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1

Surface damage studies of ETFE polymer bombarded with low energy Si ions (?100 keV)  

NASA Astrophysics Data System (ADS)

Surface studies of ethylenetetrafluoroethylene (ETFE), bombarded with Si in a high-energy tandem Pelletron accelerator, have recently been reported. Si ion bombardment with a few MeV to a few hundred keV energies was shown to be sufficient to produce damage on ETFE film. We report here the use of a low energy implanter with Si ion energies lower than 100 keV, to induce changes on ETFE films. In order to determine the radiation damage, ETFE bombarded films were simulated with SRIM software and analyzed with optical absorption photometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to show quantitatively the physical and chemical property changes. Carbonization occurs following higher dose implantation, and hydroperoxides were formed following dehydroflorination of the polymer.

Minamisawa, Renato Amaral; De Almeida, Adelaide; Budak, Satilmis; Abidzina, Volha; Ila, Daryush

2007-08-01

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

The repetitive flaking of inconel 625 by 100 keV helium ion bombardment  

NASA Astrophysics Data System (ADS)

Repetitive flaking of Inconel 625 occurs with ion bombardment doses of than 10 18 100 keV helium ions cm -2, with up to 39 exfoliations being observed after bombardment with 3 × 10 19 ions cm -2. The thickness of the flakes, measured by scanning electron microscopy, is some 30% greater than when measured by Rutherford backscattering (RBS) of 1.8 MeV helium ions. These RBS measurements compare well with the thickness of the remaining layers in the resultant craters and to the most probable range of the 100 keV helium. The area of the flakes is dictated by the grain boundaries, and when one flake is ejected, the adjacent grains are prevented from doing so since there now exists an escape route for the injected helium. A strong dose rate dependence is observed; decreasing the beam current from 640 ?A cm -2 to 64 ?A cm -2 results in a factor 20 fewer flakes being exfoliated (for the same total dose of 3 × 10 19 ions cm -2). Successive flakes decrease in area, suggesting that eventually a cratered, but stable, surface will result with the only erosion being by the much less effective mechanism of sputtering.

Whitton, J. L.; Chen, Hao Ming; Littmark, U.; Emmoth, B.

1981-05-01

4

Desorption of neutral molecules from self-assembled monolayers subjected to keV ion bombardment  

NASA Astrophysics Data System (ADS)

Laser postionization in combination with mass spectrometry was used to detect neutral molecules desorbed from self-assembled monolayers of phenethyl mercaptan and benzyl mercaptan on gold upon 8 keV Ar + bombardment. From experimentally obtained time distributions, it was determined that the majority of the desorbed neutral molecules leave the surface with low translational energies of about 0.03 eV. As the substrate temperature is reduced, the distributions become broader and shift to longer flight times. In combination with mass distributions, these results indicate that the thermal desorption process is initiated by chemical reactions in the organic layer, creating fragments of the original molecule weakly bound to the surface, prior to release.

Meserole, C. A.; Vandeweert, E.; Chatterjee, R.; Winograd, N.; Postawa, Z.

1999-03-01

5

Synthesis of amorphous boron carbide by single and multiple charged boron ions bombardment of fullerene thin films  

Microsoft Academic Search

In this paper, results of structural modification of fullerene thin films by single and multiple charged boron ions (B+, B3+) are presented. The applied ion energies were in the range of 15–45keV. The characterization of as-deposited and irradiated specimens has been performed by atomic force microscopy, Raman and Fourier transform infrared spectroscopy and UV\\/vis spectrophotometry. The results of Raman analysis

B. Todorovic-Markovic; I. Dragani?; D. Vasiljevic-Radovic; N. Romcevic; M. Romcevic; M. Dramicanin; Z. Markovic

2007-01-01

6

Study of the surface activation of ETFE by low energy (keV) Si and N bombardment  

NASA Astrophysics Data System (ADS)

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It can be applied in the field of medical physics as intra venous catheters and as radiation dosimeters. The increasing application of polymeric materials in technological and scientific fields has motivated the use of surface treatments to modify the physical and chemical properties of polymer surfaces. When a material is exposed to ionizing radiation, it suffers damage leading to surface activation depending on the type, energy and intensity of the applied radiation. In order to determine the radiation damage and the surface activation mechanism ETFE films were bombarded with keV Si and N at various fluences. The bombarded film was also analyzed with optical absorption photospectrometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy showing quantitatively the chemical nature at the damage caused by the Si and N bombardment.

Parada, M. A.; de Almeida, A.; Muntele, C.; Muntele, I.; Delalez, N.; Ila, D.

2005-12-01

7

A search for a thermal spike effect in sputtering. I. Temperature dependence of the yield at low-kev, heavy-ion bombardment  

Microsoft Academic Search

The temperature dependence of the angular-differential sputtering yield of silver has been studied for low-keV, heavy ion bombardment in order to check whether thermal spikes contribute to sputtering in this energy regime. An oscillating quartz microbalance was used as detector for sputtered particles.The measurements reported in this work pertain to sputtering of polycrystalline samples bombarded by 8 keV Ar and

K. Besocke; S. Berger; W. O. Hofer; U. Littmark

1982-01-01

8

Temperature dependence of sputtering yield of GaAs under 30 keV Ar + bombardment  

Microsoft Academic Search

Temperature dependence of total sputtering yield of GaAs(100) was studied by mass analyzed (sup 40)Ar(sup + ) at 30 keV. Result showed that at about 240deg C sputtering yield is minimum and with further increase in target temperature, the yield becomes higher. These findings are discussed in the light of ion channeling and thermal spike effect with the emission of

S. R. Bhattacharyya; D. Ghose; D. Basu

1994-01-01

9

keV fullerene interaction with hydrocarbon targets: Projectile penetration, damage creation and removal  

Microsoft Academic Search

The physics of energetic fullerene projectile penetration, damage creation and sputtering in organic solids is investigated via molecular dynamics simulations. Two models are used, the first one based on a full atomistic description of the target and the second one, using a coarse-grain prescription that was recently developed and tested for a benzene molecular crystal [E. Smiley, Z. Postawa, I.A.

Arnaud Delcorte; Barbara J. Garrison

2007-01-01

10

Strongly Enhanced Li + D Reaction in Pd Observed in Deuteron Bombardment on PdLix with Energies between 30 and 75 keV  

Microsoft Academic Search

Thick target yields of alpha particles emitted in the 6,7Li(d,alpha)4,5He reactions in PdLix and AuLix were measured as a function of the bombarding energy between 30 and 75 keV. It was found that the reaction rate in Pd at lower energies is enhanced strongly over the one predicted by the cross section for the reaction with bare nuclei, but no

Jirohta Kasagi; Hideyuki Yuki; Taiji Baba; Takashi Noda; Junji Taguchi; Masayoshi Shimokawa; Wilfried Galster

2004-01-01

11

Shadow cones formed by target atoms bombarded by 1 to 3 keV He +, Li +, Ne + and Na + ions  

NASA Astrophysics Data System (ADS)

The shadow cones of 1 to 3 keV He +, Li +, Ne + and Na + ions scattered from a variety of target atoms ranging from C to Pb are calculated by classical scattering theory using the Thomas-Fermi-Molière interatomic potential. These shadow cones are useful in the study of surface structures by the ICISS technique.

Chang, C. S.; Knipping, U.; Tsong, I. S. T.

12

Temperature dependence of sputtering yield of GaAs under 30 keV Ar(sup + ) bombardment  

NASA Astrophysics Data System (ADS)

Temperature dependence of total sputtering yield of GaAs(100) was studied by mass analyzed (sup 40)Ar(sup + ) at 30 keV. Result showed that at about 240deg C sputtering yield is minimum and with further increase in target temperature, the yield becomes higher. These findings are discussed in the light of ion channeling and thermal spike effect with the emission of weakly bound molecular components in sputtered flux. An estimate of critical temperature of annealing of a semiconductor can be made by this method.

Bhattacharyya, S. R.; Ghose, D.; Basu, D.

1994-08-01

13

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

14

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

15

Secondary ion emission from polymethacrylate LB-layers under 0.5–11 keV atomic and molecular primary ion bombardment  

Microsoft Academic Search

Secondary ion yields Y(Xiq) increase considerably when changing from atomic to molecular primary ions, whereas the parallel increase in the corresponding damage cross sections ?(Xiq) is much smaller. This results in a net increase of ion formation efficiencies E(Xiq)=Y\\/?. For a more detailed understanding of the complex sputtering and ion formation processes, in particular for molecular primary ion bombardment, the

D. Stapel; M Thiemann; A Benninghoven

2000-01-01

16

Multiple Charged Nitrogen Ion Beam Irradiation of Fullerene Thin Films  

Microsoft Academic Search

In this work, the results of structural modification of fullerene thin films bombarded by multiple charged nitrogen ions have been reported. The properties of as?deposited and irraditated fullerene thin films have been investigated by Raman and FTIR spectroscopy and AFM analysis. After irradiation by multiple charged nitrogen ions (N, N) new bondings in fullerene films have been formed and the

I. Dragani?; Z. Markovi?; Z. Stojanovi?; M. Mitri?; N. Rom?evi?; M. Rom?evi?; Z. Nikoli?

2007-01-01

17

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

18

Cosmic Bombardment.  

National Technical Information Service (NTIS)

Throughout its history, the earth has been constantly bombarded by interplanetary bodies. In the maelstrom of the earth Solar System, such collisions created our planet and then fed its growth. With time, the rate of such collisions has dropped enormously...

R. A. Hyde

1984-01-01

19

Polymeric fullerene oxide films produced by decomposition of hexanitro[60]fullerene  

Microsoft Academic Search

A new poly(fullerene oxide) thin film material has been fabricated by thermal activation and electron bombardment on hexanitro[60]fullerene (HNF) film deposited on a Au substrate, all under vacuum conditions. The reaction products in the polymerization process are analyzed by XPS, UPS, IR, TGA-MS and LDI-MS techniques. It is found that the main effect of thermal and radiation treatments is to

Run-Sheng Zhai; Arindam Das; Chien-Kui Hsu; Chau-Chung Han; Taizoon Canteenwala; Long Y. Chiang; Tung J. Chuang

2004-01-01

20

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

21

Fullerene Machines  

NASA Technical Reports Server (NTRS)

Recent computational efforts at NASA Ames Research Center and computation and experiment elsewhere suggest that a nanotechnology of machine phase functionalized fullerenes may be synthetically accessible and of great interest. We have computationally demonstrated that molecular gears fashioned from (14,0) single-walled carbon nanotubes and benzyne teeth should operate well at 50-100 gigahertz. Preliminary results suggest that these gears can be cooled by a helium atmosphere and a laser motor can power fullerene gears if a positive and negative charge have been added to form a dipole. In addition, we have unproven concepts based on experimental and computational evidence for support structures, computer control, a system architecture, a variety of components, and manufacture. Combining fullerene machines with the remarkable mechanical properties of carbon nanotubes, there is some reason to believe that a focused effort to develop fullerene nanotechnology could yield materials with tremendous properties.

Globus, Al; Saini, Subhash

1998-01-01

22

Fullerene materials  

SciTech Connect

Fullerenes are all-carbon cage molecules. The most celebrated fullerene is the soccer-ball shaped C{sub 60}, which is composed of twenty hexagons and twelve pentagons. Because its structure is reminiscent of the geodesic domes of architect R. Buckminster Fuller, C{sub 60} is called buckminsterfullerene, and all the materials in the family are designated fullerenes. Huffman and Kraetschmer`s discovery unleashed activity around the world as scientists explored production methods, properties, and potential uses of fullerenes. Within a short period, methods for their production in electric arcs, plasmas, and flames were discovered, and several companies began selling fullerenes to the research market. What is remarkable is that in all these methods, carbon atoms assemble themselves into cage structures. The capability for self-assembly points to some inherent stability of these structures that allows their formation. The unusual structure naturally leads to unusual properties. Among them are ready solubility in solvents and a relatively high vapor pressure for a pure carbon material. The young fullerene field has already produced a surprising array of structures for the development of carbon-base materials having completely new and different properties from any that were previously possible.

Malhotra, R.; Ruoff, R.S.; Lorents, D.C. [SRI International, Menlo Park, CA (United States). Molecular Physics Lab.

1995-04-01

23

Electron Emission from Tungsten under Proton Bombardment  

Microsoft Academic Search

The yield of electrons from clean polycrystalline tungsten under bombardment by protons at normal incidence has been measured as a function of proton energy in the range 50 to 225 keV. The maximum value of the yield is 1.65+\\/-0.03 electrons per proton at a proton energy of 125 keV. The tungsten surface was cleaned by flash heating a tungsten ribbon

Ronald I. Ewing

1965-01-01

24

Biogenic Fullerenes  

Microsoft Academic Search

This paper presents the hypothesis that algal remains were precursors of the fullerenes in the hard carbonaceous rock Shungite (Russia), in carbonaceous matter from the hard rocks of the Black Member of the Onaping Formation at Sudbury (Canada), and in solid, hard bitumens from Mitov (Czech Republic). The paper argues further that PAHs from the biogenic matter were transformed, perhaps

Dieter Heymann

2006-01-01

25

Fullerene Machines  

NASA Technical Reports Server (NTRS)

Fullerenes possess remarkable properties and many investigators have examined the mechanical, electronic and other characteristics of carbon SP2 systems in some detail. In addition, C-60 can be functionalized with many classes of molecular fragments and we may expect the caps of carbon nanotubes to have a similar chemistry. Finally, carbon nanotubes have been attached to t he end of scanning probe microscope (Spill) tips. Spills can be manipulated with sub-angstrom accuracy. Together, these investigations suggest that complex molecular machines made of fullerenes may someday be created and manipulated with very high accuracy. We have studied some such systems computationally (primarily functionalized carbon nanotube gears and computer components). If such machines can be combined appropriately, a class of materials may be created that can sense their environment, calculate a response, and act. The implications of such hypothetical materials are substantial.

Globus, Al; Saini, Subhash (Technical Monitor)

1998-01-01

26

Fullerene Commercial Vision  

Microsoft Academic Search

The fullerene structure was first predicted by Professor Eiji Osawa (1) in1970. The first direct observations that fullerenes might exist were made by Smalley and Kroto (2) in 1985, and the first macroscopic synthesis and isolation of fullerenes was by Huffman and Kräschmer in1990 (3). Commercial sales of fullerenes began in late 1990 by MER Corporation. Since the discovery of

James C. Withers; Raouf O. Loutfy; Timothy P. Lowe

1997-01-01

27

Flattened fullerenes  

SciTech Connect

Quantum-chemical calculations of giant flattened fullerenes C{sub n} (lentil-shaped) have been carried out. The topology, molecular and electronic structure of these fullerenes have been studied. Such molecules consist of two identical coronenoid fragments of a graphite layer, which are arranged one above the other, and a system of polycondensed five- and six-pentagons of three symmetry types (D{sub 6h}, D{sub 6d}, and D{sub 3h}) have been considered. The topology of these structures is described in terms of planar molecular graphs. Electronic structures of eleven flattened lentil-shaped C{sub n} clusters (n = 72-216) have been studied in the {pi} approximation. Most of the considered systems have closed or quasi-closed electron shells (according to Hueckel) and rather large energy gaps separating the highest occupied and lowest unoccupied MO, which is indicative of their kinetic stability. Fragments of the potential energy surfaces of the C{sub 72} and C{sub 96} fullerenes have been studied by the MNDO, AM1, and MNDO/PM3 methods. For the C{sub 96} cluster, two local energy minima, which correspond to the lentil-shaped isomers with D{sub 6h} and D{sub 6d} symmetry, have been determined. As a result of optimization of geometric parameters, it was found that all three methods give close value of heights (H = 6.7 {angstrom}) and diameters (D = 9.8 {angstrom}) for both isomers. The clusters change to quasi-two-dimensional systems (H {much_lt} D) with increasing sizes of coronenoid fragments.

Chistyakov, A.L.; Stankevich, I.V. [A.N. Nesmeyanov Institute of Organoelement Compounds, Moscow (Russian Federation)

1995-09-01

28

Photoionization of Xe in a Fullerene Ion Cage  

NASA Astrophysics Data System (ADS)

Photoionization of Xe@C60^+ endohedral fullerene ions was investigated in the photon energy range 76 - 170 eV by merging beams of ions and synchrotron radiation. A solid sample containing 5 ppm of Xe@C60 was prepared by thermally evaporating and depositing C60 onto a rotating metal cylinder that was simultaneously bombarded by a 500 eV beam of Xe^+ ions for several weeks. The sample was then evaporated into a low-power discharge in an ECR ion source, yielding a 30 - 40 fA beam of Xe@C60^+ at 6 keV. Despite a low photoionization signal count rate of approximately 0.1 Hz, a signature due to photoexcitation of the Xe 4d giant resonance is evident in the measurements. The energy position of this feature suggests that the Xe atom donates electrons to the carbon cage of Xe@C60^+. The data show no evidence for a predicted splitting of the Xe 4d giant resonance in Xe@C60 into multiple components due to interference caused by reflection of electron waves by the carbon cage. This research was supported by the Division of Chemical Sciences, Geosciences and Biosciences of the U.S. Department of Energy.

Phaneuf, Ronald; Aryal, Nagendra; Esteves, David; Thomas, Christopher; Kilcoyne, David; Aguilar, Alejandro; Cisneros, Carmen

2010-03-01

29

Switching Molecular Orientation of Individual Fullerene at Room Temperature  

PubMed Central

Reversible molecular switches with molecular orientation as the information carrier have been achieved on individual fullerene molecules adsorbed on Si (111) surface at room temperature. Scanning tunneling microscopy imaging directly demonstrates that the orientation of individual fullerene with an adsorption geometry of 5-6 bond is rotated by integral times as 30 degree after a pulse bias is applied between the STM tip and the molecule. Dependences of the molecular rotation probability on the voltage and the process of applied bias reveal that the rotation of a fullerene molecule takes place in two successive steps: the bonding between the fullerene and the Si surface is firstly weakened via electronic excitation and then low energy electron bombardment causes the molecule to rotate by certain degree.

Liu, Lacheng; Liu, Shuyi; Chen, Xiu; Li, Chao; Ling, Jie; Liu, Xiaoqing; Cai, Yingxiang; Wang, Li

2013-01-01

30

Fullerenes Formation in Flames.  

National Technical Information Service (NTIS)

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 so...

J. B. Howard

1993-01-01

31

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

32

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

33

Fullerenes and Viruses  

Microsoft Academic Search

It is well known that any, sometimes very small, changes in the chemical structure can lead to the dramatic changes in biological properties. Therefore it is necessary to divide into two different topics the studies of biological properties of fullerene and fullerene?like compounds. In the enormous variety of data on the biological activity of fullerenes it is possible to select

L. B. Piotrovsky; O. I. Kiselev

2005-01-01

34

Destruction of C 60 films by boron ion bombardment  

NASA Astrophysics Data System (ADS)

C 60 films are bombarded by 100 keV boron ion beams at doses ranging from 3 × 10 14 to 1 × 10 16/cm 2. The bombarded films are analyzed using Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray diffraction (XRD) measurements. Most C 60 soccer-balls in the implanted region in the films are found to be broken at a dose over 1 × 10 15/cm 2, while at a dose less than 6 × 10 14/cm 2 a few C 60 molecules remain undestroyed and maintain some crystal structure. The results of the analyses suggest a complete disintegration of a C 60 molecule under B + bombardment.

Ren, Zhong-Min; Xu, Xing-Long; Du, Yuan-Cheng; Ying, Zhi-Feng; Xiong, Xia-Xing; Li, Fu-Ming

1995-05-01

35

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

36

Reviews of Topical Problems: Fullerenes  

NASA Astrophysics Data System (ADS)

Contemporary studies of fullerenes-carbon clusters as C60, C70, C76, C84 etc., whose atoms are located on a spherical or ellipsoidal surface are reviewed. Fullerene structures, methods for producing them, processes involving fullerenes, and the production of fullerenes are considered. The properties of fullerites (carbon crystals consisting of fullerenes) and the properties of compounds are discussed.

Eletski?, A. V.; Smirnov, Boris M.

1993-03-01

37

Fullerenes in space.  

PubMed

The discovery and synthesis of fullerenes led to the hypothesis that they may be present and stable in interstellar space. Fullerenes have been reported in an impact crater on the LDEF spacecraft. Investigations of fullerenes in carbonaceous meteorites have yielded only small upper limits. Fullerene compounds and their ions could be interesting carrier molecules for some of the "diffuse interstellar bands" (DIBs), a long standing mystery in astronomy. We have detected two new diffuse bands that are consistent with laboratory measurements of the C60+, as first evidence for the largest molecule ever detected in space. Criteria for this identification are discussed. The inferred abundance (up to 0.9 % of cosmic carbon locked in C60+) suggests that fullerenes may play an important role in interstellar chemistry. We present new observations on DIB substructures consistent with fullerene compounds, and the search for neutral C60 in the diffuse medium. PMID:11541330

Ehrenfreund, P; Foing, B H

1997-01-01

38

Thermal insulation using fullerenes  

Microsoft Academic Search

A novel type of multi-layer vacuum insulation based on carbon nano-materials, namely fullerenes, has been demonstrated. The design is based on unique thermal insulation properties of fullerenes, arising from their electronic structure, as well as proprietary deposition technique using thin layers of reflective material as a support. As a result of experimental testing, the fabricated samples of fullerene-based insulation were

Eugene M. Wexler; R. O. Loutfy

2004-01-01

39

Optical, Mass, and Auger Spectra from e-Bombarded KBr.  

National Technical Information Service (NTIS)

We have measured the mass spectrum and optical emission lines of neutral potassium atoms ejected from KBr at T = 300/degree/K and 443/degree/K bombarded by 2-keV electrons. The room-temperature data may be complicated by the nonstoichiometry of the alkali...

E. T. Arakawa M. Kamada

1988-01-01

40

Covalent Fullerene Chemistry  

Microsoft Academic Search

The covalent functionalization of C60 has developed vigorously over the past 5 years. Several methods are now available for the formation of C60 monoadducts. Regioselective formation of multiple adducts has allowed study of the changes in chemical and physical properties that occur when the conjugated fullerene chromophore is reduced during an increase in functionalization. The systematic development of covalent fullerene

Francois Diederich; Carlo Thilgen

1996-01-01

41

Medicinal applications of fullerenes  

PubMed Central

Fullerenes have attracted considerable attention in different fields of science since their discovery in 1985. Investigations of physical, chemical and biological properties of fullerenes have yielded promising information. It is inferred that size, hydrophobicity, three-dimensionality and electronic configurations make them an appealing subject in medicinal chemistry. Their unique carbon cage structure coupled with immense scope for derivatization make them a potential therapeutic agent. The study of biological applications has attracted increasing attention despite the low solubility of carbon spheres in physiological media. The fullerene family, and especially C60, has appealing photo, electrochemical and physical properties, which can be exploited in various medical fields. Fullerene is able to fit inside the hydrophobic cavity of HIV proteases, inhibiting the access of substrates to the catalytic site of enzyme. It can be used as radical scavenger and antioxidant. At the same time, if exposed to light, fullerene can produce singlet oxygen in high quantum yields. This action, together with direct electron transfer from excited state of fullerene and DNA bases, can be used to cleave DNA. In addition, fullerenes have been used as a carrier for gene and drug delivery systems. Also they are used for serum protein profiling as MELDI material for biomarker discovery. In this review we report the aspects of medicinal applications of fullerenes.

Bakry, Rania; Vallant, Rainer M; Najam-ul-Haq, Muhammad; Rainer, Matthias; Szabo, Zoltan; Huck, Christian W; Bonn, Gunther K

2007-01-01

42

Prototype Cesium Bombardment System.  

National Technical Information Service (NTIS)

The report covers the development of a one-millipound thrust cesium bombardment ion engine system suitable for demonstrating north-south stationkeeping on the ATS-F earth-synchronous satellite for a period of one year. The program began with the developme...

R. M. Worlock E. L. James G. Gant T. Dillon G. Trump

1970-01-01

43

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

44

Energetics and fullerene fractionation  

NASA Astrophysics Data System (ADS)

The local-density-functional binding energies per carbon atom C50, C60, C70, C72, C76, C78, C84, C180, and C240 fullerenes and various isomers of these are computed at geometries that have been optimized using an empirical potential. Little is found to distinguish fullerenes that have been obtained experimentally and those that have not. It is unlikely that energetics plays a dominant role in determining which fullerenes are made in the Kra¨tschmer-Huffman process.

Dunlap, B. I.

1993-02-01

45

Reactivity of boron fullerenes  

Microsoft Academic Search

The properties of carbon and boron fullerenes are compared, and similarities and distinctions are pointed out. The ionization\\u000a potentials and electron affinities of boron nanoparticles are estimated, and the binding energy for these systems is calculated.

S. P. Ionov; G. V. Ionova; N. T. Kuznetsov

2011-01-01

46

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.

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

2010-01-01

47

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

48

Are fullerene tubules metallic  

Microsoft Academic Search

We have calculated the electronic structure of a fullerene tubule using a first-principles, self-consistent, all-electron Gaussian-orbital based local-density-functional approach. Extending these results to a model containing an electron-lattice interaction, we estimate that the mean-field transition temperature from a Peierls-distorted regime to a high-temperature metallic regime should be well below room temperature. Such fullerene tubules should have the advantages (compared to

J. W. Mintmire; B. I. Dunlap; C. T. White

1992-01-01

49

Covalent fullerene chemistry  

Microsoft Academic Search

A brief introduction to the reactivity principles governing the covalent chemistry of fullerenes is provided. The combination of synthetic fullerene and acetylene chemistry gives access to a family of novel molecular carbon allotropes with interesting physical properties. A versatile strategy for the regioselective preparation of specific bis- through hexakis-adducts of C6o based on the tether-directed remote functionalization was developed. Large

FranGois Diederich

1997-01-01

50

Combustion Synthesis of Fullerenes and Fullerenic Nanostructures In Microgravity.  

National Technical Information Service (NTIS)

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 ...

J. B. Howard

2002-01-01

51

Electron Transport in Boron Fullerenes.  

National Technical Information Service (NTIS)

The electron transport properties of B80 fullerene are studied using first-principles density functional theory in conjunction with the Landauer- Buettiker quantum transport formalism. The electron transmission in B80 fullerene is calculated to be much hi...

H. He I. Boustani R. Pandey S. P. Karna

2008-01-01

52

Electron Transport in Boron Fullerenes  

Microsoft Academic Search

The electron transport properties of B80 fullerene is studied using first-principles density functional theory in conjunction with the Landauer-Biittiker quantum transport formalism. The electron transmission in B80 fullerene is calculated to be much higher than that in C60 fullerene in the Fermi-level region. The enhanced transmission in the B80 fullerene is attributed to its spatially extended charge distribution in delocalized

Haiying He; Ravindra Pandey; Ihsan Boustani; Shashi P. Karna

2008-01-01

53

Graphitization of amorphous diamondlike carbon films by ion bombardment  

SciTech Connect

Amorphous hydrogenated carbon films prepared by glow discharge decomposition of CH/sub 4/ at a power density of 0.4 W cm/sup -2/ were bombarded with hydrogen and nitrogen ions of energies between 100 and 600 keV. The structural changes due to various ion doses were analyzed using Raman, photoluminescence, and infrared spectroscopy. Nitrogen bombardment produces essentially a hydrogen depletion in the whole dose interval as shown by the IR spectra; as a consequence there is a drop of several orders of magnitude in the integrated photoluminescence intensity, and carbon--carbon double bonds, characteristic of a graphiticlike structure, appear in the Raman spectra. The same general effects are produced under proton bombardment, but their intensities change more gradually with the ion dose, in agreement with a vacancy production mechanism.

Gonzalez-Hernandez, J.; Asomoza, R.; Reyes-Mena, A.; Rickards C., J.; Chao, S.S.; Pawlik, D.

1988-05-01

54

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

55

Extraterrestrial Helium Trapped in Fullerenes in the Sudbury Impact Structure  

NASA Technical Reports Server (NTRS)

Fullerenes (C60 and C70) in the Sudbury impact structure contain trapped helium with a He-3/He-4 ratio of 5.5 x 10(exp -4) to 5.9 x 10(exp -4). The He-3/He-4 ratio exceeds the accepted solar wind value by 20 to 30 percent and is higher by an order of magnitude than the maximum reported mantle value. Terrestrial nuclear reactions or cosmic-ray bombardment are not sufficient to generate such a high ratio. The He-3/He-4 ratios in the Sudbury fullerenes are similar to those found in meteorites and in some interplanetary dust particles. The implication is that the helium within the C60 molecules at Sudbury is of extraterrestrial origin.

Becker, Luann; Poreda, Robert J.; Bada, Jeffrey L.

1996-01-01

56

Particle Bombardment Bonding and Welding Investigation.  

National Technical Information Service (NTIS)

Particle bombardment chemistry and thermal chemistry are compared. Particle bombardment techniques for crystal growth welding and bonding are discussed. The nine different sputter arrangements used in this study for producing ion bombardment bonded coatin...

O. Heil

1967-01-01

57

Variations of carbon foil lifetimes under bombardment by N+, Ne+, Ar+ and Zn+ ions  

Microsoft Academic Search

Studies of the useful lifetime of 2-5 µg cm-2 carbon stripper foils have been made using 225 keV heavy ion beam bombardment. The foils were self supporting and were mounted both in a standard and a tension-slackened manner. In determining the quality of the foil during ion bombardment several techniques were used, in particular beam-foil spectroscopy. Here the intensity of

R. Hellborg; I. Martinson; S. T. Maniak; R. E. Irving; R. R. Haar; L. J. Curtis; D. J. Beideck

1991-01-01

58

The chemistry of fullerenes  

Microsoft Academic Search

Initially envisaged as rather unreactive, aromatic-like molecules, the fullerenes instead undergo a wide variety of reactions characteristic of alkenes. The many derivatives of C60, and the few of C70, that have now been reported offer new directions for organic chemistry.

Roger Taylor; David R. M. Walton

1993-01-01

59

Polymers containing fullerene or carbon nanotube structures  

Microsoft Academic Search

This review deals with recent progress in studies of polymeric covalent and noncovalent modifications of fullerenes (mainly C60) and carbon nanotubes (CNTs), and their applications. By using functional polymers to react with fullerenes, or synthesizing polymers in the presence of fullerenes, various kinds of polymeric fullerenes can be prepared: side-chain polymers, main-chain polymers, dendritic fullerenes, star-shaped polymers, fullerene end-capped polymers,

Changchun Wang; Zhi-Xin Guo; Shoukuan Fu; Wei Wu; Daoben Zhu

2004-01-01

60

Fullerenes with metals inside  

Microsoft Academic Search

Fullerenes with a single lanthanum atom trapped on the inside of the carbon cage were produced by laser vaporization of a lanthanum oxide\\/graphite composite rod in a flow of argon gas at 1,200 C. When sublimed wit Cââ and Cââ, they formed an air-stable film containing principally LaCââ, LaCââ, LaCââ, and LaCââ. When dissolved in toluene and exposed to air,

Yan Chai; Ting Guo; Changming Jin; Robert E. Haufler; L. P. Felipe Chibante; Jan Fure; Lihong Wang; J. Michael Alford; Richard E. Smalley

1991-01-01

61

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

62

The samarium fullerene family  

NASA Astrophysics Data System (ADS)

Among the rare earth metals samarium is expected to form an ion of the two-valent redox state in endohedral fullerene structures. As compared to thulium and europium metallofullerenes a similar distribution of carbon cage structures is expected for samarium. The samarium fullerene structures produced by the Krätschmer-Huffman method were studied with respect to the influence of the Sm-carbon ratio on the type and yield of the metallofullerenes. The chromatographic separation carried out by a two step HPLC resulted in a larger family of Sm-fullerenes (C2n, 2n=74, 78, 82, 84, 86, 88, 90, 92) encapsulating one ion as detected by mass spectrometry. Only the Sm-C76 structure was missing. No dimetallofullerenes of Sm were found. The samarium structures of C74 and C82 were characterized by UV-Vis and IR spectroscopy. The results were compared with those of EuatC74 and TmatC82. The redox state of the metal ion in the metallofullerene was shown to be Sm2+ .

Georgi, Petra; Lieb, Silvio; de San Pio, Josué Navarro; Kuran, Pavel; Dunsch, Lothar

2000-11-01

63

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

64

Desorption Induced by KEV Molecular and Cluster Projectiles  

Microsoft Academic Search

A new experimental method has been developed for studying negative secondary ion (SI) emission from solid surfaces bombarded by polyatomic primary ions of 5 to 30 keV. The method is based on the time-of-flight (TOF) analysis of primary ions which are produced by either ^ {252}Cf fission fragment induced desorption or by extraction from a liquid metal ion source, and

Matthew Glenn Blain

1990-01-01

65

The smallest fullerene without a spiral  

NASA Astrophysics Data System (ADS)

In this note, we give the result of a computer search for the smallest fullerene that does not allow a face spiral code as used by Manolopoulos and Fowler and adopted in IUPAC recommendations for fullerene nomenclature. The search enumerated all the small fullerenes on up to 400 vertices and the conclusion is that the smallest fullerene without a face spiral has 380 vertices.

Brinkmann, Gunnar; Goedgebeur, Jan; McKay, Brendan D.

2012-01-01

66

Characterization and deuterium ion bombardment behaviour of titanium carbide coatings  

NASA Astrophysics Data System (ADS)

Titanium carbide has been deposited on 304 and 316 stainless steel, Monel 400, molybdenum, copper and graphite employing electron beam evaporation technique. The coatings were characterized using AES, ESCA, RBS, SIMS and SEM. Its elemental analysis shows the presence of titanium, carbon and oxygen, with carbon being in the carbide form. Thermal cycling and fatigue testing of coatings showed its capability to withstand 4700 laser pulses of 2 KW/cm 2 and 19 ms duration without any visible change. These coatings have been bombarded at energies of 40 and 80 keV with doses of 5 × 10 20, and 2.65 × 10 20 and 6.2 × 10 20 ions/cm 2, respectively, using an unanalysed deuterium beam. In general, the bombardment has resulted in a decrease in the C/Ti atomic ratio, thereby changing the film composition. In particular, exfoliations and formation of TiD has been observed.

Agarwala, R. P.; Dua, A. K.; Pande, B. M.

1987-04-01

67

Valence-band states of ion-bombarded polystyrene  

SciTech Connect

Ion-bombarded polystyrene with a 0.5-keV Ar{sup +} beam has been investigated by means of photoelectron spectroscopy performed with synchrotron radiation. After a dose of 10{sup 15} ions/cm{sup 2} the evolution of the valence band of the bombarded sample towards an amorphous carbonlike configuration is reported. From the analysis of valence-band spectra we estimated the out-diffusion of hydrogen and showed that its electronic states remain well identified and stable until the hydrogen presence is about 35% with respect to the pristine sample. Finally, comparison with mass spectroscopy measurements on deuterated polystyrene has been performed to determine hydrogen evolution during the ion irradiation.

Terrasi, A. (Istituto di Metodologie e Tecnologie per la Microelettronica, CNR, Corso Italia 57, 95129 Catania, Italy (IT)); Foti, G. (Dipartimento di Fisica, Universita di Catania, Corso Italia 57, 95129 Catania, (Italy)); Hwu, Y. (Synchrotron Radiation Center, University of Wisconsin-Madison, 3731 Schneider Drive, Stoughton, Wisconsin 53589-3097 (USA)); Margaritondo, G. (Ecole Polytechnique Federale de Lausanne, Department de Physique, PHB-Ecublens, CH 1015 Lausanne, (Switzerland))

1991-08-01

68

Visible light emission from Krq+ ion-bombarded GaAs surface  

NASA Astrophysics Data System (ADS)

The visible light emission spectra from gallium arsenide surface are measured at different charge states of incident ion in the wavelength range 300-700nm. For 340keV Krq+ (q=17, 15) ions bombarded the GaAs surface, the experimental results show that intensities of spectral lines are related closely with the projectile potential energy.

Qiu-mei, Xu; Zhi-hu1, Yang; Ye-hong, Wu; Zhang-yong, Song; Yi-pan, Guo

2014-04-01

69

Secondary electron emission from copper surface due to neodymium and gadolinium ion bombardment.  

National Technical Information Service (NTIS)

The electron emission yields (gamma) of copper surface have been measured under bombardment with Nd(sup +) and Gd(sup +) in the energy range 0.1-2.6 keV. The ions are extracted from a new laser ion source. For both cases of Nd(sup +) and Gd(sup +), (gamma...

T. Shibata K. Ogura

1993-01-01

70

Internal energy of molecules ejected due to energetic C60 bombardment  

PubMed Central

The early stages of C60 bombardment of octane and octatetraene crystals are modeled using molecular dynamics simulations with incident energies of 5-20 keV. Using the AIREBO potential, which allows for chemical reactions in hydrocarbon molecules, we are able to investigate how the projectile energy is partitioned into changes in potential and kinetic energy as well as how much energy flows into reacted molecules and internal energy. Several animations have been included to illustrate the bombardment process. The results show that the material near the edge of the crater can be ejected with low internal energies and that ejected molecules maintain their internal energies in the plume, in contrast to a collisional cooling mechanism previously proposed. In addition, a single C60 bombardment was able to create many free and reacted H atoms which may aid in the ionization of molecules upon subsequent bombardment events.

Garrison, Barbara J.; Postawa, Zbigniew; Ryan, Kathleen E.; Vickerman, John C.; Webb, Roger P.; Winograd, Nicholas

2009-01-01

71

Optical, mass, and auger spectra from e-bombarded KBr  

SciTech Connect

We have measured the mass spectrum and optical emission lines of neutral potassium atoms ejected from KBr at T = 300/degree/K and 443/degree/K bombarded by 2-keV electrons. The room-temperature data may be complicated by the nonstoichiometry of the alkali-enriched sample surface and seem difficult to interpret. The high-temperature sample, which maintains the proper stoichiometry, produces data in support of gas-phase excitation of alkali atoms desorbed from the surface. 15 refs., 4 figs.

Arakawa, E.T.; Kamada, M.

1988-01-01

72

Case Studies in Strategic Bombardment.  

National Technical Information Service (NTIS)

This volume, the third in a series of historical case studies of important air power missions, addresses the most controversial air power mission of all: strategic bombardment. The ability of aircraft and missiles to destroy or disrupt an enemy's war...

R. C. Hall R. J. Overy S. L. McFarland W. A. Jacobs W. P. Newton

1998-01-01

73

[Antiamyloid properties of fullerene C60 derivatives].  

PubMed

A comparative estimation of the ability of complexes of fullerene C60 with polyvinylpyrrolidone and fullerene C60 derivatives (the sodium salt of the polycarboxylic derivative of fullerene C60, sodium fullerenolate), has been carried out. The fullerenes destroyed amyloid fibrils of the Abeta(1-42) peptide of the brain and the muscle X-protein. A study of the effect of fullerenes on muscle actin showed that complexes of fullerene C60 with polyvinylpyrrolidone and sodium fullerenolate did not prevent the filament formation of actin, nor did they destroy its filaments in vitro. Conversely, sodium salt of the polycarboxylic derivative of fullerene C60 destroyed actin filaments and prevented their formation. It was concluded that sodium fullerenolate and complexes of fullerene C60 with polyvinylpyrrolidone are the most effective antiamyloid compounds among the fullerenes examined. PMID:22873064

Bobylev, A G; Shpagina, M D; Bobyleva, L G; Okuneva, A D; Piotrovski?, L B; Podlubnaia, Z A

2012-01-01

74

Thermoionization and dissociation of fullerenes and endohedral fullerenes  

Microsoft Academic Search

Electron emission and unimolecular dissociation of energetically excited fullerenes and endohedral fullerenes are studied with mass spectrometry. Three experimental approaches have been developed for these studies. These are UV laser excitation time-of-flight mass spectrometry (TOF-MS), laser desorption and ionization mass spectrometry (LDI-MS), and ion-molecule collision mass spectrometry (IMC-MS). Our first experimental effort is to investigate delayed electron emission from multiphoton

Rongping Deng

2003-01-01

75

Photophysics of fullerenes: Thermionic emission.  

National Technical Information Service (NTIS)

Multiphoton ionization of fullerenes using long-pulse length lasers occurs mainly through vibrational autoionization. In many cases the laser ionization can be described as thermionic in analogy to the boiling off of electrons from a filament. Thermionic ...

R. N. Compton A. A. Tuinman J. Huang

1996-01-01

76

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

77

Detection of negative fullerene conformers  

Microsoft Academic Search

Negative fullerene metastable negative conformers have been detected using electron transfer neutral atom scattering. The anions have been produced through alkali–fullerene collision process, in an energy range well above the ion-pair formation threshold, but still low enough where only the negative parent ion is formed. The interpretation of the parent ion band structure, in time-of-flight spectra, points to the formation

R. F. M. Lobo; B. N. Vicente; F. V. Berardo; I. V. Gouveia; J. H. Ribeiro; P. Pereira

2006-01-01

78

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

79

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

80

Ion bombardment of polyimide films  

SciTech Connect

Surface modification techniques such as wet chemical etching, oxidizing flames, and plasma treatments (inert ion sputtering and reactive ion etching) have been used to change the surface chemistry of polymers and improve adhesion. With an increase in the use of polyimides for microelectronic applications, the technique of ion sputtering to enhance polymer-to-metal adhesion is receiving increased attention. For this study, the argon-ion bombardment surfaces of pyromellitic dianhydride and oxydianiline (PMDA--ODA) and biphenyl tetracarboxylic dianhydride and phenylene diamine (BPDA--PDA) polyimide films were characterized with x-ray photoelectron spectroscopy (XPS) as a function of ion dose. Graphite and high-density polyethylene were also examined by XPS for comparison of C 1/ital s/ peak width and binding-energy assignments. Results indicate that at low ion doses the surface of the polyimide does not change chemically, although adsorbed species are eliminated. At higher doses the chemical composition is altered and is dramatically reflected in the C 1/ital s/ spectra where graphiticlike structures become evident and the prominent carbonyl peak is reduced significantly. Both polyimides demonstrate similar chemical changes after heavy ion bombardment. Atomic composition of PMDA--ODA and BPDA--PDA polymers are almost identical after heavy ion bombardment.

