red wing observations, can be used to diagnose proton beam bombardment.

Henoux, J. C.; Fang, C.; Gan, W. Q.

1993-07-01

12

Internal electron emission in metal–insulator–metal thin film tunnel devices bombarded with keV argon and gold-cluster projectiles  

Microsoft Academic Search

The kinetic excitation of a solid surface under bombardment with energetic ions is studied via internal electron emission in a metal–insulator–metal junction. Particular attention was focused on the dependence of the internal emission yield on the impact angle of the projectile ions, which was measured and compared to corresponding data for external emission. We find the internal and external yields

Mario Marpe; Christian Heuser; Detlef Diesing; Andreas Wucher

2011-01-01

13

Diagnostics of non-thermal processes in chromospheric flares. 1. Hoe and Call K line profiles of an atmosphere bombarded by 10-500 keV electrons  

NASA Astrophysics Data System (ADS)

The significance of non-thermal excitation and ionization of hydrogen and CaII, by an electron beam, on the line profiles of H? and CaII K line has been investigated. Non-LTE Hot and CaII K line profiles have been calculated for the temperature distributions of semi-empirical flares models F1 and F2 (Machado et al. t980). For reasonable values of the beam energy flux and power index, the hydrogen lines are greatly strengthened and broadened, and an obvious central reversal appears. The effects are weaker for the CaII K line. These effects can be used to diagnose electron beam bombardment during a solar flare, especially at its early phase. Any semi-empirical flare model that does not take into account non-thermal effects overestimates the heating of the solar atmosphere.

Fang, C.; Henoux, J. C.; Gan, W. Q.

1993-07-01

14

M X-ray cross sections from 75 to 300 keV proton bombardment of selected 5d transition elements  

NASA Astrophysics Data System (ADS)

M X-ray production cross sections for selected thick targets of Hf, W, Re, Pt, Au and Pb impacted by 75-300 keV protons are presented and compared with ECPSSR and RPWBA theories using different atomic data bases, including comparisons with other investigators. The results for the major M X-ray transitions exhibit a universal character with respect to the reduced proton velocity in agreement with expectations from theory.

Cipolla, Sam J.

2014-07-01

15

Energy distributions of hydrocarbon secondary ions from thin organic films under keV ion bombardment: Correlation between kinetic and formation energy of ions sputtered from tricosenoic acid  

NASA Astrophysics Data System (ADS)

The kinetic energy distributions (KED) of secondary ions sputtered from tricosenoic acid films under Ga + bombardment have been presented recently [1]. Below mass 100, the positive ion spectrum of tricosenoic acid is mainly constituted by the series of C xH y+ peaks. Within each C iH y+ series, the KED of these ions broadens when the number y of hydrogen atoms decreases. In this paper, we propose a phenomenological model accounting for the characteristic behavior of these ions. It is based on an initial transfer of momentum leading to the emission of an original fragment, reflecting the chemical structure of the target, and followed by a fast reorganization when its internal energy is in excess. Consequently, the ions emitted as a result of a violent collision, carrying a large excess of internal energy, will exhibit both a broad KED and a high degree of reorganization with respect to the structure of the original fragment. This interpretation highlights the effect of the chemical and molecular structure of the organic target on the emission process of the secondary molecular ions. Indeed, this structure determines the nature of the original fragments which have proved their utility for analytical purpose. These fragments lead to intense peaks in the mass spectra, allowing the recognition of the original chemical structure of the samples (fingerprint). In addition, such secondary ions resulting from a direct emission pathway, as suggested by their very narrow KED, turn out to be the best candidates for quantification.

Delcorte, A.; Bertrand, P.

1996-09-01

16

L- and M-shell ionization cross sections determined from X-ray production in Gd and Sn by 50-300 keV proton bombardment  

SciTech Connect

A Si(Li) detector with an ultra-thin window was used to measure L and M x-ray spectra from the impact of 50-300 keV protons on thick targets of Gd and Sn. Partial sub-shell ionization cross sections were determined from analysis of the L x-rays, and for the M x-rays from Gd; only total M-shell cross sections could be obtained for Sn. The results will be compared with the PWBA and ECPSSR theories.

Cipolla, S.

1993-05-01

17

The Stability of Cosmic Fullerenes and Fullerenic Aggregates  

NASA Astrophysics Data System (ADS)

Establishing the stability of cosmic fullerenes and fullerenic aggregates is extremely relevant for a variety of reasons. For instance, the emission features of C60 and C70 fall in the same spectral region as the Un-identified InfraRed (UIR) bands, which they could contribute to. To be able to contribute to the UIR emission, however, fullerenes must be able to survive long enough against the destruction mechanisms operating in the interstellar medium. In this study we focus on the effects of collisional processing, i.e., the bombardment by energetic ions and electrons. A recent experimental/theoretical study has shown that ion collisions with C60 clusters result in the dissociation of the cluster with the simultaneous formation of covalent fullerene dimers, which could play a role as DIBs carriers. We present here our first results about the collisional processing of C60 molecules and clusters by H, He and C ions in interstellar shocks. We have adapted the models that have previously been developed to successfully treat the collisional processing of PAHs in space. The nature of the interaction and the similarities between PAHs and fullerenes make this approach appropriate. In addition, our study shows that the formation of covalent dimers following ion collisions with C60 clusters is compatible with the astrophysical conditions under consideration.

Micelotta, E. R.; Cami, J.; Peeters, E.; Zettergren, H.; Schmidt, H. T.; Cederquist, H.; Jones, A. P.; Tielens, A. G. G. M.

2014-02-01

18

Conversion of fullerenes to diamond  

DOEpatents

A method of forming synthetic diamond on a substrate. The method involves providing a substrate surface covered with a fullerene or diamond coating, positioning a fullerene in an ionization source, creating a fullerene vapor, ionizing fullerene molecules, accelerating the fullerene ions to energies above 250 eV to form a fullerene ion beam, impinging the fullerene ion beam on the substrate surface and continuing these steps to obtain a diamond film thickness on the substrate.

Gruen, Dieter M. (1324 59th St., Downers Grove, IL 60515)

1994-01-01

19

Conversion of fullerenes to diamond  

DOEpatents

A method of forming synthetic diamond on a substrate is disclosed. The method involves providing a substrate surface covered with a fullerene or diamond coating, positioning a fullerene in an ionization source, creating a fullerene vapor, ionizing fullerene molecules, accelerating the fullerene ions to energies above 250 eV to form a fullerene ion beam, impinging the fullerene ion beam on the substrate surface and continuing these steps to obtain a diamond thickness on the substrate.

Gruen, Dieter M. (1324 59th St., Downers Grove, IL 60515)

1993-01-01

20

Fullerene Nanogears  

NASA Technical Reports Server (NTRS)

The Numerical Aerospace Simulation Systems Division (NAS) of the NASA Ames Research Center, Moffett Field, California is conducting research into molecular-sized devices known as Nanotechnology. This photograph depicts two 'Fullerene Nano-gears' with multiple teeth. The hope is that one day, products can be constructed made of thousands of tiny machines that could self-repair and adapt to the environment in which they exist. Researchers have simulated attaching benzyne molecules to the outside of a nanotube to form gear teeth. Nanotubes are molecular-sized pipes made of carbon atoms. To 'drive' the gears, the supercomputer simulated a laser that served as a motor. The laser creates an electric field around the nanotube. A positively charged atom is placed on one side of the nanotube, and a negatively charged atom on the other side. The electric field drags the nanotube around like a shaft turning. Jie Han, Al Globus, Richard Jaffe and Glenn Deardorff are the authors of a technical paper detailing this technology which appears in The Journal of Nanotechnology.

1997-01-01

21

Fullerenes in Allende Meteorite  

NASA Technical Reports Server (NTRS)

The detection of fullerenes in deposits from meteor impacts has led to renewed interest in the possibility that fullerenes are present in meteorites. Although fullerenes have not previously been detected in the Murchison and Allende meteorites, the Allende meteorite is known to contain several well-ordered graphite particles which are remarkably similar in size and appearance to the fullerene-related structures carbon onions and nanotubes. We report that fullerenes are in fact present in trace amounts in the Allende meteorite. In addition to fullerenes, we detected many polycyclic aromatic hydrocarbons (PAHs) in the Allende meteorite, consistent with previous reports. In particular, we detected benzofluoranthene and corannulene (C20H10), five-membered ring structures which have been proposed as precursors to the formation of fullerene synthesis, perhaps within circumstellar envelopes or other sites in the interstellar medium.

Becker, L.; Bada, J. L.; Winans, R. E.; Bunch, T. E.

1994-01-01

22

Combustion method for producing fullerenes  

DOEpatents

A method for synthesizing fullerenes in flames is provided. Fullerenes are prepared by burning carbon-containing compounds in a flame and collecting the condensibles. The condensibles contain the desired fullerenes. Fullerene yields can be optimized and fullerene composition can be selectively varied. Fullerene yields and compositions are determined by selectively controlling flame conditions and parameters such as C/O ratio, pressure, temperature, residence time, diluent concentration and gas velocity.

Howard, Jack B. (Winchester, MA); McKinnon, J. Thomas (Boulder, CO)

1993-01-01

23

Combustion synthesis of fullerenes and fullerenic nanostructures  

E-print Network

Fullerenes are molecules comprised entirely of sp²-bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Buckyballs, a subset which contains C?? and C??, are single-shell ...

Goel, Anish

2002-01-01

24

The topology of fullerenes  

PubMed Central

Fullerenes are carbon molecules that form polyhedral cages. Their bond structures are exactly the planar cubic graphs that have only pentagon and hexagon faces. Strikingly, a number of chemical properties of a fullerene can be derived from its graph structure. A rich mathematics of cubic planar graphs and fullerene graphs has grown since they were studied by Goldberg, Coxeter, and others in the early 20th century, and many mathematical properties of fullerenes have found simple and beautiful solutions. Yet many interesting chemical and mathematical problems in the field remain open. In this paper, we present a general overview of recent topological and graph theoretical developments in fullerene research over the past two decades, describing both solved and open problems. WIREs Comput Mol Sci 2015, 5:96–145. doi: 10.1002/wcms.1207 Conflict of interest: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website. PMID:25678935

Schwerdtfeger, Peter; Wirz, Lukas N; Avery, James

2015-01-01

25

Molecular Dynamics Simulation of Damage Cascade Formation in Ion Bombarded Solids  

E-print Network

/Molecular Massively Parallel Simulator). In one subtask, we studied damage cascade interactions caused by two 2 keV Si atoms simultaneously bombarding a crystalline Si substrate. We found that the enhanced displacement creation appears primarily in the thermal spike...

Chen, Di

2012-10-19

26

Process for fullerene functionalization  

DOEpatents

Di-addended and tetra-addended Buckminster fullerenes are synthesized through the use of novel organoborane intermediates. The C{sub 60}, C{sub 70}, or higher fullerene is reacted with a borane such as BH{sub 3} in a solvent such as toluene to form an organoborane intermediate. Reaction of the organoborane such as hydrolysis with water or alcohol results in the product di-addended and tetra-addended fullerene in up to 30% yields. Dihydrofullerenes and tetrahydrofullerenes are produced by the process of the invention. 7 figs.

Cahill, P.A.; Henderson, C.C.

1995-12-12

27

Process for fullerene functionalization  

DOEpatents

Di-addended and tetra-addended Buckminster fullerenes are synthesized through the use of novel organoborane intermediates. The C.sub.60, C.sub.70, or higher fullerene is reacted with a borane such as BH.sub.3 in a solvent such as toluene to form an organoborane intermediate. Reaction of the organoborane such as hydrolysis with water or alcohol results in the product di-addended and tetra-addended fullerene in up to 30% yields. Dihydrofullerenes and tetrahydrofullerenes are produced by the process of the invention.

Cahill, Paul A. (Albuquerque, NM); Henderson, Craig C. (Dublin, CA)

1995-01-01

28

Combustion energy of fullerene soot  

SciTech Connect

The standard energy of combustion of fullerene soot generated in arc discharge was determined to be [minus]36.0 [+-] 0.5 kJ g[sup [minus]1] by oxygen-bomb combustion calorimetry. The value was much closer to those of C[sub 60] and C[sub 70] than that of graphite. This result provides an energetic reason for the remarkable yield of fullerenes in arc discharge and supports the mechanism of fullerene formation, where fullerenes are the lowest energy products. Fullerene onion formation is interpreted in terms of energy relaxation of the fullerene soot. 20 refs., 1 tab.

Man, Naoki; Nagano, Yatsuhisa; Kiyobayashi, Tetsu; Sakiyama, Minoru (Osaka Univ., Toyonaka (Japan))

1995-02-23

29

Conversion of fullerenes to diamond  

DOEpatents

A method of forming synthetic hydrogen defect free diamond or diamond like films on a substrate. The method involves providing vapor containing fullerene molecules with or without an inert gas, providing a device to impart energy to the fullerene molecules, fragmenting at least in part some of the fullerene molecules in the vapor or energizing the molecules to incipient fragmentation, ionizing the fullerene molecules, impinging ionized fullerene molecules on the substrate to assist in causing fullerene fragmentation to obtain a thickness of diamond on the substrate.

Gruen, Dieter M. (1324 59th St., Downers Grove, IL 60515)

1994-01-01

30

Conversion of fullerenes to diamonds  

DOEpatents

A method of forming synthetic diamond or diamond-like films on a substrate surface. The method involves the steps of providing a vapor selected from the group of fullerene molecules or an inert gas/fullerene molecule mixture, providing energy to the fullerene molecules consisting of carbon-carbon bonds, the energized fullerene molecules breaking down to form fragments of fullerene molecules including C.sub.2 molecules and depositing the energized fullerene molecules with C.sub.2 fragments onto the substrate with farther fragmentation occurring and forming a thickness of diamond or diamond-like films on the substrate surface.

Gruen, Dieter M. (1324 59th St., Downers Grove, IL 60515)

1995-01-01

31

Photodynamic therapy with fullerenes  

PubMed Central

Fullerenes are a class of closed-cage nanomaterials made exclusively from carbon atoms. A great deal of attention has been focused on developing medical uses of these unique molecules especially when they are derivatized with functional groups to make them soluble and therefore able to interact with biological systems. Due to their extended ?-conjugation they absorb visible light, have a high triplet yield and can generate reactive oxygen species upon illumination, suggesting a possible role of fullerenes in photodynamic therapy. Depending on the functional groups introduced into the molecule, fullerenes can effectively photoinactivate either or both pathogenic microbial cells and malignant cancer cells. The mechanism appears to involve superoxide anion as well as singlet oxygen, and under the right conditions fullerenes may have advantages over clinically applied photosensitizers for mediating photodynamic therapy of certain diseases. PMID:17973044

Mroz, Pawel; Tegos, George P.; Gali, Hariprasad; Wharton, Tim; Sarna, Tadeusz; Hamblin, Michael R.

2010-01-01

32

Fullerenes formation in flames  

NASA Technical Reports Server (NTRS)

Fullerenes are composed of carbon atoms arranged in approximately spherical or ellipsoidal cages resembling the geodesic domes designed by Buckminster Fuller, after whom the molecules were named. The approximately spherical fullerene, which resembles a soccer ball and contains sixty atoms (C60), is called buckminsterfullerene. The fullerene containing seventy carbon atoms (C70) is approximately ellipsoidal, similar to a rugby ball. Fullerenes were first detected in 1985, in carbon vapor produced by laser evaporation of graphite. The closed shell structure, which has no edge atoms vulnerable to reaction, was proposed to explain the observed high stability of certain carbon clusters relative to that of others at high temperatures and in the presence of an oxidizing gas.

Howard, Jack B.

1993-01-01

33

Fullerenes from a fulgurite  

SciTech Connect

Peaks at 720 and 840 atomic mass units were identified by mass spectrometry in a sample extracted from a fulgurite, which is a glassy rock that forms where lightning strikes the ground. The peaks are interpreted as arising from C[sub 60] and C[sub 70] and the associated peaks as produced from other fullerenes. The intense conditions generated by the lightning not only melted the rock it struck and fused the associated soil but also allowed fullerenes to form, presumably from the organic debris in the soil. 29 refs., 3 figs., 1 tab.

Daly, T.K.; Buseck, P.R.; Williams, P.; Lewis, C.F. (Arizona State Univ., Tempe (United States))

1993-03-12

34

Fullerenes from a fulgurite  

NASA Astrophysics Data System (ADS)

Peaks at 720 and 840 atomic mass units were identified by mass spectrometry in a sample extracted from a fulgurite, which is a glassy rock that forms where lightning strikes the ground. The peaks are interpreted as arising from C60 and C70 and the associated peaks as produced from other fullerenes. The intense conditions generated by the lightning not only melted the rock it struck and fused the associated soil but also allowed fullerenes to form, presumably from the organic debris in the soil.

Daly, Terry K.; Buseck, Peter R.; Williams, Peter; Lewis, Charles F.

1993-03-01

35

Fullerenes from a fulgurite.  

PubMed

Peaks at 720 and 840 atomic mass units were identified by mass spectrometry in a sample extracted from a fulgurite, which is a glassy rock that forms where lightning strikes the ground. The peaks are interpreted as arising from C(60) and C(70) and the associated peaks as produced from other fullerenes. The intense conditions generated by the lightning not only melted the rock it struck and fused the associated soil but also allowed fullerenes to form, presumably from the organic debris in the soil. PMID:17733026

Daly, T K; Buseck, P R; Williams, P; Lewis, C F

1993-03-12

36

Combustion Synthesis of Fullerenes and Fullerenic Nanostructures In Microgravity  

NASA Technical Reports Server (NTRS)

The objectives of the proposed research were to determine the effects of gravity on fullerenes formation in flames and, based on the observed effects, to develop fundamental understanding of fullerenes formation and to identify engineering principles for fullerenes production. The research method consisted of the operation of laminar diffusion flames under normal- and reduced-gravity conditions, and the collection from the flames and subsequent analysis of condensables including any fullerenes present, using coupled high performance liquid chromatography/mass spectrometry and high resolution transmission electron microscopy. The focus included fullerene molecules C60 and C70 and fullerenic nanostructures including tubes, spherules and other shapes. The normal-gravity experiments were performed at MIT and complementary reduced-gravity experiments were to have been contributed by NASA. The independent variables of interest are gravity, fuel type, fuel/oxygen ratio, pressure, gas velocity at burner, diluent type and concentration. Given the large number of variables and the absence of data on either fullerene formation in diffusion flames or gravitational effects on fullerene formation in diffusion or premixed flames, the first part of the work was exploratory while the later part involved detailed study of the most interesting mechanisms. Samples of condensable material from laminar low pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chromatography to determine the yields of fullerenes, and by high-resolution transmission electron microscopy (HRTEM) to characterize the fullerenic material, i.e., curved-layer nanostructures, on and within the soot particles. The highest concentration of fullerenes was always detected just above the visible stoichiometric surface of a flame. The percentage of fullerenes in the condensable material increases with decreasing pressure. The overall highest amount of fullerenes was found for a surprisingly high dilution fuel with argon. The maximum flame temperature seems to be of minor importance in fullerene formation. The HRTEM analysis of the soot showed an increase of the curvature of the carbon layers, and hence increased fullerenic character. After this maximum, the curvature decreases. In addition to the soot, the samples included fullerenic nanostructures, such as tubes and spheroids including highly-ordered multilayered or onion-like structures. The soot itself shows highly ordered regions that appear to have been cells of ongoing fullerenic nanostructure formation.

Howard, Jack B.; Brooker, John E. (Technical Monitor)

2002-01-01

37

Geological occurrence of fullerenes  

SciTech Connect

Using HRTEM imaging, the authors found C[sub 60] and C[sub 70] fullerenes in shungite, a Precambrian carbon-rich rock from Karelia, Russia. Compositionally, shungite represents coals of the meta-anthracite rank, characterized by low ash and sulfur contents, low volatile yields, and high carbon contents. The shungite occurs within metamorphosed sediments. The overlying rocks consist of gray dolomitized sandstones and poorly sorted silts and clays; the underlying rocks are not exposed. The shungite consists of masses containing up to 99% carbon. Diabase is interstratified with shungite-bearing rocks, and the shungite concentration increases with proximity to the diabase. Their sample comes from inclusions in the diabase. In the HRTEM images the fullerenes appear round (presumably roughly spherical in three dimensions), with white rims and black centers, almost identical to images of synthetic C[sub 60] molecules. Following the HRTEM observations, the fullerene identities were confirmed, first by time-of-flight mass spectrometry and then by more precise laser ablation, laser desorption, and thermal desorption ionization plus Fourier transform (FT) mass spectrometry. These measurements verified that the fullerenes were not generated by the laser ionization event. HRTEM images show that locally they occur in ordered arrays that resemble crystals of synthetic C[sub 60]. FT mass spectra show that the C-13/C-12 isotopic ratios for C[sub 60] and C[sub 70] fall within the normal range of terrestrial isotopic values.

Buseck, P.R.; Tsipursky, S.J.; Wang, S. (Arizona State Univ., Tempe, AZ (United States)); Hettich, R. (Oak Ridge National Lab., TN (United States))

1992-01-01

38

Ferromagnetism induced by heavy-ion irradiation in fullerene films  

NASA Astrophysics Data System (ADS)

Magnetic measurements using a superconducting quantum interference device and magnetic force microscopy were performed on fullerene films irradiated with 250keV Ar and 92MeV Si ions, to compare the effects of electronic excitation and collisional cascade on the magnetization. A ferromagnetic behavior increasing with ion fluence is observed. The magnetization is attributed to (i) the formation of an amorphous carbon network and (ii) the incorporation of oxygen in the irradiated films.

Kumar, Amit; Avasthi, D. K.; Pivin, J. C.; Tripathi, A.; Singh, F.

2006-10-01

39

Fast Atom Bombardment Mass Spectrometry.  

ERIC Educational Resources Information Center

Discusses reactions and characteristics of fast atom bombardment (FAB) mass spectroscopy in which samples are ionized in a condensed state by bombardment with xenon or argon atoms, yielding positive/negative secondary ions. Includes applications of FAB to structural problems and considers future developments using the technique. (Author/JN)

Rinehart, Kenneth L., Jr.

1982-01-01

40

Temperature dependent segregation of metals at Si–SiO2 interfaces during oxygen ion bombardment  

Microsoft Academic Search

Rutherford backscattering and channeling techniques have been used to study temperature-dependent segregation of Cu, Au, and Pd at Si–SiO2 interfaces during high dose 15 keV O+ bombardment of Si. Results illustrate a strong tendency for metals to be retained in an amorphous Si layer adjacent to the continuous SiO2 layer formed by O+ bombardment of Si. The magnitude of segregation

J. S. Williams; K. T. Short; A. E. White

1997-01-01

41

Superficial defects induced by argon and oxygen bombardments on (110) TiO 2 surfaces  

NASA Astrophysics Data System (ADS)

Compositional and chemical changes of titanium dioxide monocrystalline surfaces induced by bombardment with 4 keV argon and oxygen ions have been studied by AES, XPS and AFM. Argon ion bombardment induced strong changes in the composition and chemical state of the surface: loss of oxygen due to preferential sputtering occurred, and, related to this, Ti 4+ species were reduced to Ti 3+ and Ti 2+. During oxygen bombardment, competition between preferential sputtering of oxygen ions of the oxide surface and oxygen implantation was observed. This phenomenon was found to be strongly dependent upon the incidence angle of the oxygen ions. Moreover, an oxygen bombardment with normal incidence of the surface that had been previously submitted to an argon ion bombardment led to a restoichiometrization of the surface: no further Ti 3+ or Ti 2+ was found by XPS, only Ti 4+.

Pétigny, S.; Mostéfa-Sba, H.; Domenichini, B.; Lesniewska, E.; Steinbrunn, A.; Bourgeois, S.

1998-08-01

42

Terrestrial and Extraterrestrial Fullerenes  

Microsoft Academic Search

This paper reviews reports of occurrences of fullerenes in circumstellar media, interstellar media, meteorites, interplanetary dust particles (IDPs), lunar rocks, hard terrestrial rocks from Shunga (Russia), Sudbury (Canada) and Mitov (Czech Republic), coal, terrestrial sediments from the Cretaceous?Tertiary?Boundary and Permian?Triassic?Boundary, fulgurite, ink sticks, dinosaur eggs, and a tree char. The occurrences are discussed in the context of known and postulated

D. Heymann; L. W. Jenneskens; J. Jehli?ka; Carola Koper; E. J. Vlietstra

2003-01-01

43

Symmetry of fullerenes  

NASA Astrophysics Data System (ADS)

All fullerene isomers with up to 70 atoms have been generated and their symmetry analyzed. A safe and efficient algorithm for determination of symmetrically equivalent vertices, edges and faces in the corresponding molecular graph is outlined. The automorphism group determined in this way represents the maximal symmetry which the pertinent molecule can have. All analyzed isomers are classified by their symmetry, and the results are tabulated.

Babi, D.; Klein, D. J.; Sah, C. H.

1993-08-01

44

Diamond film growth from fullerene precursors  

DOEpatents

A method and system for manufacturing diamond film. The method involves forming a fullerene vapor, providing a noble gas stream and combining the gas with the fullerene vapor, passing the combined fullerene vapor and noble gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the fullerene and deposition of a diamond film on a substrate.

Gruen, Dieter M. (Downers Grove, IL); Liu, Shengzhong (Woodridge, IL); Krauss, Alan R. (Naperville, IL); Pan, Xianzheng (Woodridge, IL)

1997-01-01

45

Very low-energy and low-fluence ion beam bombardment of naked plasmid DNA  

NASA Astrophysics Data System (ADS)

Ion beam bombardment of biological organisms has been recently applied to mutation breeding of both agricultural and horticultural plants. In order to explore relevant mechanisms, this study employed low-energy ion beams to bombard naked plasmid DNA. The study aimed at simulation of the final stage of the process of the ion beam bombardment of real cells to check whether and how very low-energy and low-fluence of ions can induce mutation. Argon and nitrogen ions at 5 keV and 2.5 keV respectively bombarded naked plasmid DNA pGFP to very low-fluences, an order of 10 13 ions/cm 2. Subsequently, DNA states were analyzed using electrophoresis. Results provided evidences that the very low-energy and low-fluence ion bombardment indeed altered the DNA structure from supercoil to short linear fragments through multiple double strand breaks and thus induced mutation, which was confirmed by transfer of the bombarded DNA into bacteria Escherichia coli and subsequent expression of the marker gene.

Norarat, R.; Semsang, N.; Anuntalabhochai, S.; Yu, L. D.

2009-05-01

46

Tailoring surface properties of polymeric blend material by ion beam bombardment  

NASA Astrophysics Data System (ADS)

In this work, LDPE/SBR polymer blend samples were bombarded with 130 keV He and 320 keV Ar ions at different fluencies ranging from 1×1013 to 2×1016 ions cm-2. The changes in surface properties of the ion-bombarded polymers were investigated with ultraviolet-visible (UV-vis) spectroscopy, Photoluminescence (PL) and energy dispersive X-ray (EDX) techniques. The variations in the wettability, surface free energy and spreading coefficient of ion beam bombarded LDPE polymer blend samples have been studied. The UV-vis analysis revealed that the transmission spectra shifted towards lower energy region after bombardment with increasing ion fluence. This shift clearly reflects decrease in optical band gap. A remarkable decrease in the PL intensity with increasing ion beam fluence was observed. The EDX study indicates the oxygen uptake increases with increasing ion fluence. Contact angle measurements showed that wettability, surface free energy and spreading coefficient of LDPE blends samples have increased with increasing ion fluence. This increase in the wettability and surface free energy of the bombarded samples are attributed to formation of oxidized layer on the polymer surface, which apparently occurs after exposure of bombarded samples to the air.

Ali, Z. I.; Abdul-Kader, A. M.; Rizk, R. A. M.; Ali, M.

2013-10-01

47

Fullerenes Doped with Metal Halides  

NASA Astrophysics Data System (ADS)

The cage-like structure of fullerenes is a challenge to every experimentalist to put something inside—to dope the fullerenes. In fact, the research team that first identified C60 as a football-like molecule quickly succeeded in trapping metal atoms inside and in shrinking the cage around this atom by photofragmentation. In this paper we report the results of “shrink-wrapping” the fullerenes around metal halide molecules. Of special interest is the critical size (the minimum number of carbon atoms) that can still enclose the dopant. A rough model for the space available inside a carbon cage gives good agreement with the measured shrinking limits.

Martin, T. P.; Heinebrodt, M.; Näher, U.; Göhlich, H.; Lange, T.; Schaber, H.

48

Effect of ion bombardment on the field emission property of tetrapod ZnO  

NASA Astrophysics Data System (ADS)

The influences of ion bombardment on the field emission performance of tetrapod ZnO nanostructures are reported. As the scanning electron microscopy images and photoluminescence spectrum show, the tips of the field emitters are destroyed and the surface state of the field emitters is also changed after the ion bombardment. The ion bombardment has a considerable effect on the field emission properties of the tetrapod ZnO field emitters. After Ar+ ion bombardment with the energy of 3 keV and the ion current of 0.05 ?A for 30 min, the turn-on field increases about 63% and the threshold field increases about 77%, respectively. There are two main reasons for the variation in field-emission property: (1) the decrement of the field enhancement factor ?, which is caused by the variation in morphology of field emitter; (2) the increment of work function ?, which is caused by the changed concentration of the surface oxygen vacancy.

Cui, Yunkang; Zhang, Xiaobing; Lei, Wei; Di, Yunsong; Wang, Jinchan; Yang, Xiaxi

2010-03-01

49

Closed network growth of fullerenes.  

PubMed

Tremendous advances in nanoscience have been made since the discovery of the fullerenes; however, the formation of these carbon-caged nanomaterials still remains a mystery. Here we reveal that fullerenes self-assemble through a closed network growth mechanism by incorporation of atomic carbon and C(2). The growth processes have been elucidated through experiments that probe direct growth of fullerenes upon exposure to carbon vapour, analysed by state-of-the-art Fourier transform ion cyclotron resonance mass spectrometry. Our results shed new light on the fundamental processes that govern self-assembly of carbon networks, and the processes that we reveal in this study of fullerene growth are likely be involved in the formation of other carbon nanostructures from carbon vapour, such as nanotubes and graphene. Further, the results should be of importance for illuminating astrophysical processes near carbon stars or supernovae that result in C(60) formation throughout the Universe. PMID:22617295

Dunk, Paul W; Kaiser, Nathan K; Hendrickson, Christopher L; Quinn, John P; Ewels, Christopher P; Nakanishi, Yusuke; Sasaki, Yuki; Shinohara, Hisanori; Marshall, Alan G; Kroto, Harold W

2012-01-01

50

Production Of Fullerenic Soot In Flames  

DOEpatents

A method for the production of fullerenic nanostructures is described in which unsaturated hydrocarbon fuel and oxygen are combusted in a burner chamber at a sub-atmospheric pressure, thereby establishing a flame. The condensibles of the flame are collected at a post-flame location. The condensibles contain fullerenic nanostructures, such as single and nested nanotubes, single and nested nanoparticles and giant fullerenes. The method of producing fullerenic soot from flames is also described.

Howard, Jack B. (Winchester, MA); Vander Sande, John B. (Newbury, MA); Chowdhury, K. Das (Cambridge, MA)

2000-12-19

51

Production of fullerenic nanostructures in flames  

DOEpatents

A method for the production of fullerenic nanostructures is described in which unsaturated hydrocarbon fuel and oxygen are combusted in a burner chamber at a sub-atmospheric pressure, thereby establishing a flame. The condensibles of the flame are collected at a post-flame location. The condensibles contain fullerenic nanostructures, such as single and nested nanotubes, single and nested nanoparticles and giant fullerenes. The method of producing fullerenic soot from flames is also described.

Howard, Jack B. (Winchester, MA); Vander Sande, John B. (Newbury, MA); Chowdhury, K. Das (Cambridge, MA)

1999-01-01

52

Diamond film growth from fullerene precursors  

DOEpatents

A method and system are disclosed for manufacturing diamond film. The method involves forming a fullerene vapor, providing a noble gas stream and combining the gas with the fullerene vapor, passing the combined fullerene vapor and noble gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the fullerene and deposition of a diamond film on a substrate. 10 figs.

Gruen, D.M.; Liu, S.; Krauss, A.R.; Pan, X.

1997-04-15

53

Reaction of [60]fullerene With Triethylamine  

Microsoft Academic Search

[60]Fullerene reacts with neat triethylamine via an electron transfer involving an intermediate C60-radical-anion, to give a salt-like product. This decomposes to [60]fullerene upon either heating, or treatment with ultrasound. EI mass fragmentation of the product indicates an intramolecular abstraction of H from C2H5 by the [60]fullerene moiety.

Josef Pola; Adam D. Darwish; Richard A. Jackson; Harold W. Kroto; Mohamed F. Meidine; Alaa K. Abdul-Sada; Roger Taylor; David R. M. Walton

1995-01-01

54

Mechanisms of ion-bombardment-induced DNA transfer into bacterial E. coli cells  

NASA Astrophysics Data System (ADS)

As a useful ion beam biotechnology, ion-bombardment-induced DNA transfer into bacterial Escherichia coli (E. coli) cells has been successfully operated using argon ions. In the process ion bombardment of the bacterial cells modifies the cell envelope materials to favor the exogenous DNA molecules to pass through the envelope to enter the cell. The occurrence of the DNA transfer induction was found ion energy and fluence dependent in a complex manner. At ion energy of a few keV and a few tens of keV to moderate fluences the DNA transfer could be induced by ion bombardment of the bacterial cells, while at the same ion energy but to high fluences DNA transfer could not be induced. On the other hand, when the ion energy was medium, about 10-20 keV, the DNA transfer could not be induced by ion bombardment of the cells. The complexity of the experimental results indicated a complex mechanism which should be related to the complex structure of the bacterial E. coli cell envelope. A phase diagram was proposed to interpret different mechanisms involved as functions of the ion energy and fluence.

Yu, L. D.; Sangwijit, K.; Prakrajang, K.; Phanchaisri, B.; Thongkumkoon, P.; Thopan, P.; Singkarat, S.; Anuntalabhochai, S.

2014-05-01

55

Metal ion bombardment of onion skin cell wall  

SciTech Connect

Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30keV, and the implantation fluence was in the range 1014 1016 ions/cm2. The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

Sangyuenyongpipat, S.; Vilaithong, T.; Yu, L.D.; Verdaguer, A.; Ratera, I.; Ogletree, D.F.; Monteiro, O.R.; Brown, I.G.

2004-05-10

56

Molecular Structure of C70 Fullerene  

NSDL National Science Digital Library

Fullerenes are cage like, hollow molecules composed of hexagonal and pentagonal groups of carbon atoms and constitute together with carbon nanotubes the third and youngest form that elemental carbon occurs in; the other two being diamond and graphite. The name Fullerene was given to commemorate the American inventor, architect and philosopher Richard Buckminster Fuller (1895 - 1993) who designed constructions built from pentagons and hexagons. The smallest known fullerene is C60. Fullerenes have potential applications as super- and semiconductors and in material science. In the natural environment, fullerenes can be found for example in Shunga/Russia, New Zealand and Sudbury/Canada.

2002-08-26

57

Ion bombardment in RF photoguns  

SciTech Connect

A linac-ring eRHIC design requires a high-intensity CW source of polarized electrons. An SRF gun is viable option that can deliver the required beam. Numerical simulations presented elsewhere have shown that ion bombardment can occur in an RF gun, possibly limiting lifetime of a NEA GaAs cathode. In this paper, we analytically solve the equations of motion of ions in an RF gun using the ponderomotive potential of the Rf field. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper discusses possible mitigation techniques that can reduce the rate of ion bombardment.

Pozdeyev,E.; Kayran, D.; Litvinenko, V. N.

2009-05-04

58

Electron-energy-loss spectroscopy of plasmon excitations in concentric-shell fullerenes  

NASA Astrophysics Data System (ADS)

We report evidence for surface plasmon excitations in concentric-shell fullerenes. A film of these concentric-shell fullerenes with radii around 5-7 nm was produced by carbon bombardment of a silver polycrystalline target and measured by electron-energy-loss spectroscopy (EELS) in reflection geometry. These data were analyzed with the help of a dielectric theory developed for EELS in transmission geometry. Taking into account the concentric-shell-substrate interaction, the spectral shape can be explained as a combination of contributions from ?-?* interband transitions (around 13.5 eV), from the surface radial (?-?*) and tangential (?-?*) plasmons (around 14.5 eV and 16.7 eV, respectively), and from the volume plasmon (24.5 eV).

Henrard, L.; Malengreau, F.; Rudolf, P.; Hevesi, K.; Caudano, R.; Lambin, Ph.; Cabioc'h, Th.

1999-02-01

59

Cereal transformation through particle bombardment  

NASA Technical Reports Server (NTRS)

The review focuses on experiments that lead to stable transformation in cereals using microprojectile bombardment. The discussion of biological factors that affect transformation examines target tissues and vector systems for gene transfer. The vector systems include reporter genes, selectable markers, genes of agronomic interest, and vector constructions. Other topics include physical parameters that affect DNA delivery, selection of stably transformed cells and plant regeneration, and analysis of gene expression and transmission to the progeny.

Casas, A. M.; Kononowicz, A. K.; Bressan, R. A.; Hasegawa, P. M.; Mitchell, C. A. (Principal Investigator)

1995-01-01

60

Pseudorotation in fullerene anions  

NASA Astrophysics Data System (ADS)

Jahn-Teller (JT) problems are often characterised by an adiabatic potential energy surface (APES) containing either a set of isoenergetic wells or a trough of equivalent-energy points, which may be warped by higher-order coupling terms or anisotropic effects. In all three cases, the JT effect will be dynamic. Either tunnelling between the wells or rotation (of a distortion) around the trough will restore the original symmetry of the system. This motion is referred to as pseudorotation. It should be possible to observe a JT system in a distorted geometry if measurements are made on a sufficiently short timescale. In various cubic systems, this timescale has been calculated to be the order of picoseconds. Such timescales are accessible using modern methods of ultrafast spectroscopy. Measurements of pseudorotation rates can lead to important information on the strength and nature of the JT coupling present. We will present analytical calculations that allow the rate of pseudorotation to be determined in terms of the vibronic coupling parameters. We will show how these results can be applied to E ? e systems and then to the more complicated system applicable to C60- anions. This is of particular interest because of the high icosahedral symmetry of fullerene ions and also because of the many potential uses of materials containing these ions. We conclude by outlining experiments that should be capable of measuring pseudorotation in C 60 anions.

Dunn, Janette L.; Hands, Ian D.; Bates, Colin A.

2007-07-01

61

Inorganic Fullerenes, Onions, and Tubes  

ERIC Educational Resources Information Center

Buckminsterfullerene, which is in the shape of a soccer-ball was first discovered in 1985, has many applications as a good lubricant, or as a new superconductor. The synthesis of these inorganic fullerenes involves a great deal of interdisciplinary research between physicists, material scientists, engineers and chemists from various fields.

York, Andrew P. E.

2004-01-01

62

Development of Mass Spectrometric Ionization Methods for Fullerenes and Fullerene Derivatives  

EPA Science Inventory

Currently investigations into the environmental behavior of fullerenes and fullerene derivatives is hampered by the lack of well characterized standards and by the lack of readily available quantitative analytical methods. Reported herein are investigations into the utility of ma...

63

42nd Bombardment Squadron (Heavy). History of the 42nd Bombardment Squadron (Heavy) 1940 - 1944  

E-print Network

History of the 42d Bombardment Squadron (H). 1940 ? 1944. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943 - ) Air Force Historical Association..., IRIS No. 44028. Mission Reports, 18 July 1942 ? 10 August 1943. This copy of the History of the 42nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force...

United States Army Air Corps; United States Army Air Corps

1946-01-01

64

An ion beam deceleration lens for ultra-low-energy ion bombardment of naked DNA  

NASA Astrophysics Data System (ADS)

Study of low-energy ion bombardment effect on biological living materials is of significance. High-energy ion beam irradiation of biological materials such as organs and cells has no doubt biological effects. However, ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range. To investigate effects from very-low-energy ion bombardment on biological materials, an ion beam deceleration lens is necessary for uniform ion energy lower than keV. A deceleration lens was designed and constructed based on study of the beam optics using the SIMION program. The lens consisted of six electrodes, able to focus and decelerate primary ion beam, with the last one being a long tube to obtain a parallel uniform exiting beam. The deceleration lens was installed to our 30-kV bioengineering-specialized ion beam line. The final decelerated-ion energy was measured using a simple electrostatic field to bend the beam to range from 10 eV to 1 keV controlled by the lens parameters and the primary beam condition. In a preliminary test, nitrogen ion beam at 60 eV decelerated from a primary 20-keV beam bombarded naked plasmid DNA. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks. The study demonstrated that the ion bombardment with energy as low as several-tens eV was possible to break DNA strands and thus potential to cause genetic modification of biological cells.

Thopan, P.; Prakrajang, K.; Thongkumkoon, P.; Suwannakachorn, D.; Yu, L. D.

2013-07-01

65

Synthesis, properties and transformations of fullerene peroxides  

NASA Astrophysics Data System (ADS)

Methods of synthesis, properties and transformations of fullerene peroxides are considered and systematized for the first time. It is shown that the chemistry of fullerene peroxides is a new approach to functionalization of fullerenes, which has been intensively developing since 2002. Methods of synthesis, mechanisms of formation and reactions of C60 and C70 alkyl peroxides with or without epoxide moieties are discussed. Transformations of fullerene peroxides affording a wide range of fullerene derivatives containing, as addends, halogen or sulfur atoms; epoxide, dioxolane, thiirane, crown ether, aziridine and dioxetane rings, as well as hydroxyl, alkoxyl and carbonyl groups, are considered. Special attention is focused on reactions constituting the basis of a new approach — so-called molecular surgery, which enables the synthesis of open-cage fullerene derivatives. It has been demonstrated that such compounds are good candidates for designing photovoltaic cells and carriers of drugs and radionuclides (for radiopharmaceuticals). The bibliography includes 130 references.

Bulgakov, R. G.; Galimov, D. I.; Dzhemilev, U. M.

2014-08-01

66

Functionalized fullerenes in self-assembled monolayers.  

PubMed

Anisotropy of intermolecular and molecule-substrate interactions holds the key to controlling the arrangement of fullerenes into 2D self-assembled monolayers (SAMs). The chemical reactivity of fullerenes allows functionalization of the carbon cages with sulfur-containing groups, thiols and thioethers, which facilitates the reliable adsorption of these molecules on gold substrates. A series of structurally related molecules, eight of which are new fullerene compounds, allows systematic investigation of the structural and functional parameters defining the geometry of fullerene SAMs. Scanning tunnelling microscopy (STM) measurements reveal that the chemical nature of the anchoring group appears to be crucial for the long-range order in fullerenes: the assembly of thiol-functionalized fullerenes is governed by strong molecule-surface interactions, which prohibit formation of ordered molecular arrays, while thioether-functionalized fullerenes, which have a weaker interaction with the surface than the thiols, form a variety of ordered 2D molecular arrays owing to noncovalent intermolecular interactions. A linear row of fullerene molecules is a recurring structural feature of the ordered SAMs, but the relative alignment and the spacing between the fullerene rows is strongly dependent on the size and shape of the spacer group linking the fullerene cage and the anchoring group. Careful control of the chemical functionality on the carbon cages enables positioning of fullerenes into at least four different packing arrangements, none of which have been observed before. Our new strategy for the controlled arrangement of fullerenes on surfaces at the molecular level will advance the development of practical applications for these nanomaterials. PMID:21744819

Gimenez-Lopez, Maria del Carmen; Räisänen, Minna T; Chamberlain, Thomas W; Weber, Uli; Lebedeva, Maria; Rance, Graham A; Briggs, G Andrew D; Pettifor, David; Burlakov, Victor; Buck, Manfred; Khlobystov, Andrei N

2011-09-01

67

Statistical mechanics of fullerene coalescence growth  

SciTech Connect

Among the different carbon allotropes fullerenes are exceptionally intriguing for their spheroidal topology out of pentagons and hexagons. However, the dominant formation mode is still ambiguous. Here, we analyze the fullerene formation process by the statistical analysis of fullerene sizes produced in a laser-induced microplasma finding that a simple two-parameter lognormal distribution describes impressively well the cluster frequencies under various conditions. Our findings clearly reveal coalescent growth following a classical collision dynamics and disagree with several earlier assumptions.

Maul, Jochen; Berg, Thomas; Schoenhense, Gerd; Huber, Gerhard [Institut fuer Physik, Johannes Gutenberg-Universitaet, Staudingerweg 7, D-55099 Mainz (Germany); Marosits, Edit [Max Planck-Institut fuer Chemie, Becherweg 27, D-55128 Mainz (Germany)

2006-10-15

68

Fullerenes in matrices of different substances  

NASA Astrophysics Data System (ADS)

Techniques for obtaining fullerene-containing materials based on metals and semiconductors, and also on polymers and ceramics, have been developed. It has been shown that fullerenes, on introduction into the matrices of different substances, produce substantial changes in their structure and properties. In some cases fullerenes act not only as the components of composite materials but also as the reagents of chemical reactions in obtaining new substances.

Vityaz', P. A.; Shpilevskii, É. M.

2012-07-01

69

Influence of ion-beam bombardment on the optical properties of LDPE polymer blends  

NASA Astrophysics Data System (ADS)

Ion beams have been found to be widely applicable in improving the structure and physical properties of polymers. In this paper, the effect of ion bombardment on the optical properties of low density polyethylene (LDPE)/styrene butadiene rubber (SBR) blend (LDPE/SBR) was studied. Polymer samples were bombarded with 130 keV He and 320 keV Ar ions to fluencies ranging from 1 × 1013 to 2 × 1016 ions cm-2. The pristine and ion beam bombarded samples were investigated using ultraviolet-visible (UV-Vis) spectrophotometry. The optical band gap (Eg) was decreased from ~2.3 to ~1.22 eV for the pristine sample and those samples bombarded with He and Ar ions at the highest fluence. The change in the optical gap indicates the presence of a gradual phase transition for the polymer blends. With increasing ion fluence, a decrease in both the energy gap and the activation energy was observed. The number of carbon atoms (N) in a formed cluster is found to be directly proportional to ion fluence and is determined according to the modified Tauc equation.

Rizk, R. A. M.; Abdul-Kader, A. M.; Ali, M.; Ali, Z. I.

2008-10-01

70

Development of Advanced Alloys using Fullerenes  

SciTech Connect

Development of advanced alloys using fullerenes is currently underway to produce materials for use in the extravehicular mobility unit (EMU). These materials will be directed toward commercial usages as they are continually developed. Fullerenes (of which the most common is C{sub 60}) are lightweight, nanometer size, hollow molecules of carbon which can be dispersed in conventional alloy systems to enhance strength and reduce weight. In this research, fullerene interaction with aluminum is investigated and a fullerene-reinforced aluminum alloy is being developed for possible use on the EMU. The samples were manufactured using standard commercial approaches including powder metallurgy and casting. Alloys have been processed having 1.3, 4.0 and 8.0 volume fractions of fullerenes. It has been observed that fullerene dispersion is related to the processing approach and that they are stable for the processing conditions used in this research. Emphasis will be given to differential thermal analysis and wavelength dispersive analysis of the processed alloys. These two techniques are particularly useful in determining the condition of the fullerenes during and after processing. Some discussion will be given as to electrical properties of fullerene-reinforced materials. Although the aluminum and other advanced alloys with fullerenes are being developed for NASA and the EMU, the properties of these materials will be of interest for commercial applications where specific Dual-Use will be given.

Sims, J.; Wasz, M.; O`Brien, J.; Callahan, D.L.; Barrera, E.V.

1994-05-01

71

Development of Advanced Alloys using Fullerenes  

NASA Technical Reports Server (NTRS)

Development of advanced alloys using fullerenes is currently underway to produce materials for use in the extravehicular mobility unit (EMU). These materials will be directed toward commercial usages as they are continually developed. Fullerenes (of which the most common is C(sub 60)) are lightweight, nanometer size, hollow molecules of carbon which can be dispersed in conventional alloy systems to enhance strength and reduce weight. In this research, fullerene interaction with aluminum is investigated and a fullerene-reinforced aluminum alloy is being developed for possible use on the EMU. The samples were manufactured using standard commercial approaches including powder metallurgy and casting. Alloys have been processed having 1.3, 4.0 and 8.0 volume fractions of fullerenes. It has been observed that fullerene dispersion is related to the processing approach and that they are stable for the processing conditions used in this research. Emphasis will be given to differential thermal analysis and wavelength dispersive analysis of the processed alloys. These two techniques are particularly useful in determining the condition of the fullerenes during and after processing. Some discussion will be given as to electrical properties of fullerene-reinforced materials. Although the aluminum and other advanced alloys with fullerenes are being developed for NASA and the EMU, the properties of these materials will be of interest for commercial applications where specific Dual-Use will be given.

Sims, J.; Wasz, M.; O'Brien, J.; Callahan, D. L.; Barrera, E. V.

1994-01-01

72

Polycrystalline diamond formation by post-growth ion bombardment of sputter-deposited amorphous carbon films  

Microsoft Academic Search

Post-growth Ar+ ion beam bombardment (IBB) of amorphous carbon (a-C) films on Si, with energies above 1 keV, induces several structural modifications in the films, including the formation of diamond, graphite and SiC grains. X-ray diffraction (in both conventional and grazing incidence geometry) and high resolution electron microscopy were used to study the structure of the as grown films and

P. Patsalas; S. Logothetidis; P. Douka; M. Gioti; G. Stergioudis; Ph. Komninou; G. Nouet; Th. Karakostas

1999-01-01

73

Surface Erosion of Metal Molybdenum Bombarded with Energetic Hydrogen or Helium Ions  

Microsoft Academic Search

A study has been made on the surface of polycrystalline molybdenum bombarded with H2+ or He+ at energies of 15-40 keV at dose rates of 0.6-2.1 mA\\/cm2 to doses below 38 C\\/cm2 at temperatures of 250-830°C. The results show that there is no qualitative difference between the erosion properties of H2+ and He+, but that the erosion yields of He+

Shuichi Okuda; Hideo Akimune

1979-01-01

74

Extraterrestrial Helium (He@C60) Trapped in Fullerenes in the Sudbury Impact Structure  

NASA Technical Reports Server (NTRS)

Fullerenes (C60 and C70) have recently been identified in a shock-produced breccia (Onaping Formation) associated with the 1.85-Ga Sudbury Impact Crater. The presence of parts-per-million levels of fullerenes in this impact structure raises interesting questions about the processes that led to the formation of fullerenes and the potential for delivery of intact organic material to the Earth by a large bolide (e.g., asteroid or comet). Two possible scenarios for the presence of fullerenes in the Sudbury impact deposits are that (1) fullerenes are synthesized within the impact plume from the C contained in the bolide; or (2) fullerenes are already present in the bolide and survived the impact event. The correlation of C and trapped noble gas atoms in meteorites is well established. Primitive meteorites contain several trapped noble gas components that have anomalous isotopic compositions, some of which may have a presolar origin. Several C-bearing phases, including SiC, graphite, and diamond, have been recognized as carriers of trapped noble gases. It has also been suggested that fullerenes (C60 and C70) might be a carrier of noble gas components in carbonaceous chondrites. Recently, fullerenes have been detected in separate samples in the Allende meteorite. Carbon-60 is large enough to enclose the noble gases He, Ne, Ar, Kr, and Xe, but it is too small to contain diatomic gases such as N2 or triatomic gases such as CO2. Recent experimental work has demonstrated that noble gases of a specific isotopic composition can be introduced into synthetic fullerenes at high temperatures and pressures; these encapsulated gases can then be released by the breaking of one or more C bonds during step-heating under vacuum. These thermal-release patterns for He encapsulated within the C60 molecule (He@C60) are similar to the patterns for acid residues of carbonaceous chondrites, suggesting that fullerenes could be an additional carrier of trapped noble gases in acid residues of meteorites. Analysis and Results: In order to characterize the noble gas compositions of the Sudbury fullerenes, we undertook a systematic study of acid-resistant residues throughout the C-rich layer (Black member) of the Onaping Formation. Samples were demineralized and extracted using standard techniques. The Onaping extracts were analyzed using several techniques, including UV-Vis adsorption, electro spray mass spectrometry, and laser desorption (linear and reflectron) time-of-flight (TOF) mass spectrometry (LDMS). The Sudbury fullerenes were then separated and purified using HPLC coupled with a photo diode array detector. The HPLC extracts containing the purified fullerenes were loaded into a metal tube furnace within a glove box under a N atmosphere in preparation for noble gas analyses. The 3-He and 4-He content of the fullerene extracts was measured using previously reported standard techniques . Discussion: Fullerenes (C60 and C70) in the Sudbury Impact Structure have been found to contain trapped He with a 3-He/4-He ratio greater than 5 x 10(exp -4). The 3-He/4-He ratio exceeds the accepted solar value by more than 30% and is more than 10x higher than the maximum reported mantle value. Terrestrial nuclear reactions or cosmic-my bombardment are not sufficient to generate such a high ratio. The 3-He/4-He ratios in the Sudbury fullerenes are similar to those determined for interplanetary dust particles. The greater-than-solar ratios of 3-He/4-He in the Sudbury fullerenes may indicate a presolar origin, although alternative mechanisms occurring in the ISM to explain these high ratios (e.g., spallation reactions, selective He implantation, etc.) cannot be entirely ruled out. We are currently attempting to isolate enough fullerene material to measure anomalous Ne (or Kr or Xe) contained within the C60 (e.g., the "pure" 22-Ne component) and thus determine whether the Sudbury fullerenes are indeed presolar in origin.

