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1

Damage analysis of benzene induced by keV fullerene bombardment  

NASA Astrophysics Data System (ADS)

Molecular dynamics computer simulations have been used to investigate the damage of a benzene crystal induced by 5 keV C20, C60, C120 and C180 fullerene bombardment. The sputtering yield, the mass distributions, and the depth distributions of ejected organic molecules are analyzed as a function of the size of the projectile. The results indicate that all impinging clusters lead to the creation of almost hemispherical craters, and the process of crater formation only slightly depends on the size of the fullerene projectile. The total sputtering yield as well as the efficiency of molecular fragmentation are the largest for 5 keV C20, and decrease with the size of the projectile. Most of the molecules damaged by the projectile impact are ejected into the vacuum during cluster irradiation. Similar behavior does not occur during atomic bombardment where a large portion of fragmented benzene molecules remain inside the crystal after projectile impact. This “cleaning up” effect may explain why secondary ion mass spectrometry (SIMS) analysis of some organic samples with cluster projectiles can produce significantly less accumulated damage compared to analysis performed with atomic ion beams.

Czerwinski, B.; Rzeznik, L.; Paruch, R.; Garrison, B. J.; Postawa, Z.

2009-05-01

2

Erosion of volatile elemental condensed gases by keV electron and light-ion bombardment.  

National Technical Information Service (NTIS)

Erosion of the most volatile elemental gases by keV electron and light-ion bombardment has been studied at the experimental setup at Risoe. The present work includes frozen neon, argon, krypton, nitrogen, oxygen and three hydrogen isotopes, deuterium, hyd...

J. Schou

1991-01-01

3

Optical emission from metal targets bombarded by 5-20 keV argon ions  

NASA Astrophysics Data System (ADS)

The spectral composition of optical emission from high-purity iron (99.99% Fe), zirconium (99.98% Zr), and tungsten (99.96% W) targets bombarded by 5-20 keV Ar+ ions has been studied. The ion-bombardment-induced emission spectra of all metals exhibit two broad bands in the visible and IR spectral range. The first band is assigned to the emission from thermal spikes representing nanosized regions heated to 5000-6000 K, which are formed at the target surface in the course of evolution of high-density atomic collision cascades. The presence of an IR emission band is explained by the integral heating of targets to 500-800 K in the course of ion irradiation. This interpretation is confirmed by agreement between the experimentally measured and calculated temperatures in the region of thermalized collision cascades and the relative intensities of emission bands.

Ovchinnikov, V. V.; Makhin'ko, F. F.; Solomonov, V. I.; Gushchina, N. V.; Kaigorodova, O. A.

2012-01-01

4

Ion Sputtering from Organic Liquid Matrices Bombarded by KEV Metal Ions.  

NASA Astrophysics Data System (ADS)

Ion sputtering from organic liquid matrices bombarded by 7-66 keV metal ions has been systematically studied as a function of the properties of the primary ions (species, energy etc.) and of the chemical environment on the target's surface. Yields of deprotonated mononucleotides (dAMP or dGMP) from a glycerol matrix, doped with the surfactant hexadecylpyridinium acetate (HDPA), as a function of stopping power (dE/dX) can be explained by models, such as the cylindrical thermal spike model with Y = k(dE/dX - S_0)^2 (S _0 = threshold stopping power), that predict particle ejection essentially from the surface. Moreover, yields of deprotonated dAMP or dGMP generated by bombardment with polyatomic ions (Bi_3^{+2 }, Bi_2^+, Au _2^+, Au _3^+) exhibit a nonlinear enhancement over those generated by bombardment with monoatomic ions (Au^+, Bi^+). Nonlinear in this case means that the number of ions ejected by a given number of atoms colliding with a liquid matrix at essentially the same point in space and time, as is the case when the atoms are clustered into a single ion, is much greater than that produced by an equal number of atoms impacting individually on the same target at different positions and times. This enhancement can also be explained by, for example, the cylindrical thermal spike model.

Yen, Ten-Yang

5

Inferring ejection distances and a surface energy profile in keV particle bombardment experiments  

NASA Astrophysics Data System (ADS)

The disappearance cross-sections and kinetic energy distributions of fragment ions sputtered from polystyrene thin films under 12 keV 69Ga+ ion bombardment are measured using a time-of-flight spectrometer. Even though the disappearance cross-sections are often used as an indicator of radial ion beam damage, the derived radii range from 2 to 10 Å depending on the particular hydrocarbon fragment. Therefore, the disappearance cross-sections cannot be directly related to a single global quantity of damage per incident particle. Likewise, the widths of the measured kinetic energy depend on the particular hydrocarbon fragment. Both the disappearance cross-sections and the widths of the kinetic energy distribution superficially relate to fragment mass but the correlation is not perfect. We develop a hypothesis that the disappearance cross-section and the width of the kinetic energy distribution actually correlate with the ejection radius of the particular fragment. Thus, the kinetic energy distributions provide an estimate of the radial extent of the energy density in the ejection region. Our interpretations are supported by molecular dynamics simulation results. For comparison with previously reported data, our results indicate that the deposited energy profile is 4-5 times narrower than for 72.3 MeV, electronic sputtering of PVDF [Phys. Rev. Lett. 77 (1996) 667].

Delcorte, A.; Segda, B. G.; Garrison, B. J.; Bertrand, P.

2000-11-01

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

keV particle bombardment of semiconductors: A molecular-dynamics simulation  

SciTech Connect

Molecular-dynamics simulations have been performed for the keV particlebombardment of Si/l brace/110/r brace/ and Si/l brace/100/r brace/ using a many-body potential developed byTersoff. Energy and angle distributions are presented along with an analysis ofthe important ejection mechanisms. We have developed a computer logic that onlyintegrates the equations of motion of the atoms that are struck, thusdecreasing the computer time by a factor of 3 from a completemolecular-dynamics simulation.

Smith, R.; Harrison, D. E., Jr.; Garrison, B. J.

1989-07-01

8

Altered layer formation and sputtering yields for 5 keV Ar+ bombardment of MoO3 and WO3  

Microsoft Academic Search

The effects on MoO3 and WO3 due to ion bombardment using parameters typical of sputter-profiling (5 keV Ar+ at approximately 10 muA\\/cm2) were studied using proton induced X-ray emission (PIXE) and X-ray photoelectron spectroscopy (XPS). During the first 2×1015 to 2×1016 ions\\/cm2 of sputtering, structurally and chemically altered regions form. The structurally altered regions were due to amorphization. The chemically

T. J. Driscoll; L. D. McCormick; W. C. Lederer

1987-01-01

9

Angular distribution of particles sputtered from Cu, Pt and Ge targets by keV Ar+ ion bombardment  

Microsoft Academic Search

Measurements of angular distributions of material sputtered from polycrystalline copper and platinum and amorphous germanium targets by irradiation with argon ions are reported. The beam energy was varied from 1.25 keV to 320 keV (for Cu and Pt upwards from 10 keV only). All targets yielded an angular distribution more outward peaked than the cosine predicted by collision-cascade theory. The

Hans Henrik Andersen; Bjarne Stenum; Tom Sørensen; Harry J. Whitlow

1985-01-01

10

Angular Distribution of Particles Sputtered from Cu, Pt and Ge Targets by KeV Ar exp + Ion Bombardment.  

National Technical Information Service (NTIS)

Measurements of angular distributions of material sputtered from polycrystalline copper and platinum and amorphous germanium targets by irradiation with argon ions are reported. The beam energy was varied from 1.25 keV to 320 keV (for Cu and Pt upwards fr...

H. H. Andersen B. Stenum T. Soerensen H. J. Whitlow

1984-01-01

11

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

12

Molecular dynamics simulations to explore the effect of chemical bonding in the keV bombardment of Si with C60, Ne60 and 12Ne60 projectiles  

NASA Astrophysics Data System (ADS)

Depth profiling experiments using secondary ion spectrometry (SIMS) have shown effects that are characteristic to the pairing of the C60+ projectile with a Si target. Previous molecular dynamics simulations demonstrate that this unusual behavior is due to the fact that strong covalent bonds are formed between the C atoms in the projectile and the Si atoms in the target, which result in the implantation of carbon into the solid. The focus of this paper is to understand how the formation of chemical bonds affects the net sputtered yield. The results of molecular dynamics simulations of the keV bombardment of Si with C60, Ne60 and 12Ne60 at normal incidence are compared over a range of incident kinetic energies from 5 to 20 keV. The net yields with Ne60 and 12Ne60 are significantly greater than with C60 at all incident kinetic energies, with 12Ne60 having the largest values. Application of the mesoscale energy deposition footprint (MEDF) model shows that the initial deposition of energy into the substrate is similar with all three projectiles. Snapshots of the initial pathway of the projectile atoms through the substrate show a similar lateral and vertical distribution that is centered in the region of the energy footprint. Therefore, the reason for the reduced yield with C60 is that the C atoms form bonds with the Si atoms, which causes them to remain in the substrate instead of being sputtered.

Krantzman, K. D.; Garrison, B. J.

2009-02-01

13

Gold-thiolate cluster emission from SAMs under keV ion bombardment: Experiments and molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

In this contribution the emission of gold-molecule cluster ions from self-assembled monolayers (SAMs) of alkanethiols on gold is investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Layers of alkanethiols [CH3(CH2)nSH] with various chain lengths (n=8, 12, 16) have been chosen because they form well-ordered molecular monolayers on gold. First, we compare and interpret the yields and energy spectra of gold-thiolate cluster ions, obtained for different thiol sizes. Our results show that the unimolecular dissociation of larger aggregates in the acceleration section of the spectrometer constitutes a significant formation channel for gold-molecule clusters. Second, we present preliminary results of molecular dynamics simulations performed in order to improve our understanding of the cluster emission processes. These calculations have been conducted using 8 keV projectiles and a long-range term in the hydrocarbon potential in order to account for the van der Waals forces between the thiol chains.

Arezki, B.; Delcorte, A.; Chami, A. C.; Garrison, B. J.; Bertrand, P.

2003-12-01

14

Altered layer formation and sputtering yields for 5 keV Ar+ bombardment of MoO3 and WO3  

NASA Astrophysics Data System (ADS)

The effects on MoO3 and WO3 due to ion bombardment using parameters typical of sputter-profiling (5 keV Ar+ at approximately 10 ?A/cm2) were studied using proton induced X-ray emission (PIXE) and X-ray photoelectron spectroscopy (XPS). During the first 2×1015 to 2×1016 ions/cm2 of sputtering, structurally and chemically altered regions form. The structurally altered regions were due to amorphization. The chemically altered regions consisted of both stoichiometric and nonstoichiometric oxides with lower oxygen contents than the original trioxides, as well as trioxide for MoO3 and elemental W and/or W3O for WO3. The thicknesses of the chemically altered regions are comparable to the range of the incident ions for WO3 and about five times as large as the range for MoO3. The possibility of distortions in sputter-profiles of complex oxide films due to different sputtering yields for component oxides was evident in the measured sputtering yields of 2.1, 2.5, and 3.5 atoms/ion for Ta2O5, MoO3, and WO3, respectively, for normally incident ions.

Driscoll, T. J.; McCormick, L. D.; Lederer, W. C.

1987-09-01

15

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

16

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

NASA Astrophysics Data System (ADS)

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

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

1993-07-01

17

State-selective laser photoionization of neutral benzene molecules ejected from keV ion bombarded C{sub 6}H{sub 6}/Ag{l_brace}111{r_brace}  

SciTech Connect

One-color two-photon ionization spectroscopy was used to probe state-selectively neutral benzene molecules desorbed from a benzene overlayer physisorbed on a Ag{l_brace}111{r_brace} surface upon 8 keV Ar{sup +} bombardment. Time distributions were measured for benzene molecules ejected in the zero level of the molecular ground state and in the first state of the {nu}{sub 6} ' vibration. These distributions are found to show a strong dependence both on the internal energy of the ejected molecules and the degree of coverage of the Ag surface. Up to monolayer coverages, benzene molecules are ejected by direct collisions with Ag particles sputtered from the underlying substrate. Molecules with higher internal energy leave the surface with a distribution shifted towards lower flight times. At multilayer coverages, a second, thermal-like ejection mechanism gains significance. It is suggested that only molecules excited near the benzene-vacuum interface, survive the ejection process without being deexcited.

Meserole, C. A.; Vandeweert, E.; Chatterjee, R.; Chakraborty, B. R.; Garrison, B. J.; Winograd, N.; Postawa, Z. [Department of Chemistry, Pennsylvanian State University, University Park, Pennsylvania 16802 (United States); Institute of Physics, Jagellonian University, ul. Reymonta 4, PL 30-059 Krakow 16 Poland (Poland)

1998-12-16

18

Dynamic behavior of thermionic dispenser cathodes under ion bombardment  

Microsoft Academic Search

We have investigated the surface coverage and electron emission of thermionic dispenser cathodes during 3 keV Ar+ ion bombardment, thereby simulating the bombardment of the cathodes by residual gases that takes place in cathode-ray tubes as used in television sets. During the ion bombardment at the operating temperature of 1030 °C, a dynamic equilibrium is established between the sputter removal

R. Cortenraad; H. H. Brongersma; G. Gärtner; D. Raasch; A. Manenschijn

2001-01-01

19

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

20

Fullerene collisions and clusters of fullerenes  

NASA Astrophysics Data System (ADS)

Electron capture processes were studied in glancing collisions between multiply charged C60q+ ions and neutral C60 molecules at low collision energies where nuclear stopping dominates the interaction (typical energy: 10 keV; velocity vD0.024[thin space]a.u.). In addition, clusters of fullerenes were multiply ionized in collisions with highly charged slow ions and their fragmentation spectra were measured by applying multi-coincidence techniques in a second, separate experiment. Through the first experiment we show that non-fragmenting electron capture collisions do not produce free electrons in C60q+-C60 collisions (q = 1-5), i.e., the cross sections for transfer ionization processes are negligible in this charge state regime. This is in contrast to the case of atomic projectile ions where transfer ionization processes, as e.g., Cq+ + C60 --> C(q-r)+ + C60r+ --> C(q-r+1)+ + C60r+ + e-, are strong for q > 2. These results are rationalized by means of the classical over-the-barrier model for electron transfer between two C60 molecules, or between an atomic ion and a C60 molecule, where the molecules are modeled as conducting spheres. Further, the same model may also be used as a basis for understanding the present observations of limitations in the maximum numbers of charges, which might be transferred in non-fragmenting C60q+-C60 collisions (q/2 for even q and (q + 1)/2 for odd q) and in Cq+-C60 collision (here up to q charges may be transferred). In the same experiment, we have further measured scattering angles, [theta], and energy losses, [var epsilon], for the fullerene projectiles in C60q+-C60 collisions and we have found low values for both [theta] and [var epsilon], which, however, increase with the number of C2-units lost from the projectile fullerene in electron capture collisions. The critical distances for electron transfer which are deduced from the C60q+-C60 collision experiment and the Zettergren model are then used to explain the high charge mobility between the individual C60 molecules in charged (C60)n van der Waal's clusters of fullerenes, which we observe in the second experiment.

Kamalou, O.; Manil, B.; Lebius, H.; Rangama, J.; Huber, B. A.; Hvelplund, P.; Tomita, S.; Jensen, J.; Schmidt, H. T.; Zettergren, H.; Cederquist, H.

2006-05-01

21

Fullerene Superconductors.  

National Technical Information Service (NTIS)

The electrical, magnetic and optical properties of the fullerene superconductors K3C60 and Rb3C60 have been investigated. The room temperature microwave resistivity at 60 GHz of pressed powder samples of K3C60 is approximately 5m (ohms) cm. The resistivit...

R. B. Kaner

1993-01-01

22

Chemical damage and aging of ion bombarded PPS  

Microsoft Academic Search

Thin foils of commercial grade polyphenylene sulfide (PPS), 2 \\/mum thick, were bombarded with energetic H+ (300 keV), He+ (350 keV), B+ (350 keV) and Ar++ (700 keV) ions at fluences ranging from 1012 to 1015ions\\/cm2. Fourier transform infrared spectroscopy (FTIR), Rutherford backscattering analysis (RBS) and chemical elemental analysis (CHN) were performed to evaluate the chemical changes induced by ion

M. R. Rizzatti; M. A. de Araújo; R. P. Livi

2000-01-01

23

Chemical damage and aging of ion bombarded PPS  

Microsoft Academic Search

Thin foils of commercial grade polyphenylene sulfide (PPS), 2 ?m thick, were bombarded with energetic H+ (300 keV), He+ (350 keV), B+ (350 keV) and Ar++ (700 keV) ions at fluences ranging from 1012 to 1015ions\\/cm2. Fourier transform infrared spectroscopy (FTIR), Rutherford backscattering analysis (RBS) and chemical elemental analysis (CHN) were performed to evaluate the chemical changes induced by ion

M. R. Rizzatti; M. A. de Araújo; R. P. Livi

2000-01-01

24

Mobility of atoms under ion bombardment  

SciTech Connect

Argon ions bombardment (Eapprox.1KeV) of Armco iron in a cold glow discharge plasma (T< or approx. =150/sup 0/C) has been performed to investigate the mobility and behavior of the atoms in the crystal lattice and the formation of a solid solution of Argon in iron.(AIP)

Alekseevskii, V.; Gertsriken, D.; Kovtun, V.; Tyshkevich, V.; Fal'chenko, V.

1981-10-01

25

Switching molecular orientation of individual fullerene at room temperature.  

PubMed

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. PMID:24162548

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

2013-10-28

26

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

27

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

28

Fullerene superconductors  

NASA Astrophysics Data System (ADS)

The electrical, magnetic and optical properties of the fullerene superconductors K3C60 and Rb3C60 have been investigated. The room temperature microwave resistivity at 60 GHz of pressed powder samples of K3C60 is approximately 5m (ohms) cm. The resistivity drops by almost one order of magnitude on cooling to 20K, indicative of metallic behavior, before the samples superconduct at T (sub) c = 19.3K. Optical reflectivity spectra are consistent with metallic materials. An extrapolation of the frequency dependence of conductivity leads to d.c. conductivities of 1.3 x 10 (exp 3) (ohm)-l and 1.2 x 10 (exp 3) (ohm)-l for K3C60 and Rb3C60, respectively. The gap values A of 24 /cm for K3C60 and 30 /cm for Rb3C60 are consistent with weak-coupling and a BCS singlet ground state. Upper critical fields of 28-30 Tesla for K3C60 and 38-55 Tesla for Rb3C60 have been measured. The lower values are from static magnetic experiments, while the upper values used pulsed magnets.

Kaner, Richard B.

1993-06-01

29

Imaging of fullerene-like structures in CNx thin films by electron microscopy; sample preparation artefacts due to ion-beam milling.  

PubMed

The microstructure of CN(x) thin films, deposited by reactive magnetron sputtering, was investigated by transmission electron microscopy (TEM) at 200kV in plan-view and cross-sectional samples. Imaging artefacts arise in high-resolution TEM due to overlap of nm-sized fullerene-like features for specimen thickness above 5nm. The thinnest and apparently artefact-free areas were obtained at the fracture edges of plan-view specimens floated-off from NaCl substrates. Cross-sectional samples were prepared by ion-beam milling at low energy to minimize sample preparation artefacts. The depth of the ion-bombardment-induced surface amorphization was determined by TEM cross sections of ion-milled fullerene-like CN(x) surfaces. The thickness of the damaged surface layer at 5 degrees grazing incidence was 13 and 10nm at 3 and 0.8keV, respectively, which is approximately three times larger than that observed on Si prepared under the same conditions. The shallowest damage depth, observed for 0.25keV, was less than 1nm. Chemical changes due to N loss and graphitization were also observed by X-ray photoelectron spectroscopy. As a consequence of chemical effects, sputtering rates of CN(x) films were similar to that of Si, which enables relatively fast ion-milling procedure compared to carbon compounds. No electron beam damage of fullerene-like CN(x) was observed at 200kV. PMID:12524186

Czigány, Zs; Neidhardt, J; Brunell, I F; Hultman, L

2003-04-01

30

Combustion method for producing fullerenes  

DOEpatents

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

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

1993-01-01

31

Combustion method for producing fullerenes  

DOEpatents

A method for synthesizing fullerenes in flames is provided. Fullerenes are prepared by burning carbon-containing compounds in a flame and collecting the condensable. The condensable contain the desired fullerenes. Fullerene yields can be optimized and fullerene composition can be selectively varied. Fullerene yields and compositions are determined by selectively controlling flame conditions and parameters such as C/O ratio, pressure, temperature, residence time, diluent concentration and gas velocity. 4 figures.

Howard, J.B.; McKinnon, J.T.

1993-12-28

32

Migration of Mo atoms across Mo-Si interface induced by Ar+ ion bombardment  

Microsoft Academic Search

Backscattering analysis is used to investigate the effect of 150-keV Ar ion bombardment on Mo thin films evaporated on silicon. Ar ion bombardment induces the migration of Mo atoms into the underlying substrate. These migration phenomena are caused mainly by an atomic recoil process, and depend on implanted ion dose and on film thickness. These phenomena are also affected by

H. Nishi; T. Sakurai; T. Akamatsu; T. Furuya

1974-01-01

33

Extraterrestrial Helium Trapped in Fullerenes in the Sudbury Impact Structure  

Microsoft Academic Search

Fullerenes (C60 and C70) in the Sudbury impact structure contain trapped helium with a ^3He\\/^4He ratio of 5.5 x 10-4 to 5.9 x 10-4. The ^3He\\/^4He 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

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

1996-01-01

34

The generation of fullerenes.  

PubMed

We describe an efficient new algorithm for the generation of fullerenes. Our implementation of this algorithm is more than 3.5 times faster than the previously fastest generator for fullerenes - fullgen - and the first program since fullgen to be useful for more than 100 vertices. We also note a programming error in fullgen that caused problems for 136 or more vertices. We tabulate the numbers of fullerenes and IPR fullerenes up to 400 vertices. We also check up to 316 vertices a conjecture of Barnette that cubic planar graphs with maximum face size 6 are Hamiltonian and verify that the smallest counterexample to the spiral conjecture has 380 vertices. PMID:23020654

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

2012-10-12

35

Surface modification of medical polyurethane by silicon ion bombardment  

Microsoft Academic Search

The biocompatibility of Si+ implanted medical polyurethane was studied. Si ion implantation was performed at energies of 40, 60, 80, and 100 keV with doses ranging from 2 × 1013 to 2 × 1016 cm-2 at room temperature. The results show that the wettability, blood adsorption, anticoagulability and anticalcific bahaviours of the surface were changed significantly by ion bombardment. The

Li Dejun; Zhao Jie; Gu Hanqing; Lu Mozhu; Ding Fuqing; Zhang Qiqing

1993-01-01

36

Secondary ion enhancement in slow highly charged heavy ion bombardment  

Microsoft Academic Search

Carbon thin film was bombarded with high charge state Xeq+ ions, and the secondary carbon yields were measured as a function of charge state in the broad range of q = 8 to 44 at the kinetic energy of 1.0 MeV and, also, q = 44 at 175 keV. It is found that the secondary ion yields per incident ion

M. Terasawa; T. Sekioka; T. Mitamura; S. Winecki; M. P. Stöckli; C. L. Cocke

1997-01-01

37

Ion bombardment of Europa  

NASA Astrophysics Data System (ADS)

The spectral difference between Europa's leading and trailing hemispheres has long been explained as a result of magnetospheric bombardment. A closer look at the longitudinal variation of ultraviolet spectral features reveals, however, that several processes, both exogenic and endogenic, are operating on the surface (Hendrix et al., 2010, submitted; Dalton et al., 2010, in preparation). Even magnetospheric bombardment can produce a variety of exogenic patterns; each "population” of particles has a distinct bombardment pattern. Work is ongoing to connect exogenic and spectral patterns. Here we describe one piece of that ongoing work, the calculation of ion bombardment and sputtering rates. We calculated the ion bombardment rate using a program that traces ion motion given the magnetic and electric fields in the vicinity of Europa's orbit, along with information on ion composition and energies from the Voyager and Galileo missions. We conclude that the vast majority of sulfur ions impact Europa's trailing hemisphere, while the sputtering rate is more uniform, in qualitative agreement with previous work. Overall, we find that the sputtering rate at the trailing hemisphere apex (where ion flux peaks) is about 3 times that at the leading hemisphere apex. This likely results in a net erosion of Europa's entire surface, not, as some have suggested, a net deposition of ice onto the leading hemisphere. We also conclude that the energetic ion flux peaks at Europa's poles, though the sputtering rate still peaks at the equatorial trailing hemisphere apex, where the combined sputtering by "cold” and "suprathermal” ions is highest.

Cassidy, Timothy A.; Paranicas, C.; Hendrix, A.; Johnson, R. E.

2010-10-01

38

Electron bombarded semiconductor devices  

Microsoft Academic Search

The first electron bombarded semiconductor (EBS) devices have recently appeared on the market. These devices have already demonstrated that EBS has considerable promise as an important new electron device for power amplification and control. EBS devices are described with particular emphasis on power devices. The basic EBS principle, some of the analysis used in device design, general considerations in designing

A. Silzars; D. J. Bates; A. Ballonoff

1974-01-01

39

Process for fullerene functionalization  

DOEpatents

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

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

1995-01-01

40

Dynamic behavior of thermionic dispenser cathodes under ion bombardment  

NASA Astrophysics Data System (ADS)

We have investigated the surface coverage and electron emission of thermionic dispenser cathodes during 3 keV Ar+ ion bombardment, thereby simulating the bombardment of the cathodes by residual gases that takes place in cathode-ray tubes as used in television sets. During the ion bombardment at the operating temperature of 1030 °C, a dynamic equilibrium is established between the sputter removal and resupply mechanisms of the Ba and O atoms that form the dipole layer on the cathode substrate. We demonstrated that the performance of the cathodes under ion bombardment is governed by the O removal and resupply rates. It was found that the Ba resupply rate is almost an order of magnitude higher than the O resupply rate, but that the Ba can only be present on the surface bound to O atoms. Therefore, the Ba/O ratio is approximately equal to unity during the ion bombardment. Based on the investigations of the removal and resupply processes, we proposed a model that accurately describes the surface coverage and electron emission during the ion bombardment, including the dependence of the ion flux and cathode temperature.

Cortenraad, R.; van der Gon, A. W. Denier; Brongersma, H. H.; Gärtner, G.; Raasch, D.; Manenschijn, A.

2001-04-01

41

Conversion of fullerenes to diamonds  

DOEpatents

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

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

1995-01-01

42

Conversion of fullerenes to diamond  

DOEpatents

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

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

1994-01-01

43

Combustion energy of fullerene soot  

SciTech Connect

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

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

1995-02-23

44

Combustion synthesis of fullerenes  

SciTech Connect

This paper reports the isolation of C{sub 60} and C{sub 70} from combustion soot that is produced in high-temperature, low-pressure premixed flat flames. A critical parameter for high fullerene yields in combustion appears to be a very high flame temperature. Equilibrium calculations indicate that low pressures are important, but the experimental evidence is not clear at this time. Combustion synthesis yields fullerenes with a C{sub 70}/C{sub 60} ratio of about 40%, as compared with the 12% reported for electric-arc-generated fullerenes. The overall yields from carbon are very low (ca. 0.03%) but the soot studied had been produced in flames that were in no way optimized for fullerene production.

Mckinnon, J.T.; Bell, W.L. (TDA Research, Inc., Wheat Ridge, CO (US)); Barkley, R.M. (Cooperative Inst. for Research on Environmental Sciences, Boulder, CO (US))

1992-01-01

45

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

46

Induction of antioxidant enzyme activity and lipid peroxidation level in ion-beam-bombarded rice seeds  

NASA Astrophysics Data System (ADS)

Low-energy ion beam bombardment has been used to mutate a wide variety of plant species. To explore the indirect effects of low-energy ion beam on biological damage due to the free radical production in plant cells, the increase in antioxidant enzyme activities and lipid peroxidation level was investigated in ion-bombarded rice seeds. Local rice seeds were bombarded with nitrogen or argon ion beams at energies of 29-60 keV and ion fluences of 1 × 1016 ions cm-2. The activities of the antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione S-transferase (GST) and lipid peroxidation level were assayed in the germinated rice seeds after ion bombardment. The results showed most of the enzyme activities and lipid peroxidation levels in both the argon and nitrogen bombarded samples were higher than those in the natural control. N-ion bombardment could induce higher levels of antioxidant enzyme activities in the rice samples than the Ar-ion bombardment. Additional effects due to the vacuum condition were found to affect activities of some antioxidant enzymes and lipid peroxidation level. This study demonstrates that ion beam bombardment and vacuum condition could induce the antioxidant enzyme activity and lipid peroxidation level which might be due to free radical production in the bombarded rice seeds.

Semsang, Nuananong; Yu, LiangDeng

2013-07-01

47

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

48

Fullerenes from a fulgurite  

SciTech Connect

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

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

1993-03-12

49

Operation of activated-fullerene-coated field emitters in technical vacuum  

NASA Astrophysics Data System (ADS)

The operation of tungsten tip field emitters coated by activated fullerenes in technical vacuum is studied. Ways of emitter training to provide the self-reproducibility of the coatings and their long service life under intense ion bombardment in wide ranges of pressures, from 2 × 10-8 to (5-7) × 10-7 Torr, and emission currents, from (1.5-2.0) to (10-20) ?A, are developed.

Tumareva, T. A.; Sominskii, G. G.

2013-07-01

50

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

51

Nanocapillarity in fullerene tubules  

NASA Astrophysics Data System (ADS)

Fullerene tubules are shown to be highly polarizable ``molecular straws'' capable of ingesting dipolar molecules. Local-density-functional calculations on HF molecules within a finite-length tubule, of size 144 atoms, demonstrate this effect. The energy of incarceration is several times the thermal ambient at room temperature. These calculations, now feasible on desktop workstations, open the way to the study of nanoscale capillarity and to, perhaps, precise control over shielding of specific ``guest'' compounds from external electric and magnetic fields.

Pederson, Mark R.; Broughton, Jeremy Q.

1992-11-01

52

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

53

Gel behavior of keV ion irradiated polystyrene  

Microsoft Academic Search

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 (1011–1014 ions\\/cm2, keV energy). By using the Inokuty gel theory [M. Inokuti J. Appl.

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

1988-01-01

54

Diamond film growth from fullerene precursors  

DOEpatents

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

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

1997-01-01

55

Some peculiarities in the behavior of Be surfaces under bombardment by ions from a deuterium plasma  

Microsoft Academic Search

In experiments with Be mirrors bombarded by keV ions from a deuterium plasma a sharp drop of reflectance in the wavelength 220–650 nm was observed after quite low ion fluence although no mass loss of Be sample was measurable. Therefore such change of reflectance was ascribed to the transformation of the oxide layer, that naturally coats the Be mirror, into

A. F. Bardamid; A. I. Belyayeva; V. N. Bondarenko; A. A. Galuza; V. V. Gann; L. Jacobson; V. G. Konovalov; D. V. Orlinskij; I. I. Papirov; I. V. Ryzhkov; A. N. Shapoval; A. F. Shtan’; S. I. Solodovchenko; A. A. Vasil’ev; V. S. Voitsenya

2003-01-01

56

Fullerene nanomaterials potentiate hair growth  

Microsoft Academic Search

Hair loss is a common symptom resulting from a wide range of disease processes and can lead to stress in affected individuals. The purpose of this study was to examine the effect of fullerene nanomaterials on hair growth. We used shaved mice as well as SKH-1 “bald” mice to determine if fullerene-based compounds could affect hair growth and hair follicle

Zhiguo Zhou; Robert Lenk; Anthony Dellinger; Darren MacFarland; Krishan Kumar; Stephen R. Wilson; Christopher L. Kepley

2009-01-01

57

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

58

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

59

Omni-conducting fullerenes  

NASA Astrophysics Data System (ADS)

Within the graph-theoretical SPP (Source-and-Sink Potential) model, a strong omni-conductor can be defined as a molecular graph that is predicted to conduct at the Fermi level, no matter how it is connected by single-atom contacts to the wires. Exhaustive search (n?70 for general isomers; n?140 for isolated-pentagon isomers) shows that nearly all fullerene isomers Cn in the chemical size range are strong omni-conductors. The isolated-pentagon isomer of C60 is a strong omniconductor, whereas the isolated-pentagon isomer of C70, which has a non-bonding LUMO, has some insulating pairs of connections.

Fowler, P. W.; Pickup, B. T.; Todorova, T. Z.; De Los Reyes, R.; Sciriha, I.

2013-05-01

60

Ion bombardment induced smoothing of amorphous metallic surfaces: Experiments versus computer simulations  

SciTech Connect

Smoothing of rough amorphous metallic surfaces by bombardment with heavy ions in the low keV regime is investigated by a combined experimental-simulational study. Vapor deposited rough amorphous Zr{sub 65}Al{sub 7.5}Cu{sub 27.5} films are the basis for systematic in situ scanning tunneling microscopy measurements on the smoothing reaction due to 3 keV Kr{sup +} ion bombardment. The experimental results are directly compared to the predictions of a multiscale simulation approach, which incorporates stochastic rate equations of the Langevin type in combination with previously reported classical molecular dynamics simulations [Phys. Rev. B 75, 224107 (2007)] to model surface smoothing across length and time scales. The combined approach of experiments and simulations clearly corroborates a key role of ion induced viscous flow and ballistic effects in low keV heavy ion induced smoothing of amorphous metallic surfaces at ambient temperatures.

Vauth, Sebastian; Mayr, S. G. [I. Physikalisches Institut, Georg-August-Universitaet Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany)

2008-04-15

61

Metal ion bombardment of onion skin cell wall  

SciTech Connect

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

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

2004-05-10

62

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

63

Fast Atom Bombardment Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Fast atom bombardment mass spectrometry has become a powerful structural tool since the first reports of its use in 1981. Samples are ionized in the condensed state, usually in a glycerol matrix, by bombarding the matrix with xenon or argon atoms with energies of 5000 to 10,000 electron volts. This yields both positive and negative secondary ions, which are sputtered from the surface. The technique has been used to detect inorganic ion clusters to mass 25,800 and biologically active peptides to mass 5700, and it gives molecular ions of such highly polar or labile organic compounds as glycosphingolipids and polyene antibiotics. It can be especially valuable in determining the sequences of amino acids in polypeptides.

Rinehart, Kenneth L.

1982-10-01

64

Ion bombardment in RF guns  

SciTech Connect

We use the ponderomotive potential of the RF field to study the motion of ions in an RF gun. We apply this method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of the ions produced in the gun can reach the cathode if no special precautions are taken. Also, we propose simple mitigation techniques that can reduce the rate of ion bombardment.

Pozdeyev, E.; Kayran, D.; Litvinenko, V. N. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

2009-08-04

65

Production Of Fullerenic Soot In Flames  

DOEpatents

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

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

2000-12-19

66

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

67

The effects of ion bombardment of ultra-high molecular weight polyethylene  

NASA Astrophysics Data System (ADS)

Ion bombardment is a suitable tool to improve tribological properties of polymers. In this study UHMWPE samples were bombarded with 130 keV He ions to the fluences ranging from 1 × 1014 to 2 × 1016 cm-2. RBS and NRA techniques were applied to study compositional transformations induced by ion beam bombardment. Important hydrogen release was observed with increasing ion dose and was correlated with the linear energy transfer (LET). Another important effect observed was the rapid oxidation of samples, which apparently occurs after exposure of implanted samples to the air. Oxygen uptake continues during the prolonged storage of the samples in the air at RT. Up to 10 at.% of oxygen can be incorporated in the implanted layer. Changes of surface layer composition produced important increase in the layer hardness. Scratch tests revealed that the hardening of surface layers does not lead to their higher brittleness.

Turos, A.; Abdul-Kader, A. M.; Grambole, D.; Jagielski, J.; Pi?tkowska, A.; Madi, N. K.; Al-Maadeed, M.

2006-08-01

68

Molecular Structure of C70 Fullerene  

NSDL National Science Digital Library

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

2002-08-26

69

Fullerene sorting proteins  

NASA Astrophysics Data System (ADS)

Proteins bind fullerenes. Hydrophobic pockets can accommodate a carbon cage either in full or in part. However, the identification of proteins able to discriminate between different cages is an open issue. Prediction of candidates able to perform this function is desirable and is achieved with an inverse docking procedure that accurately accounts for (i) van der Waals interactions between the cage and the protein surface, (ii) desolvation free energy, (iii) shape complementarity, and (iv) minimization of the number of steric clashes through conformational variations. A set of more than 1000 protein structures is divided into four categories that either select C60 or C70 (p-C60 or p-C70) and either accommodate the cages in the same pocket (homosaccic proteins, from ????o? meaning pocket) or in different pockets (heterosaccic proteins). In agreement with the experiments, the KcsA Potassium Channel is predicted to have one of the best performances for both cages. Possible ways to exploit the results and efficiently separate the two cages with proteins are also discussed.

