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1

Mixed matrix fast atom bombardment MS analysis of fullerenes  

SciTech Connect

As the synthesis of fullerenes commands increasing attention, analysis of these molecules is crucial for the determination of chemical composition and structure. Ionization methods employed for mass spectrometric analysis of fullerenes include electron bombardment, negative chemical ionization, laser desorption, fast atom bombardment, field ionization, and, more recently, electrospray ionization, and these techniques have played a pivotal role in the development of fullerence chemistry. Fast atom bombardment mass spectrometry has not been used extensively, presumably due to the low solubility of the samples in the matrix and the poor quality spectra that have been generated. In an attempt to increase the utility of FAB/MS, the authors have examined the addition of a cosolvent to the preferred matrix material, nitrobenzyl alcohol. Several solvents including chlorobenzene, dichlorobenzene, 1-methylnaphthalene, and 1-phenylnaphthalene have been employed successfully giving marked increases in ion abundance and signal duration.

Rieger, R.A.; Iden, C.R. [SUNY, Stony Brook, NY (United States)

1994-12-31

2

Probability of self-healing in damaged graphene bombarded by fullerene  

NASA Astrophysics Data System (ADS)

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

Xu, Zhi-Cheng; Zhong, Wei-Rong

2014-06-01

3

Secondary ion emission under keV carbon cluster bombardment  

E-print Network

Secondary ion mass spectrometry (SIMS) is a surface analysis technique capable of providing isotopic and molecular information. SIMS uses keV projectiles to impinge upon a sample resulting in secondary ion emission from nanometric dimensions...

Locklear, Jay Edward

2006-10-30

4

The production and sputtering of S2 by keV ion bombardment  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

5

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

NASA Astrophysics Data System (ADS)

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

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

1981-05-01

6

Sputtering of parent-like ions from large organic adsorbates on metals under keV ion bombardment  

NASA Astrophysics Data System (ADS)

Thin films of hydrocarbon molecules, unsaturated fatty acid and low molecular weight polystyrene deposited on different metal substrates (silver, copper and gold) were bombarded by 15 keV Ga ions and the secondary ions were mass- and energy-analysed by means of a time-of-flight secondary ion mass spectrometer. The samples were studied in order to evidence the effects of different substrates and coverages on the emission of the parent and cationised molecular ions, and to gain a better understanding of the large molecular ion emission processes. Ion beam degradation studies were realised for fundamental purposes too. In general, the kinetic energy distributions of metal-cationised molecules are broad in comparison with those of the parent ions, and of the smaller polystyrene fingerprint ions. In addition, the velocity distributions of the parent ions and of the metal-cationised molecules are similar. Parent ions of aromatic molecules are, on average, more energetic than those of aliphatic molecules. In the case of metal-cationised molecules, the three hypotheses of emission of a preformed complex, recombination in the selvedge and metastable decay of larger aggregates are critically reviewed in comparison with the experimental data. The recombination hypothesis cannot account for the whole set of observations. On the other hand, the very different evolutions of the parent ions and of the metal-cationised molecules in the degradation experiments cannot be explained solely in the frame of metastable decay reactions, although the kinetic energy measurements show that a significant fraction of the parent-like ions are produced in the vacuum. The augmentation of the secondary ion kinetic energy with increasing molecule size for triacontane monomers and dimers, and for silver-cationised polystyrene oligomers, is in disagreement with the sputtering by a single cascade atom, too. Finally, the discussion outlines the conditions that must be satisfied to model the experimental observations and proposes a view of the sputtering of these large molecular cations based on multiple collision processes and possible subsequent dissociation in the vacuum.

Delcorte, A.; Bertrand, P.

1998-09-01

7

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

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

8

Investigation of carbon buildup in simulations of multi-impact bombardment of Si with 20 keV C60 projectiles.  

PubMed

Beams of single C(+) ions are used for the incorporation of Si in the synthesis of thin films of SiC, which have a wide range of technological applications. We present a theoretical investigation of the use of C60 cluster beams to produce thin films of SiC on a Si substrate, which demonstrates that there are potential advantages to using C60(+) cluster ion beams over C(+) single ion beams. Molecular dynamics simulations of the multi-impact bombardment of Si with 20 keV normal incident C60 projectiles are performed to study the buildup of carbon and the formation of a region of Si-C mixing up to a fluence of 1.6 impacts/nm(2) (900 impacts). The active region of the Si solid is defined as the portion of target that contains almost all of the C atoms and the height ranges from 3 nm to more than 7 nm below the average surface height. The C fraction in the active region is calculated as a function of fluence, and a simple model is developed to describe the dependence of the C fraction on fluence. An analytic function from this model is fit to the data from the molecular dynamics simulations and extrapolated to predict the fluence necessary to achieve equilibrium conditions in which the C fraction is constant with fluence. The fraction of C atoms at equilibrium is predicted to be 0.19, and the fluence necessary to achieve 90% of this asymptotic maximum value is equal to 4.0 impacts/nm(2). PMID:24527764

Krantzman, Kristin D; Briner, Clarissa A; Garrison, Barbara J

2014-09-18

9

Recoils, flows and explosions: surface damage mechanisms in metals and semiconductors during 50 eV-50 keV ion bombardment  

NASA Astrophysics Data System (ADS)

We review some recent simulation results on mechanisms of damage production close to a surface during ion irradiation. The simulation work encompasses studies of several metals and semiconductors at irradiation energies ranging from a few tens of eVs to 50 keV. The results show that in dense metals the presence of a surface can dramatically enhance the damage production upto energies of at least 50 keV. The added damage is mostly in the form of vacancy clusters, which can extend quite deep, ˜10 nm, in the sample. In semiconductors, by contrast, the surface in general has little effect on the damage production in bulk.

Nordlund, K.; Keinonen, J.; Ghaly, M.; Averback, R. S.

1999-01-01

10

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

NASA Astrophysics Data System (ADS)

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

Cipolla, Sam J.

2014-07-01

11

The Stability of Cosmic Fullerenes and Fullerenic Aggregates  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

12

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. PMID:24162548

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

2013-01-01

13

Conversion of fullerenes to diamond  

SciTech Connect

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

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

1993-01-01

14

Conversion of fullerenes to diamond  

SciTech Connect

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

15

Fullerenes in Allende Meteorite  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

16

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

17

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

18

Instabilities by ionic bombardment  

E-print Network

This fluid dynamics video is an entry for the Gallery of Fluid Motion of the 66th Annual Meeting of the APS-DFD. This work reveals new types of interfacial instabilities that occur during forced-spreading of dielectric films subjected to ionic bombardment. We demonstrated that keeping the ionic bombardment strength constant, the appearance of instability patterns dramatically changes by varying viscosity of the bombarded droplet.

Mahmoudi, Seyed Reza; Adamiak, Kazimierz; Castle, G S Peter; Varanasi, Kripa K

2013-01-01

19

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

20

Medicinal applications of fullerenes  

PubMed Central

Fullerenes have attracted considerable attention in different fields of science since their discovery in 1985. Investigations of physical, chemical and biological properties of fullerenes have yielded promising information. It is inferred that size, hydrophobicity, three-dimensionality and electronic configurations make them an appealing subject in medicinal chemistry. Their unique carbon cage structure coupled with immense scope for derivatization make them a potential therapeutic agent. The study of biological applications has attracted increasing attention despite the low solubility of carbon spheres in physiological media. The fullerene family, and especially C60, has appealing photo, electrochemical and physical properties, which can be exploited in various medical fields. Fullerene is able to fit inside the hydrophobic cavity of HIV proteases, inhibiting the access of substrates to the catalytic site of enzyme. It can be used as radical scavenger and antioxidant. At the same time, if exposed to light, fullerene can produce singlet oxygen in high quantum yields. This action, together with direct electron transfer from excited state of fullerene and DNA bases, can be used to cleave DNA. In addition, fullerenes have been used as a carrier for gene and drug delivery systems. Also they are used for serum protein profiling as MELDI material for biomarker discovery. In this review we report the aspects of medicinal applications of fullerenes. PMID:18203430

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

2007-01-01

21

The topology of fullerenes  

PubMed Central

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

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

2015-01-01

22

Composition changes in Ar+ and e--bombarded SiC: an attempt to distinguish ballistic and chemically guided effects  

Microsoft Academic Search

We study with Auger electron spectroscopy (AES) the composition changes in amorphous SiC films with excess (i.e. free) C induced by bombardments either with 30 keV Ar+ on with 3 KeV e-. In Ar+-bombarded films the C accumulates at the surface without apparent depletion in the bombarded region, while the Si accumulates at the surface accompanied by major depletion near

Antonio Miotello; Lucia Calliari; Roger Kelly; Nadhira Laidani; Marco Bonelli; Luis Guzman

1993-01-01

23

Process for fullerene functionalization  

DOEpatents

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

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

1995-12-12

24

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

25

Fluorescence of Fullerenes  

Microsoft Academic Search

The photophysical properties of fullerenes are selectively reviewed, with an emphasis on fluorescence.\\u000a It is shown that fullerenes display several unusual photophysical properties, such as their fluorescence\\u000a anisotropy, and also that they can be used for a more complete understanding of general photophysical\\u000a processes like charge-transfer complexation and the heavy-atom effect. In spite of the work already carried\\u000a out, knowledge of

Susana Nascimento; Carlos Baleizão; Mário N. Berberan-Santos

26

Surface layer modification of ion bombarded HDPE  

NASA Astrophysics Data System (ADS)

Press-moulded, high density polyethylene (HDPE) samples were subjected to ion bombardment and effects of the modification studied. He + ions of energy 100 keV or Ar + ions of energy 130 keV were applied in the range of dose 1-30 × 10 15/cm 2 or 1-100 × 10 14/cm 2, respectively. This paper has been focused on structural changes of the surface layer. The consequences of the modification were studied with TOF-SIMS and FTIR-IRS techniques. The results point on two mechanisms taking place simultaneously: ionization of polymer macromolecules and chain scission--resulting in creation of macroradicals. Both of them produce oxidation and lead to significant release of hydrogen. The former diminishes for the highest ion doses, however, creation of molecular oxygen cannot be excluded. The latter in the case of Ar + ion bombardment is reflected by prevailing degradation of the surface layer of HDPE. Contrary to the effect of heavy ions, He + ion bombardment was found to produce significant increase of the material hardness, which was explained by crosslinking of polyethylene. A mechanism of polyacetylene formation, proceeding finally to cross-polymerization of the polymer was proposed. Apart from structural changes, the modification revealed additionally a possibility to improve the wettability of the polymer.

Bielinski, D.; Lipinski, P.; Slusarski, L.; Grams, J.; Paryjczak, T.; Jagielski, J.; Turos, A.; Madi, N. K.

2004-08-01

27

Transmutation of fullerenes.  

PubMed

Fullerenes were pyrolyzed by subliming them into a stream of flowing argon gas and then passing them through an oven heated to approximately 1000 degrees C. C(76), C(78), and C(84) all readily lost carbons to form smaller fullerenes. In the case of C(78), some isomerization was seen. Pyrolysis of (3)He@C(76) showed that all or most of the (3)He was lost during the decomposition. C(60) passes through the apparatus with no decomposition and no loss of helium. PMID:15740143

Cross, R James; Saunders, Martin

2005-03-01

28

Gas ejection from CR-39 under ion bombardment  

NASA Astrophysics Data System (ADS)

CR-39, a polymer widely used for nuclear track detectors, was bombarded with 500 keV protons and Ar ions, and with 2.8 MeV He ions. A mass analysis of the gas ejected during bombardment yielded CO2, CO, and H2. In the case of He ions, the amount of hydrogen was monitored during the bombardment by using elastic recoil analysis. The hydrogen spectrum was unchanged in spite of the gas loss, and it was concluded that the bombarded volume was being continuously replaced by new material, with very little carbon buildup. Since the bombardment leaves a clearly visible depression on the surface, the volume of gas ejected could be measured using a profile measuring apparatus. From this it was calculated that each 2.8 MeV He ion produces 23,000 ejected atoms. Since the range of these ions is 12.8?m, an ejection rate of one atom every 0.5 nm is determined, essentially half the atoms that the ion encounters. For 500 keV protons and argon ions, there are one atom ejected every 0.9nm and one atom every 0.16nm, respectively. We therefore propose that this gas ejection will contribute in an important way to the formation of etchable tracks.

Rickards, J.; Zironi, E. P.; Andrade, E.

1992-10-01

29

Combustion Synthesis of Fullerenes and Fullerenic Nanostructures In Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

30

Geological occurrence of fullerenes  

SciTech Connect

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

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

1992-01-01

31

Fullerene thin films  

SciTech Connect

The authors have been involved in the production of the purified fullerenes C{sub 60} and C{sub 70}. Previous research into fullerene thin films has been limited to mixtures of C{sub 60} and C{sub 70}. They plan to characterize high-purity C{sub 60} and C{sub 70} films in terms of photoconductivity, electrical conductivity, and optical absorption. They hope to do their studies with samples of purities better than 99% and 85% for C{sub 60} and C{sub 70}, respectively. Present work concerns the construction of an evaporation/deposition chamber. At this meeting, they hope to have grown and begun characterization of thin films on insulating and metallic substrates both with and without an additional metallic layer in {open_quotes}sandwich{close_quotes} structure.

Coram, G.J.; Castle, J.C.; Halas, N.J.

1992-12-01

32

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

33

C 60 Fullerene Polymers  

Microsoft Academic Search

\\u000a TEM investigations were performed on high temperature and pressure C60 fullerene. A mixed phase of alternating rhombohedral lamellae and tetragonal domains is formed. At higher temperatures 900–1173\\u000a K graphitic ‘hard’ carbon phases formed, via an inter-polymer interface instability and\\/or shear mechanism. This phase exhibited\\u000a a hardness of 10–15 GPa and a high degree of elastic recovery under indentation. The kinetics

R. A. Wood; M. H. Lewis; M. R. Lees; S. M. Bennington; M. G. Cain; N. Kitamura

34

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

35

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

36

Fast Atom Bombardment Mass Spectrometry.  

ERIC Educational Resources Information Center

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

Rinehart, Kenneth L., Jr.

1982-01-01

37

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

38

Production of fullerenic nanostructures in flames  

DOEpatents

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

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

1999-01-01

39

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

40

Spheroidal geometry approach to fullerene molecules  

Microsoft Academic Search

Graphite is an example of a layered material that can be bent to form fullerenes which promise important applications in electronic nanodevices. The spheroidal geometry of a slightly elliptically deformed sphere was used as a possible approach to fullerenes. We assumed that for a small deformation the eccentricity of the spheroid e?1. We are interested in the elliptically deformed fullerenes

R. Pincak

2005-01-01

41

Electron microscope examination of the surface topography of ion-bombarded copper  

Microsoft Academic Search

Transmission electron microscopy of thin, polycrystalline copper foils has revealed the formation of a sputtering structure after bombardment at normal incidence with Xe+, Cu+, or Pb+ ions of 50 to 80 keV energy. In general, the surface of each individual grain degenerates into a “hill and valley” structure, so as to develop those {100} faces lying nearest to the plane

D. J. Mazey; R. S. Nelson; P. A. Thackery

1968-01-01

42

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

43

Continuum approximation to fullerene molecules  

Microsoft Academic Search

The electronic and elastic properties of large fullerene molecules are studied. The low-lying electronic levels are described by the Dirac equations in (2+1) dimensions, and the intramolecular modes are given by the theory of elasticity. Coupling between electrons and phonons can also be written in a simple way. The quantum dynamics of the ions is modified by the appearance of

José González; Francisco Guinea; M. Angeles H. Vozmediano

1992-01-01

44

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

45

Energy deposition control during cluster bombardment: a molecular dynamics view.  

PubMed

Molecular dynamics simulations are performed to model C60 and Au3 bombardment of a molecular solid, benzene, in order to understand the energy deposition placement as a function of incident kinetic energy and incident angle. Full simulations are performed for 5 keV projectiles, and the yields are calculated. For higher energies, 20 and 40 keV, the mesoscale energy deposition footprint model is employed to predict trends in yield. The damage accumulation is discussed in relationship to the region where energy is deposited to the sample. The simulations show that the most favorable conditions for increasing the ejection yield and decreasing the damage accumulation are when most of the projectile energy is deposited in the near-surface region. For molecular organic solids, grazing angles are the best choice for achieving these conditions. PMID:18522431

Ryan, Kathleen E; Garrison, Barbara J

2008-07-15

46

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

47

Development of Mass Spectrometric Ionization Methods for Fullerenes and Fullerene Derivatives  

EPA Science Inventory

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

48

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

49

Dynamics displayed by energetic C60 bombardment of metal overlayers on an organic substrate.  

PubMed

Cluster bombardments of 15 keV C(60) on metal-organic interfaces composed of silver atoms and octatetraene molecules were modeled using molecular dynamics computer simulations. Dynamics revealed by the simulations include the formation of holes in the metal overlayers from which underlying organic molecules are sputtered predominantly by a rapid jetlike motion and the implantation of metal atoms and clusters in the underlying organic solid. Both of these processes negatively affect the information depth for cluster bombardment of metal-organic interfaces; therefore, the simulations presented here give a clear picture of the issues associated with depth profiling through metal-organic interfaces. PMID:23301726

Kennedy, Paul E; Postawa, Zbigniew; Garrison, Barbara J

2013-02-19

50

Reactive-ion bombardment of solid surfaces; a surface spectroscopy study  

SciTech Connect

A detailed experimental study of the chemistry and kinetics of reactive ion bombardment of Si and SiO/sub 2/ is presented. In addition, the development of models for molecular-ion physical sputtering and etching kinetics is reported. The studies were performed using a unique system allowing simultaneous bombardment of the surface by 0.5 to 3.0 keV reactive ions and examination of the surface by Auger Electron Spectroscopy (AES). A comparison of the model for physical sputtering with the measured etch yields shows that etching in these systems is primarily physical (for low pressure and ion flexes <50..mu..A/cm/sup 2/). However, there is an enhancement in the etch yield for CF/sub 3//sup +/ and SF/sub 5//sup +/ bombardment of SiO/sub 2/ above what is expected for physical sputtering alone. This is attributed to the formation and desorption of volatile compounds containing carbon and sulfur, respectively. With Si, a retardation is observed in the etch yield for CF/sub 3//sup +/ bombardment which is attributed to the need to physically resputter material deposited by the bombarding ion. Analysis of the AES spectra from these surfaces has shown that a carbide has formed. With SF/sub 5//sup +/ bombardment, a retardation is not observed.

Thomson, D.J.

1987-01-01

51

Synthesis, properties and transformations of fullerene peroxides  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

52

Ion bombardment of interplanetary dust  

NASA Technical Reports Server (NTRS)

It is thought that a fraction of the interplanetary dust particles (IDP's) collected in the stratosphere by high-flying aircraft represent materials ejected from comets. An investigation is conducted regarding the effects of ion bombardment on these particles, taking into account information on ion tracks and carbon in IDP's and laboratory data on charged particle bombardment of surfaces. It is found that the observational discovery of particle tracks in certain IDP's clearly indicates the exposure of these particles to approximately 10,000 years of 1-AU equivalent solar-particle fluences. If some erasure of the tracks occurs, which is likely when an IDP enters the upper atmosphere, then somewhat longer times are implied. The effects of the erosion and enhanced adhesion produced by ions are considered.

Johnson, R. E.; Lanzerotti, L. J.

1986-01-01

53

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

54

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

55

Characterizing the Early Impact Bombardment  

NASA Technical Reports Server (NTRS)

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

Bogard, Donald D.

2005-01-01

56

Fullerenes produced by harnessing sunlight  

SciTech Connect

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

Not Available

1993-08-01

57

Production of fullerenes with concentrated solar flux  

NASA Astrophysics Data System (ADS)

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

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

1994-01-01

58

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

59

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

60

Direct transformation of graphene to fullerene.  

PubMed

Although fullerenes can be efficiently generated from graphite in high yield, the route to the formation of these symmetrical and aesthetically pleasing carbon cages from a flat graphene sheet remains a mystery. The most widely accepted mechanisms postulate that the graphene structure dissociates to very small clusters of carbon atoms such as C(2), which subsequently coalesce to form fullerene cages through a series of intermediates. In this Article, aberration-corrected transmission electron microscopy directly visualizes, in real time, a process of fullerene formation from a graphene sheet. Quantum chemical modelling explains four critical steps in a top-down mechanism of fullerene formation: (i) loss of carbon atoms at the edge of graphene, leading to (ii) the formation of pentagons, which (iii) triggers the curving of graphene into a bowl-shaped structure and which (iv) subsequently zips up its open edges to form a closed fullerene structure. PMID:20489712

Chuvilin, Andrey; Kaiser, Ute; Bichoutskaia, Elena; Besley, Nicholas A; Khlobystov, Andrei N

2010-06-01

61

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

62

Fullerene–biomolecule conjugates and their biomedicinal applications  

PubMed Central

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

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

2014-01-01

63

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

64

Production of Endohedral Fullerenes by Ion Implantation  

SciTech Connect

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

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

2007-05-31

65

Gamma-Ray Spectrometer Measurements of Fluorine and Lithium under Proton Bombardment  

Microsoft Academic Search

The spectra of the gamma-radiation emitted by lithium and fluorine under proton bombardment have been investigated with a spectrometer which measures the total energy of electron pairs produced in a thin radiator exposed to the gamma-radiation. A long-suspected 14.8-Mev gamma-ray line from the 440-kev resonance in lithium has been clearly resolved from the well-known sharp line at 17.6 Mev. The

R. L. Walker; B. D. McDaniel

1948-01-01

66

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

67

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

68

Stable transformation of papaya via microprojectile bombardment  

Microsoft Academic Search

Stable transformation of papaya (Carica papaya L.) has been achieved following DNA delivery via high velocity microprojectiles. Three types of embryogenic tissues, including immature zygotic embryos, freshly explanted hypocotyl sections, and somatic embryos derived from both, were bombarded with tungsten particles carrying chimeric NPTII and GUS genes. All tissue types were cultured prior to and following bombardment on half-strength MS

Maureen M. M. Fitch; Richard M. Manshardt; Dennis Gonsalves; Jerry L. Slightom; John C. Sanford

1990-01-01

69

Giant Fullerenes for Target Specific Drug Delivery  

NASA Astrophysics Data System (ADS)

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

Courtney, Robert; Kiefer, Boris

2013-03-01

70

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 10 3-10 4, 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.

2007-02-01

71

Fullerene growth from encapsulated graphene flakes.  

PubMed

The direct in situ observation of fullerene formation encapsulated within a graphene ridge has been made possible using an aberration corrected transmission electron microscope (AC-TEM). An atom-by-atom mechanism was proposed based on in situ AC-TEM observations. First principle calculations found a continuous energy decrease upon the addition of carbon atoms to the edge of the graphene flakes, which mimics the fullerene growth steps and supports the atom-by-atom mechanism. The ridged graphene structure worked as a container for pinning small graphene flakes and capturing carbon atoms, which increased the growth probability of the fullerene structure within the small encapsulated space. PMID:25123407

Neng, Wan; Shuang-ying, Lei; Jun, Xu; Matteo, Martini; Yi-long, Zhou; Shu, Wan; Li-tao, Sun; Qing-an, Huang

2014-10-01

72

Absolute luminescence efficiency of ion-bombarded solid argon  

NASA Astrophysics Data System (ADS)

We have directly measured the absolute efficiency of the 9.8-eV M-band luminescence from the decay of Ar*2 excimers in solid Ar bombarded by 1.5-MeV He+ and 10-50-keV H+ ions. About 54% of the electronic energy deposited by the projectiles is converted to 9.8-eV luminescence energy, or about 5.5 photons per 100-eV deposited. The efficiency is also found to be independent of ion and ion energy for those tested over a range of stopping cross sections from 6.5 to 400 eV/(1015 atoms/cm2). This work clearly establishes the M band as the major relaxation pathway for electronically deposited energy in solid Ar, a pathway that is an important source of radiation damage and sputtering and which can be affected by electron emission.

Grosjean, D. E.; Vidal, R. A.; Baragiola, R. A.; Brown, W. L.

1997-09-01

73

Comment on ``Favourable structures for higher fullerenes''  

NASA Astrophysics Data System (ADS)

A corrected version of the ring spiral computer code finds 1812 spectrally distinct fullerene isomers of C 60, 22 more isomers than are found by the independent computer enumeration method of Liu, Schmalz and Klein.

Manolopoulos, David E.

1992-05-01

74

Applications of Functionalized Fullerenes in Tumor Theranostics  

PubMed Central

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

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

2012-01-01

75

Recent advances in fullerene science (Invited)  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

76

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

77

Sputtering yields for C60 and Au3 bombardment of water ice as a function of incident kinetic energy.  

PubMed

The total sputtering yields for water ice due to kiloelectronvolt cluster bombardment have been measured and compared to the predictions made by the mesoscale energy deposition footprint (MEDF) model. For C60 bombardment, the experimental yield varies almost linearly from 820 water molecule equivalents at an incident kinetic energy of 10 keV to 10 100 water molecule equivalents at a kinetic energy of 120 keV. For Au3 bombardment, the experimental yield varies almost linearly from 630 water molecule equivalents at an incident energy of 10 keV and rises to 1200 water molecule equivalents at 25 keV. The MEDF model is used to calculate relative yield trends with respect to incident energy using short-time molecular dynamics simulations. The results of these calculations indicate that the model can effectively predict the yield trends observed for these two clusters in experiments, although there is a consistent overestimate of the predicted induced C60 yield. It is hypothesized that this overestimate can be explained by the absence of reactions and ionization processes in the current simulations. Despite this omission, experimental yield trends can be accurately predicted using relatively small amounts of computer time. The success of the model in predicting the yield of water from ice films using a variety of energies and projectiles suggests this approach may greatly aid in the optimization of experimental configurations. PMID:17503768

Russo, Michael F; Szakal, Christopher; Kozole, Joseph; Winograd, Nicholas; Garrison, Barbara J

2007-06-15

78

Fullerene derivatives as electron donor for organic photovoltaic cells  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

79

Fullerenes in Meteorites and the Nature of Planetary Atmospheres  

Microsoft Academic Search

We address the hypothesis that fullerenes are an important carrier phase for noble gases in carbonaceous chondrite meteorites. Unlike other proposed carbon carriers, nanodiamond, SiC, graphite and phaseQ, fullerenes are extractable in an organic solvent. It is this unique property, in fact, this may be why fullerene molecules or fullerene-related compounds were overlooked as a carrier phase of noble gases

Luann Becker; ROBERT J. POREDA; JOSEPH A. NUTH; FRANK T. FERGUSON; Feng Liang; W. Edward Billups

80

An electron acceptor challenging fullerenes for efficient polymer solar cells.  

PubMed

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

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

2015-02-01

81

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

82

The Effect on Cell-Adhesion of Ion-Bombardment into Collagen  

NASA Astrophysics Data System (ADS)

A study has been conducted on the dependence of cell-adhesion on ion-bombarded collagen-coated polystyrene. Type I collagen was coated onto a polystyrene plate and bombarded with Ar+ at 50 keV at doses between 1× 1013 and 1× 1016 ions/cm2. Bovine aorta endothelial cells were cultured onto ion-bombarded specimens in a culture medium. The bovine endothelial cells adhered surfaces were mounted on parallel-plate flow chambers, in a flow system prepared for cell-adhesiveness tests with a flowing shear stress of 2 Pa. Adhesion strength was measured by the number of cells adhered to the specimen per 1 mm2. The cell-adhesion of Ar+-ion-bombarded specimens increased for doses up to 1× 1014 ions/cm2, and decreased at doses above 1× 1015 ions/cm2. IR spectra showed that the structure of the collagen was destroyed as the dose increased. The increase in cell-adhesion at the lower dose region around 1× 1014 ions/cm2 is probably due to less destruction of collagen structure, and an increase in adhesion by the generation of new bonds around ion tracks in the interface between the collagen and polystyrene.

Yokoyama, Yoshiro; Tsukamoto, Takeyo; Kobayashi, Tomohiro; Iwaki, Masaya

2003-07-01

83

Computer simulation study of fullerene translocation through lipid membranes  

Microsoft Academic Search

Recent toxicology studies suggest that nanosized aggregates of fullerene molecules can enter cells and alter their functions, and also cross the blood–brain barrier. However, the mechanisms by which fullerenes penetrate and disrupt cell membranes are still poorly understood. Here we use computer simulations to explore the translocation of fullerene clusters through a model lipid membrane and the effect of high

Jirasak Wong-Ekkabut; Svetlana Baoukina; Wannapong Triampo; I.-Ming Tang; D. Peter Tieleman; Luca Monticelli

2008-01-01

84

Constructing I[subscript h] Symmetrical Fullerenes from Pentagons  

ERIC Educational Resources Information Center

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

Gan, Li-Hua

2008-01-01

85

Fullerene concentration dependent bimolecular recombination in organic photovoltaic films  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

86

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

87

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

88

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

89

Supramolecular [60]fullerene chemistry on surfaces.  

PubMed

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

Bonifazi, Davide; Enger, Olivier; Diederich, François

2007-02-01

90

Polymeric templating and alignment of fullerenes  

NASA Astrophysics Data System (ADS)

Fullerene research has advanced to elevated levels in a short period of time due to the unique chemical and physical properties of the caged molecule that have been utilized in numerous applications. Due to the spherical shape of the fullerene molecule which allows for a hollow cavity, encapsulation of atoms or small molecules can occur within the ball structure. This encapsulation creates an endohedral component that is limited from interacting with other molecules which creates potential of control over electronic information of the isolated molecule. Endohedral fullerenes have the potential as serving as the base unit in a quantum computer if control over global alignment is attained. Thus, by using the inherent self-assembling capabilities of some organic materials, ordered endohedral fullerenes can be achieved. This dissertation investigates the ability to use self-assembling strategies to obtain alignment which include ordering within a morphologically controlled copolymer matrix, forming a supramolecular polymer complex with cyclodextrin, and encapsulation within the helical wrap of polymer chains. The ultimate goal is to understand the dynamics that control association and orientation of varying fullerene-based molecules in each strategy in order to maximize control over the final alignment of endohedral elements.

Kincer, Matthew Ryan

91

Ion bombardment and disorder in amorphous silicon  

SciTech Connect

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

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

1997-07-01

92

Depth Profiling by Energetic Cluster Bombardment Dr. Barbara Garrison  

E-print Network

Depth Profiling by Energetic Cluster Bombardment Dr. Barbara Garrison Shapiro Professor of solids by energetic clusters has drawn significant attention since it has been found experimentally projectiles. These properties of energetic cluster bombardment enable the depth profiling of various inorganic

Bjørnstad, Ottar Nordal

93

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

94

Observation of ion bombardment damage in silicon  

Microsoft Academic Search

Thin films of single crystals of both n-type and p-type silicon contain disordered zones ? 50 Å in diameter, discernible in the electron microscope after bombardment with ? 10 Ne ions cm. As the dose increases these zones become more numerous until eventually (? 10 ions cm) they overlap, creating a continuous surface layer which electron diffraction shows to be

D. J. Mazey; R. S. Nelson; R. S. Barnes

1968-01-01

95

Fullerene-linked Pt nanoparticle assemblies.  

PubMed

Fullerene-Pt nanoparticle assemblies were prepared by attachment and immobilisation of different Pt nanoparticles on a gold electrode using molecular layers of C60 as a linker system. These assemblies were active for the methanol oxidation following treatment with CO. PMID:15216366

Roth, C; Hussain, I; Bayati, M; Nichols, R J; Schiffrin, D J

2004-07-01

96

Survey of Natural Fullerenes in Southwestern China  

NASA Astrophysics Data System (ADS)

Unusually high concentration of C60/C70 was discovered in a coal sample from China. Extensive analysis including TEM analysis suggests a surprising occurrence of the fullerenes in nature by shock heating, which we suggest to have been generated by coal gas explosion in the underground.

Ã'sawa, Eiji; Ozawa, Masaki; Chijiwa, Kazutoyo; Hoyanagi, Kouichi; Tanaka, Kazuyoshi; Kusunoki, Michiko

2001-10-01

97

Survey of Natural Fullerenes in Southwestern China  

NASA Astrophysics Data System (ADS)

Unusually high concentration of C60/C70 was discovered in a coal sample from China. Extensive analysis including TEM analysis suggests a surprising occurrence of the fullerenes in nature by shock heating, which we suggest to have been generated by coal gas explosion in the underground. .

Ôsawa, Eiji; Ozawa, Masaki; Chijiwa, Kazutoyo; Hoyanagi, Kouichi; Tanaka, Kazuyoshi; Kusunoki, Michiko

2001-10-01

98

Synthetic chemistry with fullerenes. Photooxygenation of olefins  

SciTech Connect

Under irradiation with visible or UV (>290 nm) light in the presence of molecular oxygen and a minute amount of fullerenes, olefins and dienes undergo ene and Diels-Alder reactions with singlet oxygen to give photooxygenation products. The regio-and stereoselectives of the photooxygenation of {beta}-myrcene, (+)-pulegone, 4-methylpent-3-en-2-ol, and (+)-limonene were very similiar to those observed in known singlet oxygen reactions, indicating that the fullerene-sensitized reaction generates free singlet oxygen. The efficiency of fullerenes and conventional sensitizers was qualitively examined by using the Diels-Alder reaction between {sup 1}O{sub 2} and furan-2-carboxylic acid as a probe. Among those examined, C{sub 70} was found to be the most effective. The reaction was the fastest and completed with as little as 0.0001 equiv of C{sub 70}. C{sub 60} and hematoporphyrin were found to be of similiar efficiency. The methanofullerene 13, which lacks one olefinic conjunction in the C{sub 60} core, was as good as C{sub 60} itself, but the aminofullerene 14, lacking six double bonds, was quite inferior. The fullerene carboxylic acid 15, which was previously shown to show considerable biochemical activity, was found to be capable of generating singlet oxygen in aqueous DMSO. 25 refs., 1 tab.