Becker, L.; Bada, J. L.; Poreda, R. J.; Bunch, T. E.

1997-01-01

75

Molecular ion emission from alkanethiol-SAMs by HCI bombardment  

NASA Astrophysics Data System (ADS)

In this work, we employ highly charged ions to study the sputtering of positive molecular fragments from two different alkanethiol self-assembled monolayers (SAMs) on gold surfaces: undecanethiol and dodecanethiol. The SAMs are bombarded with a pulsed Arq+ beam (3keV. The desorbed positive molecular ions were detected and analyzed from time-of-flight spectra, and thereby the masses and yields of secondary ions were obtained. The proton yields are dependent on the charge state of the incident ion. On the other hand, the positive molecular ion yields, such as CnHm+, are charge state independent. The positive molecular ion yields decay with the molecular size n.

Flores, Marcos; Esaulov, Vladimir; Yamazaki, Yasunori

2011-06-01

76

Blistering observed in Mylar due to H +-ion bombardment  

NASA Astrophysics Data System (ADS)

So far the blistering phenomenon due to ion implantation has been observed in metals and alloys, but no blistering has been reported in polymers like Mylar etc. A severe blistering in Mylar (polyethylene teraphthalate) has been observed by us, due to 250 keV H +-ion bombardment up to a dose level of 7×10 15 ions/cm 2, at ambient temperature. In metals and alloys the blistering is due to the pressure built up by the coalescence of the implanted gaseous species. However, in Mylar the cause is entirely different. In fact, it is attributed to the hydrogen gas released on account of the breakage of aliphatic C-H bonds of monomer, due to ion implantation. Very interesting features, like uniform unexfoliated circular blisters, circular rings (Karnavalayas) and black dots of different sizes along with their development sequence, have been observed. The observed features are explained on the basis of the aliphatic C?H bond breakage theory due to ion bombardment.

Shrinet, V.; Chaturvedi, U. K.; Agrawal, S. K.; Singh, Vakil; Nigam, A. K.

1983-05-01

77

Production of fullerenes with concentrated solar flux  

NASA Astrophysics Data System (ADS)

Research at the National Renewable Energy Laboratory (NREL) has demonstrated that fullerenes can be produced using highly concentrated sunlight from a solar furnace. Since they were first synthesized in 1989, fullerenes have been the subject of intense research. They show considerable commercial potential in advanced materials and have potential applications that include semiconductors, superconductors, high-performance metals, and medical technologies. The most common fullerene is C60, which is a molecule with a geometry resembling a soccer ball. Graphite vaporization methods such as pulsed-laser vaporization, resistive heating, and carbon arc have been used to produce fullerenes. None of these, however, seems capable of producing fullerenes economically on a large scale. The use of concentrated sunlight may help avoid the scale-up limitations inherent in more established production processes. Recently, researchers at NREL made fullerenes in NREL's 10 kW high flux solar furnace (HFSF) with a vacuum reaction chamber designed to deliver a solar flux of 1200 W/sq cm to a graphite pellet. Analysis of the resulting carbon soot by mass spectrometry and high pressure liquid chromatography confirmed the existence of fullerenes. This paper presents the method, experimental apparatus, and results of fullerene production research performed with the HFSF.

Hale, M. J.; Fields, C.; Lewandowski, A.; Bingham, C.; Pitts, R.

1994-01-01

78

Structural Reactivity of Polyhydroxylated Carbon Fullerenes  

Microsoft Academic Search

The design of fullerene-based nanomaterials has become a subject of intense investigation in the last years. Usually, these types of systems are carbon fullerene derivatives that have demonstrated to present potential applications for the development of novel technologies related to the fabrication of new electronic and optical devices. The fundamental problem in this study is strictly related to the solubility

Roberto Rivelino; Fernando de Brito Mota; Eudes E. Fileti

79

Fullerenes in Circumstellar and Interstellar Environments  

NASA Astrophysics Data System (ADS)

In recent years, the fullerene species C60 (and to a lesser extent also C70) has been reported in the mid-IR spectra of various astronomical objects. Cosmic fullerenes form in the circumstellar material of evolved stars, and survive in the interstellar medium (ISM). It is not entirely clear how they form or what their excitation mechanism is.

Cami, Jan

2015-03-01

80

Fullerenic structures and such structures tethered to carbon materials  

DOEpatents

The fullerenic structures include fullerenes having molecular weights less than that of C60 with the exception of C36 and fullerenes having molecular weights greater than C60. Examples include fullerenes C50, C58, C130, and C176. Fullerenic structure chemically bonded to a carbon surface is also disclosed along with a method for tethering fullerenes to a carbon material. The method includes adding functionalized fullerene to a liquid suspension containing carbon material, drying the suspension to produce a powder, and heat treating the powder.

Goel, Anish; Howard, Jack B.; Vander Sande, John B.

2012-10-09

81

Fullerenic structures and such structures tethered to carbon materials  

DOEpatents

The fullerenic structures include fullerenes having molecular weights less than that of C60 with the exception of C36 and fullerenes having molecular weights greater than C60. Examples include fullerenes C50, C58, C130, and C176. Fullerenic structure chemically bonded to a carbon surface is also disclosed along with a method for tethering fullerenes to a carbon material. The method includes adding functionalized fullerene to a liquid suspension containing carbon material, drying the suspension to produce a powder, and heat treating the powder.

Goel, Anish; Howard, Jack B.; Vander Sande, John B.

2010-01-05

82

Production of Endohedral Fullerenes by Ion Implantation  

SciTech Connect

The empty interior cavity of fullerenes has long been touted for containment of radionuclides during in vivo transport, during radioimmunotherapy (RIT) and radioimaging for example. As the chemistry required to open a hole in fullerene is complex and exceedingly unlikely to occur in vivo, and conformational stability of the fullerene cage is absolute, atoms trapped within fullerenes can only be released during extremely energetic events. Encapsulating radionuclides in fullerenes could therefore potentially eliminate undesired toxicity resulting from leakage and catabolism of radionuclides administered with other techniques. At the start of this project however, methods for production of transition metal and p-electron metal endohedral fullerenes were completely unknown, and only one method for production of endohedral radiofullerenes was known. They therefore investigated three different methods for the production of therapeutically useful endohedral metallofullerenes: (1) implantation of ions using the high intensity ion beam at the Oak Ridge National Laboratory (ORNL) Surface Modification and Characterization Research Center (SMAC) and fullerenes as the target; (2) implantation of ions using the recoil energy following alpha decay; and (3) implantation of ions using the recoil energy following neutron capture, using ORNL's High Flux Isotope Reactor (HFIR) as a thermal neutron source. While they were unable to obtain evidence of successful implantation using the ion beam at SMAC, recoil following alpha decay and neutron capture were both found to be economically viable methods for the production of therapeutically useful radiofullerenes. In this report, the procedures for preparing fullerenes containing the isotopes {sup 212}Pb, {sup 212}Bi, {sup 213}Bi, and {sup 177}Lu are described. None of these endohedral fullerenes had ever previously been prepared, and all of these radioisotopes are actively under investigation for RIT. Additionally, the chemistry for derivatizing the radiofullerenes for water-solubility and a method for removing exohedral radionuclides are reported. The methods and chemistry developed during this CRADA are the crucial first steps for the development of fullerenes as a method superior to existing technologies for in vivo transport of radionuclides.

Diener, M.D.; Alford, J. M.; Mirzadeh, S.

2007-05-31

83

Inhibition of Inflammatory Arthritis Using Fullerene Nanomaterials  

PubMed Central

Inflammatory arthritis (e.g. rheumatoid arthritis; RA) is a complex disease driven by the interplay of multiple cellular lineages. Fullerene derivatives have previously been shown to have anti-inflammatory capabilities mediated, in part, by their ability to prevent inflammatory mediator release by mast cells (MC). Recognizing that MC can serve as a cellular link between autoantibodies, soluble mediators, and other effector populations in inflammatory arthritis, it was hypothesized that fullerene derivatives might be used to target this inflammatory disease. A panel of fullerene derivatives was tested for their ability to affect the function of human skin-derived MC as well as other lineages implicated in arthritis, synovial fibroblasts and osteoclasts. It is shown that certain fullerene derivatives blocked Fc?R- and TNF-?-induced mediator release from MC; TNF-?-induced mediator release from RA synovial fibroblasts; and maturation of human osteoclasts. MC inhibition by fullerene derivatives was mediated through the reduction of mitochondrial membrane potential and Fc?R-mediated increases in cellular reactive oxygen species and NF-?B activation. Based on these in vitro data, two fullerene derivatives (ALM and TGA) were selected for in vivo studies using K/BxN serum transfer arthritis in C57BL/6 mice and collagen-induced arthritis (CIA) in DBA/1 mice. Dye-conjugated fullerenes confirmed localization to affected joints in arthritic animals but not in healthy controls. In the K/BxN moldel, fullerenes attenuated arthritis, an effect accompanied by reduced histologic inflammation, cartilage/bone erosion, and serum levels of TNF-?. Fullerenes remained capable of attenuating K/BxN arthritis in mast cell-deficient mice Cre-Master mice, suggesting that lineages beyond the MC represent relevant targets in this system. These studies suggest that fullerene derivatives may hold promise both as an assessment tool and as anti-inflammatory therapy of arthritis. PMID:25879437

Dellinger, Anthony L.; Cunin, Pierre; Lee, David; Kung, Andrew L.; Brooks, D. Bradford; Zhou, Zhiguo; Nigrovic, Peter A.; Kepley, Christopher L.

2015-01-01

84

Plasma ion source for in situ ion bombardment in a soft x-ray magnetic scattering diffractometer  

SciTech Connect

A new plasma ion source for in situ keV He ion bombardment of solid state samples or thin films was designed and built for ion fluences between 1 x 10{sup 12} and 1 x 10{sup 17} ions/cm{sup 2}. The system was designed to be mounted to different diffraction chambers for soft x-ray resonant magnetic scattering. Without breaking the vacuum due to He-ion bombardment, structural and magnetic modifications of the samples can be studied in situ and element specifically.

Lengemann, Daniel; Engel, Dieter; Ehresmann, Arno [Institute of Physics, EP IV, University of Kassel, Heinrich-Plett-Str.40, 34132 Kassel (Germany) and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str.40, 34132 Kassel (Germany)

2012-05-15

85

Degradation of ZnS phosphors during electron beam bombardment  

NASA Astrophysics Data System (ADS)

Samples of ZnS:Mn thin films and single crystals have been subject to electron bombardment (0.6 to 4 KeV) over a range of pressures from 1 × 10sp{-6} to 5 × 10sp{-8} Torr. Various gases including hydrogen, oxygen, and water vapor were introduced into the ambient during bombardment to assess their effects on the phosphor surface. Auger Electron Spectroscopy data indicate that electron bombardment in the presence of Osb2 and Hsb2O caused depletion of sulfur and accumulation of oxygen on the surface. Hydrogen also caused depletion of sulfur. Removal of sulfur was shown to be consistent with electron beam dissociation of molecular species to atomic hydrogen and/or oxygen, followed by a surface reaction to form high vapor pressure sulfur compounds (e.g., SOsbx and Hsb2S). A model for this electron stimulated surface reaction (ESSR) has been proposed that correlates well with the ZnS data. Concurrent increases in the oxygen and zinc APPH during bombardment in oxygen and water vapor and postdegradation analysis with X-Ray Photoelectron Spectroscopy show the conversion of the surface of ZnS to ZnO. These changes in surface chemistry, specifically the removal of sulfur and growth of the surface oxide, are also correlated to a reduction in cathodoluminescent (CL) brightness from the samples. There are three components of the degraded phosphor that could account for this loss of CL brightness: the oxide layer, the activator ion, and the host lattice. Optical absorption of light, attenuation of the primary electron beam by the oxide layer and changes in activator ion efficiency were investigated, and these factors could account for at most 13% of the brightness loss. These results indicate the majority of the brightness loss must be caused by the host lattice, ZnS. Both the degraded and reference areas of single crystal ZnS were analyzed by Secondary Ion Mass Spectrometry, which showed significantly more oxygen in the first 51 nanometers (nm) of the degraded sample as compared to the reference. Additional thermoluminescent experiments are consistent with oxygen substitution for sulfur in the lattice to form isoelectronic electron traps. The data suggest that these non-radiative traps reduce the excitation rate of the Mnsp{+2} ions, which causes reduced CL brightness.

Sebastian, Joseph Samuel

86

Giant Fullerenes for Target Specific Drug Delivery  

NASA Astrophysics Data System (ADS)

Carbon nano-structures, such as giant fullerenes, have a great potential for biological and medical applications. Most of the previous research is dedicated to investigate the use of fullerenes as vehicles for carrying medication which is chemisorbed on the outside surface of the fullerenes. In contrast, using fullerenes as an enclosure was largely abandoned due to the high strength of the carbon-carbon bonds which has been perceived to prevent the rupturing of the fullerene to release their cargo. We performed atomistic computations based on classical force fields that will address this perception. Specifically we explore the physics and chemistry of OH functionalized carbon based giant fullerenes with diameters from 0.72 nm (60 atoms) to 5.7 nm (3840 atoms). The preliminary results show that OH functionalization on these fullerenes is not only viable but also provides a pH sensitive release mechanism. Furthermore our current results show that carbon-carbon bonds can be broken in low energy biological environments in the presence of a flow induced strain field. These insights may have implications for target specific drug delivery in general and cancer treatment in particular.

Courtney, Robert; Kiefer, Boris

2013-03-01

87

Fusion mechanism in fullerene-fullerene collisions -- The deciding role of giant oblate-prolate motion  

E-print Network

We provide answers to long-lasting questions in the puzzling behavior of fullerene-fullerene fusion: Why are the fusion barriers so exceptionally high and the fusion cross sections so extremely small? An ab initio nonadiabatic quantum molecular dynamics (NA-QMD) analysis of C$_{60}$+C$_{60}$ collisions reveals that the dominant excitation of an exceptionally "giant" oblate-prolate H$_g(1)$ mode plays the key role in answering both questions. From these microscopic calculations, a macroscopic collision model is derived, which reproduces the NA-QMD results. Moreover, it predicts analytically fusion barriers for different fullerene-fullerene combinations in excellent agreement with experiments.

Jan Handt; Ruediger Schmidt

2015-03-09

88

Fusion mechanism in fullerene-fullerene collisions -- The deciding role of giant oblate-prolate motion  

E-print Network

We provide answers to long-lasting questions in the puzzling behavior of fullerene-fullerene fusion: Why are the fusion barriers so exceptionally high and the fusion cross sections so extremely small? An ab initio nonadiabatic quantum molecular dynamics (NA-QMD) analysis of C$_{60}$+C$_{60}$ collisions reveals that the dominant excitation of an exceptionally "giant" oblate-prolate H$_g(1)$ mode plays the key role in answering both questions. From these microscopic calculations, a macroscopic collision model is derived, which reproduces the NA-QMD results. Moreover, it predicts analytically fusion barriers for different fullerene-fullerene combinations in excellent agreement with experiments.

Handt, Jan

2015-01-01

89

Clusters of fullerene molecules and metal atoms  

NASA Astrophysics Data System (ADS)

Intensity anomalies in the mass spectra of (C60)n, (C60)Mx and (C60)nMx clusters can be used to identify particularly stable fullerene and fulleride units. Small, n < 147, fullerene clusters appear to have icosahedral symmetry. Multiple layers of alkaline earth metals can be deposited on single C60 molecules. The first four layers of metal are well described in terms of a periodically reoccurring icosahedral motif. The stability of alkali metal coated C60, on the other hand, is better described by the completion of shells of electrons rather than shells of atoms. Finally, data are presented for shrink-wrapping fullerenes around alkali halide molecules.

Martin, T. P.; Zimmermann, U.; Malinowski, N.; Heinebrodt, M.; Frank, S.; Tast, F.

1996-01-01

90

Growth of fullerene on Ag and hydrogen-passivated Si substrates: Effect of electron beam exposure on growth modes  

Microsoft Academic Search

We have used Auger electron spectroscopy (AES) to investigate the effect of electron beam exposure on growth modes of fullerene (C60) on substrates like Ag and hydrogen-passivated Si(111). The electron beam comprises of 3.4keV electrons, which are used in the AES study. To investigate the effect, Auger signal (AS) vs. deposition time (t) measurements were conducted in a sequential mode,

M. V. Rundhe; B. N. Dev

2008-01-01

91

Effect of alloying on ion-bombardment-induced surface topography on face-centred cubic metals  

NASA Astrophysics Data System (ADS)

Previous studies of sputter-induced topographical development have shown that it is possible to form pyramids on single-crystal fcc metals oriented in the <1131> crystallographic direction. These pyramids form when the surface is bombarded with relatively large (> 1 × 10 19cm -2) doses of Ar +, Kr + or Xe + ions in the energy range 20-41 keV. Until recently most of the work was con to pure fee metals (Cu, Pd, Ir, Ag, Au), all of which exhibit similar pyramid formation on bombardment. Later studies involving <1131> Cu, however, showed that, although pyramids form with inert-gas ion (e.g. Ar + on Cu) or self-ion (Cu + on Cu) bombardment, they are not produced when either Br +, Fe + or Ni + ions are used. This observation led to further investigations of alloying effects on topographic evolvement during sputtering. We report here a study of the influence of alloying on pyramid formation on <1131> single crystals, through comparison of that of Ni and Cu with that of Ni-8%Cu. We find that bombardment with Ar + ions can produce pyramids on Ni-8%Cu but that the conditions necessary are different from those for pure metals. We have looked for sputter-induced segregation effects in the alloy but none have been observed.

Clapham, L.; Whitton, J. L.; Mashayekhi, A.; Carter, G.; Katardjiev, I.; Nobes, M. J.

1990-03-01

92

Applications of Functionalized Fullerenes in Tumor Theranostics  

PubMed Central

Functionalized fullerenes with specific physicochemical properties have been developed for cancer diagnosis and therapy. Notably, metallofullerene is a new class of magnetic resonance imaging (MRI) contrast-enhancing agent, and may have promising applications for clinical diagnosis. Polyhydroxylated and carboxyl fullerenes have been applied to photoacoustic imaging. Moreover, in recent years, functionalized fullerenes have shown potential in tumor therapies, such as photodynamic therapy, photothermal treatment, radiotherapy and chemotherapeutics. Their antitumor effects may be associated with the modulation of oxidative stress, anti-angiogenesis, and immunostimulatory activity. While various types of novel nanoparticle agents have been exploited in tumor theranostics, their distribution, metabolism and toxicity in organisms have also been a source of concern among researchers. The present review summarizes the potential of fullerenes as tumor theranostics agents and their possible underlying mechanisms are discussed. PMID:22509193

Chen, Zhiyun; Ma, Lijing; Liu, Ying; Chen, Chunying

2012-01-01

93

Recent advances in fullerene science (Invited)  

NASA Astrophysics Data System (ADS)

The development of very high resolution FT-ICR mass spectrometers (Marshall et al, 1998) has made a wide range of new measurements possible and by combining this new technology with laser vaporization supersonic beam methods of producing carbon species (chains, rings and fullerenes), new advances in understanding of the fullerene creation mechanisms and their reactivity have been possible. In this overview, new understanding has been developed with regard to: a) closed-network growth of fullerenes (Dunk et al, 2012a); b) small endohedral species such as M ? C28 (Dunk et al., 2012b); c) metallofullerene and fullerene formation under conditions in stellar outflows with relevance to stardust (Dunk et al., 2013a) and d) The formation of heterofullerenes by direct exposure of C60 toboron vapor (Dunk et al., 2013b).

Dunk, P. W.; Mulet-Gas, M.; Rodriguez-Fortea, A.; Poblet, J. M.; Marshall, A. G.; Kroto, H. W.

2014-12-01

94

Fullerenes in electron cyclotron resonance ion sources  

SciTech Connect

Fullerene plasmas and beams have been produced in our electron cyclotron resonance ion sources (ECRIS) originally designed for other purposes. The ATOMKI-ECRIS is a traditional ion source with solenoid mirror coils to generate highly charged ions. The variable frequencies NIRS-KEI-1 and NIRS-KEI-2 are ECR ion sources built from permanent magnets and specialized for the production of carbon beams. The paper summarizes the experiments and results obtained by these facilities with fullerenes. Continuous effort has been made to get the highest C{sub 60} beam intensities. Surprisingly, the best result was obtained by moving the C{sub 60} oven deep inside the plasma chamber, very close to the resonance zone. Record intensity singly and doubly charged fullerene beams were obtained (600 and 1600 nA, respectively) at lower C{sub 60} material consumption. Fullerene derivatives were also produced. We mixed fullerenes with other plasmas (N, Fe) with the aim of making new materials. Nitrogen encapsulated fullerenes (mass: 720+14=734) were successfully produced. In the case of iron, two methods (ferrocene, oven) were tested. Molecules with mass of 720+56=776 were detected in the extracted beam spectra.

Biri, S.; Fekete, E.; Kitagawa, A.; Muramatsu, M.; Janossy, A.; Palinkas, J. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/C (Hungary); National Institute for Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Department of Experimental Physics, Technical University of Budapest, H-1521 Budapest, P.O. Box 91 (Hungary); Department of Experimental Physics, University of Debrecen, H-4026 Debrecen, Bem ter 18/A (Hungary)

2006-03-15

95

Vesta, Ceres and the Jovian Early Bombardment  

NASA Astrophysics Data System (ADS)

Vesta and Ceres are among the oldest objects that formed in the Solar System, likely predating the formation of the giant planets. Through their histories, the surfaces of the two targets of the Dawn mission would have suffered several periods of intense bombardment which shaped their present morphologies. Here we report the results of our investigation of the collisional histories of Vesta and Ceres at the time of the formation of Jupiter. The formation of the giant planet caused in fact an intense early bombardment in the asteroid belt. In those scenarios where they survived, both asteroids had their surfaces saturated by craters as big as 150 km and a few as big as 200 - 300 km. In the case of Vesta, such Jovian early bombardment would have significantly eroded the crust, likely exposing the upper mantle or causing effusive phenomena similar to lunar maria.

Turrini, D.; Coradini, A.; Magni, G.

2011-10-01

96

Symmetric nested complexes of fullerenes.  

PubMed

Large fullerenes such as C180 and C116 can be used as hosts for other molecules of the same family. Based on this idea, two complexes were designed, one in which C180 accepts a C60 molecule as a guest and the other in which C20 was placed inside C116. The behavior of these new assemblies was closer to that of a large endohedral complex rather than onion-like. There were marked differences between the systems. In the first system, there was minor interaction between the two cages but the association resulted in a more stable thermodynamic state. In the second system, there was strong electronic interchange between the cages, and the thermodynamic results suggest that such a combination might be useful for forming stable C20. PMID:25823391

Mar, Naveicy; Sansores, Luis Enrique; Muhl, Stephen; Ramos, Estrella; Salcedo, Roberto

2015-04-01

97

Program fullerene: a software package for constructing and analyzing structures of regular fullerenes.  

PubMed

Fullerene (Version 4.4) is a general purpose open-source program that can generate any fullerene isomer, perform topological and graph theoretical analysis, as well as calculate a number of physical and chemical properties. The program creates symmetric planar drawings of the fullerene graph and generates accurate molecular 3D geometries by way of force-field optimization, serving as a good starting point for further quantum theoretical treatments. It includes a number of fullerene-to-fullerene transformations, such as Goldberg-Coxeter transforms, Stone-Wales transforms, Endo-Kroto, Yoshida-Fowler, and Brinkmann-Fowler vertex insertions. The program is written in standard Fortran and C++ and can easily be installed in a Linux or UNIX environment. PMID:23559399

Schwerdtfeger, Peter; Wirz, Lukas; Avery, James

2013-06-30

98

Mn4-hinged bithiacalix[4]arenes accommodating fullerenes.  

PubMed

The calixarene-Mn(4)-calixarene dumbbell-like unit can accommodate different fullerenes with its changeable curved surfaces and the addition of fullerenes completely remodels the packing of the dumbbell units. PMID:21283855

Bi, Yanfeng; Liao, Wuping; Wang, Xiaofei; Wang, Xinwu; Zhang, Hongjie

2011-03-01

99

Fullerene derivatives as electron donor for organic photovoltaic cells  

NASA Astrophysics Data System (ADS)

We demonstrated the performance of unconventional, all-fullerene-based, planar heterojunction (PHJ) organic photovoltaic (OPV) cells using fullerene derivatives indene-C60 bisadduct (ICBA) and phenyl C61-butyric acid methyl ester as the electron donors with fullerene C70 as the electron acceptor. Two different charge generation processes, including charge generation in the fullerene bulk and exciton dissociation at the donor-acceptor interface, have been found to exist in such all-fullerene-based PHJ cells and the contribution to the total photocurrent from each process is strongly dependent on the thickness of fullerene donor. The optimized 5 nm ICBA/40 nm C70 PHJ cell gives clear external quantum efficiency responses for the long-wavelength photons corresponding to the dissociation of strongly bound Frenkel excitons, which is hardly observed in fullerene-based single layer reference devices. This approach using fullerene as a donor material provides further possibilities for developing high performance OPV cells.

Zhuang, Taojun; Wang, Xiao-Feng; Sano, Takeshi; Hong, Ziruo; Yang, Yang; Kido, Junji

2013-11-01

100

Ion bombardment and disorder in amorphous silicon  

SciTech Connect

The effect of ion bombardment during growth on the structural and optical properties of amorphous silicon are presented. Two series of films were deposited under electrically grounded and positively biased substrate conditions. The biased samples displayed lower growth rates and increased hydrogen content relative to grounded counterparts. The film structure was examined using Raman spectroscopy. The transverse optic like phonon band position was used as a parameter to characterize network order. Biased samples displayed an increased order of the amorphous network relative to grounded samples. Furthermore, biased samples exhibited a larger optical gap. These results are correlated and attributed to reduced ion bombardment effects.

Sidhu, L.S.; Gaspari, F.; Zukotynski, S.

1997-07-01

101

An electron acceptor challenging fullerenes for efficient polymer solar cells.  

PubMed

A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized. Fullerene-free polymer solar cells (PSCs) based on the ITIC acceptor are demonstrated to exhibit power conversion efficiencies of up to 6.8%, a record for fullerene-free PSCs. PMID:25580826

Lin, Yuze; Wang, Jiayu; Zhang, Zhi-Guo; Bai, Huitao; Li, Yongfang; Zhu, Daoben; Zhan, Xiaowei

2015-02-01

102

Novel multicomponent reaction of [60]fullerene: the first example of 1,4-dipolar cycloaddition reaction in fullerene chemistry.  

PubMed

The novel multicomponent reaction of [60]fullerene with dimethyl acetylenedicarboxylate and isoquinoline, quinoline or substituted quinolines was investigated. This type of reaction presents the first example of a 1,4-dipolar cycloaddition reaction in fullerene chemistry. PMID:17312957

Wang, Guan-Wu; Li, Jia-Xing

2006-11-21

103

Evaluation of the Aquatic Ecotoxicology of Fullerenes and Nanotubes  

E-print Network

Evaluation of the Aquatic Ecotoxicology of Fullerenes and Nanotubes of fullerenes and carbon nanotubes on aquatic organisms. The number of papers published on this topic is not very high and there are differences in the scientific quality. Fullerenes and carbon nanotubes appear

Fischlin, Andreas

104

Fullerene concentration dependent bimolecular recombination in organic photovoltaic films  

NASA Astrophysics Data System (ADS)

Organic photovoltaic devices made of a solution processed small molecule and a fullerene show a decrease in short circuit current with decreasing fullerene amounts. Transient absorption experiments show that the rate of bimolecular recombination increases as the system is deprived of fullerene. A simple expression for the bimolecular recombination coefficient derived by accounting for intrinsic carrier generation reproduces the observed behavior.

Kaake, Loren G.; Sun, Yanming; Bazan, Guillermo C.; Heeger, Alan J.

2013-04-01

105

Constructing I[subscript h] Symmetrical Fullerenes from Pentagons  

ERIC Educational Resources Information Center

Twelve pentagons are sufficient and necessary to form a fullerene cage. According to this structural feature of fullerenes, we propose a simple and efficient method for the construction of I[subscript h] symmetrical fullerenes from pentagons. This method does not require complicated mathematical knowledge; yet it provides an excellent paradigm for…

Gan, Li-Hua

2008-01-01

106

Sorghum genetic transformation by particle bombardment.  

PubMed

Particle bombardment transformation describes the acceleration of high-velocity microparticles coated with exotic genes through the plant-protective cell walls, in order for the introduced genes to be integrated into the host genome. This technique has proven to be an effective and versatile approach towards plant genetic modification in preceding decades. Particle bombardment has been successfully applied to cereals including rice, maize, wheat, barley, and sorghum. Historically, sorghum has been considered as one of the most recalcitrant major crops with regard to successful genetic transformation; however, tremendous progress has been made in recent years. Transformation efficiency by particle bombardment has now improved from approximately 1 % to in excess of 20 % utilizing an optimized tissue culture and DNA delivery system. The protocol described in this chapter routinely generates transformants at 10-25 % efficiency within sorghum genotype Tx430. The process generally takes 11-16 weeks from initiation of immature embryos to planting of transformants. This protocol covers the operation of both the Bio-Rad PDS-1000/He System and particle inflow gun. Three factors are crucial to an efficient particle bombardment transformation system: (1) an efficient tissue culture system, (2) a highly efficient DNA delivery system, and (3) an effective selection strategy. PMID:24243207

Liu, Guoquan; Campbell, Bradley C; Godwin, Ian D

2014-01-01

107

Liposomal Formulation of Amphiphilic Fullerene Antioxidants  

PubMed Central

Novel amphiphilic fullerene[70] derivatives that are rationally designed to intercalate in lipid bilayers are reported, as well as its vesicular formulation with surprisingly high loading capacity up to 65% by weight. The amphiphilic C70 bisadduct forms uniform and dimensionally stable liposomes with auxiliary natural phospholipids as demonstrated by buoyant density test, particle size distribution and 31P NMR. The antioxidant property of fullerenes is retained in the bipolarly functionalized C70 derivative, Amphiphilic Liposomal Malonylfullerene[70] (ALM) as well as in its liposomal formulations, as shown by both electron paramagnetic resonance (EPR) studies and in vitro reactive oxygen species (ROS) inhibition experiments. The liposomally formulated ALM efficiently quenched hydroxyl radicals and superoxide radicals. In addition, the fullerene liposome inhibited radical-induced lipid peroxidation and maintained the integrity of the lipid bilayer structure. This new class of liposomally formulated, amphipathic fullerene compounds represents a novel drug delivery system for fullerenes and provides a promising pathway to treat oxidative stress-related diseases. PMID:20839887

Zhou, Zhiguo; Lenk, Robert P.; Dellinger, Anthony; Wilson, Stephen R.; Sadler, Robert; Kepley, Christopher L.

2010-01-01

108

Supramolecular [60]fullerene chemistry on surfaces.  

PubMed

This critical review documents the exceptional range of research avenues in [60]fullerene-based monolayers showing unique and spectacular physicochemical properties which prompted such materials to have potential applications in several directions, ranging from sensors and photovoltaic cells to nanostructured devices for advanced electronic applications, that have been pursued during the past decade. It illustrates how progress in covalent [60]fullerene functionalisation led to the development of spectacular surface-immobilised architectures, including dyads and triads for photoinduced electron and energy transfer, self-assembled on a wide variety of surfaces. All of these molecular assemblies and supramolecular arrays feature distinct properties as a consequence of the presence of different molecular units and their spatial arrangement. Since the properties of [60]fullerene-containing films are profoundly controlled by the deposition conditions, substrate of adsorption, and influenced by impurities or disordered surface structures, the progress of such new [60]fullerene-based materials strongly relies on the development of new versatile and broad preparative methodologies. Therefore, the systematic exploration of the most common approaches to prepare and characterise [60]fullerene-containing monolayers embedded into two- or three-dimensional networks will be reviewed in great detail together with their main limitations. Recent investigations hinting at potential technological applications addressing many important fundamental issues, such as a better understanding of interfacial electron transfer, ion transport in thin films, photovoltaic devices and the dynamics associated with monolayer self-assembly, are also highlighted. PMID:17264939

Bonifazi, Davide; Enger, Olivier; Diederich, François

2007-02-01

109

Friction and wear of ion-implanted diamondlike carbon and fullerene films for thin-film rigid disks  

NASA Astrophysics Data System (ADS)

In this paper, DLC coatings on a rigid magnetic disk were ion implanted with nitrogen and carbon ions to improve their wear lives. Nitrogen and carbon ion implantation with a dose of 5×1015 ions cm-2 at 200 keV have shown significant improvements in the coefficient of friction and sliding wear life which suggests that ion-implanted DLCs may be more desirable overcoats. Microstructural examinations of implanted films show that these films are still amorphous with no long range order. Implanted DLC films also may be attractive as an overcoat for the slider surface. An approximately 20-nm-thick fullerene film, a new solid lubricant, was also deposited on the disk surface to reduce its friction and wear. Fullerene films exhibited lower friction, however, these readily formed a transfer film on the mating slider surface. Since any transfer and movement of the material at the head-disk interface is undesirable, fullerene films are not expected to be potential overcoats. Coefficient of friction of implanted DLC and fullerene films on a microscale was also measured and was found to be lower than that on macroscale. Microfriction values of unimplanted and implanted DLC films were comparable.

Bhushan, Bharat; Gupta, B. K.

1994-05-01

110

Production and study of metal-fullerene films  

NASA Astrophysics Data System (ADS)

The present paper describes the metal-fullerene films production by thermal evaporation and condensation under vacuum. The necessary fullerene concentration in the film has been provided by maintaining a special relation between the rates of fullerene and metal atoms fed. The preformed research of structure of fullerene containing materials show that addition of C60 molecules to the metal coatings essentially reduces the structural elements sizes to nanometrical ones that can be used in production of nanostructural materials having unique properties. The obtained result on investigation of their physical and physico-chemical properties suggest broad potentials for application of metal-fullerene films.

Schur, Dmitry V.; Shpilevsky, Eduard M.; Baklanov, Mykola M.; Lobodyuk, Oleksander O.

2002-06-01

111

Production of fullerenes using concentrated solar flux  

DOEpatents

A method of producing soot containing high amounts of fullerenes comprising: providing a primary concentrator capable of impingement of a concentrated beam of sunlight onto a carbon source to cause vaporization of carbon and subsequent formation of fullerenes, or providing a solar furnace having a primary concentrator with a focal point that concentrates a solar beam of sunlight; providing a reflective secondary concentrator having an entrance aperture and an exit aperture at the focal point of the solar furnace; providing a carbon source at the exit aperture of the secondary concentrator; supplying an inert gas over the carbon source to keep the secondary concentrator free from vaporized carbon; and impinging a concentrated beam of sunlight from the secondary concentrator on the carbon source to vaporize the carbon source into a soot containing high amounts of fullerenes.

Fields, Clark L. (Greeley, CO); Pitts, John Roland (Lakewood, CO); King, David E. (Lakewood, CO); Hale, Mary Jane (Golden, CO); Bingham, Carl E. (Denver, CO); Lewandowski, Allan A. (Evergreen, CO)

2000-01-01

112

Fullerenes and dihydrofullerenes as photodynamic sensitizers  

SciTech Connect

Fullerenes C{sub 60} and C{sub 70} are excellent photosensitizers for the production of singlet oxygen. Their properties are particularly favorable since they are unusually photostable and neither quench nor react with singlet oxygen significantly themselves; in addition, they are only extremely weakly fluorescent, which makes them particularly useful for photophysical studies. The dihydrofullerenes, which have two sp{sup 3} carbons and various functionalities attached to the fullerene molecule, have much improved solubilities in polar media and photophysical properties (triplet energy and yield, singlet oxygen yield, oxidizing properties) that are quite similar to those of the fullerenes in many cases. A number of examples will be presented and some novel synthetic reactions described.

Anderson, J.A.; Poon, T.H.W.; Zhang, X. [Univ. of California, Los Angeles, CA (United States)] [and others

1995-12-01

113

Endohedral and exohedral hybrids involving fullerenes and carbon nanotubes.  

PubMed

Since fullerenes and carbon nanotubes (CNTs) were discovered, these materials have attracted a great deal of attention in the scientific community due to their unique structures and properties. The properties of both carbon allotropes can be modulated by chemical functionalization, and merging fullerenes and CNTs combines the electronic and optical properties of CNTs with the excellent electron acceptor characteristic of fullerenes; moreover, a synergistic effect of these hybrids can be found, as the properties of both the nanotube and the fullerene are affected by the presence of the other. In these hybrids, the fullerene can be located inside (endohedral) or outside (exohedral) the CNT and both types of hybrid have specific features. CNT-fullerene hybrids have been studied for various applications, including photovoltaics, optical limiting and flame retardancy amongst others. This review outlines the progress in research on CNT-fullerene hybrids, including endohedral and exohedral combinations, their properties, functionalization, applications and outlook. PMID:22706450

Vizuete, María; Barrejón, Myriam; Gómez-Escalonilla, María José; Langa, Fernando

2012-08-01

114

Endohedral and exohedral hybrids involving fullerenes and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Since fullerenes and carbon nanotubes (CNTs) were discovered, these materials have attracted a great deal of attention in the scientific community due to their unique structures and properties. The properties of both carbon allotropes can be modulated by chemical functionalization, and merging fullerenes and CNTs combines the electronic and optical properties of CNTs with the excellent electron acceptor characteristic of fullerenes; moreover, a synergistic effect of these hybrids can be found, as the properties of both the nanotube and the fullerene are affected by the presence of the other. In these hybrids, the fullerene can be located inside (endohedral) or outside (exohedral) the CNT and both types of hybrid have specific features. CNT-fullerene hybrids have been studied for various applications, including photovoltaics, optical limiting and flame retardancy amongst others. This review outlines the progress in research on CNT-fullerene hybrids, including endohedral and exohedral combinations, their properties, functionalization, applications and outlook.

Vizuete, María; Barrejón, Myriam; Gómez-Escalonilla, María José; Langa, Fernando

2012-07-01

115

Laser controlled magnetism in hydrogenated fullerene films  

SciTech Connect

Room temperature ferromagnetic-like behavior in fullerene photopolymerized films treated with monatomic hydrogen is reported. The hydrogen treatment controllably varies the paramagnetic spin concentration and laser induced polymerization transforms the paramagnetic phase to a ferromagnetic-like one. Excess laser irradiation destroys magnetic ordering, presumably due to structural changes, which was continuously monitored by Raman spectroscopy. We suggest an interpretation of the data based on first-principles density-functional spin-unrestricted calculations which show that the excess spin from mono-atomic hydrogen is delocalized within the host fullerene and the laser-induced polymerization promotes spin exchange interaction and spin alignment in the polymerized phase.

Makarova, Tatiana L.; Shelankov, Andrei L. [Umeaa University, 90187 Umeaa (Sweden); Ioffe Physicotechnical Inst., 194021, St. Petersburg (Russian Federation); Kvyatkovskii, Oleg E. [Ioffe Physicotechnical Inst., 194021, St. Petersburg (Russian Federation); Zakharova, Irina B. [St. Petersburg State Polytechnical University, 195251, St. Petersburg (Russian Federation); Buga, Sergei G.; Volkov, Aleksandr P. [Technological Institute for Superhard and Novel Carbon Materials, 142190, Troitsk (Russian Federation)

2011-04-15

116

Diamond electrodes modified by argon ion bombardment  

NASA Astrophysics Data System (ADS)

The electrochemical properties of boron-doped chemical vapour deposited diamond films following argon ion bombardment are investigated. The argon ion treatments used produce defects at the electrode surface, but are below the amorphisation threshold for this material, and indeed can be readily reversed by sample annealing. Photoemission studies indicate downwards band-bending of about 0.8 eV as a result of the argon ion treatment, and the photoemission spectra and associated energy loss spectra are used to examine the changes occurring. The higher argon ion exposures to the surface are found to very significantly degrade the electrochemical characteristics of diamond. However for smaller ion doses, the electrochemical properties of some redox couples are not influenced by the argon ion treatments used, whereas others are strongly inhibited. The work therefore demonstrates that argon ion bombardment can be used to selectively modify the properties of diamond electrodes.

Foord, John S.; Goeting, Christiaan H.

2004-09-01

117

Molecular dynamics simulations of void and helium bubble stability in amorphous silicon during heavy-ion bombardment  

SciTech Connect

A study of void and helium (He) bubble stability in amorphous silicon (a-Si) subjected to heavy-ion bombardment was conducted with molecular dynamics simulations. The effects of incident ion energy, incident ion direction, and He pressure were investigated. He bubbles with pressures equal to or greater than 0.1 kbar were found to be stable during isotropic 2 keV xenon (Xe) irradiation. Bubbles with pressures below this limit collapsed completely. On the other hand, voids and bubbles of all pressures were stable following unidirectional 2 keV Xe bombardment. In this case, the voids and bubbles became elongated and resisted closure, a phenomenon attributed to the inability of liquid Si to wet the flat, low-curvature internal surfaces of the open-volume defect. The void closure rates varied from 55 to 180 A/dpa as the Xe projectile energy increased from 0.2 keV to 2 keV, respectively. An analytical model based on a viscous flow mechanism is presented to describe the behavior associated with the slowest closure rate. The faster rates are attributed to pressure-induced convective flow into the void.

Okuniewski, Maria A.; Ashkenazy, Yinon; Heuser, Brent J.; Averback, Robert S. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Racah Institute of Physics, Hebrew University of Jerusalem, 91904 Jerusalem, Israel and Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801 (United States)

2004-10-15

118

Cathode Ion Bombardment in RF Photoguns  

SciTech Connect

In this paper, we use the method of rapid oscillating field to solve the equation of ion motion in an RF gun. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper proposes a simple mitigation recipe that can reduce the rate of ion bombardment.

Pozdeyev,E.; Kayran, D.; Litvinenko, V.

2008-09-01

119

The influence of ion bombardment on emission properties of small dust grains  

NASA Astrophysics Data System (ADS)

Dust grains that are present in many plasma and vacuum systems and in the space usually carry a non-negligible charge. Their charging significantly depends on surface properties of the grain material. In cold plasma, charging is mainly given by electron attachment, nevertheless, when plasma becomes hot, other processes (secondary electron emission, field emission, etc.) take place. Emission properties of the grain surface could be modified by grain baking or by ion bombardment. Our study is carried out at the dust charging experiment dealing with a single dust grain electro-dynamically levitated in a 3D quadrupole trap. The grain can be exposed to the ion beam in the energy range of 100 eV-5 keV and to the electron beam in the energy range of 100 eV-10 keV. We have chosen He+ and Ar+ ions for the surface treatment and the observed influence on the surface properties is discussed in terms of secondary emission. A non-negligible shift of the secondary electron emission yield, as well as a change of energy distribution of secondary electrons, were measured after Ar+ bombardment. A preliminary study suggests that the effects of He+ and Ar+ are comparable.

Zilavy, P.; Richterova, I.; Nemecek, Z.; Safrankova, J.; Pavlu, J.

2005-10-01

120

Molecular Structure of Fullerene C60  

NSDL National Science Digital Library

Three professors are credited with the discovery of fullerenes, a family of symmetrical carbon-cage molecules. Buckyball is the the most abundant and well-known carbon-cage molecule consisting of 60 carbon atoms. This huge molecule is being studied by many scientists for its ability to serve as a conductor, insulator, semiconductor, and superconductor.

2002-08-26

121

C60 fullerene binding to DNA  

NASA Astrophysics Data System (ADS)

Fullerenes have attracted considerable attention in various areas of science and technology. Owing to their exceptional physical, chemical, and biological properties, they have many applications, particularly in cosmetic and medical products. Using the Lennard-Jones 6-12 potential function and the continuum approximation, which assumes that intermolecular interactions can be approximated by average atomic surface densities, we determine the binding energies of a C60 fullerene with respect to both single-strand and double-strand DNA molecules. We assume that all configurations are in a vacuum and that the C60 fullerene is initially at rest. Double integrals are performed to determine the interaction energy of the system. We find that the C60 fullerene binds to the double-strand DNA molecule, at either the major or minor grooves, with binding energies of -4.7 eV or -2.3 eV, respectively, and that the C60 molecule binds to the single-strand DNA molecule with a binding energy of -1.6 eV. Our results suggest that the C60 molecule is most likely to be linked to the major groove of the dsDNA molecule.

Alshehri, Mansoor H.; Cox, Barry J.; Hill, James M.

2014-09-01

122

Arranging pseudorotaxanes octahedrally around [60]fullerene  

SciTech Connect

The formation of both [2]- and [7]pseudorotaxanes, which are obtained by mixing of a dibenzylammonium derivative with mono- and hexakis-adducts of [60]fullerene bearing malonato-benzo[25]crown-8 rings, has been monitored in dichloromethane by both 1D and 2D ¹H NMR spectroscopies.

Dey, Sanjeev K. [Northwestern Univ., Evanston, IL (United States); Beurele, Florian [Northwestern Univ., Evanston, IL (United States); Olson, Mark A. [Northwestern Univ., Evanston, IL (United States); Stoddart, J. Fraser [Northwestern Univ., Evanston, IL (United States)

2011-01-01

123

Alignment strategies for fullerenes and their dimers using soft matter  

NASA Astrophysics Data System (ADS)

The overall goal of this research was to achieve alignment of endohedral fullerene dimers defined as covalently linked pairs of fullerene cages where each fullerene cage encapsulates a spin-active atom. The first section will discuss polymer-fullerene interactions from the point of view of determining how various polymer functional groups enhance or hinder the miscibility of C60. In order to successfully incorporate fullerenes into a block copolymer system, we first need to understand the basic interactions that occur between polymers and fullerenes to anticipate the upper limit of fullerenes that may be incorporated in a given polymer and potential approaches to increase this quantity. In particular, studies conducted using wide angle x-ray scattering (WAXS) of vinyl polymer-fullerene blends indicated that an increasing number of phenyl rings in the vinyl side group of the polymer leads to an increase in the miscibility. In particular, poly(9-vinylphenanthrene) (P9VPh), having three phenyl rings in the side group, showed a 6-fold improvement in miscibility limit compared to the other systems studied, polystyrene (PS) and poly(2-vinylnaphathalene) (P2VN). The degree of increase in miscibility observed with P9VPh is attributed to the ability of the vinyl aromatic structure to essentially conform to the curvature of a fullerene molecule rather than the increased potential for pi-pi interactions. These results importantly suggest that a block copolymer system can be tuned to maximize fullerene content, particularly by considering the geometry of functional groups with respect to the fullerene cage and will be discussed further in Chapter III. Second, the use of block copolymers as templates for creating ordered arrays of fullerenes is discussed. The initial goal was to disperse the fullerenes in one block of a block copolymer system and by aligning the microphase separation structure, also align the incorporated fullerenes. There are several major challenges associated with incorporating fullerenes into a block copolymer including the limited miscibility discussed in Chapter III. Furthermore, overcoming the strong inter-fullerene interactions that lead to aggregation also proves to be challenging; aggregates can disrupt the microphase structure in a block copolymer and make alignment difficult to obtain. One potential method generically used to solubilize nanoparticles within a block copolymer is modification of the nanoparticles by grafting polymer chains to the surface to solubilize the nanoparticle in a specific block. As discussed in Chapter IV, the effects of nanoparticle size and concentration on the phase behavior of lamellar-forming dPS-PMMA systems as well as the location of the fullerene star within the dPS block were studied using neutron reflectivity (NR). The scheme above has the disadvantage that modification of the fullerene cage with polymer arms dilutes the overall quantity of fullerene in the system and in the case of endohedral systems, would dilute and severely limit the overall quantity of spins available for measurement in quantum computing. For this reason we chose to investigate the formation of monolayers of amphiphilic fullerene dimers at the air/water interface using the Langmuir technique. We also studied the behavior of these materials when transferred as monolayers and multilayers to solid substrates as Langmuir-Blodgett (LB) films. The fullerene dimers in this case were modified to have at least one hydrophilic, polyethylene glycol-based ligand to balance the inherently hydrophobic nature of the fullerene cage and allow for a molecule that more closely resembled typical LB materials. Results of these studies indicated that we can form stable, close-packed monolayers and also control the orientation of the dimer at the air/water interface as well as on solid substrates by tuning the ligand chemistry as shown in Chapter V. The final approach used to achieve alignment of fullerene materials involves the interaction of fullerenes with a chemically-modified substrate either covalently or non-covale

Campbell, Katie

124

Optical limiting processes in derivatized fullerenes and porphyrins/phthalocyanines  

SciTech Connect

The authors review their results from spectral studies of the ultrafast excited-state absorption in fullerenes and derivatized fullerenes. These results allow determination of both the spectral response of reverse saturable absorption (RSA) nonlinearities such as optical limiting (OL) in fullerenes, and the dynamical response for different morphologies. The authors have investigated the effects of thin film and various sol-gel glass environments on the nanosecond OL and femtosecond dynamics of derivatized fullerenes. These data provide evidence of decay pathways which compete with the intersystem crossing to a triplet from the initial singlet states. With appropriate processing, however, the OL response of derivatized-fullerene sol-gel glasses can be enhanced to approach that of the same molecule in solution, while significantly enhancing the optical damage threshold. The optical limiting of these derivatized fullerenes is compared with that of various porphyrin and phthalocyanine molecules.

Kohlman, R.; Klimov, V.; Shi, X. [and others

1998-07-01

125

Biological activities of water-soluble fullerene derivatives  

NASA Astrophysics Data System (ADS)

Three types of water-soluble fullerene derivatives were synthesized and their biological activities were investigated. C60-dimalonic acid, an anionic fullerene derivative, showed antioxidant activity such as quenching of superoxide and relief from growth inhibition of E. coli by paraquat. C60-bis(7V,7V-dimethylpyrrolidinium iodide), a cationic fullerene derivative, has antibacterial activity and antiproliferative effect on cancer cell lines. The mechanism is suggested to be respiratory chain inhibition by reactive oxygen species produced by the cationic fullerene derivative. Proline-type fullerene derivatives showed strong inhibition activities on HIV-reverse transcriptase. The IC50 values were remarkably lower than nevirapine, a clinically used anti-HIV drug. Fullerene derivatives have a big potential for a new type of lead compound to be used as medicine.

Nakamura, S.; Mashino, T.