Bachman, B. J.; Vasile, M. J.

1989-07-01

81

Characterizing the Early Impact Bombardment  

NASA Technical Reports Server (NTRS)

The early bombardment revealed in the larger impact craters and basins on the moon was a major planetary process that affected all bodies in the inner solar system, including the Earth and Mars. Understanding the nature and timing of this bombardment is a fundamental planetary problem. The surface density of lunar impact craters within a given size range on a given lunar surface is a measure of the age of that surface relative to other lunar surfaces. When crater densities are combined with absolute radiometric ages determined on lunar rocks returned to Earth, the flux of large lunar impactors through time can be estimated. These studies suggest that the flux of impactors producing craters greater than 1 km in diameter has been approximately constant over the past approx. 3 Gyr. However, prior to 3.0 - 3.5 Gyr the impactor flux was much larger and defines an early bombardment period. Unfortunately, no lunar surface feature older than approx. 4 Gyr is accurately dated, and the surface density of craters are saturated in most of the lunar highlands. This means that such data cannot define the impactor flux between lunar formation and approx. 4 Gyr ago.

Bogard, Donald D.

2005-01-01

82

Elasticity, internal excitation, fragmentation, and charge transfer during grazing scattering of fast fullerenes from a KCl(001) surface  

NASA Astrophysics Data System (ADS)

C60+ and C70+ fullerenes with keV energies are scattered under grazing polar angles of incidence from an atomically clean and flat KCl(001) surface. For this model system of molecule surface interactions, the elastic properties of the fullerenes in front of the surface are studied by polar angular distributions. From the analysis of fragment spectra, the internal excitations of scattered molecules are deduced and excitation mechanisms are identified. Charge fractions indicate a kinematically induced neutralization of the fullerenes. Via an analysis of negatively charged fragments, the transition from a “soft” scattering event with intact outgoing fullerenes to postcollision multifragmentation is analyzed. The data are compared to three-dimensional molecular dynamics simulations based on empirical bond-order potentials.

Wethekam, S.; Merck, J.; Busch, M.; Winter, H.

2011-02-01

83

Production of fullerenes with concentrated solar flux.  

National Technical Information Service (NTIS)

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 re...

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

1994-01-01

84

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

85

Fullerene materials: Synthesis and applications  

NASA Astrophysics Data System (ADS)

Chapter 1 describes the purification of gram quantities of Csb{70} using activated charcoal flash chromatography columns. A detailed procedure on the use of these columns as well as the analysis of the purified material is given. Chapter 2 describes the production and analysis of metal-containing fullerene soots produced by plasma arc discharge. A method for dispersing nanometer-sized metal particles in porous graphite rods is presented. The metal/graphite rods are then consumed in an arc discharge reactor to form the metal-containing fullerene soots. Transmission electron microscopy and powder X-ray diffraction analysis are used to characterize the soots. Chapter 3 describes the complexation of DNA with a fullerene ammonium salt. The fullerene ammonium salt/DNA complex is easily imagable using transmission electron microscopy. The formation of these DNA complexes, as well as the preparation for imaging is discussed. Also described is the preparation of a ammonium salt derivative of ferrocene which is complexed with DNA. Chapter 4 describes the self-assembly of fullerene ammonium salts. The salts assemble into vesicle and tubule type structures. Transmission electron microscopy, powder X-ray diffraction, and energy dispersive X-ray analysis is used to investigate the structures.

Cassell, Alan Mitchell

86

Nanometer-scale sharpening and surface roughening of ZnO nanorods by argon ion bombardment  

NASA Astrophysics Data System (ADS)

We report the effects of exposing a hydrothermally grown, single crystalline ZnO nanorod array to a beam of 50 keV argon ions at room temperature. High resolution electron microscopy reveals that the ion bombardment results in a nanometer-scale roughening of the nanorod sidewalls, which were almost atomically flat in the pristine sample. Ion bombardment further causes the flat, ?100 nm diameter nanorod tips to get sharpened to ultrafine points less than 10 nm across. While tip sharpening is attributed to preferential sputtering, the formation of crystalline surface protuberances can be ascribed to surface instability due to curvature dependent sputtering and surface diffusion under argon-ion bombardment. Both the nanoscale roughening as well as the tip sharpening are expected to favorably impact a wide variety of applications, such as those involving catalysis, gas sensing, solar cells, field emission and gas discharge.

Chatterjee, Shyamal; Behera, Akshaya K.; Banerjee, Amarabha; Tribedi, Lokesh C.; Som, Tapobrata; Ayyub, Pushan

2012-07-01

87

Optical limiting with higher fullerenes  

NASA Astrophysics Data System (ADS)

Optical limiting has been investigated for higher fullerenes and compared with C60. The transmission through an aperture placed after solutions of C76, C78, and C84 in tetrahydronaphthalene was measured using Q-switched laser pulses with a wavelength of 532 nm and a pulse width of 8 ns FWHM. Unlike C60, the transmission for these higher fullerene solutions decreased linearly with increasing optical pulse energy. We attribute the linearized optical limiting response to self-defocusing of the optical beam and the absence of excited-state absorption. The ground state absorption spectra for the higher fullerenes suggest their use for optical limiting in the near infrared, and the C84-tetrahydronaphthalene solution was found to be an optical limiter at 1.064 ?m.

Kost, A. R.; Jensen, J. E.; Loufty, R. O.; Wither, J. C.

2005-03-01

88

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

89

Gel behavior of keV ion irradiated polystyrene  

SciTech Connect

Among the chemical and physical modifications induced by ion bombardment of polymers, the solubility changes are very important because of technological application for lithography in microelectronic devices. Solubility changes due to the occurrence of crosslinkings have been followed on monodisperse and polydisperse polystyrene after ion irradiations (10/sup 11/--10/sup 14/ ions/cm/sup 2/, keV energy). By using the Inokuty gel theory (M. Inokuti J. Appl. Phys. 38, 2999 (1963)), the chemical yield (crosslinking/eV) has been determined for different molecular weights and molecular weight distributions.

Calcagno, L.; Foti, G.; Licciardello, A.; Puglisi, O.

1988-10-17

90

Combined molecular dynamics and analytical model for repetitive cluster bombardment of solids  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of repetitive bombardment of solids by keV cluster beams have generated so much data that easy interpretations are not possible. Moreover, although the MD simulations remove 3-4 nm of material, that is not sufficient material to determine a depth profile. The recently developed steady-state statistical sputtering model (SS-SSM) uses information from the MD simulations and incorporates it into a set of differential equations to predict a depth profile. In this study the distributions that provide the input to the SS-SSM are compared for simulations of 15 keV bombardment of Ag(1 1 1) by C60, Au3 and Ar872 cluster beams.

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

2013-05-01

91

Fullerene-porphyrin supramolecular nanocables.  

PubMed

Novel fullerene-porphyrin supramolecular nanocables were designed and their electronic properties were studied using computational modeling and first-principles density functional theory. It is demonstrated that two well-defined fullerene-porphyrin nanocables have clear channels for charge transport by electrons and holes. These two interesting nanocables have zigzag or helical chains of [Formula: see text] molecules around a ?-stacked porphyrin core. They also have frontier electronic states which are spatially extended along the axes of the nanocables. Ballistic electronic transport is possible for ultrafast transfer of electrons along [Formula: see text] chains. We believe these supramolecular nanocables can play important roles in molecular electronics, optoelectronics and photovoltaics. PMID:24849532

Buldum, A; Reneker, D H

2014-06-13

92

Fullerene-porphyrin supramolecular nanocables  

NASA Astrophysics Data System (ADS)

Novel fullerene-porphyrin supramolecular nanocables were designed and their electronic properties were studied using computational modeling and first-principles density functional theory. It is demonstrated that two well-defined fullerene-porphyrin nanocables have clear channels for charge transport by electrons and holes. These two interesting nanocables have zigzag or helical chains of {{{\\rm{C}}}_{60}} molecules around a ?-stacked porphyrin core. They also have frontier electronic states which are spatially extended along the axes of the nanocables. Ballistic electronic transport is possible for ultrafast transfer of electrons along {{{\\rm{C}}}_{60}} chains. We believe these supramolecular nanocables can play important roles in molecular electronics, optoelectronics and photovoltaics.

Buldum, A.; Reneker, D. H.

2014-06-01

93

The structure of fullerene compounds  

NASA Astrophysics Data System (ADS)

This account reviews fullerene chemistry research at Sussex. C 60Ph 2 and C 60Ph 4 have been isolated as minor products from the reaction of C 60Cl 6 with C 6H 6 and FeCl 3. [70]Fullerene reacts with ICl in C 6H 6 producing a single isomer of C 70Cl 10 in high yield. C 70Ph 8, which has a [5,6] cage double bond that can be selectively functionalized, or C 70Ph 10 are produced by the electrophilic substitution of C 70Cl 10 into C 6H 6 in the presence of FeCl 3. C 70Ph 9OH is isolated as a minor component of foregoing reaction mixtures. Autoxidation of C 70Ph 8 yields the bislactone, C 70Ph 8O 4, which has an eleven atom ring in the surface of the cage, Cycloaddition to the [5,6] double bond of C 70Ph 8 with anthracene, C 14H 10, in C 6H 6 produces C 70Ph 8(C 14H 10). Two new methanofullerenes, C 60(CBr 2), and C 60(CHCN), are produced by treating [60]fullerene in C 6H 6 with either CH 2BrCN or CHBr 2 in the presence of LDA. Reaction of [60]fullerene with alkyl buta-2,3-dienoates in the presence of a phosphine results in [3 + 2] cycloadditions which produce alkyl 3'H-1,2-([1',2']cyclopenta)[60]fullerene-5'-carboxylates. [60]Fullerene reacts with Pt(cod) 2, producing an insoluble precipitate of PtC 60, further reaction with the bidentate ligand, Ph 2P(CH 2) nPPh 2) [ n = 2 or 3] in PhMe yields the low solubility complexes Pt( ?2-C 60)[Ph 2P(CH 2) nPPh 2)] ( n = 2 or 3). Mixing of C 6H 6 solutions of [60]fullerene with P 4 or vapour-solid reaction of [60]fullerene with P 4 results in the formation of the intercalate C 60(P 4) 2; there is no evidence for significant charge-transfer between the donor (P 4) and acceptor (C 60) molecules.

Avent, A. G.; Benito, A. M.; Birkett, P. R.; Darwish, A. D.; Hitchcock, P. B.; Kroto, H. W.; Locke, I. W.; Meidine, M. F.; O'Donovan, B. F.; Prassides, K.; Taylor, R.; Walton, D. R. M.; van Wijnkoop, M.

1997-12-01

94

Characteristic and noncharacteristic x rays produced during 1MeV argon bombardment of silicon  

Microsoft Academic Search

This work reports the first detailed examination of the noncharacteristic x-ray distribution produced during 1-MeV Ar bombardment of silicon. A crystal spectrometer was used to observe the characteristic and noncharacteristic x rays. It is shown that to within 5 eV the noncharacteristic x-ray band is continuous and tails off in the region of 1.4 keV, as required by the molecular

A. L. Lurio; J. A. Cairns; J. F. Ziegler; J. Macek

1975-01-01

95

Characteristic and noncharacteristic x rays produced during 1MeV argon bombardment of silicon  

Microsoft Academic Search

This work reports the first detailed examination of the ; noncharacteristic x-ray distribution produced during 1-MeV Ar bombardment of ; silicon. A crystal spectrometer was used to observe the characteristic and ; noncharacteristic x rays. It is shown that to within 5 eV the noncharacteristic ; x-ray band is continuous and tails off in the region of 1.4 keV, as

A. L. Lurio; J. A. Cairns; J. F. Ziegler; J. Macek

1975-01-01

96

Low-energy proton bombardment of GaAs and Si solar cells  

Microsoft Academic Search

GaAs, Si n\\/p, and Si p\\/n solar cells were irradiated with 185-530 keV protons. The short-circuit current of the GaAs and the open-circuit voltage of the Si cells decreased severely as a result of bombardment. The short-circuit current of the Si cells was independent of flux at first, but it then fell rapidly. The damage produced in both the GaAs

J. J. Wysocki; P. Rappaport; E. Davison; J. J. Loferski

1966-01-01

97

Ion Bombardment Experiments Suggesting an Origin for Organic Particles in Pre-Cometary and Cometary Ices  

NASA Technical Reports Server (NTRS)

Simple molecules frozen as mantles of interstellar and circumstellar grains and incorporated into comets are subjected to ion bombardment in the form of cosmic rays, stellar flares, stellar winds, and ions accelerated in stellar wind shocks. The total expected dosage for the variety of situations range from 10 eV/molecule for interplanetary dust subjected to solar flares to 10(exp 6) eV/molecule for material in the T Tauri environment. Utilizing a Van de Graaff accelerator and a target chamber having cryogenic and mass spectrometer capabilities, we have bombarded frozen gases in the temperature range of 10 K to 30 K with 175 keV protons. After irradiation, removal of the ice by sublimation at an elevated temperature in vacuum reveals a fluffy residue. These experiments suggest that processes resulting in the formation of organic particles found in the coma of Comet Halley, "CHON", may have included ion bombardment. Also, the moderate energy (100 keV to 500 keV) shock accelerated ion environment of bipolar outflow of stars in the planetary nebula stage such as the Red Rectangle, could produce complex molecular species which emit the observed unidentified infrared bands at 3.3 micro-m, 6.2 micro-m, 7.7 micro-m, 8.6 micro-m, and 11.3 micro-m.

Wdowiak, Thomas J.; Robinson, Edward L.; Flickinger, Gregory C.; Boyd, David A.

1997-01-01

98

Inorganic Fullerenes, Onions, and Tubes  

Microsoft Academic Search

Since the exciting and unexpected discovery of the soccerball-shaped Buckminsterfullerene (C 60 ) molecule almost two decades ago, great advances in fullerene research have been made. This includes the discovery of inorganic, noncarbon cage and nanotube structures. Of particular interest are the molybdenum and tungsten sulfides and selenides that, when viewed under an electron microscope, are remarkably similar in appearance

Andrew P. E. York

2004-01-01

99

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

100

Study of the Ar LMM spectra by He + projectile at 1250 keV, 1500 keV and 2000 keV bombardment energies  

NASA Astrophysics Data System (ADS)

The influence of He + ion impact on the Ar LMM spectra was investigated at the ESA-21 electron spectrometer using three different ion energies. Observed line relative energies to the L 3M 2,3( 1D 2) line agree well with other results, but the relative intensities of five angular-isotropic lines deviate significantly from other measurements and theory. The angular dependence of energy shifts agrees with the quantum PCI theory of Barrachina and Macek, except for directions close to 180°, where a slight enhancement of energy shift was observed. Finally, the angular distributions of the L 2M 2,3( 1S 0), ( 1d 2) and ( 3P 0,1,2) line intensities were compared to the alignment theory of Sizov and Kabachnik.

Tóth, L.; Víkor, Gy.; Ricz, S.; Pelicon, P.; Miller, R.

1994-03-01

101

Study of the Ar LMM spectra by He+ projectile at 1250 keV, 1500 keV and 2000 keV bombardment energies  

Microsoft Academic Search

The influence of He+ ion impact on the Ar LMM spectra was investigated at the ESA-21 electron spectrometer using three different ion energies. Observed line relative energies to the L3M2,3(1D2) line agree well with other results, but the relative intensities of five angular-isotropic lines deviate significantly from other measurements and theory. The angular dependence of energy shifts agrees with the

L. Tóth; Gy. Víkor; S. Ricz; P. Pelicon; R. Miller

1994-01-01

102

Organic chemistry of fullerenes: the major reactions, types of fullerene derivatives and prospects for practical use  

NASA Astrophysics Data System (ADS)

Data on the methods of functionalisation of C60 and C70 fullerenes published over the last 15 years are summarised. The general analysis of fullerene reactivity is performed. Nucleophilic and radical addition and cycloaddition reactions are considered in detail. The prospects of using fullerene derivatives as medical drug and photoactive materials for light converting devices are demonstrated.

Troshin, P. A.; Lyubovskaya, R. N.

2008-04-01

103

Organic chemistry of fullerenes: the major reactions, types of fullerene derivatives and prospects for practical use  

Microsoft Academic Search

Data on the methods of functionalisation of C60 and C70 fullerenes published over the last 15 years are summarised. The general analysis of fullerene reactivity is performed. Nucleophilic and radical addition and cycloaddition reactions are considered in detail. The prospects of using fullerene derivatives as medical drug and photoactive materials for light converting devices are demonstrated.

P A Troshin; R N Lyubovskaya

2008-01-01

104

Boron Fullerenes: A First-Principles Study  

Microsoft Academic Search

A family of unusually stable boron cages was identified and examined using first-principles local-density functional method. The structure of the fullerenes is similar to that of the B12 icosahedron and consists of six crossing double-rings. The energetically most stable fullerene is made up of 180 boron atoms. A connection between the fullerene family and its precursors, boron sheets, is made.

Nevill Gonzalez Szwacki

2008-01-01

105

Boron Fullerenes: A First-Principles Study  

Microsoft Academic Search

A family of unusually stable boron cages was identified and examined using first-principles local-density functional method.\\u000a The structure of the fullerenes is similar to that of the B12 icosahedron and consists of six crossing double-rings. The energetically most stable fullerene is made up of 180 boron atoms.\\u000a A connection between the fullerene family and its precursors, boron sheets, is made.

Nevill Gonzalez Szwacki

2008-01-01

106

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

107

Ionisation of fullerenes and fullerene clusters using ultrashort laser pulses.  

PubMed

We give a brief 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 by photoelectron spectroscopy. The ionisation rates are modelled for the intermediate situation where the excitation energy is equilibrated between electronic degrees of freedom but not yet coupled to vibrational degrees of freedom. The model is shown to describe many aspects of the experiments. New results are presented on the intra-cluster molecular fusion of fullerene molecules when van der Waals bound clusters of fullerenes are exposed to ultra-short laser pulses. Pump-probe measurements give a decay time constant for the intra-cluster fusion reaction of 520 +/- 55 fs. A comparison with monomer ionisation results suggests that the time window for the fusion reaction is influenced by the coupling of the electronic excitation energy to vibrational degrees of freedom of the molecules in the cluster. PMID:17136286

Campbell, Eleanor E B; Hansen, Klavs; Hedén, Martin; Kjellberg, Mikael; Bulgakov, Alexander V

2006-12-01

108

FULLERENES AND PROTO-FULLERENES IN INTERSTELLAR CARBON DUST  

SciTech Connect

Laboratory spectra of hydrogenated amorphous carbon (HAC) particles prepared under a variety of conditions show spectral features at 7.05, 8.5, 17.4, and 18.9 {mu}m (1418, 1176, 575, and 529 cm{sup -1}) that have been associated with emission from C{sub 60} molecules. These lines occur in the spectra even though C{sub 60} molecules as such are not present in our samples. It appears that these four spectral lines in HAC can instead be associated with precursor molecules or 'proto-fullerenes' (PFs) that subsequently react to yield C{sub 60}. We develop a model tracing the evolution and de-hydrogenation of HAC dust and show that the observation of an emission feature at 16.4 {mu}m (610 cm{sup -1}) in astronomical spectra signals the presence of the pentagonal carbon rings required for the formation of fullerenes. We suggest that the set of four IR emission lines previously identified with C{sub 60} in many objects that also show the 16.4 {mu}m feature and other polycyclic aromatic hydrocarbon bands arise from PFs rather than C{sub 60}. Tc1 is an example of a source in which de-hydrogenation has proceeded to the point where only fullerenes are present.

Duley, W. W.; Hu Anming, E-mail: wwduley@uwaterloo.ca [Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2012-01-20

109

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

110

Electron-Bombarded Silicon Spatial Light Modulator.  

National Technical Information Service (NTIS)

In electron-bombarded silicon light modulator, leaving a microchannel plate amplifier are accelerated to penetrate a silicon photodiode forming electron-hole pairs therein, resulting in significant current gains.

D. Armitage

1985-01-01

111

Ion bombardment investigations of impregnated cathodes  

NASA Astrophysics Data System (ADS)

Ion bombardment is one of the important factors limiting the performance of impregnated cathodes (=Ba dispenser cathodes) in high end television tubes or in colour monitor tubes. Hence, when designing a new gun with, e.g. higher electron beam current density, it is important also to model the influence of ion bombardment. Therefore, relations between basic parameters as a function of temperature need to be known quantitatively. In this paper, the emission slump of impregnated cathodes has been analyzed in a diode configuration in UHV with a differentially pumped Ar ion gun. The emission degeneration during and regeneration periods after ion bombardment have been investigated as function of cathode temperature, ion current and ion energy. One of the important results is, that the degeneration time coefficient is only weakly dependent on ion energy. The data matrix obtained can be used to improve the ion bombardment model applied in new electron gun design.

Zhang, Xiaobing; Gaertner, Georg

2003-06-01

112

Fullerene polymers from solid precursors  

SciTech Connect

One of the many speculations that quickly followed on the heels of the Kraetschmer-Huffman process for producing large quantities of C[sub 60] buckminsterfullerene was the possibility of stitching the molecules together to create a linear chain polymer, a [open quotes]pearl necklace[close quotes] of buckyballs. In addition to being chemically elegant and intrinsically beautiful, such a material might be expected to exhibit interesting electronic and nonlinear optical properties. Traditional solution-phase routes to fullerene polymerization have thus far resulted only in mixtures of incompletely characterized species with a high degree of cross-linking. This article reviews experiments that show that this goal might be achieved by starting from a fullerene solid precursor.

Fischer, J.E. (Univ. of Pennsylvania, Philadelphia, PA (United States) National Institute of Standards and Technology, Gaithersburg, MD (United States))

1994-06-10

113

Synthesis of germanium encapsulated fullerene  

NASA Astrophysics Data System (ADS)

A method has been described for encapsulating Ge in a fullerene cage using GeO 2 and a graphite composite rod as anode and graphite as cathode. Annealing in an inert atmosphere before arcing, and the amount of GeO 2 in the rod determined the yield of Ge doped metallofullerene. Solvent extraction using soxlet in inert atmosphere followed by calcination in air was used to isolate metallofullerene from the soot. The insertion of Ge inside the fullerene was proven by ultra violet-visible absorption spectroscopy, matrix assisted laser desorption ionization-time of flight mass spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.

Roy, Debmalya; Tripathi, N. K.; Ram, K.; Sathyamurthy, N.

2009-08-01

114

A Constructive Enumeration of Fullerenes  

Microsoft Academic Search

In this paper, a fast and complete method to enumerate fullerene structures is given. It is based on a top-down approach, and it is fast enough to generate, for example, all 1812 isomers ofC60in less than 20 s on an SGI-workstation. The method described can easily be generalized for 3-regular spherical maps with no face having more than 6 edges

Gunnar Brinkmann; Andreas W. M. Dress

1997-01-01

115

Photophysics of fullerenes: Thermionic emission  

SciTech Connect

Multiphoton ionization of fullerenes using long-pulse length lasers occurs mainly through vibrational autoionization. In many cases the laser ionization can be described as thermionic in analogy to the boiling off of electrons from a filament. Thermionic emission manifests itself as a delayed emission of electrons following pulsed laser excitation. Klots has employed quasiequilibrium theory to calculate rate constants for thermionic emission from fullerenes which seem to quantitatively account for the observed delayed emission times and the measured electron energy distributions. The theory of Klots also accounts for the thermionic emission of C{sub 60} excited by a low power CW Argon Ion laser. Recently Klots and Compton have reviewed the evidence for thermionic emission from small aggregates where mention was also made of experiments designed to determine the effects of externally applied electric fields on thermionic emission rates. The authors have measured the fullerene ion intensity as a function of the applied electric field and normalized this signal to that produced by single photon ionization of an atom in order to correct for all collection efficiency artifacts. The increase in fullerene ion signal relative to that of Cs{sup +} is attributed to field enhanced thermionic emission. From the slope of the Schottky plot they obtain a temperature of approximately 1,000 K. This temperature is comparable to but smaller than that estimated from measurements of the electron kinetic energies. This result for field enhanced thermionic emission is discussed further by Klots and Compton. Thermionic emission from neutral clusters has long been known for autodetachment from highly excited negative ions. Similarly, electron attachment to C{sub 60} in the energy range from 8 to 12 eV results in C{sub 60} anions with lifetimes in the range of microseconds. Quasiequilibrium theory (QET) calculations are in reasonable accord with these measurements.

Compton, R.N. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States); Tuinman, A.A. [Univ. of Tennessee, Knoxville, TN (United States); Huang, J. [Ames Lab., IA (United States)

1996-09-01

116

Fullerenes produced by harnessing sunlight  

SciTech Connect

Two independent groups of researchers have demonstrated that fullerenes can be produced by harnessing focused sunlight to vaporize carbon. Adapted to a large scale, generation of the carbon-cage molecules in solar furnaces might overcome yield-limiting problems associated with other fullerene production techniques, the researchers suggest. At Rice University, Houston, chemistry professor Richard E. Smalley and graduate students L.P. Felipe Chibante, Andreas Thess, J. Michael Alford, and Michael D. Diener used a parabolic mirror to focus sunlight on a graphite target to produce what appears to be a high yield of fullerenes. At the National Renewable Energy Laboratory (NREL), Golden, Colo., Roland R. Pitts, Mary Jane Hale, Carl Bingham, Allan Lewandowski, and David E.King, working in collaboration with Clark L. Fields, a chemistry professor at the University of Northern Colorado, Greeley, used NREL's high-flux solar furnace to produce soot that contains C[sub 60] and C[sub 70]. Papers describing the Rice and NREL results appeared together in last week's Journal of Physical Chemistry (97, 8696 and 8701 (1993)).

Not Available

1993-08-01

117

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

118

Theoretical study on structure of boron nitride fullerenes  

Microsoft Academic Search

We propose the parameters of the Stillinger Weber potential for hexagonal boron nitride (BN) structures. For the reliability of these parameters, the structural property of BN fullerenes is investigated. The stability of BN fullerenes increases with increasing the number of atoms, due to the reduction of the curvature effect of BN fullerenes. The structures of the relative stable fullerenes are

Won Ha Moon; Myung Sik Son; Ho Jung Hwang

2007-01-01

119

Electronic structure calculations of fullerenes and their derivatives  

Microsoft Academic Search

This book review the fullerene field from the perspective of a theoretician with emphasis on electronic structure. Topics include the theoretical methods currently used; geometry, vibrational frequencies, heats of formation and ionic and excited states of higher fullerenes; small fullerenes, tubular and polymetirc allotropes of carbon, endohedral complexes; fullerene derivatives and solid-state properties of C60 based materials.

J. Cioslowski

1995-01-01

120

Fullerenic Structures and Such Structures Tethered to Carbon Materials.  

National Technical Information Service (NTIS)

The fullerenic structures include fullerenes having molecular weights less than that of C(Sub 60) with the exception of C(sub 36) and fullerenes having molecular weights greater than C(sub 60). Examples include fullerenes C(sub 50), C(sub 58), C(sub 130),...

A. Goel J. B. Howard J. B. Vande Sande

2003-01-01

121

Kinetics of Fullerene Formation in a Contact Arc Generator  

Microsoft Academic Search

A kinetic model of the fullerene growth process in a contact arc generator is developed. On the basis of the kinetic model, the yield of the magic fullerenes C60 and C70 is calculated. The fullerene yield is determined by the temperature gradient in the fullerene formation zone, the carbon vapor concentration and the helium jet velocity in the interelectrode space.

Z. M. Markovi?; B. M. Todorovi?-Markovi?; T. Lj. Joki?; P. Pavlovi?; P. Stefanovi?; J. Blanuša; T. Nenadovi?

1998-01-01

122

Hydration behaviour of polyhydroxylated fullerenes  

NASA Astrophysics Data System (ADS)

We have performed semi-empirical as well as density functional theory calculations in order to analyse the hydration properties of both bare C60 and highly hydroxylated C60(OH)26 fullerenes. In all of our calculations, a total of 42 and 98 water molecules are always surrounding our here-considered carbon nanostructures. We found different wetting properties as a function of the chemical composition and structure of the OH-molecular over-layer covering the fullerene surface. In the case of bare C60, water adsorption reveals that the H2O species are not uniformly arranged around the carbon network but rather forms water droplets of different sizes, clearly revealing the hydrophobic nature of the C60 structure. In contrast, in the polyhydroxylated C60(OH)26 fullerenes, the degree of wetting is strongly influenced by the precise location of the hydroxyl groups. We found that different adsorbed configurations for the OH-molecular coating can lead to the formation of partially hydrated or completely covered C60(OH)26 compounds, a result that could be used to synthesize fullerene materials with different degrees of wettability. By comparing the relative stability of our hydroxylated structures in both bare and hydrated conditions we obtain that the energy ordering of the C60(OH)26 isomers can change in the presence of water. The radial distribution function of our hydrated fullerenes reveals that water near these kinds of surfaces is densely packed. In fact, by counting the number of H2O molecules which are adsorbed, by means of hydrogen bonds, to the surface of our more stable C60(OH)26 isomer, we found that it varies in the range of 5-10, in good agreement with experiments. Finally, by comparing the calculated optical absorption spectra of various C60(OH)26 structures in the presence and absence of water molecules, we note that only slight variations in the position and intensity of the electronic excitations are found, indicating that their vacuum optical properties are more or less preserved in aqueous environments.

Rodríguez-Zavala, J. G.; Barajas-Barraza, R. E.; Padilla-Osuna, I.; Guirado-López, R. A.

2011-10-01

123

Inorganic nanotubes and fullerene-like materials.  

PubMed

Following the discovery of fullerenes and carbon nanotubes, it was shown that nanoparticles of inorganic layered compounds, like MoS2, are unstable in the planar form and they form closed cage structures with polyhedral or nanotubular shapes. Various issues on the structure, synthesis, and properties of such inorganic fullerene-like structures are reviewed, together with some possible applications. PMID:12432497

Tenne, Reshef

2002-12-01

124

Boron Fullerenes: An Electronic Structure Study  

Microsoft Academic Search

Using ab initio calculations, we study electronic structure and frequency modes of B80, a member of boron fullerene family made from boron isomorphs of carbon fullerenes with additional atoms in the centers of hexagons. We also investigate geometrical and electronic structural properties of double-rings with various diameters, which are important as building blocks of boron nanotubes, and as the most

Arta Sadrzadeh; Olga Pupysheva; Ihsan Boustani; Boris Yakobson

2008-01-01

125

Optical limiting properties of [60]fullerene derivatives  

SciTech Connect

Materials such as organic dyes that are strong nonlinear absorbers are being investigated as optical limiting materials for potential applications in the protection of sensors and human eyes from laser radiations. The optical limiting properties of methano[60]fullerene and pyrrolidino[60]fullerene derivatives were investigated. 27 refs., 8 figs., 1 tab.

Sun, Ya-Ping; Riggs, J.E.; Liu, Bing [Clemson Univ., SC (United States)] [Clemson Univ., SC (United States)

1997-05-01

126

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

127

Self-assembly of the fullerenes  

Microsoft Academic Search

The account deals with a central mystery of the fullerene story: How are they made How can the fullerenes in general, and C[sub 60] in particular, possibly, be made spontaneously in high yield simply by condensing carbon vapor in a special way The mystery of how this happens in the case of carbon is still by no means fully resolved.

R. E. Smalley

1992-01-01

128

Growth and Sintering of Fullerene Nanotubes  

Microsoft Academic Search

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

D. T. Colbert; J. Zhang; S. M. McClure; P. Nikolaev; Z. Chen; J. H. Hafner; D. W. Owens; P. G. Kotula; C. B. Carter; J. H. Weaver; A. G. Rinzler; R. E. Smalley

1994-01-01

129

A Generalized Leapfrog for Fullerene Structures  

Microsoft Academic Search

The leapfrog of fullerene structures is generalized by using elementary number theory. We summarize and apply the unpublished work of Thurston on a theoretical classification of fullerenes (which shows that the number of Cn isomers is of the order of n). We pose some open questions.

Chih-Han Sah

1994-01-01

130

The first stable lower fullerene: C36  

NASA Astrophysics Data System (ADS)

A new pure carbon material, presumably composed of thirty six carbon atom molecules, has been synthesized and isolated in milligram quantities. It appears as though these molecules have a closed cage structure making them the smallest member of a new class of molecules known as fullerenes, most notably of which is the soccer ball shaped C60. However, unlike other known fullerenes, any closed, fullerene-like C36 cage will necessarily contain fused pentagon rings. Therefore, this molecule apparently violates the isolated pentagon rule, a criterion which requires isolated pentagons for stability in fullerene molecules. Striking parallels between this problem and the synthesis of other fused five member fused ring systems will be discussed. Also, it will be shown that certain biological structures known as clathrin behave in a manner which gives excellent predictions about fullerenes and nanotubes. These predictions help to explain the presence of abundant quantities of C36 in arced graphite soot.

Piskoti, C.; Zettl, A.

1998-08-01

131

Gas storage using fullerene based adsorbents  

NASA Technical Reports Server (NTRS)

This invention is directed to the synthesis of high bulk density high gas absorption capacity adsorbents for gas storage applications. Specifically, this invention is concerned with novel gas absorbents with high gravimetric and volumetric gas adsorption capacities which are made from fullerene-based materials. By pressing fullerene powder into pellet form using a conventional press, then polymerizing it by subjecting the fullerene to high temperature and high inert gas pressure, the resulting fullerene-based materials have high bulk densities and high gas adsorption capacities. By pre-chemical modification or post-polymerization activation processes, the gas adsorption capacities of the fullerene-based adsorbents can be further enhanced. These materials are suitable for low pressure gas storage applications, such as oxygen storage for home oxygen therapy uses or on-board vehicle natural gas storage. They are also suitable for storing gases and vapors such as hydrogen, nitrogen, carbon dioxide, and water vapor.

Loutfy, Raouf O. (Inventor); Lu, Xiao-Chun (Inventor); Li, Weijiong (Inventor); Mikhael, Michael G. (Inventor)

2000-01-01

132

Fullerene-biomolecule conjugates and their biomedicinal applications.  

PubMed

Fullerenes are among the strongest antioxidants and are characterized as "radical sponges." The research on biomedicinal applications of fullerenes has achieved significant progress since the landmark publication by Friedman et al in 1993. Fullerene-biomolecule conjugates have become an important area of research during the past 2 decades. By a thorough literature search, we attempt to update the information about the synthesis of different types of fullerene-biomolecule conjugates, including fullerene-containing amino acids and peptides, oligonucleotides, sugars, and esters. Moreover, we also discuss in this review recently reported data on the biological and pharmaceutical utilities of these compounds and some other fullerene derivatives of biomedical importance. While within the fullerene-biomolecule conjugates, in which fullerene may act as both an antioxidant and a carrier, specific targeting biomolecules conjugated to fullerene will undoubtedly strengthen the delivery of functional fullerenes to sites of clinical interest. PMID:24379667

Yang, Xinlin; Ebrahimi, Ali; Li, Jie; Cui, Quanjun

2014-01-01

133

Effect of plasma ion bombardment on the reflectance of Io's trailing and leading hemispheres  

NASA Technical Reports Server (NTRS)

The possible effect of a net difference in the ion bombardment flux to the surface of Io on the ratio of the reflectance spectra is investigated. Io's vapor-deposited surface layers are simulated by a laboratory-produced film of vapor-deposited SO2 with a small admixture (about 3 percent) of H2S and (about 0.1 percent) H2O. It is shown that the reflectance ratio in the UV/visible of the surface bombarded by keV ions to the unbombarded surface is surprisingly similar to the observed ratio of Io's trailing to leading hemispherical reflectance. The changes produced are either structural or involve products of species originally present in the sample.

Sack, N. J.; Baragiola, R. A.; Johnson, R. E.

1993-01-01

134

Machine Phase Fullerene Nanotechnology: 1996  

NASA Technical Reports Server (NTRS)

NASA has used exotic materials for spacecraft and experimental aircraft to good effect for many decades. In spite of many advances, transportation to space still costs about $10,000 per pound. Drexler has proposed a hypothetical nanotechnology based on diamond and investigated the properties of such molecular systems. These studies and others suggest enormous potential for aerospace systems. Unfortunately, methods to realize diamonoid nanotechnology are at best highly speculative. Recent computational efforts at NASA Ames Research Center and computation and experiment elsewhere suggest that a nanotechnology of machine phase functionalized fullerenes may be synthetically relatively accessible and of great aerospace interest. Machine phase materials are (hypothetical) materials consisting entirely or in large part of microscopic machines. In a sense, most living matter fits this definition. To begin investigation of fullerene nanotechnology, we used molecular dynamics to study the properties of carbon nanotube based gears and gear/shaft configurations. Experiments on C60 and quantum calculations suggest that benzyne may react with carbon nanotubes to form gear teeth. Han has computationally demonstrated that molecular gears fashioned from (14,0) single-walled carbon nanotubes and benzyne teeth should operate well at 50-100 gigahertz. Results suggest that rotation can be converted to rotating or linear motion, and linear motion may be converted into rotation. Preliminary results suggest that these mechanical systems can be cooled by a helium atmosphere. Furthermore, Deepak has successfully simulated using helical electric fields generated by a laser to power fullerene gears once a positive and negative charge have been added to form a dipole. Even with mechanical motion, cooling, and power; creating a viable nanotechnology requires support structures, computer control, a system architecture, a variety of components, and some approach to manufacture. Additional information is contained within the original extended abstract.

Globus, Al; Chancellor, Marisa K. (Technical Monitor)

1997-01-01

135

Ion bombardment effects in conducting polymers  

NASA Astrophysics Data System (ADS)

The modification of properties of conducting polymers by ion bombardment offers interesting possibilities for their application in the field of muelectronics and electrochemistry. Therefore foils of intrinsically conducting polymers (polypyrrole and polythiophene) were modified by noble gas ion implantation. By ion bombardment the resistivity can be increased by several orders of magnitude. This effect depends on the species, energy and ion fluence. Cyclovoltammetric experiments show the same electrochemical features for the modified foils as the untreated polymers, but the observed currents are smaller by two orders of magnitude. The conductivity of the virgin foil ( ? = 100 S/cm) is sufficient for galvanic metal deposition. The bombardment induced change of resistivity causes an inhibition of electrochemical deposition. By using masks lateral structures in the range of several ?m can be produced. During implantation the black colour of the untreated foil changes to brown depending on the implanted dose. The associated changes of the chemical structures, investigated by XPS, are discussed.

Schiestel, S.; Ensinger, W.; Wolf, G. K.

1994-06-01

136

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

137

Ease of formation of nested fullerenes  

NASA Astrophysics Data System (ADS)

Molecular mechanics calculations using CVFF force field for isolated fullerenes C60, C240, C540, C960 and the nested ones they form indicate that the process of buckyonion formation is cooperative and driven by nonbonded interactions. The calculations for the nested fullerenes involving all isomers of C70, C76 and C 80 satisfying isolated pentagon rule indicate that the complex formation with these guests is less efficient than that with the C 60. Molecular dynamics simulations for C60, C240, C540, C960 and for the quaternary complex C 60@C 240@C 540@C 960 support the cooperativity of the process of nested fullerenes formation.

Dodziuk, Helena; Dolgonos, Grigory; Lukin, Oleg

2000-10-01

138

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

139

Formation and growth of carbon nanostructures: fullerenes, nanoparticles, nanotubes and cones  

Microsoft Academic Search

Various formation models for fullerenes and other carbon nanostructures are reviewed. The formation models considered include fullerene assembling from graphite sheets, 'nautilus' model, assemblage from clusters, 'fullerene road', and carbon cluster annealing. The selection of magic fullerenes and fullerene isomers is discussed. Carbon nanoparticle formation mechanisms are analyzed and their relation to fullerene formation mechanisms is outlined. Molecular dynamics simulation

Yurii E Lozovik; Andrei M Popov

1997-01-01

140

Stability of metal nanocomposites under heavy-ion bombardment of insulators  

NASA Astrophysics Data System (ADS)

Optical transmission and ion-induced photon emission of SiO 2 (silica glass), LiNbO 3 and Al 2O 3 were measured during implantation of 60-keV Cu - or Au - ions. Conditions of stability of metal nanocomposites were determined and represented with the help of nonequilibrium phase diagrams. Formation of structures dynamically stable under ion bombardment diminished the efficiency of ion implantation for further accumulation of implants as in nanoparticles. Contributions from various radiation-induced processes (sputtering, radiation-induced diffusion, atomic collisions, electronic excitations, etc.) to formation of nanocomposites were evaluated.

Plaksin, O. A.; Takeda, Y.; Amekura, H.; Kono, K.; Kishimoto, N.

