Laser desorption/ionization of carbon clusters

Results of mass spectrometric investigations of soot by using the laser desorption/ionization (LDI) method and time of flight (TOF) mass spectrometry are presented. Several liquid fuels (benzene, tetrahydrofuran, toluene, acetonitrile, acetone, isopropanol, ethanol) were used to produce soot samples. Each soot gives specific mass spectrum of carbon clusters C_n as well as their size. The best clustering process was observed for benzene soot with the cluster size n?31. The benzene soot was applied in the detection of insulin by using the matrix-assisted laser desorption/ionization (MALDI) method.     

Radical-scavenging Ability of Hydrophilic Carbon Nanoparticles: From Fullerene to Its Soot

We have recently developed a facile synthetic method for highly water-soluble fullerene, so-called fullerenol, for the treatment of fullerene with hydrogen peroxide. This method was applied to fullerene soot to yield the corresponding new hydrophilic carbon materials, and the obtained products were subjected to infrared spectroscopy and elemental analysis. The DLS particle size analysis demonstrated the relatively high dispersion of hydrophilic fullerene soot with a diameter of ?70 nm in water, while the hydrophilic activated carbon obtained by the same treatment showed the larger aggregation with diameters of 200 and 970 nm. The surface analysis using FE-SEM showed the difference in morphology between fullerene soot and activated carbon as well as between before and after hydrophilic treatment of the soot with hydrogen peroxide. Moreover, this hydrophilic fullerene soot exhibited high antioxidant activity (%AOA) up to 87% compared with fullerenol C₆₀(OH)₃₆ (54%) and C₆₀ (50%) evaluated by β-carotene bleaching method.     

Antibacterial activity of carbon nanoparticles isolated from chimney soot

Carbon nanoparticles (CNPs) are isolated from chimney soot and characterised by various tools such as X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and ultraviolet–visible spectroscopy. The X‐ray diffraction studies confirm the presence of C₆₀ nanoparticles in the isolated sample. The thermal properties of the prepared CNPs are recorded using thermogravimetric analysis and differential thermal analysis. The analysis of the antibacterial activity of the synthesised CNPs against selected Gram‐positive and Gram‐negative bacterial strains is also investigated. The systematic study confirms that CNPs collected from chimney soot exhibit good antibacterial potency against Staphylococcus aureus, Streptococcus pyogenes, Klebsiella pneumoniae, and Proteus mirabilis.Inspec keywords: ultraviolet spectra, scanning electron microscopy, visible spectra, differential thermal analysis, thermal analysis, antibacterial activity, nanoparticles, X‐ray diffraction, nanofabrication, transmission electron microscopy, carbonOther keywords: chimney soot, transmission electron microscopy, ultraviolet–visible spectroscopy, thermal properties, thermogravimetric analysis, differential thermal analysis, antibacterial activity, carbon nanoparticles, X‐ray diffraction study, gram‐positive bacterial strains, gram‐negative bacterial strains, antibacterial potency, scanning electron microscopy, C₆₀      

Modifications of Fullerenes Extractions and Chromatographies with Different Solvents

Abstract

In the Bucky System II, based on electrical arc method, carbon soot was produced. Fullerenes C₆₀ and C₇₀ were Soxhlet extracted from the collected soot samples with toluene, chlorobenzene and with both of them successively, modifying the original methods. The yields of the both obtained toluene extracts were 5.4%. Chlorobenzene extract yield was 5.8%. After extraction of toluene insoluble soot with chlorobenzene, the entire extract yield was increased from 5.4% to 5.8%, due to modification of the existing methods. The difference of fullerenes solubilities in these solvents has been concluded. In the second part of our work toluene and chlorobenzene fullerenes extracts were separated by column chromatographies on active Al₂O₃, modifying the existing methods, by elution with hexane and mixtures of benzene, toluene, or xylene with hexane in determined ratios and orders. Identifications of buckminsterfullerene C₆₀ in the first chromatographically purified fractions were achieved by electron impact ionization (EI) mass, IR, and UV/VIS spectroscopy. The second and the third purified fullerene fractions, toluene and chlorobenzene soot extracts were characterized by IR and UV/VIS methods.     

Effect of molecular weight on fibrous PVA produced by electrospinning

The effects of polymer weight average molecular weight (M_W) on the fiber structure of electrospun polyvinylalcohol (PVA) have been studied. PVA with a degree of hydrolysis of 98–99% and with molecular weights ranging from 9000 to 186,000 g/mol was dissolved in water. The concentration (C) of the polymer in the solution was varied depending on the molecular weight. The solution was electrospun at 30 kV and the sample obtained on the collector was examined by scanning electron microscopy. It was observed that for each molecular weight, a fibrous structure was stabilized above a minimum concentration, generally corresponding to [η]C>5. The average fiber diameter was between 250 nm and 2 μm. The fiber diameter increases with M_W and concentration. At low M_W and/or concentrations ([η]C<9), the fibers exhibit a circular cross-section. Flat fibers were observed at high M_W and concentrations ([η]C>9).     