2009-04-01

126

Memory operation mechanism of fullerene-containing polymer memory  

NASA Astrophysics Data System (ADS)

The memory operation mechanism in fullerene-containing nanocomposite gate insulators was investigated while varying the kind of fullerene in a polymer gate insulator. It was cleared what kind of traps and which positions in the nanocomposite the injected electrons or holes are stored in. The reason for the difference in the easiness of programming was clarified taking the role of the charging energy of an injected electron into account. The dependence of the carrier dynamics on the kind of fullerene molecule was investigated. A nonuniform distribution of injected carriers occurred after application of a large magnitude programming voltage due to the width distribution of the polystyrene barrier between adjacent fullerene molecules. Through the investigations, we demonstrated a nanocomposite gate with fullerene molecules having excellent retention characteristics and a programming capability. This will lead to the realization of practical organic memories with fullerene-containing polymer nanocomposites.

Nakajima, Anri; Fujii, Daiki

2015-03-01

127

Genetic transformation of Cymbidium orchid by particle bombardment  

Microsoft Academic Search

A protocol is presented for genetically engineering Cymbidium orchid using particle bombardment. This protocol enabled the routine transformation of orchid plants that were previously\\u000a difficult to transform. Liquid culture was used to generate a large number of protocorm-like bodies (PLBs) to be bombarded\\u000a and to promote continued development of the bombarded meristematic tissue. Plasmid DNA (pKH200) carrying the GUS-INT and

J. Yang; H.-J. Lee; D. H. Shin; S. K. Oh; J. H. Seon; K. Y. Paek; K.-H. Han

1999-01-01

128

Aerosol Synthesis of Fullerene Nanocrystals in Controlled Flow Reactor Conditions  

Microsoft Academic Search

Fullerene nanocrystals in the size range 30–300 nm were produced starting from atomized droplets of C60 in toluene. The experiments were carried out under well-controlled conditions in a laminar flow reactor at temperatures of 20–600°C. Particle transformation and crystallization mechanisms of polydisperse and monodisperse (size classified) fullerene aerosol particles were studied. The results show that fullerene particles are roughly spherical

J. Joutsensaari; P. P. Ahonen; E. I. Kauppinen; D. P. Brown; K. E. J. Lehtinen; J. K. Jokiniemi; B. Powels; G. Van Tendeloo

2000-01-01

129

Production of high voltage by ion bombardment  

E-print Network

PRODLrCTION OF HIGH VOLTAGE BY ION BOMBARDMENT A Thesis by LUCAS CARTER PHINNEY Submitted to the Office of Graduate Studies of Texas A&M University in partial fultillment of the requirements for the degree of MASTER OF SCIENCE December 2003... additional studies and experiments through out the 1950's and 60's. Many of the experiments did not perform as hoped due to the limited technology at the time, and as a result most of the direct energy work with relation to fission fragments was stopped...

Phinney, Lucas Carter

2003-01-01

130

Modification of rubber by ion bombardment  

NASA Astrophysics Data System (ADS)

The paper presents selected effects of surface modification of rubber vulcanizates upon irradiation with He+, O+ or Ar+ ions. Changes to chemical composition and physical structure of rubber macromolecules are discussed in terms of influence of the treatment on functional properties of the vulcanizates, like friction and wettability. Hydrogen release, responsible for further crosslinking and oxidation of surface layer can protect bulk of the materials from action of external chemical factors. Effectiveness of a protective layer being formed due to ion bombardment has been examined from the point of view of thermal and ozone aging, as well as fuel resistance of the rubber vulcanizates.

Bielinski, Dariusz M.; Pieczynska, Diana; Ostaszewska, Urszula; Jagielski, Jacek

2012-07-01

131

Higher fullerenes: Compositional analysis by EDXD and molecular dynamics  

SciTech Connect

A carbon soot of higher fullerenes was studied by Energy Dispersive X-ray Diffraction (EDXD) aiming at defining the overall structure as accurately as possible to define the overall structure, without lengthy separation and purification procedures. EDXD pattern was compared with model curves obtained for single homogeneous fullerenes already crystallized and for the hypothesized C180. All fullerenes contribute to the overall experimental curve to different extents, with C96 giving the best agreement. The presence of even higher fullerenes is very likely, since the hypothesized C180 gives a very good match as well.

Carbone, Marilena [Università di Roma Tor Vergata, Via della Ricerca Scientifica 1 I-00133 Roma (Italy); Gontrani, Lorenzo, E-mail: lorenzo.gontrani@uniroma1.it [CNR-Istituto di Struttura della Materia, Via del Fosso del Cavaliere, I-00133 Roma, Italy and Dipartimento di Chimica- Università Sapienza , P.le Aldo Moro 5, I-00184 Roma (Italy)

2014-06-19

132

Biomolecular Emission by Swift Heavy Ion Bombardment  

SciTech Connect

Secondary Ion Mass spectrometry (SIMS) has been generally used in the field of material sciences. In recent years, it has also been applied for molecular imaging of biological samples. Nevertheless, molecular ions derived from the large molecules (more than 1 kDa) were detected with very low sensitivity. Plasma desorption mass spectrometry (PDMS) is known as mass spectrometry for large organic molecule. In PDMS, fission fragments bombard samples and the impact induces molecular ionization by electronic excitation. Large organic molecules are detected by using swift heavy ions in SIMS. In this work, 6 MeV Cu{sup 4+} we irradiated angiotensin II, a class of peptides. The intact molecular ions generated by swift heavy ion irradiation were analyzed by time-of-flight (TOF) measurement. The yields are compared with some other probe ions, bismuth or flurane. Swift heavy ion bombardment ionized large organic molecules more effectively than other probes. Therefore, high energy ion can be applied in high resolution molecular imaging.

Wakamatsu, Yoshinobu; Yamada, Hideaki [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto, 606-8501 (Japan); Ninomiya, Satoshi; Matsuo, Jiro [Quantum Science and Engineering Center, Kyoto University. Uji, Kyoto 611-0011 (Japan); Japan Science and Technology Agency (JST), Chiyoda, Kyoto, 102-0075 (Japan); Jones, Brian N.; Webb, Roger [Ion Beam Centre, University of Surrey, Surrey GU2 7XH (United Kingdom); Seki, Toshio [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto, 606-8501 (Japan); Japan Science and Technology Agency (JST), Chiyoda, Kyoto, 102-0075 (Japan); Aoki, Takaaki [Department of Electronic Science and Engineering, Kyoto University, Nishikyo Kyoto 615-8510 (Japan); Japan Science and Technology Agency (JST), Chiyoda, Kyoto, 102-0075 (Japan)

2011-01-07

133

Growth and sintering of fullerene nanotubes  

SciTech Connect

Carbon nanotubes produced in arcs have been found to have the form of multiwalled fullerenes, at least over short lengths. Sintering of the tubes to each other is the predominant source of defects that limit the utility of these otherwise perfect fullerene structures. The use of a water-cooled copper cathode minimized such defects, permitting nanotubes longer than 40 micrometers to be attached to macroscopic electrodes and extracted from the bulk deposit. A detailed mechanism that features the high electric field at (and field-emission from) open nanotube tips exposed to the arc plasma, and consequent positive feedback effects from the neutral gas and plasma, is proposed for tube growth in such arcs. 19 refs., 5 figs.

Colbert, D.T.; Zhang, J.; McClure, S.M.; Nikolaev, P.; Chen, Z.; Hafner, J.H. [Rice Univ., Houston, TX (United States); Owens, D.W.; Kotula, P.G.; Carter, C.B.; Weaver, J.H. [Univ. of Minnesota, Minneapolis, MN (United States)] [and others

1994-11-18

134

Preparation of fullerene/glass composites  

DOEpatents

Synthesis of fullerene/glass composites. A direct method for preparing solid solutions of C.sub.60 in silicon dioxide (SiO.sub.2) glass matrices by means of sol-gel chemistry is described. In order to produce highly concentrated fullerene-sol-gel-composites it is necessary to increase the solubility of these "guests" in a delivery solvent which is compatible with the starter sol (receiving solvent). Sonication results in aggregate disruption by treatment with high frequency sound waves, thereby accelerating the rate of hydrolysis of the alkoxide precursor, and the solution process for the C.sub.60. Depending upon the preparative procedure, C.sub.60 dispersed within the glass matrix as microcrystalline domains, or dispersed as true molecular solutions of C.sub.60 in a solid glass matrix, is generated by the present method.

Mattes, Benjamin R. (Santa Fe, NM); McBranch, Duncan W. (Santa Fe, NM); Robinson, Jeanne M. (Los Alamos, NM); Koskelo, Aaron C. (Los Alamos, NM); Love, Steven P. (Los Alamos, NM)

1995-01-01

135

Carbon and fullerene nanomaterials in plant system  

PubMed Central

Both the functionalized and non functionalized carbon nanomaterials influence fruit and crop production in edible plants and vegetables. The fullerene, C60 and carbon nanotubes have been shown to increase the water retaining capacity, biomass and fruit yield in plants up to ~118% which is a remarkable achievement of nanotechnology in recent years. The fullerene treated bitter melon seeds also increase the phytomedicine contents such as cucurbitacin-B (74%), lycopene (82%), charantin (20%) and insulin (91%). Since as little as 50 ?g mL?1 of carbon nanotubes increase the tomato production by about 200%, they may be exploited to enhance the agriculture production in future. It has been observed that, in certain cases, non functionalized multi-wall carbon nanotubes are toxic to both plants and animals but the toxicity can be drastically reduced if they are functionalized. PMID:24766786

2014-01-01

136

Carbon and fullerene nanomaterials in plant system.  

PubMed

Both the functionalized and non functionalized carbon nanomaterials influence fruit and crop production in edible plants and vegetables. The fullerene, C60 and carbon nanotubes have been shown to increase the water retaining capacity, biomass and fruit yield in plants up to ~118% which is a remarkable achievement of nanotechnology in recent years. The fullerene treated bitter melon seeds also increase the phytomedicine contents such as cucurbitacin-B (74%), lycopene (82%), charantin (20%) and insulin (91%). Since as little as 50 ?g mL-1 of carbon nanotubes increase the tomato production by about 200%, they may be exploited to enhance the agriculture production in future. It has been observed that, in certain cases, non functionalized multi-wall carbon nanotubes are toxic to both plants and animals but the toxicity can be drastically reduced if they are functionalized. PMID:24766786

Husen, Azamal; Siddiqi, Khwaja Salahuddin

2014-01-01

137

Preparation of fullerene/glass composites  

DOEpatents

Synthesis of fullerene/glass composites is described. A direct method for preparing solid solutions of C{sub 60} in silicon dioxide (SiO{sub 2}) glass matrices by means of sol-gel chemistry is described. In order to produce highly concentrated fullerene-sol-gel-composites it is necessary to increase the solubility of these ``guests`` in a delivery solvent which is compatible with the starter sol (receiving solvent). Sonication results in aggregate disruption by treatment with high frequency sound waves, thereby accelerating the rate of hydrolysis of the alkoxide precursor, and the solution process for the C{sub 60}. Depending upon the preparative procedure, C{sub 60} dispersed within the glass matrix as microcrystalline domains, or dispersed as true molecular solutions of C{sub 60} in a solid glass matrix, is generated by the present method.

Mattes, B.R.; McBranch, D.W.; Robinson, J.M.; Koskelo, A.C.; Love, S.P.

1995-05-30

138

Characteristic Fragmentation of Polysiloxane Monolayer Films by Bombardment with Monatomic and Polyatomic Primary Ions in TOF-SIMS  

NASA Astrophysics Data System (ADS)

This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs+, C{60/+} (10 keV), Bi{1/+}, and Bi{3/+} (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (Mn) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights (MW) from 600 and 1000 Da. For each film, Bi projectiles resulted in the emission of positive silver cluster ions from the substrate under the polymer overlayer and peaks corresponding to silver cluster ions with larger mass were observed by impact of polyatomic 25 keV Bi{3/+} projectiles. In addition, depending on the change of energy of Bi{3/+}, a different pattern of fragments was observed. With Cs+ and C{60/+} impact, however, the emission of silver cluster ions was not detected. In the case of C{60/+} impact for PDMS-6140, peaks corresponding to silver-cationized intact oligomers were not observed. In this paper, these results are explained by the possible bombardment mechanism for each projectile, based on its mass, energy, and split trajectories of the component atoms under the polyatomic impact.

Moon, Hye Kyoung; Wells, David D.; Gardella, Joseph A.

2012-01-01

139

Diamond films grown from fullerene precursors  

SciTech Connect

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.

Gruen, D.M.; Zuiker, C.D.; Krauss, A.R.

1995-07-01

140

PREFACE: Fullerene Nano Materials (Symposium of IUMRS-ICA2008)  

NASA Astrophysics Data System (ADS)

This volume contains peer-reviewed invited and contributed papers that were presented in Symposium N 'Fullerene Nano Materials' at the IUMRS International Conference in Asia 2008 (IUMRS-ICA 2008), which was held on 9-13 December 2008, at Nagoya Congress Center, Nagoya, Japan. Over twenty years have passed since the discovery of C60 in 1985. The discovery of superconductivity of C60 in 1991 suggested infinite possibilities for fullerenes. On the other hand, a new field of nanocarbon has been developed recently, based on novel functions of the low-dimensional fullerene nanomaterials that include fullerene nanowhiskers, fullerene nanotubes, fullerene nanosheets, chemically modified fullerenes, endohedral fullerenes, thin films of fullerenes and so forth. Electrical, electrochemical, optical, thermal, mechanical and various other properties of fullerene nanomaterials have been investigated and their novel and anomalous nature has been reported. Biological properties of fullerene nanomaterials also have been investigated both in medical applications and toxicity aspects. The recent research developments of fullerene nanomaterials cover a variety of categories owing to their functional diversity. This symposium aimed to review the progress in the state-of-the-art technology based on fullerenes and to offer the forum for active interdisciplinary discussions. 24 oral papers containing 8 invited papers and 22 poster papers were presented at the two-day symposium. Topics on the social acceptance of nanomaterials including fullerene were presented on the first day of the symposium. Biological impacts of nanomaterials and the importance of standardization of nanomaterials characterization were also shown. On the second day, the synthesis, properties, functions and applications of various fullerene nanomaterials were shown in both the oral and poster presentations. We are grateful to all invited speakers and many participants for valuable contributions and active discussions. This symposium was partly supported by the Coordination Program of Science and Technology Projects ''Developing Nanotechnologies and Engaging the Public'' conducted by the Council for Science and Technology Policy (CSTP) and funded by Special Coordination Funds for Promoting Science and Technology. Organizing committee of Symposium N (IUMRS-ICA 2008) Chair Kun'ichi Miyazawa (National Institute for Materials Science, Japan) Vice Chairs Daisuke Fujita (National Institute for Materials Science, Japan) Takatsugu Wakahara (National Institute for Materials Science, Japan) Tokushi Kizuka (Tsukuba University, Japan) Kiyoto Matsuishi (Tsukuba University, Japan) Yuichi Ochiai (Chiba University, Japan) Masaru Tachibana (Yokohama City University, Japan) Hironori Ogata (Hosei University, Japan) Tadahiko Mashino (Keio University, Japan) Ryotaro Kumashiro (Tohoku University, Japan) Hidetoshi Oikawa (Tohoku University, Japan)

Miyazawa, Kun'ichi; Fujita, Daisuke; Wakahara, Takatsugu; Kizuka, Tokushi; Matsuishi, Kiyoto; Ochiai, Yuichi; Tachibana, Masaru; Ogata, Hironori; Mashino, Tadahiko; Kumashiro, Ryotaro; Oikawa, Hidetoshi

2009-07-01

141

Synthesis of fullerene-acene dyads  

NASA Astrophysics Data System (ADS)

Organic photovoltaic (OPV) cells present potential for industrial use because of their possible low cost production. However, their relatively low efficiencies render them impractical for implementation. A comprehensive understanding of the photophysical process is necessary for eventual development of high efficiency OPV cells. Studying photophysical processes of well-defined structures such as dyad or triad molecules may give insight into their photophysical processes. In this study, we selected pentacene derivatives as electron donors and fullerenes as electron acceptors for dyad and triad molecules with well-defined structures. Several new types of organothiosubstituted 6,13-dihydropentacenes with terminal functionality including carboxylic acid, alcohol and amine groups were synthesized. A sterically hindered pentacene derivative was also prepared in order to prevent cycloaddition between C60 and pentacene. Functionalized fullerenes were synthesized for use as electron acceptors. Numerous reaction methods were attempted toward the synthesis of a donor/acceptor dyad with pentacene and fullerene derivatives. However, hydroamination of pristine C 60 using a diamino dihydropentacene derivative was the only successful method demonstrated to link C60 and dihydropentacene derivatives.

Cho, Claire Eunhye

142

The interaction of He- with fullerenes  

NASA Astrophysics Data System (ADS)

The effects of interactions between He- and clusters of fullerenes in helium nanodroplets are described. Electron transfer from He- to (C60)n and (C70)n clusters results in the formation of the corresponding fullerene cluster dianions. This unusual double electron transfer appears to be concerted and is most likely guided by electron correlation between the two very weakly bound outer electrons in He-. We suggest a mechanism which involves long range electron transfer followed by the conversion of He+into He2+, where formation of the He-He bond in He2+ releases sufficient kinetic energy for the cation and the dianion to escape their Coulombic attraction. By analogy with the corresponding dications, the observation of a threshold size of n ? 5 for formation of both (C60)n2- and (C70)n2- is attributed to Coulomb explosion rather than an energetic constraint. We also find that smaller dianions can be observed if water is added as a co-dopant. Other aspects of He- chemistry that are explored include its role in the formation of multiply charged fullerene cluster cations and the sensitivity of cluster dianion formation on the incident electron energy.

Mauracher, Andreas; Daxner, Matthias; Huber, Stefan E.; Postler, Johannes; Renzler, Michael; Denifl, Stephan; Scheier, Paul; Ellis, Andrew M.

2015-03-01

143

Transformation of cotton ( Gossypium hirsutum L.) via particle bombardment  

Microsoft Academic Search

Embryogenic suspension cultures of cotton (Gossypium hirsutum L.) were subjected to particle bombardment, where high density particles carrying plasmid DNA were accelerated towards the embryogenic plant cells. The plasmid DNA coating the particles encoded hygromycin resistance. One to two weeks following bombardment, embryogenic cotton cells were placed in proliferation medium containing 100 µg\\/ml hygromycin. Clumps of tissue which grew in

John J. Finer; Michael D. McMullen

1990-01-01

144

Optical absorption spectra and geometric e ects in higher fullerenes  

E-print Network

Optical absorption spectra and geometric e ects in higher fullerenes (Running head: Optical absorption in higher fullerenes) Kikuo Harigaya and Shuji Abe Physical Science Division, Electrotechnical of their amplitudes at the pentagons. The oscillator strengths of projected absorption almost accord with those

Harigaya, Kikuo

145

Sponge-like molecular cage for purification of fullerenes.  

PubMed

Since fullerenes are available in macroscopic quantities from fullerene soot, large efforts have been geared toward designing efficient strategies to obtain highly pure fullerenes, which can be subsequently applied in multiple research fields. Here we present a supramolecular nanocage synthesized by metal-directed self-assembly, which encapsulates fullerenes of different sizes. Direct experimental evidence is provided for the 1:1 encapsulation of C60, C70, C76, C78 and C84, and solid state structures for the host-guest adducts with C60 and C70 have been obtained using X-ray synchrotron radiation. Furthermore, we design a washing-based strategy to exclusively extract pure C60 from a solid sample of cage charged with a mixture of fullerenes. These results showcase an attractive methodology to selectively extract C60 from fullerene mixtures, providing a platform to design tuned cages for selective extraction of higher fullerenes. The solid-phase fullerene encapsulation and liberation represent a twist in host-guest chemistry for molecular nanocage structures. PMID:25424201

García-Simón, Cristina; Garcia-Borràs, Marc; Gómez, Laura; Parella, Teodor; Osuna, Sílvia; Juanhuix, Jordi; Imaz, Inhar; Maspoch, Daniel; Costas, Miquel; Ribas, Xavi

2014-01-01

146

Sponge-like molecular cage for purification of fullerenes  

NASA Astrophysics Data System (ADS)

Since fullerenes are available in macroscopic quantities from fullerene soot, large efforts have been geared toward designing efficient strategies to obtain highly pure fullerenes, which can be subsequently applied in multiple research fields. Here we present a supramolecular nanocage synthesized by metal-directed self-assembly, which encapsulates fullerenes of different sizes. Direct experimental evidence is provided for the 1:1 encapsulation of C60, C70, C76, C78 and C84, and solid state structures for the host–guest adducts with C60 and C70 have been obtained using X-ray synchrotron radiation. Furthermore, we design a washing-based strategy to exclusively extract pure C60 from a solid sample of cage charged with a mixture of fullerenes. These results showcase an attractive methodology to selectively extract C60 from fullerene mixtures, providing a platform to design tuned cages for selective extraction of higher fullerenes. The solid-phase fullerene encapsulation and liberation represent a twist in host–guest chemistry for molecular nanocage structures.

García-Simón, Cristina; Garcia-Borràs, Marc; Gómez, Laura; Parella, Teodor; Osuna, Sílvia; Juanhuix, Jordi; Imaz, Inhar; Maspoch, Daniel; Costas, Miquel; Ribas, Xavi

2014-11-01

147

Antibacterial Activity of Fullerene Water Suspensions: Effects of  

E-print Network

on fullerene derivatives show both positive and negative health effects, depending upon the derivativeAntibacterial Activity of Fullerene Water Suspensions: Effects of Preparation Method and Particle organisms and in the environment to determine how C60 can be safely used and disposed. Introduction Since

Alvarez, Pedro J.

148

Anomalous charge transport behavior of Fullerene based diodes  

NASA Astrophysics Data System (ADS)

We observed an anomalous voltage-current (V-I) characteristics of fullerene based diodes in the low temperature regime. The diodes exhibit a negative differential resistance and voltage hysteresis for opposite current sweep directions. This behavior is directly observable at temperatures below 95 K and indicates the formation of highly conductive filaments in the fullerene thin films.

Matt, G. J.; Sariciftci, N. S.; Fromherz, T.

2004-03-01

149

Highly nonlinear transport phenomena in fullerene based diodes  

NASA Astrophysics Data System (ADS)

Voltage-current measurements of fullerene based diodes in the temperature range between 295 - 15 K are presented. At temperatures below 95 K and at high current densities the diodes exhibit a voltage instability with a voltage hysteresis for opposite current sweep directions. This observation is interpreted with the formation of highly conductive current filaments in the fullerene film.

Matt, G. J.; Fromherz, T.; Neugebauer, H.; Sariciftci, N. S.

2005-09-01

150

Transport of Fullerene Nanoparticles in Saturated Porous Media  

EPA Science Inventory

The high strength, electrical conductivity, and electron affinity of fullerenes has lead to their utilization in fuel cells and drug-delivery devices, as well as in cosmetics and other applications. Though C60 fullerene is very insoluble in water, studies have shown that C60 ful...

151

Storage of nuclear materials by encapsulation in fullerenes  

DOEpatents

A method of encapsulating radioactive materials inside fullerenes for stable long-term storage. Fullerenes provide a safe and efficient means of disposing of nuclear waste which is extremely stable with respect to the environment. After encapsulation, a radioactive ion is essentially chemically isolated from its external environment.

Coppa, Nicholas V. (Los Alamos, NM)

1994-01-01

152

C20 fullerenes as superconductors? First-principles investigations  

NASA Astrophysics Data System (ADS)

Small fullerenes, such as C36, may have high density of states at the Fermi level [1] and have strong electron-phonon coupling constants compared to large fullerenes (C60, C70, C84 etc.)[2]. These fullerenes therefore are expected to have higher Tc of the superconductivity. Recent discovery of gas phase C20 cage [3] has motivated use toward the smallest fullerene superconductors. We have investigated possible condensed phases of the C20 cages and a candidate of the high Tc superconductor, by means of the density functional theory. The C20 fullerene has been found to form condensed phases in several dimensions. We will discuss the possibility of achieving the superconductivity of the investigated phases. [1] J. C. Grossman, S. G. Louie, and M. L. Cohen, Phys. Rev B60, R6941 (1999) [2] A. Devos and M. Lannoo, Phys. Rev. B58, 8236 (1998). [3] Prinzbach et al., Nature (London), 407, 60 (2000).

Miyamoto, Yoshiyuki; Saito, Mineo

2001-03-01

153

PAPER www.rsc.org/pps | Photochemical & Photobiological Sciences Ionisation of fullerenes and fullerene clusters using ultrashort laser pulses  

E-print Network

PAPER www.rsc.org/pps | Photochemical & Photobiological Sciences Ionisation of fullerenes review of the literature concerning the ultra-short pulse ionisation of fullerenes in the gas phase. Emphasis is placed on the excitation time dependence of different ionisation regimes as manifested

Hansen, Klavs

154

Fabrication of free-standing fullerene nanowire using direct electron beam writing and sacrificial dry etching  

Microsoft Academic Search

This paper reports a fabrication of doubly-supported free-standing fullerene (C60) nanowires on MEMS structures to propose an integration process of carbon nano-materials to surface-micromachined silicon devices. By irradiating vacuum-deposited fullerene film with electron beam (EB), polymerized fullerene nanowires were patterned. Then, free-standing structures of the fullerene nanowires were obtained by sacrificial etching using XeF2 gas. The fabricated fullerene nanowire was

T. Tsuchiya; T. Jomori; Y. Ura; K. Sugano; O. Tabata

2008-01-01

155

Computed molecular depth profile for C60 bombardment of a molecular solid.  

PubMed

Molecular dynamics (MD) simulations have been performed for 10 keV C60 bombardment of an octane molecular solid at normal incidence. The results are analyzed using the steady-state statistical sputtering model (SS-SSM) to understand the nature of molecular motions and to predict a depth profile of a ?-layer. The octane system has sputtering yield of ~150 nm(3) of which 85% is in intact molecules and 15% is fragmented species. The main displacement mechanism is along the crater edge. Displacements between layers beneath the impact point are difficult because the nonspherically shaped octane molecule needs a relatively large volume to move into and the molecule needs to be aligned properly for the displacement. Since interlayer mixing is difficult, the predicted depth profile is dominated by the rms roughness and the large information depth because of the large sputtering yield. PMID:24191664

Paruch, Robert J; Garrison, Barbara J; Postawa, Zbigniew

2013-12-01

156

Energy effects on the sputtering yield of Si bombarded with gas cluster ion beams  

SciTech Connect

Gas cluster ion presents various irradiation effects such as high sputtering yields. It is important to study the optimum condition of incident cluster ion beam for applications in surface modification technology. In this study, the effects of incident energy and chamber pressure on the sputtering yield with gas cluster ion bombardment were investigated. The incident mean cluster size was 2000 atoms/ion and incident energy was 10-80 keV. The number of collisions with residual gas during transportation was in the range 1-20. The sputtering yield with gas cluster ion beam increased nonlinearly with increasing incident cluster energy. However, cluster ion beam easily lose their energy by collision with residual gas, and the sputtering yield decreased rapidly. For using gas cluster ion beam efficiently, the collision frequency along transportation should be kept less than a few times.

Ichiki, K. [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto (Japan); Ninomiya, S.; Matsuo, J. [Quantum Science and Engineering Center, Kyoto University, Uji, Kyoto (Japan); CREST, Japan Science and Technology Agency (JST), Chiyoda, Tokyo (Japan); Seki, T. [Department of Nuclear Engineering, Kyoto University, Sakyo, Kyoto (Japan); CREST, Japan Science and Technology Agency (JST), Chiyoda, Tokyo (Japan); Aoki, T. [Department of Electronic Science and Engineering, Kyoto University, Nishikyo, Kyoto (Japan); CREST, Japan Science and Technology Agency (JST), Chiyoda, Tokyo (Japan)

2011-01-07

157

Multi-scale modeling of localized heating caused by ion bombardment  

NASA Astrophysics Data System (ADS)

We have developed a multiscale modeling algorithm to incorporate both a Monte Carlo (MC) ion irradiation simulator and finite element analysis to simulate ion beam heating. The spatial distribution of displacements from the MC code was input into a 3-D FEA code to predict the temperature evolution upon ion bombardment. In order to simulate the flux effect, ions were introduced stochastically. We discuss the necessity to use both grid refinement and grid coarsening techniques to make such modeling possible, thus providing a basis to evaluate the impact on the microstructure of the substrate. The aforementioned approach was applied for the case of a 16 A cm -2 beam of 6 keV Ga + ions to simulate FIB sample sectioning and thinning in a Si substrate.

Myers, Michael T.; Sencer, Bulent H.; Shao, Lin

2012-02-01

158

Angular distribution of GaAs sputtered under oblique Cs + bombardment  

NASA Astrophysics Data System (ADS)

The angular distribution of Ga and As sputtered from Gallium Arsenide (1 0 0) by a Cs + ion beam was experimentally measured through a collector technique allowing modifications of the energy and incidence angle of the ion beam. The impact energy was varied in the range of 2-10 keV and the angle of incidence from 30° to 60°. The angular distributions of emitted matter are determined by means of SIMS depth profiles. Our series of experiments show an evolution of the preferential direction of emission as well as the spreading around this direction in function of the characteristics of the ion beam. The second objective is the study of the evolution of the stoichiometry of the deposit in function of the emission angle. A decrease of the As/Ga ratio around the preferential direction of emission and an increase of this ratio for oblique emission are observed for different conditions of primary bombardment. Considering that the angular distribution depends on the depth of origin, our results suggest that the Cs + bombardment changes the stoichiometry of the near-surface layers of the sample with an enrichment of As in the outmost layers while the sub-surface region is impoverished in As due to preferential sputtering.

Verdeil, C.; Wirtz, T.; Scherrer, H.

2009-08-01

159

Photon emission produced by Kr+ ions bombardment of Cr and Cr2O3 targets  

NASA Astrophysics Data System (ADS)

The sputter induced photon spectroscopy technique was used to study the luminescence spectra of the species sputtered from chromium powder and its oxide Cr2O3, during 5 keV Kr+ ions bombardment in vacuum better than 10-7 torr. The optical spectra recorded between 350 and 470 nm exhibit discrete lines which are attributed to neutral excited atoms of chromium (Cr I lines). The experiments are also performed under 10-5 torr ultra pure oxygen partial pressure. The results demonstrate that the measured intensities of the emitted photons are always higher in the presence of oxygen and even higher than those obtained for Cr2O3 target. In the presence of oxygen vapor we assume that an oxide film is formed on the chromium surface which is responsible of the increase of photon emission. This variation in the intensities is correctly explained in the model of electron transfer processes between the excited sputtered atom and the bombarded surface. This model suggests that the structure formed on the Cr surface in the case of oxygenated chromium is closer to that of Cr2O3 oxide.

Boujlaidi, A. El; Hammoum, K.; Jadoual, L.; Jourdani, R.; Ait El Fqih, M.; Aouchiche, H.; Kaddouri, A.

2015-01-01

160

Influence of secondary ion bombardment on the composition, structure and surface properties of platinum thin films  

NASA Astrophysics Data System (ADS)

Platinum (Pt) thin films were deposited by dual ion beam sputtering (DIBS) techniques on oxidized silicon substrates maintained at ambient temperature. Argon ions with energy of 1 keV and beam current of 15 mA were used to sputter the platinum target. The films during deposition were continuously bombarded by argon from a secondary argon ion source with ion energy of 150 eV and ion current density in the range 100-250 ?A/cm 2. The influence of the secondary ion beam parameters on the grain size, composition and surface morphology of the films were studied. X-ray diffraction (XRD) of all the films showed (1 1 1) orientation with other reflections being absent which is a stable structure for FCC crystals. The grain size of the Pt films prepared by DIBS at ambient temperature were found to be higher than those prepared at higher substrate temperature by low energy plasma sputtering. The presence of Ar impurities in the sputter deposited thin films is known to modify their properties. In this paper we report a method to control the Ar content in the films by secondary Ar ion bombardment of the growing films. The modification of the surface features by secondary ion beam current was studied by scanning tunneling microscope and is also presented in this paper. The surface analysis indicates a decrease in the surface roughness for the Pt films prepared at a secondary ion beam current density of 150 ?A/cm 2.

Balaji, S.; Satyam, P. V.; Lakshminarayanan, V.; Mohan, S.

2004-05-01

161

Modification of Polymer Materials by Ion Bombardment: Case Studies  

SciTech Connect

The paper discusses possibility of application of ion beam bombardment for modification of polymers. Changes to composition, structure and morphology of the surface layer produced by the treatment and their influence on engineering and functional properties of wide range of polymer materials are presented. Special attention has been devoted to modification of tribological properties. Ion bombardment results in significant reduction of friction, which can be explained by increase of hardness and wettability of polymer materials. Hard but thin enough skin does not result in cracking but improves their abrasion resistance. Contrary to conventional chemical treatment ion beam bombardment works even for polymers hardly susceptible to modification like silicone rubber or polyolefines.

Bielinski, D. M. [Institute of Polymer and Dye Technology, Technical University of Lodz, Stefanowskiego 12/16, 90-924 Lodz (Poland); Institute for Engineering of Polymer Materials and Dyes, Division of Elastomers and Rubber Technology, Liarcerska 30, 05-820 Piastow (Poland); Jagielski, J. [Institute for Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); The Andrzej Soltan Institute of Nuclear Studies, 05-400 Otwock/Swierk (Poland); Lipinski, P.; Pieczynska, D.; Ostaszewska, U. [Institute for Engineering of Polymer Materials and Dyes, Division of Elastomers and Rubber Technology, Liarcerska 30, 05-820 Piastow (Poland); Piatkowska, A. [Institute for Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland)

2009-03-10

162

Solitonic fullerene structures in light atomic nuclei  

E-print Network

The Skyrme model is a classical field theory which has topological soliton solutions. These solitons are candidates for describing nuclei, with an identification between the numbers of solitons and nucleons. We have computed numerically, using two different minimization algorithms, minimum energy configurations for up to 22 solitons. We find, remarkably, that the solutions for seven or more solitons have nucleon density isosurfaces in the form of polyhedra made of hexagons and pentagons. Precisely these structures arise, though at the much larger molecular scale, in the chemistry of carbon shells, where they are known as fullerenes.

R. A. Battye; P. M. Sutcliffe

2001-02-16

163

Fullerenes from aromatic precursors by surface-catalysed cyclodehydrogenation.  

PubMed

Graphite vaporization provides an uncontrolled yet efficient means of producing fullerene molecules. However, some fullerene derivatives or unusual fullerene species might only be accessible through rational and controlled synthesis methods. Recently, such an approach has been used to produce isolable amounts of the fullerene C(60) from commercially available starting materials. But the overall process required 11 steps to generate a suitable polycyclic aromatic precursor molecule, which was then dehydrogenated in the gas phase with a yield of only about one per cent. Here we report the formation of C(60) and the triazafullerene C(57)N(3) from aromatic precursors using a highly efficient surface-catalysed cyclodehydrogenation process. We find that after deposition onto a platinum (111) surface and heating to 750 K, the precursors are transformed into the corresponding fullerene and triazafullerene molecules with about 100 per cent yield. We expect that this approach will allow the production of a range of other fullerenes and heterofullerenes, once suitable precursors are available. Also, if the process is carried out in an atmosphere containing guest species, it might even allow the encapsulation of atoms or small molecules to form endohedral fullerenes. PMID:18704082

Otero, Gonzalo; Biddau, Giulio; Sánchez-Sánchez, Carlos; Caillard, Renaud; López, María F; Rogero, Celia; Palomares, F Javier; Cabello, Noemí; Basanta, Miguel A; Ortega, José; Méndez, Javier; Echavarren, Antonio M; Pérez, Rubén; Gómez-Lor, Berta; Martín-Gago, José A

2008-08-14

164

Anti-influenza activity of c60 fullerene derivatives.  

PubMed

The H1N1 influenza A virus, which originated in swine, caused a global pandemic in 2009, and the highly pathogenic H5N1 avian influenza virus has also caused epidemics in Southeast Asia in recent years. Thus, the threat from influenza A remains a serious global health issue, and novel drugs that target these viruses are highly desirable. Influenza A RNA polymerase consists of the PA, PB1, and PB2 subunits, and the N-terminal domain of the PA subunit demonstrates endonuclease activity. Fullerene (C60) is a unique carbon molecule that forms a sphere. To identify potential new anti-influenza compounds, we screened 12 fullerene derivatives using an in vitro PA endonuclease inhibition assay. We identified 8 fullerene derivatives that inhibited the endonuclease activity of the PA N-terminal domain or full-length PA protein in vitro. We also performed in silico docking simulation analysis of the C60 fullerene and PA endonuclease, which suggested that fullerenes can bind to the active pocket of PA endonuclease. In a cell culture system, we found that several fullerene derivatives inhibit influenza A viral infection and the expression of influenza A nucleoprotein and nonstructural protein 1. These results indicate that fullerene derivatives are possible candidates for the development of novel anti-influenza drugs. PMID:23785493

Shoji, Masaki; Takahashi, Etsuhisa; Hatakeyama, Dai; Iwai, Yuma; Morita, Yuka; Shirayama, Riku; Echigo, Noriko; Kido, Hiroshi; Nakamura, Shigeo; Mashino, Tadahiko; Okutani, Takeshi; Kuzuhara, Takashi

2013-01-01

165

Process for the removal of impurities from combustion fullerenes  

DOEpatents

The invention generally relates to purification of carbon nanomaterials, particularly fullerenes, by removal of PAHs and other hydrocarbon impurities. The inventive process involves extracting a sample containing carbon nanomaterials with a solvent in which the PAHs are substantially soluble but in which the carbon nanomaterials are not substantially soluble. The sample can be repeatedly or continuously extracted with one or more solvents to remove a greater amount of impurities. Preferred solvents include ethanol, diethyl ether, and acetone. The invention also provides a process for efficiently separating solvent extractable fullerenes from samples containing fullerenes and PAHs wherein the sample is extracted with a solvent in which both fullerenes and PAHs are substantially soluble and the sample extract then undergoes selective extraction to remove PAHs. Suitable solvents in which both fullerenes and PAHs are soluble include o-xylene, toluene, and o-dichlorobenzene. The purification process is capable of treating quantities of combustion soot in excess of one kilogram and can produce fullerenes or fullerenic soot of suitable purity for many applications.

Alford, J. Michael; Bolskar, Robert

2005-08-02

166

Noncovalent endo-binding of fullerenes to diprotonated bisporphyrins.  

PubMed

Noncovalent binding of fullerenes to bisporphyrins was studied in the gas phase by energy-dependent collision-induced dissociation (CID) with Xe under single-collision conditions. The electrospray ionization mass spectra of calix[4]arene-linked bisporphyrins show that bisporphyrins take up to 3-4 protons, depending on the type of meso-substituents. Of the protonated bisporphyrins, the diprotonated species form stable 1:1 complexes with fullerenes (C(60) and C(70)). CID cracking patterns of the diprotonated bisporphyrins indicate that each monomeric porphyrin moiety is singly protonated. CID yield-energy curves obtained from the 1:1 diprotonated bisporphyrin-fullerene complexes suggest that a fullerene occupies the endo-binding site intercalated between the two singly protonated porphyrin moieties. In the cases of 1:2 diprotonated bisporphyrin-fullerene complexes, CID results show that one fullerene binds inside (endo-binding) and the other outside (exo-binding). The exo-binding mode is energetically almost identical to the binding of fullerenes to singly protonated porphyrin monomers. The endo-binding energy is at least twice the exo-binding energy. To gain insights into the binding mode, we optimized structures of diprotonated bisporphyrins and their 1:1 endo-complexes with fullerenes, and calculated the endo-binding energy for C(60), C(70) (end-on), and C(70) (side-on). The endo-binding of fullerenes to diprotonated bisporphyrins nearly doubles the ?-? interactions while reducing the electrostatic repulsion between the two singly protonated porphyrin moieties. The side-on binding of C(70) is favored over the end-on binding because the former exerts less steric strain to the lower rim of calixarene. PMID:21993661

Jung, Sunghan; van Paauwe, John D; Boyd, Peter D W; Shin, Seung Koo

2011-12-01

167

Arc Synthesis of Fullerenes from the Carbide of Waste Cloths  

NASA Astrophysics Data System (ADS)

A great many scraps of cotton cloth are disposed of as industrial waste through making clothes. The purpose of this study is to transform the waste into very valuable carbon compounds, that is, fullerenes. The scraps were piled and carbonized in air at 1050°C. By carbonization, the weight of the scraps decreased to 16-18%. Carbide from the scraps was used as the raw material for synthesizing fullerenes with the \\mbi{J}×\\mbi{B} arc discharge method. The soot that was deposited on the inside of the vacuum chamber contained C60 (>0.05 wt%), C70 and higher fullerenes.

Hayashi, Koichiro; Mieno, Tetsu

2000-09-01

168

Hot-atom incorporation of tritium atoms into fullerenes  

NASA Astrophysics Data System (ADS)

We have used classical hot-atom chemistry to put tritium atoms inside fullerene molecules. The tritium is generated in a nuclear reactor with the reaction Li-6(n, alpha)H-3. The hot tritium atom slows down and can end up being thermalized inside a fullerene where it is trapped. The irradiated sample is dissolved, chromatographed, and counted in a scintillation counter, showing a small tritium activity. After some time, the sample is analyzed with a sensitive mass spectrometer, and He-3 was found on heating above 400 C, showing that the tritium had decayed leaving the He-3 trapped inside the fullerene.

Jimenez-Vazquez, H. A.; Cross, R. J.; Saunders, M.; Poreda, R. J.

1994-10-01

169

Fullerenes: Synthesis, separation, characterization, reaction chemistry, and applications -- A review  

SciTech Connect

The recently discovered third allotrope of carbon, the fullerenes, area subject of very active research, particularly for chemists. They have a closed-cage structure, made by interlocking pentagonal and hexagonal panels, and are the only soluble form of carbon. In this review an attempt has been made to summarize ongoing fullerene research. The review covers methods of fullerene production and separation, mechanisms leading to closed-cage structure formation, structural characterization, reaction chemistry, and applications of this novel material. The emerging directions of research are also discussed.

Singh, H.; Srivastava, M. [Indian Inst. of Petroleum, Dehradun (India)

1995-11-01

170

Nitrogen Adsorption by Activated Carbon Saturated with Fullerenes  

NASA Astrophysics Data System (ADS)

The ability of activated coal (AC) to capture and hold fullerenes is associated with the AC pore structure and considerably differs for different ACs. To reveal the nature of the AC holding capacity, the authors studied adsorption of nitrogen by AC samples at 77K after treatment by C60 fullerene. For measurements, an Autosorb-1 (Quantachrome Instrument Co., Florida, USA) device was employed. Variations in the pore size distribution are evidence for the role of 1.5-2.0 nm pores in the holding of fullerene C60.

Grekhov, V.; Kalnacs, J.; Murashov, A.; Vilken, A.

2010-01-01

171

The Primordial History of Vesta and the Jovian Early Bombardment  

NASA Astrophysics Data System (ADS)

We report the first results of a joint study of the differentiation of Vesta and the bombardment triggered by the formation of Jupiter to assess the possible implications of the interpretation of the data supplied by the Dawn mission.

Turrini, D.; Coradini, A.; Federico, C.; Formisano, M.; Magni, G.

2012-03-01

172

Interaction of C(60) fullerene with lipids.  

PubMed

Unsaturated lipids when exposed to air at room temperature undergo a slow autoxidation. When fullerene C(60) was dissolved in selected lipids (ethyl oleate, ethyl linoleate, linseed oil and castor oil) the spectrophotometric analysis shows that the oxidation is concentrated to C(60) which is converted to an epoxide C(60)O. Thus, fullerene C(60) displays antioxidant activity not only when dissolved in unsaturated lipids but also, more generally, when dissolved in unsaturated solvents subjected to autoxidation like, for example, in cyclohexene. The behaviour of C(60) in ethyl oleate has been compared with that of the known antioxidant TMPPD (N,N',N,N,'-tetramethyl-p-phenylenediamine) in ethyl oleate. The mechanism of the antioxidant action of C(60) in lipids has been proposed. The kinetics of C(60) oxidation in lipids was determined spectrophotometrically both at room temperature in the dark and under UV irradiation. The oxidized products derived from C(60) photo-oxidation in lipids have been identified. PMID:20338159

Cataldo, Franco

2010-06-01

173

Structural investigation of keV Ar-ion-induced surface ripples in Si by cross-sectional transmission electron microscopy  

E-print Network

O2, Ge, and GaAs, though rippling has been been observed recently in metals Ag and Cu as well.4 Amorphization of Si Refs. 15,16 by heavy ion such as Ar bombardment at keV energies occurs in a dose range 1014 have to be the same everywhere. This is a very relevant question be- cause quite recently ion-enhanced

Nordlund, Kai

174

Enhancing fullerene-based solar cell lifetimes by addition of a fullerene dumbbell.  

PubMed

Cost-effective, solution-processable organic photovoltaics (OPV) present an interesting alternative to inorganic silicon-based solar cells. However, one of the major remaining challenges of OPV devices is their lack of long-term operational stability, especially at elevated temperatures. The synthesis of a fullerene dumbbell and its use as an additive in the active layer of a PCDTBT:PCBM-based OPV device is reported. The addition of only 20?% of this novel fullerene not only leads to improved device efficiencies, but more importantly also to a dramatic increase in morphological stability under simulated operating conditions. Dynamic secondary ion mass spectrometry (DSIMS) and TEM are used, amongst other techniques, to elucidate the origins of the improved morphological stability. PMID:25264304

Schroeder, Bob C; Li, Zhe; Brady, Michael A; Faria, Gregório Couto; Ashraf, Raja Shahid; Takacs, Christopher J; Cowart, John S; Duong, Duc T; Chiu, Kar Ho; Tan, Ching-Hong; Cabral, João T; Salleo, Alberto; Chabinyc, Michael L; Durrant, James R; McCulloch, Iain

2014-11-17

175

Evolution of SiC Nanocluster from Carbon Fullerene: A Density Functional Theoretic Study  

SciTech Connect

Stability of SiC fullerene type structures is still an unsolved issue as no experimental confirmation has been reported so far regarding its existence. However, theoretical reports are available in the literature where carbon fullerenes were taken as base models for SiC fullerene structures. In this present Letter we show by a systematic study on the C{sub 20} fullerene that this approach may not always produce the ground state structure in fullerene form. Instead, the energetically favorable structure could be highly distorted and open structure. However, we observed a very systematic linear trend in the evolution of binding energies of SiC clusters from the carbon fullerene.

Huda, M. N.; Ray, A. K.

2008-01-01

176

Simple and Onion-type Fullerenes shells as resonators and amplifiers  

E-print Network

We discuss the influence of a single or double fullerenes shell upon photoionization and vacancy decay of an atom, stuffed inside the fullerenes construction. The main manifestations of this influence are additional structures in the photoionization cross-section and variation of the vacancy decay probability. The main mechanisms, with which fullerenes shells affect the processes in caged atoms is the scattering of the outgoing electrons by the fullerenes shell and modification of the photon beam due to fullerenes shell polarization. General consideration will be illustrated by numeric calculations where C60 and C240 will be chosen as fullerenes and Ar and Xe as caged atoms.

Amusia, M Ya

2009-01-01

177

High Resolution Laboratory Spectroscopy of Fullerenes in Support of SOFIA  

NASA Astrophysics Data System (ADS)

Our objective is to obtain the first high-resolution (rotationally-resolved) absorption rotation- vibration spectrum of gas phase C60 and C70 in the mid infrared. The gas phase fullerenes will be prepared at low temperature using a supersonic expansion of a supercritical fluid (mixture of CO2 and toluene) containing dissolved fullerenes. The samples will be probed using a widely tunable but narrow linewidth external-cavity quantum cascade laser, along with the high sensitivity technique of high-repetition-rate cavity ringdown spectroscopy. This work is intended to support (and, indeed, enable) spectroscopy of interstellar fullerenes using the EXES high-resolution spectrometer on SOFIA. While interstellar fullerenes have been widely reported in emission through low-resolution spectroscopy with Spitzer, high-resolution absorption spectroscopy with EXES/SOFIA would provide more detailed information about their column density and excitation. This, in turn, would provide important insight into the production of these large carbonaceous molecules.

McCall, Benjamin

178

Real Time Microscopy, Kinetics, and Mechanism of Giant Fullerene Evaporation  

NASA Astrophysics Data System (ADS)

We report in situ high-resolution transmission electron microscopy observing the shrinkage of single-layer giant fullerenes (GF). At temperatures ˜2000°C, the GF volume reduces by greater than one 100-fold while the fullerene shell remains intact, evolving from a slightly polygonized to a nearly spherical shape with a smaller diameter. The number of carbon atoms in the GF decreases linearly with time until the small subbuckyball cage opens and rapidly disappears. Theoretical modeling indicates that carbon atoms are removed predominantly from the weakest binding energy sites, i.e., the pentagons, leading to the constant evaporation rate. The fullerene cage integrity is attributed to the collective behavior of interacting defects. These results constitute the first experimental evidence for the “shrink-wrapping” and “hot-giant” fullerene formation mechanisms.

Huang, J. Y.; Ding, Feng; Jiao, Kun; Yakobson, Boris I.

2007-10-01

179

Nanotribological performance of fullerene-like carbon nitride films  

NASA Astrophysics Data System (ADS)

Fullerene-like carbon nitride films exhibit high elastic modulus and low friction coefficient. In this study, thin CNx films were deposited on silicon substrate by DC magnetron sputtering and the tribological behavior at nanoscale was evaluated using an atomic force microscope. Results show that CNx films with fullerene-like structure have a friction coefficient (CoF ? 0.009-0.022) that is lower than amorphous CNx films (CoF ? 0.028-0.032). Analysis of specimens characterized by X-ray photoelectron spectroscopy shows that films with fullerene-like structure have a higher number of sp3 CN bonds and exhibit the best mechanical properties with high values of elastic modulus (E > 180 GPa) and hardness (H > 20 GPa). The elastic recovery determined on specimens with a fullerene-like CNx structure was of 95% while specimens of amorphous CNx structure had only 75% elastic recovery.

Flores-Ruiz, Francisco Javier; Enriquez-Flores, Christian Ivan; Chiñas-Castillo, Fernando; Espinoza-Beltrán, Francisco Javier

2014-09-01

180

Production and Consumption of Reactive Oxygen Species by Fullerenes  

EPA Science Inventory

Reactive oxygen species (ROS) are one of the most important intermediates in chemical, photochemical, and biological processes. To understand the environmental exposure and toxicity of fullerenes better, the production and consumption of ROS (singlet oxygen, superoxide, hydrogen ...

181

Polynuclear aromatic hydrocarbons for fullerene synthesis in flames  

DOEpatents

This invention provides improved methods for combustion synthesis of carbon nanomaterials, including fullerenes, employing multiple-ring aromatic hydrocarbon fuels selected for high carbon conversion to extractable fullerenes. The multiple-ring aromatic hydrocarbon fuels include those that contain polynuclear aromatic hydrocarbons. More specifically, multiple-ring aromatic hydrocarbon fuels contain a substantial amount of indene, methylnapthalenes or mixtures thereof. Coal tar and petroleum distillate fractions provide low cost hydrocarbon fuels containing polynuclear aromatic hydrocarbons, including without limitation, indene, methylnapthalenes or mixtures thereof.

Alford, J. Michael; Diener, Michael D.

2006-12-19

182

Icosadeltahedral geometry of fullerenes, viruses and geodesic domes  

E-print Network

I discuss the symmetry of fullerenes, viruses and geodesic domes within a unified framework of icosadeltahedral representation of these objects. The icosadeltahedral symmetry is explained in details by examination of all of these structures. Using Euler's theorem on polyhedra, it is shown how to calculate the number of vertices, edges, and faces in domes, and number of atoms, bonds and pentagonal and hexagonal rings in fullerenes. Caspar-Klug classification of viruses is elaborated as a specific case of icosadeltahedral geometry.