2006-09-01

141

TOF-ICISS study of surface damage formed by Ar ion bombardment on Si(100)  

NASA Astrophysics Data System (ADS)

The surface damage formed on a clean Si(100)-2 × 1 surface by low-energy Ar ion bombardment has been studied in situ using the impact collision ion scattering spectroscopy (ICISS) method and the time-of-flight (TOF) technique. The Ar ion energy was 1 keV and the ion doses were in the range of 10 14-10 15ions/cm 2. Channeling and focusing effects were observed very clearly on a clean and well-ordered surface. With the increase of the Ar ion dose, such channeling and focusing effects gradually disappear. The annealing process of the surface damage was also investigated.

Koji Sumitomo; Ken-ichiroTanaka; Itsuo Katayama; Fumiya Shoji; Kenjiro Oura

142

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

143

Fullerene-silica complexes for medical chemistry  

NASA Astrophysics Data System (ADS)

A quantum-chemical study of the interaction of C60 fullerene with nanosized silica was performed. It was demonstrated that a fullerene molecule forms a weakly bound complex with a pyrogenic silica (Aerosil) particle only via the interaction with the silanediol groups of the hydroxyl covering on the particle. By contrast, a fullerene molecule is not bonded to an individual siloxane cycle, and, therefore, fullerosilica gel is formed due to the retention of fullerene molecules in pores of silica gel as a result cooperative action of the siloxane cycles comprising the pore. In both cases, the predicted medico-biological action of medicinal preparations is due to the radical-like and donor-acceptor characteristics of the C60 molecule.

Sheka, E. F.

2007-06-01

144

Ambient-Atmosphere Compatible Superconducting Fullerenes.  

National Technical Information Service (NTIS)

The goal of this Phase I project was to evaluate different methods to produce ambient-atmosphere compatible superconducting fullerenes. Three approaches toward this goal were surveyed, (1) protective overlayers, (2) in-cage dopants, and (3) alternate dopa...

T. A. Miller

1993-01-01

145

Photoionization of Endohedral Atoms in Fullerene Cages  

NASA Astrophysics Data System (ADS)

The finite-element discrete variable representation combined with the method of complex coordinate rotation is implemented to investigate the hydrogenic atoms and alkali metals encapsulated by the fullerene cages. The energy levels varying with the confining potential of the fullerene cage exhibit avoided crossings caused by the so-called mirror collapse from the switch of near degenerate states. The effects of fullerene cages on photoionization of confined atoms leading to the oscillation behavior and confinement resonances in photoionization cross sections are demonstrated. The results of cross sections for hydrogen-like lithium ion as a function of the cage radius and shell thickness are presented. The emergence of the Cooper minima due to the influence of the fullerene cages is observed for endohedral lithium and sodium atoms. Comparisons are made to the existing predictions.

Lin, C. Y.; Ho, Y. K.

2013-03-01

146

Synthesis and properties of novel fullerene derivatives  

SciTech Connect

Synthesis and chemical properties of a novel fullerene-porphyrin dyad is reported. Energy/electron transfer is studied based on cyclic voltametry and UV-visible spectroscopy. {copyright} {ital 1998 American Institute of Physics.}

Da Ros, T.; Prato, M. [Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa, 1, 34127 Trieste (Italy); Guldi, D. [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46656 (United States); Alessio, E. [Dipartimento di Scienze Chimiche, Universita di Trieste, Via Giorgieri 1, 34127 Trieste (Italy); Valli, L. [Dipartimento di Scienza dei Materiali, Universita di Lecce, 73100 Lecce (Italy); Carano, M.; Paolucci, F.; Ceroni, P.; Roffia, S. [Dipartimento di Chimica G. Ciamician, Universita di Bologna, 40126 Bologna (Italy)

1998-08-01

147

Oscillations observed in electrons and scattered protons from 30–100 keV protons transiting a Si\\/Lexan\\/C layered foil  

Microsoft Academic Search

A layered foil of 4.5 ?g\\/cm2 Si, 3.6 ?g\\/cm2 Lexan, and 1.0 ?g\\/cm2 C was bombarded by protons between 30 and 100 keV. The electron yields from the Si and C surfaces at ? = 0° (unscattered), 45° (forward), and 135° (backward) with respect to the beam direction were measured at proton energies 30, 60 and 90 keV. The scattered-proton

C. C. Hsu; T. C. Chu; K. C. Hsieh; Y. C. Chang; C. C. Lo; W. C. Chiou

1996-01-01

148

Fullerene amino acid interactions. A theoretical study  

NASA Astrophysics Data System (ADS)

In this work we explore the ability of the C 60 fullerene to interact with amino acids at the DFT-B3LYP/3-21G? level of theory. The calculations suggest that the most favorable interactions of the fullerene is with arginine, leucine, and tryptophan which is related to the backbone structure of the corresponding amino acids. We propose correlations of the dissociation energies, HOMO/LUMO band gaps and hydrophobicity constants in relation to the computed quantum chemical behavior.

Leon, Aned de; Jalbout, Abraham F.; Basiuk, Vladimr A.

2008-02-01

149

Self-assembly of tubular fullerenes  

Microsoft Academic Search

Carbon nanotubes in the form of multiwalled fullerenes are shown here to self-assemble under homogeneous gas-phase conditions of carbon condensation in an inert atmosphere heated to 1200$DGR@C-conditions previously thought to be optimal only for the annealing and growth of Cââ and other spheroidal shells. Tubular fullerenes are known to be less stable than their spheroidal counterparts and have thus far

Ting Guo; P. Nikolaev; A. G. Rinzler; Daniel T. Colbert; Richard E. Smalley; D. Tomanek

1995-01-01

150

[60]Fullerene as a Novel Photoinduced Antibiotic  

Microsoft Academic Search

The antibacterial activity of [60]fullerene (C60), dissolved with poly(vinylpyrrolidone) K30 (PVP), was studied. Under photo?irradiation, C60\\/PVP aqueous solutions showed antibacterial activity, whereas PVP solution alone or fullerene solutions in the absence of light showed no activity. These results reveal that C60 is a potentially good device as a photoinduced antibacterial agent. Dedicated to Professor Akira Tanimura on the occasion of

Yoko Kai; Yuka Komazawa; Atsuko Miyajima; Naoki Miyata; Yoko Yamakoshi

2003-01-01

151

Fullerenes in the Fossil of Dinosaur Egg  

Microsoft Academic Search

By means of laser desorption post-ionization time-of flight mass specrometry (TOF) and high-pressure liquid chromatography (HPLC), fullerene C60 have been found in a fossil of dinosaur egg shell from Xixia (N33.3 E111.4), China. These techniques verified also mat fullerene C70 is virtually absent from identical egg fossil of dinosaur at XiXia. Preliminary results suggest that C60 occurrence and C70 absence

Wang Zhenxia; Li Xuepeng; Wang Wenmin; Xu Xunjiang; Zi Chao Tang; Rong-Bin Huang; Lan-Sun Zheng

1998-01-01

152

Ion-chain interaction in keV ion-beam-irradiated polystyrene  

SciTech Connect

Molecular weight distribution has been measured in monodisperse polystyrene film (MW = 9 000 amu) after ion bombardment, in the ion fluence range 10/sup 11/--10/sup 13/ ions/cm/sup 2/. The chosen beams are 100 keV He, 200 keV Ne, and 400 keV Ar. The experimental data have been interpreted in terms of a simple statistical model for cross-links. The chemical yield is found to be very high and equal to 0.30, about a factor of 10 higher than the values given in the literature for gamma irradiation (M. Dole, in The Radiation Chemistry of Macromolecules (Academic, New York, 1973), Vol. 2, Chap. 5, p. 57).

Calcagno, L.; Foti, G.; Licciardello, A.; Puglisi, O.

1987-09-21

153

Nonlinear optical properties of fullerenes and charge-transfer complexes of fullerenes  

SciTech Connect

The authors present results on the second- and third-order nonlinear optical properties of fullerenes and some of their derivatives. This is part of their effort to study general nonlinear properties of clusters. Polarizability measurements in fullerenes and in N,N-diethylaniline charge transfer complexes are reported.

Wang, Ying; Cheng, Lap-Tak [Du Pont Co., Wilmington, DE (United States)

1992-02-20

154

Functionalized fullerenes on silicon surfaces  

NASA Astrophysics Data System (ADS)

We have investigated the influence of phenyl addends on the packing and adsorption of C 60 on a solid substrate. On the Ag/Si(111)- ( 3× 3)R30° surface, the interactions of the unmodified part of the fullerene cages are not strongly affected by the addition of the phenyl groups although pronounced differences in molecular packing are observed. Phenylated C 60 may rotate to its optimum configuration and diffuse freely on this surface. In contrast it can neither rotate nor diffuse on Si(111)7×7, while on C 60/Si(111)-7×7 it can diffuse but the presence of the phenyl groups inhibits the formation of ordered layers.

Upward, M. D.; Moriarty, P.; Beton, P. H.; Birkett, P. R.; Kroto, H. W.; Walton, D. R. M.; Taylor, R.

1998-05-01

155

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

156

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

157

Paper Models for Fullerenes C60-C84.  

ERIC Educational Resources Information Center

Describes a system to construct paper models of all 51 of the possible fullerene isomers from C60 through C84. Provides students, teachers, and specialists with an inexpensive mechanism to follow the literature interplay on fullerene structures. (JRH)

Beaton, John M.

1995-01-01

158

Production of Positive Ions and Electrons in Collisions of 1-25 KeV Protons and Hydrogen Atoms with Co, CO2, CH4, and NH3.  

National Technical Information Service (NTIS)

Cross sections are reported for the production of slow, positive-ions (sigma(+)) and electrons (sigma(-)) in collisions of 1-25 keV protons and hydrogen atoms with CO, CO2, CH4, and NH3. For H(+) bombardment sigma(-) is the total ionization cross section,...

R. J. McNeal

1970-01-01

159

Theoretical study on structure of boron nitride fullerenes  

Microsoft Academic Search

We propose the parameters of the Stillinger–Weber potential for hexagonal boron nitride (BN) structures. For the reliability of these parameters, the structural property of BN fullerenes is investigated. The stability of BN fullerenes increases with increasing the number of atoms, due to the reduction of the curvature effect of BN fullerenes. The structures of the relative stable fullerenes are B16N16,

Won Ha Moon; Myung Sik Son; Ho Jung Hwang

2007-01-01

160

Analytical expressions for atom-fullerene, fullerene-fullerene and fullerene-graphite-surface interaction energies using the surface continuum approximation with an atom-atom van der Waals Buckingham potential  

Microsoft Academic Search

Using the surface continuum approximation of carbon atoms and the interatomic Buckingham potential, new analytic forms for atom-fullerene, fullerene-fullerene and fullerene-graphite interaction energies are obtained and compared with the well-known C{60}-C{60} Girifalco potential as well as the C60-graphite potential of Ruoff and Hickman both stemming from the Lennard-Jones LJ(12,6) potential. In addition, the heat of sublimation, the nearest-neighbour distance and

H. Guérin

1998-01-01

161

Ion-bombardment induced light emission from Si(1 0 0) surfaces under continuous germane exposures  

NASA Astrophysics Data System (ADS)

The intensities of the optical spectral lines emitted from a Si(1 0 0) surface under Ar + ion bombardment are studied as a function of the ion kinetic energy (1-5 keV) and the partial pressure of germane. In these experiments, the ion flux is held constant while either the bombardment energy or the partial pressure of germane is varied. The excited neutral Si (SiI, 288 nm), neutral Ge (GeI, 265 nm and 304 nm), H Balmer beta (486 nm) and H Balmer gamma (434 nm) optical lines are observed. With increasing germane partial pressure, a broad emission feature develops between 330 and 365 nm and is assigned to excited GeH 2 and/or GeH 3 species. The emission intensities of the excited neutral Si, neutral Ge, H ? and H ? optical lines from the bombarded Si(1 0 0) surface increase with greater germane partial pressures and ion kinetic energy in a manner similar to that previously observed for silane exposures. In contrast to the monotonic increase of the above emission lines with higher germane partial pressures and greater incident kinetic energies, the H Balmer alpha (656 nm) optical line exhibits unique behavior. Paralleling the behavior observed for silane exposed surfaces, the intensity of the Balmer alpha transition decreases with increasing incident ion kinetic energy at all measured partial pressures of germane.

Rajasekar, P.; Lennart, Alexis; Materer, Nicholas F.

2005-08-01

162

Photoluminescence and optical properties of He ion bombarded ultra-high molecular weight polyethylene  

NASA Astrophysics Data System (ADS)

Ion bombardment is a suitable tool to improve the physical and chemical properties of polymer surface. In this study UHMWPE samples were bombarded with 130 keV He ions to the fluences ranging from 1 × 10 12 to 1 × 10 16 cm -2. The untreated and ion beam modified samples were investigated by photoluminescence, and ultraviolet-visible (UV-vis) spectroscopy. Remarkable decrease in integrated luminescence intensity with increasing ion fluences was observed. The reduction in PL intensity with increase of ion fluence might be attributed to degradation of polymer surface and formation of defects. The effect of ion fluence on the optical properties of the bombarded surfaces was characterized. The values of the optical band gap Eg, and activation energy Ea were determined from the optical absorption. The width of the tail of the localized states in the band gap (E a) was evaluated using the Urbach edge method. With increasing ion fluences a decrease in both the energy gap and the activation energy were observed. Increase in the numbers of carbon atoms ( N) in a formed cluster with increasing the He ion fluence was observed.

Abdul-Kader, A. M.

2009-02-01

163

Formation dynamics of fullerene dimers C118+, C119+, and C120+  

NASA Astrophysics Data System (ADS)

Dumbbell-shaped fullerene dimers C118+ and C119+ have recently been observed in mass spectra resulting from collisions between clusters of C60 molecules and keV He2+ or Ar2+ ions [H. Zettergren et al., Phys. Rev. Lett. 110, 185501 (2013), 10.1103/PhysRevLett.110.185501 and F. Seitz et al., J. Chem. Phys. 139, 034309 (2013), 10.1063/1.4812790]. To unveil the formation mechanisms of these fullerene dimers, systematic molecular dynamics (MD) simulations based on the self-consistent charge density functional tight-binding method have been performed for Cn+ + C60 (n =58,59,60) collisions following prompt atom knockouts by the fast ions. The statistics from the MD simulations indicate a much higher reactivity of C59+ and C58+ fragments compared to that of C60+. It is found that the covalently bonded dumbbell-shaped fullerene dimers C118+ and C119+ can be formed at very low-collision energies within 1 ps and are stable enough to survive on the microsecond time scale of the experiment. The thermodynamic and kinetic stabilities, as well as the bonding features, have been investigated for the most stable dumbbell dimers C118+, C119+, and C120+.

Wang, Y.; Zettergren, H.; Rousseau, P.; Chen, T.; Gatchell, M.; Stockett, M. H.; Domaracka, A.; Adoui, L.; Huber, B. A.; Cederquist, H.; Alcamí, M.; Martín, F.

2014-06-01

164

On the origin of C?? fullerene solubility in aqueous solution.  

PubMed

In this work, we report that the surface hydroxylation of C60 molecules is the most likely mechanism for pristine C60 fullerenes/C60 fullerene aggregate stabilization in water, being independent of the method of C60 fullerene aqueous solution preparation. PMID:24660846

Prylutskyy, Yu I; Petrenko, V I; Ivankov, O I; Kyzyma, O A; Bulavin, L A; Litsis, O O; Evstigneev, M P; Cherepanov, V V; Naumovets, A G; Ritter, U

2014-04-15

165

Dipole polarizability of isovalent carbon and boron cages and fullerenes  

Microsoft Academic Search

Recent works have shown that the nonmetallic alpha -boron cages and fullerenes have valence electronic structures that are identical to those of the corresponding carbon cages and fullerenes to which they are structurally related. By studying the first-order response of these systems ( C60 , B80 , C240 , and B320 fullerenes and C24 and B32 cages) to an applied

Rajendra R. Zope; Tunna Baruah

2009-01-01

166

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

167

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

168

The Differential Cytotoxicity of Water-Soluble Fullerenes  

Microsoft Academic Search

We show that the cytotoxicity of water-soluble fullerene species is a sensitive function of surface derivatization; in two different human cell lines, the lethal dose of fullerene changed over 7 orders of magnitude with relatively minor alterations in fullerene structure. In particular, an aggregated form of C 60, the least derivatized of the four materials, was substantially more toxic than

Christie M. Sayes; John D. Fortner; Wenh Guo; Delina Lyon; Adina M. Boyd; Kevin D. Ausman; Yizhi J. Tao; Balaji Sitharaman; Lon J. Wilson; Joseph B. Hughes; Jennifer L. West; Vicki L. Colvin

2004-01-01

169

Fullerene Production in Tons and More: From Science to Industry  

Microsoft Academic Search

In the last decade, application of fullerenes has been proposed actively in a wide range of areas, and recent developments suggest that many of those applications are to be practical technologies. However, there has been no large?scale production enterprise for commercial usage of fullerenes. High production cost and limited availability of fullerenes have been the main obstacle in the development

Hideki Murayama; Shigeki Tomonoh; J. Michael Alford; Michael E. Karpuk

2005-01-01

170

Tritium Production from Lithium by Deuteron Bombardment  

Microsoft Academic Search

The tritium production cross section has been measured for Li6 bombarded by deuterons from 0.4 Mev to 4.0 Mev. The cross section rises fairly rapidly to 190 millibarns near 1 Mev, then more slowly to 290 millibarns near 4 Mev. The cross section for Li7 rises steeply from the 1.27 Mev threshold to 95 millibarns at 2.4 Mev; then more

R. L. Macklin; H. E. Banta

1955-01-01

171

Neutron Yields from Targets Bombarded by Electrons  

Microsoft Academic Search

The total neutron yields from thick targets bombarded by electrons were measured as a function of electron energy for the range 10 to 36 Mev. Targets ranging in thickness from one to six radiation lengths of C, Al, Cu, Ta, Pb, and U were used. The yields for 1- and 6-radiation-length targets of Pb at 34 Mev are 2.1×10-3 and

W. C. Barber; W. D. George

1959-01-01

172

Pentafluorophenyl Transfer Reaction: Preparation of Pentafluorophenyl [60]Fullerene Adducts through Opening of Fullerene Epoxide Moiety with Trispentafluorophenylborane.  

PubMed

Unlike the extensively studied perfluoroalkyl fullerene adducts, perfluorophenyl fullerene adducts are quite difficult to prepare by known methods. Trispentafluorophenylborane was found to react with fullerene epoxide to form the 1,2-perfluorophenylfullerenol. The method can be applied to both the simple epoxide C60(O) and fullerene multiadducts containing an epoxide moiety. Single crystal X-ray structure analysis confirmed the addition of the pentafluorophenyl group. PMID:24865369

Liang, Sisi; Xu, Liang; Jia, Zhenshan; Gan, Liangbing

2014-06-20

173

Ion bombardment experiments suggesting an origin for organic particles in pre-cometary and cometary ices  

NASA Technical Reports Server (NTRS)

During the Giotto and Vega encounters with Comet Halley both organic particles called CHON and energetic ions were detected. The acceleration of ions to hundreds of keV in the vicinity of the bow shock and near the nucleus may be a demonstration of a situation occurring in the early solar system (perhaps during the T Tauri stage) that led to the formation of organic particles only now released. Utilizing a Van de Graaff accelerator and a target chamber having cryogenic and mass spectrometer capabilities, frozen gases were bombarded at 10 K with 175 keV protons with the result that fluffy solid material remains after sublimation of the ice. Initial experiments were carried out with a gas mixture in parts of 170 carbon monoxide, 170 argon, 25 water, 20 nitrogen, and 15 methane formulated to reflect an interstellar composition in experiments involving the freezing out of the products of a plasma. The plasma experiments resulted in a varnish-like film residue that exhibited luminescence when excited with ultraviolet radiation, while the ion bombardment created particulate material that was not luminescent.

Wdowiak, Thomas J.; Robinson, Edward L.; Flickinger, Gregory C.; Boyd, David A.

1989-01-01

174

INFRARED STUDY OF FULLERENE PLANETARY NEBULAE  

SciTech Connect

We present a study of 16 planetary nebulae (PNe) where fullerenes have been detected in their Spitzer Space Telescope spectra. This large sample of objects offers a unique opportunity to test conditions of fullerene formation and survival under different metallicity environments because we are analyzing five sources in our own Galaxy, four in the Large Magellanic Cloud (LMC), and seven in the Small Magellanic Cloud (SMC). Among the 16 PNe studied, we present the first detection of C{sub 60} (and possibly also C{sub 70}) fullerenes in the PN M 1-60 as well as of the unusual {approx}6.6, 9.8, and 20 {mu}m features (attributed to possible planar C{sub 24}) in the PN K 3-54. Although selection effects in the original samples of PNe observed with Spitzer may play a potentially significant role in the statistics, we find that the detection rate of fullerenes in C-rich PNe increases with decreasing metallicity ({approx}5% in the Galaxy, {approx}20% in the LMC, and {approx}44% in the SMC) and we interpret this as a possible consequence of the limited dust processing occurring in Magellanic Cloud (MC) PNe. CLOUDY photoionization modeling matches the observed IR fluxes with central stars that display a rather narrow range in effective temperature ({approx}30,000-45,000 K), suggesting a common evolutionary status of the objects and similar fullerene formation conditions. Furthermore, the data suggest that fullerene PNe likely evolve from low-mass progenitors and are usually of low excitation. We do not find a metallicity dependence on the estimated fullerene abundances. The observed C{sub 60} intensity ratios in the Galactic sources confirm our previous finding in the MCs that the fullerene emission is not excited by the UV radiation from the central star. CLOUDY models also show that line- and wind-blanketed model atmospheres can explain many of the observed [Ne III]/[Ne II] ratios using photoionization, suggesting that possibly the UV radiation from the central star, and not shocks, is triggering the decomposition of the circumstellar dust grains. With the data at hand, we suggest that the most likely explanation for the formation of fullerenes and graphene precursors in PNe is that these molecular species are built from the photochemical processing of a carbonaceous compound with a mixture of aromatic and aliphatic structures similar to that of hydrogenated amorphous carbon dust.

Garcia-Hernandez, D. A.; Acosta-Pulido, J. A.; Manchado, A. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38205 La Laguna (Spain); Villaver, E. [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Garcia-Lario, P. [Herschel Science Centre, European Space Astronomy Centre, Research and Scientific Support Department of ESA, Villafranca del Castillo, P.O. Box 78, E-28080 Madrid (Spain); Stanghellini, L.; Shaw, R. A. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Cataldo, F., E-mail: agarcia@iac.es, E-mail: amt@iac.es, E-mail: eva.villaver@uam.es, E-mail: Pedro.Garcia-Lario@sciops.esa.int, E-mail: shaw@noao.edu, E-mail: letizia@noao.edu, E-mail: franco.cataldo@fastwebnet.it [Istituto Nazionale di Astrofisica-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania (Italy)

2012-12-01

175

Infrared Study of Fullerene Planetary Nebulae  

NASA Astrophysics Data System (ADS)

We present a study of 16 planetary nebulae (PNe) where fullerenes have been detected in their Spitzer Space Telescope spectra. This large sample of objects offers a unique opportunity to test conditions of fullerene formation and survival under different metallicity environments because we are analyzing five sources in our own Galaxy, four in the Large Magellanic Cloud (LMC), and seven in the Small Magellanic Cloud (SMC). Among the 16 PNe studied, we present the first detection of C60 (and possibly also C70) fullerenes in the PN M 1-60 as well as of the unusual ~6.6, 9.8, and 20 ?m features (attributed to possible planar C24) in the PN K 3-54. Although selection effects in the original samples of PNe observed with Spitzer may play a potentially significant role in the statistics, we find that the detection rate of fullerenes in C-rich PNe increases with decreasing metallicity (~5% in the Galaxy, ~20% in the LMC, and ~44% in the SMC) and we interpret this as a possible consequence of the limited dust processing occurring in Magellanic Cloud (MC) PNe. CLOUDY photoionization modeling matches the observed IR fluxes with central stars that display a rather narrow range in effective temperature (~30,000-45,000 K), suggesting a common evolutionary status of the objects and similar fullerene formation conditions. Furthermore, the data suggest that fullerene PNe likely evolve from low-mass progenitors and are usually of low excitation. We do not find a metallicity dependence on the estimated fullerene abundances. The observed C60 intensity ratios in the Galactic sources confirm our previous finding in the MCs that the fullerene emission is not excited by the UV radiation from the central star. CLOUDY models also show that line- and wind-blanketed model atmospheres can explain many of the observed [Ne III]/[Ne II] ratios using photoionization, suggesting that possibly the UV radiation from the central star, and not shocks, is triggering the decomposition of the circumstellar dust grains. With the data at hand, we suggest that the most likely explanation for the formation of fullerenes and graphene precursors in PNe is that these molecular species are built from the photochemical processing of a carbonaceous compound with a mixture of aromatic and aliphatic structures similar to that of hydrogenated amorphous carbon dust.

García-Hernández, D. A.; Villaver, E.; García-Lario, P.; Acosta-Pulido, J. A.; Manchado, A.; Stanghellini, L.; Shaw, R. A.; Cataldo, F.

2012-12-01

176

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

177

Fullerene (C60) films for solid lubrication  

SciTech Connect

The advent of techniques for producing gram quantities of a new form of stable, pure, solid carbon, designated as fullerene, opens a profusion of possibilities to be explored in many disciplines including tribology. Fullerenes take the form of hollow geodesic domes, which are formed from a network of pentagons and hexagons with covalently bonded carbon atoms. The C60 molecule has the highest possible symmetry (icosahedral) and assumes the shape of a soccer ball. At room temperature, fullerene molecules pack in an fcc lattice bonded with weak van der Waals attractions. Fullerenes can be dissolved in solvents such as toluene and benzene and are easily sublimed. The low surface energy, high chemical stability, spherical shape, weak intermolecular bonding, and high load bearing capacity of C60 molecules offer potential for various mechanical and tribological applications. This paper describes the crystal structure and properties of fullerenes and proposes a mechanism for self-lubricating action. Sublimed films of C60 have been produced and friction and wear performance of these films in various operating environments are the subject of this paper. The results of this study indicate that C60, owing to its unique crystal structure and bonding, may be a promising solid lubricant. 31 refs.

Bhushan, B.; Gupta, B.K.; Van Cleef, G.W.; Capp, C.E.; Coe, J.V. (Ohio State Univ., Columbus (United States))

1993-10-01

178

Energetics of water permeation through fullerene membrane  

PubMed Central

Lipid bilayer membranes are important as fundamental structures in biology and possess characteristic water-permeability, stability, and mechanical properties. Water permeation through a lipid bilayer membrane occurs readily, and more readily at higher temperature, which is largely due to an enthalpy cost of the liquid-to-gas phase transition of water. A fullerene bilayer membrane formed by dissolution of a water-soluble fullerene, Ph5C60K, has now been shown to possess properties entirely different from those of the lipid membranes. The fullerene membrane is several orders of magnitude less permeable to water than a lipid membrane, and the permeability decreases at higher temperature. Water permeation is burdened by a very large entropy loss and may be favored slightly by an enthalpy gain, which is contrary to the energetics observed for the lipid membrane. We ascribe this energetics to favorable interactions of water molecules to the surface of the fullerene molecules as they pass through the clefts of the rigid fullerene bilayer. The findings provide possibilities of membrane design in science and technology.

Isobe, Hiroyuki; Homma, Tatsuya; Nakamura, Eiichi

2007-01-01

179

Experimental thick-target bremsstrahlung spectra from electrons in the range 10 to 30 keV  

Microsoft Academic Search

The x-ray spectra produced by the bombardment of thick targets with monoenergetic electrons between 10 and 30 keV have been determined as a function of the incident and emission angles. Spectra have been obtained for Al, Cu, Mo, and W using a Si(Li) detector. The electron current absorbed in the target was measured and corrected for backscattering, allowing a determination

J. G. Chervenak; A. Liuzzi

1975-01-01

180

Mixing of binary metal systems by noble-gas ions of energies between 30 and 400 keV  

Microsoft Academic Search

Multilayered samples of the binary systems Au-Rh and Ni-Pt were bombarded at 77 K with He-, Ne-, Ar- and Kr-ions at energies between 30 and 400 keV. The maximum irradiation dose was 2 × 1017 ions\\/cm2. All samples were analysed by X-ray diffraction using a Seemann-Bohlin arrangement. In thermal equilibrium the system Au-Rh has vanishingly small mutual solid solubility whereas

W. Hiller; M. Buchgeister; P. Eitner; K. Kopitzki; V. Lilienthal; G. Mertler

1990-01-01

181

Optimally stuffed fullerene structures of silicon nanoclusters  

NASA Astrophysics Data System (ADS)

The stuffed fullerene structures of nanoscale silicon clusters have been studied using density functional theory. Taking Si40 as a prototype, stuffed fullerene cages with a different “stuffing/cage” ratio (i.e., Si4@Si36 , Si6@Si34 , and Si8@Si32 ) and topological structures have been constructed with the aid of local optimization by simulated annealing with tight-binding molecular dynamics. DFT minimization of these “handmade” structures show that the Si6@Si34 is the optimally stuffed cage with lowest energy, in agreement with previous unbiased genetic algorithm optimization with tight-binding method. The optimal ratio between the number of atoms on the fullerene cage and that stuffed inside can be understood by the effect of space filling. The binding energy and electronic properties of Si40 cluster is calculated and compared with available experiments.

Wang, Jinlan; Zhou, Xiaolan; Wang, Guanghou; Zhao, Jijun

2005-03-01

182

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

183

Cage Structure Distortion of Fullerenes  

NASA Astrophysics Data System (ADS)

We report an electron spin resonance (ESR) study on a C60 anion and a metal (M) encapsulated in fullerene (Cn) (a metallofullerene: M@Cn). The anisotropy components of the g-factor of C60- were determined accurately from the analysis of angular-dependent ESR spectra of single crystal C60- salt. The evaluation of the g-factor was performed according to the classification of symmetry of the C60- geometry. It was found out from the evaluation that the molecular structure of C60- should be distorted to lower symmetry, C2h or Ci. The variety of ESR spectra of metallofullerenes of La@Cns was obtained in terms of a g-factor, a hyperfine coupling constant, and a line width. In the case of the isomer I of La@C80 and the isomer II of La@C84, an abnormally large line width was measured. The molecular structure with high symmetry would reflect on the specific spin dynamics.

Kato, Tatsuhisa

184

Fullerenes in an impact crater on the LDEF spacecraft  

NASA Technical Reports Server (NTRS)

The fullerenes C60 and C70 have been found to occur naturally on Earth and have also been invoked to explain features in the absorption spectra of interstellar clouds. But no definitive spectroscopic evidence exists for fullerenes in space and attempts to find fullerenes in carbonaceous chondrites have been unsuccessful. Here we report the observation of fullerenes associated with carbonaceous impact residue in a crater on the Long Duration Exposure Facility (LDEF) spacecraft. Laser ionization mass spectrometry and Raman spectroscopy indicate the presence of fullerenes in the crater and in adjacent ejecta. Man-made fullerenes survive experimental hypervelocity (approximately 6.1 km s-1) impacts into aluminium targets, suggesting that space fullerenes contained in a carbonaceous micrometeorite could have survived the LDEF impact at velocities towards the lower end of the natural particle encounter range (<13 km s-1). We also demonstrate that the fullerenes were unlikely to have formed as instrumental artefacts, nor are they present as contaminants. Although we cannot specify the origin of the fullerenes with certainty, the most plausible source is the chondritic impactor. If, alternatively, the impact produced the fullerenes in situ on LDEF, then this suggests a viable mechanism for fullerene production in space.

Radicati di Brozolo, F.; Bunch, T. E.; Fleming, R. H.; Macklin, J.

1994-01-01

185

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

186

Biomedical applications of functionalized fullerene-based nanomaterials  

PubMed Central

Since their discovery in 1985, fullerenes have been investigated extensively due to their unique physical and chemical properties. In recent years, studies on functionalized fullerenes for various applications in the field of biomedical sciences have seen a significant increase. The ultimate goal is towards employing these functionalized fullerenes in the diagnosis and therapy of human diseases. Functionalized fullerenes are one of the many different classes of compounds that are currently being investigated in the rapidly emerging field of nanomedicine. In this review, the focus is on the three categories of drug delivery, reactive oxygen species quenching, and targeted imaging for which functionalized fullerenes have been studied in depth. In addition, an exhaustive list of the different classes of functionalized fullerenes along with their applications is provided. We will also discuss and summarize the unique approaches, mechanisms, advantages, and the aspect of toxicity behind utilizing functionalized fullerenes for biomedical applications.

Partha, Ranga; Conyers, Jodie L

2009-01-01

187

Morphological characterization of fullerene-androsterone conjugates.  

PubMed

Here we report on the self-organization characteristics in water of two diastereomer pairs of fullerene-androsterone hybrids that have the hydrophobic C60 appendage in the A and D ring of the androsterone moiety, respectively. The morphology and particle size in aqueous solution were determined by transmission electron microscopy (TEM) and dynamic light scattering (DLS), with satisfactory agreement between both techniques. In general, these fullerene derivatives are shown to organize into spherical nano-scale structures with diameters in the ranges of 10-20 and 30-50 nm, respectively. PMID:24778962

Ruiz, Alberto; Suárez, Margarita; Martin, Nazario; Albericio, Fernando; Rodríguez, Hortensia

2014-01-01

188

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

189

Synthesis and investigation of boron-doped fullerene and scandium-containing fullerene  

Microsoft Academic Search

We report on the plasmachemical synthesis of fullerene derivatives containing boron and scandium. The synthesis was conducted\\u000a at atmospheric pressure in a carbon-helium plasma jet generated by an RF arc.

G. N. Churilov; A. S. Alikhanyan; M. I. Nikitin; G. A. Glushchenko; N. G. Vnukova; N. V. Bulina; A. L. Emelina

2003-01-01

190

Fast atom bombardment mass spectrometry of peptides.  

PubMed

The contribution of mass spectrometry to the solution of problems in protein biochemistry was limited until the development of methods of ionization that do not require derivatization or prior vaporization of the sample. Fast atom bombardment (FAB), introduced by Barber et al. in 1981 (1), is one of the most important of these methods, and has been widely applied in the peptide and protein field. In the FAB experiment (Fig. 1), the sample is dissolved in a liquid of low vapor pressure, often glycerol or thioglycerol ("the matrix"), and is bombarded by a beam of energetic particles, such as xenon atoms that sputter sample molecules from the surface layers of the matrix into the mass spectrometer vacuum. Proton or other cation attachment produces abundant (positive) ions characteristic of the sample's molecular mass. A proportion of these molecular ions dissociate, producing structurally informative fragments that are generally less intense than the molecular ions, since the ionization process imparts relatively little excess energy. Negatively charged ions are also generated, and spectra may be recorded in either mode by appropriate selection of the polarity of the ion extraction voltages. At low-mass FAB, spectra are generally dominated by signals attributable to ionization of the matrix. The background of "chemical noise" extending to high mass, which gives FAB spectra their characteristic peak-at-every-mass appearance, is probably attributable to direct hits on sample and matrix molecules by the bombarding species. Figure 2 shows a typical FAB spectrum of the cyclic heptapeptide microcystin-LR, obtained from the cyanobacterium Microcystis aeruginosa. PMID:21400142

Wait, R

1993-01-01

191

Thermal properties of DLC thin films bombarded with ion beams  

Microsoft Academic Search

We have studied the change in the thermal annealing properties of diamond-like carbon (DLC) films bombarded with ion beams. The carbon films were deposited on silicon wafers by evaporating a glassy carbon material. After the depositions, the carbon films were bombarded with argon, nitrogen or helium ions. The bombardments were performed with doses ranging from 5×1015 to 5×1017ionscm?2at acceleration voltages

Y Funada; K Awazu; K Shimamura; M Iwaki

1998-01-01

192

Desorption Induced by KEV Molecular and Cluster Projectiles.  

NASA Astrophysics Data System (ADS)

A new experimental method has been developed for studying negative secondary ion (SI) emission from solid surfaces bombarded by polyatomic primary ions of 5 to 30 keV. The method is based on the time-of-flight (TOF) analysis of primary ions which are produced by either ^ {252}Cf fission fragment induced desorption or by extraction from a liquid metal ion source, and then accelerated into a field free region. The primary ions included organic monomer, dimer, and fragment ions of coronene and phenylalanine, (CsI)_ nCs ^{+} cluster ions, and Au _sp{n}{+} cluster ions. Secondary electrons, emitted from a target surface upon primary ion impact, are used to identify which primary ion has hit the surface. An event-by-event coincidence counting technique allows several secondary ion TOF spectra, correlated to several different primary ions, to be acquired simultaneously. Negative SI yields from organic (phenylalanine and dinitrostilbene), CsI, and Au surfaces have been measured for a number of different mono- and polyatomic primary ions. The results show, for example, yields ranging from 1 to 10% for phenylalanine (M-H) ^{ -}, 1 to 10% for I^{-} , and 1 to 5% for Au^{-} , with Cs_2I^ {+} and Cs_3I _sp{2}{+} clusters as projectiles. Yields for the same surfaces using Cs ^{+} primary ions are much less than 1%, indicating that SI yields are enhanced with clusters. A yield enhancement occurs when the SI yield per atom of a polyatomic projectile is greater than the SI yield of its monoatomic equivalent, at the same velocity. Thus, a (M-H) ^{-} yield increase of a factor of 50, when phenylalanine is bombarded with Cs_3I_sp{2} {+} instead of Cs^{+ }, represents a yield enhancement factor of 10. For the projectiles and samples studied, it was observed that the heavier the mass of the constituents of a projectile, the larger the enhancement effects, and that the largest yield enhancements (with CsI and Au _ n projectiles) occur for the organic target, phenylalanine. One possible explanation for the larger enhancements with organics, namely a thermal spike process, appears unlikely. Experiments with high and low melting point isomers of dinitrostilbene, bombarded with Cs _2I^{+} and Cs^{+} projectiles, showed larger Cs_2I^ {+} yield enhancements for the high melting point isomer.

Blain, Matthew Glenn

1990-01-01

193

Compositional and chemical modifications of V 2O 5 and NaVO 3 induced by N 2+ bombardment  

NASA Astrophysics Data System (ADS)

The chemical and compositional changes induced by 0.5-5 keV N 2+ bombardment of V 2O 5 and NaVO 3 have been studied by XPS. Both the atomic concentrations and the chemical states of the different constituents reach a steady state at an irradiation dose < 10 17{N 2+}/{cm 2}. As in Ar + bombardment of these targets, the vanadium is reduced to lower oxidation states. The reactive nature of the N 2+ species is however reflected by the opening of a chemical channel for oxygen removal (possibly by NO x formation) and retention of 10-20% of the impinging nitrogen in the targets mainly as vanadium nitride, VN.

Mezentzeff, P.; Lifshitz, Y.; Rabalais, J. W.

1990-01-01

194

Phase formation in Au-Al and Cu-Al thin-film systems under ion beam bombardment  

SciTech Connect

Au-Al and Cu-Al thin film bilayers were bombarded at 80 K with Kr/sup +/ ions of 60--240 keV energy. The Au/sub 2/Al+AuAl/sub 2/ and Al/sub 4/Cu/sub 9/ phases formed during bombardment and they were investigated by backscattering and x-ray diffraction techniques. In all the cases the growth kinetics is linear with the parameter (fluence x interfacial deposited energy density)/sup 1//sup ///sup 2/ suggesting a correlation with a diffusion-like process. Comparison with calculations of diffusion enhanced within the collision cascade gives good agreement with the experimental results.

Chang, C.T.; Campisano, S.U.; Cannavo, S.; Rimini, E.

1984-05-01

195

Energetic ion bombarded Fe/Al multilayers  

SciTech Connect

The utility of ion-assisted deposition is investigated to explore the possibility of counteracting the deficiency of back-reflected current of Ar neutrals in the case of lighter elements such as Al. A range of energetically ion bombarded Fe/Al multilayers sputtered with applied surface bias of 0, -200, or -400 V were deposited onto Si(111) substrates in an argon atmosphere of 4 mTorr using a computer controlled dc magnetron sputtering system. Grazing incidence reflectivity and rocking curve scans by synchrotron x rays of wavelength of 1.38 A were used to investigate the structures of the interfaces produced. Substantial evidence has been gathered to suggest the gradual suppression of interfacial mixing and reduction in interfacial roughness with increases of applied bias. The densification of the Al microstructure was noticeable and may be a consequence of resputtering attributable to the induced ion bombardment. The average interfacial roughnesses were calculated for the 0, -200, and -400 V samples to be 7{+-}0.5, 6{+-}0.5, and 5{+-}0.5 A respectfully demonstrating a 30% improvement in interface quality. Data from rocking curve scans point to improved long-range correlated roughness in energetically deposited samples. The computational code based on the recursive algorithm developed by Parratt [Phys. Rev. 95, 359 (1954)] was successful in the simulation of the specular reflectivity curves.

