Reaction Kinetics of C60 Fullerene Ozonation

It has been verified that the reaction between O₃ and C₆₀ follows the general second order reaction rate which is valid for all the reactions between ozone and unsaturated olefinic bonds: v = k[C=C][O₃]. The reaction rate constant k has been measured ≈(1.5 ± 0.3) × 10⁴ L mol^-1 s^-1. The value of this rate constant has the same order of magnitude of the rate constant measured for instance in the ozonation of 1,4-diphenylbutadiene.     

Reaction Kinetics of C60 Fullerene Ozonation

Abstract

It has been verified that the reaction between O₃ and C₆₀ follows the general second order reaction rate which is valid for all the reactions between ozone and unsaturated olefinic bonds: v = k[C?C][O₃]. The reaction rate constant k has been measured ≈(1.5 ± 0.3) × 10⁴ L mol^?1 s^?1. The value of this rate constant has the same order of magnitude of the rate constant measured for instance in the ozonation of 1,4‐diphenylbutadiene.     

Ozonides and Oxides of C60 and C70: A Review

This paper presents a literature review of studies of ozonides and oxides of C₆₀ and C₇₀.     

聚苯乙烯/富勒烯复合材料抗紫外老化性能

运用紫外加速老化熔融共混法制得C60和C70含量（质量分数）分别为1%、3%、5%的聚苯乙烯（PS）/C60和PS/C70复合膜,考察了复合膜的抗紫外线老化性能。利用红外光谱（FTIR）分析了聚苯乙烯的老化前后结构变化,用示差扫描量热法（DSC）和差热法（DTA）测试了各试样老化前后的玻璃化转变温度、分解温度,结果表明,加入C60和C70后,PS/C60和PS/C70复合材料的耐紫外老化性能大大提高,添加量为5%时复合材料的抗老化性能较好。     

C60 and Giant Fullerenes in Soot Condensed in Vapors with Variable C/H2 Ratio

A transmission electron microscope (TEM) study of individual soot grains forming fluffy carbon particles produced using the arc-discharge technique revealed close-packed arrangements of single-wall ring structures with average diameters of 0.7, 1.1, 3.0, 5.5, and 8.2 nm. These structures were hypothesized to be C₆₀ and giant, C₅₄₀, C₉₆₀, and C₁₅₀₀, fullerenes that could form by coalescence during condensation and soot agglomeration, although in situ solid-state growth cannot be excluded. Mass spectroscopy and high performance liquid chromatography (HPLC) chromatography of the samples confirmed the presence of C₆₀ fullerene in all samples giving confidence to the giant fullerene growth scenario. Our results suggest that fullerenes could be common in soot grains produced by this technique as well as being an important carbon phase in C-rich accretion disks around young stellar objects and among the dust in the interstellar medium.     

Fullerenes C60 and C70: a model for solubility by applying the correlation intensity index

Abstract

Fullerenes are materials which have many applications as in the field of chemical technology as well as in the field of biochemistry and medicine. Solubility of fullerenes in different solvents has been studied many times in the field of computational chemistry. However, analysis of different approaches which able help to solve the task of prediction of solubility fullerenes remains attractive and very important direction of scientific activity. The correlation intensity index (CII) is a new criterion of the predictive potential of models. The applying of CII together with Index of Ideality Correlation (IIC) in modeling of fullerenes solubility in various solvents by the Monte Carlo method using the CORAL software (http://www.insilico.eu/coral) indicates that applying of the CII improves the predictive potential of these models. These models can be applied for systematization of ecological, biochemical, and medicinal knowledge related to applying of fullerenes. This systematization gradually becomes a factor of key importance, since the applying of the fullerenes expanded day by day.     

HPLC Diode-Array Analysis of C60 and C70 Polymeric Fullerene Oxides (Fullerene Polymeric Ozonides)

It is shown by HPLC diode-array analysis that the C₆₀ and C₇₀ polymeric fullerene oxides ([C₆₀]-PFOs and [C₇₀]-PFOs) which are polymeric ozonides, are composed by nine different components. The ozonide derivatives of C₆₀ and C₇₀ have been proved to be practically analogous in chemical structure and composition. The most important component of both [C₆₀]-PFOs and [C₇₀]-PFOs accounts for about 3/4 of each sample. The overozonation of [C₆₀]-PFOs in methanol has been studied and shown to not produce any significant changes.     

