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.     

氯代甲烷对真空电子捕获能力研究

设计了化学物质对真空电子吸收效果评价的密度泛函理论(DFT)评价法和气相色谱-电子捕获检测器(GC-ECD)评价法,并利用两种方法对CCl₂H₂、CCl3H和CCl₄三种氯代甲烷的电子吸收效果进行了评价,并对两种方法的结果进行了对比分析。DFT评价法表明,从结构上三种氯代甲烷均表现出明显的电子吸收潜力,且CCl₂H₂、CCl₃H和CCl₄得电子潜力依次增强;GC-ECD评价法表明,CCl₂H₂、CCl₃H和CCl₄在ECD检测器上均具有较好的响应,且CCl₄响应最强,CCl₂H₂最弱。综合考虑DFT评价结果和GC-ECD评价结果,三种氯代甲烷均具有优越的电子捕获能力,且CCl₄捕获电子能力最强,CCl₃H次之,CCl₂H₂最弱;同时也说明,氯代甲烷可以作为电离层扰动物质的备选物质。     

Polyynes Formation from Electric Arc in Liquid Argon in Presence of Methane

The carbon arc in liquid argon in presence of methane produces the complete series of polyynes from C₄H₂ to C₁₂H₂ which have been collected in a cold trap and analyzed by electronic absorption spectroscopy and by liquid chromatography (HPLC-diode array). The relative abundance of the polyynes series has been determined. In addition to polyynes the decomposition of methane in the argon arc produces also vinylacetylene and naphthalene. Thermodynamic calculations explain why the polyynes are formed so easily in the carbon arc.     

Polyynes Production in a Solvent-Submerged Electric Arc Between Graphite Electrodes. III. Chemical Reactivity and Stability Toward Air, Ozone, and Light

Since polyynes are easily accessible with the submerged electric arc synthesis between graphite electrodes, the chemical behavior of polyynes solutions in different solvents has been explored. It has been found that surprisingly the polyynes solutions, with polyynes having up to 16 carbon atoms arranged in a chain, are stable in air over 1 week time in the dark. These solutions react relatively slowly with ozone while add rapidly and completely bromine. The polyynes solutions are instead quite easily photolyzed under the action of UV radiation both in air and under N₂. Two different light sources were used in the study: a low pressure mercury lamp emitting almost a monochromatic radiation at 254 nm and an high pressure mercury lamp emitting in a broad wavelength range in the ultraviolet. With the former monochromatic light source, it has been demonstrated the possibility to perform a selective photolysis of selected polyynes in a mixture of homologous series.     

Synthesis of Polyynes with Electric Arc Part 5: Detection of PAHs as Minor Products

The main products of the submerged electric arc between graphite electrodes in n-hexane and in methanol are the polyynes series. The liquid chromatographic analysis (HPLC) of the arcing products in n-hexane reveals also the presence of a mixture of polycyclic aromatic hydrocarbons (PAHs) as minor products. Naphthalene, acenaphthylene, phenanthrene, perylene, fluoranthene, benzo[b]fluoranthene, pyrene, and the related compound cyclopenta[c,d]pyrene have been identified. Even crysene and acenaphthene were reasonably identified from the PAHs mixture. The PAHs mixture appears to derive essentially from the plasmalysis of the solvent where the electric arc is conducted, while the polyynes are formed from the elemental carbon supplied from the graphite electrodes. Another minor product is represented in all cases by the formation of carbon black or carbon coke, which appears more abundant in n-hexane rather than in methanol. The different results are explained thermodynamically in terms of different carbonization tendency of the solvents used.     

STRUCTURE OF HEXA-SULFOBUTYL FULLERENES: A COMPUTATIONAL STUDY

Quantum-chemical computations are reported for hexa-sulfobutyl fullerenes C₆₀((CH₂)₄SO₃H)₆ (FC4S). FC4S represent novel water-soluble fullerene derivatives with an enhanced radical scavenging activity and also possible potential for materials science. The computations have been carried out with the standard version of the PM3 semiempirical quantum-chemical method. It is found out that the lowest among the computed eight FC4S species has the structural pattern already observed for C₆₀Cl₆. However, a larger-scale search is at present prevented by the demands on computational resources.     