Calvaresi, Matteo; Zerbetto, Francesco

2011-07-01

70

Superconductivity in doped fullerenes  

SciTech Connect

While there is not complete agreement on the microscopic mechanism of superconductivity in alkali-metal-doped C[sub 60], further research may well lead to the production of analogous materials that lose resistance at even higher temperatures. Carbon 60 is a fascinating and arrestingly beautiful molecule. With 12 pentagonal and 20 hexagonal faces symmetrically arrayed in a soccer-ball-like structure that belongs to the icosahedral point group, I[sub h], its high symmetry alone invites special attention. The publication in September 1990 of a simple technique for manufacturing and concentrating macroscopic amounts of this new form of carbon announced to the scientific community that enabling technology had arrived. Macroscopic amounts of C[sub 60] (and the higher fullerenes, such as C[sub 70] and C[sub 84]) can now be made with an apparatus as simple as an arc furnace powered with an arc welding supply. Accordingly, chemists, physicists and materials scientists have joined forces in an explosion of effort to explore the properties of this unusual molecular building block. 23 refs., 6 figs.

Hebard, A.F. (AT T Bell Labs., Murray Hill, NJ (United States))

1992-11-01

71

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

72

Nonlinear absorption and optical limiting properties of fullerene materials  

NASA Astrophysics Data System (ADS)

Optical limiting results of methanol fullerene derivatives, pendant fullerene polymers, and fullerene-styrene copolymers with different fullerene contents are reported. The optical limiting properties of the t-butyl methanol fullerene carboxylate derivative in polymethylmethacrylate films are also reported and compared with the result in solution.

Sun, Ya-Ping; Riggs, Jason E.

1997-10-01

73

Erosion of steel under bombardment with ions of a deuterium plasma  

Microsoft Academic Search

The processes of sputtering of austenitic stainless steel (similar to 316SS) under long-term bombardment with ions of deuterium plasma (energy 0.1–1.5keV) as well as effects of erosion on optical properties of steel surface are investigated. It was found that for this kind of material there is no selective etching of crystallographic defects that come out to the surface; therefore the

A. Bardamid; V. Bryk; V. Konovalov; D. V. Orlinskij; A. Shtan; A. Shapoval; S. Solodovchenko; V. Voitsenya; K. Yakimov; N. Zakharenko

2000-01-01

74

Transient effect in light emission during oxygen ion bombardment of a beryllium–copper target  

Microsoft Academic Search

Light emission from a BeCu sample under 6 keV O2+ bombardment is studied. BeI, BeII and CuI spectral lines show transient at beam-off conditions. At the base pressure of rest gas, the transients are relatively strong, especially for BeII. When the target chamber is backfilled with oxygen at high pressure, the transients become weak for BeII and CuI lines and

P. Agarwal; S. R Bhattacharyya; D Ghose

1998-01-01

75

C 2H 4 insertion into ion-bombarded porous silica  

Microsoft Academic Search

A study via infrared and X-ray-photoelectron spectroscopies of ethylene reactions with porous silica during high-energy (300 keV) argon bombardment in a C2H4 atmosphere, followed by exposure to air at room temperature or heating at 500°C in a vacuum, is reported. This study has revealed in the as-prepared sample the presence of C?C, C?O, CH2 and CH3 groups. Aging at room

G. F. Cerofolini; G. Conti; G. M. Garbasso; C. Spaggiari; L. Meda

1997-01-01

76

Electron microscope investigation of damage structure in gallium-arsenide bombarded with neon ions  

Microsoft Academic Search

Transmission electron microscopy studies of thin films of gallium arsenide have shown that the surface regions become non-crystalline (i.e. amorphous) after bombardment at 21 °C with Ne ions of energies between 40 and 100 keV. This effect occurs after ion doses of about 1 × 10 ions cm and the damaged material recrystallizes onto the underlying single crystal in an

D. J. Mazey; R. S. Nelson

1969-01-01

77

Electron microscope investigation of damage structure in gallium-arsenide bombarded with neon ions  

Microsoft Academic Search

Transmission electron microscopy studies of thin films of gallium arsenide have shown that the surface regions become non-crystalline (i.e. amorphous) after bombardment at 21 °C with Ne20 ions of energies between 40 and 100 keV. This effect occurs after ion doses of about 1 × 1015 ions cm-1 and the damaged material recrystallizes onto the underlying single crystal in an

D. J. Mazey; R. S. Nelson

1969-01-01

78

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

Microsoft Academic Search

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

Jing Zhou; Meret Hildebrandt; Ming Lu

2011-01-01

79

Energetic ion bombardment of Ag surfaces by C60+ and Ga+ projectiles.  

PubMed

The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C60+ cluster projectiles compared with Ga+ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C60+ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga+ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. The experimental findings are in reasonable agreement with recent molecular dynamics simulations. PMID:16099165

Sun, Shixin; Szakal, Christopher; Winograd, Nicholas; Wucher, Andreas

2005-10-01

80

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

81

Fullerenes in matrices of different substances  

NASA Astrophysics Data System (ADS)

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

Vityaz', P. A.; Shpilevskii, É. M.

2012-07-01

82

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

83

NEUTRON ACTIVATION AT 195 kev  

Microsoft Academic Search

Neutron activation cross sections were measured at 195 kev (50 kev ; energy spread) for about 30 isotopes, bY absolute gamma counting. Absolute ; calibration was effected by determining the RdTh-DâO neutron source ; strength with a flat response 4 pi graphite sphere neutron counter, and ; irradiating indium in the form of a thin, uniform, spherical shell. The results

W. S. Lyon; R. L. Macklin

1959-01-01

84

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

85

The effect of crystal orientation on the behavior of a polycrystalline tungsten surface under focused Ga+ ion bombardment  

NASA Astrophysics Data System (ADS)

The effect of crystal orientation on the behavior of a tungsten surface under a 30 keV focused Ga+ ion beam with different bombardment angles has been investigated by in situ scanning electron microscopy and electron backscatter diffraction. Results indicate that the grains of tungsten with various orientations behave quite differently. Grains with a (0 0 1) direction parallel to the ion beam always maintain a much smoother surface morphology with less mass removal after ion bombardment, indicating a lower sputtering yield. The orientation dependence of surface sputtering of tungsten can be used to guide the fabrication of tungsten-based first wall component in a nuclear fusion reactor.

Ran, Guang; Wu, Shenghua; Liu, Xiang; Wu, Jihong; Li, Ning; Zu, Xiaotao; Wang, Lumin

2012-10-01

86

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

87

Molecular dynamics simulations of 30 and 2 keV Ga in Si  

SciTech Connect

Focused Ga{sup +} ion beams are routinely used at high incident angles for specimen preparation. Molecular dynamics simulations of 2 and 30 keV Ga bombardment of Si(011) at a grazing angle of 88 deg. were conducted to assess sputtering characteristics and damage depth. The bombardment of atomically flat surfaces and surfaces with vacancies shows little energy transfer yielding ion reflection. The bombardment of surfaces with adatoms allows for the coupling of the energy of motion parallel to the surface into the substrate resulting in sputtering. The adatom and one other Si atom eject, and motion in the substrate occurs down to a depth of 13 A. Experimental evidence shows that sputtering is a reality, suggesting that an atomically flat surface is never achieved.

Giannuzzi, Lucille A.; Garrison, Barbara J. [FEI Company, 5350 NE Dawson Creek Drive, Hillsboro, Oregon 97124 (United States); Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802 (United States)

2007-09-15

88

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

89

Angular distribution of Ag atoms sputtered with A 5 keV Ar+ ion beam  

Microsoft Academic Search

A polycrystalline, high-purity Ag target was sputtered with a normally incident, 5 keV Ar+ ion beam under ultrahigh vacuum (UHV) conditions. Sputtered material was collected on a cylindrically shaped Al foil and subsequently analysed in an Auger electron spectrometer. The obtained results show that sputtering under UHV conditions leads to a cosine-like distribution. The distribution taken after prolonged ion bombardment

Marek Szymonski; Huang Weixing; Jens Onsgaard

1986-01-01

90

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

91

The stabilization of fused-pentagon fullerene molecules  

Microsoft Academic Search

The isolated pentagon rule (IPR) is now widely accepted as a general rule for determining the stability of all-carbon fullerene cages composed of hexagons and pentagons. Fullerenes that violate this rule have been deemed too reactive to be synthesized. The stabilization of non-IPR endohedral fullerenes depends on charge transfer from the encapsulated metal clusters (endoclusters) to fullerene cages, the electronic

Yuan-Zhi Tan; Su-Yuan Xie; Rong-Bin Huang; Lan-Sun Zheng

2009-01-01

92

Electronic structure calculations of fullerenes and their derivatives  

SciTech Connect

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.

Cioslowski, J.

1995-12-31

93

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

94

ATOMIC AND MOLECULAR PHYSICS: L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions  

Microsoft Academic Search

The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16+ions are measured. The energy of the Ar16+ions ranges from about 150 keV to 350 keV. The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data. The explanation of these experimental results is in the framework of the adiabatic direct-ionization and the binding

Jin-Zhang Xu; Juan Du; Xi-Meng Chen; Jian-Xiong Shao; Zhi-Hu Yang; Ying Cui; Zhi-Min Gao; Yu-Wen Liu

2008-01-01

95

NanoEncapsulation of Fullerene in Dendrimers  

Microsoft Academic Search

Two series of dendrimers with peripheral triethyleneglycol chains and a fullerene core have been prepared and characterized. The photophysical properties have been investigated in different solvents (toluene, dichloromethane and acetonitrile). In particular, we have shown that the fullerene triplet lifetimes are steadily increased with the dendrimer volume in all the investigated solvents. Interestingly, the triplet lifetimes of the largest fullerodendrimer

Y. Rio; J. Nierengarten; G. Accorsi; N. Armaroli

96

Stability of multiply charged fullerene ions  

Microsoft Academic Search

Spontaneous (metastable) and surface-induced decay reactions for multiply charged fullerene ions, investigated recently in Innsbruck, are reviewed. Results discussed include the mechanisms and energetics of C 2 evaporation and charge separation reactions, the secondary electron emission upon impact on gold surfaces, and surface-induced reactions of singly and multiply charged fullerene ions.

P. Scheier; B. Dünser; G. Senn; H. Drexel; H. P. Winter; F. Aumayr; G. Betz; F. Biasioli; T. Fiegele; T. D. Märk

1999-01-01

97

Fullerene (C60) Films for Solid Lubrication  

Microsoft Academic Search

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

Bharat Bhushan; B. K. Gupta; Garrett W. Van Cleef; Cynthia Capp; James V. Coe

1993-01-01

98

Electrostatic properties of fullerene-doped hydrocarbons  

Microsoft Academic Search

The paper presents the results of researches on modifying dielectric properties of hydrocarbons by the addition of fullerenes. Three hydrocarbons where analyzed - toluene, cyclohexane and n-hexane - against their electrical capacity, resistivity, dielectric loss tangent and tendency to electrification. The influence of C60 fullerene doping on all examined characteristics were determined.

T. Boczar; D. Zmarzly; P. Aksamit; M. Lorenc

2008-01-01

99

Modification of interfacial characteristics between diamondlike carbon films and substrates by using ion bombardment  

NASA Astrophysics Data System (ADS)

Ion bombardment has been used to modify the interfacial characteristics of diamondlike films produced by using a pulsed arc discharge deposition method. The films were deposited onto annealed unalloyed carbon steel substrates. Two different structures were studied. In the first configuration a 40 nm thick film was deposited directly onto a steel substrate. In the other case a buffer layer of SiC with a thickness of 20 nm was first deposited, followed by a deposition of a 40 nm thick diamondlike film. Both kinds of samples were exposed to ion bombardment of 13C ions at an energy of 50 keV with the fluences of 1015 and 5 × 1015 ions/cm2. Ion bombardment did not result in any changes in the adhesion of the diamondlike film without the buffer layer as determined by using a pull test. However, ion bombardment up to 5 × 1015 ions/cm2 of the sample with the SiC buffer layer improved the adhesion beyond the testing capability of the pull tester. The results are discussed in terms of the thermodynamical properties and computer simulations of the atomic movement at the coating/substrate interface. Preliminary tests on the effect of a high fluence of 1017 ions/cm2 on the adhesion of a diamondlike film on AISI 316 stainless steel were also performed and the results, which are complemented with secondary ion mass spectroscopy (SIMS) measurements, are presented.

Hirvonen, J.-P.; Koskinen, J.; Koponen, I.; Likonen, J.; Kattelus, H.

1993-06-01

100

Molecular dynamics investigations of surface damage produced by kiloelectronvolt self-bombardment of solids  

NASA Astrophysics Data System (ADS)

Molecular dynamics computer simulations were employed to study damage production mechanisms at solid surfaces during bombardment with kiloelectronvolt ions. Three separate mechanisms are identified: ballistic damage, viscous flow and microexplosions. Ballistic damage is created by the direct knock-on of atoms onto the surface as described within the binary collision approximation. Viscous flow refers to local melting and the forced flow of liquid onto the surface, and microexplosions occur when the high pressures in cascades lead to rupturing of the nearby surface. The relative importance of each mechanism depends on several parameters: atomic mass, melting temperature, atomic density, structure and atomic bonding of the target, and the mass and energy of the projectile. The simulations were performed for Pt, Au, Cu, Ni and Ge self-atom bombardment. Cascades in the interior of the targets were also examined to provide a comparison for the surface events. In addition several events of 4.5 keV Ne and Xe bombardment of Pt(111) were simulated for comparison with experimental studies of these same bombardments using scanning tunnelling microscopy.

Ghaly, Mai

1999-04-01

101

Erosion and modification of SO2 ice by ion bombardment of the surface of Io  

NASA Astrophysics Data System (ADS)

New measurements on the effect of slow ion bombardment of SO2 ice using Ar(+) in the 15-45 keV range are presented. Total yields for loss of SO2 are given along with the energy spectra of the ejected molecules and molecular fragments and information on the chemical changes induced by the ion bombardment. These data are used to estimate that the direct sputter ejection rate of sulfur into the Jovian plasma is of the order of 10 billion atoms/sq cm/s, that the erosion rate of fresh SO2 deposits due to sputtering is of the order of 0.001 cm/yr, and that a significant and possibly observable column density of SO3 can be produced in an SO2 front only for penetrating ion bombardment. Chemical activity occurs even in rather low-temperature SO2 ice bombardment by ions in the nuclear stopping region, and this activity is likely to increase with increasing temperature.

Johnson, R. E.; Garrett, J. W.; Boring, J. W.; Barton, L. A.; Brown, W. L.

1984-02-01

102

Neutral copper cluster sputtering yields: Ne{sup +}, Ar{sup +} and Xe{sup +} bombardment  

SciTech Connect

The sputtering of neutral metal clusters was investigated by measuring relative sputtering yields of copper clusters ejected from polycrystalline copper under 3.9 keV bombardment by Ne{sup +}, Ar{sup +} and Xe{sup +} ions at normal incidence. Yields of clusters from Ne{sup +} bombardment were lower than those from Ar{sup +} bombardment, were lower than from Xe{sup +} bombardment. Sputtering yield ratios Ne{sup +}/Ar{sup +} and Xe{sup +}/Ar{sup +} were 0.56 and 1.08. Size distribution of sputtered clusters can be fit by a power law dependence with exponents of {minus}8.1, {minus}8.2 and {minus}6.2 for Ne{sup +}, Ar{sup +} and Xe{sup +}, respectively. The similarity of the exponents of the Ne{sup +} and Ar{sup +} power law fits indicates that the sputtering yields for these two primary ions are similar while that for Xe{sup +} is substantially higher, in contrast to the sputtering yield ratio data. The difference between the two measurements can be explained by assuming a systematic uncertainty in the sputtering yield ratio measurements that makes the measured ratios lower than the true values. Assuming a value at the high end of the experimental Ne{sup +} sputtering yield range, the exponents of the power law fits exhibit a linear dependence on the total sputtering yield.

Coon, S.R.; Calaway, W.F.; Pellin, M.J.

1993-08-01

103

Mixed resolution model for C60 cluster bombardment of solid benzene  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of C60 cluster bombardment have been instrumental in elucidating physical phenomena related to the sputtering process; however, chemical phenomena can also play an important role in C60 cluster bombardment of molecular solids. Therefore, a mixed resolution model of C60 cluster bombardment is being developed, where the reactive zone is represented by an all atom region, and the remaining part of the target is described by a coarse-grained representation. A reactive many body potential describes the interactions among atoms; whereas, pair potentials describe the interactions between coarse-grained beads and between coarse-grained beads and atoms. Solid benzene is used to develop the methodology of blending the potentials. The blending of potentials is evaluated by the differences in the velocities of the pressure waves (generated by the C60 impact) between the all atom benzene, coarse-grained benzene and the mixed resolution benzene systems. Initial testing with 1 keV C60 cluster bombardment simulations show a smooth transition between regions.

Kennedy, Paul E.; Garrison, Barbara J.

2011-07-01

104

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

SciTech Connect

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

Cui Yunkang [School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Department of Basic Courses, Nanjing Institute of technology, Nanjing 210013 (China); Zhang Xiaobing; Lei Wei [School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China); Jiangsu Information Display Engineering Research Center, Nanjing 210096 (China); Di Yunsong [School of Physics and Technology, Nanjing Normal University, Nanjing 210097 (China); Wang Jinchan; Yang Xiaxi [School of Electronic Science and Engineering, Southeast University, Nanjing 210096 (China)

2010-03-15

105

Backside-thinned CCDs for keV electron detection  

NASA Astrophysics Data System (ADS)

This paper presents preliminary results on the performance of n-channel, backside-thinned charge-coupled devices (CCDs) as electron-bombarded-semiconductor (EBS) imagers for the detection of 1-10 keV electrons. The devices exhibit average EBS gains ranging from approximately 50 at 1 keV to >1600 at 10 keV. Device radiation tolerance has been investigated by exposing normally-clocked devices to 6 keV electron doses up to 0.01 Coulombs/cm(superscript 2). Room temperature pre- and post-irradiation results are presented for these key device parameters: full well capacity, dark current, and charge transfer efficiency (CTE). At the maximum dose of 0.01 Coulombs/cm(superscript 2), full well capacity decreases 9% from an initial value of 680,000 e(superscript -), and dark current increases from keV is estimated by measurement of the x-ray generation efficiency of silicon as a function of electron energy. Device stability after temperature cycling has been studied by subjecting packaged devices to vacuum bakes of 24 hours at 300 degree(s)C. Full well, CTE, EBS gain, and output amplifier performance are unchanged after the extended temperature cycle, while dark current decreases slightly by 15%. In summary, these initial results indicate that the CCD can function as both an efficient and robust electron imager.

Ravel, Mihir K.; Reinheimer, Alice L.

1991-07-01

106

Low-energy ion beam bombardment effect on the plant-cell-envelope mimetic membrane for DNA transfer  

NASA Astrophysics Data System (ADS)

This study is a systematic analysis of the mechanisms involved in ion-beam induced DNA transfer, an important application of ion beam biotechnology. Cellulose membranes were used to mimic the plant cell envelope. Ion beams of argon (Ar) or nitrogen (N) at an energy of 25 keV bombarded the cellulose membranes at fluences ranging from 1015 to 1016 ions/cm2. The damage to the ion-beam-bombarded membranes was characterized using infrared spectroscopy, a micro tensile test and scanning electron microscopy (SEM). Chain scission was the dominant radiation damage type in the membrane. DNA diffusion across the membrane was significantly increased after ion beam bombardment. The increase in DNA transfer is therefore attributed to chain scission, which increases the permeability by increasing the number of pores in the membrane.

Prakrajang, K.; Sangwijit, K.; Anuntalabhochai, S.; Wanichapichart, P.; Yu, L. D.

2012-09-01

107

Microscopic insights into the sputtering of thin organic films on Ag{111} induced by C60 and Ga bombardment.  

PubMed

Molecular dynamics computer simulations have been employed to model the bombardment of Ag{111} covered with three layers of C6H6 by 15 keV Ga and C60 projectiles. The study is aimed toward examining the mechanism by which molecules are desorbed from surfaces by energetic cluster ion beams and toward elucidating the differences between cluster bombardment and atom bombardment. The results show that the impact of the cluster on the benzene-covered surface leads to molecular desorption during the formation of a mesoscopic scale impact crater via a catapulting mechanism. Because of the high yield of C6H6 with both Ga and C60, the yield enhancement is observed to be consistent with related experimental observations. Specific energy and angle distributions are shown to be associated with the catapult mechanism. PMID:16852476

Postawa, Zbigniew; Czerwinski, Bartlomiej; Winograd, Nicholas; Garrison, Barbara J

2005-06-23

108

Mechanisms of pattern formation in grazing-incidence ion bombardment of Pt(111)  

SciTech Connect

Ripple patterns forming on Pt(111) due to 5 keV Ar{sup +} grazing-incidence ion bombardment were investigated by scanning tunneling microscopy in a broad temperature range from 100 to 720 K and for ion fluences up to 3x10{sup 20} ions/m{sup 2}. A detailed morphological analysis together with molecular dynamics simulations of single ion impacts allow us to develop atomic scale models for the formation of these patterns. The large difference in step edge versus terrace damage is shown to be crucial for ripple formation under grazing incidence. The importance of distinct diffusion processes--step adatom generation at kinks and adatom lattice gas formation--for temperature dependent transitions in the surface morphology is highlighted. Surprisingly, ion bombardment effects like thermal spike induced adatom production and planar subsurface channeling are important for pattern ordering.

Hansen, Henri; Redinger, Alex; Messlinger, Sebastian; Stoian, Georgiana; Michely, Thomas [I. Physikalisches Institut, RWTH Aachen University, 52056 Aachen (Germany); Rosandi, Yudi; Urbassek, Herbert M. [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany); Linke, Udo [Institute of Thin Films and Interfaces, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany)

2006-06-15

109

Material and energy intensity of fullerene production.  

PubMed

Fullerenes are increasingly being used in medical, environmental, and electronic applications due to their unique structural and electronic properties. However, the energy and environmental impacts associated with their commercial-scale production have not yet been fully investigated. In this work, the life cycle embodied energy of C(60) and C(70) fullerenes has been quantified from cradle-to-gate, including the relative contributions from synthesis, separation, purification, and functionalization processes, representing a more comprehensive scope than used in previous fullerene life cycle studies. Comparison of two prevalent production methods (plasma and pyrolysis) has shown that pyrolysis of 1,4-tetrahydronaphthalene emerges as the method with the lowest embodied energy (12.7 GJ/kg of C(60)). In comparison, plasma methods require a large amount of electricity, resulting in a factor of 7-10× higher embodied energy in the fullerene product. In many practical applications, fullerenes are required at a purity >98% by weight, which necessitates multiple purification steps and increases embodied energy by at least a factor of 5, depending on the desired purity. For applications such as organic solar cells, the purified fullerenes need to be chemically modified to [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM), thus increasing the embodied energy to 64.7 GJ/kg C(60)-PCBM for the specified pyrolysis, purification, and functionalization conditions. Such synthesis and processing effects are even more significant for the embodied energy of larger fullerenes, such as C(70), which are produced in smaller quantities and are more difficult to purify. Overall, the inventory analysis shows that the embodied energy of all fullerenes are an order of magnitude higher than most bulk chemicals, and, therefore, traditional cutoff rules by weight during life cycle assessment of fullerene-based products should be avoided. PMID:21332197

Anctil, Annick; Babbitt, Callie W; Raffaelle, Ryne P; Landi, Brian J

2011-02-18

110

Angular distribution of In and P particles sputtered from InP by inert-gas ion bombardment  

Microsoft Academic Search

An InP(100) surface was bombarded with 1 and 3 keV Ar+ and Xe+ ions at normal incidence in ultra-high vacuum at 153 and 293 K. We determined the angular distributions of sputtered In and P particles using a collection method. The surfaces sputtered at 153 K were free of cones, irrespective of ion species and energy. The angular distribution of

M. Tanemura; T. Aoyama; A. Otani; M. Ukita; F. Okuyama; T. K. Chini

1997-01-01

111

Fast-acting nonlinear optical limiters and switchers based on fullerenes and fullerene-like nanostructures  

NASA Astrophysics Data System (ADS)

Mechanisms of nonlinear optical limiting by fullerenes and fullerene-like nanostructures in solutions, suspensions theoretically and experimentally investigated in wide spectral range 0.3-1.1 ?m. An essential contribution of photoinduced scattering to nonlinear optical limiting was demonstrated in fullerene solutions and in suspensions of fullerene-like nanostructures. It is shown than suspensions based on fullerene-like nanostructures are the most perspective for devices design with nonlinear optical protection from laser radiation (speed less than 1 ns, dynamic range 103-104, limiting threshold 5x10-6 J/cm2, spectral range 0.3-1.1 ?m, color-comfortable vision through it, i.e. the absence of limiter color.) Devices with nonlinear optical limiters are demonstrated. The computer simulation of femtosecond range optical switchers, based on fullerene containing media was performed. Fabri-Perot interferometers, containing film of fullerene film, produced by vacuum deposition and film of fullerene-polymer solid solution were investigated. Fullerene polarization nonlinearity leads to light-induced refractive index change. The probability of interferometer reflection and transmission control by low intensity signal is demonstrated.

Belousova, I. M.; Belousov, V. P.; Mironova, N. G.; Murav'eva, T. D.; Scobelev, A. G.; Yur'ev, M. S.; Videnichev, D. A.

2007-03-01

112

On the pairwise hydrophobic interaction of fullerene  

NASA Astrophysics Data System (ADS)

Makowski et al. [9] determined the potential of mean force for the association of two fullerene molecules in TIP3P water, at room temperature, and found that the water contribution contrasts pairwise hydrophobic interaction. In the present Letter this result is rationalized by showing that the decrease in water accessible surface area upon association causes both a gain in configurational/translational entropy of water molecules and a loss of a significant fraction of fullerene-water attractive energetic interactions. The latter term proves to be larger in magnitude than the former because the carbon atom density on fullerene molecular surface is markedly greater than that of normal hydrocarbons.

Graziano, Giuseppe

2010-10-01

113

Stability of extreme ultraviolet multilayer coatings to low energy proton bombardment.  

PubMed

In this work we present results of an new experiment related to low energy protons bombardments on nano-structured optical coatings. Multilayer structures protected by different capping layers have been fabricated and exposed to low energy protons (1 keV). The experimental parameters have been selected considering the potential application of the coatings to solar mission instrumentation. Future solar missions will investigate the Sun from very close distances and optical components are constantly exposed to low energy ion particles irradiation. The experiment was repeated fixing the proton flux while varying the total dose accumulated. Results show that physical processes occurred at the uppermost interfaces can strongly damage the structure. PMID:21934844

Pelizzo, M G; Corso, Alain Jody; Zuppella, Paola; Windt, D L; Mattei, G; Nicolosi, P

2011-08-01

114

Mesoscale energy deposition footprint model for kiloelectronvolt cluster bombardment of solids.  

PubMed

Molecular dynamics simulations have been performed to model 5-keV C60 and Au3 projectile bombardment of an amorphous water substrate. The goal is to obtain detailed insights into the dynamics of motion in order to develop a straightforward and less computationally demanding model of the process of ejection. The molecular dynamics results provide the basis for the mesoscale energy deposition footprint model. This model provides a method for predicting relative yields based on information from less than 1 ps of simulation time. PMID:17037922

Russo, Michael F; Garrison, Barbara J

2006-10-15

115

Near-surface structure of low-energy-argon-bombarded Si(100)  

Microsoft Academic Search

The near-surface structure of low-energy- (0.5-1.5 keV) Ar-bombarded Si(100) has been studied using high-resolution x-ray-absorption near-edge structure spectroscopy and extended x-ray-absorption fine-structure spectroscopy with synchrotron radiation, medium-energy ion scattering, variable-energy positron-annihilation spectroscopy, and angle-resolved x-ray photoemission spectroscopy. The ion-induced defect structure for silicon, and the structure and distribution of incorporated Ar and silicon carbide formed during the dynamic mixing process

L. J. Huang; W. M. Lau; H. T. Tang; W. N. Lennard; I. V. Mitchell; P. J. Schultz; M. Kasrai

1994-01-01

116

Applications of functionalized fullerenes in tumor theranostics.  

PubMed

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

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

2012-03-01

117

External Chemical Reactivity of Fullerenes and Nanotubes.  

National Technical Information Service (NTIS)

The external chemical reactivity of graphene sheet, fullerenes and carbon nanotubes has been investigated. The total reaction energy is analyzed with several contributing terms and formulated as a function of the pyramidal angles of C atoms. We have deter...

D. Ivastava K. Cho S. Park

2001-01-01

118

Diazo compounds in the chemistry of fullerenes  

NASA Astrophysics Data System (ADS)

Experimental and theoretical data on the reactions of different diazo compounds (diazomethane, its derivatives, cyclic diazo compounds and diazocarbonyl compounds) with fullerenes are summarized. The structures and stereochemistry of cycloadducts formed in these reactions are considered.

Tuktarov, Airat R.; Dzhemilev, Usein M.

2010-09-01

119

Mechanochemistry of fullerenes and related materials.  

PubMed

The low or lack of solubility of fullerenes, carbon nanotubes and graphene/graphite in organic solvents and water severely hampers the study of their chemical functionalizations and practical applications. Covalent and noncovalent functionalizations of fullerenes and related materials via mechanochemistry seem appealing to tackle these problems. In this review article, we provide a comprehensive coverage on the mechanochemical reactions of fullerenes, carbon nanotubes and graphite, including dimerizations and trimerizations, nucleophilic additions, 1,3-dipolar cycloadditions, Diels-Alder reactions, [2 + 1] cycloadditions of carbenes and nitrenes, radical additions, oxidations, etc. It is intriguing to find that some reactions of fullerenes can only proceed under solvent-free conditions or undergo different reaction pathways from those of the liquid-phase counterparts to generate completely different products. We also present the application of the mechanical milling technique to complex formation, nanocomposite formation and enhanced hydrogen storage of carbon-related materials. PMID:23677148

Zhu, San-E; Li, Fei; Wang, Guan-Wu

2013-05-16

120

Near-infrared laser production of fullerenes  

NASA Astrophysics Data System (ADS)

We performed graphite vaporization by an iodine photodissociation laser and obtained C60 as the first by IR laser. We obtained sufficient macroscopic amount of fullerene, which enabled us to apply solvent extraction method and UV spectrophotometry.

Laska, L.; Krasa, Josef; Juha, Libor; Hamplova, Vera; Soukup, Ladislav

1994-12-01

121

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

122

REVIEW ARTICLES: Ion bombardment and implantation  

Microsoft Academic Search

The scope and importance of ion bombardment studies has in recent years been considerably extended by the realization that the surface properties of materials, and in particular the semiconductors, may be usefully modified by means of the implantation of suitable ions in the form of an accelerated beam. Whereas earlier studies of radiation damage and sputtering were confined mostly to

G. Dearnaley

1969-01-01

123

Bombardment Conductivity and Photoconductivity in Rhombic Sulphur  

Microsoft Academic Search

Using pure single crystals of rhombic sulphur, of volume of few mm3, conduction counting occurs for ?-particle bombardment but only in a region close to the negative electrode, indicating a barrier effect. If the applied voltage is increased there is an increase in the counting rate proportional to Vn where n = 0.7, but no increase in the maximum pulse

P J Dean; B S H Royce; F C Champion

1960-01-01

124

Bombardment Conductivity and Photoconductivity in Rhombic Sulphur  

Microsoft Academic Search

Using pure single crystals of rhombic sulphur, of volume of few mm3, conduction counting occurs for alpha-particle bombardment but only in a region close to the negative electrode, indicating a barrier effect. If the applied voltage is increased there is an increase in the counting rate proportional to Vn where n = 0.7, but no increase in the maximum pulse

P. J. Dean; B. S. H. Royce; F. C. Champion

1960-01-01

125

Aqueous Compatible Fullerene-Doxorubicin Conjugates  

PubMed Central

Covalent conjugates of fullerene C60 and the highly effective anticancer drug doxorubicin (DOX) were prepared and studied. The conjugation was through the amide linkage to preserve the intrinsic properties of DOX and fullerene cage. As designed, the conjugates with hydrophilic ethylene glycol spacers exhibited much improved aqueous compatibility, with significant solubility in water-DMSO mixtures. The anti-neoplastic activities of DOX were apparently unaffected in the conjugates according to evaluations in vitro with a human breast cancer cell line.

Lu, Fushen; Haque, Sk. Anwarul; Yang, Sheng-Tao; Luo, Pengju G.; Gu, Lingrong; Kitaygorodskiy, Alex; Li, Huaping; Lacher, Sebastian; Sun, Ya-Ping

2009-01-01

126

Synthesis of a porphyrin-fullerene pinwheel.  

PubMed

We disclose the synthesis of a porphyrin-fullerene pinwheel that was subsequently observed by scanning tunneling microscopy. The molecule was designed to further our understanding of fullerene-surface interactions, directional control, and surface-rolling versus pivoting capabilities of this class of nanomachines. The inner porphyrin provides the square planar configuration that might lead to realization of the pinwheel spiraling motion on surfaces. PMID:18314994

Sasaki, Takashi; Osgood, Andrew J; Kiappes, J L; Kelly, Kevin F; Tour, James M

2008-03-04

127

Inorganic nanotubes and fullerene-like nanoparticles  

Microsoft Academic Search

Although graphite, with its anisotropic two-dimensional lattice, is the stable form of carbon under ambient conditions, on nanometre length scales it forms zero- and one-dimensional structures, namely fullerenes and nanotubes, respectively. This virtue is not limited to carbon and, in recent years, fullerene-like structures and nanotubes have been made from numerous compounds with layered two-dimensional structures. Furthermore, crystalline and polycrystalline

R. Tenne

2006-01-01

128

Quantum-chemical study of endohedral fullerenes  

Microsoft Academic Search

State-of-the-art in quantum-chemical research on endohedral fullerenes is considered. Separate chapters are devoted to complexes\\u000a with noble gases, main group elements, and methals and their nitrides. The structures and the mechanisms of formation and\\u000a decomposition of these compound sare highlighted. Applicability of various quantum-chemical methods for endohedral fullerene\\u000a complexes is discussed. Problems associated with the use of the ROHF and

A. G. Starikov; O. A. Gapurenko; A. L. Buchachenko; A. A. Levin; N. N. Breslavskaya

2008-01-01

129

Fullerenes in electron cyclotron resonance ion sources  

SciTech Connect

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

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

2006-03-15

130

Volatile production in nonice materials on Solar System bodies with tenuous atmospheres by ion bombardment - Laboratory results  

NASA Astrophysics Data System (ADS)

Volatiles, inferred to be trapped in nonice materials, have been discovered on the Jovian satellites and in IDPs [McCord et al., 1998; Hibbitts et al., 2000; Flynn et al., 2002]. In general, these types of volatiles may be produced through high-energy ion bombardment of Solar System bodies that have tenuous atmospheres, from the Moon to the Saturnian satellites and beyond. The surfaces of these bodies are continually bombarded by a combination of cosmic, solar, and planetary magnetospheric radiation including UV, keV protons and Helium nuclei, and more massive keV to MeV ions. The Moon's surface contains Fe-oxides that may release water products under bombardment by solar wind protons. Many classes of asteroids and the outer planets' satellites appear to contain clays or other OH-bearing materials that could release water-products as well under bombardment. Also, organic material, likely present on surfaces other than the Moon, may participate in bombardment reactions to form carbon monoxide or dioxide. Results from our laboratory experiments conducted at the Environmental Molecular Sciences Laboratory (EMSL) accelerator facility, Pacific Northwest National Laboratory (PNNL) show that volatiles are produced during MeV ion irradiation of these types of materials. We bombarded clays, oxyhydroxides, ilmenite, and carbon-doped samples with MeV hydrogen, deuterium, oxygen, and sulfur ions at current densities of 100 to 1000 namps ( 1E12 to 1E13 ions/cm2/sec) over several minutes. Ohmic heating and outgassing of trapped atmospheric gases was minimal at the lower flux levels. Most of the irradiation effects are non-thermal and are due to ionization and momentum transfer processes. Proton or deuteron bombardment of ilmenite produces water-related molecules that are quickly released into the vacuum chamber and detected by mass spectrometry. The bombardment of carbon-doped clays appears to produce CO. This process occurs independently of any reduction of FeO involved in micrometoroid impacts [Tsay et al., 1971].

Hibbitts, C. A.; Thevuthasan, S.; Shutthanandan, V.; Orlando, T.; Hansen, G. B.; McCord, T. B.

2003-05-01

131

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

Microsoft Academic Search

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.