Study of the Ozonolysis Rate Constants' Dependence from the Degree of Oxidation of C60 Fullerene and Trans-1,4-Polychloroprene

The changes in the current values of the reaction rate constants during the C₆₀ fullerene and polychloroprene ozonolysis in solution have been investigated. The reaction has been conducted in a bubble reactor and the respective k values were determined on the basis of continuous measurement of the ozone concentration in the gas phase at the reactor outlet, under conditions of constant values of the ozone concentration at the reactor inlet. An effect of decrease in the current values of the rate constant during the conversion of the respective double bonds has been observed. It has been determined that the decrease of C₆₀ fullerene k values in the 0-70% region of conversions is about 56%. In the case of polychloroprene the reduction is 18% and 24% at degree of conversion of 70% and 90% correspondingly. The mechanism of these effects and their influence on the rate constants dependences on the degree of conversion of the respective sp² C-C bonds have been considered. A supposition about the dominant role of the chemical factors on reduction of the current k values of the C₆₀ fullerene and polychloroprene has been substantiated.     

Effect of Molecular Rotation on Vapor Phase Nucleation: Fullerenes C60 and C70

Abstract

The effect of rotational free energy of fullerenes C₆₀ and C₇₀ on homogeneous nucleation of crystals from vapor phase have been studied. Classical nucleation parameters have been estimated for the case of nucleation and crystal growth of C₆₀ and C₇₀ by Physical Vapor Transport (PVT) method under different supercooling in the range of 20–150 K, keeping the source temperatures constant. The result shows that the growth of large size single crystals is more feasible in the lower supercooling range. The effect of change in interfacial tension on the critical free energy of formation of the nuclei is also studied.     

水溶性C_(60)/C_(70)改性丙烯酸(酯)共聚物的固化反应

分别采用水溶性丙烯酸(酯)共聚物和C60/C70改性丙烯酸(酯)共聚物作主要成膜物,以甲醚化三聚氰胺树脂作固化剂,考察了聚合物引入C60/C70后,其对聚合物中羟基和羧基与固化剂中甲氧基甲基反应活性的影响。通过对固化过程的DSC和交联度测试,结果说明,在聚合物中引入C60/C70,由于其产生的空间位阻作用和电子分布效应,使聚合物中的羟基和羧基活性基团与固化剂中甲氧基甲基反应活性降低,从而导致共聚物的固化反应温度提高和固化速度的下降。     

Ozone reaction with carbon nanostructures. 1: Reaction between solid C60 and C70 fullerenes and ozone

The exposure of powdered crystals of C60 and C70 fullerenes to ozone with an O3/O2 ratio of 9.7% w/w causes their immediate oxidation. The FT-IR spectroscopy shows the formation of CO2 and the accelerated disappearance of ozone. The infrared spectra of crystalline C60 and C70 powders that were exposed to ozone show absorption bands indicating that oxidation was accompanied by formation of alpha,beta-unsaturated carboxylic groups, aldehyde and other ketonic moieties. The spontaneous decay of O3 in the O3/O2 atmosphere monitored by FT-IR spectroscopy was found to follow a pseudofirst order kinetic law with k0 = 6.9 x 10(-5) s(-1). When powdered C60 is present in the system a k(C60)(1) = 2.0 x 10(-4) s(-1); k(C70)(1) = 1.4 x 10(-4) s(-1) for C70. The accelerated disappearance of O3 is due to its adsorption/reaction with the powdered fullerenes. After about approximately 1000 s the reaction enters in a second step wherein the disappearance of O3 slows down significantly due to the lack of further reaction sites on the powdered fullerene surfaces and due to accumulated CO2 in the gas phase which exerts an inhibitory effect in the ozone spontaneous decomposition.     