Tokuyama, Hidetoshi; Nakamura, Eiichi [Tokyo Institute of Technology, Merguro, Tokyo (Japan)

1994-03-11

99

Functionalization of silicon crystal surface by energetic cluster ion bombardment.  

PubMed

We report the creation of a functional nanostructure on a Si crystal surface by 200 keV C60(++) cluster ion bombardment (CIB). We found that the modified layer produced by CIB includes two sublayers with different nanostructures. The top 24-nm-thick sublayer is an agglomeration of 5-nm-sized amorphous Si nanodots (a-Si NDs). The deeper 10-nm-thick sublayer is a transient layer of disordered Si as an interface between the a-Si top sublayer and the bulk Si(100). The top a-Si sublayer and the nc-Si transient layer are formed by the local heating effect and shock wave effect, respectively, induced by the cluster ion impacts. The photoluminescence (PL) spectra of the CIB-modified Si samples revealed an emission line centered at a photon energy of 1.92 eV. The absorption spectra of the modified samples exhibit enhanced light absorption at this photon energy. The parameters of the PL line require ascribing the emission origin to the quantum-confinement-induced optical transitions in the a-Si nanodots. The core-shell structure of a-Si NDs is confirmed by detection of an additional PL line centered at 2.5 eV. Analysis of the Rutherford backscattering (RBS) and the PL spectra implies the existence of -Si--O- bonds in the nanodot outer shells, which are responsible for the additional PL line. The obtained results demonstrate the valuable potential of CIB for the controllable fabrication of Si surface nanostructures, which is attractive for optoelectronics and nanoelectronics. The obtained results elucidate the evolution of structure modification occurring in silicon due to the injection of energetic C60 cluster ions with an energy of hundreds of keV. PMID:23447968

Lavrentiev, Vasily; Vacik, Jiri; Dejneka, Alexandr; Jastrabik, Lubomir; Vorlicek, Vladimir; Chvostova, Dagmar; Potucek, Zdenek; Narumi, Kazumasa; Naramoto, Hiroshi

2012-12-01

100

Cluster size dependence and yield linearity in cluster bombardment simulations of benzene.  

PubMed

Cluster bombardment of a molecular solid, benzene, is modeled using molecular dynamics simulations in order to investigate the effect of projectile cluster size and incident energy on the resulting yield. Using the mesoscale energy deposition footprint (MEDF) model, we are able to model large projectiles with incident energies from 5 to 140 keV and predict trends in ejection yield. The highest ejection yield at 5 keV was observed at C 20 and C 60, but shifts toward larger clusters for higher energies. These trends are explained in terms of the MEDF model. For these projectiles, all of the incident energy is deposited in the near-surface region, which is optimal for the projectile energy to contribute to the ejection yield. Because the energy is deposited in the optimal position for contributing to the ejection process, the yields increase linearly with incident energy with a slope that is nearly independent of the cluster size. PMID:18686971

Ryan, Kathleen E; Garrison, Barbara J

2008-09-01

101

Fullerenes: An extraterrestrial carbon carrier phase for noble gases  

PubMed Central

In this work, we report on the discovery of naturally occurring fullerenes (C60 to C400) in the Allende and Murchison meteorites and some sediment samples from the 65 million-year-old Cretaceous/Tertiary boundary layer (KTB). Unlike the other pure forms of carbon (diamond and graphite), fullerenes are extractable in an organic solvent (e.g., toluene or 1,2,4-trichlorobenzene). The recognition of this unique property led to the detection and isolation of the higher fullerenes in the Kratschmer/Huffmann arc evaporated graphite soot and in the carbon material in the meteorite and impact deposits. By further exploiting the unique ability of the fullerene cage structure to encapsulate and retain noble gases, we have determined that both the Allende and Murchison fullerenes and the KTB fullerenes contain trapped noble gases with ratios that can only be described as extraterrestrial in origin. PMID:10725367

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

2000-01-01

102

Fullerene-based materials research and development. LDRD final report  

SciTech Connect

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

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

1995-05-01

103

Work function of metallic surfaces bombarded with cesium ions  

NASA Astrophysics Data System (ADS)

Reduction of work function due to the build-up of cesium coverage on beryllium, molybdenum, and tungsten caused by cesium ion bombardment was investigated for incident energies between 5 eV and 1 keV. Surface characterization was performed as a function of incident ion energy and dose using Auger spectra and work function measurements. A steady state surface coverage is achieved in all cases for a dose of less than 10 16 ions/cm 2. The coverage is strongly dependent on target mass. Beryllium has nearly monolayer coverage at all beam energies, while above 150 eV molybdenum has less than 50% coverage and tungsten has less than 20% coverage. The minimum steady state work function at 60% coverage can be achieved on molybdenum and tungsten at 100 and 45 eV, respectively. The effects of hydrogen coadsorption are also examined. The development of the surface coverage occurs due to the effects of implantation, reflection, and sputtering. A Monte Carlo calculation shows that a surface coverage of cesium on beryllium inhibits sputtering, which should be true for other light elements.

Tompa, G. S.; Carr, W. E.; Seidl, M.

104

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

105

Photoconductivity in Donor-Acceptor Polyferrocenylsilane-Fullerene Composite Films  

E-print Network

-state photoconductive and photovoltaic devices using thin films of blends of poly(ferrocenylmethylphenylsilane) (PFMPSPhotoconductivity in Donor-Acceptor Polyferrocenylsilane-Fullerene Composite Films Paul W. Cyr

106

Biomolecular Emission by Swift Heavy Ion Bombardment  

NASA Astrophysics Data System (ADS)

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 Cu4+ 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; Ninomiya, Satoshi; Jones, Brian N.; Seki, Toshio; Aoki, Takaaki; Webb, Roger; Matsuo, Jiro

2011-01-01

107

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

108

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

109

Effects of ion and micrometeorite bombardment on mineral surfaces: application to Eros, the Moon, and Mercury  

NASA Astrophysics Data System (ADS)

We study in the laboratory the effects of ion and micrometeorite bombardment on mineral surfaces of airless bodies such as asteroids, the Moon, and Mercury. We use 4 keV He and 1 keV H ions to simulate the solar wind and nanosecond laser pulses to simulate micrometeorite impacts. Related to the question of the origin of the Na exospheres around the Moon and Mercury, we studied sputtering of Na from plagioclase feldspars and from Na deposited on olivine and on albite. Chemical characterization of the samples is made by X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), secondary ion mass spectrometry (SIMS), and neutral mass spectrometry. We find that ion bombardment depletes Na from the surface of the feldspars but that the Na segregates back to the surface in a few hours at room temperature. Analysis of the removal of sodium adsorbed on the surface of olivine by He ion irradiation gives a sputtering cross section in line with what is expected for knock-on sputtering, and five orders of magnitude larger than for photo-stimulated desorption. We also determined that the energy distribution of the sputtered ions has a peak at a few eV and a long tail to about 50 eV. Regarding the interpretation of NEAR data from Eros we irradiated powders of olivine with nanosecond 248 nm laser pulses and studied reflectance changes in the visible and near-infrared and chemical changes with XPS. We have collected the ejecta on a quartz-crystal microbalance to quantify the amount of ejecta per pulse. The deposit was found to be crystalline olivine. When collected on a fine-grained olivine surface, it produced visible darkening. We will also report on experiments that serve to explain sulfur depletion at Eros by the solar wind and micrometeorite bombardment. Supported by NASA Cosmochemistry and NEAR Data Analysis Programs.

Baragiola, R. A.; Loeffler, M. J.; Dukes, C. A.; Chang, W. Y.; Fitz-Gerald, J. M.; McFadden, L. A.

2004-11-01

110

Porous silica doping by ion bombardment  

SciTech Connect

A new approach to porous-silica doping is via ion bombardment and exposure of the damaged structure to a controlled atmosphere. As a case study, SiO{sub 2} samples, bombarded with Ar{sup 2+} in a CO{sub 2} ambient and suitably processed, underwent an infrared spectroscopic investigation. The resulting data could be interpreted by assuming the addition of CO{sub 2} to the SiO{sub 2} skeleton at the diradical silicon defects produced by the bombardment. This addition takes place first via the formation of a carboxylate group, which evolves after heat treatment to an ester-like center, and eventually to a carboxilic acid after exposure to water vapor. Ab initio molecular-dynamics simulations of the interaction between CO{sub 2} and a silicon diradical are consistent with the above picture and suggest also the existence of an intermediate, in which tetrahedral carbon is bonded to the two silicon atoms and to two oxygen atoms.

Cerofolini, G.F.; Meda, L.; Anselmino, A.; Ranghino, G. [EniChem--Ist. Guido Donegani, Novara (Italy)

1996-12-31

111

Biological Effects of Low Energy Ar+ Ion Bombardment on Silkworm Eggs: a Novel Animal Model  

NASA Astrophysics Data System (ADS)

In this study, we found for the first time that silkworm eggs were able to survive in vacuum for a long period of time. Subsequently, low energy Ar+ ions with different energies and fluences were used to bombard silkworm eggs so as to explore the resulting biological effects. Results showed that (i) the exposure of silkworm eggs to vacuum within 10 min did not cause significant impact on the hatching rates, while the irradiation of silkworm eggs by Ar+ ions of 25 keV or 30 keV with fluences ranging from 2.6×2.6 × 1015 ion/cm2 to 8×2.6 × 1015 ion/cm2 caused a significant impact on the hatching rates, and the hatching rates decreased with the increase in the fluence and energy level; (ii) the irradiation of silkworm eggs by Ar+ ions of 30 keV with a fluence of 8×2.6 × 1015 ion/cm2 or 9×2.6 × 1015 ion/cm2 resulted in a noticeable etching on the egg shell surface which could be observed by a scanning electron microscope; and (iii) the irradiation of silkworm eggs by Ar+ ions of 30 keV with a fluence of 9×2.6 × 1015 ion/cm2 generated several mutant phenotypes which were observed in the 5th instar silkworms and a moth.

Xu, Jiaping; Wu, Yuejin; Liu, Xuelan; Yuan, Hang; Yu, Zengliang

2009-06-01

112

Calixarene linked bis-porphyrin hosts for fullerenes and the assembly of supramolecular ferrocene-porphyrin-fullerene triads.  

E-print Network

??Porphyrins and fullerenes are excellent substituents for the construction of photoactive assemblies due to their unique redox and photoelectronic properties. Upon irradiation these assemblies can… (more)

Paauwe, John David van

2013-01-01

113

Preparation of fullerene/glass composites  

DOEpatents

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

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

1995-01-01

114

Carbon and fullerene nanomaterials in plant system  

PubMed Central

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

2014-01-01

115

Synthesis of fullerene-acene dyads  

NASA Astrophysics Data System (ADS)

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

Cho, Claire Eunhye

116

Enhancement of sputtering yields due to C60 versus Ga bombardment of Ag[111] as explored by molecular dynamics simulations.  

PubMed

The mechanism of enhanced desorption initiated by 15-keV C60 cluster ion bombardment of a Ag single crystal surface is examined using molecular dynamics computer simulations. The size of the model microcrystallite of 165,000 atoms and the sophistication of the interaction potential function yields data that should be directly comparable with experiment. The C60 model was chosen since this source is now being used in secondary ion mass spectrometry experiments in many laboratories. The results show that a crater is formed on the Ag surface that is approximately 10 nm in diameter, a result very similar to that found for Au3 bombardment of Au. The yield of Ag atoms is approximately 16 times larger than for corresponding atomic bombardment with 15-keV Ga atoms, and the yield of Ag3 is enhanced by a factor of 35. The essential mechanistic reasons for these differences is that the C60 kinetic energy is deposited closer to the surface, with the deeply penetrating energy propagation occurring via a nondestructive pressure wave. The numbers predicted by the model are testable by experiment, and the approach is extendable to include the study of organic overlayers on metals, a situation of growing importance to the SIMS community. PMID:14632043

Postawa, Zbigniew; Czerwinski, Bartlomiej; Szewczyk, Marek; Smiley, Edward J; Winograd, Nicholas; Garrison, Barbara J

2003-09-01

117

STM/STS investigations of fullerene C(60), endohedral metallofullerenes M C(82) and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Since their discovery, fullerenes and their derivatives have received great attentions because they opened many new fields in science and technology. Among them, endohedral fullerenes, fullerenes encapsulating one or more atoms in their hollow carbon cases, have been predicted to have novel properties which are unexpected for empty fullerenes. However, the difficulty in producing pure samples of endohedral fullerenes in large quantities have hindered their experimental exploration. The motivation of this research is to understand their properties. In this research, endohedral monometallofullerenes M@Csb{82} (M = Nd, Dy) have been investigated by in-situ ultra high vacuum scanning tunneling microscopy and tunneling spectroscopy. As a comparison, the well-understood fullerene Csb{60} has been studied first by the same technique. On the basal plane of cleaved highly oriented pyrolytic graphite (HOPG) (0001) surface, arriving Csb{60} molecules assemble and grow into highly ordered, extended overlayers in hexagonal-close-packing. Starting from the second layer, the growth mode of Csb{60} transforms from 2-dimensional dendrite islanding to 3-dimensional island formation upon the variation of growth rate and substrate temperature. A band gap of 1.5 ± 0.2 eV is observed in the tunneling spectroscopy of the Csb{60} films. On the contrary, endohedral metallofullerenes do not form ordered structures on HOPG surface under the same conditions of growing Csb{60} films, instead, they gather into clumped clusters. These molecules may induce a symmetric distributed (sqrt{3}×sqrt{3})R30sp° superstructure of the HOPG substrate around them. The superstructure can be realized theoretically by a computer simulation. The HOMO-LUMO gap of a single molecule is measured to be 0.6 ± 0.2 eV by tunneling spectroscopy, consistent with the UV-VIS-Near IR absorption spectrum of M@Csb{82}. On the top of Csb{60} films, Nd@Csb{82} molecules form close-packed 2-D structures of dimers, trimers, ..., and crystalline islands, while Dy@Csb{82} molecules still aggregate as 3-D clusters. The intermolecular interaction is believed to be dominated by a dipole-dipole interaction. After experiencing a strong electric field applied by an STM tip, the Nd@Csb{82} molecules will undergo a structural transformation from the close-packing to ring like configurations. The rings are well-shaped (as a hexagonal polygon), well-numbered (consisting of six or multiples of six molecules) and stable. The mechanism of the tip-driven transformation are discussed. We suggest that molecules within these rings are bonded covalently. As a byproduct, we found a new path to generate carbon nanotubes. After the overlaying mixture of Csb{60} and M@Csb{82} on an HOPG surface has been irradiated with KeV electrons, carbon nanotubes are observed laying on the surface. They are straight, clean and have diameters in the range of 2-50 nm and length up to 3 mum. The detailed atomic images of the tube walls show helical arrangements of the honeycomb structure of a graphite (0001) surface. The formation mechanism of these tubes also is discussed. Future research directions are identified. The systematic study of Lanthanide's endohedral fullerenes would uncover the roles of the metal atoms. More detailed understanding of the formation of the rings and the nanotubes from endohedral metallofullerenes could lead to finding methods for their mass production and novel applications.* ftn*Originally published in DAI Vol. 58, No. 11. Reprinted here with corrected author name.

Lin, Nian

118

Sponge-like molecular cage for purification of fullerenes.  

PubMed

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

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

2014-01-01

119

Computer simulation study of fullerene translocation through lipid membranes  

E-print Network

nanoparticles depends on their solubility in water; for example, the cytotoxicity of pristine fullerene is seven fullerene production at a scale of tons is already under way1 . Although the effects of nanoparticles impact of nanoparticles are still scarce2 . Inhaled ultrafine carbon particles deposit in the lung3

Wong-Ekkabut, Jirasak

120

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...

121

Optical absorption spectra and geometric e ects in higher fullerenes  

E-print Network

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

Harigaya, Kikuo

122

Storage of nuclear materials by encapsulation in fullerenes  

DOEpatents

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

Coppa, Nicholas V. (Los Alamos, NM)

1994-01-01

123

Incomplete Exciton Harvesting from Fullerenes in Bulk Heterojunction Solar  

E-print Network

Incomplete Exciton Harvesting from Fullerenes in Bulk Heterojunction Solar Cells George F. Burkhard-acceptor interface. This result has implications for most state of the art organic solar cells, since all of the most efficient devices use fullerenes as electron acceptors. Since their inception, organic photovoltaics (OPVs

McGehee, Michael

124

Nanoencapsulation of Fullerenes in Organic Structures with Nonpolar Cavities  

NASA Astrophysics Data System (ADS)

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

Murthy, C. N.

2005-01-01

125

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

126

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

PubMed

Adhesion of commercially produced fullerene fine particles to Cryptomeria japonica, Chamaecyparis obtusa and Camellia japonica pollen grains was investigated. The autofluorescence of pollen grains was affected by the adhesion of fullerene fine particles to the pollen grains. The degree of adhesion of fullerene fine particles to the pollen grains varied depending on the type of fullerene. Furthermore, germination of Camellia japonica pollen grains was inhibited by the adhesion of fullerene fine particles. PMID:24198486

Aoyagi, Hideki; Ugwu, Charles U

2011-01-01

127

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

PubMed Central

Adhesion of commercially produced fullerene fine particles to Cryptomeria japonica, Chamaecyparis obtusa and Camellia japonica pollen grains was investigated. The autofluorescence of pollen grains was affected by the adhesion of fullerene fine particles to the pollen grains. The degree of adhesion of fullerene fine particles to the pollen grains varied depending on the type of fullerene. Furthermore, germination of Camellia japonica pollen grains was inhibited by the adhesion of fullerene fine particles. PMID:24198486

Aoyagi, Hideki; Ugwu, Charles U

2011-01-01

128

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

129

Characteristic fragmentation of polysiloxane monolayer films by bombardment with monatomic and polyatomic primary ions in TOF-SIMS.  

PubMed

This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs(+), C(60)(+) (10 keV), Bi(1)(+), and Bi(3)(+) (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (M(n)) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights (MW) from 600 and 1000 Da. For each film, Bi projectiles resulted in the emission of positive silver cluster ions from the substrate under the polymer overlayer and peaks corresponding to silver cluster ions with larger mass were observed by impact of polyatomic 25 keV Bi(3)(+) projectiles. In addition, depending on the change of energy of Bi (3) (+) , a different pattern of fragments was observed. With Cs(+) and C(60)(+) impact, however, the emission of silver cluster ions was not detected. In the case of C(60)(+) impact for PDMS-6140, peaks corresponding to silver-cationized intact oligomers were not observed. In this paper, these results are explained by the possible bombardment mechanism for each projectile, based on its mass, energy, and split trajectories of the component atoms under the polyatomic impact. PMID:22042500

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

2012-01-01

130

Energetic ion bombarded Fe/Al multilayers  

SciTech Connect

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

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

2006-05-15

131

Callisto: A lunar-like bombardment?  

NASA Technical Reports Server (NTRS)

Voyager spacecraft imagery of the Galilean satellites in 1979 revealed Callisto and portions of Ganymede to be densely cratered, but nonetheless deficient in craters larger than 30 km relative to the cratered highlands of the Moon, Mars, and Mercury. This relative deficiency of large craters could have been due to the complete obliteration of large craters through viscous relaxation in the icy surfaces of Ganymede and Callisto at a time when their surfaces were presumably warmer and more mobile or the deficiency could have stemmed from a relative depletion of large impacting bodies in the Jupiter system, compared with the terrestial planets. To test which alternative is correct, and, specifically, to see whether Callisto was subjected to a lunar-like bombardment, two areas on the heavily cratered lunar farside were compared with an area on Callisto. It was concluded that the Moon and Callisto must have bombarded by two different populations and though viscous relaxation could have modified, or even completely obliterated, craters on Callisto's surface, it could not hve been solely responsible for the observed deficiency of large craters on Callisto relative to the moon.

Ruzicka, A.

1984-01-01

132

Solitonic fullerene structures in light atomic nuclei  

E-print Network

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

R. A. Battye; P. M. Sutcliffe

2001-02-16

133

Infrared spectroscopy of fullerene C60/anthracene adducts  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

134

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

135

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

136

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

137

Diffuse Interstellar Bands in (Proto-) Fullerene-Rich Environments  

NASA Astrophysics Data System (ADS)

The recent infrared detection of fullerenes (C60 and C70) in Planetary Nebulae (PNe) and R Coronae Borealis (RCB) stars offers a beautiful opportunity for studying the diffuse interstellar bands (DIBs) in sources where fullerenes are abundant. Here we present for the first time a detailed inspection of the optical spectra of the hot RCB star DY Cen and two fullerene PNe (Tc 1 and M 1-20), which permits us to directly explore the fullerenes - DIB connection. The DIB spectrum of DY Cen (García-Hernández et al. 2012a) is remarkably different from that in fullerene PNe (García-Hernández & Díaz-Luis 2013). In particular, Tc 1 displays unusually strong 4428 Å and 6309 Å DIBs, which are normal (or not seen) in DY Cen. On the other hand, DY Cen displays an unusually strong 6284 Å DIB that is found to be normal in fullerene PNe. We also report the detection of new broad and unidentified features centered at 4000 Å and 6525 Å in DY Cen and Tc 1, respectively. We suggest that the new 4000 Å band seen in DY Cen may be related to the circumstellar proto-fullerenes seen at infrared wavelengths (García-Hernández et al. 2012a). However, the intense 4428 Å DIB (probably also the 6309 Å DIB and the new 6525 Å band) may be related to the presence of larger fullerenes (e.g., C80, C240, C320, and C540) and buckyonions (multishell fullerenes such as C60@C240 and C60@C240@C540) in the circumstellar envelope of Tc 1 (García-Hernández & Díaz-Luis 2013).

García-Hernández, D. A.

2014-02-01

138

Cleaning of diffusion bonding surface by argon ion bombardment treatment  

NASA Astrophysics Data System (ADS)

The specimens of oxygen-free high conductivity copper, SUS304L stainless steel and pure iron were treated by argon ion bombardment and then were bonded by diffusion bonding method. The effects of argon ion bombardment treatment on faying surface morphology, tensile strength of bonding joints and inclusions at the fracture surface were investigated. The results showed that argon ion bombardment treatment was effective to remove the oxide film and contamination at the faying surface and improve the quality of joints. The tensile strength of the bonded joints was improved, and minimum bonding temperature to make the metallic bonding at the interface was lowered by argon ion bombardment treatment. At the joints with argon ion bombardment treatment, ductile fractured surface was seen and the amount of inclusions was obviously decreased.

Wang, Airu; Ohashi, Osamu; Yamaguchi, Norio; Aoki, Masanori; Higashi, Yasuo; Hitomi, Nobuteru

2003-05-01

139

Nonvalence correlation-bound anion states of spherical fullerenes.  

PubMed

We present a one-electron model Hamiltonian for characterizing nonvalence correlation-bound anion states of fullerene molecules. These states are the finite system analogs of image potential states of metallic surfaces. The model potential accounts for both atomic and charge-flow polarization and is used to characterize the nonvalence correlation-bound anion states of the C60, (C60)2, C240, and C60@C240 fullerene systems. Although C60 is found to have a single (s-type) nonvalence correlation-bound anion state, the larger fullerenes are demonstrated to have multiple nonvalence correlation-bound anion states. PMID:24978808

Voora, Vamsee K; Jordan, Kenneth D

2014-08-13

140

Interaction of C(60) fullerene with lipids.  

PubMed

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

Cataldo, Franco

2010-06-01

141

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

NASA Astrophysics Data System (ADS)

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

Banerjee, Soumik

2013-01-01

142

Enhancing Fullerene-Based Solar Cell Lifetimes by Addition of a Fullerene Dumbbell**  

PubMed Central

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

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

2014-01-01

143

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

PubMed

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

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

2014-11-17

144

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

145

Principal processes occurring at simultaneous bombardment of tungsten by carbon and deuterium ions  

SciTech Connect

Simultaneous bombardment of tungsten with deuterium and carbon leads to both tungsten erosion and implantation of carbon and deuterium in the W surface. These processes have been studied experimentally by simultaneous bombardment of magnetron deposited W layers with D and C ions at energies in the keV range. The experimental results were compared to numerical simulations using the TRIDYN code. The key parameter separating steady-state W erosion from continuous growth of a C layer on the surface is the C fraction in the incident flux. The dynamical change of the surface composition with increasing fluence was monitored in situ by ion beam analysis. The experimental results are well reproduced by the TRIDYN simulations, which are based on a kinematic model of ion scattering in the target. Significant contributions by chemical effects outside the scope of the TRIDYN model can therefore be excluded. A negligible contribution of chemical effects is also supported by the measured concentrations of retained D, which are not sufficient to create a significant contribution of chemical reactions with carbon to implantation and sputtering. Surface roughness of the specimens was found to be the key parameter for the observed shift of the transition point from continuous C layer growth to steady-state tungsten erosion with increasing D fraction in the incident ions.

Bizyukov, Ivan; Krieger, Karl [Kharkiv National University, Faculty of Physics and Technologies, 31 Kurchatov Ave., Kharkiv 61108 (Ukraine); Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany)

2007-10-01

146

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

147

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

SciTech Connect

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

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

2008-01-01

148

Simple and Onion-type Fullerenes shells as resonators and amplifiers  

E-print Network

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

Amusia, M Ya

2009-01-01

149

Fullerene-Encapsulated Atoms in the Light of Synchrotron Radiation  

SciTech Connect

Mass-selected beams of endohedral fullerene Ce-C{sub 82}{sup +} ions, of atomic Ce{sup q+} ions (q = 2, 3, 4), and of empty fullerene-cage C{sub 82}{sup +} ions were employed to study photoionization of fullerene-encapsulated and free cerium atoms. The Ce 4d inner-shell contributions to single and double ionization of the endohedral Ce-C{sub 82}{sup +} fullerene have been extracted from the data and compared with expectations based on theory and the experiments with atomic Ce ions. Dramatic reduction and redistribution of the ionization contributions to Ce 4d photoabsorption is observed. More than half of the Ce 4d oscillator strength is apparently diverted to additional decay channels of the Ce-C{sub 82}{sup +} complex.

Mueller, A.; Schippers, S. [Institut fuer Atom- und Molekuelphysik, Justus-Liebig-Universitaet, 35392 Giessen (Germany); Esteves, D. [Department of Physics, MS 220, University of Nevada, Reno, NV 89557-0058 (United States); Advanced Light Source, Lawrence Berkeley National Laboratory, MS 7-100, Berkeley, CA 94720 (United States); Habibi, M.; Phaneuf, R. A. [Department of Physics, MS 220, University of Nevada, Reno, NV 89557-0058 (United States); Kilcoyne, A. L. D.; Aguilar, A. [Advanced Light Source, Lawrence Berkeley National Laboratory, MS 7-100, Berkeley, CA 94720 (United States); Dunsch, L. [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung Dresden, D-01171 Dresden (Germany)

2009-12-03

150

Synthesis of highly quenching fullerene derivatives for biosensor applications  

E-print Network

This dissertation examines the synthesis of fullerene-based fluorescence quenchers for numerous biosensor applications. The Introduction describes the need for biosensors in our society, what they are and various biosensing ...

Pérez, Vanessa Virginia, 1981-

2004-01-01

151

How the spheroidal deformation changes the spectra of fullerenes  

Microsoft Academic Search

The spheroidal geometry of a slightly elliptically deformed sphere was used as a possible approach to fullerenes. We are interested in the elliptically deformed fullerenes like big C240 molecule. The low-lying electronic levels are described by the Dirac equation in (2+1) dimensions. We show how a small deformation of spherical geometry evokes a shift of the electronic spectra compared to

M. Pudlak; R. Pincak; V. A. Osipov

2008-01-01

152

Icosadeltahedral geometry of fullerenes, viruses and geodesic domes  

E-print Network

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

Antonio Siber

2007-11-22

153

Porphyrin-fullerene nanoparticles for treatment of hypoxic cardiopathies  

Microsoft Academic Search

In this study, low-toxic fullerene-based nanocationite particles (adducts of porphyrin with cyclohexyl fullerene C60) designated for targeted delivery of the paramagnetic stable magnesium isotope to heart muscle is reported for the first\\u000a time; these particles exhibit a sharp clinical effect of 80% recovery from tissue hypoxia in less than 24 h after a single\\u000a injection (0.03–0.1 LD50). This therapy is

N. Amirshahi; R. N. Alyautdin; S. Sarkar; S. M. Rezayat; M. A. Orlova; I. V. Trushkov; A. L. Buchachenko; D. A. Kuznetsov

2008-01-01

154

Protein interaction with hydrated C 60 fullerene in aqueous solutions  

Microsoft Academic Search

Physicochemical effects of hydrated C60 fullerenes (HyFn) on serum albumin molecules were studied using ESR spin labeling and differential scanning microcalorimetry. Molecular–colloidal solution of hydrated C60 fullerenes and their small spherical fractal clusters in water (C60FWS), was shown to stabilize protein hydration, and decrease specific surface energy in water–protein matrix in salt solutions. The mechanism of HyFn interaction with protein

S. P Rozhkov; A. S Goryunov; G. A Sukhanova; A. G Borisova; N. N Rozhkova; G. V Andrievsky

2003-01-01

155

Solid-state lithium cells based on fluorinated fullerene cathodes  

Microsoft Academic Search

The electrochemical characteristics of fullerenes and fluorinated fullerenes have been investigated by cyclic voltammetry and galvanostatic discharge using solid-state lithium cells Li\\/Li{sup +}-(MEP-7)\\/A (A = Cââ, Cââ, CââFâ, and CââFâ, MEP-7 = a polyphosphazene derivative). In the cyclic voltammograms of Cââ and Cââ, the first half-wave potential of Cââ is found to be 0.2 V more positive than that of

Ning Liu; H. Touhara; F. Okino; S. Kawasaki; Y. Nakacho

1996-01-01

156

Sputtering and surface structure modification of gold thin films deposited onto silicon substrates under the impact of 20-160 keV Ar+ ions  

NASA Astrophysics Data System (ADS)

The induced sputtering and surface state modification of Au thin films bombarded by swift Ar+ ions under normal incident angle have been studied over an energy range of (20-160) keV using three complementary techniques: Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The sputtering yields determined by RBS measurements using a 2 MeV 4He+ ion beam were found to be consistent with previous data measured within the Ar+ ion energy region E ? 50 keV, which are thus extended to higher bombarding energies. Besides, the SEM and XRD measurements clearly point out that the irradiated Au film surfaces undergo drastic modifications with increasing the Ar+ ion energy, giving rise to the formation of increasingly sized grains of preferred (1 1 1) crystalline orientations. The relevance of different sputtering yield models for describing experimental data is discussed with invoking the observed surface effects induced by the Ar+ ion irradiation.

Mammeri, S.; Ouichaoui, S.; Ammi, H.; Dib, A.

2014-10-01

157

Binding of fullerenes to amyloid beta fibrils: size matters.  

PubMed

Binding affinity of fullerenes C20, C36, C60, C70 and C84 for amyloid beta fibrils is studied by docking and all-atom molecular dynamics simulations with the Amber force field and water model TIP3P. Using the molecular mechanic-Poisson Boltzmann surface area method one can demonstrate that the binding free energy linearly decreases with the number of carbon atoms of fullerene, i.e. the larger is the fullerene size, the higher is the binding affinity. Overall, fullerenes bind to A?9-40 fibrils stronger than to A?17-42. The number of water molecules trapped in the interior of 12A?9-40 fibrils was found to be lower than inside pentamer 5A?17-42. C60 destroys A?17-42 fibril structure to a greater extent compared to other fullerenes. Our study revealed that the van der Waals interaction dominates over the electrostatic interaction and non-polar residues of amyloid beta peptides play the significant role in interaction with fullerenes providing novel insight into the development of drug candidates against Alzheimer's disease. PMID:25123396

Huy, Pham Dinh Quoc; Li, Mai Suan

2014-10-01

158

Persistent homology for the quantitative prediction of fullerene stability.  

PubMed

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

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

2015-03-01

159

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

160

Production of Mg and Al Auger electrons by noble gas ion bombardment of Mg and Al surfaces  

NASA Technical Reports Server (NTRS)

Relative production efficiencies of Mg and Al Auger electrons by He, Ne, Ar, Kr, and Xe ion bombardment are reported as a function of ion energy for energies not exceeding 3 keV. The experimental apparatus employed consisted of a LEED-Auger system equipped with an ion gun and a four-grid retarding-potential analyzer. It is found that: (1) the shape of the ion-excited Auger signal was independent of the rare gas and quite symmetric; (2) the Al signal was about an order of magnitude smaller than the Mg signal for a given bombarding species and ion-gun voltage; (3) no signal was observed for He(+) bombardment under any of the experimental conditions; (4) signal strengths were independent of temperature and ion dose; (5) the Auger production efficiencies differed by no more than a factor of two among the different gases - except for He(+) - on a given metal; (6) all the signal strengths increased with increasing ion-gun voltage, with no maximum exhibited; and (7) the apparent threshold energy for the Al signal was higher than that for the Mg signal. The differences between the results for the two metals are attributed to the fact that the Al 2p orbital lies deeper in energy and closer to the nucleus than the corresponding Mg orbital.