Antonio Siber

2007-11-22

183

Cytoprotective activities of water-soluble fullerenes in zebrafish models  

Microsoft Academic Search

Using zebrafish (Danio rerio) embryos as a model system, we compared the antioxidant and cytoprotective effects of a series of new water-soluble fullerenes 1–12. Since zebrafish embryos are transparent during the first week of life, the effects of fullerenes on multiple organ systems, including CNS, PNS, and heart, could be assessed in situ. Both positively charged and negatively charged water-soluble

Florian Beuerle; Patrick Witte; Uwe Hartnagel; Russell Lebovitz; Chuenlei Parng; Andreas Hirsch

2007-01-01

184

Is low-energy-ion bombardment generated X-ray emission a secondary mutational source to ion-beam-induced genetic mutation?  

NASA Astrophysics Data System (ADS)

Low-energy ion beam biotechnology has achieved tremendous successes in inducing crop mutation and gene transfer. However, mechanisms involved in the related processes are not yet well understood. In ion-beam-induced mutation, ion-bombardment-produced X-ray has been proposed to be one of the secondary mutation sources, but the speculation has not yet been experimentally tested. We carried out this investigation to test whether the low-energy ion-beam-produced X-ray was a source of ion-beam-induced mutation. In the investigation, X-ray emission from 29-keV nitrogen- or argon- ion beam bombarded bacterial Escherichia coli (E. coli) cells held in a metal or plastic sample holder was in situ detected using a highly sensitive X-ray detector. The ion beam bombarded bacterial cells held in different material holders were observed for mutation induction. The results led to a conclusion that secondary X-ray emitted from ion-beam-bombarded biological living materials themselves was not a, or at least a negligible, mutational source, but the ion-beam-induced X-ray emission from the metal that made the sample holder could be a source of mutation.

Thongkumkoon, P.; Prakrajang, K.; Thopan, P.; Yaopromsiri, C.; Suwannakachorn, D.; Yu, L. D.

2013-07-01

185

Photodynamic therapy with fullerenes in vivo: reality or a dream?  

PubMed Central

Photodynamic therapy (PDT) employs the combination of nontoxic photosensitizers and visible light that is absorbed by the chromophore to produce long-lived triplet states that can carry out photochemistry in the presence of oxygen to kill cells. The closed carbon-cage structure found in fullerenes can act as a photosensitizer, especially when functionalized to impart water solubility. Although there are reports of the use of fullerenes to carry out light-mediated destruction of viruses, microorganisms and cancer cells in vitro, the use of fullerenes to mediate PDT of diseases such as cancer and infections in animal models is less well developed. It has recently been shown that fullerene PDT can be used to save the life of mice with wounds infected with pathogenic Gram-negative bacteria. Fullerene PDT has also been used to treat mouse models of various cancers including disseminated metastatic cancer in the peritoneal cavity. In vivo PDT with fullerenes represents a new application in nanomedicine. PMID:22122587

Sharma, Sulbha K; Chiang, Long Y; Hamblin, Michael R

2012-01-01

186

Persistent homology for the quantitative prediction of fullerene stability.  

PubMed

Persistent homology is a relatively new tool often used for qualitative analysis of intrinsic topological features in images and data originated from scientific and engineering applications. In this article, we report novel quantitative predictions of the energy and stability of fullerene molecules, the very first attempt in using persistent homology in this context. The ground-state structures of a series of small fullerene molecules are first investigated with the standard Vietoris-Rips complex. We decipher all the barcodes, including both short-lived local bars and long-lived global bars arising from topological invariants, and associate them with fullerene structural details. Using accumulated bar lengths, we build quantitative models to correlate local and global Betti-2 bars, respectively with the heat of formation and total curvature energies of fullerenes. It is found that the heat of formation energy is related to the local hexagonal cavities of small fullerenes, while the total curvature energies of fullerene isomers are associated with their sphericities, which are measured by the lengths of their long-lived Betti-2 bars. Excellent correlation coefficients (>0.94) between persistent homology predictions and those of quantum or curvature analysis have been observed. A correlation matrix based filtration is introduced to further verify our findings. © 2014 Wiley Periodicals, Inc. PMID:25523342

Xia, Kelin; Feng, Xin; Tong, Yiying; Wei, Guo Wei

2015-03-01

187

Histopathology of fathead minnow (Pimephales promelas) exposed to hydroxylated fullerenes.  

PubMed

Hydroxylated fullerenes are reported to be very strong antioxidants, acting to quench reactive oxygen species, thus having strong potential for important and widespread applications in innovative therapies for a variety of disease processes. However, their potential for toxicological side effects is still largely controversial and unknown. Effects of hydroxylated fullerenes C60(OH)24 on the fathead minnow (Pimephales promelas) were investigated microscopically after a 72-hour (acute) exposure by intraperitoneal injection of 20 ppm of hydroxylated fullerenes per gram of body mass. Cumulative, semi-quantitative histopathologic evaluation of brain, liver, anterior kidney, posterior kidney, skin, coelom, gills and the vestibuloauditory system revealed significant differences between control and hydroxylated fullerene-treated fish. Fullerene-treated fish had much higher cumulative histopathology scores. Histopathologic changes included loss of cellularity in the interstitium of the kidney, a primary site of haematopoiesis in fish, and loss of intracytoplasmic glycogen in liver. In the coelom, variable numbers of leukocytes, including many macrophages and fewer heterophils and rodlet cells, were admixed with the nanomaterial. These findings raise concern about in vivo administration of hydroxylated fullerenes in experimental drugs and procedures in human medicine, and should be investigated in more detail. PMID:23883179

Jovanovi?, Boris; Whitley, Elizabeth M; Pali?, Dušan

2014-11-01

188

M Sub-Shell Cross Sections For 75-300 keV Proton Impact On W, Pt And Pb  

SciTech Connect

M sub-shell x-ray production cross sections from 75-300 keV proton bombardment of thick elemental targets of W, Pt, and Pb were measured and compared with ECPSSR and relativistic RPWBA-BC cross sections using different data bases of fluorescence yields, Coster-Kronig factors, and x-ray transition rates. With a few exceptions, the differences between the various data base comparisons were not significant. For different sub-shells, either ECPSSR or RPWBA-BC compared better with the measurements. In all cases, agreement with theory improved as the collision energy increased.

Cipolla, Sam J. [Physics Department, Creighton University, Omaha, NE 68178 (United States)

2011-06-01

189

Fullerenes, fulleranes and the diffuse interstellar bands  

NASA Astrophysics Data System (ADS)

A theory is described in which the diffuse interstellar bands and the far-ultraviolet extinction are both carried by the recently discovered quasi-spherical carbon shell molecules known as the fullerenes, and by their hydrides, the fulleranes. The central theme is hydrogenation: hydrogen atoms covalently bonded to the surface of a fullerane change the structure of the pi-electron system and thereby modify the optical properties, determining not only the diffuse band spectrum of the molecule but also the ultraviolet cross-section. It is supposed that the physical and chemical environment in the interstellar medium controls the degree of this hydrogenation, so that changes in the environment give rise to spatial changes in the optical and ultraviolet properties of the medium. The theory gives some account of the known tendency of the 4430-A family to be weak both in the diffuse clouds of the interstellar medium and in directions in which the far-ultraviolet extinction is high.

Webster, Adrian

1992-04-01

190

Fullerene Embedded Shape Memory Nanolens Array  

NASA Astrophysics Data System (ADS)

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy. Fullerenes were embedded into the fabricated nanolens array. Beside the energy absorption, such addition enables a remarkable enhancement in mechanical properties of shape memory polymer. The shape memory nanolens was numerically modeled to impart more in-depth understanding on the physics regarding shape recovery behavior of the fabricated nanolens. We anticipate that our strategy of combining the shape memory property with the microwave irradiation feature can provide a new pathway for nanostructured systems able to ensure a long-term durability.

Jeon, Sohee; Jang, Jun Young; Youn, Jae Ryoun; Jeong, Jun-Ho; Brenner, Howard; Song, Young Seok

2013-11-01

191

Fullerene embedded shape memory nanolens array.  

PubMed

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy. Fullerenes were embedded into the fabricated nanolens array. Beside the energy absorption, such addition enables a remarkable enhancement in mechanical properties of shape memory polymer. The shape memory nanolens was numerically modeled to impart more in-depth understanding on the physics regarding shape recovery behavior of the fabricated nanolens. We anticipate that our strategy of combining the shape memory property with the microwave irradiation feature can provide a new pathway for nanostructured systems able to ensure a long-term durability. PMID:24253423

Jeon, Sohee; Jang, Jun Young; Youn, Jae Ryoun; Jeong, Jun-Ho; Brenner, Howard; Song, Young Seok

2013-01-01

192

Fullerene Embedded Shape Memory Nanolens Array  

PubMed Central

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy. Fullerenes were embedded into the fabricated nanolens array. Beside the energy absorption, such addition enables a remarkable enhancement in mechanical properties of shape memory polymer. The shape memory nanolens was numerically modeled to impart more in-depth understanding on the physics regarding shape recovery behavior of the fabricated nanolens. We anticipate that our strategy of combining the shape memory property with the microwave irradiation feature can provide a new pathway for nanostructured systems able to ensure a long-term durability. PMID:24253423

Jeon, Sohee; Jang, Jun Young; Youn, Jae Ryoun; Jeong, Jun-ho; Brenner, Howard; Song, Young Seok

2013-01-01

193

Changes in Agglomeration of Fullerenes During Ingestion and Excretion in Thamnocephalus Platuyrus  

EPA Science Inventory

The crustacean Thamnocephalus platyurus was exposed to aqueous suspensions of fullerenes C60 and C70. Aqueous fullerene suspensions were formed by stirring C60 and C70 as received from a commercial vendor in deionized water (term...

194

Size-exclusive Nanosensor for Quantitative Analysis of Fullerene C60: A Concept Paper  

EPA Science Inventory

This paper presents the first development of a mass-sensitive nanosensor for the isolation and quantitative analyses of engineered fullerene (C60) nanoparticles, while excluding mixtures of structurally similar fullerenes. Amino-modified beta cyclodextrin (ß-CD-NH...

195

Photophysical Properties and Singlet Oxygen Generation Efficiencies of Water-Soluble Fullerene Nanoparticles  

PubMed Central

As various fullerene derivatives have been developed, it is necessary to explore their photophysical properties for potential use in photoelectronics and medicine. Here, we address the photophysical properties of newly synthesized water-soluble fullerene-based nanoparticles and polyhydroxylated fullerene as a representative water-soluble fullerene derivative. They show broad emission band arising from a wide-range of excitation energies. It is attributed to the optical transitions from disorder-induced states, which decay in the nanosecond time range. We determine the kinetic properties of the singlet oxygen (1O2) luminescence generated by the fullerene nanoparticles and polyhydroxylated fullerene to consider the potential as photodynamic agents. Triplet state decay of the nanoparticles was longer than 1O2 lifetime in water. Singlet oxygen quantum yield of a series of the fullerene nanoparticles is comparably higher ranging from 0.15 to 0.2 than that of polyhydroxylated fullerene, which is about 0.06. PMID:24893622

Stasheuski, Alexander S; Galievsky, Victor A; Stupak, Alexander P; Dzhagarov, Boris M; Choi, Mi Jin; Chung, Bong Hyun; Jeong, Jin Young

2014-01-01

196

Adsorption and thermal desorption of hollow and endohedral fullerenes on a free crystal surface  

NASA Astrophysics Data System (ADS)

A statistical theory of processes of adsorption and desorption of fullerenes on a crystal surface has been elaborated. The equilibrium concentration of a fullerene monolayer on a crystal and its temperature dependence have been estimated. Some regularities of adsorption and desorption processes have been studied. It has been found that they are determined by the temperature and the character of interaction between the fullerene molecules and between the fullerene molecules and metal atoms. The results of calculations have been compared with experimental data.

Matysina, Z. A.; Zaginaichenko, S. Yu.; Shchur, D. V.; Mil'to, O. V.

2008-03-01

197

Measurements of Neutron Capture Cross Sections for Gd Isotopes in the Energy Region from 10 keV to 90 keV  

NASA Astrophysics Data System (ADS)

The neutron capture cross sections of Gd isotopes (155Gd, 156Gd, 157Gd, and 158Gd) have been measured in the neutron energy range from 10 to 90 keV using the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology. Pulsed keV neutrons were produced from the 7Li(p,n)7Be reaction by bombarding the lithium target with the 1.5-ns bunched proton beam from the Pelletron accelerator. The incident neutron spectrum on a capture sample was measured by means of a TOF method with a 6Li-glass detector. Capture ?-rays were detected with a large anti-Compton NaI(Tl) spectrometer, employing a TOF method. A pulse-height weighting technique was applied to observed capture ?-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained by using the standard capture cross sections of 197Au. The present results were compared with the previous measurements and the evaluated values of ENDF/B-VI.

Kim, G. N.; Chung, W. C.; Ro, T. I.; Ohsaki, T.; Igashira, M.

2006-03-01

198

The study of dielectric properties of the endohedral fullerenes  

NASA Astrophysics Data System (ADS)

Dielectric response of the metal nitride fullerenes is studied using the density functional theory at the all-electron level using generalized gradient approximation. The dielectric response is studied by computing the static dipole polarizabilities using the finite field method, i.e. by numerically differentiating the dipole moments with respect to electric field. The endohedral fullerenes studied in this work are Sc3N C68(6140), Sc3N C68(6146), Sc3N C70(7854), Sc3N C70(7960), Sc3N C76(17490), Sc3N C78(22010), Sc3N C80(31923), Sc3N C80(31924), Sc3N C82(39663), Sc3N C90(43), Sc3N C90(44), Sc3N C92(85), Sc3N C94(121), Sc3N C96(186), Sc3N C98(166). Using the Voronoi and Hirschfield approaches as implemented in our NRLMOL code, we determine the atomic contributions to the total polarizability. The site-specific contributions to the polarizability of endohedral fullerenes allowed us to determine the polarizability of two subsystems: the fullerene shell and the encapsulated Sc3N unit. Our results showed that the contributions to the total polarizability from the encapsulated Sc3N units are vanishingly small. Thus, the total polarizability of the endohedral fullerene is almost entirely due to the outer fullerene shell. These fullerenes are excellent molecular models of a Faraday cage.

Bhusal, Shusil

199

Effects of Jupiter's formation and migration: the Jovian Early Bombardment  

NASA Astrophysics Data System (ADS)

The first phase in the lifetime of the Solar System is that of the Solar Nebula, when the Solar System is constituted by a circumsolar disk of gas and dust particles where planetesimals and planetary embryos are forming. The giant planets should have formed during this phase, since the nebular gas represents the source material for their gaseous envelopes. Here we report the results of our investigation of the effects of Jupiter's formation on the planetesimals populating the Solar Nebula using Vesta and Ceres as case studies. Our results show that the formation of Jupiter triggered a brief yet intense phase of bombardment, which we called the Jovian Early Bombardment and whose intensity varies with the extent and the timescale of Jupiter's migration. The data that the Dawn mission will supply on Vesta and Ceres will allow us to test the Jovian Early Bombardment hypothesis and possibly gather information on the formation and the early dynamical evolution of Jupiter.

Turrini, D.; Coradini, A.; Magni, G.

2011-10-01

200

Ni-Catalyzed direct 1,4-difunctionalization of [60]fullerene with benzyl bromides.  

PubMed

A new Ni-catalyzed direct 1,4-difunctionalization of [60]fullerene with various benzyl bromides has been developed. The use of a DMSO additive combined with a nickel catalyst is indispensable for the formation of 1,4-dibenzyl fullerenes with a variety of functional groups. The reaction proceeds through the formation of a fullerene monoradical species. PMID:25765232

Si, Weili; Zhang, Xuan; Asao, Naoki; Yamamoto, Yoshinori; Jin, Tienan

2015-03-26

201

Molecular design, study of the structures and properties of ionic fullerene compounds  

Microsoft Academic Search

The results of studies devoted to ionic compounds of fullerenes, which are of interest for the design of new materials with promising physical properties, are analyzed. The preparation methods of these compounds and their electrophysical, magnetic and optical properties, and the molecular and electronic structures of monomeric, dimeric and polymeric fullerene anions are considered. The results of investigations of fullerenes

Dmitry V Konarev; Rimma N Lyubovskaya

2012-01-01

202

Analytical description of the sputtering yields of silicon bombarded with normally incident ions  

NASA Astrophysics Data System (ADS)

Experimentally determined sputtering yields of silicon bombarded with normally incident ions were analyzed with the aim of deriving a complete analytical description of the data. The yields, covering a wide range of energies (from 50 eV to 540 keV) and primary ions of vastly different mass (from H to Xe), can be described in universal form using (i) two energy-dependent functions, the reduced nuclear stopping cross section sn and Bohdansky’s threshold function ?, (ii) a modified form of Sigmund’s ? function, only dependent on the mass ratio of projectile and target atoms, and (iii) a constant calibration factor x0N/Es, where x0 is the effective mean escape depth of sputtered atoms, N the number density of Si atoms, and Es an effective surface binding energy. Considering the fact that according to computer simulations the mean escape depth increases significantly with increasing projectile energy, the observed constancy of x0N/Es requires the assumption that Es is not a constant but contains two terms, the “true” surface binding energy Es and an additional energy-dependent term presumably reflecting the fraction of deposited energy that is lost in inelastic processes as well as in creating phonons and damage. There are indications that the sputtering yields reported for H and D bombardment as well as for heavy-ion impact at very low energies are too small by factors up to about 2, presumably due to oxygen incorporation and/or growth of surface contamination layers under nonideal vacuum conditions.

Wittmaack, Klaus

2003-12-01

203

Modification of poly(methyl methacrylate) by keV Ar deposition  

NASA Astrophysics Data System (ADS)

Classical molecular dynamics simulations are used to examine 1 keV Ar atom bombardment on the surface of poly(methyl methacrylate) (PMMA), which induces sputtering and chemical modifications to the surface. The simulations are carried out at various surface temperatures that range from 200 to 600 K. The results indicate that different fragments of PMMA, as characterized by their mass, are preferentially sputtered from the surface at the various temperatures considered. In addition, the simulations predict that small fragments are produced by the high energy deposition process. However, larger sized fragments are generated when the surface temperature is close to the glass transition temperature of PMMA. The atomic-scale processes by which these occur are elucidated by the simulations.

Su, Ya-Ting; Shan, Tzu-Ray; Sinnott, Susan B.

2009-08-01

204

Mechanisms of O2 sputtering from water ice by keV ions  

NASA Astrophysics Data System (ADS)

We have conducted experiments on the sputtering of water ice by 100 keV Ar+ between 20 and 150 K. Our findings indicate that the temperature dependence of the total sputtering yield is heavily influenced by the thermal and irradiation history of the ice, showing a complex dependence on irradiation fluence that is correlated to the ejection of O2 molecules. The results suggest that O2 produced by the ions inside the ice diffuses to the surface where it is trapped and then ejected via sputtering or thermal desorption. A high concentration of O2 can trap in a subsurface layer during bombardment at 130 K, which we relate to the formation of hydrogen and its escape from that region. A simple model allows us to determine the depth profile of the absolute concentration of O2 trapped in the ice.

Teolis, B. D.; Vidal, R. A.; Shi, J.; Baragiola, R. A.

2005-12-01

205

Electron bombardment propulsion system characteristics for large space systems  

NASA Technical Reports Server (NTRS)

The results of an anlaysis of electron bombardment ion propulsion systems for use in the transportation and on-orbit operations of large space systems are presented. Using baseline technology from the ongoing primary propulsion program and other sources, preliminary estimates of the expected characteristics of key system elements such as thrusters and propellant storage systems were performed. Projections of expected thruster performance on argon are presented based on identified constraints which limit the achievable thrust and/or power density of bombardment thrusters. System characteristics are then evaluated as a function of thruster diameter and specific impulse.

Byers, D. C.; Rawlin, V. K.

1976-01-01

206

On the 17-keV neutrino  

SciTech Connect

A brief review on the status of the 17-keV neutrino is presented. Several different experiments found spectral distortions which were consistently interpreted as evidence for a heavy neutrino admixture in {beta} decay. Recent experiments, however, rule out the existence of a 17-keV neutrino as well as escaping criticisms of earlier null results. Moreover, the majority of positive results have been reinterpreted in terms of instrumental effects, despite the need for a different explanation in each case. Anomalies persist in the low energy region of the tritium spectrum which deserve further investigation.

Hime, A.

1993-04-01

207

On the 17-keV neutrino  

SciTech Connect

A brief review on the status of the 17-keV neutrino is presented. Several different experiments found spectral distortions which were consistently interpreted as evidence for a heavy neutrino admixture in [beta] decay. Recent experiments, however, rule out the existence of a 17-keV neutrino as well as escaping criticisms of earlier null results. Moreover, the majority of positive results have been reinterpreted in terms of instrumental effects, despite the need for a different explanation in each case. Anomalies persist in the low energy region of the tritium spectrum which deserve further investigation.

Hime, A.

1993-04-01

208

Extremal fullerene graphs with the maximum Clar number  

E-print Network

A fullerene graph is a cubic 3-connected plane graph with (exactly 12) pentagonal faces and hexagonal faces. Let $F_n$ be a fullerene graph with $n$ vertices. A set $\\mathcal H$ of mutually disjoint hexagons of $F_n$ is a sextet pattern if $F_n$ has a perfect matching which alternates on and off each hexagon in $\\mathcal H$. The maximum cardinality of sextet patterns of $F_n$ is the Clar number of $F_n$. It was shown that the Clar number is no more than $\\lfloor \\frac {n-12} 6\\rfloor$. Many fullerenes with experimental evidence attain the upper bound, for instance, $\\text{C}_{60}$ and $\\text{C}_{70}$. In this paper, we characterize extremal fullerene graphs whose Clar numbers equal $\\frac{n-12} 6$. By the characterization, we show that there are precisely 18 fullerene graphs with 60 vertices, including $\\text{C}_{60}$, achieving the maximum Clar number 8, which are all constructed.

Ye, Dong

2008-01-01

209

The Jovian Early Bombardment and the Primordial Evolution of Vesta and the Asteroid Belt  

NASA Astrophysics Data System (ADS)

The formation and migration of Jupiter in the Solar Nebula triggered a short but violent phase of primordial bombardment. Here we show the implications of this Jovian Early Bombardment for the collisional evolution of the asteroid belt and of Vesta.

Turrini, D.; Coradini, A.; Magni, G.

2012-05-01

210

Liposome Formulation of Fullerene-Based Molecular Diagnostic and Therapeutic Agents  

PubMed Central

Fullerene medicine is a new but rapidly growing research subject. Fullerene has a number of desired structural, physical and chemical properties to be adapted for biological use including antioxidants, anti-aging, anti-inflammation, photodynamic therapy, drug delivery, and magnetic resonance imaging contrast agents. Chemical functionalization of fullerenes has led to several interesting compounds with very promising preclinical efficacy, pharmacokinetic and safety data. However, there is no clinical evaluation or human use except in fullerene-based cosmetic products for human skincare. This article summarizes recent advances in liposome formulation of fullerenes for the use in therapeutics and molecular imaging. PMID:24300561

Zhou, Zhiguo

2013-01-01

211

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source  

E-print Network

A synthesis technology of endohedral fullerenes such as Fe@C60 has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C60 was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Asaji, T; Uchida, T; Minezaki, H; Ishihara, S; Racz, R; Muramatsu, M; Biri, S; Kitagawa, A; Kato, Y; Yoshida, Y

2015-01-01

212

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source  

SciTech Connect

A synthesis technology of endohedral fullerenes such as Fe@C{sub 60} has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C{sub 60} was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Asaji, T., E-mail: asaji@oshima-k.ac.jp; Ohba, T. [Oshima National College of Maritime Technology, 1091-1 Komatsu, Suo-oshima, Oshima, Yamaguchi 742-2193 (Japan)] [Oshima National College of Maritime Technology, 1091-1 Komatsu, Suo-oshima, Oshima, Yamaguchi 742-2193 (Japan); Uchida, T.; Yoshida, Y. [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)] [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan); Minezaki, H.; Ishihara, S. [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)] [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan); Racz, R.; Biri, S. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem Tér 18/c (Hungary)] [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem Tér 18/c (Hungary); Muramatsu, M.; Kitagawa, A. [National Institute of Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)] [National Institute of Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Kato, Y. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)] [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2014-02-15

213

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source  

NASA Astrophysics Data System (ADS)

A synthesis technology of endohedral fullerenes such as Fe@C60 has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C60 was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Asaji, T.; Ohba, T.; Uchida, T.; Minezaki, H.; Ishihara, S.; Racz, R.; Muramatsu, M.; Biri, S.; Kitagawa, A.; Kato, Y.; Yoshida, Y.

2014-02-01

214

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, 20 May 1943 - 5 March 1944  

E-print Network

42nd Bombardment Squadron (H) Missions: 20 May 1943 ? 5 March 1944. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943 - ) Air Force Historical... Association, IRIS No. 44028. Mission Reports, 18 July 1942 ? 10 August 1943. This copy of the missions of the 42 nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air...

United States Army Air Corps

1946-01-01

215

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, April 1945 - November 1945  

E-print Network

42nd Bombardment Squadron (H) Monthly Squadron Histories and Documents April 1945 ? November 1945. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943... - ) Air Force Historical Association, IRIS No. 44028. This copy of the missions of the 42nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force Historical...

United States Army Air Corps

1946-01-01

216

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, April 1944 - November 1944  

E-print Network

42nd Bombardment Squadron (H) Monthly Squadron Histories April 1944 ? November 1944. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943... - ) Air Force Historical Association, IRIS No. 44028. This copy of the missions of the 42 nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force Historical...

United States Army Air Corps

1946-01-01

217

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, February 1944 - March 1945  

E-print Network

42nd Bombardment Squadron (H) Monthly Squadron Histories and Documents February 1944 ? March 1945. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943... - ) Air Force Historical Association, IRIS No. 44028. This copy of the missions of the 42nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force Historical...

United States Army Air Corps

1946-01-01

218

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, 18 July 1942- 7 February 1943  

E-print Network

42nd Bombardment Squadron (H) Missions: 18 July 1942 ? 7 February 1943. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943 - ) Air Force Historical... Association, IRIS No. 44028. Mission Reports, 18 July 1942 ? 10 August 1943. This copy of the missions of the 42nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from...

United States Army Air Corps

1946-01-01

219

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, 5 March 1944 - 18 August 1944  

E-print Network

42nd Bombardment Squadron (H) Missions: 5 March 1944 ? 18 August 1944. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943 - ) Air Force... Historical Association, IRIS No. 44028. This copy of the missions of the 42 nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force Historical Association, Maxwell...

United States Army Air Corps

1946-01-01

220

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, December 1944 - January 1945  

E-print Network

42nd Bombardment Squadron (H) Monthly Squadron Histories and Documents December 1944 ? January 1945. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943... - ) Air Force Historical Association, IRIS No. 44028. This copy of the missions of the 42 nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force Historical...

United States Army Air Corps

1946-01-01

221

42nd Bombardment Squadron (Heavy). Monthly Squadron Histories and Documents, 1 May 1946 - 31 July 1946  

E-print Network

42nd Bombardment Squadron (H) Monthly Squadron Histories and Documents 1 May 1946 ? 31 July 1946. 42nd Bombardment Squadron (H), 11th Bombardment Group (H), 7th Air Force (1941-January 1943); 13th Air Force (January 1943... - ) Air Force Historical Association, IRIS No. 44028. This copy of the missions of the 42 nd Bombardment Squadron was digitized from the microfilm copy (Air Force Historical Association, IRIS No. 44028) obtained from the Air Force Historical...

United States Army Air Corps; United States Army Air Corps

1946-01-01

222

Stability of carbonaceous dust analogues and glycine under UV irradiation and electron bombardment.  

PubMed

The effect of UV photon (120-200 nm) and electron (2 keV) irradiation of analogues of interstellar carbonaceous dust and of glycine were investigated by means of IR spectroscopy. Films of hydrogenated amorphous carbon (HAC), taken as dust analogues, were found to be stable under UV photon and electron bombardment. High fluences of photons and electrons, of the order of 10(19) cm(-2), were needed for a film depletion of a few percent. UV photons were energetically more effective than electrons for depletion and led to a certain dehydrogenation of the HAC samples, whereas electrons led seemingly to a gradual erosion with no appreciable changes in the hydrocarbon structure. The rates of change observed may be relevant over the lifetime of a diffuse cloud, but cannot account for the rapid changes in hydrocarbon IR bands during the evolution of some proto-planetary nebulae. Glycine samples under the same photon and electron fluxes decay at a much faster rate, but tend usually to an equilibrium value different from zero, especially at low temperatures. Reversible reactions re-forming glycine, or the build-up of less transparent products, could explain this behavior. CO2 and methylamine were identified as UV photoproducts. Electron irradiation led to a gradual disappearance of the glycine layers, also with formation of CO2. No other reaction products were clearly identified. The thicker glycine layers (a few hundred nm) were not wholly depleted, but a film of the order of the electron penetration depth (80 nm), was totally destroyed with an electron fluence of -1 x 10(18) cm(-2). A 60 nm ice layer on top of glycine provided only partial shielding from the 2 keV electrons. From an energetic point of view, 2 keV electrons are less efficient than UV photons and, according to literature data, much less efficient than MeV protons for the destruction of glycine. The use of keV electrons to simulate effects of cosmic rays on analogues of interstellar grains should be taken with care, due to the low penetration depths of electrons in many samples of interest. PMID:25302385

Maté, Belén; Tanarro, Isabel; Moreno, Miguel A; Jiménez-Redondo, Miguel; Escribano, Rafael; Herrero, Víctor J

2014-01-01

223

Jovian Early Bombardment: Planetesimal Erosion in the Inner Asteroid Belt  

NASA Astrophysics Data System (ADS)

The asteroid belt is an open window on the history of the solar system, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions (SFDs). In this work, we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depends on the SFD of the primordial planetesimals. If the asteroid belt was dominated by planetesimals less than 100 km in diameter, the primordial bombardment would have caused the erosion of bodies smaller than 200 km in diameter. If the asteroid belt was instead dominated by larger planetesimals, the bombardment would have resulted in the destruction of bodies as big as 500 km.

Turrini, D.; Coradini, A.; Magni, G.

2012-05-01

224

JOVIAN EARLY BOMBARDMENT: PLANETESIMAL EROSION IN THE INNER ASTEROID BELT  

SciTech Connect

The asteroid belt is an open window on the history of the solar system, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions (SFDs). In this work, we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depends on the SFD of the primordial planetesimals. If the asteroid belt was dominated by planetesimals less than 100 km in diameter, the primordial bombardment would have caused the erosion of bodies smaller than 200 km in diameter. If the asteroid belt was instead dominated by larger planetesimals, the bombardment would have resulted in the destruction of bodies as big as 500 km.

Turrini, D.; Coradini, A.; Magni, G., E-mail: diego.turrini@ifsi-roma.inaf.it [Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100, 00133, Rome (Italy)

2012-05-01

225

Bombardment-diffused coatings and ion beam mixing  

Microsoft Academic Search

It has been known for some years that ion bombardment of a material will bring about a redistribution of its constituents. This can take place by a direct recoil process or as a result of collisional relocation within the collision cascade, known as cascade mixing. Alternatively, there are several mechanisms of radiation enhanced diffusion which may occur if the temperature

G. Dearnaley

1982-01-01

226

The Terrestrial Record of an Extended Late Heavy Bombardment  

NASA Astrophysics Data System (ADS)

Terrestrial ejecta layers 3.2–3.5 billion years old record the frequency and effects of large asteroid impacts during late Late Heavy Bombardment. They indicate that the Earth’s surface continued to be battered by large impacts as late as 3.2 Ga.

Lowe, D. R.; Byerly, G. R.

2015-02-01

227

Sputtering due to Coulomb explosion in highly charged ion bombardment  

Microsoft Academic Search

Sputtering processes of silicon in the bombardment of highly charged ions (HCIs) are studied using molecular dynamics simulation. Assuming the potential energy of the HCI transferred to target is stored as the electrostatic energy of Si atoms ionized by the HCI, the Si ions up to 375 are embedded on a Si(100) surface as an initial condition, resulting in Coulomb

M. Terasawa; Z. A. Insepov; T. Sekioka; A. A. Valuev; T. Mitamura

2003-01-01

228

Low energy ion bombardment of metal nanoclusters on graphite  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of 100 eV Ar and Xe ion bombardment of copper clusters, which consisted of 13 and 39 Cu atoms on a (0 0 0 1) graphite surface, have been performed. Energy distributions of backscattered Ar and Xe ions were analyzed. The influence of the cluster size on the Ar and Xe ion energy distributions are discussed.

Kornich, G. V.; Betz, G.; Zaporojtchenko, V.; Pugina, K. V.

2007-02-01

229

The Technique of High Intensity Bombardment with Fast Particles  

Microsoft Academic Search

Recent improvements in cyclotron technique have led, in the case of the 37? cyclotron at the University of California, to the utilization of beams of such intensity that nearly a kilowatt of power must be dissipated in the target. To maintain high operating efficiency it is desirable that targets should be bombarded in elementary form rather than as compounds, and

Franz N. D. Kurie

1939-01-01

230

The formation of cosmic fullerenes from arophatic clusters  

E-print Network

Fullerenes have recently been identified in space and they may play a significant role in the gas and dust budget of various astrophysical objects including planetary nebulae (PNe), reflection nebulae (RNe) and H II regions. The tenuous nature of the gas in these environments precludes the formation of fullerene materials following known vaporization or combustion synthesis routes even on astronomical timescales. We have studied the processing of hydrogenated amorphous carbon (a-C:H or HAC) nano-particles and their specific derivative structures, which we name "arophatics", in the circumstellar environments of young, carbon-rich PNe. We find that UV-irradiation of such particles can result in the formation of fullerenes, consistent with the known physical conditions in PNe and with available timescales.

Micelotta, Elisabetta R; Cami, Jan; Peeters, Els; Bernard-Salas, Jeronimo; Fanchini, Giovanni

2012-01-01

231

Tuning Fullerene Electronic Properties: From Single Molecules to Extended Monolayers  

NASA Astrophysics Data System (ADS)

Fullerenes provide powerful building blocks for creating nanostructures with unique electronic properties due to their flexible electronic structure. This behavior arises through a combination of molecular energy levels, intramolecular Coulomb forces, electron-phonon coupling, and local charging. When molecules are placed at an interface, substrate charge transfer and screening effects also play an important role. We have used cryogenic scanning tunneling spectroscopy to examine the interplay of these factors in determining molecular electronic structure from the single molecule regime all the way up to the full monolayer regime. We find that it is possible to reversibly change the charge state of individual fullerenes through single-atom doping, and we have examined how molecular electronic structure is influenced by extended monolayer formation and surface screening effects. We observe strong variations in local molecular electronic structure due to charge doping, and in local electron-phonon coupling due to fullerene composition.

Crommie, Michael

2005-03-01

232

A search for diffuse bands in fullerene planetary nebulae: evidence of diffuse circumstellar bands  

NASA Astrophysics Data System (ADS)

Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some planetary nebulae (PNe) now enable us to study the DIBs towards fullerene-rich space environments. We search DIBs in the optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC 418). Special attention is given to DIBs which are found to be unusually intense towards these fullerene sources. In particular, an unusually strong 4428 Å absorption feature is a common charateristic of fullerene PNe. Similar to Tc 1, the strongest optical bands of neutral C60 are not detected towards IC 418. Our high-quality (S/N > 300) spectra for PN Tc 1, together with its large radial velocity, permit us to search for the presence of diffuse bands of circumstellar origin, which we refer to as diffuse circumstellar bands (DCBs). We report the first tentative detection of two DCBs at 4428 and 5780 Å in the fullerene-rich circumstellar environment around the PN Tc 1. Laboratory and theoretical studies of fullerenes in their multifarious manifestations (carbon onions, fullerene clusters, or even complex species formed by fullerenes and other molecules like PAHs or metals) may help solve the mystery of some of the diffuse band carriers. Appendix A is available in electronic form at http://www.aanda.org

Díaz-Luis, J. J.; García-Hernández, D. A.; Kameswara Rao, N.; Manchado, A.; Cataldo, F.

2015-01-01

233

Formation and Functionality of Fullerene Fibers  

NASA Astrophysics Data System (ADS)

A method has been found which produces single-walled carbon nanotubes in high yield. These elongated fullerenes are hollow carbon tubes uniformly 1.2 nm in diameter, >20 =B5m in length,=20 constructed of a single hexagonally-bonded graphene sheet wrapped into a cylinder, with hemispherical endcaps involving 6 pentagons. They are produced by laser vaporization of a composite rod of graphite with 1-2 atom percent of a catalyst such as 1:1 Ni/Co, inside a quartz tube at 1200^oC. The yield is greater than 50% of all the carbon vaporized. The nanotubes are found to be aligned to form ropes of 10-100 parallel tubes held together in a closed-packed hexagonal array by van der Waals forces. The ropes are often found with overall length greater than 0.1 mm. Due to their expected high electrical conductivity, especially when doped with metals either down the hollow inside region or on the outside, intercalated in the triangular gaps between the adjacent tubes, these new materials may provide the first source of wires on the nanometer scale whose electrical conduction is truly metallic. It may also be possible to make them much longer. The experiments that produced these high-yield single-walled nanotubes are discussed in the context of other recent work on single- and multi-wall nanotubes, and a detailed growth mechanism is described.

Colbert, Daniel T.

1996-03-01

234

C?? fullerene promotes lung monolayer collapse.  

PubMed

Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C?? fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m(-1)). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m(-1)). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo, which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant. PMID:25589571

Barnoud, Jonathan; Urbini, Laura; Monticelli, Luca

2015-03-01

235

Mutual interplay of light harvesting and triplet sensitizing in a perylene bisimide antenna-fullerene dyad.  

PubMed

A flexible organic dyad consisting of a perylene bisimide antenna covalently linked to a [60]fullerene has been synthesized and studied by electrochemistry, steady-state spectroscopy, and time-resolved spectroscopy. We found that the energy absorbed by the perylene bisimide is transferred to the fullerene with an efficiency close to 100%. The fullerene in turn undergoes intersystem crossing followed by triplet energy transfer back to the perylene bisimide with an efficiency of at least 20%. Hence the perylene bisimide unit acts as an antenna for the fullerene, i.e., effectively extending the fullerene absorption far into the visible spectral range, while at the same time the fullerene acts as a triplet sensitizer for the perylene bisimide. This has severe consequences for the exploitation of the dye antenna-fullerene concept for light harvesting in solar cells. PMID:20578770

Hofmann, Christiane C; Lindner, Stefan M; Ruppert, Michaela; Hirsch, Andreas; Haque, Saif A; Thelakkat, Mukundan; Köhler, Jürgen

2010-07-22

236

Defect Induced Intrinsic Ferromagnetism in Fullerene Thin Films  

NASA Astrophysics Data System (ADS)

The occurrence of intrinsic ferromagnetism in energetic ion irradiated fullerene films is reported. The magnetic properties of irradiated fullerene films are studied by superconducting quantum interference device and electron spin resonance. Raman spectroscopy measurement has been performed to investigate the structural transformation at high fluence. The role of electronic energy density deposition by the ions on their magnetic properties is investigated. The origin of magnetic signal in irradiated films is due to the generation of an amorphous carbon network consisting sp2/sp3 bonded carbon atoms.

Kumar, Amit; Avasthi, Devesh Kumar; Pivin, Jean Claude

2008-12-01

237

Graph-theoretic independence as a predictor of fullerene stability  

NASA Astrophysics Data System (ADS)

The independence number of the graph of a fullerene, the size of the largest set of vertices such that no two are adjacent (corresponding to the largest set of atoms of the molecule, no pair of which are bonded), appears to be a useful selector in identifying stable fullerene isomers. The experimentally characterized isomers with 60, 70 and 76 atoms uniquely minimize this number among the classes of possible structures with, respectively, 60, 70 and 76 atoms. Other experimentally characterized isomers also rank extremely low with respect to this invariant. These findings were initiated by a conjecture of the computer program Graffiti.

Fajtlowicz, S.; Larson, C. E.

2003-08-01

238

Argon bombardment-induced topography and sputter yields on Si 0.84Ge 0.16  

NASA Astrophysics Data System (ADS)

The argon ion sputter yields of epitaxial Si 0.84Ge 0.16 films on a Si substrate are presented for different ion energies (0.5-5 keV) and angles of incidence (0-70°). The results were obtained by using atomic force microscopy (AFM) to determine the sputter depths of shielded samples. There was reasonable agreement between the experimental sputter yields and the predictions from the Sigmund theory. The results showed the applicability of this method using AFM to determine sputter yields of thin films. The surface topographies of the unbombarded and sputtered surfaces were characterised by AFM and were quantified in terms of the rms roughness. The results showed that very little topography developed on the surfaces due to the ion bombardment. The rms roughness exhibited no significant dependence on the ion energy or the angle of incidence. There was only a slight correlation with the ion dose density.

van der Berg, N. G.; Malherbe, Johan B.; Odendaal, R. Q.; Goodman, S. A.; Premachandra, K.

2002-06-01

239

Na-D line emission from rock specimens by proton bombardment - Implications for emissions from Jupiter's satellite Io  

NASA Technical Reports Server (NTRS)

The effectiveness of low-keV range protons in producing Na line emission from selected sodium-bearing rock and mineral samples is examined. Laboratory experiments show that substantial Na-D line emission is produced by 3- to 5-keV proton bombardment of silicate and halite rock powders. It is found that emission intensity and energy efficiency are directly proportional to sodium content and are dependent on total dose, dose rate, and proton energy. Na-D photon emission is considered to emanate predominantly from sputtered sodium slightly above the target surfaces. It is concluded that the Na-D line emission directly excited during surface sputtering by Jovian magnetospheric protons appears to be an observable component in the Jovian satellite Io emission.

Nash, D. B.; Matson, D. L.; Johnson, T. V.; Fanale, F. P.

1975-01-01

240

The 17-keV neutrino  

NASA Astrophysics Data System (ADS)

The experimental evidence of a distortion in the ?-spectra of 3H, 35S, 63Ni, 14C and IBEC-spectrum of 71Ge is reviewed. The distortions seen in the five nuclei are consistent with their interpretation as the signal of the emission of a neutrino of 17-keV mass and mixing angle of 0.1. Some of the implications of this discovery are reviewed.

Simpson, John J.

1992-07-01

241

Intravenous coronary angiography utilizing K-emission and bremsstrahlung X-rays produced by electron bombardment  

SciTech Connect

The screening of the general population for coronary artery disease would be practical if a method existed for visualizing the extent of occlusion after an intravenous injection of contrast agent. Measurements performed with synchrotron radiation at SSRL and NSLS have shown that such an intravenous angiography procedure would be possible with an intense source of monochromatic X-rays. Because of the high cost of an electron synchrotron, theoretical analysis and experiments using inanimate phantoms has been undertaken to demonstrate the feasibility of using the spectrum produced by two appropriately chosen anode materials when bombarded with electrons in the 100--500 keV energy range for angiography. By using the X-rays emitted at 120{degree} to the incident electron direction, about 20--30% of the X-ray intensity would be due to K-emission lines. Calculations using the TIGERP Monte Carlo Code, have shown that high quality angiograms of human coronary arteries should be possible with a contrast agent containing ytterbium, if an electron beam pulses of 16 kJ were used for each anode target. The experimental program supported in part by the DOE has consisted of these theoretical calculations and experiments at the Dynamitron Electron Accelerator Facility at BNL.

NONE

1992-12-31

242

Energy dependence of the sputtering yield of silicon bombarded with neon, argon, krypton, and xenon ions  

SciTech Connect

Sputtering yields of Si were determined for bombardment with Ne, Ar, Kr, and Xe ions at normal incidence in the energy range 0.2--20 keV under ultrahigh vacuum conditions (<10/sup -7/ Pa). Mass selection was employed and the energy spread was limited to a few electron volts. High fluences in excess of 10/sup 18/ cm/sup -2/ were used to obtain stationary state yields. A special method was adopted for the yield determination, involving accurate current integration and eroded crater volume measurement with a micromechanical stylus. As a spinoff of the adopted technique, relative sputtering yields for Mo could also be determined. Our data agree with the sparse other recent experimental results. Discrepancies with older data sets are sizeable but can be attributed to our improved beam definition and better surface conditions. The measured yields are, even quantitatively, in surprisingly good agreement with predictions from Sigmund's linear cascade theory in the low and intermediate energy range. At higher energy the yields fall off more rapidly than the theory predicts, the deviations increasing with decreasing projectile mass. This behavior cannot be explained entirely in terms of the parameters and assumptions entering the Sigmund model. Various proposed empirical modifications and alternatives for Sigmund's theory are critically examined and a new quite useful simplification of the latter is derived.

Zalm, P.C.

1983-05-01

243

Monte Carlo simulation of characteristic x-ray emission from thick samples bombarded by kiloelectronvolt electrons  

NASA Astrophysics Data System (ADS)

We describe systematic Monte Carlo (MC) calculations of characteristic K and L x-ray emission from thick samples bombarded by kiloelectronvolt electrons. The simulations were performed using the general-purpose MC code PENELOPE, which was modified by introducing a new database of electron-impact ionization cross sections calculated from the distorted-wave Born approximation (DWBA). The calculated yields, defined as the number of photons emerging from the target per unit solid angle and per incident electron, are compared with experimental measurements available from the literature, which pertain to single-element materials with atomic numbers ranging from Z = 6 up to Z = 82 and electron beam energies from a few kiloelectronvolts up to 40 keV. To reveal the dependence of the characteristic x-ray yields on the adopted ionization cross sections, simulations were also performed using cross sections based on the plane-wave Born approximation (PWBA). Our calculations confirm that, in the considered energy range, the DWBA is considerably more accurate than the PWBA.

Bote, D.; Llovet, X.; Salvat, F.

2008-05-01

244

Preferable orientation of spherical fullerene inside boron nitride nanotubes  

NASA Astrophysics Data System (ADS)

We provide a systematic analytical method for preferable orientation calculations of spherical fullerenes in single-walled boron nitride nanotubes. Based on the reaction energy calculations, both the minimum entering radii and the energetically favorable radii for encapsulating C60, C80 and C180 molecules in boron nitride nanotubes have been proposed. The van der Waals energy as a function of the various orientations of the encapsulated fullerene molecule is shown by a potential contour map, from which we find that the low-energy state appears in the symmetry axis orientation of the encapsulated fullerene molecules with a different size. We thus propose a new systematic analytical method for optimal orientation predictions of spherical fullerenes in the confinement condition, which is based on the symmetry axis but not the method proposed in previous literature, such as using pentagons, double-bonds, and hexagons to analyze the preferable orientation of confined C60. Our results show that the C60 molecule in boron nitride nanotubes exhibits three lowest energy states corresponding to the five-, two- and three-fold axis orientations in three radii intervals, while only two preferable orientations—the five- and three-fold axis orientations have been observed for encapsulated C80 and C180 molecules.

Ma, Fengxian; Yao, Zhen; Yao, Mingguang; Liu, Ran; Zou, Bo; Cui, Tian; Liu, Bingbing

2013-02-01

245

Fullerene-Based Symmetry in Hibiscus rosa-sinensis Pollen  

PubMed Central

The fullerene molecule belongs to the so-called super materials. The compound is interesting due to its spherical configuration where atoms occupy positions forming a mechanically stable structure. We first demonstrate that pollen of Hibiscus rosa-sinensis has a strong symmetry regarding the distribution of its spines over the spherical grain. These spines form spherical hexagons and pentagons. The distance between atoms in fullerene is explained applying principles of flat, spherical, and spatial geometry, based on Euclid’s “Elements” book, as well as logic algorithms. Measurements of the pollen grain take into account that the true spine lengths, and consequently the real distances between them, are measured to the periphery of each grain. Algorithms are developed to recover the spatial effects lost in 2D photos. There is a clear correspondence between the position of atoms in the fullerene molecule and the position of spines in the pollen grain. In the fullerene the separation gives the idea of equal length bonds which implies perfectly distributed electron clouds while in the pollen grain we suggest that the spines being equally spaced carry an electrical charge originating in forces involved in the pollination process. PMID:25003375

Andrade, Kleber; Guerra, Sara; Debut, Alexis

2014-01-01

246

Fullerene-based symmetry in Hibiscus rosa-sinensis pollen.  

PubMed

The fullerene molecule belongs to the so-called super materials. The compound is interesting due to its spherical configuration where atoms occupy positions forming a mechanically stable structure. We first demonstrate that pollen of Hibiscus rosa-sinensis has a strong symmetry regarding the distribution of its spines over the spherical grain. These spines form spherical hexagons and pentagons. The distance between atoms in fullerene is explained applying principles of flat, spherical, and spatial geometry, based on Euclid's "Elements" book, as well as logic algorithms. Measurements of the pollen grain take into account that the true spine lengths, and consequently the real distances between them, are measured to the periphery of each grain. Algorithms are developed to recover the spatial effects lost in 2D photos. There is a clear correspondence between the position of atoms in the fullerene molecule and the position of spines in the pollen grain. In the fullerene the separation gives the idea of equal length bonds which implies perfectly distributed electron clouds while in the pollen grain we suggest that the spines being equally spaced carry an electrical charge originating in forces involved in the pollination process. PMID:25003375

Andrade, Kleber; Guerra, Sara; Debut, Alexis

2014-01-01

247

Fullerenes, fulleranes and polycyclic aromatic hydrocarbons in the Allende meteorite  

NASA Technical Reports Server (NTRS)

In this paper, we confirm our earlier observations of fullerenes (C60 and C70) in the Allende meteorite (Becker et al., 1994a, 1995). Fullerene C60 was also detected in two separate C-rich (approximately 0.5-1.0%) dark inclusions (Heymann et al., 1987) that were hand picked from the Allende sample. The amounts of C60 detected were approximately 5 and approximately 10 ppb, respectively, which is considerably less than what was detected in the Allende 15/21 sample (approximately 100 ppb; Becker et al., 1994a, 1995). This suggests that fullerenes are heterogeneously distributed in the meteorite. In addition, we present evidence for fulleranes, (C60Hx), detected in separate samples by laser desorption (reflectron) time-of-flight (TOF) mass spectrometry (LDMS). The LDMS spectra for the Allende extracts were remarkably similar to the spectra generated for the synthetic fullerane mixtures. Several fullerane products were synthesized using a Rh catalyst (Becker et al., 1993a) and separated using high-performance liquid chromatography (HPLC). Polycyclic aromatic hydrocarbons (PAHs) were also observed ppm levels) that included benzofluoranthene and corannulene, a cup-shaped molecule that has been proposed as a precursor molecule to the formation of fullerenes in the gas phase (Pope et al., 1993).

Becker, L.; Bunch, T. E.

1997-01-01

248

ODD CYCLE TRANSVERSALS AND INDEPENDENT SETS IN FULLERENE GRAPHS  

E-print Network

ODD CYCLE TRANSVERSALS AND INDEPENDENT SETS IN FULLERENE GRAPHS LUERBIO FARIA, SULAMITA KLEIN is an odd cycle (edge) transversal if its removal results in a bipartite graph; the smallest size of an odd cycle transversal of G is denoted by odd(G). Finding a minimum odd cycle transversal of a graph

Boyer, Edmond

249

Hybrid uranium-oxalate fullerene topology cage clusters  

SciTech Connect

Inorganic–organic hybrid cage clusters containing 36 and 60 uranyl peroxide polyhedra and 6 or 30 oxalate groups self-assemble in aqueous solution under ambient conditions. These clusters, which are derivatives of fullerene topologies, were crystallized for structure analysis, and are readily dissolved intact in water.