Ying Wang; Lap-Tak Cheng

1992-01-01

132

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

133

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

2013-04-04

134

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

135

Chronology and sources of lunar impact bombardment  

NASA Astrophysics Data System (ADS)

The Moon has suffered intense impact bombardment ending at 3.9 Gyr ago, and this bombardment probably affected all of the inner Solar System. Basin magnetization signatures and lunar crater size-distributions indicate that the last episode of bombardment at about 3.85 Gyr ago was less extensive than previously thought. We explore the contribution of the primordial Mars-crosser population to early lunar bombardment. We find that Mars-crosser population initially decays with a 80-Myr half-life, with the long tail of survivors clustering on temporarily non-Mars-crossing orbits between 1.8 and 2 AU. These survivors decay with half-life of about 600 Myr and are progenitors of the extant Hungaria asteroid group in the same region. We estimate the primordial Mars-crosser population contained about 0.01-0.02 Earth masses. Such initial population is consistent with no lunar basins forming after 3.8 Gya and the amount of mass in the Hungaria group. As they survive longer and in greater numbers than other primordial populations, Mars-crossers are the best candidate for forming the majority of lunar craters and basins, including most of the Nectarian system. However, this remnant population cannot produce Imbrium and Orientale basins, which formed too late and are too large to be part of a smooth bombardment. We propose that the Imbrian basins and craters formed in a discrete event, consistent with the basin magnetization signatures and crater size-distributions. This late "impactor shower" would be triggered by a collisional disruption of a Vesta-sized body from this primordial Mars-crossing population (Wetherill, G.W. [1975]. Proc. Lunar Sci. Conf. 6, 1539-1561) that was still comparable to the present-day asteroid belt a 3.9 Gya. This tidal disruption lead to a short-lived spike in bombardment by non-chondritic impactors with a non-asteroidal size-frequency distribution, in agreement with available evidence. This body ("Wetherill's object") also uniquely matches the constraints for the parent body of mesosiderite meteorites. We propose that the present-day sources of mesosiderites are multi-km-sized asteroids residing in the Hungaria group, that have been implanted there soon after the original disruption of their parent 3.9 Gyr ago.

?uk, Matija

2012-03-01

136

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

137

Fullerenes  

Microsoft Academic Search

Although carbon represents just one of over one hundred known chemical elements, it plays a vital role in nature and represents a very important building block of nanomaterials and nanostructures. The reason for this critical role is the propensity for carbon to bond in so many different ways. Many of nature’s most important biological compounds, for example, carbohydrates, proteins, lipids,

Harry C. Dorn; James C. Duchamp

138

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…

Gan, Li-Hua

2008-01-01

139

Cathode Ion Bombardment in RF Photoguns  

SciTech Connect

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

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

2008-09-01

140

Angular and energy dependence of ion bombardment of Mo/Si multilayers  

SciTech Connect

The process of ion bombardment is investigated for the fabrication of Mo/Si multilayer x-ray mirrors using e-beam evaporation. The ion treatment is applied immediately after deposition of each of the Si layers to smoothen the layers by removing an additional thickness of the Si layer. In this study the parameters of Kr{sup +} ion bombardment have been optimized within the energy range 300 eV{endash}2 keV and an angular range between 20{degree} and 50{degree}. The optical performance of the Mo/Si multilayers is determined by absolute measurements of the near-normal-incidence reflectivity at 14.4 nm wavelength. The multilayer structures are analyzed further with small-angle reflectivity measurements using both specular reflectivity and diffuse x-ray scattering. The optimal smoothening parameters are obtained by determining the effect of ion bombardment on the interface roughness of the Si layer. The optimal conditions are found to be 2 keV at 50{degree} angle of incidence with respect to the surface. These settings result in 47{percent} reflectivity at 85{degree} ({lambda}=14.4 nm) for a 16-period Mo/Si multilayer mirror, corresponding to an interface roughness of 0.21 nm rms. Analysis shows that the interface roughness is determined by ion induced viscous flow, an effect which increases with ion energy as well as angle of incidence. In order to determine the effect of intermixing of the Si and Mo atoms, the penetration depth of the Kr{sup +} ions is calculated as a function of ion energy and angle of incidence. Furthermore, the angular dependence of the etch yield, obtained from the {ital in situ} reflectivity measurements, is investigated in order o determine the optimal ion beam parameters for the production of multilayer mirrors on curved substrates. {copyright} {ital 1997 American Institute of Physics.}

Voorma, H.; Louis, E.; Bijkerk, F. [FOM-Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439 MN Nieuwegein (The Netherlands); Abdali, S. [Danish Space Research Institute, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)

1997-08-01

141

Destruction of CO ice and formation of new molecules by irradiation with 28 keV O 6+ ions  

Microsoft Academic Search

The effect of solar wind on cometary ice was studied by using oxygen ions with energy near to that corresponding to their maximum abundance in space for bombarding CO ice. This gas was condensed on a CsI substrate at 14K and irradiated by 28keV 18O6+ ions up to a final fluence of 1.3×1016cm?2. We have used a methodology in which

A. L. F. de Barros; E. Seperuelo Duarte; L. S. Farenzena; E. F. da Silveira; A. Domaracka; H. Rothard; P. Boduch

2011-01-01

142

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

143

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

144

Effect of Ar+, N2+, He+ and H2+ bombardment on the composition and structure of CNx layers  

NASA Astrophysics Data System (ADS)

Amorphous CNx layers of high N-content, close to CN stoichiometry, were prepared by reacting a graphite target with nitrogen in DC plasma. The CN layers were subjected to 2keV Ar+, He+, H2+ and also to 2 and 4keV N2+ bombardment at fluences in the range of 1015-1017ions/cm2. Changes in chemical composition and structure were followed by X-ray photoelectron and Infra red spectroscopy. The broad asymmetric C1s and N1s line shapes manifested several bonding states assignable by IR mainly to single and conjugated C--N and also a small amount of C---N species. Ion bombardment caused preferential removal of N with simultaneous formation of different C-C bonds. Conjugated C--N bonds seemed to be more stable at ion bombardment than the other C-N type bonds. No evidence of appreciable transformation to the favourable sp3 C-N species could be detected.

Bertóti, I.; Mohai, M.; Tóth, A.; Zelei, B.

1999-01-01

145

Steady-state Cs surface concentration on Si and Ge after low energy Cs + bombardment by SIMS  

NASA Astrophysics Data System (ADS)

To understand negative ion formation under Cs + bombardment, we have studied the steady-state Cs depth distribution in Si and Ge with a focus on high-resolution analysis conditions i.e. Cs + energies between 500 eV and 5 keV and impact angles from 0° to 60°. The in situ internal Cs depth profiles have been measured with a low energy O 2+ beam (0.5-1 keV) similar to the work of Yoshikawa [S. Yoshikawa, H. Morita, et al., Appl. Surf. Sci. 203-204 (2003) 252-255]. To minimize the distortions on Cs profiles, a non-oxidizing condition (at impact angle 60°) was chosen instead of an oxidizing condition. The internal Cs profiles in Si have a flat saturation region near the surface, with an intensity independent from the bombardment conditions. Only the profile width scales with impact angles and energies. Whereas in the Ge-case, a Gaussian profile is always obtained. Based on the internal Cs profiles, a possible near surface altered layer formation in Si and Ge under Cs bombardment is suggested.

Chen, P.; Janssens, T.; Vandervorst, W.

2006-07-01

146

Formation and emission of gold and silver carbide cluster ions in a single C60- surface impact at keV energies: Experiment and calculations  

Microsoft Academic Search

Impact of fullerene ions (C60-) on a metallic surface at keV kinetic energies and under single collision conditions is used as an efficient way for generating gas phase carbide cluster ions of gold and silver, which were rarely explored before. Positively and negatively charged cluster ions, AunCm+ (n = 1-5, 1 <= m <= 12), AgnCm+ (n = 1-7, 1

Y. Cohen; V. Bernshtein; E. Armon; A. Bekkerman; E. Kolodney

2011-01-01

147

Nanostructural magnetism of polymeric fullerene crystals  

SciTech Connect

The nature of magnetism in all-carbon crystals composed of polymeric layers of covalently bound fullerene (C{sub 60}) molecules is considered. The results of quantum-chemical calculations performed using the unrestricted Hartree-Fock approximation and the semiempirical AM1 method are presented. It is shown that the exchange integrals J of both a free C{sub 60} molecule and a monomer unit of the polymer are too large ensure the required magnetic susceptibility of the fullerene crystal. However, the J value exhibits an approximately n-fold decrease for an oligomer molecule consisting of n C{sub 60} units. Therefore, in the case of large n, the exchange integral can be reduced to a low level sufficient to provide for a significant magnetic susceptibility. A nanosize (scaly) model of the observed magnetism is proposed that is consistent with recent experimental data, which are indicative of a nanostructural character of magnetic fullerene samples.

Sheka, E. F., E-mail: sheka@icp.ac.ru; Zaets, V. A. [Peoples Friendship University (Russian Federation); Ginzburg, I. Ya. [Russian Academy of Sciences, Institute for Problems of Chemical Physics (Russian Federation)

2006-11-15

148

Dynamics of carbon nanotube growth from fullerenes.  

PubMed

The growth of double-walled carbon nanotubes from peapods was studied. The transformation was monitored by the decrease of fullerene Raman lines, the growth of inner tube Raman lines, and the development of X-ray diffraction patterns. A visual check of the growth process by HRTEM provided additional information. From the difference in time constants for the bleaching of fullerene Raman lines and for the growth of nanotube Raman lines, the existence of an intermediate phase was concluded that was eventually observed in X-ray diffraction and HRTEM. Time constants for the growth of large diameter inner tubes were up to a factor two larger than for small diameter inner tubes. The results fully support the fullerene coalescence growth model triggered by Stone-Wales transformations. PMID:17608446

Pfeiffer, Rudolf; Holzweber, Matthias; Peterlik, Herwig; Kuzmany, Hans; Liu, Zheng; Suenaga, Kazu; Kataura, Hiromichi

2007-07-03

149

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

150

X-ray diffraction study of stress relaxation in cubic boron nitride films grown with simultaneous medium-energy ion bombardment  

NASA Astrophysics Data System (ADS)

Relaxation of the intrinsic stress of cubic boron nitride (cBN) thin films has been studied by x-ray diffraction (XRD) using synchrotron light. The stress relaxation has been attained by simultaneous medium-energy ion bombardment (2-10 keV) during magnetron sputter deposition, and was confirmed macroscopically by substrate curvature measurements. In order to investigate the stress-release mechanisms, XRD measurements were performed in in-plane and out-of-plane geometry. The analysis shows a pronounced biaxial state of compressive stress in the cBN films grown without medium-energy ion bombardment. This stress is partially released during the medium-energy ion bombardment. It is suggested that the main path for stress relaxation is the elimination of strain within the cBN grains due to annealing of interstitials.

Abendroth, B.; Gago, R.; Eichhorn, F.; Möller, W.

2004-12-01

151

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

152

Modification of rubber by ion bombardment  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

153

Sputtered neutral SinCm clusters as a monitor for carbon implantation during C60 bombardment of silicon  

NASA Astrophysics Data System (ADS)

The incorporation of carbon atoms into a silicon surface under bombardment with 40-keV C60+ ions is investigated using time-of-flight mass spectrometry of sputtered neutral and ionized SinCm clusters. The neutral particles emitted from the surface are post-ionized by strong field infrared photoionization using a femtosecond laser system operated at a wavelength of 1400/1700 nm. From the comparison of secondary ion and neutral spectra, it is found that the secondary ion signals do not reflect the true partial sputter yields of the emitted clusters. The measured yield distribution is interpreted in terms of the accumulating carbon surface concentration with increasing C60 fluence. The experimental results are compared with those from recent molecular dynamics simulations of C60 bombardment of silicon.

Wucher, A.; Kucher, A.; Winograd, N.; Briner, C. A.; Krantzman, K. D.

2011-06-01

154

Modulation transfer function and detective quantum efficiency of electron bombarded charge coupled device detector for low energy electrons  

SciTech Connect

The use of a thinned back-side illuminated charge coupled device chip as two-dimensional sensor working in direct electron bombarded mode at optimum energy of the incident signal electrons is demonstrated and the measurements of the modulation transfer function (MTF) and detective quantum efficiency (DQE) are described. The MTF was measured for energy of electrons 4 keV using an edge projection method and a stripe projection method. The decrease of the MTF for a maximum spatial frequency of 20.8 cycles/mm, corresponding to the pixel size 24x24 {mu}m, is 0.75{approx_equal}-2.5 dB, and it is approximately the same for both horizontal and vertical directions. DQE was measured using an empty image and the mixing factor method. Empty images were acquired for energies of electrons from 2 to 5 keV and for various doses, ranging from nearly dark image to a nearly saturated one. DQE increases with increasing energy of bombarded electrons and reaches 0.92 for electron energy of 5 keV. For this energy the detector will be used for the angle- and energy-selective detection of signal electrons in the scanning low energy electron microscope.

Horacek, Miroslav [Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, Kralovopolska 147, CZ-61264 Brno (Czech Republic)

2005-09-15

155

C60 fullerene aggregation in aqueous solution.  

PubMed

In the present work we develop a novel approach for quantification of the energetics of C60 fullerene aggregation in aqueous media in terms of equilibrium aggregation constant KF. In particular, it is shown that the experimental determination of the magnitude of KF is possible only within the framework of the 'up-scaled aggregation model', considering the C60 fullerene water solution as a solution of fullerene clusters. Using dynamic light scattering (DLS) data we report the value, K(F) = 56,000 M(-1), which is in good agreement with existing theoretical estimates and the results of energetic analyses. It is suggested that the proposed 'up-scaled model' may be used in any instances of non-specific aggregation resulting in formation of large spherical particles. The measurement of the translational diffusion coefficient and the dimensions of the light scattering particles using a DLS approach with respect to C60 fullerene aggregates is found to contain significant systematic errors originating from the interaction effect that is well-known for micellar solutions. As a result, corrections to the equations associated with DLS data are proposed. PMID:23660696

Prylutskyy, Yuriy I; Buchelnikov, Anatoly S; Voronin, Dmitry P; Kostjukov, Viktor V; Ritter, Uwe; Parkinson, John A; Evstigneev, Maxim P

2013-05-10

156

Spacer-Controlled Multiple Functionalization of Fullerenes  

Microsoft Academic Search

The chapter provides a survey of the development and applications of the tether- and template-directed regio- and, in the occurrence, stereoselective multifunctionalization of fullerenes over the past ten years. After a presentation of the first tether-directed remote functionalization of C 60, a broad spectrum of applications is reviewed according to the involved reaction types. The most frequently used chemistry consists

Carlo Thilgen; Sergey Sergeyev; François Diederich

157

Structural motifs and the stability of fullerenes  

Microsoft Academic Search

Full geometry optimization has been performed within the semiempirical QCFF\\/PI model for the 1812 fullerene structural isomers of Cââ 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

S. J. Austin; P. W. Fowler; D. E. Manolopoulos; G. Orlandi; F. Zerbetto

1995-01-01

158

Fullerene nanoarchitectonics: from zero to higher dimensions.  

PubMed

The strategic design of nanostructured materials, the properties of which could be controlled across different length scales and which, at the same time, could be used as building blocks for the construction of devices and functional systems into new technological platforms that are based on sustainable processes, is an important issue in bottom-up nanotechnology.Such strategic design has enabled the fabrication of materials by using convergent bottom-up and top-down strategies. Recent developments in the assembly of functional fullerene (C60) molecules, either in bulk or at interfaces, have allowed the production of shape-controlled nano-to-microsized objects that possess excellent optoelectronic properties, thus enabling the fabrication of optoelectronic devices. Because fullerene molecules can be regarded as an ideal zero-dimensional (0D) building units with attractive functions, the construction of higher-dimensional objects, that is, 1D, 2D, and 3D nanomaterials may realize important aspects of nanoarchitectonics. This Focus Review summarizes the recent developments in the production of nanostructured fullerenes and techniques for the elaboration of fullerene nanomaterials into hierarchic structures. PMID:23589223

Shrestha, Lok Kumar; Ji, Qingmin; Mori, Taizo; Miyazawa, Kun'ichi; Yamauchi, Yusuke; Hill, Jonathan P; Ariga, Katsuhiko

2013-04-15

159

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

160

Biomolecular Emission by Swift Heavy Ion Bombardment  

SciTech Connect

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

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

2011-01-07

161

Mechanism of production and the current density effects of doubly charged ion emission from Cd-bombarded Nb and V targets  

Microsoft Academic Search

Secondary emission of doubly-charged postive ions from 3–15 keV Cd ion-bombarded polycrystalline Nb and V samples at target current densities (Jp) in the range 0–1.4 mA cm has been studied in detail. For each target the ratio of doubly-charged to singly-charged ion currents (Is\\/Is )has been found to be 0.01 at low beam current densities and does not vary appreciably

N. Ray; P. Rajasekar; P. Chakraborty; S. D. Dey

1991-01-01

162

Time Dependent Spectral Emission of Proton Bombarded Aerogels.  

National Technical Information Service (NTIS)

The University of Arizona 2 MV Van de Graaff accelerated 1 MeV protons to bombard aerogel targets. The spectroscopic emission characteristics of proton bombarded aerogels 1.68 mm - 5.50 mm thick were studied, particularly the emission as a function of bom...

E. W. Marsh

1998-01-01

163

Mycotoxin analysis by fast atom bombardment tandem mass spectrometry.  

PubMed

Positive fast atom bombardment tandem mass spectrometry is demonstrated to be an effective technique for determination of crude aflatoxins and sterigmatocystin-related compounds. The molecular ion was selected by the first system and bombarded to produce characteristic daughter ions that could be used to identify mycotoxins in mixtures and with the same molecular weight. PMID:2745376

Uyakul, D; Isobe, M; Goto, T

164

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

Microsoft Academic Search

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

John J. Finer; Michael D. McMullen

1990-01-01

165

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

166

Beyond Bombardment: Subjectivity, Visual Culture, and Art Education  

ERIC Educational Resources Information Center

Beginning with an understanding of visual culture as a postmodern discourse, this article argues for more focused attention to how visual culture presents a critical rethinking of subjectivity within art education. Through an analysis of a language of bombardment, a discourse that positions the subject as bombarded by media messages, this article…

Eisenhauer, Jennifer F.

2006-01-01

167

Thermal transport in C20 fullerene-chained carbon nanobuds  

NASA Astrophysics Data System (ADS)

Carbon nanobuds, which are hybrid fullerene-nanotube structures, have previously shown glimpses of their potential in nanotechnology applications. By performing molecular dynamics simulations, a novel study of thermal conduction in a compact form of carbon nanobuds is presented. We demonstrate that nanobuds conduct thermal energy relatively well, within an order compared to nanotubes. Alike their close relatives--the carbon peapod, this essentially extends the dimensionality of thermal management applications. A rigorous calculation of the vibrational entropy and specific heat at the interfacial locations suggests that both functions are relatively identical in magnitude at fullerene-fullerene and fullerene-nanotube interfaces. Two common nanobud configurations are compared: while both are comparable in mechanical stability, a type 2 carbon nanobud (perfect fullerene, nanotube with vacancies) is less thermally conductive than a type 1 nanobud (perfect fullerene, perfect nanotube) due to more scattering of long-wavelength modes at the defect sites of the nanotube.

Loh, G. C.; Baillargeat, D.

2013-03-01

168

Synthesis of Endohedral Fullerene Using ECR Ion Source  

SciTech Connect

We are developing an ECRIS apparatus which is designed for the production of endohedral fullerenes. Our promising approaches to produce the endohedral fullerenes using the ECRIS are the ion-ion collision reaction of fullerenes and the other atom in their mixture plasma and simple ion implantation of atom into fullerene layer. In this study, we tried to synthesize the endohedral nitrogen-fullerenes by ion implantation. N{sup +} beam was irradiated to a fullerene target with a specific energy and dose. As a result, we could observe the peak of N+C{sub 60} from targets after N{sup +} beam irradiation with TOF-SIMS and LDI-TOF-MS.

Minezaki, Hidekazu [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama (Japan); Uchida, Takashi [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama (Japan); Tanaka, Kiyokatsu; Asaji, Toyohisa [Tateyama Machine Co., Ltd., 30 Shimonoban, Toyama, Toyama (Japan); Muramatsu, Masayuki; Kitagawa, Atsushi [National Institute of Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage, Chiba (Japan); Kato, Yushi [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka (Japan); Racz, Richard; Biri, Sandor [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen (Hungary); Yoshida, Yoshikazu [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama (Japan); Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama (Japan)

2011-01-07

169

Carbon arc production of heptagon-containing fullerene[68  

Microsoft Academic Search

A carbon heptagon ring is a key unit responsible for structural defects in sp2-hybrized carbon allotropes including fullerenes, carbon nanotubes and graphenes, with consequential influences on their mechanical, electronic and magnetic properties. Previous evidence concerning the existence of heptagons in fullerenes has been obtained only in off-line halogenation experiments through top-down detachment of a C2 unit from a stable fullerene.

Yuan-Zhi Tan; Rui-Ting Chen; Zhao-Jiang Liao; Jia Li; Feng Zhu; Xin Lu; Su-Yuan Xie; Jun Li; Rong-Bin Huang; Lan-Sun Zheng

2011-01-01

170

Radiation?Induced Synthesis of Fullerene?Silica Hybrid Nanomaterials  

Microsoft Academic Search

C60 fullerene has been radiation grafted on bare and functionalized silica surface with mercaptopropyl moieties in toluene solution. The resulting fullerene?silica hybrid nanomaterials have been characterized by FT?IR and solid state C CP?MAS NMR spectroscopy and compared to the radiolysis products of C60 in toluene. It has been found that fullerene is grafted on silica surface but, because the radiation

Franco Cataldo; Giancarlo Angelini; Edo Lilla; Ornella Ursini

2007-01-01

171

Synthesis and characterization of the first fullerene-peptide  

SciTech Connect

Functionalization of C{sub 60} is a field of substantial interest. Interest has grown in the are of functionalized fullerenes for pharmacological applications. In this vein, the authors report the first synthesis and structural characterization of a fullerene-peptide. NMR, FTIR, circular dichroism, and UV-Vis spectroscopy were used in the characterization of the peptide. The product clearly evidences properties of fullerenes and of peptides. 15 refs., 4 figs.

Prato, M. [Universita di Trieste (Italy); Bianco, A.; Maggini, M.; Scorrano, G.; Toniolo, C. [Universita di Padova (Italy); Wudl, F. [Univ. of California, Santa Barbara, CA (United States)

1993-10-08

172

Magnetic properties and valence states of fullerene complexes  

Microsoft Academic Search

As a consequence of the bucky-ball structure of the fullerenes two kinds of fullerene complexes are formed: endohedral and exohedral complexes. The endohedral fullerenes Sc at C82, Y at C82 and La at C82 show ESR spectra with hyperfine splittings resulting from the nuclear spin of the metal ion. Scandium, yttrium and lanthanum are in the 3+ state in the

Anton Bartl; Lothar Dunsch; Juergen Froehner; Gotthard Seifert; Dieter Eckert; Manfred Wolf; Karl-Hartmut Mueller

1997-01-01

173

Structural characterization and molecular dynamics of fullerene or fullerene-derivative nanowhiskers  

NASA Astrophysics Data System (ADS)

Recently, a new type of fibrous fullerene crystals called fullerene nanowhisker has been reported by a liquid-liquid interfacial precipitation method using saturated m-xylene solution of fullerene and isopropyl alcohol. Considerable interests have been generated in the structure and properties of fullerene or fullerene-derivative nanowhiskers. In this study, we present the results of structural characterization and molecular dynamics of C60, C70 and C61H2 --nanowhiskers(NWs) by x-ray diffraction and solid state NMR. The XRD pattern of as-grown C60-NWs have a hexagonal structure with lattice constants of a=23.732 and c=10.126. Both solid-state ^13C-CP/MAS and wideline ^1H-NMR measurement clearly shows that m-xylene molecules are included in NWs. Both lineshape and spin-lattice relaxation time of wideline ^13C-NMR measurements clearly show that C60-NWs exhibited the phase transition at 250 K. Detailed results on the molecular dynamics and the other properties for C60-, C70- or C61H2-NWs will be presented.

Ogata, Hironori; Motohashi, Satoru

2007-03-01

174

Ion bombardment of Ni(110) studied with inverse photoemission, LEED, and simulations  

NASA Astrophysics Data System (ADS)

Inverse Photoemission Spectroscopy (IPES) performed on clean Ni(110) reveals an unoccupied electronic surface state ˜2eV above the Fermi level at the =Y point of the surface Brillouin Zone. Ion bombardment (sputtering) of the sample creates vacancies and adatoms, which reduce the intensity of the representative state peak in IPES spectra. While the intensity of this IPES peak decreases with sputtering, well-defined diffraction spots in the surface LEED pattern give way to more diffuse ones with higher background intensity. Quantization of these permits analysis of their intensity profiles. Results of these techniques are presented for various sputtering conditions with 1keV Ne ^+ and compared to previous results for 500eV Ar ^+ on the same sample. Finally, we connect sputtering trends in the IPES and LEED data to Monte Carlo simulations of the sputtering process.

Young, Benjamin; Warner, Jim; Heskett, David

2013-03-01

175

Light emission from sputtered aluminum atoms and ions produced by ion bombardment  

NASA Astrophysics Data System (ADS)

Photon emission originating from sputtering of a polycrystalline aluminum surface under 1-10keV ion (H+, He+, Ar+, Kr+ and Xe+) bombardment has been studied. Measured photon emission yields from the 3d 2D3/2 resonance transition of sputtered excited Al atoms and calculated nuclear stopping powers are compared. The results demonstrate that elastic collisions play a major role in photon emission. Moreover, measurements of photon intensity as a function of the distance from the target surface show that decays of sputtered excited ions Al+ and Al2+ are faster than decays of excited Al atoms, and less affected by cascade repopulation and de-excitation of fast ions. Radiation and Isotope Application Division, PINSTECH, Islamabad, Pakistan.

Qayyum, A.; Akhtar, M. N.; Riffat, T.

2005-04-01

176

Unexpectedly high sputtering yield of carbon at grazing angle of incidence ion bombardment  

SciTech Connect

The relative sputtering yield of amorphous carbon with respect to polycrystalline nickel at Ar-ion bombardment was determined by means of Auger electron spectroscopy depth profiling as a function of the angle of incidence and projectile energy in the ranges of 49 deg. -88 deg. and 0.3-1 keV, respectively. It was found that the relative sputtering yield Y{sub C}/Y{sub Ni} strongly increases with angle of incidence from 49 deg. to 82 deg. . At around 80 deg. the sputtering yield of C is higher than that of Ni. Above 82 deg. no dependence on the angle of incidence was found. The relative sputtering yield weakly depends on the energy of the projectile. The experimental results will be explained by the help of transport of ion in solid (TRIM) simulations.

Barna, A.; Menyhard, M.; Kotis, L.; Kovacs, Gy. J.; Radnoczi, G.; Zalar, A.; Panjan, P. [Research Institute for Technical Physics and Materials Science, Budapest H-1525 P.O. Box 49 (Hungary); Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

2005-07-15

177

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

178

Thin fullerene-containing films synthesized by ion beam sputtering of fullerene mixtures with doping additives in vacuum  

Microsoft Academic Search

A new approach to the synthesis of films containing fullerenes and doping elements is described. It is suggested that a cluster\\u000a mechanism of the target sputtering by accelerated ions makes possible the deposition of fullerenes on a substrate with a certain\\u000a probability for dopant atoms being introduced into the cavities of fullerene molecules and a higher probability of their occurrence

A. P. Semenov; I. A. Semenova; N. V. Bulina; V. A. Lopatin; N. S. Karmanov; G. N. Churilov

2005-01-01

179

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

180

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

181

Intense Soft X-ray Production By Plasma Discharge Bombardment of a Deuterated Target  

NASA Astrophysics Data System (ADS)

Intense soft (1-2 keV) X-ray emission was recently observed from a metal target such as Ti or Pd which serves as the cathode in a high current, pulsed deuterium plasma discharge tube[1]. These experimental results are briefly reviewed here along with the design and inital operation of a new experiment at the U of Illinois. This unique configuration provides a significantly higher intensity of soft x-rays than previously reported for conventional accelerator ion beam bombardment of metal targets. It is proposed that the high emission in present experiments is related to anomalous transfer of energy through recoil events when a highly loaded (large D/metal atom ratio) metal hydride is bombarded with the very high current ion beam obtained via a pulsed plasma discharge (vs. lower current accelerators). Then energy associated with the deuteron desorption/flow from the overheated cathode surface creates non-equilibrium lattice phonons, which in turn excite a "metastable" super-cell state in the loaded metal. [1] A.G. Lipson, A.S. Roussetski, A.B. Karabut, G.H. Miley, "Enhancement of DD-reaction and X-ray Generation in High-Current Deuterium Glow Discharge at Voltages 0.8-2.5 kV", JETP Lett.,(2003).

Yang, Yang; Miley, George H.; Lipson, Andrei; Luo, Nie; Karabut, Alexander

2004-11-01

182

Preparation of fullerene/glass composites  

DOEpatents

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

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

1995-05-30

183

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

184

Ambient-atmosphere compatible superconducting fullerenes  

NASA Astrophysics Data System (ADS)

The goal of this phase 1 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 dopants. A source of electrons for the conduction band derived from the lowest unoccupied molecular orbitals, other than reactive alkali metals, is desired. All three methods demonstrated interesting and tantalizing results. Potassium doped fullerene films were produced in our high vacuum (HV) deposition chamber. Difficulties in transporting potassium from the shipping container to the deposition chamber were solved by using a kerosene/isopropanol bath. Measuring electric resistivity proved to be an effective method of monitoring the doping process. Protective overlayers of doped fullerence films were formed with various combinations of electrical conductors and insulators. The electrically insulating layers could be tested immediately at MER, while the metallic layers required cryogenic measurements.

Miller, T. A.

1993-02-01

185

Synthesis and Characterization of a Fullerene Derivatives  

Microsoft Academic Search

Through this paper we are proposing chemically modified fullerol as a fluorescent indicator. We examined the esterification of a fullerol, C60(OH)n, and determined the emission properties which have been directly linked to their chemical structures. As “fullerol” is a mixture of polyhydroxylated fullerenes, the separation of C60(OH)n and their esters have been attempted by using polyacrylamide gel electrophoresis (PAGE).

Shunichi Aikawa; Yasuhiko Yoshida; Shinji Hatae; Satoko Nishiyama; D. Sakthi Kumar

2007-01-01

186

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

187

Ultrananocrystalline Diamond Films from Fullerene Precursors  

Microsoft Academic Search

Fullerenes are unique sources of carbon vapor. The molecule C60 has an equivalent carbon vapor pressure near to 1 Torr at the very modest temperature of 600 C. Fragmentation produces primarily\\u000a carbon dimer C2, resulting in highly supersaturated carbon vapor, which condenses, surprisingly, to form ultrananocrystalline diamond films.\\u000a This new form of diamond (3–5 nm crystallite size) is phase-pure as

Dieter M. Gruen

2001-01-01

188

Electronic and optical processes in Fullerene films  

Microsoft Academic Search

This work primarily focuses on the archetypal fullerene, which is C60. C60 is electron rich and yet can be six fold reduced, taking on up to six additional electrons. Interest in the electrical properties of the solid state C60 were intensified when it was observed that it could be chemically doped with alkali metals, producing a metallic state A1C60, and

Naomi Brant

2006-01-01

189

Diamond films grown from fullerene precursors  

SciTech Connect

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

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

1995-07-01

190

Modification of Polymer Materials by Ion Bombardment: Case Studies  

NASA Astrophysics Data System (ADS)

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.; Jagielski, J.; Lipinski, P.; Pieczynska, D.; Ostaszewska, U.; Piatkowska, A.

2009-03-01

191

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

192

Ion bombardment and adsorption studies on ilmenite (FeTiO3) by X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The effects of 5 KeV argon and oxygen ion bombardment on FeTiO3 (ilmenite) at low temperatures have been studied using X-ray photoelectron spectroscopy (XPS). Also, using this same technique, the adsorption of O2, NO, N2O, and CO at 300 K and the adsorption of O2 and D2O at 150K have been studied. Argon and oxygen ion bombardment of ilmenite have confirmed earlier studies on metal oxides that argon ions generally reduce the anion species while oxygen ions generally oxidize the anion species. The two iron states involved were Fe sup +2 and Fe sup O. The reduction of Ti sup +4 was not verified although a significant shift in the Ti(2p1,3) binding energies toward the metallic state was observed after oxygen ion bombardment at low temperatures. At temperatures above 150K, O2 adsorbs dissociatively on ilmenite while D2O adsorbs molecularly below 170K. Above 300 K No, N2O, and CO do not appear to adsorb dissociatively. Low temperature adsorption of D2O was found to be inhibited by predosing the ilmenite with O2.

Schulze, P. D.

1983-09-01

193

Fullerene antioxidants decrease organophosphate-induced acetylcholinesterase inhibition in vitro  

Microsoft Academic Search

Although organophosphate (OP)-induced acetylcholinesterase (AChE) inhibition is the critical mechanism causing toxicities that follow exposure, other biochemical events, including oxidative stress, have been reported to contribute to OP toxicity. Fullerenes are carbon spheres with antioxidant activity. Thus, we hypothesized that fullerenes could counteract the effects of OP compounds and tested this hypothesis using two in vitro test systems, hen brain

Marion Ehrich; Roger Van Tassell; Yunbo Li; Zhiguo Zhou; Chris L. Kepley

2011-01-01

194

Storage of nuclear materials by encapsulation in fullerenes  

SciTech Connect

A method is described for 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, N.V.

1994-09-27

195

A Molecular Dynamics Simulation for the Formation Mechanism of Fullerene  

Microsoft Academic Search

The formation mechanism of fullerene, a new type of carbon molecule with a hollow caged structure, was studied using a molecular dynamics method. In order to simulate the basic reaction process observed in the arc-discharge or the laser vaporization fullerene generation, we have calculated the clustering process starting from randomly located isolated carbon atoms. Here, an empirical many- body carbon

Shigeo MARUYAMA; Yasutaka YAMAGUCHI; T. Takagi; S. Matsumoto

1994-01-01

196

Carbon arc production of heptagon-containing fullerene[68  

PubMed Central

A carbon heptagon ring is a key unit responsible for structural defects in sp2-hybrized carbon allotropes including fullerenes, carbon nanotubes and graphenes, with consequential influences on their mechanical, electronic and magnetic properties. Previous evidence concerning the existence of heptagons in fullerenes has been obtained only in off-line halogenation experiments through top-down detachment of a C2 unit from a stable fullerene. Here we report a heptagon-incorporating fullerene C68, tentatively named as heptafullerene[68], which is captured as C68Cl6 from a carbon arc plasma in situ. The occurrence of heptagons in fullerenes is rationalized by heptagon-related strain relief and temperature-dependent stability. 13C-labelled experiments and mass/energy conservation equation simulations show that heptafullerene[68] grows together with other fullerenes in a bottom-up fashion in the arc zone. This work extends fullerene research into numerous topologically possible, heptagon-incorporating isomers and provides clues to an understanding of the heptagon-involved growth mechanism and heptagon-dependent properties of fullerenes.

Tan, Yuan-Zhi; Chen, Rui-Ting; Liao, Zhao-Jiang; Li, Jia; Zhu, Feng; Lu, Xin; Xie, Su-Yuan; Li, Jun; Huang, Rong-Bin; Zheng, Lan-Sun

2011-01-01

197

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...

198

Fullerene Type Multilayer Insulation Blanket on a Spherical Cold Surface  

Microsoft Academic Search

Fullerene type multilayer insulation blanket is proposed for the insulation around a spherical cold surface, and has been applied to a 10 liter spherical tank of liquid nitrogen. As fullerene has 32 faces with 90 edges, 32 polygons of stacked insulation sheets must be connected each other to fabricate such a MLI blanket. The MLI blanket has 90 slots at

T. Ohmori; T. Shinozaki; H. Kaneko

2010-01-01

199

Determination of random and aligned stopping powers for 80–300 keV protons in silicon by back-scattering measurements  

Microsoft Academic Search

The proton stopping powers random and aligned along the channels [1101, [100], and [111] of silicon single crystals, in the energy range 80–300 keV, have been determined by measuring the energy of the protons back-scattered by a damaged layer previously produced by ion bombardment. The depth of this reference damage peak has been measured by using the technique introduced by

F. Cembali; F. Zignani

1977-01-01

200

Transgenic sorghum plants via microprojectile bombardment.  