Al-Busaidy, M.S.; Crapper, M.D. [College Science, Physics Department, Sultan Qaboos University, P.O. Box 36, Al-Khod 123 (Oman); Department of Physics, Loughborough University, Loughborough (United Kingdom)

2006-05-15

196

Designing Fullerene Separation Materials: A Theoretical Study  

Microsoft Academic Search

Fullerenes, among other carbon nanostructures, are very promising as potential components for the development of nanodevices and nanomachines. One of the current hurdles in developing such devices is obtaining components\\/molecules of the same size in sufficient quantity. Typically, when carbon nanostructures are synthesized, a distribution of sizes is generated. Therefore, an efficient separation technique is needed. A computational model that

Michael Foster; Karl Sohlberg

2012-01-01

197

Fullerenes and Fulleranes in Meteorites Revisited  

NASA Astrophysics Data System (ADS)

Fullerenes C60 and C70 and the fullerane C60H2 were not found in the toluene extract from 200 g of the C3V carbonaceous chondrite Allende by high-performance liquid chromatography (HPLC). Two distinct substances in the HPLC chromatogram of the extract, called A? and A?, were found to have absorption spectra in the wavelength range 300-650 nm similar in shape to that of C60. The HPLC chromatograms of A? and A? show conclusively that A? and A? are not C60, C70, C60O, or C60H2. The mass spectrometric analysis shows that A? and A? do not contain any fullerene derivatives in the mass range 722 to 800. However, A? may contain corannulene (C20H10), a suggested precursor in the formation of C60 by condensation of carbon vapor. The discrepancy between the results of Becker et al. and Heymann remains essentially unresolved, but the probability of finding fullerenes or fulleranes in samples of the Allende, or other meteorites, has now become very small. The implications of the new results for theories of fullerene and fullerane formation in stellar and interstellar media are that these substances, if they formed in such environments, apparently were destroyed in the interstellar cloud from which the solar system formed, did not survive the formation of the solar system, or did not survive the formation of meteorites.

Heymann, Dieter

1997-11-01

198

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

199

Screening of fullerene toxicity by hemolysis assay.  

PubMed

Fullerene is a compound formed during carbon burst that has been produced synthetically starting from the 1990s. The spherical shape and the characteristic carbon bonds of this allotrope (C(60)) have made it a suitable molecule for many applications. During the last decade, the low aqueous solubility of this molecule has been improved by chemical functionalization allowing the use of fullerene derivatives in biological fluids. The characterization of the toxicity potential of fullerenes is therefore of growing interest for any biomedical application. Intravenous injection is one of the possible routes of their administrations and therefore red blood cells are among the first targets of fullerene cytotoxicity. Human red blood cells are easily available and separated from plasma. Membrane disruption by toxic compounds is easily detected in red blood cells as release of hemoglobin in the cell medium, which can be assayed spectrophotometrically at ? = 415 nm. Due to the high molar extinction coefficient of hemoglobin, the assay can be performed on a small amount of both red blood cells and the test compounds, which might be available only in small quantities. So, the hemolysis assay is a simple screening test, whose results can guide further investigations on cytotoxicity in more complex experimental models. PMID:22975967

Tramer, Federica; Da Ros, Tatiana; Passamonti, Sabina

2012-01-01

200

IEC plasma discharge for fullerene production  

Microsoft Academic Search

Summary form only given, as follows. One approach to fullerene production is the a use of a hydrocarbon such as methane in a plasma discharge. The efficiency of this approach is hampered, however, because hydrogen atoms in the discharge can quench the recombination of carbon atoms prior to full C60 formation. Inertial electrostatic confinement (IEC) offers a possible solution, however.

B. Jurczyk; G. H. Miley

1998-01-01

201

Fullerenes in the highly excited state  

Microsoft Academic Search

Under high intensity illumination, the optical and electronic properties of fullerenes are seen to undergo dramatic, nonlinear changes. The photoluminescence emission is seen to increase with approximately the third power of the input intensity above an apparent threshold intensity. Associated with this nonlinear increase is the emergence of a long lifetime emission component and a redshifting of the emission spectrum.

H. J. Byrne; W. K. Maser; M. Kaiser; L. Akselrod; J. Anders; W. W. Rühle; X.-Q. Zhou; A. Mittelbach; S. Roth

1993-01-01

202

Broadband electroluminescent emission from fullerene crystals  

Microsoft Academic Search

The observation of electroluminescence from crystalline fullerenes is described and discussed for the first time. Using gold and aluminium electrodes as contacts, a broad band emission spectrum, extending from 400 nm to 1100 nm is observed. The spectrum has a primary maximum at 920 nm and a weaker feature centered on 420 nm. The spectral characteristics are independent of the

A. T. Werner; J. Anders; H. J. Byrne; W. K. Maser; M. Kaiser; A. Mittelbach; S. Roth

1993-01-01

203

Ultrafast nonlinear optical response of higher fullerenes  

NASA Astrophysics Data System (ADS)

Experimental results are presented concerning the electronic nonlinear optical response of C60 and higher fullerenes, i.e. C70, C76, C82, C84 and C92 under 100 fsec, 800 nm laser excitation. The Optical Kerr Effect technique is employed for the determination of the magnitude of the third order nonlinear susceptibility.

Koudoumas, E.; Couris, Stelios

2003-04-01

204

Preferable Fullerenes and Clar-Sextet Cages  

Microsoft Academic Search

All 558 fullerenes satisfying the isolated-pentagon rule and having no more than 96 vertices are generated and analyzed. A novel subclass of cages of especially favored ?-network “topology” is identified, given several structural characterizations, and all such cages of up to 120 vertices are generated and analyzed.

X. Liu; D. J. Klein; T. G. Schmalz

1994-01-01

205

Electron transport in carbon nanotubes encapsulating fullerenes  

Microsoft Academic Search

We study the transport properties of hybrid carbon nanotubes that contain a carbon nanotube capsule and a chain of fullerenes. We find that electron transmissions through the outer tubes are very sensitive to the alignment of inner shells. For a (5,5) capsule in the (10,10) tube, mirror symmetries in cross sections determine the lineshape of antiresonances. For a chain of

D.-H. Kim; H.-S. Sim; K. J. Chang

2001-01-01

206

Tailoring optical properties of WO3 films in the visible to infrared range by ion bombardment and its description by an oscillator model  

Microsoft Academic Search

Evaporated and sputtered tungstentrioxide (WO3) films were bombarded with 300-keV He+ and Ar+ ions, respectively, and the resulting changes of the real [n(lambda)] and imaginary [k(lambda)] parts of the refractive index in the visible to infrared range of the wavelength lambda were determined in situ. The primary effect of an ion-induced blue coloration is directly reflected by an absorption band

Matthias Merz; Johannes Eisenmenger; Bernd Heinz; Paul Ziemann

2002-01-01

207

Advances in fast-atom-bombardment mass spectroscopy  

Microsoft Academic Search

A comparison of fast atom bombardment and field desorption mass spectrometry was made to determine relative sensitivity and applicability. A series of glycosphingolipids and a series of protected oligonucleotides of known structure were analyzed to ascertain the potential utility of fast atom bombardment mass spectrometry in the structural elucidation of novel compounds in these classes. Negative ion mass markers were

Hemling

1986-01-01

208

Magnetospheric ion bombardment profiles of satellites - Europa and Dione  

Microsoft Academic Search

Bombardment profiles generated by tracking ions in magnetospheric plasmas onto the surface of a satellite with a suitable description of the ion motion are used to calculate the spatial dependence across a satellite surface of the ion bombardment\\/implantation rate for satellites embedded in planetary magnetospheric plasmas. Attention is given to the results of a parameter study; a general dependency on

M. K. Pospieszalska; R. E. Johnson

1989-01-01

209

Transformation of 12 different plasmids into soybean via particle bombardment  

Microsoft Academic Search

Particle bombardment offers a simple method for the introduction of DNA into plant cells. Multiple DNA fragments may be introduced on a single plasmid or on separate plasmids (co-transformation). To investigate some of the properties and limits of co-transformation, 12 different plasmids were introduced into embryogenic suspension culture tissue of soybean [Glycine max (L.) Merrill] via particle bombardment. The DNAs

Masood Z. Hadi; Michael D. McMullen; John J. Finer

1996-01-01

210

Dark Blue Ring developed by Electron Bombardment in Rock Salt  

Microsoft Academic Search

WE have recently studied the effect of electron bombardment on rock salt crystal obtained from the Halle Company in Germany. It was found that the blue or colloidal coloration was produced on the surface of the specimen bombarded with electrons at high temperature1. In the course of the experiments we have also observed that the dark blue rings or circles

S. Yoshida; T. Ikeda

1960-01-01

211

Fullerene-based materials research and development. LDRD final report  

SciTech Connect

The chemistry and physical properties of fullerenes, the third, molecular allotrope of carbon, have been studied using both experimental and computational techniques. Early computational work investigated the stability of fullerene isomers and oxides, which was followed by extensive work on hydrogenated fullerenes. Our work led to the first synthesis of a polymer containing C{sub 60} and the synthesis of the simplest hydrocarbon derivatives of C{sub 60} and C{sub 70}. The excellent agreement between theory and experiment ({plus_minus} 0.1 kcal/mol in the relative stability of isomers) has provided insight into the chemical nature of fullerenes and has yielded a sound basis for prediction of the structure of derivatized fullerenes. Such derivatives are the key to the preparation of fullerene-based materials.

Cahill, P A; Henderson, C C; Rohlfing, C M; Loy, D A; Assink, R A; Gillen, K T; Jacobs, S J; Dugger, M T

1995-05-01

212

Fullerenes: An extraterrestrial carbon carrier phase for noble gases  

PubMed Central

In this work, we report on the discovery of naturally occurring fullerenes (C60 to C400) in the Allende and Murchison meteorites and some sediment samples from the 65 million-year-old Cretaceous/Tertiary boundary layer (KTB). Unlike the other pure forms of carbon (diamond and graphite), fullerenes are extractable in an organic solvent (e.g., toluene or 1,2,4-trichlorobenzene). The recognition of this unique property led to the detection and isolation of the higher fullerenes in the Kratschmer/Huffmann arc evaporated graphite soot and in the carbon material in the meteorite and impact deposits. By further exploiting the unique ability of the fullerene cage structure to encapsulate and retain noble gases, we have determined that both the Allende and Murchison fullerenes and the KTB fullerenes contain trapped noble gases with ratios that can only be described as extraterrestrial in origin.

Becker, Luann; Poreda, Robert J.; Bunch, Ted E.

2000-01-01

213

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

214

Structure property relationships for the nonlinear optical response of fullerenes  

NASA Astrophysics Data System (ADS)

We present a phenomenological theory of nonlinear optical response of fullerenes. An empirical tight-binding model is used in conjunction with a classical electromagnetic picture for the screening. Since in bulk media such a picture of screening corresponds to the self- consistent field approach, the only additional approximation involved in our approach is the neglect of nonlocality. We obtain reliable estimates for the linear and nonlinear susceptibilities of C60, C70, C76 and other pure carbon fullerenes and also substituted fullerenes. The relatively large values of (beta) that we obtain for C76 and substituted fullerenes appear promising for the development of fullerene-based nonlinear optical materials. Our phenomenological picture of screening provides a good understanding of the linear absorption spectra of higher fullerenes and predicts that a comparison of the one-photon and multi-photon spectra will provide an insight into screening effects in these systems.

Rustagi, Kailash C.; Ramaniah, Lavanya M.; Nair, Selvakumar V.

1994-11-01

215

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.

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

2012-01-01

216

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

217

Feldspathic granulitic impactites and pre-final bombardment lunar evolution  

NASA Technical Reports Server (NTRS)

It is suggested that feldspathic granulitic impactites, which are characterized by a high model plagioclase content of between 70 and 80%, all formed in the period after consolidation of the lunar crust and before the final bombardment. The granulitic impactites contain essentially no KREEP component, which suggests that KREEP appeared on the lunar surface mostly after the formation of the granulitic impactites, at about the start of the final bombardment. The granulite metamorphism indicated by the matrix textures of these samples requires 1000 C temperatures for prolonged periods of time. The apparent sequence of formation is granulitic impactites before the final bombardment, crystalline-matrix breccias during the final bombardment, and vitric-matrix breccias after the final bombardment. The sequence is consistent with a described thermal model of breccia lithification and with characteristics of the decay of the meteorite flux rate.

Warner, J. L.; Phinney, W. C.; Bickel, C. E.; Simonds, C. H.

1977-01-01

218

Surface chemical modification of fullerene by mechanochemical treatment  

NASA Astrophysics Data System (ADS)

In this study different encapsulating agents have been used for chemical modification of fullerenes. Fullerenes have reacted with tetrahydrofuran, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and ethylene vinyl acetate-ethylene vinyl versatate at room temperature under mechanical milling. The obtained powder has been dispersed in water by ultrasonication. The fullerene based colloids have been characterized by UV-vis, FTIR, Raman spectroscopy and atomic force microscopy. FTIR and Raman analysis have shown the presence of C 60 after surface functionalization.

Todorovi? Markovi?, B.; Jokanovi?, V.; Jovanovi?, S.; Kleut, D.; Drami?anin, M.; Markovi?, Z.

2009-06-01

219

Polythermal solubility of fullerenes in higher isomeric carboxylic acids  

Microsoft Academic Search

The solubility of individual fullerenes C60 and C70 and a fullerene mixture enriched in higher fullerenes (C60 38.8, C70 33.0, C76–78 5.6, C84 8.6, C90 2.6, and C96 3.3%) in higher isomeric carboxylic acids was studied within the 20–80C temperature range; the corresponding solubility\\u000a polytherms are presented.

K. N. Semenov; O. V. Arapov; A. K. Pyartman; V. A. Keskinov; V. V. Lishchuk; N. A. Charykov; N. I. Alekseev

2007-01-01

220

Topological edge properties of C60+12 n fullerenes  

PubMed Central

Summary A molecular graph M is a simple graph in which atoms and chemical bonds are the vertices and edges of M, respectively. The molecular graph M is called a fullerene graph, if M is the molecular graph of a fullerene molecule. It is well-known that such molecules exist for even integers n ? 24 or n = 20. The aim of this paper is to investigate the topological properties of a class of fullerene molecules containing 60 + 12n carbon atoms.

Mottaghi, A

2013-01-01

221

Fullerene Materials for Lithium-ion Battery Applications  

Microsoft Academic Search

Novel and high-performance anode materials based on modified fullerene materials, for lithium-ion rechargeable batteries were\\u000a developed. The technical feasibility of lithium-ion intercalation and de-intercalation based on the degree of anion or atomic\\u000a modification of the fullerene was examined. In this approach the fullerene molecule is viewed as a large anchor molecule to\\u000a which various anion or atoms can be attached

Raouf O. Loutfy; S. Katagiri

222

Progress in Fullerene Chemistry: From Exohedral Functionalization to Heterofullerenes  

Microsoft Academic Search

Various types of cycloaddition such as [2+1], [2+3], and Diels-Alder reactions have been investigated for the purpose of exohedral functionalization of [60]fullerene and also in few cases of [70]fullerene. Thermal and photochemical activation have been used and lead to a variety of new fullerene derivatives which may be further functionalizable. In addition, a new approach to aza-heterofullerenes has been developed

Johannes Averdung; Gregorio Torres-Garcia; Heinrich Luftmann; Ingo Schlachter; Jochen Mattay

1996-01-01

223

[Study of cytotoxicity of fullerene C60 derivatives].  

PubMed

We investigated the cytotoxicity of the fullerene C60 derivatives. We showed that complexes of C60 fullerene with polyvinylpyrrolidone (m.w. of polyvinylpyrrolidone 10000 and 25000), C60-NO2-proline and C60-alanine had no toxic effect on HEp-2 cells. Sodium salt of polycarboxylic derivative of fullerene C60 exerted a pronounced toxic effect on this cell culture. PMID:23136765

Bobylëv, A G; Okuneva, A D; Bobylëva, L G; Fadeeva, I S; Fadeev, R S; Salmov, N N; Poddubnaia, Z A

2012-01-01

224

Protective Fullerene (C60) Packaging System for Microelectromechanical Systems Applications  

NASA Technical Reports Server (NTRS)

The invention involves a method for locating the probe of a scanning tunneling micrograph a predetermined distance from its conducting surface, and specifically the deposition of a monolayer of fullerene C60 onto the conducting plate. The Fullerene C60 molecule is approximately spherical and a monolayer of fullerene has a thickness of one nanometer. By providing a monolayer of fullerene on the conducting surface and locating the probe on the surface of the monolayer, a distance of one nanometer can be established between the probe tip and the conducting surface.

Olivas, John D. (Inventor)

2001-01-01

225

Higher fullerenes: Compositional analysis by EDXD and molecular dynamics  

NASA Astrophysics Data System (ADS)

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; Gontrani, Lorenzo

2014-06-01

226

Processing and characterization of copper-fullerene systems  

NASA Astrophysics Data System (ADS)

Nanocrystalline copper-fullerene thin films were simultaneously co-deposited by copper evaporation and fullerene sublimation, and annealed over a range from 200 to 800sp°C for 8 hours in flowing argon. Scanning electron microscopy, transmission electron microscopy, electron probe micro analysis, x-ray diffraction and extended x-ray absorption fine structure analysis were used to characterize the films before and after annealing. These analyses show that fullerenes were dispersed at a microscopic level in the uniform thin films by the co-deposition technique. The fullerenes were observed to segregate at the copper grains boundaries. The copper grains were refined with the nanosize fullerene particles during the co-deposition. Comparing to the pure copper thin films, grain growth in the fullerene-copper thin films was significantly suppressed by the dispersed fullerenes when the annealing temperature was lower than 400sp°C. Grain growth occurred when the films annealed above 400sp°C where the fullerenes were separated from the copper matrix. Furthermore, a model for a Cu-Csb{60} system was proposed to provide a better understanding of the interactions between copper atoms and fullerene molecules. This model suggests that fullerene segregation and its concentrations at the copper grain boundaries are the two major factors in determining the microstructures of the copper-fullerene thin films during co-deposition and annealing. The Zener pinning theory was used to explain the copper grain size stabilization with the fullerene dispersion. It was revealed that the stabilized grain size is a function of the grain boundary saturation concentrations of the fullerenes. The oxidation of the films, the formation of holes and hillocks were also explored. Bulk copper-fullerene composites were processed by powder metallurgy with dry and wet mixing techniques. Fullerene dispersion was achieved at an intergranular level. Hot isostatic pressing was applied during sintering to control porosity. The copper grain sizes at sintering temperatures over a range from 850 to 1050sp°C for 2 hours in flowing argon were determined with metallographic technique. The relationships between grain growth, sample porosity and fullerene addition were discussed.

Sheng, Xiayang

227

Generation of singlet oxygen in fullerene-containing media: 2. Fullerene-containing solutions  

SciTech Connect

The generation of singlet oxygen in fullerene solutions is studied by luminescence methods upon excitation by pulsed, repetitively pulsed, and continuous radiation sources. The concentration of singlet oxygen in solutions is measured in stationary and pulsed irradiation regimes. The rate constants of quenching of O{sub 2}({sup 1}{delta}{sub g}) by fullerenes C{sub 70} and C{sub 60} in the CCl{sub 4} solution are measured to be (7.2{+-}0.1)x10{sup 7} L mol{sup -1} s{sup -1} and less than 6x10{sup 4} L mol{sup -1} s{sup -1}, respectively. The temperature and photolytic variations in the generation properties of the fullerene solution exposed to intense continuous radiation are studied by the methods of optical and EPR spectroscopy. Pulsed irradiation resulted in the production of singlet oxygen in suspensions of fullerene-like structures, in particular, astralenes. A liquid pulsed singlet-oxygen generator based on the fullerene solution in CCl{sub 4} is developed and studied, in which the yield of O{sub 2} ({sup 1}{delta}{sub g}) to the gas phase at concentrations up to 5x10{sup 16} cm{sup -3} is obtained. (laser applications and other topics in quantum electronics)

Bagrov, I V; Belousova, I M; Grenishin, A S; Danilov, O B; Ermakov, A V; Kiselev, V M; Kislyakov, I M; Murav'eva, T D; Sosnov, E N [Institute for Laser Physics, Federal State Unitary Enterprise, Scientific and Industrial Corporation 'Vavilov State Optical Institute', St. Petersburg (Russian Federation)

2008-03-31

228

Fullerene sugar balls: a new class of biologically active fullerene derivatives.  

PubMed

Among the large variety of bioactive C60 derivatives, fullerene derivatives substituted with sugar residues, that is, glycofullerenes, are of particular interest. The sugar residues are not only solubilizing groups; their intrinsic biological properties also provide additional appealing features to the conjugates. The most recent advances in the synthesis and the biological applications of glycofullerenes are summarized in the present review article with special emphasis on globular glycofullerenes, that is, fullerene sugar balls, constructed on a hexa-substituted fullerene scaffold. The high local concentration of carbohydrates around the C60 core in fullerene sugar balls is perfectly suited to the binding of lectins through the "glycoside cluster effect", and these compounds are potential anti-adhesive agents against bacterial infection. Moreover, mannosylated fullerene sugar balls have shown antiviral activity in an Ebola pseudotyped infection model. Finally, when substituted with peripheral iminosugars, dramatic multivalent effects have been observed for glycosidase inhibition. These unexpected observations have been rationalized by the interplay of interactions involving the catalytic site of the enzyme and non-glycone binding sites with lectin-like abilities. PMID:24678063

Nierengarten, Iwona; Nierengarten, Jean-François

2014-06-01

229

Emission of neutral molecules from ion-bombarded thiol self-assembled monolayers  

NASA Astrophysics Data System (ADS)

We have investigated ion-stimulated desorption of neutral molecules emitted from 8 keV Ar + ion-bombarded self-assembled monolayers (SAMs) of phenethyl mercaptan (PEM) C 6H 5CH 2CH 2-SH and 2-(4 '-methyl-biphenyl-4yl)-ethanethiol (BP2) CH 3C 6H 4C 6H 4CH 2CH 2-SH deposited on Au(1 1 1) substrate. Neutral molecules were detected by laser postionization mass spectrometry. Only molecular fragments were detected from ion-bombarded systems. The mass spectra obtained for sputtered and gas phase fragments indicate that molecules recorded during ion bombardment were indeed emitted from the surface and were not the result of photofragmentation induced by the ionizing laser beam. From experimentally obtained time-of-flight (TOF) distributions, it was determined that the majority of desorbed neutral molecules leave the surface with very low translational energies. As the sample temperature is reduced, the distributions become broader and shift to longer flight times. The shift is more pronounced for molecules from BP2 and increases with the mass of the recorded molecular fragment. We postulate that the emission of molecules is initiated by processes which gently break molecular bonds (e.g., chemical reactions, secondary electrons). The formed fragments are loosely bound to the surface and can be removed by evaporation. At the investigated temperature range (170-350 K), the observed emission delay is attributed to the time required for the molecule to evaporate from the surface and is not influenced by the bond breaking rate.

Postawa, Z.; Meserole, C. A.; Cyganik, P.; Szymo?ska, J.; Winograd, N.

2001-08-01

230

Solubility of Fullerenes in Fatty Acids Esters: A New Way to Deliver In Vivo Fullerenes. Theoretical Calculations and Experimental Results  

Microsoft Academic Search

The biological effects of fullerenes and, in particular, of C60 have been recognized since long time. One of the problems which hindered the application of fullerenes in medicinal chemistry\\u000a regards their insolubility in water and water-based fluids. In the present chapter it is reported that C60 and C70 fullerenes are soluble in vegetable oils, in general, in esters of fatty

Franco Cataldo

2008-01-01

231

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

232

Blistering of molybdenum-base alloy TZM under helium ion bombardment  

SciTech Connect

Polycrystalline TZM alloy samples have been irradiated at room temperature with helium ions of energy from 75--350 keV in high vacuum. Irradiation parameters such as ion energy, total dose, and ion flux were varied, and the surfaces were examined in a scanning electron microscope. The critical dose for blister formation was found to lie between 4 and 7 x 10/sup 17/ ions cm/sup -2/ and is independent of the beam flux in the range 6.7 x 10/sup 13/--2 x 10/sup 15/ ions cm/sup -2/ s/sup -1/. However, within this flux range the average blister diameter increases with the flux and the blister number density, and the exfoliation maximizes at an intermediate flux. Blister-cover thickness for TZM is found to be less than that for molybdenum, although the average blister diameter for the two materials differs only at the highest energy used. When the TZM surface is successively bombarded with varying ion energies, blistering is reduced compared to monoenergetic helium bombardment, but this reduction is not as substantial as for pure molybdenum.

Daly, J.G.; Sinha, M.K.

1980-06-01

233

Self-organized antireflecting nano-cone arrays on Si (100) induced by ion bombardment  

NASA Astrophysics Data System (ADS)

Self-organized nano-cone arrays are fabricated on Si (100) by means of Ar+ ion bombardment at normal incidence with ion energy of 1.5 keV and current density of 1000 µA cm-2. The nano-structured Si surface appears black as seen by the naked eye. The measured reflectance of the surface is less than 11% over the wavelength range from 350 to 2000 nm as compared to that of >~30% for the polished Si. An enhancement of more than 25% in absorption is observed in this region. The cones are densely distributed over the surface with an average height of ~350 nm and base width of ~250 nm. Incorporation of metal atoms such as Fe and Cr is found to be mandatory for the formation of the nano-structures during ion bombardment. High-resolution electron spectra show that for each cone, the apex is metal-enriched, and the rest is nearly free of metal atoms, showing good crystallinity with the same crystallographic orientation as the substrate.

Zhou, Jing; Hildebrandt, Meret; Lu, Ming

2011-03-01

234

Fe K? line emission from the Arches cluster region - evidence for ongoing particle bombardment?  

NASA Astrophysics Data System (ADS)

Context. Bright Fe-K? line emission at 6.4 keV is a unique characteristic of some of the dense molecular complexes present in the Galactic center region. Whether this X-ray fluorescence is due largely to the irradiation of the clouds by X-ray photons or is, at least in part, the result of cosmic-ray particle bombardment, remains an interesting open question. Aims: We present the results of XMM-Newton observations performed over the last eight years of the region surrounding the Arches cluster in the Galactic center. We study the spatial distribution and temporal behaviour of the Fe-K? emission with the objective of identifying the likely source of the excitation. Methods: We have constructed an Fe-K? fluence map in a narrow energy band of width 128 eV centered on 6.4 keV. We use this to localize the brightest fluorescence features in the vicinity of the Arches cluster. We have investigated the variability of the 6.4-keV line emission of several clouds through spectral fitting of the EPIC MOS data with the use of a modelled background, which avoids many of the systematics inherent in local background subtraction. We also employ spectral stacking of both EPIC PN and MOS data to search for evidence of an Fe-K edge feature imprinted on the underlying X-ray continuum. Results: The lightcurves of the Fe-K? line emission from three bright molecular knots close to the Arches cluster were found to be constant over the 8-year observation window. However, West of the cluster, we found a bright cloud which shows the fastest Fe-K? variability yet seen in a molecular cloud in the Galactic center region. The time averaged spectra of the molecular clouds revealed no convincing evidence of the 7.1-keV edge feature, albeit with only weak constraints. The EW of the 6.4-keV line emitted by the clouds near to the cluster was found to be ~1.0 keV. Conclusions: The observed Fe-K? line flux and the high value of the EW suggest an origin of the fluorescence in the photoionization of the MCs by X-ray photons, although excitation by cosmic-ray particles is not specifically excluded. For the three clouds nearest to the Arches cluster, the identification of the source of these X-rays as an earlier outburst on Sgr A* is at best tentative, although not entirely ruled out by the observations. On the other hand, the hardness of the nonthermal component associated with the 6.4-keV line emission might be best explained in terms of the bombardment of the clouds by cosmic-ray particles emanating from the Arches cluster itself. The relatively short-timescale variability seen in the 6.4-keV line emission from the cloud to the west of the cluster is most likely the result of its X-ray illumination by a nearby transient X-ray source.

Capelli, R.; Warwick, R. S.; Porquet, D.; Gillessen, S.; Predehl, P.

2011-06-01

235

Solubility of Fullerenes in Fatty Acids Esters: A New Way to Deliver In Vivo Fullerenes. Theoretical Calculations and Experimental Results  

NASA Astrophysics Data System (ADS)

The biological effects of fullerenes and, in particular, of C60 have been recognized since long time. One of the problems which hindered the application of fullerenes in medicinal chemistry regards their insolubility in water and water-based fluids. In the present chapter it is reported that C60 and C70 fullerenes are soluble in vegetable oils, in general, in esters of fatty acids and in free fatty acids. These results pave the way in the utilization of vegetable oils as vehicles in the delivery of fullerenes for both topical applications and internal use (e.g., intramuscular injection).

Cataldo, Franco

236

Transport of fullerene molecules along graphene nanoribbons  

PubMed Central

We study the motion of C60 fullerene molecules and short-length carbon nanotubes on graphene nanoribbons. We reveal that the character of the motion of C60 depends on temperature: for T < 150?K the main type of motion is sliding along the surface, but for higher temperatures the sliding is replaced by rocking and rolling. Modeling of the buckyball with an included metal ion demonstrates that this molecular complex undergoes a rolling motion along the nanoribbon with the constant velocity under the action of a constant electric field. The similar effect is observed in the presence of the heat gradient applied to the nanoribbon, but mobility of carbon structures in this case depends largely on their size and symmetry, such that larger and more asymmetric structures demonstrate much lower mobility. Our results suggest that both electorphoresis and thermophoresis can be employed to control the motion of carbon molecules and fullerenes.

Savin, Alexander V.; Kivshar, Yuri S.

2012-01-01

237

Boron hydride analogues of the fullerenes  

SciTech Connect

The BH moiety is isoelectronic with C. We have studied the stability of the (BH)[sub 60] analogue of the C[sub 60] fullerene as well as the dual-structure (BH)[sub 32] icosahedron, both of them being putative structures, by performing local-density-functional electronic calculations. To aid in our analysis, we have also studied other homologues of these systems. We find that the latter, i.e., the dual structure, is the more stable although the former is as stable as one of the latter's lower homologues. Boron hydrides, it seems, naturally form the dual structures used in algorithmic optimization of complex fullerene systems. Fully relaxed geometries are reported as well as electron affinities and effective Hubbard [ital U] parameters. These systems form very stable anions and we conclude that a search for BH analogues of the C[sub 60] alkali-metal supeconductors might prove very fruitful.

Quong, A.A. (Sandia Livermore National Laboratory, Livermore, California 94551-0969 (United States)); Pederson, M.R.; Broughton, J.Q. (Naval Research Laboratory, Washington, D.C. 20375 (United States))

1994-08-15

238

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.

2014-01-01

239

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

240

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

241

Transport of fullerene molecules along graphene nanoribbons  

NASA Astrophysics Data System (ADS)

We study the motion of C60 fullerene molecules and short-length carbon nanotubes on graphene nanoribbons. We reveal that the character of the motion of C60 depends on temperature: for T < 150 K the main type of motion is sliding along the surface, but for higher temperatures the sliding is replaced by rocking and rolling. Modeling of the buckyball with an included metal ion demonstrates that this molecular complex undergoes a rolling motion along the nanoribbon with the constant velocity under the action of a constant electric field. The similar effect is observed in the presence of the heat gradient applied to the nanoribbon, but mobility of carbon structures in this case depends largely on their size and symmetry, such that larger and more asymmetric structures demonstrate much lower mobility. Our results suggest that both electorphoresis and thermophoresis can be employed to control the motion of carbon molecules and fullerenes.

Savin, Alexander V.; Kivshar, Yuri S.

2012-12-01

242

Phase diagram of model Cn >= 70 fullerenes  

NASA Astrophysics Data System (ADS)

Recent studies have confirmed that model C60 has a stable liquid phase confined to a rather narrow temperature range; in this letter we determine the phase diagram of model C70 and show that also this fullerene possesses a liquid phase whose existence range is wider than that of C60. A "corresponding state"behaviour of C60 and C70, emerging from a description in terms of reduced quantities of both the interaction potential and the phase diagrams' parameters, is then extended to higher-order fullerenes. Critical- and triple-point densities and temperatures of C76, C84 and C92 are thereby predicted. The decreasing accuracy of such a representation of Cn > 70 phase behaviour with increasing n is discussed in relation to the model potential features.

Abramo, M. C.; Caccamo, C.; Costa, D.; Pellicane, G.

2001-05-01

243

Boron hydride analogues of the fullerenes  

Microsoft Academic Search

The BH moiety is isoelectronic with C. We have studied the stability of the (BH)[sub 60] analogue of the C[sub 60] fullerene as well as the dual-structure (BH)[sub 32] icosahedron, both of them being putative structures, by performing local-density-functional electronic calculations. To aid in our analysis, we have also studied other homologues of these systems. We find that the latter,

Andrew Quong; Mark Pederson; Jeremy Broughton

1994-01-01

244

Boron hydride analogues of the fullerenes  

Microsoft Academic Search

The BH moiety is isoelectronic with C. We have studied the stability of the (BH)60 analogue of the C60 fullerene as well as the dual-structure (BH)32 icosahedron, both of them being putative structures, by performing local-density-functional electronic calculations. To aid in our analysis, we have also studied other homologues of these systems. We find that the latter, i.e., the dual

Andrew A. Quong; Mark R. Pederson; Jeremy Q. Broughton

1994-01-01

245

Fullerenes surface gratings for liquid crystal alignment  

SciTech Connect

We report on the formation of surface structures by photopolymerization of C{sub 60} and C{sub 70} in isotropic solutions. The structures show the same periodicity of the interference patterns used for photopolymerization and behave as diffraction gratings. Mass spectrometry confirmed that the deposited material contains polymerized fullerenes, while the structure of the deposit was investigated by atomic force microscopy. We have also shown that these periodic structures are useful for inducing mesophase orientation.

Talarico, Mara; Carbone, Giovanni; Barberi, Riccardo; Golemme, Attilio [Centro di Eccellenza MIUR CEMIF.CAL, Universita della Calabria, 87036 Rende (Italy)

2004-07-26

246

Optical limiting materials based on fullerene derivatives  

SciTech Connect

A functionalized fulleropyrrolidine has been synthesized and investigated for optical limiting applications. Solid materials have been prepared for optical limiting devices by incorporation in sol-gel glasses. Their nonlinear transmission properties have been measured and found comparable with those of solution samples. We show that clustering of the fullerene spheres, which might affect the optical limiting properties, is not relevant. Multilayer structures following a bottleneck design are prepared and their NL transmission properties are characterized. (c) 1999 American Institute of Physics.

Prato, Maurizio [Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa, 1, 34127 Trieste, (Italy); Maggini, Michele [Centro Meccanismi di Reazioni Organiche del CNR, Dipartimento di Chimica Organica, Universita di Padova, (Italy); Scorrano, Gianfranco [Centro Meccanismi di Reazioni Organiche del CNR, Dipartimento di Chimica Organica, Universita di Padova, (Italy); Brusatin, Giovanna [Dipartimento di Ingegneria Meccanica, Universita di Padova, (Italy); Guglielmi, Massimo [Dipartimento di Ingegneria Meccanica, Universita di Padova, (Italy); Meneghetti, Moreno [Dipartimento di Chimica Fisica, Universita di Padova, (Italy); Signorini, Raffaella [Dipartimento di Chimica Fisica, Universita di Padova, (Italy); Bozio, Renato [Dipartimento di Chimica Fisica, Universita di Padova, (Italy); Guldi, Dirk M. [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46656 (United States)

1999-09-30

247

Some New Aspects of Chlorination of Fullerenes  

Microsoft Academic Search

The effect of the reagent ratio, reaction time and power of the reagent on the product composition in chlorination of [60]fullerene was studied. Chlorofullerenes C60Cl6, C60Cl8, C60Cl10, C60Cl12, C60Cl14, and C60Cl26 were synthesized and characterized by chemical analysis, FTIR, C NMR, and MALDI TOF mass spectrometry. The experimental data supported the coexistence of several isomers of C60Cln (n = 8, 10, 12,

P. A. Troshin; O. Popkov; R. N. Lyubovskaya

2003-01-01

248

Nanomedicine: Fullerene and Carbon Nanotube Biology  

Microsoft Academic Search

Nanotechnology is the focus of major government research initiatives worldwide, for example in the USA - the National Nanotechnology\\u000a Initiative (www.nano.gov) [1]. It has been recognized that fullerenes and carbon nanotubes are one of the key building blocks for nanoscale materials\\u000a [2]. Considering the especially rich chemistry of C60 and its 1 nm dimensions (Figure 1A), one expects that applications

Stephen R. Wilson

249

Optical Properties of Fullerene-Based Materials  

Microsoft Academic Search

In this dissertation I have presented results of my optical studies of fullerene-based solids: pristine solid C_{60}, alkali-metal (M) doped C_{60} rm(M_6C_{60}) and phototransformed C_{60}.. Raman scattering and infrared spectroscopy were used to study the vibrational modes and it was found that modes observed experimentally were intramolecular modes whose frequencies were found in reasonable agreement with theoretical predictions for an

Ying Wang

1993-01-01

250

Supramolecular ordering in oligothiophene-fullerene monolayers.  

PubMed

Scanning tunneling microscopy (STM) of monolayers comprising oligothiophene and fullerene molecular semiconductors reveals details of their molecular-scale phase separation and ordering with potential implications for the design of organic electronic devices, in particular future bulk heterojunction solar cells. Prochiral terthienobenzenetricarboxylic acid (TTBTA) self-assembles at the solution/graphite interface into either a porous chicken wire network linked by dimeric hydrogen bonding associations of COOH groups (R(2)(2) (8)) or a close-packed network linked in a novel hexameric hydrogen bonding motif (R(6)(6) (24)). Analysis of high-resolution STM images shows that the chicken wire phase is racemically mixed, whereas the close-packed phase is enantiomerically pure. The cavities of the chicken wire structure can efficiently host C60 molecules, which form ordered domains with either one, two, or three fullerenes per cavity. The observed monodisperse filling and long-range co-alignment of fullerenes is described in terms of a combination of an electrostatic effect and the commensurability between the graphite and molecular network, which leads to differentiation of otherwise identical adsorption sites in the pores. PMID:19919147

MacLeod, Jennifer M; Ivasenko, Oleksandr; Fu, Chaoying; Taerum, Tyler; Rosei, Federico; Perepichka, Dmitrii F

2009-11-25

251

Structural motifs and the stability of fullerenes  

SciTech Connect

Full geometry optimization has been performed within the semiempirical QCFF/PI model for the 1812 fullerene structural isomers of C{sub 60} formed by 12 pentagons and 20 hexagons. All are local minima on the potential energy hypersurface. Correlations of total energy with many structural motifs yield highly scattered diagrams, but some exhibit linear trends. Penalty and merit functions can be assigned to certain motifs: inclusion of a fused pentagon pair entails an average penalty of 111 kJ mol{sup -1}; a generic hexagon triple costs 23 kJ mol{sup -1}; a triple (open or fused) comprising a pentagon between two hexagonal neighbors gives a stabilization of 19 kJ mol{sup -1}. These results can be understood in terms of the curved nature of fullerene molecules: pentagons should be isolated to avoid sharp local curvature, hexagon triples are costly because they enforce local planarity and hence imply high curvature in another part of the fullerene surface, but hexagon-pentagon-hexagon triples allow the surface to distribute steric strain by warping. The best linear fit is found for H, the second moment of the hexagon-neighbor-index signature, which fits the total energies with a standard deviation of only 53 kJ mol{sup -1} and must be minimized for stability; this index too can be interpreted in terms of curvature. 26 refs., 5 figs.

Austin, S.J.; Fowler, P.W. [Univ. of Exeter (United Kingdom); Manolopoulos, D.E. [Univ. of Nottingham (United Kingdom); Orlandi, G.; Zerbetto, F. [Universita di Bologna (Italy)

1995-05-18

252

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

253

Cesium Ion Bombardment of Metal Surfaces  

NASA Astrophysics Data System (ADS)

The steady state cesium coverage due to cesium ion bombardment of molybdenum and tungsten has been studied for the incident energy range below 500 eV. When a sample is exposed to a positive cesium ion beam, the work function decreases until steady state is reached with a total dose of less than (DBLTURN)1*10('16) ions/cm('2), for both tungsten and molybdenum. A steady state minimum work function surface is produced at an incident energy of (DBLTURN)100 eV for molybdenum and at an incident energy of (DBLTURN)45 eV for tungsten. Increasing the incident energy results in an increase in the work function corresponding to a decrease in the surface coverage of cesium. At incident energies less than that giving the minimum work function, the work function approaches that of cesium metal. At a given bombarding energy the cesium coverage of tungsten is uniformly less than that of molybdenum. The effects of hydrogen gas coadsorption have also been examined. Hydrogen coadsorption does not have a large effect on the steady state work functions. The largest shifts in the work function due to the coadsorption of hydrogen occur on the samples when there is no cesium present. A theory describing the steady state coverage has been developed and is used to make predictions for other materials. A simple sticking and sputtering relationship, not including implantation, cannot account for the steady state coverage. At low concentrations, cesium coverage of a target is proportional to the ratio of (1-(beta))/(gamma) where (beta) is the reflection coefficient and (gamma) is the sputter yield. High coverages are produced on molybdenum due to implantation and low backscattering, because molybdenum is lighter than cesium. For tungsten the high backscattering and low implantation result in low coverages. The implications of these results for negative hydrogen surface conversion sources are clear, molybdenum is a better material than tungsten since a much lower work function surface is maintained on molybdenum at converter operating energies.

Tompa, Gary S.