Ling, Jie; Wallace, Christine M.; Szymanowski, Jennifer E.S.; Burns, Peter C

2010-01-01

250

Isotopic fractionation during fullerene, nanotube, and nanopolyhedra formation  

SciTech Connect

The production of fullerenes by electrical arcing or resistively heating produces a number of other products including nanotubes and nanopolyhedra, microtubes, and pyrolytic carbon. The mechanism of formation of these different products is still speculative. We report here that the isotopic distributions in the various products named above differ, and this sheds new light on the mechanism by which they are formed. We electrically arced graphite rods of high purity (99.99% C) in a helium atmosphere according to the general procedure for preparing fullerenes. Pyrolytic carbon on the shell of the cathode deposit has an isotopic ratio close to that of the graphite. This is strong evidence that the pyrolytic carbon is formed by a mechanism different from nanotube, nanopolyhedra, or soot formation. We conclude that nanotubes and nanopolyhedra, pyrolytic carbon, microtubes, and fullerene soot in the arcing process are formed by different mechanisms. The nanotubes and nanopolyhedra are produced preferentially from ions with lowest mass-to-charge ratio and atoms. It is probable that the nanotubes and nanopolyhedra are formed by direct electrode-electrode interchange of charged monoatomic ions. Fullerene soot is formed from species with higher mass-to-charge ratios which can escape the electromagnetic field of the arc. 18 refs., 1 tab.

Pallasser, R.; Pang, L.S.K.; Prochazka, L.; Rigby, D.; Wilson, M.A. (CSIRO Division of Petroleum Resources, North Ryde, NSW (Australia))

1993-12-01

251

Preferable orientation of spherical fullerene inside boron nitride nanotubes.  

PubMed

We provide a systematic analytical method for preferable orientation calculations of spherical fullerenes in single-walled boron nitride nanotubes. Based on the reaction energy calculations, both the minimum entering radii and the energetically favorable radii for encapsulating C(60), C(80) and C(180) molecules in boron nitride nanotubes have been proposed. The van der Waals energy as a function of the various orientations of the encapsulated fullerene molecule is shown by a potential contour map, from which we find that the low-energy state appears in the symmetry axis orientation of the encapsulated fullerene molecules with a different size. We thus propose a new systematic analytical method for optimal orientation predictions of spherical fullerenes in the confinement condition, which is based on the symmetry axis but not the method proposed in previous literature, such as using pentagons, double-bonds, and hexagons to analyze the preferable orientation of confined C(60). Our results show that the C(60) molecule in boron nitride nanotubes exhibits three lowest energy states corresponding to the five-, two- and three-fold axis orientations in three radii intervals, while only two preferable orientations-the five- and three-fold axis orientations have been observed for encapsulated C(80) and C(180) molecules. PMID:23334189

Ma, Fengxian; Yao, Zhen; Yao, Mingguang; Liu, Ran; Zou, Bo; Cui, Tian; Liu, Bingbing

2013-02-13

252

Optical Spectroscopy of the Fullerenes C(60) and C(70)  

Microsoft Academic Search

The fullerenes are a recently discovered third allotrope of carbon. The ability to produce these unusual molecules in gram quantities has led to intensive investigation of their properties. Optical spectroscopies provide powerful tools for investigating the electronic states of materials. We have used the techniques of resonant Raman scattering (RRS), electroabsorption (EA), cw and transient photomodulation (PM) and transient photoinduced

David J. Dick

1996-01-01

253

Quantum transport through single and multilayer icosahedral fullerenes  

NASA Astrophysics Data System (ADS)

We use a tight-binding Hamiltonian and Green functions methods to calculate the quantum transmission through single-wall fullerenes and bilayered and trilayered onions of icosahedral symmetry attached to metallic leads. The electronic structure of the onion-like fullerenes takes into account the curvature and finite size of the fullerenes layers as well as the strength of the intershell interactions depending on to the number of interacting atom pairs belonging to adjacent shells. Misalignment of the symmetry axes of the concentric iscosahedral shells produces breaking of the level degeneracies of the individual shells, giving rise some narrow quasi-continuum bands instead of the localized discrete peaks of the individual fullerenes. As a result, the transmission function for non symmetrical onions is rapidly varying functions of the Fermi energy. Furthermore, we found that most of the features of the transmission through the onions are due to the electronic structure of the outer shell with additional Fano-like antiresonances arising from coupling with or between the inner shells.

Lovey, Daniel A.; Romero, Rodolfo H.

2013-10-01

254

Nanostructure enhanced ionic transport in fullerene reinforced solid polymer electrolytes.  

PubMed

Solid polymer electrolytes, such as polyethylene oxide (PEO) based systems, have the potential to replace liquid electrolytes in secondary lithium batteries with flexible, safe, and mechanically robust designs. Previously reported PEO nanocomposite electrolytes routinely use metal oxide nanoparticles that are often 5-10 nm in diameter or larger. The mechanism of those oxide particle-based polymer nanocomposite electrolytes is under debate and the ion transport performance of these systems is still to be improved. Herein we report a 6-fold ion conductivity enhancement in PEO/lithium bis(trifluoromethanesulfonyl) imide (LiTFSI)-based solid electrolytes upon the addition of fullerene derivatives. The observed conductivity improvement correlates with nanometer-scale fullerene crystallite formation, reduced crystallinities of both the (PEO)6:LiTFSI phase and pure PEO, as well as a significantly larger PEO free volume. This improved performance is further interpreted by enhanced decoupling between ion transport and polymer segmental motion, as well as optimized permittivity and conductivity in bulk and grain boundaries. This study suggests that nanoparticle induced morphological changes, in a system with fullerene nanoparticles and no Lewis acidic sites, play critical roles in their ion conductivity enhancement. The marriage of fullerene derivatives and solid polymer electrolytes opens up significant opportunities in designing next-generation solid polymer electrolytes with improved performance. PMID:25733054

Sun, Che-Nan; Zawodzinski, Thomas A; Tenhaeff, Wyatt E; Ren, Fei; Keum, Jong Kahk; Bi, Sheng; Li, Dawen; Ahn, Suk-Kyun; Hong, Kunlun; Rondinone, Adam J; Carrillo, Jan-Michael Y; Do, Changwoo; Sumpter, Bobby G; Chen, Jihua

2015-03-11

255

Would Diamond Nanorods Be Stronger than Fullerene Nanotubes?  

E-print Network

Would Diamond Nanorods Be Stronger than Fullerene Nanotubes? Olga Shenderova,, Donald Brenner of literature ab initio data, we show that diamond nanorods would have a brittle fracture force and a zero on the orientation of the diamond nanorod. The energetic stability of diamond nanorods is predicted by molecular

Brenner, Donald W.

256

Quenching and Sensitizing Fullerene Photoreactions by Natural Organic Matter  

EPA Science Inventory

Effects of natural organic matter (NOM) on the photoreaction kinetics of fullerenes (i.e., C60 and fullerenol) were investigated using simulated sunlight and monochromatic radiation (365 nm). NOM from several sources quenched (slowed) the photoreaction of C60 aggregates in water ...

257

Jovian Early Bombardment: planetesimal erosion in the inner asteroid belt  

E-print Network

The asteroid belt is an open window on the history of the Solar System, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions. In this work we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depen...

Turrini, Diego; Magni, Gianfranco

2012-01-01

258

Bombardment of Metal Surfaces by Slow-Moving Electrons  

Microsoft Academic Search

Secondary Electrons Produced by Electronic Bombardment of Nickel.-The main features of the apparatus used are: an equi-potential nitrate-coated Pt cathode heated by radiation from a tungsten spiral filament; a series of insulated diaphragms to limit the beam of primary rays and for use in determining their velocity; and a long Faraday cylinder in front of which the nickel target could

H. E. Farnsworth

1922-01-01

259

Electron Bombardment Ion Source for Low Energy Beams  

Microsoft Academic Search

A high current, electron bombardment ion source of simple design and suitable for low energy ion beam production is described. The source produces ion beams in the energy range from a few electron volts to several kilo-electron volts with an energy spread of a fraction of 1 eV, with high current density (5 ?A?cm2 at 25 eV), and without the

S. Dworetsky; R. Novick; W. W. Smith; N. Tolk

1968-01-01

260

Simplified construction and performance of a device for particle bombardment  

Microsoft Academic Search

A modified particle inflow gun (PIG), that utilized a plastic vacuum chamber, was compared with a conventional PIG by bombarding cantaloupe (Cucumis melo L.) cotyledon basal quarters with plasmid pBI221 (Clontech Inc.) containing a ß-glucuronidase (GUS) gene adsorbed onto tungsten particles. Both guns produced an equivalent number of transient GUS foci when tested at 410 kPa (60 psi), 620 kPa

D. J. Gray; E. Hiebert; C. M. Lin; M. E. Compton; D. W. McColley; R. J. Harrison; V. P. Gaba

1994-01-01

261

Structure and hardness of materials after electron bombardment  

Microsoft Academic Search

1.As the result of electron bombardment there are substantial changes in the structure and properties of Armco iron and steel 45 due simultaneously to thermal and radiation effects.2.After irradiation, the hardness of Armco iron reaches HV 180, annealed steel 45 HV 300, and normalized steel 45 HV 540.3.The microhardness in the section of the sample along the axis of the

M. M. Krasnoshchekov; A. E. Speshinskii; E. A. Markovskii

1978-01-01

262

Anomalous Photofragmentation of Fullerene Doped in Silica Aerogel-Enhanced Formation of Odd-Numbered ``Fullerene'' Fragments  

NASA Astrophysics Data System (ADS)

Photofragmentation of fullerene-doped silica aerogels has been investigated by the excimer laser ablation reflectron time-of-flight mass spectrometric technique. Great enhancement in the formation of odd-numbered `fullerene' fragments has been observed in the negative-ion channel for the chemically doped aerogel sample. Generally, odd-numbered species C57, C55, C53 and C51 appeared in the mass spectra. Under optimal experimental conditions C55 can be even more intense than the neighbouring even-numbered carbon clusters. In contrast, for the physically-doped sample, just like pristine C60, only weak odd-numbered fragments were observed. In the positive-ion channel, the behaviour of all these samples is similar, no odd-numbered species was ever detected. A mechanism related to the interaction between the fullerene dopant and the silica aerogel host is suggested for the anomalous enhancement of the odd-numbered cluster formation. A preliminary discussion on the structures of the odd-numbered `fullerene' fragments is given.

Kong, Qing-Yu; Zhao, Li; Zhuang, Jun; Qian, Shi-Xiong; Li, Yu-Fen; Wang, Jue

2001-12-01

263

[60]Fullerene Displacement from (Dihapto-Buckminster-Fullerene) Pentacarbonyl Tungsten(0): An Experiment for the Inorganic Chemistry Laboratory, Part II  

ERIC Educational Resources Information Center

The kinetics experiments on the ligand-C[subscript 60] exchange reactions on (dihapto-[60]fullerene) pentacarbonyl tungsten(0), ([eta][superscript 2]-C[subscript 60])W(CO)[subscript 5], form an educational activity for the inorganic chemistry laboratory that promotes graphical thinking as well as the understanding of kinetics, mechanisms, and the…

Cortes-Figueroa, Jose E.; Moore-Russo, Deborah A.

2006-01-01

264

Effect of fullerene tris-adducts on the photovoltaic performance of P3HT:fullerene ternary blends.  

PubMed

Fullerene tris-adducts have the potential of achieving high open-circuit voltages (V(OC)) in bulk heterojunction (BHJ) polymer solar cells (PSCs), because their lowest unoccupied molecular orbital (LUMO) level is higher than those of fullerene mono- and bis-adducts. However, no successful examples of the use of fullerene tris-adducts as electron acceptors have been reported. Herein, we developed a ternary-blend approach for the use of fullerene tris-adducts to fully exploit the merit of their high LUMO level. The compound o-xylenyl C60 tris-adduct (OXCTA) was used as a ternary acceptor in the model system of poly(3-hexylthiophene) (P3HT) as the electron donor and the two soluble fullerene acceptors of OXCTA and fullerene monoadduct (o-xylenyl C60 monoadduct (OXCMA), phenyl C61-butyric acid methyl ester (PCBM), or indene-C60 monoadduct (ICMA)). To explore the effect of OXCTA in ternary-blend PSC devices, the photovoltaic behavior of the device was investigated in terms of the weight fraction of OXCTA (W(OXCTA)). When W(OXCTA) is small (<0.3), OXCTA can generate a synergistic bridging effect between P3HT and the fullerene monoadduct, leading to simultaneous enhancement in both V(OC) and short-circuit current (J(SC)). For example, the ternary PSC devices of P3HT:(OXCMA:OXCTA) with W(OXCTA) of 0.1 and 0.3 exhibited power-conversion efficiencies (PCEs) of 3.91% and 3.96%, respectively, which were significantly higher than the 3.61% provided by the P3HT:OXCMA device. Interestingly, for W(OXCTA) > 0.7, both V(OC) and PCE of the ternary-blend PSCs exhibited nonlinear compositional dependence on W(OXCTA). We noted that the nonlinear compositional trend of P3HT:(OXCMA:OXCTA) was significantly different from that of P3HT:(OXCMA:o-xylenyl C60 bis-adduct (OXCBA)) ternary-blend PSC devices. The fundamental reasons for the differences between the photovoltaic trends of the two different ternary-blend systems were investigated systemically by comparing their optical, electrical, and morphological properties. PMID:23574307

Kang, Hyunbum; Kim, Ki-Hyun; Kang, Tae Eui; Cho, Chul-Hee; Park, Sunhee; Yoon, Sung Cheol; Kim, Bumjoon J

2013-05-22

265

Crystalline co-assemblies of functional fullerenes in methanol with enhanced charge transport.  

PubMed

Supramolecular arrangement of conjugated molecules has crucial influence on their material properties. For fullerenes and metallofullerenes, tight and ordered packing is beneficial for intermolecular charge transport and energy transfer, but it is tricky to achieve, especially for functionalized cages due to the often extensive solvation and steric effects of functional groups. In this study, we use an amphiphilic fullerene derivative soluble in methanol to form co-assemblies with insoluble fullerene derivatives, pristine fullerene, and metallofullerene via strong ?-? interactions. These mixtures are processable in methanol and show fullerene-templated crystalline structures in spin-cast films. Devices are successfully fabricated on a field-effect transistor platform with this approach, and all co-assemblies show metallic-like conductive properties with significantly enhanced conductivity compared to the pure amphiphilic fullerene derivative. PMID:25633304

Zhang, Jianyuan; Li, Chang-Zhi; Williams, Spencer T; Liu, Shengqiang; Zhao, Ting; Jen, Alex K-Y

2015-02-18

266

Nanoscale surface structuring during ion bombardment of elemental semiconductors  

NASA Astrophysics Data System (ADS)

Nano-patterning of surfaces with uniform ion bombardment yields a rich phase-space of topographic patterns. Particle irradiation can cause surface ultra-smoothing or self-organized nanoscale pattern formation in surface topography. Topographic pattern formation has previously been attributed to the effects of the removal of target atoms by sputter erosion. In this thesis, the surface morphology evolution of Si(100) and Ge(100) during low energy ion bombardment of Ar+ and Kr+ ions, respectively, is studied. Our facilities for studies of surface processes at the National Synchrotron Light Source (NSLS) allow in-situ characterization of surface morphology evolution during ion bombardment using grazing incidence small angle x-ray scattering (GISAXS). This technique is used to measure in reciprocal space the kinetics of formation or decay of correlated nanostructures on the surface, effectively measuring the height-height correlations. A linear model is used to characterize the early time kinetic behavior during ion bombardment as a function of ion beam incidence angle. The curvature coefficients predicted by the widely used erosive model of Bradley and Harper are quantitatively negligible and of the wrong sign when compared to the observed effect in both Si and Ge. A mass-redistribution model explains the observed ultra-smoothing at low angles, exhibits an instability at higher angles, and predicts the observed 45° critical angle separating these two regimes in Si. The Ge surface evolution during Kr+ irradiation is qualitatively similar to that observed for Ar+ irradiation of Si at the same ion energy. However, the critical angle for Ge cannot be quantitatively reproduced by the simple mass redistribution model. Crater function theory, as developed by Norris et al., incorporates both mass redistributive and erosive effects, and predicts constraining relationships between curvature coefficients. These constraints are compared to experimental data of both Si and Ge. There is good agreement at low incidence angles; however, at higher angles the data disagrees with the predictions of the crater function formalism. This calls into question the ability of crater function theory to model the surface morphology evolution during ion bombardment.

Anzenberg, Eitan

2013-01-01

267

Effects of operating conditions on the fullerene synthesis and its purification  

Microsoft Academic Search

Electric arc method was employed in this work to investigate the fullerene synthesis under various operating conditions. An elaborate apparatus was designed for the experimental studies. For fullerene separation and purification, a modified Soxhlet extraction column packed with alumina or alumina\\/granular activated carbon (GAC) was utilized. The fullerene?containing soot was generated from ultra?pure graphite rods in a quartz reactor in

Sheng H. Lin; Yu W. Chang

1999-01-01

268

Molecular design, study of the structures and properties of ionic fullerene compounds  

NASA Astrophysics Data System (ADS)

The results of studies devoted to ionic compounds of fullerenes, which are of interest for the design of new materials with promising physical properties, are analyzed. The preparation methods of these compounds and their electrophysical, magnetic and optical properties, and the molecular and electronic structures of monomeric, dimeric and polymeric fullerene anions are considered. The results of investigations of fullerenes in various charge states by electronic, IR, EPR and 13C NMR spectroscopies are presented. The bibliography includes 266 references.

Konarev, Dmitry V.; Lyubovskaya, Rimma N.

2012-04-01

269

M-shell x-ray production cross sections from 75-300 keV proton impact on Hf, Re, and Au  

NASA Astrophysics Data System (ADS)

M x-ray spectra from 75-300 keV proton bombardment of thick elemental targets of Hf, Re, and Au were measured using a ultra-thin window Si(Li) detector. Spectral analysis yielded x-ray production cross sections of the major x-ray transitions M?, M?, M?, M2N4, M1O3 representative of vacancy filling of the five M sub-shells. Results are compared with predictions from non-relativistic ECPSSR and relativistic RPWBA-BC theories.

Cipolla, Sam

2011-06-01

270

Synthesis of Fullerenes in Low Pressure Benzene/Oxygen Diffusion Flames  

NASA Technical Reports Server (NTRS)

The interest in fullerenes is strongly increasing since their discovery by Kroto et al. in 1985 as products of the evaporation of carbon into inert gas at low pressure. Due to their all carbon closed-shell structure, fullerenes have many exceptional physical and chemical properties and a large potential for applications such as superconductors, sensors, catalysts, optical and electronic devices, polymers, high energy fuels, and biological and medical materials. This list is still growing, because the research on fullerenes is still at an early stage. Fullerenes can be formed not only in a system containing only carbon and an inert gas, but also in premixed hydrocarbon flames under reduced pressure and fuel rich conditions. The highest yields of fullerenes in flames are obtained under conditions of substantial soot formation. There is a need for more information on the yields of fullerenes under different conditions in order to understand the mechanisms of their formation and to enable the design of practical combustion systems for large-scale fullerene production. Little work has been reported on the formation of fullerenes in diffusion flames. In order to explore the yields of fullerenes and the effect of low pressure in diffusion flames, therefore we constructed and used a low pressure diffusion flame burner in this study.

Hebgen, Peter; Howard, Jack B.

1999-01-01

271

Time resolved spectroscopy and gain studies of Fullerenes C60 and C70  

NASA Astrophysics Data System (ADS)

The fluorescence decay time of Fullerenes C60 and C70 in pure form as well as in mixture with Coumarin C440 and Quinizarine dyes are studied. Results indicate that the decay of pure fullerenes is constant throughout the solute concentration and it is also independent of excitation wavelength, whereas in the case of mixture with dyes different behavior is noticed. We have also calculated the Stern-Volmer quenching constant and optical gain of both the fullerenes from which it is found that the optical gain is positive for Fullerene C70 only in a very narrow range of concentration.

Qaiser, Darakhshan; Khan, Mohd. Shahid; Singh, R. D.; Khan, Zahid H.

2013-09-01

272

Tuning the interactions between electron spins in fullerene-based triad systems  

PubMed Central

Summary A series of six fullerene–linker–fullerene triads have been prepared by the stepwise addition of the fullerene cages to bridging moieties thus allowing the systematic variation of fullerene cage (C60 or C70) and linker (oxalate, acetate or terephthalate) and enabling precise control over the inter-fullerene separation. The fullerene triads exhibit good solubility in common organic solvents, have linear geometries and are diastereomerically pure. Cyclic voltammetric measurements demonstrate the excellent electron accepting capacity of all triads, with up to 6 electrons taken up per molecule in the potential range between ?2.3 and 0.2 V (vs Fc+/Fc). No significant electronic interactions between fullerene cages are observed in the ground state indicating that the individual properties of each C60 or C70 cage are retained within the triads. The electron–electron interactions in the electrochemically generated dianions of these triads, with one electron per fullerene cage were studied by EPR spectroscopy. The nature of electron–electron coupling observed at 77 K can be described as an equilibrium between doublet and triplet state biradicals which depends on the inter-fullerene spacing. The shorter oxalate-bridged triads exhibit stronger spin–spin coupling with triplet character, while in the longer terephthalate-bridged triads the intramolecular spin–spin coupling is significantly reduced. PMID:24605154

Lebedeva, Maria A; Chamberlain, Thomas W; Davies, E Stephen; Thomas, Bradley E; Schröder, Martin

2014-01-01

273

Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer  

SciTech Connect

In this work, we report the functionalization of flat Si(100) surfaces with a calix[8]arene derivative through a thermal hydrosilylation process, followed by docking with [60]fullerene. Chemical grafting of calix[8]arene on silicon substrates was evaluated by X-ray photoelectron spectroscopy, whereas host-guest immobilization of fullerene was demonstrated by atomic force microscopy and sessile drop water contact angle measurements. Surface topographical variations, modelled on the basis of calix[8]arene and [60]fullerene geometrical parameters, are consistent with the observed morphological features relative to surface functionalization and to non-covalent immobilization of [60]fullerene.

Busolo, Filippo; Silvestrini, Simone; Maggini, Michele [Department of Chemical Sciences, ITM-CNR University of Padova, Via F. Marzolo 1, 35131 Padova (Italy)] [Department of Chemical Sciences, ITM-CNR University of Padova, Via F. Marzolo 1, 35131 Padova (Italy); Armelao, Lidia [Department of Chemical Sciences, IENI-CNR and INSTM, University of Padova, Via F. Marzolo 1, 35131 Padova (Italy)] [Department of Chemical Sciences, IENI-CNR and INSTM, University of Padova, Via F. Marzolo 1, 35131 Padova (Italy)

2013-10-28

274

Effect of Self-Assembly of Fullerene Nano-Particles on Lipid Membrane  

PubMed Central

Carbon nanoparticles can penetrate the cell membrane and cause cytotoxicity. The diffusion feature and translocation free energy of fullerene through lipid membranes is well reported. However, the knowledge on self-assembly of fullerenes and resulting effects on lipid membrane is poorly addressed. In this work, the self-assembly of fullerene nanoparticles and the resulting influence on the dioleoylphosphtidylcholine (DOPC) model membrane were studied by using all-atom molecular dynamics simulations with explicit solvents. Our simulation results confirm that gathered small fullerene cluster can invade lipid membrane. Simulations show two pathways: 1) assembly process is completely finished before penetration; 2) assembly process coincides with penetration. Simulation results also demonstrate that in the membrane interior, fullerene clusters tend to stay at the position which is 1.0 nm away from the membrane center. In addition, the diverse microscopic stacking mode (i.e., equilateral triangle, tetrahedral pentahedral, trigonal bipyramid and octahedron) of these small fullerene clusters are well characterized. Thus our simulations provide a detailed high-resolution characterization of the microscopic structures of the small fullerene clusters. Further, we found the gathered small fullerene clusters have significant adverse disturbances to the local structure of the membrane, but no great influence on the global integrity of the lipid membrane, which suggests the prerequisite of high-content fullerene for cytotoxicity. PMID:24204827

Zhang, Saiqun; Mu, Yuguang; Zhang, John Z. H.; Xu, Weixin

2013-01-01

275

Influence of low energy Ar-ion bombardment on monolayer Ni/W(1 0 0)  

NASA Astrophysics Data System (ADS)

The changes in the morphological and structural properties of monolayer nickel thin films on tungsten induced by low energy Ar+ ion bombardment at varying fluencies have been explored using scanning tunneling microscopy and low energy electron diffraction, respectively, in this work. ~1 monolayer (ML) nickel films were grown on W(1 0 0) by electron beam evaporation under ultra high vacuum conditions at room temperature. It was found that the pseudomorphic growth observed in as-grown films was disrupted by the ion bombardment process with additional phases of Ni appearing in the ion bombarded samples. Increase in bombardment time lead to a pronounced phase transition to the hcp phase of Ni. Also, the ion bombardment induced the formation of larger nanostructures (with increasing particulate sizes) from the epitaxial monolayer in the as-deposited sample. Further, the magnetization and magnetic orientation were studied and it was observed that the bombardment induced a weak ferromagnetism in as-grown paramagnetic Ni film.

Gopalakrishnan, C.; Ramaswamy, S.; Ganesh, K. R.; Jeganathan, K.

2014-02-01

276

Transformation of white spruce ( Picea glauca) somatic embryos by microprojectile bombardment  

Microsoft Academic Search

Cotyledonary somatic embryos of white spruce [Picea glauca (Moench) Voss] were subjected to microprojectile bombardment with a gene construct containing a gus::nptll fusion gene. Somatic embryos were used to re-induce the embryogenic tissue after bombardments. Histochemical assay using X-gluc as a substrate showed that all the embryos (100%) were GUS positive 48 h after bombardment. However, only thirteen out of

V. R. Bommineni; R. N. Chibbar; R. S. S. Datla; E. W. T. Tsang

1993-01-01

277

Stable transformation of the food yam Dioscorea alata L. by particle bombardment  

Microsoft Academic Search

A biolistic particle gun was used to deliver genetic material into intact yam cells. Cultured suspension cells of D. alata were bombarded with microprojectiles coated with pBI221.2 DNA and histochemical assays were carried out to show transient GUS expression in bombarded cells. Stably transformed D. alata cells were recovered from cultured cells after bombardment with microprojectiles coated with pRT99gus harbouring

Mahmut Tiir; Charles Ainsworth; Sinclair H. Mantell

1993-01-01

278

Interface engineering for efficient fullerene-free organic solar cells  

NASA Astrophysics Data System (ADS)

We demonstrate the role of zinc oxide (ZnO) morphology and addition of an acceptor interlayer to achieve high efficiency fullerene-free bulk heterojunction inverted organic solar cells. Nanopatterning of the ZnO buffer layer enhances the effective light absorption in the active layer, and the insertion of a twisted perylene acceptor layer planarizes and decreases the electron extraction barrier. Along with an increase in current homogeneity, the reduced work function difference and selective transport of electrons prevent the accumulation of charges and decrease the electron-hole recombination at the interface. These factors enable an overall increase of efficiency to 4.6%, which is significant for a fullerene-free solution-processed organic solar cell.

Shivanna, Ravichandran; Rajaram, Sridhar; Narayan, K. S.

2015-03-01

279

Recombination in polymer-fullerene bulk heterojunction solar cells  

SciTech Connect

Recombination of photogenerated charge carriers in polymer bulk heterojunction (BHJ) solar cells reduces the short circuit current (J{sub sc} ) and the fill factor (FF). Identifying the mechanism of recombination is, therefore, fundamentally important for increasing the power conversion efficiency. Light intensity and temperature-dependent current-voltage measurements on polymer BHJ cells made from a variety of different semiconducting polymers and fullerenes show that the recombination kinetics are voltage dependent and evolve from first-order recombination at short circuit to bimolecular recombination at open circuit as a result of increasing the voltage-dependent charge carrier density in the cell. The “missing 0.3 V” inferred from comparison of the band gaps of the bulk heterojunction materials and the measured open-circuit voltage at room-temperature results from the temperature dependence of the quasi-Fermi levels in the polymer and fullerene domains—a conclusion based on the fundamental statistics of fermions.

Cowan, Sarah; Roy, Anshuman; Heeger, Alan

2010-01-01

280

Influence of Substrate on Crystallization in Polythiophene/fullerene Blends  

SciTech Connect

The nanoscale morphology of the active layer in organic, bulk heterojunction (BHJ) solar cells is crucial to device performance. Often a combination of casting conditions and post deposition thermal treatment is used to optimize the morphology. In general, the development of microscopic crystals is deleterious, as the exciton diffusion length is {approx}10 nm. We find that the microscopic crystallization behavior in polythiophene/fullerene blends is strongly influenced by the substrate on which the BHJ is cast. With a silicon oxide substrate, the crystal nucleation density is high and significant crystallization occurs at a temperature of 140 C. On more hydrophobic substrates, significantly higher temperatures are required for observable crystallization. This difference is attributed to the interfacial segregation of the PCBM, controlled by the substrate surface energy. The substrate dependence of crystallization has significant implications on the fullerene crystal growth mechanisms and practical implications for device studies.

C He; D Germack; J Kline; D Delongchamp; D Fischer; C Snyder; M Toney; J Kushmerick; L Richter

2011-12-31

281

Cationic Fullerenes Are Effective and Selective Antimicrobial Photosensitizers  

PubMed Central

Summary Fullerenes are soccer ball-shaped molecules composed of carbon atoms, and, when derivatized with functional groups, they become soluble and can act as photosensitizers. Antimicrobial photodynamic therapy combines a nontoxic photosensitizer with harmless visible light to generate reactive oxygen species that kill microbial cells. We have compared the antimicrobial activity of six functionalized C60 compounds with one, two, or three hydrophilic or cationic groups in combination with white light against gram-positive bacteria, gram-negative bacteria, and fungi. After a 10 min incubation, the bis- and tris-cationic fullerenes were highly active in killing all tested microbes (4–6 logs) under conditions in which mammalian cells were comparatively unharmed. These compounds performed significantly better than a widely used antimicrobial photosensitizer, toluidine blue O. The high selectivity and efficacy exhibited by these photosensitizers encourage further testing for antimicrobial applications. PMID:16242655

Tegos, George P.; Demidova, Tatiana N.; Arcila-Lopez, Dennisse; Lee, Haeryeon; Wharton, Tim; Gali, Hariprasad; Hamblin, Michael R.

2011-01-01

282

Fullerene peapods: In-situ conductivity study during synthesis  

NASA Astrophysics Data System (ADS)

We report in-situ measurement of the conductivity during the synthesis of C60-filled single-walled carbon nanotubes (SWNTs), so-called fullerene peapods. The synthesis was performed in a sealed quartz tube at 773 K by using the sublimation of C60 into the hollow space of the SWNTs. The change in the resistance in the SWNT buckypaper was monitored during the C60-filling process, and the temperature dependence of the resistance was compared to that for empty SWNTs and fullerene peapods. The SWNT networks became more metallic due to the encapsulation of C60, and a reduced temperature dependence of the resistivity was observed in the peapods, with an overall decrease in the resistivity. The interaction between the SWNT and C60 molecules, changing the electronic properties of SWNTs, can provide a way to functionalize the SWNTs.

You, Young Gyu; Kim, Sung Won; Uhm, Tae Woo; Jhang, Sung Ho; Park, Yung Woo

2014-06-01

283

Self sputtering yields of silver under bombardment with polyatomic projectiles  

NASA Astrophysics Data System (ADS)

Molecular dynamics (MD) have been employed to model self sputtering yields of an Ag(1 1 1) surface under bombardment with Ag m ( m = 1, 2, 3, 4) projectiles. It is shown that the effect of projectile orientation on the sputter yield decreases strongly with increasing m and becomes practically negligible under Ag 4 impact. For polyatomic projectiles we observe a nonlinear yield enhancement which is discussed in terms of the collisional spike model of Sigmund and Claussen. It is shown that the MD simulation provides a unique method to determine the essential input parameters T0 and entering that model.

Duvenbeck, A.; Lindenblatt, M.; Wucher, A.

2005-01-01

284

Compositional changes in alloys during ion bombardment at elevated temperatures.  

SciTech Connect

Near-surface compositional changes in alloys during ion bombardment have been studied theoretically. The employed scheme operates with a stable target, and the effects of preferential sputtering, collisional mixing, radiation-enhanced diffusion, and Gibbsian and radiation-induced segregation are allowed for. High-fluence composition profiles were determined directly from a nonlinear integro-differential equation, after insertion of feasible input, by means of an efficient iteration procedure developed recently. The dependence of the composition profile on input parameters such as target temperature and defect mobility has been examined for Ni-Cu, Ni-Ge and Ni-Pd alloys and compared to experimental results.

Sckerl, M. W.; Lam, N. Q.; Sigmund, P.; Materials Science Division; Odense Univ.

1998-04-01

285

Single impact crater functions for ion bombardment of silicon  

SciTech Connect

The average effect of a single 500 eV incident argon ion on a silicon surface is studied using molecular dynamics simulations. More than 10{sup 3} ion impacts at random surface points are averaged for each of seven incidence angles, from 0 deg. to 28 deg. off normal, to determine a local surface height change function, or a crater function. The crater shapes are mostly determined by mass rearrangement; sputtering has a relatively small effect. Analytical fitting functions are provided for several cases, and may serve as input into kinetic Monte Carlo calculations or stability analyses for surfaces subjected to ion bombardment.

Kalyanasundaram, N.; Ghazisaeidi, M.; Freund, J. B.; Johnson, H. T. [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2008-03-31

286

Conductance enhancement of polymethylmethacrylate bombarded by low-energy ions  

NASA Astrophysics Data System (ADS)

It has been found that films of polymethylmethacrylate (PMMA) show a substantial conductance after bombardment by Ar ions with energy of 250-1250 eV. The appearance of the conductance is attributed to graphitization processes in the subsurface layer. As the energy of ions increases, the conductivity of PMMA is greatly enhanced. We have found that, at low electric fields, the conductance is provided by variable range hopping with a strong influence of Coulomb interactions. At high electric fields, the transformed PMMA reveals non-Ohmic behavior: the conductance is an exponential function of E/T.

Koval, Y.; Fistul, M. V.; Müller, P.

2005-09-01

287

Hemolytic effects of water-soluble fullerene derivatives.  

PubMed

A series of water-soluble fullerene C(60) derivatives has been investigated for their cytotoxic and hemolytic properties, with the aim to correlate structure with toxicity. We observed that cationic chains induce significant toxicity while the presence of neutral or anionic moieties did not produce any response in our model. A validation of these experimental observations has been performed by theoretical studies in which hydrophilic and hydrophobic surface areas were correlated quantitatively with hemolytic properties. PMID:15615520

Bosi, Susanna; Feruglio, Luigi; Da Ros, Tatiana; Spalluto, Giampiero; Gregoretti, Barbara; Terdoslavich, Michela; Decorti, Giuliana; Passamonti, Sabina; Moro, Stefano; Prato, Maurizio

2004-12-30

288

Optimizing Conditions for Ultrasound Extraction of Fullerenes from Coal Matrices  

Microsoft Academic Search

Conditions for ultrasound toluene extraction of synthetic C60 added to powdered bituminous coal were tested. High?performance liquid chromatography (HPLC) was used to determine the fullerene content in the obtained extracts. The results indicated a possible negative effect of sample demineralization (HCl\\/HF) and N2 purging on the extraction yield of C60. On the contrary, a 30% yield increase was registered when

Petr Vítek; Jan Jehli?ka; Otakar Frank; V?ra Hamplová; Zde?ka Pokorná; Libor Juha; Zbyn?k Bohá?ek

2009-01-01

289

Single or functionalized fullerenes interacting with heme group  

SciTech Connect

The heme group is responsible for iron transportation through the bloodstream, where iron participates in redox reactions, electron transfer, gases detection etc. The efficiency of such processes can be reduced if the whole heme molecule or even the iron is somehow altered from its original oxidation state, which can be caused by interactions with nanoparticles as fullerenes. To verify how such particles alter the geometry and electronic structure of heme molecule, here we report first principles calculations based on density functional theory of heme group interacting with single C{sub 60} fullerene or with C{sub 60} functionalized with small functional groups (?CH{sub 3}, ?COOH, ?NH{sub 2}, ?OH). The calculations shown that the system heme + nanoparticle has a different spin state in comparison with heme group if the fullerene is functionalized. Also a functional group can provide a stronger binding between nanoparticle and heme molecule or inhibit the chemical bonding in comparison with single fullerene results. In addition heme molecule loses electrons to the nanoparticles and some systems exhibited a geometry distortion in heme group, depending on the binding energy. Furthermore, one find that such nanoparticles induce a formation of spin up states in heme group. Moreover, there exist modifications in density of states near the Fermi energy. Although of such changes in heme electronic structure and geometry, the iron atom remains in the heme group with the same oxidation state, so that processes that involve the iron might not be affected, only those that depend on the whole heme molecule.

Costa, Wallison Chaves; Diniz, Eduardo Moraes, E-mail: eduardo.diniz@ufma.br [Departamento de Física, Universidade Federal do Maranhão, Avenida dos Portugueses, 1966, CEP 65080-805, São Luís - MA (Brazil)

2014-09-15

290

Functionalized multiwall carbon nanotubes incorporated polymer\\/fullerene hybrid photovoltaics  

Microsoft Academic Search

Multiwall carbon nanotubes are introduced into poly(3-hexylthiophene) and {[}6,6] phenyl C(61) butyric acid methyl fullerene, bulk heterojunction organic photovoltaic devices. Utilization of nanotubes requires chemical modifications for compatibility with solution processable photovoltaics. Better dispersions of carbon nanotubes in organic solvents are achieved by acid functionalization of tubes. Pristine and acid treated multiwall carbon nanotubes have been incorporated into the photoactive

N. A. Nismy; A. A. D. T. Adikaari; S. R. P. Silva

2010-01-01

291

Functionalized multiwall carbon nanotubes incorporated polymer\\/fullerene hybrid photovoltaics  

Microsoft Academic Search

Multiwall carbon nanotubes are introduced into poly(3-hexylthiophene) and [6,6] phenyl C61 butyric acid methyl fullerene, bulk heterojunction organic photovoltaic devices. Utilization of nanotubes requires chemical modifications for compatibility with solution processable photovoltaics. Better dispersions of carbon nanotubes in organic solvents are achieved by acid functionalization of tubes. Pristine and acid treated multiwall carbon nanotubes have been incorporated into the photoactive

N. A. Nismy; A. A. D. T. Adikaari; S. R. P. Silva

2010-01-01

292

Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad  

Microsoft Academic Search

We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene)) that is end capped with the fullerene derivative PCB ([6,6]-phenyl-C61-butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound

Natalie Banerji; Jason Seifter; Mingfeng Wang; Eric Vauthey; Fred Wudl; Alan J. Heeger

2011-01-01

293

Understanding charge transfer in carbon nanotube-fullerene bulk heterojunctions.  

PubMed

Semiconducting single-walled carbon nanotube/fullerene bulk heterojunctions exhibit unique optoelectronic properties highly suitable for flexible, efficient, and robust photovoltaics and photodetectors. We investigate charge-transfer dynamics in inverted devices featuring a polyethylenimine-coated ZnO nanowire array infiltrated with these blends and find that trap-assisted recombination dominates transport within the blend and at the active layer/nanowire interface. We find that electrode modifiers suppress this recombination, leading to high performance. PMID:25797180

Gong, Maogang; Shastry, Tejas A; Cui, Qiannan; Kohlmeyer, Ryan R; Luck, Kyle A; Rowberg, Andrew; Marks, Tobin J; Durstock, Michael F; Zhao, Hui; Hersam, Mark C; Ren, Shenqiang

2015-04-01

294

Subpicosecond photoinduced electron transfer from conjugated polymers to functionalized fullerenes  

Microsoft Academic Search

We report time-resolved excited state absorption measurements which demonstrate subpicosecond photoinduced electron transfer using soluble derivatives of poly(p-phenylene vinylene) as donors blended with a functionalized fullerene (methanofullerene) as acceptor. The subpicosecond photoinduced absorption spectra of the polymer\\/methanofullerene blends show that electron transfer from the donor to the acceptor occurs within a picosecond of photoexcitation of the conjugated polymer. Precise determination

B. Kraabel; Jan C. Hummelen; D. Vacar; D. Moses; N. S. Sariciftci; A. J. Heeger; F. Wudl

1996-01-01

295

Photoabsorption spectra of Xe atoms encapsulated inside fullerenes  

NASA Astrophysics Data System (ADS)

The photoabsorption spectra of Xe atoms encapsulated inside the C180 and C240 have been investigated using the time-dependent density-functional theory (TDDFT) and compared with the result of our short range spherical well. The calculations are performed in the energy region of the Xe 4d giant resonance and assumed the central location of the Xe atom inside the fullerenes. The Xe-C180 and Xe-C240 binding energies along the high symmetry direction, the z axis have been evaluated as well. The obtained curves show the possibility of other Xe positions. The main features of the confinement resonances for the Xe atoms in the center of the C180 and C240 may be estimated by the formula E(eV) = 67.55 + (12.25n/ 2r)2, where r is the radius in Å of the fullerene, n is the integer number 2, 3, 4, 5, ..., and E (eV) is the location of a confinement peak. The calculations indicate that if the radius of a fullerene equals an integer (?2) × the half wave length of the photoelectron, then at this photon energy we may observe a confinement peak. The photoabsorption spectra of Xe atoms encaged in the center of the C58, C56 and C54 have also been studied. The results demonstrate that, except for the Xe atom inside C58, which has similar confinement resonances as those of the Xe atom inside C60, the Xe atoms inside C54 and C56 have completely different spectra. It is concluded that the quantum confinement resonances will be destroyed if the shape of the fullerene is deformed significantly from a sphere.

Chen, Zhifan; Msezane, Alfred Z.

2015-03-01

296

Is the Use of Fullerene in Photodynamic Therapy Effective for Atherosclerosis?  

SciTech Connect

The purpose of this study was to evaluate Fullerene as a therapeutic photosensitizer in the treatment of atherosclerosis. An atherosclerotic experimental rabbit model was prepared by causing intimal injury to bilateral external iliac arteries using balloon expansion. In four atherosclerotic rabbits and one normal rabbit, polyethylene glycol-modified Fullerene (Fullerene-PEG) was infused into the left external iliac artery and illuminated by light emitting diode (LED), while the right external iliac artery was only illuminated by LED. Two weeks later, the histological findings for each iliac artery were evaluated quantitatively and comparisons were made among atherosclerotic Fullerene+LED artery (n = 4), atherosclerotic light artery (n = 4), normal Fullerene+LED artery (n = 1), and normal light artery (n = 1). An additional two atherosclerotic rabbits were studied by fluorescence microscopy, after Fullerene-PEG-Cy5 complex infusion into the left external iliac artery, for evaluation of Fullerene-PEG incorporated within the atherosclerotic lesions. The degree of atherosclerosis in the atherosclerotic Fullerene+LED artery was significantly (p < 0.05) more severe than that in the atherosclerotic LED artery. No pathological change was observed in normal Fullerene+LED and LED arteries. In addition, strong accumulation of Fullerene-PEG-Cy5 complex within the plaque of the left iliac artery of the two rabbits was demonstrated, in contrast to no accumulation in the right iliac artery. We conclude that infusion of a high concentration of Fullerene-PEG followed by photo-illumination resulted not in a suppression of atherosclerosis but in a progression of atherosclerosis in experimental rabbit models. However, this intervention showed no adverse effects on the normal iliac artery.

Nitta, Norihisa, E-mail: r34nitta@belle.shiga-med.ac.jp; Seko, Ayumi; Sonoda, Akinaga; Ohta, Shinichi; Tanaka, Toyohiko; Takahashi, Masashi; Murata, Kiyoshi [Shiga University of Medical Science, Department of Radiology (Japan); Takemura, Shizuki [Shiga University of Medical Science, Department of Pathology (Japan); Sakamoto, Tsutomu [Koka General Hospital, Department of Radiology (Japan); Tabata, Yasuhiko [Kyoto University, Department of Biomaterials, Field of Tissue Engineering (Japan)

2008-03-15

297

[70]fullerene-based materials for organic solar cells.  

PubMed

The synthesis, characterization and photovoltaic study of two novel derivatives of [70]fullerene, phenyl-C??-propionic acid propyl ester ([70]PCPP) and phenyl-C??-propionic acid butyl ester ([70]PCPB), are reported. [70]PCPP and [70]PCPB outperform the conventional material (6,6)-phenyl-C??-butyric acid methyl ester ([70]PCBM) in solar cells based on poly(2-methoxy-5-{3',7'-dimethyloctyloxy}-p-phenylene vinylene) (MDMO-PPV) as a donor polymer using chlorobenzene (CB) or dichlorobenzene (DCB) as solvents. AFM data suggest that improvement of the device efficiency should be attributed to the increased phase compatibility between the novel C?? derivatives and the polymer matrix. [70]PCPP and [70]PCBM showed more or less equally high performances in solar cells comprising poly(3-hexylthiophene) (P3HT) as a donor polymer. Optical modeling revealed that the application of [70]fullerene derivatives as acceptor materials in P3HT-based bulk heterojunction solar cells might give approximately 10?% higher short circuit current densities than using C??-based materials such as [60]PCBM. The high solubility of [70]PCPP and [70]PCPB and their good compatibility with the donor polymers suggest these fullerene derivatives as promising electron acceptor materials for use in efficient bulk heterojunction organic solar cells. PMID:21226221

Troshin, Pavel A; Hoppe, Harald; Peregudov, Alexander S; Egginger, Martin; Shokhovets, Sviatoslav; Gobsch, Gerhard; Sariciftci, N Serdar; Razumov, Vladimir F

2011-01-17

298

The Environmental Fate of C60 Fullerenes: A Holistic Approach  

NASA Astrophysics Data System (ADS)

The manufacture and use of carbon-based nanoparticles, for which C60 fullerenes can be considered a proxy, has grown exponentially in the past decade, and nanotechnology is now a multi-billion dollar industry, spanning disciplines such as cosmetics, biotechnology, and agriculture. Despite this, almost nothing is known of the fate of these compounds in the environment. Based upon the strong radical scavenging properties of many of these substances there are a variety of microbial and photochemical-mediated oxidative fates that will transform the physicochemical properties and control the residence time of these compounds in nature. It is essential that these fates, as well as the fates of the products of the degradation of carbon nanoparticles, are known. For instance, conversion of C60 fullerenes to hydroxylated or carboxylated analogs will shift the manner in which they partition between soils and sediments and water as well as how they interact with cell membranes. This paper combines our findings on the microbial activity of C60 fullerenes, one of the most common types of manufactured carbon nanoparticles, along with recent literature to develop potential chemical decay trajectories in oxidative environmental settings. We show what is known about the environmental fate of this type of nanomaterial and also areas where further research is needed.

Schreiner, K. M.; Filley, T. R.; Blanchette, R. A.; Jafvert, C.; Bolskar, R.

2007-12-01

299

Study of urological devices coated with fullerene-like nanoparticles  

NASA Astrophysics Data System (ADS)

Insertion of endoscopes and other medical devices into the human body are ubiquitous, especially among aged males. The applied force for the insertion/extraction of the device from the urethra must overcome endoscope-surface-human-tissue interactions. In daily practice a gel is applied on the endoscope surface, in order to facilitate its entry into the urethra, providing also for local anesthesia. In the present work, a new solid-state lubricant has been added to the gel, in order to reduce the metal-urethra interaction and alleviate the potential damage to the epithelial tissue. For that purpose, a urethra model was designed and fabricated, which allowed a quantitative assessment of the applied force for extraction of the endoscope from a soft polymer-based ring. It is shown that the addition of MoS2 nanoparticles with fullerene-like structure (IF-MoS2) and in particular rhenium-doped nanoparticles (Re:IF-MoS2) to Esracain gel applied on the metal-lead reduced the friction substantially. The Re:IF-MoS2 showed better results than the undoped fullerene-like nanoparticles and both performed better than the gel alone. The mechanism of friction reduction is attributed to fullerenes' ability to roll and act as a separator between the active parts of the model.

Goldbart, Ohad; Elianov, Olga; Shumalinsky, Dmitry; Lobik, Leonid; Cytron, Shmuel; Rosentsveig, Rita; Wagner, H. Daniel; Tenne, Reshef

2013-08-01

300

Alternative approaches to onion-like icosahedral fullerenes.  

PubMed

The fullerenes of the C60 series (C60, C240, C540, C960, C1500, C2160 etc.) form onion-like shells with icosahedral Ih symmetry. Up to C2160, their geometry has been optimized by Dunlap & Zope from computations according to the analytic density-functional theory and shown by Wardman to obey structural constraints derived from an affine-extended Ih group. In this paper, these approaches are compared with models based on crystallographic scaling transformations. To start with, it is shown that the 56 symmetry-inequivalent computed carbon positions, approximated by the corresponding ones in the models, are mutually related by crystallographic scalings. This result is consistent with Wardman's remark that the affine-extension approach simultaneously models different shells of a carbon onion. From the regularities observed in the fullerene models derived from scaling, an icosahedral infinite C60 onion molecule is defined, with shells consisting of all successive fullerenes of the C60 series. The structural relations between the C60 onion and graphite lead to a one-parameter model with the same Euclidean symmetry P63mc as graphite and having a c/a = ?(2) ratio, where ? = 1.618… is the golden number. This ratio approximates (up to a 4% discrepancy) the value observed in graphite. A number of tables and figures illustrate successive steps of the present investigation. PMID:24572318

Janner, A

2014-03-01

301

Fullerene-bisadduct acceptors for polymer solar cells.  

PubMed

Polymer solar cells (PSCs) have drawn great attention in recent years for their simple device structure, light weight, and low-cost fabrication in comparison with inorganic semiconductor solar cells. However, the power-conversion efficiency (PCE) of PSCs needs to be increased for their future application. The key issue for improving the PCE of PSCs is the design and synthesis of high-efficiency conjugated polymer donors and fullerene acceptors for the photovoltaic materials. For the acceptor materials, several fullerene-bisadduct acceptors with high LUMO energy levels have demonstrated excellent photovoltaic performance in PSCs with P3HT as a donor. In this Focus Review, recent progress in high-efficiency fullerene-bisadduct acceptors is discussed, including the bisadduct of PCBM, indene-C60 bisadduct (ICBA), indene-C70 bisadduct (IC70BA), DMPCBA, NCBA, and bisTOQC. The LUMO levels and photovoltaic performance of these bisadduct acceptors with P3HT as a donor are summarized and compared. In addition, the applications of an ICBA acceptor in new device structures and with other conjugated polymer donors than P3HT are also introduced and discussed. PMID:23853151

Li, Yongfang

2013-10-01

302

Controlling Active Layer Morphology in Polymer/Fullerene Solar Cells  

NASA Astrophysics Data System (ADS)

The active layer in most polymer solar cells is based on the bulk heterojunction (BHJ) design. BHJs are prepared by arresting the phase separation of a polymer/fullerene blend to produce a nanoscale, interpenetrating network. Such non-equilibrium structures are very difficult to control and reproduce, posing a significant challenge for fundamental structure-property investigations. We demonstrate a new approach to control the active layer morphology with a simple two-step process: First, a thin film of poly(3-hexylthiophene) (P3HT) is cross-linked into stable nanostructures or microstructures with electron-beam lithography [1]. Second, a soluble fullerene is spun-cast on top of the patterned polymer to complete the heterojunction. Significantly, irradiated P3HT films retain good optoelectronic properties and bilayer P3HT/fullerene heterojunctions yield power-conversion efficiencies near 0.5%. We have performed preliminary studies with model nanostructured devices and we find that efficiency increases with interfacial area [2]. These model devices are very valuable for fundamental studies because the interfacial area is accurately measured with small-angle X-ray scattering, and the active layer can be ``deconstructed'' for imaging with atomic force microscopy. [4pt] [1] S. Holdcroft, Adv. Mater. 2001, 13, 1753-1765.[0pt] [2] He et al., Adv Funct. Mater. 2011, 21, 139-146.

Moungthai, Suchanun; Mahadevapuram, Nikhila; Stein, Gila

2012-02-01

303

Fullerene derivatives as electron acceptors for organic photovoltaic cells.  

PubMed

Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells. PMID:24749413

Mi, Dongbo; Kim, Ji-Hoon; Kim, Hee Un; Xu, Fei; Hwang, Do-Hoon

2014-02-01

304

Study of urological devices coated with fullerene-like nanoparticles.  