PubMed Central

Transgenic sorghum plants have been obtained after microprojectile bombardment of immature zygotic embryos of a drought-resistant sorghum cultivar, P898012. DNA delivery parameters were optimized based on transient expression of R and C1 maize anthocyanin regulatory elements in scutellar cells. The protocol for obtaining transgenic plants consists of the delivery of the bar gene to immature zygotic embryos and the imposition of bialaphos selection pressure at various stages during culture, from induction of somatic embryogenesis to rooting of regenerated plantlets. One in about every 350 embryos produced embryogenic tissues that survived bialaphos treatment; six transformed callus lines were obtained from three of the eight sorghum cultivars used in this research. Transgenic (T0) plants were obtained from cultivar P898012 (two independent transformation events). The presence of the bar and uidA genes in the T0 plants was confirmed by Southern blot analysis of genomic DNA. Phosphinothricin acetyltransferase activity was detected in extracts of the T0 plants. These plants were resistant to local application of the herbicide Ignite/Basta, and the resistance was inherited in T1 plants as a single dominant locus. Images Fig. 1 Fig. 2 Fig. 4 Fig. 5

Casas, A M; Kononowicz, A K; Zehr, U B; Tomes, D T; Axtell, J D; Butler, L G; Bressan, R A; Hasegawa, P M

1993-01-01

201

Cyclocarbon coalescence: Mechanisms for tailor-made fullerene formation  

SciTech Connect

The availability of macroscopic quantities of fullerenes has resulted in a vast number of physical and chemical studies of these new materials. However, the mechanisms that lead to the formation of these spherical carbon allotropes are not well understood. Mass spectral evidence has been obtained for the size-selective growth of fullerenes through the coalescence of cyclo[n]carbons, molecular carbon allotropes consisting of monocyclic rings with n carbon atoms. Whereas coalescence of cyclo[30]carbon (cyclo-C[sub 30]) produces predominantly buckminsterfullerene (C[sub 60]), the smaller rings cyclo-C[sub 18] and cyclo-C[sub 24] preferentially produce fullerene C[sub 70] through distinct intermediates. The present studies not only provide new insights into fullerene formation mechanisms but also raise the possibility of tailoring the size distributions of fullerenes by variation of the appropriate properties of the precursors. 20 refs., 2 figs.

McElvany, S.W.; Ross, M.M. (Naval Research Lab., Washington, DC (United States)); Goroff, N.S. (Univ. of California, Los Angeles (United States)); Diederich, F. (Universitaetstrasse 16, Zuerich (Switzerland))

1993-03-12

202

FORMATION OF FULLERENES IN H-CONTAINING PLANETARY NEBULAE  

SciTech Connect

Hydrogen depleted environments are considered an essential requirement for the formation of fullerenes. The recent detection of C{sub 60} and C{sub 70} fullerenes in what was interpreted as the hydrogen-poor inner region of a post-final helium shell flash planetary nebula (PN) seemed to confirm this picture. Here, we present strong evidence that challenges the current paradigm regarding fullerene formation, showing that it can take place in circumstellar environments containing hydrogen. We report the simultaneous detection of polycyclic aromatic hydrocarbons (PAHs) and fullerenes toward C-rich and H-containing PNe belonging to environments with very different chemical histories such as our own Galaxy and the Small Magellanic Cloud. We suggest that PAHs and fullerenes may be formed by the photochemical processing of hydrogenated amorphous carbon. These observations suggest that modifications may be needed to our current understanding of the chemistry of large organic molecules as well as the chemical processing in space.

GarcIa-Hernandez, D. A.; Manchado, A. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, 38200 La Laguna (Spain); GarcIa-Lario, P. [Herschel Science Centre, European Space Astronomy Centre, Research and Scientific Support Department of ESA, Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid (Spain); Stanghellini, L.; Shaw, R. A. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Villaver, E. [Departamento de Fisica Teorica C-XI, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Szczerba, R. [N. Copernicus Astronomical Center, Rabianska 8, 87-100 Torun (Poland); Perea-Calderon, J. V., E-mail: agarcia@iac.e, E-mail: amt@iac.e, E-mail: Pedro.Garcia-Lario@sciops.esa.in, E-mail: shaw@noao.ed, E-mail: letizia@noao.ed, E-mail: eva.villaver@uam.e, E-mail: szczerba@ncac.torun.p, E-mail: Jose.Perea@sciops.esa.in [European Space Astronomy Centre, INSA S. A., P.O. Box 50727, E-28080 Madrid (Spain)

2010-11-20

203

Some Applications of Fast Atom Bombardment Mass Spectrometry.  

National Technical Information Service (NTIS)

The fast bombardment (FAB) ionisation source for mass spectrometry (MS) is introduced, and the advantages over other ionisation techniques are discussed. Experimental factors are fully described. In initial work, FABMS is applied to the direct analysis of...

J. Hodson A. J. Pidduck

1985-01-01

204

Strategic Bombardment: The Legacy of the Air Corps Tactical School,  

National Technical Information Service (NTIS)

This is a historical study of the contributions to the development of strategic bombardment in American airpower by the Air Corps Tactical School. The study follows strategic though from the foundation laid by Brigadier General William Mitchell through it...

A. M. Berry

1987-01-01

205

Deuterium permeation through carbon-coated tungsten during ion bombardment  

Microsoft Academic Search

Deuterium permeation during ion bombardment through tungsten membranes coated by amorphous carbon films was investigated and compared with the permeation through bare tungsten. The membrane was bombarded by D3+ ions with energies of 200 and 1200 eV\\/D at a temperature of 873 K. The thickness of the amorphous carbon film was 120–170 nm. Detailed characterization of the carbon films were

Yu. Gasparyan; M. Mayer; A. Pisarev; A. Wiltner; C. Adelhelm; F. Koch; M. Rasinski; J. Roth

2011-01-01

206

Transgene inheritance in plants genetically engineered by microprojectile bombardment  

Microsoft Academic Search

Microprojectile bombardment to deliver DNA into plant cells represents a major breakthrough in the development of plant transformation\\u000a technologies and accordingly has resulted in transformation of numerous species considered recalcitrant toAgrobacterium- or protoplast-mediated transformation methods. This article attempts to review the current understanding of the molecular\\u000a and genetic behavior of transgenes introduced by microprojectile bombardment. The characteristic features of the

Wojciech P. Pawlowski; David A. Somers

1996-01-01

207

Effects of transverse motion on electron back bombardment in standing wave linear accelerators  

SciTech Connect

Electron back bombardment in standing wave linear accelerators LINACS is an undesirable phenomenon which can cause the electron gun cathode to overheat and destroy electron optics. It is related not only to longitudinal motion factors, but also to transverse motion factors. This paper analyzes the effects of transverse motion on electron back bombardment and points out that owing to transverse motion, only part of the backward motion electrons can back bombard the electron gun cathode surface. The authors provide methods for calculating back bombardment beam envelopes, back bombardment ratios, back bombardment currents, and back bombardment power.

Benguang, G.; Huizhang, W.

1995-11-08

208

Production of Fullerenes from Various Carbon Materials by Means of the JxB Arc Method  

Microsoft Academic Search

In order to improve production efficiencies of fullerenes, the JxB arc method has been developed and increase of production rates of fullerenes and decrease of carbon deposition on a cathode are obtained. For mass production of higher fullerenes and endohedral metallo-fullerenes, a revolver-type fullerene producer with the JxB arc has been developed, where as much as 50 carbon material rods

Tetsu Mieno; Mohammad K. H. Bhuiyan

2000-01-01

209

The effect of fullerenes and functionalized fullerenes on Daphnia magna phototaxis and swimming behavior.  

PubMed

The effects of carbon fullerenes (C(60) ) on the environment is a growing concern as the use of nanotechnology continues to increase. Previous studies have reported alteration in Daphnia magna behavior, including increased hopping frequency, heart rate, and appendage movement in response to tetrahydrofuran-solubilized C(60) and increased hopping rate and appendage movement in response to tetrahydrofuran-solubilized C(60) HxC(70) Hx exposure. The objective of the current study was to evaluate effects of water-stirred C(60) and sonicated carboxylic acid functionalized fullerenes (fC(60) ) on D. magna behavior. Behavioral endpoints are important because changes in behavior can influence predator avoidance behaviors, alter predation risk, and potentially lead to population-level effects in D. magna. To evaluate the potential effect of fullerenes on phototactic behavior, D. magna were exposed to 545.4?µg/L C(60) and 545.6?µg/L fC(60) , and vertical position was monitored. Daphnia magna were also exposed to 545.4?µg/L C(60) , 545.6?µg/L fC(60) , and 829.3?µg/L fC(60) , and swimming movements were recorded. Fullerenes altered the vertical migration response of D. magna to the addition of food, but D. magna vertical position response to predator cues was similar for fullerenes and controls. In addition, D. magna reduced swimming speed when exposed to C(60) , but other components of D. magna swimming behavior were not affected. This research supports previous findings and suggests that C(60) may influence D. magna behavior and highlights the need for further research on sublethal behavioral modifications in aquatic organisms in response to nanomaterials. PMID:21184527

Brausch, Kathryn A; Anderson, Todd A; Smith, Philip N; Maul, Jonathan D

2011-01-21

210

High-quality epitaxial growth of {gamma}-alumina films on {alpha}-alumina sapphire induced by ion-beam bombardment  

SciTech Connect

We report the formation of epitaxial {gamma}-alumina thin films on {alpha}-alumina substrates induced by ion-beam bombardment. Single-crystal (0001) {alpha}-alumina was coated with 70-nm amorphous-alumina thin films and then bombarded with either 360-keV argon ions or 180-keV oxygen ions at 400, 500, and 600 {degree}C. Ion-channeling measurements showed a consistent minimum yield of 50% for the aluminum in the grown films. Cross-sectional transmission-electron microscopy revealed the formation of {gamma}-alumina epitaxially grown onto {alpha}-alumina with an orientation relationship [1{bar 1}0](111){gamma}{parallel}[01{bar 1}0](0001){alpha}. The epitaxy of {gamma}-alumina was further confirmed by x-ray-diffraction {phi} scans. This study indicates that ion-beam bombardment at 400--600 {degree}C not only induces the amorphous-to-{gamma} phase transformation but also effectively eliminates {l_brace}111{r_brace} twins of {gamma}-alumina, which are normally observed after thermal annealing at 800--900 {degree}C.

Yu, N.; McIntyre, P.C.; Nastasi, M.; Sickafus, K.E. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1995-12-15

211

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

SciTech Connect

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

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

2011-06-01

212

Anti-Influenza Activity of C60 Fullerene Derivatives  

PubMed Central

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.

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

213

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

2013-06-13

214

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

215

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

216

Formation of new materials in fullerenes by using nuclear recoil  

NASA Astrophysics Data System (ADS)

The formation of Sb or Te atom-incorporated fullerenes has been investigated by using radionuclides produced by nuclear reactions. From the trace of radioactivities of 120Sb(122Sb) or 121Te after High Pressure Liquid Chromatography (HPLC), it was found that the formation of endohedral fullerenes or heterofullerenes in atoms of Sb or Te is possible by a recoil process following the nuclear reactions. To confirm the produced materials, ab initio molecular-dynamics simulations based on an all-electron mixed-basis approach was carried out. We present possibility of the formation of endohedral fullerenes or substitutional heterofullerenes incorporated with Sb or Te atoms. .

Ohtsuki, T.; Ohno, K.; Shiga, K.; Kawazoe, Y.; Maruyama, Y.; Shikano, K.; Masumoto, K.

2001-04-01

217

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

218

Feasibility of fullerene waste as carbonaceous adsorbent  

SciTech Connect

This note investigates using the waste soot generated in fullerene manufacture as an adsorbent. Both oven-dried and air-activated samples of waste soot are compared with three commercially available powdered activated carbons (PACs): Nuchar-SA, HDH, and Calgon-RC. Three model compounds were chosen for adsorption tests--TCE, Benzene, and Phenol--representing a small branched molecule, a small nonpolar ring molecule, and relatively polar ring molecule. Additionally, the effectiveness of total organic carbon (TOC) removal from wastewater was evaluated. Oven-dried soot performed poorly as compared to the commercial carbons, but activation of the waste soot for 60 min at 450 C in air resulted in an activated carbon (aFWS) with properties similar to those of commercially available PACs. The aFWS performed better than one would predict from the typical characterization measures of iodine number, molasses number, and methylene blue number. The data for phenol suggest some functional groups are created during the activation of the waste soot. These results show that large-scale fullerene manufacturing can be a zero-waste industry, because its primary waste product can be converted into a useful material.

Cleveland, T.G.; Garg, S.; Rixey, W.G. [Univ. of Houston, TX (United States). Dept. of Civil and Environmental Engineering

1996-03-01

219

Interaction of C(60) fullerene with lipids.  

PubMed

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

Cataldo, Franco

2010-03-23

220

Modular functionalization of carbon nanotubes and fullerenes.  

PubMed

A series of highly efficient, modular zwitterion-mediated transformations have been developed which enable diverse functionalization of carbon nanotubes (CNTs, both single-walled and multi-walled) and fullerenes. Three functionalization strategies are demonstrated. (1) Trapping the charged zwitterion intermediate with added nucleophiles allows a variety of functional groups to be installed on the fullerenes and carbon nanotubes in a one-pot reaction. (2) Varying the electrophile from dimethyl acetylenedicarboxylate to other disubstituted esters provides CNTs functionalized with chloroethyl, allyl, and propargyl groups, which can further undergo S(N)2 substitution, thiol addition, or 1,3-dipolar cycloaddition reactions. (3) Postfunctionalization transformations on the cyclopentenones (e.g., demethylation and saponification) of the CNTs lead to demethylated or hydrolyzed products, with high solubility in water (1.2 mg/mL for MWCNTs). CNT aqueous dispersions of the latter derivatives are stable for months and have been successfully utilized in preparation of CNT-poly(ethylene oxide) nanocomposite via electrospinning. Large-scale MWCNT (10 g) functionalization has also been demonstrated to show the scalability of the zwitterion reaction. In total we present a detailed account of diverse CNT functionalization under mild conditions (60 degrees C, no strong acids/bases, or high pressure) and with high efficiency (1 functional group per 10 carbon atoms for SWCNTs), which expand the utility of these materials. PMID:19480427

Zhang, Wei; Sprafke, Johannes K; Ma, Minglin; Tsui, Emily Y; Sydlik, Stefanie A; Rutledge, Gregory C; Swager, Timothy M

2009-06-24

221

[60]fullerene-pyrrolidine-N-oxides.  

PubMed

Eight members of a new family of fullerene derivatives, [60]fulleropyrrolidine-N-oxides, have been synthesized and characterized. Facile oxidation, by a peracid, of the parent [60]fulleropyrrolidine gave clean conversions into the product molecules, in which the tertiary amine is transformed into a quaternary amine bearing an oxygen atom. The reaction is very selective, favoring the nitrogen atom of the pyrrolidine ring in preference to epoxidation of the fullerene cage. The 1H NMR shows an AB quartet splitting pattern, characteristic of nonequivalent hydrogens in the pyrrolidine ring and at a chemical shift displacement of 0.8 ppm downfield. Other methods of characterization are described, including MS, differential scanning calorimetry, thermogravimetric analysis, HPLC, UV/vis, and IR. Conclusive evidence for the formation of an N-oxide moiety is provided by the synthesis, oxidation, and NMR characterization of a novel [60]fulleropyrrolidine containing a 15N isotope, showing an 85 ppm downfield heteroatom chemical shift. Preliminary details of the effects of substitution on the reactivity of the pyrrolidine ring are also reported. PMID:16496988

Brough, Peter; Klumpp, Cedric; Bianco, Alberto; Campidelli, Stephane; Prato, Maurizio

2006-03-01

222

XPS analysis of surface compositional changes in InSb 1- xBi x (111) due to low-energy Ar + ion bombardment  

NASA Astrophysics Data System (ADS)

Surface compositional changes induced by multistep 0.2-1.0 keV Ar + ion bombardment and subsequent annealing of the single crystalline (111) InSb 1- xBi x ( x?0.005) epitaxial layer have been studied for the first time by X-ray photoelectron spectroscopy (XPS). Application of Ar + ion beam with energy ?0.5 keV produced only a slight increase of the Sb/In concentration ratio above 1.0. On the other hand, 1 keV Ar + bombardment was found as the most efficient preparation step which led to the removal of the surface oxide (identified here as Sb 2O x), severe reduction of surface carbon content, but also to a decrease of Sb/In ratio towards anion deficiency (Sb/In<0.8). Subsequent short time anneal at 310°C became sufficient to reach nearly stoichiometric Sb/In ratio in the surface region. Final XPS measurements of the sputter-cleaned and annealed surface revealed that admixing of Bi into InSb does not shift the binding energies of Sb 3d and In 3d core-levels of the host compound. The binding energy of Bi 4f in InSb 1- xBi x was found to be the same as in elemental Bi.

Iwanowski, R. J.; Heinonen, M. H.; Raczy?ska, J.; Fronc, K.

2000-01-01

223

Topographic and crystallographic characterization of a grazing-ion-bombarded GaAs(110) surface by time-of-flight ion-scattering spectrometry  

SciTech Connect

We studied the topography and the atomic structure of a clean GaAs(110) surface by time-of-flight ion-scattering spectrometry (TOF-ISS). In a first series of measurements the surface was cleaned by standard cycles of ion bombardment and annealing (500 eV Ar{sup +}, 500{degree}C). This method was very efficient to remove surface contaminants but not to smooth out the damage produced in TOF-ISS experiments. A cleaning method consisting of grazing bombardment with 20 keV Ar{sup +} combined with annealing at 500{degree}C resulted in a clear improvement of the surface flatness. This was confirmed by measurements of electron energy distributions recorded under grazing proton bombardment and by a topographical analysis with an atomic force microscope. The crystallographic structure of the grazing ion bombarded surface was then studied by TOF-ISS. The quasisingle backscattered intensity measured for 5 keV Ne{sup +} presented strong variations with the incident and azimuthal angles which are consistent with the generally accepted relaxed GaAs(110) surface. From the comparison of critical angles measured and focusing regions calculated with a code recently developed we have obtained an As-Ga first interlayer spacing {Delta}Z=(0.66{plus_minus}0.08){Angstrom}, and the spacings between the first and second As layers {Delta}Z{sub 1,2}{sup As}=(2.25{plus_minus}0.08) {Angstrom} and between the first and second Ga layers {Delta}Z{sub 1,2}{sup Ga}=(1.57{plus_minus}0.1) {Angstrom}. {copyright} {ital 1997} {ital The American Physical Society}

Gayone, J.E.; Pregliasco, R.G.; Gomez, G.R.; Sanchez, E.A.; Grizzi, O. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica and Consejo Nacional de Investigaciones Cientificas y Tecnicas, 8400 San Carlos de Bariloche, Rio Negro (Argentina)

1997-08-01

224

Fullerenes and the 4430 Å Diffuse Interstellar Band  

NASA Astrophysics Data System (ADS)

The photoabsorption spectra of single-shell icosahedral fullerenes are investigated in the region of the strongest diffuse interstellar band at 4430 Å. According to Hückel and Pariser-Parr-Pople models, several fullerenes (C80, C240, C320, and C540) present transitions in the vicinity of this band. The same semiempirical models also predict a high density of transitions in the UV that may explain the 2175 Å bump in the extinction curve of the interstellar medium. It appears that fullerenes could be responsible of these two major features of interstellar absorption. Using the theoretical cross sections and available empirical data on the 4430 Å band, we estimate abundances of ~0.05 molecules per million hydrogen atoms for these fullerenes in regions of the interstellar medium with an excess color index of E(B-V)=1.0.

Iglesias-Groth, Susana

2007-06-01

225

Synthesis of a linear benzo[3]phenylene–[60]fullerene dyad  

Microsoft Academic Search

The synthesis of a new linear benzo[3]phenylene–[60]fullerene dyad 1 is achieved over 10 steps in 15% overall yield by using an efficient sequence combining a double cobalt(I)-mediated cyclotrimerization with a Bingel reaction.

Sébastien Taillemite; Corinne Aubert; Denis Fichou; Max Malacria

2005-01-01

226

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

227

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

228

Production and Consumption of Reactive Oxygen Species by Fullerenes  

EPA Science Inventory

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

229

Adhesion of evaporated titanium films to ion-bombarded polyethylene  

SciTech Connect

Ti films were deposited onto high-density polyethylene (HDPE) samples by electron-beam evaporation. Prior to film deposition the samples were i-italicn-italic s-italici-italict-italicu-italic pretreated by Ar ion bombardment using a sputter ion gun. The adhesion of the films, determined as the pull strength required for film failure, was measured as a function of ion dose. HDPE substrates processed at two different temperatures were examined. The adhesion of the Ti films to HDPE samples processed at roughly-equal150 /sup 0/C increased with the ion dose to a steady-state value corresponding to the cohesive strength of the HDPE substrate. The adhesion to the samples processed at roughly-equal200 /sup 0/C increased to a maximum and then decreased for further ion bombardment to a level of the same order as that for films deposited onto as-prepared samples. The effects of the ion bombardment upon the HDPE surface chemistry were examined by means of x-ray photoelectron spectroscopy (XPS). The ion bombardment resulted in dehydrogenation and cross linking of the surface region and for prolonged ion bombardment, a graphitelike surface was obtained. The film/substrate interface as well as the initial Ti film growth were examined by XPS analysis. A chemical interaction which resulted in Ti--C bonds was observed at the interface. The Ti film growth followed a pronounced three-dimensional growth mode on as-prepared surfaces whereas the ion bombardment resulted in a change toward a more two-dimensional growth mode. The difference in adhesion behavior for the two types of HDPE substrates was found to be due to a difference in the amounts of low molecular weight products present within the substrates.

Bodoe, P.; Sundgren, J.

1986-08-01

230

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

231

Antioxidant Properties of Water-Soluble Fullerene Derivatives  

Microsoft Academic Search

\\u000a Due to their inherent electronic properties, fullerenes are considered as radical sponges being capable of effectively quenching\\u000a reactive oxygen species (ROS). The most promising candidates for potential pharmaceutical applications are therefore water-soluble\\u000a fullerene derivatives, since they provide reasonable biological availability. In light of these considerations, we give an\\u000a overview over the most recent concepts for designing and synthesizing real water-soluble

Florian Beuerle; Russell Lebovitz; Andreas Hirsch

2008-01-01

232

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

233

Fullerenes, Noble Gases and the Flux of Extraterrestrial Debris to  

NASA Astrophysics Data System (ADS)

The discovery of fullerenes in deposits associated with two separate impact events involving a large bolide with the Earth suggests that these carbon (C) molecules may also be an indicator of extraterrestrial (ET) events over geologic time. Fullerenes were detected in carbon-rich breccias (Onaping Fm.) associated with the 1.85 byr Sudbury Crater (Becker et al., Science 265, 1994) and in clay sediments within the 65 myr old Cretaceous/Tertiary (K/T) boundary (Heymann et al., Science 265, 1994). To determine the origin of the Sudbury fullerenes, we searched for noble gases trapped inside the fullerene molecules (Saunders et al., Science 259, 1993). The Sudbury fullerenes contain trapped 3He/4He ratios (~5.5 times 10^{-4}) similar to those found in meteorites and some interplanetary dust particles (Becker et al., Science 272, 1996). Preliminary measurements of He in a continental K/T fullerene residue from Raton Basin (Colorado) revealed ^3He/^4He ratios some 100 times above air. A marine K/T residue from Stevns Klint, (Denmark) revealed ^3He/^4He ratios several thousand times above air in the high temperature fraction! We attribute the anomalously high ^3He/^4He ratios and high ^3He concentration in Stevns Klint to the abundance of higher fullerenes in the residue. The high ^3He/^4He ratio in the K/T fullerenes suggests that they were present in the bolide and somehow survived the impact event. Confirmation of these results could have broad implications concerning the importance of exogenous delivery in providing carbon, volatiles and perhaps other organics to the early Earth's crustal reservoir.

Becker, Luann; Poreda, Robert; Bunch, Ted

234

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

235

plutonium isotopic analysis in the 30 KeV to 210 KeV range  

SciTech Connect

Low-Energy Gamma-ray Spectroscopy (LEGS) is a nondestructive assay (NDA) technique developed in the 1980s. In 1999, it was modified to include a physical-based model for the energy dependent efficiency. It uses the gamma rays in the energy range from approximately 30 keV to 210 keV, except the 100-keV region. This energy region provides intense, well-separated gamma rays from the principal isotopes of plutonium. For applications involving small quantities (mg to g) of freshly separated plutonium in various chemical forms, it is ideally suited for accurate real-time or near real-time isotopic analysis. Since the last modification, LEGS has been incorporated into the FRAM code (Fixed-energy Response-function Analysis with Multiple efficiency), version 4. FRAM v4 is capable of analyzing the peaks in the whole energy range from 30 keV to 1 MeV, including the X-ray region. The new capability of analyzing the peaks in the 100-keV region greatly enhances the plutonium analysis in the 30 keV to 2 10 keV ranges of the traditional LEGS. We now can analyze both the freshly separated and aged plutonium with greater accuracy.

Vo, Duc T.; Li, T. K. (Tien K.)

2001-01-01

236

Fullerenes C60 and C70 in flames.  

PubMed

The fullerenes C60 and C70 were first identified in carbon vapour produced by laser irradiation of graphite, and have recently been produced in macroscopic quantities by vaporization of graphite with resistive heating. It has also been suggested that fullerenes might be formed in sooting flames, and indeed all-carbon ions with mass/charge ratios suggestive of fullerenes have been detected in flames. These species were assumed to have the cage structures of fullerenes, but the mass spectroscopic evidence could not establish this conclusively. We have now collected samples of condensible compounds and soot from hydrocarbon combustion under a range of conditions, and analysed these using conventional techniques in an effort to detect fullerenes. Spectroscopic studies reveal the presence of C60 and C70 in yields and ratios that depend on temperature, pressure, carbon/oxygen ratio and residence time in the flame. Control of these conditions allows optimal yields of 3 g of fullerenes per kilogram of fuel carbon burned, and variation of the C70/C60 ratio over the range 0.26-5.7. PMID:2067575

Howard, J B; McKinnon, J T; Makarovsky, Y; Lafleur, A L; Johnson, M E

1991-07-11

237

Fullerene derivatives protect endothelial cells against NO-induced damage  

NASA Astrophysics Data System (ADS)

Functional fullerene derivatives have been demonstrated with potent antioxidation properties. Nitric oxide (NO) is a free radical that plays a part in leading to brain damage when it is accumulated to a high concentration. The possible scavenging activity of NO by the hydroxylated fullerene derivative C60(OH)22 and malonic acid derivative C60(C(COOH)2)2 was investigated using primary rat brain cerebral microvessel endothelial cells (CMECs). Results demonstrate that sodium nitroprusside (SNP), used as an NO donor, caused a marked decrease in cell viability and an increase in apoptosis. However, fullerene derivatives can remarkably protect against the apoptosis induced by NO assault. In addition, fullerene derivatives can also prevent NO-induced depolymerization of cytoskeleton and damage of the nucleus and accelerate endothelial cell repair. Further investigation shows that the sudden increase of the intercellular reactive oxygen species (ROS) induced by NO was significantly attenuated by post-treatment with fullerene derivatives. Our results suggest that functional fullerene derivatives are potential applications for NO-related disorders.

Lao, Fang; Li, Wei; Han, Dong; Qu, Ying; Liu, Ying; Zhao, Yuliang; Chen, Chunying

2009-06-01

238

Optical heating and rapid transformation of functionalized fullerenes  

NASA Astrophysics Data System (ADS)

Irradiating single-walled carbon nanotubes can lead to heat generation or ignition. These processes could be used in medical and industrial applications, but the poor solvent compatibility and high aspect ratios of nanotubes have led to concerns about safety. Here, we show that certain functionalized fullerenes, including polyhydroxy fullerenes (which are known to be environmentally safe and to have therapeutic properties) are heated or ignited by exposure to low-intensity (<102 W cm-2) continuous-wave laser irradiation. We also show that polyhydroxy fullerenes and other functionalized fullerenes can be transformed into single-walled nanotubes, multiwalled nanotubes and carbon onions without the presence of a catalyst by exposure to low-intensity laser irradiation in an oxygen-free environment. To demonstrate the potential usefulness of these processes in applications, we disrupted animal cells dosed with polyhydroxy fullerenes by exposing them to a near-infrared laser for a few seconds, and also ignited an explosive charge in contact with a particle of carboxy fullerenes.

Krishna, Vijay; Stevens, Nathanael; Koopman, Ben; Moudgil, Brij

2010-05-01

239

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

PubMed

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

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

2011-12-01

240

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

2013-08-05

241

Electron and hole mobility in solution-processed small molecule-fullerene blend: Dependence on the fullerene content  

NASA Astrophysics Data System (ADS)

We present a study of electron and hole mobility in blends of the solution-processed small molecule (DTS(PTTh2)2):fullerene as a function of the fullerene content. The mobilities are measured using the Field-Effect Transistor device configuration with the blend as the material in the channel. The hole mobility of the small molecule increases when about 10% of [6-6]-phenyl C71 butyric acid methyl ester (PC70BM) is added and then decreases at higher fullerene content. The electron mobility always increases as the fullerene content increases. Balanced charge transport occurred at 70:30 and 60:40 donor to acceptor ratios in the DTS(PTTh2)2:PC70BM system. The observation of balanced charge mobility agrees well with the reported solar cell performance.

Ko Ko Kyaw, Aung; Hwan Wang, Dong; Tseng, Hsin-Rong; Zhang, Jie; Bazan, Guillermo C.; Heeger, Alan J.

2013-04-01

242

G-Factors of the 264 KeV and 632 KeV States in exp 77 As.  

National Technical Information Service (NTIS)

The integral perturbed angular correlation technique has been used to measure the g-factors of the 264 keV and 632 keV nuclear levels in exp 77 As. The g-factor of the 264 keV (5/2 exp - ) state with tau = 450+-30 ps was determined through the 367-264 keV...

F. C. Zawislak J. Schaf J. M. Gualda R. N. Saxena R. P. Livi

1978-01-01

243

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

2009-04-09

244

Anisotropic hot electron emission from fullerenes.  

PubMed

Photoelectron spectra for fullerenes C(60) and C(70) ionized using 800 nm laser pulses with pulse durations from 120 to 1000 fs show thermal electron kinetic energy distributions but they also exhibit angular anisotropy with respect to the laser light polarization. The effective temperature of electrons, measured along the laser polarization direction, is significantly higher than in the perpendicular direction. We explain this observation by considering that the emission of the thermal electrons is uncorrelated with the phase of the laser pulse, unlike directly ionized electrons, and, depending on the time of emission, they may experience an additional "kick" from the vector potential of the laser field when they are emitted from the molecule. PMID:22559476

Johansson, J O; Fedor, J; Goto, M; Kjellberg, M; Stenfalk, J; Henderson, G G; Campbell, E E B; Hansen, K

2012-04-28

245

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. 334.950 Section 334...REGULATIONS § 334.950 Pacific Ocean at San Clemente Island, California; Navy shore bombardment areas. (a) The danger...

2013-07-01

246

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...

247

Field-induced transition from room-temperature ferromagnetism to diamagnetism in proton-irradiated fullerene.  

PubMed

Room-temperature ferromagnetism in proton-irradiated C60 fullerene is demonstrated. The ferromagnetism turns into diamagnetism intrinsic to the fullerene as the magnetic field increases above a critical field. PMID:23946203

Lee, Kyu Won; Kweon, Hyocheon; Lee, Cheol Eui

2013-08-15

248

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...

249

Permittivity of low-concentration C60 fullerene solutions in p-xylene  

NASA Astrophysics Data System (ADS)

The frequency dependence of the permittivity of C60 fullerene solutions in p-xylene has been determined at various small concentrations of fullerene molecules. The results are discussed using notions of the solution structure.

Ginzburg, B. M.; Tuichiev, Sh.; Shukhiev, S.

2009-06-01

250

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

251

Evidence for the Timing of the Early Bombardment of Mars  

Microsoft Academic Search

The analysis of the SNC meteorite, ALH 84001, which now appears to be a sample of the ancient crust of Mars[1], provides a new avenue to investigate the period of intense planetary bombardment of the early solar system. The sharp cutoff in lunar highland ages close to 3900 Ga has been widely used as a time marker for heavily cratered

R. A. Ash; S. F. Knott; G. Turner

1995-01-01

252

Compositional Evolution of Saturn's Rings Due to Meteoroid Bombardment  

Microsoft Academic Search

In this paper we address the question of compositional evolution in planetary ring systems subsequent to meteoroid bombardment. The huge surface area to mass ratio of planetary rings ensures that this is an important process, even with current uncertainties on the meteoroid flux. We develop a new model which includes both direct deposition of extrinsic meteoritic “pollutants” and ballistic transport

Jeffrey N. Cuzzi; Paul R. Estrada

1998-01-01

253

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 × 1015 to 3.3 × 1017 Co/cm2 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

254

Development of an efficient transformation system for Catharanthus roseus cell cultures using particle bombardment  

Microsoft Academic Search

We have developed an efficient direct DNA transfer procedure for the facile engineering of Catharanthus roseus cell cultures. Particle bombardment of callus derived from leaf material permitted rapid selection and establishment of transgenic cell lines. Transgenic callus were recovered at a frequency of between 60–80% of total callus bombarded with a single plasmid. Bombardment using two separate plasmids resulted in

Frédérique Hilliou; Paul Christou; Mark J. Leech

1999-01-01

255

The development of a fullerene based hydrogen storage system  

SciTech Connect

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project objective was to evaluate hydrogen uptake by fullerene substrates and to probe the potential of the hydrogen/fullerene system for hydrogen fuel storage. As part of this project, the authors have completed and tested a fully automated, computer controlled system for measuring hydrogen uptake that is capable of handling both a vacuum of 1 x 10{sup -6} torr and pressures greater than 200 bars. The authors have first established conditions for significant uptake of hydrogen by fullerenes. Subsequently, hydrogenation and dehydrogenation of pure and catalyst-doped C60 was further studied to probe suitability for hydrogen storage applications. C60 {center_dot} H18.7 was prepared at 100 bar H2 and 400 C, corresponding to hydrogen uptake of 2.6 wt%. Dehydrogenation of C60 {center_dot} H18.7 was studied using thermogravimetric and powder x-ray diffraction analysis. The C60 {center_dot} H18.7 molecule was found to be stable up to 430 C in Ar, at which point the release of hydrogen took place simultaneously with the collapse of the fullerene structure. X-ray diffraction analysis performed on C60 {center_dot} H18.7 samples dehydrogenated at 454 C, 475 C, and 600 C showed an increasing volume fraction of amorphous material due to randomly oriented, single-layer graphine sheets. Evolved gas analysis using gas chromatography and mass spectroscopy confirmed the presence of both H{sub 2} and methane upon dehydrogenation, indicating decomposition of the fullerene. The remaining carbon could not be re-hydrogenated. These results provide the first complete evidence for the irreversible nature of fullerene hydrogenation and for limitations imposed on the hydrogenation/dehydrogenation cycle by the limited thermal stability of the molecular crystal of fullerene.

Brosha, E.L.; Davey, J.R.; Garzon, F.H.; Gottesfeld, S.

1998-11-01

256

ATOMIC AND MOLECULAR PHYSICS: L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions  

NASA Astrophysics Data System (ADS)

The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16+ions are measured. The energy of the Ar16+ions ranges from about 150 keV to 350 keV. The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data. The explanation of these experimental results is in the framework of the adiabatic direct-ionization and the binding energy modified BEA approximation. We consider, in the slow asymmetric collisions such as Ar and Mo/Zr, the transient united atoms (UA) are formed during the ion-surface interaction and the direct-ionization is the main mechanism for the inner-shell vacancy production. Generally, the theoretical results are in good agreement with the experimental data.

Xu, Jin-Zhang; Du, Juan; Chen, Xi-Meng; Shao, Jian-Xiong; Yang, Zhi-Hu; Cui, Ying; Gao, Zhi-Min; Liu, Yu-Wen

2008-05-01

257

Inflammogenic effect of well-characterized fullerenes in inhalation and intratracheal instillation studies  

Microsoft Academic Search

BACKGROUND: We used fullerenes, whose dispersion at the nano-level was stabilized by grinding in nitrogen gas in an agitation mill, to conduct an intratracheal instillation study and an inhalation exposure study. Fullerenes were individually dispersed in distilled water including 0.1% Tween 80, and the diameter of the fullerenes was 33 nm. These suspensions were directly injected as a solution in

Yasuo Morimoto; Masami Hirohashi; Akira Ogami; Takako Oyabu; Toshihiko Myojo; Ken-ichiro Nishi; Chikara Kadoya; Motoi Todoroki; Makoto Yamamoto; Masahiro Murakami; Manabu Shimada; Wei-Ning Wang; Kazuhiro Yamamoto; Katsuhide Fujita; Shigehisa Endoh; Kunio Uchida; Naohide Shinohara; Junko Nakanishi; Isamu Tanaka

2010-01-01

258

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

259

Theoretical study on aluminum carbide endohedral fullerene-Al4C@C80.  

PubMed

The possibility of a new endohedral fullerene with a trapped aluminum carbide cluster, Al(4)C@C(80)-I( h ), was theoretical investigated. The geometries and electronic properties of it were investigated using density functional theory methods. The Al(4)C unit formally transfers six electrons to the C(80) cage which induces stabilization of Al(4)C@C(80). A favorable binding energy, relatively large HOMO-LUMO gap, electron affinities and ionization potentials suggested the Al(4)C@C(80) is rather stable. The analysis of vertical ionization potential and vertical electron affinity indicate Al(4)C@C(80) is a good electron acceptor. PMID:23160935

Lu, Qi Liang; Song, Wen Jun; Meng, Jun Wei; Wan, Jian Guo

2012-11-17

260

What makes fullerene acceptors special as electron acceptors in organic solar cells and how to replace them.  