Ferrante, J.; Pepper, S. V.

1976-01-01

161

Fullerene embedded shape memory nanolens array.  

PubMed

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

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

2013-01-01

162

Fullerene Embedded Shape Memory Nanolens Array  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

163

Synthesis separation characterization of partially reduced fullerenes  

SciTech Connect

The Birch reduction of C{sub 60} is known to result in the formation of C{sub 60}H{sub 36}. The authors have investigated the reduction of C{sub 60} using much less powerful reducing conditions. Specifically, the authors have investigated partial hydrogenation and zinc/acid reductions under a variety of conditions. Regardless of the conditions, the same series of three products as determined by gel-permeation chromatography (GPC) was obtained. The authors have used preparative GPC to isolate these bands and have investigated their chromatographic behavior, absorption spectra, and mass spectrometry. In this talk the synthesis, separation, and characterization of these compounds will be presented, and discuss the possible structures of these partially reduced fullerenes.

Meier, M.S.; Selegue, J.P.; Vance, V.K.; Corbin, P.L. [Univ. of Kentucky, Lexington, KY (United States)

1993-12-31

164

Dispersion interaction stabilizes sterically hindered double fullerenes.  

PubMed

By state-of-the-art quantum chemical methods, we show that for bulky functional groups like cyclohexane, [20]fullerene, dodecahedrane, and C60, the attractive dispersion interaction can have a greater impact on stereochemistry than the repulsive steric effect, making the compact isomer the more stable one. In particular, for the double C60 adduct of pentacene 1, the syn isomer should be the main product instead of the anti one inferred in the original synthesis experiment (Y. Murata et?al., J. Org. Chem. 1999, 64, 3483). With and without dispersion interactions taken into account, the Gibbs energy difference ?G(syn-anti) is -6.36 and +1.15?kcal?mol(-1), respectively. This study reminds us that dispersion interactions as well as electrostatic or hyperconjugation effects, etc. can lead to some unusual stereochemical phenomena. PMID:25165020

Zhang, Jun; Dolg, Michael

2014-10-20

165

Fullerene Embedded Shape Memory Nanolens Array  

PubMed Central

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

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

2013-01-01

166

Origin of nonlinear sputtering during nanocluster bombardment of metals Juha Samela* and Kai Nordlund  

E-print Network

Origin of nonlinear sputtering during nanocluster bombardment of metals Juha Samela* and Kai by nanocluster beams.3 The sputtering yield of nanocluster bombardment is non- linear with cluster size bombardment simulations.11,12 The mechanism of nanocluster bombardment is not only an interesting scientific

Nordlund, Kai

167

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

PubMed Central

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

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

2014-01-01

168

Synthesis of Molecules by Cosmic Ion Bombardment  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

169

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

170

Synthesis and Solution Properties of Water-soluble Fullerene Polymeric Systems.  

E-print Network

??Water-soluble fullerene containing polymers comprising of poly(2-(dimethylamino) ethyl methacrylate)-fullerene (PDMAEMA-C60) with targeting moieties, poly(oligo(ethylene glycol) methyl ether methacrylate)-C60 (POEGMA-C60), nanocrystalline cellulose-fullerene (NCC-C60) and NCC-C60-POEGMA were… (more)

Yao, Zhaoling

2011-01-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

172

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

173

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

174

Liposome Formulation of Fullerene-Based Molecular Diagnostic and Therapeutic Agents  

PubMed Central

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

Zhou, Zhiguo

2013-01-01

175

Theoretical investigation of bilayer fullerene C60@C540 in term of its biomedical application  

NASA Astrophysics Data System (ADS)

The results of theoretical study of bilayer fullerene C60@C540 are presented in this paper. In order to identify regularities of internal fullerene movement in the field of the outer shell retaining potential multiwell potential of C60 and C540 fullerenes interaction was calculated. On the basis of the two-shell fullerene structure topology data and analysis of the fullerenes interaction energy surface relief possible options of C60 tunneling between potential wells are predicted. Compiled forecast is confirmed by the data of numerical experiment.

Glukhova, O. E.; Kolesnikova, A. S.; Slepchenkov, M. M.; Shunaev, Vl. V.

2014-03-01

176

Characterization of naturally-occurring and modified fullerenes by Fourier transform mass spectrometry  

NASA Astrophysics Data System (ADS)

Fourier transform mass spectrometry (FTMS) employing both laser desorption/ionization and thermal desorption/electron ionization is useful for the detection and structural characterization of fullerenes and chemically-modified fullerenes. Examination of a carbon-rich shungite rock sample from Russia by transmission electron microscopy and FTMS provided evidence of naturally-occurring fullerenes. Ion-molecule reactions can be studied with FTMS to investigate the electron affinities of modified fullerenes. By monitoring charge exchange reactions, the electron affinities of C60Fx (x=44,46) and C70Fy (y=52,54) were found to be substantially higher than the values for the parent fullerenes.

Hettich, Robert L.; Jin, Changming; Compton, Robert N.; Buseck, Peter R.; Tsipursky, Semeon J.

1993-10-01

177

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

PubMed

A synthesis technology of endohedral fullerenes such as Fe@C60 has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C60 was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction. PMID:24593515

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

2014-02-01

178

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

179

C60 fullerene promotes lung monolayer collapse.  

PubMed

Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C60 fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m(-1)). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m(-1)). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo, which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant. PMID:25589571

Barnoud, Jonathan; Urbini, Laura; Monticelli, Luca

2015-03-01

180

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

181

Fullerene mediated hydrogen release in lithium borohydride  

NASA Astrophysics Data System (ADS)

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

Scheicher, Ralph; Li, Sa; Jena, Puru

2010-03-01

182

Direct optical excitation of a fullerene-incarcerated metal ion  

E-print Network

The endohedral fullerene Er3N@C80 shows characteristic 1.5 micron photoluminescence at cryogenic temperatures associated with radiative relaxation from the crystal-field split Er3+ 4I13/2 manifold to the 4I15/2 manifold. Previous observations of this luminescence were carried out by photoexcitation of the fullerene cage states leading to relaxation via the ionic states. We present direct non-cage-mediated optical interaction with the erbium ion. We have used this interaction to complete a photoluminescence-excitation map of the Er3+ 4I13/2 manifold. This ability to interact directly with the states of an incarcerated ion suggests the possibility of coherently manipulating fullerene qubit states with light.

Jones, M A G; Briggs, G A D; Taylor, R A; Ardavan, A; Jones, Mark A G; Porfyrakis, Kyriakos; Taylor, Robert A; Ardavan, Arzhang

2006-01-01

183

Direct optical excitation of a fullerene-incarcerated metal ion  

E-print Network

The endohedral fullerene Er3N@C80 shows characteristic 1.5 micron photoluminescence at cryogenic temperatures associated with radiative relaxation from the crystal-field split Er3+ 4I13/2 manifold to the 4I15/2 manifold. Previous observations of this luminescence were carried out by photoexcitation of the fullerene cage states leading to relaxation via the ionic states. We present direct non-cage-mediated optical interaction with the erbium ion. We have used this interaction to complete a photoluminescence-excitation map of the Er3+ 4I13/2 manifold. This ability to interact directly with the states of an incarcerated ion suggests the possibility of coherently manipulating fullerene qubit states with light.

Mark A G Jones; Kyriakos Porfyrakis; G Andrew D Briggs; Robert A Taylor; Arzhang Ardavan

2006-04-20

184

Theoretical Study of Stabilization of Fullerene-like Silicon Cages  

NASA Astrophysics Data System (ADS)

We extend our work on fullerenes^1, by exploring the stabilization of fullerene-like silicon cages through intercalation of carbon atoms. Ab initio theoretical techniques are used to derive the physical and chemical properties of various (Si60)mCn systems (m = 1-3, n =1-10). The first phase of our investigation focuses on endohedral and exohedral complexes of a single Si60 withCn clusters. Electron correlation effects are incorporated using both Many Body Perturbation Theory (MBPT) and Density Functional Theories (DFT). The second phase of the investigation examines the interactions of the fullerene-like silicon "super molecules" with the small carbon clusters. The properties discussed will include bondlengths, ground-state energies, optimum absorbate distances, dissociation channels, and dissociation energies are presented. Possibilities exist for applications in silicon-based electronics at the nano scale. *A. S. Hira and A. K. Ray, Phys. Rev. A 52, 141(1995); A 54, 2205(1996).

Hira, Ajit; Moya-Leyba, Nichole; Bulnes, Daniel

2005-03-01

185

THE FORMATION OF COSMIC FULLERENES FROM AROPHATIC CLUSTERS  

SciTech Connect

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.; Cami, Jan; Peeters, Els; Fanchini, Giovanni [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada)] [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada); Jones, Anthony P.; Bernard-Salas, Jeronimo, E-mail: emicelot@uwo.ca [Institut d'Astrophysique Spatiale, CNRS/Universite Paris Sud, F-91405 Orsay (France)] [Institut d'Astrophysique Spatiale, CNRS/Universite Paris Sud, F-91405 Orsay (France)

2012-12-10

186

Antioxidant Properties of Water-Soluble Fullerene Derivatives  

NASA Astrophysics Data System (ADS)

Due to their inherent electronic properties, fullerenes are considered as radical sponges being capable of effectively quenching reactive oxygen species (ROS). The most promising candidates for potential pharmaceutical applications are therefore water-soluble fullerene derivatives, since they provide reasonable biological availability. In light of these considerations, we give an overview over the most recent concepts for designing and synthesizing real water-soluble fullerene compounds. Several studies concerning the quenching activities against ROS-like Superoxide radical anion of some of these novel compounds are reviewed. We finally present first promising investigations about cytoprotective and neuroprotective activities of several carboxyfullerenes in zebrafish embroys as a mammalian model system. By comparing the activities for different addition patterns and other structural changes some first conclusions concerning a structure-function relationship can be drawn.

Beuerle, Florian; Lebovitz, Russell; Hirsch, Andreas

187

Advancement and problems of fullerene-oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

188

Au irradiation by 25-keV Au n ( n=1-65 600 ) clusters  

NASA Astrophysics Data System (ADS)

Although surface processes induced by single ionized atom irradiation are reasonably well understood, the use of atomic clusters as irradiation projectiles can give rise to nonlinear effects due to high deposited energy densities and the presence of many cluster atoms in a small surface region. A well known fact is that high energy density cascades at surfaces due to cluster bombardment can lead to enhanced sputtering yields. We use molecular dynamics simulations to study the irradiation of gold surfaces by 25-keV Au n ( n=1-65 600) clusters. We show that the sputtering yields by the clusters are, quite surprisingly, roughly constant for cluster sizes n=2-7600. This effect arises from the formation of surface heat spikes, resulting in violent microexplosions of the surface layers.

Salonen, E.; Nordlund, K.; Keinonen, J.

2003-12-01

189

Mechanisms of O2 Sputtering from Water Ice by keV Ions  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

191

On the 17-keV neutrino  

SciTech Connect

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

Hime, A.

1993-04-01

192

On the 17-keV neutrino  

SciTech Connect

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

Hime, A.

1993-04-01

193

Genetic transformation of sweet potato by particle bombardment.  

PubMed

Transient and stable expression of foreign genes has been achieved in sweet potato using the particle bombardment system of gene delivery. Callus and root isolates of two genotypes (Jewel and TIS-70357) with positive signs of transformation have been recovered. Tungsten microcarriers coated with plasmid DNA (pBI 221 containing the gusA gene) were accelerated at high velocity using a biolistic device into sweet potato target tissues. Histochemical examination of bombarded leaf and petiole explants revealed that most had cells expressing the gusA gene. When explants were cultured, calli and roots developed in most bombarded tissues. Similar results but with a lower frequency of transformation were observed when the plasmid pBI 121 (with gusA and antibiotic resistance npt II genes) was employed and bombarded explants cultured on an antibiotic selection medium. Subcultured roots and calli were positive for gusA expression when tested even after one year of in vitro culture, and thus the expression of the foreign gene is fairly stable. The particle bombardment approach of gene delivery appears to have a potential for generating transgenic sweet potatoes with useful agronomic traits. PMID:24213484

Prakash, C S; Varadarajan, U

1992-03-01

194

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

195

Fullerenes: A New Carrier Phase for Noble Gases in Meteorites  

NASA Technical Reports Server (NTRS)

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

Becker, Luann

2004-01-01

196

Genetic transformation of silver birch (Betula pendula) by particle bombardment.  

PubMed

We used in vitro callus and shoot cultures as target material for genetic transformation of silver birch (Betula pendula Roth) by particle bombardment. Cultivation of in vitro shoot cultures before particle bombardment and a long selection period, combined with a high concentration of selective agent after bombardment, led to the production of transformed plantlets that were stable, and no escapes were found among the tree lines produced. Clonal variation in transformation efficiency was found in transient expression of the beta-glucuronidase gene in callus cultures and in plantlets transformed by stable integration of the ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (RbcS) and neomycin phosphotransferase (npt2) genes. PMID:12651425

Valjakka, Maarit; Aronen, Tuija; Kangasjärvi, Jaakko; Vapaavuori, Elina; Häggman, Hely

2000-05-01

197

Covalent dyads of porphyrin-fullerene and perylene-fullerene for organic photovoltaics: Spectroscopic and photocurrent studies  

NASA Astrophysics Data System (ADS)

Supermolecular complexes of zinc porphyrin or perylenediimide as covalent dyads with fullerene (C 60) in chloroform and as Langmuir-Blodgett layers on an Au substrate were studied. In our studies we have used following spectroscopic methods: electronic absorption, fluorescence and electron spin resonance in solution. Also infrared absorption spectra in a KBr pellet and reflectance-absorption in Langmuir-Blodgett layers were monitored. Photocurrent generation in a photoelectrochemical cell was also studied. The redistribution of charge both upon porphyrin linkage to C 60 and when the systems are deposited on the Au substrate was shown. Photocurrent examinations show a great influence of the fullerene presence on photoresponse of the systems.

Wróbel, Danuta; Lewandowska, Kornelia

2011-07-01

198

Genetic Transformation of Maize Cells by Particle Bombardment  

PubMed Central

Intact maize cells were bombarded with microprojectiles bearing plasmid DNA coding for selectable (neomycin phosphotransferase [NPT II]) and screenable (?-glucuronidase [GUS]) marker genes. Kanamycin-resistant calli were selected from bombarded cells, and these calli carried copies of the NPT II and GUS genes as determined by Southern blot analysis. All such calli expressed GUS although the level of expression varied greatly between transformed cell lines. These results show that intact cells of important monocot species can be stably transformed by microprojectiles. Images Figure 2 Figure 3 PMID:16667039

Klein, Theodore M.; Kornstein, Laura; Sanford, John C.; Fromm, Michael E.

1989-01-01

199

Effect of a Fullerene Water Suspension on Bacterial  

E-print Network

transition temperature, and membrane fluidity. P. putida decreased its levels of unsaturated fatty acids cells showed slightly increased phase transition temperatures (Tm) and increased membrane fluidityEffect of a Fullerene Water Suspension on Bacterial Phospholipids and Membrane Phase Behavior J I

Alvarez, Pedro J.

200

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

201

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

202

Hybrid uranium-oxalate fullerene topology cage clusters  

SciTech Connect

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

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

2010-01-01

203

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

Microsoft Academic Search

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

David J. Dick

1996-01-01

204

Are Biogenic PAHs Precursors for Fullerenes on Earth?  

NASA Astrophysics Data System (ADS)

C60 fullerene in shungite and in bitumen from the Bohemian Massif could have formed in situ in two steps: 1. Cyclotrimerization of the PAH C20H12. 2. Dehydrogenation of C60H30 to C60. The necessary heat was provided during metamorphism.

Heymann, D.

2002-03-01

205

Fullerene-based symmetry in Hibiscus rosa-sinensis pollen.  

PubMed

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

Andrade, Kleber; Guerra, Sara; Debut, Alexis

2014-01-01

206

Fullerene-Based Symmetry in Hibiscus rosa-sinensis Pollen  

PubMed Central

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

Andrade, Kleber; Guerra, Sara; Debut, Alexis

2014-01-01

207

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 ...

208

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. PMID:20138243

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

2010-01-01

209

Would Diamond Nanorods Be Stronger than Fullerene Nanotubes?  

E-print Network

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

Brenner, Donald W.

210

Carbon Nanotube and Fullerene Emissions from Spark-Ignited Engines  

Microsoft Academic Search

Particles were collected from the exhaust of Indian autorickshaws with natural gas and gasoline-fueled spark-ignited engines. Transmission electron microscopy was used to determine the size and shape of 2121 systematically selected particles. Particles were largely soot agglomerates and other types documented in the literature, but approximately 10% of the nonvolatile particles were multiwalled carbon nanotubes and fullerenes, forms of crystalline

C. D. Lagally; C. C. O. Reynolds; A. P. Grieshop; M. Kandlikar; S. N. Rogak

2012-01-01

211

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

PubMed

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

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

2014-01-01

212

Silicon solar cells exposed to electron bombardment: Thermovoltaic properties  

Microsoft Academic Search

The thermovoltaic effect has been discovered for the first time in single-crystal silicon n\\u000a +-p structures consisting of an intermediate product for conventional solar cells exposed to 1-meV electron bombardment at a\\u000a dose D = 1015 cm?2.

B. M. Abdurakhmanov; L. O. Olimov; F. S. Abdurazzakov; Z. N. Alad’ina

2010-01-01

213

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

214

Low energy electron bombardment induced surface contamination of Ru mirrors  

E-print Network

Low energy electron bombardment induced surface contamination of Ru mirrors A. Al-Ajlonya , A., Albany, NY 12203, USA ABSTRACT The impact of secondary electrons induced contamination of the Ru surface of electrons irradiation along with slight oxidation of pure Ru surface. All chemical changes were discussed

Harilal, S. S.

215

Advances in fast-atom-bombardment mass spectroscopy  

SciTech Connect

A comparison of fast atom bombardment and field desorption mass spectrometry was made to determine relative sensitivity and applicability. A series of glycosphingolipids and a series of protected oligonucleotides of known structure were analyzed to ascertain the potential utility of fast atom bombardment mass spectrometry in the structural elucidation of novel compounds in these classes. Negative ion mass markers were also developed. Fast atom bombardment was found to be one-to-two orders of magnitude more sensitive than field desorption based on the analysis of a limited number of compounds from several classes. Superior sensitivity was not universal and field desorption was clearly better in certain cases. In the negative ion mode in particular, fast atom bombardment was found to be a useful tool for the determination of the primary structure of glycosphingolipids and oligonucleotides. Carbohydrate sequence and branching information, and a fatty acid and lipid base composition were readily obtained from the mass spectra of glycosphingolipids while bidirectional nucleotide sequence, nucleotide base, and protecting group assignments were obtained for oligonucleotides. Based on this knowledge, a tentative structure of a human peripheral nervous system glycosphingolipid implicated in certain cases of disorders such as amyotrophic lateral sclerosis, Lou Gehrig's Disease, was proposed. Suitable negative ion mass markers were found in dispersions of poly(ethylene) and poly(propylene)glycols in a triethylenetetramine matrix, a matrix which also proved useful in the analysis of glycosphingolipids. These polyglycol dispersions provided ions for calibration to 2300 daltons.

Hemling, M.E.

1986-01-01

216

Functional transient genetic transformation of Arabidopsis leaves by biolistic bombardment  

E-print Network

with genetically modified Arabidopsis plants. Floral dip, however, is designed for the production of transgenicFunctional transient genetic transformation of Arabidopsis leaves by biolistic bombardment Shoko. Arabidopsis thaliana is the most widely used model organism for plant biology research due to the availability

Citovsky, Vitaly

217

[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

218

Molecular dynamics study of polystyrene bond-breaking and crosslinking under C60 and Arn cluster bombardment  

NASA Astrophysics Data System (ADS)

Molecular dynamics computer simulations are used to elucidate the bond-breaking and crosslinking processes induced by 2.5 keV C60 and Arn cluster bombardment in an amorphous sec-butyl-terminated polystyrene sample. The obtained results indicate that replacement of C60 by Ar18 or Ar60 projectiles leads to the decrease of the number of broken bonds and, hence, to the decrease of formation of new intra- and intermolecular (crosslinking) bonds. When the number of atoms in the Arn cluster is increased from 60 to 250 or more, the total number of broken bonds and the total number of newly created bonds reach a zero value. Additional comparison to the case of a fullerite crystal reveals that the change of material properties leads to almost 7.5-fold reduction of the efficiency of the crosslinking process.

Czerwinski, Bartlomiej; Postawa, Zbigniew; Garrison, Barbara J.; Delcorte, Arnaud

2013-05-01

219

Molecular projectile effects for kinetic electron emission from carbon- and metal-surfaces bombarded by slow hydrogen ions  

NASA Astrophysics Data System (ADS)

Total yields for kinetic electron emission (KE) have been determined for impact of hydrogen monomer-, dimer- and trimer-ions (impact energy <10 keV) on atomically clean surfaces of carbon-fiber inforced graphite used as first-wall armour in magnetic fusion devices. The data are compared with KE yields for impact of same projectile ions on atomically clean highly oriented pyrolytic graphite and polycrystalline gold. We discuss KE yields for the different targets if bombarded by equally fast molecular and atomic ions in view to "projectile molecular effects" (different yields per proton for equally fast atomic and molecular ions), which are expected from calculated electronic projectile energy losses in these target materials.

Cernusca, S.; Winter, HP.; Aumayr, F.; Díez Muiño, R.; Juaristi, J. I.

2003-04-01

220

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

221

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

PubMed

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

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

2015-02-18

222

Theoretical study of the electronic structure of fullerene-cubane cocrystals  

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

223

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

SciTech Connect

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

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

2012-01-01

224

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

Microsoft Academic Search

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

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

2001-01-01

225

Functionalization of [60]Fullerene Using a Novel Chemical Vapor Modification Method  

Microsoft Academic Search

Gas phase reactions of [60]fullerene with hydrogen atoms and\\/or methyl radicals have been performed by hot filament chemical vapor modification (CVM) to produce hydrogenated and\\/or methylated [60]fullerene. The CVM process parameters such as the time of reaction, pressure, and percentage of methane diluted in hydrogen have been varied so as to obtain the addended fullerene reaction products. Mass spectrometry and

Sara M. C. Vieira; W. Ahmed; Paul R. Birkett; Christopher A. Rego; Sotirios Kotsiris; Thomas Drewello

2005-01-01

226

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

227

Prediction of the behavior for fullerene C20 inside the icosahedral outer shell of C240  

NASA Astrophysics Data System (ADS)

In this work, we study the behavioral regularity of fullerene C20 inside the icosahedral outer shell of fullerene C240. The feature of such two-shell fullerenes is that the internal fullerene will move at low temperatures in a certain way: between the potential wells. The aim of this work is to reveal the regularities for motion of small fullerenes in nanospace of large external icosahedral fullerene, including the identification of the spatial configuration for a multi-well potential of interaction between two objects and prediction of possible movement for the internal object between potential wells. For the fullerene C20 it was found twenty potential wells in the direction of the fifth order axes for icosahedron of fullerene C240 cage, thirty towards in the direction of the middle of the ribs and twenty potential wells towards centers of the faces of the icosahedron. The prediction of possible moving for the internal object between potential wells and the regularities of this movement were made based on the relief analysis of the interaction energy surface of fullerenes. The numerical simulation of C20 motion in the field of C240 was carried out to test the prediction of movement. As results of the experiment, it was found that the fullerene C20 is easy to jump between the potential wells even at low temperatures up to 300K. Molecular dynamics simulations confirmed our conclusions about regularities of C20 movement between potential wells. Thus, one can conclude that the analysis of the topology of the energy surface of van der Waals interaction between the components of nanoparticles gives a true predictive picture of the regularities of the internal molecule behavior. Probably, the phenomenon of fullerene C20 movement in a cell of another fullerene can be used in modern technologies, such as determining a local temperature by increase of jumping velocity.

Glukhova, O. E.; Kolesnikova, A. S.; Slepchenkov, M. M.; Shunaev, V. V.

2014-05-01

228

Synthesis and properties of novel water-soluble fullerene-glycine derivatives as new materials for cancer therapy.  

PubMed

Novel water-soluble fullerene-glycine derivatives were synthesized by means of simple organic chemistry. They are completely soluble in water, yielding a clear brown solution. The products were characterized by fourier transform infrared (FTIR), ultraviolet-visible spectroscopy (UV-Vis), (1)H NMR, (13)C NMR, thermogravimetric analyses (TGA), and scanning electron microscopy (SEM). The assembly behavior of water-soluble fullerene-glycine derivatives was investigated by SEM. The results show that the fullerene-glycine derivatives create morphology that is sphere-like. The cytotoxicity to cancer cell lines of the fullerene-glycine derivatives was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) and flow cytometry. The results show that fullerene-glycine derivatives exhibit mortality and apoptosis of the cells which increased with the increase of fullerene-glycine derivative concentration. The cytotoxicity mechanism of fullerene-glycine derivatives was investigated for the first time. Novel water-soluble fullerene-glycine derivatives were synthesized by means of simple organic chemistry. The products were characterized by FTIR, UV-Vis, (1)H NMR, (13)C NMR, TGA, and SEM. The bioactivities of fullerene-glycine derivative materials have been tested, and the results show that compared with the fullerene complex, the fullerene-glycine derivative materials exhibit mortality and apoptosis of the cells which increased with the increase of fullerene-glycine derivative concentration. SEM images showed the macrostructure of fullerene-glycine derivative materials was spheres. PMID:25578702

Jiang, Guichang; Yin, Fen; Duan, Jihua; Li, Guangtao

2015-01-01

229

Effect of cluster size in kiloelectronvolt cluster bombardment of solid benzene.  

PubMed

Emission of benzene molecules by 5-keV cluster bombardment of a range of carbon projectiles from C6H6 to C180 is studied by a coarse-grained molecular dynamics (MD) technique. This approach permits calculations that are not feasible using more complicated potential energy functions, particularly as the interesting physics associated with the ion impact event approaches the mesoscale. These calculations show that the highest ejection yields are associated with clusters that deposit their incident energy 15-20 A below the surface. The highest yield for the projectiles is produced by the C20 and C60 projectiles. The results from the MD simulations are also compared favorably to an analytical model based on fluid dynamics to describe the energy deposition. The analytical model is then utilized to extend the range of the calculations to higher incident energies. The issue of the relative amount of chemical fragmentation and intact molecular desorption is also examined for the benzene crystal. These results show that damage accumulation at high-incident fluence should not be problematic and that it should be possible to perform molecular depth profiling via secondary ion mass spectrometry experiments. In general, the approach presented here illustrates the power of combining a simplified MD method with analytical strategies for describing a length scale that is difficult to achieve with traditional MD calculations. PMID:17222012

Smiley, Edward J; Winograd, Nicholas; Garrison, Barbara J

2007-01-15

230

Nanometer-scale patterning of alkali halide surfaces by ion bombardment  

NASA Astrophysics Data System (ADS)

Structural properties of alkali halide surfaces (KBr, KI, and RbI) have been modified by low energy Ar + ion beam bombardment. The morphology developed on the irradiated surfaces was investigated by the atomic-force microscopy (contact mode) under UHV conditions. The results indicate that for the incidence angles between 30° and 40° a periodic ripple morphology is developed with the ripple vector parallel to the beam direction, whereas for the angles larger than 60° the vector is perpendicular to the beam. The average surface roughness and the wavelength of the ion-induced periodic structures were measured as a function of the ion fluence (10 13-10 18 ions/cm 2), the beam energy (1-5 keV), and the sample temperature (from 300 K to 600 K). The results are explained in terms of a new atomic-scale model taking into account the fact that ion sputtering of alkali halides in the investigated energy range is dominated by electronic processes rather than ballistic collisions.

Saeed, S. R.; Sinha, O. P.; Krok, F.; Szymonski, M.

2008-12-01

231

Desorption and surface topography changes induced by He + ion bombardment of alkali halides  

NASA Astrophysics Data System (ADS)

Desorption fluxes from alkali halide (RbI, KBr) crystals under 5 keV He + bombardment and the corresponding surface topography evolution were investigated by means of quadruple mass spectroscopy (QMS) and dynamic force microscopy (DFM) in UHV. Although, for the energy range of He + ions used, desorption of alkali halides occurs predominantly via electronic processes, there are significant differences between the ion-stimulated desorption (ISD) and the electron-stimulated desorption (ESD). The latter proceeds in a layer-by-layer mode and, as a result, oscillating desorption fluxes are observed. For ISD the DFM images show that the surface erosion does not follow the layer-by-layer scheme and no oscillation in desorption fluxes are found but they exhibit monotonic decrease to some saturation level. We suggest that these differences between electron- and ion-stimulated desorption are caused by ballistic processes disturbing the perfect lattice and introducing defects in the bulk and at the surface. Such lattice defects can act as recombination centres for diffusing Frenkel defects and inhibit the desorption process. Additionally, projectiles colliding violently with top-layer ions introduce additional nucleation centres for vacancies on the surface which lead to the surface erosion in the multi-layer mode.

Krok, F.; Kolodziej, J. J.; Such, B.; Czuba, P.; Piatkowski, P.; Struski, P.; Szymonski, M.

2004-12-01

232

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

SciTech Connect

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

NONE

1992-12-31

233

Models of the surface of aluminum mirrors bombarded by ions from a deuterium plasma  

NASA Astrophysics Data System (ADS)

Changes in the optical properties of samples of aluminum-alloy mirrors caused by ion bombardment with ions from a deuterium plasma, which imitates conditions that can exist upon the operation of the first mirrors for diagnostics of plasma in an ITER, have been investigated. The basic methods of studying the mirror surfaces were ellipsometry and reflectometry; as an additional procedure, Auger electron spectroscopy was used. It has been found that the coefficient of reflection of mirrors decreases as a result of irradiation by ions with an energy of ˜1 keV, but it can be restored by the subsequent irradiation by ions with a lower energy (˜60 eV). The complex of experimental studies that were performed was used as a base for the selection of a mathematical model for a correct interpretation of ellipsometric data. The results of multiple-angle and spectral ellipsometry were analyzed in terms of the models of a clean surface and single-layer films. On the basis of the analysis of experimental data and simulation of the effective medium, we proposed a mechanism, which explains the results of the experiment; this mechanism is based on (1) the chemical processes in the surface layer in the first cycle of “degradation-restoration” and (2) the development of roughness as a result of a sequence of procedures of “degradation-restoration.”

Belyaeva, A. I.; Galuza, A. A.; Savchenko, A. A.

2010-08-01

234

Synthesis of Fullerenes in Low Pressure Benzene/Oxygen Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

Hebgen, Peter; Howard, Jack B.

1999-01-01

235

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

SciTech Connect

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

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

2013-10-28

236

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

237

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

238

Shape-Persistent Arylene Ethynylene Organic Hosts for Fullerenes.  

PubMed

Shape-persistent host molecules that are constructed solely through covalent bonds have been extensively investigated as alternatives to supramolecular architectures, which have shown interesting applications such as guest encapsulation and release, catalysis, and molecular recognition. Similar to the supramolecular self-assembly process, recent rapid development of dynamic covalent chemistry has enabled the covalent assembly of complex organic molecules that exhibit a finite cavity of well-defined shape and size. Alkyne metathesis represents an emerging dynamic covalent reaction, which provides rigid and linear acetylene linkages. In this account, we describe the dynamic assembly of shape-persistent arylene ethynylene cages with various shapes and sizes through one-step alkyne metathesis. The controlled cage-fullerene binding and the potential application of these cages in fullerene purification are also discussed. PMID:25464153

Yu, Chao; Jin, Yinghua; Zhang, Wei

2014-12-01

239

Fullerene peapods: In-situ conductivity study during synthesis  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

240

Molecular dynamics simulations of hydrogen bombardment of tungsten carbide surfaces  

SciTech Connect

The interaction between energetic hydrogen and tungsten carbide (WC) is of interest both due to the use of hydrogen-containing plasmas in thin-film manufacturing and due to the presence of WC in the divertor of fusion reactors. In order to study this interaction, we have carried out molecular dynamics simulations of the low-energy bombardment of deuterium impinging onto crystalline as well as amorphous WC surfaces. We find that prolonged bombardment leads to the formation of an amorphous WC surface layer, regardless of the initial structure of the WC sample. Loosely bound hydrocarbons, which can erode by swift chemical sputtering, are formed at the surface. Carbon-terminated surfaces show larger sputtering yields than tungsten-terminated surfaces. In both cumulative and noncumulative simulations, C is seen to sputter preferentially. Implications for mixed material erosion in ITER are discussed.

