Effects of Intense Ultrasound Treatment of C60 Solutions

Abstract

C₆₀ was treated at room temperature, in air with intense ultrasound in the following solvents; decalin, tetralin. cyclohexane and CCl₄. It is shown by UV-VIS and FT-IR spectroscopy that in decalin and in tetralin the dominant reaction seems to be a sono-oxidation, although more complex reactions involving the solvent take place. In CC1₄ sono-oxidation is accompanied by an extensive sono-polymerization. Products in CCl₄ are C₆₀O, C₆₀O₂ and others; the sonopolymer collected from sonicated CCl₄ was easily identified by FT-IR spectroscopy. Sonopolymerization occurs also in decalin and tetralin and is promoted by free radicals as in the case of CCl₄. No reactions are observed in cyclohexane due to the very low solubility of C₆₀ in this solvent and the poor cavitation ability of cyclohexane under the action of ultrasound.     

Ultrasound induced growth of C60 fullerites over KBr

C₆₀ fullerites of millimeter to centimeter sizes were synthesized by ultrasound induced charging of C₆₀ over KBr surface in C₆₀/benzene solution at room temperature in the absence of ultrahigh vacuum. C₆₀ fullerites prepared by this method are found to be extremely brittle. C₆₀ fullerites can be prepared in large scale in a cost effective way using this method.     

C60薄膜的热处理性能研究

通过对Ｓｉ（１００）衬底上Ｃ６０薄膜在不同温度处理后的ＡＥＳ谱线研究发现,Ｃ_６０分子于９７３Ｋ时开始分解,生成石墨类碳碎片,１０７３Ｋ时Ｃ原子已与Ｓｉ原子键合形成ＳｉＣ,１１２３Ｋ时Ｃ_６０分子全部分解,这一研究结果对解释Ｃ_６０分子促进金刚石成核将起到重要作用．     

Structure and Thermophysical Properties of Fullerene C60 Aqueous Solutions

The structure and thermophysical properties of fullerene C₆₀aqueous solutions were investigated both experimentally and theoretically. The aggregation kinetics results indicated that the structure of fullerene C₆₀aggregates in water could be described as a fractal system. The IR and electronic absorption spectra obtained confirm the presence of the crystalline phase in aqueous solution. The numerical values of thermodynamic coefficients _P, _T, _S,c _P, andc _V, and sound velocity were determined from the measured (P–V–T) data. The vibrational spectrum of the crystalline structure (T_hsymmetry group) formed from the hydrated single fullerene C₆₀molecules in aqueous solutions was calculated using the molecular dynamics approach.     

Effects of Mechanical Grinding on C60 And Ca5C60 Superconductor

Abstract

The effects of mechanical grinding on polycrystalline C₆₀ and Ca₅C₆₀ superconductor are examined. It has been found that mechanical grinding may severely degrade phases of C₆₀ (fcc) and Ca₅C₆₀ (sc). The grinding destroys the long-range ordering of crystals and produces a partial amorphous state. The damage of crystal leads to the disappearance of superconductivity for Ca₅C₆₀. The samples with an amorphous phase can be recrystallized by annealing at 600°C for pure C₆₀ and Ca₅C₆₀. Magnetic susceptibility measurements indicated that the superconductivity of the degraded sample did not recover easily to the initial state.     

Non-Rigid Treatment of Interactions Between C60 Molecules

Abstract

Atom-atom van der Waals interaction energies are compared between bimolecular clusters of C₆₀ and circumcoronene, a model of graphite, with the aid of molecular mechanics. The minimum in the potential energy curve of the former is shallower and higher than the latter. Average equilibrium distance (3.08 Å) in the bimolecular cluster C₆₀–C₆₀ agrees well with the experimental value (2.96 Å). Equilibrium configurations of the C₆₀–C₆₀ cluster contain quite a few inter-cage atom-pairs in the repulsive region. Analysis of molecular as well as electronic structure in the closest possible approach under stringent conditions indicate that C₆₀ molecule is highly resilient ball.     

Why are Solutions of C60-Piperazine Purple at pH 11?

The C₆₀-piperazine mono adduct was synthesized by the reaction of C₆₀ and piperazine. The saturated C₆₀-piperazine aqueous solution was colorless when pH is 8 or below. A purple color was developed when pH is around 9 and the pink color is most intense at pH 11. The color of the C₆₀-piperazine solution fades out when pH is approaching 12 from 11, and the solution remains colorless when pH is 13 or higher. The UV-Vis spectra of the C₆₀-piperazine solution were recorded at pH 4, 11 and 14. The mono-protonated C₆₀-piperazine was identified to be responsible for the purple color observed. The computational investigation of the un-protonated, mono-protonated and di-protonated C₆₀-piperazine was conducted at the PM3 and ZINDO(s) levels of theory. Vibronic coupling of the Jahn-Teller active vibrational mode to the electronic transition was applied to re-generate the weak absorption between 550-600 nm in the UV-Vis spectrum of the mono-protonated C₆₀-piperazine.     