PubMed

Low lying excited states of the fullerene anion promote a faster charge separation in organic solar cells containing fullerene derivatives as electron acceptors. Alternative electron acceptors, not based on fullerenes but that share the same property, can be easily designed. On the other hand, it is unlikely for a generic electron acceptor to replicate this fullerene characteristic by chance. PMID:23192958

Liu, Tao; Troisi, Alessandro

2012-11-27

261

Influence of particle bombardment on microstructure and internal stresses of refractory metal suicides on silicon  

NASA Astrophysics Data System (ADS)

First results on microstructural changes and stress relaxation in thin refractory metal suicide films (TaSi2 and MoSi2) caused by particle bombardment are reported. The polycrystalline films had initial tensile stresses of some 109 Pa. Exposed to irradiation with Ge ions of 400 keV, both suicides showed a similar stress relaxation behaviour as a function of dose. During room-temperature implantation the initial tensile stress rapidly decreased and turned into compressive stress. Continuous irradiation partly relaxed the compressive stress and resulted in a saturation value of some -108 Pa. With increasing implantation temperature, the buildup of compressive stress gradually vanished, leaving only the initial decrease of tensile stress which finally approached zero. Based on microstructural investigations (TEM and X-ray diffraction) it is proposed to explain this behaviour by the combined action of two processes: relaxation of tensile stress by a volume increase due to irradiation-induced amorphization, and Frenkel defect production and relaxation of compressive stress by irradiation-induced densification of amorphous regions and/or Frenkel defect elimination.

Hardtke, Ch.; Schilling, W.; Ullmaier, H.

1991-07-01

262

The possible role of anisotropy in kinetic electronic excitation of solids by particle bombardment  

NASA Astrophysics Data System (ADS)

The kinetic excitation of a solid surface by impact of energetic particles is investigated by means of internal electron emission across a buried metal-insulator-metal (MIM) tunnel junction. By bombarding the top metal surface of such a device with keV noble gas ions, internal emission yields were determined as a function of projectile impact energy and angle of incidence with respect to the surface normal. In order to understand the observed impact angle dependence, we apply a modified formalism originally published to describe external electron emission. As a result, we find that the measured data can be explained by assuming the spatial distribution of excited electrons propagating towards the buried oxide interface to be strongly influenced by the projectile impact angle. A simple ballistic model assuming excited electrons generated by direct collisions with the projectile to preferably propagate along the direction of the original projectile motion, while electrons excited by scattering from moving recoils propagate isotropically, appears to describe the observed experimental data quite well.

Heuser, C.; Marpe, M.; Diesing, D.; Wucher, A.

2011-06-01

263

Surface confined self-assembled fullerene nanoclusters: a microscopic study  

NASA Astrophysics Data System (ADS)

The structure of the C60-fullerene terminated aminothiol self-assembled monolayers (SAM) generated by tethering the fullerene molecules to the surface of 11-amino-1-undecane thiol (11-AUT) SAM on gold surface was investigated by dynamic contact angle measurements, Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). A two-step procedure was followed consisting of the chemisorption of the amine-terminated organosulfur compound on oriented gold, followed by its reaction at the solid liquid interface with C60 fullerenes. Covalent binding of fullerenes to these attachment layers was accessed by the above experimental techniques. IR-RAS showed several major features in the C60 skeleton ring vibration region along with all the characteristic features of the amino thiol. With increase in carbon to sulfur ratio, appearance of C 1s shake-up satellite peak due to characteristic ? ?* transition of the C60 backbone confirmed the NH2 binding at the 6,6 double bond of the C60 cage. Atomic force microscopy showed smooth, homogeneous areas of the monomolecular films, covered by regular small microcrystalline grains on the fullerene-terminated monolayer surface. Possible explanations for these experimental findings are discussed.

Sahoo, Rashmi R.; Patnaik, Archita

2005-05-01

264

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

265

[sup 3]He NMR study looks at fullerene aromaticity  

SciTech Connect

Is C[sub 60] aromatic What seems like a simple question has had a number of answers since the discovery of C[sub 60] and other fullerenes in 1985. Now, an ingenious set of experiments using endohedral C[sub 60] and C[sub 70] species with helium-3 atoms trapped inside the fullerene cages is providing new information about the aromatic nature of the fullerenes. The experiments showed that helium-3 nuclei encapsulated in C[sub 60] and C[sub 70] are shielded by 6 ppm and 29 ppm, respectively, relative to free [sup 3]He. These shieldings are unexpectedly large, indicating significant diamagnetic ring currents in C[sub 60] and very large ones in C[sub 70]. As far as C[sub 60]'s aromaticity is concerned, many traditional measures of aromaticity cannot easily be applied to the fullerenes. Ring currents are a diagnostic tool to detect aromaticity. With the fullerenes, they are about the only tool one has. The ring currents detected suggest that these compounds are aromatic.

Baum, R.

1994-02-28

266

The first stable lower fullerene: C{sub 36}  

SciTech Connect

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 C{sub 60}. However, unlike other known fullerenes, any closed, fullerene-like C{sub 36} 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 C{sub 36} in arced graphite soot. {copyright} {ital 1998 American Institute of Physics.}

Piskoti, C.; Zettl, A. [Department of Physics, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

1998-08-01

267

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

268

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

2005-09-04

269

Intense keV energy polar rain  

SciTech Connect

Polar rain is usually a weak, diffuse precipitation of electrons with intensities below 0.1 erg/cm{sup 2} s and temperatures around 80 eV. Occasionally, it can have much higher fluxes and temperatures. The authors carried out an investigation using an automated search of the DMSP F7 polar cap precipitation over a 1,100-day interval to find all the days with reasonably intense (> 10{sup 6} eV/cm{sup 2} s sr) fluxes in one or more {ge}1-keV electron channels above 80 MLAT. After they eliminated precipitation associated with polar cap arcs, 17 such days were found. For 11 days, the precipitation was at least 0.4 erg/cm{sup 2} s, and on 4 days it reached a few ergs/cm{sup 2} s (for example, n = 0.85/cm{sup 3}, and kT = 2,000 eV). A fairly uniform polar rain over the polar caps at this intensity approximately equals the hemispherical energy flux over the entire auroral oval. Like ordinary polar rain, the keV precipitation occurs in only one hemisphere and is generally accompanied by an often high-density polar rain at more typical energies. No particular association with storms or poststorm quieting was evident in our sample; instead, the results appear to be consistent with the model of Fairfield and Scudder, in that there is an apparent association between intense keV polar rain and low solar-wind densities. The keV electrons were not observed within the cusp proper, futher supporting the concept of polar rain as a special component of the solar-wind electron population. A peristent gap between the poleward edge of auroral electron precipitation and the occurrence of polar rain is observed; the gap is largest at dusk, smaller at dawn, still smaller near midnight, and nonexistent on the dayside. They interpret the field lines poleward of the auroral-oval precipitation and equatorward of polar rain as recently closed field lines.

Newell, P.T.; Meng, Ching-I. (Johns Hopkins Univ., Laurel, MD (USA))

1990-06-01

270

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

271

TEM study of diamond films grown from fullerene precursors  

SciTech Connect

Transmission Electron Microscope (TEM) techniques are applied to study the microstructure of diamond films grown from fullerene precursors. Electron diffraction and electron energy loss spectra (EELS) collected from the diamond films correspond to that of bulk diamond. Microdiffraction, high resolution images and EELS help determine that the first diamond grains that nucleate from fullerene precursors generally form on a thin amorphous carbon interlayer and seldom directly on the silicon substrate. Grain size measurements reveal nanocrystalline diamond grains. Cross section TEM images show that the nanocrystalline diamond grains are equiaxed and not columnar nor dendritic. The microstructure of small equiaxed grains throughout the film thickness is believed responsible for the very smooth surfaces of diamond films grown from fullerene precursors.

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

1995-11-01

272

DFT study on a fullerene doped with Si and N  

NASA Astrophysics Data System (ADS)

DFT calculations are applied for some stable C60, C59Si, and C59N hetero fullerenes. Sn and Ge atoms are doped at the same position of C60. Computations are carried out at the B3LYP/cc pVDZ levels. In this work the effects of the heteroatoms, Si and N, on the structural properties of the fullerene have been studied. The structure, energetic and relative stabilities of the compounds were compared and analyzed with each other. In addition, vibrations spectra of proposed stable neutral species, as well as the infrared intensities are calculated. From the data obtained from calculation, we found that there is strong correlation between the stability of pure C60 fullerene molecule and the numbers of different C-C bonds.

Beigi, Hossein Shirani IL

2013-09-01

273

Van der Waals Coefficients for Nanostructures: Fullerenes Defy Conventional Wisdom  

NASA Astrophysics Data System (ADS)

The van der Waals coefficients between quasispherical nanostructures can be modeled accurately and analytically by those of classical solid spheres (for nanoclusters) or spherical shells (for fullerenes) of uniform valence electron density, with the true static dipole polarizability. Here, we derive analytically and confirm numerically from this model the size dependencies of the van der Waals coefficients of all orders, showing, for example, that the asymptotic dependence for C6 is the expected n2 for pairs of nanoclusters An-An, each containing n atoms, but n2.75 for pairs of single-walled fullerenes Cn-Cn. Large fullerenes are argued to have much larger polarizabilities and dispersion coefficients than those predicted by either the standard atom pair-potential model or widely used nonlocal van der Waals correlation energy functionals.

Ruzsinszky, Adrienn; Perdew, John P.; Tao, Jianmin; Csonka, Gábor I.; Pitarke, J. M.

2012-12-01

274

The Formation of Cosmic Fullerenes from Arophatic Clusters  

NASA Astrophysics Data System (ADS)

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

Micelotta, Elisabetta R.; Jones, Anthony P.; Cami, Jan; Peeters, Els; Bernard-Salas, Jeronimo; Fanchini, Giovanni

2012-12-01

275

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

276

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

277

Secondary ion emission from condensed CO bombarded by fission fragments  

Microsoft Academic Search

Frozen CO was bombarded by ?65MeV fission fragments and the emitted secondary ions were analyzed by time-of-flight mass spectrometry. Target was kept at UHV conditions and its temperature was varied from 25K up to complete sublimation of the ice film. The observed positive cluster ion series are well represented by the chemical expression (CO)mCn+, where m and n?0, and the

L. S. Farenzena; R. Martinez; P. Iza; C. R. Ponciano; M. G. P. Homem; A. Naves de Brito; E. F. da Silveira; K. Wien

2006-01-01

278

Back bombardment for dispenser and lanthanum hexaboride cathodes  

Microsoft Academic Search

The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode's temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf

Mahmoud Bakr; R. Kinjo; Y. W. Choi; M. Omer; K. Yoshida; S. Ueda; M. Takasaki; K. Ishida; N. Kimura; T. Sonobe; T. Kii; K. Masuda; H. Ohgaki; H. Zen

2011-01-01

279

CALIFORNIUM ISOTOPES FROM BOMBARDMENT OF URANIUM WITH CARBONIONS  

Microsoft Academic Search

The recent production and identification of isotopes of elements with atomic numbers up to six higher than the target element through bombardment with hexapositive 120-Mev carbon ions made it seem worthwhile to apply this technique to the transuranium region. Accordingly, small pieces of natural uranium metal (about 0.5 mil thick and 205 cm by 0.6 cm area) were irradiated in

A. Ghiorso; S. G. Thompson; G. T. Seaborg

1950-01-01

280

Transgenic coffee fruits from Coffea arabica genetically modified by bombardment  

Microsoft Academic Search

The genetic modification of Coffea arabica fruits is an important tool for the investigation of physiological characteristics and functional validation of genes related\\u000a to coffee bean quality traits. In this work, plants of C. arabica cultivar Catuaí Vermelho were successfully genetically modified by bombardment of embryogenic calli. Calli were obtained\\u000a from 90% of the leaf explants cultivated in a callogenesis-inducing

Erika V. S. Albuquerque; Welcimar G. Cunha; Aulus E. A. D. Barbosa; Poliene M. Costa; João B. Teixeira; Giovanni R. Vianna; Glaucia B. Cabral; Diana Fernandez; Maria F. Grossi-de-Sa

2009-01-01

281

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

282

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

283

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

284

Quantification of steroid conjugates using fast atom bombardment mass spectrometry  

SciTech Connect

Fast atom bombardment/mass spectrometry or liquid secondary ion mass spectrometry provides the capability for direct analysis of steroid conjugates (sulfates, glucuronides) without prior hydrolysis or derivatization. During the analysis of biologic extracts, limitations on the sensitivity of detection arise from the presence of co-extracted material which may suppress or obscure the analyte signal. A procedure is described for the quantitative determination of dehydroepiandrosterone sulfate in serum which achieved selective isolation of the analyte using immunoadsorption extraction and highly specific detection using tandem mass spectrometry. A stable isotope-labeled analog (( 2H2)dehydroepiandrosterone sulfate) was used as internal standard. Fast atom bombardment of dehydroepiandrosterone sulfate yielded abundant (M-H)- ions that fragmented following collisional activation to give HSO4-; m/z 97. During fast atom bombardment/tandem mass spectrometry of serum extracts, a scan of precursor ions fragmenting to give m/z 97 detected dehydroepiandrosterone sulfate and the (2H2)-labeled analog with a selectivity markedly superior to that observed using conventional mass spectrometry detection. Satisfactory agreement was observed between quantitative data obtained in this way and data obtained by gas chromatography/mass spectrometry of the heptafluorobutyrates of dehydroepiandrosterone sulfate and (2H2)dehydroepiandrosterone sulfate obtained by direct derivatization. 21 refs.

Gaskell, S.J. (Baylor College of Medicine, Houston, TX (USA))

1990-10-01

285

Nonlinear refractive properties of organometallic fullerene-C60 derivatives  

NASA Astrophysics Data System (ADS)

We have studied the nonlinear refractive properties of the organometalic fullerene-C60 derivatives fac- and mer- [bis (1,2-diphenylphosphino) ethane] (tricarbonyl)(?2-fullerene-C60) chromium and molybdenum using the Z-scan method. These compounds change from being self-defocusing to self-focusing as the input light intensity increases. The experimental results have been interpreted using rate-equation theory. Critical conditions for the occurrence of this kind of transition have been elucidated for the steady-state situation.

Fang, Guangyu; Mo, Yulong; Song, Yinglin; Wang, Yuxiao; Li, Chunfei; Song, Licheng

2002-05-01

286

Graph-theoretic independence as a predictor of fullerene stability  

NASA Astrophysics Data System (ADS)

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

Fajtlowicz, S.; Larson, C. E.

2003-08-01

287

Putting atoms and molecules into chemically opened fullerenes.  

PubMed

We studied Ar, Kr, CO, and N(2) going into and out of a chemically opened fullerene, 1. We measured the equilibrium constant, K(eq), for the formation of X@1. K(eq) is particularly large for Ar, probably due to the large van der Waals attraction between the Ar atom and the fullerene cage. We measured rate constants and activation energies for the unimolecular reaction X@1-->X + 1 (X = Ar, CO, N(2)). The reactions show an unusually small pre-exponential factor, probably due to the loose binding of X inside the cage. PMID:19209931

Stanisky, Christopher M; Cross, R James; Saunders, Martin

2009-03-11

288

Fullerene isomers of C 60. Kekulé counts versus stability  

NASA Astrophysics Data System (ADS)

A count of Kekulé structures for all 1812 distinct fullerene isomers of C 60 shows that 20 isomers surpass the count of 12500 for icosahedral C 60, and demonstrates the lack of correlation between molecular-orbital indices of stability and raw Kekulé counts for fullerenes. Analysis of Kekulé structures in terms of benzenoid, cyclopentenoid and cyclopentadienoid rings reveals the source of the stability of icosahedral C 60 in a localised model to be the fact that uniquely amongst the 1812 structural isomers it has a Fries Kekulé structure where all hexagons contain three double bonds and all pentagons none.

Austin, S. J.; Fowler, P. W.; Hansen, P.; Monolopoulos, D. E.; Zheng, M.

1994-10-01

289

Penta(pyrenyl)[60]fullerenes: pyrene-pyrene and [60]fullerene-pyrene interactions in the crystal and in solution.  

PubMed

A new type of fullerene-pyrene hybrid molecule, C(60)Ar(5)R [Ar=1-pyrenyl, 4-(1-pyrenyl)C(6)H(4), 4-{(1-pyrenyl)CO(2)}C(6)H(4), and 4-{(1-pyrenyl)(CH(2))(3)CO(2)}C(6)H(4); R=H and Me] was synthesized by a regioselective penta-addition reaction using organocopper reagents. The compounds were investigated using electrochemical measurements, DFT calculations, single-crystal X-ray structural analysis, and spectroscopic and fluorescence measurements. Intramolecular and intermolecular fullerene-pyrene and pyrene-pyrene interactions were characterized in the crystals. Fluorescence measurements in dilute solutions suggested the presence of intramolecular fullerene-pyrene and pyrene-pyrene interactions. PMID:18637652

Matsuo, Yutaka; Morita, Kouhei; Nakamura, Eiichi

2008-09-01

290

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

291

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

292

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

293

Biochemical and hematologic effects of polyvinylpyrrolidone-wrapped fullerene C60 after oral administration.  

PubMed

The fullerene C60 is used in consumer products such as cosmetics owing to its antioxidative effects and is being developed for nanomedical applications. However, knowledge regarding the safety of fullerene C60, especially after oral administration, is sparse. Here, we examined the safety of fullerene C60 in mice after 7 d of exposure to orally administered polyvinylpyrrolidone (PVP)-wrapped fullerene C60 (PVP-fullerene C60). Mice treated with PVP-fullerene C60 showed few changes in the plasma levels of various markers of kidney and liver injury and experienced no significant hematologic effects. Furthermore, the histology of the colon of PVP-fullerene C60-treated mice was indistinguishable from that of control mice. These results suggest that PVP-fullerene C60 lacks toxicity after high-dose oral administration and indicate that PVP-fullerene C60 can be considered safe for oral medication. These data provide basic information that likely will facilitate the production of safe and effective forms of fullerene C60. PMID:23444781

Yamashita, K; Yoshioka, Y; Pan, H; Taira, M; Ogura, T; Nagano, T; Aoyama, M; Nagano, K; Abe, Y; Kamada, H; Tsunoda, S I; Aoshima, H; Nabeshi, H; Yoshikawa, T; Tsutsumi, Y

2013-01-01

294

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

295

Absolute Stereochemistry of Chiral C 60 Fullerene Bis-Adducts  

Microsoft Academic Search

To determine the absolute configuration of chiral fullerene bis-adducts, we have studied the double Bingel reaction of C 60 with chiral tether (2 S ,3 S )-( m )- 9 derived from ( R , R )-(+)-tartaric acid, and have succeeded in isolating two possible chiral bis-adducts 10a (5%) and 10b (2%) in addition to the C s -symmetrically added

Kazuhiro Yoshida; Shuichi Osawa; Kenji Monde; Masataka Watanabe; Nobuyuki Harada

2002-01-01

296

Energetics of fullerenes with four-membered rings  

Microsoft Academic Search

The energetic cost of introducing square faces to fullerenes with adjacent pentagons is investigated theoretically. Relative energies of all 1735 hypothetical Cââ cages that can be assembled from square, pentagonal, and hexagonal faces are calculated within two independent semiempirical models. All isomers are found to lie in local minima on the potential surface. The QCFF\\/PI (quantum consistent force field\\/Ï) and

P. W. Fowler; D. Mitchell; T. Heine; G. Seifert; R. Schmidt; D. E. Manolopoulos; G. Orlandi; F. Zerbetto

1996-01-01

297

Quantum transport through single and multilayer icosahedral fullerenes  

NASA Astrophysics Data System (ADS)

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

Lovey, Daniel A.; Romero, Rodolfo H.

2013-10-01

298

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); Kasashima, Eiji; Yashima, Eiji; Okamoto, Yoshio [Nagoya Univ. (Japan)

1997-02-05

299

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

300

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 ...

301

UV photostability of PMMA-C60 fullerene composition  

NASA Astrophysics Data System (ADS)

Thermal decomposition of pure poly(methyl methacrylate) (PMMA) and its composition with C60 fullerene before and after UV irradiation has been studied by thermodesorption mass spectrometry (TDMS). It is established that low-temperature depolymerization of UV-irradiated PMMA is suppressed in its composition with C60. Possible molecular stabilization mechanisms are discussed.

Pozdnyakov, O. F.; Popov, E. O.; Pozdnyakov, A. O.

2012-12-01

302

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  

NASA Astrophysics Data System (ADS)

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 the compressibility of fullerite calculated from these new expressions compare favourably with the experimental values and those obtained from the Girifalco potential. The interaction energy of Li@C{60} is also studied. De nouvelles formes analytiques pour les potentiels d'interaction atome-fullerène, fullerène-fullerène et fullerène-graphite sont obtenues à partir de distributions continues d'atomes de carbone et du potentiel interatomique de Buckingham. Celles-ci sont comparées aux potentiels C{60}-C{60} de Girifalco et C{60}-graphite de Ruoff et Hickmann résultant tous deux du potentiel de Lennard-Jones LJ(12,6). La chaleur latente de sublimation, la distance entre plus proche voisin et la compressibilité du C60 solide calculées à partir de ces nouvelles expressions sont en bon accord avec les valeurs expérimentales et avec celles obtenues à partir du potentiel de Girifalco. L'énergie d'interaction du système Li@C{60} est également étudiée.

Guérin, H.

1998-03-01

303

Surface Morphology of Diamond-Like Carbon Film and Si Wafer Milled with 30 keV Gallium Focused Ion Beam  

NASA Astrophysics Data System (ADS)

Focused ion beam (FIB) technology is becoming increasingly important for submicron device processing. However, the generation of ripples on the substrate surface bombarded with an FIB at off-normal ion incidences will become a problem in three-dimensional fabrication using an FIB. Therefore, we have examined the 30 keV Ga-FIB milling of a single-crystal Si wafer and a diamond-like carbon (DLC) film deposited on a Si wafer by FIB chemical vapor deposition (CVD). After FIB milling, samples inclined at 45° were observed by scanning ion microscopy (SIM) to determine the surface morphology. As a result, we confirmed the 30 keV Ga-FIB milling conditions resulting in the generation of ripples on a DLC film and a single-crystal Si wafer. Then, we obtained ripple-free milling conditions for these materials.

Takashi Kaito,; Masatoshi Yasutake,; Anto Yasaka,; Iwao Miyamoto,

2010-06-01

304

Contribution of backscattered electrons to the total electron yield produced in collisions of 8-28 keV electrons with tungsten  

NASA Astrophysics Data System (ADS)

It is shown experimentally that under energetic electron bombardment the backscattered electrons from solid targets contribute significantly (˜80%) to the observed total electron yield, even for targets of high backscattering coefficients. It is further found that for tungsten (Z=74) with a backscattering coefficient of about 0.50, about 20% of the total electron yield is contributed by the total secondary electrons for impact energies in the range of 8-28 keV. The yield of true backscattered electrons at normal incidence (? _0), total secondary electrons (?) and the total electron yield (?_{tot}) produced in collisions of 8-28 keV electrons with W have been measured and compared with predictions of available theories. The present results indicate that the constant-loss of primary electrons in the target plays a significant role in producing the secondary electrons and that it yields a better fit to the experiment compared to the power-law.

Yadav, R. K.; Shanker, R.

2007-03-01

305

Implantation of anatase thin film with 100 keV 56Fe ions: Damage formation and magnetic behaviour  

NASA Astrophysics Data System (ADS)

We have investigated the damage morphology and magnetic properties of titanium dioxide thin films following implantation with Fe ions. The titanium dioxide films, having a polycrystalline anatase structure, were implanted with 100 keV 56Fe+ ions to a total fluence of 1.3 × 1016 ions/cm2. The ion bombardment leads to an amorphized surface with no indication of the presence of secondary phases or Fe clusters. The ion-beam induced damage manifested itself by a marked change in surface morphology and film thickness. A room temperature ferromagnetic behaviour was observed by SQUID in the implanted sample. It is believed that the ion-beam induced damage and defects in the polycrystalline anatase film were partly responsible for the observed magnetic response.

Jensen, J.; Sanz, R.; Martin, D.; Surpi, A.; Kubart, T.; Vázquez, M.; Hernandez-Velez, M.

2009-08-01

306

Analysis of particle bombardment parameters to optimise DNA delivery into wheat tissues  

Microsoft Academic Search

The objective of this study was to identify the major parameters controlling DNA delivery by particle bombardment to wheat\\u000a (Triticum aestivum L.) scutellum and inflorescence tissue. The main factors studied were the DNA\\/gold precipitation process, bombardment parameters\\u000a and tissue culture variables. Efficiency of DNA (uidA gene) delivery was assessed by scoring transient GUS expression in bombarded tissues. Of the parameters

S. Rasco-Gaunt; A. Riley; P. Barcelo; P. A. Lazzeri

1999-01-01

307

Properties of ion-bombarded fused quartz for integrated optics.  

PubMed

Development of techniques for production of carefully controlled, low-loss optical waveguides in solid dielectric materials is essential to development of integrated optical circuits for signal processing in future optical communications systems. Ion implantation offers an attractive possibility because of the refractive index and film thickness control possible by this technique. To evaluate this possibility we have investigated some of the optical properties of ion-bombarded fused quartz. A variety of ions ranging from helium ions to bismuth ions has been used. We have concentrated on refractive index and optical loss variations (on those implants into which a beam could be launched) as effected by (1) ion species and dose, (2) surface preparation, (3) surface temperature during bombardment, and (4) postbombardment annealing. This paper does not attempt to give an inclusive account of all the results obtained but principally discusses the best results so far, which are those using lithium ions. For lithium ion bombardment we have observed approximately linear variation of refractive index at 6328 A with dose n = n(0) + 2.1 x 10(-21)C, where n(0) is the prebombardment value (= 1.458 for fused quartz), and C is the ion concentration in ions/cm(3) (C < 2.2 x 10(19)). The optical absorption decreases significantly with increase in substrate temperature during implantation, and losses less than 0.2 dB/cm have been achieved. The refractive index change appears to be primarily due to disorder produced by the incident particles rather than a chemical doping effect as evidenced by postbombardment annealing studies. PMID:20119140

Standley, R D; Gibson, W M; Rodgers, J W

1972-06-01

308

[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

309

Conductance enhancement of polymethylmethacrylate bombarded by low-energy ions  

SciTech Connect

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

Koval, Y.; Fistul, M.V.; Mueller, P. [Physikalisches Institut III der Universitaet Erlangen-Nuernberg, Erwin-Rommel Strasse 1, 91058 Erlangen (Germany)

2005-09-15

310

Electron bombarded CCD - First results with a prototype tube  

NASA Astrophysics Data System (ADS)

The aim of this paper is to show the relevance of the electron bombardment technique of photon counting for astronomical applications, using results obtained both in the laboratory and on the sky with a prototype tube. The potential astronomical applications discussed are in techniques requiring high time resolution, either in an analog or a photon counting mode (wavefront analysis, speckle interferometry, multitelescope interferometry, etc.) and observation of rapidly varying objects. Current prototypes will be used to achieve wavefront analysis in the near future. The first priority in further technical development must obviously be to develop a larger and faster CCD.

Cuby, J. G.; Richard, J. C.; Lemonier, M.

1990-07-01

311

Modifications of magnetic anisotropy and magnetization reversal in [Co0.4 nm/Pd0.7 nm]50 multilayers induced by 10 keV-He ion bombardment  

NASA Astrophysics Data System (ADS)

[Co0.4 nm/Pd0.7 nm]50 multilayers with Pd film thicknesses in the first ferromagnetic maximum of interlayer exchange coupling display almost purely perpendicular-to-plane anisotropy and labyrinth stripe domain patterns in remanence. Their magnetization reversal is characterized by domain nucleation starting at a defined field HN and domain wall movement in a defined magnetic field range. The modification of the magnetization reversal by 10 keV He ion bombardment due to the reduced magnetic anisotropy has been investigated by polar magneto-optical Kerr effect, by vibrating sample magnetometry, and by magnetic force microscopy at room temperature. It is shown that the ion bombardment creates and increases areas with ferromagnetic in-plane anisotropy and proportions of the sample showing superparamagnetism, the latter predominantly in the deeper layers.

Ehresmann, Arno; Hellwig, Olav; Buhl, Oliver; David Müglich, Nicolas; Weis, Tanja; Engel, Dieter

2012-09-01

312

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

2013-05-06

313

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

314

Effect of Boron doping on the electronic properties of the fullerenes of different sizes  

SciTech Connect

We report the results of the effect of Boron doping in C{sub n}; n = 28, 32, 36, 40, 44, 50 and 60 using the first principle calculation based on density functional theory. The HOMO-LUMO gap changes significantly with the decreasing fullerene size below C{sub 60}, with maximum gap observed for C{sub 32}. The HOMO-LUMO gap of Boron doped fullerenes varies significantly w.r.t. pure fullerenes. Also, the gap decreases for C{sub n-m}B{sub m}X, the boron doped fullerenes with exohedral alkali metals for n = 28, 32, 36, 40, 44, 50 and 60; m = 1 to 4; X = Li, Na and K. The Mulliken charge transfer from the exohedral alkali metals towards the various fullerene cages is altered marginally by the boron doping in fullerenes and follows the order K>Na>Li.

Agnihotri, Deepak [Department of Applied Sciences, Rayat and Bahra Institute of Engg. and Biotechnology, Sahauran, Mohali, Punjab 140104 (India); Sharma, Hitesh [Department of Physics, Punjab Technical University, Jalandhar, Punjab 144601 (India)

2011-12-12

315

Investigation of multilayer X-ray optics for the 6 keV to 20 keV energy range.  

PubMed

The X-ray optics group at the Swiss Light Source in co-operation with RIT (Rigaku Innovative Technologies) have investigated seven different multilayer samples. The goal was to find an ideal multilayer structure for the energy range between 6?keV and 20?keV in terms of energy resolution and reflectivity. Such multilayer structures deposited on substrates can be used as X-ray monochromators or reflecting synchrotron mirrors. The measured reflectivities agree with the simulated ones. They cover a reflectivity range from 45% to 80% for energies between 6?keV and 10?keV, and 80% to 90% for energies between 10?keV and 20?keV. The experimentally measured energy resolution of the samples lies between 0.3% and 3.5%. PMID:22898944

Oberta, P; Platonov, Y; Flechsig, U

2012-08-03

316

Effect of fullerene coating on silicon thin film anodes for lithium rechargeable batteries  

Microsoft Academic Search

To improve the electrochemical performances of Si thin film anodes for lithium rechargeable batteries, fullerene thin films\\u000a are prepared by plasma-assisted evaporation methods to be used as coating materials. Analyses via Raman and X-ray photoelectron\\u000a spectroscopy indicate that amorphous polymeric films originated from fullerene are formed on the surface of the silicon thin\\u000a film. The electrochemical performance of these fullerene-coated

Arenst Andreas Arie; Wonyoung Chang; Joong Kee Lee

2010-01-01

317

Inhalation Toxicity and Lung Toxicokinetics of C60 Fullerene Nanoparticles and Microparticles  

Microsoft Academic Search

While several recent reports have described the toxicity of water-soluble C60 fullerene nanoparticles, none have reported the toxicity resulting from the inhalation exposures to C60 fullerene nanoparticles or microparticles. To address this knowledge gap, we exposed male rats to C60 fullerene nanoparticles (2.22 mg\\/m 3 , 55 nm diameter) and microparticles (2.35 mg\\/m3, 0.93 mm diameter) for 3 h a

Gregory L. Baker; Amit Gupta; Mark L. Clark; Blandina R. Valenzuela; Lauren M. Staska; Sam J. Harbo; Judy T. Pierce; Jeffery A. Dill

2008-01-01

318

Materials for Flexible Organic Photovoltaic Cells: Conjugated Polymer MEH?PPV\\/Fullerene Composites  

Microsoft Academic Search

A series of azahomofullerenes and poly(amino)fullerenes were synthesized. Photoluminescence (PL) and photovoltaic (PV) measurements were performed on the composite films of conjugated polymer MEH?PPV with fullerene derivatives to investigate the influence of an electron acceptor on the charge?transfer process between components of PV system. We found that the PL of MEH?PPV is strongly quenched by the admixture of the fullerene

N. G. Spitsina; I. P. Romanova; A. A. Lobach; I. K. Yakuschenko; A. S. Lobach; M. G. Kaplunov; I. V. Tolstov; M. M. Triebel; E. L. Frankevich

2006-01-01

319

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

NASA Astrophysics Data System (ADS)

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

Konarev, Dmitry V.; Lyubovskaya, Rimma N.

2012-04-01

320

Effect of ambient gas and pressure on fullerene synthesis in induction thermal plasma  

Microsoft Academic Search

Fabrication of fullerenes (C60, C70, etc.) by direct evaporation of C–Si mixed powder using radio frequency inductively coupled thermal plasma were made to find a suitable gas kind and pressure for fullerene synthesis. The results showed that: (1) 150 Torr lower pressure and He\\/Ar mixed gas are more suitable for fullerene synthesis than higher pressure and pure Ar gas, and

C. Wang; A Inazaki; T Shirai; Y Tanaka; T Sakuta; H Takikawa; H Matsuo

2003-01-01

321

Open-cage Fullerene-like Graphitic Carbons as Catalysts for Oxidative Dehydrogenation of Isobutane  

Microsoft Academic Search

We report herein a facile synthesis of fullerene-like cages, which can be opened and closed through simple thermal treatments. A glassy carbon with enclosed fullerene-like cages of 2-3 nm was synthesized through a soft-template approach that created open mesopores of 7 nm. The open mesopores provided access to the fullerene-like cages, which were opened and closed through heat treatments in

Chengdu Liang; Hong Xie; Viviane Schwartz; Jane Y Howe; Sheng Dai; Steven H. Overbury

2009-01-01

322

Design, synthesis and testing of fullerene-functionalized devices and machines  

Microsoft Academic Search

Herein is described the design, synthesis and testing of molecules that contain fullerenes as essential parts. In chapter 1, a series of multiple fullerene terminated oligo(p-phenylene ethynylene) (OPE) hybrid compounds was synthesized through a newly developed in situ ethynylation method. Electronic and optical interactions between the fullerenes and the OPE backbones were investigated by UV\\/Vis spectroscopy, cyclic voltammetry (CV), and

Yasuhiro Shirai

2006-01-01

323

Concentration-dependent variations in the density of C60 fullerene solutions in aromatic solvents  

NASA Astrophysics Data System (ADS)

The densities of C60 fullerene solutions in benzene, toluene, and p-xylene have been determined by pyknometry and studied as a function of the fullerene concentration in solution. All dependences exhibit a non-monotonic character, whereby the density initially decreases, passes through a minimum, and then grows with increasing fullerene concentration. The position of the minimum shifts toward greater C60 concentrations on the passage from benzene to toluene and p-xylene.

Ginzburg, B. M.; Tuichiev, Sh.; Tabarov, S. Kh.

2007-08-01

324

A MD study of low energy boron bombardment on silicon  

NASA Astrophysics Data System (ADS)

Low energy boron bombardment of silicon has been simulated at room temperature by means of molecular dynamics (MD). Tersoff potential T3 was used in the simulation smoothly linked to the universal potential. The boron-silicon interaction was simulated following the ideas of Tersoff for the SiC potential but modified to take into account, in the B-Si interaction, whether or not the neighbours of either of both are entirely or partially boron or silicon atoms. (001) Si-C with (/2×1) reconstruction surface was bombarded with boron at energies of 200 and 500 eV, which were initially chosen as good representative values of the low energy range of interest. Reliable results require a reasonable good statistic so that 100 impact points were chosen which were uniformly distributed over a representative area of a (/2×1) surface. Special care was taken to determine the kind of damage produced in a Si crystal by the slowing down of boron. It is described in detail the way to determine vacancies and interstitials. The damage produced can be classified in regions were the accumulation of damage does not allow to identify properly the type of defects produced and regions in which defects are isolated and can be beautifully identified in terms of the potential energy variation and the displacements of their neighbours. Clusters of vacancies and interstitials are determined. Mean number of interstitials, vacancies, adatoms, sputtering, etc. are summarised in a table. Range distributions of boron are also determined.

Pérez-Martín, A. M. C.; Domínguez-Vázquez, J.; Jiménez-Rodríguez, J. J.

2000-04-01

325

Temperature aspects of pulsed ion bombardment in an austenitic alloy  

SciTech Connect

The influence of pulsed ion irradiation to a damage level of 10 dpa at temperatures from 843 to 1023/sup 0/K has been studied in a quaternary Fe-17Cr-17Ni-2.5Mo austenitic alloy. Pulsing periods of either 60 s on/60 s off or 1 s on/1 s off were used, together with continuous bombardment as a control. Helium (200 appM) was supplied either by simultaneous or room temperature preimplantation, or omitted. While most specimens experienced only 2 to 3/sup 0/K temperature fluctuations with the beam pulses, certain specimens were deliberately allowed to undergo 15 to 50/sup 0/K variations. Pulsed irradiation effects were found to range from little effect at 843/sup 0/K, through a notable modification in the relationship between helium and cavity parameters at 938/sup 0/K (near the peak swelling temperature), to a substantial reduction of swelling at 1023/sup 0/K. The influence of the simultaneous temperature excursions compared with constant-temperature pulsed ion bombardment (mostly compared at 843/sup 0/K) was small. These results are interpreted in terms of the effects of pulsing and helium on the stability of cavities at high temperatures through the critical size and number of gas atoms needed for a small cavity to begin bias-driven void growth.