Traeskelin, P.; Juslin, N.; Nordlund, K. [Association EURATOM-Tekes, Accelerator Laboratory, University of Helsinki, P.O. Box 43, FIN-00014 (Finland); Erhart, P. [Institut fuer Materialwissenschaft, Technische Universitaet Darmstadt, Petersenstrasse 23, D-64287 Darmstadt (Germany)

2007-05-01

241

Fullerene C 60 in Solid Bitumen Accumulations in NeoProterozoic Pillow-Lavas at Mítov (Bohemian Massif)  

Microsoft Academic Search

Fullerene C60occurs at extremely low concentration (0.2?0.3 ppm) in hard solid bitumen that was accumulated in the pillow lava bodies exposed at M?tov (Tepl?-Barrandian Neo-proterozoic of the Bohemian Massif). No higher fullerenes were documented. The C60fullerene and its precursors are present in non-graphitic and non-graphitizable carbonaceous matter. Inclusions of fullerene are found embedded within glass-like carbons that are found within

Jan Jehli?ka; Otakar Frank

2006-01-01

242

Twenty Years of Promises: Fullerene in Medicinal Chemistry  

NASA Astrophysics Data System (ADS)

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

da Ros, Tatiana

243

The Electronic Structure of Transition Metal Coated Fullerenes  

Microsoft Academic Search

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

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

1998-01-01

244

Single or functionalized fullerenes interacting with heme group  

SciTech Connect

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

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

2014-09-15

245

Fullerenes found in the permo-triassic mass extinction period  

Microsoft Academic Search

Fullerenes have been identified by high-performance liquid chromatography with UV-visible spectroscopic analysis of toluene extracts of deep sea claystones from Permo-Triassic (P\\/T) boundary sections in the Inuyama area, central Japan. The analysis reveals the presence of 10-20 parts per trillion of C60 only in the dark-colored rock samples, suggesting the anoxia at the time of the P\\/T boundary 250 million

Takuya Chijiwa; Toshinari Arai; Toshiki Sugai; Hisanori Shinohara; Mineo Kumazawa; Masao Takano; Shin-iti Kawakami

1999-01-01

246

Carbon Nanotube and Fullerene Emissions from Spark-Ignited Engines  

Microsoft Academic Search

Particles were collected from the exhaust of Indian auto-rickshaws with natural gas- and gasoline-fueled spark-ignited engines. Transmission electron microscopy was used to determine the size and shape of 2121 systematically-selected particles. Particles were largely soot agglomerates and other types documented in the literature, but approximately 10% of the non-volatile particles were multi-walled carbon nanotubes and fullerenes, forms of crystalline carbon

C. D. Lagally; C. C. O. Reynolds; A. P. Grieshop; M. Kandlikar; S. N. Rogak

2011-01-01

247

Light-Particle Spectra from the Nitrogen Bombardment of Oxygen  

Microsoft Academic Search

Energy spectra and angular distributions were measured for protons and alpha particles resulting from the nitrogen bombardment of oxygen. It was found that the angular distributions of protons are reasonably isotropic whereas alpha particles are peaked in the forward direction. The energy distributions at various angles were compared with the predictions of a simple level density formula w=Cexp[2(aE*)12]. The constant

M. L. Halbert; A. Zucker

1959-01-01

248

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

SciTech Connect

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

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

2008-03-15

249

Fullerene derivatives as electron acceptors for organic photovoltaic cells.  

PubMed

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

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

2014-02-01

250

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

251

Nanoscale fullerene compression of an yttrium carbide cluster.  

PubMed

The nanoscale parameters of metal clusters and lattices have a crucial influence on the macroscopic properties of materials. Herein, we provide a detailed study on the size and shape of isolated yttrium carbide clusters in different fullerene cages. A family of diyttrium endohedral metallofullerenes with the general formula of Y(2)C(2n) (n = 40-59) are reported. The high field (13)C nuclear magnetic resonance (NMR) and density functional theory (DFT) methods are employed to examine this yttrium carbide cluster in certain family members, Y(2)C(2)@D(5)(450)-C(100), Y(2)C(2)@D(3)(85)-C(92), Y(2)C(2)@C(84), Y(2)C(2)@C(3v)(8)-C(82), and Y(2)C(2)@C(s)(6)-C(82). The results of this study suggest that decreasing the size of a fullerene cage with the same (Y(2)C(2))(4+) cluster results in nanoscale fullerene compression (NFC) from a nearly linear stretched geometry to a constrained "butterfly" structure. The (13)C NMR chemical shift and scalar (1)J(YC) coupling parameters provide a very sensitive measure of this NFC effect for the (Y(2)C(2))(4+) cluster. The crystal structural parameters of a previously reported metal carbide, Y(2)C(3) are directly compared to the (Y(2)C(2))(4+) cluster in the current metallofullerene study. PMID:22497289

Zhang, Jianyuan; Fuhrer, Tim; Fu, Wujun; Ge, Jiechao; Bearden, Daniel W; Dallas, Jerry; Duchamp, James; Walker, Kenneth; Champion, Hunter; Azurmendi, Hugo; Harich, Kim; Dorn, Harry C

2012-05-23

252

Alternative approaches to onion-like icosahedral fullerenes.  

PubMed

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

Janner, A

2014-03-01

253

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

254

Intensity distributions of reflected surface channeling protons scattered on surfaces of electron-bombarded alkali halide crystals  

NASA Astrophysics Data System (ADS)

We have examined the surface-channeling of 550 keV protons on electron-bombarded KBr(0 0 1) surfaces at grazing incidence. On the surface, electron-stimulated desorption (ESD) resulting from the irradiation of 5 keV electrons changes the surface morphology. In order to investigate the change of the surface morphology, the luminous intensity distributions observed on a fluorescent screen (scattering patterns) of the reflected protons under the surface-channeling conditions are measured. Normalized specular intensity of the protons oscillates, and the results of computer simulations show that the period of the intensity oscillation agrees with the period of layer-by-layer desorption. The measured period of the oscillation is comparable to the simulated one, i.e., the period of the desorption, however, the measured amplitude of the oscillation is weak. This shows that the layer-by-layer desorption of the experimental surface is observed but is not as remarkable as that of the perfect surface introduced in the simulation.

Fukazawa, Y.; Kihara, K.; Iwamoto, K.; Susuki, Y.

2013-11-01

255

Conformationally Constrained Macrocyclic Diporphyrin-Fullerene Artificial Photosynthetic Reaction Center  

PubMed Central

Photosynthetic reaction centers convert excitation energy from absorbed sunlight into chemical potential energy in the form of a charge-separated state. The rates of the electron transfer reactions necessary to achieve long-lived, high-energy charge-separated states with high quantum yields are determined in part by precise control of the electronic coupling among the chromophores, donors and acceptors, and of the reaction energetics. Successful artificial photosynthetic reaction centers for solar energy conversion have similar requirements. Control of electronic coupling in particular necessitates chemical linkages between active component moieties that both mediate coupling and restrict conformational mobility so that only spatial arrangements that promote favorable coupling are populated. Toward this end, we report the synthesis, structure and photochemical properties of an artificial reaction center containing two porphyrin electron donor moieties and a fullerene electron acceptor in a macrocyclic arrangement involving a ring of 42 atoms. The two porphyrins are closely spaced, in an arrangement reminiscent of that of the special pair in bacterial reaction centers. The molecule is produced by an unusual cyclization reaction that yields mainly a product with C2 symmetry and trans-2 disubstitution at the fullerene. The macrocycle maintains a rigid, highly-constrained structure that was determined by UV-vis spectroscopy, NMR, mass spectrometry, and molecular modeling at the semi-empirical PM6 and DFT (B3LYP/6-31G**) levels. Transient absorption results for the macrocycle in 2-methyltetrahydrofuran reveal photoinduced electron transfer from the porphyrin first excited singlet state to the fullerene to form a P•+-C60•?-P charge separated state with a time constant of 1.1 ps. Photoinduced electron transfer to the fullerene excited singlet state to form the same charge-separated state has a time constant of 15 ps. The charge-separated state is formed with a quantum yield of essentially unity and has a lifetime of 2.7 ns. The ultrafast charge separation coupled with charge recombination that is over 2000 times slower is consistent with a very rigid molecular structure having a small reorganization energy for electron transfer, relative to related porphyrin-fullerene molecules. PMID:21319796

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

2011-01-01

256

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

PubMed

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

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

2015-02-01

257

Supramolecular fullerene polymers and networks directed by molecular recognition between calix[5]arene and C60.  

PubMed

A biscalix[5]arene-C60 supramolecular structure was utilized for the development of supramolecular fullerene polymers. Di- and tritopic hosts were developed to generate the linear and network supramolecular polymers through the complexation of a dumbbell-shaped fullerene. The molecular association between the hosts and the fullerene were carefully studied by using (1) H?NMR, UV/Vis absorption, and fluorescence spectroscopy. The formation of the supramolecular fullerene polymers and networks was confirmed by diffusion-ordered (1) H?NMR spectroscopy (DOSY) and solution viscometry. Upon concentrating the mixtures of di- or tritopic hosts and dumbbell-shaped fullerene in the range of 1.0-10?mmol?L(-1) , the diffusion coefficients of the complexes decreased, and the solution viscosities increased, suggesting that large polymeric assemblies were formed in solution. Scanning electron microscopy (SEM) was used to image the supramolecular fullerene polymers and networks. Atomic force microscopy (AFM) provided insight into the morphology of the supramolecular polymers. A mixture of the homoditopic host and the fullerene resulted in fibers with a height of (1.4±0.1)?nm and a width of (5.0±0.8)?nm. Interdigitation of the alkyl side chains provided secondary interchain interactions that facilitated supramolecular organization. The homotritopic host generated the supramolecular networks with the dumbbell-shaped fullerene. Honeycomb sheet-like structures with many voids were found. The growth of the supramolecular polymers is evidently governed by the shape, dimension, and directionality of the monomers. PMID:25302995

Hirao, Takehiro; Tosaka, Masatoshi; Yamago, Shigeru; Haino, Takeharu

2014-12-01

258

Impact of Local Curvature and Structural Defects on Graphene-C60 Fullerene Fusion Reaction Barriers  

E-print Network

properties.1-6 In recent years, it has been realized that hybrid materials composed of graphene and other lowImpact of Local Curvature and Structural Defects on Graphene-C60 Fullerene Fusion Reaction Barriers the energetics of the graphene-C60 fullerene fusion. We show that there is an optimal value of the bond

Deymier, Pierre

259

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

E-print Network

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

Ayres, Virginia

260

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

E-print Network

Assembly of carbon nanotubes and alkylated fullerenes: nanocarbon hybrid towards photovoltaic and a fullerene (C60) derivative with long alkyl chains was constructed as a donor­acceptor pair for photovoltaics as attractive candidates for the development of light- energy harvesting and photovoltaic materials because

Nabben, Reinhard

261

Correlation of Fullerene Structure to its Miscibility in P3HT and OPV Function  

NASA Astrophysics Data System (ADS)

The miscibility of four fullerenes, bis-PCBM, ICBA, Thio-PCBM and PC70BM in poly(3-hexylthiophene) (P3HT) is determined by neutron reflectivity by monitoring the intermixing of P3HT and fullerene bilayers with thermal annealing. The miscibility limit of these fullerenes in P3HT ranges from 11% to 26%, where the bis-adduct fullerenes exhibit a lower miscibility in P3HT than singly functionalized fullerenes. The correlation of miscibility to device performance indicates that sufficient polymer/fullerene miscibility is crucial to rationally optimize organic photovoltaic active layers. Low miscibility of conjugated polymer and fullerene in the amorphous phase decreases the probability of exciton dissociation and enhances the recombination of free charge-carriers. Moreover, the results indicate that the average surface-to-surface distance between fullerenes must be less than approximately of 5-7 å to minimize charge traps and allow sufficient charge transport in the mixed phase to improve photovoltaic performance.

Dadmun, Mark; Chen, Huipeng; Peet, Jeff

2013-03-01

262

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

E-print Network

Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some Planetary Nebulae (PNe) now enable us to study the DIBs towards fullerene-rich space environments. We search DIBs in the optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC 418). Special attention is given to DIBs which are found to be unusually intense towards these fullerene sources. In particular, an unusually strong 4428A absorption feature is a common charateristic to fullerene PNe. Similarly to Tc 1, the strongest optical bands of neutral C60 are not detected towards IC 418. Our high-quality (S/N > 300) spectra for PN Tc 1 together with its large radial velocity permits us to search for the presence of diffuse bands of circumstellar origin which we refer to as diffuse circumstellar bands (DCBs). We report the first tentative detection of two DCBs at 4428 and 5780 A in the fullerene-rich ci...

Diaz-Luis, J J; Rao, N Kameswara; Manchado, A; Cataldo, F

2014-01-01

263

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

264

Navya Biomedical Technologies, LLC Developing Fullerenes to Image and Destroy Tumors  

E-print Network

Navya Biomedical Technologies, LLC Developing Fullerenes to Image and Destroy Tumors Navya Biomedical Technologies, LLC (Navya) is a privately held biotechnology company that de- signs, develops, and commercializes novel proprietary polyhydroxy fullerenes to non-invasively image and destroy solid tumors

Jawitz, James W.

265

TEMPERATURE-DEPENDENT RAMAN SPECTROSCOPY OF FULLERENE AND CARBORANE NANOCAR WHEELS  

E-print Network

TEMPERATURE-DEPENDENT RAMAN SPECTROSCOPY OF FULLERENE AND CARBORANE NANOCAR WHEELS B. Shih1,2 , C. Raman spectroscopy is used to study the spinning and sliding behavior of the wheels on different-Dependent Raman Spectroscopy of Fullerene Nanocar Wheels Acknowledgement This material is based upon work

Mellor-Crummey, John

266

Supramolecular [60]Fullerene Liquid Crystals Formed By Self-Organized Two-Dimensional Crystals.  

PubMed

Fullerene-based liquid crystalline materials have both the excellent optical and electrical properties of fullerene and the self-organization and external-field-responsive properties of liquid crystals (LCs). Herein, we demonstrate a new family of thermotropic [60]fullerene supramolecular LCs with hierarchical structures. The [60]fullerene dyads undergo self-organization driven by ?-? interactions to form triple-layer two-dimensional (2D) fullerene crystals sandwiched between layers of alkyl chains. The lamellar packing of 2D crystals gives rise to the formation of supramolecular LCs. This design strategy should be applicable to other molecules and lead to an enlarged family of 2D crystals and supramolecular liquid crystals. PMID:25327867

Zhang, Xiaoyan; Hsu, Chih-Hao; Ren, Xiangkui; Gu, Yan; Song, Bo; Sun, Hao-Jan; Yang, Shuang; Chen, Erqiang; Tu, Yingfeng; Li, Xiaohong; Yang, Xiaoming; Li, Yaowen; Zhu, Xiulin

2014-10-19

267

Relevance of surface viscous flow, surface diffusion, and ballistic effects in keV ion smoothing of amorphous surfaces  

NASA Astrophysics Data System (ADS)

Surface viscous flow, surface diffusion, and ballistic effects have recently been discussed as possible atomic-scale mechanisms to explain the dramatic smoothing reactions observed during keV ion bombardment of amorphous surfaces. By employing multiscale modeling, viz. a combination of molecular dynamics and continuum rate equations, we compare the relevance of the individual processes at room temperature. This is achieved by calculating diffusion constants, viscosities, and lateral transport due to momentum transfer. Depending on the surface structure size, we find the dominance of surface viscous flow or ballistic effects. The findings are found to be valid for both strong and fragile glasses, as represented by amorphous Si and CuTi, respectively.

Vauth, Sebastian; Mayr, S. G.

2007-06-01

268

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

Microsoft Academic Search

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

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

1993-01-01

269

Comparative Computational Study of Interaction of C60-Fullerene and Tris-Malonyl-C60-Fullerene Isomers with Lipid Bilayer: Relation to Their Antioxidant Effect  

PubMed Central

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

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

2014-01-01

270

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. PMID:21774800

2011-01-01

271

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

SciTech Connect

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

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

1995-12-31

272

Sputtering and reflection under cluster bombardment of solids  

NASA Astrophysics Data System (ADS)

Using molecular-dynamics simulation, we study the sputtering induced by energetic impacts of projectile clusters containing N=100 and 1000 atoms. Both a metallic target and a van-der-Waals-bonded material are studied. We focus on self-bombardment at perpendicular incidence. The total emission yield is composed of the sputter yield of the target material and the reflection yield of reflected projectile cluster atoms. The dependence of these yields on the impact energy shows a slow transition from reflection- to sputter-dominated emission. Similarities and differences between the emission yield of metals and of van-der-Waals-bonded materials are discussed.

Anders, Christian; Urbassek, Herbert M.

2013-11-01

273

Chemical functionalization and modification of carbon nanotubes through ion bombardment  

NASA Astrophysics Data System (ADS)

Classical molecular dynamics simulations have been performed to investigate the chemical functionalization of single-walled (SWNT) and double-walled carbon nanotubes (DWNT) through CH3+ ion bombardment at 10, 45, and 80 eV. The simulations show that the process is highly efficient and that chemical functionalization occurs at every incident ion energy considered. However, significant differences in the response of the SWNTs and DWNTs are predicted from the simulations. At 45 and 80 eV defect formation and cross-linking between nearby nanotubes occurs. These new defect structures could substantially alter the mechanical and electrical properties of nanotubes

Ni, Boris; Sinnott, Susan B.

2001-07-01

274

Electron-bombarded CCD detectors for ultraviolet atmospheric remote sensing  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

275

Beyond fullerenes: design of nonfullerene acceptors for efficient organic photovoltaics.  

PubMed

New electron-acceptor materials are long sought to overcome the small photovoltage, high-cost, poor photochemical stability, and other limitations of fullerene-based organic photovoltaics. However, all known nonfullerene acceptors have so far shown inferior photovoltaic properties compared to fullerene benchmark [6,6]-phenyl-C60-butyric acid methyl ester (PC60BM), and there are as yet no established design principles for realizing improved materials. Herein we report a design strategy that has produced a novel multichromophoric, large size, nonplanar three-dimensional (3D) organic molecule, DBFI-T, whose ?-conjugated framework occupies space comparable to an aggregate of 9 [C60]-fullerene molecules. Comparative studies of DBFI-T with its planar monomeric analogue (BFI-P2) and PC60BM in bulk heterojunction (BHJ) solar cells, by using a common thiazolothiazole-dithienosilole copolymer donor (PSEHTT), showed that DBFI-T has superior charge photogeneration and photovoltaic properties; PSEHTT:DBFI-T solar cells combined a high short-circuit current (10.14 mA/cm(2)) with a high open-circuit voltage (0.86 V) to give a power conversion efficiency of 5.0%. The external quantum efficiency spectrum of PSEHTT:DBFI-T devices had peaks of 60-65% in the 380-620 nm range, demonstrating that both hole transfer from photoexcited DBFI-T to PSEHTT and electron transfer from photoexcited PSEHTT to DBFI-T contribute substantially to charge photogeneration. The superior charge photogeneration and electron-accepting properties of DBFI-T were further confirmed by independent Xenon-flash time-resolved microwave conductivity measurements, which correctly predict the relative magnitudes of the conversion efficiencies of the BHJ solar cells: PSEHTT:DBFI-T > PSEHTT:PC60BM > PSEHTT:BFI-P2. The results demonstrate that the large size, multichromophoric, nonplanar 3D molecular design is a promising approach to more efficient organic photovoltaic materials. PMID:25265412

Li, Haiyan; Earmme, Taeshik; Ren, Guoqiang; Saeki, Akinori; Yoshikawa, Saya; Murari, Nishit M; Subramaniyan, Selvam; Crane, Matthew J; Seki, Shu; Jenekhe, Samson A

2014-10-15

276

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

NASA Astrophysics Data System (ADS)

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

Heinrichova, Patricie; Vala, Martin; Weiter, Martin

2014-01-01

277

Synthesis and characterization of novel fullerenes and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Since the discovery of Buckminsterfullerene, the soccerball shaped carbon-caged molecule consisting of 60 carbon atoms, there has been much speculation about the stability of other "fullerenes" with less than 60 carbon atoms. Although several fullerenes with greater than 60 carbon atoms have since been isolated in bulk, the only evidence of lower fullerenes has come from minute-quantity gas phase experiments. This thesis presents work on the first ever bulk synthesis, extraction and characterization of a lower fullerene: C36. By exploring the parameter space of the Kratschmer-Huffman graphite arc-discharge method, C36 was produced in milligram quantities. This new material which was extracted with pyridine was found by electron diffraction to form a covalently bonded solid with a d-spacing of 6.68 A. This material is electrically insulating in its pure form but it becomes conducting upon intercalation with alkali metals. The resistance vs temperature behavior of the alkali intercalated samples is consistent with variable range hopping. From microwave-loss measurements and current vs. voltage data, there are preliminary results that may indicate the presence of a very small superconducting fraction in these alkali doped samples. This result would be consistent with predictions by Grossman, Cote, Cohen and Louie that a certain isomer of C 36 with D6h symmetry has an exceptionally strong electron-phonon coupling constant. Other developments described in this thesis include a method of synthesizing multi-walled carbon nanotubes in high yield at an accelerated rate using a low pressure mixture of nitrogen and helium as the buffer gas. Also, a simple technique has been developed for synthesizing magnetic nickel-iron clusters that are coated with both electrical insulators and electrical conductors. These clusters may have a variety of applications in the fields of magnetic recording and biochemistry where magnetic manipulation of cells is important. Finally, a preliminary study of doping effects in multi-walled carbon nanotubes was conducted. This study showed that the transport properties of these nanotubes changed dramatically upon intercalation with both oxygen and potassium.

Piskoti, Charles Richard

278

Viruses and Fullerenes - Symmetry as a Common Thread?  

E-print Network

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

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

2014-01-01

279

Viruses and Fullerenes - Symmetry as a Common Thread?  

E-print Network

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

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

2014-02-18

280

Polarization effects in C60 fullerene complexes of alkali ions  

NASA Astrophysics Data System (ADS)

We introduce a secular semiempirical model of the Pariser-Parr-Pople type to reproduce the electronic structure and polarizability of the C60 fullerene. The model is then used to simulate the response of this molecule to an electric charge and estimate its polarization energy. By expressing the charge potential at the C60-cage surface as a multipole expansion, an analytical form is obtained for the polarization energy. Application of these results to endo- and exohedral complexes of alkali ions gives data in rather good agreement with recent ab initio calculations [Hira and Ray, Phys. Rev. A 52, 141 (1995)].

Ruiz, A.; Hernández-Rojas, J.; Bretón, J.; Gomez Llorente, J. M.

1998-09-01

281

Photophysical properties of novel water soluble fullerene derivatives  

NASA Astrophysics Data System (ADS)

The spectroscopic and photophysical properties for a series of bis-adduct derivatives of C 60 have been studied using a combination of time-resolved and steady state techniques, including picosecond single photon counting and laser flash photolysis. The electronic absorption and fluorescence spectra are red shifted with respect to those of C 60. As with the parent fullerene, the main deactivation channel of the excited singlet state is intersystem crossing with the yields of singlet oxygen ranging from 0.63 to 0.97. Our results demonstrate that the photophysical properties depend on the addition pattern of the addends.

Foley, Sarah; Bosi, Susanna; Larroque, Christain; Prato, Maurizio; Janot, Jean-Marc; Seta, Patrick

2001-12-01

282

Synthesis of endohedral iron-fullerenes by ion implantation  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

283

Electrically conducting porphyrin and porphyrin-fullerene electropolymers  

DOEpatents

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

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

2014-03-11

284

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, we 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. [copyright] 1994 American Institute of Physics

Schirber, J.E.; Samara, G.A.; Morosin, B.; Assink, R.; Loy, D. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)); Wang, H.; Williams, J. (Argonne National Laboratories, Argonne, Illinois 60439 (United States)); Murphy, D.; Kortan, A.R.; Rossiensky, M.; Zhou, O. (AT T Bell Laboratories, Murray Hill, New Jersey 07974 (United States)); Zhu, Q.; Kniaz, K.; Fischer, J.E. (University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States))

1994-07-10

285

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

286

Synthesis of endohedral iron-fullerenes by ion implantation.  

PubMed

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

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

2014-02-01

287

Synthesis of endohedral iron-fullerenes by ion implantation  

SciTech Connect

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

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

2014-02-15

288

Dielectrophoretic and electrophoretic force analysis of colloidal fullerenes in a nematic liquid-crystal medium  

NASA Astrophysics Data System (ADS)

This research focuses on the electrokinetic motion of fullerenes suspended in liquid crystal host medium, which are investigated in the homogeneously aligned nematic liquid crystal cells driven by in-plane field. We investigated the effect of electrophoretic and dielectrophoretic forces and related parameters of the colloidal fullerenes in liquid crystals. The electrophoretic mobility, zeta potential, and critical voltage have been evaluated. Fullerenes suspended in liquid crystal medium migrated toward the positive electrode, but were pulled back in the opposite direction when the polarity was reversed especially at low frequency range (<5Hz) . At higher electric field and higher frequency ranges, the net displacement of fullerenes has been observed. We demonstrate that the dielectrophoretic force dominated the motion in the colloidal fullerenes by a proper analysis of different electrophoretic parameters. In addition, the electrodynamics of fullerenes was explained by applying the theory of the dielectrophoresis and Schwarz’s formula. We propose a model to estimate the density of fullerenes suspended in liquid crystal medium.

Srivastava, Anoop Kumar; Kim, Miyoung; Kim, Sung Min; Kim, Mi-Kyung; Lee, Kyu; Lee, Young Hee; Lee, Myong-Hoon; Lee, Seung Hee

2009-11-01

289

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

290

Molecular dynamics simulation of graphene bombardment with Si ion  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations with Tersoff-Ziegler-Biersack-Littmark (Tersoff-ZBL) potential and adaptive intermolecular reactive empirical bond order (AIREBO) potential are performed to study the effect of irradiated graphene with silicon ion at several positions and energy levels of 0.1-1000 eV. The simulations reveal four processes: absorption, replacement, transmission and damage. At energies below 110 eV, the dominant process is absorption. For atom in group (a), the process that takes place is replacement, in which the silicon ion removes one carbon atom and occupies the place of the eliminated atom at the incident energy of 72-370 eV. Transmission is present at energies above 100 eV for atom in group (d). Damage is a very important process in current bombardment, and there are four types of defects: single vacancy, replacement-single vacancy, double vacancy and nanopore. The simulations provide a fundamental understanding of the silicon bombardment of graphene, and the parameters required to develop graphene-based devices by controlling defect formation.

Qin, Xin-Mao; Gao, Ting-Hong; Yan, Wan-Jun; Guo, Xiao-Tian; Xie, Quan

2014-03-01

291

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. PMID:19764203

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

2009-01-01

292

Occurrence of natural fullerenes in low grade metamorphosed Proterozoic shungite from Karelia, Russia  

NASA Astrophysics Data System (ADS)

We report on the occurrence of fullerenes in Proterozoic shungite (˜2 Ga) from the shungite mine, Kondopoga, Karelia, Russia (62.12°N 34.17°E). The presence of fullerenes has been confirmed by mass spectrometry, with peaks at 360 and 720 amu (atomic mass unit), powder X-ray diffraction showing ten diffraction peaks corresponding to the fullerite structure with a = 1.4201(5) nm, and 13C nuclear magnetic resonance (NMR) spectroscopic studies, showing a peak at 143.2 ppm. In the Kondopoga shungite mine, fullerenes occur in silty shales that have experienced greenshist facies metamorphism.

Parthasarathy, G.; Srinivasan, R.; Vairamani, M.; Ravikumar, K.; Kunwar, A. C.

1998-11-01

293

Binding of fullerenes and nanotubes to MscL  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

294

Tuning of electronic properties of fullerene-oligothiophene layers  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

295

Plasmons in a superlattice of fullerenes or metallic shells  

NASA Astrophysics Data System (ADS)

A theory for the collective plasma excitations in a linear periodic array of spherical two-dimensional electron gases (S2DEGs) is presented. This is a simple model for an ultra thin and narrow microribbon of fullerenes or metallic shells. Coulomb coupling between electrons located on the same sphere and on different spheres is included in the random-phase approximation. Electron hopping between spheres is neglected in these calculations. The resulting plasmon-dispersion equation is solved numerically. Results are presented for a superlattice of single-wall S2DEGs as a function of the wave vector. The plasmon dispersions are obtained for different spherical separations. We show that the one-dimensional translational symmetry of the lattice is maintained in the plasmon spectrum. Additionally, we compare the plasmon dispersion when the superlatice direction is parallel or perpendicular to the axis of quantization. However, because of anisotropy in the Coulomb matrix elements, there is anticrossing in the plasmon dispersion only in the direction perpendicular to the quantization axis. The S2DEG may serve as a simple model for fullerenes, when their energy bands are far apart.

Balassis, Antonios; Gumbs, Godfrey

2014-08-01

296

Binding of fullerenes and nanotubes to MscL  

PubMed Central

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

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

2014-01-01

297

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

PubMed

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

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

2012-09-26

298

Origin of the cataclysmic Late Heavy Bombardment period of the terrestrialplanets  

Microsoft Academic Search

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

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

2005-01-01

299

Particle bombardment and the genetic enhancement of crops: myths and realities  

Microsoft Academic Search

DNA transfer by particle bombardment makes use of physical processes to achieve the transformation of crop plants. There is no dependence on bacteria, so the limitations inherent in organisms such as Agrobacterium tumefaciens do not apply. The absence of biological constraints, at least until DNA has entered the plant cell, means that particle bombardment is a versatile and effective transformation

Fredy Altpeter; Niranjan Baisakh; Roger Beachy; Ralph Bock; Teresa Capell; Paul Christou; Henry Daniell; Karabi Datta; Swapan Datta; Philip J. Dix; Claude Fauquet; Ning Huang; Ajay Kohli; Hans Mooibroek; Liz Nicholson; Thi Thanh Nguyen; Gregory Nugent; Krit Raemakers; Andrea Romano; David A. Somers; Eva Stoger; Nigel Taylor; Richard Visser

2005-01-01

300

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

Microsoft Academic Search

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

Leo Szilard; T. A. Chalmers

1934-01-01

301

Synergistic Effect of Fullerene-Capped Gold Nanoparticles on Graphene Electrochemical Supercapacitors  

E-print Network

and R. Whyman, “Synthesis of Thiol-Derivatized Gold Nanopar-the synthesis of graphene/fullerene-capped gold nanoparticlegold nanospacers are intro- duced) [11]. Here, we report a novel route of synthesis and

Yong, Virginia; Hahn, H. Thomas

2013-01-01

302

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

E-print Network

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

Ravi, P.

303

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

2013-10-28

304

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

PubMed

We present a paradigm in constructing very stable, faceted nanotube and fullerene structures by laterally joining nanoribbons or patches of different planar phosphorene phases. Our ab initio density functional calculations indicate that these phases may form very stable, nonplanar joints. Unlike fullerenes and nanotubes obtained by deforming a single-phase planar monolayer at substantial energy penalty, we find faceted fullerenes and nanotubes to be nearly as stable as the planar single-phase monolayers. The resulting rich variety of polymorphs allows us to tune the electronic properties of phosphorene nanotubes and fullerenes not only by the chiral index but also by the combination of different phosphorene phases. In selected phosphorene nanotubes, a metal-insulator transition may be induced by strain or by changing the number of walls. PMID:25494080

Guan, Jie; Zhu, Zhen; Tománek, David

2014-11-28

305

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

306

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

NASA Astrophysics Data System (ADS)

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

Guan, Jie; Zhu, Zhen; Tománek, David

2014-11-01

307

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

308

A Unique Photon Bombardment System for Space Applications  

NASA Technical Reports Server (NTRS)

The innovative Electromagnetic Radiation Collection and Concentration System (EMRCCS) described is the foundation for the development of a multiplicity of space and terrestrial system formats. The system capability allows its use in the visual, infrared, and ultraviolet ranges of the spectrum for EM collection, concentration, source/receptor tracking, and targeting. The nonimaging modular optical system uses a physically static position aperture for EM radiation collection. Folded optics provide the concentration of the radiation and source autotracking. The collected and concentrated electromagnetic radiation is utilized in many applications, e.g., solar spectrum in thermal and associative photon bombardment applications for hazardous waste management, water purification, metal hardening, hydrogen generation, photovoltaics, etc., in both space and terrestrial segment utilization. Additionally, at the high end of the concentration capability range, i.e., 60,000+, a solar-pulsed laser system is possible.

Klein, E. J.

1993-01-01

309

Bombarding Cancer: Biolistic Delivery of therapeutics using Porous Si Carriers  

PubMed Central

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

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

2013-01-01

310

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

311

Dynamic shielding during ion bombardment of Ba dispenser cathodes  

NASA Astrophysics Data System (ADS)

Ion bombardment (IB) resistivity is a key parameter for cathodes to be operated in TV tubes and CMT's over lifetimes of several years. Thus, accelerated stress tests with much higher ion dose rates than those present in real tube environment are normally used. Here, IB resistivity of Os/Ru-I and top layer Scandate cathodes was investigated. It was observed by variation of the dose rates, that Ba resupply modified the survived ion dose and led to a dynamic shielding of the rest of the surface complex/dipole below Ba. Enhanced IB resistivity w.r.t. total ion dose was observed for reduced ion dose rates. Based on a model of shielding an extrapolation from stress tests to real tube conditions has been established, where the correction factor is in the range of 1-8, depending on the test conditions.

Gärtner, G.; Geittner, P.; Raasch, D.; Ritz, A.; Wiechert, D. U.

1999-05-01

312

Development of Knife-Edge Ridges on Ion-Bombarded Surfaces Miranda Holmes-Cerfon,1, 2  

E-print Network

Development of Knife-Edge Ridges on Ion-Bombarded Surfaces Miranda Holmes-Cerfon,1, 2 Wei Zhou,1, 3 bombardment of a modestly sloped surface can create knife-edge like ridges with extremely high slopes. Small pre-fabricated pits expand under ion bombardment, and the collision of two such pits creates knife

Bertozzi, Andrea L.