Effect of CH4 and H2 on CVD of SiC and TiC for possible fabrication of SiC/TiC/C FGM

SiC and TiC coatings were deposited by CVD on graphite substrates and the effect of the variation of the methane (CH₄) and hydrogen (H₂) ratio on deposition was investigated. SiCl₄, TiCl₄ and CH₄ were used as sources of Si, Ti and C. In case of the SiC coatings, stoichiometric SiC was obtained when the ratios of CH₄/(SiCl₄ + CH₄)andH₂/(SiCl₄ + CH₄) are 0.4 and 10, respectively. Stoichiometric TiC was also obtained under similar conditions. In order to obtain non-stoichiometric materials for possible fabrication of functionally gradient materials (FGM), a change of microstructure and composition was observed with changes of the CH₄ and H₂ ratio. As a result, SiC, TiC and C contents were more easily controlled by a change of the H₂ ratio compared to the CH₄ ratio for SiC and TiC deposition. It has been verified that the change of the H₂ ratio is more desirable for possible manufacturing of SiC/TiC/C FGM.     

Carbon Nanotubes Grown on the Surface of Cathode Deposit by Arc Discharge

Carbon nanotubes prepared by de arc discharge of graphite electrodes in He and CH₄ gas took markedly different morphology. Thick nanotubes embellished with many carbon nanoparticles were obtained by evaporation under high CH₄ gas pressure and high arc current. Thin and long carbon nanotubes were obtained under a CH₄ gas pressure of 50Torr and an arc current of 20A for the anode with a diameter of 6mm.     

Detection of Buckminsterfullerene in Usual Soots and Commercial Charcoals

It was confirmed that soot produced by free burning of small hydrocarbons like benzene and cyclohexane generally contains less than 0.1 ppm of C₆₀. Small, but measurable amounts of C₆₀ were found in two samples of charcoal, providing the first indication of fullerene formation in the solid state.     

An aqueous ZnCl2/Fe(bpy)3Cl2 flow battery with mild electrolyte

The kinetics of electrode reaction was investigated by cyclic voltammetry, and cyclic voltammograms show that the reversibility of the Fe(bpy)₃²⁺/Fe(bpy)₃³⁺ electrode reaction is better than that of the Zn/Zn²⁺ electrode reaction on the graphite disc. However, the Fe(bpy)₃²⁺ ion diffusion in electrolyte is subject to greater resistance than that of the Zn²⁺ ion one. The stability of the Fe(bpy)₃Cl₂ solution was investigated by UV–vis spectroscopy, and the performance of a mild redox flow battery employing ZnCl₂ and Fe(bpy)₃Cl₂ in the NaCl aqueous solution with various membranes as the separator was also investigated. It was found that the Celgard 3501 membrane cannot effectively prevent Fe(bpy)₃²⁺ ions from leaking into anolyte, leading to the rapid failure of the flow battery. Although the Nafion 115 membrane can be polluted by Fe(bpy)₃²⁺ ions, it is not invalidated. The Nafion 115 membrane shows good selectivity, which can avoid Fe(bpy)₃²⁺ ions from leakage into anolyte. The ZnCl₂/Fe(bpy)₃Cl₂ flow battery with the Nafion 115 membrane exhibits the capacity retention of 80% after 200 cycles.     