Study of the Submerged Electric Arc in Hexane in Presence of C60 Fullerene

The effect of the electric arc between graphite electrodes submerged in n-hexane solutions of C₆₀ fullerene has been studied by electronic absorption spectroscopy, liquid chromatographic analysis (HPLC-DAD), and FT-IR spectroscopy. The experimental results show that C₆₀ does not appear able to inhibit the polyynes' formation at the concentration used. Polyynes are formed in large amounts as usual from the graphite arc, and polycyclic aromatic hydrocarbons have been detected as by-products. Prolonged arcing causes the disappearance of C₆₀ from the solution. There is experimental evidence that C₆₀ undergoes radical addition reactions during the early stages of arcing.     

Fe／C60复合材料低温烧结扩散现象的扫描电镜研究

用ＳＦＭ研究了采用粉末冶金法合成的Ｆｅ／Ｃ６０复合材料低温结的扩散现象。结果表明，烧结后Ｃ６０由块状聚晶扩散形态针状或须状物，并分布于Ｆｅ粒子表面及缝隙中。     

Computations of metal-covered C60 and C70

Semiempirical quantum-chemical PM3 calculations are reported for a new class of exohedral metallo-fullerenes – metal-coated or metal-covered fullerenes: C₆₀M_n and C₇₀M_n. The exohedral species have been observed in gas phase, however, their geometrical and electronic structures are not known yet. Relatively-even metal-atom distributions over the fullerene rings are considered – such regular forms are computed for M = Be, Mg, Al. Three selected types of stoichiometries are treated in particular: C₆₀M₁₂/C₇₀M₁₂ (metal atoms above all pentagons), C₆₀M₂₀/C₇₀M₂₅ (metal atoms above all hexagons), and C₆₀M₃₂/C₇₀M₃₇ (metal atoms above all rings). If an odd number of electrons should result (Al), the related cation is computed, or one metal atom added or removed. This interesting arrangement above the rings is possible only for some types of atoms, while other elements are localized above bonds or atoms, or inside the cage, or even react and destroy the cage. Other limitation comes from the parametrization of the computational technique used – the PM3 semiempirical method is parametrized only for some selected metals. Metal-layer atomization heats are suggested as a stability measure. Structural characteristics are also presented and interesting reductions of the cage symmetry are found. Their relationship to Jahn–Teller effect is discussed. The metal covered fullerenes can represent models for metal catalysis in the nanotube synthesis and could eventually lead to new interesting materials.     

On the Action of Ultraviolet Light on C70 Fullerene

C₇₀ was photopolymerized in solution of CCl₄ under nitrogen flow by an high pressure mercury lamp. The resulting photoproduct was still soluble in common solvents and has been studied by electronic and FT-IR spectroscopy. FT-IR spectroscopy reveals a very peculiar band pattern never reported to date for C₇₀ photoproduct. Since this band pattern is very similar to that of C₆₀ photopolymer, it suggests that C₇₀ photoproduct should have a chemical structure very close to that assigned to C₆₀ photopolymer and piezopolymer.

The role played by CCl₄ in C₇₀ photopolymerization seems to be comparable to that already reported for C₆₀, i.e. it acts as a polymerization promoter.     

On the Action of γ Radiation on Solid C60 and C70 Fullerenes: A Comparison with Graphite Irradiation

C₆₀ and C₇₀ fullerene have been treated in sealed flasks under Ar with γ radiation using radiation dosages ranging from 10 to 1000 kGy. The treated samples studied by electronic and FT-IR spectroscopy have not shown any evidence about fullerenes decomposition or radiopolymerization. However, through Raman spectroscopy it was possible to observe that γ radiation induces C₆₀ dimerization and trimerization. It has additionally been discovered that γ-treated C₆₀ (oligomerized) can be easily photopolymerized in the solid state by post-irradiation with laser light at 514 nm while this phenomenon has not been observed by using laser light at 782 nm and considerably higher laser power. Previously to this study, C₆₀ photopolymerization was known to occur only by using ultraviolet light.

For comparison also graphite was irradiated with 1000 kGy of γ radiation. Irradiated graphite shows considerably changes in its Raman spectrum, showing the formation of glassy carbon domains, perhaps carbon onions. The l_d bandshift to 1310 cm^-1 could be interpreted in terms of formation of hexagonal diamond.     