313

Sputter yields of insulators bombarded with hyperthermal multiply charged ions  

NASA Astrophysics Data System (ADS)

The total sputter yield for Au, Si, GaAs, SiO2, MgO, LiF and NaCl bombarded with hyperthermal highly charged Arq+ ions (q = 1-9) has been measured. Only for alkali halides (LiF, NaCl) and to some extent for SiO2 potential sputtering (enhancement of the sputter yield with increasing charge state of the primary ion) has been observed. All other targets showed normal collision induced sputtering. From that result it is obvious that the mechanisms for sputtering can not be explained by the Coulomb explosion model, because in this model insulators like MgO and semiconductors like Si and GaAs should also show charge state dependence of the sputtering yield. Alkali halides and SiO2 are materials which are known for strong electron phonon coupling where electronic excitations in the valence band are localized by formation of self trapped excitons (STE) and/or self trapped holes (STH). During bombardment with highly charged ions the neutralization process in front of, at and below the surface causes the formation of STE and/or STH. Therefore the potential sputtering can be explained as a defect mediated sputtering process which is well known in electron stimulated desorption (ESD) where the decay of STH and/or STE into different colour centers leads at the end to the desorption of neutralized anions. The also created neutral cations are either evaporated (as it is the case for the alkali halides) or have to be removed by momentum transfer by the impinging projectiles. Therefore it is very likely that in the case of SiO2 for very low impact energy mainly only oxygen is enhanced sputtered, the surface is enriched in Si and the potential sputtering effect decreases with increasing ion dose.

Varga, P.; Neidhart, T.; Sporn, M.; Libiseller, G.; Schmid, M.; Aumayr, F.; Winter, H. P.

1997-01-01

314

Effects of Pin-up Oxygen on [60]Fullerene for Enhanced Antioxidant Activity  

PubMed Central

The introduction of pin-up oxygen on C60, such as in the oxidized fullerenes C60O and C60On, induced noticeable increase in the antioxidant activity as compared to pristine C60. The water-soluble inclusion complexes of fullerenes C60O and C60Onreacted with linoleic acid peroxyl radical 1.7 and 2.4 times faster, respectively.

2008-01-01

315

A new application area for fullerenes: voltage stabilizers for power cable insulation.  

PubMed

Fullerenes are shown to be efficient voltage-stabilizers for polyethylene, i.e., additives that increase the dielectric strength of the insulation material. Such compounds are highly sought-after because their use in power-cable insulation may considerably enhance the transmission efficiency of tomorrow's power grids. On a molal basis, fullerenes are the most efficient voltage stabilizers reported to date. PMID:25504254

Jarvid, Markus; Johansson, Anette; Kroon, Renee; Bjuggren, Jonas M; Wutzel, Harald; Englund, Villgot; Gubanski, Stanislaw; Andersson, Mats R; Müller, Christian

2015-02-01

316

Size-controlled recrystallization of fullerene by gas–antisolvent process  

Microsoft Academic Search

Gas–antisolvent (GAS) process using CO2 successfully prepared crystals of fullerene (C60) from a toluene solution through a precipitation. Particle sizes of precipitated C60 could be easily controlled by changing the initial pressurization rate of CO2, the temperature at the initial pressurization, and the quantity of C60. Fullerene particles obtained by GAS method had regular octahedral shapes, whereas the particles obtained

Shunsuke Mochizuki; Akira Teramoto; Fuyuko Yamashita; Yasuhiko Kasama; Yoshiyuki Sato; Hiroshi Inomata

2010-01-01

317

Predicting Real Optimized Materials: Novel Nitrogen-Containing Fullerenes and Nanotubes  

SciTech Connect

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 theoretical calculations. The proposed research allows for a predictive method to control the electronic properties of fullerenes and nanotubes that could pave the way for controlled fabrication of molecular circuits and nanotube networks.

Manaa, M R

2003-07-15

318

Modeling of Induction Plasma Process for Fullerene Synthesis: Effect of Plasma Gas Composition and Operating Pressure  

Microsoft Academic Search

A mathematical model has been developed on the continuous synthesis of fullerenes by direct evaporation of carbon-containing\\u000a materials using induction thermal plasma technology. The main purpose of this study is to numerically investigate the effect\\u000a of plasma gas composition and operating pressure on the fullerene formation. The simulation results confirmed that Ar–He mixture\\u000a plasma is more efficient than argon plasma

K. S. KimA; A. Moradian; J. Mostaghimi; Gervais Soucy

2010-01-01

319

Nonlinear resistivity and critical behavior of metal-overlayer percolation systems on epitaxial fullerene films  

Microsoft Academic Search

Fullerene (C60 and C70) films were epitaxially grown on fresh (001) mica with the fcc closed-packed plane parallel to the substrate surface. Metal overlayers were deposited onto these fullerene films in an ultrahigh-vacuum chamber, and in situ resistance measurements were performed. With increasing current, we observed a reversible resistance variation and irreversible breakdown. Near the percolation threshold, we find the

J. Q. Wu; W. B. Zhao; J. Chen; K. Wu; Z. J. Wang; J. L. Zhang; C. Y. Li; D. L. Yin; Z. N. Gu; Z. X. Jin; X. H. Zhou

1996-01-01

320

Chemistry of Fullerenes on the Earth and in the Solar System: A 1995 Review  

NASA Astrophysics Data System (ADS)

Fullerenes C(sub)60 and C(sub)70, the all-carbon molecules with closed-cage structures were discovered in 1990 in shungite from the Kola peninsula. Subsequent discoveries in terrestrial materials include a fulgurite from Colorado, clays and marls from several locations on the Cretaceous-Tertiary boundary, and carbon-rich breccias from the Sudbury impact structure. A search for fullerenes in the carbon-rich materials anthraxolite, shungite, and thucholite, however, failed to find them.

Heymann, D.

1996-03-01

321

Growth of silicon carbide on silicon via reaction of sublimed fullerenes and silicon  

Microsoft Academic Search

Epitaxial silicon carbide films are grown on Si(100) substrates at a surface temperature of 1,200 K via fullerene precursors. Films have been grown up to a thickness of 2,500 â«. The growth rate of the SiC film is not limited by the surface reaction rate of fullerene with silicon at these temperatures, rather by the arrival rate of the reactants

A. V. Hamza; M. Balooch

1996-01-01

322

Photofabrication of fullerene-shelled quantum dots supramolecular nanoparticles for solar energy harvesting.  

PubMed

Quantum dots-based electron donor-acceptor systems play a rising role in the design of renewable and carbon-free energy harvesting technologies. In this article, we discuss the photofabrication of fullerene-shelled quantum dots supramolecular nanoparticles, in which the fullerene shell acts as not only a well-defined electron acceptor but also a robust protecting layer against the photocorrosion of the quantum dot core. We evaluate the ensemble and single-molecule electron transfer from the core to the shell in the nanoparticles and the photocurrent response of a photoelectrochemical cell constructed using the nanoparticles. The supramolecular nanoparticle has been prepared by the covalent tethering of a fullerene-thiol monolayer to the quantum dot followed by the photochemical reactions of free fullerene-thiol to the tethered monolayer. The nanoparticles are characterized using scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Correlated single-photon emission and the two-state ON-OFF photoluminescence show that single quantum dots are included in the supramolecular nanoparticles. The fullerene-shells suppress the blinking of single quantum dots by acting as well-defined electron traps, without allowing the transfer of Auger electrons to unknown traps. Electron transfer from the quantum dot-core to the fullerene-shell is apparent from the short ON and OFF durations in the photoluminescence intensity trajectories of single quantum dots, quenching of the photoluminescence intensity and lifetime of quantum dots at the ensemble level, and the characteristic transient absorption band of the anion radical of fullerene. We next construct a photoelectrochemical cell using the supramolecular nanoparticles, and the transferred electron is externally driven in the cell to generate ?400 ?A/cm(2) photocurrent. Electron transfer from the highly stable quantum dots to the protecting fullerene-shells places the supramolecular nanoparticles among the most promising antenna systems for the construction of cost-effective and stable next generation solar energy harvesting systems. PMID:22260241

Shibu, Edakkattuparambil Sidharth; Sonoda, Akinari; Tao, Zhuoqiz; Feng, Qi; Furube, Akihiro; Masuo, Sadahiro; Wang, Li; Tamai, Naoto; Ishikawa, Mitsuru; Biju, Vasudevanpillai

2012-02-28

323

Enantioselective Cycloaddition of Münchnones onto [60]Fullerene: Organocatalysis versus Metal Catalysis  

PubMed Central

Novel chiral catalytic systems based on both organic compounds and metal salts have been developed for the enantioselective [3 + 2] cycloaddition of münchnones onto fullerenes and olefins. These two different approaches proved to be efficient and complementary in the synthesis of optically active pyrrolino[3,4:1,2][60]fullerenes with high levels of enantiomeric excess and moderate to good conversions. Further functionalization of the pyrrolinofullerene carboxylic acid derivatives has been carried out by esterification and amidation reactions. PMID:24483247

2014-01-01

324

Electric-arc synthesis of soot with a high content of higher fullerenes  

NASA Astrophysics Data System (ADS)

The influence of potassium carbonate additions from 1 to 12 wt % and the helium pressure on the content of higher fullerenes C76, C78, C80, C82, C84, C86, etc., in soot is studied. The optimum conditions of the evaporation of composite graphite electrodes are found: they provide the formation of soot with a high content of higher fullerenes (up to 11.4 wt %) in an extract.

Kareev, I. E.; Nekrasov, V. M.; Bubnov, V. P.

2015-01-01

325

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

326

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

Microsoft Academic Search

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

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

2000-01-01

327

Formation mechanism and yield of molecules ejected from ZnS, CdS, and FeS2 during ion bombardment  

NASA Astrophysics Data System (ADS)

Neutral species ejected from single crystals of ZnS, CdS, and FeS2 during ion bombardment by 3 keV Ar(sup +) were detected by laser post-ionization followed by time-of-flight mass spectrometry. While metal atoms (Fe, Zn, Cd) and S2 were the dominant species observed, substantial amounts of S, FeS, Zn2, ZnS, Cd2, and CdS were also detected. The experimental results demonstrate that molecules represent a larger fraction of the sputtered yield than was previously believed from secondary ion mass spectrometry experiments. In addition, the data suggest that the molecules are not necessarily formed from adjacent atoms in the solid and that a modified form of the recombination model could provide a mechanism for their formation.

Nikzad, S.; Calaway, W. F.; Pellin, M. J.; Young, C. E.; Gruen, D. M.; Tombrello, T. A.

328

Pharmacokinetics of a water-soluble fullerene in rats.  

PubMed Central

Fullerenes are the recently discovered third allotropic form of carbon. The biological activities of these compounds are being studied for various purposes. The bis(monosuccinimide) derivative of p p'-bis(2-amino-ethyl)-diphenyl-C60 (MSAD-C60) is a water-soluble fullerene derivative. MSAD-C60 has been shown to have antiviral activity against human immunodeficiency virus types 1 and 2 in vitro and to have virucidal and anti-human immunodeficiency virus protease activities. Moreover, MSAD-C60 has been shown to be well tolerated in mice after intraperitoneal administration. The purpose of the present study was to develop a high-performance liquid chromatographic analytical methodology for MSAD-C60 and to characterize the preclinical pharmacokinetics of the compound in rats. Following intravenous administration of the fullerene derivative at a dose of 15 mg/kg of body weight, the concentrations of MSAD-C60 in plasma declined either bi- or triexponentially. The mean terminal-phase half-life of MSAD-C60 was 6.8 +/- 1.1 h (mean +/- standard deviation). Binding studies indicated that the compound is greater than 99% bound to plasma proteins. The average total clearance of the compound was 0.19 +/- 0.06 liter/h/kg. Urine samples obtained 24 h after intravenous administration did not contain detectable levels of the compound, indicating the absence of a significant renal clearance mechanism. The steady-state volume of distribution of MSAD-C60 averaged 2.1 +/- 0.8 liters/kg, indicating that the compound distributes into tissues. At a dose of 15 mg/kg, MSAD-C60 appeared to be well tolerated. However, a dose of 25 mg/kg resulted in shortness of breath and violent movement of the rats, followed by death within 5 min of dosing. Further controlled toxicity studies are needed to fully evaluate the toxicity of the compound. PMID:8891126

Rajagopalan, P; Wudl, F; Schinazi, R F; Boudinot, F D

1996-01-01

329

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

NASA Astrophysics Data System (ADS)

We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene)) that is end capped with the fullerene derivative PCB ([6,6]-phenyl-C61-butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound without attached fullerene (P3HT-OH). Fluorescence upconversion measurements reveal that the partial fluorescence quenching of PCB-P3HT in THF is multiphasic and occurs on an average time scale of 100 ps, in parallel to excited-state relaxation processes. Judging from ultrafast transient absorption experiments, the origin of the quenching is excitation energy transfer from the P3HT donor to the PCB acceptor. Due to the much higher solubility of P3HT compared to PCB in THF, the PCB-P3HT dyad molecules self-assemble into micelles. When pure C60 is added to the solution, it is incorporated into the fullerene-rich center of the micelles. This dramatically increases the solubility of C60 but does not lead to significant additional quenching of the P3HT fluorescence by the C60 contained in the micelles. In PCB-P3HT thin films drop-cast from THF, the micelle structure is conserved. In contrast to solution, quantitative and ultrafast (<150 fs) charge separation occurs in the solid-state films and leads to the formation of long-lived mobile charge carriers with characteristic transient absorption signatures similar to those that have been observed in P3HT:PCBM bulk heterojunction blends. While ?-stacking interactions between neighboring P3HT chains are weak in the micelles, they are strong in thin films drop-cast from ortho-dichlorobenzene. Here, PCB-P3HT self-assembles into a network of long fibers, clearly seen in atomic force microscopy images. Ultrafast charge separation occurs also for the fibrous morphology, but the transient absorption experiments show fast loss of part of the charge carriers due to intensity-induced recombination and annihilation processes and monomolecular interfacial trap-mediated or geminate recombination. The yield of the long-lived charge carriers in the highly organized fibers is however comparable to that obtained with annealed P3HT:PCBM blends. PCB-P3HT can therefore be considered as an active material in organic photovoltaic devices.

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

2011-08-01

330

Strongly reduced fragmentation and soft emission processes in sputtered ion formation from amino acid films under large Ar(n)+ (n ? 2200) cluster ion bombardment.  

PubMed

The analysis of organic and biological substances by secondary-ion mass spectrometry (SIMS) has greatly benefited from the use of cluster ions as primary bombarding species. Thereby, depth profiling and three-dimensional (3D) imaging of such systems became feasible. Large Ar(n)(+) cluster ions may constitute a further improvement in this direction. To explore this option, size-selected Ar(n)(+) cluster ions with 300 ? n ? 2200 (bombarding energies 5.5 and 11 keV) were used to investigate the emission of positive secondary ions from four amino acid specimens (arginine, glycine, phenylalanine, and tyrosine) by time-of-flight SIMS. For all cluster sizes, the protonated molecule of the respective amino acid is observed in the mass spectra. With increasing cluster size the number of fragment ions decreases strongly in relation to the intact molecules, to the extent that the fraction of fragment ions amounts to less than 10% in some cases. Such 'soft' emission processes also lead the ejection of dimers and even multimers of the amino acid molecules. In the case of the phenylalanine, secondary ion species composed of up to at least seven phenylalanine moieties were observed. Tentatively, the ionization probability of the emitted molecules is envisaged to depend on the presence of free protons in the emission zone. Their number can be expected to decrease concurrently with the decreasing amount of fragmentation for large Ar(n)(+) cluster ions (i.e. for low energies per cluster atom). PMID:22215571

Gnaser, Hubert; Ichiki, Kazuya; Matsuo, Jiro

2012-01-15

331

Energy landscape of fullerene materials: A comparion of boron to boron nitride and carbon  

NASA Astrophysics Data System (ADS)

After the discovery of the C60 fullerene some 25 years ago, many more hollow and endohedrally doped structures made out of various elements have been proposed theoretically. However, since no other fullerenes have been synthesized up to date, the question arises whether experimentalists have just not yet found a way to synthesize these theoretically predicted fullerenes, or whether they do not exist at all in nature. Following the theoretical discovery of the B80 fullerene by Szwacki et al, various other fullereneand stuffed fullerene structures were proposed but none of them could be synthesized in the laboratory yet. Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glass like. Medium size boron clusters exhibit many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nano structures.

de, Sandip

2012-02-01

332

On the formation of fullerenes in H-rich circumstellar environments  

NASA Astrophysics Data System (ADS)

Hydrogen depleted environments have been considered an essential requirement for the efficient formation of fullerene molecules in circumstellar/interstellar environments. In particular, the hydrogen-poor, helium-rich, and carbon-rich character of the gas around R Coronae Borealis (RCB) stars has been suggested to be a promising site for the efficient formation of these complex molecules. These suggestions are not supported by the Spitzer Space Telescope observations presented here, showing that infrared transitions of fullerenes are seen together with polycyclic aromatic hydrocarbon (PAH) features in H-containing Planetary Nebulae (PNe) and the two least H-deficient (hydrogen deficiency of only ~10-100) RCB stars. Present observations of fullerenes in PNe and RCB stars suggest that both PAHs and fullerenes may be formed by the photochemical processing of hydrogenated amorphous carbon (HAC), although other chemical routes cannot be discarded. We present accurate C60 and C70 abundances and C70/C60 ratios by using the most recent laboratory data on C60 and C70 fullerenes, which give us essential information about the conditions and the chemical route for fullerene formation in H-rich circumstellar/interstellar environments.

Garcia-Hernandez, D. A.

2011-05-01

333

Fullerene-containing phases obtained from aqueous dispersions of carbon nanoparticles  

NASA Astrophysics Data System (ADS)

The hydration of fullerenes and shungite carbon nanoclusters in aqueous dispersions at various carbon concentrations is studied on frozen samples by EPR with spin probes. It is found that, for stable dispersions of both substances (at carbon concentrations of 0.1 mg/ml), the probe rotation frequency versus 1/T dependences exhibit a plateau in the range 243 257 K, which is probably associated with the peculiarities of freezing of water localized near hydrophobic structures of carbon nanoclusters. Solid phases isolated from supersaturated aqueous dispersions of fullerenes and shungites by slow evaporation of water at temperatures higher than 0°C are examines by electron diffraction and electron microscopy. It is established that obtained films of fullerenes contain at least two phases: fullerite with a face-centered cubic lattice and a phase similar in interplanar spacing and radically different in distribution of intensities of diffraction peaks. It is concluded that this phase is formed by the interaction of fullerenes and water (an analogous phase is found in shungite carbon films). It is found that the morphology of the new crystal phase is characterized by globules of size 20 to 70 nm, for fullerenes, and 10 to 400 nm for shungites. It is established that processes of crystallization of fullerites and fullerene-containing phases are very sensitive to temperature: a decrease in the temperature (within the range from 40 to 1°C) is accompanied by an increase in the new phase content.

Rozhkov, S. P.; Kovalevskii, V. V.; Rozhkova, N. N.

2007-06-01

334

Theoretical study of phthalocyanine–fullerene complex for a high efficiency photovoltaic device using ab initio electronic structure calculation  

Microsoft Academic Search

Many fullerene-based supramolecules have been proposed as potential organic photovoltaic devices, with their electrochemical and photo-electrochemical properties measured under light illumination. Phthalocyanine possesses good electron-donating properties due to its large easily ionised ?-electron system, whereas fullerene is good ?-electron acceptor which can be connected with other organic molecules. A phthalocyanine–fullerene-based supramolecular system is therefore a potential material candidate for a

Hiroshi Mizuseki; Nobuaki Igarashi; Rodion V. Belosludov; Amir A. Farajian; Yoshiyuki Kawazoe

2003-01-01

335

Effect of nitrogen atomic percentage on N+-bombarded MWCNTs in cytocompatibility and hemocompatibility  

NASA Astrophysics Data System (ADS)

N+-bombarded multi-walled carbon nanotubes (N+-bombarded MWCNTs), with different nitrogen atomic percentages, were achieved by different N ion beam currents using ion beam-assisted deposition (IBAD) on MWCNTs synthesized by chemical vapor deposition (CVD). Characterizations of N+-bombarded MWCNTs were evaluated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and contact angle. For comparison, the in vitro cytocompatibility of the N+-bombarded MWCNTs with different N atomic percentages was assessed by cellular adhesion investigation using human endothelial cells (EAHY926) and mouse fibroblast cells (L929), respectively. The results showed that the presence of nitrogen in MWCNTs accelerated cell growth and proliferation of cell culture. The higher nitrogen content of N+-bombarded MWCNTs, the better cytocompatibility. In addition, N+-bombarded MWCNTs with higher N atomic percentage displayed lower platelet adhesion rate. No hemolysis can be observed on the surfaces. These results proved that higher N atomic percentage led N+-bombarded MWCNTs to better hemocompatibility.

Zhao, Mengli; Cao, Ye; Liu, Xiaoqi; Deng, Jianhua; Li, Dejun; Gu, Hanqing

2014-03-01

336

Effect of nitrogen atomic percentage on N+-bombarded MWCNTs in cytocompatibility and hemocompatibility.  

PubMed

N+-bombarded multi-walled carbon nanotubes (N+-bombarded MWCNTs), with different nitrogen atomic percentages, were achieved by different N ion beam currents using ion beam-assisted deposition (IBAD) on MWCNTs synthesized by chemical vapor deposition (CVD). Characterizations of N+-bombarded MWCNTs were evaluated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and contact angle. For comparison, the in vitro cytocompatibility of the N+-bombarded MWCNTs with different N atomic percentages was assessed by cellular adhesion investigation using human endothelial cells (EAHY926) and mouse fibroblast cells (L929), respectively. The results showed that the presence of nitrogen in MWCNTs accelerated cell growth and proliferation of cell culture. The higher nitrogen content of N+-bombarded MWCNTs, the better cytocompatibility. In addition, N+-bombarded MWCNTs with higher N atomic percentage displayed lower platelet adhesion rate. No hemolysis can be observed on the surfaces. These results proved that higher N atomic percentage led N+-bombarded MWCNTs to better hemocompatibility. PMID:24666845

Zhao, Mengli; Cao, Ye; Liu, Xiaoqi; Deng, Jianhua; Li, Dejun; Gu, Hanqing

2014-01-01

337

Erosion of frozen sulfur dioxide by ion bombardment - Applications to Io  

NASA Technical Reports Server (NTRS)

The erosion of frozen SO2 due to bombardment by both light and heavy ions (He and F) was measured for bombarding energies of 0.08 to 1.3 MeV/amu. The number of SO2 molecules ejected from the target per incident ion (i.e., the sputtering yield) was 50 for 1.5 MeV He ions and 7300 for 6 MeV F ions. Ion bombardment followed by heating produced an oxygen/sulfur residue which was much more stable against subsequent ion bombardment than the initial frozen SO2. The erosion rate of SO2 frost on Jupiter's moon Io depends strongly on the elemental composition and energy spectra of the magnetospheric ion flux which bombards the surface. The combined effects of ion bombardment and heating which produced residues on the target substrates may also occur on Io from magnetospheric ion bombardment and heating by volcanism. The experimental results compare favorably with a new model of the sputtering process which considers the energy loss of the incident ion to electronic excitation in the target.

Melcher, C. L.; Lepoire, D. J.; Cooper, B. H.; Tombrello, T. A.

1982-01-01

338

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

PubMed Central

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

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

2013-01-01

339

Tuning the Morphology and Performance of Low Bandgap Polymer: Fullerene Heterojunctions via Solvent Annealing in Selective Solvents  

SciTech Connect

Low bandgap polymer (LBG):fullerene mixtures are some of the most promising organic photovoltaic active layers. Unfortunately, there are no post-deposition treatments available to rationally improve the morphology and performance of as-cast LBG:fullerene OPV active layers, where thermal annealing usually fails. Therefore, there is a glaring need to develop postdeposition methods to guide the morphology of LBG:fullerene bulk heterojunctions towards targeted structures and performance. In this paper, the structural evolution of PCPDTBT:PCBM mixtures with solvent annealing (SA) is examined, focusing on the effect of solvent quality of the fullerene and polymer in the annealing vapor on morphological evolution and device performance. The results indicate that exposure of this active layer to the solvent vapor controls the ordering of PCPDTBT and PCBM phase separation very effectively, presumably by inducing component mobility as the solvent plasticizes the mixture. These results also unexpectedly indicate that solvent annealing in a selective solvent provides a method to invert the morphology of the LBG:fullerene mixture from a polymer aggregate dispersed in a polymer:fullerene matrix to fullerene aggregates dispersed in a polymer:fullerene matrix. The judicious choice of solvent vapor, therefore, provides a unique method to exquisitely control and optimize the morphology of LBG conjugated polymer/fullerene mixtures.

Chen, Huipeng [ORNL; Hsiao, Yu-Che [ORNL; Hu, Bin [ORNL; Dadmun, Mark D [ORNL

2014-01-01

340

Polychiral semiconducting carbon nanotube-fullerene solar cells.  

PubMed

Single-walled carbon nanotubes (SWCNTs) have highly desirable attributes for solution-processable thin-film photovoltaics (TFPVs), such as broadband absorption, high carrier mobility, and environmental stability. However, previous TFPVs incorporating photoactive SWCNTs have utilized architectures that have limited current, voltage, and ultimately power conversion efficiency (PCE). Here, we report a solar cell geometry that maximizes photocurrent using polychiral SWCNTs while retaining high photovoltage, leading to record-high efficiency SWCNT-fullerene solar cells with average NREL certified and champion PCEs of 2.5% and 3.1%, respectively. Moreover, these cells show significant absorption in the near-infrared portion of the solar spectrum that is currently inaccessible by many leading TFPV technologies. PMID:25101896

Gong, Maogang; Shastry, Tejas A; Xie, Yu; Bernardi, Marco; Jasion, Daniel; Luck, Kyle A; Marks, Tobin J; Grossman, Jeffrey C; Ren, Shenqiang; Hersam, Mark C

2014-09-10

341

Dynamically fluctuating electric dipole moments in fullerene-based magnets  

NASA Astrophysics Data System (ADS)

We report here the direct evidence of the existence of a permanent electric dipole moment in both crystal phases of a fullerene-based magnet--the ferromagnetic ?-phase and the antiferromagnetic ?'-phase of tetra-kis-(dimethylamino)-ethylene-C60 (TDAE-C60)--as determined by dielectric measurements. We propose that the permanent electric dipole originates from the pairing of a TDAE molecule with surrounding C60 molecules. The two polymorphs exhibit clear differences in their dielectric responses at room temperature and during the freezing process with dynamically fluctuating electric dipole moments, although no difference in their room-temperature structures has been previously observed. This result implies that two polymorphs have different local environment around the molecules. In particular, the ferromagnetism of the ?-phase is founded on the homogeneous molecule displacement and orientational ordering. The formation of the different phases with respect to the different rotational states in the Jahn-Teller distorted C60s is also discussed.

Kambe, Takashi; Oshima, Kokichi

2014-09-01

342

Surface chemical reactions of Al induced by low-energy D 2+, N 2+, CO +, and CO 2+ ion bombardment  

NASA Astrophysics Data System (ADS)

AES and SIMS studies have been carried out on chemical reactions induced by 0.5-4 keV D +2, N 2+, CO +, and CO 2+ ion beams on an Al surface. D 2+ impact on Al foils in an ultrahigh vacuum or in a D 2 atmosphere produces secondary ions, AID +,AID 2+ and Al 2D +, in addition to Al + and Al 2+. These ions are also produced by Ar + impact on Al foils in a D 2 atmosphere. Results obtained on their yields suggest that these D-atom containing secondary ions are produced from aluminium deutendes formed by successive chemical reactions induced by D 2. The Al surface bombarded with N +2 was covered with A1N completely or partially, depending on the impact energy of N 2+. The Al surface partially covered with A1N was found to undergo rapid, complete oxidation when exposed to O 2 gas. The results obtained for CO + and CO 2+ impact showed that CO + impact produces Al 4C 3, selectively, while CO 2+ impact produces both Al 4C 3 and aluminium oxide.

Nagai, Siro

1991-07-01

343

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

344

Growth of diamond-like carbon films using low energy ion beam sputter - bombardment deposition with Ar ions  

NASA Astrophysics Data System (ADS)

An alternative to a widely used ion assisted deposition method has been developed where a single beam of low energy Ar ions is used to simultaneously sputter a graphite target and to bombard a growing film. By placing the substrate at low incident angles to the axis of the ion beam and therefore subjecting the growing film to the additional ion energy we aimed to promote the formation of sp3 bonding. Sp2 rich amorphous carbon (a-C) and diamond-like carbon (DLC) films with significant fractions of sp3 bonding were formed by sputtering from a Kaufmann - type ion source. Experimental results revealed that when the substrate was placed at grazing angles to the incoming ions no DLC, but only polymeric a-C films were produced as a result of a secondary resputtering process. For DLC synthesis the optimal angles of the target and the substrate to the ion flux were found to be 30° and 0° respectively and the ion energies of 0.8 - 1.0 keV.

Rybachuk, M.; Bell, J. M.

2008-03-01

345

Changes in a surface of polycrystalline aluminum upon bombardment with argon ions  

NASA Astrophysics Data System (ADS)

The interaction between argon ions and a natural oxide layer of polycrystalline aluminum is studied via Auger electron (AE) and electron energy loss (EEL) spectroscopy. It is found that bombardment with argon ions whose energy is lower than the Al2O3 sputtering threshold results in the accumulation of bombarding ions in interstitial surface voids, thus forming a supersaturated solid solution of target atoms and bombarding ions of argon and nitrogen entrapped by the ion beam from the residual gas of the working chamber of the spectrometer.

Ashkhotov, O. G.; Ashkhotova, I. B.; Bliev, A. P.; Magkoev, T. T.; Krymshokalova, D. A.

2014-10-01

346

Anisotropic rearrangement of the substrate atoms during Ar bombardment on Pd(0 0 1) surface  

NASA Astrophysics Data System (ADS)

Using a three-dimensional molecular dynamics (MD) simulation, we investigated the atomic scale rearrangement that occurs on a Pd(0 0 1) surface after energetic bombardment by Ar at room temperature. High energy Ar bombardment provoked the significant rearrangement of Pd atoms in a ballistic manner with a fourfold symmetric lateral distribution aligned along the <1 1 0> direction. The MD simulation of uniform Ar bombardment at normal incidence on a Pd surface reproduced the experimentally observed fourfold symmetric nano-scale surface structure. The present result supports that the ballistic rearrangement of the substrate atoms plays an important role in the ion induced surface structure evolution.

Kim, Sang-Pil; Kim, Byung-Hyun; Kim, Haeri; Lee, Kwang-Ryeol; Chung, Yong-Chae; Seo, Jikeun; Kim, Jae-Sung

2011-11-01

347

Influence of Natural Organic Matter on Aggregation, Deposition, and Transport of Fullerene Colloids in Aqueous Systems  

NASA Astrophysics Data System (ADS)

Engineered fullerenes are increasingly being used in commercial products (e.g., skin and eye creams, tennis racquets, and lubricants) that may become a significant source for environmental release. A thorough understanding of fullerenes' aggregation in aqueous phase and deposition/transport in porous media is needed for evaluating the environmental persistence of fullerenes and subsequent human or ecological exposure. A number of recent studies have shown that fullerenes form stable colloidal aggregates in aqueous media and that their environmental behaviors largely depend on solution chemistry including ionic strength, solution pH, and the presence of natural organic matter (NOM). Nonetheless, the lack of systematic studies on NOM interaction with fullerene colloids and the coupling of this interaction with ionic strength and solution pH make predicting environmental behaviors of fullerenes a difficult task. In this study, electrophoretic mobility (EM), particle size, and aggregation kinetics of C60 colloidal suspensions were measured under a range of ionic strength (1.5-500.5 mM), solution pH (4, 7.8, and 10), and humic (0-9 mg C/L) or fulvic (0-11 mg C/L) acid concentrations. The EM data could be modeled with Ohshima's soft particle theory to probe thickness, softness, and charge density of adsorbed NOM layers on fullerene colloids. Under select conditions that represent low and high mobility, deposition studies using a quartz crystal microbalance and transport experiments in saturated and unsaturated sand columns will be conducted. It is anticipated that NOM may alter the transport of fullerene C60 differently in unsaturated media compared with saturated media. Our preliminary results showed that humic acid is more effective than fulvic acid in stabilizing fullerene suspensions and the extent of this stabilizing effect is a function of ionic strength when buffered at pH 7.8 with 0.5 mM NaHCO3. The findings of this study will help better assess the fate and transport of fullerene C60 in surface water, the vadose zone, and groundwater.

Zhang, W.; Rattanaudompol, U.; Powell, T.; Bouchard, D.

