Properties Of C60 Research Articles

Thermal and Tribological Properties of Fullerene‐Containing Composite Systems. Part 1. Thermal Stability of Fullerene‐Polymer Systems

The techniques of mass‐spectrometric thermal analysis, differential scanning calorimetry, differential thermogravimetry, and wide‐angle x‐ray analysis of thermal and oxidative degradation of two types of fullerene‐containing polymer systems (FCPS) were studied: 1) FCPS with covalent interaction of fullerene C60 with polymers; 2) FCPS representing mixtures of C60 with polymers in which interaction of components is realized only by means of Van‐der‐Waals' forces. In both types of FCPS the electron acceptation properties of C60 are manifested. In some systems of the first type, a great decrease in thermal stability of a polymer component was observed; in systems of the second type the ability of fullerene C60 to play a role of “trap” of free radicals is especially manifested. The polymer matrix also influences the thermal behavior of fullerene C60. In particular, fullerene can serve as a specific “probe” of chemical processes that occur during thermal degradation of a polymer. Different polystyrenes and poly(methyl methacrylate)s containing 1–10 mass% C60 (FCPS) were investigated.

Interaction Between C60 and Gases under Pressure

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Interaction between C60 and gases under pressure

A brief review is given of the interaction between fullerite C60 and various gases under elevated pressure. Subjects discussed include the formation of ordered interstitial gas-fullerene compounds, reactions between intercalated gases and fullerene molecules to form new endohedral and exohedral compounds, and changes in the structure and properties of C60 because of intercalated gas atoms or molecules.

Preparation of C 60 bonded Poly(N-vinylcarbazole) with C 60 Cln/CuCl/Bpy catalyst system

C60 bonded poly(N-vinylcarbazole) has been synthesized by C60Cln (the average value of n is 20)/CuCl/2,2'-bipyridine (Bpy) catalyst system and its structure was analyzed by UV-Vis and proton NMR. The polymerization mechanism was proposed proceeding via an atom transfer radical polymerization (ATRP). The photoconducting properties of C60 bonded poly(N-vinylcarbazole) was better than poly(N-vinylcarbazole) initiated by AIBN.

Photophysics of C 60 and C 60 - in faujasite zeolites

While the intercalation of C60 and the formation of C 60 - in the supercages of NaX and NaY are confirmed by using 129Xe NMR and ESR, the photophysical properties of C60 and C 60 - are characterized by monitoring transient reflectance spectra and kinetics, fluorescence kinetics, and diffuse reflectance spectra. C 60 - is considerably more abundant in NaY than in NaX. This difference is explained in terms of polarity difference between two zeolites. Both C60 and C 60 - have remarkably elongated excited-state lifetimes due to their collision-free environment in zeolitic nanocavities although C 60 - has much shorter lifetimes than C60. C 60 - , in particular, shows intense absorption and emission due to its reduced symmetry in zeolites.

Intercalation of O2 and its Effect on the Properties of C60 and C70 Solids

The intercalation of O2 in C60 and C70 solids have been studied. In both gas effusion spectra of C60 and C70 powder exposed to O2 at room temperature, two evolution peaks of O2 are found near 80 and 150°C. In both C60 and C70 powder, the peak near 80°C does not depend on a heating ratio and the peak near 150°C shifts to higher temperature with the heating ratio. The activation energy on diffusion of O2 in C60 and C70 solids are ∼0.27eV and ∼0.46eV, respectively. The number of O2 intercalated in C70 powder is larger than that in C60 powder. Electron spin density of 02-intercalated C60 film is larger than that of C70 film. The effect on the properties of C60 and C70 solids by the intercalation of O2 are discussed.

