Science.gov

Sample records for c-60 molecule adsorbed

  1. "Soft" metallic contact to isolated C60 molecules.

    PubMed

    Glowatzki, Hendrik; Bröker, Benjamin; Blum, Ralf-Peter; Hofmann, Oliver T; Vollmer, Antje; Rieger, Ralph; Müllen, Klaus; Zojer, Egbert; Rabe, Jürgen P; Koch, Norbert

    2008-11-01

    C60 adsorbed on a monolayer of hexaazatriphenylene-hexanitrile (HATCN) on Ag(111) is investigated by ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling microscopy. UPS and quantum-mechanical modeling show that HATCN chemisorbed on Ag(111) displays metallic character. This metallic molecular layer decouples C60 electronically from the Ag substrate and simultaneously acts both as template for the stable adsorption of isolated C60 molecules at room temperature and as "soft" metallic contact for subsequently deposited molecules. PMID:18954123

  2. Electrostatic propulsion using C60 molecules

    NASA Technical Reports Server (NTRS)

    Leifer, Stephanie D.; Rapp, Donald; Saunders, Winston A.

    1992-01-01

    An evaluation is made of the potential benefits of C60 molecules as a basis for ion propulsion. Because C60 is storable, its use may result in a larger usable propellant fraction than previous methods of cluster ion propulsion. C60 may also relax such engineering constraints as grid spacing, which restrict the performance of noble gas ion propulsion. The behavior of C60 in a plasma discharge environment, as well as various electron impact cross sections of the molecule, will greatly afftect the feasibility of the concept.

  3. Electrostatic Propulsion Using C60 Molecules

    NASA Technical Reports Server (NTRS)

    Leifer, Stephanie D.; Saunders, Winston A.

    1993-01-01

    Report proposes use of C60 as propellant material in electrostatic propulsion system of spacecraft. C60, C70, and similar molecules, have recently been found to have characteristics proving advantageous in electrostatic propulsion. Report discusses these characteristics and proposes experiments to determine feasibility of concept.

  4. Vibration-rotation spectroscopy of molecules trapped inside C60.

    PubMed

    Cross, R James

    2008-08-01

    A simple model is developed to treat the energy levels and spectroscopy of diatomic molecules inside C 60. The C 60 cage is treated as spherically symmetric, and the coupling to the C 60 vibrations is ignored. The remaining six degrees of freedom correspond to the vibrations and rotations of the diatomic molecule and the rattling vibration of the molecule inside the cage. By using conservation of angular momentum, we can remove two of these motions and simplify the calculations. The resulting energy levels are simple and can be labeled by a set of quantum numbers. The IR and Raman spectra look like those of gas-phase diatomic molecules at low temperatures. At higher temperatures, hot bands due to the low-frequency rattling mode appear, and the spectrum becomes congested, looking like a solution spectrum. PMID:18598014

  5. Effective medium theory for a system of C60 molecules

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2016-06-01

    An effective medium theory is developed to study the effective permittivity of a system of C60 molecules. We use a two-dimensional, spherical, two-fluid hydrodynamic model to describe the linear response of the π and σ electrons over the each C60 molecule. A general expression for the electromagnetic wave attenuation coefficient of the system is then deduced, and its functional dependence on the filling factor is presented. Furthermore, the dispersion characteristics of electromagnetic oscillations of the system are studied.

  6. Structure and dynamics of C60 molecules on Au(111)

    SciTech Connect

    Shin, Heekeun; Schwarze, A; Diehl, R D; Pussi, K; Colombier, A; Gaudry, E.; Ledieu, J; McGuirk, G M; Serkovic Loli, L N; Fournee, V; Wang, Lin-Lin; Schull, G; Berndt, R

    2014-06-01

    Earlier studies of C60 adsorption on Au(111) reported many interesting and complex features. We have performed coordinated low-energy electron diffraction, scanning tunneling microscopy (STM), and density functional theory studies to elucidate some of the details of the monolayer commensurate (2√3 × 2√3)R30° phase. We have identified the adsorption geometries of the two states that image as dim and bright in STM. These consist of a C60 molecule with a hexagon side down in a vacancy (hex-vac) and a C60 molecule with a carbon-carbon 6:6 bond down on a top site (6:6-top), respectively. We have studied the detailed geometries of these states and find that there is little distortion of the C60 molecules, but there is a rearrangement of the substrate near the C60 molecules. The two types of molecules differ in height, by about 0.7 Å, which accounts for most of the difference in their contrast in the STM images. The monolayer displays dynamical behavior, in which the molecules flip from bright to dim, and vice versa. We interpret this flipping as the result of the diffusion of vacancies in the surface layers of the substrate. Our measurements of the dynamics of this flipping from one state to the other indicate that the activation energy is 0.66 ± 0.03 eV for flips that involve nearest-neighbor C60 molecules, and 0.93 ± 0.03 for more distant flips. Based on calculated activation energies for vacancies diffusing in Au, we interpret these to be a result of surface vacancy diffusion and bulk vacancy diffusion. These results are compared to the similar system of Ag(111)-(2√3 × 2√3)R30°-C60. In both systems, the formation of the commensurate C60 monolayer produces a large number of vacancies in the top substrate layer that are highly mobile, effectively melting the interfacial metal layer at temperatures well below their normal melting temperatures.

  7. Jellium model potentials for the C60 molecule and the photoionization of endohedral atoms, A@C60

    NASA Astrophysics Data System (ADS)

    Baltenkov, A. S.; Manson, S. T.; Msezane, A. Z.

    2015-09-01

    Approximating the C60 shell as a collection of carbon atoms, the potential experienced by a confined atom has been calculated within the framework of the self-consistent spherical jellium model. It has been found that the potential well in this model has a cusp-shaped Lorentz-like profile. The parameters of the model Lorentz-bubble potential (depth and thickness) have been selected so that in the potential well there would be an electronic level corresponding to the experimental electron affinity of the C60 molecule. The spatial distribution of the positive charge of the C-atomic nuclei and the negative charge of the electron clouds forming the electrostatic potential of C60, as a whole, has been analyzed using the Poisson equation. It is demonstrated that the often used radial square-well potential to approximate the C60 corresponds to a non-physical charge density for the C60 molecule. This analysis demonstrates that the phenomenological potentials simulating the C60 shell potential should belong to a family of potentials with a non-flat bottom and non-parallel potential walls similar to the Lorentz-bubble potential. The photoionization cross-sections of a hydrogen atom localized at the center of the C60 shell have been calculated as well. It is found that confinement oscillations in the cross-sections are exhibited within the framework of the cusp-shaped potential model and these oscillations are essentially the same as those in the case of the potential wells with well-defined borders (parallel walls), thereby demonstrating that the inherent characteristic distances of the potential, e.g., radii of the potential walls, or the distances between potential walls, are not necessary to produce confinement resonances; this should be a general result for atoms or molecules confined in near-spherical fullerenes.

  8. In situ x-ray photoelectron spectroscopic and density-functional studies of Si atoms adsorbed on a C60 film.

    PubMed

    Onoe, Jun; Nakao, Aiko; Hara, Toshiki

    2004-12-01

    The interaction between C(60) and Si atoms has been investigated for Si atoms adsorbed on a C(60) film using in situ x-ray photoelectron spectroscopy (XPS) and density-functional (DFT) calculations. Analysis of the Si 2p core peak identified three kinds of Si atoms adsorbed on the film: silicon suboxides (SiO(x)), bulk Si crystal, and silicon atoms bound to C(60). Based on the atomic percent ratio of silicon to carbon, we estimated that there was approximately one Si atom bound to each C(60) molecule. The Si 2p peak due to the Si-C(60) interaction demonstrated that a charge transfer from the Si atom to the C(60) molecule takes place at room temperature, which is much lower than the temperature of 670 K at which the charge transfer was observed for C(60) adsorbed on Si(001) and (111) clean surfaces [Sakamoto et al., Phys. Rev. B 60, 2579 (1999)]. The number of electrons transferred between the C(60) molecule and Si atom was estimated to be 0.59 based on XPS results, which is in good agreement with the DFT result of 0.63 for a C(60)Si with C(2v) symmetry used as a model cluster. Furthermore, the shift in binding energy of both the Si 2p and C 1s core peaks before and after Si-atom deposition was experimentally obtained to be +2.0 and -0.4 eV, respectively. The C(60)Si model cluster provides the shift of +2.13 eV for the Si 2p core peak and of -0.28 eV for the C 1s core peak, which are well corresponding to those experimental results. The covalency of the Si-C(60) interaction was also discussed in terms of Mulliken overlap population between them. PMID:15634092

  9. C60 molecules grown on a Si-supported nanoporous supramolecular network: a DFT study.

    PubMed

    Boukari, Khaoula; Duverger, Eric; Stephan, Régis; Hanf, Marie-Christine; Sonnet, Philippe

    2014-07-28

    C60 fullerene assemblies on surfaces have attracted considerable attention because of their remarkable electronic properties. Now because of the competition between the molecules-substrate and the molecule-molecule interactions, an ordered C60 array is rather difficult to obtain on silicon surfaces. Here we present density functional theory simulations on C60 molecules deposited on a TBB (1,3,5-tri(1'-bromophenyl)benzene) monolayer lying on the Si(111)-boron surface (denoted SiB). The C60 molecules are located in the nanopores formed by the TBB network. Adsorption energy calculations show that the SiB surface governs the C60 vertical position, whereas the TBB network imposes the C60 lateral position, and stabilizes the molecule as well. The low charge density between the C60 and the SiB substrate on one hand, and on the other hand between the C60 and the TBB molecules, indicates that no covalent bond is formed between the C60 and its environment. However, according to charge density differences, a drastic charge reorganisation takes place between the Si adatoms and the C60 molecule, but also between the C60 and the surrounding TBB molecules. Finally, calculations show that a C60 array sandwiched between two TBB molecular layers is stable, which opens up the way to the growth of 3D supramolecular networks. PMID:24920165

  10. Interfacial and intermolecular interactions determining the rotational orientation of C60 adsorbed on Au(111)

    NASA Astrophysics Data System (ADS)

    Paßens, Michael; Karthäuser, Silvia

    2015-12-01

    Close-packed monolayers of fullerenes on metallic substrates are very rich systems with respect to their rotational degrees of freedom and possible interactions with different adsorption sites or next neighbours. In this connection, we report in detail on the (2√3 × 2√3)R30°-superstructure of C60 with respect to the Au(111)-surface. We use molecular orbital imaging in systematic UHV-STM studies to reveal the delicate balance of interfacial and intermolecular interactions in this system. Thus, bright C60-molecules in 5:6-top and 6:6-top geometries are observed depending on the respective next neighbours. Moreover, tiny changes in the appearance of the unoccupied molecular orbitals of dim C60-molecules in hex-vac positions are identified which are caused by the respective interaction with the facets surrounding the Au-vacancy.

  11. Energetics and Electronic Structures of C60 Included Within [n]Cyclacene Molecules

    NASA Astrophysics Data System (ADS)

    Kigure, Shota; Okada, Susumu

    2013-09-01

    We report the geometric and electronic structures of C60 included within cyclic hydrocarbon molecules, i.e., [n]cyclacene molecules. We found that the C60 included within the [n]cyclacene molecules ([n]cyclacene\\supsetC60) are energetically stable and that the inclusion reactions are exothermic for the [n]cyclacene molecules where n is larger than 16. Because of quantum confinement of the electronic states of the guest C60 molecule by the host [n]cyclacene, the electronic structure of [n]cyclacene\\supsetC60 is complex. The energy gap between the highest occupied states and the lowest unoccupied states is opened between the electronic states of the guest and host molecules.

  12. Spatially mapping the spectral density of a single C60 molecule

    SciTech Connect

    Lu, Xinghua; Grobis, M.; Khoo, K.H.; Louie, Steve G.; Crommie, M.F.

    2002-07-01

    We have used scanning tunneling spectroscopy to spatially map the energy-resolved local density of states of individual C60 molecules on the Ag(100) surface. Spectral maps were obtained for molecular states derived from the C60 HOMO, LUMO, and LUMO + 1 orbitals, revealing new details of the spatially inhomogeneous C60 local electronic structure. Spatial inhomogeneities are explained using ab initio pseudopotential density functional calculations. These calculations emphasize the need for explicitly including the C60-Ag interaction and STM tip trajectory to understand the observed C60 local electronic structure.

  13. STM study of C60F18 high dipole moment molecules on Au(111)

    NASA Astrophysics Data System (ADS)

    Bairagi, K.; Bellec, A.; Chumakov, R. G.; Menshikov, K. A.; Lagoute, J.; Chacon, C.; Girard, Y.; Rousset, S.; Repain, V.; Lebedev, A. M.; Sukhanov, L. P.; Svechnikov, N. Yu.; Stankevich, V. G.

    2015-11-01

    Scanning tunneling microscopy and spectroscopy studies of C60F18 molecules deposited on Au(111) are reported and compared to C60 molecules both at liquid helium temperature and room temperature (RT). Whereas adsorption and electronic properties of C60F18 single molecules were studied at low temperature (LT), self-assemblies were investigated at RT. In both cases, the fluorine atoms of the C60F18 molecules are pointed towards the surface. Individual C60F18 molecules on Au(111) have a HOMO-LUMO gap of 2.9 eV. The self-assembled islands exhibit a close-packed hexagonal lattice with amorphous borders. The comparison with C60 molecules clearly demonstrates the influence of the C60F18 electric dipole moment (EDM) on the electronic properties of single molecules and on the thermodynamics of self-assembled islands. Besides, the apparent height value of a separate molecule increases in a self-assembly environment as a result of a depolarization phenomenon.

  14. Transport characteristics of a single C60-molecule junction revealed by multiple Andreev reflections

    NASA Astrophysics Data System (ADS)

    Hiraoka, Ryoichi; Arafune, Ryuichi; Tsukahara, Noriyuki; Kawai, Maki; Takagi, Noriaki

    2014-12-01

    We have determined the number of transport channels and the value of the transmission coefficients of a single molecular junction by measuring the multiple Andreev reflections (MARs) with a scanning tunneling microscope (STM). By precisely positioning a Nb STM tip to a single C60 molecule on Pb(111), a single molecular junction was fabricated in which the C60 molecule connects with the two superconducting electrodes. From the subharmonic gap structures arising from MARs in the current-voltage characteristics together with the tunneling spectrum of the C60 molecule, we found that unoccupied molecular orbitals of C60 extending to the Fermi level provide three electronic transport channels in the molecular junction. We also found that the transmission coefficients depend on the contact geometry of the molecule. These results demonstrate that the combination of the STM imaging with the MARs measurement provides an effective path for investigating the electronic transport properties through a single molecule sandwiched by two superconducting electrodes.

  15. Theoretical study of the charge transport through C60-based single-molecule junctions

    NASA Astrophysics Data System (ADS)

    Bilan, S.; Zotti, L. A.; Pauly, F.; Cuevas, J. C.

    2012-05-01

    We present a theoretical study of the conductance and thermopower of single-molecule junctions based on C60 and C60-terminated molecules. We first analyze the transport properties of gold-C60-gold junctions and show that these junctions can be highly conductive (with conductances above 0.1G0, where G0=2e2/h is the quantum of conductance). Moreover, we find that the thermopower in these junctions is negative due to the fact that the lowest unoccupied molecular orbital dominates the charge transport, and its magnitude can reach several tens of microvolts per kelvin, depending on the contact geometry. On the other hand, we study the suitability of C60 as an anchoring group in single-molecule junctions. For this purpose, we analyze the transport through several dumbbell derivatives using C60 as anchors, and we compare the results with those obtained with thiol and amine groups. Our results show that the conductance of C60-terminated molecules is rather sensitive to the binding geometry. Moreover, the conductance of the molecules is typically reduced by the presence of the C60 anchors, which in turn makes the junctions more sensitive to the functionalization of the molecular core with appropriate side groups.

  16. Short-pulse laser-produced plasma from C60 molecules

    SciTech Connect

    Wuelker, Cornelius; Theobald, Wolfgang; Ouw, Donald; Schaefer, Fritz P.; Chichkov, Boris N.

    1995-05-01

    The first experimental observations of a plasma produced in a vapor of C60 molecules with a high-intensity subpicosecond KrF laser (6x10{sup 15} W/cm{sup 2}) are reported. It differs from a plasma created in an ordinary carbon preplasma by reaching much higher ionization stages under the same experimental conditions. This remarkable property of C60 molecules (and other clusters) opens new prospects for short-pulse driven X-ray lasers.

  17. The Adsorption of C60 fullerene molecules on Nanostructured Au (111)

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Guo, Quanmin; Palmer, Richard

    2009-03-01

    The sub-monolayer growth of C60 molecules on the Au (111) surface has been studied using STM in ultra high vacuum. The C60 molecules tend to form close-packed layers due to a strong inter-molecular interaction. However, within the close-packed layer, there are finer, secondary structures that are specific to each of all the three C60/Au interfacial structures ((23x23)R30 , in-phase (R0 ) and R14 ) observed [1]. This is a consequence of the molecule-substrate interaction and our findings demonstrate a much more complex structural variation at the molecule-substrate interface than previously assumed. Furthermore, within the R14 C60 layer, slightly darker molecules (30 pm lower) aligned along the ã11-2õdirection with a ˜6 nm spacing are observed and these molecules are arranged in a reasonably well-ordered two-dimensional lattice. C60 molecules are also found to decorate the elbow sites of the herringbone reconstructed Au(111) even at room, and when fullerenes are deposited to arrays of fabricated monolayer gold stripes (gold-fingers) [2], the molecules show step-specific attachment where the step edges with the (111) micro-facet are preferentially populated.[0pt] [1] X. Zhang, F. Yin, R. E. Palmer and Q. Guo, Surf. Sci. 602 (2008) 885-892.[0pt] [2] Q. Guo, F. Yin and R. E. Palmer, Small 1 (2005) 76-79.

  18. Alignment of paired molecules of C60 within a hexagonal platform networked through hydrogen-bonds.

    PubMed

    Hisaki, Ichiro; Nakagawa, Shoichi; Sato, Hiroyasu; Tohnai, Norimitsu

    2016-07-28

    We demonstrate, for the first time, that a hydrogen-bonded low-density organic framework can be applied as a platform to achieve periodic alignment of paired molecules of C60, which is the smallest example of a finite-numbered cluster of C60. The framework is a layered assembly of a hydrogen-bonded 2D hexagonal network (LA-H-HexNet) composed of dodecadehydrotribenzo[18]annulene derivatives. PMID:27417325

  19. Chemistry and temperature-assisted dehydrogenation of C60H30 molecules on TiO2(110) surfaces.

    PubMed

    Sánchez-Sánchez, Carlos; Martínez, José Ignacio; Lanzilotto, Valeria; Biddau, Giulio; Gómez-Lor, Berta; Pérez, Rubén; Floreano, Luca; López, María Francisca; Martín-Gago, José Ángel

    2013-11-21

    The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited, under ultra-high vacuum, a submonolayer coverage of C60H30 and studied, by a combination of experimental techniques (STM, XPS and NEXAFS) and theoretical methods, the different chemical on-surface interaction stages induced by the increasing temperature. We show that room temperature adsorbed molecules exhibit a weak interaction and freely diffuse on the surface, as previously reported for other aromatics. Nevertheless, a slight annealing induces a transition from this (meta)stable configuration into chemisorbed molecules. This adsorbate-surface interaction deforms the C60H30 molecular structure and quenches surface diffusion. Higher annealing temperatures lead to partial dehydrogenation, in which the molecule loses some of the hydrogen atoms and LUMO levels spread in the gap inducing a net total energy gain. Further annealing, up to around 750 K, leads to complete dehydrogenation. At these temperatures the fully dehydrogenated molecules link between them in a bottom-up coupling, forming nanodomes or fullerene-like monodisperse species readily on the dielectric surface. This work opens the door to the use of on-surface chemistry to generate new bottom-up tailored structures directly on high-K dielectric surfaces. PMID:24071968

  20. Gate-tunable large negative tunnel magnetoresistance in Ni-C60-Ni single molecule transistors.

    PubMed

    Yoshida, Kenji; Hamada, Ikutaro; Sakata, Shuichi; Umeno, Akinori; Tsukada, Masaru; Hirakawa, Kazuhiko

    2013-02-13

    We have fabricated single C(60) molecule transistors with ferromagnetic Ni leads (FM-SMTs) by using an electrical break junction method and investigated their magnetotransport. The FM-SMTs exhibited clear gate-dependent hysteretic tunnel magnetoresistance (TMR) and the TMR values reached as high as -80%. The polarity of the TMR was found to be always negative over the entire bias range studied here. Density functional theory calculations show that hybridization between the Ni substrate states and the C(60) molecular orbitals generates an antiferromagnetic configuration in the local density of states near the Fermi level, which gives a reasonable explanation for the observed negative TMR. PMID:23327475

  1. Direct Observation of a Gas Molecule (H2, Ar) Swallowed by C60

    SciTech Connect

    Sawa, H.; Kakiuchi, T.; Wakabayashi, Y.; Murata, Y.; Murata, M.; Komatsu, K.; Yakigaya, K.; Takagi, H.; Dragoe, N.

    2007-01-19

    Various types of endohedral fullerene complexes are known to date. The well known metallofullerenes are generally produced by arc-discharge method, but the use of such extremely drastic conditions is apparently not suitable for encapsulation of unstable molecules or gases. We recently succeeded in incorporation of a H2 molecule or an Ar atom in 100% into a C60. In order to observe the endohedral gas molecule directly, the X-ray diffraction analysis using synchrotron radiation were carried out. We observed a gas molecule encapsulated in each fullerene cage using structure analysis and the maximum entropy method. These gas molecules are floating inside of the hollow cavities and are completely isolated from the outside.

  2. Thiol-based molecular overlayers adsorbed on C60: Role of the end-group and charge state on the stability of the complexes

    NASA Astrophysics Data System (ADS)

    Chavira-Quintero, R.; Guirado-López, R. A.

    2013-11-01

    We present pseudo-potential density functional theory calculations dedicated to analyze the stability and electronic properties of thiol-based molecular overlayers adsorbed on C60. We consider short molecules having a S atom as a headgroup, alkyl chains containing one to three C atoms, and a CH3 species as a terminal group. The thiol molecules are bonded to the carbon surface (through the S atom) with adsorption energies that vary in the range of ˜1-2 eV and with S-C bond lengths of ˜1.8 Å. For neutral C60(SCH3)n complexes, low energy atomic configurations are obtained when the thiol groups are distributed on the surface forming small molecular domains (e.g., pairs, trimers, or tetramer configurations of neighboring thiol molecules). In contrast, less stable random distributions are defined by orientationally disordered overlayers with highly distorted underlying carbon networks. The inclusion of London dispersion interaction slightly affects the structure of the molecular coating but increases the adsorption energies by values as large as 0.3 eV. Interestingly, the relative stability of the previous adsorbed phases differ from the one obtained when considering single sulfur adsorption on C60, a result that reveals the crucial role played by the terminal CH3 groups on the structure of the molecular coating. The positive (negative) charging of the [C60(SCH3)n]±q complexes, with q as large as 8e, changes the geometrical structure and the chemical nature of the ligand shell inducing lateral molecular displacements, S-S bonding between neighboring thiols, as well as the partial degradation of the molecular coating. Finally, we consider the stability of two-component mixed overlayers formed by the coadsorption of CH3-, OH-, and NH2-terminated alkanethiols of the same length. In agreement with the results found on Au surfaces, we obtain lowest energy atomic configurations when molecular domains of a single component are stabilized on C60, a result that could be of

  3. Self-interaction corrections applied to Mg-porphyrin, C60, and pentacene molecules

    NASA Astrophysics Data System (ADS)

    Pederson, Mark R.; Baruah, Tunna; Kao, Der-you; Basurto, Luis

    2016-04-01

    We have applied a recently developed method to incorporate the self-interaction correction through Fermi orbitals to Mg-porphyrin, C60, and pentacene molecules. The Fermi-Löwdin orbitals are localized and unitarily invariant to the Kohn-Sham orbitals from which they are constructed. The self-interaction-corrected energy is obtained variationally leading to an optimum set of Fermi-Löwdin orbitals (orthonormalized Fermi orbitals) that gives the minimum energy. A Fermi orbital, by definition, is dependent on a certain point which is referred to as the descriptor position. The degree to which the initial choice of descriptor positions influences the variational approach to the minimum and the complexity of the energy landscape as a function of Fermi-orbital descriptors is examined in detail for Mg-porphyrin. The applications presented here also demonstrate that the method can be applied to larger molecular systems containing a few hundred electrons. The atomization energy of the C60 molecule within the Fermi-Löwdin-orbital self-interaction-correction approach is significantly improved compared to local density approximation in the Perdew-Wang 92 functional and generalized gradient approximation of Perdew-Burke-Ernzerhof functionals. The eigenvalues of the highest occupied molecular orbitals show qualitative improvement.

  4. Self-interaction corrections applied to Mg-porphyrin, C60, and pentacene molecules.

    PubMed

    Pederson, Mark R; Baruah, Tunna; Kao, Der-You; Basurto, Luis

    2016-04-28

    We have applied a recently developed method to incorporate the self-interaction correction through Fermi orbitals to Mg-porphyrin, C60, and pentacene molecules. The Fermi-Löwdin orbitals are localized and unitarily invariant to the Kohn-Sham orbitals from which they are constructed. The self-interaction-corrected energy is obtained variationally leading to an optimum set of Fermi-Löwdin orbitals (orthonormalized Fermi orbitals) that gives the minimum energy. A Fermi orbital, by definition, is dependent on a certain point which is referred to as the descriptor position. The degree to which the initial choice of descriptor positions influences the variational approach to the minimum and the complexity of the energy landscape as a function of Fermi-orbital descriptors is examined in detail for Mg-porphyrin. The applications presented here also demonstrate that the method can be applied to larger molecular systems containing a few hundred electrons. The atomization energy of the C60 molecule within the Fermi-Löwdin-orbital self-interaction-correction approach is significantly improved compared to local density approximation in the Perdew-Wang 92 functional and generalized gradient approximation of Perdew-Burke-Ernzerhof functionals. The eigenvalues of the highest occupied molecular orbitals show qualitative improvement. PMID:27131541

  5. Peas in a pod: quasi-one-dimensional C60 molecules in a nanotube

    NASA Astrophysics Data System (ADS)

    Gatica, Silvina M.; Mercedes Calbi, M.; Cole, Milton W.

    2003-03-01

    We evaluate the equation of state of the quasi-one-dimensional phase of C60 molecules in small carbon nanotubes, nicknamed "peas in a pod"[1,2]. The pressure and chemical potential are evaluated as functions of the temperature and density, within the approximation of nearest neighbor interactions and classical statistical mechanics. A phase transition to a 3D anisotropic condensed phase is predicted as a result of the interaction between molecules in adjacent tubes. [1] B.W. Smith, M. Monthioux and D.E. Luzzi, Nature 296, 323 (1998). [2] M. Hodak, L.A. Girifalco, Phys. Rev. B 64, 035407 (2001), Chem. Phys. Lett. 350, 405 (2001); L.A. Girifalco and M. Hodak, App. Phys. A, in press.

  6. Specific features of the glass transition in C60 fullerite saturated with carbon monoxide molecules: Photoluminescence studies

    NASA Astrophysics Data System (ADS)

    Zinoviev, P. V.; Zoryansky, V. N.; Stetsenko, Yu. E.; Danchuk, V. V.

    2016-02-01

    Low temperature (20-230 K) spectral-luminescence studies were conducted on C60 fullerite saturated with carbon monoxide in a physisorption regime. Substantial changes in the photoluminescence characteristics of C60-CO solutions with different impurity concentrations were found already for short intercalation times. Strong dependence of the CO solubility on the saturation temperature was revealed by analyzing the contribution of "deep X-traps" to the luminescence. Furthermore, it was found that filling of the octahedral voids by CO molecules occurs with a lower gradient of the impurity distribution into the bulk C60 crystals as compared with N2. The temperature dependences of the integral emission intensity for the samples with different concentrations of carbon monoxide were studied. For the first time, using the spectral-luminescence method, it was revealed that CO molecules, in contrast to H2 and N2, exhibit a significant effect on the formation of the orientational glass and the rotational dynamics of C60 molecules. Within the model of the transfer of electronic excitation in C60 crystals, the effect of polar CO molecules on the reorientation of C60 molecules and the change in the nature of their rotation in concentrated C60-CO solutions, leading to the observed strong shift of the temperatures of orientational Tc and glass Tg transitions to lower temperatures accompanied by "blurring" of the transition boundaries, were explained.

  7. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  8. Trap states in ZnPc:C60 small-molecule organic solar cells

    NASA Astrophysics Data System (ADS)

    Burtone, Lorenzo; Fischer, Janine; Leo, Karl; Riede, Moritz

    2013-01-01

    Trap states are known to be one of the key parameters limiting charge transport in organic semiconductors and hence the performance of organic solar cells. Here, small-molecule organic solar cells based on a bulk heterojunction between zinc-phtalocyanine (ZnPc) and the fullerene C60 are characterized according to their trapping nature by noninvasive methods and under ambient conditions. We show how impedance spectroscopy, applied to systematically varied device structures, reveals the trap localization as well as its occupation mechanisms. Further insight is given from investigations of different device working points and illumination intensities. Thus, we find the traps to be bulk states in the active layer with an electron-trapping nature. They can be described by a Gaussian energy distribution of 55 meV width, centered at 0.46 eV below the electron transport level and with a concentration of 3.5 × 1016 cm-3. Moreover, the trap states act as recombination centers in the presence of injected or photogenerated charge carriers. The results are confirmed by electrical simulations.

  9. Rotations and vibrations of water molecule inside the fullerene cage: infrared study of H2O@C60

    NASA Astrophysics Data System (ADS)

    Room, Toomas; Shugai, A.; Nagel, U.; Mamone, S.; Krachmalnicoff, A.; Whitby, R. J.; Levitt, M. H.; Nishida, T.; Murata, Y.; Lei, Xuegong; Li, Yongjun; Turro, N. J.

    2015-03-01

    Water is the second molecule after hydrogen what has been trapped inside the cage of a C60 molecule by the molucular surgery method. We studied isolated water molecule isotopologs H2O, D2O, and HDO in the solid phase at cryogenic temperatures using IR spectroscopy. The water molecule rotation transitions were observed in the THz and vibration-rotation transitions in the mid-IR range. The slow conversion between para and ortho water allowed us to record the time evolution of spectra and to separate ortho and para absorption lines of water. The similarity of the rotation spectrum of caged water to water in the gas phase indicates that water is free to rotate in the C60 cage even at temperature as low as 3 K. However, spectral lines show a splitting of about 0.5 meV what is not compatible with the icosahedral symmetry of C60. Different models (e.g. crystal field effects in solid C60, C60 cage distortions) will be discussed. This work was supported by institutional research funding IUT23-3 of the Estonian Ministry of Education and Research.

  10. Mercator maps of orientations of a C60 molecule in single-walled nanotubes with distinct radii

    SciTech Connect

    Michel, K.H.; Verberck, B.; Nikolaev, A.V.