2011-12-01

348

The molecular mechanism of fullerene-inhibited aggregation of Alzheimer's ?-amyloid peptide fragment  

NASA Astrophysics Data System (ADS)

Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of ?-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-? (A?) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent ?-sheet formation of A?(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on A?(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the ?-sheet formation of A?(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of ?-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and A?(16-22) peptides significantly weaken the peptide-peptide interaction that is important for ?-sheet formation, thus retarding A?(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of A?(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease.Amyloid deposits are implicated in the pathogenesis of many neurodegenerative diseases such as Alzheimer's disease (AD). The inhibition of ?-sheet formation has been considered as the primary therapeutic strategy for AD. Increasing data show that nanoparticles can retard or promote the fibrillation of amyloid-? (A?) peptides depending on the physicochemical properties of nanoparticles, however, the underlying molecular mechanism remains elusive. In this study, our replica exchange molecular dynamics (REMD) simulations show that fullerene nanoparticle - C60 (with a fullerene : peptide molar ratio greater than 1 : 8) can dramatically prevent ?-sheet formation of A?(16-22) peptides. Atomic force microscopy (AFM) experiments further confirm the inhibitory effect of C60 on A?(16-22) fibrillation, in support of our REMD simulations. An important finding from our REMD simulations is that fullerene C180, albeit with the same number of carbon atoms as three C60 molecules (3C60) and smaller surface area than 3C60, displays an unexpected stronger inhibitory effect on the ?-sheet formation of A?(16-22) peptides. A detailed analysis of the fullerene-peptide interaction reveals that the stronger inhibition of ?-sheet formation by C180 results from the strong hydrophobic and aromatic-stacking interactions of the fullerene hexagonal rings with the Phe rings relative to the pentagonal rings. The strong interactions between the fullerene nanoparticles and A?(16-22) peptides significantly weaken the peptide-peptide interaction that is important for ?-sheet formation, thus retarding A?(16-22) fibrillation. Overall, our studies reveal the significant role of fullerene hexagonal rings in the inhibition of A?(16-22) fibrillation and provide novel insight into the development of drug candidates against Alzheimer's disease. Electronic supplementary information (ESI) available: The description of REMD simulations, analysis parameters, and AFM imaging of A?(16-22) aggregation with and without C60 nanoparticles, and three figures. The figures show the initial states, the convergence check for all the REMD runs, the PDF of the centroid distance (d) between the aromatic rings of Phe and its closest carbon ring, and the PDF of the

Xie, Luogang; Luo, Yin; Lin, Dongdong; Xi, Wenhui; Yang, Xinju; Wei, Guanghong

2014-07-01

349

Compositional Evolution of Saturn's Rings Due to Meteoroid Bombardment  

NASA Technical Reports Server (NTRS)

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 of the increasingly polluted ring material as impact ejecta. Our study includes detailed radiative transfer modeling of ring particle spectral reflectivities based on refractive indices of realistic constituents. Voyager data have shown that the lower optical depth regions in Saturn's rings (the C ring and Cassini Division) have darker and less red particles than the optically thicken A and B rings. These coupled structural-compositional groupings have never been explained; we present and explore the hypothesis that global scale color and compositional differences in the main rings of Saturn arise naturally from extrinsic meteoroid bombardment of a ring system which was initially composed primarily, but not entirely, of water ice. We find that the regional color and albedo differences can be understood if all ring material was initially identical (primarily water ice, based on other data, but colored by tiny amounts of intrinsic reddish, plausibly organic, absorber) and then evolved entirely by addition and mixing of extrinsic, nearly neutrally colored. plausibly carbonaceous material. We further demonstrate that the detailed radial profile of color across the abrupt B ring - C ring boundary can.constrain key unknown parameters in the model. Using new alternates of parameter values, we estimate the duration of the exposure to extrinsic meteoroid flux of this part of the rings, at least, to be on the order of 10(exp 8) years. This conclusion is easily extended by inference to the Cassini Division and its surroundings as well. This geologically young "age" is compatible with timescales estimated elsewhere based on the evolution of ring structure due to ballistic transport, and also with other "short timescales" estimated on the grounds of gravitational torques. However, uncertainty in the flux of interplanetary debris and in the ejects yield may preclude ruling out a ring age as old as the solar system at this time.

Cuzzi, J.; Estrada, P.; Young, Richard E. (Technical Monitor)

1997-01-01

350

The Impact of Fullerene Structure on Its Miscibility with P3HT and Its Correlation of Performance in Organic Photovoltaics  

SciTech Connect

Neutron reflectivity experiments are utilized to obtain the miscibility limit of four different fullerenes, bis-PCBM, ICBA, thio-PCBM, and PC70BM, in poly(3-hexylthiophene) (P3HT). The intermixing of P3HT and fullerene bilayers is monitored by neutron reflectivity before and after thermal annealing, providing quantification of the miscibility and interdiffusion of the fullerene within P3HT. These results indicate that the miscibility limit of these fullerenes in P3HT ranges from 11% to 26%, where the bis-adduct fullerenes exhibit lower miscibility in P3HT, which is also verified by small angle neutron scatting (SANS). The in-plane morphology of the P3HT:fullerene mixtures was also examined by SANS, which shows a decrease in domain size and an increase in the specific interfacial area between the fullerene and the polymer with the bis-fullerenes. Correlation of miscibility and morphology to device performance indicates that polymer/ fullerene miscibility is crucial to rationally optimize the design of fullerenes for use in organic photovoltaics. Bis-PCBM has a higher open circuit voltage (Voc) than PC60BM with P3HT; however, device performance of bis-PCBM based devices is lower than that of PC60BM based devices. This decrease in performance is attributed to the lower miscibility of bis-PCBM in P3HT, which decreases the probability of exciton dissociation and enhances the recombination of free charge carriers in the miscible region. Moreover, the minimum distance between fullerenes in the miscible region to facilitate intermolecular transport is identified as 11 .

Chen, Huipeng [ORNL; Peet, Jeff [Konarka Technologies, Inc.; Hsiao, Yu-Che [ORNL; Hu, Bin [University of Tennessee, Knoxville (UTK); Dadmun, Mark D [ORNL

2014-01-01

351

The Impact of Fullerene Structure on its Miscibility with P3HT and its Correlation of Performance in Organic Photovoltaics.  

SciTech Connect

Neutron reflectivity experiments are utilized to obtain the miscibility limit of four different fullerenes, bis-PCBM, ICBA, thio-PCBM, and PC70BM, in poly(3-hexylthiophene) (P3HT). The intermixing of P3HT and fullerene bilayers is monitored by neutron reflectivity before and after thermal annealing, providing quantification of the miscibility and interdiffusion of the fullerene within P3HT. These results indicate that the miscibility limit of these fullerenes in P3HT ranges from 11% to 26%, where the bis-adduct fullerenes exhibit lower miscibility in P3HT, which is also verified by small angle neutron scatting (SANS). The in-plane morphology of the P3HT:fullerene mixtures was also examined by SANS, which shows a decrease in domain size and an increase in the specific interfacial area between the fullerene and the polymer with the bis-fullerenes. Correlation of miscibility and morphology to device performance indicates that polymer/fullerene miscibility is crucial to rationally optimize the design of fullerenes for use in organic photovoltaics. Bis-PCBM has a higher open circuit voltage (Voc) than PC60BM with P3HT; however, device performance of bis-PCBM based devices is lower than that of PC60BM based devices. This decrease in performance is attributed to the lower miscibility of bis-PCBM in P3HT, which decreases the probability of exciton dissociation and enhances the recombination of free charge carriers in the miscible region. Moreover, the minimum distance between fullerenes in the miscible region to facilitate intermolecular transport is identified as 11 .

Chen, Huipeng [ORNL] [ORNL; Hsiao, Yu-Che [ORNL] [ORNL; Hu, Bin [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Dadmun, Mark D [ORNL] [ORNL

2014-01-01

352

Fullerene-enhanced accumulation of p,p'-DDE in agricultural crop species.  

PubMed

The effect of C(60) fullerene exposure on the accumulation of dichlorodiphenyldichloroethylene (p,p'-DDE; DDT metabolite) by Cucurbita pepo L. (zucchini), Glycine max L. (soybean), and Solanum lycopersicum L. (tomato) was determined. The plants were grown in 125 mL jars of vermiculite amended with 0 or 40 mg of C(60) fullerenes. Prior to planting, the jars were amended with 40 mL solution containing 100 ng/mL of p,p'-DDE with 0 or 100 mg/L humic acid. During three weeks of growth, plants were watered with the same p,p'-DDE containing solutions. Total shoot p,p'-DDE levels in nonfullerene exposed tomato, soybean, and zucchini were 26.9, 131, and 675 ng, respectively; total root DDE content for the three plants was 402, 5970, and 5830 ng, respectively. Fullerenes increased the shoot p,p'-DDE content of zucchini by 29%; contaminant levels in soybean shoots were decreased by 48% but tomato shoot content was unaffected. The root and total plant p,p'-DDE content of all three species was significantly increased by fullerene exposure; enhanced contaminant uptake ranged from 30 to 65%. Humic acid, regardless of fullerene presence or plant type, significantly decreased the p,p'-DDE uptake. Fullerenes were detected in the roots of all plants but were not detected in plant shoots in the initial study. In a follow up study with zucchini designed to maximize biomass for extraction, over half the analyzed stems contained fullerenes at 60.5 to 4490 ng/g. These findings show that the carbon-based nanomaterials may significantly alter the accumulation and potentially the toxicity of cocontaminants in agricultural systems. PMID:22856886

De La Torre-Roche, Roberto; Hawthorne, Joseph; Deng, Yingqing; Xing, Baoshan; Cai, Wenjun; Newman, Lee A; Wang, Chen; Ma, Xingmao; White, Jason C

2012-09-01

353

Tailoring buckybowls for fullerene recognition. A dispersion-corrected DFT study.  

PubMed

A series of buckybowls with different sizes and structures have been tested as potential receptors of fullerenes C60, C70 and C40. Among these bowls are corannulene (C20H10), sumanene (C21H12), pinakene (C28H14), hemifullerene (C30H12), circumtrindene (C36H12), pentaindenocorannulene (C50H20) and bowl-shaped hexabenzocoronene derivatives. An exhaustive study, taking into account different orientations of fullerenes, was performed in order to obtain the most favourable arrangement for interacting with the bowls. Complexes were optimised at the SCC-DFTB-D level and interaction energies were obtained at the B97-D2/TZVP level including BSSE corrections. Comparison with the full B97-D2/TZVP results (optimisation plus interaction energies) suggests that the B97-D2/TZVP//SCC-DFTB-D approach may be a useful screening tool for designing fullerene receptors. Regarding the "catching" ability of the different buckybowls, it can be concluded that the shape of a buckybowl plays a crucial role in its success. Thus, it seems that the addition of flaps at the bowl rim by benzannelation is an effective strategy for enhancing the interaction with fullerenes, providing enough flexibility to extend the contact surface with the fullerene moiety. Accordingly, a bowl-shaped hexabenzocoronene derivative (C72H24) showed the best ability among the buckybowls evaluated for catching the fullerenes C60, C70 and C40; it is noteworthy that, when interacting with C60, the interaction energy is three times that corresponding to the prototypical buckybowl, corannulene. On the contrary, the more rigid and compact is the structure of a buckybowl, the smaller its ability to interact with fullerenes. PMID:25648351

Josa, Daniela; González-Veloso, Iván; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M

2015-02-18

354

The reactivity of endohedral fullerenes. What can be learnt from computational studies?  

PubMed

The last two decades have witnessed major advances in the synthesis and characterization of endohedral fullerenes. These species have interesting physicochemical properties with many potential interesting applications in the fields of magnetism, superconductivity, nonlinear optical properties, radioimmunotherapy, and magnetic resonance imaging contrast agents, among others. In addition to the synthesis and characterization, the chemical functionalization of these species has been a main focus of research for at least four reasons: first, to help characterize endohedral fullerenes that could not be well described structurally otherwise; second, to generate materials with fine-tuned properties leading to enhanced functionality in one of their multiple potential applications; third, to produce water-soluble endohedral fullerenes needed for their use in medicinal sciences; and fourth, to generate electron donor-acceptor conjugates that can be used in solar energy conversion/storage. The functionalization of these species has been achieved through different types of reactions, the most common being the Diels-Alder reactions, 1,3-dipolar cycloadditions, Bingel-Hirsch reactions, and free-radical reactions. It has been found that the performance of these reactions in endohedral fullerenes may be quite different from that of the empty fullerenes. Indeed, encapsulated species have a large influence on the thermodynamics, kinetics, and regiochemistry of these reactions. A detailed understanding of the changes in chemical reactivity due to incarceration of atoms or clusters of atoms is essential to assist the synthesis of new functionalized endohedral fullerenes with specific properties. This Perspective seeks to highlight the key role played by computational chemistry in the analysis of the chemical reactivity of these systems. It is shown that the information obtained through calculations is highly valuable in the process of designing new materials based on endohedral fullerenes. PMID:21109874

Osuna, Sílvia; Swart, Marcel; Solà, Miquel

2011-03-01

355

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

Code of Federal Regulations, 2012 CFR

...ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS...bombardment areas. (a) The danger zones. (1) The waters of the...These areas are used for various surface and air gunnery and...

2012-07-01

356

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

Code of Federal Regulations, 2010 CFR

...ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS...bombardment areas. (a) The danger zones. (1) The waters of the...These areas are used for various surface and air gunnery and...

2010-07-01

357

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

...ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS...bombardment areas. (a) The danger zones. (1) The waters of the...These areas are used for various surface and air gunnery and...

2014-07-01

358

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

Code of Federal Regulations, 2013 CFR

...ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS...bombardment areas. (a) The danger zones. (1) The waters of the...These areas are used for various surface and air gunnery and...

2013-07-01

359

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

Code of Federal Regulations, 2011 CFR

...ARMY, DEPARTMENT OF DEFENSE DANGER ZONE AND RESTRICTED AREA REGULATIONS...bombardment areas. (a) The danger zones. (1) The waters of the...These areas are used for various surface and air gunnery and...

2011-07-01

360

Electron emission from surfaces resulting from low energy positron bombardment  

NASA Astrophysics Data System (ADS)

Measurements of the energy distribution of electrons resulting from very low energy positron bombardment of a polycrystalline Au and Cu(100) surfaces provide evidence for a single step transition from an unbound scattering state to an image potential bound state. The primary positron energy threshold for secondary electron emission and cutoff in the secondary electron energy spectra are consistent with a process in which an incident positrons make a transition from a scattering state to a surface-image potential bound while transferring all of the energy difference to an outgoing secondary electron. Estimates of the probability of this process as a function of incident positron energy are also presented. Background free Auger spectra of the MVV transition in Cu and the OVV transition in Au were obtained by setting the incident positron beam energy below the secondary electron emission threshold. Auger electron emission resulted from the annihilation of surface state positrons with core electrons. The low energy tail associated with the low energy CVV Auger transitions in Cu and Au were found to have integrated intensity several times larger than Auger peak providing strong evidence for multi-electron Auger processes.

Mukherjee, S.; Shastry, K.; Weiss, A. H.

2009-03-01

361

Electron emission from surfaces resulting from low energy positron bombardment  

NASA Astrophysics Data System (ADS)

Measurements of the secondary electron energy spectra resulting from very low energy positron bombardment of a polycrystalline Au and Cu (100) surfaces are presented that provide evidence for a single step transition from an unbound scattering state to an image potential bound state. The primary positron energy threshold for secondary electron emission and energy cutoff of the positron induced secondary electron energy peak are consistent with an Auger like process in which an incident positron make a transition from a scattering state to a surface-image potential bound while transferring all of the energy difference to an outgoing secondary electron. We term this process: the Auger mediated quantum sticking effect (AQSE). The intensities of the positron induced secondary electron peak are used to estimate the probability of this process as a function of incident positron energy. Positron annihilation induced Auger spectra (PAES) of Cu and Au are presented that are free of all primary beam induced secondary electron background. This background was eliminated by setting the positron beam energy below AQSE threshold. The background free PAES spectra obtained include the first measurements of the low energy tail of CVV Auger transitions all the way down to zero kinetic energy. The integrated intensity of this tail is several times larger than Auger peak itself which provides strong evidence for multi-electron Auger processes.

Mukherjee, Saurabh

362

Molecular dynamics simulations of cumulative helium bombardments on tungsten surfaces  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations were performed to study the cumulative bombardments of low-energy (60-200 eV) helium atoms on tungsten surfaces. The behaviour of helium and the response of tungsten surface were investigated. The helium incident energy and tungsten temperature play important roles on the formation and growth of helium clusters. The temperature can promote the coalescence of helium clusters and increase the size of the helium clusters. The rupture of the helium clusters has also been observed. During the formation of helium clusters, the interstitial tungsten atoms are produced and evolve into bundles of <1 1 1> crowdions, which would be constrained around the helium clusters for a long time. However, they will finally move onto the top surface along the <1 1 1> direction, which results in stacking the tungsten atoms on the surface. The complex combination effects of the helium clusters and the interstitial atoms result in the growth of the surfaces. Besides, several tungsten atoms were ejected from tungsten surfaces.

Li, Min; Cui, Jiechao; Wang, Jun; Hou, Qing

2014-10-01

363

Back-bombardment compensation in microwave thermionic electron guns  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

364

Comet impacts and chemical evolution on the bombarded earth  

NASA Technical Reports Server (NTRS)

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

Oberbeck, Verne R.; Aggarwal, Hans

1992-01-01

365

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

366

Molecular Dynamics Simulation of Damage Cascade Formation in Ion Bombarded Solids  

E-print Network

OF DAMAGE CASCADE FORMATION IN ION BOMBARDED SOLIDS A Thesis by DI CHEN Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August... 2011 Major Subject: Nuclear Engineering MOLECULAR DYNAMICS SIMULATION OF DAMAGE CASCADE FORMATION IN ION BOMBARDED SOLIDS A Thesis by DI CHEN Submitted to the Office of Graduate Studies of Texas A&M University in partial...

Chen, Di

2012-10-19

367

Measurement of positional isotope exchange rates in enzyme catalyzed reactions by fast atom bombardment mass spectrometry  

E-print Network

MEASUREMENT OF POSITIONAL ISOTOPE EXCHANGE RATES IN ENZYME CATALYZED REACTIONS BY FAST ATOM BOMBARDMENT MASS SPECTROMETRY A Thesis by LARRY NAYNE HILSCHER Submitted to the Gradu te College of Texas A&M University in partial fulfil" mert... of the requiremer ts for the degree of MASTEP. QF SCIENCE August 1985 Major Subject: Chemistry MEASUREMENT OF POSITIONAL ISOTOPE EXCHANGE RATES IN ENZYME CATALYZED REACTIONS BY FAST ATOM BOMBARDMENT MASS SPECTROMETRY A Thesis LARRY NAYNE HILSCHER Approved...

Hilscher, Larry Wayne

1985-01-01

368

Lunar samples, lunar accretion and the early bombardment of the moon  

NASA Technical Reports Server (NTRS)

The cratering history of the moon is reexamined taking data acquired over the last decade into account along with a newly accepted concept concerning the moon's origin. It is found that predictions of a heavy bombardment are not fulfilled by lunar characteristics as understood from sample and remote sensing studies, nor by lunar accretion history. There is strong evidence for the reality for a short, intense, cataclysmic bombardment at about 3.85 Ga.

Ryder, Graham

1990-01-01

369

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

370

Compact bis-adduct fullerenes and additive-assisted morphological optimization for efficient organic photovoltaics.  

PubMed

Bis-adduct fullerenes surrounded by two insulating addends sterically attenuate intermolecular interaction and cause inferior electron transportation. In this research, we have designed and synthesized a new class of bis-adduct fullerene materials, methylphenylmethano-C60 bis-adduct (MPC60BA), methylthienylmethano-C60 bis-adduct (MTC60BA), methylphenylmethano-C70 bis-adduct (MPC70BA), and methylthienylmethano-C70 bis-adduct (MTC70BA), functionalized with two compact phenylmethylmethano and thienylmethylmethano addends via cyclopropyl linkages. These materials with much higher-lying lowest unoccupied molecular orbital (LUMO) energy levels successfully enhanced the Voc values of the P3HT-based solar cell devices. The compact phenylmethylmethano and thienylmethylmethano addends to promote fullerene intermolecular interactions result in aggregation-induced phase separation as observed by the atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the poly(3-hexylthiophene-2,5-diyl) (P3HT)/bis-adduct fullerene thin films. The device based on the P3HT/MTC60BA blend yielded a Voc of 0.72 V, a Jsc of 5.87 mA/cm(2), and a fill factor (FF) of 65.3%, resulting in a power conversion efficiency (PCE) of 2.76%. The unfavorable morphologies can be optimized by introducing a solvent additive to fine-tune the intermolecular interactions. 1-Chloronaphthalene (CN) having better ability to dissolve the bis-adduct fullerenes can homogeneously disperse the fullerene materials into the P3HT matrix. Consequently, the aggregated fullerene domains can be alleviated to reach a favorable morphology. With the assistance of CN additive, the P3HT/MTC60BA-based device exhibited enhanced characteristics (a Voc of 0.78 V, a Jsc of 9.04 mA/cm(2), and an FF of 69.8%), yielding a much higher PCE of 4.92%. More importantly, the additive-assisted morphological optimization is consistently effective to all four compact bis-adduct fullerenes regardless of the methylphenylmethano or methylthienylmethano scaffolds as well as C60 or C70 core structures. Through the extrinsic additive treatment, these bis-adduct fullerene materials with compact architectures show promise for high-performance polymer solar cells. PMID:25285727

Lai, Yun-Yu; Liao, Ming-Hung; Chen, Yen-Ting; Cao, Fong-Yi; Hsu, Chain-Shu; Cheng, Yen-Ju

2014-11-26

371

Isolation and FTIR analysis of endohedral L3-xMxN@C80 (0 ? × ? 3) fullerenes  

NASA Astrophysics Data System (ADS)

L3-xMxN@C80 (0 ? × ? 3; M = Sc, Y, Tb, Ho, Er) fullerenes have been isolated and studied by FTIR spectroscopy. Ionic radii and cage size are shown to affect the structure of the encaged trimetal nitride cluster. A correlation between cluster size, metal-nitrogen bond strength and stability of M3N@C80 fullerenes is proposed.

Krause, M.; Noack, J.; Marczak, R.; Georgi, P.; Dunsch, L.

2003-10-01

372

Encapsulation of pristine fullerene C60 within block copolymer micelles through interfacial instabilities of emulsion droplets.  

PubMed

We report a facile and versatile strategy to encapsulate pristine fullerene (C60) within spherical or wormlike block copolymer micelles through interfacial instability of emulsion droplets. C60 and amphiphilic block copolymer polystyrene-b-poly(ethylene oxide) were firstly dispersed in chloroform. The resulting solution was emulsified with aqueous sodium dodecylsulfate solution by simply shaking it. The emulsion droplets were collected in an open container and the solvent was allowed to evaporate. During solvent evaporation, the emulsion droplets became unstable and broke into tiny droplets, i.e., interfacial instabilities occurred, triggering the formation of uniform spherical micelles with encapsulated fullerenes in the micellar cores. More interestingly, fullerene addition induced a morphological transition from cylindrical micelles to string-of-vesicles and then to spherical micelles with increasing fullerene contents of 5 wt%, 10 wt%, and 30 wt%, respectively. We show that the optical properties of the confined C60 molecules can be modified by varying the quantity of fullerenes in the micelles. In addition, poly(3-hexylthiophene) (P3HT) can be co-encapsulated with C60 into the micellar cores when P3HT was dissolved in the initial polymer solution prior to emulsification. Presence of C60 in the micellar cores induced fluorescence quenching of P3HT due to photoinduced energy transfer from electron-donating P3HT to electron-accepting C60 molecules. Hybrid micelles with well-controlled structures and components can be potentially useful in the area of photodynamic therapy and photovoltaics. PMID:24461821

Li, Weikun; Zhu, Xiaoguang; Wang, Jianying; Liang, Ruijing; Li, Jingyi; Liu, Shanqin; Tu, Guoli; Zhu, Jintao

2014-03-15

373

Co-Exposure with Fullerene May Strengthen Health Effects of Organic Industrial Chemicals  

PubMed Central

In vitro toxicological studies together with atomistic molecular dynamics simulations show that occupational co-exposure with C60 fullerene may strengthen the health effects of organic industrial chemicals. The chemicals studied are acetophenone, benzaldehyde, benzyl alcohol, m-cresol, and toluene which can be used with fullerene as reagents or solvents in industrial processes. Potential co-exposure scenarios include a fullerene dust and organic chemical vapor, or a fullerene solution aerosolized in workplace air. Unfiltered and filtered mixtures of C60 and organic chemicals represent different co-exposure scenarios in in vitro studies where acute cytotoxicity and immunotoxicity of C60 and organic chemicals are tested together and alone by using human THP-1-derived macrophages. Statistically significant co-effects are observed for an unfiltered mixture of benzaldehyde and C60 that is more cytotoxic than benzaldehyde alone, and for a filtered mixture of m-cresol and C60 that is slightly less cytotoxic than m-cresol. Hydrophobicity of chemicals correlates with co-effects when secretion of pro-inflammatory cytokines IL-1? and TNF-? is considered. Complementary atomistic molecular dynamics simulations reveal that C60 co-aggregates with all chemicals in aqueous environment. Stable aggregates have a fullerene-rich core and a chemical-rich surface layer, and while essentially all C60 molecules aggregate together, a portion of organic molecules remains in water. PMID:25473947

Róg, Tomasz; Cramariuc, Oana; Vanhala, Esa; Tornaeus, Jarkko; Taberman, Helena; Jänis, Janne; Alenius, Harri; Vattulainen, Ilpo; Laine, Olli

2014-01-01

374

Formation of a new electric material: Fullerene/metal polycrystalline film  

SciTech Connect

An investigation of the formation behavior and mechanism of onion like fullerene/metal polycrystalline film under electron beam irradiation is presented. Metallic nanoparticles of Al, Au and Pt having diameters of 1{approximately}35 nm, were supported on an amorphous carbon film with thickness of about 20 nm. The amorphous carbon film transformed into onion-like fullerene film under electron beam irradiation, with intensity about 10{sup 20} e/cm{sup 2}{center{underscore}dot}sec using high resolution transmission electron microscopy. The transformation mechanism and growth morphology have been investigated. It is found that the nucleation and growth process of onion-like fullerenes from amorphous carbon were divided into several steps: Firstly, a few elliptic shells of carbon were induced under Al, Au or Pt nanoparticles; secondly, a gradual reorganization took place into the structures composed of quasi-concentric spheroid or sphered graphite, i.e., onion like fullerenes, and finally, fullerenes were bonded to each other into a film.

Xu, Bingshu; Tanaka, Shunichiro

1997-07-01

375

Enhancement of titanium dioxide photocatalysis with polyhydroxy fullerenes  

NASA Astrophysics Data System (ADS)

Semiconductor photocatalysts, particularly TiO2, are attracting extensive research for destruction of environmentally hazardous chemicals (e.g., organic pollutants, greenhouse gases) and hazardous bioparticulates (e.g., bacterial endospores, emerging pathogens) because they can achieve complete mineralization without generation of toxic byproducts. Several attempts have been made to improve the quantum efficiency of TiO2 by conjugating it with conductors such as metals and organic molecules for scavenging the photo-generated electrons. Another class of materials well known for their electron accepting properties is carbon nanotubes and fullerenes. TiO2 (anatase polymorph) was coated on multi-wall carbon nanotubes by sol-gel coating and the resulting nanocomposites were found to inactivate bacterial endospores two times faster than Degussa P25 (gold standard), but were ineffective against Escherichia coli. This was attributed to their high aspect ratio, which prevented contact with the fimbriae covered cell-wall of E. coli. Water-soluble and non-toxic polyhydroxy fullerenes (PHF) were employed as alternate to the TiO2 coated MWNT. Adsorption of PHF molecules onto TiO2 by electrostatic interaction was demonstrated. PHF-TiO 2 nanocomposites enhanced the photocatalytic activity of TiO2 for dye degradation and E. coli inactivation. Surface coverage of TiO2 nanoparticles by PHF molecules determined the extent of enhancement, with an optimum at 2--7% surface coverage. The rate of photocatalytic dye degradation by the TiO2-PHF nanocomposite was 2.6 times the rate found with TiO2 alone. The hypothesis that scavenging of photo-generated electrons and therefore higher generation of hydroxyl radicals is the mechanism for the observed enhancement was validated. The concentration of hydroxyl radicals generated by PHF-TiO 2 nanocomposite was up to 60% greater than the concentration obtained with TiO2 alone as determined with EPR. Influence of functional groups of PHF on its electron scavenging ability and stability was determined. Fresh and aged forms of PHF were characterized by MS, FTIR, XPS and TGA. Higher concentrations of impure groups were detrimental to stability and electron scavenging ability of PHF. A ratio of impure groups to hydroxyl groups of 0.27 was associated with successful enhancement by PHF, whereas a ratio of 1.66 was associated with no enhancement. Guidelines for effective formulation of PHF-TiO2 nanocomposites were developed.

Krishna, Vijay B.

2007-05-01

376

Electron energy loss spectra from polycrystalline Cr and Cr 2O 3 before and after surface reduction by Ar + bombardment  

NASA Astrophysics Data System (ADS)

Electron energy loss spectra (ELS) have been obtained from polycrystalline Cr and Cr 2O 3 before and after surface reduction by 2 keV Ar + bombardment. The primary electron energy used in the ELS measurements was systematically varied from 100 to 1150 eV in order to distinguish surface versus bulk loss processes. Two predominant loss features in the ELS spectra obtained from Cr metal at 9.0 and 23.0 eV are assigned to the surface and bulk plasmon excitations, respectively, and a number of other features arising from single electron transitions from both the bulk and surface Cr 3d bands to higher-lying states in the conduction band are also present. The ELS spectra obtained from Cr 2O 3 exhibit features that originate from both interband transitions and charge-transfer transitions between the Cr and O ions as well as the bulk plasmon at 24.4 eV. The ELS feature at 4.0 eV arises from a charge-transfer transition between the oxygen and chromium ions in the two surface layers beneath the chemisorbed oxygen layer, and the ELS feature at 9.8 eV arises from a similar transition involving the chemisorbed oxygen atoms. The intensity of the ELS peak at 9.8 eV decreases after Ar + sputtering due to the removal of chemisorbed oxygen atoms. Sputtering also increases the number of Cr 2+ states on the surface, which in turn increases the intensity of the 4.0 eV feature. Furthermore, the ELS spectra obtained from the sputtered Cr 2O 3 surface exhibit features characteristic of both Cr 0 and Cr 2O 3, indicating that Ar + sputtering reduces Cr 2O 3. The fact that neither the surface- nor the bulk-plasmon features of Cr 0 can be observed in the ELS spectra obtained from sputtered Cr 2O 3 while the loss features due to Cr 0 interband transitions are clearly present indicates that Cr 0 atoms form small clusters lacking a bulk metallic nature during Ar + bombardment of Cr 2O 3.

Weaver, Jason F.; Hagelin-Weaver, Helena A. E.; Hoflund, Gar B.; Salaita, Ghaleb N.

2006-09-01

377

Electron-electron correlations in fullerene C{sub 60} probed by incoherent scattering of x rays  

SciTech Connect

The static structure factor of electrons in fullerene has been obtained by a properly designed x-ray diffraction experiment. Due to the intense diffuse scattering caused by the orientational disorder of the C{sub 60} molecules in fullerene, the experiment presented several difficulties. Nonetheless, the data were accurate enough to provide an estimate of the exchange-correlation energy and to make a valuable comparison of the static structure factors of fullerene and diamond. The observed value of the exchange-correlation energy, which is larger in fullerene than in diamond, suggests a clear link between carbon polymorphism and dynamic electron correlations. The experimental data of static structure factor of fullerene, together with the derived exchange-correlation contribution to the cohesion and the pair-correlation function, offer an interesting test on the validity of the local-density treatment of the electron correlations in solids.

Petrillo, C.; Sacchetti, F.; Orecchini, A. [Dipartimento di Fisica, Universita di Perugia, I-06123 Perugia (Italy) and CNR-INFM CRS-Soft, Rome (Italy); De Renzi, R.; Ricco, M. [Dipartimento di Fisica, Universita di Parma and CNISM, I-43100 Parma (Italy)

2006-08-15

378

Growth of all-carbon horizontally aligned single-walled carbon nanotubes nucleated from fullerene-based structures  

PubMed Central

All-carbon single-walled carbon nanotubes (SWCNTs) were successfully synthesized, nucleated using a fullerene derivative. A systematic investigation into the initial preparation of C60 fullerenes as growth nucleators for the SWCNTs was conducted. Enhancement in the yield of the produced SWCNT has been achieved with exploring different dispersing media for the fullerenes, the period, and environment of the initial thermal treatment of the fullerenes in addition to the use of different fullerene-based structures. The systematic studies significantly advance our understanding of the growth of the all-carbon catalyst-free single-walled carbon nanotubes. Field-effect transistors were fabricated using the catalyst-free SWCNT and then electrically characterized, showing current capacity as high as the well-studied catalyst-assisted nanotubes. PMID:23742117

2013-01-01

379

Compact, maintainable 80-KeV neutral beam module  

DOEpatents

A compact, maintainable 80-keV arc chamber, extractor module for a neutral beam system immersed in a vacuum of <10.sup.-2 Torr, incorporating a nested 60-keV gradient shield located midway between the high voltage ion source and surrounding grounded frame. The shield reduces breakdown or arcing path length without increasing the voltage gradient, tends to keep electric fields normal to conducting surfaces rather than skewed and reduces the peak electric field around irregularities on the 80-keV electrodes. The arc chamber or ion source is mounted separately from the extractor or ion accelerator to reduce misalignment of the accelerator and to permit separate maintenance to be performed on these systems. The separate mounting of the ion source provides for maintaining same without removing the ion accelerator.