254

Energetics of the formation of dimers and solids of boron nitride fullerenes  

Microsoft Academic Search

Molecular and solid forms of boron nitride, based on stoichiometric and nonstoichiometric fullerenes, are predicted by means of first-principles calculations. Our study of the energetics of dimer formation indicates that the reactivity of boron nitride fullerenes depends strongly on the stoichiometry. The stoichiometric fullerenes form strong covalent bonds between the tips of neighboring cages, while the tips of nitrogen-rich fullerenes

Simone S. Alexandre; R. W. Nunes; H. Chacham

2002-01-01

255

Magnetic molecules made of nitrogen or boron-doped fullerenes  

Microsoft Academic Search

By using density functional theory we investigate the electronic structure of a fullerene C60 molecule doped with nitrogen atoms. We find that as long as the number of the impurity atoms is odd the doped fullerene turns magnetic, with its magnetic moment determined by the way the impurities are bonded with the carbon cage. For even number of impurities the

Chih-Kai Yang

2008-01-01

256

Octahedral boron nitride fullerenes formed by electron beam irradiation  

Microsoft Academic Search

Here we report on the formation of fullerenes with a reduced number of layers (typically <=3) in boron nitride (BN) which was subjected to in situ electron irradiation at 20 and 490 °C in a high resolution 300 kV transmission electron microscope (HRTEM). The BN fullerenes exhibited B\\/N stoichiometry of ~1 as confirmed by electron energy loss spectroscopy using a

D. Golberg; Y. Bando; O. Stéphan; K. Kurashima

1998-01-01

257

Pulse-width modulation effects on fullerene electrochromism  

Microsoft Academic Search

Thin films of Buckminsterfullerene exhibit a reversible electrochromic effect when electrochemically intercalated with alkali metal or alkali earth ions. The degree of reversibility depends on the ratio of intercalated ions to fullerene molecules, both in the bulk film thickness and in localized stoichiometric gradients. High ratios of ions to fullerenes product films with limited electrochromic reversibility. These films are also

Gregory A. Konesky

1999-01-01

258

Protective Fullerene (C60) Packaging System for Microelectromechanical Systems Applications  

NASA Technical Reports Server (NTRS)

The invention involves tunneling tips to their conducting surface, and specifically the deposition of a monolayer of fullerene C60 onto the conducting plate surface to protect the tunneling tip from contact. The Fullerene C60 molecule is approximately spherical, and a monolayer of fullerene has a thickness of one nanometer, such that a monolayer thereby establishing the theoretical distance desired between the MEMS tunneling tip and the conducting plate. Exploiting the electrical conductivity of C60 the tip can be accurately positioned by simply monitoring conductivity between the fullerene and the tunneling tip. By monitoring the Conductivity between the tip and the fullerene layer as the tip is brought in proximity, the surfaces can be brought together without risk of contacting the underlying conducting surface. Once the tunneling tip is positioned at the one nanometer spacing, with only the monolayer of fullerene between the tunneling tip and the conducting plate, the monolayer of C60, can be broken down thermally and removed chemically leaving only the tunneling tip and the conducting plate at the ideal tunneling spacing. Alternatively, the properties of fullerene allow the tunneling process to occur directly across the fullerene monolayer.

Olivas, John D. (Inventor)

2004-01-01

259

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

260

Cellular localisation of a water-soluble fullerene derivative  

Microsoft Academic Search

Fullerenes are a new class of compounds with potential uses in biology and medicine and many insights were made in the knowledge of their interaction with various biological systems. However, their interaction with organised living systems as well as the site of their potential action remains unclear. In this work, we have demonstrated that a fullerene derivative could cross the

Sarah Foley; Colin Crowley; Monique Smaihi; Claude Bonfils; Bernard F Erlanger; Patrick Seta; Christian Larroque

2002-01-01

261

Common Electronic Structure and Pentagon Pairing in Extractable Fullerenes  

Microsoft Academic Search

We have found the bunching of the lowest three unoccupied states and the pentagon pairing in extractable fullerenes. These should be related to each other since lower unoccupied states are found to be spatially distributed on pentagons. In addition, the presence of both prevalent and rare structural units constituting extractable fullerenes has been revealed. A series of these findings sheds

Susumu Saito; Susumu Okada; Shin-Ichi Sawada; Noriaki Hamada

1995-01-01

262

Fullerene derivatives as electron donor for organic photovoltaic cells  

SciTech Connect

We demonstrated the performance of unconventional, all-fullerene-based, planar heterojunction (PHJ) organic photovoltaic (OPV) cells using fullerene derivatives indene-C{sub 60} bisadduct (ICBA) and phenyl C{sub 61}-butyric acid methyl ester as the electron donors with fullerene C{sub 70} 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 C{sub 70} 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, E-mail: xf-wang@yz.yamagata-u.ac.jp, E-mail: ziruo@yz.yamagata-u.ac.jp; Sano, Takeshi; Kido, Junji [Department of Organic Device Engineering, Graduate School of Engineering, and Research Center for Organic Electronics (ROEL), Yamagata University, Yonezawa 992-8510 (Japan)] [Department of Organic Device Engineering, Graduate School of Engineering, and Research Center for Organic Electronics (ROEL), Yamagata University, Yonezawa 992-8510 (Japan); Hong, Ziruo, E-mail: xf-wang@yz.yamagata-u.ac.jp, E-mail: ziruo@yz.yamagata-u.ac.jp [Department of Organic Device Engineering, Graduate School of Engineering, and Research Center for Organic Electronics (ROEL), Yamagata University, Yonezawa 992-8510 (Japan) [Department of Organic Device Engineering, Graduate School of Engineering, and Research Center for Organic Electronics (ROEL), Yamagata University, Yonezawa 992-8510 (Japan); Department of Materials Science and Engineering, University of California, Los Angeles, California 90095 (United States); Yang, Yang [Department of Materials Science and Engineering, University of California, Los Angeles, California 90095 (United States)] [Department of Materials Science and Engineering, University of California, Los Angeles, California 90095 (United States)

2013-11-11

263

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...

264

SOLUBILITY CORRELATION OF [60]FULLERENE IN DIFFERENT SOLVENTS  

Microsoft Academic Search

The solubility of [60]fullerene in various solvents has been correlated to the molar volume ratio of [60]fullerene and the respective solvent. The solubility varies linearly with the molar volume for the alcohol series and the heteroatom containing solvents, though specific interactions of the charge transfer type seem to dominate in the case of aromatic hydrocarbons and the halogenated solvents. The

C. N. Murthy; K. E. Geckeler

2001-01-01

265

PAH bombardment by energetic particles: models and astrophysical implications  

NASA Astrophysics Data System (ADS)

Polycyclic Aromatic Hydrocarbons (PAHs) are an important and ubiquitous component of the Interstellar Medium (ISM) of galaxies. Interstellar PAHs are apparently able to withstand the rigors of the harsh environment of the ISM for some some 100 million years and thus are resilient against processing by UV and X-ray photons and supernova shock waves. PAHs in space are mainly studied through their characteristic emission bands, due to infrared fluorescence following the absorption of UV photons. This is the reason why the photophysics of PAHs in space has been extensively investigated. On the other hand, PAHs are also strongly affected by collisional processes, i.e. bombardment by high-velocity ions and electrons, arising from interstellar shocks, hot gas and cosmic rays. However, very little was known about the physics of the interaction between PAHs and high energy particles, especially in terms of PAH damage and destruction. This lack of information had made the interpretation of PAH observations difficult in regions subjected to such processes. Our research aims to fill this key gap in our understanding of the physics behind collisional processing of PAHs and to clarify how this affects the PAH evolution in the astrophysical context. We first describe the models we have developed, that take into account the molecular nature of the target PAH and allow for the first time a quantitative description of the collisional processing of PAH molecules by ions and electrons with energies between 10 eV and 10 keV (in shocks and hot gas) and between 5 MeV and 10 GeV (in cosmic rays). Specific models were needed because PAHs are molecules and not small solid fragments, thus the classical approach from solid state physics cannot be applied. We then show the applications of our models to observations, estimating the lifetime of PAHs against collisional processing in specific objects. We discuss the astrophysical implications of our findings on the considered sample, which includes very different objects such as supernova remnants, normal/starburst galaxies and galaxy clusters.

Micelotta, E.; Jones, A.; Tielens, A.

2011-05-01

266

Synthesis of Molecules by Cosmic Ion Bombardment  

NASA Astrophysics Data System (ADS)

The population of known trans-neptunian objects (TNOs) is growing as new members are being detected and further characterized by both visible and near-IR observers. Good evidence exists that the spectra of TNOs are dominated by absorptions of either water or methane ice. The existence of N2, CO and possibly NH#3 ices is also likely. During their lifetimes, these icy bodies experience a weak, but constant energetic ion radiation environment that drives chemical reactions in their surface ices that ultimately result in a non- volatile tholin. To better understand the formation of more complex and less volatile molecules in irradiated ices, we have performed radiation chemical experiments on icy materials at 10 - 100 K. Gas-phase molecules, or molecular mixtures, are frozen in a vacuum chamber and then exposed to a beam of MeV protons to mimic cosmic-ray bombardment. Changes in ice composition are followed in situ with IR spectroscopy after irradiations, and during warming. In this presentation we will focus on the identity of low temperature and thermally stable radiation products in known outer solar system ices. Our results address likely radiation chemical mechanisms, the stability and evolution of species, and the identification of species awaiting detection. This research is funded through NASA's Planetary Atmospheres and Planetary Geology and Geophysics programs. 691.gsfc.nasa.gov/cosmic.ice.lab

Moore, M. H.; Reggie, H. L.

2006-12-01

267

Effects of Ion Bombardment on the Morphology of Lead Films.  

National Technical Information Service (NTIS)

The effects of ion bombardment on the morphology of compact lead films were investigated with spectroscopic ellipsometry, Auger electron spectroscopy (AES), and scanning electron microscopy. Lead films of under 100 nm in thickness were prepared by electro...

M. J. Armstrong R. H. Muller

1984-01-01

268

Pursuing the 17 keV Neutrino  

NASA Astrophysics Data System (ADS)

Evidence both for and against the existence of a 17 keV neutrino presents an unresolved conundrum. The experimental status is reviewed, emphasizing recent attempts to clarify the issue and thoughts on how the situation might be improved.

Hime, A.

269

Nanoencapsulation of Fullerenes in Organic Structures with Nonpolar Cavities  

NASA Astrophysics Data System (ADS)

The formation of supramolecular structures, assemblies, and arrays held together by weak intermolecular interactions and non-covalent binding mimicking natural processes has been used in applications being anticipated in nanotechnology, biotechnology and the emerging field of nanomedicine. Encapsulation of C60 fullerene by cyclic molecules like cyclodextrins and calixarenes has potential for a number of applications. Similarly, biomolecules like lysozyme also have been shown to encapsulate C60 fullerene. This poster article reports the recent trends and the results obtained in the nanoencapsulation of fullerenes by biomolecules containing nonpolar cavities. Lysozyme was chosen as the model biomolecule and it was observed that there is no covalent bond formed between the bimolecule and the C60 fullerene. This was confirmed from fluorescence energy transfer studies. UV Vis studies further supported this observation that it is possible to selectively remove the C60 fullerene from the nonpolar cavity. This behavior has potential in biomedical applications

Murthy, C. N.

2005-01-01

270

Fullerene fine particles adhere to pollen grains and affect their autofluorescence and germination  

PubMed Central

Adhesion of commercially produced fullerene fine particles to Cryptomeria japonica, Chamaecyparis obtusa and Camellia japonica pollen grains was investigated. The autofluorescence of pollen grains was affected by the adhesion of fullerene fine particles to the pollen grains. The degree of adhesion of fullerene fine particles to the pollen grains varied depending on the type of fullerene. Furthermore, germination of Camellia japonica pollen grains was inhibited by the adhesion of fullerene fine particles.

Aoyagi, Hideki; Ugwu, Charles U

2011-01-01

271

A fullerene molecular tip can detect localized and rectified electron tunneling within a single fullerene-porphyrin pair  

PubMed Central

A fullerene molecular tip was used to detect electron tunneling from a single porphyrin molecule. Electron tunneling was found to occur locally from an electron-donating moiety of the porphyrin to the fullerene through charge-transfer interaction between them. In addition, electron tunneling within the single fullerene–porphyrin pair exhibited rectifying behavior in which electrons can be driven only at the direction from the porphyrin to the fullerene. It is demonstrated that localized electron tunneling enables us to spatially visualize the frontier orbital of the porphyrin involved in electron tunneling. In addition, rectification demonstrates that the fullerene–porphyrin pair constitutes a molecular rectifier. We believe that molecular tips bring insight into intermolecular electron transmission toward realization of molecular electronics as shown here.

Nishino, Tomoaki; Ito, Takashi; Umezawa, Yoshio

2005-01-01

272

Small-angle X-ray scattering study of the structure of powder fullerene C60 and fullerene soot  

NASA Astrophysics Data System (ADS)

Powder samples of fullerene C60 and fullerene soot have been studied by the small-angle X-ray scattering method. The radii of gyration of scattering elements have been determined by constructing small-angle diffraction patterns in Guinier coordinates. The data obtained agree well with the results of wide-angle X-ray scattering study, the available data on the structure of the powder fullerene C60 prepared by the Huffman-Krätschmer technique, and the structure of the C60 molecules. Conglomerates of two C60 molecules, along with crystallites ˜20 nm in size that are distributed in an amorphous matrix, are present in fullerene powders. Fullerene soot contains C60 crystallites 20-25 nm in size and graphite crystallites ˜2-3 nm in size that are distributed in an amorphous matrix.

Ginzburg, B. M.; Tu?chiev, Sh.; Tabarov, S. Kh.; Shepelevski?, A. A.

2007-03-01

273

Structure and stability of molybdenum sulfide fullerenes.  

PubMed

MoS2 nanooctahedra are believed to be the smallest stable closed-cage structures of MoS2, i.e., the genuine inorganic fullerenes. Here a combination of experiments and density functional tight binding calculations with molecular dynamics annealing are used to elucidate the structures and electronic properties of octahedral MoS2 fullerenes. Through the use of these calculations MoS2 octahedra were found to be stable beyond nMo > 100 but with the loss of 12 sulfur atoms in the six corners. In contrast to bulk and nanotubular MoS2, which are semiconductors, the Fermi level of the nanooctahedra is situated within the band, thus making them metallic-like. A model is used for extending the calculations to much larger sizes. These model calculations show that, in agreement with experiment, the multiwall nanooctahedra are stable over a limited size range of 104-105 atoms, whereupon they are converted into multiwall MoS2 nanoparticles with a quasi-spherical shape. On the experimental side, targets of MoS2 and MoSe2 were laser-ablated and analyzed mostly through transmission electron microscopy. This analysis shows that, in qualitative agreement with the theoretical analysis, multilayer nanooctahedra of MoS2 with 1000-25 000 atoms (Mo + S) are stable. Furthermore, this and previous work show that beyond approximately 105 atoms fullerene-like structures with quasi-spherical forms and 30-100 layers become stable. Laser-ablated WS2 samples yielded much less faceted and sometimes spherically symmetric nanocages. PMID:17165987

Bar-Sadan, M; Enyashin, A N; Gemming, S; Popovitz-Biro, R; Hong, S Y; Prior, Yehiam; Tenne, R; Seifert, G

2006-12-21

274

Oxygen intake in ion irradiated fullerene films  

NASA Astrophysics Data System (ADS)

The present work reports the change in the oxygen content in energetic ion irradiated fullerene films. The oxygen contents in irradiated films have been studied using on-line elastic recoil detection analysis (ERDA) and off-line X-ray photo electron emission (XPS) and nuclear reaction analysis (NRA) techniques. The XPS and NRA techniques show that the oxygen content increases with ion fluence, whereas on-line ERDA measurements reveal that the oxygen content decreases with ion fluence. These experiments give clear evidence that oxygen content in irradiated films increases after exposure to the atmospheric oxygen.

Kumar, Amit; Khan, S. A.; Kumar, Manvendra; Agarwal, D. C.; Singh, Fouran; Tripathi, A.; Govind; Shivaprasad, S. M.; Salomon, J.; Pichon, L.; Pivin, J. C.; Avasthi, D. K.

2008-04-01

275

Possible mechanisms of fullerene C?? antioxidant action.  

PubMed

Novel mechanism of antioxidant activity of buckminsterfullerene C?? 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 C?? 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

276

Fullerene-bound dendrimers. Soluble, isolated carbon clusters  

SciTech Connect

The coupling of compact dendritic macromolecules with prefunctionalized fullerenes is now described. This synthetic strategy, involving two species containing a precise number of functional groups, gives greater control over the formation of polymer-fullerene hybrid structures. Phenol-functionalized fullerenes have been prepared by reaction of C[sub 60] with bis(p-methoxyphenyl)diazomethane followed by hydrolysis of the methyl ethers with BBr[sub 3]. This synthesis has been tailored to yield a 6-6 bridged methano fullerene derivative carrying only two phenolic sites as the major product. Polyether dendrimers prepared by the convergent synthesis route are ideally suited for attachment to phenol-functionalized buckyballs since they carry a single electrophilic site at their focal point, and their attachment to phenolic moieties has been studied extensively. The formation of fullerene-bound dendrimers was accomplished by reaction of each of the two phenolic groups located at the surface of the functionalized fullerene with the single benzylic bromide group at the focal point of a fourth-generation dendrimer in the presence of K[sub 2]CO[sub 3]. Purification by flash chromatography or precipitation gave only partial separation of the products; as a result, preparative SEC was used to obtain samples of each of the products. A [sup 1]H NMR spectrum of the desired product, in which two dendrimers are attached to the surface of the fullerene, is shown. 9 refs., 2 figs.

Wooley, K.L.; Hawker, C.J.; Frechet, J.M.J. (Cornell Univ., Ithaca, NY (United States)); Wudl, F.; Srdanov, G.; Shi, S.; Li, C.; Kao, M. (Univ. of California, Santa Barbara, CA (United States))

1993-10-20

277

Infrared spectroscopy of fullerene C60/anthracene adducts  

NASA Astrophysics Data System (ADS)

Recent Spitzer Space Telescope observations of several astrophysical environments such as planetary nebulae, reflection nebulae and R Coronae Borealis stars show the simultaneous presence of mid-infrared features attributed to neutral fullerene molecules (i.e. C60) and polycyclic aromatic hydrocarbons (PAHs). If C60 fullerenes and PAHs coexist in fullerene-rich space environments, then C60 may easily form adducts with a number of different PAH molecules, at least with catacondensed PAHs. Here we present the laboratory infrared spectra (˜2-25 ?m) of C60 fullerene and anthracene Diels-Alder mono- and bis-adducts as produced by sonochemical synthesis. We find that C60/anthracene Diels-Alder adducts display spectral features strikingly similar to those from C60 (and C70) fullerenes and other unidentified infrared emission features. Thus, fullerene adducts - if formed under astrophysical conditions and are stable/abundant enough - may contribute to the infrared emission features observed in fullerene-containing circumstellar/interstellar environments.

García-Hernández, D. A.; Cataldo, F.; Manchado, A.

2013-09-01

278

Partitioning and solubility of C60 fullerene in lipid membranes  

NASA Astrophysics Data System (ADS)

Carbon nanoparticles (CNPs) are considered to be among the most promising nanomaterials, with applications in many different areas of technology. Most CNPs can enter both artificial lipid membranes and living cells, and are biologically active. The interaction of CNPs with lipid membranes is of great interest because biological activity requires crossing or breaking lipid membranes. Moreover, lipid bilayers have been proposed to be efficient solubilizing agents for C60 and C70 fullerenes. In this comment, we review the literature on fullerene partitioning and dispersion in lipid membranes, considering both the experimental and the simulation literature, and highlighting similarities and differences. Both experiments and simulations confirm that fullerenes partition to the membrane interior, although experimental information on the location of fullerene molecules is only qualitative. On the other hand, the fullerene dispersion state is difficult to assess experimentally, and appears to depend on the details of the methodology used for the preparation of fullerene-loaded liposomes. Although some degree of aggregation is confirmed by most experiments, the extent of the aggregation is uncertain. Large aggregates observed in the presence of lipid membranes are unlikely to be found within the membrane, as they are orders of magnitude larger than the membrane thickness. Simulations carried out so far yielded contrasting results. Both atomistic and some coarse-grained simulations indicated that fullerene dimerization in lipid membranes should be significantly less favorable than that in bulk alkanes, but the physical reasons for this are still unclear.

Rossi, G.; Barnoud, J.; Monticelli, L.

2013-05-01

279

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

280

Laser-desorption mass spectrometry and induced coalescence of fullerenes  

NASA Astrophysics Data System (ADS)

This article reviews the evolution of the UCLA fullerene research over the past two years from the perspective of laser desorption mass spectrometry (LDMS). As a fast and sensitive analytical method, it has critically contributed to a wide range of fullerene related research projects. Immediately after the discovery of a method for making C60, C70 and selected higher fullerenes in macroscopic amounts, a concerted effort in different laboratories led to the isolation and structure determination of C76, C78, C82 and tentatively C84. Simultaneously with the work on pure fullerene, important progress was achieved in the synthesis of metallofullerenes and derivatized fullerenes. LDMS continually documented progress or failure in extraction, isolation and synthesis and helped to plan future research. Recently, synthesis of C60 and larger fullerenes from precursors, e.g., C18(CO)6, and coalescence reactions of fullerenes, induced by high fluence of the desorption laser, introduced a new aspect of this otherwise exclusively analytical method.

Yeretzian, Chahan X.; Alvarez, Marcos M.; DiCamillo, Barbara; Whetten, Robert L.

1993-07-01

281

Metal nitride cluster fullerenes: their current state and future prospects.  

PubMed

The world of endohedral fullerenes was significantly enlarged over the past seven years by the cluster fullerenes, which contain structures such as the M(2)C(2) carbides and the M(3)N nitrides. While the carbide clusters are generated under the standard arc-burning conditions according to stabilization conditions, the nitride cluster fullerenes (NCFs) are formed by varying the composition of the cooling gas atmosphere in the arc-burning process. The special conditions for NCF synthesis is described in detail and the optimum conditions for the production of NCFs as the main product in fullerene syntheses are given. A general review of all NCFs reported to date consists of the structures, properties, and stability of the NCFs as well as the abundance of the NCFs in the fullerene soot. It is shown that all cages with even carbon atoms from C(68) to C(98) are available as endohedral nitride cluster structures (with the exception of C(72), C(74), and C(76)). Specifically, the NCFs form the largest number of structures that violate the isolated pentagon rule (IPR). Finally some practical applications of these cluster fullerenes are illustrated and an outlook is given, taking the superior stability of these endohedral fullerenes into account. PMID:17657757

Dunsch, Lothar; Yang, Shangfeng

2007-08-01

282

Charged fullerenes as high-capacity hydrogen storage media.  

PubMed

Using first-principles calculations within density functional theory, we explore systematically the capacity of charged carbon fullerenes Cn (20 fullerenes can be dramatically enhanced to 0.18-0.32 eV, a desirable range for potential room-temperature, near ambient applications. The enhanced binding is delocalized in nature, surrounding the whole surface of a charged fullerene, and is attributed to the polarization of the hydrogen molecules by the high electric field generated near the surface of the charged fullerene. At full hydrogen coverage, these charged fullerenes can gain storage capacities of up to approximately 8.0 wt %. We also find that, contrary to intuitive expectation, fullerenes containing encapsulated metal atoms only exhibit negligible enhancement in the hydrogen binding strength, because the charge donated by the metal atoms is primarily confined inside the fullerene cages. These predictions may prove to be instrumental in searching for a new class of high-capacity hydrogen storage media. PMID:17718530

Yoon, Mina; Yang, Shenyuan; Wang, Enge; Zhang, Zhenyu

2007-09-01

283

On the Excitation and Formation of Circumstellar Fullerenes  

NASA Astrophysics Data System (ADS)

Recently, we reported the first detection of fullerenes (C60, C70) in space, specifically in Tc1, a young planetary nebulae (PNe). Once injected into the ISM, these stable species survive and are thus probably widespread in the Galaxy where they contribute to interstellar extinction, heating processes, and complex chemical reactions. Following our discovery, fullerenes have now been detected in a wide range of sources (post-AGBs, PNe, reflection nebula, HII regions, H-poor stars, and YSOs), showing that when conditions are favorable, fullerenes are formed in large quantities. The challenge resides now in determining its excitation mechanisms (fluorescence vs. thermal), as this sets their diagnostic value. To this end we have analyzed the mid-IR spectrum of three fullerene-rich PNe Tc1, SMP SMC 16, and SMP LMC 56 and compared them with thermal and fluorescence models. The strength of the fullerene bands in the three planetary nebulae is very similar, while the strength of the radiation field, is markedly different. Additionally, the spatial profile of different dust components in Tc1 indicates that the fullerene emission (C60) peaks far away from the central source. All this is hard to reconcile with a thermal origin for the fullerene excitation, and thus favors fluorescence as the excitation mechanism. In addition, the spectra in the three PNe show a strong broad plateau with substructure in the 6-9um range, and which is likely related to the fullerene formation mechanism. We present model spectra for 3 nm radius HAC particles and show that these can reproduce the 6-9um plateau, which may imply that fullerenes are formed by photo-chemical processing of hydrogenated amorphous carbon (HAC) nano-particles.

Bernard-Salas, Jeronimo; Cami, J.; Peeters, E.; Jones, A. P.; Micelotta, E.; Groenewegen, M. A.

2013-01-01

284

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

285

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

SciTech Connect

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 {gamma}-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 {gamma}-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. [School of Physics and Energy Science, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Chung, W. C.; Ro, T. I. [Department of Physics, Dong-A University, 840 Hadan 2-dong, Saha-gu, Busan 604-714 (Korea, Republic of); Ohsaki, T.; Igashira, M. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1-N1-26, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan)

2006-03-13

286

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

287

A Catalog of Diffuse Interstellar Bands in Fullerene-Containing Planetary Nebulae  

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 in fullerene-rich space environments. We have studied the presence of DIBs in the optical spectra (~3300-9400 Å) of two fullerene-containing PNe (Tc 1 and M 1-20). Special attention is given to DIBs which are found to be unusually intense in fullerene-containing PNe; several of these DIBS have not previously been reported. Fullerenes larger than C60 (and C70) and multishell fullerenes may be possible candidate carriers for the unusual DIBs seen in fullerene-rich environments.

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

2014-02-01

288

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

289

[Factors influence on transformation by particle bombardment in Indica rice].  

PubMed

Four factors influence on transformation of indica rice, which were high osmotic treatment; different explant as the target tissue; pressure of rupture disk and quantity of plasmid DNA, were investigated in this experiment. High osmotic treatment of target tissue prior to and after bombardment increased 3.2-fold for Gus transient expression than control. The best treatment of high osmotic was that the target tissues were kept in the target-bed medium which contained 0.4-0.6 mol/L sorbitol and manitol each for 4 h prior to bombardment and for 16 h after bombardment. Four explants: scutellum from mature seed, young panicle, embryogenic callus and suspension cells of indica rice were tested as target explant by particle bombardment. The results of Gus transient showed that the highest expression was scutellum and for other three explants, the order from high to low was young panicle, embryogenic callus and suspension cell. Transgenic plants were obtained from all of the explants except young panicle. For the pressure of rupture disk on transformation, 1100 psi or 1300 psi of the pressure of rupture disk were best one for the transformation and higher than 1300 psi could damage the target tissue which become black and died in the following culture duration. For the quantity of plasmid DNA, the results showed that 0.83 microgram of plasmid DNA per bombardment was preferred for the transformation of indica rice. PMID:12548856

Tao, L Z; Xu, Q S; Liang, C Y; Ling, D H

2000-03-01

290

Fullerene and the origin of life.  

PubMed

The role of carbon in the development of life and as the structural backbone of all organisms is universally accepted and an essential part of evolution. However, the molecular basis is largely unknown and the interactions of carbon with nitrogen and oxygen in space are enigmatic. In 1985, the previously unknown form of carbon, coined fullerene, was discovered. We hypothesize that by virtue of the unique properties of fullerene, this hollow, ultra-robust, large, purely carbon molecule was the earliest progenitor of life. It acted as a stable universal biologic template on which small molecules spontaneously assembled and then formed, by further assembly, a surface mantle (here termed rosasome) of larger molecules. We submit that this process, by its inherent flexibility, initiated evolution, allowing the emergence of parallel diverse rosasome lines responding selectively to varying spatial environments. For example, rosasomal lines mantled with nucleotide and peptide layers are conceived as primordial forerunners of the ubiquitous ribosome. Moreover, the parallel independent and interdependent evolution of rosasome lines would be more rapid than sequential development, refute precedence of either DNA or RNA, and explain the evolution of integration of two subunits with different structures and functions in ribosomes and of the triplet nature of the codon. Based on recent astronomical data, this hypothesis supports the concept that life is not a singularity. This concept also suggests a potential vehicle for therapeutics, biotechnology and genetic engineering. PMID:23193780

Goodman, Geoffrey; Gershwin, M Eric; Bercovich, Dani

2012-10-01

291

Fullerene synthesis by laser pyrolysis of hydrocarbons  

NASA Astrophysics Data System (ADS)

A novel route for the synthesis of carbon soots containing fullerenes has been developed i.e. the pyrolysis of hydrocarbons in gas, vapour or aerosol phase, which are heated and decomposed through the absorption of IR photons emitted by a high power CW CO2 laser. Hydrocarbons such as benzene (+ cyclopentadiene), acetylene or ethylene have been tested, pure or mixed with an oxidizer agent (nitrous oxide or oxygen) and/or a sensitizer (sulfur hexafluoride). The fullerenes were identified in the soots obtained by using as precursor the benzene/oxygen or acetylene/oxygen mixture. When these compounds are produced in significant amounts they can be detected directly in the as-formed soots by Fourier Transform Infrared Spectroscopy (FTIR). For small quantities, a Soxhlet extraction procedure is necessary and the extracts are characterized by FTIR and by other methods which are more sensitive, like mass spectrometry or High Performance Liquid Chromatography (HPLC) coupled with ultraviolet-visible spectroscopy. The influence of the operating conditions is discussed.

Armand, X.; Herlin, N.; Voicu, I.; Cauchetier, M.

1997-11-01

292

Mechanisms of O2 Sputtering from Water Ice by keV Ions  

NASA Technical Reports Server (NTRS)

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.

2005-01-01

293

Molecular dynamics study of self-agglomeration of charged fullerenes in solvents  

NASA Astrophysics Data System (ADS)

The agglomeration of fullerenes in solvents is an important phenomenon that is relevant to controlled synthesis of fullerene-based nanowires as well as fullerene-based composites. The molecular aggregation in solvents depends on the atomistic interactions of fullerene with the solvent and is made complicated by the fact that fullerenes accrue negative surface charges when present in solvents such as water. In the present work, we simulated fullerenes of varying size and shape (C60, C180, C240, and C540) with and without surface charges in polar protic (water), polar aprotic (acetone), and nonpolar (toluene) solvents using molecular dynamics method. Our results demonstrate that uncharged fullerenes form agglomerates in polar solvents such as water and acetone and remain relatively dispersed in nonpolar toluene. The presence of surface charge significantly reduces agglomerate size in water and acetone. Additionally, the relative influence of surface charge on fullerene agglomeration depends on the size and geometry of the fullerene with larger fullerenes forming relatively smaller agglomerates. We evaluated the diffusion coefficients of solvent molecules within the solvation shell of fullerenes and observed that they are much lower than the bulk solvent and are strongly associated with the fullerenes as seen in the corresponding radial distribution functions. To correlate agglomerate size with the binding energy between fullerenes, we evaluated the potential of mean force between fullerenes in each solvent. Consistent with the solubility of fullerenes, binding energy between fullerenes is the greatest in water followed by acetone and toluene. The presence of charge decreases the binding energy of fullerenes in water and thus results in dispersed fullerenes.

Banerjee, Soumik

2013-01-01

294

An alternative type of fullerene products from the reaction of [60]fullerene with alkoxides and subsequent derivatization.  

PubMed

Reaction of [60]fullerene with freshly prepared RCH(2)CH(2)ONa/RCH(2)CH(2)OH (R = H, Me, Et, Ph) in anhydrous toluene in the presence of air unexpectedly afforded fullerene products with a C(60)-fused tetrahydrofuran ring skeleton and an acetal moiety, which could be further transformed into C(60)-fused dihydrofurans, tolyl-substituted C(60)-fused tetrahydrofuran, and methanofullerenes bearing a formyl group by boron trifluoride etherate. Possible reaction mechanisms are proposed to explain the formation of different fullerene products. PMID:19505103

Wang, Guan-Wu; Lu, Yong-Ming; Chen, Zhong-Xiu; Wu, Shi-Hui

2009-07-01

295

Magnetospheric ion bombardment profiles of satellites - Europa and Dione  

SciTech Connect

Bombardment profiles generated by tracking ions in magnetospheric plasmas onto the surface of a satellite with a suitable description of the ion motion are used to calculate the spatial dependence across a satellite surface of the ion bombardment/implantation rate for satellites embedded in planetary magnetospheric plasmas. Attention is given to the results of a parameter study; a general dependency on ion gyroradius and pitch angle is noted, together with a strong dependence of access to the leading hemisphere on pitch-angle distribution. Gyromotion is found to cause differences in the bombardment of the inner and outer hemisphere. Reasonable speed and pitch-angle distributions are used to calculate profiles for sulfur ions incident on Europa and oxygen ones incident on Dione. 28 references.

Pospieszalska, M.K.; Johnson, R.E.

1989-03-01

296

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

297

Repulsive solvent-induced interaction between C60 fullerenes in water.  

PubMed

The role of water-fullerene interactions in the behavior of C60 in aqueous solution was investigated utilizing realistic Lennard-Jones (LJ) and repulsive Weeks-Chandler-Anderson (WCA) potentials. Strong water-fullerene dispersion interactions in the LJ potential dramatically influence the hydration of the fullerene promoting the formation of a high-density hydration shell of water. In contrast to the WCA potential, the water liquid phase between fullerenes remains stable with decreasing fullerene separation, resulting in a repulsive solvent-induced contribution to the fullerene potential of mean force. PMID:15697603

Li, Liwei; Bedrov, Dmitry; Smith, Grant D

2005-01-01

298

Phase equilibria in the fullerene C 60 -fullerene C 70 -hexane- o -xylene-dimethylformamide system  

Microsoft Academic Search

The phase diagram of the hexane-o-xylene-dimethylformamide ternary liquid system was studied at T = 298.15 K. The diagram contained the regions of homogeneous solutions and two-phase liquid systems (systems with stratification),\\u000a phase I being enriched in dimethylformamide and phase II, in hexane. The distribution of fullerenes C60 and C70 was considered at various concentrations and simultaneous presence in sections at

V. A. Keskinov; A. K. Pyartman; N. A. Charykov; O. V. Arapov; A. A. Pronkin; V. V. Lishchuk; V. V. Leonov

2008-01-01

299

Phase equilibria in the fullerene C60-fullerene C70-hexane- o-xylene-dimethylformamide system  

Microsoft Academic Search

The phase diagram of the hexane- o-xylene-dimethylformamide ternary liquid system was studied at T = 298.15 K. The diagram contained the regions of homogeneous solutions and two-phase liquid systems (systems with stratification), phase I being enriched in dimethylformamide and phase II, in hexane. The distribution of fullerenes C60 and C70 was considered at various concentrations and simultaneous presence in sections

V. A. Keskinov; A. K. Pyartman; N. A. Charykov; O. V. Arapov; A. A. Pronkin; V. V. Lishchuk; V. V. Leonov

2008-01-01

300

Multilayer diffraction at 104 keV  

NASA Technical Reports Server (NTRS)

We have measured the diffraction peak of a W:Si synthetic multilayer reflector at 104 keV using the High Energy Bonse-Hart Camera at the X-17B hard X-ray wiggler beam line of the National Synchrotron Light Source at Brookhaven National Laboratory. The characteristics of the diffraction peak are described and compared to theory.

Krieger, Allen S.; Blake, Richard L.; Siddons, D. P.

1993-01-01

301

Preparation and optical limiting properties of polycarbonates containing fullerene unit  

NASA Astrophysics Data System (ADS)

Polycarbonates (PCs) convalently linked 1,2-(1 ',1 ',2 ',2 '-tetracyanomethanoxymethano)[60]fullerene (TCNEO-C 60) and N-methyl-pyrrolidino[60]fullerene (MPYLD-C 60) with interesting optical limiting behavior are obtained by direct reaction of PC with TCNEO-C 60 and MPYLD-C 60, respectively, using AlCl 3 as catalyst. The electron-accepting ability of TCNEO-C 60 (acceptor-C 60) is stronger than that of C 60 and MPYLD-C 60, and TCNEO-C 60-PCs limit strong 532 nm optical pulses more effectively than C 60-PC and MPYLD-C 60-PC. This suggests that increasing the electron-accepting ability of fullerene will be effective in improving the optical limiting properties of PC containing fullerene unit.

Li, Yuliang; Wang, Shu; Li, Fengying; Du, Chimin; Shi, Zhiqiang; Zhu, Daoben; Song, Yinglin

2001-04-01

302

Measurement of the gravitational acceleration of fullerene molecules  

NASA Astrophysics Data System (ADS)

Gravitational acceleration has been measured with high precision using macroscopic probes and for a few quantum probes. A recent diffraction experiment (Arndt M et al 1999 Nature 401 680) has demonstrated the wave-particle duality for the C60 fullerene molecules. In this paper, a new method to measure gravitational acceleration with fullerene molecules is proposed. The g value is deduced from the measurement of the phase shift of a thermal beam in a three-grating Mach-Zehnder interferometer. The experimental setup and the uncertainty sources are discussed. A measurement with a precision of 1 × 10-4 is feasible with 108 thermal fullerene molecules and gratings with 500 nm period. The precision achievable by the proposed method is limited by the velocity spread of the fullerene beam.

Poggiani, Rosa

2003-02-01

303

Molar extinction coefficient of fullerenes and related hydrogenated derivatives ``fulleranes''  

NASA Astrophysics Data System (ADS)

Fullerenes, the carbon molecules with 60 and 70 atoms, were recently detected in a series of planetary nebulae, in protoplanetary nebulae and in other astrophysical objects. The detection and the quantitative determination of these molecules was made possible by the measurement of their reference infrared spectra and the relative molar extinction coefficients and integrated molar absorptivity on laboratory scale. It is expected that also fulleranes the hydrogenated derivatives of C60 and C70 may be present in the same objects where fullerenes were detected. This prompted us to synthesize the hydrogenated fullerenes, to record their infrared spectra and the measure the molar extinction coefficients and integrated molar absorptivity on laboratory scale to have a reference in the search of these fullerene derivatives in space

Cataldo, Franco; Iglesias-Groth, Susana; Manchado, Arturo

2012-08-01

304

Hydrogen storage in fullerenes and in an organic hydride.  

National Technical Information Service (NTIS)

While the authors have demonstrated the importance and usefulness of thermal management to the hydrogen storage in fullerenes, their recent effort has concentrated on materials improvement and physical model development. In this paper, they report the res...

J. C. Wang R. W. Murphy F. C. Chen R. O. Loutfy E. Veksler

1998-01-01

305

Role of Conformation in - Interactions and Polymer/Fullerene Miscibility  

SciTech Connect

The origin of the miscibility between C60 fullerene and a series of phenylic vinyl polymers has been investigate using a combination of wide-angle x-ray (WAXS) and neutron (WANS) scattering and density functional theory (DFT) computational modeling. The solubility limit of the C60 in the polymers was found to increase non-linearly with increasing phenylic groups in the side-chain from 1 wt% in polystyrene (PS) to 12 wt% in poly(9-vinyl phenanthrene) (P9VPh). The DFT calculations showed that the polymer interacts with the fullerene preferentially with the phenylic groups in these vinyl polymers. However, due to the backbone these phenyl groups are unable to form the energetically favorable T-junction or planar - stacks with the fullerene, and are randomly oriented to the cage. The non-linear increase in solubility is believed to be associated with shape conformity of the three ring phenanthrene to the curvature of the fullerene.

Sumpter, Bobby G [ORNL; Bucknall, David G. [Georgia Institute of Technology; Thio, Yonathan S [ORNL; Gurun, Bilge [Georgia Institute of Technology; Campbell, Katie [Georgia Institute of Technology

2011-01-01

306

On Toroidal Azulenoids and Other Shapes of Fullerene Cage  

Microsoft Academic Search

The possibility of toroidal cages of carbon with repeating five and seven membered ring pairs (azulene units) upon their surfaces is briefly discussed. Some of the difficulties in recognising possible fullerene cage shapes are pointed out.

E. C. Kirby

1994-01-01

307

Hydrogen storage in fullerenes and in an organic hydride  

SciTech Connect

While the authors have demonstrated the importance and usefulness of thermal management to the hydrogen storage in fullerenes, their recent effort has concentrated on materials improvement and physical model development. In this paper, they report the results of this effort as follows: (1) Liquid phase hydrogenation of fullerenes indicated that more than 6 wt% capacity can be obtained at 180 C, 350--400 psi; (2) Dehydrogenation of fullerenes hydrides below 225 C was demonstrated using an Ir-based P-C-P pincer complex catalyst; (3) Cyclic hydrogenation and dehydrogenation tests of an organic hydride at 7 wt% capacity were conducted at 180--260 C; and (4) Physical models developed for fullerenes were determined to be applicable to this organic hydride (with much smaller activation energies).