    2005-09-27

    We study the confinement of a C60 molecule encapsulated in a cylindrical nanotube as a function of the tube radius. Drawing the Mercator maps of the potential, we find two distinct molecular orientations; for tubes with small radii, RT < or approx. 7 A, a fivefold axis of the molecule coincides with the tube long axis, for larger radii, RT > or approx. 8 A, a threefold axis of the molecule coincides with the tube long axis. These different orientations are caused by the relative importance of the repulsive and the attractive parts of the van der Waals potentials of the molecule with the tube wall for small and large tubes respectively. Experimental evidence is provided by the apparent splitting of Ag modes of the C60 molecule in resonant Raman scattering.

  11. Features of self-aggregation of C60 molecules in toluene prepared by different methods

    NASA Astrophysics Data System (ADS)

    Makhmanov, Urol; Ismailova, Oksana; Kokhkharov, Abdulmutallib; Zakhidov, Erkin; Bakhramov, Sagdilla

    2016-05-01

    Structural and dimensional features of C60 aggregates in toluene solution prepared in two different ways - equilibrium and strongly non-equilibrium - were studied by high-resolution transmission electron microscopy and atomic-force microscopy methods. It was found that in solutions prepared by the non-equilibrium method (stirring of solution of C60 by a mechanical rotator), large quasispherical aggregates (with a diameter of up to ∼ 380 ± 20 nm) of nanoporous structure with fractal size D ≈ 2.13 were synthesized. In the case of solutions C60, which were prepared by the equilibrium method (without the use of external mechanical influences on solution), the formation of densely packed monomolecular fullerene aggregates with a diameter of not more than 50 nm was observed.

  12. Room-temperature repositioning of individual C60 molecules at Cu steps: Operation of a molecular counting device

    NASA Astrophysics Data System (ADS)

    Cuberes, M. T.; Schlittler, R. R.; Gimzewski, J. K.

    1996-11-01

    C60 molecules absorbed on a monoatomic Cu step have been reversibly repositioned at room temperature with the tip of a scanning tunneling microscope by performing controlled displacements along the step direction. We demonstrate the feasibility of building an abacus on the nanometer scale using single molecules as ``counters,'' Cu monoatomic steps as ``rods'' that constrain the molecular motion to one dimension, and the scanning tunneling microscope as an ``actuator'' for counting operations.

  13. Diffusion and self-assembly of C60 molecules on monolayer graphyne sheets

    PubMed Central

    Ozmaian, Masoumeh; Fathizadeh, Arman; Jalalvand, Morteza; Ejtehadi, Mohammad Reza; Allaei, S. Mehdi Vaez

    2016-01-01

    The motion of a fullerene (C60) on 5 different types of graphyne is studied by all-atom molecular dynamics simulations and compared with former studies on the motion of C60 on graphene. The motion shows a diffusive behavior which consists of either a continuous motion or discrete movements between trapping sites depending on the type of the graphyne sheet. For graphyne-4 and graphyne-5, fullerenes could detach from the surface of the graphyne sheet at room temperature which was not reported for similar cases on graphene sheets. Collective motion of a group of fullerenes interacting with a graphyne studied and it is shown that fullerenes exhibit stable assemblies. Depending on the type of graphyne, these assemblies can have either single or double layers. The mobility of the assembled structures is also dependent on the type of the graphyne sheet. The observed properties of the motion suggests novel applications for the complexes of fullerene and monolayer graphynes. PMID:26912386

  14. Size selective hydrophobic adsorbent for organic molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Hickey, Gregory S. (Inventor)

    1997-01-01

    The present invention relates to an adsorbent formed by the pyrolysis of a hydrophobic silica with a pore size greater than 5 .ANG., such as SILICALITE.TM., with a molecular sieving polymer precursor such as polyfurfuryl alcohol, polyacrylonitrile, polyvinylidene chloride, phenol-formaldehyde resin, polyvinylidene difluoride and mixtures thereof. Polyfurfuryl alcohol is the most preferred. The adsorbent produced by the pyrolysis has a silicon to carbon mole ratio of between about 10:1 and 1:3, and preferably about 2:1 to 1:2, most preferably 1:1. The pyrolysis is performed as a ramped temperature program between about 100.degree. and 800.degree. C., and preferably between about 100.degree. and 600.degree. C. The present invention also relates to a method for selectively adsorbing organic molecules having a molecular size (mean molecular diameter) of between about 3 and 6 .ANG. comprising contacting a vapor containing the small organic molecules to be adsorbed with the adsorbent composition of the present invention.

  15. Phase separation analysis of bulk heterojunctions in small-molecule organic solar cells using zinc-phthalocyanine and C60

    NASA Astrophysics Data System (ADS)

    Schünemann, Christoph; Wynands, David; Wilde, Lutz; Hein, Moritz Philipp; Pfützner, Steffen; Elschner, Chris; Eichhorn, Klaus-Jochen; Leo, Karl; Riede, Moritz

    2012-06-01

    To achieve efficient organic solar cells, donor and acceptor molecules are mixed in the photoactive layer to form a so-called bulk heterojunction. Due to molecular interactions, a certain degree of phase separation between donor and acceptor domains arises, which is necessary to achieve efficient charge extraction within the absorber layer. However, the mechanism that induces the phase separation is not fully understood and gaining detailed information about the molecular arrangement within these blend layers is quite challenging. We show that grazing incidence x-ray diffraction, combined with variable angle spectroscopic ellipsometry is a suitable way to investigate the molecular structure of blend layers in detail, consisting of a mixture of zinc-phthalocyanine (ZnPc) and C60. The degree of phase separation within the blend layer is influenced by substrate heating during the co-evaporation of ZnPc and C60 and by a variation of the mixing ratio. The effect of different blend layer morphologies on optical and electrical device performance is investigated by solar cell characterization and mobility measurements. We find that the molecular arrangement of C60 provides the essential driving force for efficient phase separation. Whereas spherical C60 molecules are able to form crystalline domains when deposited at elevated substrate temperatures, no ZnPc crystallites are observed, although the planar ZnPc molecules are not randomly oriented but standing upright within its domains. Comparing specular and grazing incidence x-ray diffraction, we find that only the latter method is able to detect nanocrystalline C60 in thin films due to its polycrystalline nature and small sized nanocrystallites. Solar cell measurements show an increase in fill factor and external quantum efficiency signal for blends with enhanced phase separation, induced by higher substrate temperatures. However, grazing incidence x-ray diffraction measurements reveal that ZnPc and C60 already form

  16. Movement of Ng2 molecules confined in a C60 cage: An ab initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Khatua, Munmun; Pan, Sudip; Chattaraj, Pratim K.

    2014-08-01

    An ab initio molecular dynamics study on Ng2@C60 (Ng = Hesbnd Kr) systems is performed to analyze the movement of Ng2 molecules inside a C60 cage. Within 500 fs time window, the He2 undergoes precession encompassing translation, vibration and rotation readily whereas other Ng2 molecules show usual vibration but the degrees of translation and rotation decrease with an increase in size of the Ng atoms. Increase in interaction between the Ng centers and cage carbons and an increased distortion of cage in moving from He to Kr seem to be responsible for this. During the movement, the Ng2 units behave as single entity. To check the kinetic stability of these systems through ab initio molecular dynamics study since they are thermodynamically unstable. Frenking et al. [40] argued about the free precession of the Ng2 units inside the cage on the basis of the very small energy differences between differently oriented Ng2 units. We need to check whether these Ng2 units really precess inside the C60 cage at room temperature and if yes then by what extent, up to 500 fs time scale. To check whether these weakly interacting He2 and Ne2 systems can be termed as molecules we would like to analyze the Ngsbnd Ng bond distance values at different time steps. In order to check the applicability of maximum hardness principle and minimum electrophilicity principle during time evolution of these endohedrally trapped systems the variation of hardness and electrophilicity with time during simulation and their correlation with the change in energy of the systems are studied.

  17. Quick synthesis of highly aligned or randomly oriented nanofibrous structures composed of C60 molecules via self-assembly

    NASA Astrophysics Data System (ADS)

    Kurosu, Shunji; Fukuda, Takahiro; Maekawa, Toru

    2013-06-01

    Assemblies, which are composed of nanoparticles such as nanofibres, have been intensively studied in recent years. This has particularly been the case in the field of biomedicine, where the aim is to develop efficient methodologies for capturing and separating target biomolecules and cells and/or encouraging bio-chemical reactions, utilizing the extremely high surface area to volume ratio of assemblies. There is an urgent need for the development of a quick synthesis method of forming nanofibrous structures on the surface of biomedical microchips and devices for the investigation of the interactions between biomolecules/cells and the nanostructures. Here, we produce nanofibrous structures composed of C60 molecules, which are aligned in one direction or randomly oriented, by dissolving C60 molecules and sulphur in benzene and evaporating a droplet of the solution on a glass substrate under appropriate conditions. The synthesis time is as short as 30 s. Sulphur is extracted and nanofibres are crystallized by leaving them in supercritical carbon dioxide.

  18. Imaging the wave functions of adsorbed molecules

    PubMed Central

    Lüftner, Daniel; Ules, Thomas; Reinisch, Eva Maria; Koller, Georg; Soubatch, Serguei; Tautz, F. Stefan; Ramsey, Michael G.; Puschnig, Peter

    2014-01-01

    The basis for a quantum-mechanical description of matter is electron wave functions. For atoms and molecules, their spatial distributions and phases are known as orbitals. Although orbitals are very powerful concepts, experimentally only the electron densities and -energy levels are directly observable. Regardless whether orbitals are observed in real space with scanning probe experiments, or in reciprocal space by photoemission, the phase information of the orbital is lost. Here, we show that the experimental momentum maps of angle-resolved photoemission from molecular orbitals can be transformed to real-space orbitals via an iterative procedure which also retrieves the lost phase information. This is demonstrated with images obtained of a number of orbitals of the molecules pentacene (C22H14) and perylene-3,4,9,10-tetracarboxylic dianhydride (C24H8O6), adsorbed on silver, which are in excellent agreement with ab initio calculations. The procedure requires no a priori knowledge of the orbitals and is shown to be simple and robust. PMID:24344291

  19. Charge transfer excitations in water-soluble sulfonated zinc-phthalocyanine (ZnPcS) donor molecules coupled to C60

    NASA Astrophysics Data System (ADS)

    Zope, Rajendra; Basurto, Luis; Olguin, Marco; Baruah, Tunna

    2013-03-01

    We present a study of charge transfer (CT) excited states for a recently synthesized group of water-soluble sulfonated zinc-phthalocyanine (ZnPcS) donor molecules coupled to C60. The ZnPcS donors (ZnPcS2, ZnPcS3, and ZnPcS4) are promising materials for achieving solar cell device production with the photoactive area prepared from aqueous solution. Experimentally, decreasing the number of sulfonate substituent groups for ZnPc increased the photocurrent and lowered the open circuit voltage VOC. Measurements show that the VOC is largest for ZnPc-S4/C60 and lowest for ZnPc-S3/C60. The degree of sulfonation and the measured device VOC does not result in the expected pattern of values based on donor-acceptor HOMO/LUMO energy differences. Variations in film morphology may account for the unexpected pattern of VOC values. Our charge transfer excited state calculations show that the lowest CT excitation energy among the group of ZnPcS/C60 donor-acceptor pairs corresponds to the disulfonated ZnPc/C60 system. The largest CT excited state energies belong to the tetrasulfonated ZnPc/C60 complex. We also examine the effect of geometrical orientation on the CT energies for the ZnPcS donor-acceptor pairs.

  20. C_60 Nanotips for Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Halas, N. J.

    1997-03-01

    Individual C_60 molecules are shown to provide stable conductive molecular tunneling sites, or nanotips, on the probe tip of a scanning tunneling microscope (STM). The chemisorptive attachment and subsequent imaging of discrete single molecules on an STM tip apex have been previously reported.(K. F. Kelly, D. Sarkar, S. Prato, J. S. Resh, G. D. Hale, and N. J. Halas, J. Vac. Sci. Tech. B14), 593 (1996). Functionalizing an STM tip with a C_60 molecular adsorbate alters the density of states near the Fermi energy of the tip tunneling site and modifies its imaging characteristics. These tips have permitted the observation of threefold symmetric electron scattering surrounding point defects on graphite surfaces, an effect which could not be observed using bare metal tips.(K. F. Kelly, D. Sarkar, G. D. Hale, S. J. Oldenburg, and N. J. Halas, Science 273), 1371 (1996).

  1. Adsorbed molecules in external fields: Effect of confining potential.

    PubMed

    Tyagi, Ashish; Silotia, Poonam; Maan, Anjali; Prasad, Vinod

    2016-12-01

    We study the rotational excitation of a molecule adsorbed on a surface. As is well known the interaction potential between the surface and the molecule can be modeled in number of ways, depending on the molecular structure and the geometry under which the molecule is being adsorbed by the surface. We explore the effect of change of confining potential on the excitation, which is largely controlled by the static electric fields and continuous wave laser fields. We focus on dipolar molecules and hence we restrict ourselves to the first order interaction in field-molecule interaction potential either through permanent dipole moment or/and the molecular polarizability parameter. It is shown that confining potential shapes, strength of the confinement, strongly affect the excitation. We compare our results for different confining potentials. PMID:27387127

  2. Yttrium-dispersed C60 fullerenes as high-capacity hydrogen storage medium

    NASA Astrophysics Data System (ADS)

    Tian, Zi-Ya; Dong, Shun-Le

    2014-02-01

    Interaction between hydrogen molecules and functionalized C60 is investigated using density functional theory method. Unlike transition metal atoms that tend to cluster on the surface, C60 decorated with 12 Yttrium atoms on each of its 12 pentagons is extremely stable and remarkably enhances the hydrogen adsorption capacity. Four H2 molecules can be chemisorbed on a single Y atom through well-known Dewar-Chatt-Duncanson interaction. The nature of bonding is a weak physisorption for the fifth adsorbed H2 molecule. Consequently, the C60Y12 complex with 60 hydrogen molecules has been demonstrated to lead to a hydrogen storage capacity of ˜6.30 wt. %.

  3. Inhomogeneous distribution of organic molecules adsorbed in sol gel glasses

    NASA Astrophysics Data System (ADS)

    Meneses-Nava, M. A.; Chávez-Cerda, S.; Sánchez-Villicaña, V.; Sánchez-Mondragón, J. J.; King, T. A.

    1999-09-01

    The effects of the porous matrix upon the radiative characteristics of quinine sulphate doped sol-gel glasses are investigated. The broadenings of the absorption and fluorescence spectra are explained by the attachment of the molecules on distorted sites or in a non-planar fashion, creating an inhomogeneous distribution of adsorbed molecules. For this reason, each emitting center relaxes with its own characteristics. This inhomogeneous distribution is also supported by the non-exponential and the wavelength dependence of the fluorescence decay.

  4. New Volleyballenes: Y20C60 and La20C60

    PubMed Central

    Wang, Jing; Liu, Ying

    2016-01-01

    Two new stable Volleyballenes, the Y20C60 and La20C60 molecular clusters, are proposed on the basis of first-principles density functional theory. In conjunction with recent findings for the scandium system, these findings establish Volleyballene M20C60 molecules as a general class of stable molecules within the fullerene family. Both Y20C60 and La20C60 molecules have Th point group symmetries and relatively large HOMO-LUMO gaps. PMID:27487765

  5. New Volleyballenes: Y20C60 and La20C60

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Liu, Ying

    2016-08-01

    Two new stable Volleyballenes, the Y20C60 and La20C60 molecular clusters, are proposed on the basis of first-principles density functional theory. In conjunction with recent findings for the scandium system, these findings establish Volleyballene M20C60 molecules as a general class of stable molecules within the fullerene family. Both Y20C60 and La20C60 molecules have Th point group symmetries and relatively large HOMO-LUMO gaps.

  6. New Volleyballenes: Y20C60 and La20C60.

    PubMed

    Wang, Jing; Liu, Ying

    2016-01-01

    Two new stable Volleyballenes, the Y20C60 and La20C60 molecular clusters, are proposed on the basis of first-principles density functional theory. In conjunction with recent findings for the scandium system, these findings establish Volleyballene M20C60 molecules as a general class of stable molecules within the fullerene family. Both Y20C60 and La20C60 molecules have Th point group symmetries and relatively large HOMO-LUMO gaps. PMID:27487765

  7. Probing atomic positions of adsorbed ammonia molecules in zeolite.

    PubMed

    Ye, Lin; Lo, Benedict T W; Qu, Jin; Wilkinson, Ian; Hughes, Tim; Murray, Claire A; Tang, Chiu C; Tsang, Shik Chi Edman

    2016-02-25

    Atomic positions and interactions between adsorbed guest molecules, such as ammonia in H-ZSM-5 microporous solids, are for the first time revealed by making use of the change in the periodical scattering parameter using in situ synchrotron powder X-ray diffraction combined with refinement within experimental errors. PMID:26833032

  8. Charge transport in C60-based dumbbell-type molecules: mechanically induced switching between two distinct conductance states.

    PubMed

    Moreno-García, Pavel; La Rosa, Andrea; Kolivoška, Viliam; Bermejo, Daniel; Hong, Wenjing; Yoshida, Koji; Baghernejad, Masoud; Filippone, Salvatore; Broekmann, Peter; Wandlowski, Thomas; Martín, Nazario

    2015-02-18

    Single molecule charge transport characteristics of buckminsterfullerene-capped symmetric fluorene-based dumbbell-type compound 1 were investigated by scanning tunneling microscopy break junction (STM-BJ), current sensing atomic force microscopy break junction (CS-AFM-BJ), and mechanically controlled break junction (MCBJ) techniques, under ambient conditions. We also show that compound 1 is able to form highly organized defect-free surface adlayers, allowing the molecules on the surface to be addressed specifically. Two distinct single molecule conductance states (called high G(H)(1) and low G(L)(1)) were observed, depending on the pressure exerted by the probe on the junction, thus allowing molecule 1 to function as a mechanically driven molecular switch. These two distinct conductance states were attributed to the electron tunneling through the buckminsterfullerene anchoring group and fully extended molecule 1, respectively. The assignment of conductance features to these configurations was further confirmed by control experiments with asymmetrically designed buckminsterfullerene derivative 2 as well as pristine buckminsterfullerene 3, both lacking the G(L) feature. PMID:25651069

  9. Hydrogen molecule on lithium adsorbed graphene: A DFT study

    NASA Astrophysics Data System (ADS)

    Kaur, Gagandeep; Gupta, Shuchi; Gaganpreet, Dharamvir, Keya

    2016-05-01

    Electronic structure calculations for the adsorption of molecular hydrogen on lithium (Li) decorated and pristine graphene have been studied systematically using SIESTA code [1] within the framework of the first-principle DFT under the Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA)[2], including spin polarization. The energy of adsorption of hydrogen molecule on graphene is always enhanced by the presence of co-adsorbed lithium. The most efficient adsorption configuration is when H2 is lying parallel to lithium adsorbed graphene which is in contrast to its adsorption on pristine graphene (PG) where it prefers perpendicular orientation.

  10. Candidate Source of Flux Noise in SQUIDs: Adsorbed Oxygen Molecules.

    PubMed

    Wang, Hui; Shi, Chuntai; Hu, Jun; Han, Sungho; Yu, Clare C; Wu, R Q

    2015-08-14

    A major obstacle to using superconducting quantum interference devices (SQUIDs) as qubits is flux noise. We propose that the heretofore mysterious spins producing flux noise could be O_{2} molecules adsorbed on the surface. Using density functional theory calculations, we find that an O_{2} molecule adsorbed on an α-alumina surface has a magnetic moment of ~1.8 μ_{B}. The spin is oriented perpendicular to the axis of the O-O bond, the barrier to spin rotations is about 10 mK. Monte Carlo simulations of ferromagnetically coupled, anisotropic XY spins on a square lattice find 1/f magnetization noise, consistent with flux noise in Al SQUIDs. PMID:26317742

  11. Theory of raman scattering from molecules adsorbed at semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Ueba, H.

    1983-09-01

    A theory is presented to calculate the Raman polarizability of an adsorbed molecule at a semiconductor surface, where the electronic excitation in the molecular site interacts with excitons (elementary excitations in the semiconductor) through non-radiative energy transfer between them, in an intermediate state in the Raman scattering process. The Raman polarizability thus calculated is found to exhibit a peak at the energy corresponding to a resonant excitation of excitons, thereby suggesting the possibility of surface enhanced Raman scattering on semiconductor surfaces. The mechanism studied here can also give an explanation of a recent observation of the Raman excitation profiles of p-NDMA and p-DMAAB adsorbed on ZnO or TiO 2, where those profiles were best described by assuming a resonant intermediate state of the exciton transition in the semiconductors. It is also demonstrated that in addition to vibrational Raman scattering, excitonic Raman scattering of adsorbed molecules will occur in the coupled molecule-semiconductor system, where the molecular returns to its ground electronic state by leaving an exciton in the semiconductor. A spectrum of the excitonic Raman scattering is expected to appear in the background of the vibrational Raman band and to be characterized by the electronic structure of excitons. A desirable experiment is suggested for an examination of the theory.

  12. A simple model for electronic properties of surface adsorbed molecules

    NASA Astrophysics Data System (ADS)

    Dhakal, Rajesh; Schwalm, William

    We adapt a minimal approximation to one electron quantum theory of molecules referred as Fast Accurate Kinetic Energy method. This in principle handles large complex molecular structures with less computational effort to compute electronic properties of adsorbed molecules. Kinetic energy integrals are calculated accurately but multi-electron potential energy integrals are approximated. The neighboring atom interactions are included also. For layers of isopthalic acids formed on pyrolytic graphite the configuration changes as a function of length of hydrocarbon tails. We study properties of this system as a function of tail length.

  13. SPR-MS: from identifying adsorbed molecules to image tissues

    NASA Astrophysics Data System (ADS)

    Masson, Jean-François; Breault-Turcot, Julien; Forest, Simon; Chaurand, Pierre

    2015-03-01

    Surface plasmon resonance (SPR) sensors have become valuable analytical sensors for biomolecule detection. While SPR is heralded with high sensitivity, label-free and real-time detection, nonspecific adsorption and detection of ultralow concentrations remain issues. Nonspecific adsorption can be minimized using adequate surface chemistry. For example, we have employed peptide monolayers to reduce nonspecific adsorption of crude serum or cell lysate. It is important to uncover the nature of molecules nonspecifically adsorbing to surfaces in these biofluids, to further improve understanding of the nonspecific adsorption processes. Mass spectrometry (MS) provides a complementary tool to SPR to identify biomolecule adsorbed to surface. Trypsic digestion of the proteins adsorbed to surfaces led to identification of characteristic peptides from the proteins involved in nonspecific adsorption. Nonspecific adsorption in crude cell lysate results mainly from lipids, as confirmed with SPR and MS but proteins were observed on some surfaces. In another application of SPR and MS, imaging SPR can be used in combination to imaging MS to image tissue sections. Thin sections of mouse liver were inserted in the fluidic chamber of a SPRi instrument and proteins were transferred to the SPRi chip. The SPR chip was then imaged using MALDI imaging MS to identify the biomolecules that were transferred to the SPRi chip.

  14. Buckling of C60 whiskers

    NASA Astrophysics Data System (ADS)

    Asaka, Koji; Kato, Ryoei; Miyazawa, Kun'ichi; Kizuka, Tokushi

    2006-08-01

    The authors demonstrated the mechanics of materials for crystalline whiskers composed of C60 molecules; compressive deformation of the whiskers was observed by in situ transmission electron microscopy with simultaneous force measurement by means of an optical cantilever method, as used in atomic force microscopy. In response to compression along the long axis, the whiskers bent first elastically, then buckled. A whisker with 160nm diameter fractured brittlely at a strain of 0.08. According to Euler's formula, Young's modulus of the whisker was estimated to be 32-54GPa, which is 160%-650% of that of C60 bulk crystals.

  15. Quantum Bound States in a C-C60 System

    NASA Astrophysics Data System (ADS)

    Adam, R. M.; Sofianos, S. A.

    2015-03-01

    We investigate the quantum mechanical system of a carbon "test atom" in the proximity of a C60 molecule, both inside and outside the fullerene "cage". Two sets of bound states are found to exist, a deeply bound set inside the cage and another weakly bound set outside it. Tunnelling between these regions is highly unlikely to happen because of the extreme height and width of the potential barrier. However, we predict that a layer of atoms could be adsorbed onto C60 by forming a quantum mechanical bound state, with the adsorbed atoms being concentrated above the "panels" of the buckyball, consistent with "bucky onions" observed experimentally. Until now analysis of such fullerene systems has been via classical mechanics, but a quantum approach reveals new insights.

  16. Controlling spins in adsorbed molecules by a chemical switch

    PubMed Central

    Wäckerlin, Christian; Chylarecka, Dorota; Kleibert, Armin; Müller, Kathrin; Iacovita, Cristian; Nolting, Frithjof; Jung, Thomas A.; Ballav, Nirmalya

    2010-01-01

    The development of chemical systems with switchable molecular spins could lead to the architecture of materials with controllable magnetic or spintronic properties. Here, we present conclusive evidence that the spin of an organometallic molecule coupled to a ferromagnetic substrate can be switched between magnetic off and on states by a chemical stimulus. This is achieved by nitric oxide (NO) functioning as an axial ligand of cobalt(II)tetraphenylporphyrin (CoTPP) ferromagnetically coupled to nickel thin-film (Ni(001)). On NO addition, the coordination sphere of Co2+ is modified and a NO–CoTPP nitrosyl complex is formed, which corresponds to an off state of the Co spin. Thermal dissociation of NO from the nitrosyl complex restores the on state of the Co spin. The NO-induced reversible off–on switching of surface-adsorbed molecular spins observed here is attributed to a spin trans effect. PMID:20975713

  17. The encapsulated lithium effect on the first hyperpolarizability of C60Cl2 and C60F2.

    PubMed

    Song, Yao-Dong; Wang, Liang; Wu, Li-Ming; Chen, Qiao-Ling; Liu, Fa-Kun; Tang, Xiao-Wen

    2016-02-01

    In this paper, we report a study on the structure and first hyperpolarizability of C60Cl2 and C60F2. The calculation results show that the first hyperpolarizabilities of C60Cl2 and C60F2 were 172 au and 249 au, respectively. Compared with the fullerenes, the first hyperpolarizability of C60Cl2 increased from 0 au to 172 au, while the first hyperpolarizability of C60F2 increased from 0 au to 249 au. In order to further increase the first hyperpolarizability of C60Cl2 and C60F2, Li@C60Cl2 and Li@C60F2 were obtained by introducing a lithium atom to C60Cl2 and C60F2. The first hyperpolarizabilities of Li@C60Cl2 and Li@C60F2 were 2589 au and 985 au, representing a 15-fold and 3.9-fold increase, respectively, over those of C60Cl2 and C60F2. The transition energies of four molecules (C60Cl2, Li@C60Cl2, C60F2, Li@C60F2) were calculated, and were found to be 0.17866 au, 0.05229 au, 0.18385 au, and 0.05212 au, respectively. A two-level model explains why the first hyperpolarizability increases for Li@C60Cl2 and Li@C60F2. PMID:26841975

  18. Dynamics of photoinduced electron transfer from adsorbed molecules into solids

    NASA Astrophysics Data System (ADS)

    Gundlach, L.; Ernstorfer, R.; Willig, F.

    2007-08-01

    Ultrafast interfacial electron transfer from the donor orbital of organic chromophores into empty electronic acceptor states of a semiconductor and of a metal was investigated by two-photon photoemission spectroscopy (2PPE). Experimental tools and procedures have been developed for carrying out wet-chemistry preparation of the molecule/solid interface. The organic chromophore perylene was investigated with several different bridge/anchor groups on TiO2(110). One perylene compound was investigated for comparison on Ag(110). Angle and polarization dependent 2PPE measurements revealed the orientation of the perylene chromophore on the surface as controlled by the adsorption geometry of the respective anchor group on TiO2. UPS measurements gave the position of the HOMO level of the chromophore with respect to the Fermi level of the solid. The donor level of each molecule was found high enough to fulfill the “wide band limit” of heterogeneous electron transfer dynamics. Time constants for heterogeneous electron transfer were extracted from 2PPE transients. A difference by a factor of four was found, 13 fs against 47 fs, when a conjugated bond was exchanged for a saturated bond in the otherwise identical bridge group. The two different contributions to the 2PPE transients arising firstly from the excited state of the chromophore and secondly from the injected electrons were separated by measuring the latter contribution separately in the case of instantaneous interfacial electron transfer realized with catechol as adsorbate. The time scales measured for the electron transfer step and for the subsequent electron escape process from the surface into the bulk of TiO2 showed both good agreement with recent theoretical predictions of other groups for these systems.

  19. Polarizabilities of Adsorbed and Assembled Molecules: Measuring the Conductance through Buried Contacts

    PubMed Central

    2010-01-01

    We have measured the polarizabilities of four families of molecules adsorbed to Au{111} surfaces, with structures ranging from fully saturated to fully conjugated, including single-molecule switches. Measured polarizabilities increase with increasing length and conjugation in the adsorbed molecules and are consistent with theoretical calculations. For single-molecule switches, the polarizability reflects the difference in substrate−molecule electronic coupling in the ON and OFF conductance states. Calculations suggest that the switch between the two conductance states is correlated with an oxidation state change in a nitro functional group in the switch molecules. PMID:21077677

  20. C60 fullerene binding to DNA

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  1. Electronic structure, conductivity and superconductivity of metal doped C60

    SciTech Connect

    Haddon, R.C.

    1993-12-31

    The curvature and topology required for fullerene formation strongly enhances the electronegativity of the carbon clusters and as a result C60 readily accepts electrons. Solid C60 undergoes doping with a variety of metals to produce intercalation compounds which are conductors. In the case of the alkali metals the predominant phases present are: C60, A3C60, and A6C60. The A3C60 compounds are formed from C60 by occupancy of the interstitial sites of the fcc lattice. These phases constitute the first 3-dimensional organic conductors and for A=K, Rb the A3C60 compounds are superconductors with transition temperatures of Tc=19 and 28K, respectively. There is evidence to suggest that the superconductivity in these systems is driven by the intramolecular vibrations of the reduced C60 molecule. Recent experiments on a variety of metal doped C60 thin films will be presented.

  2. Quasielastic neutron scattering from adsorbed water molecules on pyrogenic silica surfaces

    NASA Astrophysics Data System (ADS)

    Tumanov, A. A.; Zarko, V. I.

    1994-04-01

    Quasielastic neutron scattering (QNS) from hydrated samples of high dispersion (Aerosil) and of porous dioxide silicon was investigated. The broadening of the QNS peak analysis permits one to obtain the effective diffusion coefficient D of adsorbed water molecules. It was obtained that the D-value increases with silica hydration. The mean square displacement of the water molecules from equilibrium < x2> equals approximately 0.1 Å 2 and does not depend on the quantity of adsorbed water.

  3. Sublimed C60 films for tribology

    NASA Astrophysics Data System (ADS)

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

    1993-06-01

    Fullerenes take the form of hollow, geodesic domes, which are formed from a network of pentagons and hexagons. The C60 molecule has the highest possible symmetry (icosahedral) and assumes the shape of a soccer ball. At room temperature, fullerene molecules pack in a face-centered-cubic lattice bonded with weak van der Waals attractions. Fullerenes can be dissolved in solvents such as toluene and benzene and easily sublimed. The resilience, high load bearing capacity, low surface energy, high chemical stability, and spherical shape of C60 molecules and weak intermolecular bonding offer great potential for various mechanical and tribological applications. Sublimed films of C60 have been produced and friction and wear performance of these films in various operating environments are the subject of this letter.