Packan, N.H.

1983-01-01

326

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 × 1011 and 1 × 1016 protons/cm2 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 1014 protons/cm2.

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

2005-12-01

327

Formula for the total stopping power from 2 keV to 10 keV for a metal  

NASA Astrophysics Data System (ADS)

On the basis of the range-energy relationship, the relationships ( L 2-10) among the total stopping power from 2 keV to 10 keV for a metal ( S 2-10), the energy exponent ( n 2-10), the primary energy at the surface ( W p0), and the parameter ( A 2-10) were deduced. In addition, the relationships ( L 10-30) among the total stopping power from 10 keV to 30 keV for a metal ( S 10-30), the energy exponent ( n 10-30), W p0 and the parameter ( A 10-30) were obtained. According to some relationships between the parameters of the secondary electron yield from 2 keV to 10 keV for a metal ( ? 2-10), the composition of the secondary electron yield from 10 keV to 30 keV for a metal ( ? 10-30), L 2-10, and L 10-30, the universal formula for expressing S 2-10 as a function of S 10-30, ? 2-10, ? 10-30, the backscattered coefficient ( ?) from 2 keV to 10 keV, ? from 10 keV to 30 keV and W p0 was deduced. The S 2-10 calculated from this universal formula and the S 2-10 measured experimentally were compared, and we conclude that the formula presented in this paper is universal for S 2-10.

Xie, Ai-Gen; Lai, Min; Zhang, Chen-Yi

2013-01-01

328

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

329

On a model of fullerene formation from polymers under MeV ion impact  

NASA Astrophysics Data System (ADS)

Fullerenes - large even-numbered carbon clusters with a closed three-dimensional structure - can be formed in the gas phase by different methods, including laser ablation of graphite and other carbon containing materials. A method for production of macroscopic amounts of predominantly C60 by electric arc graphite vaporization in He atmosphere has lead to an explosive growth in fullerene research. Recently it has been demonstrated that fullerenes are also formed in the electronic sputtering of a specific polymer - poly(vinylidenedifluoride), PVDF - by swift MeV atomic ions. In a model for formation of fullerenes in MeV ion impact on polymer surfaces we assume that fullerenes result from carbon atom condensation in the dense axially expanding plasma in the MeV ion infratrack. Gas-flow concepts are employed to explain the ejection of the fullerenes. The temporal and radial dependence of the temperature in the track region is described on the basis of the linear thermoconductivity theory for thermal sources with cylindrical symmetry. The dependence of the fullerene yield on the MeV ion stopping power and on the number of atoms in the cluster is calculated by taking into account a requirement of minimal plasma temperature for fullerene formation. Calculations for the average cluster velocity are also performed and compared to experimental data. Finally we argue that both the model and the experimental findings bear implications for the mechanism of fullerene formation in general, providing estimates of the required time frame and spatial domain.

Bitensky, I. S.; Demirev, P.; Sundqvist, B. U. R.

1993-07-01

330

Studies of C60, C70 and Other Fullerenes: Synthesis, Derivatization, Electrochemistry, Lubricant Properties and New Composite Materials.  

National Technical Information Service (NTIS)

New designs for fullerene generators have been developed, including systems for producing endohedral species with metals inside the C60 or C70 cages. Also, focussed solar energy has been utilized for fullerene production. Electrochemical studies have led ...

R. E. Smalley J. L. Margrave R. H. Hauge L. J. Wilson W. E. Billups

1995-01-01

331

Ion-bombardment-enhanced grain growth in germanium, silicon, and gold thin films  

Microsoft Academic Search

Grain growth has been studied in polycrystalline thin films of Ge, Si, and Au during ion bombardment. The phenomenon has been characterized by varying the ion dose, ion energy, ion flux, ion species, substrate temperature, and thin-film deposition conditions. Films bombarded with Si+, Ar+, Ge+, Kr+, and Xe+ exhibited enhanced grain growth which was weakly temperature dependent and proportional to

Harry A. Atwater; Carl V. Thompson; Henry I. Smith

1988-01-01

332

Ion bombardment induced formation of micro-craters in plant cell envelopes  

Microsoft Academic Search

Ion beam bombardment of biological material has been recently applied for gene transfer in both plant and bacterial cells. A consistent physical mechanism for this significant result has not yet been developed. A fundamental question about the mechanism is the possible formation of pathways due to ion bombardment that are responsible for the gene transfer. We have carried out investigations

S. Sangyuenyongpipat; L. D. Yu; T. Vilaithong; I. G. Brown

2006-01-01

333

Stable Genetic Transformation of Intact Nicotiana Cells by the Particle Bombardment Process  

Microsoft Academic Search

We show that the genetic transformation of Nicotiana tabacum can be achieved by bombarding intact cells and tissues with DNA-coated particles. Leaves or suspension culture cells were treated with tungsten microprojectiles carrying plasmid DNA containing a neomycin phosphotransferase gene. Callus harboring the foreign gene was recovered from the bombarded tissue by selection on medium containing kanamycin. Kanamycin-resistant plants have subsequently

Theodore M. Klein; Elisabeth C. Harper; Zora Svab; John C. Sanford; Michael E. Fromm; Pal Maliga

1988-01-01

334

Transgenic perennial ryegrass ( Lolium perenne) plants from microprojectile bombardment of embryogenic suspension cells  

Microsoft Academic Search

Transgenic forage-type perennial ryegrass (Lolium perenne L.) plants have been obtained by microprojectile bombardment of embryogenic suspension cells using a chimeric hygromycin phosphotransferase (hph) gene construct driven by rice Actl 5? regulatory sequences. Parameters for the bombardment of embryogenic suspension cultures with the particle inflow gun were partially optimized using transient expression assays of a chimeric ?-glucuronidase (gusA) gene driven

Germán Spangenberg; Zeng-yu Wang; Xinli Wu; Jutta Nagel; Ingo Potrykus

1995-01-01

335

In vivo and in vitro Gene Transfer to Mammalian Somatic Cells by Particle Bombardment  

Microsoft Academic Search

Chimeric chloramphenicol acetyltransferase and beta-galactosidase marker genes were coated onto fine gold particles and used to bombard a variety of mammalian tissues and cells. Transient expression of the genes was obtained in liver, skin, and muscle tissues of rat and mouse bombarded in vivo. Similar results were obtained with freshly isolated ductal segments of rat and human mammary glands and

Ning-Sun Yang; Joe Burkholder; Beth Roberts; Brian Martinell; Dennis McCabe

1990-01-01

336

Hyperfine coupling of endohedral fullerene Sc@C82  

NASA Astrophysics Data System (ADS)

The hyperfine coupling of the endohedral metallofullerene, Sc@C82, which is a candidate qubit for quantum computing, has been investigated theoretically and experimentally. Using density functional theory (DFT), we have systematically studied the molecular structures and energetics of nine isomers of C82 and Sc@C82 fullerenes. DFT predicts that the most stable isomer has C2v symmetry with the Sc atom lying off-centre along the C2 symmetry axis and forming partially covalent bonds with a carbon hexagonal ring of the fullerene cage. The hyperfine couplings between the unpaired electron spin and the Sc and C atoms have been calculated and compared to the electron spin resonance (ESR) spectra. The experimental isotropic hyperfine coupling constants confirm the C2v symmetry predicted for the ground state isomer. Furthermore, the calculated anisotropy of the hyperfine coupling tensor is in good agreement with low temperature experimental measurements. www.nanotech.org

Lee, Seung Mi; Herbert, B. J.; Nguyen-Manh, D.; Ardavan, A.; van Tol, J.; Horsfield, A. P.; Morley, G. W.

2005-03-01

337

Resonance energies of fullerenes with 4-membered rings  

SciTech Connect

We report the resonance energies (RES) of several fullerenes with 4-membered rings and their isomers with only 5- and 6-membered rings computed using the conjugated-circuit model [RE(CC)] and the topological resonance energy (TRE) model. Both aromaticity indices were normalized by dividing by the size of the considered fullerene [RE(CC)/e and TRE/e]. The results parallel the predictions by Gao and Herndon using the much more advanced SCF-UHF {pi}-electron approach. A good linear correlation is found between the topologically defined indices [RE(CC)/e and TRE/d] and normalized SCF-UHF {pi}-electron energy. 26 refs., 2 figs., 3 tabs.

Babic, D.; Trinajstic, N. [Rugjer Boskovic Institute, Zagreb (Croatia)

1995-08-15

338

Improved bulk heterojunction organic solar cells employing C70 fullerenes  

NASA Astrophysics Data System (ADS)

We show that the fullerene C70 is suitable to replace fullerene C60, which is commonly used as electron transporter and acceptor in small-molecule organic solar cells. It is shown that the higher absorption of C70 leads to high external quantum efficiencies of over 50% in the spectral range of 500-700 nm. By optimizing the energy level alignment to hole transport layers, the absorption, and the ratio of C70:zinc phthalocyanine (ZnPc) in a bulk heterojunction solar cell, an efficiency of ?=2.87% is achieved. This is a substantial improvement over an identical solar cell employing C60 having ?=2.27%. The efficiency increase is due to a higher photocurrent, while fill factor and open-circuit voltage for C70 and C60-containing organic solar cells remain comparable.

Pfuetzner, Steffen; Meiss, Jan; Petrich, Annette; Riede, Moritz; Leo, Karl

2009-06-01

339

Study of fullerene epoxide electroreduction and electropolymerization processes  

SciTech Connect

The electrochemical behavior of C{sub 60}O at a gold electrode in o-dichlorobenzene, dichloromethane, and a mixture of toluene and acetonitrile was studied in the potential range from 0.4 to -1.5 V. Three one-electron transfer steps were observed for C{sub 60}O within this potential window. The first and the third electron transfers are attributed to the reduction of the fullerene cage. The product of the first electron transfer is found to undergo a solvent- and rate-dependent decomposition to C{sub 60}. The irreversible transfer of the second electron, attributed to the presence of the epoxide oxygen, leads to a substantial change in fullerene structure and initiates polymer formation for which the kinetics of growth are found to be strongly solvent dependent. 21 refs., 9 figs.

Winkler, K.; Costa, D.A.; Balch, A.L.; Fawcett, W.R. [Univ. of California, Davis, CA (United States)

1995-11-30

340

Strong Correlation Effects in Fullerene Molecules and Solids  

NASA Astrophysics Data System (ADS)

Fullerenes (C20, C36, C60) are a family of Carbon cage molecules that have exactly twelve pentagons. The most famous Fullerene is C60 (``bucky ball''), which when being doped with three electrons per molecule will exhibit superconductivity. Here we describe electronic structures of these molecules with a tight-binding Hubbard model and solve the model with quantum Monte Carlo simulations and exact diagonalization method. We will show how the electronic correlation gets stronger as the molecule becomes more curved, how the strong electronic correlations change the Huckel molecular energy levels, and how we compare the single-particle excitation spectrum for the C60 molecular solid to the photoemission experiments.

Lin, Fei

2011-10-01

341

Solar energy: application to the production of fullerenes  

NASA Astrophysics Data System (ADS)

We have shown previously that the high intensity of solar radiation obtained with the Odeillo (France) solar furnace facilities, can be used to vaporize graphite in an inert-gas atmosphere and to produce fullerenes. After a short survey of the vaporization - condensation method used here, we discuss some of the growth mechanisms of these molecules and possible ways to increase the yield, which can reach 20% in the best cases. These experiments point out the principal factors controlling the fullerene yield, such as temperature, pressure and the gas flow rate of the inert gas or the density of carbon atoms in the vaporization zone. Using these observations, the next developments of the method are currently in preparation using a 1 MW solar furnace.

Laplaze, D.; Bernier, P.; Flamant, G.; Lebrun, M.; Brunelle, A.; Della-Negra, S.

1996-11-01

342

Plasma Polymerization for Protein Patterning: Reversible Formation with Fullerene Modification  

NASA Astrophysics Data System (ADS)

Partial plasma polymerization for coexistence of hydrophobic/hydrophilic area in several ten micrometer size is the typical technique for protein patterning. A hydrophobic hexamethyldisiloxane plasma-polymerized film (HMDS PPF) was deposited on a glass substrate and this surface was partially modified by subsequent nitrogen plasma treatment (hydrophilic surface, HMDS-N PPF) with a patterned shadow mask. An antibody protein (F(ab')2 fragment of anti-human immunoglobulin G) was selectively adsorbed onto the HMDS-N area and was not adsorbed onto the HMDS area. Distinct 80× 80µm2 square spots surrounded by a non-protein adsorbed 80µm-wide grid were observed. Then, when the protein modified by fullerene was used, the reversible patterning was obtained. This indicated that the modification by fullerene changed the hydrophilic nature of F(ab')2 protein to hydrophobic one, as a result, the modified protein was selectively adsorbed onto hydrophobic area.

Takahashi, Hayato; Murata, Naoya; Muguruma, Hitoshi

343

Photoinduced charge transfer from polymers to fullerene molecules revisited.  

NASA Astrophysics Data System (ADS)

We study the process of photoinduced charge transfer (PCT) between conjugated polymers and fullerene molecules as electron acceptors, using the technique of picosecond transient, and steady state photomodulation at various modulation frequencies and temperatures. The polymers studied were MEH-PPV and regio-regular P3HT [RR-P3HT], which are some of the common polymers that are used in organic photovoltaic, as well as polyfluorene [PFO] with optical gap in the blue spectral range; whereas the fullerene molecules where C60, C70 and their PCBM variations. In all cases we found PCT as evident by the formation of strong photoinduced absorption (PA) polaron bands in the mid ir spectral range. Surprisingly we also found PCT with photon energy below the polymer optical gap. This below-gap PCT process will be discussed and compared with the more usual PCT process with above gap excitation.

Drori, Tomer; Sheng, Chuanxiang; Ndobe, Alex; Yang, Cungeng; Tong, Minghong; Vardeny, Valy

2007-03-01

344

Ultrafast dynamics in blends of ?-conjugated polymers/fullerenes  

NASA Astrophysics Data System (ADS)

We have studied the ultrafast dynamics of photogenerated charges and excitons in a variety of ?-conjugated polymer/fullerene blends using the transient pump-probe photomodulation (PM) spectroscopy with ˜ 100 fs resolution. These composites serve as active layers in organic photovoltaic devices with high power conversion quantum yield, due to the existence of a photoinduced charge transfer (PCT) reaction between the polymer and the fullerene molecules. Our transient PM spectrum spans a broad energy range from 0.1-2.4 eV, and this allows us to monitor the transient behavior of the various photoinduced absorption (PA) bands of polarons and excitons in the PM spectrum; as well as the transient exciton stimulated emission, and photobleaching (PB) of the ground state. The PB dynamics reflect the ground state recovery; hence, it can be used to determine the long-lived polaron photogeneration quantum efficiency in these systems.

Singh, Sanjeev; Tong, Minghong; Sheng, Chuanxiang; Vardeny, Zeev

2008-03-01

345

Rare Earth Oxide-Treated Fullerene and Titania Composites with Enhanced Photocatalytic Activity for the Degradation of Methylene Blue  

Microsoft Academic Search

Rare earth oxide-treated fullerene and titania composites (Y-fullerene\\/TiO2) were prepared by the sol-gel method. The products had interesting surface compositions. X-ray diffraction patterns of the composites showed that the Y-fullerene\\/TiO2 composites contained a single and clear anatase phase. The surface properties were observed by scanning electron microscopy, which gave a characterization of the texture on the Y-fullerene\\/TiO2 composites and showed

Zada MENG; Lei ZHU; Jong-geun CHOI; Chong-yeon PARK; Won-chun OH

2011-01-01

346

Growth of fullerene fragments using the Diels-Alder cycloaddition reaction: first step towards a C60 synthesis by dimerization.  

PubMed

Density Functional Theory has been used to model the Diels-Alder reactions of the fullerene fragments triindenetriphenilene and pentacyclopentacorannulene with ethylene and 1,3-butadiene. The purpose is to prove the feasibility of using Diels-Alder cycloaddition reactions to grow fullerene fragments step by step, and to dimerize fullerene fragments, as a way to obtain C??. The dienophile character of the fullerene fragments is dominant, and the reaction of butadiene with pentacyclopentacorannulene is favored. PMID:23434874

Mojica, Martha; Méndez, Francisco; Alonso, Julio A

2013-02-13

347

Effect of ion bombardment during the low-mobility growth of metallic superlattices  

NASA Astrophysics Data System (ADS)

The effect of ion bombardment on the structure of sputtered Mo/Fe superlattices (with periodicities 9 to 30 A) grown at a substrate temperature of 300 K and either with or without low-energy ion bambardment was investigated using XRD. All samples displayed growth of the amorphous phase below 17-A periodicity, at which point the crystalline phase first appeared; above 23-A periodicity, only the crystalline phase occurred. Limited ion bombardment was found to reduce the coherency in the crystalline phase, while heavy bombardment, sufficient to promote some mixing, resulted in improved coherency, although not to the level observed in films with no bombardment. Low energy ions and bombardment of mainly the iron layer of the Mo/Fe superlattices was found to produce little mixing and to increase the overall planarity of the interfaces which resulted in improved X-ray reflectivity. This could be important in the manufacture of improved VUV and X-ray multilayer optical components.

Window, B.; Sharples, F.

1988-10-01

348

Local magnetism in rare-earth metals encapsulated in fullerenes  

Microsoft Academic Search

Local magnetic properties of rare-earth (RE) atoms encapsulated in fullerenes have been characterized using x-ray magnetic circular dichroism and x-ray absorption spectroscopy (XAS). The orbital and spin contributions of the magnetic moment have been determined through sum rules and theoretical model calculations, and have been found to be highly reduced compared to those of the corresponding free RE3+ ions. Crystal-field

C. de Nadaï; A. Mirone; S. S. Dhesi; P. Bencok; N. B. Brookes; I. Marenne; P. Rudolf; N. Tagmatarchis; H. Shinohara; T. J. S. Dennis

2004-01-01

349

Preparation, Characterization, Functionalization and Application of Dimeric Fullerene Oxides  

Microsoft Academic Search

The synthesis, isolation, characterization, functionalization and application of furan?like bridged dimeric fullerene oxides are reported. A synthesis of C130O in yields of 20% is presented. A preparation of highly pure, soluble mono?, bis? and tris?adducts of a diazoalkane addition reaction and a Bingel cyclopropanation reaction on C120O in preparative amounts using conventional laboratory methods is reported. A synthesis of regio?controlled

Lars Weber; Steffi Sensfuss; Uwe Ritter; Peter Scharff

2009-01-01

350

Core photoionization satellites in fullerene and related model systems  

Microsoft Academic Search

The so-called shake-up satellites accompanying C{sub 1s} photoionization in Cââ have been studied theoretically by means of INDO\\/CI. It is found that the lowest shake-up satellites in Cââ correspond to global charge-transfer excitations that move charge from the opposite side of the fullerene cage to the core-hole region, whereas higher-energy satellites tend to move charge from regions nearer to the

Sten Lunell; Christer Enkvist; Martin Agback; Svante Svensson

1994-01-01

351

Novel gas separation membranes containing covalently bonded fullerenes  

Microsoft Academic Search

In this work, we report superior mass transport properties of polymers prepared by the covalent coupling of supermolecular carbon cages (e.g., fullerenes, bucky balls) to a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) polymer. Dispersing the bucky balls into the polymer reduces gas permeability, whereas covalent bonding enhances permeability up to 80% in comparison to the pure PPO. Gas pair selectivity, however, is not

Dana M. Sterescu; Lydia Bolhuis-Versteeg; Vegt van der Nico F. A; Dimitrios F. Stamatialis; Matthias Wessling

2004-01-01

352

Twenty Years of Promises: Fullerene in Medicinal Chemistry  

Microsoft Academic Search

\\u000a Many biological activities have been envisioned for fullerenes and some of them seem to be very promising. The lack of solubility\\u000a in biologically friendly environments is the major obstacle in the development of this field. The possibility of multiple\\u000a fuctionalization can be exploited to get more soluble compounds but, up to now, only a few polyadducts, presenting perfectly\\u000a defined geometry,

Tatiana Da Ros

353

Sub-Kelvin transport spectroscopy of fullerene peapod quantum dots  

NASA Astrophysics Data System (ADS)

The authors have studied electrical transport properties of individual C60 fullerene peapods, i.e., single-wall carbon nanotubes encapsulating C60 molecules. Their measurements indicated power lawlike temperature dependencies of linear conductance similar to those for empty nanotubes. At temperatures below 30 K, peapod devices behaved as highly regular individual quantum dots showing regular Coulomb blockade oscillations. Signatures of Kondo physics appeared at the lowest measurement temperature of 315 mK.

Utko, Pawel; Nyga?Rd, Jesper; Monthioux, Marc; Noé, Laure

2006-12-01

354

Design, synthesis and testing of fullerene-functionalized devices and machines  

NASA Astrophysics Data System (ADS)

Herein is described the design, synthesis and testing of molecules that contain fullerenes as essential parts. In chapter 1, a series of multiple fullerene terminated oligo(p-phenylene ethynylene) (OPE) hybrid compounds was synthesized through a newly developed in situ ethynylation method. Electronic and optical interactions between the fullerenes and the OPE backbones were investigated by UV/Vis spectroscopy, cyclic voltammetry (CV), and differential optical Kerr effect (DOKE) experiment. Enhanced nonlinear optical (NLO) performance of some of the fullerene-OPE hybrids is presumably due to the occurrence of periconjugation and/or charge transfer effects between the fullerene and OPE moieties in the excited state. This result indicates that the use of such fullerene-derivatized conjugated oligomers aids the quest for NLO devices. In chapter 2, fullerene-wheeled single molecular nanomachines, namely nanocars and nanotrucks, are presented. These nanovehicles are composed of spherical fullerene wheels, freely rotating alkynyl axles, and a molecular chassis. The use of spherical wheels based on C60 and freely rotating axles based on alkynes permits directed nanoscale rolling of the molecular structure on gold surfaces. The rolling motion observed by scanning tunneling microscope (STM) resembles the same motion performed by macroscopic entities in which rolling occurs perpendicular to the axles. This study underscores the ability to control directionality of motion in molecular-sized nanostructures through precise molecular design and synthesis. Chapter 3 describes that the seemingly simple and widely employed approach to self-assembly of fullerene-derivatives on gold surfaces can be complicated due to multilayer formation and head-to-tail assemblies resulting from the strong fullerene-fullerene and fullerene-gold interactions. These anomalies were not examined in detail in previous studies on fullerene self-assembled monolayers (SAMs) but were clearly detected in the present work using surface characterization techniques including ellipsometry, CV, and X-ray photoelectron spectroscopy (XPS). This study specifically addresses the need to properly characterize and control fullerene-thiol assemblies on gold before evaluating subsequent device performances. Finally, chapter 4 describes the synthesis and testing of a motorized nanocar. Kinetics studies in solution show that the motor indeed rotates upon irradiation with 365 nm light, and the fullerene-free carborane wheel system is an essential design feature for motor operation.

Shirai, Yasuhiro

355

Charge transfer excitations in cofacial fullerene-porphyrin complexes  

NASA Astrophysics Data System (ADS)

Porphyrin and fullerene donor-acceptor complexes have been extensively studied for their photo-induced charge transfer characteristics. We present the electronic structure of ground states and a few charge transfer excited states of four cofacial porphyrin-fullerene molecular constructs studied using density functional theory at the all-electron level using large polarized basis sets. The donors are base and Zn-tetraphenyl porphyrins and the acceptor molecules are C60 and C70. The complexes reported here are non-bonded with a face-to-face distance between the porphyrin and the fullerene of 2.7 to 3.0 A?. The energies of the low lying excited states including charge transfer states calculated using our recent excited state method are in good agreement with available experimental values. We find that replacing C60 by C70 in a given dyad may increase the lowest charge transfer excitation energy by about 0.27 eV. Variation of donor in these complexes has marginal effect on the lowest charge transfer excitation energy. The interfacial dipole moments and lowest charge transfer states are studied as a function of face-to-face distance.

Zope, Rajendra R.; Olguin, Marco; Baruah, Tunna

2012-08-01

356

Hybrid photoactive fullerene derivative-ruboxyl nanostructures for photodynamic therapy.  

PubMed

Here we report the investigation of photophysical properties and photodynamic action of two novel water soluble hybrid molecular structures based on [60]fullerene dyads bearing covalently attached residues of anthracycline antibiotic "ruboxyl". Molecular structures of the designed compounds were confirmed by IR and UV-VIS absorption spectroscopy, electrospray mass spectrometry (compound 5), and (1)H and (13)C NMR spectroscopy. Dynamic light scattering, steady-state and kinetic fluorimetry and UV-VIS absorption spectroscopy techniques were used to study the behavior of the synthesized hybrid molecular structures in aqueous solutions. Photodynamic activity of the compounds was evaluated by monitoring the O2(-) generation under visible light irradiation using the NBT test. It has been shown that the anthracycline chromophore (ruboxyl moiety possesses no photodynamic activity) behaves as an efficient photosensitizer for the fullerene core operating via the energy and/or the electron transfer pathways. The presented approach opens up wide opportunities for the design of various fullerene-based donor-acceptor systems with enhanced photodynamic properties potentially suitable for biomedicinal applications. PMID:23712714

Kotelnikov, Alexander I; Rybkin, Alexander Yu; Khakina, Ekaterina A; Kornev, Alexey B; Barinov, Alexander V; Goryachev, Nikolay S; Ivanchikhina, Anastasiya V; Peregudov, Alexander S; Martynenko, Vyacheslav M; Troshin, Pavel A

2013-05-28

357

In vivo gene delivery by cationic tetraamino fullerene.  

PubMed

Application of nanotechnology to medical biology has brought remarkable success. Water-soluble fullerenes are molecules with great potential for biological use because they can endow unique characteristics of amphipathic property and form a self-assembled structure by chemical modification. Effective gene delivery in vitro with tetra(piperazino)fullerene epoxide (TPFE) and its superiority to Lipofectin have been described in a previous report. For this study, we evaluated the efficacy of in vivo gene delivery by TPFE. Delivery of enhanced green fluorescent protein gene (EGFP) by TPFE on pregnant female ICR mice showed distinct organ selectivity compared with Lipofectin; moreover, higher gene expression by TPFE was found in liver and spleen, but not in the lung. No acute toxicity of TPFE was found for the liver and kidney, although Lipofectin significantly increased liver enzymes and blood urea nitrogen. In fetal tissues, neither TPFE nor Lipofectin induced EGFP gene expression. Delivery of insulin 2 gene to female C57/BL6 mice increased plasma insulin levels and reduced blood glucose concentrations, indicating the potential of TPFE-based gene delivery for clinical application. In conclusion, this study demonstrated effective gene delivery in vivo for the first time using a water-soluble fullerene. PMID:20194788

Maeda-Mamiya, Rui; Noiri, Eisei; Isobe, Hiroyuki; Nakanishi, Waka; Okamoto, Koji; Doi, Kent; Sugaya, Takeshi; Izumi, Tetsuro; Homma, Tatsuya; Nakamura, Eiichi

2010-03-01

358

Study of urological devices coated with fullerene-like nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

359

Fullerene-bisadduct acceptors for polymer solar cells.  

PubMed

Polymer solar cells (PSCs) have drawn great attention in recent years for their simple device structure, light weight, and low-cost fabrication in comparison with inorganic semiconductor solar cells. However, the power-conversion efficiency (PCE) of PSCs needs to be increased for their future application. The key issue for improving the PCE of PSCs is the design and synthesis of high-efficiency conjugated polymer donors and fullerene acceptors for the photovoltaic materials. For the acceptor materials, several fullerene-bisadduct acceptors with high LUMO energy levels have demonstrated excellent photovoltaic performance in PSCs with P3HT as a donor. In this Focus Review, recent progress in high-efficiency fullerene-bisadduct acceptors is discussed, including the bisadduct of PCBM, indene-C60 bisadduct (ICBA), indene-C70 bisadduct (IC70 BA), DMPCBA, NCBA, and bisTOQC. The LUMO levels and photovoltaic performance of these bisadduct acceptors with P3HT as a donor are summarized and compared. In addition, the applications of an ICBA acceptor in new device structures and with other conjugated polymer donors than P3HT are also introduced and discussed. PMID:23853151

Li, Yongfang

2013-07-12

360

New fullerene-based mixed materials: Synthesis and characterization  

SciTech Connect

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors present results of broadband femtosecond transient absorption and broadband nanosecond optical limiting studies of C{sub 60} and derivatized C{sub 60}. They have investigated both solutions and solid-state mixed materials (sol-gel glass hosts doped with fullerene guests). They show that derivatized fullerenes provide enhanced solubility and processability, with a ground-state absorption extended into the infrared compared with C{sub 60}. They have extensively studied both the dynamic optical response and the excited-state absorption cross sections of solutions and solids for multiple wavelengths in the visible to near infrared. Wavelength-dependent studies show that the optical limiting response improves monotonically at longer wavelengths, demonstrating broadband limiting in all 6,6 mono-adducts and neat C{sub 60}. The authors report new approaches to processing sol-gel glass/fullerene composites to improve the optical limiting performance of solid-state materials to approach the response of solution limiters.

McBranch, D.; Kohlman, R.; Klimov, V.; Grigorova, M.; Shi, X.; Smilowitz, L.; Mattes, B.R. [Los Alamos National Lab., NM (US); Wang, H.; Wudl, F. [Univ. of California, Santa Barbara, CA (US)

1998-11-01

361

In vivo gene delivery by cationic tetraamino fullerene  

PubMed Central

Application of nanotechnology to medical biology has brought remarkable success. Water-soluble fullerenes are molecules with great potential for biological use because they can endow unique characteristics of amphipathic property and form a self-assembled structure by chemical modification. Effective gene delivery in vitro with tetra(piperazino)fullerene epoxide (TPFE) and its superiority to Lipofectin have been described in a previous report. For this study, we evaluated the efficacy of in vivo gene delivery by TPFE. Delivery of enhanced green fluorescent protein gene (EGFP) by TPFE on pregnant female ICR mice showed distinct organ selectivity compared with Lipofectin; moreover, higher gene expression by TPFE was found in liver and spleen, but not in the lung. No acute toxicity of TPFE was found for the liver and kidney, although Lipofectin significantly increased liver enzymes and blood urea nitrogen. In fetal tissues, neither TPFE nor Lipofectin induced EGFP gene expression. Delivery of insulin 2 gene to female C57/BL6 mice increased plasma insulin levels and reduced blood glucose concentrations, indicating the potential of TPFE-based gene delivery for clinical application. In conclusion, this study demonstrated effective gene delivery in vivo for the first time using a water-soluble fullerene.

Maeda-Mamiya, Rui; Noiri, Eisei; Isobe, Hiroyuki; Nakanishi, Waka; Okamoto, Koji; Doi, Kent; Sugaya, Takeshi; Izumi, Tetsuro; Homma, Tatsuya; Nakamura, Eiichi

2010-01-01

362

The Environmental Fate of C60 Fullerenes: A Holistic Approach  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

363

Study of urological devices coated with fullerene-like nanoparticles.  

PubMed

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

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

2013-09-21

364

Fluorescence quenching of fulvic acids by fullerene in water.  

PubMed

Fullerene can be suspended in water as nanoscaled-fullerene-aggregates (nC(60)). However, little is known about its biogeochemical cycling in natural waters. In this paper, the interactions between nC(60) and fulvic acids were investigated using fluorescence spectroscopy and fluorescence quenching titration. The results show that the intrinsic fluorescence of fulvic acids was static quenched by adding nC(60). The association constants (log K) of fulvic acids and nC(60) were estimated using a modified Ryan-Weber nonlinear model, and ranged from 6.76 to 7.41 l/mol. The log K was not significantly affected by the concentration levels of fulvic acids from 5.0 to 20.0 mg/l. The log K increased at low pH 3-5, but remained constant at high pH ranging from 5 to 11. The hydrophobic and ?-? interactions were the likely primary mechanisms. The present observation will be helpful in understanding the environmental behavior of fullerene in natural aquatic ecosystems. PMID:23022947

Wu, Fengchang; Bai, Yingchen; Mu, Yunsong; Pan, Bo; Xing, Baoshan; Lin, Ying

2012-09-25

365

Controlling Active Layer Morphology in Polymer/Fullerene Solar Cells  

NASA Astrophysics Data System (ADS)

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

Moungthai, Suchanun; Mahadevapuram, Nikhila; Stein, Gila

2012-02-01

366

Entanglement in Fullerene End-Capped Linear Polymers  

NASA Astrophysics Data System (ADS)

We studied the viscoelastic behavior of fullerene (C60) end- caped linear polymers, such as the C60-polybutadiene and C60-poly (butadiene-co-styrene). Those polymers were synthesized through anionic polymerization of butadiene and styrene in hexane, where the living ends were capped with the C60 via an epoxybutane bridging. Rheological measurements showed that for polymer chains of one end attached with C60, the polymer dynamics in the terminal zone were profoundly affected by the presence of fullerene, while the dynamics in the entanglement plateau were nearly unaffected; whereas for polymer chains of two ends attached with two C60, the polymer dynamics in the entanglement plateau were profoundly affected by the presence of fullerene, while the dynamics in the terminal zone were less affected. Given that the diameter for a ``reptation-tube'' is about 5nm, but the diameter for a C60 buckball is only about 0.7 nm, can this phenomenon be explained by the existing reptation models?

Wang, Xiaorong; Yan, Yuan-Yong

2007-03-01

367

Measurements of Neutron Capture Cross Sections for DY Isotopes in the Energy Region from 10 TO 90 KEV  

NASA Astrophysics Data System (ADS)

The neutron capture cross sections of Dy isotopes (161Dy, 162Dy, 163Dy, and 164Dy) 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.; Min, Y. G.; Ro, T. I.; Kim, H. D.; Ahn, J. K.; Mizuno, S.; Ohsaki, T.; Igashira, M.

2003-06-01

368

Recent developments of the electron-bombarded CCD image tubes  

NASA Astrophysics Data System (ADS)

The results of more than 10 years experience in design and manufacturing of thinned back-side illuminated CCDs of different types are summed up. Based upon the EB CCDs created, the family of intensified electron-bombarded CCD image tubes has been designed, fabricated and tested. This family includes: the single-stage Gen I type EB CCD devices with the 532*580 and 780*580 pixels CCDs; the `hybrid' (the EB CCD tube plus GenyI image intensifier) devices; and the EB CCD tubes with the 40 mm photocathode and image demagnification factor 3:1. The results of tests of these devices are presented and discussed. Besides, the near future projects concerning EB CCD tubes with the 80 mm photocathode and with image demagnification factor 5:1, and EB CCD tubes with solar blind photocathodes for the UV and EUV applications are briefly described.

Dalinenko, Ilia N.; Kossov, Vladimir G.; Kozlov, V. N.; Lazovsky, Leonid Y.; Malyarov, Alexandre V.; Vishnevsky, Grigory I.; Vydrevitch, Michail G.; Zhuk, A.

1997-06-01

369

Sputtering yield of Pu bombarded by fission Fragments from Cf  

SciTech Connect

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

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

2008-01-01

370

Uses of ion bombardment in thin-film deposition  

SciTech Connect

Use of plasma- and ion-beam-modified surfaces and surface coatings in continually expanding in engineering disciplines. The purpose of these modifications and treatments is to impart favorable properties, such as wear resistance and lubricity, to the surfaces, while at the same time retaining the strength or toughness of the bulk materials. Energetic-ion bombardment can be used to modify the structural and chemical properties of surfaces or applied coatings. Ion-implantation has been used for many years, and recently, other surface-modification techniques, among them ion-beam mixing and ion-beam-assisted deposition, have attracted attention because they permit application of highly adherent lubricious and wear-resistant films. In this paper, ion-beam techniques are described from the viewpoint of ion-surface interactions, and some avenues for the engineering of tribological surfaces are presented. 100 refs., 4 figs.

Erck, R.A.; Fenske, G.R.; Erdemir, A.

1990-10-01

371

Changes of Dust Grain Properties Under Particle Bombardment  

SciTech Connect

The dust in space environments is exposed to particle bombardment. Under an impact of ions, electrons, and photons, the charge of a particular grain changes and, in some cases, the grain structure can be modified. The present study deals with spherical melamine formaldehyde resin grains that are frequently used in many dusty plasmas and microgravity experiments and it concentrates on the influence of the electron beam impact on a grain size. We have performed series of experiments based on the SEM technique. Our investigation has shown that the electron impact can cause a significant increase of the grain size. We discuss changes of material properties and consequences for its applications in laboratory and space experiments.