Excitonic effects in linear and nonlinear optical properties ofC60

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Fullerenes under high pressures

This paper reviews the properties and phases of fullerenes and their derivatives and compounds under high pressures. For obvious reasons most of the paper deals with C60 but the materials reviewed also include C70, simple derivatives of C60, carbon nanotubes, and intercalation compounds of C60 with both acceptors and donors, mainly alkali metals. After a brief overview of high-pressure techniques and the structures and properties of C60 at atmospheric pressure, the structural phase diagram of C60 from atmospheric pressure to above 40GPa (400kbar) is reviewed. The evolution with pressure of the orientational and translational structure of 'normal' molecular C60 in the range up to 1-5GPa (depending on temperature) is discussed in some detail, as is the appearance of a large number of polymeric phases at higher pressures and temperatures, some of them known to have extreme mechanical properties. At very high static (or shock) pressures or temperatures, C60 transforms into ordered or disordered forms of diamond or graphite. The phase diagram is reasonably well investigated up to near 10GPa, but at higher pressures there are still large gaps in our knowledge. Available experimental data for the physical properties of both monomeric and polymeric C60 under high pressures are reviewed as far as possible. The compression behaviour of C60 has been well investigated and is discussed in detail because of its basic importance, but optical, electrical and lattice properties have also been studied for several of the many structural phases of C60. Whenever possible, experimental data are compared with the results of theoretical calculations. The phase diagram and properties of C70 are much less known because of the larger complexity caused by the anisotropy of the molecule, and very little is known about most compounds of C60. However, noble-gas intercalation in C60 has been reasonably well investigated. Finally, the high-pressure properties of superconducting alkali-metalintercalated C60 are briefly reviewed.

Possibility of the Existence of Non-Carbon Fullerenes: Ab Initio HF and DFT/B3LYP Studies of the IV Main Group Fullerene-Like Species

A comprehensive investigation of the equilibrium geometries, cohesive energies, and electronic properties of the IV main group fullerene-like compounds C60, Si60, Ge60, Sn60, and Pb60, has been performed by ab initio molecular modeling at the HF/Lanl1DZ and B3LYP/Lanl1DZ levels. In addition, the effect of the basis set on the structure and properties of C60 and Si60 has been examined at the STO-3G, Lanl1DZ, and 6-31G(d) levels. Our calculations confirmed the possibility of the existence of these species. It was found that the values of the relative bond alternation, cohesive energy, HOMO−LUMO gap, and the ionization potential of the molecules decrease monotonically in going down the IVth group from C60 to Pb60. The obtained data for Ge60 is rather similar to the one for Si60, and also the molecular parameters for Sn60 are close to the appropriate values both for Si60 and Ge60.

Optical Properties from Composites of C60 and FAU Zeolite

We have investigated the photophysical properties of C60 (guest)-FAU zeolite (host) composite, focusing mainly on the properties of a single crystallite using microscopic techniques (UV-Vis-IR absorption and photoluminescence). The composite C60-FAU is of great interest because it exhibits new optical properties different from that of either C60 powder or FAU zeolite.

Electrochemical Study of Inclusion Complexes of Fullerene

Fullerenes' (C60 and C70) inclusion complexes of γ-CD and DMβCD were modified on the glassy carbon electrode and the behavior of their cyclic voltammograms was studied. The results show that CD inclusion complexes have large effects on the fullerene's electrochemical properties. The different effects of γ-CD and DMβCD on the electrochemical properties of C60 and C70 were also compared.

Study of the Electrochemical Properties of C60 Modified Carbon Paste Electrode and Its Application for Nitrobenzene Quantitation Based on Electrocatalytic Reduction

ABSTRACT A C60 modified carbon paste electrode(MCPE) was prepared and its electrochemical properties in tetrabutylammonium hydroxide/CH3CN/H2O solutions were studied. Two pairs of mono-electron quasi-reversible redox peaks were obtained and characterized. The experimental results revealed that this electrode had a good electrocatalytic reduction response for nitrobenzene in these conditions. The catalytic reduction current had a good linear relationship to the concentration of nitrobenzene. The linear range of nitrobenzene concentration was between 5.0×10−5∼6.0×10−3mol/L. The detection limit was 3.0×10−5mol/L.