Storage Stability of Polyynes and Cyanopolyynes in Solution and the Effect of Ammonia or Hydrochloric Acid

The storage stability of an acetonitrile solution of polyynes and monocyanopolyynes was studied by liquid chromatographic analysis for about 50 days at room temperature in a closed Pyrex flask. Monocyanopolyynes decomposition starts immediately after their synthesis; the decomposition can be approximated by a pseudo-first-order kinetic law and the rate constant is dependent from the length of the monocyanopolyyne chains, being faster for longer chains. For instance, for HC₇N the decomposition rate is k=-3.4×10^-7 s^-1 but becomes -7.0×10^-5 s^-1 for HC₁₃N decay, 204 times faster than the decay of the former compound. Polyynes mixed with monocyanopolyynes in the same CH₃CN show an induction time before starting to decompose. The induction time appears linked to the decomposition of monocyanopolyynes, which seems to protect the polyynes from the decomposition. Once the monocyanopolyynes are vanished also the decomposition of polyynes starts with a slower kinetics than monocyanopolyynes and following the rule that longer chains disappear at higher speed than shorter chains. For example, the pseudo-first-order rate constant for C₈H₂ is k=-1.31×10^-8 s^-1. Ammonia exerts a deleterious effect on monocyanopolyynes. In fact, ammonia addition to an acetonitrile solution of monocyanopolyynes causes their immediate decomposition due to a nucleophilic addition of ammonia to the polyyne chains. Instead, hydrogen-teminated polyynes are much more resistant toward the nucleophilic addition of ammonia. Hydrochloric acid does not influence the stability of polyynes and monocyanopolyynes.     

The Role of Boron Nitride in Graphite Plasma Arcs

Novel graphitic nanostructures (e.g. nanotubes, graphitic onions, polyhedral particles, hemitoroidal nanotube caps and branched nanotubes) are produced by arcing graphite electrodes, containing hexagonal-BN, in inert atmospheres. The introduction of BN or B inside the graphite anode generates long (≤ 20μm) and well graphitised carbon nanotubes exhibiting boron at their tips. High Resolution Electron Microscopy (HRTEM), Scaning Electron Microscopy (SEM), Electron Energy Loss Spectroscopy (EELS) and X-ray powder diffraction studies reveal the production of B₄C crsytals, in addition to little amounts of BC₃ nanotubes. Mass spectrometry (MS) studies over the generated soots indicate high yields of large fullerenes (e.g. C₇₀, C₇₆, and C₈₄) and thermo-Gravimetric analysis (TGA) of the nanostructures show high oxidation resistance.     

Some New Aspects of Chlorination of Fullerenes

The effect of the reagent ratio, reaction time and power of the reagent on the product composition in chlorination of [60]fullerene was studied. Chlorofullerenes C₆₀Cl₆, C₆₀Cl₈, C₆₀Cl₁₀, C₆₀Cl₁₂, C₆₀Cl₁₄, and C₆₀Cl₂₆ were synthesized and characterized by chemical analysis, FTIR, ¹³C NMR, and MALDI TOF mass spectrometry. The experimental data supported the coexistence of several isomers of C₆₀Cl_n (n = 8, 10, 12, 14, 26); the mixtures were not separated so far. Semiempirical calculations (AM1, PM3) were used to analyze the addition patterns and resulted in the most favorable structures of C₆₀Cl_8-26. Chlorination of C₇₀ under various conditions invariably yielded C₇₀Cl₁₀.     

Effects of Intense Ultrasound Treatment of C60 Solutions

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.     

Synthesis of Lanthanofullerenes by Laser Ablation Using Pulsed and CW-Nd:YAG Lasers

Endohedral lanthanum fullerenes, La@C₆₀, La@C₈₂ and La₂C₈₀, were synthesized by ablation of graphite and La₂O₃ in flowing Ar buffer gas with a 1064 nm beam from a pulsed-Nd: YAG laser in which the graphite was heated by the CW-Nd:YAG laser up to 2500 °C. The La-fullerenes were also prepared by laser ablation of a lanthanum-graphite composite rod. The extractant fullerenes from the carbon soot were analyzed by laser-desorption time of flight mass spectrometry (LD-TOF MS). The relative yield of La@C₈₂, increased with increasing temperature of the rod in the range of 700-2300 °C.     