  4. Relaxation dynamics of surface-adsorbed water molecules in nanoporous silica probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Ru; Liu, Kao-Hsiang; Mou, Chung-Yuan; Sun, Chi-Kuang

    2015-08-01

    Relaxation dynamics of an exclusively adsorbed water molecule in mesoporous silica MCM-41-S was studied by using terahertz spectroscopy. With the temperature controlled from 0 to 50 °C, we observed strongly frequency- and temperature-dependent dielectric relaxation responses, implying that, unlike ice, surface-adsorbed water molecules retained flourishing picosecond dynamics. Based on the Debye relaxation model, a relaxation time constant was found to increase from 1.77 to 4.83 ps when the water molecule was cooled from 50 to 0 °C. An activation energy of ˜15 kJ/mol, which was in close agreement with a hydrogen-bonding energy, was further extracted from the Arrhenius analysis. Combined with previous molecular dynamics simulations, our results indicate that the reorientation relaxation originated from the "flip-flop" rotation of a three hydrogen-bonded surface-adsorbed water molecule.

  5. Laser electrospray mass spectrometry of adsorbed molecules at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Brady, John J.; Judge, Elizabeth J.; Simon, Kuriakose; Levis, Robert J.

    2010-02-01

    Atmospheric pressure mass analysis of solid phase biomolecules is performed using laser electrospray mass spectrometry (LEMS). A non-resonant femtosecond duration laser pulse vaporizes native samples at atmospheric pressure for subsequent electrospray ionization and transfer into a mass spectrometer. LEMS was used to detect a complex molecule (irinotecan HCl), a complex mixture (cold medicine formulation with active ingredients: acetaminophen, dextromethorphan HBr and doxylamine succinate), and a biological building block (deoxyguanosine) deposited on steel surfaces without a matrix molecule.

  6. Properties Of N@C60-Derived Peapods

    NASA Astrophysics Data System (ADS)

    Gembus, A.; Simon, F.; Jánossy, A.; Kuzmany, H.; Dinse, K.-P.

    2004-09-01

    Using pulsed EPR techniques, the basic spin relaxation properties of N@C60-based peapods were determined. In contrast to narrow line spectra typical for N@C60 in solid solution or in a C60 matrix, substantial line broadening is observed for the SWCNT-encapsulated N@C60 molecules, which might be indicative for uniaxial cage distortion by interaction with the nanotube.

  7. Auger electron spectroscopy as a tool for measuring intramolecular charges of adsorbed molecules

    NASA Astrophysics Data System (ADS)

    Magkoev, T. T.

    A way for the determination of the values of intramolecular charges of adsorbed molecules of some binary dielectrics, based on Auger electron spectroscopy (AES), is proposed. These values can be obtained from the coverage dependences of the ratios of intensities of anion KL 23L 23 and KL 1L 1 Auger transitions, which are sensitive to the amount of charge at the 2p-orbitals. As an example, MgO adsorbed on Mo(110) is presented.

  8. Auger electron spectroscopy as a tool for measuring intramolecular charges of adsorbed molecules

    NASA Astrophysics Data System (ADS)

    Magkoev, T. T.

    1993-10-01

    A way for the determination of the values of intramolecular charges of adsorbed molecules of some binary dielectrics, based on Auger electron spectroscopy (AES), is proposed. These values can be obtained from the coverage dependences of the ratios of intensities of anion KL 23L 23 and KL 1L 1 Auger transitions, which are sensitive to the amount of charge at the 2p-orbitals. As an example, MgO adsorbed on Mo(110) is presented.

  9. Transient magnetization of core excited organic molecules adsorbed on graphene

    NASA Astrophysics Data System (ADS)

    Ravikumar, Abhilash; Baby, Anu; Lin, He; Brivio, Gian Paolo; Fratesi, Guido

    This work presents a density functional theory based computational investigation of electronic and magnetic properties of physisorbed and chemisorbed organic molecules on graphene in the ground state and core excited one at low molecular coverage. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, it is found that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the contrary, when graphene is covalently functionalized, the system is magnetic in the ground state presenting two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore. This project has received funding from the European Union Seventh Framework Programme under grant agreement n∘ 607232 [THINFACE].

  10. Rotational Spectromicroscopy: Imaging the Orbital Interaction between Molecular Hydrogen and an Adsorbed Molecule.

    PubMed

    Li, Shaowei; Yuan, Dingwang; Yu, Arthur; Czap, Gregory; Wu, Ruqian; Ho, W

    2015-05-22

    A hydrogen molecule can diffuse freely on the surface and be trapped above an adsorbed molecule within the junction of a scanning tunneling microscope. The trapped dihydrogen exhibits the properties of a free rotor. Here we show that the intermolecular interaction between dihydrogen and Mg-porphyrin (MgP) can be visualized by imaging j=0 to 2 rotational excitation of dihydrogen. The interaction leads to a weakened H-H bond and modest electron donation from the dihydrogen to the lowest unoccupied molecular orbital of MgP, a process similarly observed for the interaction between dihydrogen and an adsorbed Au atom. PMID:26047242

  11. Rotational Spectromicroscopy: Imaging the Orbital Interaction between Molecular Hydrogen and an Adsorbed Molecule

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; Yuan, Dingwang; Yu, Arthur; Czap, Gregory; Wu, Ruqian; Ho, W.

    2015-05-01

    A hydrogen molecule can diffuse freely on the surface and be trapped above an adsorbed molecule within the junction of a scanning tunneling microscope. The trapped dihydrogen exhibits the properties of a free rotor. Here we show that the intermolecular interaction between dihydrogen and Mg-porphyrin (MgP) can be visualized by imaging j =0 to 2 rotational excitation of dihydrogen. The interaction leads to a weakened H-H bond and modest electron donation from the dihydrogen to the lowest unoccupied molecular orbital of MgP, a process similarly observed for the interaction between dihydrogen and an adsorbed Au atom.

  12. Film growth and surface reactions of C60 on Si(100)H(2×1)

    NASA Astrophysics Data System (ADS)

    Schmidt, J.; Hunt, M. R. C.; Miao, P.; Palmer, R. E.

    1997-10-01

    High-resolution electron-energy-loss spectroscopy (HREELS) has been used to characterize C60 films up to 4 monolayers thick grown at room temperature on hydrogen-terminated Si(100). Our results show that compared with C60 films on clean Si(100) surfaces a considerably higher degree of order in the as-deposited films is achieved. At low coverages the observed C60 vibrational modes and the Si-H vibrations of the substrate are essentially unshifted, indicating a van der Waals-type interaction between C60 and Si(100)H(2×1). After annealing at 450 K the film order is substantially increased. Annealing at 600 K results in desorption of the C60 multilayers and a hydrogen-transfer reaction from the surface to the adsorbed monolayer molecules. When annealing the sample at 800 K, the remaining surface terminating hydrogen desorbs and evidence for a change in the C60 bonding configuration is found. Finally, flashing the sample at 1300 K leads to the formation of silicon carbide.

  13. STM imagery and density functional calculations of C60 fullerene adsorption on the 6H-SiC(0001)-3×3 surface

    NASA Astrophysics Data System (ADS)

    Ovramenko, T.; Spillebout, F.; Bocquet, F. C.; Mayne, A. J.; Dujardin, G.; Sonnet, Ph.; Stauffer, L.; Ksari, Y.; Themlin, J.-M.

    2013-04-01

    Scanning tunneling microscopy (STM) studies of the fullerene C60 molecule adsorbed on the silicon carbide SiC(0001)-3×3 surface, combined with density functional theory (DFT) calculations, show that chemisorption of individual C60 molecules occurs through the formation of one bond to one silicon adatom only in contrast to multiple bond formation on other semiconducting surfaces. We observe three stable adsorption sites with respect to the Si adatoms of the surface unit cell. Comprehensive DFT calculations give different adsorption energies for the three most abundant sites showing that van der Waals forces between the C60 molecule and the neighboring surface atoms need to be considered. The C60 molecules are observed to form small clusters even at low coverage indicating the presence of a mobile molecular precursor state and nonnegligible intermolecular interactions.

  14. Fullerene (C60) films for solid lubrication

    SciTech Connect

    Bhushan, B.; Gupta, B.K.; Van Cleef, G.W.; Capp, C.E.; Coe, J.V. )

    1993-10-01

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

  15. Dynamics of Molecules Adsorbed in Zeolitic Systems: Neutron Scattering and MD Simulation Studies

    SciTech Connect

    Mitra, S.; Sharma, V. K.; Mukhopadhyay, R.

    2011-07-15

    Zeolites represent a class of technologically important materials because of their characteristic properties of molecular sieving and catalysis, which makes them indispensable in the petroleum industries. While the catalytic properties depend upon many factors, a major role is played by the dynamics of hydrocarbon gases. In order to be able to tailor make these materials for use in industry for catalytic and sieving purposes, it is important to understand the dynamical properties of the guest molecules adsorbed in the zeolitic materials. It is of interest to study the effects of size and shape of guest molecules and also the host zeolitic structure, governing the diffusion mechanism of the adsorbed species. Here we report the results of Quasielastic Neutron Scattering (QENS) and classical molecular dynamics (MD) simulation studies of two hydrocarbons namely acetylene and propylene adsorbed in two structurally different zeolites Na-Y and ZSM-5.

  16. Molecular simulation of C 60 adsorption onto a TiO 2 rutile (1 1 0) surface

    NASA Astrophysics Data System (ADS)

    Carvalho, A. J. Palace; Ramalho, J. P. Prates

    2010-06-01

    A Monte Carlo molecular simulation study is presented on the adsorption and growth of C 60 films on the surface of the (1 1 0) face of rutile. Simulations are performed for a temperature of 600 K using atomistic models both for the fullerene molecules and the TiO 2 surface. It is found in this work that C 60 is adsorbed preferably in an ordered arrangement along the surface depressions over the exposed undercoordinated Ti cations. At low densities adsorption occurs preferably at alternate rows, with locations in consecutive rows being occupied appreciably only at higher C 60 densities. At low densities, the fullerene molecules tend to aggregate into islands in the surface plane. Additional layers of C 60 form only as the density increases, and do so before a monolayer is completed in all consecutive rows. Full monolayer capacity obtained at the highest densities is about 0.9 C 60 molecules per nm 2, but this is only achieved by completing the packing of molecules in interstices at a slightly upper level. The fraction of the molecules that lie closest to the surface only amounts to 0.6 molecules per nm 2.

  17. Giant Hysteresis of Single-Molecule Magnets Adsorbed on a Nonmagnetic Insulator.

    PubMed

    Wäckerlin, Christian; Donati, Fabio; Singha, Aparajita; Baltic, Romana; Rusponi, Stefano; Diller, Katharina; Patthey, François; Pivetta, Marina; Lan, Yanhua; Klyatskaya, Svetlana; Ruben, Mario; Brune, Harald; Dreiser, Jan

    2016-07-01

    TbPc2 single-molecule magnets adsorbed on a magnesium oxide tunnel barrier exhibit record magnetic remanence, record hysteresis opening, perfect out-of-plane alignment of the magnetic easy axes, and self-assembly into a well-ordered layer. PMID:27159732

  18. Dynamics of water molecules adsorbed by silica and resin SGK-7

    NASA Astrophysics Data System (ADS)

    Lisichkin, Yu. V.; Sakharova, L. A.; Tumanov, A. A.

    2014-01-01

    This paper has presented neutron spectroscopy data on the dynamics of light water molecules adsorbed in the cation exchanger (ion-exchange resin) SGK-7 and on the surface of aerosils (highly dispersed pyrogenic silica) with different levels of hydration. The measurements have been performed on a DIN-2PI spectrometer (Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research, Dubna, Russia). The characteristics of the diffusive and vibrational motions of adsorbed water molecules have been determined from the experimental neutron scattering spectra. The data obtained in the quasi-elastic neutron scattering region have been analyzed using a model accounting for the effects of restricted translational and rotational diffusion. The results have demonstrated a significant decrease in the diffusion mobility of adsorbed water molecules as compared to conventional (bulk) water. In particular, the self-diffusion coefficient decreases several times, and the diffusion rate is the lower, the smaller is the thickness of the hydration layer. The dependences of the intensity and half-width of the quasi-elastic scattering peak on the magnitude of the neutron momentum transfer q in the scattering process exhibit a nonmonotonic character. This indicates manifestation of the effects of restricted translational diffusion, rotational diffusion, and jump diffusion. The partial distributions of vibrational frequencies of hydrogen atoms of water molecules adsorbed by the cation exchanger and aerosils have been obtained from the inelastic neutron scattering data.

  19. Superconductivity at 45 K in Rb/Tl codoped C60 and C60/C70 mixtures

    NASA Astrophysics Data System (ADS)

    Iqbal, Zafar; Baughman, Ray H.; Khare, Sandeep; Murthy, N. S.; Ramakrishna, B. L.; Bornemann, Hans J.; Morris, Donald E.

    1991-11-01

    The appearance of superconductivity at relatively high temperatures in alkali metal-doped C60 fullerene provides the challenge to both understand the nature and origin of the superconductivity and to determine the upper limit of the superconducting transition temperature (Tc). Toward the latter goal, it is shown that doping with potassium-thallium and rubidium-thallium alloys in the 400 to 430 C temperature range increases the Tc of C60/C70 mixtures to 25.6 K and above 45 K, respectively. Similar increases in Tc were also observed on analogous doping of pure C60. Partial substitution of potassium with thallium in interstitial sites between C60 molecules is suggested by larger observed unit cell parameters than for the K3C60 and K4C60 phases. Contrary to previous results for C60 doped with different alkali metals, such expansion does not alone account for the changes in critical temperature.

  20. Vibrational dynamics of fullerene molecules adsorbed on metal surfaces studied with synchrotron infrared radiation

    SciTech Connect

    P. Rudolf; R. Raval; P. Dumas; Gwyn P. Williams

    2002-04-01

    Infrared (IR) spectroscopy of chemisorbed C{sub 60} on Ag (111), Au (110) and Cu (100) reveals that a non-IR-active mode becomes active upon adsorption, and that its frequency shifts proportionally with the charge transferred from the metal to the molecule by about 5 cm{sup -1} per electron. The temperature dependence of the frequency and the width of this IR feature have also been followed for C{sub 60>}/Cu (100) and were found to agree well with a weak anharmonic coupling (dephasing) to a low-frequency mode, which we suggest to be the frustrated translational mode of the adsorbed molecules.

    Additionally, the adsorption is accompanied by a broadband reflectance change, which is interpreted as due to the scattering of conduction electrons of the metal surface by the adsorbate. The reflectance change allows determination of the friction coefficient of the C{sub 60} molecules, which results in rather small values ({approx}2 x 10{sup 9}s{sup -1} for Ag and Au, and {approx}1.6 x 10{sup 9}s{sup -1} for Cu), consistent with a marked metallic character of the adsorbed molecules.

    Pre-dosing of alkali atoms onto the metal substrates drastically changes the IR spectra recorded during subsequent C{sub 60} deposition: anti-absorption bands, as well as an increase of the broadband reflectance, occur and are interpreted as due to strong electron-phonon coupling with induced surface states.

  1. Rod-like cyanophenyl probe molecules nanoconfined to oxide particles: Density of adsorbed surface species

    NASA Astrophysics Data System (ADS)

    Frunza, Stefan; Frunza, Ligia; Ganea, Constantin Paul; Zgura, Irina; Brás, Ana Rita; Schönhals, Andreas

    2016-02-01

    Surface layers have already been observed by broadband dielectric spectroscopy for composite systems formed by adsorption of rod-like cyanophenyl derivates as probe molecules on the surface of oxide particles. In this work, features of the surface layer are reported; samples with different amounts of the probe molecules adsorbed onto oxide (nano) particles were prepared in order to study their interactions with the surface. Thermogravimetric analysis (TGA) was applied to analyze the amount of loaded probe molecules. The density of the surface species ns was introduced and its values were estimated from quantitative Fourier transform infrared spectroscopy (FTIR) coupled with TGA. This parameter allows discriminating the composites into several groups assuming a similar interaction of the probe molecules with the hosts of a given group. An influence factor H is further proposed as the ratio of the number of molecules in the surface layer showing a glassy dynamics and the number of molecules adsorbed tightly on the surface of the support: It was found for aerosil composites and used for calculating the maximum filling degree of partially filled silica MCM-41 composites showing only one dielectric process characteristic for glass-forming liquids and a bulk behavior for higher filling degrees.

  2. Modeling the binding of fulvic acid by goethite: the speciation of adsorbed FA molecules

    NASA Astrophysics Data System (ADS)

    Filius, Jeroen D.; Meeussen, Johannes C. L.; Lumsdon, David G.; Hiemstra, Tjisse; van Riemsdijk, Willem H.

    2003-04-01

    Under natural conditions, the adsorption of ions at the solid-water interface may be strongly influenced by the adsorption of organic matter. In this paper, we describe the adsorption of fulvic acid (FA) by metal(hydr)oxide surfaces with a heterogeneous surface complexation model, the ligand and charge distribution (LCD) model. The model is a self-consistent combination of the nonideal competitive adsorption (NICA) equation and the CD-MUSIC model. The LCD model can describe simultaneously the concentration, pH, and salt dependency of the adsorption with a minimum of only three adjustable parameters. Furthermore, the model predicts the coadsorption of protons accurately for an extended range of conditions. Surface speciation calculations show that almost all hydroxyl groups of the adsorbed FA molecules are involved in outer sphere complexation reactions. The carboxylic groups of the adsorbed FA molecule form inner and outer sphere complexes. Furthermore, part of the carboxylate groups remain noncoordinated and deprotonated.

  3. Adsorbed Oxygen Molecules as a Possible Source of Flux Noise in SQUIDs

    NASA Astrophysics Data System (ADS)

    Shi, Chuntai; Wang, Hui; Hu, Jun; Yu, Clare; Wu, Ruqian

    2015-03-01

    One of the dominant source of flux noise in SQUIDs is flux noise which has been attributed to mysterious fluctuating magnetic spins on the surface. We propose that the spins producing flux noise could be adsorbed O2 molecules that have a magnetic moment of about 2 μB. Using density functional calculations, we studied O2 molecules adsorbed on a sapphire surface. We find that the barrier for spin rotation is small enough to allow almost free spin reorientation due to thermal excitations at low temperatures. Monte Carlo simulations of a 2D XY spin model yields 1 / f noise where f is frequency. This work was supported by 1000 Talent Program of China through Fudan University. Work at UCI was supported by DOE-BES (Grant No. DE-FG02-05ER46237) and the Army Research Office (Grant No. W911NF-10-1-0494).

  4. Stability, structural and electronic properties of benzene molecule adsorbed on free standing Au layer

    NASA Astrophysics Data System (ADS)

    Katoch, Neha; Kapoor, Pooja; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.

    2016-05-01

    We report stability and electronic properties of benzene molecule adsorbed on the Au atomic layer within the framework of density function theory (DFT). Horizontal configuration of benzene on the top site of Au monolayer prefers energetically over other studied configurations. On the adsorption of benzene, the ballistic conductance of Au monolayer is found to decrease from 4G0 to 2G0 suggesting its applications for the fabrications of organic sensor devices based on the Au atomic layers.

  5. Orientation and heat capacity of horizontally adsorbed molecules in electric fields

    NASA Astrophysics Data System (ADS)

    Liao, Ying-Yen

    2014-02-01

    The orientation and the heat capacity of horizontally adsorbed molecules are investigated in static electric fields. We evaluate the energy spectrum and the wave function to probe the rotational characteristics of the molecule. Numerical results indicate that the electric field and the effect of quantum confinement lead to anticrossing behaviors in the energy levels. The orientation reveals a stepped feature due to the anticrossing in the ground state. Moreover, the heat capacity displays two peaks near the anticrossing. By means of comparison, each peak of the heat capacity corresponds to a particular degree of orientation.

  6. Sc20C60: a volleyballene

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Ma, Hong-Man; Liu, Ying

    2016-06-01

    An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as ``Volleyballene''. Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (~1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable.An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as ``Volleyballene''. Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (~1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable. Electronic supplementary information (ESI) available: Sc20C60: a Volleyballene_SI. See DOI: 10.1039/c5nr07784b

  7. Preparation and performance of chitosan encapsulated activated charcoal (ACCB) adsorbents for small molecules.

    PubMed

    Chandy, T; Sharma, C P

    1993-01-01

    A technique is described to encapsulate activated charcoal for haemoperfusion to be used in an artificial liver support. Activated charcoal was encapsulated within chitosan matrix (ACCB) in different concentrations, and was used as the supports for perfusion of a mixture of solutes, having molecular weight ranges from 60 to 69,000; under a flow rate of 8 ml/min. It seems the ACCB may be a good adsorbent system for the removal of toxic uric acid, creatinine, bilirubin, etc., from solutions; while larger molecules such as albumin are adsorbed less. The encapsulated charcoal did not leach out from the matrix during perfusion, and the system may be useful for detoxification of blood. The haemolytic potential of ACCB has been compatible with polystyrene control tubes. However, further studies are needed to determine their behaviour under clinical conditions. PMID:8263676

  8. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    PubMed Central

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-01-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures. PMID:26891851

  9. Homeotropic orientation of a nematic liquid crystal by bent-core molecules adsorbed on its surface

    NASA Astrophysics Data System (ADS)

    Hwang, Jiyong; Yang, Seungbin; Lee, Hyojin; Kim, Jongyoon; Lee, Ji-Hoon; Kang, Shin-Woong; Choi, E.-Joon

    2015-06-01

    We reported the promotion of a homeotropic alignment of a nematic liquid crystal (NLC) by bent-core liquid-crystal (BLC) Molecules adsorbed its surface. The BLC was mixed at various concentrations with the NLC, and the mixtures were injected into an empty cell with a cell gap of 13 μm. Although the pure NLC showed a heterogeneous orientation, the BLC-NLC mixture was gradually transformed to a homeotropic alignment with increasing concentration of the BLC. We investigated the surface topography of the samples by using an atomic force microscopy (AFM) and found that the BLC molecules were segregated into a polyimide (PI) surface and formed protrusion domains with diameters of 50-100 nm. The BLC protrusions might promote the homeotropic orientation of the NLC molecules.

  10. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    NASA Astrophysics Data System (ADS)

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-02-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures.

  11. Ultra-sensitive fluorescence spectroscopy of isolated surface-adsorbed molecules using an optical nanofiber.

    PubMed

    Stiebeiner, A; Rehband, O; Garcia-Fernandez, R; Rauschenbeutel, A

    2009-11-23

    The strong radial confinement and the pronounced evanescent field of the guided light in optical nanofibers yield favorable conditions for ultra-sensitive surface spectroscopy of molecules deposited on the fiber. Using the guided mode of the nanofiber for both excitation and fluorescence collection, we present spectroscopic measurements on 3,4,9,10-perylenetetracarboxylic dianhydride molecules (PTCDA) at ambient conditions. Surface coverages as small as 1 per thousand of a compact monolayer still give rise to fluorescence spectra with a good signal to noise ratio. Moreover, we analyze and quantify the self-absorption effects due to reabsorption of the emitted fluorescence light by circumjacent surface-adsorbed molecules distributed along the fiber waist. PMID:19997412

  12. Structure formation in adsorbed overlayers comprising functional cross-shaped molecules: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Kasperski, Adam; Nieckarz, Damian; Szabelski, Paweł

    2015-11-01

    Surface confined self-assembly of functional star-shaped organic molecules is a promising method to create nanoporous networks with tailorable structure and functions. In this work we use the Monte Carlo simulation method to demonstrate how the morphology of these supramolecular assemblies can be tuned by manipulating intrinsic parameters of the building blocks and modified by the presence of co-adsorbed metal atoms. To that purpose we study the 2D self-assembly of planar cruciform molecules modeled as collections of interconnected segments, some of which were activated to represent discrete interaction centers. We consider a few exemplary adsorbed systems in which the molecules with different size, aspect ratio and intramolecular distribution of active centers form superstructures stabilized by short-range segment-segment interactions or by metal-segment interactions. These two situations correspond to supramolecular assemblies sustained by, for example, hydrogen bonding and metal-organic ligand coordination, respectively. The simulated results show that proper encoding of intramolecular interactions into the cruciform building bricks allows for directing the self-assembly towards largely diversified structures ranging from nanoclusters to porous grids. The obtained findings can facilitate designing and optimization of molecular networks comprising cross-shaped units including functionalized porphyrins and phthalocyanines and they can be helpful in preliminary selection of these building blocks.

  13. Sc20C60: a volleyballene.

    PubMed

    Wang, Jing; Ma, Hong-Man; Liu, Ying

    2016-06-01

    An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as "Volleyballene". Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (∼1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable. PMID:26878201

  14. Thermal and Electronic Fluctuations of Flexible Adsorbed Molecules: Azobenzene on Ag(111)

    NASA Astrophysics Data System (ADS)

    Maurer, Reinhard J.; Liu, Wei; Poltavsky, Igor; Stecher, Thomas; Oberhofer, Harald; Reuter, Karsten; Tkatchenko, Alexandre

    2016-04-01

    We investigate the thermal and electronic collective fluctuations that contribute to the finite-temperature adsorption properties of flexible adsorbates on surfaces on the example of the molecular switch azobenzene C12 H10 N2 on the Ag(111) surface. Using first-principles molecular dynamics simulations, we obtain the free energy of adsorption that accurately accounts for entropic contributions, whereas the inclusion of many-body dispersion interactions accounts for the electronic correlations that govern the adsorbate binding. We find the adsorbate properties to be strongly entropy driven, as can be judged by a kinetic molecular desorption prefactor of 1024 s-1 that largely exceeds previously reported estimates. We relate this effect to sizable fluctuations across structural and electronic observables. A comparison of our calculations to temperature-programed desorption measurements demonstrates that finite-temperature effects play a dominant role for flexible molecules in contact with polarizable surfaces, and that recently developed first-principles methods offer an optimal tool to reveal novel collective behavior in such complex systems.

  15. Thermal and Electronic Fluctuations of Flexible Adsorbed Molecules: Azobenzene on Ag(111).

    PubMed

    Maurer, Reinhard J; Liu, Wei; Poltavsky, Igor; Stecher, Thomas; Oberhofer, Harald; Reuter, Karsten; Tkatchenko, Alexandre

    2016-04-01

    We investigate the thermal and electronic collective fluctuations that contribute to the finite-temperature adsorption properties of flexible adsorbates on surfaces on the example of the molecular switch azobenzene C_{12}H_{10}N_{2} on the Ag(111) surface. Using first-principles molecular dynamics simulations, we obtain the free energy of adsorption that accurately accounts for entropic contributions, whereas the inclusion of many-body dispersion interactions accounts for the electronic correlations that govern the adsorbate binding. We find the adsorbate properties to be strongly entropy driven, as can be judged by a kinetic molecular desorption prefactor of 10^{24}  s^{-1} that largely exceeds previously reported estimates. We relate this effect to sizable fluctuations across structural and electronic observables. A comparison of our calculations to temperature-programed desorption measurements demonstrates that finite-temperature effects play a dominant role for flexible molecules in contact with polarizable surfaces, and that recently developed first-principles methods offer an optimal tool to reveal novel collective behavior in such complex systems. PMID:27104719

  16. Optimal High-TC Superconductivity in Cs3C60

    NASA Astrophysics Data System (ADS)

    Harshman, Dale; Fiory, Anthony

    The highest superconducting transition temperatures in the (A1-xBx)3C60 superconducting family are seen in the A15 and FCC structural phases of Cs3C60 (optimized under hydrostatic pressure), exhibiting measured values for near-stoichiometric samples of TC0 meas . = 37.8 K and 35.7 K, respectively. It is argued these two Cs-intercalated C60 compounds represent the optimal materials of their respective structures, with superconductivity originating from Coulombic e- h interactions between the C60 molecules, which host the n-type superconductivity, and mediating holes associated with the Cs cations. A variation of the interlayer Coulombic pairing model [Harshman and Fiory, J. Supercond. Nov. Magn. 28 ̲, 2967 (2015), and references therein] is introduced in which TC0 calc . ~ 1 / lζ , where l relates to the mean spacing between interacting charges on surfaces of the C60 molecules, and ζ is the average radial distance between the surface of the C60 molecules and the neighboring Cs cations. For stoichiometric Cs3C60, TC0 calc . = 38.08 K and 35.67 K for the A15 and FCC macrostructures, respectively; the dichotomy is attributable to differences in ζ.

  17. Alignment and assembly of adsorbed collagen molecules induced by anisotropic chemical nanopatterns.

    PubMed

    Denis, Frédéric A; Pallandre, Antoine; Nysten, Bernard; Jonas, Alain M; Dupont-Gillain, Christine C

    2005-10-01

    Collagen, a protein widely used to control cell-material interactions, is known to self-assemble in solution. Supramolecular structures also form on material surfaces following collagen adsorption. Herein, we report the use of anisotropic, flat, surface chemical nanopatterns, which consist of alkyl-terminated tracks drawn in an oligo(ethylene glycol)-terminated matrix, to direct collagen adsorption. As revealed by atomic force microscopy, the spontaneous collagen adsorption performed on such patterned substrates results in the accumulation of collagen on the hydrophobic tracks. Moreover, the width of the tracks (30-90 nm), which is much smaller than the length of the collagen molecule (approximately 300 nm), is the origin of preferential alignment of the molecules and of their assembly into continuous bundles of adsorbed collagen. This chemical guidance effect due to self-confinement of proteins upon adsorption may bring novel and valuable applications, specifically in biomaterials science and cell growth control. PMID:17193383

  18. Molecular resonant dissociation of surface-adsorbed molecules by plasmonic nanoscissors

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenglong; Sheng, Shaoxiang; Zheng, Hairong; Xu, Hongxing; Sun, Mengtao

    2014-04-01

    The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis, photosynthesis and the degradation of plastic, it is hard to break individual molecular bonds for those molecules adsorbed on the surface because of the weak light-absorption in molecules and the redistribution of the resulting vibrational energy both inside the molecule and to its surrounding environment. Here we show how to overcome these obstacles with a plasmonic hot-electron mediated process and demonstrate a new method that allows the sensitive control of resonant dissociation of surface-adsorbed molecules by `plasmonic' scissors. To that end, we used a high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) setup to dissociate resonantly excited NC2H6 fragments from Malachite green. The surface plasmons (SPs) excited at the sharp metal tip not only enhance the local electric field to harvest the light incident from the laser, but crucially supply `hot electrons' whose energy can be transferred to individual bonds. These processes are resonant Raman, which result in some active chemical bonds and then weaken these bonds, followed by dumping in lots of indiscriminant energy and breaking the weakest bond. The method allows for sensitive control of both the rate and probability of dissociation through their dependence on the density of hot electrons, which can be manipulated by tuning the laser intensity or tunneling current/bias voltage in the HV-TERS setup, respectively. The concepts of plasmonic scissors open up new versatile avenues for the deep understanding of in situ surface-catalyzed chemistry.The ability to break individual bonds or specific modes in chemical reactions is an ardently sought goal by chemists and physicists. While photochemistry based methodologies are very successful in controlling e.g. photocatalysis

  19. Energetics and structural characterization of C60 polymerization in BN and carbon nanopeapods

    NASA Astrophysics Data System (ADS)

    Trave, Andrea; Ribeiro, Filipe J.; Louie, Steven G.; Cohen, Marvin L.