Wang, J.C.; Murphy, R.W.; Chen, F.C. [Oak Ridge National Lab., TN (United States). Energy Div.; Loutfy, R.O.; Veksler, E.; Li, W. [Materials and Electrochemical Research Corp., Tucson, AZ (United States)

1998-05-29

308

Study on the keV neutron capture reaction in 56Fe and 57Fe  

NASA Astrophysics Data System (ADS)

The neutron capture cross-sections and the radiative capture gamma-ray spectra from the broad resonances of 56Fe and 57Fe in the neutron energy range from 10 to 90keV and 550keV have been measured with an anti-Compton NaI(Tl) detector. Pulsed keV neutrons were produced from the 7Li 7Be reaction by bombarding the lithium target with the 1.5ns bunched proton beam from the 3MV Pelletron accelerator. The incident neutron spectrum on a capture sample was measured by means of a time-of-flight (TOF) method with a 6Li -glass detector. The number of weighted capture counts of the iron or gold sample was obtained by applying a pulse height weighting technique to the corresponding capture gamma-ray pulse height spectrum. The neutron capture gamma-ray spectra were obtained by unfolding the observed capture gamma-ray pulse height spectra. To achieve further understanding on the mechanism of neutron radiative capture reaction and study on physics models, theoretical calculations of the -ray spectra for 56Fe and 57Fe with the POD program have been performed by applying the Hauser-Feshbach statistical model. The dominant ingredients to perform the statistical calculation were the Optical Model Potential (OMP), the level densities described by the Mengoni-Nakajima approach, and the -ray transmission coefficients described by -ray strength functions. The comparison of the theoretical calculations, performed only for the 550keV point, show a good agreement with the present experimental results.

Wang, Taofeng; Lee, Manwoo; Kim, Guinyun; Ro, Tae-Ik; Kang, Yeong-Rok; Igashira, Masayuki; Katabuchi, Tatsuya

2014-03-01

309

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

NASA Astrophysics Data System (ADS)

Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes in solvents with strong SANS contrast (e.g., CS2). The dimensions of C60, C70, and C84 moieties derived from neutron scattering via standard Guinier analysis are typically ~8% higher than calculated from the atomic coordinates. However, when the SANS data are fitted to an appropriate model form factor, there is good agreement between the measured and calculated values and the results are independent of the fullerene concentration within the experimental errors. Deuterated solvents (e.g., toluene-d8) have a high scattering length density (SLD), which is close to that of C60, C70, and C84, so there is virtually no SANS contrast with the solvent and these particles are practically ``invisible'' in such media. Conversely, the negative scattering length of hydrogen lowers the SLD, giving strong contrast with toluene-d8 and SANS may therefore be used to study the size and shapes of buckyballs modified with H1-containing materials. These may also be studied via neutron transmission measurements and this paper describes complementary studies of cyclohexane-substituted fullerenes.

Melnichenko, Y. B.; Wignall, G. D.; Compton, R. N.; Bakale, G.

1999-09-01

310

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

SciTech Connect

Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes in solvents with strong SANS contrast (e.g., CS{sub 2}). The dimensions of C{sub 60}, C{sub 70}, and C{sub 84} moieties derived from neutron scattering via standard Guinier analysis are typically {approximately}8{percent} higher than calculated from the atomic coordinates. However, when the SANS data are fitted to an appropriate model form factor, there is good agreement between the measured and calculated values and the results are independent of the fullerene concentration within the experimental errors. Deuterated solvents (e.g., toluene-d{sub 8}) have a high scattering length density (SLD), which is close to that of C{sub 60}, C{sub 70}, and C{sub 84}, so there is virtually no SANS contrast with the solvent and these particles are practically {open_quotes}invisible{close_quotes} in such media. Conversely, the negative scattering length of hydrogen lowers the SLD, giving strong contrast with toluene-d{sub 8} and SANS may therefore be used to study the size and shapes of buckyballs modified with H{sup 1}-containing materials. These may also be studied via neutron transmission measurements and this paper describes complementary studies of cyclohexane-substituted fullerenes. {copyright} {ital 1999 American Institute of Physics.}

Melnichenko, Y.B.; Wignall, G.D. [Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States)] [Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States); Compton, R.N. [Departments of Chemistry and Physics, University of Tennessee, Knoxville, Tennessee 37996 (United States)] [Departments of Chemistry and Physics, University of Tennessee, Knoxville, Tennessee 37996 (United States); Bakale, G. [Division of Radiation Biology, Case Western Reserve University, Ohio 44106-4942 (United States)] [Division of Radiation Biology, Case Western Reserve University, Ohio 44106-4942 (United States)

1999-09-01

311

Controlling surface hydroxylation of nanoporous silica by ion bombardment  

NASA Astrophysics Data System (ADS)

Due to a large fraction of undercoordinated surface atoms in nanoporous solids, the surface composition could have a profound effect on their properties. Here, we use mass spectrometry to study ion-beam-induced desorption from silica aerogels. Results show that the dominant ion-beam-induced desorption species is the hydrogen molecule. Bombardment with ions of different masses causes dehydroxylation of silica nanoligaments, with the desorption efficiency scaling linearly with the electronic stopping power of ions. These results demonstrate that ion bombardment can be used for controlling surface hydroxylation of nanoporous silica.

Van Cleve, E.; Charnvanichborikarn, S.; Kucheyev, S. O.

2012-11-01

312

Modification of molecular transitions in fullerene films under ion impacts  

SciTech Connect

The photoluminescence properties of as-deposited and 90 MeV Si ion irradiated fullerene films are reported. The irradiation of fullerene films leads to some enhancement or quenching in molecular transition intensities (photoluminescence intensities) depending on the ion fluence. These effects are explained in terms of lowering in the energy level symmetry resulting from induced chemical disordering. The structural modifications occurring upon irradiation were investigated using Fourier transform infrared and UV-vis spectroscopies.

Kumar, Amit [Institut Neel, Centre National de la Recherche Scientifique (CNRS) and Universite Joseph Fourier (UJF), 25 rue des Martyrs, BP166, 38042 Grenoble Cedex 9 (France); Podhorodecki, A.; Misiewicz, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Avasthi, D. K. [Material Science Group, Inter-University Accelerator Centre, Aruna Asaf Ali Marg, PB-10502, New Delhi 110067 (India); Pivin, J. C. [Centre Spectrometrie Nucleaire et de Spectrometrie de Masse (CSNSM), IN2P3-CNRS, Batiment 108, Orsay Campus 91405 (France)

2009-01-15

313

Magnetic molecules made of nitrogen or boron-doped fullerenes  

Microsoft Academic Search

By using density functional theory, we investigate the electronic structure of a fullerene C60 molecule doped with a nitrogen atom on its surface. We find that the impurity is strongly bonded to the carbon cage and the C60N molecule has a large magnetic moment of 3.00muB. We also study the adsorption of a boron atom on the fullerene. The bonding

Chih-Kai Yang

2008-01-01

314

Boron fullerenes: From B80 to hole doped boron sheets  

Microsoft Academic Search

We demonstrate the existence of a family of stable boron fullerenes containing 80n2 atoms that is related to the family of 60n2 carbon icosahedral fullerene series and is compatible with the recently proposed stable boron sheets composed of triangular and hexagonal motifs. All electron density-functional calculations on the B320 , B720 , B1280 , and B2000 confirm their stability and

Rajendra R. Zope; Tunna Baruah; K. C. Lau; Amy Y. Liu; M. R. Pederson; B. I. Dunlap

2009-01-01

315

Snub boron nanostructures: Chiral fullerenes, nanotubes and planar sheet  

Microsoft Academic Search

We design a new class of electronically stable boron nanostructures, viz.: 60n2 boron fullerene family, boron nanotubes, and a planar boron sheet, which like the ?-boron sheet, consists of triangular and hexagonal motifs and has symmetrically arranged hexagonal holes. The binding energy of the proposed new boron sheet is only 0.02eV\\/atom lower than the ?-boron sheet. The 60n2 boron fullerenes

Rajendra R. Zope; Tunna Baruah

2011-01-01

316

BN substitution reaction of fullerene using an excimer laser irradiation  

Microsoft Academic Search

A heterofullerene in which carbon atoms of the fullerene cage are substituted by heteroatoms (boron and nitrogen) was synthesized by a BN substitution reaction of fullerene C60 upon irradiation with a KrF excimer laser at room temperature. The products were purified by a high performance liquid chromatography and analyzed with a double focusing mass spectrometer, revealing that BNC58 (m\\/z 721)

T. Nakamura; K. Ishikawa; A. Goto; M. Ishihara; T. Ohana; Y. Koga

2001-01-01

317

Photo-induced and thermal processes in fullerene solutions  

NASA Astrophysics Data System (ADS)

The experimental investigations of photo-induced quenching of singlet oxygen luminescence in fullerene solutions (C 60 and C 70 in CCI 4) at optical pumping have shown presence of dependence of 1g?g 0 II lifetime in a solution on initial fullerene concentration, optical pumping intensity and temperature of the solution. The increase of any of these three factors results in the reduction of the singlet oxygen lifetime in the solution, and for C 70 these effects are much stronger than for C 60. It is shown that at pulse optical excitation the solution C 60 is stable and restores the properties some time after the influence. These effects can not be explained by only thermal mechanism, the major part is played by process of formation of fullerene-oxygen complexes which as a quencher for the state 1?g 0 II. These complexes are unstable and are decomposed later into initial components. The initial fullerene C 60 concentration is completely restored in the solution. The initial fullerene C 70 concentration is partly restored in the solution. All these conclusions are based on the results of the study of absorption spectra of fullerene solutions before and some time after the influence on solutions of pulse optical excitation. For CW irradiation, the effects of photoinduced quenching of singlet oxygen luminescence in fullerene solutions have been studied as well. These phenomena are to be considered when developing a generators of singlet oxygen for fullerene-oxygen-iodine laser. The temperature of solution also plays an important role in the development of singlet oxygen generators. To increase the generator efficiency it is necessary to cool the solution efficiently.

Bagrov, I. V.; Belousova, I. M.; Danilov, O. B.; Kiselev, V. M.; Murav'eva, T. D.; Sosnov, E. N.

2007-04-01

318

Porous nanotubes and fullerenes based on covalent organic frameworks  

Microsoft Academic Search

We apply first-principles calculations to predict the stability of porous nanotubes and fullerenes based on covalent organic frameworks (COF’s). Two-dimensional COF’s are extended sheets of covalently linked organic units forming porous materials composed only of light elements. We show that such sheets may be rolled up to form stable nanotubes, and, based on energetic aspects, even a fullerene-based COF might

Maurisan A. Lino; André A. Lino; Mário S. C. Mazzoni

2007-01-01

319

Fullerene derivatives: an attractive tool for biological applications  

Microsoft Academic Search

The fullerene family, and especially C60, has very appealing photo-, electro-chemical and physical properties, which can be exploited in many and different biological fields. Fullerene is able to fit inside the hydrophobic cavity of HIV proteases, inhibiting the access of substrates to the catalytic site of the enzyme. It can be used as radical scavenger; in fact some water-soluble derivatives

Susanna Bosi; Tatiana Da Ros; Giampiero Spalluto; Maurizio Prato

2003-01-01

320

Selective functionalization on [60]fullerene governed by tether length  

Microsoft Academic Search

In order to accomplish the selective synthesis of [60]fullerene bisadducts, the reactions of [60]fullerene with compounds in which two α,α`-dibromo-o-xylene moieties connected by an oligomethylene chain (n = 2-5) were investigated. By this method, only two isomers (cis-2- and cis-3-isomers) were selectively obtained when n = 2 and 3, while another isomer (e-isomer) was obtained when n = 5. When

Masumi Taki; Sachiko Sugita; Yosuke Nakamura; Jun Nishimura; Eiji Kasashima; Eiji Yashima; Yoshio Okamoto

1997-01-01

321

Chemical transformations on the [60] fullerene framework via aziridination processes  

Microsoft Academic Search

Isolation of closed 6,6-bridged aziridinofullerenes 2 by reaction of [60] fullerene with singlet oxycarbonylnitrenes is accompanied by small amounts of previously undetected closed 5,6-adducts 4, thought to arise by trapping of triplet nitrenes. Isomerization of the 6,6-bridged adducts to the corresponding oxazolo[4?,5?:1,2] [60] fullerene derivatives 3 occurs upon heating with the exception of the tert-butoxycarbonyl adduct which eliminates isobutene and

Malcolm R. Banks; J. I. G. Cadogan; Ian Gosney; Philip K. G. Hodgson; Patrick R. R. Langridge-Smith; David W. H. Rankin

1996-01-01

322

Morphology of polymer\\/fullerene bulk heterojunction solar cells  

Microsoft Academic Search

Within the different organic photovoltaic devices the conjugated polymer\\/fullerene bulk heterojunction approach is one of the foci of today's research interest. These devices are highly dependent on the solid state nanoscale morphology of the two components (donor\\/acceptor) in the photoactive layer. The need for finely phase separated polymer-fullerene blends is expressed by the limited exciton diffusion length present in organic

Harald Hoppe; Niyazi Serdar Sariciftci

2006-01-01

323

3He and 4He sorption isotherms by Fullerene crystals  

Microsoft Academic Search

We report 3He and 4He sorption isotherms on C60\\/C70 Fullerene polycrystals. The temperature ranges are for 3He, from 1.55K to 3.37K and, for 4He, from 1.57K to 4.14K. The results give strong evidence that both of the isotopes intercalate into the Fullerene crystal. This opens up the possibility to study the property of 3D quantum fluid confined in this way.

C. P. Chen; S. Mehta; F. M. Gasparini

1994-01-01

324

Energetics of large carbon clusters: Crossover from fullerenes to nanotubes  

Microsoft Academic Search

The energetics of large-sized fullerenes and carbon nanotubes is investigated through first-principles pseudopotential calculations for the carbon cluster of CN (60<=N<=540). The strain energy due to the presence of pentagons, in addition to the curvature effect, makes an important contribution to the energetics of the fullerenes and nanotubes and accurately describes the N dependence of the energy of the spherical

Kyuho Lee; Seungwu Han; Jaejun Yu; Jisoon Ihm

2002-01-01

325

Fullerenes and Interplanetary Dust at the Permian-Triassic Boundary  

NASA Astrophysics Data System (ADS)

We recently presented new evidence that an impact occurred ~250 million years ago at the Permian-Triassic boundary (PTB), triggering the most severe mass extinction in the history of life on Earth. We used a new extraterrestrial tracer, fullerene, a third carbon carrier of noble gases besides diamond and graphite. By exploiting the unique properties of this molecule to trap noble gases inside of its caged structure (helium, neon, argon), the origin of the fullerenes can be determined. Here, we present new evidence for fullerenes with extraterrestrial noble gases in the PTB at Graphite Peak, Antarctica, similar to PTB fullerenes from Meishan, China and Sasayama, Japan. In addition, we isolated a 3He-rich magnetic carrier phase in three fractions from the Graphite Peak section. The noble gases in this magnetic fraction were similar to zero-age deep-sea interplanetary dust particles (IDPs) and some magnetic grains isolated from the Cretaceous-Tertiary boundary. The helium and neon isotopic compositions for both the bulk Graphite Peak sediments and an isolated magnetic fraction from the bulk material are consistent with solar-type gases measured in zero-age deep-sea sediments and point to a common source, namely, the flux of IDPs to the Earth's surface. In this instance, the IDP noble gas signature for the bulk sediment can be uniquely decoupled from fullerene, demonstrating that two separate tracers are present (direct flux of IDPs for 3He vs. giant impact for fullerene).

Poreda, Robert J.; Becker, Luann

2003-01-01

326

Recognition of hydrogen isotopomers by an open-cage fullerene.  

PubMed

We present our study on the recognition of hydrogen isotopes by an open-cage fullerene through determination of binding affinity of isotopes H?/HD/D? with the open-cage fullerene and comparison of their relative molecular sizes through kinetic-isotope-release experiments. We took advantage of isotope H?/D? exchange that generated an equilibrium mixture of H?/HD/D? in a stainless steel autoclave to conduct high-pressure hydrogen insertion into an open-cage fullerene. The equilibrium constants of three isotopes with the open-cage fullerene were determined at various pressures and temperatures. Our results show a higher equilibrium constant for HD into open-cage fullerene than the other two isotopomers, which is consistent with its dipolar nature. D? molecule generally binds stronger than H? because of its heavier mass; however, the affinity for H? becomes larger than D? at lower temperature, when size effect becomes dominant. We further investigated the kinetics of H?/HD/D? release from open-cage fullerene, proving their relative escaping rates. D? was found to be the smallest and H? the largest molecule. This notion has not only supported the observed inversion of relative binding affinities between H? and D?, but also demonstrated that comparison of size difference of single molecules through non-convalent kinetic-isotope effect was applicable. PMID:23918711

Murata, Yasujiro; Chuang, Shih-Ching; Tanabe, Fumiyuki; Murata, Michihisa; Komatsu, Koichi

2013-09-13

327

Towards a fullerene-based quantum computer  

NASA Astrophysics Data System (ADS)

Molecular structures appear to be natural candidates for a quantum technology: individual atoms can support quantum superpositions for long periods, and such atoms can in principle be embedded in a permanent molecular scaffolding to form an array. This would be true nanotechnology, with dimensions of order of a nanometre. However, the challenges of realizing such a vision are immense. One must identify a suitable elementary unit and demonstrate its merits for qubit storage and manipulation, including input/output. These units must then be formed into large arrays corresponding to an functional quantum architecture, including a mechanism for gate operations. Here we report our efforts, both experimental and theoretical, to create such a technology based on endohedral fullerenes or 'buckyballs'. We describe our successes with respect to these criteria, along with the obstacles we are currently facing and the questions that remain to be addressed.

Benjamin, Simon C.; Ardavan, Arzhang; Briggs, G. Andrew D.; Britz, David A.; Gunlycke, Daniel; Jefferson, John; Jones, Mark A. G.; Leigh, David F.; Lovett, Brendon W.; Khlobystov, Andrei N.; Lyon, S. A.; Morton, John J. L.; Porfyrakis, Kyriakos; Sambrook, Mark R.; Tyryshkin, Alexei M.

2006-05-01

328

Optical and magnetic properties of boron fullerenes.  

PubMed

We report linear response properties of the recently proposed boron fullerenes [N. Gonzalez Szwacki et al., Phys. Rev. Lett., 2007, 98, 166804]: magnetic susceptibilities, static dipole polarizabilities and dynamical polarizabilities (i.e. optical and near ultraviolet absorption spectra), calculated from first principles within the (time-dependent) density-functional theory framework. We find that all clusters except B80 are diamagnetic. The strong cancellation between diamagnetic and paramagnetic currents in B80 leads to a very small value for its susceptibility that turns out to be slightly paramagnetic. Static polarizabilities increase linearly with the number of B atoms. Furthermore, the absorption spectrum of B80 is very different from the one of its carbon counterpart C60, exhibiting a low absorption threshold of about 1.5 eV and many peaks in the visible and near ultraviolet. This can be understood by the analysis of the wavefunctions involved in the low energy transitions. PMID:19475170

Botti, Silvana; Castro, Alberto; Lathiotakis, Nektarios N; Andrade, Xavier; Marques, Miguel A L

2009-06-14

329

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.

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

2013-01-01

330

Trifluoromethylated [60]Fullerenes: Synthesis and Characterization  

Microsoft Academic Search

The high temperature reaction of C60 with silver(I) trifluoroacetate followed by 500°C sublimation and HPLC purification has led to the characterization of the trifluoromethyl?[60]fullerenes 1,4?C60(CF3)2, Cs?C60(CF3)4, C1?C60(CF3)4, and C1?C60(CF3)6 by EI?MS and F NMR. The compounds C1?C60(CF3)4 and C1?C60(CF3)6 were obtained with 90+% compositional purity. A sample of C60(CF3)2 also contained ca. 15–20% of a Cs?symmetry isomer of C60(CF3)4. The

Alexey A. Goryunkov; Ilya N. Ioffe; Igor V. Kuvychko; Tatyana S. Yankova; Vitaly Y. Markov; Alexey A. Streletskii; Donald L. Dick; Lev N. Sidorov; Olga V. Boltalina; Steven H. Strauss

2005-01-01

331

33 CFR 334.950 - Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas.  

Code of Federal Regulations, 2013 CFR

... false Pacific Ocean at San Clemente Island, California; Navy shore bombardment...950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment...landing in the waters east of San Clemente Island. (2) All persons in the area...

2013-07-01

332

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...

333

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...

334

Cosmic bombardment 2: Intercepting the bomblets cost-efficiently  

NASA Astrophysics Data System (ADS)

In the present paper, we consider ways-and-means of dealing with earthstrikes of micro-asteroids, bodies which are so small --- and so numerous --- that they strike the Earth every century to every year. These are time-scales so brief that they are of interest to contemporary human individuals and institutions. We are particularly concerned with not only the detection and disposal of cosmic objects which threaten to bombard the Earth, but with practical questions such as cost-to-benefit ratios and implementing means for planetary defenses which are at once near-term, robust and unquestionably acceptable. In the sections which follow, we briefly review those aspects of the cosmic bombardment of the Earth which are of concern during the next several decades. We first take note of the frequency with which the Earth will be struck by asteroids of various sizes and note the corresponding physical damage levels. Then, we translate this into economic damage levels, so as to arrive at the denominator of the cost-benefit ratio of a shield against such bombardment. Next, we consider how such a shield might be realized, emphasizing minimization of its total operating cost (amortization plus operation-and-maintenance) while providing the required reliability. Having developed a cost estimate, we then discuss the cost-benefit ratio of defending humans and their works on this planet from cosmic bombardment.

Wood, Lowell; Hyde, Rod; Ishikawa, Muriel Y.

1990-05-01

335

Blitz: discursive bombardments in 'the war on terror'  

Microsoft Academic Search

This is a composite thesis realised in a sound installation titled Blitz: Discursive bombardments in ‘the war on terror’ with a supporting exegesis. The exegesis offers a context for the project in sound art theory and practice, focussing specifically on the history of experimental ‘electrovocal’ expressive forms. It provides an account of the artist’s perspectives on the topic itself: contemporary

Jennifer M Brown

2008-01-01

336

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

337

THE CHARACTERISTIC DISINTEGRATION OF AGED IRON IN ION BOMBARDMENT  

Microsoft Academic Search

The basic principles of the characteristic disintegration of iron in ion ; bombandment were solved. It is shown that it is a matter of a section of slip ; bands, which are made visible by ion bombardment. The visualization is in direct ; relationship with the age of the iron. Its origin comes from the ; presence of carbon and

A. Masin; V. Havel

1959-01-01

338

Ion bombardment of materials containing alkali metals of alkaline earths  

Microsoft Academic Search

Experiments show that argon ion bombardment of many substances results in the chemical sensitization of the irradiated surface. As a consequence, subsequent exposure to atmospheric water vapor causes evolution of hydrogen, and in certain cases leads to severe surface corrosion. The effect occurs on targets containing elements from the first and second column of the periodic table, and therefore includes

E. H. Hirsch; T. R. Adams

1978-01-01

339

Radiation damage from heavy ion bombardment in high purity aluminum  

SciTech Connect

Aluminum is used as a structural material in research reactors and experimental facilities for high energy physics. The objective of this thesis is to demonstrate the effect of injected copper ions on aluminum and the effect inert helium gas has on the nucleation of voids in aluminum. Pure aluminum was irradiated with copper ions, and aluminum containing helium was bombarded with aluminum ions. Preinjected helium was used because of the neutron promoted (n,..cap alpha..) reaction and because of its inert nature. The results of these irradiations with and without helium are compared to results from other related studies performed with heavy ions and with neutron irradiations. Well annealed samples of high purity aluminum without helium and those containing 0.1, 1.0, 10 at ppm of helium were bombarded with copper ions and aluminium ions to doses between 0.2 dpa to greater than 20 dpa at temperatures ranging from 25C to 200 C. The displacement rates were 5 x 10/sup -4/ to 1 x 10/sup -3/ dpa/sec. Copper ion irradiations produced theta precipitation at the end of ion range and heterogeneous cocentrations of vacancy loops throughout the damage zone. Self-ion bombardments produced lower concentrations of dislocation tangles and vacancy loops. When helium was preinjected by a radioactive ..cap alpha.. source, ion bombardment produced voids. No voids were ever observed in helium free ion bombarded aluminum samples after doses of more than 20 dpa. The temperature effect on void formation followed current theoretical trends in which the void density decreases with increasing temperature and the void size increases with increasing temperature.

McLaurin, S.K.

1984-01-01

340

Thermally induced amorphous to crystalline transformation of argon ion bombarded GaAs studied with surface Brillouin and Raman scattering  

NASA Astrophysics Data System (ADS)

Surface Brillouin scattering (SBS) and Raman spectroscopy have been used to investigate the recrystallisation of an amorphous layer of GaAs created on single crystal (0 0 1) GaAs by ion bombardment with 100 keV argon ions with a fluence of 5 × 1016 ions/cm2 at a temperature of ˜65 °C. Samples were isochronally annealed and the light scattering measurements were performed after each annealing step. The SBS studies confirm structural changes resulting in continuous stiffening of the layer beginning above 200 °C and finally attaining a maximum value above 500 °C. The Raman studies show evidence of full recrystallisation above 500 °C, with the appearance of both LO and TO peaks indicating that the reformed layer is polycrystalline.

Jakata, K.; Wamwangi, D. M.; Sumanya, C.; Mathe, B. A.; Erasmus, R. M.; Naidoo, S. R.; Comins, J. D.

2012-09-01

341

Lifetime measurement of the 167.1 keV state in {sup 41}Ar  

SciTech Connect

The Advanced-Time-Delayed method was used to measure lifetimes of the states in {sup 41}Ar populated in the {beta} decay of {sup 41}Cl. The nuclei {sup 41}Cl were produced at ISOLDE by 1.4-GeV proton bombardment of a thick UC{sub x} target and mass-separated as molecular ions, XeCl{sup +}. Our measured half-life of the 167.1-keV state, T{sub 1/2}=315(15) ps, is significantly lower than the previously measured value of 410(30) ps. We have also determined T{sub 1/2}=260(80) ps and T{sub 1/2}{<=}46 ps for the 515.9- and 1867.7-keV states, respectively. These are the shortest lifetimes measured so far with the ultrafast timing method using the new LaBr{sub 3}(Ce) crystals for {gamma}-ray detection.

White, E. R. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46616 (United States); Mach, H. [Institute for Structure and Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46616 (United States); Department of Nuclear and Particle Physics, Uppsala University, Post Office Box 535, S-75121 Uppsala (Sweden); Fraile, L. M. [ISOLDE, PH Department, CERN, CH-1211 Geneva 23 (Switzerland); Koester, U. [ISOLDE, PH Department, CERN, CH-1211 Geneva 23 (Switzerland); Institut Laue-Langevin, Boite Postale 156, F-38042 Grenoble Cedex (France); Arndt, O. [Institut fuer Kernchemie, Universitaet Mainz, Fritz-Strassmann Weg 2, D-55128 Mainz (Germany); Blazhev, A.; Braun, N.; Fransen, C.; Jolie, J. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstrasse 77, D-50937 Koeln (Germany); Boelaert, N. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstrasse 77, D-50937 Koeln (Germany); Department of Subatomic and Radiation Physics, Ghent University, B-9000 Ghent (Belgium); Borge, M. J. G.; Boutami, R.; Reillo, E.-M.; Tengblad, O. [Instituto de Estructura de la Materia, CSIC, E-28006 Madrid (Spain); Bradley, H. [Department of Nuclear and Particle Physics, Uppsala University, Post Office Box 535, S-75121 Uppsala (Sweden); School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia); Dlouhy, Z.; Ugryumov, V. [Nuclear Physics Institute, AS CR, CZ-25068, Rez (Czech Republic); Fynbo, H. O. U. [Institut for Fysik og Astronomi, Aarhus Universitet, DK-8000 Aarhus C (Denmark); Hinke, Ch.; Kroell, T. [Physics Department, Technical University Munich, D-85748 Garching (Germany)] (and others)

2007-11-15

342

Sputtering of (100) Si by 350 keV Co implantation  

NASA Astrophysics Data System (ADS)

Silicon (100) substrates have been implanted with 350 keV Co to fluences in the range 7.2 × 10 15 to 3.3 × 10 17 Co/cm 2 at temperatures near 100 ° C and 450 ° C. Rutherford backscattering profiles of the implanted Co were analyzed by the computer code MEASTRI to extract values for the sputtering coefficient, S, of Si by Co at these temperatures. At the lower temperatures S =1.1± 0.2 results from the analysis, while at 450 °C we obtain S=1.8 ± 0.2. The value predicted by the Matsunanu/Yamamura formula is S = 1.6. Our results are consistent with those of Nizam and Benazeth-Colombie which show a similar variation in S for 40 keV Ar + bombardment of (100) Si in the temperature range 50-550 °C. This temperature variation is interpreted as due to an altered surface binding energy resulting from surface rearrangement at the higher temperatures.

Brice, D. K.; Barbour, J. C.

1989-04-01

343

Selective and high-yield synthesis of higher fullerenes  

SciTech Connect

Fullerenes have been prepared by dc arc synthesis with graphite (anode) rods containing light elements such as B, Si, or Al in a series of concentrations. Furthermore, the influence of mixing N{sub 2} (g) with He(g) on the yield of higher fullerenes has been addressed. For each type of experiment, the relative fullerene yields are obtained from the relative peak areas in surface analysis by laser ionization-mass spectrometry (SALI-MS) spectra and the absolute yield of C{sub 60} and C{sub 70} from calibrated HPLC; the relative yields in SALI-MS represent closely the nascent distribution in the primary soots. We determine the approximate absolute yields of higher fullerenes, for which extinction coefficients are not yet available for HPLC analysis, by scaling the absolute C{sub 60} and C{sub 70} yields with the relative concentrations from SALI-MS. The most prominent increased higher fullerene yield was obtained with a 1% B-doped graphite rod with a 2:100 volume mixture of N{sub 2}(g): He(g); the absolute yield of C{sub 60} was reduced from 8.85% to 2.75%, and the yield of higher fullerenes such as C{sub 78} and C{sub 84} was increased by a factor of 2 over the pure C, pure He(g) case. We conclude that using a B-doped graphite rod and mixing in small amounts of N{sub 2}(g) into He(g) enhances both the absolute and relative yields of higher fullerenes. 18 refs., 4 figs., 3 tabs.

Tohji, K.; Paul, A.; Moro, L.; Malhotra, R.; Lorents, D.C.; Ruoff, R.S. [SRI International, Menlo Park, CA (United States)

1995-12-14

344

Preparation and characterization of stable aqueous higher-order fullerenes  

NASA Astrophysics Data System (ADS)

Stable aqueous suspensions of nC60 and individual higher fullerenes, i.e. C70, C76 and C84, are prepared by a calorimetric modification of a commonly used liquid-liquid extraction technique. The energy requirement for synthesis of higher fullerenes has been guided by molecular-scale interaction energy calculations. Solubilized fullerenes show crystalline behavior by exhibiting lattice fringes in high resolution transmission electron microscopy images. The fullerene colloidal suspensions thus prepared are stable with a narrow distribution of cluster radii (42.7 ± 0.8 nm, 46.0 ± 14.0 nm, 60 ± 3.2 nm and 56.3 ± 1.1 nm for nC60, nC70, nC76 and nC84, respectively) as measured by time-resolved dynamic light scattering. The ?-potential values for all fullerene samples showed negative surface potentials with similar magnitude ( - 38.6 ± 5.8 mV, - 39.1 ± 4.2 mV, - 38.9 ± 5.8 mV and - 41.7 ± 5.1 mV for nC60, nC70, nC76 and nC84, respectively), which provide electrostatic stability to the colloidal clusters. This energy-based modified solubilization technique to produce stable aqueous fullerenes will likely aid in future studies focusing on better applicability, determination of colloidal properties, and understanding of environmental fate, transport and toxicity of higher-order fullerenes.

Aich, Nirupam; Flora, Joseph R. V.; Saleh, Navid B.

2012-02-01

345

Temperature-dependent mechanisms of lithium erosion from lithium-based liquid metals under low-energy bombardment  

NASA Astrophysics Data System (ADS)

Erosion from liquids under low-energy, light-particle bombardment has been studied at the Ion-surface Interaction Experiment (IIAX) facility at the University of Illinois^1. A variety of liquids are studied including lithium, tin-lithium and tin. Quartz crystal microbalance technology is used to measure lithium erosion including evaporation and sputtering under a variety of surface conditions, temperatures and incident particle energies. In addition to these measurements, this work includes self-consistent modeling done with VFTRIM-3D ^2 and TRVMC-95. Results indicate that the near-surface deposited energy density and temperature-dependent surface binding energy are important mechanisms in understanding the erosion behavior of liquid metals as the sample temperature and incident particle energy is varied. The study includes measurements with H^+, D^+, He^+, Ne^+, Ar^+ and Li^+ bombardment at energies between 0.1-1.0 keV and 45-degree incidence. ^1J.P. Allain, D.N. Ruzic, M.R. Hendricks, J. Nucl. Mater. 290-293 (2001) 180. ^2D.N. Ruzic, Nuclear Instrum. Methods B 47 (1990) 118.

Allain, J. P.; Coventry, M. D.; Ruzic, D. N.

2002-11-01

346

Visible-light-mediated addition of ?-aminoalkyl radicals to [60]fullerene by using photoredox catalysts.  

PubMed

The functionalization of fullerene has been extensively studied and various fullerene derivatives have been synthesized. We have succeeded in the functionalization of [60]fullerene by using ?-aminoalkyl radicals generated by visible-light-mediated single-electron oxidation of ?-silylamines as synthetic intermediates. In these reactions, the introduction of diarylamino groups, which are useful electron donors, has been easily achieved. PMID:24700543

Miyake, Yoshihiro; Ashida, Yuya; Nakajima, Kazunari; Nishibayashi, Yoshiaki

2014-05-12

347

A novel BF2-chelated azadipyrromethene-fullerene dyad: synthesis, electrochemistry and photodynamics.  

PubMed

The synthesis, structure, electrochemistry and photodynamics of a BF(2)-chelated azadipyrromethene-fullerene dyad are reported in comparison with BF(2)-chelated azadipyrromethene without fullerene. The attachment of fullerene resulted in efficient generation of the triplet excited state of the azadipyrromethene via photoinduced electron transfer. PMID:22083226

Amin, Anu N; El-Khouly, Mohamed E; Subbaiyan, Navaneetha K; Zandler, Melvin E; Fukuzumi, Shunichi; D'Souza, Francis

2012-01-01

348

Modeling the self-assembly of functionalized fullerenes on solid surfaces using Monte Carlo simulations  

Microsoft Academic Search

Since their discovery 25 years ago, carbon fullerenes have been widely studied for their unique physicochemical properties and for applications including organic electronics and photovoltaics. For these applications it is highly desirable for crystalline fullerene thin films to spontaneously self-assemble on surfaces. Accordingly, many studies have functionalized fullerenes with the aim of tailoring their intermolecular interactions and controlling interactions with

Gregory J. Bubnis

2010-01-01

349

Solubility of fullerenes in n -alkanoic acids C 2 –C 9  

Microsoft Academic Search

The solubility of fullerene C60 and a fullerene mixture [C60 (75%), C70 (24%), C76–80 (1%)] in linear alkanoic acids (C2–C9) was determined at 20°C. The solubilities of C60 and a fullerene mixture in carboxylic acids were examined in relation to the number of carbon atoms in the carboxylic acid.

K. N. Semenov; N. A. Charykov; A. K. Pyartman; V. A. Keskinov; V. V. Lishchuk; O. V. Arapov; N. I. Alekseev

2007-01-01

350

Impact of physicochemical properties of engineered fullerenes on key biological responses  

SciTech Connect

Engineered fullerenes are widely integrated into several commercial and medical products and are now also being recognized as byproducts of many industrial activities. For most applications fullerenes have to be chemically modified. Surface modification of fullerenes can potentially impact their effect on biosystems. The purpose of the current study was to establish criteria to correlate fullerene structure to biological responses. We report studies of cellular responses induced by three different types of fullerenes that provide varying chemical and physical properties such as electronic behavior, solubility, and degree of agglomeration. Using a systematic and multipronged approach for material characterization and employing critical biological endpoints, we determined the impact of the physicochemical properties of fullerenes on cellular interactions. We examined the ability of these fullerenes to regulate intracellular oxidative stress, necrosis and apoptosis in human monocytic THP1 cells. Results indicate that the carboxylate derivatization of fullerenes was the determining factor in their ability to induce apoptosis. In contrast, the dispersion characteristics of fullerenes were found to be more relevant when considering their redox function. We also established a significant role for functionalization-dependent fullerene-regulation of the caspase proteases in the elicited responses. In addition, there was a notable increase in the level of several anti-oxidant enzymes. Collectively, the results clearly indicate that the physicochemical properties of fullerenes significantly influence the elicited biological response, thus impacting future applications. This study is an initial effort to lay the groundwork for routine correlation and predictive analysis on engineered fullerenes, thus expediting their use.

Rebecca, Martin [B-7, Bioscience Div, Los Alamos National Laboratory, M888, TA 43, HRL-1, Los Alamos, NM 87545 (United States); Hsing-Lin, Wang [C-PCS: Physical Chem and Applied Spectroscopy, Los Alamos National Laboratory, J567, TA-46, Building 0535, Room 110, Los Alamos, NM 87545 (United States); Jun, Gao [B-7, Bioscience Div, Los Alamos National Laboratory, M888, TA 43, HRL-1, Los Alamos, NM 87545 (United States); Srinivas, Iyer [B-8, Bioscience Div, Los Alamos National Laboratory, M888, TA 43, HRL-1, Los Alamos, NM 87545 (United States); Gabriel, Montano A.; Jennifer, Martinez; Andrew, Shreve P.; Bao Yuping [MPA-CINT: Center for Integrated Nanotechnologies, Los Alamos National Laboratory K771, TA-03, Building 1420, Los Alamos, NM 87545 (United States); Wang, C.-C. [C-PCS: Physical Chem and Applied Spectroscopy, Los Alamos National Laboratory, J567, TA-46, Building 0535, Room 110, Los Alamos, NM 87545 (United States); Chang Zhong [MPA-CINT: Center for Integrated Nanotechnologies, Los Alamos National Laboratory K771, TA-03, Building 1420, Los Alamos, NM 87545 (United States); Gao Yuan [Sensor Research and Development Corporation, 17 Godfrey Drive, Orono, ME 04473 (United States); Rashi, Iyer [B-7, Bioscience Div, Los Alamos National Laboratory, M888, TA 43, HRL-1, Los Alamos, NM 87545 (United States)], E-mail: rashi@lanl.gov

2009-01-01

351

Solubilization of fullerene C 60 in micellar solutions of different solubilizers  

Microsoft Academic Search

Fullerene (C60), the third carbon allotrope, is a classical engineered material with the potential application in biomedicine. However, extremely high hydrophobicity of fullerene hampers its direct biomedical evaluation and application. In this work, we investigated the solubilization of fullerene using 9 different solubility enhancers: Tween 20, Tween 60, Tween 80, Triton X-100, PVP, polyoxyethylene (10) lauryl ether, n-dodecyl trimethylammonium chloride,

Vukosava Milic Torres; Mihalj Posa; Branislava Srdjenovic; Ana Luísa Simplício

2011-01-01

352

The Role of the Oxygen Molecule in the Photolysis of Fullerenes  

Microsoft Academic Search

Experiments designed to clarify the role of molecular oxygen in the photolysis of fullerene are described. The formation of oxygen-fullerene adducts, both in fullerene solutions in various solvents and in micro-crystallites formed by evaporating these solutions, and their photolysis was studied under various experimental conditions. The results confirm that the role of oxygen in the photolysis process in these systems

L. Juha; M. Fárníková; V. Hamplová; J. Kodymová; A. Müllerová; J. Krása; L. Láska; O. Špalek; P. Kubát; L. Stibor; E. Koudoumas; S. Couris

2000-01-01

353

Radical Bulk Polymerization of Styrene in the Presence of Fullerene[60  

Microsoft Academic Search

The polymerization of styrene in the presence of fullerene[60] using AIBN as the initiator as well as under thermal polymerization conditions was investigated. The results indicate that the polymer yields decrease with an increase of the amount of fullerene present during the initiated and thermal polymerization. Thus, an inhibitory effect of fullerene[60] on the radical polymerization of styrene can be

N. Arsalani; K. E. Geckeler

1996-01-01

354

Stability and reversibility of the electrochromic effect in fullerene thin films  

Microsoft Academic Search

The electrochromic effect is observed in fullerene thin films when, under applied electric field, various ionic species are intercalated into the interstitial spaces between fullerene molecules. Within limits, the process is electrically reversible. Residual oxygen, both in the electrolyte system and in the fullerene thin film itself, as well as trace water levels, significantly degrade electrochromic stability. The degree of

Gregory A. Konesky

1997-01-01

355

Molecular dynamics studies of the C(60) fullerene associations in aqueous solutions and a biological membrane  

NASA Astrophysics Data System (ADS)

The associative behavior of C60 fullerenes in water and a biological membrane was studied using computer molecular dynamics (MD) simulations. Multiple histogram method combined with umbrella sampling technique was used in calculating the fullerene pairwise free energy as a function of separation. It was observed that water wets the fullerene surface due to the high fullerene atomic density and therefore the strong fullerene-water dispersion interaction. Despite the fact of the insolubility of fullerenes, water was found to promote the dispersion of fullerenes in aqueous solution. A decomposition of the solvent-induced potential of mean force between fullerenes into entropy and energy (enthalpy) contributions revealed that the water-induced repulsion between fullerenes is energetic in origin, contrasting strongly to entropy-driven association observed for conventional non-polar solutes. The repulsive interaction was observed to decrease at elevated temperature due to an increasing contribution from a relatively weak entropy-driven association. The surface curvature effect was surveyed by studying nanoparticles of different shapes (fullerene, carbon nanotubes and graphenes) with similar chemical structures. As for a potential application of fullerene in biomedical systems, the poly(ethylene oxide) (PEO) modified fullerene derivative interactions in aqueous solution and the bare fullerene-fullerene interactions inside a dimyristoylphosphatidylcholine (DMPC) lipid bilayer were investigated. It shows that while the attraction between two PEO-modified fullerenes is stronger and longer range than that between two bare C60 fullerenes in aqueous solution, the PEO-modified fullerenes do not phase-separate in water but rather aggregate in chainlike clusters at concentrations where unmodified fullerenes completely phase-separate. The results of pairwise fullerene interactions inside a DMPC lipid shows that fullerenes, constrained in the same lateral plane, was found to be significantly less attractive inside the lipid bilayer than in an alkane melt of the same molecular weight as the surfactant tails. Contrasting to small hydrophobic solutes, fullerene situates off the bilayer center in favor of the stronger dispersion interactions with the denser region of the bilayer.