Fink, Joel H. (Livermore, CA); Molvik, Arthur W. (Livermore, CA)

1980-01-01

380

Modification of surface band bending of diamond by low energy argon and carbon ion bombardment  

NASA Astrophysics Data System (ADS)

Argon and carbon ion bombardment of p-diamond at 500-5000 eV in ultrahigh vacuum were studied by in situ x-ray photoelectron spectroscopy (XPS) and low energy electron diffraction analysis. Both argon and carbon ion bombardment at room temperature in the present energy range created a defective surface layer. The radiation damage was manifested by the introduction of a distinct C 1s peak (referred to as the ``defect'' peak later) with a binding energy about 1 eV less than that of the bulklike diamond peak, and by the introduction of some additional filled states (referred to as the ``filled states'') near the valence band edge of diamond. It was found that in comparison to argon bombardment, carbon bombardment was more efficient in producing the filled states but less efficient in raising the C 1s defect peak. While the filled states disappeared by annealing at about 500 °C, the C 1s defect peak did not change much even with a 1000 °C anneal. These results suggest that the C 1s defect peak, which has also been observed on reconstructed diamond surfaces after hydrogen desorption [see, e.g., B. B. Pate, Surf. Sci. 165, 83(1986)], is associated with vacancy formation and aggregation which give some ``internal surfaces'' with a behavior like a reconstructed atomically clean diamond surface. The filled states introduced by ion bombardment are associated with interstitials or interstitial clusters. The amount of residual defects was found to increase with both an increasing bombardment dose and energy. For an argon bombardment at 1000 eV to a dose of 5×1014/cm2, the defective layer was estimated to be about 1.5 nm. Further, it was found that the radiation damage, particularly the ``vacancy defects'', could only be annealed (at 1000 °C) when the dose was below 5×1014/cm2 at a bombardment energy of 500 eV. XPS band bending analyses also showed that room temperature bombardment induced a small reduction (0.2 eV) of the surface Fermi level position (EFs) on the p-diamond. However, subsequent vacuum annealing caused a rather large increase of EFs. But the EFs data from about 20 bombarded and annealed samples were always less than 2.2 eV. Thus the formation of an n-type diamond was not observed.

Lau, W. M.; Huang, L. J.; Bello, I.; Yiu, Y. M.; Lee, S.-T.

1994-04-01

381

Aggregation and interactions of C 60 and C 70 fullerenes in neat N-methylpyrrolidinone and in N-methylpyrrolidinone/toluene mixtures  

NASA Astrophysics Data System (ADS)

A strong solvatochromic effect leading to the loss of the fine structure of UV-visible spectra and to the change of the specific absorption was observed for C 60 and C 70 fullerenes in N-methylpyrrolidinone (NMP). The C 60 and C 70 fullerene interactions in NMP solutions were studied by using time resolved fluorescence polarization anisotropy and dynamic light scattering techniques aiming to the determination of fullerene sizes. The process was studied as time dependent in toluene/NMP solutions and both the formation of fullerenes aggregates and specific interactions between fullerenes and NMP were observed.

Alfè, M.; Apicella, B.; Barbella, R.; Bruno, A.; Ciajolo, A.

2005-03-01

382

Fabrication and conductive properties of multilayered ultrathin films designed by layer-by-layer assembly of water-soluble fullerenes.  

PubMed

Fullerene ultrathin films were fabricated by layer-by-layer (LbL) assembly of an anionic fullerene C(61)(COO(-))(2) (FDCA) and poly(diallyldimethylammonium chloride) (PDDA) or a cationic fullerene C(60)C(2)H(4)N(CH(3))(2)(+) (FMAC) and poly(sodium 4-styrenesulfonate) (PSS). The dynamic light scattering and zeta-potential measurements revealed that both water-soluble fullerenes are stably dispersed as polyelectrolytes with a diameter of 20-70 nm for FDCA and 60-180 nm for FMAC in aqueous solutions. In spite of such large fullerene aggregates, the thickness of fullerene LbL films increased regularly by a few nanometers with each deposition, and the resultant LbL films were homogeneous. For FMAC/PSS LbL films, the monolayer thickness was evaluated to be 4 nm for FMAC and 0.5 nm for the PSS layer. In other words, the volume fraction of the fullerene moiety is as high as approximately 80 vol %. The conductivity of fullerene LbL films was comparable to that of a C(60)-dispersed polystyrene film with a similar fullerene fraction, suggesting that there exist effective percolating networks due to the high fullerene fraction in the LbL films. The electron mobility of FMAC/PSS LbL films was as high as 3 x 10(-5) cm(2) V(-1) s(-1), which is comparable to the hole mobility of poly(p-phenylenevinylene) LbL films reported previously. PMID:20695593

Masuda, Kohji; Abe, Takefumi; Benten, Hiroaki; Ohkita, Hideo; Ito, Shinzaburo

2010-08-17

383

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

384

Did Saturn's rings form during the Late Heavy Bombardment ?  

E-print Network

The origin of Saturn\\' s massive ring system is still unknown. Two popular scenarios - the tidal splitting of passing comets and the collisional destruction of a satellite - rely on a high cometary flux in the past. In the present paper we attempt to quantify the cometary flux during the Late Heavy Bombardment (LHB) to assess the likelihood of both scenarios. Our analysis relies on the so-called Nice model of the origin of the LHB (Tsiganis et al., 2005; Morbidelli et al., 2005; Gomes et al., 2005) and on the size distribution of the primordial trans-Neptunian planetesimals constrained in Charnoz & Morbidelli (2007). We find that the cometary flux on Saturn during the LHB was so high that both scenarios for the formation of Saturn rings are viable in principle. However, a more detailed study shows that the comet tidal disruption scenario implies that all four giant planets should have comparable ring systems whereas the destroyed satellite scenario would work only for Saturn, and perhaps Jupiter. This is because in Saturn\\'s system, the synchronous orbit is interior to the Roche Limit, which is a necessary condition for maintaining a satellite in the Roche zone up to the time of the LHB. We also discuss the apparent elimination of silicates from the ring parent body implied by the purity of the ice in Saturn \\' s rings. The LHB has also strong implications for the survival of the Saturnian satellites: all satellites smaller than Mimas would have been destroyed during the LHB, whereas Enceladus would have had from 40% to 70% chance of survival depending on the disruption model. In conclusion, these results suggest that the LHB is the sweet moment for the formation of a massive ring system around Saturn.

Sebastien Charnoz; Alessandro Morbidelli; Luke H. Dones; Julien Salmon

2008-09-29

385

A Nano-sized Supramolecule Beyond the Fullerene Topology.  

PubMed

The reaction of [Cp(Bn) Fe(?(5) -P5 )] (1) (Cp(Bn) =?(5) -C5 (CH2 Ph)5 ) with CuI selectively yields a novel spherical supramolecule (CH2 Cl2 )3.4 @[(Cp(Bn) FeP5 )12 {CuI}54 (MeCN)1.46 ] (2) showing a linkage of the scaffold atoms which is beyond the Fullerene topology. Its extended CuI framework reveals an outer diameter of 3.7?nm-a size that has not been reached before using five-fold symmetric building blocks. Furthermore, 2 shows a remarkable solubility in CH2 Cl2 , and NMR spectroscopy reveals that the scaffold of the supramolecule remains intact in solution. In addition, a novel 2D polymer [{Cp(Bn) Fe(?(5) -P5 )}2 {Cu6 (?-I)2 (?3 -I)4 }]n (3) with an uncommon structural motif was isolated. Its formation can be avoided by using a large excess of CuI in the reaction with 1. PMID:25288480

Dielmann, Fabian; Heindl, Claudia; Hastreiter, Florian; Peresypkina, Eugenia V; Virovets, Alexander V; Gschwind, Ruth M; Scheer, Manfred

2014-12-01

386

Preparation and biodistribution of radiolabeled fullerene C60 nanocrystals  

NASA Astrophysics Data System (ADS)

The present study describes for the first time a procedure for the radiolabeling of fullerene (C60) nanocrystals (nanoC60) with Na 125I, as well as the biodistribution of radiolabeled nanoC60 (125I-nanoC60). The solvent exchange method with tetrahydrofuran was used to make colloidal water suspensions of radiolabeled nanoC60 particles. The radiolabeling procedure with the addition of Na 125I to tetrahydrofuran during dissolution of C60 gave a higher radiochemical yield of radiolabeled nanoC60 particles in comparison to the second option, in which Na 125I was added after C60 was dissolved. Using photon correlation spectroscopy and transmission electron microscopy, 125I-nanoC60 particles were found to have a crystalline structure and a mean diameter of 200-250 nm. The 125I-nanoC60 had a particularly high affinity for human serum albumin, displaying 95% binding efficiency after 1 h. Biodistribution studies of 125I-nanoC60 in rats indicated significant differences in tissue accumulation of 125I-nanoC60 and the radioactive tracer Na 125I. The higher accumulation of radiolabeled nanoC60 was observed in liver and spleen, while accumulation in thyroid, stomach, lungs and intestines was significantly lower in comparison to Na 125I. In addition to being useful for testing the biological distribution of nanoC60, the described radiolabeling procedure might have possible applications in cancer radiotherapy.

Nikoli?, Nadežda; Vranješ-Ðuri?, Sanja; Jankovi?, Drina; Ðoki?, Divna; Mirkovi?, Marija; Bibi?, Nataša; Trajkovi?, Vladimir

2009-09-01

387

Fullerenes dissolve gold in a sequence of phase transformations.  

NASA Astrophysics Data System (ADS)

We present the observation of a field induced diffusion of noble metals (Au, Ag) and related phase transformations in fullerenes. The metal intercalation was performed by a dry electrolysis from the electrode into the polycrystalline C_60 and C_70 thin films. It was detected by in situ and space resolved conductivity measurements at different temperatures and applied voltages. Under the applied d.c. voltage the film resistivity evolves in time decreasing by several order of magnitudes and passing through the minima (one for C_60 and two for C_70 films). The current voltage characteristics being non linear at the beginning of the process became completely ohmic at the resistivity saturation regime. The time resistivity behavior is described on the basis of electric field stimulated diffusion of metal ions from the contact going on via the interstitials of crystal lattice and filling them in a sequence of stoichiometric phases. It starts mostly through octahedral sites forming locally the rock salt phase M_1C_60, A_1C_70. The process continues through the tetrahedral sites. The resistivity minima correspond to a formation of local phases M_3C_60 and respectively A_1C_70 and A_4C_70. The resistivity is saturated by formation of phases M_6C_60 A_6C_70. In contrast to A_xC_60 the phases A_xC_70 are stable only in the applied electric field.

Kirova, N.; Firlej, L.

1998-03-01

388

Dynamically fluctuating electric dipole moments in fullerene-based magnets  

PubMed Central

We report here the direct evidence of the existence of a permanent electric dipole moment in both crystal phases of a fullerene-based magnet—the ferromagnetic ?-phase and the antiferromagnetic ??-phase of tetra-kis-(dimethylamino)-ethylene-C60 (TDAE-C60)—as determined by dielectric measurements. We propose that the permanent electric dipole originates from the pairing of a TDAE molecule with surrounding C60 molecules. The two polymorphs exhibit clear differences in their dielectric responses at room temperature and during the freezing process with dynamically fluctuating electric dipole moments, although no difference in their room-temperature structures has been previously observed. This result implies that two polymorphs have different local environment around the molecules. In particular, the ferromagnetism of the ?-phase is founded on the homogeneous molecule displacement and orientational ordering. The formation of the different phases with respect to the different rotational states in the Jahn–Teller distorted C60s is also discussed. PMID:25236361

Kambe, Takashi; Oshima, Kokichi

2014-01-01

389

Optimal covering of C60 fullerene by rare gases.  

PubMed

Putative global energy minima of clusters formed by the adsorption of rare gases on a C(60) fullerene molecule, C(60)X(N) (X=Ne, Ar, Kr, Xe; N ? 70), are found using basin-hopping global optimization in an empirical potential energy surface. The association energies per rare gas atom as a function of N present two noticeable minima for Ne and Ar and just one for Kr and Xe. The minimum with the smallest N is the deepest one and corresponds to an optimal packing monolayer structure; the other one gives a monolayer with maximum packing. For Kr and Xe, optimal and maximum packing structures coincide. By using an isotropic average form of the X-C(60) interaction, we have established the relevance of the C(60) surface corrugation on the cluster structures. Quantum effects are relevant for Ne clusters. The adsorption of these rare gases on C(60) follows patterns that differ significantly from the ones found recently for He by means of experimental and theoretical methods. PMID:22920119

Acosta-Gutiérrez, S; Bretón, J; Gomez Llorente, J M; Hernández-Rojas, J

2012-08-21

390

A peptide topological template for the dispersion of [60]fullerene in water.  

PubMed

Solubilization of [60]fullerene in water is a major challenge for biological and medical applications. To this purpose in this communication we describe for the first time a new dispersing system based on a peptide topological template. The presence of two carbobenzyloxy groups on the peptide side chains allows ?-? interactions with [60]fullerene leading to the formation of stable supramolecular nanocomposites by means of mechanochemical methods. In particular, by high speed vibration milling colloidal dispersions (mean particle diameter 63 nm) containing up to 1.3 mg mL(-1) of [60]fullerene were obtained. Its presence in water was verified through UV-Vis and MALDI-TOF measurements, while its concentration was determined by thermogravimetric analysis. PMID:25372360

Bartocci, S; Mazzier, D; Moretto, A; Mba, M

2015-01-14

391

Adsorption and manipulation of endohedral and higher fullerenes on Si(100)-2×1  

NASA Astrophysics Data System (ADS)

The adsorption of the endohedral fullerene, La@C82, and the higher fullerene, C84, on Si(100)-2×1 is investigated using a scanning tunneling microscope (STM) operating in ultrahigh vacuum. Both molecules are found to adsorb directly above the dimer rows that are formed on the Si(100)-2×1 surface, as well as in trough sites midway between dimer rows. Adsorption above dimer rows, not observed for C60, is attributed to the larger radius of curvature of these fullerene cages. The response of La@C82 to manipulation by the tip of the STM is also investigated. Molecules in either adsorption site may be manipulated with a threshold gap impedance ˜1.0 G?. Owing to a near-commensurability between the molecular diameter of La@C82 and the lattice constant of the Si(100) surface, close-packed arrangements of molecules may be formed.

Butcher, M. J.; Nolan, J. W.; Hunt, M. R.; Beton, P. H.; Dunsch, L.; Kuran, P.; Georgi, P.; Dennis, T. J.

2003-03-01

392

Preparation of cluster states with endohedral fullerenes in single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We propose two scalable methods for generation of cluster states with arrays of endohedral fullerenes 15N@C60 residing in single-walled carbon nanotubes (SWCNTs) using direct and indirect methods, respectively. The direct method makes use of a series of controlled-phase flip (CPF) gates by electron spin resonance pulses of selective frequencies and durations, where the CPF gates are realized by magnetic-dipole couplings between the electron spins of the nearest-neighbour fullerenes in SWCNTs. The indirect method resorts to auxiliary mobile electron as the flying qubit, which transfers quantum information from one site to another. This greatly releases the requirements for the distance between fullerenes in SWCNTs. The decoherence effect and experimental feasibility are also discussed based on currently available technology.

Hu, Y. M.; Chen, C. Y.; Yang, W. L.; Feng, M.

2012-05-01

393

Boosting activation of oxygen molecules on c60 fullerene by boron doping.  

PubMed

The activation of oxygen molecules on boron-doped C60 fullerene (C59 B) and the subsequent water formation reaction are systematically investigated by using hybrid density functional calculations. Results indicate that C59 B shows a favorable ability to activate oxygen molecules both kinetically and thermodynamically. The oxygen molecule is first adsorbed on the boron atom, which is identified to be the most reactive site in C59 B for O2 adsorption because of its high positive charge and spin density. The adsorption structure C59 B?O2 can further isomerize to form two products with small reaction barriers. Water formation reactions upon these two structures are energetically favorable and suggest a four-electron mechanism for the oxygen reduction reaction catalyzed by C59 B. This work provides a reliable theoretical insight into the catalytic properties of boron-doped fullerene, which is believed to be helpful to explore fullerene catalysts. PMID:25399745

Li, Qiao-Zhi; Zheng, Jia-Jia; Dang, Jing-Shuang; Zhao, Xiang

2015-02-01

394

Synthesis and spectroscopy of fullerenes and the discovery of Roto-Bucky  

SciTech Connect

Macroscopic synthetic techniques for producing fullerene molecules have been developed which include the carbon arc and laser vaporization approaches. The pentagon rule' kinetic growth mechanism for the fullerenes is proposed to explain this facile process. The reactor technology for generating fullerene molecules is generalized. Resonant two-photon ionization measurements have yielded the triplet state lifetimes and electronic spectroscopy of C[sub 60] and C[sub 70] in a supersonic molecular beam. The technique and results are described in detail. An unusual type of C[sub 60][center dot] Ar[sup +] complex has been detected through fragmentation studies in a tandem time-of-flight mass spectrometer. Rotational stabilization is proposed as the mechanism leading to the long lifetime of this and similar species.

Haufler, R.E.

1992-01-01

395

Endohedral fullerenes: A way to control resonant high-order harmonic generation  

SciTech Connect

We investigate the high-order harmonic generation in ordinary buckyball C{sub 60}, endohedral In-C{sub 60} fullerene, and endohedral Sb-C{sub 60} fullerene by means of time-dependent density functional theory. In all cases the resonant enhancement of several high-order harmonics in the plateau region up to two orders of magnitude was predicted. Theoretical investigation of absorption spectra of C{sub 60} showed absorption peaks in the regions of the resonant HHG enhancement. In both endohedral fullerenes, peaks of plasmon absorption and resonance enhancement were shifted toward the corresponding atomic resonant transitions, which may be used to control the spectral distribution of groups of resonant harmonics and obtain bright attosecond pulse trains.

Redkin, P. V. [Samarkand State University, Samarkand 140104 (Uzbekistan); Danailov, M. B. [Sincrotrone Trieste, Trieste I-34149 (Italy); Ganeev, R. A. [Institute of Electronics, Tashkent 100125 (Uzbekistan)

2011-07-15

396

Growth of silicon carbide on silicon via reaction of sublimed fullerenes and silicon  

SciTech Connect

Epitaxial silicon carbide films are grown on Si(100) substrates at a surface temperature of 1,200 K via fullerene precursors. Films have been grown up to a thickness of 2,500 {angstrom}. The growth rate of the SiC film is not limited by the surface reaction rate of fullerene with silicon at these temperatures, rather by the arrival rate of the reactants Si (by diffusion from substrate or from gas phase) or fullerene. This results in rapid film growth. Films have been characterized by low energy electron diffraction, ultraviolet photoelectron spectroscopy and Auger electron spectroscopy. Stoichiometric, epitaxial SiC films are grown. Supply of silicon to the growing SiC surface via sublimation greatly reduces the tendency for silicon diffusion to form voids at the Si/SiC interface.

Hamza, A.V.; Balooch, M. [Lawrence Livermore National Lab., CA (United States). Chemistry and Materials Science Directorate

1996-02-01

397

MONO1001: A source for singly charged ions applied to the production of multicharged fullerene beams  

NASA Astrophysics Data System (ADS)

The present article reports on a recent study of the production of multiply charged fullerene beams based on an electron cyclotron resonance (ECR) ion source (ECRIS). As collision studies in fundamental physics are demanding intense beams of multiply charged ions of small molecules, clusters, and particularly of fullerenes, we have further developed the ion source ECRIS MONO1000 [P. Jardin et al., Rev. Sci. Instrum. 73, 789 (2002)], originally devoted to produce singly charged ions, towards the production of multiply charged fullerene beams. In this article, the test measurements performed at the Electrostatic Ion Storage Ring Århus rf power (ELISA) facility will be described. Typical mass spectra (from pure C60 and C70 powder) will be shown and the influence of several source parameters (rf power, support gas, gas pressure,…) will be discussed specifying the conditions necessary for an optimum ion source operation.

Maunoury, L.; Andersen, J. U.; Cederquist, H.; Huber, B. A.; Hvelplund, P.; Leroy, R.; Manil, B.; Pacquet, J. Y.; Pedersen, U. V.; Rangamma, J.; Tomita, S.

2004-05-01

398

Using photoexcited triplet states to probe small-molecule endohedral fullerenes by ESR  

NASA Astrophysics Data System (ADS)

Ortho to para conversion of molecular hydrogen H2 can be catalyzed by the use of a coupled paramagnet such as a fullerene in its triplet state. The recently synthesized endohedral fullerenes H2@C60 and H2@C70 were photoexcited to their long lived triplet state (S= 1) and probed by electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) spectroscopic techniques. With these techniques we characterized both spin systems by extracting the hyperfine interaction the kinetic parameters of the triplet state and the spin relaxation times. The observed variations of the linewidths and the lineshape are discussed in the context of a dynamic Jahn-Teller effect. Irradiation of the H2@C70 at different temperatures reveals that the fullerene triplet state can serve as a spin catalyst for ortho to para interconversion while for the triplet H2@C60 no appreciable interconversion is observed

Filidou, Vasileia; Mamone, Salvatore; Bagno, Alessandro; Rastrelli, Federico; Murata, Yasujiro; Komatsu, Koichi; Lei, Xuegong; Li, Yongjun; Turro, Nicholas J.; Levitt, Malcolm H.; Morton, John J. L.

2013-03-01

399

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

400

Designing a C84 fullerene as a specific voltage-gated sodium channel blocker  

NASA Astrophysics Data System (ADS)

Fullerene derivatives demonstrate considerable potential for numerous biological applications, such as the effective inhibition of HIV protease. Recently, they were identified for their ability to indiscriminately block biological ion channels. A fullerene derivative which specifically blocks a particular ion channel could lead to a new set of drug leads for the treatment of various ion channel-related diseases. Here, we demonstrate their extraordinary potential by designing a fullerene which mimics some of the functions of ?-conotoxin, a peptide derived from cone snail venom which potently binds to the bacterial voltage-gated sodium channel (NavAb). We show, using molecular dynamics simulations, that the C84 fullerene with six lysine derivatives uniformly attached to its surface is selective to NavAb over a voltage-gated potassium channel (Kv1.3). The side chain of one of the lysine residues protrudes into the selectivity filter of the channel, while the methionine residues located just outside of the channel form hydrophobic contacts with the carbon atoms of the fullerene. The modified C84 fullerene strongly binds to the NavAb channel with an affinity of 46 nM but binds weakly to Kv1.3 with an affinity of 3 mM. This potent blocker of NavAb may serve as a structural template from which potent compounds can be designed for the targeting of mammalian Nav channels. There is a genuine need to target mammalian Nav channels as a form of treatment of various diseases which have been linked to their malfunction, such as epilepsy and chronic pain.

Hilder, Tamsyn A.; Chung, Shin-Ho

2013-07-01

401

Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons  

PubMed Central

We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (~4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons. PMID:20969428

Zheng, Yi; Sanche, Léon

2011-01-01

402

The readout of the fullerene-based quantum computing by a scanning tunneling microscope  

E-print Network

We consider to detect the electron spin of a doped atom, i.e., a nitrogen or a phosphorus, caged in a fullerene by currently available technique of the scanning tunneling microscope (STM), which actually corresponds to the readout of a qubit in the fullerene-based quantum computing. Under the conditions of polarized STM current and Coulomb blockade, we investigate the tunneling matrix elements involving the exchange coupling between the tunneling polarized electrons and the encapsulated polarized electron, and calculate the variation of the tunneling current with respect to different orientations of the encapsulated electron spin. The experimental feasibility of our scheme is discussed under the consideration of some imperfect factors.

M. Feng; G. J. Dong; B. Hu

2006-10-11

403

Correlation between charge transfer exciton recombination and photocurrent in polymer/fullerene solar cells  

SciTech Connect

We correlate carrier recombination via charge transfer excitons (CTEs) with the short circuit current, J{sub sc}, in polymer/fullerene solar cells. Near infrared photoluminescence spectroscopy of CTE in three blends differing for the fullerene acceptor, gives unique insights into solar cell characteristics. The energetic position of the CTE is directly correlated with the open-circuit voltage, V{sub oc}, and more important J{sub sc} decreases with increasing CTE emission intensity. CTE emission intensity is discussed from the perspective of blend morphology. The work points out the fundamental role of CTE recombination and how optical spectroscopy can be used to derive information on solar cell performances.

Hallermann, Markus; Da Como, Enrico; Feldmann, Jochen [Photonics and Optoelectronics Group, Department of Physics, CeNS Ludwig-Maximilians-University, 80799 Munich (Germany); Izquierdo, Marta; Filippone, Salvatore; Martin, Nazario [Department of Organic Chemistry, Universidad Complutense de Madrid, 28040 Madrid (Spain); Juechter, Sabrina; Hauff, Elizabeth von [Institute of Physics, Energy and Semiconductor Research Laboratory, University of Oldenburg, 26111 Oldenburg (Germany)

2010-07-12

404

Theory of normal and superconducting properties of fullerene-based solids  

SciTech Connect

Recent experiments on the normal-state and superconducting properties of fullerene-based solids are used to constrain the proposal theories of the electronic nature of these materials. In general, models of superconductivity based on electron pairing induced by phonons are consistent with electronic band theory. The latter experiments also yield estimates of the parameters characterizing these type H superconductors. It is argued that, at this point, a ``standard model`` of phonons interacting with itinerant electrons may be a good first approximation for explaining the properties of the metallic fullerenes.

Cohen, M.L.

1992-10-01

405

Theory of normal and superconducting properties of fullerene-based solids  

SciTech Connect

Recent experiments on the normal-state and superconducting properties of fullerene-based solids are used to constrain the proposal theories of the electronic nature of these materials. In general, models of superconductivity based on electron pairing induced by phonons are consistent with electronic band theory. The latter experiments also yield estimates of the parameters characterizing these type H superconductors. It is argued that, at this point, a standard model'' of phonons interacting with itinerant electrons may be a good first approximation for explaining the properties of the metallic fullerenes.

Cohen, M.L.

1992-10-01

406

Topologically closed macromolecules made of single walled carbon nanotubes-'super'-fullerenes.  

PubMed

We propose and theoretically investigated a new class of topologically closed macromolecules built using single walled carbon nanotubes. These macromolecules are based on the fullerene architecture. Classical molecular dynamics simulations were used to predict their stability, thermal, vibrational, and mechanical properties. These macromolecules, named 'super'-fullerenes, present high porosity, low density (approximately 1 g/cm3), and high surface area (approximately equal 2500 m2/g). Our results predict gas phase specific heat of about 0.4 Jg(-1)K(-1) at room temperature and high flexibility under compressive strains. These properties make these hypothetical macromolecules good candidates for gas storage material and biomolecular sieves. PMID:21128429

Coluci, V R; dos Santos, R P B; Galvão, D S

2010-07-01

407

Relative stability of boron fullerenes: A dispersion-corrected density-functional study  

NASA Astrophysics Data System (ADS)

We have studied the stability of various boron fullerene structures via dispersion-corrected desity-functional calculations. Our results reveal that the energy order of fullerenes strongly depends on the exchange-correlation functional employed in the calculation. A systematic study elucidates the importance of incorporating dispersion forces to account for the intricate interplay of two and three centered bonding in boron nano-structures. Futhermore, the inclusion of dispersion correction stabilizes high symmetry conformations that are vibrationaly unstable in the preceding density-functional calculations. We also discuss the use of graphics unit processor accelerated algorithms for the calculations.

Riche, Larry; Gunasinghe, Rosi; Wang, Xiao-Qian

2012-03-01

408

Fullerene isoniazid conjugate--a tuberculostat with increased lipophilicity: synthesis and evaluation of antimycobacterial activity.  

PubMed

A fullerene-isoniazid conjugate has been synthesized by 1, 3 dipolar cycloaddition reaction of fullerene (C(60)) with isonicotinic acid (4-formyl-benzylidene) hydrazide and N-methylglycine. The identity and purity of the compound was confirmed by elemental analysis, (1)H NMR, (13)C NMR and MALDI-TOF mass spectral analysis. Stable water suspension, in which the particles of the synthesized conjugate were made to aggregate in nanosize, was successfully tested for antimycobacterial activity against Mycobacterium avium and strains of Mycobacterium tuberculosis- H(37)Rv & H6/99 at concentration as low as 0.50 microg/mL. PMID:19366360

Kumar, Anish; Patel, Gaurang; Menon, Shobhana Karuveettil

2009-05-01

409

[Toxicological and sanitary characteristics of fullerene C60 administered to the rat gastrointestinal tract].  

PubMed

A four-week experiment dealing with the intragastric administration of fullerene C60 dispersion to rats has established that this substance in a dose of 1 to 10 mg/kg body weight causes a number of changes in the parameters of animals, such as reductions in relative liver weight and isoform CYP 1A2 activity and increases in glutathione reductase activity, eosinophils, and neutrophils. It is concluded that fullerene can affect the animals when orally given in the doses studied. PMID:22834278

Shipelin, V A; Arianova, E A; Trushina, E N; Avren'eva, L I; Batishcheva, S Iu; Cherkashin, A V; Soto, S Kh; Lashneva, N V; Gmoshinski?, I V; Khotimchenko, S A

2012-01-01

410

Inner-shell photoionization of fullerenes C20 and C60 within the "Dirac bubble" model  

NASA Astrophysics Data System (ADS)

The "Dirac bubble" (?-potential) model is applied to description of the structure of fullerenes C20 and C60 and photoelectron states. Energy spectra for ? valence orbitals for both fullerenes are obtained. Photoionization from two innermost delocalized electrons states (1s and 2p) is considered. The s-,p-,d- scattering phaseshifts are calculated, they demonstrate clear resonance properties which have oscillation in energy. Partial and total photoionization cross sections are obtained, the latter reveal an interesting "serrated" structure. Intriguing high-energy asymptotics is deduced, ? ~ ?-5/2 sin2 (kR).

Kashenock, G. Yu; Pratt, R. H.

2009-11-01

411

Effects of fullerene C60 on proteomic profile of Danio rerio fish embryos.  

PubMed

The effects of phosphatidylcholine-based phospholipid nanoparticles containing fullerene C60 on Danio rerio fish embryos were studied. Exposure of the embryos with the nanoparticles for 48 h did not lead to appreciable changes in the number of protein bands in SDS-PAGE in comparison with the control (exposure in medium with phosphatidylcholine). Mass spectrometric identification of proteins showed differences in the proteomic profiles of the samples. The content of vitellogenins changed after exposure with phosphatidylcholine-based nanoparticles with C60 fullerenes. This could indicate low toxicity of the nanoparticles towards D. rerio embryos under experimental conditions. PMID:24770760

Kuznetsova, G P; Larina, O V; Petushkova, N A; Kisrieva, Yu S; Samenkova, N F; Trifonova, O P; Karuzina, I I; Ipatova, O M; Zolotaryov, K V; Romashova, Yu A; Lisitsa, A V

2014-03-01

412

Grazing incidence imaging from 10 to 40 keV  

Microsoft Academic Search

The prospects for imaging X rays at energies from 10 to 40 keV with grazing incidence optics are explored. The scientific rationale and existing laboratory measurements are reviewed. Measurements of reflectivity using possible mirror materials are described. Iridium-coated float glass gives an improved performance over gold by the factor predicted by theory, but both had a lower absolute level. This

Martin Elvis; Daniel G. Fabricant; Paul Gorenstein

1988-01-01

413

Compact 300 keV electron gun for radiation processing  

SciTech Connect

A new self-shielded system for surface radiation treatments has been developed, based on a 300 keV electron gun, able to irradiate a 100 mmx10 mm area. The compact and durable system described in this paper provides the required dose of treatment for several industrial or scientific research applications, with a good reproducibility of the parameters.

Auditore, L.; Barna, R.C.; De Pasquale, D.; Interdonato, S.; Italiano, A.; Trifiro, A.; Trimarchi, M. [INFN-Gruppo Collegato di Messina, I-98166 Messina (Italy); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy); INFN-Gruppo Collegato di Messina, I-98166 Messina (Italy); INFN-Gruppo Collegato di Messina, I-98166 Messina (Italy); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy)

2005-12-15

414

KevJumba and the Adolescence of YouTube  

ERIC Educational Resources Information Center

This article considers the significance of YouTube as a pedagogical space from which young people can play participatory roles as theorists in their own constructions as popular cultural subjects. Drawing upon the public profile of "KevJumba," a teenager who makes videos of himself on YouTube, the article suggests that representational practices…

Saul, Roger

2010-01-01

415

Hard x-ray spectra from laser-generated plasmas recorded by the HENEX spectrometer in the 1 keV40 keV energy range  

Microsoft Academic Search

Hard x-ray spectra were recorded by the High Energy Electronic X-Ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1 keV to 20 keV energy range and one quartz(10-11) transmission crystal (Laue geometry) covering the 11 keV to 40 keV range.

J. F. Seely; C. A. Back; C. Constantin; R. W. Lee; H.-K. Chung; L. T. Hudson; C. I. Szabo; A. Henins; G. E. Holland; R. Atkin

2005-01-01

416

High-energy argon ion bombardment of alkali iodides at low temperatures  

NASA Astrophysics Data System (ADS)

The mixed alkali iodide K0.8Rb0.2I has been bombarded with 13.6 MeV/A argon ions over a range of temperatures. Unlike KI and RbI that show class-I behaviour at low temperature under energetic heavy ion bombardment, K0.8Rb0.2I displays distinctly different behaviour. At 20 K, the F centre production is totally suppressed and is negligible at 100 K; the formation of F+-I centre pairs would only in part account for this effect. The overall production rate of defects at 20 K is larger than that at 100 K. During the lowest temperature bombardment at 20 K, defect species such as H and I centres, which are known to have low thermal stability, are observed suggesting that thermal spike effects do not appear to affect the creation and stabilisation of the defects. At all temperatures of ion bombardment the F/V centre ratio in K0.8Rb0.2I is much smaller than that in the pure iodides KI and RbI. Nonetheless the halogen interstitial centres as studied by annealing and subsequent Raman measurements appear relatively similar. The results indicate a modified defect production mechanism in K0.8Rb0.2I under heavy ion bombardment; in support of this conclusion X-irradiation of the mixed crystal at 100 and 200 K showed conventional behaviour.