    2004-11-01

    As in the case of carbon nanotubes, also boron nitride nanotubes may host arrays of C60 molecules and form a nanopeapod (NPP). The observed separation between C60 molecules in BN NPP’s is consistently shorter than in carbon NPP’s, which influences their electronic properties. Here we report on total-energy pseudopotential density functional theory (DFT) calculations for polymerized and nonpolymerized C60 chains, and optimize their atomic structures to provide a description of their energetic landscape. A fully polymerized C60 chain and a C60 dimer are found to be more stable than nonpolymerized C60 , respectively, by 0.89 and 0.38eV/C60 . The geometry and energetics of an encapsulated C60 chain is not significantly different with respect to the isolated molecule. Encapsulation energies in BN and carbon NPP’s are, respectively, 1.56 and 1.67eV/C60 , which are significantly larger than the calculated activation energy for C60 polymerization, supporting the hypothesis that encapsulated C60 ’s in NPP’s are partially polymerized. Band structure analysis show that polymerization does not affect the gap width of the C60 chain. BN NPP’s are semiconductors with a gap width determined by the C60 . The lowest unoccupied C60 states lie just above the Fermi level in metallic carbon NPP’s and charge transfert could take place, affecting the C60 geometry.

  20. Formation of buckminsterfullerene (C60) in interstellar space

    PubMed Central

    Berné, Olivier; Tielens, A. G. G. M.

    2012-01-01

    Buckminsterfullerene (C60) was recently confirmed as the largest molecule identified in space. However, it remains unclear how and where this molecule is formed. It is generally believed that C60 is formed from the buildup of small carbonaceous compounds in the hot and dense envelopes of evolved stars. Analyzing infrared observations, obtained by Spitzer and Herschel, we found that C60 is efficiently formed in the tenuous and cold environment of an interstellar cloud illuminated by strong ultraviolet (UV) radiation fields. This implies that another formation pathway, efficient at low densities, must exist. Based on recent laboratory and theoretical studies, we argue that polycyclic aromatic hydrocarbons are converted into graphene, and subsequently C60, under UV irradiation from massive stars. This shows that alternative—top-down—routes are key to understanding the organic inventory in space. PMID:22198841

  1. Formation of buckminsterfullerene (C60) in interstellar space

    NASA Astrophysics Data System (ADS)

    Berné, Olivier; Tielens, Alexander G. G. M.

    2012-01-01

    Buckminsterfullerene (C60) was recently confirmed to be the largest molecule identified in space. However, it remains unclear how, and where this molecule is formed. It is generally believed that C60 is formed from the build up of small carbonaceous compounds, in the hot and dense envelopes of evolved stars. Analyzing infrared observations, obtained by Spitzer and Herschel, we found that C60 is efficiently formed in the tenuous and cold environment of an interstellar cloud illuminated by strong ultraviolet (UV) radiation fields. This implies that another formation pathway, efficient at low densities, must exist. Based on recent laboratory and theoretical studies, we argue that Polycyclic Aromatic Hydrocarbons are converted into graphene, and subsequently C60, under UV irradiation from massive stars. This shows that alternative - top-down - routes are key to understanding the organic inventory in space.

  2. Orientation-dependent C-60 electronic structures revealed byphotoemission spectroscopy

    SciTech Connect

    Brouet, V.; Yang, W.L.; Zhou, X.J.; Choi, H.J.; Louie, S.G.; Cohen, M.L.; Goldoni, A.; Parmigiani, F.; Hussain, Z.; Shen, Z.X.

    2008-01-17

    We observe, with angle-resolved photoemission, a dramaticchange in the electronic structure of two C60 monolayers, deposited,respectively, on Ag (111) and (100) substrates, and similarly doped withpotassium to half filling of the C60 lowest unoccupied molecular orbital.The Fermi surface symmetry, the bandwidth, and the curvature of thedispersion at gamma point are different. Orient ations of the C60molecules on the two substrates are known to be the main structuraldifference between the two monolayers, and we present new band-structurecalculations for some of these orientations. We conclude thatorientations play a key role in the electronic structure offullerides.

  3. Symmetry-selected spin-split hybrid states in C60/ferromagnetic interfaces

    NASA Astrophysics Data System (ADS)

    Li, Dongzhe; Barreteau, Cyrille; Kawahara, Seiji Leo; Lagoute, Jérôme; Chacon, Cyril; Girard, Yann; Rousset, Sylvie; Repain, Vincent; Smogunov, Alexander

    2016-02-01

    The understanding of orbital hybridization and spin polarization at the organic-ferromagnetic interface is essential in the search for efficient hybrid spintronic devices. Here, using first-principles calculations, we report a systematic study of spin-split hybrid states of C60 deposited on various ferromagnetic surfaces: bcc-Cr(001), bcc-Fe(001), bcc-Co(001), fcc-Co(001), and hcp-Co(0001). We show that the adsorption geometry of the molecule with respect to the surface crystallographic orientation of the magnetic substrate as well as the strength of the interaction play a crucial role in the spin polarization of the hybrid orbitals. We find that a large spin polarization in vacuum above the buckyball can only be achieved if the molecule is adsorbed upon a bcc-(001) surface by its pentagonal ring. Therefore, bcc-Cr(001), bcc-Fe(001), and bcc-Co(001) are the optimal candidates. Spin-polarized scanning tunneling spectroscopy measurements on single C60 adsorbed on Cr(001) and Co/Pt(111) also confirm that the symmetry both of the substrate and of the molecular conformation has a strong influence on the induced spin polarization. Our finding may give valuable insights for further engineering of spin filtering devices through single molecular orbitals.

  4. Evidence for endohedral muonium in K(x) C60 and consequences for electronic structure

    NASA Technical Reports Server (NTRS)

    Kiefl, R. F.; Duty, T. L.; Schneider, J. W.; Macfarlane, A.; Chow, K.; Elzey, J. W.; Mendels, P.; Morris, G. D.; Brewer, J. H.; Ansaldo, E. J.

    1992-01-01

    Positive muons injected into solid C60, K4C60, and K6C60 form vacuumlike muonium with a (6-12) percent probability. Observation of coherent spin precession of muonium establishes that all three materials are nonmagnetic and nonconducting at low temperatures. From the temperature dependence of the signals we estimate the electronic band gaps in K4C60 and K6C60 to be considerably smaller than in C60. The similarity of the muonium centers supports a model in which a muonium atom is caged inside the C60 molecule in pure C60 or the C60 exp -x molecular ion in K(x)C60.

  5. Mechanism of charge transfer and its impacts on Fermi-level pinning for gas molecules adsorbed on monolayer WS2.

    PubMed

    Zhou, Changjie; Yang, Weihuang; Zhu, Huili

    2015-06-01

    Density functional theory calculations were performed to assess changes in the geometric and electronic structures of monolayer WS2 upon adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO). The most stable configuration of the adsorbed molecules, the adsorption energy, and the degree of charge transfer between adsorbate and substrate were determined. All evaluated molecules were physisorbed on monolayer WS2 with a low degree of charge transfer and accept charge from the monolayer, except for NH3, which is a charge donor. Band structure calculations showed that the valence and conduction bands of monolayer WS2 are not significantly altered upon adsorption of H2, H2O, NH3, and CO, whereas the lowest unoccupied molecular orbitals of O2, NO, and NO2 are pinned around the Fermi-level when these molecules are adsorbed on monolayer WS2. The phenomenon of Fermi-level pinning was discussed in light of the traditional and orbital mixing charge transfer theories. The impacts of the charge transfer mechanism on Fermi-level pinning were confirmed for the gas molecules adsorbed on monolayer WS2. The proposed mechanism governing Fermi-level pinning is applicable to the systems of adsorbates on recently developed two-dimensional materials, such as graphene and transition metal dichalcogenides. PMID:26049513

  6. Single-Molecule Magnets: Giant Hysteresis of Single-Molecule Magnets Adsorbed on a Nonmagnetic Insulator (Adv. Mater. 26/2016).

    PubMed

    Wäckerlin, Christian; Donati, Fabio; Singha, Aparajita; Baltic, Romana; Rusponi, Stefano; Diller, Katharina; Patthey, François; Pivetta, Marina; Lan, Yanhua; Klyatskaya, Svetlana; Ruben, Mario; Brune, Harald; Dreiser, Jan

    2016-07-01

    In Tb(Pc)2 single-molecule magnets, where Pc is phthalocyanine, adsorbed on magnesium oxide, the fluctuations of the terbium magnetic moment are strongly suppressed in contrast to the adsorption on silver. On page 5195, J. Dreiser and co-workers investigate that the molecules are perfectly organized by self-assembly, as seen in the scanning tunnelling microscopy image (top part of the design). The molecules are probed by circularly polarized X-rays depicted as green spirals. PMID:27383020

  7. Room temperature differential conductance measurements of triethylamine molecules adsorbed on Si(001).

    PubMed

    Naitabdi, Ahmed; Rochet, François; Carniato, Stéphane; Bournel, Fabrice; Gallet, Jean-Jacques

    2016-08-17

    We have measured the differential conductance of the triethylamine molecule (N(CH2CH3)3) adsorbed on Si(001)-2 × 1 at room temperature using scanning tunneling spectroscopy. Triethylamine can be engaged in a dative bonding with a silicon dimer, forming a Si-Si-N(CH2CH3)3 unit. We have examined the datively bonded adduct, either as an isolated molecule, or within an ordered molecular domain (reconstructed 4 × 2). The differential conductance curves, supported by DFT calculations, show that in the explored energy window (±2.5 near the Fermi level) the main features stem from the uncapped dangling bonds of the reacted dimer and of the adjacent unreacted ones that are electronically coupled The formation of a molecular domain, in which one dimer in two is left unreacted, is reflected in a shift of the up dimer atom occupied level away from the Fermi level, likely due to an increased π-bonding strength. In stark contrast with the preceding, pairs of dissociated molecule (a minority species) are electronically decoupled from the dimer dangling bond states. DFT calculation show that the lone-pair of the Si-N(CH2CH3)2 is a shallow level, that is clearly seen in the differential conductance curve. PMID:27499070

  8. Imaging the wave functions of adsorbed molecules using angle-resolved photoemmision data

    NASA Astrophysics Data System (ADS)

    Lüftner, Daniel; Ules, Thomas; Reinisch, Eva Maria; Koller, Georg; Soubatch, Serguei; Tautz, F. Stefan; Ramsey, Michael G.; Puschnig, Peter

    2014-03-01

    The frontier electronic orbitals of molecules are the prime determinants of the respective compounds' chemical, electronic, and optical properties. Although orbitals are very powerful concepts, experimentally only the electron densities and energy levels are directly observable. As has been shown in recent publications, angle-resolved photoemission (ARPES) intensity maps of organic molecular layers are related to the absolute value of the Fourier transform of the initial state molecular orbital. However, the lost phase information impedes the back-transformation of the orbital into real space. Here, we show how molecular orbital images as well as the absent phase information can be retrieved by applying an iterative procedure which takes experimental ARPES maps as input and only assumes spatial confinement of the orbital. The method is demonstrated for several molecular orbitals of two proto-typical pi-conjugated molecules: the LUMO, HOMO, and HOMO-1 of pentacene, and the LUMO and HOMO of PTCDA. The technique is simple and robust and further emphasizes the capabilities of ARPES looking at spatial distributions of wave functions of adsorbed molecules thereby complementing data obtained from scanning probe methods.

  9. Effect of resonance dipole-dipole interaction on spectra of adsorbed SF6 molecules.

    PubMed

    Dobrotvorskaia, Anna N; Kolomiitsova, Tatiana D; Petrov, Sergey N; Shchepkin, Dmitriy N; Smirnov, Konstantin S; Tsyganenko, Alexey A

    2015-09-01

    Adsorption of SF6 on zinc oxide and on silicalite-1 was investigated by a combination of IR spectroscopy with the calculations of spectra by means of a modernized model, developed previously for liquids. Comparison of the experimental spectra and the results of modeling shows that the complex band shapes in spectra of adsorbed molecules with extremely high absorbance are due to the strong resonance dipole-dipole interaction (RDDI) rather that the surface heterogeneity or the presence of specific surface sites. Perfect agreement between calculated and observed spectra was found for ZnO, while some dissimilarity in band intensities for silicalite-1 was attributed to complicated geometry of molecular arrangement in the channels. PMID:25897721

  10. Superconductivity at 52 K in hole-doped C60.

    PubMed

    Schön, J H; Kloc, C; Batlogg, B

    2000-11-30

    Superconductivity in electron-doped C60 was first observed almost ten years ago. The metallic state and superconductivity result from the transfer of electrons from alkaline or alkaline-earth ions to the C60 molecule, which is known to be a strong electron acceptor. For this reason, it is very difficult to remove electrons from C60--yet one might expect to see superconductivity at higher temperatures in hole-doped than in electron-doped C60, because of the higher density of electronic states in the valence band than in the conduction band. We have used the technique of gate-induced doping in a field-effect transistor configuration to introduce significant densities of holes into C60. We observe superconductivity over an extended range of hole density, with a smoothly varying transition temperature Tc that peaks at 52 K. By comparison with the well established dependence of Tc on the lattice parameter in electron-doped C60, we anticipate that Tc values significantly in excess of 100 K should be achievable in a suitably expanded, hole-doped C60 lattice. PMID:11117735

  11. Intermolecular artifacts in probe microscope images of C60 assemblies

    NASA Astrophysics Data System (ADS)

    Jarvis, Samuel Paul; Rashid, Mohammad Abdur; Sweetman, Adam; Leaf, Jeremy; Taylor, Simon; Moriarty, Philip; Dunn, Janette

    2015-12-01

    Claims that dynamic force microscopy has the capability to resolve intermolecular bonds in real space continue to be vigorously debated. To date, studies have been restricted to planar molecular assemblies with small separations between neighboring molecules. Here we report the observation of intermolecular artifacts over much larger distances in 2D assemblies of C60 molecules, with compelling evidence that in our case the tip apex is terminated by a C60 molecule (rather than the CO termination typically exploited in ultrahigh resolution force microscopy). The complete absence of directional interactions such as hydrogen or halogen bonding, the nonplanar structure of C60, and the fullerene termination of the tip apex in our case highlight that intermolecular artifacts are ubiquitous in dynamic force microscopy.

  12. New Phases of C60 Synthesized at High Pressure

    NASA Astrophysics Data System (ADS)

    Iwasa, Y.; Arima, T.; Fleming, R. M.; Siegrist, T.; Zhou, O.; Haddon, R. C.; Rothberg, L. J.; Lyons, K. B.; Carter, H. L., Jr.; Hebard, A. F.; Tycko, R.; Dabbagh, G.; Krajewski, J. J.; Thomas, G. A.; Yagi, T.

    1994-06-01

    The fullerene C60 can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C60 on reheating to 300^circC at ambient pressure. For synthesis temperatures between 300^circ and 400^circC and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a_o = 13.6 angstroms. When treated at 500^circ to 800^circC at the same pressure, C60 transforms into a rhombohedral structure with hexagonal lattice parameters of a_o = 9.22 angstroms and c_o = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C60 molecules are linked.

  13. Does Moisture Influence the Chemical Detection of Gas Molecules Adsorbed on Single-Wall Carbon Nanotubes?

    NASA Astrophysics Data System (ADS)

    Yu, Ming; Tian, W. Q.; Jayanthi, C. S.; Wu, S. Y.

    2009-03-01

    In this work, the role of water in the detection of hydrazine (N2H4) by a single-wall carbon nanotube (SWCNT) is investigated using first principles electronic structure calculations (DFT/GGA--USPP)[1]. This calculation is undertaken to interpret the experimental resistivity measurements for N2H4 adsorbed on SWCNT that reveal an n-type behavior [2]. Our preliminary theoretical studies of the adsorption of N2H4 on SWCNT revealed physisorption for N2H4 and an unaltered band structure for the SWCNT [3]. This prompted us to look into the role of water on the bonding of N2H4 to the SWCNT. We found that, by introducing a monolayer of water film on the (8,0) SWCNT, the adsorption of N2H4 can introduce occupied states near the Fermi level, exhibiting an n-type behavior. However, the introduction of just few water molecules was not sufficient to influence the electronic structure of N2H4/SWCNT. Presently, we are studying the influence of water films on the chemical detection of a variety of other gas molecules (N2, NH3, etc.) by SWCNTs, and the results from such studies will also be reported. [1]. G. Kresse et al. Phys. Rev. B 54, 11169 (1996). [2]. S. Desai, et al. (APS, March 2008). [3]. M. Yu, et al. (APS, March 2008).

  14. C60 as a Probe for Astrophysical Environments

    NASA Astrophysics Data System (ADS)

    Brieva, A. C.; Gredel, R.; Jäger, C.; Huisken, F.; Henning, T.

    2016-08-01

    The C60 molecule has been recently detected in a wide range of astrophysical environments through its four active intramolecular vibrational modes (T 1u) near 18.9, 17.4, 8.5, and 7.0 μm. The strengths of the mid-infrared emission bands have been used to infer astrophysical conditions in the fullerene-rich regions. Widely varying values of the relative intrinsic strengths (RIS) of these four bands are reported in laboratory and theoretical papers, which impedes the derivation of the excitation mechanism of C60 in the astrophysical sources. The spectroscopic analysis of the C60 samples produced with our method delivers highly reproducible RIS values of 100, 25 ± 1, 26 ± 1 and 40 ± 4. A comparison of the inferred C60 emission band strengths with the astrophysical data shows that the observed strengths cannot be explained in terms of fluorescent or thermal emission alone. The large range in the observed 17.4 μm/18.9 μm emission ratios indicates that either the emission bands contain significant contributions from emitters other than C60, or that the population distribution among the C60 vibrational modes is affected by physical processes other than thermal or UV excitation, such as chemo-luminescence from nascent C60 or possibly Poincaré fluorescence resulting from an inverse internal energy conversion. We have carefully analyzed the effect of the weakly active fundamental modes and second order modes in the mid-infrared spectrum of C60, and propose that neutral C60 is the carrier of the unidentified emission band at 6.49 μm which has been observed in fullerene-rich environments.

  15. Assessment Of C60 As A Propellant Material For Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Rapp, Don; Leifer, Stephanie D.

    1995-01-01

    Report presents analyses and data to support proposed use of C60 (buckminsterfullerene) as alternative to Xe, current propellent material of choice for use in ion thrusters. Concept of using C60 for this purpose described in "Electrostatic Propulsion Using C60 Molecules" (NPO-18526).

  16. Electronic structure and binding geometry of tetraphenylporphyrin-derived molecules adsorbed on metal and metal oxide surfaces

    NASA Astrophysics Data System (ADS)

    Coh, Senia

    Tetraphenylporphyrin (TPP)-derived molecules have been studied extensively as efficient photosensitizers when chemisorbed on the metal oxide substrates in dye-sensitized solar cells. Still, many fundamental electronic properties of the dye/oxide interface are not understood and need careful consideration. In this thesis we present a comprehensive study of the electronic structure, energy level alignment and the adsorption geometry of the TPP-derived dye molecules adsorbed on TiO2(110), ZnO(1120) and Ag(100) single crystal surfaces using ultra-high vacuum (UHV) based surface sensitive techniques. The alignment of the molecular energy levels with respect to the TiO 2 and ZnO band edges for all TPP-derived molecules we studied was found to be insensitive to either the nature of the functional groups located on the phenyl rings, presence of zinc as a central metal ion and different binding geometry of the molecules. Binding geometry, molecule-molecule interaction and the aggregation effects in the adsorbed layer, that were observed in the UV-visible spectra of the molecules adsorbed on ZnO substrate were not observed in the ultraviolet photoemission (UPS) and inverse photoemission (IPS) spectra of the occupied and unoccupied molecular states. Using near edge X-ray absorption fine structure (NEXAFS) and scanning tunneling microscopy (STM), binding geometry of the two representative TPP-derivatives was directly determined to be upright, with the porphyrin ring under large angle with respect to the surface for the p-ZnTCPP molecules and with the porphyrin ring parallel to the surface for the m-ZnTCPP molecules. We observe that the energies and the energy level alignment of the ZnTPP molecular levels measured in UPS and IPS depend on the substrate on which the molecules are adsorbed (Ag(100) or TiO2(110) single crystal surfaces). The differences are attributed to different charge screening properties of these two materials. Image charges created in the substrates during

  17. Biological applications of hydrophilic C60 derivatives (hC60s)- a structural perspective.

    PubMed

    Zhu, Xiaolei; Sollogoub, Matthieu; Zhang, Yongmin

    2016-06-10

    Reactive oxygen species (ROS) generation and radical scavenging are dual properties of hydrophilic C60 derivatives (hC60s). hC60s eliminate radicals in dark, while they produce reactive oxygen species (ROS) in the presence of irradiation and oxygen. Compared to the pristine C60 suspension, the aqueous solution of hC60s is easier to handle in vivo. hC60s are diverse and could be placed into two general categories: covalently modified C60 derivatives and pristine C60 solubilized non-covalently by macromolecules. In order to present in detail, the above categories are broken down into 8 parts: C60(OH)n, C60 with carboxylic acid, C60 with quaternary ammonium salts, C60 with peptide, C60 containing sugar, C60 modified covalently or non-covalently solubilized by cyclodextrins (CDs), pristine C60 delivered by liposomes, functionalized C60-polymer and pristine C60 solubilized by polymer. Each hC60 shows the propensity to be ROS producer or radical scavenger. This preference is dependent on hC60s structures. For example, major application of C60(OH)n is radical scavenger, while pristine C60/γ-CD complex usually serves as ROS producer. In addition, the electron acceptability and innate hydrophobic surface confer hC60s with O2 uptake inhibition, HIV inhibition and membrane permeability. In this review, we summarize the preparation methods and biological applications of hC60s according to the structures. PMID:27049677

  18. The analysis of surface-adsorbed organic molecules by alkali-assisted MIES combined with UPS(He I)

    NASA Astrophysics Data System (ADS)

    Günster, J.; Ochs, D.; Dieckhoff, S.; Kempter, V.

    1996-12-01

    Metastable impact electron spectroscopy (MIES) in combination with UPS(He I) is applied to the study of s-triazine and triethoxytriazine molecules adsorbed on Si(100) either alone or in combination with cesium atoms. It is demonstrated that the presence of the Cs atoms facilitates the identification of the adsorbed species considerably. It is concluded that (i) non-dissociative adsorption of the studied organic molecules occurs whereby the basal rings of the molecules lie flat on the silicon surface, in accordance with previous studies by Bu and Lin, (ii) the binding of the molecules to the surface is mainly via the lone pair orbitals of the nitrogen in the ring, and (iii) s-triazine reacts strongly with oxygen which bonds to the carbon atoms of the triazine ring.

  19. Photocorrosion inhibition and enhancement of photocatalytic activity for ZnO via hybridization with C60.

    PubMed

    Fu, Hongbo; Xu, Tongguang; Zhu, Shengbao; Zhu, Yongfa

    2008-11-01

    C60 molecules with monomolecular layer state dispersed on the surface of ZnO and formed the hybridized interaction between ZnO and C60. C60-hybridized ZnO photocatalyst showed enhanced photocatalytic activity for the degradation of the organic dye and the photocorrosion of ZnO was successfully inhibited bythe hybridization of C60 molecules. The photocorrosion inhibition of ZnO by C60 molecule could be attributed to the reduced activation of surface oxygen atom. The enhanced photocatalytic activity for C60-hybridized ZnO was originated from the high migration efficiency of photoinduced electrons on the interface of C60 and ZnO, which was produced by the interaction of C60 and ZnO with a conjugative pi-system. The enhancement degree of photocatalytic activity was strongly depended on the coverage of C60 molecules on the surface of ZnO nanoparticles, and the optimum hybridization effect was found at a weight ratio of 1.5% (C60/ZnO). The hybridization of C60 with semiconductors could be used to improve the photocatalytic activity as well as the photostability. PMID:19031903

  20. Nanosegregation in Na2C60

    SciTech Connect

    Klupp, G.; Kamaras, K.; Matus, P.; Kiss, L.F.; Kovats, E.; Pekker, S.; Nemes, N.M.; Quintavalle, D.; Janossy, A.

    2005-09-27

    There is continuous interest in the nature of alkali metal fullerides containing C{sub 60}{sup 4-} and C{sub 60}{sup 2-}, because these compounds are believed to be nonmagnetic Mott-Jahn-Teller insulators. This idea could be verified in the case of A4C60, but Na2C60 is more controversial. By comparing the results of infrared spectroscopy and X-ray diffraction, we found that Na2C60 is segregated into 3-10 nm large regions. The two main phases of the material are insulating C60 and metallic Na3C60. We found by neutron scattering that the diffusion of sodium ions becomes faster on heating. Above 470 K Na2C60 is homogeneous and we show IR spectroscopic evidence of a Jahn-Teller distorted C{sub 60}{sup 2-} anion.

  1. Barriers to intramolecular rotation determined from the temperature dependence of the Henry constant in the region of adsorbed molecule rigidity failure

    NASA Astrophysics Data System (ADS)

    Dolgonosov, A. M.; Prudkovskii, A. G.

    2008-05-01

    A distribution for the rigid and nonrigid adsorbed molecule forms was found. Adsorbed molecule rigidity failure was shown to be accompanied by a weak nonlinear effect, which manifested itself as a temperature dependence of the Henry constant. A method for the determination of the barrier to intramolecular rotation from the temperature dependence of the molecule adsorption constant was suggested. Barriers to rotation about the C-C and C-O bonds were determined for several molecules.

  2. Superconductivity in alkali-doped C60

    NASA Astrophysics Data System (ADS)

    Ramirez, Arthur P.

    2015-07-01

    Superconductivity in alkali-doped C60 (A3C60, A = an alkali atom) is well described by an s-wave state produced by phonon mediated pairing. Moderate coupling of electrons to high-frequency shape-changing intra-molecular vibrational modes produces transition temperatures (Tc) up to 33 K in single-phase material. The good understanding of pairing in A3C60 offers a paradigm for the development of new superconducting materials.

  3. Structural and Electrical Investigation of C60-Graphene Vertical Heterostructures.

    PubMed

    Kim, Kwanpyo; Lee, Tae Hoon; Santos, Elton J G; Jo, Pil Sung; Salleo, Alberto; Nishi, Yoshio; Bao, Zhenan

    2015-06-23

    Graphene, with its unique electronic and structural qualities, has become an important playground for studying adsorption and assembly of various materials including organic molecules. Moreover, organic/graphene vertical structures assembled by van der Waals interaction have potential for multifunctional device applications. Here, we investigate structural and electrical properties of vertical heterostructures composed of C60 thin film on graphene. The assembled film structure of C60 on graphene is investigated using transmission electron microscopy, which reveals a uniform morphology of C60 film on graphene with a grain size as large as 500 nm. The strong epitaxial relations between C60 crystal and graphene lattice directions are found, and van der Waals ab initio calculations support the observed phenomena. Moreover, using C60-graphene heterostructures, we fabricate vertical graphene transistors incorporating n-type organic semiconducting materials with an on/off ratio above 3 × 10(3). Our work demonstrates that graphene can serve as an excellent substrate for assembly of molecules, and attained organic/graphene heterostructures have great potential for electronics applications. PMID:26027690

  4. Photoemission study of Li@C60

    NASA Astrophysics Data System (ADS)

    Yagi, Hajime; Ogasawara, Naoko; Zenki, Masashi; Miyazaki, Takafumi; Hino, Shojun

    2016-05-01

    Ultraviolet and X-ray photoelectron spectra (UPS and XPS) of thin films prepared by either depositing or applying [Li@C60]+(PF6)- on the substrates are presented. The UPS and XPS of [Li@C60]+(PF6)- applied films suggest that PF6- anions come out from the surface by annealing at 250 °C. The UPS and XPS of the deposited thin films indicate that the film does not contain PF6- anion but is composed of only Li@C60. Changing the sublimation temperature reveals that encapsulated Li cations begin to escape from the C60 cage when heated above 550 °C.

  5. Direct comparison of the electronic coupling efficiency of sulfur and selenium alligator clips for molecules adsorbed onto gold electrodes

    NASA Astrophysics Data System (ADS)

    Patrone, L.; Palacin, S.; Bourgoin, J. P.

    2003-05-01

    Scanning tunneling microscopy experiments have been performed to compare the electronic coupling provided by S and by Se used as alligator clips for bisthiol- and biselenol-terthiophene molecules adsorbed onto gold. The molecules were inserted in a dodecanethiol (DT) self-assembled monolayer. Their apparent height above the dodecanethiol matrix was used as a measure of the electronic coupling strength corresponding to S and Se, respectively. We show that the insertion behaviors of the two molecules are qualitatively the same, and that Se provides systematically a better coupling link than S, whatever the tunneling conditions.

  6. Direct comparison of the electronic coupling efficiency of sulfur and selenium anchoring groups for molecules adsorbed onto gold electrodes

    NASA Astrophysics Data System (ADS)

    Patrone, L.; Palacin, S.; Bourgoin, J. P.; Lagoute, J.; Zambelli, T.; Gauthier, S.

    2002-08-01

    We performed air and ultra-high vacuum scanning tunneling microscopy experiments in order to compare the electronic coupling provided by S and by Se used as alligator clips for bisthiol- and biselenol-terthiophene molecules adsorbed onto gold. The molecules were inserted in a dodecanethiol self-assembled monolayer. Their apparent height above the dodecanethiol matrix was used as a measure of the electronic coupling strength corresponding to S and Se, respectively. We show that the insertion behaviors of the two molecules are qualitatively the same, and that Se provides systematically a better coupling link than S whatever the tunneling conditions.

  7. Theoretical study of the structures and first hyperpolarizabilities of C60Cl n and Li@C60Cl n (n = 4, 6, 8, 10).

    PubMed

    Song, Yao-Dong; Wang, Liang; Wu, Li-Ming

    2016-06-01

    We recently reported (Song Y-D et al., 2016, J Mol Model 22:50) that doping with Li greatly affects the static first hyperpolarizability of C60Cl2. In this work, with a view to creating nonlinear optical materials with high thermodynamic stability and wide transparent regions, a series of Li@C60Cl n (n = 4, 6, 8, 10) were designed. The structures, electrostatic potentials, electronic structures, absorption spectra, and linear and nonlinear optical properties of C60Cl n and Li@C60Cl n were systematically investigated using density functional theory (DFT) methods. The results of our calculations indicated that the stability of these molecules decreases in the order Li@C60Cl10 > Li@C60Cl8 > Li@C60Cl6 > Li@C60Cl4. It is clear that the number of Cl atoms greatly influences the stability of Li@C60Cl n . Li@C60Cl n showed greater thermodynamic stability than Li@C60Cl2. We also investigated the first hyperpolarizabilities of Li@C60Cl n and found them to be 2973, 3640, 4307, and 2627 au for n = 4, 6, 8, and 10, respectively-higher than that of Li@C60Cl2. Finally, we noted that the transparent region could be modulated by increasing the number of Cl atoms: Li@C60Cl n possess wider transparent regions than that of Li@C60Cl2. We therefore believe that this study has highlighted an effective method for designing nonlinear optical materials with high thermodynamic stability and wide transparent regions. PMID:27188724

  8. Tunneling Spectroscopy Studies of Urea, Thiourea, and Selected Phosphonate Molecules Adsorbed on Aluminum Oxide

    NASA Astrophysics Data System (ADS)

    Crowder, Charles D.