PubMed

Insertion of endoscopes and other medical devices into the human body are ubiquitous, especially among aged males. The applied force for the insertion/extraction of the device from the urethra must overcome endoscope-surface-human-tissue interactions. In daily practice a gel is applied on the endoscope surface, in order to facilitate its entry into the urethra, providing also for local anesthesia. In the present work, a new solid-state lubricant has been added to the gel, in order to reduce the metal-urethra interaction and alleviate the potential damage to the epithelial tissue. For that purpose, a urethra model was designed and fabricated, which allowed a quantitative assessment of the applied force for extraction of the endoscope from a soft polymer-based ring. It is shown that the addition of MoS2 nanoparticles with fullerene-like structure (IF-MoS2) and in particular rhenium-doped nanoparticles (Re:IF-MoS2) to Esracain gel applied on the metal-lead reduced the friction substantially. The Re:IF-MoS2 showed better results than the undoped fullerene-like nanoparticles and both performed better than the gel alone. The mechanism of friction reduction is attributed to fullerenes' ability to roll and act as a separator between the active parts of the model. PMID:23884307

Goldbart, Ohad; Elianov, Olga; Shumalinsky, Dmitry; Lobik, Leonid; Cytron, Shmuel; Rosentsveig, Rita; Wagner, H Daniel; Tenne, Reshef

2013-09-21

305

Phase changes in insulators produced by particle bombardment  

NASA Astrophysics Data System (ADS)

The problem of phase changes in halides, oxides, carbides, and borides as produced by particle bombardment is considered, with the object of reducing the known examples to the minimum number of mechanisms. The phase changes are grouped topologically, the first group consisting of those which are confined to the outer surface. These are most often caused by electronic sputtering, but near-threshold elastic collisions may be important with substances like Ta 2O 5 where the components have a large mass difference. The second group consists of changes which extend beyond the outer surface. Such changes can be initiated by an outer-layer change, by bombardment-induced redistribution, and, in principle, by Gibbsian segregation. The third group consists of bulk changes brought about with inert beams and includes the more conventional phase changes. Most examples fit rather well into subgroups involving, respectively, dispersed point defects (e.g. randomization of NbO), mobile point defects (e.g. metal colloid formation in a halide), or the cascade itself (e.g. some instances of amorphization). The final group consists of bulk changes brought about with chemically active beams. As with the third category, it is convenient to subdivide according to whether the point defects are dispersed (e.g. H + implanted in an oxide) or mobile (e.g. metal ions implanted in an oxide at elevated temperatures).

Kelly, Roger

1981-05-01

306

Atom penetration from a thin film into the substrate during sputtering by polyenergetic Ar{sup +} ion beam with mean energy of 9.4 keV  

SciTech Connect

Penetration of alien atoms (Be, Ni) into Be, Al, Zr, Si and diamond was investigated under Ar{sup +} ion bombardment of samples having thermally evaporated films of 30--50 nm. Sputtering was carried out using a wide energy spectrum beam of Ar{sup +} ions of 9.4 keV to dose D = 1 {times} 10{sup 16}--10{sup 19} ion/cm{sup 2}. Implanted atom distribution in the targets was measured by Rutherford backscattering spectrometry (RBS) of H{sup +} and He{sup +} ions with energy of 1.6 MeV as well as secondary ion mass-spectrometry (SIMS). During the bombardment, the penetration depth of Ar atoms increases with dose linearly. This depth is more than 3--20 times deeper than the projected range of bombarding ions and recoil atoms. This is a deep action effect. The analysis shows that the experimental data for foreign atoms penetration depth are similar to the data calculated for atom migration through the interstitial site in a field of internal (lateral) compressive stresses created in the near-surface layer of the substrate as a result of implantation. Under these experimental conditions atom ratio r{sub i}/r{sub m} (r{sub i} -- radius of dopant, r{sub m} -- radius target of substrate) can play a principal determining role.

Kalin, B.A.; Gladkov, V.P.; Volkov, N.V.; Sabo, S.E. [Moscow Engineering Physics Inst. (Russian Federation)

1995-12-31

307

Conformationally Constrained Macrocyclic Diporphyrin?Fullerene Artificial Photosynthetic Reaction Center  

SciTech Connect

Photosynthetic reaction centers convert excitation energy from absorbed sunlight into chemical potential energy in the form of a charge-separated state. The rates of the electron transfer reactions necessary to achieve long-lived, high-energy charge-separated states with high quantum yields are determined in part by precise control of the electronic coupling among the chromophores, donors, and acceptors and of the reaction energetics. Successful artificial photosynthetic reaction centers for solar energy conversion have similar requirements. Control of electronic coupling in particular necessitates chemical linkages between active component moieties that both mediate coupling and restrict conformational mobility so that only spatial arrangements that promote favorable coupling are populated. Toward this end, we report the synthesis, structure, and photochemical properties of an artificial reaction center containing two porphyrin electron donor moieties and a fullerene electron acceptor in a macrocyclic arrangement involving a ring of 42 atoms. The two porphyrins are closely spaced, in an arrangement reminiscent of that of the special pair in bacterial reaction centers. The molecule is produced by an unusual cyclization reaction that yields mainly a product with C{sub 2} symmetry and trans-2 disubstitution at the fullerene. The macrocycle maintains a rigid, highly constrained structure that was determined by UV?vis spectroscopy, NMR, mass spectrometry, and molecular modeling at the semiempirical PM6 and DFT (B3LYP/6-31G**) levels. Transient absorption results for the macrocycle in 2-methyltetrahydrofuran reveal photoinduced electron transfer from the porphyrin first excited singlet state to the fullerene to form a P{sup •+}?C{sub 60}{sup •?}?P charge separated state with a time constant of 1.1 ps. Photoinduced electron transfer to the fullerene excited singlet state to form the same charge-separated state has a time constant of 15 ps. The charge-separated state is formed with a quantum yield of essentially unity and has a lifetime of 2.7 ns. The ultrafast charge separation coupled with charge recombination that is over 2000 times slower is consistent with a very rigid molecular structure having a small reorganization energy for electron transfer, relative to related porphyrin?fullerene molecules.

Garg, Vikas; Kodis, Gerdenis; Chachisvilis, Mirianas; Hambourger, Michael; Moore, Ana L.; Moore, Thomas A.; Gust, Devens

2011-01-01

308

Facile construction of well-defined fullerene-dendrimer supramolecular nanocomposites for bioapplications.  

PubMed

Well-defined fullerene-dendrimer supramolecular nanocomposites exhibiting uniform size, controlled morphology, high fullerene inclusion efficiency, excellent water solubility, and non-toxicity were facilely fabricated through complexation of carboxyfullerenes with poly(ethylene glycol)-modified poly(amidoamine) dendrimers. PMID:25580012

Li, Xiaojie; Watanabe, Yasuo; Yuba, Eiji; Harada, Atsushi; Haino, Takeharu; Kono, Kenji

2015-02-18

309

Changes in Agglomeration of Fullerenes During Ingestion and Excretion in Thamnocephalus Platyurus  

EPA Science Inventory

The crustacean Thamnocephalus platyurus was exposed to aqueous suspensions of fullerenes C60 and C70. Aqueous fullerene suspensions were formed by stirring C60 and C70 as received from a commercial vendor in deionized water (termed aqu/C60 and aqu/C70) for approximately 100 d. Th...

310

Nano Materials They sound like characters in a miniature fantasyland: fullerene, nanotube and quantum dot. But  

E-print Network

71 Nano Materials They sound like characters in a miniature fantasyland: fullerene, nanotube size, interact directly with target cells, proteins and viruses. Introducing fullerenes, nanotubes and other mini-marvels continued A land whose stones are iron, and out of whose hills you can dig copper

Maoz, Shahar

311

Assembly of carbon nanotubes and alkylated fullerenes: nanocarbon hybrid towards photovoltaic applications  

E-print Network

Assembly of carbon nanotubes and alkylated fullerenes: nanocarbon hybrid towards photovoltaic alkyl chains and the sidewalls of a single- walled carbon nanotube (SWCNT), a nanocarbon hybrid of SWCNT and a fullerene (C60) derivative with long alkyl chains was constructed as a donor­acceptor pair for photovoltaics

Nabben, Reinhard

312

Carbon Onion Films-Molecular Interactions of Multi-Layer Fullerenes Raed A. Alduhaileb,1  

E-print Network

Carbon Onion Films-Molecular Interactions of Multi-Layer Fullerenes Raed A. Alduhaileb,1 Virginia M-8550, Japan ABSTRACT The evolution of carbon onion structure from spherical to polyhedral is correlated-shell fullerenes, or carbon onions, are under investigation as a nano-property enabled solid lubricant

Ayres, Virginia

313

Water-soluble fullerene materials for bioapplications: photoinduced reactive oxygen species generation  

Technology Transfer Automated Retrieval System (TEKTRAN)

The photoinduced reactive oxygen species (ROS) generation from several water-soluble fullerenes was examined. Macromolecular or small molecular water-soluble fullerene complexes/derivatives were prepared and their 1O2 and O2•- generation abilities were evaluated by EPR spin-trapping methods. As a r...

314

Fullerene Nanoparticles Exhibit Greater Retention in Freshwater Sediment than in Model Porous Media  

EPA Science Inventory

Increasing production and use of fullerene-based nanomaterials underscore the need to determine their mobility in environmental transport pathways and potential ecological exposures. This study investigated the transport of two fullerenes (i.e., aqu/C(60) and water-soluble C(60) ...

315

Ni-dispersed fullerenes: Hydrogen storage and desorption properties Weon Ho Shin and Seong Ho Yang  

E-print Network

Ni-dispersed fullerenes: Hydrogen storage and desorption properties Weon Ho Shin and Seong Ho Yang could be viable alternatives to reversible hydrogen storage. It is demonstrated that a single Ni coated-dispersed fullerenes are considered to be the novel hydrogen storage media capable of storing 6.8 wt % H2, thus

Goddard III, William A.

316

Adsorption and thermal desorption of fullerenes on the surface of a crystal  

NASA Astrophysics Data System (ADS)

A statistical theory of adsorption and thermal desorption of fullerenes in a multi-layer fullerite film on a crystal surface is developed. The equilibrium fullerene concentration is calculated as a function of temperature, film thickness, and energy constants of the system. The developing process of desorption with increase in temperature, which was observed experimentally, is validated.

Matysina, Z. A.; Zaginaichenko, S. Yu.; Schur, D. V.

2007-09-01

317

[Effect of C60 fullerene on viscoelastic properties of human erythrocytes membrane].  

PubMed

The effect of C60 fullerene aqueous colloid solution (C60FAS) on viscoelastic properties of human erythrocytes membrane has been studied. It was established that the effect of C60FAS on erythrocytes depends on the medium osmolality and concentration of C60 fullerene in it. In particular, in isotonic solution (0,15 mol/l NaCl) adding C60 fullerene in concentrations from 0,7 to 28 ?mol/l did not cause the hemolytic damage of cells. In hypotonic medium when introducing C60 fullerene (7 ?mol/l concentration) at the beginning of erythrocyte hemolysis its stimulating effect was maximal and when adding C60FAS in 20 s after hemolysis start no this process stimulation is observed. This points to the changes in viscoelastic properties of erythrocyte membranes even during the first seconds of its interaction with C60 fullerene. PMID:25566674

Shpakova, N M; Nipot, O S; Ishchenko, I O; Pryluts'ka, S V; Bohuts'ka, K I; Cherepanov, V V; Sandomyrs'ky?, B P; Pryluts'ky?, Iu I

2014-01-01

318

Fullerene mixtures enhance the thermal stability of a non-crystalline polymer solar cell blend  

NASA Astrophysics Data System (ADS)

Printing of polymer:fullerene solar cells at high speed requires annealing at temperatures up to 140 °C. However, bulk-heterojunction blends that comprise a non-crystalline donor polymer often suffer from insufficient thermal stability and hence rapidly coarsen upon annealing above the glass transition temperature of the blend. In addition, micrometer-sized fullerene crystals grow, which are detrimental for the solar cell performance. In this manuscript, we present a strategy to limit fullerene crystallization, which is based on the use of fullerene mixtures of the two most common derivatives, PC61BM and PC71BM, as the acceptor material. Blends of this fullerene mixture and a non-crystalline thiophene-quinoxaline copolymer display considerably enhanced thermal stability and largely retain their photovoltaic performance upon annealing at elevated temperatures as high as 170 °C.

Lindqvist, Camilla; Bergqvist, Jonas; Bäcke, Olof; Gustafsson, Stefan; Wang, Ergang; Olsson, Eva; Inganäs, Olle; Andersson, Mats R.; Müller, Christian

2014-04-01

319

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

SciTech Connect

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.

Ali, R.; Berry, H.G.; Cheng, S. [and others

1996-03-01

320

Evidence Supporting an Early as Well as Late Heavy Bombardment on the Moon  

NASA Technical Reports Server (NTRS)

Evidence supporting an intense early bombardment on the Moon in addition to the traditional Late Heavy Bombardment at approx. 4 BY ago include the distribution of N(50) Crater Retention Ages (CRAs) for candidate basins, a variety of absolute age scenarios for both a "young" and an "old" Nectaris age, and the decreasing contrasts in both topographic relief and Bouguer gravity with increasing CRA.

Frey, Herbert

2015-01-01

321

Chemical Separation of the Radioactive Element from its Bombarded Isotope in the Fermi Effect  

Microsoft Academic Search

Following the pioneer experiment of Fermi, it has been found by Fermi, Amaldi, D'Agostino, Rasetti and Segrè that many elements up to the atomic number 30, when bombarded by neutrons from a radon-beryllium source, are transmuted into a radioactive element which is chemically different from the bombarded element. In several cases of this type, they succeeded in separating chemically the

Leo Szilard; T. A. Chalmers

1934-01-01

322

Origin of the cataclysmic Late Heavy Bombardment period of the terrestrialplanets  

Microsoft Academic Search

The petrology record on the Moon suggests that a cataclysmic spike in the cratering rate occurred ~700 million years after the planets formed; this event is known as the Late Heavy Bombardment (LHB). Planetary formation theories cannot naturally account for an intense period of planetesimal bombardment so late in Solar System history. Several models have been proposed to explain a

R. Gomes; H. F. Levison; K. Tsiganis; A. Morbidelli

2005-01-01

323

Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets  

Microsoft Academic Search

The petrology record on the Moon suggests that a cataclysmic spike in the cratering rate occurred ,700 million years after the planets formed1; this event is known as the Late Heavy Bombard- ment (LHB). Planetary formation theories cannot naturally account for an intense period of planetesimal bombardment so late in Solar System history2. Several models have been proposed to explain

R. Gomes; H. F. Levison; K. Tsiganis; A. Morbidelli

1998-01-01

324

Thermal/electron irradiation assisted coalescence of Sc3N@C80 fullerene in carbon nanotube and evidence of charge transfer between pristine/coalesced fullerenes and nanotubes  

NASA Astrophysics Data System (ADS)

Sc3N@C80 fullerenes are inserted inside carbon nanotubes (CNTs). The results show that the thermal stability of Sc3N@C80 fullerenes is around 1200 °C for the fullerenes resting on the wall of CNTs. Internal fullerenes show stability up to 1300 °C, which portrays them as one of most stable types of fullerenes. Electron irradiation of the peapods at 90 kV leads to the formation of capsules inside the CNTs at 5 × 109 e nm-2 electron dosage. This value is an order of magnitude higher than the threshold of electron-induced damage in C60 molecules. Electron energy loss spectroscopy confirms the presence of Sc atoms in capsules. Encapsulation of fullerenes and capsule formation changes the oxidation state of Sc atoms from +2.5 towards +3. This is an evidence of charge transfer between the fullerene/capsule cage and CNT walls.

Fallah, Ahmadreza; Yonetani, Yuki; Senga, Ryosuke; Hirahara, Kaori; Kitaura, Ryo; Shinohara, Hisanori; Nakayama, Yoshikazu

2013-11-01

325

Importance of the donor:fullerene intermolecular arrangement for high-efficiency organic photovoltaics.  

PubMed

The performance of organic photovoltaic (OPV) material systems are hypothesized to depend strongly on the intermolecular arrangements at the donor:fullerene interfaces. A review of some of the most efficient polymers utilized in polymer:fullerene PV devices, combined with an analysis of reported polymer donor materials wherein the same conjugated backbone was used with varying alkyl substituents, supports this hypothesis. Specifically, the literature shows that higher-performing donor-acceptor type polymers generally have acceptor moieties that are sterically accessible for interactions with the fullerene derivative, whereas the corresponding donor moieties tend to have branched alkyl substituents that sterically hinder interactions with the fullerene. To further explore the idea that the most beneficial polymer:fullerene arrangement involves the fullerene docking with the acceptor moiety, a family of benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione polymers (PBDTTPD derivatives) was synthesized and tested in a variety of PV device types with vastly different aggregation states of the polymer. In agreement with our hypothesis, the PBDTTPD derivative with a more sterically accessible acceptor moiety and a more sterically hindered donor moiety shows the highest performance in bulk-heterojunction, bilayer, and low-polymer concentration PV devices where fullerene derivatives serve as the electron-accepting materials. Furthermore, external quantum efficiency measurements of the charge-transfer state and solid-state two-dimensional (2D) (13)C{(1)H} heteronuclear correlation (HETCOR) NMR analyses support that a specific polymer:fullerene arrangement is present for the highest performing PBDTTPD derivative, in which the fullerene is in closer proximity to the acceptor moiety of the polymer. This work demonstrates that the polymer:fullerene arrangement and resulting intermolecular interactions may be key factors in determining the performance of OPV material systems. PMID:24932575

Graham, Kenneth R; Cabanetos, Clement; Jahnke, Justin P; Idso, Matthew N; El Labban, Abdulrahman; Ngongang Ndjawa, Guy O; Heumueller, Thomas; Vandewal, Koen; Salleo, Alberto; Chmelka, Bradley F; Amassian, Aram; Beaujuge, Pierre M; McGehee, Michael D

2014-07-01

326

Comparative computational study of interaction of C60-fullerene and tris-malonyl-C60-fullerene isomers with lipid bilayer: relation to their antioxidant effect.  

PubMed

Oxidative stress induced by excessive production of reactive oxygen species (ROS) has been implicated in the etiology of many human diseases. It has been reported that fullerenes and some of their derivatives-carboxyfullerenes-exhibits a strong free radical scavenging capacity. The permeation of C60-fullerene and its amphiphilic derivatives-C3-tris-malonic-C60-fullerene (C3) and D3-tris-malonyl-C60-fullerene (D3)-through a lipid bilayer mimicking the eukaryotic cell membrane was studied using molecular dynamics (MD) simulations. The free energy profiles along the normal to the bilayer composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) for C60, C3 and D3 were calculated. We found that C60 molecules alone or in clusters spontaneously translocate to the hydrophobic core of the membrane and stay inside the bilayer during the whole period of simulation time. The incorporation of cluster of fullerenes inside the bilayer changes properties of the bilayer and leads to its deformation. In simulations of the tris-malonic fullerenes we discovered that both isomers, C3 and D3, adsorb at the surface of the bilayer but only C3 tends to be buried in the area of the lipid headgroups forming hydrophobic contacts with the lipid tails. We hypothesize that such position has implications for ROS scavenging mechanism in the specific cell compartments. PMID:25019215

Bozdaganyan, Marine E; Orekhov, Philipp S; Shaytan, Alexey K; Shaitan, Konstantin V

2014-01-01

327

Optical radiation from regions downstream of mercury bombardment thrusters  

NASA Technical Reports Server (NTRS)

A 0.5 meter focal length, plane grating monochromator was used to measure the radiance of spectral radiation emanating from regions downstream of a mercury bombardment thruster. The wavelength range investigated was 2800 A. This radiation was due primarily to the radiative decay of excited mercury atoms exhausted from the thruster. Radiance values ranged from 10 to the minus 11th power to 10 to the minus 9th power W/sq cm sr, varying with wavelength. For resonant radiation, the spectral radiance may exceed 10 to the minus 8th power W/sq cm sr. From such radiance measurements, it was concluded that the thruster background radiation should not interfere with the control functions of a star tracker viewing through the thruster exhaust, provided that the tracker is designed to operate with a sufficiently small field of view.

Milder, N. L.; Sovey, J. S.

1972-01-01

328

Spontaneous Pattern Formation on Ion Bombarded Si(001)  

SciTech Connect

Pattern formation on surfaces undergoing low-energy ion bombardment is a common phenomenon. Here, a recently developed in situ spectroscopic light scattering technique was used to monitor periodic ripple evolution on Si(001) during Ar(+) sputtering. Analysis of the rippling kinetics indicated that under high flux sputtering at low temperatures the concentration of mobile species on the surface is saturated, and, surprisingly, is both temperature and ion flux independent. This is due to an effect of ion collision cascades on the concentration of mobile species. This new understanding of surface dynamics during sputtering allowed us to measure straighforwardly the activation energy for atomic migration on the surface to be 1.2+0.1 eV. The technique is generalizable to any material, including high temperature and insulating materials for which surface migration energies are notoriously difficult to measure.

Chason, Eric; Erlebacher, Jonah, Aziz, Michael J.; Floro, Jerrold A.; Sinclair, Michael B.

1999-04-26

329

Ion-trap electrode preparation with Ne$^+$ bombardment  

E-print Network

We describe an ex-situ surface-cleaning procedure that is shown to reduce motional heating from ion-trap electrodes. This precleaning treatment, to be implemented immediately before the final assembly and vacuum processing of ion traps, removes surface contaminants remaining after the electrode-fabrication process. We incorporate a multi-angle ion-bombardment treatment intended to clean the electrode surfaces and interelectrode gaps of microfabricated traps. This procedure helps to minimize redeposition in the gaps between electrodes that can cause electrical shorts. We report heating rates in a stylus-type ion trap prepared in this way that are lower by one order of magnitude compared to a similar untreated stylus-type trap using the same experimental setup.

K. S. McKay; D. A. Hite; Y. Colombe; R. Jördens; A. C. Wilson; D. H. Slichter; D. T. C. Allcock; D. Leibfried; D. J. Wineland; D. P. Pappas

2014-06-06

330

Sputtering yield of Pu bombarded by fission Fragments from Cf  

SciTech Connect

We present results on the yield of sputtering of Pu atoms from a Pu foil, bombarded by fission fragments from a {sup 252}Cf source in transmission geometry. We have found the number of Pu atoms/incoming fission fragments ejected to be 63 {+-} 1. In addition, we show measurements of the sputtering yield as a function of distance from the central axis, which can be understood as an angular distribution of the yield. The results are quite surprising in light of the fact that the Pu foil is several times the thickness of the range of fission fragment particles in Pu. This indicates that models like the binary collision model are not sufficient to explain this behavior.

Danagoulian, Areg [Los Alamos National Laboratory; Klein, Andreas [Los Alamos National Laboratory; Mcneil, Wendy V [Los Alamos National Laboratory; Yuan, Vincent W [Los Alamos National Laboratory

2008-01-01

331

Bombarding Cancer: Biolistic Delivery of therapeutics using Porous Si Carriers  

NASA Astrophysics Data System (ADS)

A new paradigm for an effective delivery of therapeutics into cancer cells is presented. Degradable porous silicon carriers, which are tailored to carry and release a model anti-cancer drug, are biolistically bombarded into in-vitro cancerous targets. We demonstrate the ability to launch these highly porous microparticles by a pneumatic capillary gene gun, which is conventionally used to deliver cargos by heavy metal carriers. By optimizing the gun parameters e.g., the accelerating gas pressure, we have successfully delivered the porous carriers, to reach deep targets and to cross a skin barrier in a highly spatial resolution. Our study reveals significant cytotoxicity towards the target human breast carcinoma cells following the delivery of drug-loaded carriers, while administrating empty particles results in no effect on cell viability. The unique combination of biolistics with the temporal control of payload release from porous carriers presents a powerful and non-conventional platform for designing new therapeutic strategies.

Zilony, Neta; Tzur-Balter, Adi; Segal, Ester; Shefi, Orit

2013-08-01

332

Bombarding Cancer: Biolistic Delivery of therapeutics using Porous Si Carriers  

PubMed Central

A new paradigm for an effective delivery of therapeutics into cancer cells is presented. Degradable porous silicon carriers, which are tailored to carry and release a model anti-cancer drug, are biolistically bombarded into in-vitro cancerous targets. We demonstrate the ability to launch these highly porous microparticles by a pneumatic capillary gene gun, which is conventionally used to deliver cargos by heavy metal carriers. By optimizing the gun parameters e.g., the accelerating gas pressure, we have successfully delivered the porous carriers, to reach deep targets and to cross a skin barrier in a highly spatial resolution. Our study reveals significant cytotoxicity towards the target human breast carcinoma cells following the delivery of drug-loaded carriers, while administrating empty particles results in no effect on cell viability. The unique combination of biolistics with the temporal control of payload release from porous carriers presents a powerful and non-conventional platform for designing new therapeutic strategies. PMID:23975675

Zilony, Neta; Tzur-Balter, Adi; Segal, Ester; Shefi, Orit

2013-01-01

333

Universality of Spectator Fragmentation at Relativistic Bombarding Energies  

E-print Network

Multi-fragment decays of 129Xe, 197Au, and 238U projectiles in collisions with Be, C, Al, Cu, In, Au, and U targets at energies between E/A = 400 MeV and 1000 MeV have been studied with the ALADIN forward-spectrometer at SIS. By adding an array of 84 Si-CsI(Tl) telescopes the solid-angle coverage of the setup was extended to \\theta_lab = 16 degree. This permitted the complete detection of fragments from the projectile-spectator source. The dominant feature of the systematic set of data is the Z_bound universality that is obeyed by the fragment multiplicities and correlations. These observables are invariant with respect to the entrance channel if plotted as a function of Z_bound, where Z_bound is the sum of the atomic numbers Z_i of all projectile fragments with Z_i \\geq 2. No significant dependence on the bombarding energy nor on the target mass is observed. The dependence of the fragment multiplicity on the projectile mass follows a linear scaling law. The reasons for and the limits of the observed universality of spectator fragmentation are explored within the realm of the available data and with model studies. It is found that the universal properties should persist up to much higher bombarding energies than explored in this work and that they are consistent with universal features exhibited by the intranuclear cascade and statistical multifragmentation models. PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.-q

A. Schuettauf; W. D. Kunze; A. Woerner; M. Begemann-Blaich; Th. Blaich; D. R. Bowman; R. J. Charity; A. Cosmo; A. Ferrero; C. K. Gelbke; C. Gross; W. C. Hsi; J. Hubele; G. Imme; I. Iori; P. Kreutz; G. J. Kunde; V. Lindenstruth; M. A. Lisa; W. G. Lynch; U. Lynen; M. Mang; T. Moehlenkamp; A. Moroni; W. F. J. Mueller; M. Neumann; B. Ocker; C. A. Ogilvie; G. F. Peaslee; J. Pochodzalla; G. Raciti; Th. Rubehn; H. Sann; C. Schwarz; W. Seidel; V. Serfling; L. G. Sobotka; J. Stroth; L. Stuttge; S. Tomasevic; W. Trautmann; A. Trzcinski; M. B. Tsang; A. Tucholski; G. Verde; C. W. Williams; E. Zude; B. Zwieglinski

1996-06-18

334

Possible Mechanisms of Fullerene C60 Antioxidant Action  

PubMed Central

Novel mechanism of antioxidant activity of buckminsterfullerene C60 based on protons absorbing and mild uncoupling of mitochondrial respiration and phosphorylation was postulated. In the present study we confirm this hypothesis using computer modeling based on Density Functional Theory. Fullerene's geroprotective activity is sufficiently higher than those of the most powerful reactive oxygen species scavengers. We propose here that C60 has an ability to acquire positive charge by absorbing inside several protons and this complex could penetrate into mitochondria. Such a process allows for mild uncoupling of respiration and phosphorylation. This, in turn, leads to the decrease in ROS production. PMID:24222918

Chistyakov, V. A.; Smirnova, Yu. O.; Prazdnova, E. V.; Soldatov, A. V.

2013-01-01

335

An experiment to study fullerene formation under reduced gravity  

NASA Technical Reports Server (NTRS)

The activity of the summer focused on the design and construction of key components of a carbon arc/inert gas reactor for fullerene production, that is suitable for reduced gravity experiments onboard the KC-135 aircraft. The apparatus will be configured for both floor-mount and free-floating operation providing access to reduction to 10(exp -2) and 10(exp -3) of normal respectively. It is planned to incorporate 'seat belt' restraints that will allow a safe transition from reduced gravity free-float to full gravity, at the end of the parabolic.

Wdowiak, Thomas J.

1992-01-01

336

Switching in C60-fullerene based field effect transistors  

NASA Astrophysics Data System (ADS)

We are reporting on the electrical properties of a bottom gate C60-fullerene based n-channel organic field effect transistor. The C60 thin film was epitaxially grown using hot wall epitaxy on top of an organic dielectric divinyltetramethyldisiloxane-bis(benzocyclobutene). The device performance depends on the growth parameters during the C60 film growth. Optimization of the growth parameters leads to a C60 film of a low total number of traps, and the drain-source current is increased by two orders in magnitude. We propose that the high current-densities are caused by space charge limited currents beside the gate induced space charge.

Matt, G. J.; Singh, Th. B.; Sariciftci, N. S.; Montaigne Ramil, A.; Sitter, H.

2006-06-01

337

Synthesis of endohedral iron-fullerenes by ion implantation.  

PubMed

In this paper, we discuss the results of our study of the synthesis of endohedral iron-fullerenes. A low energy Fe(+) ion beam was irradiated to C60 thin film by using a deceleration system. Fe(+)-irradiated C60 thin film was analyzed by high performance liquid chromatography and laser desorption/ ionization time-of-flight mass spectrometry. We investigated the performance of the deceleration system for using a Fe(+) beam with low energy. In addition, we attempted to isolate the synthesized material from a Fe(+)-irradiated C60 thin film by high performance liquid chromatography. PMID:24593524

Minezaki, H; Ishihara, S; Uchida, T; Muramatsu, M; Rácz, R; Asaji, T; Kitagawa, A; Kato, Y; Biri, S; Yoshida, Y

2014-02-01

338

Electrically conducting porphyrin and porphyrin-fullerene electropolymers  

DOEpatents

Compounds with aryl ring(s) at porphyrin meso position(s) bearing an amino group in position 4 relative to the porphyrin macrocycle, and at least one unsubstituted 5 (hydrogen-bearing) meso position with the 10-, 15-, and/or 20-relationship to the aryl ring bearing the amino group, and metal complexes thereof, feature broad spectral absorption throughout the visible region. These compounds are electropolymerized to form electrically conducting porphyrin and porphyrin-fullerene polymers that are useful in photovoltaic applications. The structure of one such electrically conducting porphyrin polymer is shown below. ##STR00001##

Gust, Jr., John Devens; Liddell, Paul Anthony; Gervaldo, Miguel Andres; Bridgewater, James Ward; Brennan, Bradley James; Moore, Thomas Andrew; Moore, Ana Lorenzelli

2014-03-11

339

Synthesis of endohedral iron-fullerenes by ion implantation  

SciTech Connect

In this paper, we discuss the results of our study of the synthesis of endohedral iron-fullerenes. A low energy Fe{sup +} ion beam was irradiated to C{sub 60} thin film by using a deceleration system. Fe{sup +}-irradiated C{sub 60} thin film was analyzed by high performance liquid chromatography and laser desorption/ ionization time-of-flight mass spectrometry. We investigated the performance of the deceleration system for using a Fe{sup +} beam with low energy. In addition, we attempted to isolate the synthesized material from a Fe{sup +}-irradiated C{sub 60} thin film by high performance liquid chromatography.

Minezaki, H.; Ishihara, S. [Graduate School of Engineering, Toyo University, 2100, Kujirai, Kawagoe, Saitama 350-8585 (Japan)] [Graduate School of Engineering, Toyo University, 2100, Kujirai, Kawagoe, Saitama 350-8585 (Japan); Uchida, T., E-mail: uchida-t@toyo.jp [Bio-Nano Electronics Research Centre, Toyo University, 2100, Kujirai, Kawagoe, Saitama 350-8585 (Japan); Muramatsu, M.; Kitagawa, A. [National Institute of Radiological Sciences (NIRS), 4-9-1, Anagawa, Inage-ku, Chiba-shi, Chiba 263-8555 (Japan)] [National Institute of Radiological Sciences (NIRS), 4-9-1, Anagawa, Inage-ku, Chiba-shi, Chiba 263-8555 (Japan); Rácz, R.; Biri, S. [Institute of Nuclear Research (ATOMKI), Bem tér 18/C, H-4026 Debrecen (Hungary)] [Institute of Nuclear Research (ATOMKI), Bem tér 18/C, H-4026 Debrecen (Hungary); Asaji, T. [Oshima National College of Maritime Technology, 1091-1, Komatsu Suou Oshima-city Oshima, Yamaguchi 742-2193 (Japan)] [Oshima National College of Maritime Technology, 1091-1, Komatsu Suou Oshima-city Oshima, Yamaguchi 742-2193 (Japan); Kato, Y. [Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita-shi, Osaka 565-0871 (Japan)] [Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita-shi, Osaka 565-0871 (Japan); Yoshida, Y. [Graduate School of Engineering, Toyo University, 2100, Kujirai, Kawagoe, Saitama 350-8585 (Japan) [Graduate School of Engineering, Toyo University, 2100, Kujirai, Kawagoe, Saitama 350-8585 (Japan); Bio-Nano Electronics Research Centre, Toyo University, 2100, Kujirai, Kawagoe, Saitama 350-8585 (Japan)

2014-02-15

340

Viruses and Fullerenes - Symmetry as a Common Thread?  

E-print Network

We apply here the principle of affine symmetry to the nested fullerene cages (carbon onions) that arise in the context of carbon chemistry. Previous work on affine extensions of the icosahedral group has revealed a new organisational principle in virus structure and assembly. We adapt this group theoretic framework here to the physical requirements dictated by carbon chemistry, and show that we can derive mathematical models for carbon onions within this affine symmetry approach. This suggests the applicability of affine symmetry in a wider context in Nature, as well as offering a novel perspective on the geometric principles underpinning carbon chemistry.

Dechant, Pierre-Philippe; Keef, Tom; Twarock, Reidun

2014-01-01

341

Viruses and Fullerenes - Symmetry as a Common Thread?  

E-print Network

We apply here the principle of affine symmetry to the nested fullerene cages (carbon onions) that arise in the context of carbon chemistry. Previous work on affine extensions of the icosahedral group has revealed a new organisational principle in virus structure and assembly. We adapt this group theoretic framework here to the physical requirements dictated by carbon chemistry, and show that we can derive mathematical models for carbon onions within this affine symmetry approach. This suggests the applicability of affine symmetry in a wider context in Nature, as well as offering a novel perspective on the geometric principles underpinning carbon chemistry.

Pierre-Philippe Dechant; Jess Wardman; Tom Keef; Reidun Twarock

2014-02-18

342

Energy versus charge transfer in ?-conjugated polymer:fullerene blends  

NASA Astrophysics Data System (ADS)

The article is focused on the detailed elucidation of fluorescence quenching by charge and/or energy transfer in ?-conjugated polymers. The processes were studied in blends of MDMO-PPV, Tg-PPV, PCDTBT and PCBTDPP with fullerenes PC60BM and PC70BM in chlorobenzene. Fluorescence quenching was evaluated by the Perrin equation for static quenching and quenching sphere radiuses were calculated. These radiuses were found to be the same as the Förster critical distances for resonance energy transfer. It was concluded that energy transfer prevails over charge transfer under the conditions where the donor and acceptor are not in close contact.

Heinrichova, Patricie; Vala, Martin; Weiter, Martin

2014-01-01

343

Radial distribution function of C sub 60 : Structure of fullerene  

SciTech Connect

The structure of C{sub 60}, fullerene clusters in the solid state has been obtained by a radial distribution function (rdf) determination. Neutron-diffraction measurements extending to {ital Q} values of 45 A {sup {minus}1} yield rdf with thirteen distinct features at 300 K. This corresponds to the predicted number of groups of distances for the truncated icosohedral structure with thermal broadening. A comparison of the rdf with those predicted from other studies, as well as modeling, indicate important differences and provide an improved estimate of double- and single-bond distances.

Li, F. (Department of Physics, Penn State University, University Park, Pennsylvania 16802 (United States)); Ramage, D. (Department of Chemistry, Penn State University, University Park, Pennsylvania 16802 (United States)); Lannin, J.S. (Department of Physics, Penn State University, University Park, Pennsylvania 16802 (United States)); Conceicao, J. (Department of Chemistry, Rice University, Houston, Texas 77251 (United States))

1991-12-15

344

Fullerenes, PAH, Carbon Nanostructures, and Soot in Low Pressure Diffusion Flames  

NASA Technical Reports Server (NTRS)

The formation of fullerenes C60 and C7O is known to occur in premixed laminar benzene/oxygen/argon flames operated at reduced pressures. High resolution transmission electron microscopy (HRTEM) images of material collected from these flames has identified a variety of multishelled nanotubes and fullerene 'onions' as well as some trigonous structures. These fullerenes and nanostructures resemble the material that results from commercial fullerene production systems using graphite vaporization. As a result, combustion is an interesting method for fullerenes synthesis. If commercial scale operation is to be considered, the use of diffusion flames might be safer and less cumbersome than premixed flames. However, it is not known whether diffusion flames produce the types and yields of fullerenes obtained from premixed benzene/oxygen flames. Therefore, the formation of fullerenes and carbon nanostructures, as well as polycyclic aromatic hydrocarbons (PAH) and soot, in acetylene and benzene diffusion flames is being studied using high performance liquid chromatography (HPLC) and high resolution transmission electron microscopy (HRTEM).

Grieco, William J.; Lafleur, Arthur L.; Rainey, Lenore C.; Taghizadeh, Koli; VanderSande, John B.; Howard, Jack B.

1997-01-01

345

Chemical effects of Ne(+) bombardment on the MoS2(0001) surface studied by high-resolution photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The effect of 1-keV Neon cation bombardment on the clean Molybdenum disulfide (0001) - 1 x 1 surface with fluences between 4 x 10 to the 14th power Ne(+)/sq cm was studied using high-resolution photoelectron spectroscopy excited with synchrotron radiation. Spectra of the Mo-3d and S-2p core levels were measured with photon energies that ensured that the kinetic energy of their photoelectrons was the same, resulting in the same depth being probed for both core levels. For lower fluences, S vacancy defect formation occurs in the MoS2 lattice, with the concurrent formation of a small amount (less than 10 percent) of dispersed elemental molybdenum Mo(0). For fluences greater than approx. 1 x 10 to the 16th power Ne(+)/sq cm, the Mo(0) is the predominant species in the surface region, while the remaining species consists of amorphous MoS(2-x) and polysulfide species. Valence band spectra taken with photon energies of 152 eV and 225 eV were consistent with the core level results. The movement of the valence band maximum toward the Fermi level indicated the formation of a metallic surface region. A qualitative depth distribution of the chemical species present after Ne(+) bombardment was determined.

Lince, Jeffrey R.; Stewart, Thomas B.; Hills, Malina M.; Fleischauer, Paul D.; Yarmoff, Jory A.; Taleb-Ibrahimi, Amina

1989-03-01

346

Linear attenuation coefficients of tissues from 1 keV to 150 keV  

NASA Astrophysics Data System (ADS)

The linear attenuation coefficients and three interaction processes have been computed for liver, kidney, muscle, fat and for a range of x-ray energies from 1 keV to 150 keV. Molecular photoelectric absorption cross sections were calculated from atomic cross section data. Total coherent (Rayleigh) and incoherent (Compton) scattering cross sections were obtained by numerical integration over combinations of F2m(x) with the Thomson formula and Sm(x) with the Klein-Nishina formula, respectively. For the coherent (Rayleigh) scattering cross section calculations, molecular form factors were obtained from recent experimental data in the literature for values of x<1 Å-1 and from the relativistic modified atomic form factors for values of x?1 Å-1. With the inclusion of molecular interference effects in the coherent (Rayleigh) scattering, more accurate knowledge of the scatter from these tissues will be provided. The number of elements involved in tissue composition is 5 for liver, 47 for kidney, 44 for muscle and 3 for fat. The results are compared with previously published experimental and theoretical linear attenuation coefficients. In general, good agreement is obtained. The molecular form factors and scattering functions and cross sections are incorporated into a Monte Carlo program. The energy distributions of x-ray photons scattered from tissues have been simulated and the results are presented.

Böke, Aysun

2014-09-01

347

Efficient and Rapid C. elegans Transgenesis by Bombardment and Hygromycin B Selection  

PubMed Central

We report a simple, cost-effective, scalable and efficient method for creating transgenic Caenorhabditis elegans that requires minimal hands-on time. The method combines biolistic bombardment with selection for transgenics that bear a hygromycin B resistance gene on agar plates supplemented with hygromycin B, taking advantage of our observation that hygromycin B is sufficient to kill wild-type C. elegans at very low concentrations. Crucially, the method provides substantial improvements in the success of bombardments for isolating transmitting strains, the isolation of multiple independent strains, and the isolation of integrated strains: 100% of bombardments in a large data set yielded transgenics; 10 or more independent strains were isolated from 84% of bombardments, and up to 28 independent strains were isolated from a single bombardment; 82% of bombardments yielded stably transmitting integrated lines with most yielding multiple integrated lines. We anticipate that the selection will be widely adopted for C. elegans transgenesis via bombardment, and that hygromycin B resistance will be adopted as a marker in other approaches for manipulating, introducing or deleting DNA in C. elegans. PMID:24130756

Radman, Inja; Greiss, Sebastian; Chin, Jason W.

2013-01-01

348

Optical signal demultiplexing and conversion in the fullerene-oligothiophene-CdS system  

NASA Astrophysics Data System (ADS)

We report the photoelectrochemical photocurrent switching (PEPS) effect in the system based on a C60 derivatives and nanostructured cadmium sulfide. Rapid and efficient photocurrent switching upon changes of the electrode potential was observed. This process relies on the photocurrent generation by semiconducting particles and interfacial electron transfer reactions governed by the redox chemistry of fullerene derivatives (fullerene-oligothiophene dyads) with molecular oxygen as a final electron acceptor. Surprisingly, fullerene derivatives without thiophene moieties were much less efficient as CdS modifiers. These peculiar photoelectrochemical properties were applied for construction of an optoelectronic logic device.

Lewandowska, Kornelia; Podborska, Agnieszka; Kwolek, Przemys?aw; Kim, Tae-Dong; Lee, Kwang-Sup; Szaci?owski, Konrad

2014-11-01

349

Higher-Order Harmonic Generation from Fullerene by Means of the Plasma Harmonic Method  

SciTech Connect

We demonstrate, for the first time, high-order harmonic generation from C{sub 60} by an intense femtosecond Ti:sapphire laser. Laser-produced plasmas from C{sub 60}-rich epoxy and C{sub 60} films were used as the nonlinear media. Harmonics up to the 19th order were observed. The harmonic yield from fullerene-rich plasma is about 25 times larger compared with those produced from a bulk carbon target. Structural studies of plasma debris confirm the presence and integrity of fullerenes within the plasma plume, indicating fullerenes as the source of high-order harmonics.

Ganeev, R. A. [Institut National de la Recherche Scientifique, Energie, Materiaux et Telecommunications, 1650 Lionel-Boulet, Varennes, Quebec J3X 1S2 (Canada); Scientific Association Akadempribor, Academy of Sciences of Uzbekistan, Akademgorodok, Tashkent 100125 (Uzbekistan); Bom, L. B. Elouga; Abdul-Hadi, J.; Ozaki, T. [Institut National de la Recherche Scientifique, Energie, Materiaux et Telecommunications, 1650 Lionel-Boulet, Varennes, Quebec J3X 1S2 (Canada); Wong, M. C. H.; Brichta, J. P.; Bhardwaj, V. R. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

2009-01-09

350

Novel synthesis and characterization of five isomers of (C(70))(2) fullerene dimers.  

PubMed

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV-vis-NIR absorption and mass spectroscopy. PMID:11782162

Forman, Grant S; Tagmatarchis, Nikos; Shinohara, Hisanori

2002-01-16

351

Polymer-fullerene miscibility: a metric for screening new materials for high-performance organic solar cells.  

PubMed

The improvement of the power conversion efficiency (PCE) of polymer bulk heterojunction (BHJ) solar cells has generally been achieved through synthetic design to control frontier molecular orbital energies and molecular ordering of the electron-donating polymer. An alternate approach to control the PCE of a BHJ is to tune the miscibility of the fullerene and a semiconducting polymer by varying the structure of the fullerene. The miscibility of a series of 1,4-fullerene adducts in the semiconducting polymer, poly(3-hexylselenophene), P3HS, was measured by dynamic secondary ion mass spectrometry using a model bilayer structure. The microstructure of the bilayer was investigated using high-angle annular dark-field scanning transmission microscopy and linked to the polymer-fullerene miscibility. Finally, P3HS:fullerene BHJ solar cells were fabricated from each fullerene derivative, enabling the correlation of the active layer microstructure to the charge collection efficiency and resulting PCE of each system. The volume fraction of polymer-rich, fullerene-rich, and polymer-fullerene mixed domains can be tuned using the miscibility leading to improvement in the charge collection efficiency and PCE in P3HS:fullerene BHJ solar cells. These results suggest a rational approach to the design of fullerenes for improved BHJ solar cells. PMID:22974056

Treat, Neil D; Varotto, Alessandro; Takacs, Christopher J; Batara, Nicolas; Al-Hashimi, Mohammed; Heeney, Martin J; Heeger, Alan J; Wudl, Fred; Hawker, Craig J; Chabinyc, Michael L

2012-09-26

352

Tuning of electronic properties of fullerene-oligothiophene layers  

NASA Astrophysics Data System (ADS)

Electronic properties of fullerene derivatives containing oligothiophene pendant chain (1-3 thiophene moieties) were investigated using the Kelvin probe technique and quantum chemistry methods. For electrochemical examination of these systems, Langmuir-Blodgett (LB) layers were prepared by the deposition on a gold substrate. The analysis of the experimental data shows that the value of the work function depends strongly on the length of oligothiophene chain. Similar dependence was also found for the surface photovoltage measurements conducted for the layers consisting of multiple LB films of the examined compounds deposited on gold surfaces. The assumption has been made that these changes are associated with the influence of oligothiophene chain on the electrostatic potential distribution near the surface of the sample. The hypothesis was confirmed by the results of DFT calculations, which revealed that the value of Fermi level energy shifts in the opposite direction to the determined work function. The key highlights of this study are as follows: electronic structure tuning by oligothiophene side chain; DFT calculation on fullerene-thiophene system; work function measurements of thin molecular layers.

Lewandowska, Kornelia; Pilarczyk, Kacper; Podborska, Agnieszka; Kim, Tae-Dong; Lee, Kwang-Sup; Szaci?owski, Konrad

2015-01-01

353

Fullerene nanowires as a versatile platform for organic electronics  

NASA Astrophysics Data System (ADS)

The development of organic semiconducting nanowires that act as charge carrier transport pathways in flexible and lightweight nanoelectronics is a major scientific challenge. We report on the fabrication of fullerene nanowires that is universally applicable to its derivatives (pristine C60, methanofullerenes of C61 and C71, and indene C60 bis-adduct), realized by the single particle nanofabrication technique (SPNT). Nanowires with radii of 8-11 nm were formed via a chain polymerization reaction induced by a high-energy ion beam. Fabrication of a poly(3-hexylthiophene) (P3HT): [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) bulk heterojunction organic photovoltaic cell including PC61BM nanowires with precisely-controlled length and density demonstrates how application of this methodology can improve the power conversion efficiency of these inverted cells. The proposed technique provides a versatile platform for the fabrication of continuous and uniform n-type fullerene nanowires towards a wide range of organic electronics applications.

Maeyoshi, Yuta; Saeki, Akinori; Suwa, Shotaro; Omichi, Masaaki; Marui, Hiromi; Asano, Atsushi; Tsukuda, Satoshi; Sugimoto, Masaki; Kishimura, Akihiro; Kataoka, Kazunori; Seki, Shu

2012-08-01

354

Fullerene nanowires as a versatile platform for organic electronics  

PubMed Central

The development of organic semiconducting nanowires that act as charge carrier transport pathways in flexible and lightweight nanoelectronics is a major scientific challenge. We report on the fabrication of fullerene nanowires that is universally applicable to its derivatives (pristine C60, methanofullerenes of C61 and C71, and indene C60 bis-adduct), realized by the single particle nanofabrication technique (SPNT). Nanowires with radii of 8–11?nm were formed via a chain polymerization reaction induced by a high-energy ion beam. Fabrication of a poly(3-hexylthiophene) (P3HT): [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) bulk heterojunction organic photovoltaic cell including PC61BM nanowires with precisely-controlled length and density demonstrates how application of this methodology can improve the power conversion efficiency of these inverted cells. The proposed technique provides a versatile platform for the fabrication of continuous and uniform n-type fullerene nanowires towards a wide range of organic electronics applications. PMID:22934128

Maeyoshi, Yuta; Saeki, Akinori; Suwa, Shotaro; Omichi, Masaaki; Marui, Hiromi; Asano, Atsushi; Tsukuda, Satoshi; Sugimoto, Masaki; Kishimura, Akihiro; Kataoka, Kazunori; Seki, Shu

2012-01-01

355

Li-doped fullerene structures: a molecular modelling study  

NASA Astrophysics Data System (ADS)

Materials with exceptionally high contents of carbon are used in technologies with various degrees of added value, from quasi-amorphous materials for carbon electrodes used in e.g. lithium batteries to highly organized materials comprising e.g. nanotubes and fullerenes. The present study aims to test the feasibility of predicting the properties of carbon based materials using (i) molecular modelling and simulation techniques; (ii) application to fullerene as an idealized model of nano-pores in carbon materials; and (iii) available experimental data regarding the behaviour of carbon materials for lithium batteries as validation data. It has been found that the increase in the H/C atomic ratio has an ambivalent impact on the structural stability of lithium-doped carbon materials, with the ultimate lithium-doped material being the result of the 'tug of war' between the folding of the 'house-of-cards' structure due to increased flexibility of the idealized pore scaffold and the pore expansion due to the doping process coupled with the increase in structural flexibility. With regard to molecular motors, the simulations demonstrate that small numbers of hydrogenated defects may induce large enough structural changes to damage the smoothness of the surface of the nanogears, but the insertion of lithium atoms may stabilize this deleterious effect.

Nicolau, Dan V.

2005-04-01

356

Binding of fullerenes and nanotubes to MscL  

PubMed Central

Multi-drug resistance is becoming an increasing problem in the treatment of bacterial infections and diseases. The mechanosensitive channel of large conductance (MscL) is highly conserved among prokaryotes. Evidence suggests that a pharmacological agent that can affect the gating of, or block the current through, MscL has significant potential as a new class of antimicrobial compound capable of targeting a range of pathogenic bacteria with minimal side-effects to infected patients. Using molecular dynamics we examine the binding of fullerenes and nanotubes to MscL and demonstrate that both are stable within the MscL pore. We predict that fullerenes will attenuate the flow of ions through MscL by reducing the pore volume available to water and ions, but nanotubes will prevent pore closure resulting in a permanently open pore. Moreover, we confirm experimentally that it is possible to attenuate the flow of ions through MscL using a C60-? cyclodextrin complex. PMID:25030051

Hilder, Tamsyn A.; Ridone, Pietro; Nakayama, Yoshitaka; Martinac, Boris; Chung, Shin-Ho

2014-01-01

357

Production and decay of highly-charged fullerene ions  

NASA Astrophysics Data System (ADS)

Highly-charged fullerene ions C{60/z+} and C{70/z+} with charge states up to z=7 have been produced in an electron impact ion source of a two sector field mass spectrometer by using ion source operating conditions similar to those used in EBIT sources. The stability of these ions was investigated quantitatively in the two field free regions of the mass spectrometer. It was found that besides C2 evaporation the dominant fission process for ions with charges larger than +2 is the loss of a charged C{2/+} unit via a super-asymmetric charge separation reaction C{60/z+} ? C{58/(z-1)+}+C{2/+} and C{70/z+} ? C{68/(z-1)+}+C{2/+}, respectively. The most important finding from these studies is that this super-asymmetric dissociation reaction proceeds via a three stage reaction sequence involving an electron transfer reaction at the second stage between a receding C2 unit and the remaining highly-charged fullerene cage.