Thermal Reactions of C60 with Siliranes: Carbosilylation and Silylene Addition of Fullerenes

Thermal reactions of C₆₀ with siliranes (1a, b) afforded carbosilylated C₆₀ derivatives. When a bicyclic fused silirane (1c) was employed instead of 1a and 1b, a silylene adduct and its hydrolyzed compound were obtained through thermal extrusion of silylenes from 1c. These products were determined to be 1,2-adducts at 6,6-junctions of C₆₀ by MS, UV, and NMR analyses. These results provide a complementary method to the photochemical addition of reactive silicon compounds, which have been long employed for silylation of C₆₀. Electrochemical analyses revealed the redox properties of the silylated products, indicating the perturbation caused by silyl groups introduced on the C₆₀ cage. Theoretical calculations were also conducted for understanding of the electronic property of the silylated product.     

The fabrication of PPV/C60 composite nanofibers with highly optoelectric response by optimization solvents and electrospinning technology

We have successfully loaded C60 into a PPV precursor using CS2 and ethanol as mixed solvents and fabricated uniform PPV/C60 composite nanofibers by electrospinning for the first time. C60 was homogeneously distributed in nanofibers. The PL spectra analysis confirmed the formation of a composite and revealed the obvious fluorescent quenching comparing with pure PPV nanofibers. Countable electrospun composite nanofibers on a Au interdigitated electrode showed a fast and highly optoelectric response under 100 mW/cm² light irradiation by a Xe lamp. The results showed that photo induced charge transfer took place at the interface of PPV and C60 and suggested the great potential in the field of micro/nano organic optoelectric devices, especially in micro/nano organic photoswitches.     

2D and 3D Crystal Forms of the C36 Fullerenes: Geometrical and Electronic Structure

Abstract

In the present work calculations of geometrical structure and electronic properties of the covalent crystal consisted of hexagonal close packaged layers of C₃₆ fullerenes in 2D & 3D cases are carried out. The analysis of the stability and formation paths of such crystal according to PM3 semiempirical method was performed. Extended Huckel theory has been applied to electron spectra calculations. Comparison of the structure with similar fullerene and nanotube structures was carried out and effect of geometry to electron properties is discussed. In the work the values of 6.695 and 6.763 Å for the lattice constants were obtained with good agreement with experiment (Piskoti, C.; Yarger, J.; Zettl, A. C₃₆, a new carbon solid. Nature 1998, 393, 771), and value of 1.50 eV in 2D case and 1.88 eV in 3D case was obtained for bandgap.     

Fullerane, the Hydrogenated C60 Fullerene: Properties and Astrochemical Considerations

Hydrogenated C₆₀ fullerene, C₆₀H₃₆ was prepared in different solvents using Zn/HCl as reducing agents. The structure of C₆₀H₃₆ was confirmed both by electronic and FT-IR spectroscopy and the purity of the reaction product was checked by HPLC analysis. It has been confirmed that C₆₀H₃₆ is not stable in air, especially in presence of light which enhances the oxidation. The oxidation of C₆₀H₃₆ was studied by FT-IR spectroscopy and by differential scanning calorimetry (DSC) in air; the formation of hydroxyl groups on the fullerene cage and ketonic groups (involving cage breakdown) have been detected. Furthermore, the action of O₃ on C₆₀H₃₆ was investigated and it has been found that O₃ exerts practically the same effect of air but causing an enhanced cage breakdown. The thermal stability of C₆₀H₃₆ was checked by a thermogravimetric analysis (TGA) coupled with a differential thermal analysis (DTA) under N₂ flow. The vaporization of C₆₀H₃₆ occurs at very high temperature: the DTA trace has shown an endothermic peak at 540°C (at a heating rate of 20°C/min). C₆₀H₃₆ shows an electronic absorption spectrum with a maximum at about 217 nm and it is able to match both in position and in half width the peak at 217.5 nm observed in the spectrum of the interstellar extinction of light which was attributed to hydrogenated, radiation processed and thermally annealed carbon dust. Similarly, the absorption spectrum of C₆₀H₃₆ is able to match several infrared emission bands (called UIBs) detected from certain astrophysical objects like the protoplanetary nebulae (PPNe). It is proposed that hydrogenated fullerenes can be used as model compounds in the laboratory simulation studies of interstellar carbon dust.