Pariselle, M. A.; Comins, J. D.; Ramstein, B.; Lefrant, S.; Spiesser, M.; Balanzat, E.

2000-05-01

417

Ultra-low-energy (<10 eV/u) ion beam bombardment effect on naked DNA  

NASA Astrophysics Data System (ADS)

Since ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range, it is very interesting to know effects from ultra-low-energy ion interaction with DNA for understanding ion-beam-induced genetic mutation. Tens-keV Ar- and N-ion beams were decelerated to ultra-low energy ranging from 20 to 100 eV, or only a few to 10 eV/u, to bombard naked plasmid DNA. The bombarded DNA was analyzed using gel electrophoresis for DNA form changes. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks after bombarded by tens-eV ion beam. N-ion beam was found more effective in inducing DNA change and mutation than Ar-ion beam. The study demonstrated that the ion bombardment with energy as low as several-tens eV was able to break DNA strands and thus potentially to cause genetic modification of biological cells. The experimental results were discussed in terms of direct atomic collision between the ions and DNA atoms.

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

2014-05-01

418

Wobbling The Galactic Disk with Bombardment of Satellite Galaxies  

NASA Astrophysics Data System (ADS)

We propose to assess the effect of impacts of large visible satellite galaxies on a disk, as well as the relevance of the continuing bombardment of the Galactic disk by dark matter clumps as predicted by the current cosmological framework that can wobble the disk, heating it and eventually exciting ragged spiral structures. In particular, we make detailed predictions for observable features such as spiral arms, rings and their associated stars in galactic disks and relate them to the physical processes that drive their formation and evolution in our Milky Way galaxy and nearby spirals. To do this, we will combine analytic methods and numerical simulations that allow us to calculate observables, which we will compare to present and forthcoming observations. Our methodology utilizes a combination of state of the art hydrodynamic simulations of galaxy evolution and multi- wavelength radiative transfer simulations. Our primary goals are: (1) To identify the physical processes that are responsible for spiral structure formation observed in our Milky Way and nearby disk galaxies, from the flocculent to grand- designed spiral galaxies and to provide observable signatures to be compared with data on nearby galaxies combining maps of 24 micron emission (Spitzer) and cold gas, CO (Heracles) and HI (THINGS). (2) To explore different morphologies of spiral galaxies: from the multi-armed galaxies to the Milky Way sized galaxies with few arms. (3) For a Milky Way disk we will assess the effect of impacts of substructures passing through the disk to origin the asymmetry in the number density of stars recently discovered from SDSS and SEGUE data and confirmed from RAVE data. We will also investigate the disk heating in the vertical plane due to the formation of vertical oscillations that are produced by the impact and migration of stars in the disk as consequence of the heating as compared to the classical stellar migration mechanism. (4) We will measure the spiral pattern speed and the velocity ellipsoid of the stars, and we will determine the contribution of the spiral arms to the heating of the stellar disk and to the radial migration of stars in the disk when the disk is perturbed by internal agents as giant molecular clouds. Our methodology has the potential to discern the detailed physical processes occurring in stellar disks with higher detail compared to previous simulations done in isolation or cosmological simulations of individual galaxies. The results of our work will provide a comprehensive guide for interpreting observations from upcoming GAIA, SDSS-IV, Spitzer and HST and future observations with JWST.

D'Onghia, Elena

419

Sputtering of Al nanoclusters by 1-13 keV monatomic or polyatomic ions studied by Molecular Dynamics simulations  

NASA Astrophysics Data System (ADS)

Molecular Dynamics (MD) simulations were employed to study sputtering of freestanding and supported spherical Al nanoclusters with 2-10 nm diameters under bombardment by Al1 and Al13 projectiles with energies of 1-13 keV at normal and oblique incidence. Both monatomic and clustered yields of secondary emission are found to be larger than those for (1 1 1) flat surface of the bulk Al (at equal irradiation conditions). In some events, target nanocluster receives a backward momentum and therefore its major part (more than 1/2 of the mass) is ejected due to produced secondary emission mainly towards the substrate direction. This “recoil effect” is found more pronounced under the impact of cluster projectiles and its probability decreases with increase of the target cluster size. A restricted number of MD simulations were performed to verify whether this “recoil effect” is strong enough to desorb a 4 nm Al nanocluster off an Al (1 1 1) substrate. Desorption was observed under oblique Al13 impact within the impact parameter range of 0.6-0.9.

Zhurkin, Evgeny E.; Grigorev, Petr Yu.

2013-05-01

420

Molecular dynamics simulations of sputtering of Langmuir-Blodgett multilayers by keV C(60) projectiles.  

PubMed

Coarse-grained molecular dynamics computer simulations are applied to investigate fundamental processes induced by an impact of keV C(60) projectile at an organic overlayer composed of long, well-organized linear molecules. The energy transfer pathways, sputtering yields, and the damage induced in the irradiated system, represented by a Langmuir-Blodgett (LB) multilayers composed from molecules of bariated arachidic acid, are investigated as a function of the kinetic energy and impact angle of the projectile and the thickness of the organic system. In particular, the unique challenges of depth profiling through a LB film vs. a more isotropic solid are discussed.The results indicate that the trajectories of projectile fragments and, consequently, the primary energy can be channeled by the geometrical structure of the overlayer. Although, a similar process is known from sputtering of single crystals by atomic projectiles, it has not been anticipated to occur during C(60) bombardment due to the large size of the projectile. An open and ordered molecular structure of LB films is responsible for such behavior. Both the extent of damage and the efficiency of sputtering depend on the kinetic energy, the impact angle, and the layer thickness. The results indicate that the best depth profiling conditions can be achieved with low-energy cluster projectiles irradiating the organic overlayer at large off-normal angles. PMID:20174461

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

2009-04-01

421

Molecular packing and electronic processes in amorphous-like polymer bulk heterojunction solar cells with fullerene intercalation.  

PubMed

The interpenetrating morphology formed by the electron donor and acceptor materials is critical for the performance of polymer:fullerene bulk heterojunction (BHJ) photovoltaic (PV) cells. In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c] thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative. Grazing incidence X-ray scattering measurements reveal the lower-ordered nature of the BHJ system as well as an intermixing morphology with intercalation of fullerene molecules between the PFBT-T20TT lamella. Steady-state and transient photo-induced absorption spectroscopy reveal ultrafast charge transfer (CT) at the PFBT-T20TT/fullerene interface, indicating that the CT process is no longer limited by exciton diffusion. Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner. Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain. PMID:24909640

Xiao, Ting; Xu, Haihua; Grancini, Giulia; Mai, Jiangquan; Petrozza, Annamaria; Jeng, U-Ser; Wang, Yan; Xin, Xin; Lu, Yong; Choon, Ng Siu; Xiao, Hu; Ong, Beng S; Lu, Xinhui; Zhao, Ni

2014-01-01

422

Binary short-range colloidal assembly of magnetic iron oxides nanoparticles and fullerene (nC60) in environmental media.  

PubMed

Colloidal assembly of nC60 fullerene with naturally abundant magnetic iron oxide NPs will affect their fate and transformation in environmental media. In solution, fullerene association to aggregating iron oxide NPs/clusters greatly enhanced the overall colloidal stability. Development of depletion-mediated structured fullerene layers between pure and surface modified ?Fe2O3 NPs possibly resulted in such stabilization. Here, we also report that on air-water interface, association of fullerene to pure and humic acid (HA7) coated ?Fe2O3 NPs led to the formation of ordered assemblies, e.g., binary wires and closed-packed "crystalline" and "glassy" structures in the presence and absence of electrolytes suggesting immobilization of the former. The interaction of fullerene to Fe3O4 NPs and clusters also produced ordered assemblies along with amorphous aggregates. Fullerene interaction with Fe3O4 NPs in low concentration of HA1 and Na(+) at pH 6 formed dendritic growth and polycrystalline circular assemblies on air-water interface. HRTEM study further revealed that the monolayer circular assemblies were highly ordered but structural degeneracy was evident in multilayers. Therefore, interfacial assemblies of fullerene with iron oxide NPs resulted in short-range periodic structures with concomitant immobilization and reduction in availability of the former, especially in soils or sediments rich in the latter. PMID:25222921

Ghosh, Saikat; Pradhan, Nihar R; Mashayekhi, Hamid; Dickert, Stefan; Thantirige, Rukshan; Tuominen, Mark T; Tao, Shu; Xing, Baoshan

2014-10-21

423

Molecular Packing and Electronic Processes in Amorphous-like Polymer Bulk Heterojunction Solar Cells with Fullerene Intercalation  

PubMed Central

The interpenetrating morphology formed by the electron donor and acceptor materials is critical for the performance of polymer:fullerene bulk heterojunction (BHJ) photovoltaic (PV) cells. In this work we carried out a systematic investigation on a high PV efficiency (>6%) BHJ system consisting of a newly developed 5,6-difluorobenzo[c]125 thiadiazole-based copolymer, PFBT-T20TT, and a fullerene derivative. Grazing incidence X-ray scattering measurements reveal the lower-ordered nature of the BHJ system as well as an intermixing morphology with intercalation of fullerene molecules between the PFBT-T20TT lamella. Steady-state and transient photo-induced absorption spectroscopy reveal ultrafast charge transfer (CT) at the PFBT-T20TT/fullerene interface, indicating that the CT process is no longer limited by exciton diffusion. Furthermore, we extracted the hole mobility based on the space limited current (SCLC) model and found that more efficient hole transport is achieved in the PFBT-T20TT:fullerene BHJ as compared to pure PFBT-T20TT, showing a different trend as compared to the previously reported highly crystalline polymer:fullerene blend with a similar intercalation manner. Our study correlates the fullerene intercalated polymer lamella morphology with device performance and provides a coherent model to interpret the high photovoltaic performance of some of the recently developed weakly-ordered BHJ systems based on conjugated polymers with branched side-chain. PMID:24909640

Xiao, Ting; Xu, Haihua; Grancini, Giulia; Mai, Jiangquan; Petrozza, Annamaria; Jeng, U-Ser; Wang, Yan; Xin, Xin; Lu, Yong; Choon, Ng Siu; Xiao, Hu; Ong, Beng S.; Lu, Xinhui; Zhao, Ni

2014-01-01

424

Are Fullerenes Relevant to Cosmochemistry? A New Finding  

NASA Technical Reports Server (NTRS)

The abundances of noble gases found in primitive, carbonaceous meteorites are unexpected when compared with our Sun. Known as Q-gases (Q for some unknown carrier dubbed quintessence ), this anomaly has remained a mystery since it was discovered in 1975. Q-gases are characterized by increasing depletions with decreasing atomic number (Z) relative to solar noble gases and normalized to 132Xe (Figure 1). This Q-gas mass fractionation is unexplained, and its investigation is important to understanding the origin of the solar system. However, the subject is fraught with controversy, in part due to the complex nature of Q and in part due to claims of some researchers that cannot be reproduced by other investigators. The topic is discussed in numerous places [e.g., 1-4], with models of Q falling into two basic categories, both involving carbon entrapment of noble gases. First (Group A), there is the conservative two-dimensional view that Q-gases are adsorbed or sorbed onto a "labyrinth" of graphite or carbon grains [5-9], or they undergo active capture onto growing surfaces [6]. Second (Group B), there is the view holding to the remarkable property of carbon discovered in 1985. Carbon can curl up into closed geometries of hexagon- and pentagon-shaped carbon-ring configurations, a property ignored completely by Group A. Group B thinks of Q as a three-dimensional structure of endohedral carbon cages like fullerenes, carbon onions, or some class of carbon nanotubes [3, 4, 10]. Group B does not exclude Group A effects.

Wilson, T. L.; Mittlefehldt, D. W.

2008-01-01

425

Infrared spectroscopy of hydrogenated fullerenes (fulleranes) at extreme temperatures  

NASA Astrophysics Data System (ADS)

The infrared spectra, as well as the integrated molar absorptivity (?) and the molar extinction coefficient (?) of each infrared transition of the hydrogenated fullerenes (known as fulleranes) C60H36, C60H18 and C70H38, and a mixture of fulleranes generally referred to as 77 per cent of C60Hx and 22 per cent C70Hy with x?y > 30, are presented and discussed. These data are useful for the search, identification and quantitative determination of fulleranes in space after the recent discovery that their parent molecules, C60 and C70, are more abundant in space than initially thought, being present in a variety of H-rich circumstellar environments such as planetary nebulae and only mild H-deficient R Coronae Borealis stars, and in the interstellar medium. It is shown that the C-H stretching band of the fulleranes C60H36, C60H18 and C70H38, and their mixture may be most useful for the identification of these molecules because their ? and ? values are unique in terms of strength, overcoming by far the typical ? and ? values of reference molecules such as adamantane and docosane, as well as typical ? literature data for aliphatic molecules. In contrast to the rather simple infrared spectra of C60H36 and C60H38, the infrared spectra of two C60H18 isomers are reported as characterized by a rich number of bands which may allow an easier identification than the higher homologues. The dependence of the infrared bands of fulleranes on temperature was studied over a wide range of temperatures (from -180°C to +250°C) and extrapolated to 0 K.

Iglesias-Groth, Susana; García-Hernández, D. A.; Cataldo, Franco; Manchado, Arturo

2012-07-01

426

MeV Proton Irradiation Effects on Fullerenes and Graphite  

SciTech Connect

Ion irradiation of graphite and other carbon allotropes is a versatile tool for manipulating their physical, chemical and even magnetic properties. Fullerene films, when irradiated with 2 MeV protons, display soft-ferromagnetic ordering at 5 K. At 300 K both pristine and irradiated films show diamagnetic behaviour.Magnetisation data in the temperature range of 2-300 K, in 1 T applied field, for the irradiated film show much stronger temperature dependence compared to a pristine film. The ion irradiation study has been further extended to the graphite system. Poly-crystalline graphite samples were irradiated with 2.25MeV protons at a fluence of 2x10{sup 17} ions/cm2.Magnetic ordering in highly oriented pyrolytic graphite samples have been reported earlier under similar irradiation conditions [Esquinazi et. al. Phys. Rev. Lett. 91 (2003) 227201]. In that study, the authors attribute the observed irradiation induced magnetic ordering to the formation of a mixed sp{sup 2}-sp{sup 3} hybridized carbon atoms. Here we present Raman and X-ray photoelectron spectroscopic studies on pristine and irradiated graphite samples. Irradiated samples are found to show an increased number of sp3 hybridized carbon atoms. However, the Raman spectrum, specially the second order data, do indicate that the nature of the graphene lattice structure has been preserved in the irradiated samples. The formation of a mixed sp{sup 2}-sp{sup 3} hybridization in graphite structure, which might be responsible for magnetism,will be discussed.

Mathew, S. [Institute of Physics, Sachivalaya Marg, Bhubaneswar-751005 (India); Dev, B. N. [Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkota 700 032 (India)

2008-10-23

427

Evolution of isolated copper clusters under low-energy argon ion bombardment  

NASA Astrophysics Data System (ADS)

The molecular dynamics simulation of the evolution of clusters of copper in a vacuum under low-energy argon ion bombardment has been performed. The clusters consisting of 26, 78, and 390 atoms have been studied at a bombarding particle energy ranging from 1 to 800 eV. The potential of the interaction between copper atoms has been simulated using the embedded atom method, whereas the interaction of copper atoms with argon atoms has been described using the Ziegler-Biersack-Littmark potential. As a result of the simulation, time dependences of the temperature and potential energy and the numerical values of the sputtering coefficients of free clusters under the ion bombardment have been obtained.

Shyrokorad, D. V.; Kornich, G. V.

2014-12-01

428

Metal-Atom Impact on the Self-Assembly of Cup-and-Ball Metalloporphyrin-Fullerene Conjugates.  

PubMed

A fullerene ammonium derivative has been combined with different metalloporphyrin-crown ether receptors to generate very stable supramolecules. The combination of fullerene-porphyrin and ammonium-crown ether interactions leads to a strong chelate effect as evidenced by a high effective molarity (3.16?M). The different parameters influencing the stability of the supramolecular ensembles, in particular the nature of the metal in the porphyrin moiety, have been rationalized with the help of theoretical calculations thus providing new insights into fullerene-porphyrin interactions. PMID:25431361

Moreira, Luis; Calbo, Joaquín; Illescas, Beatriz M; Aragó, Juan; Nierengarten, Iwona; Delavaux-Nicot, Béatrice; Ortí, Enrique; Martín, Nazario; Nierengarten, Jean-François

2015-01-19

429

Spectral and theoretical studies on effective and selective non-covalent interaction between tetrahexylporphyrins and fullerenes  

NASA Astrophysics Data System (ADS)

The host-guest interaction of zinc(II) 5,10,15,20-tetrahexylporphyrin (Zn-THP) and its free base (H 2-THP) with fullerenes (C 60 and C 70) has been studied in toluene medium. Binding constants ( K) for H 2- and Zn-THP complexes of fullerenes were determined by UV-vis, fluorescence and NMR spectroscopic techniques. Large K values of C 70/THP complexes ( K) were obtained in the range of 1.4-2.5 × 10 4 M -1, while those of C 60/THP complexes ( K) were smaller (1.0-3.2 × 10 3 M -1). These results show that the K is about 10 times as large as K in both THPs ( K/ K = 10). Enthalpies of formation ( ?Hf°) for various fullerene/THP complexes were estimated by ab initio calculations; ?Hf° for C 60/H 2-THP, C 70/H 2-THP, C 60/Zn-THP and C 70/Zn-THP complexes are 5.82, 2.80, 2.31 and 1.54 kcal mol -1, respectively. The trends in ?Hf° support the experimental results of selective complexation of THPs towards C 70 over C 60 and fullerenes towards Zn-THP over H 2-THP.

Bhattacharya, Sumanta; Ujihashi, Naruto; Aonuma, Shuji; Kimura, Takahide; Komatsu, Naoki

2007-11-01

430

Spectral and theoretical studies on effective and selective non-covalent interaction between tetrahexylporphyrins and fullerenes.  

PubMed

The host-guest interaction of zinc(II) 5,10,15,20-tetrahexylporphyrin (Zn-THP) and its free base (H2-THP) with fullerenes (C60 and C70) has been studied in toluene medium. Binding constants (K) for H2- and Zn-THP complexes of fullerenes were determined by UV-vis, fluorescence and NMR spectroscopic techniques. Large K values of C70/THP complexes (KC70 ) were obtained in the range of 1.4-2.5 x 10(4)M(-1), while those of C60/THP complexes (KC60) were smaller (1.0-3.2 x10(3)M(-1)). These results show that the KC70 is about 10 times as large as KC60 in both THPs (KC70/KC60 = 10). Enthalpies of formation (DeltaHf degrees) for various fullerene/THP complexes were estimated by ab initio calculations; DeltaHf degrees for C60/H2-THP, C70/H2-THP, C60/Zn-THP and C70/Zn-THP complexes are 5.82, 2.80, 2.31 and 1.54 kcal mol(-1), respectively. The trends in DeltaHf degrees support the experimental results of selective complexation of THPs towards C70 over C60 and fullerenes towards Zn-THP over H2-THP. PMID:17320469

Bhattacharya, Sumanta; Ujihashi, Naruto; Aonuma, Shuji; Kimura, Takahide; Komatsu, Naoki

2007-11-01

431

Quantum Size Effects in the Polarizability of Carbon Fullerenes G. K. Gueorguiev,1  

E-print Network

beams. Many fundamental discoveries are associated with the development of such techniques, notably the observation of electronic shell and supershell structure in alkali metal clusters [1], or the discovery molecules have been carried out. The lack of microscopic results for other fullerene structures

432

Theoretical Study of Chlorin-Fullerene Supramolecular Complexes for Photovoltaic Devices  

Microsoft Academic Search

The current general trend in the research and development of photovoltaic elements is toward the production of lower cost devices. An encouraging breakthrough in the development of highly efficient materials has been achieved by mixing electron-donor type polymers with suitable electron acceptors. Many fullerene-based supramolecules have been proposed as potential organic photovoltaic devices. We investigate the geometric and electronic structure

Hiroshi Mizuseki; Nobuaki Igarashi; Rodion V. Belosludov; Amir A. Farajian; Yoshiyuki Kawazoe

2003-01-01

433

Express Letter Fullerene-like carbon nanostructures in the Allende meteorite  

E-print Network

Express Letter Fullerene-like carbon nanostructures in the Allende meteorite P.J.F. Harris aY *, R meteorite. The structure of the carbon is rather disordered, consisting of curved and faceted graphene; Allende meteorite; carbonaceous chondrites; transmission electron microscopy; carbon 1. Introduction

Harris, Peter J F

434

Fullerenes: non-transition metal clusters as rechargeable magnesium battery cathodes.  

PubMed

We discovered that non-transition metal clusters have great potential as rechargeable Mg battery cathodes. Fullerene (C60), one of the prototype materials, was discharged and recharged with a remarkable rate capability. This unique rate performance is attributed to its capability to delocalize electrons on the entire cluster rather than to individual atoms. PMID:25461490

Zhang, Ruigang; Mizuno, Fuminori; Ling, Chen

2015-01-21

435

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

E-print Network

Highly dispersed carbon nanotubes in organic media for polymer:fullerene photovoltaic devices Gwang photovoltaic device are fabricated using homogeneously dispersed carbon nanotubes (CNTs) in a polymer and by the fabrica- tion of an organic thin film transistor. An organic solar cell was fabricated from these com

Hong, Soon Hyung

436

The development of nanoscale morphology in polymer:fullerene photovoltaic blends during solvent casting  

E-print Network

The development of nanoscale morphology in polymer:fullerene photovoltaic blends during solvent heterojunction organic photovoltaic (OPV) device is dependent both on the electronic properties of the constituent materials and on the nanoscale morphology of the active semiconductor layer thin-film. Here we use

Travis, Adrian

437

[Characterization of fullerene C60 peroral toxicity to rats in the 92-day experiment].  

PubMed

Toxicity of fullerene C60 in male Wistar rats under conditions of a daily intragastric administration at doses of 0.1; 1 and 10 mg/kg body weight for 92 days was studied. Integral, biochemical, physiological, hematological, immunological indicators were determined that characterized the body condition of animals together with fullerene C60 biodistribution in organs and tissues of rats. Majority of the results didn't show any influence of fullerene C60 on animals treated with it in the whole range of doses studied. On the other hand, some of the data not related to the action of the components used in carrier solution, demonstrated dose-dependent variation: found increased activity on 21-35% in the CYP2B1 at doses of 1 mg/kg and 10 mg/kg body weight, and reduced concentration of uric acid and increasing concentrations of urea at 10 mg/kg body weight. Nevertheless, these changes were within the physiological range of variability. However, it is worth noting an important significant (p = 0.02) increase of the absorption for antigenic proteins in the digestive tract in animals treated with fullerene C60 at a dose of 10 mg/kg, suggesting a marked effect on the intestinal wall. PMID:23461168

Shipelin, V A; Avren'eva, L I; Guseva, G V; Trushina, É N; Mustafina, O K; Selifanov, A V; Soto, S Kh; Mal'tsev, G Iu; Gmoshinski?, I V; Khotimchenko, S A

2012-01-01

438

1st International Symposium on Nanocarbons (ISNC2013) --Fullerenes, Endofullerenes, Carbon Nanotubes, Graphenes  

E-print Network

Nanotubes, Graphenes and Carbon Nanostructures () Date: June 16th ­ 21st, 2013 Venue: University Lecture1 1st International Symposium on Nanocarbons (ISNC2013) -- Fullerenes, Endofullerenes, Carbon in Carbon Cages: Structural Elucidation and Chemical Modification 12:05-12:25 IS_2: Baoyun Sun (Institute

Zhou, Yi-Feng

439

Probing the morphology of novel non-fullerene based bulk heterojunction solar cells  

NASA Astrophysics Data System (ADS)

Organic semiconductors are promising for low-cost, large-area electronics such as organic photovoltaics (OPVs). OPVs require an active layer that is an intimate mixture of an electron donor, usually a conjugated polymer, and an electron acceptor, typically a fullerene. While fullerene-based OPVs show high efficiencies, the inability to tune its electronic levels limits the open circuit voltage, so alternative acceptors are desirable. Here, we report on blend films consisting of a polymer donor, poly(3-hexylthiophene) (P3HT), and a novel acceptor, decacyclene triimide (DTI), that display good solar power conversion efficiencies (PCE) as-cast. The PCE of these blends decreases significantly with thermal annealing, unlike P3HT:fullerene blends. NEXAFS spectroscopy and grazing incidence wide angle X-ray scattering suggest the PCE decrease is due to the formation of hexagonally packed DTI columns with an in-plane ?-? stacking direction, resulting in poor electron transport out-of-plane. Polarized resonant soft X-ray scattering suggests that the ?-? stacking directions are orthogonal at interfaces between DTI and P3HT domains. These results demonstrate the importance of blend morphology in OPV efficiency and key differences between DTI-based and fullerene-based blends.

Su, Gregory; Pho, Toan; Wudl, Fred; Kramer, Edward; Chabinyc, Michael

2013-03-01

440

Self-assembly and Photo-patterning in Polymer-fullerene Nanocomposite Thin Films  

NASA Astrophysics Data System (ADS)

We report the directed self assembly of fullerenes in polymer thin films. The fullerenes are found to assemble spontaneously into spinodally coordinated clusters upon thermal annealing. The process yields well-defined structures, ranging from sparse heterogeneous nucleation to dense spinodal-like morphologies with tuneable characteristic spatial frequency and amplitude which coarsen with time, following well-defined scaling laws [1]. Mapping of this self assembly process utilized both real and reciprocal space techniques: optical and scanning force microscopy and neutron reflectivity. With external fields: light exposure and substrate surface energy, we demonstrate further tuneability over nanocomposite thin film morphology and substantial improvement on ultrathin film stability. By modulating the external fields on nanocomposite film with photomask, followed by thermal annealing, the film morphology and stability can be directed into various patterns, including a prototype polymer-fullerene circuit [2]. These results provide insights into fullerene self assembly in polymers and underscore their photoactive nature, an effect of great interest in the performance and stability of organic photovoltaics (OPV). [1] Wong H C and Cabral J T 2010 Phys. Rev. Lett. 105 038301 and 2011 Macromolecules 44 4530. [2] Wong H C, Higgins A M, Wildes A, Douglas J F, Cabral J T 2012 Adv. Mater. In Press.

Wong, Him Cheng; Higgins, Anthony; Wildes, Andrew; Douglas, Jack; Cabral, Joao

2013-03-01

441

Fullerene C70 as a p-type donor in organic photovoltaic cells  

NASA Astrophysics Data System (ADS)

Fullerenes and their derivatives have been widely used as n-type materials in organic transistor and photovoltaic devices. Though it is believed that they shall be ambipolar in nature, there have been few direct experimental proofs for that. In this work, fullerene C70, known as an efficient acceptor, has been employed as a p-type electron donor in conjunction with 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile as an electron acceptor in planar-heterojunction (PHJ) organic photovoltaic (OPV) cells. High fill factors (FFs) of more than 0.70 were reliably achieved with the C70 layer even up to 100 nm thick in PHJ cells, suggesting the superior potential of fullerene C70 as the p-type donor in comparison to other conventional donor materials. The optimal efficiency of these unconventional PHJ cells was 2.83% with a short-circuit current of 5.33 mA/cm2, an open circuit voltage of 0.72 V, and a FF of 0.74. The results in this work unveil the potential of fullerene materials as donors in OPV devices, and provide alternative approaches towards future OPV applications.

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

2014-09-01

442

UV Irradiation and Humic Acid Mediate Aggregation of Aqueous Fullerene (nC60) Nanoparticles  

EPA Science Inventory

The transport and fate of engineered nanomaterials is affected by multiple environmental factors, including sunlight and natural organic matter. In this study, the initial aggregation kinetics of aqueous fullerene (nC60) nanoparticles before and after UVA irradiation was investig...

443

Pressure induced manifold enhancement of Li-kinetics in FCC fullerene.  

PubMed

The reduction of the diffusion energy barrier for Li in electrodes is one of the required criteria to achieve better performances in Li ion batteries. Using density functional theory based calculations, we report a pressure induced manifold enhancement of Li-kinetics in bulk FCC fullerene. Scanning of the potential energy surface reveals a diffusion path with a low energy barrier of 0.62 eV, which reduces further under the application of hydrostatic pressure. The pressure induced reduction in the diffusion barrier continues till a uniform volume strain of 17.7% is reached. Further enhancement of strain increases the barrier due to the repulsion caused by C-C bond formation between two neighbouring fullerenes. The decrease in the barrier is attributed to the combined effect of charge transfer triggered by the enhanced interaction of Li with the fullerene as well as the change in profile of the local potential, which becomes more attractive for Li. The lowering of the barrier leads to an enhancement of two orders of magnitude in Li diffusivity at room temperature making pressurized bulk fullerene a promising artificial solid electrolyte interface (SEI) for a faster rechargeable battery. PMID:25197835

Das, Deya; Han, Sang Soo; Lee, Kwang-Ryeol; Singh, Abhishek K

2014-10-21

444

Photodynamic Inactivation of Enveloped Viruses by Fullerene: Study of Efficacy and Safety  

NASA Astrophysics Data System (ADS)

Viruses are the most dangerous contaminants of human blood and blood products. The purpose of this study was to investigate the light-mediated virus-inactivating properties of fullerene and its effect on the intactness of biological fluids. Influenza virus was propagated in chicken embryos, and a water suspension of C60 fullerene was added to the allantoic fluid. The fluid was light-irradiated with a constant flow of oxygen through the specimen, and the dynamics of the virus titer were studied in Madin-Darby canine kidney (MDCK) cells. The morphology of the virions was studied by electron microscopy (EM). The electrophoretic pattern of the proteins in the allantoic fluid and blood plasma, as well as the growth properties of the calf serum were compared before and after 6h of irradiation. A dramatic drop of infectious titer (from 6 to 0 log10 EID50) in the virus was observed within 2h after the start of irradiation. No change in the titers was observed in control specimens without the fullerene, or light, or oxygen. EM revealed numerous defects in the morphology of the virions (destruction of the outer membrane) leading to the loss of infectious properties in the virus. Based on comparison of proteins and growth properties of the serum, no differences were revealed between intact and irradiated biological fluids. Water-insoluble fullerenes may therefore be considered an effective and safe way to inactivate enveloped viruses in biological materials including blood products.

Zarubaev, Vladimir V.; Belousova, Inna; Rylkov, Vladimir; Slita, Alexander; Sirotkin, Alexey; Anfimov, Pavel; Muraviova, Tatyana; Starodubtsev, Andrey

445

Thermodynamics of allotropic modifications of carbon: Synthetic diamond, graphite, fullerene C 60 and carbyne  

Microsoft Academic Search

In an adiabatic vacuum calorimeter, a temperature dependence of heat capacity of four allotropic modifications of carbon, viz, synthetic diamond, graphite, carbyne and fullerene C60, has been studied in the (5–340) K range. The diamond sample studied is a commercial crystalline product containing impurities, according to a certificate, in an amount less than 1%; graphite is a spectrally pure crystalline

B. V. Lebedev; L. Ya. Tsvetkova; K. B. Zhogova

1997-01-01

446

Implications and potential applications of bactericidal fullerene water suspensions: effect of nC60 concentration,  

E-print Network

antibacterial activity to physiologically different bacteria in low-salts media over a wide range of exposure of nC60 on the health of aquatic ecosystems and suggest novel alternatives for disinfection and microbial control. Key words | bacteria, fullerenes, nanomaterial, nC60 INTRODUCTION With the current

Alvarez, Pedro J.

447

Physicochemical Characterization and Thermodynamic Studies of Nanoemulsion-Based Transdermal Delivery System for Fullerene  

PubMed Central

Fullerene nanoemulsions were formulated in palm kernel oil esters stabilized by low amount of mixed nonionic surfactants. Pseudoternary phase diagrams were established in the colloidal system of PKOEs/Tween 80 : Span 80/water incorporated with fullerene as antioxidant. Preformulation was subjected to combination of high and low energy emulsification methods and the physicochemical characteristics of fullerene nanoemulsions were analyzed using electroacoustic spectrometer. Oil-in-water (O/W) nanoemulsions with particle sizes in the range of 70–160?nm were formed. The rheological characteristics of colloidal systems exhibited shear thinning behavior which fitted well into the power law model. The effect of xanthan gum (0.2–1.0%,?w/w) and beeswax (1–3%,?w/w) in the estimation of thermodynamics was further studied. From the energetic parameters calculated for the viscous flow, a moderate energy barrier for transport process was observed. Thermodynamic study showed that the enthalpy was positive in all xanthan gum and beeswax concentrations indicating that the formation of nanoemulsions could be endothermic in nature. Fullerene nanoemulsions with 0.6% or higher xanthan gum content were found to be stable against creaming and flocculation when exposed to extreme environmental conditions. PMID:25165736

Basri, Mahiran; Tripathy, Minaketan; Abdul-Malek, Emilia

2014-01-01

448

Anion-Dependent Aggregate Formation and Charge Behavior of Colloidal Fullerenes (n-C60)  

EPA Science Inventory

The fate and transport of colloidal fullerenes (n-C60) in the environment is likely to be guided by electrokinetic and aggregation behavior. In natural water bodies inorganic ions exert significant effects in determining the size and charge of n-C60 nanoparticles. Although the ef...