    Experimental and calculated inelastic electron tunneling intensities were compared for several of the vibrational modes of thiourea adsorbed on aluminum oxide. The partial charge model of Kirtley, Scalapino, and Hansma was used to compute the theoretical intensities of each mode. The required partial charges were determined using a method developed by Momany. Essentially, the Coulomb potential resulting from point charges located at atom sites was fitted to the quantum mechanical electrostatic potential of a molecule calculated from Hartree-Fock theory. The effect of a vibrational mode pattern on the electrostatic potential of a molecule was investigated. This effect could not be acceptably modeled with a single point charge located on each atom, so one charge was used to represent the positive nucleus of each atom and a second charge was used to represent the valence cloud. The valence charge was allowed to move independently of the nuclear charge during a molecular vibration, and the motions of the two charges were found to be very different for hydrogen atoms. This model gave very reasonable agreement between the theoretical and observed relative intensities for the in plane vibrational modes of thiourea. An acceptable set of out of plane force constants could not be found. This caused problems in the interpretation of the out of plane relative intensities. Based on the in plane modes, it was concluded that thiourea bonded to aluminum oxide with the sulfur atom near the oxide and the sulfur-carbon bond perpendicular to the aluminum oxide surface. Quantum mechanical electrostatic potentials were also calculated for urea, phosphoric acid (PA), methylphosphonic acid (MPA), hydroxymethylphosphonic acid (HMP), and nitrotrismethylphosphonic acid (NTMP). Electron tunneling spectra were taken for PA, HMP and NTMP, and the observed frequencies were compared to values obtained from Fourier transform infrared, infrared and Raman spectroscopy. Upward shifts in the P=O and P

  9. Protective Fullerene (C60) Packaging System for Microelectromechanical Systems Applications

    NASA Technical Reports Server (NTRS)

    Olivas, John D. (Inventor)

    2001-01-01

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

  10. Quenching of fluorescence in C60 fulleropyrrolidines by chloroform

    NASA Astrophysics Data System (ADS)

    Parveen, Abdulrazack; Sughanya, Venkatesan; Nagarajan, Samuthira

    2016-01-01

    Functionalized [C60] fullerene, fulleropyrrolidines were synthesized and their photophysical properties are studied. The absorption and emission patterns are altered in fulleropyrrolidines, when compared with C60. Fluorescence of the molecules is quenched by CHCl3 in toluene solution at room temperature. Effect of nature and length of side chains in fulleropyrrolidine on quenching is investigated. Results suggested that the fluorescence intensity increased with increase in carbon chain length and the Stern-Volmer plot intercept values are indirectly proportional to the number of the carbons.

  11. Interaction of C(60) fullerene with lipids.

    PubMed

    Cataldo, Franco

    2010-06-01

    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

  12. Nonlinear spectroscopy of C60 single crystal

    NASA Astrophysics Data System (ADS)

    Zamboni, Roberto; Muccini, Michele; Danieli, R.; Taliani, Carlo; Mohn, H.; Muller, W.; ter Meer, Hans-Ulrich

    1994-11-01

    Two-photon excitation measurements of C60 single crystal at 4 K have been performed. The TPE spectrum shows a sharp band at 1.846 eV which is assigned to the C60 lowest forbidden Frenkel singlet exciton of T1g symmetry. This assignment is supported by the analysis of Herzberg-Teller induced photoluminescence.

  13. 15 CFR 8c.60 - Communications.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Communications. 8c.60 Section 8c.60 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE... Communications. (a) The agency shall take appropriate steps to ensure effective communication with...

  14. 15 CFR 8c.60 - Communications.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false Communications. 8c.60 Section 8c.60 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE... Communications. (a) The agency shall take appropriate steps to ensure effective communication with...

  15. 15 CFR 8c.60 - Communications.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 15 Commerce and Foreign Trade 1 2013-01-01 2013-01-01 false Communications. 8c.60 Section 8c.60 Commerce and Foreign Trade Office of the Secretary of Commerce ENFORCEMENT OF NONDISCRIMINATION ON THE... Communications. (a) The agency shall take appropriate steps to ensure effective communication with...

  16. Solubility of C60 in solvent mixtures.

    PubMed

    Kulkarni, Pradnya P; Jafvert, Chad T

    2008-02-01

    The potential large-scale production of fullerene C60 and its widespread use in consumer products may translate into occupational and public exposure and in long-term environmental exposure. To assess the risk and fate of C60 in the environment, it is important to understand its solvate formation in common industrial solvents as the solvates may affect various properties of C60 including reactivity and toxicity, particularly when solvates occur in C60 clusters. In this study, the solubility measurements in mixed solvent system can provide useful information about solvate formation. The solubility of C60 was measured in pure toluene, tetrahydrofuran, ethanol, and acetonitrile to be 3000, 11, 1.4, and 0.04 mg/L, respectively. Additionally, the solubility of C60 was measured in mixtures of toluene-acetonitrile, toluene-ethanol, toluene-tetrahydrofuran, and acetonitrile-tetrahydrofuran. The solubility data were modeled with some accuracy using Wohl's equation. The estimated crystal energy term for C60 in tetrahydrofuran was different than that in the other solvents, indicating that the C60 solid phase in equilibrium with tetrahydrofuran solution may be a solvated crystal. PMID:18323111

  17. Transport properties of the H2O@C60-dimer-based junction.

    PubMed

    Zhu, Chengbo; Wang, Xiaolin

    2015-09-23

    Theoretical predictions play an important role in finding potential applications in molecular electronics. Fullerenes have a number of potential applications, and the charge flow from a single C60 molecule to another becomes more versatile and more interesting after doping. Here, we report the conductance of two H2O@C60 molecules in series order and how the number of encapsulated water molecules influences the transport properties of the junction. Encapsulating an H2O molecule into one of the C60 cages increases the conductance of the dimer. Negative differential resistance is found in the dimer systems, and its peak-to-valley current ratio depends on the number of encapsulated H2O molecules. The conductance of the C60 dimer and the H2O@C60 dimer is two orders of magnitude smaller than that of the C60 monomer. Furthermore, we demonstrate that the conductance of the molecular junctions based on the H2O@C60 dimer can be tuned by moving the encapsulated H2O molecules. The conductance is H2O-position dependent. Our findings indicate that H2O@C60 can be used as a building block in C60-based molecular electronic devices and sensors. PMID:26325223

  18. Transport properties of the H2O@C60-dimer-based junction

    NASA Astrophysics Data System (ADS)

    Zhu, Chengbo; Wang, Xiaolin

    2015-09-01

    Theoretical predictions play an important role in finding potential applications in molecular electronics. Fullerenes have a number of potential applications, and the charge flow from a single C60 molecule to another becomes more versatile and more interesting after doping. Here, we report the conductance of two H2O@C60 molecules in series order and how the number of encapsulated water molecules influences the transport properties of the junction. Encapsulating an H2O molecule into one of the C60 cages increases the conductance of the dimer. Negative differential resistance is found in the dimer systems, and its peak-to-valley current ratio depends on the number of encapsulated H2O molecules. The conductance of the C60 dimer and the H2O@C60 dimer is two orders of magnitude smaller than that of the C60 monomer. Furthermore, we demonstrate that the conductance of the molecular junctions based on the H2O@C60 dimer can be tuned by moving the encapsulated H2O molecules. The conductance is H2O-position dependent. Our findings indicate that H2O@C60 can be used as a building block in C60-based molecular electronic devices and sensors.

  19. Mapping intermolecular bonding in C60

    PubMed Central

    Sundqvist, Bertil

    2014-01-01

    The formation of intermolecular bonds in C60 has been investigated in detail at pressures below 2.2 GPa and up to 750 K. Fullerene samples were heated in a temperature gradient to obtain data on the formation of dimers and low-dimensional polymers along isobars. Intermolecular bonding was analyzed ex situ by Raman scattering, using both intramolecular modes and intermolecular stretching modes. Semi-quantitative reaction maps are given for the formation of dimers and chains. The activation energy for dimer formation decreases by 0.2 meV pm−1 when intermolecular distances decrease and dimer formation is noticeably affected by the rotational state of molecules. Above 400–450 K larger oligomers are formed; below 1.4 GPa most of these are disordered, with small domains of linear chains, but above this the appearance of stretching modes indicates the existence of ordered one-dimensional polymers. At the highest pressures and temperatures two-dimensional polymers are also observed. PMID:25145952

  20. Effects of molecule-insulator interaction on geometric property of a single phthalocyanine molecule adsorbed on an ultrathin NaCl film

    NASA Astrophysics Data System (ADS)

    Miwa, Kuniyuki; Imada, Hiroshi; Kawahara, Shota; Kim, Yousoo

    2016-04-01

    The adsorption structure and orientation of a metal-free phthalocyanine (H2Pc ) and a magnesium phthalocyanine (MgPc) on a bilayer of NaCl films were investigated both theoretically and experimentally by means of first-principles calculations based on density functional theory and by scanning tunneling microscopy. H2Pc is adsorbed with its center over the sodium cation, and H-N bonds in the molecule are aligned with the [100] or [010] surface direction of a bilayer (001)-terminated NaCl film. The most stable structures of MgPc on the NaCl film show two kinds of orientations corresponding to the molecule rotated by ±7∘ relative to the [110] surface direction, with the Mg cation positioned over the chlorine anion in both cases. The energetic barrier for switching between these orientations is as low as 9.0 meV, and during an STM measurement, an orientational change of MgPc can be observed. The interaction between the adsorbed molecule and the NaCl film were analyzed in terms of dispersion interaction, Mg-Cl chemical bonding, and electrostatic interaction. It is found that the small electrostatic interaction between the molecule and the film gives a dominant contribution to determining the molecular orientation. Our detailed and comprehensive studies of the molecule-insulator interaction will provide knowledge to understand and control the properties of molecules on an insulating material.

  1. A study of thermally activated delayed fluorescence in C 60

    NASA Astrophysics Data System (ADS)

    Salazar, Filipa A.; Fedorov, Aleksandre; Berberan-Santos, Mário N.

    1997-06-01

    The existence of thermally activated delayed fluorescence in C 60 is demonstrated by the study of the temperature dependence (291-353 K) of the fluorescence intensity of C 60 degassed solutions. The determined singlet-triplet energy gap, 35 ± 2 kJ/mol, agrees with the value calculated from previously reported fluorescence and low temperature phosphorescence spectra for this molecule (35 kJ/mol). The estimated quantum yield of triplet formation, 0.8 ± 0.1, agrees with previous determinations. The fluorescence lifetime of C 60, also measured, τ = 1.1 ns, does not change appreciably with excitation wavelength, degassing nor with temperature, in the range 243-343 K.

  2. Electron transport properties and spin modulation effect analysis for C60, Au@C60 and Ag@C60

    NASA Astrophysics Data System (ADS)

    Wang, Fangyuan; Li, Guiqin

    2016-04-01

    The electron transport properties of C60, Au@C60 and Ag@C60 junctions between Au electrodes are investigated with density functional theory and the first-principle nonequilibrium Greens function. Density of states and transmission possibility as functions of energy are examined, and current-voltage characteristics of all these models are calculated with and without spin correction. With spin correction, we find a spin-current difference in Au@C60 as large as an order of magnitude. It may be used to obtain high-purity arbitrary spin current. By comparing the calculation results with and without spin correction, we attribute this spin difference to the spin resonance between transmission electrons and the valence electron of endohedral Au atom.

  3. Electronically Excited C2 from Laser Photodissociated C60

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Scott, Carl D.; Nikolaev, Pavel; Smalley, Richard E.

    1999-01-01

    Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C2 and, at early times, also from a black body continuum. The C2 radiation is observed only when C60 is excited by green (532 nm) and not with IR (1064 nm) laser radiation at energy densities of about 1.5 J/square cm. Transient measurements indicate that there are two characteristic periods of decay of radiation. The first period, lasting about 2 micro seconds, has a characteristic decay time of about 0.3 micro seconds. The second period, lasting at least 50 micro seconds, has a characteristic decay time of about 5 micro seconds. These characteristic times are thought to be associated with cooling of C60 molecules or nanosized carbon particles during the early period; and with electronically excited C2 that is a decomposition product of laser excited C60, C58, ... molecules during the later period.

  4. First-principles investigation of organic photovoltaic materials C60, C70, [C60]PCBM , and bis-[C60]PCBM using a many-body G0W0 -Lanczos approach

    NASA Astrophysics Data System (ADS)

    Qian, Xiaofeng; Umari, Paolo; Marzari, Nicola

    2015-06-01

    We present a first-principles investigation of the excited-state properties of electron acceptors in organic photovoltaics including C60, C70, [6,6]-phenyl-C61-butyric-acid-methyl-ester ([C60]PCBM ), and bis-[C60]PCBM using many-body perturbation theory within the Hedin's G0W0 approximation and an efficient Lanczos approach. Calculated vertical ionization potentials (VIP) and vertical electron affinities (VEA) of C60 and C70 agree very well with experimental values measured in the gas phase. The density of states of all three molecules is also compared to photoemission and inverse photoemission spectra measured on thin films, and they exhibit a close agreement—a rigid energy-gap renormalization owing to intermolecular interactions in the thin films. In addition, it is shown that the low-lying unoccupied states of [C60]PCBM are all derived from the highest-occupied molecular orbitals and the lowest-unoccupied molecular orbitals of fullerene C60. The functional side group in [C60]PCBM introduces a slight electron transfer to the fullerene cage, resulting in small decreases of both VIP and VEA. This small change of VEA provides a solid justification for the increase of open-circuit voltage when replacing fullerene C60 with [C60]PCBM as the electron acceptor in bulk heterojunction polymer solar cells.

  5. Preparation of C60 by Detonation Technique

    NASA Astrophysics Data System (ADS)

    Wei, Xianfeng; Han, Yong; Long, Xinping

    2012-11-01

    A mixture of TNT (Trinitrotoluene) and natural graphite was detonated in a vacuum container which was immersed into cooling water; detonation products were collected for detecting. The results of mass spectroscopy, high performance liquid chromatography showed significant signals of C60, which proved that C60 could be synthesized by detonating the mixture of TNT/graphite and the detonation pressure was around 12.3 GPa and the detonation temperature was around 1985 K.

  6. Charge transfer interactions of a Ru(II) dye complex and related ligand molecules adsorbed on Au(111)

    SciTech Connect

    Britton, Andrew J.; Weston, Matthew; O'Shea, James N.; Taylor, J. Ben; Rienzo, Anna; Mayor, Louise C.

    2011-10-28

    The interaction of the dye molecule, N3 (cis-bis(isothiocyanato)bis(2,2{sup '}-bipyridyl-4,4{sup '}-dicarboxylato) -ruthenium(II)), and related ligand molecules with a Au(111) surface has been studied using synchrotron radiation-based electron spectroscopy. Resonant photoemission spectroscopy (RPES) and autoionization of the adsorbed molecules have been used to probe the coupling between the molecules and the substrate. Evidence of charge transfer from the states near the Fermi level of the gold substrate into the lowest unoccupied molecular orbital (LUMO) of the molecules is found in the monolayer RPES spectra of both isonicotinic acid and bi-isonicotinic acid (a ligand of N3), but not for the N3 molecule itself. Calibrated x-ray absorption spectroscopy and valence band spectra of the monolayers reveals that the LUMO crosses the Fermi level of the surface in all cases, showing that charge transfer is energetically possible both from and to the molecule. A core-hole clock analysis of the resonant photoemission reveals a charge transfer time of around 4 fs from the LUMO of the N3 dye molecule to the surface. The lack of charge transfer in the opposite direction is understood in terms of the lack of spatial overlap between the {pi}*-orbitals in the aromatic rings of the bi-isonicotinic acid ligands of N3 and the gold surface.

  7. Hugoniot of C60 fullerite: new results

    NASA Astrophysics Data System (ADS)

    Milyavskiy, Vladimir; Utkin, Alexander; Zhuk, Andrey; Yakushev, Vladislav; Fortov, Vladimir

    2005-07-01

    Recently, we have experimentally studied shock compressibility of C60 fullerite and sound velocity in shock-compressed fullerite at the pressure range up to ˜50 GPa [1]. In this work we present the results of new shock experiments executed with C60 fullerite in the same pressure range. On the base of new experimental results, we have made some correction of our concept [1] of the processes occurring in C60 fullerite at shock compression. In particular, the anomalous behavior of the rear surface velocity profiles was detected at pressure ˜9 GPa [1]. Additional experiments have shown that this anomalous behavior was caused by jump of the sound velocity in C60 because of formation of more hard carbon phase. We assume that it is a polymerized C60 phase. In the pressure region 9-25 GPa, destruction of this phase and formation of a graphite-like carbon occurs. With further growth of shock pressure, phase transition of the graphite-like carbon to a diamond-like phase is observed with a transition onset pressure ˜25 GPa. If shock pressures higher than ˜33 GPa, Hugoniot of C60 is determined by the thermodynamic properties of the diamond-like phase. [1] V.V. Milyavskiy, A.V. Utkin, E.B. Zaretsky, A.Z. Zhuk, V.V. Yakushev, V.E. Fortov. AIP CP 706 (2004) 667.

  8. IR absorptions of C60(+) and C60(-) in neon matrixes.

    PubMed

    Kern, Bastian; Strelnikov, Dmitry; Weis, Patrick; Böttcher, Artur; Kappes, Manfred M

    2013-08-29

    C60(+) ions were produced by electron-impact ionization of sublimed C60, collimated into an ion beam, turned 90° by an electrostatic deflector to separate them from neutrals, mass filtered by a radio frequency quadrupole, and co-deposited with Ne on a cold 5 K gold-coated sapphire substrate. Infrared absorption spectroscopy revealed the additional presence of C60 and C60(-) in the as-prepared cryogenic matrixes. To change the C60(+)/C60(-) ratio, CCl4 or CO2 electron scavengers were added to the matrix gas. Also taking into account DFT calculations, we have identified nine new previously unpublished IR absorptions of C60(+) and seven of C60(-) in Ne matrixes. Our measurements are in very good agreement with DFT calculations, predicting D5d C60(+) and D3d C60(-) ground states. The new results may be of interest regarding the presence of C60 and C70 (as well as ions thereof) in Space. PMID:23902528

  9. James C. McGroddy Prize Talk: What Was New About C60

    NASA Astrophysics Data System (ADS)

    Haddon, Robert

    2008-03-01

    C60 was named molecule of the year by Science in 1991, and in this talk I will discuss what I consider to be the most novel features of the molecule. In some ways C60 is truly unique and the discovery of the molecule in 1985 and its subsequent synthesis in 1990 blazed a trail of new chemical and physical properties that is unlikely to be surpassed by any other molecule. I will discuss the electronic structure of C60, its magnetism, and the conductivity and superconductivity shown by the alkali metal-doped phases.

  10. Nitrogen-embedded buckybowl and its assembly with C60

    PubMed Central

    Yokoi, Hiroki; Hiraoka, Yuya; Hiroto, Satoru; Sakamaki, Daisuke; Seki, Shu; Shinokubo, Hiroshi

    2015-01-01

    Curved π-conjugated molecules have attracted considerable interest because of the unique properties originating from their curved π surface. However, the synthesis of such distorted molecules requires harsh conditions, which hamper easy access to heteroatom-containing curved π systems. Here we report the synthesis of a π-extended azacorannulene with nitrogen in its centre. The oxidation of 9-aminophenanthrene provides tetrabenzocarbazole, which is converted to the azabuckybowl through palladium-catalysed intramolecular coupling. The electron-donating nature and curved π surface of the azabuckybowl enable its tight association with C60 in solution and solid states. High charge mobility is observed for the azabuckybowl/C60 assembly. This compound may be of interest in the fields of curved π systems as fullerene hosts, anisotropic π donors and precursors to nitrogen-containing nanocarbon materials. PMID:26337912

  11. C60 oxide as a key component of aqueous C60 colloidal suspensions.

    PubMed

    Murdianti, Befrika S; Damron, Joshua T; Hilburn, Martha E; Maples, Randall D; Hikkaduwa Koralege, Rangika S; Kuriyavar, Satish I; Ausman, Kevin D

    2012-07-17

    Stable aqueous fullerene colloidal suspensions (nC(60)) are demonstrated to rely on the [6,6]-closed epoxide derivative of the fullerene (C(60)O) for stability. This derivative is present, though often unrecognized, in small quantities in nearly all C(60) starting materials due to a reaction with air. The low-yield formation of nC(60) from organic solvent solutions results from a preferential partitioning and thus enrichment of C(60)O in the colloidal particles. This partitioning is significantly retarded in the nC(60) synthesis method that does not involve organic solvent solutions: long-term stirring in water. Instead, this method relies on trace levels of ozone in the ambient atmosphere to produce sufficient C(60)O at the surfaces of the nC(60) particles to allow stable suspension in water. Controlled-atmosphere syntheses, deliberate C(60)O enrichment, light scattering measurements, and extraction followed by HPLC analysis and UV-visible absorption spectroscopy support the above model of nC(60) formation and stabilization. PMID:22703564

  12. Heat capacity measurements of atoms and molecules adsorbed on evaporated metal films

    SciTech Connect

    Kenny, T.W.

    1989-05-01

    Investigations of the properties of absorbed monolayers have received great experimental and theoretical attention recently, both because of the importance of surface processes in practical applications such as catalysis, and the importance of such systems to the understanding of the fundamentals of thermodynamics in two dimensions. We have adapted the composite bolometer technology to the construction of microcalorimeters. For these calorimeters, the adsorption substrate is an evaporated film deposited on one surface of an optically polished sapphire wafer. This approach has allowed us to make the first measurements of the heat capacity of submonolayer films of /sup 4/He adsorbed on metallic films. In contrast to measurements of /sup 4/He adsorbed on all other insulating substrates, we have shown that /sup 4/He on silver films occupies a two-dimensional gas phase over a broad range of coverages and temperatures. Our apparatus has been used to study the heat capacity of Indium flakes. CO multilayers, /sup 4/He adsorbed on sapphire and on Ag films and H/sub 2/ adsorbed on Ag films. The results are compared with appropriate theories. 68 refs., 19 figs.

  13. SiC formation on Si(100) via C 60 precursors

    NASA Astrophysics Data System (ADS)

    De Seta, M.; Tomozeiu, N.; Sanvitto, D.; Evangelisti, F.

    2000-07-01

    The interaction between C 60 molecules and the Si(100) surface and the preparation of silicon-carbide thin films by thermal reaction of C 60 molecules with the Si(100) surface have been investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, reflection high-energy electron diffraction and atomic force microscopy measurements. The effects of annealing temperature and C 60 coverage on the SiC formation will be discussed. It is found that the C 60 molecules bond covalently with silicon, and the number of bonds increase upon increasing the annealing temperature. Annealing at T≥830°C entails the formation of stoichiometric silicon carbide clusters that coalesce to form a continuous SiC layer when the C 60 coverage is greater than one monolayer. Deep pits acting as silicon diffusion channels are present with dimensions that increase with the amounts of C 60. The interaction of C 60 with the SiC surface was also investigated. It is found that a similar covalent interaction is present in the two systems C 60/Si and C 60/SiC.

  14. Protective Fullerene (C60) Packaging System for Microelectromechanical Systems Applications

    NASA Technical Reports Server (NTRS)

    Olivas, John D. (Inventor)

    2004-01-01

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

  15. Orientational and magnetic ordering of buckyballs in TDAE-C60

    SciTech Connect

    Mihailovic, D.; Arcon, D.; Venturini, P.; Blinc, R.; Omerzu, A.; Cevc, P.

    1995-04-01

    Spin ordering in the low-temperature magnetic phase is directly linked to the orientational ordering of C60 molecules in organically doped fullerene derivatives. Electron spin resonance and alternating current susceptometry measurements on tetrakis (dimethylamino) ethylene-C60 (TDAE-C60) (Curie temperature T(sub c) = 16 kelvin) show a direct coupling between spin and merohedral degrees of freedom. This coupling was experimentally demonstrated by showing that ordering the spins in the magnetic phase imprints a merohedral order on the solid or, conversely, that merohedrally ordering the C60 molecules influences the spin order at low temperature. The merohedral disorder gives rise to a distribution of pi-electron exchange interactions between spins on neighboring C60 molecules, suggesting a microscopic origin for the observed spin-glass behavior of the magnetic state. 18 refs.

  16. Inversion Symmetry Breaking in Endohedral C_60

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis; Anderson, Frederick

    1998-03-01

    A pseudo--Jahn--Teller model describing central atom distortions is proposed for endohedral fullerenes of the form A@C_60 where A is either a rare gas or a metal atom. A critical (dimensionless) coupling gc is found, at or below which the symmetric configuration is stable and above which inversion symmetry is broken. Vibronic parameters are given for selected endohedral fullerenes.

  17. Ortho-para conversion of endohedral water in the fullerene C60 at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Shugai, Anna; Nagel, U.; Rõõm, T.; Mamone, S.; Concistrè, M.; Meier, B.; Krachmalnicoff, A.; Whitby, R. J.; Levitt, M. H.; Lei, Xuegong; Li, Yongjun; Turro, N. J.

    2015-03-01

    Water displays the phenomenon of spin isomerism in which the two proton spins either couple to form a triplet (ortho water, I = 1) or a singlet nuclear spin state (para water, I = 0). Here we study the interconversion of para and ortho water. The exact mechanism of this process is still not fully understood. In order to minimize interactions between molecules we use a sample where a single H2O is trapped in the C60 molecular cage (H2O@C60)andH2O@C60iscrystallized.H2O@C60 has long-lived ortho state and ortho-para conversion kinetics is non-exponential at LHeT. We studied mixtures of H2O@C60, D2O@C60 and C60 using IR absorption, NMR and dielectric measurements. We saw the speeding up of the interconversion with the growth of H2O@C60 concentration in C60 or when D2O@C60 was added. At some temperatures the kinetics is exponential. Models are discussed in order to explain the T and concentration dependence of ortho-para interconversion kinetics. This work was supported by institutional research funding IUT23-3 of the Estonian Ministry of Education and Research.

  18. Synthesis of C60H2 by rhodium-catalyzed hydrogenation of C60

    NASA Technical Reports Server (NTRS)

    Becker, L.; Evans, T. P.; Bada, J. L.; Miller, S. L. (Principal Investigator)

    1993-01-01

    Reduction of C60 with rhodium(0) on alumina and hydrogen in deuterated benzene (C6D6) at ambient temperature and pressure yields a mixture of hydrogenated compounds; C60H2 has been characterized as the major product in 14% yield based on 1H NMR.

  19. Charge-transfer photodissociation of adsorbed molecules via electron image states

    SciTech Connect

    Jensen, E. T.

    2008-01-28

    The 248 and 193 nm photodissociations of submonolayer quantities of CH{sub 3}Br and CH{sub 3}I adsorbed on thin layers of n-hexane indicate that the dissociation is caused by dissociative electron attachment from subvacuum level photoelectrons created in the copper substrate. The characteristics of this photodissociation-translation energy distributions and coverage dependences show that the dissociation is mediated by an image potential state which temporarily traps the photoelectrons near the n-hexane-vacuum interface, and then the charge transfers from this image state to the affinity level of a coadsorbed halomethane which then dissociates.

  20. Charge transfer and formation of conducting C60 monolayers at C60/noble-metal interfaces

    NASA Astrophysics Data System (ADS)

    Nouchi, Ryo; Kanno, Ikuo

    2005-05-01

    The resistance of a conducting C60 monolayer formed on a polycrystalline Ag film was found to be 0.7±0.1kΩ by in situ resistance measurements. By another series of in situ resistance measurements, the surface scattering cross sections, whose magnitude represents the relative amount of transferred charge, were evaluated as 100Å2 for C60/Au, and 150Å2 for C60/Cu and C60/Ag systems. However, comparison with previous results obtained for monolayers formed on Au and Cu films showed that the resistances of conducting C60 monolayers do not show a simple dependence on the transferred charge. Atomic force microscopy measurements revealed that the grain size of the underlying noble metals also plays an important role.

  1. Raman study on a bulk-heterojunction film of pentacene and C60

    NASA Astrophysics Data System (ADS)

    Iwasawa, Yasuhiro; Furukawa, Yukio

    2015-09-01

    We measured the 785-nm excited Raman spectrum of a pentacene:C60 blend film. The 1462-, 492-, and 268-cm-1 bands of C60 showed broadening in bandwidth and downward shifts in peak wavenumbers, whereas such broadening and downward shifts were not observed for pentacene. These results indicate that there are pentacene crystallites among the amorphous C60. The intensity ratio of the 1598-cm-1 (B3g) and the 1534-cm-1 (Ag) bands indicates that pentacene molecules have standing orientations. The appearance of a 514-cm-1 band (F1u) and the splitting of the Hg bands of C60 indicate symmetry lowering induced by the interaction between pentacene and C60 molecules.

  2. Adsorbed states of chlorophenol on Cu(110) and controlled switching of single-molecule junctions

    NASA Astrophysics Data System (ADS)

    Okuyama, H.; Kitaguchi, Y.; Hattori, T.; Ueda, Y.; Ferrer, N. G.; Hatta, S.; Aruga, T.

    2016-06-01

    A molecular junction of substituted benzene (chlorophenol) is fabricated and controlled by using a scanning tunneling microscope (STM). Prior to the junction formation, the bonding geometry of the molecule on the surface is characterized by STM and electron energy loss spectroscopy (EELS). EELS shows that the OH group of chlorophenol is dissociated on Cu(110) and that the molecule is bonded nearly flat to the surface via an O atom, with the Cl group intact. We demonstrate controlled contact of an STM tip to the "available" Cl group and lift-up of the molecule while it is anchored to the surface via an O atom. The asymmetric bonding motifs of the molecule to the electrodes allow for reversible control of the junction.

  3. Adsorbed states of chlorophenol on Cu(110) and controlled switching of single-molecule junctions.

    PubMed

    Okuyama, H; Kitaguchi, Y; Hattori, T; Ueda, Y; Ferrer, N G; Hatta, S; Aruga, T

    2016-06-28

    A molecular junction of substituted benzene (chlorophenol) is fabricated and controlled by using a scanning tunneling microscope (STM). Prior to the junction formation, the bonding geometry of the molecule on the surface is characterized by STM and electron energy loss spectroscopy (EELS). EELS shows that the OH group of chlorophenol is dissociated on Cu(110) and that the molecule is bonded nearly flat to the surface via an O atom, with the Cl group intact. We demonstrate controlled contact of an STM tip to the "available" Cl group and lift-up of the molecule while it is anchored to the surface via an O atom. The asymmetric bonding motifs of the molecule to the electrodes allow for reversible control of the junction. PMID:27369529

  4. How hottest geometries and adsorptive parameters influence the SER(R)S spectra of Methylene Blue molecules adsorbed on nanocolloidal gold particles of varied sizes?