Li, Liwei

356

Roughening and smoothing behavior of single crystal Si by low energy Ar + ion bombardment  

NASA Astrophysics Data System (ADS)

We examined the dependence of smoothing or roughening behavior on the initial surface roughness of single crystal Si. An atomically flat cleaved Si surface of roughness 0.038 nm rms and a Si wafer substrate roughness of 0.12 nm rms were sputtered by 0.2-3 keV Ar + ion beam at normal ion incidence. Surface morphology was observed by atomic force microscope (AFM) under DFM mode. Result shows that the rough surface ( R = 0.12 nm rms) becomes smooth ( R = 0.068 nm rms) and the smooth surface ( R = 0.038 nm rms) becomes rough ( R = 0.068 nm rms) due to low energy Ar + ion beam sputtering process and both finally saturates at 0.068 nm rms. The saturated roughness R sat depends on ion beam energy and increases with increasing beam energy. To understand the roughening mechanism, we studied the dynamic scaling theory and measured the roughness exponent ? and growth exponent ?. The values of ? = 1.03 and ? = 0.28 are in agreement with the Cuerno's one dimensional simulation of the Linear diffusion equation with noise, that corresponds to the initial stage of dynamic scaling of ion bombardment.

Pahlovy, S. A.; Mahmud, S. F.; Yanagimoto, K.; Aikawa, N.; Miyamoto, I.

2012-02-01

357

Scintillation degradation of YAG: Ce under low-energy ion bombardment  

NASA Astrophysics Data System (ADS)

We have measured the degradation of the scintillation yield of single crystal YAG: Ce under He+?irradiation at low energies between 28 and 58 keV. The scintillator was irradiated at the rare isotope ReAccelerator (ReA) facility at the National Superconducting Cyclotron Laboratory (NSCL). The scintillation emission is attributed to its rapid 5d-4f transition of Ce3+ ions. As the bombardment time increases, an exponential decay of the light output is observed due to the induced radiation damage of the crystal lattice. Color centers formed by the radiation damage are likely to act as exciton capturing centers, leading to a quench of the scintillator yield. It is possible that these color centers are oxygen vacancies with trapped electrons or the formation of Ce4+ and Y2+. The decrease of the experimentally observed light yield as a function of particle fluence is found to be in fair agreement with the Birks model. Analysis indicates that the damage cross section of scintillation centers slightly decreases with the ion energy. The value of the relative exciton capture probability for YAG: Ce is considerably small compared to the magnitude proposed by Birks for anthracene under ?-particle irradiation. On the other hand, the half brightness fluence is estimated to be larger at higher energy because the ion particles create less damaged centers per unit of path length and activate more luminescence centers. Therefore, the scintillator degrades slower and exhibits better scintillation efficiency under higher-energy irradiation.

Lin, L. Y.; Benatti, C.; Perdikakis, G.; Leitner, D.; Krause, S. W.; Yurkon, J.

2013-01-01

358

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

359

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

360

Rotor-stator molecular crystals of fullerenes with cubane  

NASA Astrophysics Data System (ADS)

Cubane(C8H8) and fullerene(C60) are famous cage molecules with shapes of platonic or archimedean solids. Their remarkable chemical and solid-state properties have induced great scientific interest. Both materials form polymorphic crystals of molecules with variable orientational ordering. The idea of intercalating fullerene with cubane was raised several years ago but no attempts at preparation have been reported. Here we show that C60 and similarly C70 form high-symmetry molecular crystals with cubane owing to topological molecular recognition between the convex surface of fullerenes and the concave cubane. Static cubane occupies the octahedral voids of the face-centred-cubic structures and acts as a bearing between the rotating fullerene molecules. The smooth contact of the rotor and stator molecules decreases significantly the temperature of orientational ordering. These materials have great topochemical importance: at elevated temperatures they transform to high-stability covalent derivatives although preserving their crystalline appearance. The size-dependent molecular recognition promises selective formation of related structures with higher fullerenes and/or substituted cubanes.

Pekker, Sándor; Kováts, Éva; Oszlányi, Gábor; Bényei, Gyula; Klupp, Gyöngyi; Bortel, Gábor; Jalsovszky, István; Jakab, Emma; Borondics, Ferenc; Kamarás, Katalin; Bokor, Mónika; Kriza, György; Tompa, Kálmán; Faigel, Gyula

2005-10-01

361

ON THE EXCITATION AND FORMATION OF CIRCUMSTELLAR FULLERENES  

SciTech Connect

We compare and analyze the Spitzer mid-infrared spectrum of three fullerene-rich planetary nebulae in the Milky Way and the Magellanic Clouds: Tc1, SMP SMC 16, and SMP LMC 56. The three planetary nebulae share many spectroscopic similarities. The strongest circumstellar emission bands correspond to the infrared active vibrational modes of the fullerene species C{sub 60} and little or no emission is present from polycyclic aromatic hydrocarbons. The strengths of the fullerene bands in the three planetary nebulae are very similar, while the ratios of the [Ne III]15.5 {mu}m/[Ne II]12.8 {mu}m fine structure lines, an indicator of the strength of the radiation field, are markedly different. This raises questions about their excitation mechanism and we compare the fullerene emission to fluorescent and thermal models. In addition, the spectra show other interesting and common features, most notably in the 6-9 {mu}m region, where a broad plateau with substructure dominates the emission. These features have previously been associated with mixtures of aromatic/aliphatic hydrocarbon solids. We hypothesize on the origin of this band, which is likely related to the fullerene formation mechanism, and compare it with modeled hydrogenated amorphous carbon that present emission in this region.

Bernard-Salas, J.; Jones, A. P. [Institut d'Astrophysique Spatiale, CNRS/Universite Paris-Sud 11, F-91405 Orsay (France); Cami, J.; Peeters, E.; Micelotta, E. R. [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Groenewegen, M. A. T., E-mail: jbernard@ias.u-psud.fr [Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels (Belgium)

2012-09-20

362

Using surface plasmonics to turn on fullerene's dark excitons  

NASA Astrophysics Data System (ADS)

Using our recently proposed Bethe-Salpeter G0W0 formulation, we explore the optical absorption spectra of fullerene (C60) near coinage metal surfaces (Cu, Ag, and Au). We pay special attention to how the surface plasmon ?S influences the optical activity of fullerene. We find that the lower-energy fullerene excitons at 3.77 and 4.8 eV only weakly interact with the surface plasmon. However, we find that the surface plasmon strongly interacts with the most intense fullerene ? exciton, i.e., the dipolar mode at ?? +?6.5 eV, and the quadrupolar mode at ?? -?6.8 eV. When fullerene is close to a copper surface (z0?5.3 Å), the dipolar mode ?+ and "localized" surface plasmons in the molecule/surface interface hybridize to form two coupled modes which both absorb light. As a result, the molecule gains an additional optically active mode. Moreover, in resonance, when ?S??±, the strong interaction with the surface plasmon destroys the ?- quadrupolar character and it becomes an optically active mode. In this case, the molecule gains two additional very intense optically active modes. Further, we find that this resonance condition, ?S??±, is satisfied by silver and gold metal surfaces.

Despoja, V.; Mowbray, D. J.

2014-05-01

363

Photoabsorption spectra of small fullerenes and Si-heterofullerenes  

NASA Astrophysics Data System (ADS)

We study the spectral properties of two kinds of derivatives of the carbon fullerene C60, small fullerenes and Si-heterofullerenes, by ab initio calculations. The principal method of study is the time-dependent density-functional theory in its full time-propagation form. C20, C28, C32, C36, and C50, the most stable small fullerenes in the range of C20-C50, are found to have characteristic features in their optical absorption spectra, originating from the geometry of the molecules in question. The comparison of measured and calculated absorption spectra is found to be a useful tool in differentiating between different, almost isoenergetic ground state structure candidates of small fullerenes. Substitutionally doped fullerenes are of interest due to their enhanced chemical reactivity. It is suggested that the doping degree can be obtained by studying the absorption spectra. For example, it is observed that the spectra gradually change when doping C60 up to C48Si12 so that absorption in the visible and near infrared regions increases.

Koponen, Laura; Puska, Martti J.; Nieminen, Risto M.

2008-04-01

364

Energy and photoinduced electron transfer in porphyrin-fullerene dyads  

SciTech Connect

Time-resolved fluorescence and absorption techniques have been used to investigate energy and photoinduced electron transfer in a covalently linked free-base porphyrin-fullerene dyad and its zinc analogue. In toluene, the porphyrin first excited singlet states decay in about 20 ps by singlet-singlet energy transfer to the fullerene. The fullerene first excited singlet state is not quenched and undergoes intersystem crossing to the triplet, which exists in equilibrium with the porphyrin triplet state. In benzonitrile, photoinduced electron transfer from the porphyrin first excited singlet state to the fullerene competes with energy transfer. The fullerene excited singlet state is also quenched by electron transfer from the porphyrin. Overall, the charge-separated state is produced with a quantum yield approaching unity. This state lives for 290 ps in the free-base dyad and 50 ps in the zinc analog. These long lifetimes suggest that such dyads may be useful as components of more complex light-harvesting systems. 32 refs., 12 figs., 1 tab.

Kuciauskas, D.; Lin, S.; Seely, G.R.; Moore, A.L.; Moore, T.A.; Gust, D. [Arizona State Univ., Tempe, AZ (United States)] [Arizona State Univ., Tempe, AZ (United States); Drovetskaya, T.; Reed, C.A. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States); Boyd, P.D.W. [Univ. of Auckland (New Zealand)] [Univ. of Auckland (New Zealand)

1996-09-26

365

Fullerene data mining using bibliometrics and database tomography  

PubMed

Database tomography (DT) is a textual database analysis system consisting of two major components: (1) algorithms for extracting multiword phrase frequencies and phrase proximities (physical closeness of the multiword technical phrases) from any type of large textual database, to augment (2) interpretative capabilities of the expert human analyst. DT was used to derive technical intelligence from a fullerenes database derived from the Science Citation Index and the Engineering Compendex. Phrase frequency analysis by the technical domain experts provided the pervasive technical themes of the fullerenes database, and phrase proximity analysis provided the relationships among the pervasive technical themes. Bibliometric analysis of the fullerenes literature supplemented the DT results with author/journal/institution publication and citation data. Comparisons of fullerenes results with past analyses of similarly structured near-earth space, chemistry, hypersonic/supersonic flow, aircraft, and ship hydrodynamics databases are made. One important finding is that many of the normalized bibliometric distribution functions are extremely consistent across these diverse technical domains and could reasonably be expected to apply to broader chemical topics than fullerenes that span multiple structural classes. Finally, lessons learned about integrating the technical domain experts with the data mining tools are presented. PMID:10661546

Kostoff; Braun; Schubert; Toothman; Humenik

2000-01-01

366

Non-IPR fullerenes with properly closed shells.  

PubMed

Fullerenes with properly closed shells (having exactly half their adjacency eigenvalues strictly positive) are rare. All reported examples obey the isolated-pentagon rule (IPR), usually considered a necessary condition of overall stability, and fall into three series (leapfrogs, carbon cylinders and sporadic closed shells). It is shown here that there also exist fullerenes with properly closed shells that violate the IPR ('super-sporadic' fullerenes). All have negative LUMO eigenvalues of small magnitude. Exhaustive search finds four examples with 160 or fewer vertices: one isomer of C(120), two of C(156) and one of C(160). The first three contain single pentagon pairs and the fourth, a linear triple of fused pentagons. Larger examples can be found. A capping construction gives a series of properly closed shell fullerenes of C(3)/C(3v) symmetry, each with a single fully fused triple of pentagons and ?632 vertices. Tubular extension of the C(120) example leads a series of C(1)/C(s) isomer pairs with ?168 vertices, retaining the single pentagon adjacency and approaching isospectrality with increasing size. Both constructions are conjectured to lead to an infinite number of super-sporadic fullerenes. PMID:20936217

Fowler, Patrick W; Myrvold, Wendy

2010-11-28

367

Rotor-stator molecular crystals of fullerenes with cubane.  

PubMed

Cubane (C8H8) and fullerene (C60) are famous cage molecules with shapes of platonic or archimedean solids. Their remarkable chemical and solid-state properties have induced great scientific interest. Both materials form polymorphic crystals of molecules with variable orientational ordering. The idea of intercalating fullerene with cubane was raised several years ago but no attempts at preparation have been reported. Here we show that C60 and similarly C70 form high-symmetry molecular crystals with cubane owing to topological molecular recognition between the convex surface of fullerenes and the concave cubane. Static cubane occupies the octahedral voids of the face-centred-cubic structures and acts as a bearing between the rotating fullerene molecules. The smooth contact of the rotor and stator molecules decreases significantly the temperature of orientational ordering. These materials have great topochemical importance: at elevated temperatures they transform to high-stability covalent derivatives although preserving their crystalline appearance. The size-dependent molecular recognition promises selective formation of related structures with higher fullerenes and/or substituted cubanes. PMID:16142242

Pekker, Sándor; Kováts, Eva; Oszlányi, Gábor; Bényei, Gyula; Klupp, Gyöngyi; Bortel, Gábor; Jalsovszky, István; Jakab, Emma; Borondics, Ferenc; Kamarás, Katalin; Bokor, Mónika; Kriza, György; Tompa, Kálmán; Faigel, Gyula

2005-10-01

368

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

PubMed

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. PMID:24593515

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

369

Tuning the properties of polymer bulk heterojunction solar cells by adjusting fullerene size to control intercalation  

SciTech Connect

We demonstrate that intercalation of fullerene derivatives between the side chains of conjugated polymers can be controlled by adjusting the fullerene size and compare the properties of intercalated and nonintercalated poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT):fullerene blends. The intercalated blends, which exhibit optimal solar-cell performance at 1:4 polymer:fullerene by weight, have better photoluminescence quenching and lower absorption than the nonintercalated blends, which optimize at 1:1. Understanding how intercalation affects performance will enable more effective design of polymer:fullerene solar cells.

Cates, N.C.

2010-02-24

370

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

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

371

Fullerene nanostructure design with cluster ion impacts  

Microsoft Academic Search

50keV C60+ cluster ions have been applied for modification of the C60 film structure. The modification is found to be sensitive to the ion dose. The cluster ion irradiation with the doses lower than 25×1014ions\\/cm2 leads to formation of the pyramid-like nanodots on the film surface. In parallel, Raman spectra show the C60 quality improvement in solid state suggesting film

Vasily Lavrentiev; Jiri Vacik; Hiroshi Naramoto; Kazumasa Narumi

2009-01-01

372

Semiconductor surface diffusion: Effects of low-energy ion bombardment  

SciTech Connect

We offer a revised mechanism to describe our previous measurements of surface diffusion under low-energy ion bombardment in the Ge/Si(111) system. We show that direct ion-induced motion of diffusing atoms (the effect commonly cited as important in ion beam assisted deposition) cannot account for these observations. Instead, we rationalize the results through processes in which ions create long-lived surface vacancies or spatially extended defects that heal continuously during bombardment. These ideas rationalize several important aspects of the experimental data that were previously unexplained, including the appearance of ion effects at very low ion fluxes, the simple Arrhenius behavior of the diffusivity, the rough magnitudes of the observed energy thresholds, and the ion-induced inhibition of diffusion at high temperatures.

Ditchfield, R.; Seebauer, E. G.

2001-03-15

373

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

SciTech Connect

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

Melnichenko, Y.B.; Wignall, G.D.; Affholter, K.A. [and others

1997-01-01

374

Polarizability of fullerene [2+2]-dimers: a DFT study.  

PubMed

Currently, the exaltation of polarizability of (C60)2 dimers has been predicted with DFT-methods (D. Sh. Sabirov, RSC Adv., 2013, 3(42), 19430). It consists of an increase in the polarizability when two C60 molecules are united, forming a [2+2]-dimer. In the present work, we point attention to the bicage structures of the other fullerenes, which are promising compounds for nano-applications. We have performed the first density-functional theory study on the polarizability of fullerene [2+2]-dimers (Cn)2 (n = 20, 24, 30, 36, 50, and 70) and shown that the exaltation of polarizability is typical for all the members of the fullerenes family. PMID:24798931

Sabirov, Denis Sh; Terentyev, Anton O; Bulgakov, Ramil G

2014-06-25

375

Excellent magnetic properties of fullerene encapsulated ferromagnetic nanoclusters  

NASA Astrophysics Data System (ADS)

Ferromagnetic nanoclusters are very useful for a magnetic recording. However, application of ferromagnetic nanoclusters is limited due to air-oxidation. One way to solve air-oxidation is to encapsulate ferromagnetic nanoclusters with inert materials such as carbon when they are produced. This allows us to keep excellent magnetic properties for a long time. In this work, we report a very simple synthetic method of fullerene (i.e., onions and nanotubes) encapsulated ferromagnetic nickel and cobalt nanoclusters by thermally decomposing metallocene vapors with a resistive heater. Protection from air-oxidation was tested by annealing encapsulated ferromagnetic nanoclusters in air up to ˜180°C for half a day and then, recording XRD patterns. No oxide peaks were observed in the XRD patterns, indicating that oxidation protection via fullerene encapsulation is very good. Magnetic property measurement showed that both fullerene encapsulated nickel and cobalt nanoclusters possessed excellent magnetic properties.

Lee, G. H.; Huh, S. H.; Jeong, J. W.; Ri, H.-C.

2002-05-01

376

Advancement and problems of fullerene-oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The methods of improving the efficiency of a fullerene-oxygen-iodine laser are investigated. In the course of this research, we developed new fullerene coatings that possess better mechanical and radiative hardness, as well as higher efficiency of singlet oxygen generation. We show that, by using these coatings, the energy yield per unit volume of the active medium can be increased to 9 J/l, which is almost two times higher than the previous result. The energy efficiency of the laser can also be increased by a factor of nearly two. At the same time, several problems were revealed that hinder the further improvement of the laser efficiency and its long-term operation with stable parameters of the output radiation. We outline principal approaches to further optimization of the laser design that would help to overcome the negative factors and make it possible to create a fullerene-oxygen-iodine laser with high and stable parameters of the output radiation.

Grenishin, A. S.; Kiselev, V. M.; Kislyakov, I. M.; Pavlova, A. L.; Sosnov, E. N.

2010-01-01

377

Ion Bombardment of Microprotrusions in High Gradient Accelerating Structures  

SciTech Connect

This paper starts from a brief overview of theoretical studies of high-gradient accelerating structures at the University of Maryland. The rest of the paper is devoted to the analysis of ion bombardment of small protrusions in such structures. First, this problem is studied analytically. Then, some results of particle-in-cell simulations performed with the use of code WARP are presented and discussed.

Nusinovich, Gregory S.; Kashyn, Dmytro; Antonsen, Thomas Jr.; Haber, Irving [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742-3511 (United States)

2010-11-04

378

Reconciling HED Collisional Ages with the Lunar Late Heavy Bombardment  

NASA Astrophysics Data System (ADS)

The nature of the lunar Late Heavy Bombardment (LHB), a period of increased bombardment of the Moon 3.9Gyr ago, continues to be debated because many lunar samples provide only circumstantial evidence about the epoch of large basin formation. Independent constraints can be placed by meteorite 40Ar-39Ar ages reset in asteroid impact events. The best examples are perhaps offered by the howardite, eucrite and diogenite (HED) meteorites long suggested to come from asteroid Vesta, a paradigm that has been strengthened by recent findings of NASA's Dawn mission. The distribution of HED impact ages shows a spike near 4.45Gyr, an apparent gap, and then numerous ages between 3.4-4.1Gyr. Intriguingly, the overall HED impact age distribution shares several common aspects with lunar data, and prompted us to further investigate these similarities. The starting consensus was that the HED impact age pattern should reflect the bombardment history of Vesta and main belt asteroids, which are constantly surrounded by impactors. However, if that were true, then why should HEDs impact ages show a gap from 4.1 to 4.45Gyr, when collisions in the main belt were commonplace according to dynamical models? We found -thanks to hydrocode simulations- that impacts among main belt asteroids are very inefficient in resetting the Ar-Ar clock due to their low average impact velocity ( 5km/s). We suggest that the HED impact ages were reset by impacts from Earth-crossing impactors on highly eccentric orbits located outside the current boundary of the main asteroid belt. The advantage of this model is that it naturally explains the similar age distribution of HEDs and lunar samples. In particular, we conclude that HED ages between 3.4-4.1Gyr record a “vestan” heavy bombardment, analogous to the lunar LHB. We also infer that the oldest impact ages recorded in HEDs constrain the leftover planetesimal population in the terrestrial planet region.

Marchi, Simone; Bottke, W. F.; Cohen, B.; Wuennemann, K.; Morbidelli, A.; De Sanctis, M. C.; Kring, D. A.; McSween, H. Y.; O'Brien, D. P.; Schenk, P.; Raymond, C. A.; Russell, C. T.

2012-10-01

379

B14: an all-boron fullerene.  

PubMed

Experiments revealed that small boron cluster anions and cations are (quasi-)planar. For neutral boron cluster, (quasi-)planar motifs are also suggested to be global minimum by many theoretical studies, and a structural transformation from quasi-planar to double-ring tubular structures occurs at B(20). However, a missing opportunity is found for neutral B(14), which is a flat cage and more stable than the previous quasi-planar one by high level ab initio calculations. The B(14) cage has a large HOMO-LUMO gap (2.69 eV), and NICS values reveal that it is even more aromatic than the known most aromatic quasi-planar B(12) and double-ring B(20), which indicates a close-shell electronic structure. Chemical bonding analysis given by AdNDP reveals that the B(14) cage is an all-boron fullerene with 18 delocalized ?-electrons following the 2(n+1)(2) rule of spherical aromaticity. The geometry and bonding features of the B(14) cage are unique denying conversional thinking. PMID:22423832

Cheng, Longjiu

2012-03-14

380

Fullerene mediated hydrogen release in lithium borohydride  

NASA Astrophysics Data System (ADS)

Complex metal hydrides possess many properties which make them attractive as a storage medium for hydrogen, but typically, catalysts are required to lower the hydrogen desorption temperature and to facilitate hydrogen uptake in the form of a reversible reaction. The overwhelming focus in the search for catalyzing agents has been on compounds containing titanium, but the precise mechanism of their actions remains somewhat obscure. A recent experiment has now shown that fullerene (C60) can also act as catalysts for the hydrogen uptake and release in lithium borohydride (LiBH4). In an effort to understand the involved mechanism, we have employed density functional theory to carry out a detailed study of the interaction between this complex metal hydride and the carbon nanomaterial. Considering a step-wise reduction of the hydrogen content in LiBH4, we find that the presence of C60 can lead to a substantial reduction of the involved H-removal energies. This catalyzing effect is explained by us as a consequence of the interaction between the BHx^- part and the C60 entity.

Scheicher, Ralph; Li, Sa; Jena, Puru

2010-03-01

381

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

382

Theory of superconducting Tc of doped fullerenes  

NASA Astrophysics Data System (ADS)

We develop the nonadiabatic polaron theory of superconductivity of MxC60 taking into account the polaron band narrowing and realistic electron-phonon and Coulomb interactions. We argue that the crossover from the BCS weak-coupling superconductivity to the strong-coupling polaronic and bipolaronic superconductivity occurs at the BCS coupling constant ?~1 independent of the adiabatic ratio, and there is nothing ``beyond'' Migdal's theorem except small polarons for any realistic electron-phonon interaction. By the use of the polaronic-type function and the ``exact'' diagonalization in the truncated Hilbert space of vibrons (``phonons'') we calculate the ground-state energy and the electron spectral density of the C-60 molecule. This allows us to describe the photoemission spectrum of C-60 in a wide energy region and determine the electron-phonon interaction. The strongest coupling is found with the high-frequency pinch Ag(2) mode and with the Frenkel exciton. We clarify the crucial role of high-frequency bosonic excitations in doped fullerenes which reduce the bare bandwidth and the Coulomb repulsion allowing the intermediate- and low-frequency phonons couple two small polarons in a Cooper pair. The Eliashberg-type equations are solved for low-frequency phonons. The value of the superconducting Tc, its pressure dependence and the isotope effect are found in remarkable agreement with the available experimental data.

Alexandrov, A. S.; Kabanov, V. V.

1996-08-01

383

Ultralow thermal conductivity of fullerene derivatives  

NASA Astrophysics Data System (ADS)

Recently, Duda [J. C. Duda, P. E. Hopkins, Y. Shen, and M. C. Gupta, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.110.015902 110, 015902 (2013)] reported that the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) has the lowest thermal conductivity ? ever observed in a fully dense solid, ? ? 0.03 W m-1 K-1. We have investigated a variety of phases and microstructures of PCBM and the closely related compound [6,6]-phenyl-C61-butyric acid n-butyl ester (PCBNB) and find that the thermal conductivities of PCBM and PCBNB films are mostly limited to the range 0.05 < ? < 0.06 W m-1 K-1 with a few samples having slightly higher ?. The conductivities we observe are ?70% larger than reported by Duda but are still “ultralow” in the sense that the thermal conductivity is a factor of ?3 below the conductivity predicted by the minimum thermal conductivity model using an estimate of the thermally excited modes per molecule.

Wang, Xiaojia; Liman, Christopher D.; Treat, Neil D.; Chabinyc, Michael L.; Cahill, David G.

2013-08-01

384

Endohedral Fullerenes for Organic Photovoltaic Devices  

SciTech Connect

So far, one of the fundamental limitations of organic photovoltaic (OPV) device power conversion efficiencies (PCEs) has been the low voltage output caused by a molecular orbital mismatch between the donor polymer and acceptor molecules. Here, we present a means of addressing the low voltage output by introducing novel trimetallic nitride endohedral fullerenes (TNEFs) as acceptor materials for use in photovoltaic devices. TNEFs were discovered in 1999 by Stevenson et al.; for the first time derivatives of the TNEF acceptor, Lu{sub 3}N{at}C{sub 80}, are synthesized and integrated into OPV devices. The reduced energy offset of the molecular orbitals of Lu{sub 3}N{at}C{sub 80} to the donor, poly(3-hexyl)thiophene (P3HT), reduces energy losses in the charge transfer process and increases the open circuit voltage (V{sub oc}) to 260 mV above reference devices made with [6,6]-phenyl-C{sub 61}-butyric methyl ester (C{sub 60}-PCBM) acceptor. PCEs >4% have been observed using P3HT as the donor material. This work clears a path towards higher PCEs in OPV devices by demonstrating that high-yield charge separation can occur with OPV systems that have a reduced donor/acceptor lowest unoccupied molecular orbital energy offset.

Ross, R. B.; Cardona, C. M.; Guldi, D. M.; Sankaranarayanan, S. G.; Reese, M. O.; Kopidakis, N.; Peete, J.; Walker, B.; ZBazan, G. C.; Van Keuren, E.; Holloway,; B. C.; Drees, M.

2009-03-01

385

Spin-on carbon using fullerene derivatives  

NASA Astrophysics Data System (ADS)

Progress in lithographic resolution has made the adoption of extremely thin photoresist films necessary for the fabrication of `2× nm' structures to prevent issues such as resist collapse during development. While there are resists with high etch durability, ultimately etch depth is limited by resist thickness. A possible solution is the use of a multilayer etch stack. For organic hardmasks a carbon-rich material is preferred as carbon possesses a high etch resistance in silicon etch plasma processes. In terms of manufacturability it is beneficial to spin coat the carbon layer instead of using chemical vapor deposition, but the presence of carbon-hydrogen bonds in typical spin on carbon leads to line wiggling during the etch. We have previously introduced a fullerene based `spin on carbon' (SoC) with high etch durability and reported on material characterization. Here we show recent advances in material development and work towards commercialization. The low hydrogen level in the material allows for high resolution etching without wiggling.

Frommhold, A.; Brown, A. G.; Lada, T.; Palmer, R. E.; Robinson, A. P. G.

2014-03-01

386

Cluster--surface scattering in a reflectron collider: probing fullerenes by surface impact  

NASA Astrophysics Data System (ADS)

In this article, recent cluster--surface collision experiments are reviewed from the perspective of fullerene research. A detailed description of the method and the reflectron time-of-flight surface collider (reflectron collider), designed and built in Los Angeles, will be given first, to show how pulsed cluster-ion-beams are mass and energy selected, collided with specific surfaces and the various outcomes studied. In the second part, we outline several applications together with the scientific impact surface collision experiments have had on several fullerene-related research subjects. This includes impact-induced dissociation experiments, to probe stability and structural resilience, rebound velocity distributions from solid surfaces to reveal energetic and dynamic aspects of the scattering process, and rates of delayed electron emission from impact-heated fullerenes. Impact experiments also have turned out to be a useful tool to examine structural hypotheses as demonstrated on coalescence products from fullerene--fullerene reactions, fullerene derivatives and on metallo-fullerenes.

Yeretzian, Chahan; Beck, Rainer D.; Whetten, Robert L.

1994-08-01

387

Theory of the Miscibility of Fullerenes in Random Copolymer Melts  

SciTech Connect

We combine polymer integral equation theory and computational chemistry methods to study the interfacial structure, effective interactions, miscibility and spatial dispersion mechanism of fullerenes dissolved in specific random AB copolymer melts characterized by strong non-covalent electron donor-acceptor interactions with the nanofiller. A statistical mechanical basis is developed for designing random copolymers to optimize fullerene dispersion at intermediate copolymer compositions. Pair correlation calculations reveal a strong sensitivity of interfacial packing near the fullerene to copolymer composition and adsorption energy mismatch. The potential of mean force between fullerenes displays rich trends, often non-monotonic with copolymer composition, reflecting a non-additive competition between direct filler attractions and polymer-mediated bridging and steric stabilization. The spinodal phase diagrams are in qualitative agreement with recent solubility limit experimental observations on three systems, and testable predictions are made for other random copolymers. The distinctive non-monotonic variation of miscibility with copolymer composition is found to be primarily a consequence of composition-dependent, spatially short-range attractions between the A and B monomers with the fullerene. A remarkably rich, polymer-specific temperature dependence of the spinodal diagram is predicted which reflects the thermal sensitivity of spatial correlations which can result in fullerene miscibility either increasing or decreasing with cooling. The calculations are contrasted with a simpler effective homopolymer model and the random structure Flory-Huggins model. The former appears to be qualitatively reasonable but can incur large quantitative errors since it misses preferential packing of monomers near nanoparticles, while the latter appears to fail qualitatively due to its neglect of all spatial correlations.

Dadmun, Mark D [ORNL; Sumpter, Bobby G [ORNL; Schweizer, Kenneth [University of Illinois; Banerjee, Debapriya [University of Illinois, Urbana-Champaign

2013-01-01

388

Single-fullerene manipulation inside a carbon nanotube  

NASA Astrophysics Data System (ADS)

Here we are representing the results of the tight-binding molecular modeling of the process of the synthesis of the dimer (C28)2 and the retinoid-C60 linked molecules inside a carbon nanotube. The nanotube is located between two electrodes connected with a power source. The positively charged fullerene C60 moves from one end of the tube to the other. The motion of C60 is controlled by an external electric field. Moving fullerene C60 compresses the molecules located in one of the nanotube ends. The located molecules undergone axial compression moves toward each other. When the pressure created in the tube provides both the overlap of ?-electrons of the C28 fullerenes and the covalent bonds formation, the intermediate phase of the (C28)2 dimer is synthesized: (C28)2 [6 + 6]. The pressure becomes equal to ~35 TPa. After returning the fullerene C60 to the initial state, the (C28)2 dimer is izomerized with the reorientation in the tube field. So, (C28)2 transfers to the stable phase (C28)2 [1+1]. If the moving fullerene C60 compresses the retinol-molecule then synthesis of retinoid-C60 linked molecules takes place. In conclusion, the dimer/polymer synthesis inside the carbon nanotube is real, the dimers and polymers are stable and may be synthesized in the field of the holding potential nanotube, and the fullerene polymerization in the nanotube guarantees the absence of any additives in the final product. The motion of the atoms is determined by the classical molecular modeling method where Newton's equations of motion are integrated with a third-order Nordsieck predictor corrector. Time steps of 0.15-0.25 fs were used in the simulations.

Glukhova, O. E.; Kirillova, I. V.; Saliy, I. N.; Slepchenkov, M. M.

2011-02-01

389

An Upper Bound for the Clar Number of Fullerene Graphs  

Microsoft Academic Search

A fullerene graph is a three-regular and three-connected plane graph exactly 12 faces of which are pentagons and the remaining\\u000a faces are hexagons. Let F\\u000a \\u000a n\\u000a be a fullerene graph with n vertices. The Clar number c(F\\u000a \\u000a n\\u000a ) of F\\u000a \\u000a n\\u000a is the maximum size of sextet patterns, the sets of disjoint hexagons which are all M-alternating for a

Heping Zhang; Dong Ye

2007-01-01

390

Oscillation of nested fullerenes (carbon onions) in carbon nanotubes  

Microsoft Academic Search

Nested spherical fullerenes, which are sometimes referred to as carbon onions, of I\\u000a \\u000a h\\u000a symmetries which have N(n) carbon atoms in the nth shell given by N(n) = 60n\\u000a 2 are studied in this paper. The continuum approximation together with the Lennard-Jones potential is utilized to determine\\u000a the resultant potential energy. High frequency nanoscale oscillators or gigahertz oscillators created from fullerenes and

Ngamta Thamwattana; James M. Hill

2008-01-01

391

Template ordered open-grid arrays of paired endohedral fullerenes.  

PubMed

Developing useful molecular systems, such as planar networks for novel molecular electronics, requires the ability to control the way molecules assemble at surfaces. Here we report how an oxide crystal surface can be used as a template to controllably order endohedral fullerenes, Er3N@C80, into two-dimensional (2D) open-grid arrays. The crystal surface is made of highly ordered oxide nanostructures which self-assemble on the surface of SrTiO3(001). This method of molecular ordering can be applied to other fullerenes and has the potential to provide a basis for developing a wide range of molecular architectures. PMID:17061850

Deak, David S; Silly, Fabien; Porfyrakis, Kyriakos; Castell, Martin R

2006-11-01

392

Organic and organometallic derivatives of dihydrogen-encapsulated [60]fullerene.  

PubMed

Regioselective multi-addition reaction of organocopper and amine compounds onto dihydrogen-encapsulated [60]fullerene, H2@C60, produced a variety of organic and organometallic derivatives of H2@C60. The X-ray crystallographic analysis of dihydrogen-encapsulated bucky ferrocene, Fe(H2@C60Ph5)C5H5, showed the presence of the dihydrogen molecule located almost in the center but slightly away from the ferrocene moiety. The 1H NMR chemical shift values for the encapsulated molecular hydrogen indicated that these values are susceptible to the magnetic environment of the inside as well as the outside of the fullerene cage. PMID:16332038

Matsuo, Yutaka; Isobe, Hiroyuki; Tanaka, Takatsugu; Murata, Yasujiro; Murata, Michihisa; Komatsu, Koichi; Nakamura, Eiichi

2005-12-14

393

Molecular fusion within fullerene clusters induced by femtosecond laser excitation  

NASA Astrophysics Data System (ADS)

Molecular fusion is induced in clusters of fullerene molecules on excitation with fs laser pulses. The dependence of the mass distributions of the fused products on the initial cluster distribution are studied and results for (C60)N and (C70)N clusters are compared. The fused products decay by emitting C2 molecules and the fragmentation spectrum is used to determine the initial excitation energy of the fused species. The threshold excitation energy needed to induce fusion is consistent with the energetic thresholds for molecular fusion of fullerenes determined previously in single collision experiments.

Hedén, M.; Kjellberg, M.; Bulgakov, A. V.; Hansen, K.; Campbell, E. E. B.

2007-07-01

394

[60]Fullerene anions in aqueous solutions (EPR study)  

Microsoft Academic Search

Photochemically and electrochemically reduced [60]fullerene encapsulated in ?-cyclodextrin ([60]fullerene\\/?-CD) forms in aqueous solution four radical products (T, X, A, B) identified by EPR with the following g-values and peak-to-peak widths, pp: T: gT = 2.0015, ppT = 0.02 mT; X: gX = 2.0012, ppX = 0.028 mT; A: gA = 2.0000, ppA = 0.105 mT; B: gB = 2.0005, ppB

Andrej Staško; Vlasta Brezová; Peter Rapta; Klaus-Dieter Asmus; Dirk M. Guldi

1996-01-01

395

Fullerenes: A New Carrier Phase for Noble Gases in Meteorites  

NASA Technical Reports Server (NTRS)

The major focus of our research effort has been to measure the noble gases encapsulated within fullerenes, a new carbon carrier phase and compare it to the myriad of components found in the bulk meteorite acid residues. We have concentrated on the carbonaceous chondrites (Allende, Murchison and Tagish Lake) since they have abundant noble gases, typically with a planetary signature that dominates the stepped-release of the meteorite bulk acid residue. They also contain an extractable fullerene component that can be isolated and purified from the same bulk material.

Becker, Luann

2004-01-01

396

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

397

Mixing of binary metal systems by noble-gas ions of energies between 30 and 400 keV  

NASA Astrophysics Data System (ADS)

Multilayered samples of the binary systems Au-Rh and Ni-Pt were bombarded at 77 K with He-, Ne-, Ar- and Kr-ions at energies between 30 and 400 keV. The maximum irradiation dose was 2 × 10 17 ions/cm 2. All samples were analysed by X-ray diffraction using a Seemann-Bohlin arrangement. In thermal equilibrium the system Au-Rh has vanishingly small mutual solid solubility whereas the phase diagram of the system Ni-Pt shows that the two metals form a continuous series of solid solutions. By irradiation of Au-Rh samples with Kr-ions a single-phase metastable solid solution was produced. Irradiation with Ar- and Ne-ions results in extension of the terminal solid solubilities. Irradiation with 400 keV He-ions did not cause any mixing. This is in contrast to the experiments with 30 keV He-ions for which we could observe partial mixing. By ion irradiation of Ni-Pt samples solid solutions were produced in all cases. The results are discussed in the frame of the thermal spike model of ion beam mixing.

Hiller, W.; Buchgeister, M.; Eitner, P.; Kopitzki, K.; Lilienthal, V.; Mertler, G.

1990-03-01

398

Generation of singlet oxygen in fullerene-containing media: 1. Photodesorption of singlet oxygen from fullerene-containing surfaces  

SciTech Connect

It is shown that upon irradiation of fullerene-containing surfaces by laser or flashlamp pulses, oxygen adsorbed by these surfaces efficiently escapes to the gas phase. The observation of luminescence pulses in the spectral region of 762 and 1268 nm confirms the presence of oxygen molecules in the excited singlet state in the desorbed oxygen. The conditions for optimisation of the efficiency of singlet-oxygen production are studied. It is shown that singlet oxygen at the concentration sufficient for obtaining operation of a fullerene-oxygen-iodine laser can be produced in this way. (laser applications and other topics in quantum electronics)

Belousova, I M; Belousov, V P; Danilov, O B; Ermakov, A V; Kiselev, V M; Kislyakov, I M; Sosnov, E N [Institute for Laser Physics, Federal State Unitary Enterprise, Scientific and Industrial Corporation 'Vavilov State Optical Institute', St. Petersburg (Russian Federation)

2008-03-31

399

Alkaloid-fullerene systems through photocycloaddition reactions.  