Au电极作用下C60、2C60与4C60富勒烯分子的电子传输特性

采用扩展的Hückel方法与格林函数方法,研究了Au电极作用下,C60富勒烯、2C60和4C60聚合体分子的电子结构与导电性,并对它们的电子结构与电子输运特性进行了对比.研究结果表明,C60、2C60或4C60富勒烯分子与Au电极 "接触"后,其HOMO、LUMO间的能隙减小;C60、2C60或4C60分子与Au电极之间的结合既有共价键的成分,又有离子键的成分,其中,C60、4C60分子与Au电极结合的离子键特征更为明显;三种富勒烯分子的电子输运性能依次具有C60>2C60>4C60分子的顺序.     

Study of Undersaturated C60 Solutions in Cs2 by Small Angle Neutron Scattering

We measured precisely, using the Small Angle Neutron Scattering (SANS) technique, the radius of the carbon nuclei shell of the C₆₀ molecule, in spite of its small value. For this purpose, controlled undersaturated solutions of C₆₀ in CS₂, where theC₆₀ molecules are individually distributed, were studied in the room temperature range. Absolute measurements also allowed us to extract from the contrast in scattering length the partial molecular volume of the molecule C₆₀ in solution in CS2.     

Study of Undersaturated C60 Solutions in Cs2 by Small Angle Neutron Scattering

Abstract

We measured precisely, using the Small Angle Neutron Scattering (SANS) technique, the radius of the carbon nuclei shell of the C₆₀ molecule, in spite of its small value. For this purpose, controlled undersaturated solutions of C₆₀ in CS₂, where theC₆₀ molecules are individually distributed, were studied in the room temperature range. Absolute measurements also allowed us to extract from the contrast in scattering length the partial molecular volume of the molecule C₆₀ in solution in CS2.     

Effects of Annealing on the Conductivity of C60 Thin Films

Films of C₆₀, at different stages of annealing of T_t=200°and 300°C have been electrically characterized over the temperature domain from -130°C to T_t. X-ray diffraction revealed a random polycrystalline fee structure with stacking defects of an intrinsic nature, due to deposition conditions. The value of room-temperature conductivity was found to be in the range (6.3-1.0) *10^-10 (0cm)^-1. In the stable annealed state the conductivity showed an activated temperature dependence above 423 K and a non-activated dependence below 330-280 K. The activation energies E_a = 0.8 eV (film thickness 0.70 μm) and E_a = 1.0 eV (film thickness 2.40 μm) were in good agreement with the energy gap values (1.63 eV and 2.08 eV) which were deduced from the absorption spectral dependence. Annealing decreased the non-activated contribution to conduction, extending the intrinsic conduction temperature range.     

Intramolecular Negative-Effect in the Alkali-Metal-Doped C60; A2C60 and A4C60

It is investigated theoretically why alkali-metal-doped C₆₀, A_xC₆₀, is a nonmagnetic semiconductor for x=2 and 4. We find that this is the consequence of the intramolecular negative- U effect due to the strong electron-phonon interaction and the weak Hund coupling between conduction electrons.     

Electronic structure and electrical transport characteristics of C60, 2C60 and 4C60 fullerene molecules

The extended H?ckel method and the Green s function method were used to calculate the electronic structure and electrical transport of Au electrode-C₆₀, 2C₆₀ or 4C₆₀ fullerene-Au electrode systems. Furthermore, their electronic structure and electrical transport characteristics were compared and analyzed. The results show that (i) owing to the contact with the Au electrodes, the C₆₀, 2C₆₀ and 4C₆₀ molecules change in their electronic structures significantly, and their energy gaps between LUMO and HOMO are narrow; (ii) the bonding between C₆₀, 2C₆₀ or 4C₆₀ fullerene and Au electrodes is partially covalent and partially electrovalent; and (iii) the conductance of the three fullerenes conforms to the order of C₆₀>2C₆₀>4C₆₀.     

Rb3C60单晶薄膜制备及Rb3C60/C60相界面稳定性研究

通过控制蒸发源电流、源和样品间距及扩散时间,室温下在C60单晶(111)解理面上制备出Rb3C60.用低温同步辐射角分辨光电子谱测量了样品的能带结构.观察到的能带色散表明样品为单晶薄膜.用X光电子谱首次研究了Rb3C60与C60相界面的稳定性.结果表明温度低于约420 K时界面是稳定的.     

Solubility of C60

All the published data on the solubility of C₆₀ in 140 organic and inorganic solvents are summarized and the critical features of the experimental techniques are treated. Data on die temperature dependence of solubility are also listed and analyzed. Experimental evidences on the molecular state of dissolved C₆₀ as well as the interactions between the solute and solvents are discussed.     

Band Gaps of Na2C60 and K4C60

respectively.