    PubMed

    Roy, Sannak Dutta; Ghosh, Manash; Chowdhury, Joydeep

    2015-12-01

    The SER(R)S spectra of Methylene Blue (MB) molecule adsorbed on gold nanocolloidal particles (AuNCs) have been investigated. The adsorptive parameters of the molecule adsorbed on AuNCs have been evaluated with the aid of Fluorescence Spectroscopy study. Fluorescence spectroscopic studies have been further applied to understand the concentration of probe molecule actually adsorbed on AuNC surfaces. Gigantic enhancements ∼10(6)-10(16) orders of magnitude have been recorded for the enhanced Raman bands in the SER(R)S spectra. Three-dimensional Finite Difference Time Domain (3D-FDTD) simulations studies have been carried out to predict the distributions of electric fields around the possible nanoaggregated hot geometries considered to be responsible for the huge enhancements of SER(R)S bands of the MB molecule. PMID:26172467

  5. On the vibrational modes of C 60

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.; Gorman, John P.

    1996-03-01

    The vibrational spectrum of C 60 is compared to the spectrum of a classical isotropic elastic spherical shell. We show correlations between the low frequency modes of C 60 and those of the spherical shell. We find the spherical model gives the approximate frequency ordering for the low frequency modes. We estimate a Poisson ratio of σ ≈ 0.30 and a transverse speed of sound of υs ≈ 1800 m/s for the equivalent elastic shell. We also find that ω( M1) /ω( M0) = √ 3/2 for the shell modes M 0 and M 1, independent of elastic constants. We find that this ratio compares favorably with an experimental value of 1.17.

  6. Ferroelectricity in (K@C60)n

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2000-09-01

    A theoretical analysis of the ground state of long-chain (K@C60)n is presented. Within mean field theory, a ferroelectric ground state is found to be stable because of the pseudo-Jahn-Teller mixing of the b1u and the b2g band with a zone-center optical phonon involving the displacement of the endohedral K- ions. A phase diagram for this model is derived in the narrow bandwidth regime.

  7. Electronic pair binding and Hund's rule violations in doped C60

    NASA Astrophysics Data System (ADS)

    Jiang, Hong-Chen; Kivelson, Steven

    2016-04-01

    We calculate the electronic properties of the t -J model on a C60 molecule using the density-matrix renormalization group and show that Hund's first rule is violated and that for an average of three added electrons per molecule, an effective attraction (pair binding) arises for intermediate values of t /J . Specifically, it is energetically favorable to put four electrons on one C60 and two on a second rather than putting three on each. Our results show that a dominantly electronic mechanism of superconductivity is possible in doped C60.

  8. Mechanism of charge transfer and its impacts on Fermi-level pinning for gas molecules adsorbed on monolayer WS{sub 2}

    SciTech Connect

    Zhou, Changjie; Zhu, Huili; Yang, Weihuang

    2015-06-07

    Density functional theory calculations were performed to assess changes in the geometric and electronic structures of monolayer WS{sub 2} upon adsorption of various gas molecules (H{sub 2}, O{sub 2}, H{sub 2}O, NH{sub 3}, NO, NO{sub 2}, and CO). The most stable configuration of the adsorbed molecules, the adsorption energy, and the degree of charge transfer between adsorbate and substrate were determined. All evaluated molecules were physisorbed on monolayer WS{sub 2} with a low degree of charge transfer and accept charge from the monolayer, except for NH{sub 3}, which is a charge donor. Band structure calculations showed that the valence and conduction bands of monolayer WS{sub 2} are not significantly altered upon adsorption of H{sub 2}, H{sub 2}O, NH{sub 3}, and CO, whereas the lowest unoccupied molecular orbitals of O{sub 2}, NO, and NO{sub 2} are pinned around the Fermi-level when these molecules are adsorbed on monolayer WS{sub 2}. The phenomenon of Fermi-level pinning was discussed in light of the traditional and orbital mixing charge transfer theories. The impacts of the charge transfer mechanism on Fermi-level pinning were confirmed for the gas molecules adsorbed on monolayer WS{sub 2}. The proposed mechanism governing Fermi-level pinning is applicable to the systems of adsorbates on recently developed two-dimensional materials, such as graphene and transition metal dichalcogenides.

  9. Electronic Structure of Crystalline Buckyballs: fcc-C60

    NASA Astrophysics Data System (ADS)

    Jalali-Asadabadi, Saeid; Ghasemikhah, E.; Ouahrani, T.; Nourozi, B.; Bayat-Bayatani, M.; Javanbakht, S.; Aliabad, H. A. Rahnamaye; Ahmad, Iftikhar; Nematollahi, J.; Yazdani-Kachoei, M.

    2016-01-01

    The electronic properties of pristine fcc-C60 are calculated by utilizing a variety of density functional theory (DFT) approaches including the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA), PBE-GGA+DFT-D3(vdW), Engel and Vosko GGA (EV-GGA), GGA plus Hubbard U parameter (GGA+U), hybrids Becke-Perdew-Wang hybrid functional (B3PW91), Becke-Lee-Yang-Parr hybrid functional (B3LYP), the PBE exchange-correlation functional (PBE0), and Tran and Blaha regular and non-regular modified Becke and Johnson (TB-mBJ) potential within a DFT frame work using augmented plane waves plus local orbital method. The comparison of the calculated results with the experimental values shows that the non-regular TB-mBJ method reproduces a correct experimental direct band gap of 2.12 eV at X symmetry for this compound. The effectiveness of this theoretical approach in the reproduction of the experimental band gap is due to the proper treatment of the electrons in the interstitial region of the crystal. Our results show that the C60 clusters are weakly interacting with each other in the fcc crystal. This study also reveals that the five-fold degeneracies of the isolated C60 molecule due to its icosahedral symmetry are completely lifted at an X symmetry point by the crystal field.

  10. C60-derived nanobaskets: stability, vibrational signatures, and molecular trapping.

    PubMed

    dos Santos, S G; Pires, M S; Lemos, V; Freire, V N; Caetano, E W S; Galvão, D S; Sato, F; Albuquerque, E L

    2009-09-30

    C(60)-derived nanobaskets, with chemical formulae (symmetry point group) C(40)H(10) (C(5v)), C(39)H(12) (C(3v)), C(46)H(12) (C(2v)), were investigated. Molecular dynamic simulations (MDSs) indicate that the molecules preserve their bonding frame for temperatures up to 300 K (simulation time 100 ps), and maintain atomic cohesion for at least 4 ps at temperatures up to 3500 K. The infrared spectra of the C(60)-derived nanobaskets were simulated through density functional theory (DFT) calculations, allowing for the attribution of infrared signatures specific to each carbon nanobasket. The possibility of using C(60)-derived nanobaskets as molecular containers is demonstrated by performing a DFT study of their bonding to hydrogen, water, and L-alanine. The carbon nanostructures presented here show a higher bonding energy (approximately 1.0 eV), suggesting that a family of nanostructures, C(n)-derived (n = 60,70,76,80, etc) nanobaskets, could work as molecular containers, paving the way for future developments such as tunable traps for complex molecular systems. PMID:19724106

  11. The influence of distribution of hydroxyl groups on vibrational spectra of fullerenol C60(OH)24 isomers: DFT study.

    PubMed

    Dawid, A; Górny, K; Gburski, Z

    2015-02-01

    The infrared and Raman spectra of C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been investigated using first principle DFT calculations at the B3LYP/6-31G(d,p) level of theory. The important features of the obtained geometries have been measured and compared to experimental results. The reference calculations of C60 molecule geometry and vibrational spectra have been made and compared to available experimental data. The striking differences of infrared spectra between C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been shown and discussed. The OH modes have been identified as the most sensitive to C60(OH)24 isomer configuration. The C-C stretching modes in the Raman spectra of the C60(OH)24 molecule have been found as a potential sensor of OH groups distribution over fullerene C60 surface. PMID:25223813

  12. A theoretical study of the ozonolysis of C60: primary ozonide formation, dissociation, and multiple ozone additions.

    PubMed

    Chapleski, Robert C; Morris, John R; Troya, Diego

    2014-04-01

    We present an investigation of the reaction of ozone with C60 fullerene using electronic structure methods. Motivated by recent experiments of ozone exposure to a C60 film, we have characterized stationary points in the potential energy surface for the reactions of O3 with C60 that include both the formation of primary ozonide and subsequent dissociation reactions of this intermediate that lead to C-C bond cleavage. We have also investigated the addition of multiple O3 molecules to the C60 cage to explore potential reaction pathways under the high ozone flux conditions used in recent experiments. The lowest-energy product of the reaction of a single ozone molecule with C60 that results in C-C bond breakage corresponds to an open-cage C60O3 structure that contains ester and ketone moieties at the seam. This open-cage product is of much lower energy than the C60O + O2 products identified in prior work, and it is consistent with IR experimental spectra. Subsequent reaction of the open-cage C60O3 product with a second ozone molecule opens a low-energy reaction pathway that results in cage degradation via the loss of a CO2 molecule. Our calculations also reveal that, while full ozonation of all bonds between hexagons in C60 is unlikely even under high ozone concentration, the addition of a few ozone molecules to the C60 cage is favorable at room temperature. PMID:24549406

  13. Preparation and surface enhanced Raman scattering behavior of Ag-coated C60 nanoclusters

    NASA Astrophysics Data System (ADS)

    Kang, Shi-Zhao; Yin, Die-er; Li, Xiangqing; Mu, Jin

    2013-12-01

    Ag-coated C60 nanoclusters were prepared and characterized with X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption isotherm measurement. The Ag-coated C60 nanoclusters were assembled on the glass substrate to form a thin film using the layer-by-layer technique. Meanwhile, the surface enhanced Raman scattering (SERS) of musk xylene adsorbed on the film of Ag-coated C60 nanoclusters was explored. The results indicated that the film of Ag-coated C60 nanoclusters was a unique SERS-active substrate with a detection limit of 10-9 mol L-1 for musk xylene. Furthermore, the surface enhanced mechanisms were discussed preliminarily.

  14. Molecular dynamics and the phase transition in solid C60

    NASA Astrophysics Data System (ADS)

    Tycko, R.; Dabbagh, G.; Fleming, R. M.; Haddon, R. C.; Makhija, A. V.; Zahurak, S. M.

    1991-09-01

    The molecular reorientational dynamics in two phases of solid C60 with C-13 NMR measurements are characterized. A change in the nature of the dynamics, indicated by a change in kinetic parameters extracted from spin-lattice relaxation data, occurs at the phase transition at 260 K. Above the transition, the molecules appear to execute continuous rotational diffusion; below the transition, they appear to jump between symmetry-equivalent orientations. This interpretation is consistent with the X-ray-diffraction results of Heiney et al. (1991) as well as the NMR relaxation and spectral data.

  15. Effects of non-local exchange on core level shifts for gas-phase and adsorbed molecules

    SciTech Connect

    Van den Bossche, M.; Grönbeck, H.; Martin, N. M.; Gustafson, J.; Lundgren, E.; Hakanoglu, C.; Weaver, J. F.

    2014-07-21

    Density functional theory calculations are often used to interpret experimental shifts in core level binding energies. Calculations based on gradient-corrected (GC) exchange-correlation functionals are known to reproduce measured core level shifts (CLS) of isolated molecules and metal surfaces with reasonable accuracy. In the present study, we discuss a series of examples where the shifts calculated within a GC-functional significantly deviate from the experimental values, namely the CLS of C 1s in ethyl trifluoroacetate, Pd 3d in PdO and the O 1s shift for CO adsorbed on PdO(101). The deviations are traced to effects of the electronic self-interaction error with GC-functionals and substantially better agreements between calculated and measured CLS are obtained when a fraction of exact exchange is used in the exchange-correlation functional.

  16. Hindered and modulated rotational states and spectra of adsorbed diatomic molecules

    SciTech Connect

    Shih, Y.T.; Chuu, D.S.; Mei, W.N.

    1996-10-01

    Both vertical and horizontal adsorption configurations of a diatomic molecule were modeled as the rigid rotor with which the spatial motion was confined by a finite conical well. In addition to the polar hindering potential, a sinusoidal azimuthal modulation, which bears the local symmetry of the adsorption site, was incorporated. Eigenfunctions for different models were expressed analytically in terms of the hypergeometric functions, and eigenvalues were solved numerically. We found that the rotational energy levels exhibit oscillatory behavior when plotted as functions of the hindrance angle. This particular phenomenon was interpreted as the occurrence of resonance transmission of the rotor wave function at certain hindrance condition. We also found that the rotational levels were grouped into bands when the azimuthal modulation strength was increased. The solutions were used to calculate the rotational-state distribution of desorbed molecules, and agreement with the previous experiment was obtained. {copyright} {ital 1996 The American Physical Society.}

  17. Energy spectrum of C60 fullerene

    NASA Astrophysics Data System (ADS)

    Mironov, G. I.; Murzashev, A. I.

    2011-11-01

    The energy spectrum of the C60 fullerene has been calculated in terms of the Shubin-Vonsovskii-Hubbard model using an approximation of static fluctuations. Based on the spectrum, the optical absorption bands at 4.84, 5.88, and 6.30 eV observed experimentally have been successfully explained. It has been concluded that the model used is applicable for the calculation of the energy spectrum and the energy properties of other nanosystems, such as fullerenes of higher orders, carbon nanotubes, and grafen planes.

  18. Enhanced photoluminescence of C 60 incorporated into interlayers of hydrotalcite

    NASA Astrophysics Data System (ADS)

    Ding, Weiping; Gu, Gang; Zhong, Wei; Zang, Wen-Cheng; Du, Youwei

    1996-11-01

    Strong photoluminescence of sodium-reduced C 60 incorporated into interlayers of hydrotalcite is observed. This phenomenon is correlated to the fact that the reduced C 60 is positioned between positively charged layers of the anion clay. The interaction between the layers and reduced C 60 alters the photophysical properties of C 60 and relaxes the electron transition inhibition, thus enhancing photoluminescence.

  19. Identification of More Interstellar C60+ Bands

    NASA Astrophysics Data System (ADS)

    Walker, G. A. H.; Bohlender, D. A.; Maier, J. P.; Campbell, E. K.

    2015-10-01

    Based on gas-phase laboratory spectra at 6 K, Campbell et al. confirmed that the diffuse interstellar bands (DIBs) at 9632.7 and 9577.5 Å are due to absorption by the fullerene ion {{{C}}}60+. They also reported the detection of two other, weaker bands at 9428.5 and 9365.9 Å. These lie in spectral regions heavily contaminated by telluric water vapor lines. We acquired CFHT ESPaDOnS spectra of HD 183143 close to the zenith and chopped with a nearby standard to correct for the telluric line absorption which enabled us to detect a DIB at 9365.9 Å of relative width and strength comparable to the laboratory absorption. There is a DIB of similar strength and FWHM at 9362.5 Å. A stellar emission feature at 9429 Å prevented detection of the 9428.5 Å band. However, a CFHT archival spectrum of HD 169454, where emission is absent at 9429 Å, clearly shows the 9428.5 Å DIB with the expected strength and width. These results further confirm {{{C}}}60+ as a DIB carrier. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  20. Switching orientation of adsorbed molecules: Reverse domino on a metal surface

    NASA Astrophysics Data System (ADS)

    Braatz, C. R.; Esat, T.; Wagner, C.; Temirov, R.; Tautz, F. S.; Jakob, P.

    2016-01-01

    A thus far unknown phase of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) on Ag(111), characterized by an all perpendicular orientation of the planar molecules and bound to the Ag substrate through the carboxyl oxygen atoms has been identified using infrared absorption spectroscopy and scanning tunneling microscopy. Its formation process requires second layer NTCDA to squeeze into empty spaces between relaxed monolayer NTCDA molecules. Remarkably, this process causes initially parallel oriented NTCDA to likewise adopt the new, highly inclined adsorption geometry. According to our SPA-LEED and STM findings, the new phase displays a distinct long range order and shows a pronounced tendency to form 1D rows or narrow islands. We suggest that extra NTCDA preferentially transforms into the upright configuration close to existing islands and attaches to them, i.e. the transformation process proceeds in a directed and recurrent manner (reverse domino scenario). Identical processing starting with a compressed NTCDA/Ag(111) monolayer leads to a purely parallel oriented bilayer, that is, the NTCDA monolayer phase is retained and merely acts as a passive template for bilayer NTCDA. The new vertical NTCDA phase represents an unusual molecular system with π-orbitals oriented parallel to a metal surface. A substantially reduced coupling of these orbitals to Ag(111) electronic levels is conjectured, which will have a major impact on intermolecular couplings and electronically excited state lifetimes.

  1. Electron transfer mediation by aqueous C60 aggregates in H2O2/UV advanced oxidation of indigo carmine

    NASA Astrophysics Data System (ADS)

    Ge, Ling; Moor, Kyle; Zhang, Bo; He, Yiliang; Kim, Jae-Hong

    2014-10-01

    C60 fullerene has long been known to exhibit favorable electron accepting and shuttling properties, but little is known about the possibility of electron transfer mediation by fullerene aggregates (nC60) in water. In this study, we investigated the electron shuttling capabilities of nC60 using UV/H2O2 as a model oxidation process in the presence of an electron donor, indigo carmine (IC). nC60 addition to the IC/H2O2 system was found to drastically increase IC degradation and shift the reactive oxygen species (ROS) balance, favoring the formation of superoxide and perhydroxyl radical species compared to hydroxyl radicals. Results indicate that nC60 can act as an electron mediator, where the adsorbed IC donates an electron to nC60, which is subsequently transferred to H2O2 or perhydroxyl radical.C60 fullerene has long been known to exhibit favorable electron accepting and shuttling properties, but little is known about the possibility of electron transfer mediation by fullerene aggregates (nC60) in water. In this study, we investigated the electron shuttling capabilities of nC60 using UV/H2O2 as a model oxidation process in the presence of an electron donor, indigo carmine (IC). nC60 addition to the IC/H2O2 system was found to drastically increase IC degradation and shift the reactive oxygen species (ROS) balance, favoring the formation of superoxide and perhydroxyl radical species compared to hydroxyl radicals. Results indicate that nC60 can act as an electron mediator, where the adsorbed IC donates an electron to nC60, which is subsequently transferred to H2O2 or perhydroxyl radical. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03647f

  2. Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: Tribo-polymers from α-pinene, pinane, and n-decane

    NASA Astrophysics Data System (ADS)

    He, Xin; Barthel, Anthony J.; Kim, Seong H.

    2016-06-01

    The mechanochemical reactions of adsorbed molecules at sliding interfaces were studied for α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22) on a stainless steel substrate surface. During vapor phase lubrication, molecules adsorbed at the sliding interface could be activated by mechanical shear. Under the equilibrium adsorption condition of these molecules, the friction coefficient of sliding steel surfaces was about 0.2 and a polymeric film was tribochemically produced. The synthesis yield of α-pinene tribo-polymers was about twice as much as pinane tribo-polymers. In contrast to these strained bicyclic hydrocarbons, n-decane showed much weaker activity for tribo-polymerization at the same mechanical shear condition. These results suggested that the mechanical shear at tribological interfaces could induce the opening of the strained ring structure of α-pinene and pinane, which leads to polymerization of adsorbed molecules at the sliding track. On a stainless steel surface, such polymerization reactions of adsorbed molecules do not occur under typical surface reaction conditions. The mechanical properties and boundary lubrication efficiency of the produced tribo-polymer films are discussed.

  3. Two-dimensional van der Waals C60 molecular crystal

    PubMed Central

    Reddy, C. D.; Gen Yu, Zhi; Zhang, Yong-Wei

    2015-01-01

    Two-dimensional (2D) atomic crystals, such as graphene and transition metal dichalcogenides et al. have drawn extraordinary attention recently. For these 2D materials, atoms within their monolayer are covalently bonded. An interesting question arises: Can molecules form a 2D monolayer crystal via van der Waals interactions? Here, we first study the structural stability of a free-standing infinite C60 molecular monolayer using molecular dynamic simulations, and find that the monolayer is stable up to 600 K. We further study the mechanical properties of the monolayer, and find that the elastic modulus, ultimate tensile stress and failure strain are 55–100 GPa, 90–155 MPa, and 1.5–2.3%, respectively, depending on the stretching orientation. The monolayer fails due to shearing and cavitation under uniaxial tensile loading. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the monolayer are found to be delocalized and as a result, the band gap is reduced to only 60% of the isolated C60 molecule. Interestingly, this band gap can be tuned up to ±30% using strain engineering. Owing to its thermal stability, low density, strain-tunable semi-conducting characteristics and large bending flexibility, this van der Waals molecular monolayer crystal presents aplenty opportunities for developing novel applications in nanoelectronics. PMID:26183501

  4. Two-dimensional van der Waals C60 molecular crystal

    NASA Astrophysics Data System (ADS)

    Reddy, C. D.; Gen Yu, Zhi; Zhang, Yong-Wei

    2015-07-01

    Two-dimensional (2D) atomic crystals, such as graphene and transition metal dichalcogenides et al. have drawn extraordinary attention recently. For these 2D materials, atoms within their monolayer are covalently bonded. An interesting question arises: Can molecules form a 2D monolayer crystal via van der Waals interactions? Here, we first study the structural stability of a free-standing infinite C60 molecular monolayer using molecular dynamic simulations, and find that the monolayer is stable up to 600 K. We further study the mechanical properties of the monolayer, and find that the elastic modulus, ultimate tensile stress and failure strain are 55-100 GPa, 90-155 MPa, and 1.5-2.3%, respectively, depending on the stretching orientation. The monolayer fails due to shearing and cavitation under uniaxial tensile loading. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the monolayer are found to be delocalized and as a result, the band gap is reduced to only 60% of the isolated C60 molecule. Interestingly, this band gap can be tuned up to ±30% using strain engineering. Owing to its thermal stability, low density, strain-tunable semi-conducting characteristics and large bending flexibility, this van der Waals molecular monolayer crystal presents aplenty opportunities for developing novel applications in nanoelectronics.

  5. Infrared spectroscopy of water clusters co-adsorbed with hydrogen molecules on a sodium chloride film

    NASA Astrophysics Data System (ADS)

    Yamakawa, Koichiro; Fukutani, Katsuyuki

    2016-06-01

    Hydrogen gas containing a trace of water vapor was dosed on a vacuum-evaporated sodium chloride film at 13 K, and water clusters formed on the substrate were investigated by infrared absorption spectroscopy. Absorption bands due to (H2O)n clusters with n = 3-6 and an induced absorption band due to hydrogen were clearly observed. With increasing gas dosage, the intensities of the cluster bands increased linearly while the intensity of the hydrogen band was constant. This suggests that the water clusters were formed in two-dimensional matrices of hydrogen. We found that the water clusters did exist on the surface upon heating even after the hydrogen molecules had desorbed. A further rise of the substrate temperature up to 27 K yielded the formation of larger clusters, (H2O)n with n > 6 . We also discuss the origins of the two bands of the trimer in terms of pseudorotation and a metastable isomer.

  6. DFT study of hydrogen storage in Pd-decorated C60 fullerene

    NASA Astrophysics Data System (ADS)

    El Mahdy, A. M.

    2015-11-01

    Hydrogen storage reactions on Pd-doped C60 fullerene are investigated by using the state-of-the-art density functional theory calculations. The Pd atom prefers to bind at the bridge site between two hexagonal rings, and can bind up to four hydrogen molecules with average adsorption energies of 0.61, 0.45, 0.32, and 0.21 eV per hydrogen molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 5.8 wt%. While the desorption activation barriers of the complexes nH2 + Pd-C60 with n = 1 are outside the department of energy (DOE) domain (-0.2 to -0.6 eV), the desorption activation barriers of the complexes nH2 + Pd-C60 with n = 2-4 are inside this domain. While the interaction of 1H2 with Pd + C60 is irreversible at 459 K, the interaction of 2H2 with Pd + C60 is reversible at 529 K. The hydrogen storage of the irreversible 1H2 + Pd-C60 and reversible 2H2 + Pd-C60 interactions are characterised in terms of densities of states, infrared, Raman, and proton magnetic resonance spectra, electrophilicity, and statistical thermodynamic stability.

  7. Modulation of nanocavity plasmonic emission by local molecular states of C60 on Au(111).

    PubMed

    Geng, Feng; Zhang, Yang; Yu, Yunjie; Kuang, Yanmin; Liao, Yuan; Dong, Zhenchao; Hou, Jianguo

    2012-11-19

    We investigate the modulation of C60 monolayers on the nanocavity plasmonic (NCP) emission on Au(111) by tunneling electron excitation from a scanning tunneling microscope (STM) tip. STM induced luminescence spectra show not only suppressed emission, but also significant redshift of NCP emission bands on the C60 molecules relative to the bare metal surface. The redshift, together with the bias- and coverage-dependent emission feature, indicates that the C60 molecules act beyond a pure dielectric spacer, their electronic states are heavily involved in the inelastic tunneling process for plasmonic emission. A modified quantum cutoff relation is proposed to explain qualitatively the observed emission feature at both bias polarities. We also demonstrate molecularly resolved optical contrast on the C60 monolayer and discuss the contrast mechanism briefly. PMID:23187525

  8. Orientation-Dependent C60 Electronic Structures Revealed byPhotoemission Spectroscopy

    SciTech Connect

    Brouet, V.; Yang, W.L.; Zhou, X.J.; Choi, H.J.; Louie, S.G.; Cohen, M.L.; Goldoni, A.; Parmigiani, F.; Hussain, Z.; Shen, Z.X.

    2004-11-05

    We observe, with angle-resolved photoemission, a dramatic change in the electronic structure of two C60 monolayers, deposited,respectively, on Ag (111) and (100) substrates, and similarly doped with potassium to half filling of the C60 lowest unoccupied molecular orbital.The Fermi surface symmetry, the bandwidth, and the curvature of the dispersion at Gamma point are different. Orientations of the C60molecules on the two substrates are known to be the main structural difference between the two monolayers, and we present new band-structure calculations for some of these orientations. We conclude that orientations play a key role in the electronic structure of fullerides.

  9. Tuning the conductance of H2O@C60 by position of the encapsulated H2O

    NASA Astrophysics Data System (ADS)

    Zhu, Chengbo; Wang, Xiaolin

    2015-12-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors.

  10. Tuning the conductance of H2O@C60 by position of the encapsulated H2O

    PubMed Central

    Zhu, Chengbo; Wang, Xiaolin

    2015-01-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

  11. Tuning the conductance of H2O@C60 by position of the encapsulated H2O.

    PubMed

    Zhu, Chengbo; Wang, Xiaolin

    2015-01-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green's function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

  12. New approach for sensitive photothermal detection of C60 and C70 fullerenes on micro-thin-layer chromatographic plates.

    PubMed

    Suszyński, Zbigniew; Zarzycki, Paweł K

    2015-03-10

    In this paper the pulse thermovision (photothermal) detection and quantification methods of C60 and C70 fullerenes are presented. Quantification results are compared with optical and fluorescence measurements. Target components were separated under isothermal conditions (30 °C) on micro-TLC plates (RP18WF254S) using n-hexane as the mobile phase. The principle of described analytical protocol is based on sensitive measurement of the temperature contrast generated within TLC stationary phase and fullerenes spots after white light pulse excitation. It has been demonstrated that observed temperature contrast is mainly driven by the optical properties of fullerenes (UV-vis absorption spectra). Contrary to the commonly applied optical reflection or transmission techniques the proposed thermovision method involves dissipated light. The results of presented experimental work have revealed that both types of quantitative measurements provide similar outcome despite the key differences in the signal origin. However, it has been found that thermovision method was characterized by smaller value of LOD, particularly for C60 molecule. We demonstrated that application of correlation technique to post-acquisition analysis of the sequence of temperature contrast images significantly increase detection limits of fullerenes, even in comparison to fluorescence quenching detection mode. Moreover, the thermal contrast images and particularly, computed correlation image, allow detection of stationary phase layer nonuniformities, including changes in the adsorbent thickness and thermal conductivity. Therefore, invented pulsed thermovision methodology can be additionally used for fast quality screening of home made and commercially available TLC plates. PMID:25732314

  13. Photon-exposure-dependent photon-stimulated desorption for obtaining photolysis cross section of molecules adsorbed on surface by monochromatic soft x-ray photons.

    PubMed

    Chou, L-C; Jang, C-Y; Wu, Y-H; Tsai, W-C; Wang, S-K; Chen, J; Chang, S-C; Liu, C-C; Shai, Y; Wen, C-R

    2008-12-01

    Photon-exposure-dependent positive- and negative-ion photon-stimulated desorption (PSD) was proposed to study the photoreactions and obtain the photolysis cross sections of molecules adsorbed on a single-crystal surface by monochromatic soft x-ray photons with energy near the core level of adsorbate. The changes in the F(+) and F(-) PSD ion yields were measured from CF(3)Cl molecules adsorbed on Si(111)-7x7 at 30 K (CF(3)Cl dose=0.3x10(15) molecules/cm(2), approximately 0.75 monolayer) during irradiation of monochromatic soft x-ray photons near the F(1s) edge. The PSD ion yield data show the following characteristics: (a) The dissociation of adsorbed CF(3)Cl molecules is due to a combination of direct photodissociation via excitation of F(1s) core level and substrate-mediated dissociation [dissociative attachment and dipolar dissociation induced by the photoelectrons emitting from the silicon substrate]. (b) the F(+) ion desorption is associated with the bond breaking of the surface CF(3)Cl, CF(2)Cl, CFCl, and SiF species. (c) the F(-) yield is mainly due to DA and DD of the adsorbed CF(3)Cl molecules. (d) The surface SiF is formed by reaction of the surface Si atom with the neutral fluorine atom, F(+), or F(-) ion produced by scission of C-F bond of CF(3)Cl, CF(2)Cl, or CFCl species. A kinetic model was proposed for the explanation of the photolysis of this submonolayer CF(3)Cl-covered surface. Based on this model and the variation rates of the F(+)F(-) signals during fixed-energy monochromatic photon bombardment at 690.2 and 692.6 eV [near the F(1s) edge], the photolysis cross section was deduced as a function of energy. PMID:19063541

  14. EPR study of radical reactions of C 60 dimer connected by a silicon bridge and single bond (C 60SiPh 2C 60)

    NASA Astrophysics Data System (ADS)

    Tumanskii, B. L.; Kalina, O. G.; Sokolov, V. I.; Chistyakov, A. L.; Stankevich, I. V.; Han, A.; Murata, Y.; Komatsu, K.

    2004-09-01

    Radical reactions of C 60 dimer connected by a silicon bridge and single bond (C 60SiPh 2C 60) were studied by EPR-spectroscopy. Attack of phosphoryl radicals or 2,2,6,6-tetramethylpiperidine- N-oxyl on the silicon atom leads to radical substitution of the fullerene and formation of a new fullerenyl radical, the structure of the former being confirmed by quantum-chemical calculations (DFT). The formation of only one type of spin-adduct on addition of phosphoryl radicals to the fullerene core is associated with small distortion of the fullerene cage in C 60SiPh 2C 60. Geometry of fullerene core in dimer differs only slightly from C 60 owing probably to flexibility of Si-C and C-C bonds which share a five-membered ring.