Pavlu, J.; Richterova, I.; Safrankova, J.; Nemecek, Z. [Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic); Fujita, D. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

2008-09-07

372

Spontaneous Pattern Formation on Ion Bombarded Si(001)  

SciTech Connect

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

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

1999-04-26

373

AFM surface investigation of polyethylene modified by ion bombardment  

NASA Astrophysics Data System (ADS)

Polyethylene (PE) was irradiated with 63keV Ar+ and 155keV Xe+ ions to fluences of 1x1013 to 3x1015cm-2 with ion energies being chosen in order to achieve approximately the same penetration depth for both species. The PE surface morphology was examined by means of atomic force microscopy (AFM), whereas the concentration of free radicals and conjugated double bonds, both created by the ion irradiation, were determined using electron paramagnetic resonance (EPR) and UV-VIS spectroscopy, respectively. As expected, the degradation of PE was higher after irradiation with heavier Xe+ ions but the changes in the PE surface morphology were more pronounced for Ar+ ions. This newly observed effect can be explained by stronger compaction of the PE surface layer in the case of the Xe+ irradiation, connected with a reduction of free volume available.

Švor?ík, V.; Arenholz, E.; Hnatowicz, V.; Rybka, V.; Öchsner, R.; Ryssel, H.

1998-07-01

374

Size-dependent effect of ion bombardment on Au nanoparticles on top of various substrates: Thermodynamically dominated capillary forces versus sputtering  

SciTech Connect

Hexagonally ordered arrays of Au nanoparticles exhibiting narrow size distributions were prepared on top of Si wafers with either a thin native oxide or a thick thermally oxidized layer as well as on top of crystalline (0001)-oriented sapphire substrates. Subsequent irradiation of these nanoparticles by 200 keV Ar{sup +} and Xe{sup +}, respectively, in combination with transmission electron microscopy analysis (TEM) corroborated the previously reported phenomenon of bombardment-induced burrowing of metallic nanoparticles into SiO{sub x} while conserving their spherical shape [X. Hu et al., J. Appl. Phys. 92, 3995 (2002)]. Performing the ion irradiations on particle ensembles of different radii R{sub 0} (1.3 nm{<=}R{sub 0}{<=}5.3 nm) and determining the burrowing effect by atomic force microscopy combined with TEM provide sufficient statistics to allow a quantitative description of this effect. In addition to the thermodynamic driving forces necessary for the burrowing effect, sputtering of the nanoparticles due to the ion bombardment has to be included to arrive at an excellent theoretical description of the experimental data. The magnitude of sputtering can be quantified for the Au/sapphire system, where the burrowing effect is found to be completely suppressed. In that case, the theoretical description can even be improved by assuming a size-dependent sputtering coefficient for the Au nanoparticles. Combining this type of sputtering with the thermodynamically driven burrowing effect delivers a consistent model for all ion bombarded Au nanoparticles on top of SiO{sub x}. Specifically, the residual heights of the Ar{sup +}- or Xe{sup +}-induced burrowing of Au nanoparticles can be scaled on top of each other if plotted versus the average displacements per target atom rather than versus the applied ion fluences.

Klimmer, A.; Ziemann, P.; Biskupek, J.; Kaiser, U.; Flesch, M. [Institute of Solid State Physics, Ulm University, 89069 Ulm (Germany); Electron Microscopy Group, Ulm University, 89069 Ulm (Germany)

2009-04-15

375

A computational atomistic study of the relaxation of ion-bombarded c-Si on experimental time-scales: an application of the kinetic Activation Relaxation Technique  

NASA Astrophysics Data System (ADS)

The kinetic activation relaxation technique (kinetic ART) method, an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search,ootnotetextL. K. B'eland, P. Brommer, F. El-Mellouhi, J.-F. Joly and N. Mousseau, Phys. Rev. E 84, 046704 (2011). is used to study the relaxation of c-Si after Si^- bombardment at 3 keV. We describe the evolution of the damaged areas at room-temperature and above for periods of the order of seconds, treating long-range elastic deformations exactly. We assess the stability of the nanoscale structures formed by the damage cascade and the mechanisms that govern post-implantation annealing.

Béland, Laurent Karim; Mousseau, Normand

2012-02-01

376

Silicide formation at HfO{sub 2}-Si and ZrO{sub 2}-Si interfaces induced by Ar{sup +} ion bombardment  

SciTech Connect

The effect of ion bombardment with Ar{sup +} at several keV energy ranges resulting in silicide formation at HfO{sub 2}-Si and ZrO{sub 2}-Si interfaces has been investigated in situ with x-ray photoelectron spectroscopy. The set of spectra recorded during the growth of thin HfO{sub 2} and ZrO{sub 2} layers on Si(100) was compared to those obtained during subsequent sputtering with an Ar{sup +} beam. It is shown that the Ar{sup +} ion beam affects the MeO{sub 2}-Si (Me=Hf,Zr) interface at thickness {<=}3 nm, inducing the formation of a silicide layer {approx}2 nm in thickness. The proposed mechanism of silicide formation including the depletion of the interface in oxygen due to its preferential sputtering and subsequent Hf-Si intermixing is corroborated by computer simulations.

Lebedinskii, Yuri; Zenkevich, Andrei [Moscow Engineering Physics Institute, 115409 Moscow (Russian Federation)

2004-11-01

377

Chemistry of acenes, [60]fullerenes, cyclacenes and carbon nanotubes  

NASA Astrophysics Data System (ADS)

In the present work, we studied the chemistries of acenes, cyclacenes, [60]fullerenes and CNTs. Acenes are well known organic semiconductors. Pentacene is a benchmark organic semiconductor due to low HOMO-LUMO gap and high charge carrier mobilities in its thin film. Its poor solubility and instability, however, limit its utility and overall cost effectiveness. We successfully synthesized several sulfur-functionalized acene derivatives that overcome these problems. However, we also encountered difficulties to aromatize some of these derivatives. To circumvent these problems, we studied some new synthetic routes to sulfur-functionalized anthracenes, pentacenes and nonacenes. Additionally, the electronic properties of substituted acenes were compared using high level DFT calculations. According to our unrestricted DFT calculations, significant spin characters associated with thio-substituted nonacenes are likely the reason for their instabilities and difficult syntheses. Our UV-Vis-NIR studies reveal acene characteristics in acene quinones and hydroxyacenes that are dissolved in concentrated sulfuric acid. Cyclacenes may be useful precursors to synthesize SWNTs with uniform dimensions. We explored the supramolecular assembly of a bis[60]fullerene adduct of a 2,3,9,10-tetrasubstituted pentacene as a method to produce a [24]cyclacene framework. To that end, we synthesized the bis[60]fullerene adduct of 2,3,9,10-tetraiodomethyl-6,13-diphenylpentacene. The synthesis of a cyclacene framework via intermolecular cycloaddition of bis[60]fullerene adducts requires further study. According to our unrestricted broken symmetry calculations for different functionalized [n]cyclacenes, HOMO-LUMO gaps and spin characters are impacted by the presence and location of alkylthio and/or arylthio functional groups on the [n]cyclacene skeleton. [60]Fullerene is known to form polysultone and chlorinated derivatives when treated with fuming sulfuric acid (FSA) and chlorosulfonic acid (CSA), respectively, at room temperature. Based on our preliminary study, we predict that MWNTs react with boiling CSA and they are unreactive toward boiling FSA. The CSA treated MWNTs showed less bundling and broken tips in their AFM and TEM images. We studied the self-assembly of carboxylated-SWNTs and polystyrene latex (PSL) particles on different substrates. We believe that carboxylated-SWNTs have stronger interactions with amino or carboxy terminated PSL than unsubstituted PSL particles. According to our SEM analysis, self-assembly of the nanocomposites is moderately substrate dependent.

Pramanik, Chandrani

378

Plasma-Chemical Synthesis of Nanosized Powders-Nitrides, Carbides, Oxides, Carbon Nanotubes and Fullerenes  

NASA Astrophysics Data System (ADS)

In this article the plasma-chemical synthesis of nanosized powders (nitrides, carbides, oxides, carbon nanotubes and fullerenes) is reviewed. Nanosized powders - nitrides, carbides, oxides, carbon nanotubes and fullerenes have been successfully produced using different techniques, technological apparatuses and conditions for their plasma-chemical synthesis.

Katerina, Zaharieva; Gheorghi, Vissokov; Janis, Grabis; Slavcho, Rakovsky

2012-11-01

379

Synthesis of cyclotriveratrylene dendrimers and their supramolecular complexes with fullerene C60  

Microsoft Academic Search

Dendrimers with cyclotriveratrylene core and polybenzyl ether branches were synthetised by a convergent Fréchet approach. The cyclotriveratrylene was obtained by trimerisation of phenolic allyl ether of vanillyl alcohol and its structure was characterised by X-ray diffraction. The synthesised dendrimers of first and second generations were used to obtain the supramolecular complexes with fullerene C60. The ability of the fullerene C60

I. V. Lijanova; J. Flores Maturano; J. G. Domínguez Chávez; K. E. Sánchez Montes; S. Hernandez Ortega; T. Klimova; M. Martínez-García

2009-01-01

380

Dynamic control of dendrimer-fullerene association by axial coordination to the core.  

PubMed

The effect of axial coordination of pyridine derivatives to the core porphyrin on the fullerene encapsulation of the 4th generation carbazole-phenylazomethine dendrimer (ZnPG2-2) was investigated. The axial coordination of large (bulky) pyridine derivatives affects the cavity in an allosteric manner, and the size-selectivity of the fullerene association could be controlled. PMID:23788379

Albrecht, Ken; Kasai, Yuto; Kuramoto, Yasunori; Yamamoto, Kimihisa

2013-06-21

381

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

EPA Science Inventory

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

382

INTERACTION OF A WATER SOLUBLE FULLERENE DERIVATIVE WITH REACTIVE OXYGEN SPECIES AND MODEL ENZYMATIC SYSTEMS  

Microsoft Academic Search

Fullerenes are a new class of compounds with potential uses in biology and medicine but little is known about their interaction with biological systems. Fullerenes were reported to be pro- or anti-oxidants depending on their structure or on experimental conditions. This work presents the effects of dendrofullerene, a water soluble derivative of C60, on model biological systems from both perspectives.

Sarah Foley; Anthony D. M. Curtis; Andreas Hirsch; Michael Brettreich; André Pelegrin; Patrick Seta; Christian Larroque

2002-01-01

383

Testing for fullerenes in geologic materials: Oklo carbonaceous substances, Karelian shungites, Sudbury Black Tuff  

NASA Astrophysics Data System (ADS)

Fullerenes have been reported from diverse geologic environments since their discovery in shungite from Karelian Russia. Our investigation is prompted by the presence of onionskin-like structures in some carbonaceous substances associated with the fossil nuclear fission reactors of Oklo, Gabon. The same series of extractions and the same instrumental techniques, laser desorption ionization and high-resolution mass spectroscopy (electron-impact mass spectroscopy), were employed to test for fullerenes in samples from three different localities: two sites containing putative fullerenes (Sudbury Basin and Russian Karelia) and one new location (Oklo, Gabon). We confirm the presence of fullerenes (C60 and C70) in the Black Tuff of the Onaping Formation impact breccia in the Sudbury Basin, but we find no evidence of fullerenes in shungite samples from various locations in Russian Karelia. Analysis of carbonaceous substances associated with the natural nuclear fission reactors of Oklo yields no definitive signals for fullerenes. If fullerenes were produced during sustained nuclear fission at Oklo, then they are present below the detection limit (˜100 fmol), or they have destabilized since formation. Contrary to some expectations, geologic occurrences of fullerenes are not commonplace.

Mossman, David; Eigendorf, Guenter; Tokaryk, Dennis; Gauthier-Lafaye, François; Guckert, Kristal D.; Melezhik, Victor; Farrow, Catharine E. G.

2003-03-01

384

Characterization of large area flexible plastic solar cells based on conjugated polymer\\/fullerene composites  

Microsoft Academic Search

The development of solar cells based on composites of organic conjugated semi-conducting polymers with fullerene derivatives can provide a new method in the exploitation of solar energy. Organic solar cells must fulfill the criteria of stability, efficiency and reduction of production costs to find new applications. Specially, the bulk donor-acceptor heterojunctions between conjugated polymers and fullerenes have been successfully utilized

Desta Gebeyehu; F. Padinger; C. J. Brabec; T. Fromherz; J. C. Hummelen; N. S. Sariciftci

1999-01-01

385

A Systematic Investigation of Electrospray Ionization of C3 Isomer of tris Malonic Acid Fullerene  

Microsoft Academic Search

1 , we reported the discovery of appropriate methods for producing both positive and negative ions of these compounds by electrospray mass spectrometry. That work was performed with fullerene compounds that were a mixture of hexa and pentacarboxylic acid isomers. In this work, the electrospray of the pure C3 isomer of tris malonic acid fullerene is investigated in a systematic

Michael A. Grayson; Eva G. Lovett; Laura L. Dugan; Michael L. Gross

386

Synthesis of confined electrically conducting carbon nanowires by heavy ion irradiation of fullerene thin film  

SciTech Connect

Conducting nanowires parallel to each other, embedded in fullerene matrix are synthesized by high energy heavy ion irradiation of thin fullerene film at low fluence (up to 5x10{sup 11} ions/cm{sup 2}). The conductivity of the conducting zone is about seven orders of magnitude higher than that of the fullerene matrix. The conducting nanowires are evidenced by conducting atomic force microscopy. The typical diameter of the conducting tracks is observed to be about 40-100 nm. The creation of conducting wires is explained by transformation of fullerene to conducting form of carbon in the ion track, surrounded by the polymerized zone. The polymerization of fullerene is evidenced by Fourier transform infrared spectroscopy.

Kumar, Amit; Avasthi, D. K.; Tripathi, A.; Kabiraj, D.; Singh, F.; Pivin, J. C. [Materials Science Group, Inter University Accelerator Centre, Post Box 10502, New Delhi 110067 (India); CSNSM, Ba circumflex timent 108, 91405 Orsay Campus (France)

2007-01-01

387

Adverse effects of fullerenes (nC60) spiked to sediments on Lumbriculus variegatus (Oligochaeta).  

PubMed

Effects of fullerene-spiked sediment on a benthic organism, Lumbriculus variegatus (Oligochaeta), were investigated. Survival, growth, reproduction, and feeding rates were measured to assess possible adverse effects of fullerene agglomerates produced by water stirring and then spiked to a natural sediment. L. variegatus were exposed to 10 and 50 mg fullerenes/kg sediment dry mass for 28 d. These concentrations did not impact worm survival or reproduction compared to the control. Feeding activities were slightly decreased for both concentrations indicating fullerenes' disruptive effect on feeding. Depuration efficiency decreased in the high concentration only. Electron and light microscopy and extraction of the worm fecal pellets revealed fullerene agglomerates in the gut tract but not absorption into gut epithelial cells. Micrographs also indicated that 16% of the epidermal cuticle fibers of the worms were not present in the 50 mg/kg exposures, which may make worms susceptible to other contaminants. PMID:21852027

Pakarinen, K; Petersen, E J; Leppänen, M T; Akkanen, J; Kukkonen, J V K

2011-08-17

388

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

SciTech Connect

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

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

1996-03-01

389

Optical limiting and excited-state absorption in fullerene solutions and doped glasses  

SciTech Connect

We report the ground state and excited state optical absorption spectra in the visible and near infrared for several substituted fullerenes and higher fullerenes in toluene solutions. Based on these measurements, broadband predictions of the optical limiting performance of these molecules can be deduced. These predictions are then tested at 532 to 700 nm in intensity-dependent transmission measurements. We observe optical limiting in all fullerenes measured; higher fullerenes show the greatest potential for limiting in the near infrared (650-1000 nm), while substituted C{sub 60} shows optimal limiting in the visible (450-700 nm). We observe dramatically reduced limiting for solid forms of C{sub 60} (thin films and C{sub 60}-doped porous glasses), indicating that efficient optical limiting in fullerenes requires true molecular solutions.

McBranch, D.; Smilowitz, L.; Klimov, V. [and others

1995-09-01

390

Surface morphology evolution during low energy ion bombardment of silicon and gallium antimonide  

NASA Astrophysics Data System (ADS)

Ion bombardment is a widely used technique to modify the properties of materials for technological applications. In recent years, surface evolution during ion bombardment has also attracted considerable fundamental interest because of the desire to better understand the physical processes occurring at the surface and the frequent instability of surfaces to the spontaneous formation of nanostructures during bombardment. In this research, the surface morphology evolution of Silicon(100) and Gallium Antimonide(100) during low energy Argon ion bombardment was studied using real-time grazing-incidence small angle X-ray scattering and ex-situ atomic force microscopy. The surface morphology evolution of Si during ion bombardment as a function of substrate temperature was examined. Although, the surface was amorphized during bombardment at room temperature, above approximately 400°C a transition from amorphous to crystalline structure occurred. Above 500°C, the surface remained crystalline and the growing corrugations exhibited dynamic scaling with power law growth in amplitude and characteristic length scale. The ripple formation by off normal incidence low energy ion bombardment and ripple smoothening by normal incidence ion bombardment at room temperature were studied. Using real-time X-ray scattering, an exponential growth of the intensities during ripple formation was observed confirming that the early time kinetics obeyed the Bradley-Harper model. However, at later times the growth slowed and deviated from the predictions of the linear model. Ripple smoothening experiments, on the other hand, showed that the ripple structures eroded during normal incidence ion bombardment, possibly due to an additional lateral atomic smoothening mechanism active at these incidence angles. The real-time measurements showed that the small length scales decayed faster than the large length scales as predicted by the linear model, however the decay mechanisms were more complex than expected from existing linear theory. It was observed that, although Si surfaces remained smooth during bombardment at room temperature when a small amount of Molybdenum atoms was supplied to the surface during ion bombardment, correlated structures with two different characteristic length scales developed. The shorter length scale features ("dots") coarsened with time until they reached a constant spatial wavelength. The longer length scale corrugations associated with kinetic roughening, however, continued to grow in amplitude during bombardment. The evolution of this kinetic roughening could be described by the Family-Vicsek scaling hypothesis. A new noise term associated with inhomogeneities in local relaxation was proposed to quantitatively explain the early time kinetics. In addition, in-situ wafer curvature measurements were performed during ion bombardment to study the real-time stress state of the surface. The measurements showed that initially a compressive stress developed during bombardment, likely due to amorphization of the surface. However, seeding caused a larger tensile stress to develop with further bombardment, possibly due to the formation of higher density regions around the Mo seed atoms on the surface. The effects of this large tensile stress on the surface instability and the formation of the nanodots were also examined. Simulations of existing continuum equations of surface morphology evolution during normal incidence ion bombardment at room temperature were performed to study the effects of individual terms on the surface morphology, as well as their relations with each other. It was observed that the noisy Kuramoto-Sivashinsky model could only qualitatively predict the surface evolution, but could not reproduce all of the experimental results. Finally, the morphology evolution of GaSb(100) surfaces during ion bombardment at different energies was also studied. Formation of correlated nanodots with a length scale of approximately 30 nm was observed during bombardment at room temperature without seeding.

Ozaydin-Ince, Gozde

391

Deuterium transport through 304 and 304L stainless steel at low driving pressures and 15 keV deuteron bombardment. Final report  

Microsoft Academic Search

The permeation rate of D through 304 and 304L stainless steel for driving pressures 10 to 10¹ Pa (10 to 10³ torr) were measured over the temperature range 650 to 1050°K. Two 51 mu m and one 127 mu m, 304 samples and one 127 mu m, electropolished 304L sample were studied. The steady-state permeation rate varied linearly with p\\/sup

H. K. Perkins; T. Noda

1976-01-01

392

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

PubMed Central

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

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

2013-01-01

393

Influence of C{sub 60} morphology on high-order harmonic generation enhancement in fullerene-containing plasma  

SciTech Connect

The morphologies of the fullerene targets and the ablated fullerenes to determine the optimal conditions of excitation of the C{sub 60}-containing targets have been analyzed. The optimization of fullerene-containing plasma conditions allowed the enhanced harmonic generation in these plasmas using laser radiation of different wavelengths, pulse durations, and phase modulation. A comparison between the harmonic generation in single-atom/ion-containing plasmas (using bulk carbon, silver, and indium targets) and fullerene-rich plasma plumes showed better conversion efficiency for the latter medium. The influence of phase modulation of the fundamental radiation in fullerene plasmas on the spectral properties of harmonics has been studied.

Ganeev, R. A. [Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Institute of Electronics, Uzbekistan Academy of Sciences, Akademgorodok, 33, Dormon Yoli Street, Tashkent 100125 (Uzbekistan); Singhal, H.; Naik, P. A.; Chakera, J. A.; Srivastava, A. K.; Dhami, T. S.; Joshi, M. P.; Gupta, P. D. [Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

2009-11-15

394

Power and Charge Deposition and Electron Transport in Disordered SiO2 Layers Under Electron Bombardment  

NASA Astrophysics Data System (ADS)

Power and charge deposition in multilayer dielectrics from electron bombardment is dependent on the flux and energy-dependent electron penetration depth of the electron beam. Using the Continuous Slow Down Approximation (CSDA), a composite analytical formula has been developed to approximate the electron range which can be related to the dose rate, deposited power and Radiation Induced Conductivity (RIC). Based on the constituent layer geometry and material, the deposited charge can also be inferred. Three separate pulsed electron beam experiments were conducted to measure charge deposition, power dependent cathodoluminescence and RIC. The power and charge deposition experiments measured the net surface potential, electrode currents and electron induced luminescence of disordered SiO2 multilayer dielectrics with a grounded or floating conductive middle layer, using beam energies from 200 eV to 25 keV at 40 K to room temperature. These results showed that the power and charge deposition's dependence on electron beam flux and incident energy compare favorably with the model predictions. The RIC experiments measured electrode currents using disordered SiO2 layers from 40 K to 320 K with dose rates from 10-5 Gy/s to 10-1 Gy/s. The onset of RIC in the energy-dependant depth of the RIC region provides an explanation for observed retrograde charging.

Dennison, Gregory Wilson, Jr.; Jensen, Amberly E.; Dekany, Justin

2013-03-01

395

Relative sputter rate measured in Cu/Co multilayer using Ar+ ion bombardment at grazing angle of incidence  

NASA Astrophysics Data System (ADS)

The relative sputter rate of copper with respect to cobalt was determined by means of Auger electron spectroscopy depth profiling a Co/Cu multilayer structure as a function of the angle of incidence in the range of 47°-86° at 1 keV Ar+ ion bombardment. It was found that the relative Cu/Co sputter rate, YCu/YCo, decreases from 47° to 82°, exhibiting a minimum at 82°. Above 82° it sharply increases. In the literature we did not find sputtering yield data for such sputtering conditions. TRIM simulation and the Yamamura et al. (Y. Yamamura, Y. Itayekawa, and N. Itoh, Nagoya University of Plasma Physics Report JPPJ-AM-26) equation were compared with the experimental data. Though both predict the increase of YCu/YCo at high angles of incidence, the agreement between the theories and experiment is poor. Reasonably good agreement between the measurements and TRIM simulation was found if the surface binding energy of Cu was chosen to be an unphysical low value.

Barna, A.; Menyhard, M.; Zsolt, G.; Khanh, N. Q.; Zalar, A.; Panjan, P.

2003-01-01

396

Influence of ion bombardment induced patterning of exchange bias in pinned artificial ferrimagnets on the interlayer exchange coupling  

SciTech Connect

Artificial ferrimagnets have many applications as, e.g., pinned reference electrodes in magnetic tunnel junctions. It is known that the application of ion bombardment (IB) induced patterning of the exchange bias coupling of a single layer reference electrode in magnetic tunnel junctions with He ions is possible. For applications as, e.g., special types of magnetic logic, a combination of the IB induced patterning of the exchange bias coupling and the implementation of an artificial ferrimagnet as reference electrode is desirable. Here, investigations for a pinned artificial ferrimagnet with a Ru interlayer, which is frequently used in magnetic tunnel junctions, are presented. It is shown that in this kind of samples the exchange bias can be increased or rotated by IB induced magnetic patterning with 10 keV He ions without a destruction of the antiferromagnetic interlayer exchange coupling. An IrMn/Py/Co/Cu/Co stack turned out to be more sensitive to the influence of IB than the Ru based artificial ferrimagnet.

Hoeink, V.; Schmalhorst, J.; Reiss, G. [Thin Films and Nanostructures, Department of Physics, Bielefeld University, P.O. Box 100131, 33501 Bielefeld (Germany); Weis, T.; Lengemann, D.; Engel, D.; Ehresmann, A. [Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Kassel University, Heinrich-Plett-Strasse 40, D-34132 Kassel (Germany)

2008-06-15

397

Controllable synthesis of fullerene nano/microcrystals and their structural transformation induced by high pressure  

NASA Astrophysics Data System (ADS)

Fullerene molecules are interesting materials because of their unique structures and properties in mechanical, electrical, magnetic, and optical aspects. Current research is focusing on the construction of well-defined fullerene nano/microcrystals that possess desirable structures and morphologies. Further tuning the intermolecular interaction of the fullerene nano/microcrystals by use of pressure is an efficient way to modify their structures and properties, such as creation of nanoscale polymer structures and new hybrid materials, which expands the potential of such nanoscale materials for direct device components. In this paper, we review our recent progress in the construction of fullerene nanostructures and their structural transformation induced by high pressure. Fullerene nano/microcrystals with controllable size, morphology and structure have been synthesized through the self-assembly of fullerene molecules by a solvent-assisted method. By virtue of high pressure, the structures, components, and intermolecular interactions of the assemblied fullerene nano/microcrystals can be finely tuned, thereby modifying the optical and electronic properties of the nanostructures. Several examples on high pressure induced novel structural phase transition in typical fullerene nanocrystals with C60 or C70 cage serving as building blocks are presented, including high pressure induced amorphization of the nanocrystals and their bulk moduli, high pressure and high temperature (HPHT) induced polymerization in C60 nanocrystals, pressure tuned reversible polymerization in ferrocene-doped C60/C70 single crystal, as well as unique long-range ordered crystal with amorphous nanoclusters serving as building blocks in solvated C60 crystals, which brings new physical insight into the understanding of order and disorder concept and new approaches to the design of superhard carbon materials. The nanosize and morphology effects on the transformations of fullerene nanocrystals have also been discussed. These results provide the foundation for the fabrication of pre-designed and controllable geometries, which is critical in fullerenes and relevant materials for designing nanometer-scale electronic, optical, and other devices.

Yao, Ming-Guang; Du, Ming-Run; Liu, Bing-Bing

2013-09-01

398

Theoretical cross sections for keV antiprotons  

NASA Astrophysics Data System (ADS)

Partial and total close-coupled semiclassical (impact parameter) cross sections and total classical Monte-Carlo cross sections for interactions inbar p + Ps andbar p, p+H collisions are computed in the intermediate keV range for antiprotons,bar p, up to 100 keV lab. Total cross sections for antihydrogen,bar H, formation are found to be large, 10-20×10-16 cm2 in a wider energy range than was anticipated earlier, up to some 20 keV lab. New estimates of cross sections for ionisation of atomic hydrogen by antiproton impact are reported for the low-energy range 1 30 keV lab where they are 10-20×10-17 cm2, being much larger than the corresponding cross sections for ionisation of hydrogen by proton impact. Data for excitation of H bybar p impact is also presented.

Ermolaev, A. M.

1989-03-01

399

Implications of the 17 keV neutrino  

SciTech Connect

Constraints on the theoretical interpretation of the 17 keV neutrino are reviewed. A simple understanding of the 17 keV neutrino is provided by flavon models, which involve the spontaneous breaking of Abelian lepton symmetries and have only the usual three light neutrino species. Signatures for this class of models include neutrino oscillations, tau decay to an electron and a flavon, and invisible decay modes of the Higgs boson to two flavons.

Hall, L.J.

1991-06-01

400

25keV neutron beam facility at NBS  

Microsoft Academic Search

An iron-filtered, neutron-beam facility that provides a well collimated source of 25-keV neutrons has been developed at the National Bureau of Standards (NBS) Reactor. For selected physics experiments and monoenergetic calibration of neutron dosimeters, the beam flux may be tailored to provide 5 x 10⁵n.cm⁻².s⁻¹ with 99 percent 25-keV neutrons. For other experiments, such as calibration of fast-neutron spectrometers, fluxes

E. D. McGarry; I. G. Schroder

1975-01-01

401

Effect of proton bombardment on InAs dots and wetting layer in laser structures  

SciTech Connect

The effect of proton bombardment on carrier lifetime and photoluminescence of InAs quantum dots was measured. Optical absorption and transmission electron microscopy show the dots retain their integrity under bombardment. A decrease in ground state photoluminescence with increasing dose is not explained by the decrease in dot carrier lifetime alone, but also by bombardment-induced non-radiative recombination in the wetting layer, which reduces the dot electron population at fixed excitation. To exploit the relative radiation immunity of quantum dots, it is necessary to maximise the dot density and capture probability per dot to minimize the effect of wetting layer recombination.

O'Driscoll, I.; Blood, P.; Smowton, P. M.; Sobiesierski, A. [School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Gwilliam, R. [Advanced Technology Institute, FEPS, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2012-06-25

402

Evidence for the Timing of the Early Bombardment of Mars  

NASA Astrophysics Data System (ADS)

The analysis of the SNC meteorite, ALH 84001, which now appears to be a sample of the ancient crust of Mars[1], provides a new avenue to investigate the period of intense planetary bombardment of the early solar system. The sharp cutoff in lunar highland ages close to 3900 Ga has been widely used as a time marker for heavily cratered objects throughout the solar system. However, it is not yet established whether the heavy bombardment which affected the Moon was a solar system wide event or was local to the Earth-Moon system. There is some evidence, from the distribution of Ar-Ar ages of meteorites, of extensive resetting by impacts on their parent bodies, in the interval between 4500 and 3500 Ma, but the distribution is broader and less well established than the lunar case[2]. The full answer will only appear when the detailed chronology of the martian highlands is established. In the meantime we have carried out Ar-Ar analyses of ALH 84001. These show clearly that this meteorite was involved in outgassing events at a time close to the time of the so-called lunar cataclysm. The results of analysing three samples of ALH 84001 are summarized in Table 1, which appears here in the hard copy. The potassium content of all three samples analysed are extremely low, ~100 ppm, consistent with the origin of ALH 84001 as a mafic cumulate. The major carrier of potassium is maskelinite and it is the formation and outgassing of this which our analyses presumably date. The release patterns of 40Ar/39Ar as a function of temperature show structure which is interpreted as the result of 39Ar recoil. There is evidence of only minor recent loss of radiogenic 40Ar associated with the low temperature fractions. The 40Ar/K ratio and inferred age are calculated by summing all the gas released above these low temperature fractions. The exposure age of ALH 84001 inferred from the ratio of the high temperature 38Ar and Ca-derived 37Ar is close to 15 Ma. Cl abundances are inferred from the low temperature neutron-induced 38Ar and appear to correlate roughly with the trapped 36Ar, which mainly derives from the terrestrial atmosphere. This suggests that an appreciable fraction of the Cl is terrestrial, though some of indigenous origin is present in the carbonate. One feature which is difficult to understand is the apparent absence in our samples based on a 40Ar/36Ar vs. 39Arl36Ar, of any clear evidence of 40Ar from the martian atmosphere. The 40Ar-39Ar age inferred for ALH 84001 is clearly similar to those which are typical of the lunar highlands. This result provides the earliest evidence from Mars in support of the view that the late bombardment was a widespread event. References: [1] Mittlefehldt D. W. (1994) Meteoritics, 29, 214-221. [2] Turner G. (1988) in Meteorites and the Early Solar System, 276-288.

Ash, R. A.; Knott, S. F.; Turner, G.

1995-09-01

403

Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light  

PubMed Central

WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3.

2011-01-01

404

Liquid chromatography/mass spectrometry investigation of the reversed-phase separation of fullerenes and their derivatives  

SciTech Connect

The separation of fullerenes and their derivatives on four commercially available reversed-phase columns was investigated using liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization. Three octadecylsilica stationary phases were incapable of adequately separating the fullerenes according to the number of carbons. However, baseline resolution of nearly all the fullerenes (up to at least C[sub 96]) was achieved with a 2-(1-pyrenyl)ethylsilica phase. The resolution of individual fullerene isomers, on the other hand, was best accomplished with a polymeric octadecylsilica bonded phase. A proposed mechanism for this unique ability combines the shape selectivity of polymeric phases, previously recognized for planar polycyclic aromatic hydrocarbons, and the different molecular footprints of the isomers. This retention mechanism can also be used to explain the increasingly lower retention times of successively substituted fullerenes; groups bonded to the fullerene surface appear to disrupt adsorptive interactions between the fullerene molecular footprints and the stationary phases. 44 refs., 8 figs.

Anacleto, J.F. (Dalhousie Univ., Halifax, Nova Scotia (Canada)); Quilliam, M.A. (National Research Council, Halifax, Nova Scotia (Canada))

1993-09-01

405

Microstructure and biocompatibility investigation of biomaterial alumina after 30 keV and 60 keV nitrogen ion implantation  

Microsoft Academic Search

Polycrystalline alumina is widely used as biomaterial. It is being used as hip joints, tooth roots etc. Commercially available polycrystalline alumina samples were implanted with 30 keV and 60 keV energy N+ ions at different ion doses ranging from 5×1015 ions\\/cm2 to 5×1017 ions\\/cm2. Change in surface structure is studied using optical microscope. Compound formation at the surface of alumina is confirmed with GXRD.

Deep Shikha; Usha Jha; S. K. Sinha; P. K. Barhai; K. G. M. Nair; S. Dash; A. K. Tyagi; S. Kalavathy; D. C. Kothari

2009-01-01

406

Radiation damage of lithium ceramics by ion bombardment  

NASA Astrophysics Data System (ADS)

Lithium compounds are being considered as fusion reactor breeder blanket ceramics. The present studies will examine the stability of the Li-compounds to radiation damage effects, and to the formation of non-crystalline phases. Ion bombardment studies have been carried out to determine damage cross-sections of the crystal structures of Li2SiO3, Li2ZrO3 to 7 MeV Si ions. Monolayers of fine powders, less than 5 ? particle size, are examined by X-ray diffraction and scanning electron microscopy before and after irradiation. The lithium compounds damage readily becoming largely non-crystalline by 4 ions/nm2 with damage cross-sections of 0.8 +/- 0.1 nm2 for Li2SiO3 and 0.66 + 0.05 nm2 for Li2ZrO3. By contrast, Li2O has a fluorite structure and is expected to remain crystalline.

Özkan, H.; Karioris, F. G.; Eridon, J.; Cartz, L.

1990-02-01

407

Wavelength tunability of ion-bombardment-induced ripples on sapphire  

SciTech Connect

A study of ripple formation on sapphire surfaces by 300-2000 eV Ar{sup +} ion bombardment is presented. Surface characterization by in-situ synchrotron grazing incidence small angle x-ray scattering and ex-situ atomic force microscopy is performed in order to study the wavelength of ripples formed on sapphire (0001) surfaces. We find that the wavelength can be varied over a remarkably wide range--nearly two orders of magnitude--by changing the ion incidence angle. Within the linear theory regime, the ion induced viscous flow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30 deg. . In this model, relaxation is confined to a few nm thick damaged surface layer. The behavior at high temperature suggests relaxation by surface diffusion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface diffusion or viscous flow relaxation.

Zhou Hua; Wang Yiping; Zhou Lan; Headrick, Randall L.; Oezcan, Ahmet S.; Wang Yiyi; Oezaydin, Goezde; Ludwig, Karl F. Jr.; Siddons, D. Peter [Department of Physics, University of Vermont, Burlington, Vermont 05405 (United States); Department of Physics, Boston University, Massachusetts 02215 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2007-04-15

408

Comet impacts and chemical evolution on the bombarded Earth  

NASA Astrophysics Data System (ADS)

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

Oberbeck, Verne R.; Aggarwal, Hans

1991-09-01

409

Compact electron gun based on secondary emission through ionic bombardment.  

PubMed

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

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

2011-05-11

410

IR laser action on fullerene-doped organic systems  

NASA Astrophysics Data System (ADS)

An optical limiting of the laser radiation over IR range in organic compounds based on polyimide has been studied. The non-linear transmission at a wavelength of 1315 nm as well as spectral properties of the compounds have been investigated. The result obtained have been explained by the donor-acceptor interaction mechanism that affects nonlinear- optical properties of organic molecules. The fullerene-doped polyimide structures have been determined to be effective optical limiting materials for attenuating a power density of more than 2 J cm2 in the IR range.

Kamanina, Natalia V.; Bagrov, Ig. V.; Belousova, Inna M.; Zhevlakov, Aleksandr P.

2001-06-01

411

Role of pressure in the study of fullerenes  

SciTech Connect

Although fullerenes and their compounds are very new and exhibit new phenomena, pressure has already been an important factor in the characterization and study of these materials. In order to illustrate this, the authors will review collaborative studies on: (i) the effect of pressure on alkali and alkaline earth doped C{sub 60} superconductors, (ii) the effect of pressure and pressure medium on the ordering temperature of C{sub 60}, and (iii) the role of pressure in the study of the feasibility of using C{sub 60} as ``lattice sieves`` for separation of gases.