Matt, S.; Dünser, B.; Senn, G.; Scheier, P.; Märk, T. D.

1996-12-01

358

Vibrational properties of small fullerene assembled thin films  

NASA Astrophysics Data System (ADS)

Cluster-assembled carbon thin films have been the subject of increasing interest. The presence of fullerenic structures embedded in an amorphous matrix could give rise to disordered carbon systems with novel mechanical properties; furthermore the control of the deposition energy and the mass distribution of the clusters can open the way to building materials with a tunable sp^2 to sp^3 site ratio. Recently Raman spectroscopy has been used to characterize cluster-assembled thin films[1]. However, the interpretation of measured spectra in terms of the microscopic struture is not fully understood. In order to gain insight about the relationship between vibrational and structural properties, we have computed the phonon spectrum and the Raman activity of a thin film model obtained with a computer simulation by assembling small fullerenes [2]. Our results allow us to correlate the various features of the Raman spectrum to different local bonding configurations in the computer generated model, and to suggest an interpretation of recent experimental data. [1] P. Milani et al. J. Appl. Phys. (in press), and references therein. [2] A. Canning, G. Galli and J. Kim, Phys. Rev. Lett. 78, 4442 (1997).

Ordejón, Pablo; Galli, Giulia

1998-03-01

359

Binding of fullerenes and nanotubes to MscL  

NASA Astrophysics Data System (ADS)

Multi-drug resistance is becoming an increasing problem in the treatment of bacterial infections and diseases. The mechanosensitive channel of large conductance (MscL) is highly conserved among prokaryotes. Evidence suggests that a pharmacological agent that can affect the gating of, or block the current through, MscL has significant potential as a new class of antimicrobial compound capable of targeting a range of pathogenic bacteria with minimal side-effects to infected patients. Using molecular dynamics we examine the binding of fullerenes and nanotubes to MscL and demonstrate that both are stable within the MscL pore. We predict that fullerenes will attenuate the flow of ions through MscL by reducing the pore volume available to water and ions, but nanotubes will prevent pore closure resulting in a permanently open pore. Moreover, we confirm experimentally that it is possible to attenuate the flow of ions through MscL using a C60-? cyclodextrin complex.

Hilder, Tamsyn A.; Ridone, Pietro; Nakayama, Yoshitaka; Martinac, Boris; Chung, Shin-Ho

2014-07-01

360

Computer simulations on collision-sequence mechanisms: Bombardment of single-crystalline Cu(100) by Ar ions  

SciTech Connect

The development of collision-cascade anisotropies and the collision-sequence mechanisms in single-crystalline Cu are studied employing the binary-collision lattice-simulation code COSIPO and the distributions of the recoil vector fluxes. The vector fluxes are directly related to other statistical distribution functions of recoils and to the angular distributions of sputtered particles. Single-crystal Cu(100) is bombarded with normally incident 5-keV Ar ions. In addition to depth resolution of the recoil vector fluxes, the evolution of anisotropies is studied as a function of energy. The effect of various types of collision sequences on the fluxes may be treated separately. The collision cascade is found to be highly anisotropic at different depths and energies of recoils, and it is dominated by focusing along the {l angle}110{r angle} directions. The development of the collision cascade is entirely governed by crystal structure. A diversity of mechanisms responsible for creating the chains exists. The contributions of various collision chain mechanisms to recoil flux distributions and observed spot patterns are discussed. Thermal vibrations shorten the collision sequences and decrease the contribution of chains to the flux distributions, except in the case of defocused chains. Their fraction increases when thermal vibrations are included.

Likonen, J. (Technical Research Centre of Finland, Reactor Laboratory, Otakaari 3 A, SF-02150 Espoo (Finland)); Hautala, M. (Department of Physics, University of Helsinki, Siltavuorenpenger 20 D, SF-00170 Helsinki (Finland))

1990-09-01

361

Implications of a 17 keV neutrino for baryogenesis  

NASA Astrophysics Data System (ADS)

There is some experimental evidence for a 17 keV component of the electron neutrino, in the form of the recent observations of kinks in the beta-decay spectra of tritium, 14C, 35S and 63Ni. In this paper I show that most particle-physics models consistent with the 17 keV neutrino require a baryogenesis scale below ~ 106 GeV. Furthermore, models with a 17 keV neutrino typically contain new sources of CP violation, and the cosmological baryon asymmetry could be generated by anomalous electroweak interactions during a first-order weak phase transition.

Nelson, Ann E.

1992-08-01

362

Examination of vapor sorption by fullerene, fullerene-coated surface acoustic wave sensors, graphite, and low-polarity polymers using linear solvation energy relationships  

SciTech Connect

The sorption of vapors by fullerene is compared with the sorption of vapors by an assembled fullerene thin film on a surface acoustic wave vapor sensor. A linear solvation energy relationship derived for solid fullerene at 298 K was used to calculate gas/solid partition coefficients for the same vapors as those examined using the vapor sensor. This relationship correctly predicted the relative vapor sensitivities observed with the vapor sensor. A new linear solvation energy relationship for vapor adsorption by graphite at 298 K has been determined, and solid fullerene and solid graphite are found to be quite similar in their vapor sorption properties. Comparisons have also been made with linear organic and inorganic polymers, including poly(isobutylene), poly(epichorophydrin), OV25, and OV202. In all cases, sorption is driven primarily by dispersion interactions. The assembled fullerene material is generally similar in vapor selectivity to the other nonpolar sorbent materials considered but yields less sensitive vapor sensors than linear organic polymers. 39 refs., 2 figs., 2 tabs.

Grate, J.W. [Pacific Northwest Lab., Richland, WA (United States); Abraham, M.H.; Du, C.M. [Univ. College London (United Kingdom); McGill, R.A. [Geo-Centers, Inc., Fort Washington, MD (United States); Shuely, W.J. [Army Edgewood Research, Development and Engineering Center, Aberdeen Proving Ground, MD (United States)

1995-06-01

363

The 1 keV to 200 keV X-ray Spectrum of NGC 2992 and NGC 3081  

E-print Network

The Seyfert 2 galaxies NGC 2992 and NGC 3081 have been observed by INTEGRAL and Swift. We report about the results and the comparison of the spectrum above 10 keV based on INTEGRAL IBIS/ISGRI, Swift/BAT, and BeppoSAX/PDS. A spectrum can be extracted in the X-ray energy band ranging from 1 keV up to 200 keV. Although NGC 2992 shows a complex spectrum below 10 keV, the hard tail observed by various missions exhibits a slope with photon index = 2, independent on the flux level during the observation. No cut-off is detectable up to the detection limit around 200 keV. In addition, NGC 3081 is detected in the INTEGRAL and Swift observation and also shows an unbroken Gamma = 1.8 spectrum up to 150 keV. These two Seyfert galaxies give further evidence that a high-energy cut-off in the hard X-ray spectra is often located at energies E_C >> 100 keV. In NGC 2992 a constant spectral shape is observed over a hard X-ray luminosity variation by a factor of 11. This might indicate that the physical conditions of the emitting hot plasma are constant, while the amount of plasma varies, due to long-term flaring activity.

Volker Beckmann; Neil Gehrels; Jack Tueller

2007-04-20

364

Nano-engineered materials based on fullerenes: synthesis and biomedical applications  

NASA Astrophysics Data System (ADS)

The nanoengineering of various materials for biomedical application has became in the last decade one of the most important research areas, due to the continuous struggle to find new and more efficient instruments for the therapy of cancer and other diseases. Attempts to obtain functionalized derivatives of fullerene seek the synthesis of watersoluble materials, in order to investigate their effects in physiological conditions. International studies on the biological properties of fullerenes and their derivatives, are now targeted towards anti-tumor effects, pharmacology and their involvement in oxidative stress. Their toxicity, demonstrated both in vitro and in vivo is important for characterization and selection of applications. Phototoxicity of some molecules of fullerenes has been identified as future therapeutic tool. The present paper describes the synthesis, characterization and some biomedical applications of some nanomaterials based on fullerenes.

Fierascu, Radu Claudiu; Dumitriu, Irina; Ion, Rodica Mariana; Neagu, Monica; Constantin, Carolina; Stavaru, Crina

2010-11-01

365

Photorefractive effects in polymer dissolved liquid crystal composites dopes with fullerene derivatives  

NASA Astrophysics Data System (ADS)

We investigated the photorefractive performance of the polymer dissolved liquid crystalline composite (PDLCC), in which liquid crystalline polymer and low-molar-mass liquid crystal are miscible without phase separation, doped with three kinds of fullerene derivatives with different length of alkyl groups. The photorefractive performance was improved for the photorefractive PDLCC doped with fullerene derivatives with long length of alkyl groups. The photorefractive grating formation originates in the cooperative reorientation of the liquid crystalline director and the space charge field was estimated using the elastic continuum theory and the field for the PDLCC doped with the functionalized fullerene with longer alkyl side groups was larger than that for the PDLCC doped with conventional fullerene C60.

Ono, Hiroshi; Hasebe, Ryoya; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

2013-07-01

366

Highly dispersed carbon nanotubes in organic media for polymer:fullerene photovoltaic devices  

E-print Network

Highly dispersed carbon nanotubes in organic media for polymer:fullerene photovoltaic devices Gwang photovoltaic device are fabricated using homogeneously dispersed carbon nanotubes (CNTs) in a polymer. All rights reserved. 1. Introduction Organic photovoltaic (OPV) materials promise the production

Hong, Soon Hyung

367

Production of fullerenes and single-wall carbon nanotubes by high-temperature pulsed arc discharge  

NASA Astrophysics Data System (ADS)

Fullerenes and single-wall carbon nanotubes (SWNTs) have been produced for the first time by the high-temperature pulsed arc-discharge technique, which has developed in this laboratory. Fullerenes are identified quantitatively by high-performance liquid chromatography (HPLC), and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal a significant amount of production of bundles of SWNTs in soot. The pulse arc production of fullerenes and SWNTs favors the high-temperature (?1000 °C), long pulses (?1 ms) and a heavy rare gas such as Ar or Kr as a buffer gas. We have found that fullerenes and SWNTs have complementary relationships in their early stage of production. The details of the pulsed arc discharge have been obtained by observing the transition from the pulsed arc discharge to the steady arc discharge while increasing the pulse width.

Sugai, Toshiki; Omote, Hideki; Bandow, Shunji; Tanaka, Nobuo; Shinohara, Hisanori

2000-04-01

368

Temperature Field Measurement During the Arc-Discharge Fullerene Generation Process  

E-print Network

, Toshio Takagi, Yoshio Kaji and Mitsuru Inoue The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 of fullerene Thermocouples Graphite AnodeGraphite Cathode He Stepping MotorStepping Motor Water Cooled Cylinder

Maruyama, Shigeo

369

Creation of a gradient polymer-fullerene interface in photovoltaic devices by thermally controlled interdiffusion  

NASA Astrophysics Data System (ADS)

Efficient polymer-fullerene photovoltaic devices require close proximity of the two materials to ensure photoexcited electron transfer from the semiconducting polymer to the fullerene acceptor. We describe studies in which a bilayer system consisting of spin-cast 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene copolymer (MEH-PPV) and sublimed C60 is heated above the MEH-PPV glass transition temperature in an inert environment, inducing an interdiffusion of the polymer and the fullerene layers. With this process, a controlled, bulk, gradient heterojunction is created bringing the fullerene molecules within the exciton diffusion radius of the MEH-PPV throughout the film to achieve highly efficient charge separation. The interdiffused devices show a dramatic decrease in photoluminescence and concomitant increase in short circuit currents, demonstrating the improved interface.

Drees, M.; Premaratne, K.; Graupner, W.; Heflin, J. R.; Davis, R. M.; Marciu, D.; Miller, M.

2002-12-01

370

Synthesis, identification, and benzene solubility of the piperidine, pyrrolidine, and morpholine derivatives of fullerene C60  

NASA Astrophysics Data System (ADS)

Synthesis of the piperidine, pyrrolidine, and morpholine derivatives of fullerene C60 and their identification by electronic and IR spectroscopy were reported. The solubility of these derivatives in benzene at temperatures from 20 to 80°C was studied.

Semenov, K. N.; Charykov, N. A.; Keskinov, V. A.

2013-01-01

371

Synthesis and Self-assembly of [60]Fullerene Containing Sulfobetaine Polymer in Aqueous Solution  

E-print Network

A series of well-defined stimuli responsive water soluble [60]fullerene (C??) containing polymers such as polyelectrolytes (polyacids and polybases), polyampholyte and polyzwitterionic polymers were synthesized using atom ...

Ravi, P.

372

Electronic correlation effects in a fullerene molecule studied by the variational Monte Carlo method  

SciTech Connect

Electron-correlation effects in the fullerene molecule and its ions are investigated in the framework of the Hubbard model. The variational Monte Carlo method and the Gutzwiller wave function are used. Most attention is paid to the case of intermediate interactions, but also the strong coupling limit, where the Hubbard model reduces to the antiferromagnetic Heisenberg model, is considered for the fullerene molecule. In this case we obtain a very low variational ground state energy. Futher, we have calculated the main spin correlation functions in the ground state. Only short-range order is found. The pairing energy of two electrons added to a fullerene molecule or to a fullerene ion is also calculated. Contrary to the results obtained by second-order perturbation theory, pair binding is not found.

Krivnov, V.Y. (Institute of Chemical Physics, Russian Academy of Sciences, Kosygina 4, 117 977 Moscow (Russian Federation)); Shamovsky, I.L. (Institute of Chemical Physics, Russian Academy of Sciences, Kosygina 4, 117 977 Moscow (Russian Federation) Chemistry Department, University of West Indies Mona Campus, St. Andrew, Kingston 7 (Jamaica)); Tornau, E.E. (Semiconductor Physics Institute, Gostauto 11, 2600, Vilnius (Lithuania)); Rosengren, A. (Department of Theoretical Physics, Royal Institute of Technology, S-100 44 Stockholm (Sweden))

1994-10-15

373

High Stability of Faceted Nanotubes and Fullerenes of Multiphase Layered Phosphorus: A Computational Study  

NASA Astrophysics Data System (ADS)

We present a paradigm in constructing very stable, faceted nanotube and fullerene structures by laterally joining nanoribbons or patches of different planar phosphorene phases. Our ab initio density functional calculations indicate that these phases may form very stable, nonplanar joints. Unlike fullerenes and nanotubes obtained by deforming a single-phase planar monolayer at substantial energy penalty, we find faceted fullerenes and nanotubes to be nearly as stable as the planar single-phase monolayers. The resulting rich variety of polymorphs allows us to tune the electronic properties of phosphorene nanotubes and fullerenes not only by the chiral index but also by the combination of different phosphorene phases. In selected phosphorene nanotubes, a metal-insulator transition may be induced by strain or by changing the number of walls.

Guan, Jie; Zhu, Zhen; Tománek, David

2014-11-01

374

Zirconium Minerals from Mars, Moon and Earth Indicate Crustal 'Refugia' on Early Bombardment Surfaces  

NASA Astrophysics Data System (ADS)

A comparison of the shock microstructural and U-Pb histories of zirconium minerals from the bombardment epoch of Mars, Moon and Earth points to perseverance of early planetary crustal domains throughout the large impactor flux.

Moser, D. E.

2015-02-01

375

Abstract Transgene loci in 16 transgenic oat (Avena sativa L.) lines produced by microprojectile bombard-  

E-print Network

Abstract Transgene loci in 16 transgenic oat (Avena sativa L.) lines produced by microprojectile and rearrange- ments. Key words Genetic engineering · Oat (A. sativa L.) · Microprojectile bombardment · FISH

Pawlowski, Wojtek

376

JOURNAL OF MASS SPECTROMETRY, VOL. 31, 855-860 (1996) Application of Fast Atom Bombardment Combined  

E-print Network

a Streptomyces spp. Its structure elucidation was carried out with fast atom bombardment mass spectrometry (FABMS a Streptomyces spp. Nigericin was first isolated from a Streptomyces spp. by Berger et al." an

Kim, Myung Soo

377

Comet impacts and chemical evolution on the bombarded earth  

NASA Technical Reports Server (NTRS)

Amino acids yields for previously published shock tube experiments are used with minimum Cretaceous-Tertiary (K/T) impactor mass and comet composition to predict AIB amino acid K/T boundary sediment column density. The inferred initial concentration of all amino acids in the K/T sea and in similar primordial seas just after 10 km comet impacts would have been at least 10 exp -7 M. However, sinks for amino acids must also be considered in calculating amino acid concentrations after comet impacts and in assessing the contribution of comets to the origin of life. The changing concentration of cometary amino acids due to ultraviolet light is compared with the equilibrium concentration of amino acids produced in the sea from corona discharge in the atmosphere, deposition in water, and degradation by ultraviolet light. Comets could have been more important than endogenous agents for initial evolution of amino acids. Sites favorable for chemical evolution of amino acids are examined, and it is concluded that chemical evolution could have occurred at or above the surface even during periods of intense bombardment of earth before 3.8 billion years ago.

Oberbeck, Verne R.; Aggarwal, Hans

1992-01-01

378

Effect of argon ion bombardment on amorphous silicon carbonitride films  

NASA Astrophysics Data System (ADS)

Amorphous silicon carbonitride (a-SiCN:H) films were synthesized by radiofrequency (RF) Plasma Enhanced Vapor Chemical Deposition (PECVD) using hexamethyldisilazane (HMDSN) as precursor compound. Then, the films were post-treated by Plasma Immersion Ion Implantation (PIII) in argon atmosphere from 15 to 60 min. The hardness of the film enhanced after ion implantation, and the sample treated at 45 min process showed hardness greater than sixfold that of the untreated sample. This result is explained by the crosslinking and densification of the structure. Films were exposed to oxygen plasma for determining of the etching rate. It decreased monotonically from 33 Å/min to 19 Å/min for the range of process time, confirming structural alterations. Hydrophobic character of the a-SiCN:H films were modified immediately after ion bombardment, due to incorporation of polar groups. However, the high wettability of the films acquired by the ion implantation was diminished after aging in air. Therefore, argon PIII made a-SiCN:H films mechanically more resistant and altered their hydrophobic character.

Batocki, R. G. S.; Mota, R. P.; Honda, R. Y.; Santos, D. C. R.

2014-04-01

379

Actinide production from xenon bombardments of curium-248  

SciTech Connect

Production cross sections for many actinide nuclides formed in the reaction of /sup 129/Xe and /sup 132/Xe with /sup 248/Cm at bombarding energies slightly above the coulomb barrier were determined using radiochemical techniques to isolate these products. These results are compared with cross sections from a /sup 136/Xe + /sup 248/Cm reaction at a similar energy. When compared to the reaction with /sup 136/Xe, the maxima in the production cross section distributions from the more neutron deficient projectiles are shifted to smaller mass numbers, and the total cross section increases for the production of elements with atomic numbers greater than that of the target, and decreases for lighter elements. These results can be explained by use of a potential energy surface (PES) which illustrates the effect of the available energy on the transfer of nucleons and describes the evolution of the di-nuclear complex, an essential feature of deep-inelastic reactions (DIR), during the interaction. The other principal reaction mechanism is the quasi-elastic transfer (QE). Analysis of data from a similar set of reactions, /sup 129/Xe, /sup 132/Xe, and /sup 136/Xe with /sup 197/Au, aids in explaining the features of the Xe + Cm product distributions, which are additionally affected by the depletion of actinide product yields due to deexcitation by fission. The PES is shown to be a useful tool to predict the general features of product distributions from heavy ion reactions.

Welch, R.B.

1985-01-01

380

Compact electron gun based on secondary emission through ionic bombardment.  

PubMed

We present a new compact electron gun based on the secondary emission through ionic bombardment principle. The driving parameters to develop such a gun are to obtain a quite small electron gun for an in-flight instrument performing Electron Beam Fluorescence measurements (EBF) on board of a reentry vehicle in the upper atmosphere. These measurements are useful to characterize the gas flow around the vehicle in terms of gas chemical composition, temperatures and velocity of the flow which usually presents thermo-chemical non-equilibrium. Such an instrument can also be employed to characterize the upper atmosphere if placed on another carrier like a balloon. In ground facilities, it appears as a more practical tool to characterize flows in wind tunnel studies or as an alternative to complex electron guns in industrial processes requiring an electron beam. We describe in this paper the gun which has been developed as well as its different features which have been characterized in the laboratory. PMID:22163896

Diop, Babacar; Bonnet, Jean; Schmid, Thomas; Mohamed, Ajmal

2011-01-01

381

Back-bombardment compensation in microwave thermionic electron guns  

NASA Astrophysics Data System (ADS)

The development of capable, reliable, and cost-effective compact electron beam sources remains a long-standing objective of the efforts to develop the accelerator systems needed for on-site research and industrial applications ranging from electron beam welding to high performance x-ray and gamma ray light sources for element-resolved microanalysis and national security. The need in these applications for simplicity, reliability, and low cost has emphasized solutions compatible with the use of the long established and commercially available pulsed microwave rf sources and L-, S- or X-band linear accelerators. Thermionic microwave electron guns have proven to be one successful approach to the development of the electron sources for these systems providing high macropulse average current beams with picosecond pulse lengths and good emittance out to macropulse lengths of 4-5 microseconds. But longer macropulse lengths are now needed for use in inverse-Compton x-ray sources and other emerging applications. We describe in this paper our approach to extending the usable macropulse current and pulse length of these guns through the use of thermal diffusion to compensate for the increase in cathode surface temperature due to back-bombardment.

Kowalczyk, Jeremy M. D.; Madey, John M. J.

2014-12-01

382

Compact Electron Gun Based on Secondary Emission Through Ionic Bombardment  

PubMed Central

We present a new compact electron gun based on the secondary emission through ionic bombardment principle. The driving parameters to develop such a gun are to obtain a quite small electron gun for an in-flight instrument performing Electron Beam Fluorescence measurements (EBF) on board of a reentry vehicle in the upper atmosphere. These measurements are useful to characterize the gas flow around the vehicle in terms of gas chemical composition, temperatures and velocity of the flow which usually presents thermo-chemical non-equilibrium. Such an instrument can also be employed to characterize the upper atmosphere if placed on another carrier like a balloon. In ground facilities, it appears as a more practical tool to characterize flows in wind tunnel studies or as an alternative to complex electron guns in industrial processes requiring an electron beam. We describe in this paper the gun which has been developed as well as its different features which have been characterized in the laboratory. PMID:22163896

Diop, Babacar; Bonnet, Jean; Schmid, Thomas; Mohamed, Ajmal

2011-01-01

383

Redox Properties of Isozazolo[60]fullerenes with Regard to Substituents and Molecular Structure  

Microsoft Academic Search

A series of isoxazolo[60]fullerene derivatives 1(a-k), 5 and 6(l-n) have been synthesized by [2+3]cycloadditions of the corresponding nitriloxides to C60. The phenyl-, 1,4- and 1,2-biphenyl substituents are substituted with electron donor groups in different distances and orientations in order to determine their influence on the redox properties of these fullerene derivatives. The redox- behavior was measured by cyclic voltammetry. In

H. Irngartinger; T. Escher

2001-01-01

384

Fragmentation Mechanism of Fullerenes in the Positive and Negative Ion Channels  

Microsoft Academic Search

We have performed the photofragmentation studies of pristine C60 and C60\\/C70 composites on the reflectron time-of-flight mass spectrometer (RTOF MS) in the positive and negative ion channels. The mechanism of the formation of daughter fullerenes in the negative ion channel and the enhancement of fullerene coalescence reactions have been discussed and compared to our previous studies on the linear TOF.

Qing-Yu Kong; Li Zhao; Jun Zhuang; Shi-Xiong Qian; Yu-Fen Li

2001-01-01

385

Photo-induced charge transfer in fullerene-oligothiophene dyads - A quantum-chemical study  

NASA Astrophysics Data System (ADS)

The excited states of fullerene-oligothiophene dyads were studied by quantum-chemical methods in respect of their theoretical suitability as solar-cell materials. Compared to the constituents a significant extension of the absorption spectra to the red has been found caused by optically excitable charge transfer states. These states seem to be responsible for the low energy conversion efficiency of fullerene-oligothiophene dyads in photovoltaic devices.

Beenken, Wichard J. D.

2009-02-01

386

Addition of dihydromethano group to fullerenes to improve the performance of bulk heterojunction organic solar cells.  

PubMed

Adding a compact dihydromethano (CH2 ) group to a 58?-indene fullerene (C60 (Ind)) creates a 56?-electron dihydromethano/indene fullerene (C60 (CH2 )(Ind)) and raises the LUMO level with only a minimal increase in size. This class of compounds features reduced conjugation that raises the LUMO level, and a high electron mobility because of the small CH2 addend. PMID:23996807

Matsuo, Yutaka; Kawai, Junya; Inada, Hiroshi; Nakagawa, Takafumi; Ota, Hitoshi; Otsubo, Saika; Nakamura, Eiichi

2013-11-20

387

Bell-state preparation for fullerene based electron spins in distant peapod nanotubes  

E-print Network

We propose a potentially practical scheme, in combination with the Bell-state analyzer [Zhang et al., Phys. Rev. A 73, 014301 (2006)], to generate Bell states for two electron spins confined, respectively, in two distant fullerenes. To this end, we consider the endohedral fullerenes staying in single walled carbon nanotubes (SWCNTs) and employ auxiliary mobile electrons and selective microwave pulses. The application and the experimental feasibility of our scheme are discussed.

W. L. Yang; H. Wei; X. L. Zhang; M. Feng

2008-09-18

388

Thermal stability of carbon nanotubes, fullerene and graphite under spark plasma sintering  

NASA Astrophysics Data System (ADS)

The thermal stabilities of carbon nanotubes, fullerene and graphite were investigated under spark plasma sintering (SPS). Results were compared with data from synchrotron radiation in situ high temperature X-ray diffraction of these materials. Part of the nanotubes and fullerene transformed into diamond under SPS, but graphite kept stable. There was no diamond conversion in the in situ X-ray diffraction experiments under the same condition. Their phase transitional mechanism indicated the presence of plasmas during the SPS operation.

Zhang, Faming; Mihoc, Carmen; Ahmed, Furqan; Lathe, Christian; Burkel, Eberhard

2011-06-01

389

Endo-Fullerenes and Doped Diamond Nanocrystallite Based Solid-State Qubits  

NASA Technical Reports Server (NTRS)

This viewgraph presentation provides information on the use of endo-fullerenes and doped diamond nanocrystallites in the development of a solid state quantum computer. Arrays of qubits, which have 1/2 nuclear spin, are more easily fabricated than arrays of similar bare atoms. H-1 can be encapsulated in a C20D20 fullerene, while P-31 can be encapsulated in a diamond nanocrystallite.

Park, Seongjun; Srivastava, Deepak; Cho, K.

2001-01-01

390

Fullerene nanoparticles exhibit greater retention in freshwater sediment than in model porous media.  

PubMed

Increasing production and use of fullerene-based nanomaterials underscore the need to determine their mobility in environmental transport pathways and potential ecological exposures. This study investigated the transport of two fullerenes (i.e., aqu/C(60) and water-soluble C(60) pyrrolidine tris-acid [C(60) PTA]) in columns packed with model porous media (Iota quartz and Ottawa sand) and a sediment from Call's creek under saturated and unsaturated steady-state flows. The fullerenes had the least retention in Iota quartz, and the greatest retention in the sediment at near neutral pH, correlating with the degree of grain surface chemical heterogeneity (e.g., amorphous Al hydroxides concentration increasing in the order of Iota quartzfullerene retention in the sediment. In accordance with the XDLVO energy calculations, C(60) PTA was less retained than aqu/C(60) at near neutral pH, due to its greater hydrophilicity measured by tolune-water partition coefficient, as well as smaller particle sizes revealed by atomic force microscopy. Fullerene retention exhibited a strong dependency on solution pH that could be explained partly by the pH-dependent surface charge of fullerenes and grain surface, and partly by increased hydrophobicity of C(60) PTA when solution pH approaches its isoelectric point (IEP). Finally, fullerene retention was enhanced in unsaturated media, implying that fullerenes may be more attenuated in the vadose zone than in groundwater. PMID:22445188

Zhang, Wei; Isaacson, Carl W; Rattanaudompol, U-sa; Powell, Tremaine B; Bouchard, Dermont

2012-06-01

391

Synthesis, atomic structures and properties of carbon and boron nitride fullerene materials  

Microsoft Academic Search

Carbon (C) and boron nitride (BN) fullerene materials (clusters, onions, intercalation, nanopolyhedra, nanotubes and nanocapsules) were synthesized by polymer pyrolysis, chemical reaction, arc-melting and electron-beam irradiation. Atomic structure and formation mechanism were investigated by high-resolution electron microscopy, energy dispersive spectroscopy and electron energy-loss spectroscopy. Fullerene clusters and atomic clouds (atom hopping) were formed on the surface of the C and

Takeo Oku; Takanori Hirano; Masaki Kuno; Takafumi Kusunose; Koichi Niihara; Katsuaki Suganuma

2000-01-01

392

Effects of Pin-up Oxygen on [60]Fullerene for Enhanced Antioxidant Activity  

PubMed Central

The introduction of pin-up oxygen on C60, such as in the oxidized fullerenes C60O and C60On, induced noticeable increase in the antioxidant activity as compared to pristine C60. The water-soluble inclusion complexes of fullerenes C60O and C60Onreacted with linoleic acid peroxyl radical 1.7 and 2.4 times faster, respectively.

2008-01-01

393

Electric-arc synthesis of soot with a high content of higher fullerenes  

NASA Astrophysics Data System (ADS)

The influence of potassium carbonate additions from 1 to 12 wt % and the helium pressure on the content of higher fullerenes C76, C78, C80, C82, C84, C86, etc., in soot is studied. The optimum conditions of the evaporation of composite graphite electrodes are found: they provide the formation of soot with a high content of higher fullerenes (up to 11.4 wt %) in an extract.

Kareev, I. E.; Nekrasov, V. M.; Bubnov, V. P.

2015-01-01

394

A new application area for fullerenes: voltage stabilizers for power cable insulation.  

PubMed

Fullerenes are shown to be efficient voltage-stabilizers for polyethylene, i.e., additives that increase the dielectric strength of the insulation material. Such compounds are highly sought-after because their use in power-cable insulation may considerably enhance the transmission efficiency of tomorrow's power grids. On a molal basis, fullerenes are the most efficient voltage stabilizers reported to date. PMID:25504254

Jarvid, Markus; Johansson, Anette; Kroon, Renee; Bjuggren, Jonas M; Wutzel, Harald; Englund, Villgot; Gubanski, Stanislaw; Andersson, Mats R; Müller, Christian

2015-02-01

395

A perfect match: fullerene guests in star-shaped oligophenylenevinylene mesogens.  

PubMed

Star-shaped oligophenylenevinylene (OPV) mesogens are shape-persistent and possess formally large void space. A mesogen with three styrene repeating units packs densely in a columnar helical arrangement. Attachment of one fullerene through a short spacer results in an exceptional increase of the mesophase stability. X-ray scattering and modeling evidence a triple-helical arrangement in which the fullerene perfectly fills the void space between the arms of the star mesogen. PMID:25656050

Lehmann, Matthias; Hügel, Markus

2015-03-23

396

Induction plasma synthesis of fullerenes and nanotubes using carbon black–nickel particles  

Microsoft Academic Search

The existence of fullerenes (as allotropes of carbon) was established in the mid-1980s and during the last 15–18 years, systematic efforts have been devoted to improve the methods of their synthesis, including plasma-based system methods. The work presented here is focused on the investigation of fullerenes synthesis, using a radio frequency plasma reactor. The main objectives were to explore the

G. Cota-Sanchez; G. Soucy; A. Huczko; H. Lange

2005-01-01

397

Spectroscopic second-harmonic generation during Ar+ -ion bombardment of Si(100)  

Microsoft Academic Search

Spectroscopic and real time optical second-harmonic generation (SHG) has been applied to gain insight into the surface and interface processes during low-energy (70-1000eV) Ar+ -ion bombardment of H terminated Si(100). The Ar+ -ion bombardment of the crystalline silicon (c-Si) , which creates a layer of amorphous silicon (a-Si) , has been studied in the SH photon energy range of 2.7-3.5eV

J. J. H. Gielis; P. M. Gevers; A. A. E. Stevens; H. C. W. Beijerinck; W. M. M. Kessels

2006-01-01

398

Particle-In-Cell/Monte Carlo Simulation of Ion Back Bombardment in Photoinjectors  

SciTech Connect

In this paper, we report on studies of ion back bombardment in high average current dc and rf photoinjectors using a particle-in-cell/Monte Carlo method. Using H{sub 2} ion as an example, we observed that the ion density and energy deposition on the photocathode in rf guns are order of magnitude lower than that in a dc gun. A higher rf frequency helps mitigate the ion back bombardment of the cathode in rf guns.

Qiang, Ji; Corlett, John; Staples, John

2009-03-02

399

Microprojectile bombardment of plant tissues increases transformation frequency by Agrobacterium tumefaciens  

Microsoft Academic Search

Bombardment of plant tissues with microprojectiles in an effective method of wounding to promote Agrobacterium-mediated transformation. Tobacco cv. Xanthi leaves and sunflower apical meristems were wounded by microprojectile bombardment prior to application of Agrobacterium tumefaciens strains containing genes within the T-DNA encoding GUS or NPTII. Stable kanamycin-resistant tobacco transformants were obtained using an NPTII construct from particle\\/plasmid, particle-wounded\\/Agrobacterium-treated or scalpel-wounded\\/Agrobacterium-treated

Dennis Bidney; Chris Scelonge; Joanie Martich; Monique Burrus; Lynn Sims; Gary Huffman

1992-01-01

400

Proposal for a hardness measurement technique without indentor by gas-cluster-beam bombardment  

Microsoft Academic Search

Large gas-cluster-ion bombardment has been shown to be a unique tool for generating a variety of bombarding effects over a broad range of acceleration energies. A hardness measurement technique is proposed in this paper based on the use of the effect of crater formation by large gas-cluster beams. The cluster impact leaves a hemispherical crater on a surface, the size

Zinetulla Insepov; Rafael Manory; Jiro Matsuo; Isao Yamada

2000-01-01

401

Ion bombardment and its effects on the optical properties of metals  

NASA Technical Reports Server (NTRS)

An experimental program, to evaluate the change in total hemispherical emittance and solar absorptance of engineering metals used on spacecraft and in spacecraft instrumentation systems, is presented. Three materials, titanium alloy, pure aluminum, and electrolytic copper, were used in the experiment. Results show that emittance, absorptance, and alpha/epsilon ratio of the materials were changed by ion bombardment. The time before the change occurs depends upon the material used, the intensity of bombardment, and the environment assumed.

Anderson, D. L.

1964-01-01

402

Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad  

NASA Astrophysics Data System (ADS)

We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene)) that is end capped with the fullerene derivative PCB ([6,6]-phenyl-C61-butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound without attached fullerene (P3HT-OH). Fluorescence upconversion measurements reveal that the partial fluorescence quenching of PCB-P3HT in THF is multiphasic and occurs on an average time scale of 100 ps, in parallel to excited-state relaxation processes. Judging from ultrafast transient absorption experiments, the origin of the quenching is excitation energy transfer from the P3HT donor to the PCB acceptor. Due to the much higher solubility of P3HT compared to PCB in THF, the PCB-P3HT dyad molecules self-assemble into micelles. When pure C60 is added to the solution, it is incorporated into the fullerene-rich center of the micelles. This dramatically increases the solubility of C60 but does not lead to significant additional quenching of the P3HT fluorescence by the C60 contained in the micelles. In PCB-P3HT thin films drop-cast from THF, the micelle structure is conserved. In contrast to solution, quantitative and ultrafast (<150 fs) charge separation occurs in the solid-state films and leads to the formation of long-lived mobile charge carriers with characteristic transient absorption signatures similar to those that have been observed in P3HT:PCBM bulk heterojunction blends. While ?-stacking interactions between neighboring P3HT chains are weak in the micelles, they are strong in thin films drop-cast from ortho-dichlorobenzene. Here, PCB-P3HT self-assembles into a network of long fibers, clearly seen in atomic force microscopy images. Ultrafast charge separation occurs also for the fibrous morphology, but the transient absorption experiments show fast loss of part of the charge carriers due to intensity-induced recombination and annihilation processes and monomolecular interfacial trap-mediated or geminate recombination. The yield of the long-lived charge carriers in the highly organized fibers is however comparable to that obtained with annealed P3HT:PCBM blends. PCB-P3HT can therefore be considered as an active material in organic photovoltaic devices.

Banerji, Natalie; Seifter, Jason; Wang, Mingfeng; Vauthey, Eric; Wudl, Fred; Heeger, Alan J.

2011-08-01

403

Theoretical study of phthalocyanine–fullerene complex for a high efficiency photovoltaic device using ab initio electronic structure calculation  

Microsoft Academic Search

Many fullerene-based supramolecules have been proposed as potential organic photovoltaic devices, with their electrochemical and photo-electrochemical properties measured under light illumination. Phthalocyanine possesses good electron-donating properties due to its large easily ionised ?-electron system, whereas fullerene is good ?-electron acceptor which can be connected with other organic molecules. A phthalocyanine–fullerene-based supramolecular system is therefore a potential material candidate for a

Hiroshi Mizuseki; Nobuaki Igarashi; Rodion V. Belosludov; Amir A. Farajian; Yoshiyuki Kawazoe

2003-01-01

404

Frontispiece: Supramolecular Interaction of Fullerenes with a Curved ?-Surface of a Monomeric Quadruply Ring-Fused Porphyrin.  

PubMed

Fullerenes Supramolecular complexation of fullerenes with a monomeric zinc(II) complex of a ring-fused porphyrin derivative, having a concave ?-conjugated surface induced by the axial coordination of pyridine, has been confirmed by spectroscopic measurements and X-ray diffraction analysis, as discussed by T. Ishizuka, T. Kojima et?al. in their Communication on page?5302?ff. Shape matching between fullerenes and the porphyrin is shown to be crucial for the strong interaction. PMID:25787754

Saegusa, Yuta; Ishizuka, Tomoya; Kojima, Tatsuhiro; Mori, Shigeki; Kawano, Masaki; Kojima, Takahiko

2015-03-27

405

Palladium-Catalyzed Decarboxylative Annulation of 2-Arylbenzoic Acids with [60]Fullerene via C-H Bond Activation.  

PubMed

A convenient and highly efficient palladium-catalyzed decarboxylative annulation of 2-arylbenzoic acids with [60]fullerene has been exploited to synthesize the novel and scarce [60]fullerene-fused dihydrophenanthrenes. The use of Lewis acid ZnCl2 is crucial for the success of the present formal [4 + 2] annulation reaction. Plausible reaction pathways leading to the observed products have been proposed, and the electrochemistry of the fullerene products has also been investigated. PMID:25700187

Zhou, Dian-Bing; Wang, Guan-Wu

2015-03-01

406

Coarse-grain Molecular Dynamics Study of Fullerene Transport across a Cell Membrane  

E-print Network

The study of the ability of drug molecules to enter cells through the membrane is of vital importance in the field of drug delivery. In cases where the transport of the drug molecules through the membrane is not easily accomplishable, other carrier molecules are used. Spherical fullerene molecules have been postulated as potential carriers of highly hydrophilic drugs across the plasma membrane. Here we report the coarse-grain molecular dynamics study of the translocation of C60 fullerene and its derivatives across a cell membrane modeled as a 1, 2-distearoyl-sn-glycero-3-phosphocholine (DSPC) bilayer. Simulation results indicate that pristine fullerene molecules enter the bilayer quickly and reside within it. The addition of polar functionalized groups makes the fullerenes less likely to reside within the bilayer but increases their residence time in bulk water. Addition of polar functional groups to one half of the fullerene surface, in effect creating a Janus particle, offers the most promise in developing fullerene models that can achieve complete translocation through the membrane bilayer.

Sridhar Akshay; Bharath Srikanth; Amit Kumar; Ashok Kumar Dasmahapatra

2015-03-14

407

Influence of defects in the carbon network on the static polarizability of fullerenes  

NASA Astrophysics Data System (ADS)

The static polarizability of the C60, C70, C80, and C186 fullerenes has been calculated within the semiempirical MNDO approximation implemented in the MOPAC quantum-chemical program package. It is demonstrated that the results obtained are comparable with experimental data and the results of the ab initio B3LYP method using the 6-31 G( d, p) basis set. The influence of topological defects (five-, seven-, and eight-membered rings), vacancies produced by removing pentagons, and nitrogen and boron atoms on the geometric parameters and the polarizability of the C60, C240, and C540 fullerenes has been investigated by the MNDO method. It is revealed that the polarizability of the fullerene with topological defects is higher than the polarizability of the perfect icosahedral fullerene. The formation of vacancies in the carbon cage leads to a linear decrease in the polarizability of the fullerene and an increase in the specific polarizability. The polarizability of the heterofullerene with nitrogen or boron atoms spaced apart in the carbon cage is higher than that of the fullerene with heteroatoms located adjacent to each other.

Sedel'Nikova, O. V.; Bulusheva, L. G.; Okotrub, A. V.

2009-04-01

408

Incorporation of pure fullerene into organoclays: towards C60-pillared clay structures.  

PubMed

In this work, we demonstrate the successful incorporation of pure fullerene from solution into two-dimensional layered aluminosilicate minerals. Pure fullerenes are insoluble in water and neutral in terms of charge, hence they cannot be introduced into the clay galleries by ion exchange or intercalation from water solution. To overcome this bottleneck, we organically modified the clay with quaternary amines by using well-established reactions in clay science in order to expand the interlayer space and render the galleries organophilic. During the reaction with the fullerene solution, the organic solvent could enter into the clay galleries, thus transferring along the fullerene molecules. Furthermore, we demonstrate that the surfactant molecules, can be selectively removed by either simple ion-exchange reaction (e.g., interaction with Al(NO3)3 solution to replace the surfactant molecules with Al(3+) ions) or thermal treatment (heating at 350?°C) to obtain novel fullerene-pillared clay structures exhibiting enhanced surface area. The synthesized hybrid materials were characterized in detail by a combination of experimental techniques including powder X-ray diffraction, transmission electron microscopy, X-ray photoemission, and UV/Vis spectroscopy as well as thermal analysis and nitrogen adsorption-desorption measurements. The reported fullerene-pillared clay structures constitute a new hybrid system with very promising potential for the use in areas such as gas storage and/or gas separation due to their high surface area. PMID:23589152

Tsoufis, Theodoros; Georgakilas, Vasileios; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Rudolf, Petra; Gournis, Dimitrios

2013-06-10

409

Stepwise computational synthesis of fullerene C{sub 60} derivatives. Fluorinated fullerenes C{sub 60}F{sub 2k}  

SciTech Connect

Reactions of fullerene C{sub 60} with atomic fluorine are studied by the unrestricted broken spin symmetry Hartree-Fock (UBS HF) approach implemented in semiempirical codes based on the AMI technique. The calculations are focused on a successive addition of a fluorine atom to the fullerene cage following the indication of the highest chemical susceptibility of the cage atom, which is calculated at each step. The proposed computational synthesis is based on the effectively unpaired-electron concept of the chemical susceptibility of fullerene atoms. The obtained results are analyzed from the standpoints of energy, symmetry, and the composition abundance. A good fitting of the data to experimental findings proves a creative role of the suggested synthetic methodology.

Sheka, E. F., E-mail: sheka@icp.ac.r [Peoples' Friendship University of Russia, General Physics Department (Russian Federation)

2010-09-15

410

Propagation of ripple patterns on Si during ion bombardment  

NASA Astrophysics Data System (ADS)

The lateral propagation of surface ripples on Si, generated by Xe ion irradiation with and without codeposition of Fe surfactant atoms, was investigated by scanning electron microscopy with the help of micron-sized marker structures prepared by focused ion beam milling. For 10-keV Xe ion irradiation of Si at oblique incidence between 62 and 70°, we determine lateral ripple propagation velocities varying from -1.9 to +2.9 nm per 1015 Xe ions/cm2. The propagation direction changes from opposite to the projected direction of the incident ion beam to along the projected beam direction within a narrow angular regime. At 67°, the pattern is almost static. The result is in good agreement with predictions from the theoretical model of Bradley and Harper. For perpendicular incident 5-keV Xe ions and oblique codeposition of Fe surfactant atoms, we find that ripple patterns propagate across the surface with a negative ripple propagation velocity of about -0.7 nm per 1015 Xe ions/cm2, i.e., opposite to the projected deposition direction of Fe surfactant atoms. The novel experimental method to determine the lateral ripple propagation based on markers set with a focused ion beam system does not require an in situ analysis and can therefore be applied in general to analyze the dynamics of ion beam-induced patterns.

Hofsäss, H.; Zhang, K.; Gehrke, H. G.; Brüsewitz, C.

2013-08-01

411

Tuning the Morphology and Performance of Low Bandgap Polymer: Fullerene Heterojunctions via Solvent Annealing in Selective Solvents  

SciTech Connect

Low bandgap polymer (LBG):fullerene mixtures are some of the most promising organic photovoltaic active layers. Unfortunately, there are no post-deposition treatments available to rationally improve the morphology and performance of as-cast LBG:fullerene OPV active layers, where thermal annealing usually fails. Therefore, there is a glaring need to develop postdeposition methods to guide the morphology of LBG:fullerene bulk heterojunctions towards targeted structures and performance. In this paper, the structural evolution of PCPDTBT:PCBM mixtures with solvent annealing (SA) is examined, focusing on the effect of solvent quality of the fullerene and polymer in the annealing vapor on morphological evolution and device performance. The results indicate that exposure of this active layer to the solvent vapor controls the ordering of PCPDTBT and PCBM phase separation very effectively, presumably by inducing component mobility as the solvent plasticizes the mixture. These results also unexpectedly indicate that solvent annealing in a selective solvent provides a method to invert the morphology of the LBG:fullerene mixture from a polymer aggregate dispersed in a polymer:fullerene matrix to fullerene aggregates dispersed in a polymer:fullerene matrix. The judicious choice of solvent vapor, therefore, provides a unique method to exquisitely control and optimize the morphology of LBG conjugated polymer/fullerene mixtures.

Chen, Huipeng [ORNL; Hsiao, Yu-Che [ORNL; Hu, Bin [ORNL; Dadmun, Mark D [ORNL

2014-01-01

412

Fullerene derivatives incorporating phosphoramidous ylide and phosphoramidate: synthesis and property.  

PubMed

The reaction of dimethyl acetylenedicarboxylate (DMAD) with C(60) in the presence of hexamethylphosphorous triamide (HMPT) or hexaethylphosphorus triamide (HEPT) results in fullerene derivatives incorporating HMPT or HEPT ylides. The ylide derivatives exhibit unusual electronic absorptions in the visible region (435-660 nm), likely due to the presence of the ylide moiety. Electrochemical studies revealed that the first reductive potential of these compounds was more negative relative to those of both C(60) (DeltaE = 130 mV) and a simple Bingel adduct (DeltaE = 90 mV). A phosphoramidate side product, which resulted from the addition of HMPT or HEPT to C(60) followed by hydrolysis, exhibited a featureless absorption spectrum in the visible region and a more negative first reductive potential (DeltaE = 70 mV) relative to that of C(60). PMID:19485352

Chen, Sheng-Yuan; Cheng, Rai-Long; Tseng, Cheng-Kuo; Lin, Ya-Shiuan; Lai, Li-Hsiang; Venkatachalam, Rajesh Kumar; Chen, Yu-Chie; Cheng, Chien-Hong; Chuang, Shih-Ching

2009-07-01

413

Plasmon excitations in photo- and electron impact ionization of fullerenes  

NASA Astrophysics Data System (ADS)

We study collective electron excitations (also referred to as plasmons) in the C60 fullerene in the processes of photoionization and electron inelastic scattering. To reveal the contribution of collective electron excitations, we utilize the plasmon resonance approximation. It is shown that within this framework the photoionization cross section is described as a sum of two contributions, which represent two coupled modes of the surface plasmon. The electron energy loss spectra of C60 are described by three contributions, namely by the two modes of the surface plasmon and the volume plasmon. The results of calculations are in good agreement with experimental data on photoionization and electron inelastic scattering of C60. We show that the collective excitations play a significant role in the ionization process and provide a dominant contribution to the spectra.

Verkhovtsev, A. V.; Korol, A. V.; Solov'yov, A. V.

2013-06-01

414

Polychiral semiconducting carbon nanotube-fullerene solar cells.  

PubMed

Single-walled carbon nanotubes (SWCNTs) have highly desirable attributes for solution-processable thin-film photovoltaics (TFPVs), such as broadband absorption, high carrier mobility, and environmental stability. However, previous TFPVs incorporating photoactive SWCNTs have utilized architectures that have limited current, voltage, and ultimately power conversion efficiency (PCE). Here, we report a solar cell geometry that maximizes photocurrent using polychiral SWCNTs while retaining high photovoltage, leading to record-high efficiency SWCNT-fullerene solar cells with average NREL certified and champion PCEs of 2.5% and 3.1%, respectively. Moreover, these cells show significant absorption in the near-infrared portion of the solar spectrum that is currently inaccessible by many leading TFPV technologies. PMID:25101896

Gong, Maogang; Shastry, Tejas A; Xie, Yu; Bernardi, Marco; Jasion, Daniel; Luck, Kyle A; Marks, Tobin J; Grossman, Jeffrey C; Ren, Shenqiang; Hersam, Mark C

2014-09-10

415

Tunable porosities and shapes of fullerene-like spheres.  

PubMed

The formation of reversible switchable nanostructures monitored by solution and solid-state methods is still a challenge in supramolecular chemistry. By a comprehensive solid state and solution study we demonstrate the potential of the fivefold symmetrical building block of pentaphosphaferrocene in combination with Cu(I) halides to switch between spheres of different porosity and shape. With increasing amount of CuX, the structures of the formed supramolecules change from incomplete to complete spherically shaped fullerene-like assemblies possessing an Ih -C80 topology at one side and to a tetrahedral-structured aggregate at the other. In the solid state, the formed nano-sized aggregates reach an outer diameter of 3.14 and 3.56?nm, respectively. This feature is used to reversibly encapsulate and release guest molecules in solution. PMID:25759976

Dielmann, Fabian; Fleischmann, Matthias; Heindl, Claudia; Peresypkina, Eugenia V; Virovets, Alexander V; Gschwind, Ruth M; Scheer, Manfred

2015-04-13

416

Fullerenes in the cretaceous-tertiary boundary layer  

SciTech Connect

High-pressure liquid chromatography with ultraviolet-visible spectral analysis of toluene extracts of samples from two Cretaceous-Tertiary (K-T) boundary sites in New Zealand has revealed the presence of C[sub 60] at concentrations of 0.1 to 0.2 parts per million of the associated soot. This technique verified also that fullerenes are produced in similar amounts in the soots of common flames under ambient atmospheric conditions. Therefore, the C[sub 60] in the K-T boundary layer may have originated in the extensive wildfires that were associated with the cataclysmic impact event that terminated the Mezozoic era about 65 million years ago.

Heymann, D.; Chibante, L.P.F.; Smalley, R.E. (Rice Univ., Houston, TX (United States)); Brooks, R.R. (Massey Univ., Palmerston North (New Zealand)); Wolbach, W.S. (Illinois Wesleyan Univ., Bloomington, IL (United States))

1994-07-29

417

Search for fullerenes and PAHs in the diffuse interstellar medium  

NASA Astrophysics Data System (ADS)

Recent studies suggest carbon-containing molecules as the best candidates for carriers of the unidentified diffuse interstellar bands (DIBs). considering their abundance and ability to form stable bonds in interstellar space. We have searched for new DIBs in the near-IR and have detected two new diffuse bands that are consistent with laboratory measurements of C 60+ in a neon matrix. Criteria for this possible identification are discussed. From these observations and the DIB treasured absorption. we estimate that up to 0.9% of interstellar carbon could be in the form of C 60+ We also searched for poly cyclic aromatic hydrocarbon (PAH) canons and have derived corresponding limits for the presence of the coronene C 24H 12 and ovalene C 32H 14 cations in space. We have studied the ionization properties of these PAH cations, which could explain their selective destruction. From these results we discuss the role of fullerenes and PAHs as possible DIB carriers.