Halogen and Interhalogen Reactions with [60]Fullerene: Preparation and Characterization of C60C24 and C60C18F14

U.V. irradiation of a solution of [60]fullerene in carbon tetrachloride saturated with chlorine gave a yellow solid, the negative ion FAB mass spectrum of which is consistent with the presence of C₆₀Cl₂₄ When a solution of [60]fullerene in CCl₄was mixed with IF₅, a yellow solid was deposited in the denser IF₅ layer. The negative ion FAB mass spectrum of this material indicated it to be C₆₀C₁₈F₁₄ This result provides the first confirmation that halogenation of Merenes is a radical process. Fluorination of C₆₀Br₈ gave a range of fluorinated products, having a maximum fluorine content of ca. 36 fluorines per cage, and with either C₆₀F₁₈ or its mono-oxide as major species. EI mass spectrometry of the products at various temperatures indicates that the more highly fluorinated fiiilerenes are either less stable to heat, or are more volatile.     

Stacking Defects in C60 Films

The structure of pollycrystalline C₆₀ films prepared by sublimation from 99.9% pure C₆₀ powder and from graphite soot was investigated by X-ray diffraction. A complex fcc (111) line was found in the former samples. Comparison of experimental and simulated (111) profiles allowed to assess quantitatively the degree of stacking disorder introduced during the growth of the film. Probabilities could be derived for continuation of already started fcc and hep sequences, thereby characterizing the statistical microstructure of the C₆₀ films. Also, the relative magnitudes of inter- and intra-layer disorder can be estimated. The films deposited from graphite soot show a high structural disorder.     

Structure and Arrangement of Carbon Microparticles of Electrodes during Fullerene Synthesis in Inert Gases (Ar, He)

The cathode slag structure and the graphite anode surface have been investigated. Dependence of geometrical parameters of the slag from the time has been found. Efficiency of C₆₀ generation was increased with arcing time. Use of cathode with closed hole reduced the yield of C₆₀     

g-C3N4/Bi12O17Cl2复合物的制备及其光催化性能

以硝酸铋、氯化钠和氢氧化钠为原料用液相沉淀法制备g-C₃N₄/Bi₁₂O₁₇Cl₂复合光催化剂,并用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis DRS)等手段表征其组成、微观形貌和性能,以罗丹明B为模拟污染物研究了在可见光照射下g-C₃N₄对g-C₃N₄/Bi₁₂O₁₇Cl₂复合光催化剂活性的影响及其光催化机理。结果表明,2% (质量分数) g-C₃N₄/Bi₁₂O₁₇Cl₂复合光催化剂的光催化性能最好,见光90 min后对罗丹明B的降解率达到98%。     

A STUDY ON THE THERMAL STABILITY TO 1000°C OF VARIOUS CARBON ALLOTROPES AND CARBONACEOUS MATTER BOTH UNDER NITROGEN AND IN AIR

The thermal behavior of graphite, C₆₀ fullerene, fullerene black (carbon soot containing fullerenes), extracted fullerene black and diamond has been analyzed to 1000°C by TGA-DTA (thermogravimetric analysis and differential thermal analysis) under a nitrogen flow at a heating rate of 20°C/min. Very small weight losses have been recorded in the case of graphite and diamond. Furthermore no diamond graphitization has been observed. The sublimation of pure C₆₀ and the fullerene fraction of fullerene black (both pristine and extracted) has been observed and discussed.

The combustion reaction in air flow of graphite, C₆₀ and C₇₀ fullerenes, fullerene black (both unextracted and extracted), carbon nanotubes and diamond has been studied by TGA-DTA at a heating rate of 20°C/min. C₇₀ fullerene and fullerene black have been found to be the most reactive carbon materials with O₂. The role played by C₇₀ in the degradation of fullerites has been discussed. Among the carbon materials examined, the best resistance to O₂ attack has been shown by diamond and carbon nanotubes. The behavior of graphite is intermediate between diamond and fullerene blacks. The behavior of C₆₀ fullerene appears closer to that of graphite although it appears to be more reactive with O₂. Samples of graphite and carbon blacks N375 and N234 have been studied by TGA-DTA in air flow before and after a radiation treatment with neutrons or γ radiation. The effect of the radiation damage in the combustion reaction of these carbon materials has been discussed.