Schirber, J.E.; Samara, G.A.; Morosin, B.; Assink, R.; Loy, D. [Sandia National Labs., Albuquerque, NM (United States); Wang, H.; Williams, J. [Argonne National Lab., IL (United States); Murphy, D.; Kortan, A.R.; Rossiensky, M.; Zhou, O. [AT and T Bell Labs., Murray Hill, NJ (United States); Zhu, Q.; Kniaz, K.; Fischer, J.E. [Univ. of Pennsylvania, Philadelphia, PA (United States)

1993-08-01

412

Radial distribution function of C sub 60 : Structure of fullerene  

SciTech Connect

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

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

1991-12-15

413

Polarity-dependent forming in ion bombarded amorphous silicon memory devices  

SciTech Connect

Polarity-dependent forming in ion bombarded metal-semiconductor-metal (MSM) memory devices of hydrogenated amorphous silicon is reported. It is shown that prior to ion bombardment, current transport in the MSM devices is asymmetric and is controlled by the Schottky barriers at two MS junctions. Upon bombardment, however, there is a bulk component to the current and the I-V characteristics of the devices become symmetric at low bias voltages. The forming voltage in the bombarded devices shows polarity dependence. For positive bias applied on the top contact, we find that devices form at the same electric field independent of the thickness of the amorphous silicon while for negative voltage on the top contact, the electric field needed for forming increases with the thickness. A model involving the difference in energy deposition and heat sinking for the two polarities is proposed.

Gateru, R.G.; Orwa, J.O.; Shannon, J.M. [Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2005-01-15

414

Ion peening and stress relaxation induced by low-energy atom bombardment of covalent solids  

SciTech Connect

Using molecular-dynamics simulation, we study the buildup and relaxation of stress induced by low-energy ({le}150 eV) atom bombardment of a target material. The effect is brought out most clearly by using an initially compressed specimen. As target material, we employ Si, based on the Tersoff potential. By varying the bond strength in the potential, we can specifically study its effect on damage production and stress changes. We find that in general, stress is relaxed by the atom bombardment; only for low bombarding energies and strong bonds, atom bombardment increases stress. We rationalize this behavior by considering the role of energized atoms and of recoil-implanted target atoms.

Koster, Monika; Urbassek, Herbert M.

2001-06-01

415

ESCA Studies of Metal-Oxygen Surfaces Using Argon and Oxygen Ion-Bombardment.  

National Technical Information Service (NTIS)

ESCA has been used to monitor alternations of catalytically and electrochemically important metal-oxygen surfaces following exposure to Ar(+) and O2(+) ion bombardment. This treatment resulted not only in sputtering, but also, in many cases, in reduction ...

K. S. Kim W. E. Baitinger J. W. Amy N. Winograd

1974-01-01

416

Propagation of ripple patterns on Si during ion bombardment  

NASA Astrophysics Data System (ADS)

The lateral propagation of surface ripples on Si, generated by Xe ion irradiation with and without codeposition of Fe surfactant atoms, was investigated by scanning electron microscopy with the help of micron-sized marker structures prepared by focused ion beam milling. For 10-keV Xe ion irradiation of Si at oblique incidence between 62 and 70°, we determine lateral ripple propagation velocities varying from ?1.9 to +2.9 nm per 1015 Xe ions/cm2. The propagation direction changes from opposite to the projected direction of the incident ion beam to along the projected beam direction within a narrow angular regime. At 67°, the pattern is almost static. The result is in good agreement with predictions from the theoretical model of Bradley and Harper. For perpendicular incident 5-keV Xe ions and oblique codeposition of Fe surfactant atoms, we find that ripple patterns propagate across the surface with a negative ripple propagation velocity of about ?0.7 nm per 1015 Xe ions/cm2, i.e., opposite to the projected deposition direction of Fe surfactant atoms. The novel experimental method to determine the lateral ripple propagation based on markers set with a focused ion beam system does not require an in situ analysis and can therefore be applied in general to analyze the dynamics of ion beam-induced patterns.

Hofsäss, H.; Zhang, K.; Gehrke, H. G.; Brüsewitz, C.

2013-08-01

417

Electro-chemo-mechanical characteristics of fullerene-reinforced ionic polymer-metal composite transducers  

NASA Astrophysics Data System (ADS)

In this paper, the effects of fullerene as a reinforcing agent in Nafion-based ionic polymer-metal composite transducers were investigated in view of the electro-chemo-mechanical characteristics including sensing capabilities, specific electro-mechanical energy efficiency and blocking forces. Substantial variation in the crystallinity of fullerene-Nafion membranes even with the addition of low concentrations was observed in the x-ray diffraction data. The flower-like fullerene agglomerations observed in the scanning electron microscope images of the direct mixing samples between fullerenes and Nafion disappeared in the present solvent recasting method and good dispersions of fullerenes in the Nafion matrix were observed in the atomic force microscopy images. The Fourier transform infrared spectroscopy in conjunction with its complementary x-ray photon spectroscopy showed strong electrostatic and chemical interactions between fullerenes and sulfonated moieties of Nafion. Present results show that the 0.5 wt% fullerene-reinforced ionic polymer-metal composite transducer shows nearly three times the blocking force, twice the tip displacement, three times the sensed voltage and three times the electro-mechanical energy efficiency in comparison with a pure Nafion-based IPMC transducer.

Oh, Il-Kwon; Jung, Jung-Hwan; Jeon, Jin-Han; Vadahanambi, Sridhar

2010-07-01

418

The Role of Polycyclic Aromatic Hydrocarbons in the Study of Fullerene Formation  

NASA Astrophysics Data System (ADS)

Two approaches intended to elucidate the fullerene -formation mechanism are presented. The first of these involves pyrolytic synthesis of fullerenes from hydrocarbon ring structures known as polycyclic aromatic hydrocarbons (PAH's). Following work by Taylor et al. (Nature 366, 728, 1993), C_{60} is made by heating a naphthalene vapor/argon mixture to approximately 1000^circC. The use of several precursor PAH's, including naphthalene, is examined in this work. The second approach involves the intentional poisoning of carbon-arc fullerene production by the addition of hydrogen (H_2) to the quenching atmosphere. By adding hydrogen in varying amounts one produces both PAH's and chain molecules, possibly representing interrupted steps of the pathway leading to fullerenes. Various analytical techniques are employed to examine both approaches. It is shown by mass spectrometry that pyrolytic synthesis is not indicative of the fullerene-formation mechanism of the carbon-arc technique pioneered by Kratschmer et al. (Nature 347, 354, 1990). In addition to mass spectrometry, Fourier-transform infrared and ultra-violet/visible absorption spectroscopy, high-performance liquid-chromatography, and Raman-scattering spectroscopy are brought to bear in the analysis of the hydrogen-poisoning approach. From the analysis the PAH molecules formed in the hydrogen poisoning of the carbon-arc do not appear to comprise a pathway to fullerene formation. However, there is evidence indicating that chains, produced as a result of hydrogen contamination of the carbon-arc technique, are related to the formation of fullerene molecules.

Zumwalt, Michael Crane

1995-01-01

419

Transgenic Italian ryegrass ( Lolium multiflorum ) plants from microprojectile bombardment of embryogenic suspension cells  

Microsoft Academic Search

Transgenic forage-type Italian ryegrass (Lolium multiflorum Lam.) plants have been obtained by microprojectile bombardment of embryogenic suspension cells using a chimeric hygromycin phosphotransferase (hph) gene construct driven by riceActl 5' regulatory sequences. Parameters for the bombardment of embryogenic suspension cultures with the particle inflow gun were partially optimized using transient expression assays of a chimericß-glucuronidase (gusA) gene driven by the

X. Ye; Z.-Y. Wang; X. Wu; I. Potrykus; G. Spangenberg

1997-01-01

420

Transgenic Italian ryegrass (Lolium multiflorum) plants from microprojectile bombardment of embryogenic suspension cells  

Microsoft Academic Search

Transgenic forage-type Italian ryegrass (Lolium multiflorum Lam.) plants have been obtained by microprojectile bombardment of embryogenic suspension cells using a chimeric hygromycin phosphotransferase (hph) gene construct driven by rice Act1 5' regulatory sequences. Parameters for the bombardment of embryogenic suspension cultures with the particle inflow gun were partially optimized using transient expression assays of a chimeric #-glucuronidase (gusA) gene driven

X. Ye; Z.-Y. Wang; X. Wu; I. Potrykus; G. Spangenberg

1997-01-01

421

Efficient selection and regeneration of creeping bentgrass transformants following particle bombardment  

Microsoft Academic Search

We have established an efficient genetic transformation system for creeping bentgrass (Agrostis palustris Huds.) using particle bombardment. The transformation was performed using the plasmid pZO1052 which contains the reporter\\u000a ?-glucuronidase (uidA) gene and the selectable marker hygromycin phosphotransferase (hph) gene. Transformed calli and plants were obtained via particle bombardment followed by selection of transformants on medium\\u000a containing 200 mg\\/l of

L. Xiao; S.-B. Ha

1997-01-01

422

Microprojectile bombardment of plant tissues increases transformation frequency by Agrobacterium tumefaciens  

Microsoft Academic Search

Bombardment of plant tissues with microprojectiles in an effective method of wounding to promote Agrobacterium-mediated transformation. Tobacco cv. Xanthi leaves and sunflower apical meristems were wounded by microprojectile bombardment prior to application of Agrobacterium tumefaciens strains containing genes within the T-DNA encoding GUS or NPTII. Stable kanamycin-resistant tobacco transformants were obtained using an NPTII construct from particle\\/plasmid, particle-wounded\\/Agrobacterium-treated or scalpel-wounded\\/Agrobacterium-treated

Dennis Bidney; Chris Scelonge; Joanie Martich; Monique Burrus; Lynn Sims; Gary Huffman

1992-01-01

423

Low-energy electron spectrum of a copper target bombarded by ?-particles of 238Pu  

NASA Astrophysics Data System (ADS)

The (? e) time coincidence method is applied to study the low-energy electron spectrum of a copper target bombarded by ?-particles of 238Pu. Ionization of atoms bombarded by charged particles is considered as the shaking of electrons into the continuous spectrum due to a sudden perturbation by a flying particle. A comparison of experimental and calculated distributions showed good agreement, which confirms the accuracy of the ionization description as a result of the shaking effect.

Kupryashkin, V. T.; Sidorenko, L. P.; Feoktistov, A. I.; Rovenskykh, E. P.

2011-04-01

424

Genetic transformation of chickpea ( Cicer arietinum L.) with insecticidal crystal protein gene using particle gun bombardment  

Microsoft Academic Search

Here, we report the establishment of an efficient particle gun bombardment mediated genetic transformation in chickpea (Cicer arietinum L.) using cryIAc gene of Bacillus thuringiensis. Explants were bombarded with recombinant plasmids engineered for the expression of cryIAc transgene in plants and stable transformants regenerated in presence of benzyladenine, kinetin and kanamycin. Transformation\\u000a frequency showed dependence on explant type, cultivars, plasmids,

Shivani Indurker; Hari S. Misra; Susan Eapen

2007-01-01

425

Genetic transformation of Cavendish banana ( Musa spp. AAA group) cv 'Grand Nain' via microprojectile bombardment  

Microsoft Academic Search

An effective method has been developed for the stable transformation and regeneration of Cavendish banana (Musa spp. AAA group) cv 'Grand Nain' by microprojectile bombardment. Embryogenic cell suspensions were initiated using immature\\u000a male flowers as the explant. Cells were co-bombarded with the neomycin phosphotransferase (nptII) selectable marker gene under the control of a banana bunchy top virus (BBTV) promoter or

D. K. Becker; B. Dugdale; M. K. Smith; R. M. Harding; J. L. Dale

2000-01-01

426

Polygonisation of Ionic Single Crystals --- a New Effect of Swift Ion Bombardment  

Microsoft Academic Search

Isostructural oxide single crystals of the fluorite structure: stabilized cubic zirconia and UO2 were bombarded at room temperature with 72 MeV iodine ions or 340 MeV Xe ions, respectively. The aim of this paper was the study of structural transformations induced by ion bombardment in two different regimes: at 72 MeV where the radiation damage production is strongly influenced by

A. Turos; L. Nowicki; F. Garrido; L. Thome; R. Fromknecht; J. Domagala

1999-01-01

427

Production of transgenic gentian plants by particle bombardment of suspension-culture cells  

Microsoft Academic Search

Cell suspension cultures were established from leaf explants of gentian (Gentiana triflora×G. scabra) for the generation of transgenic plants by particle bombardment. The parameters for the bombardment of suspension culture\\u000a cells with a particle gun were examined by monitoring the transient expression of a gene for ?-glucuronidase driven by the\\u000a cauliflower mosaic virus (CaMV) 35S promoter. We found that prior

K. Hosokawa; R. Matsuki; Y. Oikawa; S. Yamamura

2000-01-01

428

Particle-In-Cell/Monte Carlo Simulation of Ion Back Bombardment in Photoinjectors  

SciTech Connect

In this paper, we report on studies of ion back bombardment in high average current dc and rf photoinjectors using a particle-in-cell/Monte Carlo method. Using H{sub 2} ion as an example, we observed that the ion density and energy deposition on the photocathode in rf guns are order of magnitude lower than that in a dc gun. A higher rf frequency helps mitigate the ion back bombardment of the cathode in rf guns.

Qiang, Ji; Corlett, John; Staples, John

2009-03-02

429

Efficient and stable transformation of hop ( Humulus lupulus L.) var. Eroica by particle bombardment  

Microsoft Academic Search

To the best of our knowledge, this is the first accurate and reliable protocol for hop (Humulus lupulus L.) genetic transformation using particle bombardment. Based on the highly productive regeneration system previously developed\\u000a by us for hop var. Eroica, two efficient transformation protocols were established using petioles and green organogenic nodular\\u000a clusters (GONCs) bombarded with gusA reporter and hpt selectable

Dora Batista; Sandra Fonseca; Susana Serrazina; Andreia Figueiredo; Maria Salomé Pais

2008-01-01

430

State-resolved study of keV sputtered neutral atoms by resonance ionization spectroscopy  

SciTech Connect

We have performed simultaneous measurements of energy-, and angle-resolved distributions of Ni atoms desorbed from a single crystal Ni{l_brace}100{r_brace} surface bombarded by 5 keV Ar{sup +} ions. Ground state and six low-lying excited states from the a{sup 3}FJ (J=4,3,2) and a{sup 3}DJ (J=3,2,1) manifolds as well as a{sup 1}D2 have been investigated along different azimuths. Both a{sup 3}FJ and a{sup 1}D2 states have closed shell electronic structure, 3d{sup 8}4s{sup 2}, while the a{sup 3}DJ states are open shell electronic states, 3d{sup 9}4s{sup 1}. Angle-integrated energy distributions demonstrate a strong dependence on the electronic structure while the magnitude of the excitation energy does not significantly alter the results. This is the first conclusive evidence that electronic structure rather than excitation energy is the primary factor in determining kinetic energy distributions of sputtered neutral species. Population distribution among the seven electronic states are obtained through two sets of measurements performed on two experimental apparati: one measures the energy- and angle-integrated resonance ionization signal intensities of the sputtered Ni; the other measures the resonance ionization signal intensities of thermally evaporated Ni atoms with a known heating temperature. The experiment results show that the population distribution is very different from Boltzman-type distribution with a{sup 3}D3 and a{sup 3}D2 states more intensely populated. The work also illustrates the power of RIS to perform quantum state specific measurements on fast moving atoms.

He Chun; Postawa, Z.; Rosencrance, S.; Chatterjee, R.; Garrison, B. J.; Winograd, N. [Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

1995-04-01

431

Quantitative Analysis of Fullerene Nanomaterials in Environmental Systems: A Critical Review  

PubMed Central

The increasing production and use of fullerene nanomaterials has led to calls for more information regarding the potential impacts that releases of these materials may have on human and environmental health. Fullerene nanomaterials, which are comprised of both fullerenes and surface-functionalized fullerenes, are used in electronic, optic, medical and cosmetic applications. Measuring fullerene nanomaterial concentrations in natural environments is difficult because they exhibit a duality of physical and chemical characteristics as they transition from hydrophobic to polar forms upon exposure to water. In aqueous environments, this is expressed as their tendency to initially (i) self assemble into aggregates of appreciable size and hydrophobicity, and subsequently (ii) interact with the surrounding water molecules and other chemical constituents in natural environments thereby acquiring negative surface charge. Fullerene nanomaterials may therefore deceive the application of any single analytical method that is applied with the assumption that fullerenes have but one defining characteristic (e.g., hydrophobicity). [1] We find that analytical procedures are needed to account for the potentially transitory nature of fullerenes in natural environments through the use of approaches that provide chemically-explicit information including molecular weight and the number and identity of surface functional groups. [2] We suggest that sensitive and mass-selective detection, such as that offered by mass spectrometry when combined with optimized extraction procedures, offers the greatest potential to achieve this goal. [3] With this review, we show that significant improvements in analytical rigor would result from an increased availability of well characterized authentic standards, reference materials, and isotopically-labeled internal standards. Finally, the benefits of quantitative and validated analytical methods for advancing the knowledge on fullerene occurrence, fate, and behavior are indicated.

Isaacson, Carl W.; Kleber, Markus; Field, Jennifer A.

2009-01-01

432

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

PubMed

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

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

2002-01-16

433

Biological Effects in Cell Cultures of Fullerene C 60 : Dependence on Aggregation State  

Microsoft Academic Search

\\u000a The mechanisms of biological action of various fullerene preparations – water-soluble C60\\/polyvinylpyrrolidone (C60\\/PVP) complex and solid-state pristine fullerene C60 (fullerene on the surfaces [FoS]), in cell-free system and in different cell cultures were studied. In the cell-free system\\u000a the C60\\/PVP complex showed the pro-oxidant activity. On the other hand, FoS in the darkness proved to be antioxidant (AO) and was

Levon B. Piotrovsky; Mikhail Yu. Eropkin; Elena M. Eropkina; Marina A. Dumpis; Oleg I. Kiselev

434

Effect of fullerene C60 on ATPase activity and superprecipitation of skeletal muscle actomyosin.  

PubMed

Creation of new biocompatible nanomaterials, which can exhibit the specific biological effects, is an important complex problem that requires the use of last accomplishments of biotechnology. The effect of pristine water-soluble fullerene C60 on ATPase activity and superprecipitation reaction of rabbit skeletal muscle natural actomyosin has been revealed, namely an increase of actomyosin superprecipitation and Mg2+, Ca(2+)- and K(+)-ATPase activity by fullerene was investigated. We conclude that this finding offers a real possibility for the regulation of contraction-relaxation of skeletal muscle with fullerene C60. PMID:23808306

Andreichenko, K S; Prylutska, S V; Medynska, K O; Bogutska, K I; Nurishchenko, N E; Prylutskyy, Yu I; Ritter, U; Scharff, P

435

Inhibition of DNA restrictive endonucleases by aqueous nanoparticle suspension of methanophosphonate fullerene derivatives and its mechanisms  

Microsoft Academic Search

Aqueous nanoparticle suspension of fullerene and its derivatives are currently attracting much attention. To determine the\\u000a effects of aqueous nanoparticle suspension of a mono-methanophosphonate fullerene and bis-methanophosphonate fullerene (denoted\\u000a as n-MMPF and n-BMPF, respectively) on the activities of DNA restrictive endonucleases, plasmid pEGFP-N1 was cleaved at a single but differently\\u000a restrictive site by EcoR I, BamH I, and isozymes Cfr9

GaoGuang Song; Lu Yao; Cheng Huang; Xin Xie; Xin Tan; XinLin Yang

2009-01-01

436

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

SciTech Connect

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

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

2009-01-09

437

Clustering dynamics of fullerenes in C 60/C 70-chemically modified poly(N-vinylcarbazole)  

NASA Astrophysics Data System (ADS)

The clustering dynamics of fullerenes in C 60/C 70-chemically modified poly(N-vinylcarbazole) was studied by laser desorption TOF mass spectrometry. From the evolution of the mass spectra in the negative and positive-ion channels with increasing laser shots the fragmentation and aggregation (growth and coalescence) dynamics as well as the key role played by PVK and its dissociation products were discussed. The results indicate that the bonds between the PVK chain and fullerene cages are easily broken under laser interaction and the fullerene cages ruptured from the chain are in active excited states favorable to the clustering of the cages.

Zhao, Li; Zhang, Jun; Zhang, Rongjun; Li, Yufen; Chen, Yu; Cai, Ruifang; Huang, Zuen

1996-12-01

438

Nitrogen and argon adsorption and SEM characterization of C{sub 60} and C{sub 60/}/C{sub 70} fullerenes: Comparison with graphite  

SciTech Connect

The surface and pore structure properties of the C{sub 60} and C{sub 60}/C{sub 70} fullerene powders were studied by means of scanning electron microscopy, helium pycnometry, and 77.4 K nitrogen and argon adsorption. The pore structure of fullerene powders is macroporous and consists mainly of the voids between the fullerene aggregates. In the major part of the adsorption monolayer, both nitrogen and argon interactions with fullerenes are weaker than with graphite, possibly because of the reduction of the gas molecule-mirror image effect in the case of fullerenes. In Henry`s law limit, however, nitrogen and argon adsorption on fullerenes is quantitatively similar to that on graphite because of the adsorption potential enhancement in the spaces between the surface fullerene molecules. In the multilayer regime, nitrogen adsorption on both fullerenes becomes similar to that on graphite. Both fullerenes behave similarly with respect to the adsorption of the studied gases.

Gusev, V.Y.; Ruetsch, S. [TRI/Princeton, NJ (United States); Popeko, L.A. [St. Petersburg Inst. of Nuclear Physics, Gatchina (Russian Federation); Popeko, I.E. [Semi-Alloys Co., Mount Vernon, NY (United States)

1999-08-05

439

The structure of fullerene films and their metallocene doping  

SciTech Connect

Hexagonal close-packed (HCP) C{sub 60} and C{sub 70} films have been prepared by the Langmuir method and examined by electron microscopy and electron-diffraction analysis. It has been shown that the vacuum deposition of a C{sub 60} + C{sub 70} mixture results in the formation of a film with small sized grains and a distorted C{sub 60}-HCP structure. The simultaneous deposition of C{sub 60} and ferrocene results in the formation of a film with a changed morphology and an electron-diffraction pattern that contains a variable amount of ferrocene depending on the experimental conditions. The electron-diffraction pattern corresponds to the presence of the known molecular complex C{sub 60}[(C{sub 5}H{sub 5}){sub 2}Fe]{sub 2}. The analogous simultaneous deposition of fullerene C{sub 60} and cobaltocene results in the formation of a C{sub 60} film stable in air and water, which contains carbon and cobalt (from the data of X-ray fluorescence, electron microscopy and microdiffraction). It has a different morphology and different diffraction patterns than pure C{sub 60} films and, depending on the cobaltocene content (relative to that of fullerene), appears to be a fullerite film doped with various amounts of cobaltocenium fulleride, which is an ionic compound.

Domrachev, G.A.; Kaverin, B.S.; Domracheva, E.G. [Institute of Organometallic Chemistry, Nizhnii Novgorod (Russian Federation)] [and others

1995-02-01

440

In vivo evaluation of carbon fullerene toxicity using embryonic zebrafish  

PubMed Central

There is a pressing need to develop rapid whole animal-based testing assays to assess the potential toxicity of engineered nanomaterials. To meet this challenge, the embryonic zebrafish model was employed to determine the toxicity of fullerenes. Embryonic zebrafish were exposed to graded concentrations of fullerenes [C60, C70, and C60(OH)24] during early embryogenesis and the resulting morphological and cellular responses were defined. Exposure to 200 ?g/L C60 and C70 induced a significant increased in malformations, pericardial edema, and mortality; while the response to C60(OH)24 exposure was less pronounced at concentrations an order of magnitude higher. Exposure to C60 induced both necrotic and apoptotic cellular death throughout the embryo. While C60(OH)24 induced an increase in embryonic cellular death, it did not induce apoptosis. Our findings concur with results obtained in other models indicating that C60(OH)24 is significantly less toxic than C60. These studies also suggest that that the embryonic zebrafish model is well-suited for the rapid assessment of nanomaterial toxicity.

Usenko, Crystal Y.; Harper, Stacey L.; Tanguay, Robert L.

2007-01-01

441

Photodetachment of fullerene monoanions and dianions in a Penning trap  

NASA Astrophysics Data System (ADS)

Singly and doubly charged fullerene anions were introduced into gas phase by means of electrospray starting from a solution containing a very efficient electron donor compound. Following isolation and trapping, mass selected anions were irradiated with a ns-pulse from a Nd:YAG laser at the third harmonic (h[nu] = 3.5 eV) in order to study (delayed) photoemission. We present results on the laser-fluence dependence of photoemission for singly charged C76- and C84- as well as for doubly charged C762-. Results are discussed in terms of statistical electron emission as opposed to direct detachment. They are further analyzed to give information on the number of photons necessary to induce delayed electron emission on the experimental time scale. The averaged absolute absorption cross-sections obtained were about 0.6-0.8 Å2 for all species probed. The agreement between experimental data and statistical modelling shows that electronic excitations which rapidly relax to vibrationally hot ions provide the dominant contributions to the 355 nm absorption cross-sections. As a corollary, we show that direct single-electron detachment is a minor process for the singly charged fullerene anions having a cross-section <0.02 Å2. For C762-, electron emission follows an absorption law in which single-photon excitation is the leading contribution. From the data we deduce a Coulomb barrier height for C762- of 1.20 eV.

Concina, Bruno; Neumaier, Marco; Hampe, Oliver; Kappes, Manfred M.

2006-05-01

442

Novel chemistry of elemental carbon: Graphite, fullerenes and nanotubes  

NASA Astrophysics Data System (ADS)

The goal of this work was to examine the chemistry that one can do with various fluorinated forms of elemental carbon. As a prelude to the experimental worked out for this thesis, a brief discussion of the various allotropic forms of carbon is given followed by a brief discussion of elemental fluorine and fluorination procedures. Graphite fluorides have been defluorinated with ammonia, trimethyl amine and hydrazine and functionalized with organolithium species to give soluble, submicron sized graphitic particles. C60 has been fluorinated to yield C60Fn species which n is predominately 42--46. These fluorinated fullerenes were then reacted with organolithium species to yield highly alkylated species having properties which differed greatly from C60 or their fluorinated counterparts. While the fluorination of graphite and fullerenes has been reported before, the fluorination of single wall carbon nanotubes (SWNTs) has not. The first report of the fluorination of SWNTs is described here as is our finding that hydrazine can defluorinate the "fluorotubes" to regenerate the original SWNTs. It was also determined that the fluorotubes were soluble in alcohol solvents and that reactions could be carried out on them while in solution. Using a technique which we developed here at Rice called "Ultrasonic assistance," we were able to react the fluorotubes with organolithium species in solution to yield alkylated SWNTs which could then be isolated by filtration and dissolved in chloroform.

Mickelson, Edward Thomas

1999-11-01

443

Seeded quantum FEL at 478 keV  

SciTech Connect

We present for the first time the concept of a seeded {gamma} quantum Free-Electron-Laser (QFEL) at 478 keV, which has very different properties compared to a classical. The basic concept is to produce a highly brilliant {gamma} beam via SASE. To produce highly intense and coherent {gamma} beam, we intend to use a seeded FEL scheme. Important for the production of such a {gamma} beam are novel refractive {gamma}-lenses for focusing and an efficient monochromator, allowing to generate a very intense and coherent seed beam. The energy of the {gamma} beam is 478 keV, corresponding to a wavelength in the sub-Angstrom regime (1/38 A). To realize a coherent {gamma} beam at 478 keV, it is necessary to use a quantum FEL design. At such high radiation energies a classical description of the {gamma}-FEL becomes wrong.

Guenther, M. M.; Jentschel, M.; Thirolf, P. G.; Seggebrock, T.; Habs, D. [Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany); Institut Laue-Langevin, F-38042 Grenoble (Germany); Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching, Germany and Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany)

2012-07-09

444

Back bombardment for dispenser and lanthanum hexaboride cathodes  

NASA Astrophysics Data System (ADS)

The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6?s duration, the DC cathode experiences a large change in the temperature compared with LaB6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method.

Bakr, Mahmoud; Kinjo, R.; Choi, Y. W.; Omer, M.; Yoshida, K.; Ueda, S.; Takasaki, M.; Ishida, K.; Kimura, N.; Sonobe, T.; Kii, T.; Masuda, K.; Ohgaki, H.; Zen, H.

2011-06-01

445

Fundamental studies of the cluster ion bombardment of water ice  

NASA Astrophysics Data System (ADS)

The fundamental sputtering properties of water ice are of interest for molecular depth profiling of biological samples in their native environment. We report on a method of studying amorphous water ice films of precise thicknesses in which pure water vapor is condensed onto a pre-cooled, silver-coated quartz crystal microbalance (QCM). This scheme allows for the determination of water ice sputter yields for any primary projectile as well as providing a means for studying escape depths of atoms and molecules beneath the deposited water ice layer. Specifically, we find a removal of approximately 2500 water molecule equivalents/20 keV C60+ projectile with an underlying silver ion escape depth of 7.0 Å.

Szakal, Christopher; Kozole, Joseph; Winograd, Nicholas

2006-07-01

446

Dual growth modes in ion bombarded Si surfaces  

SciTech Connect

Morphological studies were done on Si (001) surfaces after rastering them with a 1 keV O{sub 2}{sup +} ion beam at an angle. The resulting mounded morphology was studied using atomic force microscopy (AFM) measurements. The roughness at different length scales were further extracted and quantified from AFM measurements using scaling analysis. Results indicate two growth regimes of the evolving surface which were evident from the power spectral density (PSD) and interface width analysis of the eroded surfaces. Initially the growth is unstable followed by a stable regime of the nanostructures evolved after about 35 minutes of erosion. Temporal studies done on these surfaces show the onset of shadowing at higher sputtering times thus indicating the breakdown of the growth model at these times.

Dhillon, Prabhjeet Kaur; Sarkar, Subhendu [Department of Physics, Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab - 140 001 (India)

2012-06-05

447

Compton Profiles of Silver with 662 keV ?-Rays  

NASA Astrophysics Data System (ADS)

The isotropic Compton profiles of Ag for two thicknesses, 2 mm and 4 mm, have been measured by means of 662 keV ?-rays from Cs137 source. A HpGe detector with resolution of 190 eV at 5.9 keV was used to detect the backward scattering photons. Comparison with the renormalized-free-atom model calculations was made, and the agreement between the experimental and the calculated values has been found to be good for the electron configuration 4d105s1.

Chang, Chu-Nan; Lee, Syh-Bin; Chen, Chuhn-Chih

1991-12-01

448

Classical-trajectory Monte Carlo calculations of the electronic stopping cross section for keV protons and antiprotons impinging on hydrogen atoms  

NASA Astrophysics Data System (ADS)

Using the classical-trajectory Monte Carlo (CTMC) method, the electronic stopping cross sections of hydrogen atoms by protons and antiprotons impact are calculated. The results show that the CTMC method compares fairly well with previous quantum mechanics calculations of the stopping cross sections for the same colliding pairs. It turns out therefore that the CTMC method constitutes a reliable and, computationally speaking, convenient alternative to calculate the stopping of ions in matter. The present results also show that the stopping appears to be particularly sensitive to the angular momentum (L) of the electron orbit. In the case of protons, the highest sensitivity to L becomes evident around the energy of the maximum stopping. While for antiprotons the largest sensitivity of the stopping to L is observed down at low bombarding energies, i.e., below 10 keV.

Custidiano, Ernesto R.; Jakas, Mario M.

2005-08-01

449

Marker-free transgenic corn plant production through co-bombardment.  

PubMed

The use of particle gun for the production of marker-free plants is scant in published literature. Perhaps this is a reflection of the widely held notion that the events generated through bombardment tend to have multiple copies of transgenes, usually integrated at a single locus, features which precludes segregating away the selectable marker gene. However, our previous studies have shown that single-copy integrants are obtained at a high frequency if limited quantity of DNA is used for bombardment. Also, the concatemerized insertion of transgenes has been demonstrated to be greatly reduced if "cassette DNA" is employed in place of whole plasmid DNA for bombardment. Based on the above findings, in the present study the feasibility of co-bombardment was evaluated for the production of marker-free plants in corn, employing a combination of limited quantity DNA and cassette DNA approaches for bombardment. Transgenic events were generated after co-bombardment of a selectable marker cassette containing the nptII gene (2.5 ng per shot) and a GUS gene cassette (15 ng per shot). Among these events single-copy integrants for nptII gene occurred at an average frequency of 68% within which the co-expression frequency of GUS and nptII genes ranged from 41% to 80%. Marker-free corn plants could be identified from the progeny of 28 out of the 103 R0 co-expressing events screened. The results demonstrate that by using cassette DNA and low quantities of DNA for bombardment, marker-free plants are produced at efficiencies comparable to that of Agrobacterium-based co-transformation methods. PMID:19701639

Shiva Prakash, N; Bhojaraja, R; Shivbachan, S K; Hari Priya, G G; Nagraj, T K; Prasad, V; Srikanth Babu, V; Jayaprakash, T L; Dasgupta, Santanu; Spencer, T Michael; Boddupalli, Raghava S

2009-08-22

450

Hybrid chalcogenide nanoparticles: 2D-WS2 nanocrystals inside nested WS2 fullerenes.  

PubMed

The MOCVD assisted formation of nested WS2 inorganic fullerenes (IF-WS2) was performed by enhancing surface diffusion with iodine, and fullerene growth was monitored by taking TEM snapshots of intermediate products. The internal structure of the core-shell nanoparticles was studied using scanning electron microscopy (SEM) after cross-cutting with a focused ion beam (FIB). Lamellar reaction intermediates were found occluded in the fullerene particles. In contrast to carbon fullerenes, layered metal chalcogenides prefer the formation of planar, plate-like structures where the dangling bonds at the edges are stabilized by excess S atoms. The effects of the reaction and annealing temperatures on the composition and morphology of the final product were investigated, and the strength of the WS2 shell was measured by intermittent contact-mode AFM. The encapsulated lamellar structures inside the hollow spheres may lead to enhanced tribological activities. PMID:23982722

Hoshyargar, Faegheh; Corrales, Tomas P; Branscheid, Robert; Kolb, Ute; Kappl, Michael; Panthöfer, Martin; Tremel, Wolfgang

2013-09-24

451

Plasmon-plasmon coupling in buckyonion fullerenes: Photoexcitation of interlayer plasmonic cross modes  

NASA Astrophysics Data System (ADS)

Considering the photoionization of a two-layer fullerene-onion system, C60@C240, strong plasmonic couplings between the nested fullerenes are predicted [1]. The resulting hybridization produces four cross-over plasmons generated from the bonding and antibonding mixing of excited charge clouds of individual fullerenes. The properties of these hybrid plasmons are also greatly different from the plasmons that exist in isolated C60 and C240. This suggests the possibility of designing buckyonions exhibiting plasmon resonances with specified properties as candidates for nanomaterial plasmonics. The results can further motivate future research to modify the resonances by encaging atoms, molecules or clusters in multi-layered fullerenes.[4pt] [1] M.A. McCune, R. De, M.E. Madjet, H.S. Chakraborty, and S.T. Manson, J. Phys. B Fast Track Comm. 44, 241002 (2011).

McCune, Matt; de, Ruma; Madjet, Mohamed; Chakraborty, Himadri; Manson, Steve

2012-06-01

452

Effect of C60 fullerene additives on the mechanical properties of low-density polyethylene films  

NASA Astrophysics Data System (ADS)

We have studied the effect of C60 fullerene additives on the mechanical properties (strength, Young's modulus, elongation at break) of thin low-density polyethylene films tested for uniaxial extension.

Tuichiev, Sh.; Tabarov, S. Kh.; Rashidov, Dzh.; Shoimov, U.; Ginzburg, B. M.

2008-01-01

453

Predicting Real Optimized Materials: Novel Nitrogen-Containing Fullerenes and Nanotubes.  

National Technical Information Service (NTIS)

We propose to investigate the possible configurations, electronic, conducting and energetic properties of nitrogen-containing carbon fullerenes and single-walled nanotubes with nitrogen contents up to 30% using first principle density functional theoretic...

M. R. Manaa

2003-01-01

454

Effect of Peierls transition in armchair carbon nanotube on dynamical behaviour of encapsulated fullerene  

PubMed Central

The changes of dynamical behaviour of a single fullerene molecule inside an armchair carbon nanotube caused by the structural Peierls transition in the nanotube are considered. The structures of the smallest C20 and Fe@C20 fullerenes are computed using the spin-polarized density functional theory. Significant changes of the barriers for motion along the nanotube axis and rotation of these fullerenes inside the (8,8) nanotube are found at the Peierls transition. It is shown that the coefficients of translational and rotational diffusions of these fullerenes inside the nanotube change by several orders of magnitude. The possibility of inverse orientational melting, i.e. with a decrease of temperature, for the systems under consideration is predicted.

2011-01-01

455