Solid C60: preparation and characterization†

Abstract Buckminsterfullerene, C 60, was prepared in gram quantities by contact arc vaporization of a graphitic soot followed by extraction with toluene. After evaporation of toluene, the solid residue was characterized by mass spectrometry, high-performance liquid chromatography, IR- and UV-spectroscopy, X-ray diffraction and electron microscopy. The IR spectrum showed bands at 1429, 1183, 577 and 528 cm−1. Broader features were also observed in the UV (the strongest at 332, 270 and 208 nmrpar;. The transmission micrographs of typical crystals of the C60 show thin platelets, rods and stars with hexagonal symmetry. Analysis of X-ray diffraction and electron diffraction data confirms that the molecules have the anticipated ‘fullerene’ structure. The solid-state and molecular properties of C60 can now be studied in detail.

Solvent Effects on C60 Excited State Cross Sections

AbstractA survey study of solvent effects on the linear and nonlinear absorption properties of C60 has been done. The nonlinear absorption measurements are done at 694 nm with a Q-switched Nd:YAG pumped dye laser. In conjunction with this study a three level rate equation system has been solved analytically and the model results used to extract effective excited state cross sections. A difference and a ratio are calculated from the effective excited state cross section and the ground state cross section. The analysis demonstrates that it is this difference and the initial transmission which determine the critical fluence for the onset of nonlinear absorption. The saturation behavior is determined by the ratio of the cross sections and the initial transmission. Based on these findings C60 is shown to have some of the highest reported nonlinear absorption properties at 694 nm. The effective excited state cross sections at 694 nm are reported for the solutions and correlations to the solvent types demonstrated.

ESR Studies of the Anion Radicals of the Fullerene: C60n- (n = 1, 2, and 3).

ABSTRACTThe results of ESR studies on several anion radicals of the fullerene C60, C60n-(n = 1, 2, and 3), in the solvents benzonitrile, dichloromethane, pyridine and tetrahydrofuran containing 0.1 M TBAClO4 are reported and discussed. The samples are prepared by electrochemical reduction techniques which allow the preparation of samples which contain, quantitatively, the desired anionie species. The results of ESR spectral studies on the anions in frozen solutions as a function of temperature are presented. The ESR lineshapes and linewidths are dependent upon the solvent and the temperature. The g-values are weakly dependent upon temperature. The results obtained from this study are presented and discussed in terms of the unique physical structure and properties of C60.

Electronic Effects of Adducts on C60: A Molecular Orbital Analysis

ABSTRACTBuckmisterfullerene, C60, has attracted great interest because of its carbon-cage structure and potential applications in the field of superconductivity when doped with alkali metals. The icosahedral framework of C60 has been confirmed by X-ray analysis of an osmylated C60, called ‘Bunnyball’. Little theoretical work has been done to understand the electronic mechanism of C60 and substituted C60. This work has focused on electronic properties of C60 and the bunnyball with hypothetical analogs metal substitutions to understand the electronic effects of adducts on the bunnyball. In this analysis, the osmylated C60and hypothetical analogs were studied by extended Hückel methods. Molecular orbital(MO) interaction diagrams constructed from Density of States (DOS) analysis of the bunnyballs are presented. The results suggest electronic effects induced by substitution /adduct strongly affect electronic population in the C60 unit.

Optical Properties of C60 and M6C60 (M=K, Rb, Cs) films

ABSTRACTWe report the optical properties of C60 determined from the variable angle ellipsometry and near normal incidence reflection / transmission (R.T) experiments, and of M6C60 from the R, T experiments. The measurements were performed on thin films (d∼1000 Å) of C60 and M6C60 deposited on both Si(100) and suprasil substrates. The onset for strong absorption across the HOMO-LUMO gap in CgQ is measured to be -2.3 eV, slightly larger than the gap values obtained from the x-ray photoelectron spectroscopy (XPS) and electron-energy-loss spectroscopy (EELS) experiments. The observed peak positions in ε2(ω) for M6C60 and C60 compares well with the recent band structure calculations and suggests that the M6C60 compounds exhibit only a weak hybridization between the C60 and M states.