PubMed

The photocycloaddition of tertiary amines to ¿60fullerene (C(60)) is an interesting and useful reaction. We wished to extend the applications of this type of reaction through an investigation of the photoaddition of alkaloids to C(60) for the purpose of synthesizing novel and complex photoadducts that are difficult to obtain by usual methods. Irradiation of tazettine (2) or gramine (3) with C(60) in toluene leads to formation of one monoadduct (6 or 7), whereas scandine (1a) or 10-hydroxyscandine (1b) reacts with C(60) photochemically to give two products, the expected ¿6,6 monoadduct (5a, 5b) and a new type of monoadduct with a bis-¿6, 6 closed structure (4a, 4b). These new structures were characterized by UV-vis, FT-IR, (1)H NMR, (13)C NMR, (1)H-(1)H COSY, ROESY, HMQC (heteronuclear multiple-quantum coherence), and HMBC (heteronuclear multiple-bond connectivity) spectroscopy. The techniques of time-of-flight secondary ion MS (TOF-SIMS) and field desorption MS (FD-MS) were used for the mass determination. (3)He NMR analysis of the product mixture from photoaddition of 1a to C(60) containing a (3)He atom ((3)He@C(60)) led to two peaks at -9.091 and -11.090 ppm relative to gaseous (3)He, consistent with formation of a ¿6, 6-closed monoadduct and a bis-¿6,6 closed adduct. Presumably, the bis-¿6, 6 closed adducts are formed by an intramolecular ¿2 + 2 cycloaddition of the vinyl group to the adjacent 6,6-ring junction of C(60) after the initial photocycloaddition. PMID:10864768

Guo, L W; Gao, X; Zhang, D W; Wu, S H; Wu, H M; Li, Y J; Wilson, S R; Richardson, C F; Schuster, D I

2000-06-16

400

Optimization of fullerene-based negative tone chemically amplified fullerene resist for extreme ultraviolet lithography  

NASA Astrophysics Data System (ADS)

While the technological progress of Next Generation Lithography (NGL) steadily continues, further progress is required before successful insertion in high volume manufacturing is possible. A key issue is the development of new resists suitable to achieve higher lithographic resolution with acceptable sensitivity and line edge roughness. Molecular resists have been a primary focus of interest for NGL because they promise high resolution and small line edge roughness (LER), but no suitable resist candidate has emerged yet that fulfills all of the industry's criteria. We have previously shown first extreme ultraviolet lithography (EUVL) exposures for a new fullerene derivative based three-component negative tone chemically amplified resist with suitable properties close to or within the target range of the resist metrics as set out in the International Technology Roadmap for Semiconductors for 2016. Here we present the results of our efforts to optimize the EUVL performance of our resist system especially with regards to LER.

Frommhold, A.; Yang, D. X.; McClelland, A.; Xue, X.; Ekinci, Y.; Palmer, R. E.; Robinson, A. P. G.

2014-03-01

401

Selective functionalization on [60]fullerene governed by tether length  

SciTech Connect

In order to accomplish the selective synthesis of [60]fullerene bisadducts, the reactions of [60]fullerene with compounds in which two {alpha},{alpha}`-dibromo-o-xylene moieties connected by an oligomethylene chain (n = 2-5) were investigated. By this method, only two isomers (cis-2- and cis-3-isomers) were selectively obtained when n = 2 and 3, while another isomer (e-isomer) was obtained when n = 5. When n = 4, a complex mixture of bisadducts was formed and has not been separated so far. cis-2-Bisadducts have been, for the first time, selectively obtained in the fullerene chemistry. The structures of bisadducts were determined on the basis of {sup 1}H, {sup 13}C NMR, IR, UV-vis, and mass spectroscopies. According to the NMR experiments, the symmetries of cis-2-, cis-3-, and e-isomers were concluded to be C{sub s}, C{sub 2} and C{sub 1}, respectively. Chiral cis-3- and e-bisadducts were successfully resolved into the respective enantiomers on a chiral HPLC column, although cis-2-bisadducts only gave a single peak. The UV-vis spectra of cis-2-, cis-3-, and e-bisadducts were remarkably different from one another. Specifically, the e-bisadducts showed a characteristic absorption peak around 420 nm. The cleavage of the oligomethylene chain produced the corresponding [60]fullerene derivatives possessing two phenol moieties. These compounds are applicable to further functionalization. 28 refs., 4 figs., 3 tabs.

Taki, Masumi; Sugita, Sachiko; Nakamura, Yosuke; Nishimura, Jun [Gunma Univ, Kiryu (Japan)] [Gunma Univ, Kiryu (Japan); Kasashima, Eiji; Yashima, Eiji; Okamoto, Yoshio [Nagoya Univ. (Japan)] [Nagoya Univ. (Japan)

1997-02-05

402

Uptake and distribution of fullerenes in human mast cells  

PubMed Central

Fullerenes are carbon cages of variable size that can be derivatized with various side chain moieties resulting in compounds that are being developed into nanomedicines. While fullerene use in several pre-clinical in vitro and in vivo models of disease has demonstrated their potential as diagnostic and therapeutic agents, little is known about how they enter cells, what organelles they target, and the time course for their cellular deposition. Fullerenes (C70) that have previously been shown to be potent inhibitors of mast cell (MC)-mediated allergic inflammation were conjugated with Texas Red (TR) and used in conjunction with confocal microscopy to determine mechanisms of uptake, the organelle localization, and the duration they can be detected in situ. We show C70-TR are non-specifically endocytosed into MC where they are shuttled throughout the cytoplasm, lysosomes, mitochondria, and into endoplasmic reticulum at different times. No nuclear or secretory granule localization was observed. The C70-TR remained detectable within cells at one week. These studies show MC endocytose fullerenes where they are shuttled to organelles involved with calcium and reactive oxygen species (ROS) production which may explain their efficacy as cellular inhibitors.

Dellinger, Anthony; Zhou, Zhiguo; Norton, Sarah K.; Lenk, Robert; Conrad, Daniel; Kepley, Christopher L.

2010-01-01

403

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

404

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

405

The E -phase of boron nitride as a fullerene  

Microsoft Academic Search

The set of structural and physicochemical characteristics of theE-phase of boron nitride, synthesized more than 30 years ago by shock-wave treatment, indicates that it is a 3D polymerized\\u000a form of fullerene.

S. S. Batsanov

1998-01-01

406

Structural stability of the $B_{80}$ fullerene against defect formation  

Microsoft Academic Search

Using a systematic search algorithm we identify several types of point defects in the boron fullerene with 80 atoms. All these point defect leave the cage structure intact. In addition the cage structure is also very stable with respect to elastic deformations and addition or removal of atoms.

Kuo Bao; Stefan Goedecker; Luigi Genovese; Alexey Neelov; S. Alireza Ghasemi; Thierry Deutsch

2009-01-01

407

Theory of scanning tunneling spectroscopy of fullerene peapods  

NASA Astrophysics Data System (ADS)

A theory for the hybridization of tube and encapsulant derived electronic states is developed for fullerene peapods: carbon nanotubes encapsulating molecular C60. The interaction between tube and encapsulant is constrained by symmetry and it is studied using a long-wavelength theory of the tube states and a nearly free particle theory of the ball orbitals. Calculations of the local densities of states, resolved in energy and position, are obtained for the gapped bands of a nanotube interacting with a single encapsulated fullerene, with an encapsulated dimer, and with a periodic fullerene peapod lattice. The calculations identify features in the bound state and scattering spectra of the tube produced by hybridization with the encapsulant. For the peapod lattice we identify (a) a narrow defect induced electronic band, (b) a hybridization gap resulting from the strong mixing of tube and ball degrees of freedom, and (c) Bragg gaps produced by electron motion in a periodic defect potential. The theory provides a good description of the prominent features of the measured electronic spectra of fullerene peapods obtained by low-temperature scanning tunneling microscopy.

Kane, C. L.; Mele, E. J.; Johnson, A. T.; Luzzi, D. E.; Smith, B. W.; Hornbaker, D. J.; Yazdani, A.

2002-12-01

408

Fullerene dimers (C60/C70) for energy harvesting.  

PubMed

A new family of fullerene-based compounds, namely, soluble [60]- and [70]fullerene homodimers and the [60]/[70]heterodimer linked through 2-pyrazolino-pyrrolidino bridges, has been synthesised by simple procedures and in high yield. Electrochemical studies confirm their suitability to act as electron acceptors in combination with poly(3-hexylthiophene-2,5-diyl) (P3HT). Their optical properties in solution and in the solid state were studied. A significantly stronger absorption in [70]fullerene-containing dimers relative to [60]homodimer in solution in the visible range was observed. Furthermore, in all donor-acceptor blends studied an efficient charge transfer was observed by means of photoluminescence (PL), photoinduced absorption and light-induced electron spin resonance spectroscopy. The [70]homodimer was found to be a distinctive species, being the strongest PL quencher and most efficient acceptor with the longest lifetime of the charge-separated (polaron) states. As a consequence, bulk-heterojunction solar cells based on this novel [70]homodimer blended with P3HT demonstrated the highest quantum and power conversion efficiencies of 37 and 1 %, respectively, compared to those of [60]fullerene dimers. PMID:19894231

Delgado, Juan L; Espíldora, Eva; Liedtke, Moritz; Sperlich, Andreas; Rauh, Daniel; Baumann, Andreas; Deibel, Carsten; Dyakonov, Vladimir; Martín, Nazario

2009-12-14

409

The Electronic Structure of Transition Metal Coated Fullerenes  

NASA Astrophysics Data System (ADS)

Clusters composed of fullerene molecules with an outer shell of transition metal atoms in the composition C_60M_62 (M being a transition metal) have been produced with laser vaporisation techniques(F. Tast, N. Malinowski, S. Frank, M. Heinebrodt, I.M.L. Billas, and T. P. Martin, Z. Phys D 40), 351 (1997).. We have studied several of these very large systems with a parallel version of the all-electron NRLMOL cluster code. Optimized geometries of the metal encased fullerenes C_60Ti_62 and C_60V_62 are presented along with their HOMO-LUMO gaps, electron affinities, ionization energies, and cohesive energies. We compare the stability of these clusters to relaxed met-car structures (e.g. Ti_8C_12) and to relaxed rocksalt metal-carbide fragments (TiC)n with n=8 and 32. In addition to metal-coated fullerenes we consider the possibility of a trilayered structure consisting of a small shell of metal atoms enclosed by a metal coated fullerene. The nature of bonding in these systems is analyzed by studying the electronic charge distributions.

Patton, David C.; Pederson, Mark R.; Kaxiras, Efthimios

1998-03-01

410

Supersymmetry in spherical molecules and fullerenes under perpendicular magnetic fields  

NASA Astrophysics Data System (ADS)

Methods of supersymmetric quantum mechanics are used to obtain analytical solutions for massless Dirac electrons in spherical molecules, including fullerenes, in the presence of magnetic fields. The solutions for Dirac massive charges are also obtained via the solutions of the Dirac-Weyl equation.

Jakubský, V.; Kuru, ?.; Negro, J.; Tristao, S.

2013-04-01

411

Supersymmetry in spherical molecules and fullerenes under perpendicular magnetic fields.  

PubMed

Methods of supersymmetric quantum mechanics are used to obtain analytical solutions for massless Dirac electrons in spherical molecules, including fullerenes, in the presence of magnetic fields. The solutions for Dirac massive charges are also obtained via the solutions of the Dirac-Weyl equation. PMID:23553418

Jakubský, V; Kuru, S; Negro, J; Tristao, S

2013-04-24

412

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.

Andrade, Kleber; Guerra, Sara; Debut, Alexis

2014-01-01

413

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

414

[60]Fullerene anions in aqueous solutions (EPR study)  

NASA Astrophysics Data System (ADS)

Photochemically and electrochemically reduced [60]fullerene encapsulated in ?-cyclodextrin ([60]fullerene/?-CD) forms in aqueous solution four radical products ( T, X, A, B) identified by EPR with the following g-values and peak-to-peak widths, pp: T: g T = 2.0015 , pp T = 0.02 mT; X: g X = 2.0012 , pp X = 0.028 mT; A: g A = 2.0000 , pp A = 0.105 mT; B: g B = 2.0005 , pp B = 0.05 mT. Radical A was also characterized with a near-IR band at 1085 nm, and assigned to [60]fullerene mono-anion, T to a [60]fullerene excited triplet state, X is possibly a primary mono-anion in the ?-CD superstructure, and B a di-anion or an associate form of mono-anion. Like radiolytic and flash photolytic studies, the retarded reduction of carboxylic derivatives suggests the formation of aggregates.

Staško, Andrej; Brezová, Vlasta; Rapta, Peter; Asmus, Klaus-Dieter; Guldi, Dirk M.

1996-11-01

415

Holographic Grating Formation in Fullerene Doped Nematic Liquid Crystal.  

National Technical Information Service (NTIS)

We have observed a novel electro-optical effect in fullerene and other dye-doped nematic liquid crystal films. These processes require low optical power and are characterized by millisecond response speed. We have also observed transient and persistent ho...

I. C. Khoo

1995-01-01

416

Chromatographic fractionation of fullerenes containing noble gas atoms  

NASA Astrophysics Data System (ADS)

Buckminsterfullerence containing krypton atoms inside the cage was partially separated from empty fullerene via column chromatography. The krypton content of portions of the peak emerging from the column was determined by the pyrolytic release of the krypton followed by mass spectrometry. It was found that material emerging more slowly is about 30% enriched over a faster fraction.

Saunders, M.; Khong, A.; Shimshi, R.; Jiménez-Vázquez, H. A.; Cross, R. J.

1996-01-01

417

Enhancing Polymer-Fullerene Miscibility Through Enthalpic Interactions  

NASA Astrophysics Data System (ADS)

Using both theoretical and experimental methods, the use of functional groups in controlling the miscibility between various polymers and fullerenes has been investigated. Molecular dynamics simulations with unmodified C60 and C60 dimers indicated that the number and connectivity of phenyl rings as functional groups, polymer backbone spacing, and aromaticity are all factors in fullerene miscibility. To distinguish between entropic and enthalpic factors, UV-visible spectroscopy was used to determine fullerene solubility with a variety of solvents and to also determine association constants with solvents and polymers. A distinct time dependency for complex formation with many of the fullerene- organic materials investigated was observed as evidenced by a change in solution color with time. Stern-Volmer approximations and fluorescence quenching were used to examine the association of C60 with a series of poly(para-phenylene ethynylene)s, cyclic polystyrene (PS), and linear PS. The fluorescence quenching of these materials by C60 indicates an association between C60 and the polymer. WAXS studies have shown the formation of C60 aggregates in PS at concentrations of C60 as low as 1 wt%.

Campbell, Katie; Bucknall, David; Thio, Yonathan; Beckham, Haskell; Bunz, Uwe; Hannon, Adam; Zappas, Andrew; Hatiboglu, Bilge; Kempf, Michael

2009-03-01

418

The solubility of fullerenes in n-alkanols-1  

NASA Astrophysics Data System (ADS)

The isothermal and polythermal solubility of C60 and fullerene mixture (60% C60, 39% C70, and 1% C76-90) in unbranched saturated alcohols C1-C11 was studied over the temperature range 20-80°C. The isotherms and polytherms of solubility are presented and characterized.

Semenov, K. N.; Charykov, N. A.; Arapov, O. V.

2008-08-01

419

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 ...

420

Zigzag and spiral configurations for fullerenes in carbon nanotubes  

Microsoft Academic Search

The success or otherwise of nanoscale devices hinges on a correct understanding of the physical effects at this scale. Research in nanotechnology is predominantly through either experimentation using electron and atomic force microscopy or through large-scale computation using molecular dynamics simulation. In this paper, we employ elementary mechanical principles and classical modelling procedures to investigate the packing of C60 fullerene

Duangkamon Baowan; Ngamta Thamwattana; James M. Hill

2007-01-01

421

Fullerenes as an Example of Basic Research in Industry  

Microsoft Academic Search

Some recent trends in industrial basic research are considered. They are driven by a highly competitive global marketplace. The discussion focusses on two recent major scientific advances which have been pursued in industry: high-temperature superconductivity and C60 with its chemical family. Fullerenes appear to be appropriate candidates for basic research in industry.

E. Wasserman

1993-01-01

422

The biological mechanisms and physicochemical characteristics responsible for driving fullerene toxicity.  

PubMed

This review provides a comprehensive critical review of the available literature purporting to assess the toxicity of carbon fullerenes. This is required as prior to the widespread utilization and production of fullerenes, it is necessary to consider the implications of exposure for human health. Traditionally, fullerenes are formed from 60 carbon atoms, arranged in a spherical cage-like structure. However, manipulation of surface chemistry and molecular makeup has created a diverse population of fullerenes, which exhibit drastically different behaviors. The cellular processes that underlie observed fullerene toxicity will be discussed and include oxidative, genotoxic, and cytotoxic responses. The antioxidant/cytoprotective properties of fullerenes (and the attributes responsible for driving these phenomena) have been considered and encourage their utilization within the treatment of oxidant-mediated disease. A number of studies have focused on improving the water solubility of fullerenes in order to enable their exploitation within biological systems. Manipulating fullerene water solubility has included the use of surface modifications, solvents, extended stirring, and mechanical processes. However, the ability of these processes to also impact on fullerene toxicity requires assessment, especially when considering the use of solvents, which particularly appear to enhance fullerene toxicity. A number of the discussed investigations were not conducted to reveal if fullerene behavior was due to their nanoparticle dimensions but instead addressed the biocompatibility and toxicity of fullerenes. The hazards to human health, associated with fullerene exposure, are uncertain at this time, and further investigations are required to decipher such effects before an effective risk assessment can be conducted. PMID:19901017

Johnston, Helinor J; Hutchison, Gary R; Christensen, Frans M; Aschberger, Karin; Stone, Vicki

2010-04-01

423

Secondary ion yields produced by keV atomic and polyatomic ion impacts on a self-assembled monolayer surface  

PubMed

A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd. PMID:10407327

Harris; Baker; Van Stipdonk MJ; Crooks; Schweikert

1999-01-01

424

Electron-bombarded CCD detectors for ultraviolet atmospheric remote sensing  

NASA Technical Reports Server (NTRS)

Electronic image sensors based on charge coupled devices operated in electron-bombarded mode, yielding real-time, remote-readout, photon-limited UV imaging capability are being developed. The sensors also incorporate fast-focal-ratio Schmidt optics and opaque photocathodes, giving nearly the ultimate possible diffuse-source sensitivity. They can be used for direct imagery of atmospheric emission phenomena, and for imaging spectrography with moderate spatial and spectral resolution. The current state of instrument development, laboratory results, planned future developments and proposed applications of the sensors in space flight instrumentation is described.

Carruthers, G. R.; Opal, C. B.

1983-01-01

425

[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

426

Study of a hydrogen-bombardment process for molecular cross-linking within thin films  

SciTech Connect

A low-energy hydrogen bombardment method, without using any chemical additives, has been designed for fine tuning both physical and chemical properties of molecular thin films through selectively cleaving C-H bonds and keeping other bonds intact. In the hydrogen bombardment process, carbon radicals are generated during collisions between C-H bonds and hydrogen molecules carrying {approx}10 eV kinetic energy. These carbon radicals induce cross-linking of neighboring molecular chains. In this work, we focus on the effect of hydrogen bombardment on dotriacontane (C{sub 32}H{sub 66}) thin films as growing on native SiO{sub 2} surfaces. After the hydrogen bombardment, XPS results indirectly explain that cross-linking has occurred among C{sub 32}H{sub 66} molecules, where the major chemical elements have been preserved even though the bombarded thin film is washed by organic solution such as hexane. AFM results show the height of the perpendicular phase in the thin film decreases due to the bombardment. Intriguingly, Young's modulus of the bombarded thin films can be increased up to {approx}6.5 GPa, about five times of elasticity of the virgin films. The surface roughness of the thin films can be kept as smooth as the virgin film surface after thorough bombardment. Therefore, the hydrogen bombardment method shows a great potential in the modification of morphological, mechanical, and tribological properties of organic thin films for a broad range of applications, especially in an aggressive environment.

Liu, Y.; Yang, J. [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario (Canada); Yang, D. Q.; Nie, H.-Y.; Lau, W. M. [Surface Science Western, University of Western Ontario, London, Ontario (Canada)

2011-02-21

427

Density functional theory based molecular dynamics simulation study on the bulk modulus of multi-shell fullerenes  

NASA Astrophysics Data System (ADS)

We investigate the bulk modulus of single- and double-shell fullerenes as a function of diameter and shell distance at various temperatures using the DFT-based molecular dynamics simulation method. We found that total energies depend on the diameter and shell distance. The obtained results indicate that, with increasing diameter of single-shell fullerenes, the bulk modulus increases up to C180 fullerene and then decreases for larger diameter fullerenes. The bulk modulus of double-shell fullerenes is higher than both its internal and external constructing fullerenes and decreases as the shell distance increases. The bulk moduli of the considered systems are very weakly affected by the temperature.

Ahangari, M. Ghorbanzadeh; Fereidoon, A.; Ganji, M. Darvish; Sharifi, N.

2013-08-01

428

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

429

6129keV line of 16O  

Microsoft Academic Search

The mass-doublet-scale based energy of the 6129-keV gamma ray of 16O is reevaluated in light of a recent determination of the deuteron binding energy. The result is 6129.142 +\\/- 0.032 keV. No serious descrepancy exists between this result and a recently measured value based on the wavelength (Au) standard. RADIOACTIVITY 16O, deduced energy of 6129-keV transition based on mass scale.

E. B. Shera

1982-01-01

430

Small-angle X-ray scattering study of the structure of powder fullerene C{sub 60} and fullerene soot  

SciTech Connect

Powder samples of fullerene C{sub 60} and fullerene soot have been studied by the small-angle X-ray scattering method. The radii of gyration of scattering elements have been determined by constructing small-angle diffraction patterns in Guinier coordinates. The data obtained agree well with the results of wide-angle X-ray scattering study, the available data on the structure of the powder fullerene C{sub 60} prepared by the Huffman-Kraetschmer technique, and the structure of the C{sub 60} molecules. Conglomerates of two C{sub 60} molecules, along with crystallites {approx}20 nm in size that are distributed in an amorphous matrix, are present in fullerene powders. Fullerene soot contains C{sub 60} crystallites 20-25 nm in size and graphite crystallites {approx}2-3 nm in size that are distributed in an amorphous matrix.

Ginzburg, B. M. [Russian Academy of Sciences, Institute of Problems of Mechanical Engineering (Russian Federation)], E-mail: ginzburg@tribol.ipme.ru; Tuichiev, Sh.; Tabarov, S. Kh. [Tajik State University (Tajikistan); Shepelevskii, A. A. [Russian Academy of Sciences, Institute of Problems of Mechanical Engineering (Russian Federation)

2007-03-15

431

Electrospinning of poly(L-lactide) nanofibers encapsulated with water-soluble fullerenes for bioimaging application.  

PubMed

Photoluminescent fullerene nanoparticles/nanofibers have potential applications in bioimaging. A novel fluorescent nanofibrous material, consisting of fullerene nanoparticles and poly(L-lactide) (PLLA), was fabricated via a simple electrospinning method, and the composite nanofibers were characterized by various techniques such as scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and transmission electron microscopy (TEM). The nanofibers were uniform, and their surfaces were reasonably smooth, with the average diameters of fibers ranging from 300 to 600 nm. The fullerene nanoparticles were encapsulated within the composite nanofibers, forming a core-shell structure. The nanofiber scaffolds showed excellent hydrophilic surface due to the addition of water-soluble fullerene nanoparticles. The composite nanofibers used as substrates for bioimaging in vitro were evaluated with human liver carcinoma HepG2 cells, the fullerene nanoparticles signal almost displayed in every cell, implying the potential of fluorescent fullerene nanoparticles/PLLA nanofibers to be used as scaffolds for bioimaging application. PMID:23327807

Liu, Wanyun; Wei, Junchao; Chen, Yiwang; Huo, Ping; Wei, Yen

2013-02-01

432

Theoretical study of the electronic structure of fullerene-cubane cocrystals  

NASA Astrophysics Data System (ADS)

We present a first-principles study of the electronic structure of fullerene-cubane cocrystals, using density-functional theory at the local-density approximation level. The band structure is calculated along high-symmetry lines and compared with that of the fcc fullerene. We also present a study of the effect of possible potassium doping. We find potassium doping to have a similar effect on the density of states in the fullerene-cubane as in the pure fullerene. Charge transfer between the components of the studied materials is also calculated by Bader charge analysis. The possibility of a very small charge transfer between the cubane and the fullerene in the undoped fullerene-cubane cocrystal is discussed.

Zólyomi, V.; Koltai, J.; Kürti, J.; Pekker, S.

2008-09-01

433

Energy distribution of bombarding ions in plasma etching of dielectrics  

NASA Astrophysics Data System (ADS)

In plasma etching for microelectronics fabrication, a sheath electric field accelerates ions into the substrate so they strike at normal incidence, contributing energy and reactive species to enable anisotropic etch profiles. The energy of the bombarding ions is typically controlled coarsely with a sinusoidal bias voltage applied to the substrate electrode, producing a broad bimodal ion energy distribution (IED) at the substrate. By systematically tailoring the shape of the waveform, the energies and relative fluxes of the two IED peaks are varied independently over a 100-500 eV range in a fluorocarbon-based helicon plasma, while silicon dioxide and photoresist etch rates are monitored. A 100 eV IED peak was combined with a higher energy peak, with the energy and relative flux of the high energy group as variables in the experiment. A relatively small contribution of high energy ions is found to lead to considerable etch rate enhancement, higher than predicted by a linear combination of single-peak etch rates at the two energies. Because high energy ion bombardment is known to suppress fluorocarbon deposition, it seems likely that changes in surface chemical composition in their presence enhances the contribution of lower energy ions to etching reactions.

Buzzi, F L; Ting, Y-H; Wendt, A E

2009-05-01

434

ETFE polymer bombarded with 1 MeV proton  

NASA Astrophysics Data System (ADS)

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It has high impact resistance and useful mechanical properties. ETFE can be used as components of pumps, valves, tie wraps, and electrical components. It can also be applied in the field of medical physics as intra venous catheters and as radiation dosimeter. When a material is exposed to the ionizing radiation, it suffers damage that depends on the type, energy and intensity of the radiation. In order to determine the radiation damage mechanism, ETFE films were bombarded with 1 MeV protons to the fluence between 1 × 10 11 and 1 × 10 16 protons/cm 2 and the chemical species emitted during the bombardment were measured with residual gas analysis (RGA) and show that HF gas is the entity preferentially emitted. Optical absorption photospectrometry (OAP) and attenuated total reflectometry fourier transform infrared (ATR-FTIR) shows quantitative chemical evidence of the damage. Our results show that damage is detectable at low proton fluence, but damage that can compromise the application in dosimetry occurs only for fluence greater than 10 14 protons/cm 2.

Parada, M. A.; de Almeida, A.; Muntele, I.; Muntele, C.; Delalez, N.; Ila, D.

2005-12-01

435

Remarkable diversity of carbon–carbon bonds: structures and properties of fullerenes, carbon nanotubes, and graphene  

Microsoft Academic Search

Large scientific community has been passionate in understanding different carbon nanostructures for last two decades. In this\\u000a review, we present the general description of low-dimensional carbon allotropes such as fullerenes (0D), carbon nanotubes\\u000a (1D), and graphene (2D). These structures have unique diversity of carbon–carbon bonds. Structures and electronic properties\\u000a of fullerenes, small closed carbon cages, and giant fullerenes are illustrated.

T. C. Dinadayalane; Jerzy Leszczynski

2010-01-01

436

A theoretical study of the stability trends of boron nitride fullerenes  

Microsoft Academic Search

We perform first-principles calculations to study the relative stability of boron nitride fullerenes BnNm. We consider fullerenes with octahedral, icosahedral and tubular shapes, in a size range with (n+m) between 20 and 288. A scaling analysis allows the total energy comparisons to extend to larger sizes. We find that tubular-shaped fullerenes are as stable as octahedral-shaped ones for (n+m)?80. We

Ronaldo J. C. Batista; Mário S. C. Mazzoni; Hélio Chacham

2006-01-01

437

A new family of chiral boron fullerenes and related planar boron sheet  

Microsoft Academic Search

Using the recent idea of balancing two-center and three-center bondings between boron atoms, a new class of stable chiral boron nanostructures (fullerenes and nanotubes) is designed. The structures of these fullerenes consist of triangular and hexagonal motifs similar to those seen in the most stable alpha-boron sheet and the B80 fullerene. The binding energy of the new sheet is only

Rajendra Zope; Tunna Baruah

2010-01-01

438

Atomic structure and electronic state of boron nitride fullerenes and nanotubes  

Microsoft Academic Search

Boron nitride (BN) fullerenes and nanotubes were obtained by applying the arc-melting method to a powder mixture of boron and iron oxide in a nitrogen gas. BN fullerenes of size 0.7nm were observed. Angular tips of BN nanotubes of diameter 6.6nm and length 50–100nm were also observed. When using a powder mixture of boron and gold, BN fullerenes and nanotubes

Takanori Hirano; Takeo Oku; Katsuaki Suganuma

2000-01-01

439

Stoichiometric boron nitride fullerenes with homopolar B–B and N–N bonds  

Microsoft Academic Search

A new class of boron nitride fullerenes, which are stoichiometric and presents homopolar bonds, is proposed in this work. A combined first-principles\\/elastic-model approach predicts that stoichiometric fullerenes with more than 1000 atoms which present homopolar bonds are energetically more stable than those without homopolar bonds. The HOMO–LUMO gap of stoichiometric fullerenes with homopolar bonds is 1.7eV smaller than that of

Ronaldo J. C. Batista

2010-01-01

440

Boron nitride fullerene B36N36 doped with transition metal atoms: First-principles calculations  

Microsoft Academic Search

We perform first-principles calculations for the interaction of the transition metal atoms Fe, Co, and W, as well as the FeO molecule, with the boron nitride fullerene B36N36 . The stable structure of the atom-fullerene complexes may have the dopant atom either at the center of the cage or making covalent bonds with the fullerene wall, with similar total energies.

Ronaldo J. C. Batista; Mário S. C. Mazzoni; Helio Chacham

2007-01-01

441

Assemblies of carbon and boron-nitrogen nanotubes and fullerenes: Structure and properties  

Microsoft Academic Search

This review concerns assemblies of the main carbon nanostructures (fullerenes and nanotubes) generated by interactions between\\u000a similar and dissimilar species. The two major families of these nanomaterials are reviewed: (1) assemblies with weak (van\\u000a der Waals) bonds between fullerenes and\\/or nanotubes (fullerites, nanopeapods, nanotube bundles, and nanotubular crystals)\\u000a and (2) assemblies formed by covalently bonded (polymerized) fullerenes and\\/or nanotubes (covalent

A. L. Ivanovskii

2008-01-01

442

Modeling Charge Transfer in Fullerene Collisions via Real-Time Electron Dynamics  

SciTech Connect

An approach for performing real-time dynamics of electron transfer in a prototype redox reaction that occurs in reactive collisions between neutral and ionic fullerenes is discussed. The quantum dynamical simulations show that the electron transfer occurs within 60 fs directly preceding the collision of the fullerenes, followed by structural changes and relaxation of electron charge. The consequences of real-time electron dynamics are fully elucidated for the far from equilibrium processes of collisions between neutral and multiply charged fullerenes.

Jakowski, Jacek [ORNL; Irle, Stephan [ORNL; Morokuma, Keiji [ORNL; Sumpter, Bobby G [ORNL

2012-01-01

443

Superplasticity in a fullerene-dispersed Mg–Al–Zn alloy composite  

Microsoft Academic Search

A 1 mass% fullerene-dispersed Mg–Al–Zn alloy composite with an initial matrix grain size of 2?m was processed by extruding a mixture of magnesium machined chips and fullerene powder. The composite exhibited superplasticity, with an elongation of 256% at 548K even at a relatively high strain rate of 10?2s?1. The addition of fullerene had little effect on the flow stress, whereas

H. Watanabe; M. Fukusumi; K. Ishikawa; T. Shimizu

2006-01-01

444

Spherical Bilayer Vesicles of Fullerene-Based Surfactants in Water: A Laser Light Scattering Study  

Microsoft Academic Search

The low solubility of fullerenes in aqueous solution limits their applications in biology. By appropriate substitution, the fullerenes can be transformed into stabilized anions that are water soluble and can form large aggregated structures. A laser light scattering study of the association behavior of the potassium salt of pentaphenyl fullerene (Ph5C60K) in water revealed that the hydrocarbon anions Ph5C60- associate

Shuiqin Zhou; Christian Burger; Benjamin Chu; Masaya Sawamura; Noriaki Nagahama; Motoki Toganoh; Ulrich E. Hackler; Hiroyuki Isobe; Eiichi Nakamura

2001-01-01

445

NMR characterization of isomers of C78, C82 and C84 fullerenes  

Microsoft Academic Search

FOLLOWING the development of a method for bulk synthesis of C60 and other fullerenes1, the isolation of higher fullerenes ranging from C76 to C96 has been achieved using chromatographic techniques2-5. Whereas C60 and C70 have unique, high-symmetry structures6, theoretical calculations for fullerenes larger than C76 have suggested that each may exist in at least two isomeric forms7. For C84, 24

Koichi Kikuchi; Nobuo Nakahara; Tomonari Wakabayashi; Shinzo Suzuki; Haruo Shiromaru; Yoko Miyake; Kazuya Saito; Isao Ikemoto; Masatsune Kainosho; Yohji Achiba

1992-01-01

446

Electronic structure of the trimetal nitride fullerene Dy3 N@ C80  

Microsoft Academic Search

We report on a detailed study of the electronic properties of the newly synthesized trimetal nitride fullerene Dy3N@C80 (isomer I) using high-energy spectroscopies as probes. From ultraviolet photoemission and C1s absorption spectroscopies we observe that the occupied and unoccupied electronic structures of the fullerene cage are very similar to those of other trimetal nitride fullerenes and hence both spectra exhibit

H. Shiozawa; H. Rauf; T. Pichler; D. Grimm; X. Liu; M. Knupfer; M. Kalbac; S. Yang; L. Dunsch; B. Büchner; D. Batchelor

2005-01-01

447

Observation of fullerenes (C60-C70) associated with LDEF crater number 31  

NASA Technical Reports Server (NTRS)

The presence of fullerenes in and around the LDEF crater number 31 is reported. This crater has a high C level associated with it, and is interpreted as having been produced by the impact of a C-rich micrometeoroid. Fullerenes are large 3-D C structures, among which the species C sub 60 (MW 720) and C sub 70 (MW 840) are preeminent. Fullerenes have several UV absorption bands, hence fullerenes should be detectable using UV laser ionization time-of-flight mass spectrometry. We use a LIMA-2A instrument with pulsed UV laser (266 nm) to search for high mass C species associated with LDEF crater number 31. The mass range was 0 to 1200 amu. Low ablating laser power levels were used (less than or = 5 x 10 exp 7 W/sq. cm); 200 mass spectra were acquired and summed. We observed high mass signals near m/z 720, exhibiting 24 amu separation, which is characteristic of fullerenes. Alkali ion signals were also observed. Little or no C clusters of intermediate mass were observed. We interpret the signals around m/z 720 as fullerenes, mainly C sub 60+ with lower levels of C sub 70+. We propose that the mechanism that produces these signals is resonant multiphoton ionization (REMPI). This selective mechanism explains why low mass C cluster ions are not observed along with the fullerenes, since they have much higher ionization potentials. This finding is unexpected, since up to now the search for fullerenes in extraterrestrial materials has not been successful. We conclude that the fullerenes became associated with crater number 31 in space. Two alternative (and exciting) scenarios are being considered at this time: either the fullerenes were carried by the C-rich projectile that formed crater number 31, or the fullerenes formed upon impact with the LDEF. We show the results of experiments at the ARC Vertical Gun Facility, which may establish some constraints on the origin of the fullerenes.

Radicatidibrozolo, Filippo; Fleming, R. H.; Bunch, T. E.

1992-01-01

448

Repulsive solvent-induced interaction between C60 fullerenes in water  

Microsoft Academic Search

The role of water-fullerene interactions in the behavior of C60 in aqueous solution was investigated utilizing realistic Lennard-Jones (LJ) and repulsive Weeks-Chandler-Anderson (WCA) potentials. Strong water-fullerene dispersion interactions in the LJ potential dramatically influence the hydration of the fullerene promoting the formation of a high-density hydration shell of water. In contrast to the WCA potential, the water liquid phase between

Liwei Li; Dmitry Bedrov; Grant D. Smith

2005-01-01

449

Electronic properties of peapods: effects of fullerene rotation and different types of tube  

Microsoft Academic Search

Effects of encapsulated fullerene rotation on peapod electronic properties are studied by using Slater-Koster tight-binding calculations. We found that the encapsulated fullerenes can rotate freely in the space of a (10, 10) tube at room temperature, and the rotation of fullerenes will affect C60@(10,10) peapod electronic properties significantly; generally, orientational disorder will remove the sharp features of the average density

Jiangwei Chen; Jinming Dong

2004-01-01

450

Half-life measurements for the 50 keV and 162 keV states in 132I  

NASA Astrophysics Data System (ADS)

132Te was produced via the 232Th (?, fission) reaction at the Variable Energy Cyclotron , Calcutta. 132Te was separated in carrier-free form from the fission products by radiochemical separation and the half-lives for the 50 keV and 162 keV states of 132I were determined to be 2.94±0.11 ns and 0.55±0.04 ns respectively. The present results differ significantly from the previously reported half-lives of 7.14 ns and 3.57 ns for the 50 keV and 162 keV states respectively.

Das, S. K.; Guin, R.; Saha, S. K.

1999-01-01

451

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

PubMed

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. PMID:24182072

Busolo, Filippo; Silvestrini, Simone; Armelao, Lidia; Maggini, Michele

2013-10-28

452

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.

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

2013-01-01

453

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

454

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

455

Colloidal structure and stabilization mechanism of aqueous solutions of unmodified fullerene C{sub 60}  

SciTech Connect

Despite the inability of fullerenes to be directly dissolved in water, there are methods for preparing stable dispersions of fullerenes in water without any particular modifications of the fullerene or addition of stabilizers. The colloidal properties of such systems prepared by replacing the solvent and structural changes in them during coagulation have been studied. The coagulation dynamics has been investigated by spectroscopy and small-angle neutron scattering. The results obtained confirm the colloidal nature of such systems. During coagulation, particles retain a large volume of water around them, an indication of interaction between fullerene and water during solution stabilization.

Khokhryakov, A. A., E-mail: art@nf.jinr.ru; Kyzyma, O. A. [Joint Institute for Nuclear Research (Russian Federation); Bulavin, L. A. [Shevchenko National University (Ukraine); Len, A. [Research Institute for Solid-State Physics and Optics (Hungary); Avdeev, M. V.; Aksenov, V. L. [Joint Institute for Nuclear Research (Russian Federation)

2007-05-15

456

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

457

Nonlinear optical properties of solutions of heavy fullerenes in the near-ultraviolet region  

NASA Astrophysics Data System (ADS)

Nonlinear optical properties (particularly optical limiting) are determined for solutions of heavy fullerenes C76 + C78 + C84 + C90 + …, in the near-ultraviolet region (? ? 280 ± 7 nm). It is shown that no optical limiting is observed in solutions of light fullerenes (C60 and C70), but found in solutions of water-soluble fullerenol-d (a mixture of oxypolyalcohols of fullerene C60-C60(OH) n1O n2, with their sodium salts) based on light fullerenes.

Sherstnev, V. V.; Charykov, N. A.; Semenov, K. N.; Alekseev, N. I.; Keskinov, V. A.; Krokhina, O. A.

2011-09-01

458

Spectroscopy of Fullerenes, Fulleranes and PAHs in the UV, Visible and Near Infrared Spectral Range  

NASA Astrophysics Data System (ADS)

The spectra of fullerenes C60 and C70, higher fullerenes C76, C78 and C84 and hydrogenated fullerenes (fulleranes) were studied in laboratory in the UV and in the visible spectral range and could be used for searching and recognizing these molecules in space. Furthermore, the radical cation spectra of all the mentioned fullerene series and also of a series of large and very large polycyclic aromatic hydrocarbons (PAHs) were generated in the laboratory and studied in the near infrared spectral range.

Cataldo, F.; García-Hernández, D. A.; Manchado, A.; Iglesias-Groth, S.

2014-02-01

459

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

NASA Astrophysics Data System (ADS)

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; Armelao, Lidia; Maggini, Michele

2013-10-01

460

Orbiting atoms and C60 fullerenes inside carbon nanotori  

NASA Astrophysics Data System (ADS)

The discovery of carbon nanostructures, such as carbon nanotubes and C60 fullerenes, has generated considerable interest for potential nanoelectronic applications. One such device is the high frequency nanoscale gigahertz oscillator. Several studies investigating these oscillators demonstrate that sliding an inner-shell inside an outer-shell of a multiwalled carbon nanotube generates oscillatory frequencies in the gigahertz range. Research has shown that the oscillation is sensitive to the diameter and the helicity of the tube and that the inner tube length can be used to tune the frequency, such that the smaller the inner tube length the higher the frequency of oscillation, suggesting that a C60 fullerene might provide the ultimate core. Recently, researchers have observed single continuous toroidal nanotubes with no beginning or end, effectively a single-walled carbon nanotube closed around onto itself so that the two open ends fuse together, stabilized by van der Waals forces alone, to form a perfect ``nanotorus.'' The question arises as to whether it is possible to create a C60- nanotorus oscillator or orbiter, comprising a C60 fullerene orbiting around the inside of a nanotorus. The C60- nanotorus orbiter has yet to be constructed and the aim here is to assess its feasibility by examining the dominant mechanics of this potential nanoscale device. As in previous studies, the Lennard-Jones potential is used to calculate the interatomic forces acting on the fullerene due to the nonbonded interactions. Furthermore, other relevant forces are examined. Initially, we investigate th