Ehrenfreund, P.; Foing, B. H.

1995-02-01

418

Optimizing conditions for ultrasound extraction of fullerenes from coal matrices  

SciTech Connect

Conditions for ultrasound toluene extraction of synthetic C60 added to powdered bituminous coal were tested. High-performance liquid chromatography (HPLC) was used to determine the fullerene content in the obtained extracts. The results indicated a possible negative effect of sample demineralization (HCl/HF) and N{sub 2} purging on the extraction yield of C60. On the contrary, a 30% yield increase was registered when the coal was pre-extracted with pentane or pentane/toluene. The best conditions for C60 recovery in the investigated mixtures are 30min of sonication at 280-285K. The effects of sample filtration, sequential extraction, ultrasound bath power and treatments of C60 solution alone are also discussed.

Vitek, P.; Jehlicka, J.; Frank, O.; Hamplova, V.; Pokorna, Z.; Juha, L.; Bohacek, Z. [Charles University Prague, Prague (Czech Republic)

2009-07-01

419

Composition changes in bombarded oxides and carbides: the distinction between ballistic, chemically guided, and chemically random behavior  

NASA Astrophysics Data System (ADS)

When oxides or carbides are bombarded it is commonly observed that new phases or compositions appear. Like ion beam mixing, the changes fall into categories which we term ballistic, chemically guided motion of defects, and chemically random motion of defects. An example of a ballistic change is a near-threshold process, as when O is lost from Ta 2O 5 or C is lost from TaC due to 1 keV He + impact. Chemically guided defects are inferred when the changes correlate with thermodynamics (i.e. with the enthalpy increase), volatility, Gibbsian segregation, or defect-induced transport. For example, O loss from transition metal oxides is conventionally taken as chemically guided by virtue of correlating with thermodynamics. Likewise, C loss from SiC in some cases correlates with the C being transported to the surface and then being subject to sputtering. Chemically random processes, in which thermodynamics, etc. are not relevant, are believed to occur when oxides are bombarded with N + or N 2+. A typical example is found with TiO 2, where O 2+ impact leads to TiO 2.00 and Ar + impact to TiO 1.66, the latter being equivalent to the Ti 2O 3 seen by electron diffraction. Finally, N 2+ impact leads to TiO 1.12N 0.60, and since the sum O+ N is similar to O alone after Ar + impact we infer a random replacement of O by N. A similar pattern is shown by B 2C 3, Al 2O 3, SiO 2, GeO 2, ZrO 2, V 2O 5, and Nb 2O 5. A somewhat different response is shown by SiC. Here N + impact leads to a replacement of C by N but the sum C + N significantly exceeds the initial C content. Evidently the replacement is not stoichiometric but it still constitutes a clear example of chemically random behavior.

Kelly, Roger; Bertóti, Imre; Miotello, Antonio

1993-06-01

420

Did Saturn's rings form during the Late Heavy Bombardment ?  

E-print Network

The origin of Saturn\\' s massive ring system is still unknown. Two popular scenarios - the tidal splitting of passing comets and the collisional destruction of a satellite - rely on a high cometary flux in the past. In the present paper we attempt to quantify the cometary flux during the Late Heavy Bombardment (LHB) to assess the likelihood of both scenarios. Our analysis relies on the so-called Nice model of the origin of the LHB (Tsiganis et al., 2005; Morbidelli et al., 2005; Gomes et al., 2005) and on the size distribution of the primordial trans-Neptunian planetesimals constrained in Charnoz & Morbidelli (2007). We find that the cometary flux on Saturn during the LHB was so high that both scenarios for the formation of Saturn rings are viable in principle. However, a more detailed study shows that the comet tidal disruption scenario implies that all four giant planets should have comparable ring systems whereas the destroyed satellite scenario would work only for Saturn, and perhaps Jupiter. This is because in Saturn\\'s system, the synchronous orbit is interior to the Roche Limit, which is a necessary condition for maintaining a satellite in the Roche zone up to the time of the LHB. We also discuss the apparent elimination of silicates from the ring parent body implied by the purity of the ice in Saturn \\' s rings. The LHB has also strong implications for the survival of the Saturnian satellites: all satellites smaller than Mimas would have been destroyed during the LHB, whereas Enceladus would have had from 40% to 70% chance of survival depending on the disruption model. In conclusion, these results suggest that the LHB is the sweet moment for the formation of a massive ring system around Saturn.

Sebastien Charnoz; Alessandro Morbidelli; Luke H. Dones; Julien Salmon

2008-11-02

421

Exploring the Mysteries of the Early Bombardment of the Moon  

NASA Astrophysics Data System (ADS)

The earliest bombardment history of the Moon is recorded in the observed lunar basins (i.e., D > 300 km diameter craters). The beginning of the basin-forming epoch is unknown, but the oldest basins cannot be older than the 4.46 Ga lunar crust (here defined as t0). The age of the oldest known basin, South Pole-Aitken, is unknown, but the youngest basins, Imbrium and Orientale, formed 3.8 Ga. Of the remaining basins, only Serenitatis has a undisputed age (3.89 Ga). Taking together with data from smaller craters and lunar samples, many groups have tried to piece together what happened to the Moon between t0 and 3.8 Ga. This has led to two dominant scenarios: (i) the basins were produced by a terminal cataclysm that caused a spike in the impactor flux 3.8-4.0 Ga and (ii) the basins came from the tail end of a monotonically-decreasing impactor population created by planet formation processes. Interestingly, there may be room for both scenarios to work at some level. For (i), consider that planetesimals leftover from terrestrial planet formation were likely scattered up to high eccentricities and inclinations by planetary embryos; these objects were long-lived enough that some should have struck the Moon after t0. In addition, scattering events produced by embryos/planets residing in/near the primordial asteroid and comet populations should have also provided some basin-forming impactors. For (ii), the Nice model provides a plausible dynamical mechanism capable of creating a spike of comets/asteroid impactors 3.8-4.0 Ga. A complicating factor in all of this, however, is the unknown initial and collisionally-evolved size distributions of these populations, which may strongly affect the actual impact signature left on the Moon from (i) and (ii). We have a lot of work to do!

Bottke, William, Jr.

2008-09-01

422

Chemical Reaction and Flow Modeling in Fullerene and Nanotube Production  

NASA Technical Reports Server (NTRS)

The development of processes to produce fullerenes and carbon nanotubes has largely been empirical. Fullerenes were first discovered in the soot produced by laser ablation of graphite [1]and then in the soot of electric arc evaporated carbon. Techniques and conditions for producing larger and larger quantities of fullerenes depended mainly on trial and error empirical variations of these processes, with attempts to scale them up by using larger electrodes and targets and higher power. Various concepts of how fullerenes and carbon nanotubes were formed were put forth, but very little was done based on chemical kinetics of the reactions. This was mainly due to the complex mixture of species and complex nature of conditions in the reactors. Temperatures in the reactors varied from several thousand degrees Kelvin down to near room temperature. There are hundreds of species possible, ranging from atomic carbon to large clusters of carbonaceous soot, and metallic catalyst atoms to metal clusters, to complexes of metals and carbon. Most of the chemical kinetics of the reactions and the thermodynamic properties of clusters and complexes have only been approximated. In addition, flow conditions in the reactors are transient or unsteady, and three dimensional, with steep spatial gradients of temperature and species concentrations. All these factors make computational simulations of reactors very complex and challenging. This article addresses the development of the chemical reaction involved in fullerene production and extends this to production of carbon nanotubes by the laser ablation/oven process and by the electric arc evaporation process. In addition, the high-pressure carbon monoxide (HiPco) process is discussed. The article is in several parts. The first one addresses the thermochemical aspects of modeling; and considers the development of chemical rate equations, estimates of reaction rates, and thermodynamic properties where they are available. The second part addresses modeling of the arc process for fullerene and carbon nanotube production using O-D, 1-D and 2-D fluid flow models. The third part addresses simulations of the pulsed laser ablation process using time-dependent techniques in 2-D, and a steady state 2-D simulation of a continuous laser ablation process. The fourth part addresses steady state modeling in O-D and 2-D of the HiPco process. In each of the simulations, there is a variety of simplifications that are made that enable one to concentrate on one aspect or another of the process. There are simplifications that can be made to the chemical reaction models , e.g. reduction in number of species by lumping some of them together in a representative species. Other simulations are carried out by eliminating the chemistry altogether in order to concentrate on the fluid dynamics. When solving problems with a large number of species in more than one spatial dimension, it is almost imperative that the problem be decoupled by solving for the fluid dynamics to find the fluid motion and temperature history of "particles" of fluid moving through a reactor. Then one can solve the chemical rate equations with complex chemistry following the temperature and pressure history. One difficulty is that often mixing with an ambient gas is involved. Therefore, one needs to take dilution and mixing into account. This changes the ratio of carbon species to background gas. Commercially available codes may have no provision for including dilution as part of the input. One must the write special solvers for including dilution in decoupled problems. The article addresses both ful1erene production and single-walled carbon nanotube (SWNT) production. There are at least two schemes or concepts of SWNT growth. This article will only address growth in the gas phase by carbon and catalyst cluster growth and SW T formation by the addition of carbon. There are other models that conceive of SWNT growth as a phase separation process from clusters me up carbon and metal catalyst, with the carbon precipitating from the cluster as it co

Scott, Carl D.; Farhat, Samir; Greendyke, Robert B.

2004-01-01

423

In search of fullerene-based superacids: synthesis, X-ray structure, and DFT study of C60(C2F5)(5)H.  

PubMed

Simply super! The perfluoroalkylfullerene C(60)(C(2)F(5))(5) H is the first structurally characterized perfluoroalkylated fullerene-based acid and is also predicted to be the first gas-phase fullerene-based superacid. PMID:21721060

Kuvychko, Igor V; Shustova, Natalia B; Avdoshenko, Stanislav M; Popov, Alexey A; Strauss, Steven H; Boltalina, Olga V

2011-08-01

424

Ion-beam-assisted hexagonal diamond formation from C60 fullerene  

Microsoft Academic Search

Ions are commonly believed to be detrimental to diamond growth because of the high degree of lattice disorder induced by ion bombardments. In this paper, we examine the possibility of preparing diamond using thermally evaporated C60 and simultaneous bombardment with Ne+ ions. It is found that the diamonds can be grown on Si wafers in the appropriate substrate temperature and

X. D. Zhu; Y. H. Xu; H. Naramoto; K. Narumi; A. Miyashita; K. Miyashita

2003-01-01

425

Influence of Natural Organic Matter on Aggregation, Deposition, and Transport of Fullerene Colloids in Aqueous Systems  

NASA Astrophysics Data System (ADS)

Engineered fullerenes are increasingly being used in commercial products (e.g., skin and eye creams, tennis racquets, and lubricants) that may become a significant source for environmental release. A thorough understanding of fullerenes' aggregation in aqueous phase and deposition/transport in porous media is needed for evaluating the environmental persistence of fullerenes and subsequent human or ecological exposure. A number of recent studies have shown that fullerenes form stable colloidal aggregates in aqueous media and that their environmental behaviors largely depend on solution chemistry including ionic strength, solution pH, and the presence of natural organic matter (NOM). Nonetheless, the lack of systematic studies on NOM interaction with fullerene colloids and the coupling of this interaction with ionic strength and solution pH make predicting environmental behaviors of fullerenes a difficult task. In this study, electrophoretic mobility (EM), particle size, and aggregation kinetics of C60 colloidal suspensions were measured under a range of ionic strength (1.5-500.5 mM), solution pH (4, 7.8, and 10), and humic (0-9 mg C/L) or fulvic (0-11 mg C/L) acid concentrations. The EM data could be modeled with Ohshima's soft particle theory to probe thickness, softness, and charge density of adsorbed NOM layers on fullerene colloids. Under select conditions that represent low and high mobility, deposition studies using a quartz crystal microbalance and transport experiments in saturated and unsaturated sand columns will be conducted. It is anticipated that NOM may alter the transport of fullerene C60 differently in unsaturated media compared with saturated media. Our preliminary results showed that humic acid is more effective than fulvic acid in stabilizing fullerene suspensions and the extent of this stabilizing effect is a function of ionic strength when buffered at pH 7.8 with 0.5 mM NaHCO3. The findings of this study will help better assess the fate and transport of fullerene C60 in surface water, the vadose zone, and groundwater.

Zhang, W.; Rattanaudompol, U.; Powell, T.; Bouchard, D.

2011-12-01

426

Dual growth modes in ion bombarded Si surfaces  

SciTech Connect

Morphological studies were done on Si (001) surfaces after rastering them with a 1 keV O{sub 2}{sup +} ion beam at an angle. The resulting mounded morphology was studied using atomic force microscopy (AFM) measurements. The roughness at different length scales were further extracted and quantified from AFM measurements using scaling analysis. Results indicate two growth regimes of the evolving surface which were evident from the power spectral density (PSD) and interface width analysis of the eroded surfaces. Initially the growth is unstable followed by a stable regime of the nanostructures evolved after about 35 minutes of erosion. Temporal studies done on these surfaces show the onset of shadowing at higher sputtering times thus indicating the breakdown of the growth model at these times.

Dhillon, Prabhjeet Kaur; Sarkar, Subhendu [Department of Physics, Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab - 140 001 (India)

2012-06-05

427

Antioxidant effects of water-soluble fullerene derivatives against ultraviolet ray or peroxylipid through their action of scavenging the reactive oxygen species in human skin keratinocytes  

Microsoft Academic Search

Chemically generated hydroxyl radicals were scavenged by PEG-modified fullerene, hydroxy-fullerene and isostearate-mixed fullerene as efficiently as ascorbic acid (Asc) or its 2-O-phosphorylated derivative (A2P) as shown by the DMPO-spin trap\\/ESR method. Enzymatically generated superoxide anion radicals were also scavenged by PEG-modified or PVP-entrapped fullerene similarly as done by Asc or A2P. Some reactive oxygen species (ROS) such as hydroperoxides and

Li Xiao; Hiroya Takada; Kentaro Maeda; Mari Haramoto; Nobuhiko Miwa

2005-01-01

428

The molecular mechanism of fullerene-inhibited aggregation of Alzheimer's ?-amyloid peptide fragment  

NASA Astrophysics Data System (ADS)

Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of ?-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-? (A?) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent ?-sheet formation of A?(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on A?(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the ?-sheet formation of A?(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of ?-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and A?(16-22) peptides significantly weaken the peptide-peptide interaction that is important for ?-sheet formation, thus retarding A?(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of A?(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease.Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of ?-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-? (A?) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent ?-sheet formation of A?(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on A?(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the ?-sheet formation of A?(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of ?-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and A?(16-22) peptides significantly weaken the peptide-peptide interaction that is important for ?-sheet formation, thus retarding A?(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of A?(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease. Electronic supplementary information (ESI) available: The description of REMD simulations, analysis parameters, and AFM imaging of A?(16-22) aggregation with and without C60 nanoparticles, and three figures. The figures show the initial states, the convergence check for all the REMD runs, the PDF of the centroid distance (d) between the aromatic rings of Phe and its closest carbon ring, and the PDF of the

Xie, Luogang; Luo, Yin; Lin, Dongdong; Xi, Wenhui; Yang, Xinju; Wei, Guanghong

2014-07-01

429

Fullerene-enhanced accumulation of p,p'-DDE in agricultural crop species.  

PubMed

The effect of C(60) fullerene exposure on the accumulation of dichlorodiphenyldichloroethylene (p,p'-DDE; DDT metabolite) by Cucurbita pepo L. (zucchini), Glycine max L. (soybean), and Solanum lycopersicum L. (tomato) was determined. The plants were grown in 125 mL jars of vermiculite amended with 0 or 40 mg of C(60) fullerenes. Prior to planting, the jars were amended with 40 mL solution containing 100 ng/mL of p,p'-DDE with 0 or 100 mg/L humic acid. During three weeks of growth, plants were watered with the same p,p'-DDE containing solutions. Total shoot p,p'-DDE levels in nonfullerene exposed tomato, soybean, and zucchini were 26.9, 131, and 675 ng, respectively; total root DDE content for the three plants was 402, 5970, and 5830 ng, respectively. Fullerenes increased the shoot p,p'-DDE content of zucchini by 29%; contaminant levels in soybean shoots were decreased by 48% but tomato shoot content was unaffected. The root and total plant p,p'-DDE content of all three species was significantly increased by fullerene exposure; enhanced contaminant uptake ranged from 30 to 65%. Humic acid, regardless of fullerene presence or plant type, significantly decreased the p,p'-DDE uptake. Fullerenes were detected in the roots of all plants but were not detected in plant shoots in the initial study. In a follow up study with zucchini designed to maximize biomass for extraction, over half the analyzed stems contained fullerenes at 60.5 to 4490 ng/g. These findings show that the carbon-based nanomaterials may significantly alter the accumulation and potentially the toxicity of cocontaminants in agricultural systems. PMID:22856886

De La Torre-Roche, Roberto; Hawthorne, Joseph; Deng, Yingqing; Xing, Baoshan; Cai, Wenjun; Newman, Lee A; Wang, Chen; Ma, Xingmao; White, Jason C

2012-09-01

430

Synthesis, characterization, and reversible hydrogen sorption study of sodium-doped fullerene  

NASA Astrophysics Data System (ADS)

Herein is presented a novel, straightforward route to the synthesis of an alkali metal-doped fullerene as well as a detailed account of its reversible and enhanced hydrogen sorption properties in comparison to pure C60. This work demonstrates that a reaction of sodium hydride with fullerene (C60) results in the formation of a sodium-doped fullerene capable of reversible hydrogen sorption via a chemisorption mechanism. This material not only demonstrated reversible hydrogen storage over several cycles, it also showed the ability to reabsorb over three times the amount of hydrogen (relative to the hydrogen content of NaH) under optimized conditions. The sodium-doped fullerene was hydrogenated on a pressure composition temperature (PCT) instrument at 275?° C while under 100 bar of hydrogen pressure. The hydrogen desorption behavior of this sodium-doped fullerene hydride was observed over a temperature range up to 375?° C on the PCT and up to 550?° C on the thermogravimetric analysis (TGA). Powder x-ray diffraction verifies the identity of this material as being Na6C60. Characterization of this material by thermal decomposition analysis (e.g. PCT and TGA methods), as well as FT-IR and mass spectrometry, indicates that the hydrogen sorption activity of this material is due to the reversible formation of a hydrogenated fullerene (fullerane). However, the reversible formation of fullerane was found to be greatly enhanced by the presence of sodium. It was also demonstrated that the addition of a catalytic amount of titanium (via TiO2 or Ti(OBu)4) further enhances the hydrogen sorption process of the sodium-doped fullerene material.

Knight, Douglas A.; Teprovich, Joseph A., Jr.; Summers, Andrew; Peters, Brent; Ward, Patrick A.; Compton, Robert N.; Zidan, Ragaiy

2013-11-01

431

Functionalized fullerenes mediate photodynamic killing of cancer cells: Type I versus Type II photochemical mechanism  

PubMed Central

Photodynamic therapy (PDT) employs the combination of non-toxic photosensitizers (PS) and harmless visible light to generate reactive oxygen species (ROS) and kill cells. Most clinically studied PS are based on the tetrapyrrole structure of porphyrins, chlorins and related molecules, but new non-tetrapyrrole PS are being sought. Fullerenes are soccer-ball shaped molecules composed of sixty or seventy carbon atoms and have attracted interest in connection with the search for biomedical applications of nanotechnology. Fullerenes are biologically inert unless derivatized with functional groups, whereupon they become soluble and can act as PS. We have compared the photodynamic activity of six functionalized fullerenes with 1, 2, or 3 hydrophilic or 1, 2, or 3 cationic groups. The octanol-water partition coefficients were determined and the relative contributions of Type I photochemistry (photogeneration of superoxide in the presence of NADH) and Type II photochemistry (photogeneration of singlet oxygen) were studied by measurement of oxygen consumption, 1270-nm luminescence and EPR spin-trapping of the superoxide product. We studied three mouse cancer cell lines: (J774, LLC and CT26) incubated for 24 h with fullerenes and illuminated with white light. The order of effectiveness as PS was inversely proportional to the degree of substitution of the fullerene nucleus for both the neutral and cationic series. The mono-pyrrolidinium fullerene was the most active PS against all cell lines and induced apoptosis 4–6 hours after illumination. It produced diffuse intracellular fluorescence when dichlorodihydrofluorescein was added as an ROS probe suggesting a Type I mechanism for phototoxicity. We conclude that certain functionalized fullerenes have potential as novel PDT agents and phototoxicity may be mediated both by superoxide and by singlet oxygen. PMID:17664135

Mroz, Pawel; Pawlak, Anna; Satti, Minahil; Lee, Haeryeon; Wharton, Tim; Gali, Hariprasad; Sarna, Tadeusz; Hamblin, Michael R.

2007-01-01

432

Compact, maintainable 80-KeV neutral beam module  

DOEpatents

A compact, maintainable 80-keV arc chamber, extractor module for a neutral beam system immersed in a vacuum of <10.sup.-2 Torr, incorporating a nested 60-keV gradient shield located midway between the high voltage ion source and surrounding grounded frame. The shield reduces breakdown or arcing path length without increasing the voltage gradient, tends to keep electric fields normal to conducting surfaces rather than skewed and reduces the peak electric field around irregularities on the 80-keV electrodes. The arc chamber or ion source is mounted separately from the extractor or ion accelerator to reduce misalignment of the accelerator and to permit separate maintenance to be performed on these systems. The separate mounting of the ion source provides for maintaining same without removing the ion accelerator.

Fink, Joel H. (Livermore, CA); Molvik, Arthur W. (Livermore, CA)

1980-01-01

433

Effects of Mo Seeding on the Formation of Si Nanodots During Low-Energy Ion Bombardment  

SciTech Connect

Effects of seed atoms on the formation of nanodots on silicon surfaces during normal incidence Ar+ ion bombardment at room temperature are studied with real-time grazing-incidence small-angle x-ray scattering (GISAXS), real-time wafer curvature stress measurements and ex situ atomic force microscopy. Although Si surfaces remain smooth during bombardment at room temperature, when a small amount of Mo atoms is supplied to the surface during ion bombardment, the development of correlated structures ('dots') is observed. Stress measurements show that initially a compressive stress develops during bombardment, likely due to amorphization of the surface and insertion of argon. However, seeding causes a larger tensile stress to develop with further bombardment, possibly due to the formation of higher density regions around the Mo seed atoms on the surface. Detailed fits of the GISAXS evolution during nanostructure growth show that the instability is larger than predicted by the Bradley-Harper theory of curvature-dependent sputter yield. These results suggest that the tensile stress is playing a dominant role in driving the nanodot formation.

Ozaydin,G.; Ludwig, Jr., K.; Zhou, H.; Headrick, R.

2008-01-01

434

Stable transformation of the food yam Dioscorea alata L. by particle bombardment.  

PubMed

A biolistic particle gun was used to deliver genetic material into intact yam cells. Cultured suspension cells of D. alata were bombarded with microprojectiles coated with pBI221.2 DNA and histochemical assays were carried out to show transient GUS expression in bombarded cells. Stably transformed D. alata cells were recovered from cultured cells after bombardment with microprojectiles coated with pRT99gus harbouring both the nptII and uidA genes. Bombarded cells were selected on a medium containing geneticin (G418). Two months after bombardment, calli resistant to G418 were assayed for GUS expression. There was a 100% correlation between resistance to G418 and GUS expression. From these calli, four cell lines were established and GUS activity in each line was determined fluorometrically. The use of a specific GUS inhibitor showed that the GUS activity was due to the introduced uidA gene rather than to any intrinsic GUS-like activity originating from the plant. Incorporation of the introduced DNA into the plant genomic DNA was confirmed by Southern analysis. PMID:24197354

Tör, M; Ainsworth, C; Mantell, S H

1993-05-01

435

Ultra-low-energy (<10 eV/u) ion beam bombardment effect on naked DNA  

NASA Astrophysics Data System (ADS)

Since ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range, it is very interesting to know effects from ultra-low-energy ion interaction with DNA for understanding ion-beam-induced genetic mutation. Tens-keV Ar- and N-ion beams were decelerated to ultra-low energy ranging from 20 to 100 eV, or only a few to 10 eV/u, to bombard naked plasmid DNA. The bombarded DNA was analyzed using gel electrophoresis for DNA form changes. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks after bombarded by tens-eV ion beam. N-ion beam was found more effective in inducing DNA change and mutation than Ar-ion beam. The study demonstrated that the ion bombardment with energy as low as several-tens eV was able to break DNA strands and thus potentially to cause genetic modification of biological cells. The experimental results were discussed in terms of direct atomic collision between the ions and DNA atoms.

Thopan, P.; Thongkumkoon, P.; Prakrajang, K.; Suwannakachorn, D.; Yu, L. D.

2014-05-01

436

PAPER www.rsc.org/analyst | The Analyst Fullerene-impregnated ionic liquid stationary phases for gas  

E-print Network

PAPER www.rsc.org/analyst | The Analyst Fullerene-impregnated ionic liquid stationary phases for gas chromatography Chieu D. Tran* and Santhosh Challa Received 30th October 2007, Accepted 28th chromatography (GC). In this method, ionic liquids (ILs) are used as solvents to coat fullerenes (C60, amino-C60

Reid, Scott A.

437

Fullerenes, nanotubes, and graphite as matrices for collision mechanism in secondary ion mass spectrometry: determination of cyclodextrin.  

PubMed

A technique for improving the sensitivity of high mass molecular analysis is described. Three carbon species, fullerenes, single walled carbon nanotubes, and highly ordered pyrolytic graphite are introduced as matrices for the secondary ion mass spectrometry analysis of cyclodextrin (C(42)H(70)O(35), 1134 u). The fullerene and nanotubes are deposited as single deposition, and 10, 20, or 30 deposition films and cyclodextrin is deposited on top. The cyclodextrin parent-like ions and two fragments were analyzed. A 30 deposition fullerene film enhanced the intensity of cationized cyclodextrin with Na by a factor of 37. While the C(6)H(11)O(5) fragment, corresponding to one glucopyranose unit, increased by a factor of 16. Although fragmentation on fullerene is not suppressed, the intensity is twice as low as the parent-like ion. Deprotonated cyclodextrin increases by 100× and its C(8)H(7)O fragment by 10×. While the fullerene matrix enhances secondary ion emission, the nanotubes matrix film generates a basically constant yield. Graphite gives rise to lower intensity peaks than either fullerene or nanotubes. Scanning electron microscopy and atomic force microscopy provide images of the fullerene and nanotubes deposition films revealing flat and web structured surfaces, respectively. A "colliding ball" model is presented to provide a plausible physical mechanism of parent-like ion enhancement using the fullerene matrix. PMID:21952781

Stupavska, Monika; Jerigova, Monika; Michalka, Miroslav; Hasko, Daniel; Szoecs, Vojtech; Velic, Dusan

2011-12-01

438

Electrochemistry of (Dihapto-Buckminster-Fullerene) Pentacarbonyl Tungsten(0): An Experiment for the Inorganic Chemistry Laboratory, Part III  

ERIC Educational Resources Information Center

Cyclic voltammetry experiments on [60]fullerene, (C[subscript 60]), and (dihapto-[60]fullerene) pentacarbonyl tungsten(0), ([eta][superscript 2]-C[subscript 60])W(CO)[subscript 5], constitute an educational experiment for the inorganic chemistry laboratory with a primary objective to teach the chemical interpretation of a voltammogram, in…

Igartua-Nieves, Elvin; Ocasio-Delgado, Yessenia; Rivera-Pagan, Jose; Cortes-Figueroa, Jose E.

2007-01-01

439

Fullerenes, Nanotubes, and Graphite as Matrices for Collision Mechanism in Secondary Ion Mass Spectrometry: Determination of Cyclodextrin  

NASA Astrophysics Data System (ADS)

A technique for improving the sensitivity of high mass molecular analysis is described. Three carbon species, fullerenes, single walled carbon nanotubes, and highly ordered pyrolytic graphite are introduced as matrices for the secondary ion mass spectrometry analysis of cyclodextrin (C42H70O35, 1134 u). The fullerene and nanotubes are deposited as single deposition, and 10, 20, or 30 deposition films and cyclodextrin is deposited on top. The cyclodextrin parent-like ions and two fragments were analyzed. A 30 deposition fullerene film enhanced the intensity of cationized cyclodextrin with Na by a factor of 37. While the C6H11O5 fragment, corresponding to one glucopyranose unit, increased by a factor of 16. Although fragmentation on fullerene is not suppressed, the intensity is twice as low as the parent-like ion. Deprotonated cyclodextrin increases by 100× and its C8H7O fragment by 10×. While the fullerene matrix enhances secondary ion emission, the nanotubes matrix film generates a basically constant yield. Graphite gives rise to lower intensity peaks than either fullerene or nanotubes. Scanning electron microscopy and atomic force microscopy provide images of the fullerene and nanotubes deposition films revealing flat and web structured surfaces, respectively. A "colliding ball" model is presented to provide a plausible physical mechanism of parent-like ion enhancement using the fullerene matrix.

Stupavska, Monika; Jerigova, Monika; Michalka, Miroslav; Hasko, Daniel; Szoecs, Vojtech; Velic, Dusan

2011-12-01

440

Compact bis-adduct fullerenes and additive-assisted morphological optimization for efficient organic photovoltaics.  

PubMed

Bis-adduct fullerenes surrounded by two insulating addends sterically attenuate intermolecular interaction and cause inferior electron transportation. In this research, we have designed and synthesized a new class of bis-adduct fullerene materials, methylphenylmethano-C60 bis-adduct (MPC60BA), methylthienylmethano-C60 bis-adduct (MTC60BA), methylphenylmethano-C70 bis-adduct (MPC70BA), and methylthienylmethano-C70 bis-adduct (MTC70BA), functionalized with two compact phenylmethylmethano and thienylmethylmethano addends via cyclopropyl linkages. These materials with much higher-lying lowest unoccupied molecular orbital (LUMO) energy levels successfully enhanced the Voc values of the P3HT-based solar cell devices. The compact phenylmethylmethano and thienylmethylmethano addends to promote fullerene intermolecular interactions result in aggregation-induced phase separation as observed by the atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the poly(3-hexylthiophene-2,5-diyl) (P3HT)/bis-adduct fullerene thin films. The device based on the P3HT/MTC60BA blend yielded a Voc of 0.72 V, a Jsc of 5.87 mA/cm(2), and a fill factor (FF) of 65.3%, resulting in a power conversion efficiency (PCE) of 2.76%. The unfavorable morphologies can be optimized by introducing a solvent additive to fine-tune the intermolecular interactions. 1-Chloronaphthalene (CN) having better ability to dissolve the bis-adduct fullerenes can homogeneously disperse the fullerene materials into the P3HT matrix. Consequently, the aggregated fullerene domains can be alleviated to reach a favorable morphology. With the assistance of CN additive, the P3HT/MTC60BA-based device exhibited enhanced characteristics (a Voc of 0.78 V, a Jsc of 9.04 mA/cm(2), and an FF of 69.8%), yielding a much higher PCE of 4.92%. More importantly, the additive-assisted morphological optimization is consistently effective to all four compact bis-adduct fullerenes regardless of the methylphenylmethano or methylthienylmethano scaffolds as well as C60 or C70 core structures. Through the extrinsic additive treatment, these bis-adduct fullerene materials with compact architectures show promise for high-performance polymer solar cells. PMID:25285727

Lai, Yun-Yu; Liao, Ming-Hung; Chen, Yen-Ting; Cao, Fong-Yi; Hsu, Chain-Shu; Cheng, Yen-Ju

2014-11-26

441

Velocity effects on fullerene and oxide nanoparticle deposition in porous media.  

PubMed

Products of nanochemistry have been proposed in a number of applications ranging from soil stabilization and cosmetics to groundwater remediation. A fundamental understanding of the transport properties of these materials is essential to assess their efficacy and environmental impact in such applications. In this work, we consider the effect of flow on nanoparticle transport and deposition in porous media. The transport of three aqueous suspensions of fullerenes in a well-characterized porous medium is compared with that of two oxide nanomaterials at two flow rates. Despite significant differences in surface chemistry and size, the fullerenes exhibited an unexpected and similar breakthrough behavior at the higher flow rate. A striking characteristic of the fullerene breakthrough curves obtained at the higher Darcy velocity was an initial enhancement in nanoparticle deposition shortly after the passage of the first pore volume of suspension, followed by an increase in passage. This velocity-sensitive "affinity transition" in the initial deposition of nanoparticles in the porous medium was observed for fullerene-based materials only at the higher velocity and was in no case observed for silica or titania nanoparticles. The removal of fullerene-based nanoparticles was observed to converge to a level that was independent of flow velocity, suggesting that under these conditions time scales for attachment or reorganization on the surface are greater than the time scale for transport to collector surfaces. PMID:15382867

Lecoanet, Hélène F; Wiesner, Mark R

2004-08-15

442

Co-Exposure with Fullerene May Strengthen Health Effects of Organic Industrial Chemicals  

PubMed Central

In vitro toxicological studies together with atomistic molecular dynamics simulations show that occupational co-exposure with C60 fullerene may strengthen the health effects of organic industrial chemicals. The chemicals studied are acetophenone, benzaldehyde, benzyl alcohol, m-cresol, and toluene which can be used with fullerene as reagents or solvents in industrial processes. Potential co-exposure scenarios include a fullerene dust and organic chemical vapor, or a fullerene solution aerosolized in workplace air. Unfiltered and filtered mixtures of C60 and organic chemicals represent different co-exposure scenarios in in vitro studies where acute cytotoxicity and immunotoxicity of C60 and organic chemicals are tested together and alone by using human THP-1-derived macrophages. Statistically significant co-effects are observed for an unfiltered mixture of benzaldehyde and C60 that is more cytotoxic than benzaldehyde alone, and for a filtered mixture of m-cresol and C60 that is slightly less cytotoxic than m-cresol. Hydrophobicity of chemicals correlates with co-effects when secretion of pro-inflammatory cytokines IL-1? and TNF-? is considered. Complementary atomistic molecular dynamics simulations reveal that C60 co-aggregates with all chemicals in aqueous environment. Stable aggregates have a fullerene-rich core and a chemical-rich surface layer, and while essentially all C60 molecules aggregate together, a portion of organic molecules remains in water. PMID:25473947

Róg, Tomasz; Cramariuc, Oana; Vanhala, Esa; Tornaeus, Jarkko; Taberman, Helena; Jänis, Janne; Alenius, Harri; Vattulainen, Ilpo; Laine, Olli

2014-01-01

443

Formation of a new electric material: Fullerene/metal polycrystalline film  

SciTech Connect

An investigation of the formation behavior and mechanism of onion like fullerene/metal polycrystalline film under electron beam irradiation is presented. Metallic nanoparticles of Al, Au and Pt having diameters of 1{approximately}35 nm, were supported on an amorphous carbon film with thickness of about 20 nm. The amorphous carbon film transformed into onion-like fullerene film under electron beam irradiation, with intensity about 10{sup 20} e/cm{sup 2}{center{underscore}dot}sec using high resolution transmission electron microscopy. The transformation mechanism and growth morphology have been investigated. It is found that the nucleation and growth process of onion-like fullerenes from amorphous carbon were divided into several steps: Firstly, a few elliptic shells of carbon were induced under Al, Au or Pt nanoparticles; secondly, a gradual reorganization took place into the structures composed of quasi-concentric spheroid or sphered graphite, i.e., onion like fullerenes, and finally, fullerenes were bonded to each other into a film.

Xu, Bingshu; Tanaka, Shunichiro

1997-07-01

444

An all-purpose building block: B12N12 fullerene  

NASA Astrophysics Data System (ADS)

We have theoretically shown that the boron nitride fullerene cage B12N12 is an all-purpose building block for fabricating multifarious BN nanotubes. Firstly, we investigated the stability and structural of the boron nitride fullerene cage B12N12 and the polymerized derivatives obtained from it. Interestingly we found out that two B12N12 cages can spontaneously form one BN nanotube with two closed ends through the structural transformation when one cage meets another. These results indicated that the fullerene B12N12 can be polymerized to build various remarkable polymers through the spontaneous structural transformation when they are together, which all have planer or tridimensional shapes with a hollow tubular structure, even at the juncture of the coalesced B12N12. Simultaneously, after the structure optimization, the quadrangles at the juncture of the coalesced B12N12 disappear to form a perfect surface only composed of hexagons. Then, we calculated the energy of all the considered nanostructures. The polymerization of the fullerene B12N12 is exothermic and thus can form very stable derivative polymers. These theoretical conclusions stimulate us to use the fullerene B12N12 as an all-purpose building block to construct various BN nanostructures for purpose of fundamental research and potential applications.

Li, J. L.; He, T.; Yang, G. W.

2012-02-01

445

1-Aryl-4-silylmethyl[60]fullerenes: synthesis, properties, and photovoltaic performance.  

PubMed

The efficient nucleophilic addition of aryl Grignard reagents (aryl=4-MeOC(6)H(4), 4-Me(2)NC(6)H(4), Ph, 4-CF(3)C(6)H(4), and thienyl) to C(60) in the presence of DMSO produced 1,2-arylhydro[60]fullerenes after acid treatment. The reactions of the anions of these arylhydro[60]fullerenes with either dimethylphenylsilylmethyl iodide or dimethyl(2-isopropoxyphenyl)silylmethyl iodide yielded the target compounds, 1-aryl-4-silylmethyl[60]fullerenes. The properties and structures of these 1-aryl-4-silylmethyl[60]fullerenes (aryl=4-MeOC(6)H(4), thienyl) were examined by electrochemical studies, X-ray crystallography, flash-photolysis time-resolved microwave-conductivity (FP-TRMC) measurements, and electron-mobility measurements by using a space-charge-limited current (SCLC) model. Organic photovoltaic devices with a polymer-based bulk heterojunction structure and small-molecule-based p-n and p-i-n heterojunction configurations were fabricated by using 1-aryl-4-silylmethyl[60]fullerenes as an electron acceptor. The most efficient device exhibited a power-conversion efficiency of 3.4% (short-circuit current density: 8.1 mA/cm(2), open-circuit voltage: 0.69 V, fill factor: 0.59). PMID:23023947

Matsuo, Yutaka; Oyama, Hiromi; Soga, Iwao; Okamoto, Toshihiro; Tanaka, Hideyuki; Saeki, Akinori; Seki, Shu; Nakamura, Eiichi

2013-01-01

446

Detection of fullerenes (C60 and C70) in commercial cosmetics  

PubMed Central

Detection methods are necessary to quantify fullerenes in commercial applications to provide potential exposure levels for future risk assessments of fullerene technologies. The fullerene concentrations of five cosmetic products were evaluated using liquid chromatography with mass spectrometry to separate and specifically detect C60 and C70 from interfering cosmetic substances (e.g., castor oil). A cosmetic formulation was characterized with transmission electron microscopy, which confirmed that polyvinylpyrrolidone encapsulated C60. Liquid-liquid extraction of fullerenes from control samples approached 100% while solid-phase and sonication in toluene extractions yielded recoveries of 27–42%. C60 was detected in four commercial cosmetics ranging from 0.04 to 1.1 ?g/g, and C70 was qualitatively detected in two samples. A single-use quantity of cosmetic (0.5 g) may contain up to 0.6 ?g of C60, demonstrating a pathway for human exposure. Steady-state modeling of fullerene adsorption to biosolids is used to discuss potential environmental releases from wastewater treatment systems. PMID:21300421

Benn, Troy M.; Westerhoff, Paul; Herckes, Pierre

2013-01-01

447

Interplay between fullerene surface coverage and contact selectivity of cathode interfaces in organic solar cells.  

PubMed

Interfaces play a determining role in establishing the degree of carrier selectivity at outer contacts in organic solar cells. Considering that the bulk heterojunction consists of a blend of electron donor and acceptor materials, the specific relative surface coverage at the electrode interfaces has an impact on the carrier selectivity. This work unravels how fullerene surface coverage at cathode contacts lies behind the carrier selectivity of the electrodes. A variety of techniques such as variable-angle spectroscopic ellipsometry and capacitance-voltage measurements have been used to determine the degree of fullerene surface coverage in a set of PCPDTBT-based solar cells processed with different additives. A full screening from highly fullerene-rich to polymer-rich phases attaching the cathode interface has enabled the overall correlation between surface morphology (relative coverage) and device performance (operating parameters). The general validity of the measurements is further discussed in three additional donor/acceptor systems: PCPDTBT, P3HT, PCDTBT, and PTB7 blended with fullerene derivatives. It is demonstrated that a fullerene-rich interface at the cathode is a prerequisite to enhance contact selectivity and consequently power conversion efficiency. PMID:23611512

Guerrero, Antonio; Dörling, Bernhard; Ripolles-Sanchis, Teresa; Aghamohammadi, Mahdieh; Barrena, Esther; Campoy-Quiles, Mariano; Garcia-Belmonte, Germà

2013-05-28

448

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

SciTech Connect

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.

Huffman, D.R.

1996-06-05

449

Charge transfer structure-reactivity dependence of fullerene-single-walled carbon nanotube heterojunctions.  

PubMed

Charge transfer at the interface between single-walled carbon nanotubes (SWCNTs) of distinct chiral vectors and fullerenes of various molecular weights is of interest both fundamentally and because of its importance in emerging photovoltaic and optoelectronic devices. One approach for generating isolated, discretized fullerene-SWCNT heterojunctions for spectroscopic investigation is to form an amphiphile, which is able to disperse the latter at the single-SWCNT level in aqueous solution. Herein, we synthesize a series of methanofullerene amphiphiles, including derivatives of C60, C70, and C84, and investigated their electron transfer with SWCNT of specific chirality, generating a structure-reactivity relationship. In the cases of two fullerene derivatives, lipid-C61-polyethylene glycol (PEG) and lipid-C71-PEG, band gap dependent, incomplete quenching was observed across all SWCNT species, indicating that the driving force for electron transfer is small. This is further supported by a variant of Marcus theory, which predicts that the energy offsets between the nanotube conduction bands and the C61 and C71 LUMO levels are less than the exciton binding energy in SWCNT. In contrast, upon interfacing nanotubes with C85 methanofullerene, a complete quenching of all semiconducting SWCNT is observed. This enhancement in quenching efficiency is consistent with the deeper LUMO level of C85 methanofullerene in comparison with the smaller fullerene adducts, and suggests its promise as for SWCNT-fullerene heterojunctions. PMID:23848070

Hilmer, Andrew J; Tvrdy, Kevin; Zhang, Jingqing; Strano, Michael S

2013-08-14

450

Skin intervention of fullerene-integrated nanoemulsion in structural and collagen regeneration against skin aging.  

PubMed

Despite the fact that intrinsic oxidative stress is inevitable, the extrinsic factor such as ultraviolet radiation enhances reactive oxygen species (ROS) generation resulting in premature skin aging. Nanoemulsion was loaded with fullerene, a strong free radical scavenger, and its efficacy to provide protection and regenerative effect against ROS-induced collagen breakdown in human skin was studied. Stable fullerene nanoemulsions were formulated using high shear homogenization and ultrasonic dispersion technique. An open trial was conducted using fullerene nanoemulsion on skin twice a day for 28 days. The mean collagen score significantly increased (P<0.05) from 36.53±4.39 to 48.69±5.46 with 33.29% increment at the end of the treatment. Biophysical characteristics of skin revealed that skin hydration was increased significantly (P<0.05) from 40.91±7.01 to 58.55±6.08 corneometric units (43.12% increment) and the water was able to contain within the stratum corneum without any increased in transepidermal water loss. In the in vitro safety evaluation, fullerene nanoemulsion showed no acute toxicity on 3T3 fibroblast cell line for 48h and no indication of potential dermal irritation. Hence, the fullerene nanoemulsion may assist in protecting collagen from breakdown with cosmeceutical benefit. PMID:25619806

Ngan, Cheng Loong; Basri, Mahiran; Tripathy, Minaketan; Abedi Karjiban, Roghayeh; Abdul-Malek, Emilia

2015-04-01

451

Effect of dispersion on adsorption of atrazine by aqueous suspensions of fullerenes.  

PubMed

With the widespread application of fullerenes, it is critical to assess their environmental behaviors and their impacts on the transport and bioavailability of organic contaminants. The effects of fullerene particle size, chemistry of the solution, and natural organic matter on the adsorption of atrazine by aqueous dispersions of fullerenes (C(60)) were investigated in this work. The results showed that the Polanyi-Manes model could fit the adsorption isotherms well. Smaller sizes of fullerene particles led to increased available sites and, consequently, enhanced the adsorption of atrazine on C(60). However, intensely dispersed C(60) systems might not possess suitably high adsorptive capacities due to surface chemistry change. Adsorption of atrazine by aqueous dispersions of C(60) increased with a decrease in the pH of the solution. Introduction of humic acid significantly reduced the size of the C(60) particles, and resulted in the increase of the adsorption amount. Fullerene materials, once released into the aquatic environment, are inclined to form aqueous suspensions with different degrees of dispersion, which would greatly affect the transport and fate of organic contaminants. PMID:21692500

Gai, Ke; Shi, Baoyou; Yan, Xiaomin; Wang, Dongsheng

2011-07-15

452

Distribution of fullerene nanomaterials between water and model biological membranes.  

PubMed

Biological membranes are one of the important interfaces between cells and pollutants. Many polar and hydrophobic chemicals can accumulate within these membranes. For this reason, artificial biological membranes are appealing surrogates to complex organisms for assessing the bioaccumulation potential of engineered nanomaterials (ENMs). To our knowledge, this work presents the first quantitative study on the distribution of fullerene ENMs between lipid bilayers, used as model biological membranes, and water. We evaluated the lipid bilayer-water association coefficients (K(lipw)) of aqueous fullerene aggregates (nC(60)) and fullerol (C(60)(ONa)(x)(OH)(y), x + y = 24). Kinetic studies indicated that fullerol reached apparent equilibrium more rapidly than nC(60) (2 h versus >9 h). Nonlinear isotherms can describe the distribution behavior of nC(60) and fullerol. The lipid bilayer-water distributions of both nC(60) and fullerol were pH-dependent with the accumulation in lipid bilayers increasing systematically as the pH decreased from 8.6 (natural water pH) to 3 (the low end of physiologically relevant pH). This pH dependency varies with the zeta potentials of the ENMs and leads to patterns similar to those previously observed for the lipid bilayer-water distribution behavior of ionizable organic pollutants. The K(lipw) value for nC(60) was larger than that of fullerol at a given pH, indicating a greater propensity for nC(60) to interact with lipid bilayers. For example, at pH 7.4 and an aqueous concentration of 10 mg/L, K(lipw) was 3.5 times greater for nC(60) (log K(lipw) = 2.99) relative to fullerol (log K(lipw) = 2.45). Comparisons with existing aquatic organism bioaccumulation studies suggested that the lipid bilayer-water distribution is a potential method for assessing the bioaccumulation potentials of ENMs. PMID:21854052

Hou, Wen-Che; Moghadam, Babak Yaghoubi; Westerhoff, Paul; Posner, Jonathan D

2011-10-01

453

Origin of 200-keV interplanetary electrons.  

NASA Technical Reports Server (NTRS)

The suggestion by Lin et al. (1972) that a distinct spectral feature exists at about 200 keV, which could be due to a neutron-decay electron component of either solar or galactic origin, is examined. Alternative sources models, including production by nearby galactic objects or acceleration at the outer boundary of the solar system, are also considered.

Ramaty, R.; Cline, T. L.; Fisk, L. A.

1972-01-01

454

KevJumba and the Adolescence of YouTube  

ERIC Educational Resources Information Center

This article considers the significance of YouTube as a pedagogical space from which young people can play participatory roles as theorists in their own constructions as popular cultural subjects. Drawing upon the public profile of "KevJumba," a teenager who makes videos of himself on YouTube, the article suggests that representational practices…

Saul, Roger

2010-01-01

455

Staff Sergeant James C. Stephens Jr., 11th Bombardment Group, 42nd Squadron  

E-print Network

at the Air Force base gave Matt Phil’s phone number. Phil suggested that I purchase a copy of Gray Geese Calling, which was a history of the 11 th Bombardment Group, and a copy of Guadalcanal, which is thought by some to be the definitive account... couple of published sources: Grey Geese Calling is a history of the 11 th Bombardment Group Heavy in the Pacific from 1940 to 1945 and Guadalcanal by Richard B. Frank which provides a history of the assault on that island. The 11 th Bomb Group...

Stephens, Paul; Stephens, Paul

2008-07-30

456

Effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen  

SciTech Connect

The effect of coincident ion bombardment on the oxidation of Si (100) by atomic oxygen has been examined under ultrahigh vacuum conditions by employing molecular beam techniques and x-ray photoelectron spectroscopy. Ion bombardment leads to a significant enhancement in the rate of oxidation. By modulating both the oxygen and ion (Ar{sup +} ) fluxes several possible mechanisms for the enhanced rate can be eliminated. Of the remaining possibilities, a mechanism involving competition between ion-induced oxygen incorporation and sputtering appears most likely.

Engstrom, J.R.; Bonser, D.J.; Engel, T. (Department of Chemistry, BG-10, University of Washington, Seattle, Washington 98195 (US))

1989-11-20

457

Sputtering of Al nanoclusters by 1-13 keV monatomic or polyatomic ions studied by Molecular Dynamics simulations  

NASA Astrophysics Data System (ADS)

Molecular Dynamics (MD) simulations were employed to study sputtering of freestanding and supported spherical Al nanoclusters with 2-10 nm diameters under bombardment by Al1 and Al13 projectiles with energies of 1-13 keV at normal and oblique incidence. Both monatomic and clustered yields of secondary emission are found to be larger than those for (1 1 1) flat surface of the bulk Al (at equal irradiation conditions). In some events, target nanocluster receives a backward momentum and therefore its major part (more than 1/2 of the mass) is ejected due to produced secondary emission mainly towards the substrate direction. This “recoil effect” is found more pronounced under the impact of cluster projectiles and its probability decreases with increase of the target cluster size. A restricted number of MD simulations were performed to verify whether this “recoil effect” is strong enough to desorb a 4 nm Al nanocluster off an Al (1 1 1) substrate. Desorption was observed under oblique Al13 impact within the impact parameter range of 0.6-0.9.

Zhurkin, Evgeny E.; Grigorev, Petr Yu.

2013-05-01

458

New synthesis method of fullerenes using microwave-induced naphthalene-nitrogen plasma at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A new synthesis method of fullerenes has been investigated for microwave induced naphthalene-nitrogen plasma at atmospheric pressure using a cylindrical coaxial cavity. The toluene extract solution of soot obtained after discharges showed HPLC peaks with retention times corresponding well to those of C60 and C70. The production of fullerenes was also confirmed by mass-spectrometric analysis. Gas temperature of nitrogen plasma determined from radiative transitions of N2+ was 3800-5700 K. From a comparison of the gas temperature and the incident microwave power, it was found that the reaction efficiency for fullerenes decreases with the increase in the gas temperature of the plasma and shows a maximum at about 4500 K.

Ikeda, Tetsuya; Kamo, Toshihiro; Danno, Minoru

1995-08-01

459

A method for diffraction-based identification of annealing-produced restructuring of amorphous fullerene  

E-print Network

A method is suggested for estimation of structural properties of amorphous fullerene and its derivatives produced by vacuum annealing. The method is based on the fitting of the neutron or x-ray powder diffraction patterns for scattering wave vector's modulus in the range from few units to several tens of inverse nanometers. The respective inverse problem assumes that the structured component of a sample can be described with a limited num