  15. Aqueous solubilization of C60 fullerene by natural protein surfactants, latherin and ranaspumin-2.

    PubMed

    Vance, Steven J; Desai, Vibhuti; Smith, Brian O; Kennedy, Malcolm W; Cooper, Alan

    2016-01-01

    C60 fullerene is not soluble in water and dispersion usually requires organic solvents, sonication or vigorous mechanical mixing. However, we show here that mixing of pristine C60 in water with natural surfactant proteins latherin and ranaspumin-2 (Rsn-2) at low concentrations yields stable aqueous dispersions with spectroscopic properties similar to those previously obtained by more vigorous methods. Particle sizes are significantly smaller than those achieved by mechanical dispersion alone, and concentrations are compatible with clusters approximating 1:1 protein:C60 stoichiometry. These proteins can also be adsorbed onto more intractable carbon nanotubes. This promises to be a convenient way to interface a range of hydrophobic nanoparticles and related materials with biological macromolecules, with potential to exploit the versatility of recombinant protein engineering in the development of nano-bio interface devices. It also has potential consequences for toxicological aspects of these and similar nanoparticles. PMID:27214760

  16. Probing Exciton Diffusion and Dissociation in Single-Walled Carbon Nanotube-C60 Heterojunctions.

    PubMed

    Dowgiallo, Anne-Marie; Mistry, Kevin S; Johnson, Justin C; Reid, Obadiah G; Blackburn, Jeffrey L

    2016-05-19

    The efficiency of thin-film organic photovoltaic (OPV) devices relies heavily upon the transport of excitons to type-II heterojunction interfaces, where there is sufficient driving force for exciton dissociation and ultimately the formation of charge carriers. Semiconducting single-walled carbon nanotubes (SWCNTs) are strong near-infrared absorbers that form type-II heterojunctions with fullerenes such as C60. Although the efficiencies of SWCNT-fullerene OPV devices have climbed over the past few years, questions remain regarding the fundamental factors that currently limit their performance. In this study, we determine the exciton diffusion length in the C60 layer of SWCNT-C60 bilayer active layers using femtosecond transient absorption measurements. We demonstrate that hole transfer from photoexcited C60 molecules to SWCNTs can be tracked by the growth of narrow spectroscopic signatures of holes in the SWCNT "reporter layer". In bilayers with thick C60 layers, the SWCNT charge-related signatures display a slow rise over hundreds of picoseconds, reflecting exciton diffusion through the C60 layer to the interface. A model based on exciton diffusion with a Beer-Lambert excitation profile, as well as Monte Carlo simulations, gives the best fit to the data as a function of C60 layer thickness using an exciton diffusion length of approximately 5 nm. PMID:27127916

  17. Polymeric fullerene chains in RbC60 and KC60

    NASA Astrophysics Data System (ADS)

    Stephens, Peter W.; Bortel, G.; Faigel, G.; Tegze, M.; Jánossy, A.; Pekker, S.; Oszlanyi, G.; Forró, L.

    1994-08-01

    NEARLY all of the molecular crystals containing C60, formed at ambient pressure1,2 have inter-fullerene separations of the order of 10 Å - the expected distance based on the molecular van der Waals radii. The sole exceptions are the room-temperature phases of AC60 (where A denotes K, Rb or Cs), which are formed by reversible solid-state transformation from high-temperature (>150 °C) phases3. These phases have lattice parameters about 9% shorter in one direction, and in addition RbC60 has magnetic properties suggestive of a one-dimensional metal4. We suggested in ref. 4 that this short distance may be due to covalent bonding between neighbouring C60 molecules. Here we provide direct evidence for such bonding from powder X-ray diffraction studies of RbC60 and KC60 . The linkage is through a [2+2] cycloaddition, which has been hypothesized to take place during photopolymerization of solid C60 (ref. 5), and which has also been proposed6 for RbC60. Such inter-fullerene linkages are calculated7,8 to be the preferred mode of dimerization of C60. The AC60 phases thus provide an example of a thermal phase transition driven by the reversible formation and breaking of covalent bonds.

  18. IR, NIR, and UV Absorption Spectroscopy of C60(2+) and C60(3+) in Neon Matrixes.

    PubMed

    Kern, Bastian; Strelnikov, Dmitry; Weis, Patrick; Böttcher, Artur; Kappes, Manfred M

    2014-02-01

    C60(2+) and C60(3+) were produced by electron-impact ionization of sublimed C60 and charge-state-selectively codeposited onto a gold mirror substrate held at 5 K together with neon matrix gas containing a few percent of the electron scavengers CO2 or CCl4. This procedure limits charge-changing of the incident fullerene projectiles during matrix isolation. IR, NIR, and UV-vis spectra were then measured. Ten IR absorptions of C60(2+) were identified. C60(3+) was observed to absorb in the NIR region close to the known vibronic bands of C60(+). UV spectra of C60, C60(+), and C60(2+) were almost indistinguishable, consistent with a plasmon-like nature of their UV absorptions. The measurements were supported by DFT and TDDFT calculations, revealing that C60(2+) has a singlet D5d ground state whereas C60(3+) forms a doublet of Ci symmetry. The new results may be of interest regarding the presence of C60(2+) and C60(3+) in space. PMID:26276592

  19. Light-Initiated Transformation of C60 Clusters in Water

    EPA Science Inventory

    Although Buckminster fullerene (C60) has an extremely low water solubility (~8 ng/L), the formation of stable clusters (aqu/nC60) not only greatly increases the mass of C60 dispersed in water, but also alters its physicochemical properties. This research focused on investigating ...

  20. Investigation of Photochemical Properties of C60 Aggregates in Water

    EPA Science Inventory

    As an emerging new material with unique structure and properties, the behavior and fate of Buckminster fullerene (C60) in natural waters has gained increasing attention. Although the water solubility of C60 is extremely low, the formation of C60 aggregates in water could alter th...

  1. Retention of Aqu/C60 Nanoparticles on Quartz Surfaces

    EPA Science Inventory

    Studies have shown that C60 fullerene can form stable suspensions of colloidal sized particles in water resulting in C60 aqueous concentrations many orders of magnitude above C60’s aqueous solubility. These studies have raised concern over the mobility and distribution of fuller...

  2. The Curators of the University of Missouri Modeling the Infrared Emission of C_60 in Space

    NASA Astrophysics Data System (ADS)

    Li, Aigen

    Fullerenes are cage-like molecules of pure carbon, such as C_60, C_70, C_76, and C_84. C_60, also known as buckminsterfullerene, is the most stable fullerene and has a soccer- ball like structure. The presence of fullerenes in space has been suggested and observationally explored since their first synthesis in the laboratory in 1985 by Harry Kroto and his colleagues which earned them the 1996 Nobel prize in chemistry. C_60 (as well as C_70) has recently been detected in reflection nebulae, post-AGB stars, protoplanetary nebulae, planetary nebulae, Herbig Ae/Be stars, and young stellar objects through their characteristic infrared emission bands. The formation of C_60 in interstellar and circumstellar environments is not firmly established. Experimental studies have shown that C_60 can be made by gas-phase condensation (e.g. through vaporization of graphite) in a hydrogen-poor environment. In view of the simultaneous detection of C_60 and PAHs in hydrogen-rich interstellar and circumstellar regions, it has also been suggested that C_60 could be generated by the decomposition of hydrogenated amorphous carbon, or the destruction of PAHs, both induced by shocks and/or UV photoprocessing. The phase (gas or solid) and excitation mechanism of C_60 in interstellar and circumstellar conditions are also hotly debated in the literature. One model suggests that C_60 is attached to dust and emits in solid-phase at the equilibrium temperature of the dust. Another model suggests that C_60 is stochastically excited by UV photons and emits in the gas-phase. We prefer the latter model as in interstellar and circumstellar conditions the energy content of a C_60 molecule is often smaller than the energy of a single starlight photon and C_60 is expected to undergo stochastical heating. We propose a two-year project to model the vibrational excitation of C_60 and calculate its infrared emission spectra in a wide variety of regions (e.g. reflection nebulae excited by stars of a range of

  3. Advanced carbon-based material C60 modification using partially ionized cluster and energetic beams

    NASA Astrophysics Data System (ADS)

    Yuancheng, Du; Zhongmin, Ren; Zhifeng, Ying; Ning, Xu; Fuming, Li

    1997-06-01

    Two processes have been undertaken using Partially ionized cluster deposition (PICBD) and energetic ion bombardment beams deposition (IBD) respectively. C60 films deposited by PICBD at V=0 and 65 V, which result in highly textured close-packed structure in orientation (110) and being more polycrystalline respectively, the resistance of C60 films to oxygen diffusion contamination will be improved. In the case of PICBD, the ionized C60 soccer-balls molecules in the evaporation beams will be fragmented in collision with the substrate under the elevated accelerating fields Va. As a new synthetic IBD processing, two low energy (400 and 1000 eV) nitrogen ion beams have been used to bombard C60 films to synthesize the carbon nitride films.

  4. Structural transitions of SWNT filled with C60 under high pressure

    NASA Astrophysics Data System (ADS)

    Yong-gang, Zou; Li, Xu; Kun, Tian; He, Zhang; Xiao-hui, Ma; Ming-guang, Yao

    2016-05-01

    Raman spectra of C60 filled single-walled carbon nanotubes (C60@SWNTs) with diameters of 1.3–1.5 nm have been studied under high pressure. A plateau in the pressure dependence of the G-band frequency at around 10 GPa was observed in both experiments with 514 nm and 830 nm excitation lasers, which is similar to the high pressure behaviors of pristine SWNTs. This structural transition has been assigned to the transformation into a peanut-like structure of the nanotubes. At pressure below 2 GPa, no obvious Raman signature related to the structural transition of nanotubes was observed, unlike what has been reported for C70 filled nanotubes. We discussed this point in terms of the arrangement differences of C60 and C70 molecules inside the nanotubes. At higher pressure up to 15 GPa, a graphite-like pressure evolution was observed in our C60@SWNTs.

  5. Ordered phases of ethylene adsorbed on charged fullerenes and their aggregates☆

    PubMed Central

    Zöttl, Samuel; Kaiser, Alexander; Daxner, Matthias; Goulart, Marcelo; Mauracher, Andreas; Probst, Michael; Hagelberg, Frank; Denifl, Stephan; Scheier, Paul; Echt, Olof

    2014-01-01

    In spite of extensive investigations of ethylene adsorbed on graphite, bundles of nanotubes, and crystals of fullerenes, little is known about the existence of commensurate phases; they have escaped detection in almost all previous work. Here we present a combined experimental and theoretical study of ethylene adsorbed on free C60 and its aggregates. The ion yield of (C60)m(C2H4)n+ measured by mass spectrometry reveals a propensity to form a structurally ordered phase on monomers, dimers and trimers of C60 in which all sterically accessible hollow sites over carbon rings are occupied. Presumably the enhancement of the corrugation by the curvature of the fullerene surface favors this phase which is akin to a hypothetical 1 × 1 phase on graphite. Experimental data also reveal the number of molecules in groove sites of the C60 dimer through tetramer. The identity of the sites, adsorption energies and orientations of the adsorbed molecules are determined by molecular dynamics calculations based on quantum chemical potentials, as well as density functional theory. The decrease in orientational order with increasing temperature is also explored in the simulations whereas in the experiment it is impossible to vary the temperature. PMID:25843960

  6. Screening of C60 crystallization using a microfluidic system.

    PubMed

    Shinohara, Kyosuke; Fukui, Takeshi; Abe, Hiroaki; Sekimura, Naoto; Okamoto, Koji

    2006-07-18

    We have carried out screening of C60 crystallization using a simple liquid/liquid interfacial precipitation method in a microfluidic device. By controlling the time, temperature, and concentration, various metastable phases of C60 crystals were found, including tubes, spheres, open-ended hollow columns, stars, branches, and trees. The obtained C60 crystal shapes are similar to those of snow crystals. These findings suggest an urgent need to screen C60 crystallization for the development of fullerene C60 drugs. PMID:16830986

  7. Colloidal Properties of Aqueous Fullerenes: Isoelectric Points and Aggregation Kinetics of C60 and C60 Derivatives

    EPA Science Inventory

    Aqueous colloidal suspensions of C-60 (aqu/C-60) and the C-60 derivatives PCBM ([6,6]-phenyl C-61-butyric acid methyl ester) and the corresponding butyl and octyl esters, PCBB and PCBO (aqu/PCB-R, where R is an alkyl group), were produced by stirring in double deionized water for...

  8. C60 fullerenes from combustion of common fuels.

    PubMed

    Tiwari, Andrea J; Ashraf-Khorassani, Mehdi; Marr, Linsey C

    2016-03-15

    Releases of C60 fullerenes to the environment will increase with the growth of nanotechnology. Assessing the potential risks of manufactured C60 requires an understanding of how its prevalence in the environment compares to that of natural and incidental C60. This work describes the characterization of incidental C60 present in aerosols generated by combustion of five common fuels: coal, firewood, diesel, gasoline, and propane. C60 was found in exhaust generated by all five fuels; the highest concentrations in terms of mass of C60 per mass of particulate matter were associated with diesel and coal. Individual aerosols from these combustion processes were examined by transmission electron microscopy. No relationship was found between C60 content and either the separation of graphitic layers (lamellae) within the particles, nor the curvature of those lamellae. Estimated global emissions of incidental C60 to the atmosphere from coal and diesel combustion range from 1.6 to 6.3 t yr(-1), depending upon combustion conditions. These emissions may be similar in magnitude to the total amount of manufactured C60 produced on an annual basis. Consequent loading of incidental C60 to the environment may be several orders of magnitude higher than has previously been modeled for manufactured C60. PMID:26789363

  9. Characterization of the intercalate C60(CO2)x by powder neutron diffraction

    NASA Astrophysics Data System (ADS)

    James, M.; Kennedy, S. J.; Elcombe, M. M.; Gadd, G. E.

    1998-12-01

    The intercalate compound C60(CO2)x has been synthesized by hot isostatically pressing C60 under 170 MPa of CO2 and 350 °C. Neutron powder diffraction studies conducted on C60(CO2)x between room temperature and 5 K have been analyzed using Rietveld techniques and reveal a structural transition between a high-temperature (>~250 K) face-centered cubic phase [Fm3¯m, a=14.224(2) Å (293 K)] and a low-temperature (<~150 K) monoclinic phase [P21/n, a=9.7438(9) Å, b=9.7473(9) Å, c=14.6121(11) Å, β=90.390(6)° (5 K)]. The CO2 molecules occupy the octahedral interstices between the C60 molecules and are oriented along the body diagonal of the high-temperature phase. In the low-temperature phase they are tilted slightly away from the c axis so as to place the oxygen atoms adjacent to the center of a pentagonal face on the C60 molecules.

  10. Buckminsterfullerene C60 — a surface with curvature and interesting properties

    NASA Astrophysics Data System (ADS)

    Rosén, Arne; Wästberg, Bo

    1992-05-01

    Molecular cluster calculations within the local density approximation have been performed in a study of the electronic structure of the truncated icosahedral C60 also known as "Buckminsterfullerene" and C60 doped with K, B and N. Evaluated ionisation energies for C60 are found to be in good agreement with recently observed gas phase and solid-state photoelectron spectra. Excitation energies evaluated in the 1-10 eV energy range are also found to reproduce UV, IR and HREELS spectra. Calculations for the KC60 molecule, with the K atom located at the centre of the cage, show how the valence electron from K is transferred to the LUMO state of the bare C60 molecule. Doping with a B or N atom in the centre of the cage creates a different structure with a partly occupied level in the band gap, similar to the donor and acceptor levels in traditionally doped semiconductors. Doping by substitution of two of the carbon atoms in the cage with X = B or N, as modelled with the C58X2 cluster, gives a different structure with a splitting of the HOMO and LUMO levels in the bare C60 molecule.

  11. Role of electron energy loss in modification of C60 thin films by swift heavy ions

    NASA Astrophysics Data System (ADS)

    Bajwa, Navdeep; Ingale, Alka; Avasthi, D. K.; Kumar, Ravi; Tripathi, A.; Dharamvir, Keya; Jindal, V. K.

    2008-09-01

    This paper presents a comparative study of the effects of irradiation by swift heavy ions (SHIs) with Se values ranging from 80 to 1270 eV/Å and fluence ranges varying between 1010 and 1014 ions/cm2 incident on thin films of C60. The control over Se is exercised through the choice of ion species for irradiation (O, Ni, and Au). Structural changes in C60 were investigated quantitatively using Raman spectroscopy. The results indicate that at low fluences polymer formation takes place whereas at high fluences there is complete fragmentation of C60, resulting in amorphous carbon formation. Measured values of band gap and in situ resistivity decrease with fluence. This result is consistent with the structural modifications observed by Raman spectroscopy. The composition of the polymer fraction formed (e.g., the content of two dimensional polymerized network of C60 molecules) as well as that of a-C (e.g., the content of nanographite) also vary with Se of the ion used. A phenomenological model, taking into account the ion track, enables us to explain the trend of polymer formation as well as fragmentation of C60, with increasing fluence of SHI. The cross section for damage (fragmentation of C60 molecules) has two values—one effective at low fluences and the other at high fluences. By arriving at a quantitative formula giving the fraction of polymer/damaged C60 molecules at any given fluence, we are able to predict the fluence and ion species required for a given amount of polymerization/damage or vice versa. Effort has been made to correlate Se and Sn values to the damage cross sections using data from this work along with those from other experiments using keV and MeV ions.

  12. Metal-oxide-semiconductor diodes containing C60 fullerenes for non-volatile memory applications

    NASA Astrophysics Data System (ADS)

    Beckmeier, Daniel; Baumgärtner, Hermann

    2013-01-01

    For non-volatile memories, silicon-oxide-nitride-oxide-silicon or floating gate structures are used to store information by charging and discharging electronic states reversibly. In this article, we propose to replace the floating gate by C60 molecules. This would allow more defined programming voltages because of the discrete molecular energy levels and a higher resistance to tunneling oxide defects because of the weak electrical connection between the single molecules. Such C60 MOS diode structures are produced and their electrical properties are analyzed regarding current transport and charging mechanism of the molecules. To create the MOS structures, C60 molecules (5% of a monolayer) are evaporated onto a part of a clean silicon wafer and covered by amorphous silicon in situ in an ultra high vacuum system. Then the wafer is oxidized in wet atmosphere at just 710 °C through the C60 layer. The goal is to produce a clean oxide above and under the molecules without destroying them. Aluminum gate contacts are defined on top of these layers to perform complementary capacitance voltage (CV) and current voltage (IV) measurements. First, the gate voltage is swept to analyze the injection current, then CV measurements are performed after each sweep to analyze the charge state of the C60 layer and the oxide quality. Reference diodes without C60 on the same wafer show an identical Fowler-Nordheim (FN) tunneling behavior for currents injected from silicon or from aluminum, respectively. In the CV curves, no pronounced flatband voltage shift is observable. In diodes with C60, for negative gate voltages, a classical FN tunneling is observed and compared to theory. The electron injection from silicon shows a different tunneling current behavior. It starts at a lower electric field and has a smaller slope then a FN current would have. It is identified as a trap-assisted tunneling (TAT) current caused by oxidation-induced traps under the C60 layer. It is modeled by an

  13. Electron Impact Excitation of C60 Adducts: Flourescence From C60OH and C60H Species

    NASA Technical Reports Server (NTRS)

    Trajmar, S.; Kanik, I.

    1996-01-01

    An investigation concerning possible visible and UV photon emissions by gas phase C(sub 60) ( and C(sub 70)) samples under electron impact excitation was caried out in the 180-750 nm spectral region. Radiation resembling OH (A (sup 2)pi {leads to}X (sup 2){summation}) emission bands and H Balmer series was observed. Based on our investigations, it is concluded that none of the observed emission was associated with the fullerene molecule itself but with the C(sub 60)OH and C(sub 60)H adducts (which are present in the fullerene samples). We also conclude that in these adducts, simultaneous ionization and excitation take place under electron impact and the excited ionic species (C(sub 60)+OH* and C(sub 60)+H*) decay by radiation which was observed in our experiments. These surprising results reveal an interesting new character of buckyball adducts.

  14. Carbon Nanotubes Investigated by N@C60 and N@C70 Spin Probes

    NASA Astrophysics Data System (ADS)

    Corzilius, B.; Gembus, A.; Dinse, K.-P.; Simon, F.; Kuzmany, H.

    2005-09-01

    Nitrogen atoms encapsulated in C60 can be used to detect small deviations from spherical symmetry via deformation-induced non-vanishing Zero-Field-Splitting (ZFS). In this context, experiments were performed by using these electronic quartet spin probes to investigate single wall carbon nanotubes. Time-fluctuating ZFS interaction would be indicative for rotational and/or translational degrees of freedom. Using pulsed EPR techniques, spin relaxation rates of N@C60 and also of N@C70 molecules with inherent static ZFS were measured. The analysis of their temperature dependence gave information about the dynamics of N@C60 and N@C70 molecules confined to the inside of the tubes.

  15. Direct patterning of a cyclotriveratrylene derivative for directed self-assembly of C60

    NASA Astrophysics Data System (ADS)

    Osner, Zachary R.; Nyamjav, Dorjderem; Holz, Richard C.; Becker, Daniel P.

    2011-07-01

    A novel apex-modified cyclotriveratrylene (CTV) derivative with an attached thiolane-containing lipoic acid linker was directly patterned onto gold substrates via dip-pen nanolithography (DPN). The addition of a dithiolane-containing linker to the apex of CTV provides a molecule that can adhere to a gold surface with its bowl-shaped cavity directed away from the surface, thereby providing a surface-bound CTV host that can be used for the directed assembly of guest molecules. Subsequent exposure of these CTV microarrays to C60 in toluene resulted in the directed assembly of predesigned, spatially controlled, high-density microarrays of C60. The molecular recognition capabilities of this CTV template toward C60 provides proof-of-concept that supramolecular CTV scaffolds can be directly patterned onto surfaces providing a foundation for the development of organic electronic and optoelectronic materials.

  16. Electronic Pair-Binding and Hund's Rule Violations in Doped C60

    NASA Astrophysics Data System (ADS)

    Jiang, Hong-Chen; Kivelson, Steven

    We calculate the electronic properties of the t-J model on a C60 molecule using the density-matrix renormalization group and show that Hund's first rule is violated and that for an average of three added electron per molecule, an effective attraction (pair-binding) arises for intermediate values of t=J. Specifically, it is energetically favorable to put four electrons on one C60 and two on a second rather than putting three on each. Our results show that a dominantly electronic mechanism of superconductivity is possible in doped C60. HCJ and SAK were supported by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract DE-AC02-76SF00515.

  17. Photon-exposure-dependent photon-stimulated desorption for obtaining photolysis cross section of molecules adsorbed on surface by monochromatic soft x-ray photons

    SciTech Connect

    Chou, L.-C.; Jang, C.-Y.; Wu, Y.-H.; Tsai, W.-C.; Wang, S.-K.; Chen, J.; Chang, S.-C.; Liu, C.-C.; Shai, Y.; Wen, C.-R.

    2008-12-07

    Photon-exposure-dependent positive- and negative-ion photon-stimulated desorption (PSD) was proposed to study the photoreactions and obtain the photolysis cross sections of molecules adsorbed on a single-crystal surface by monochromatic soft x-ray photons with energy near the core level of adsorbate. The changes in the F{sup +} and F{sup -} PSD ion yields were measured from CF{sub 3}Cl molecules adsorbed on Si(111)-7x7 at 30 K (CF{sub 3}Cl dose=0.3x10{sup 15} molecules/cm{sup 2}, {approx}0.75 monolayer) during irradiation of monochromatic soft x-ray photons near the F(1s) edge. The PSD ion yield data show the following characteristics: (a) The dissociation of adsorbed CF{sub 3}Cl molecules is due to a combination of direct photodissociation via excitation of F(1s) core level and substrate-mediated dissociation [dissociative attachment and dipolar dissociation induced by the photoelectrons emitting from the silicon substrate]. (b) the F{sup +} ion desorption is associated with the bond breaking of the surface CF{sub 3}Cl, CF{sub 2}Cl, CFCl, and SiF species. (c) the F{sup -} yield is mainly due to DA and DD of the adsorbed CF{sub 3}Cl molecules. (d) The surface SiF is formed by reaction of the surface Si atom with the neutral fluorine atom, F{sup +}, or F{sup -} ion produced by scission of C-F bond of CF{sub 3}Cl, CF{sub 2}Cl, or CFCl species. A kinetic model was proposed for the explanation of the photolysis of this submonolayer CF{sub 3}Cl-covered surface. Based on this model and the variation rates of the F{sup +}/F{sup -} signals during fixed-energy monochromatic photon bombardment at 690.2 and 692.6 eV[near the F(1s) edge], the photolysis cross section was deduced as a function of energy.

  18. Continuous-time core-level photon-stimulated desorption spectroscopy for monitoring soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface

    SciTech Connect

    Chou, L.-C.; Wen, C.-R.

    2006-05-15

    Continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was proposed for monitoring the soft x-ray-induced reactions of molecules adsorbed on a single-crystal surface. Monochromatic synchrotron radiation was used as a soft x-ray light source in the photon-induced reactions of CF{sub 3}Cl adsorbed on a Si(111)-7x7 surface at 30 K and also as a probe for studying the produced fluorination states of the bonding surface Si atom in the positive-ion PSD spectroscopy. The F{sup +} PSD spectrum was obtained by monitoring the F{sup +} signal as a function of incident photon energy near the Si(2p) edge (98-110 eV). Sequential F{sup +} PSD spectra were measured as a function of photon exposure at four adsorbate coverages (the first dose=0.3x10{sup 15} molecules/cm{sup 2}, the second dose=0.8x10{sup 15} molecules/cm{sup 2}, the third dose=2.2x10{sup 15} molecules/cm{sup 2}, and the fourth dose=3.2x10{sup 15} molecules/cm{sup 2}). For the first and second CF{sub 3}Cl-dosed surfaces, the sequential F{sup +} PSD spectra show the variation of their shapes with photon exposure and indicate the formation of surface SiF species. The sequential F{sup +} PSD spectra for the third and fourth CF{sub 3}Cl-dosed surfaces also show the variation of their shapes with photon exposure and depict the production of surface SiF and SiF{sub 3} species.

  19. C60-DOM interactions and effects on C60 apparent solubility: a molecular mechanics and density functional theory study.

    PubMed

    Wang, Zhuang; Chen, Jingwen; Sun, Qian; Peijnenburg, Willie J G M

    2011-08-01

    Dissolved organic matter (DOM) plays a critical role in the transport of carbon nano-particles (e.g. C(60)) in the aquatic environment. However, the mechanism for C(60)-DOM interactions and its environmental implications needs further investigations. In this study, the interaction of C(60) with relevant reference compounds of DOM (DOM(R)) is computationally simulated by molecular mechanics and density functional theory (DFT). All the C(60)-DOM(R) complexes are firstly optimized by classical annealing, and then DFT using the Dmol(3) code. The adsorption energies of C(60) on DOM(R) were computed. The computed electrostatic potential indicates that DOM(R) are electron acceptors in the C(60)-DOM(R) complexes, and the thermodynamic calculations indicate that electrostatic interaction is the dominant driving force for the C(60)-gallic acid complexation process in water. The presence of DOM(R) increases the apparent water solubility of C(60). It is also observed that the C(60) apparent water solubility decrease with the increase of the energy gaps of frontier molecular orbitals (E(LUMO)-E(HOMO)) for each C(60)-DOM(R) complex. These findings indicate that computational simulation is an important tool for predicting the behavior and fate of carbon nano-particles in the aquatic environment. PMID:21419494

  20. Epitaxial Templating of C60 with a Molecular Monolayer.

    PubMed

    Rochford, L A; Jones, T S; Nielsen, C B

    2016-09-01

    Commensurate epitaxial monolayers of truxenone on Cu (111) were employed to template the growth of monolayer and bilayer C60. Through the combination of STM imaging and LEED analysis we have demonstrated that C60 forms a commensurate 8 × 8 overlayer on truxenone/Cu (111). Bilayers of C60 retain the 8 × 8 periodicity of templated monolayers and although Kagome lattice arrangements are observed these are explained with combinations of 8 × 8 symmetry. PMID:27540868

  1. Preparation of C 60 single crystalline thin film by ionized cluster beam deposition and ion implantation into single crystalline C 60 thin film

    NASA Astrophysics Data System (ADS)

    Isoda, Satoru; Kawakubo, Hiroaki; Nishikawa, Satoshi; Wada, Osamu

    1996-05-01

    We have succeeded in preparing single crystalline C 60 thin film of a lateral extension in the order of several millimeters on mica by ionized cluster beam (ICB) deposition. During the growth process, planar dendrite-like single crystalline islands were observed by an atomic force microscope (AFM). It was concluded from reflection high-energy electron diffraction (RHEED) and transmission electron diffraction (TED) analyses that these islands grow hetero-epitaxially on mica. As the deposition process continues, the single crystalline islands coalesce and finally form a giant single crystal without grain boundaries between the former islands. This layered dendrite-like crystal growth is considered to be due to the ICB process, namely, ionizing molecules and accelerating them. Furthermore, the effect of ion (P +, B +, Ar +) implantation into C 60 thin films on the molecular structure and the conductivity has been studied under various implantation conditions. It was found from the analyses of FT-IR and Raman spectroscopies that the soccer-ball-like structure of C 60 changes into a diamond-like carbon (DLC) structure with an implantation energy higher than 40 keV, whereas the structure undergoes virtually no change with 10 keV implantation. As for conductivity changes under the lower implantation energy condition, the minimum dose of P + ions required to increase the conductivity from the non-doped value (10 12 cm -2) is 10 times lower than in the case of Ar + implantation. The conductivity change for the P + implantation could be explained satisfactorily not only by the effect of chemically-modified C 60 but also by the effect of a charge-transfer state between C 60 and implanted ions. It was concluded from these results that the conductivity of the C 60 film can be controlled over a wide range based on the carrier generation mechanism, which depends on the implantation conditions.

  2. When a nanoparticle meets a superhalogen: a case study with C60 fullerene.

    PubMed

    Sikorska, Celina

    2016-07-28

    The ability of a selected nanoparticle to form stable systems with superhalogens (i.e. AlF4, AlCl4, MgF3, MgCl3, LiF2, LiCl2, and LiI2) is examined on the basis of theoretical considerations supported by ab initio calculations. It is demonstrated that the C60 fullerene molecule should form stable and strongly bound (C60)˙(+)(superhalogen)(-) radical cation salts when combined with an appropriately chosen superhalogen radical (acting as an oxidizing agent). The conclusion is supported by providing: (i) the structural deformation of superhalogens and C60 nanoparticles upon ionization, (ii) predicted charge flow between the fullerene and each superhalogen (which allows estimating the amount of electron density withdrawn from the C60 molecule during the ionization process), (iii) the localization of the spin density distribution, and (iv) the interaction energies for the compounds obtained both at the B3LYP/6-31+G(d) level and at the B3LYP-D3/6-31+G(d) level. Solvent effects have been considered in the present study by means of the polarizable continuum model. It is found that the stability of C60/superhalogen species can be improved in solvents. We believe that the results provided in this contribution may likely be of prospective relevance in the future studies on the issue of binding and removal of this potentially risky nanoparticle. PMID:27346461

  3. Laboratory confirmation of C60(+) as the carrier of two diffuse interstellar bands.

    PubMed

    Campbell, E K; Holz, M; Gerlich, D; Maier, J P

    2015-07-16

    The diffuse interstellar bands are absorption lines seen towards reddened stars. None of the molecules responsible for these bands have been conclusively identified. Two bands at 9,632 ångströms and 9,577 ångströms were reported in 1994, and were suggested to arise from C60(+) molecules (ref. 3), on the basis of the proximity of these wavelengths to the absorption bands of C60(+) measured in a neon matrix. Confirmation of this assignment requires the gas-phase spectrum of C60(+). Here we report laboratory spectroscopy of C60(+) in the gas phase, cooled to 5.8 kelvin. The absorption spectrum has maxima at 9,632.7 ± 0.1 ångströms and 9,577.5 ± 0.1 ångströms, and the full widths at half-maximum of these bands are 2.2 ± 0.2 ångströms and 2.5 ± 0.2 ångströms, respectively. We conclude that we have positively identified the diffuse interstellar bands at 9,632 ångströms and 9,577 ångströms as arising from C60(+) in the interstellar medium. PMID:26178962

  4. Computer simulations of the Adsorption of Xenon onto a C60 monolayer on Ag (111)

    NASA Astrophysics Data System (ADS)

    Gatica, Silvina; Cole, Milton; Diehl, Renee

    2007-03-01

    We performed Grand Canonical Monte Carlo simulations to study the adsorption of Xenon on a substrate composed of C60 molecules placed on top of a Ag(111) surface. The C60 molecules form a commensurate structure at a distance of 0.227 nm above the Ag surface. The interaction potential between the Xe atoms and the substrate has two contributions: from the C60 molecules and from the Ag atoms. In the simulations, the interaction with the Ag surface was computed using an ab initio van der Waals potential, varying as 1/d^3. The interaction between the Xe atoms and each C60 molecule was computed using a potential previously developed by Hernandez et.al. (E. S. Hernandez, M. W. Cole and M. Boninsegni, ``Wetting of spherical surfaces by quantum fluids'', J. Low Temp. Phys. 134, 309-314 (2004)), who integrated the Lennard Jones interaction over the surface of a spherical buckyball. The total potential has especially attractive 3-fold sites, positioned 0.4 nm above the point between each three buckyballs. The low coverage uptake populates those sites, and then continues forming a monolayer. The adsorption isotherms show several steps, typical of substrates that have distinct adsorption sites. We compare the results with the experimental data.

  5. Synthesis and characterization of tetrakis-silylated C60 isomers.

    PubMed

    Maeda, Yutaka; Rahman, G M Aminur; Wakahara, Takatsugu; Kako, Masahiro; Okamura, Mutsuo; Sato, Soichi; Akasaka, Takeshi; Kobayashi, Kaoru; Nagase, Shigeru

    2003-08-22

    A photochemical reaction of C(60) with disilane in a 2:3 ratio affords the isomer mixture of the tetrakis-adduct of C(60)((t)BuPh(2)Si)(4) as the major product. The use of a three-stage HPLC separation system isolated three of their isomers. Their structural assignments were based on FAB mass, UV-vis, NMR, and cyclic voltammetry (CV) measurements. The CV analysis showed that the terakis-adduct has lower oxidation and higher reduction potentials than the bis-adduct C(60)((t)BuPh(2)Si)(2) and the parent C(60). PMID:12919050

  6. Photoexcitation of a volume plasmon in C60 ions

    SciTech Connect

    Scully, S.W.J.; Emmons, E.D.; Gharaibeh, M.F.; Phaneuf, R.A.; Kilcoyne, A.L.D.; Schlachter, A.S.; Schippers, S.; Muller, A.; Chakraborty, H.S.; Madjet, M.E.; Rost, J.M.

    2005-06-21

    Neutral C60 is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for C60(sup+), C60(sup2+), and C60(sup3+) ions in the 17 75eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.

  7. Self-assembling of C60-imidazole and C60-pyridine adducts in the Langmuir and Langmuir-Blodgett films via complex formation with water-soluble zinc porphyrins

    NASA Astrophysics Data System (ADS)

    Marczak, Renata; Noworyta, Krzysztof; Kutner, Wlodzimierz; Gadde, Suresh; D'Souza, Francis

    2003-10-01

    The C60-pyridine, C60py, and C60-imidazole, C60im, adducts were found to self-assemble in films floating onto aqueous solutions of zinc tetrakis (N-methylpyridinium)porphyrin cation, Zn(TMPyP), or zinc tetrakis (4-sulfonatophenyl)porphyrin anion, Zn(TPPS). This self assembling was due to axial ligation of the C60 adducts (acceptors) by Zn porphyrins (donors), which lead to the formation of relatively stable donor-acceptor dyads in the water-air interfaces. The films were compressed in a Langmuir trough and characterized by isotherms of surface pressure vs. area per molecule as well as by the Brewster angle microscopy imaging. All systems formed stable aggregated Langmuir films of the "expanded liquid" type. Extensive compression of the films resulted in two-dimensional phase transitions. The area per molecule at infinite dilution of the adducts in films increased in the order: water<0.1 mM Zn(TPPS)<0.1 mM Zn(TPMyP). Comparison of the determined and calculated values of area per molecule indicated that orientation of porphyrins in the complexes was parallel with respect to the interface plane. The Langmuir films were transferred, by using the Langmuir-Blodgett technique, onto quartz slides. The UV-vis spectroscopic study of these films revealed that Zn porphyrins were transferred together with the C60 adducts and that the transfer efficiency increased in the order: C60py-Zn(TPPS)<C60py-Zn(TMPyP)<C60im-Zn(TPPS)<C60im-Zn(TMPyP), i.e., in accord with the increase of stability of the respective dyads in solutions.

  8. Analyses of the Binding between Water Soluble C60 Derivatives and Potential Drug Targets through a Molecular Docking Approach

    PubMed Central

    Liu, Junjun; Zhang, Houjin

    2016-01-01

    Fullerene C60, a unique sphere-shaped molecule consisting of carbon, has been proved to have inhibitory effects on many diseases. However, the applications of C60 in medicine have been severely hindered by its complete insolubility in water and low solubility in almost all organic solvents. In this study, the water-soluble C60 derivatives and the C60 binding protein’s structures were collected from the literature. The selected proteins fall into several groups, including acetylcholinesterase, glutamate racemase, inosine monophosphate dehydrogenase, lumazine synthase, human estrogen receptor alpha, dihydrofolate reductase and N-myristoyltransferase. The C60 derivatives were docked into the binding sites in the proteins. The binding affinities of the C60 derivatives were calculated. The bindings between proteins and their known inhibitors or native ligands were also characterized in the same way. The results show that C60 derivatives form good interactions with the binding sites of different protein targets. In many cases, the binding affinities of C60 derivatives are better than those of known inhibitors and native ligands. This study demonstrates the interaction patterns of C60 derivatives and their binding partners, which will have good impact on the fullerene-based drug discovery. PMID:26829126

  9. C60 chain phases on ZnPc/Ag(111) surfaces: Supramolecular organization driven by competing interactions.

    PubMed

    Jin, W; Liu, Q; Dougherty, D B; Cullen, W G; Reutt-Robey, J E; Weeks, J; Robey, S W

    2015-03-14

    Serpentine chain C60 phases were observed in scanning tunneling microscopy (STM) images of C60 layers on zinc phthalocyanine (ZnPc) or pentacene covered Ag(111) and Au(111) surfaces. This low-density, quasi-one-dimensional organization contrasts starkly with the close-packed hexagonal phases observed for C60 layers on bare metal substrates. STM was employed to perform a detailed investigation of these chain structures for C60/ZnPc/Ag(111) heterolayers. Motivated by the similarity of these chain phases, and the chain and stripe organization occurring in dipole-fluid systems, we investigated a model based on competing van der Waals attractions and electrostatic repulsions between C60 molecules as an explanation for the driving force behind these monolayer phases. Density functional theory (DFT) calculations revealed significant charge transfer to C60 from the Ag(111) substrate, through the intervening ZnPc layer, inducing electrostatic interactions between C60 molecules. Molecular dynamics simulations performed with attractive van der Waals interactions plus repulsive dipole-dipole interactions reproduced the C60 chain phases with dipole magnitudes consistent with DFT calculations. PMID:25770499

  10. C60 chain phases on ZnPc/Ag(111) surfaces: Supramolecular organization driven by competing interactions

    NASA Astrophysics Data System (ADS)

    Jin, W.; Liu, Q.; Dougherty, D. B.; Cullen, W. G.; Reutt-Robey, J. E.; Weeks, J.; Robey, S. W.

    2015-03-01

    Serpentine chain C60 phases were observed in scanning tunneling microscopy (STM) images of C60 layers on zinc phthalocyanine (ZnPc) or pentacene covered Ag(111) and Au(111) surfaces. This low-density, quasi-one-dimensional organization contrasts starkly with the close-packed hexagonal phases observed for C60 layers on bare metal substrates. STM was employed to perform a detailed investigation of these chain structures for C60/ZnPc/Ag(111) heterolayers. Motivated by the similarity of these chain phases, and the chain and stripe organization occurring in dipole-fluid systems, we investigated a model based on competing van der Waals attractions and electrostatic repulsions between C60 molecules as an explanation for the driving force behind these monolayer phases. Density functional theory (DFT) calculations revealed significant charge transfer to C60 from the Ag(111) substrate, through the intervening ZnPc layer, inducing electrostatic interactions between C60 molecules. Molecular dynamics simulations performed with attractive van der Waals interactions plus repulsive dipole-dipole interactions reproduced the C60 chain phases with dipole magnitudes consistent with DFT calculations.

  11. Growth and Potential Damage of Human Bone-Derived Cells Cultured on Fresh and Aged C60/Ti Films

    PubMed Central

    Kopova, Ivana; Lavrentiev, Vasily; Vacik, Jiri; Bacakova, Lucie

    2015-01-01

    Thin films of binary C60/Ti composites, with various concentrations of Ti ranging from ~ 25% to ~ 70%, were deposited on microscopic glass coverslips and were tested for their potential use in bone tissue engineering as substrates for the adhesion and growth of bone cells. The novelty of this approach lies in the combination of Ti atoms (i.e., widely used biocompatible material for the construction of stomatological and orthopedic implants) with atoms of fullerene C60, which can act as very efficient radical scavengers. However, fullerenes and their derivatives are able to generate harmful reactive oxygen species and to have cytotoxic effects. In order to stabilize C60 molecules and to prevent their possible cytotoxic effects, deposition in the compact form of Ti/C60 composites (with various Ti concentrations) was chosen. The reactivity of C60/Ti composites may change in time due to the physicochemical changes of molecules in an air atmosphere. In this study, we therefore tested the dependence between the age of C60/Ti films (from one week to one year) and the adhesion, morphology, proliferation, viability, metabolic activity and potential DNA damage to human osteosarcoma cells (lines MG-63 and U-2 OS). After 7 days of cultivation, we did not observe any negative influence of fresh or aged C60/Ti layers on cell behavior, including the DNA damage response. The presence of Ti atoms resulted in improved properties of the C60 layers, which became more suitable for cell cultivation. PMID:25875338

  12. Electron spin resonance study of Rb xC 60 and K xC 60 powders

    NASA Astrophysics Data System (ADS)

    Feng, S. Q.; Jia, Y. Q.; Zhu, S. L.; Fu, J. S.; Wu, E.; Mao, J. C.; Han, R. S.; Gu, Z. N.; Zhou, X. H.; Jin, Z. X.

    1993-11-01

    Rb and K doped C 60 compounds are prepared by the vapor-solid reaction method. Superconductive shielding fraction is determined as 35-75% for Rb xC 60 and 10% for K xC 60. Electron spin resonance (ESR) measurements in absorption mode are performed in the temperature range of 5-300 K. A strong ESR signal at g=2.002 for Rb xC 60 and g=2.003 for K xC 60 has been observed. The g-value is nearly independent upon temperature for both Rb xC 60 and K xC 60 while the linewidth behaves differently, increasing from 2.0 G at 5 K to 6.0 G at 250 K in Rb xC 60 and remaining constant of 2.3 G in K xC 60. No drastic change of the ESR spectra is observed with the onset of superconductivity, leading to a conclusion that the observed dominant ESR signal originates from a non-superconducting phase.

  13. Pseudotenfold symmetry in pentane-solvated C60 and C70

    NASA Astrophysics Data System (ADS)

    Fleming, R. M.; Kortan, A. R.; Hessen, B.; Siegrist, T.; Thiel, F. A.; Marsh, P.; Haddon, R. C.; Tycko, R.; Dabbagh, G.; Kaplan, M. L.; Mujsce, A. M.

    1991-07-01

    Crystals of C60 or C70 cocrystallized with n-pentane grow as elongated, ten-sided columns. X-ray diffraction shows ordering of C60 or C70 molecules along the column and a remarkable tenfold symmetry normal to the column. The ratio of the x-ray-diffraction vectors of the two lowest-order diffraction spots is nearly equal to the ``golden ratio,'' τ. Despite these similarities with decagonal, quasicrystalline order, the diffraction indicates crystalline order with a twinned unit cell.

  14. [Stability of C60 nanoparticles in aquatic systems].

    PubMed

    Fang, Hua; Shen, Bing-Bing; Jing, Jie; Lu, Ji-Lai; Wang, Yuan

    2014-04-01

    The influences of storage time, pH, electrolytes and organic matters on the stability of two different suspensions of C60 nanoparticles were investigated. The results showed that the C60 nanoparticles prepared by solvent substitution (C60/son) were more stable than that prepared by prolonged stirring (C60/aq), and kept stable for a period of time. Higher pH enhanced the stability of C60 nanoparticles. The presence of electrolyte made a dramatic decrease in the surface zeta potential and an increase in the particle size. The aggregation process of C60 nanoparticles exhibited slow and rapid regions, which was found to be consistent with the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. The critical coagulation concentration (CCC) values of C60/son, obtained from the intersection of the interpolated lines through the slow and fast regions, were estimated as 321 mmol x L(-1) NaCl, 316 mmol x L(-1) KCl, 9.6 mmol x L(-1) MgCl2 and 6.7 mmol x L(-1) CaCl2. The CCC values of C60/aq were estimated as 295 mmol x L(-1) NaCl, 278 mmol x L(-1) KCl, 7.8 mmol x L(-1) MgCl2 and 5.9 mmol x L(-1) CaCl2, which were much higher than their concentrations in natural waters. The presence of humic acid enhanced the stability of C60 nanoparticles, which was attributable to steric repulsion. Therefore, C60 nanoparticles will keep relatively stable in typical aquatic environments. PMID:24946585

  15. Infrared Spectroscopy and Catalysis Research: Infrared spectra of adsorbed molecules provide important information in the study of catalysis.

    PubMed

    Eischens, R P

    1964-10-23

    The examples discussed here represent only a small part of the published work relating to infrared spectra of adsorbed molecules. The publications in this field indicate that infrared spectroscopy is being used for surface chemistry research in about 50 laboratories throughout the world. This effort is mainly devoted to problems related to catalysis, and in this field infrared spectroscopy is the most widely used physical tool for surface chemistry studies. The general acceptance of infrared spectroscopy is primarily due to the fact that it provides information which is pertinent to the understanding of surface reactions on an atomic scale. During the last decade significant progress has also been made in the classical chemical techniques of catalysis study and in utilization of physical tools which depend on phenomena of magnetism, conductivity, low-energy electron diffraction, and electron emission. Probably the most important progress has been in the field of inorganic chemistry, where dramatic advances have been made in knowledge of metal coordination compounds. Such knowledge is vital to the understanding of catalysis on metal surfaces. I believe this progress has produced an attitude of sophisticated optimism among catalysis researchers with regard to eventual understanding of heterogeneous catalysis. This attitude is closely related to the realization that there is no "secret of catalysis" which places catalytic action beyond the limits of ordinary chemical knowledge (22). This view implies that the chemical aspects of heterogeneous catalysis are not unique and that the use of solid catalysts merely provides a highly effective exposure of catalytic atoms and facilitates separation of the products from the catalyst. Many capable catalysis researchers believe that studies of homogeneous catalysis provide the most direct route for the study of heterogeneous catalysis. Obviously homogeneous reactions catalyzed by compounds containing only one or two metal atoms

  16. Carbon fullerenes (C60s) can induce inflammatory responses in the lung of mice

    SciTech Connect

    Park, Eun-Jung; Kim, Hero; Kim, Younghun; Yi, Jongheop; Choi, Kyunghee; Park, Kwangsik

    2010-04-15

    Fullerenes (C60s) occur in the environment due to natural and anthropogenic sources such as volcanic eruptions, forest fires, and the combustion of carbon-based materials. Recently, production and application of engineered C60s have also rapidly increased in diverse industrial fields and biomedicine due to C60' unique physico-chemical properties, so toxicity assessment on environmental and human health is being evaluated as a valuable work. However, data related to the toxicity of C60s have not been abundant up to now. In this study, we studied the immunotoxic mechanism and change of gene expression caused by the instillation of C60s. As a result, C60s induced an increase in sub G1 and G1 arrest in BAL cells, an increase in pro-inflammatory cytokines such as IL-1, TNF-alpha, and IL-6, and an increase of Th1 cytokines such as IL-12 and IFN-r in BAL fluid. In addition, IgE reached the maximum at 1 day after treatment in both BAL fluid and the blood, and decreased in a time-dependent manner. Gene expression of the MHC class II (H2-Eb1) molecule was stronger than that of the MHC class I (H2-T23), and an increase in T cell distribution was also observed during the experiment period. Furthermore, cell infiltration and expression of tissue damage related genes in lung tissue were constantly observed during the experiment period. Based on this, C60s may induce inflammatory responses in the lung of mice.

  17. Fullerene C60 as a multifunctional system for drug and gene delivery

    NASA Astrophysics Data System (ADS)

    Montellano, Alejandro; da Ros, Tatiana; Bianco, Alberto; Prato, Maurizio

    2011-10-01

    The fullerene family, and especially C60, has delighted the scientific community during the last 25 years with perspective applications in a wide variety of fields, including the biological and the biomedical domains. Several biomedical uses have been explored using water-soluble C60-derivatives. However, the employment of fullerenes for drug delivery is still at an early stage of development. The design and synthesis of multifunctionalized and multimodal C60 systems able to cross the cell membranes and efficiently deliver active molecules is an attracting challenge that involves multidisciplinary strategies. Promising results have emerged in the last years, bringing fullerenes again to the front of interest. Herein, the state of the art of this emerging field is presented and illustrated with some of the most representative examples.

  18. Disclinations in C60 molecular layers on WO2/W (110 ) surfaces

    NASA Astrophysics Data System (ADS)

    Bozhko, S. I.; Taupin, V.; Lebyodkin, M.; Fressengeas, C.; Levchenko, E. A.; Radikan, K.; Lübben, O.; Semenov, V. N.; Shvets, I. V.

    2014-12-01

    A scanning tunneling microscopy study of a planar close-packed C60 hexagonal molecular layer on a WO2/W (110 ) substrate reveals the existence of C60 domains exhibiting two preferred orientations at an angle with an underlying periodic groove structure in the substrate. An analysis of the van der Waals interactions between substrate and layer retrieves the observed misorientations as those corresponding to minima in the interaction energy of the substrate-layer system. The misorientation between two C60 domains is accommodated in a tilt boundary by a linear array of molecular structural units identified as disclination dipoles, i.e., rotational defects in the hexagonal structure of the layer. A field theory of disclinations and dislocations is used to construct maps of the elastic energy, strains, curvatures, and stresses induced by the lattice defects over the layer. The predicted regions of high compression are found to overlap with those where the fullerene molecules do not undergo rotation.

  19. Experimental and theoretical determination of the magnetic susceptibility of C60 and C70

    NASA Astrophysics Data System (ADS)

    Haddon, R. C.; Schneemeyer, L. F.; Waszczak, J. V.; Glarum, S. H.; Tycko, R.; Dabbagh, G.; Kortan, A. R.; Muller, A. J.; Mujsce, A. M.; Rosseinsky, M. J.; Zahurak, S. M.; Makhija, A. V.; Thiel, F. A.; Raghavachari, K.; Cockayne, E.; Elser, V.

    1991-03-01

    THE magnetic susceptibility of C60 and the possibility of magnetic-field-induced π-electron ring currents in this carbon spheroid have been of interest since the initial experiments on carbon clusters1. If the molecule is regarded as a sphere with a radius of 3.5 Å, on which 60 electrons are free to move, the Pauling ring-current model predicts a ring-current diamagnetic susceptibility 41 times the π-electron ring-current magnetic susceptibility of benzene with the field normal to the plane of the six-membered ring2,3. London theory predicts, however, that the π-electron ring currents in C60 should be weakly paramagnetic or diamagnetic, depending on the relative bond strengths used in the calculation2,3. With the availability of macroscopic quantities of C60 (ref. 4), it is now possible to study experimentally the magnetic properties of the molecule. Here we report on such measurements. We find that the diamagnetism of C60 is small, a result that we attribute to excited-state paramagnetic contributions to the π-electron ring-current magnetic susceptibility. Thus C60 seems to be an aromatic molecule with a vanishingly small π-electron ring-current magnetic susceptibility. We have performed similar measurements on C70, which indicate an appreciable π-electron diamagnetism, consistent with theoretical calculations. We attribute the differences in magnetic properties of these two molecules to their different fractions of five-membered ring structures. The fullerenes may thus constitute a class of compounds of 'ambiguous' aromatic character, traditional measures of which will not provide an adequate classification.

  20. Axis-dependent magnetic behavior of C60 and C60(10+). consequences of spherical aromatic character.

    PubMed

    Muñoz-Castro, A

    2015-06-28

    The magnetic response of C60 has been studied and compared to its spherical aromatic counterpart C60(10+), focusing on the overall and local shielding tensors. A high axis dependence behavior at the outside region of the structure is characterized, unravelling a characteristic pattern of the local chemical shift anisotropy as a consequence of the spherical aromatic behavior. PMID:26022142

  1. Addition reaction of alkyl radical to C60 fullerene: Density functional theory study

    NASA Astrophysics Data System (ADS)

    Tachikawa, Hiroto; Kawabata, Hiroshi

    2016-02-01

    Functionalized fullerenes are known as a high-performance molecules. In this study, the alkyl-functionalized fullerenes (denoted by R-C60) have been investigated by means of the density functional theory (DFT) method to elucidate the effects of functionalization on the electronic states of fullerene. Also, the reaction mechanism of alkyl radicals with C60 was investigated. The methyl, ethyl, propyl, and butyl radicals (denoted by n = 1-4, where n means the number of carbon atoms in the alkyl radical) were examined as alkyl radicals. The DFT calculation showed that the alkyl radical binds to the carbon atom of C60 at the on-top site, and a strong C-C single bond is formed. The binding energies of alkyl radicals to C60 were distributed in the range of 31.8-35.1 kcal mol-1 at the CAM-B3LYP/6-311G(d,p) level. It was found that the activation barrier exists before alkyl addition, the barrier heights were calculated to be 2.1-2.8 kcal mol-1. The electronic states of R-C60 complexes were discussed on the basis of the theoretical results.

  2. Relative Photoionization Cross Sections of Super-Atom Molecular Orbitals (SAMOs) in C60.

    PubMed

    Bohl, Elvira; Sokół, Katarzyna P; Mignolet, Benoit; Thompson, James O F; Johansson, J Olof; Remacle, Francoise; Campbell, Eleanor E B

    2015-11-25

    The electronic structure and photoinduced dynamics of fullerenes, especially C60, is of great interest because these molecules are model systems for more complex molecules and nanomaterials. In this work we have used Rydberg Fingerprint Spectroscopy to determine the relative ionization intensities from excited SAMO (Rydberg-like) states in C60 as a function of laser wavelength. The relative ionization intensities are then compared to the ratio of the photoionization widths of the Rydberg-like states, computed in time-dependent density functional theory (TD-DFT). The agreement is remarkably good when the same photon order is required to energetically access the excited states. This illustrates the predictive potential of quantum chemistry for studying photoionization of large, complex molecules as well as confirming the assumption that is often made concerning the multiphoton excitation and rapid energy redistribution in the fullerenes. PMID:26551039

  3. Shock compression and equation of state of C60 fullerite

    NASA Astrophysics Data System (ADS)

    Milyavskiy, Vladimir; Khishchenko, Konstantin; Utkin, Alexander; Yakushev, Vladislav; Zhuk, Andrey; Fortov, Vladimir

    2007-06-01

    Recently, we have experimentally studied shock compressibility of C60 fullerite and sound velocity in shock-compressed fullerite [1]. The Hugoniot of C60 fullerite had a set of peculiarities. Appearance of a rather hard carbon phase was detected at shock pressure ˜ 9 GPa. We assume that it is a 2D-polymerized C60 phase. With increase of shock pressure, destruction of this phase and formation of a graphite-like carbon occurs. With further increase of shock pressure, the graphite- like carbon transforms to a diamond-like phase. If shock pressure is higher than ˜ 33 GPa, shock compressibility of C60 fullerite is determined by the thermodynamic properties of the diamond-like phase. The results of the shock-wave measurements were used for the description of thermodynamic properties of C60 fullerite and products of its transformations in a wide range of pressures and temperatures. A semiempirical equation of state for the simple cubic phase of C60 fullerite is proposed. The EOS we have developed for fullerite C60 provides a consistent representation of the available experimental data. The work was supported by RFBR. [1] Milyavskiy V.V., Utkin A.V., Zhuk A.Z., Yakushev V.V. and Fortov V.E. Diamond and Rel. Mat. 14 (2005) 1920.

  4. C60 fullerene soil sorption, biodegradation, and plant uptake.

    PubMed

    Avanasi, Raghavendhran; Jackson, William A; Sherwin, Brie; Mudge, Joseph F; Anderson, Todd A

    2014-01-01

    Assessments of potential exposure to fullerenes and their derivatives in the environment are important, given their increasing production and use. Our study focused on fate processes that determine the movement and bioavailability of fullerenes in soil. We evaluated the sorption, biodegradation, and plant uptake of C60 fullerene using (14)C-labeled C60 solutions in water produced by either solvent exchange with tetrahydrofuran or sonication/extended mixing in water. Organic carbon appeared to have an important influence on C60 soil sorption. The log Koc values for (14)C60 were equivalent for sandy loam and silt loam (3.55 log[mL/g]) but higher for loam (4.00 log[mL/g]), suggesting that other factors, such as pH, clay content and mineralogy, and cation exchange capacity, also influence C60 soil sorption. There was little (14)CO2 production in the silt loam or the sandy loam soil after 754 and 328 days, respectively, suggesting high resistance of C60 to mineralization in soil. Plant uptake was generally low (∼7%), with most of the uptaken (14)C accumulating in the roots (40-47%) and smaller amounts of accumulation in the tuber (22-23%), stem (12-16%), and leaves (18-22%). Our results indicate that C60 released to the environment will not be highly bioavailable but will likely persist in soil for extended periods. PMID:24521447

  5. Observation and analysis of Fano-like lineshapes in the Raman spectra of molecules adsorbed at metal interfaces

    NASA Astrophysics Data System (ADS)

    Dey, S.; Banik, M.; Hulkko, E.; Rodriguez, K.; Apkarian, V. A.; Galperin, M.; Nitzan, A.

    2016-01-01

    Surface-enhanced Raman scattering (SERS) from bipyridyl ethylene adsorbed on gold dumbbells shows Fano-like spectra at high incident light intensity. This is accompanied by an increased electronic temperature, while no vibrational anti-Stokes scattering is observed. Theory indicates that interference between vibrational and electronic Raman scattering can yield such asymmetric scattering lineshapes. The best fit to observations is however obtained by disregarding this coupling and accounting for the detailed lineshape of the continuous electronic component of the SERS.

  6. High-T c superconductivity in potassium-doped fullerene, K xC 60, via coupled C 60 (pπ) cluster molecular orbitals and dynamic Jahn-Teller coupling

    NASA Astrophysics Data System (ADS)

    Johnson, K. H.; McHenry, M. E.; Clougherty, D. P.

    1991-11-01

    Recently observed superconductivity at 18 K in potassium-doped fullerene, K xC 60, may be due to Cooper pairing of partially occupied icosahedral C 60 cluster t 1u (pπ) molecular orbitals, induced by cooperative dynamic Jahn-Teller coupling of these orbitals to “soft-mode” vibrations of the C 60 molecules, leading to a BCS-like mechanism. Predicted are a nonvanishing isotope effect and Tc increasing to 30 K or more with optimization of doping, and significant effects with pressure.

  7. Crystallinity and properties of C60 nanotubes improved by annealing and alcohol-soaking

    NASA Astrophysics Data System (ADS)

    Naito, K.; Matsuishi, K.

    2009-04-01

    Well-uniformed C60 nanotubes were grown at -20 °C with irradiation of red light using C60-saturated pyridine solution and isopropyl alcohol by a liquid-liquid interfacial precipitation method without ultrasonic pulverization. We attempted to improve their crystallinity by two post-treatments; thermal annealing and alcohol-soaking. The crystallinity of as-grown and dried C60 nanotubes, which was poor due to the evaporation of solvent molecules from crystals in the drying process, was improved by annealing around 220 °C for 5 hours in vacuum. Dramatic improvement of crystallinity of as-grown samples was achieved by soaking into methanol and then drying in air. Raman, infrared and X-ray diffraction results suggest that the methanol-soaked samples exhibit a solvated tetragonal structure. The crystallinity improved by methanol-soaking did not degrade after removal of methanol molecules from samples by thermal annealing. Photo-polymerization of the structurally-improved C60 nanotubes was examined to investigate an effect of crystallinity on the polymerization kinetics.

  8. Dependence of the band structure of C-60 monolayers on molecularorientations and doping observed by angle resolved photoemission

    SciTech Connect

    Brouet, V.; Yang, W.L.; Zhou, X.J.; Hussain, Z.; Shen, Z.X.

    2008-01-17

    We present angle resolved photoemission studies of C60monolayers deposited on Ag surfaces. The electronic structure of thesemonolayers is derived from the partial filling of the narrow, 6-folddegenerated, C60 conduction band. By comparing the band structure in twomonolayers deposited, respectively, on Ag(111) and Ag(100), we show thatthe molecular degree of freedom, in this case the relative orientationsbetween C60 molecules, is essential to describe the band structure. Wefurther show that the evolution of the band as a function of doping doesnot follow a rigid band-filling picture. Phase separation is observedbetween a metallic and an insulating phase, which might be a result ofstrong correlations.

  9. Aggregation and Deposition of C60 in Aqueous Systems

    EPA Science Inventory

    The extremely low water solubility of many fullerenes precludes aqueous solution processing for engineering applications and minimizes the potential for fullerene environmental effects in aqueous environments. However, studies have shown that C60 fullerene can form stable colloi...

  10. Structure and photophysics in C 60-micellar solutions

    NASA Astrophysics Data System (ADS)

    Eastoe, Julian; Crooks, Esther R.; Beeby, Andrew; Heenan, Richard K.

    1995-11-01

    Routes to the preparation of monomeric and colloidal C 60 in micellar solutions of non-ionic surfactants are described. UV-visible spectra and small-angle neutron scattering provide clear evidence for these two different forms. The micelles serve to stabilise the excited triplet state 3C 60 and the lifetime τT is increased by a factor of 3 as compared to 3C 60 in toluene. Furthermore, with monomeric dispersions in the presence of the electron donor DABCO, the radical anion C 60- is formed, with an unusually long lifetime τA = 16 ms. This lifetime is approximately 270 times longer than for γ-cyclodextrin. stabilised systems.