Quantitative Determination of C60 and C70 in Soot Extracts by High Performance Liquid Chromatography and Mass Spectrometric Characterization

Abstract

A quantitative HPLC method was applied to determine the amounts of C₆₀ and C₇₀ present in extracts of soot produced in the electric arc reactor and in flames. The combustion method was found to yield a higher C₇₀/C₆₀ ratio (0.67) compared with the evaporation experiment where the C₇₀/C₆₀ ratio amounts to 0.27.     

Optical measurement in carbon nanotubes formation by pulsed laser ablation

Carbon nanotubes (CNTs) were produced by laser ablation of a graphite composite target in argon and nitrogen ambient gas. To investigate the effect of nitrogen gas on CNTs formation, the plasma plume was examined using optical emission spectroscopy. The vibrational temperature of C₂ molecules was estimated by fitting of a Swan band spectrum. The temperature in N₂ ambient gas is lower than that in Ar ambient gas. In a nitrogen atmosphere, the spectrum intensity of C₂ Swan band was enhanced and CN violet system was also observed. Soot collected in the reaction tube was observed using FE-SEM and TEM. The soot deposited in the nitrogen gas contained more bundled CNTs than those in Ar ambience.     

Acceleration of Tri-Addition to [70]Fullerene by “Nanom Black” Fullerene Soot

We report the structure and properties of a fullerene soot called “Nanom Black,” which is prepared by removing fullerenes from the soot formed in fullerene production. Nanom Black remarkably accelerates the regioselective tri-addition of phenylcopper reagent to C₇₀, giving C₇₀Ph₃H at a reaction rate approximately 50-fold that in the absence of Nanom Black. Transmission electron microscopy, X-ray diffraction, and Raman data on Nanom Black are presented, and a mechanistic rationale is discussed.     

Detection of Buckminsterfullerene in Usual Soots and Commercial Charcoals

Abstract

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.     

Computations on Metallofullerenes Derivatized during Extraction: La@C80-C6H3Cl2 and La@C82-C6H3Cl2

Recently, an extraction of la metallofullerenes from soot using 1,2,4-trichlorobenzene has been reported for La@C₈₀ and La@C₈₂. In both cases, the cages were derivatized by the solvent (forming La@C₈₀-C₆H₃Cl₂ and La@C₈₂-C₆H₃Cl₂) and the following X-ray analysis disclosed rather unexpected cages: C₈₀(C _2v ;3) and C₈₂(C _3v ;7). In order to explain the challenging observations, a two-step computational treatment is presented. The first step deals with the high-temperature gas-phase formation of the underivatized endohedrals while the second step models the reaction with the solvent. The Gibbs free energies were evaluated for representative temperatures and the computational scheme was able to confirm high relative populations for the observed derivatized cages.     

An Invariant of Carbon Arc Synthesis of Fullerenes

Abstract

The yields of fullerenes C₆₀ and C₇₀ were determined in a wide range of controlled parameters. The total yield of fullerenes varied from 3 to 24%. The molar relative contents C₆₀/C₇₀ appeared to be constant for all samples of toluene extracts of the soot and equal to 5.06 ± 0.1. The accuracy of this constancy (± 2%) was determined by application of a special mathematical processing to the spectra of toluene extracts.     

The excellent soft magnetic properties and corrosion behaviour of nanocrystalline FePCCu alloys

The effects of the addition of Cu on the crystallisation behaviour, soft magnetic properties, and corrosion behaviour of Fe_84-xP₉C₇Cu_x (x = 0–1.15) alloys were investigated. The experimental results demonstrate that the glass-forming ability of this alloy was improved and the soft magnetic properties of the alloy system were enhanced by proper Cu addition. FePCCu nanocrystalline alloys with a dispersed α-Fe phase were obtained by appropriately annealing the melt-spun ribbons at 693 K for 2 min. The Fe_83.25P₉C₇Cu_0.75 nanocrystalline alloy exhibited a high saturation magnetic flux density, B _s , of 1.64 T; a low coercivity, H _c , of 3.9 A/m; and a high effective permeability, μ _e , of 21,000 at 1 kHz. These characteristics are superior to corresponding properties of FePC alloys. Furthermore, the corrosion resistance of this nanocrystalline alloy increases when elevating the annealing temperature and was confirmed to be improved with respect to the corresponding amorphous alloy. These results indicate that this alloy is a promising soft magnetic material.     

Characterization of the surface layer due to oxygen for the hydrogen related C-SiC films

The films containing C and about 80%SiC were deposited by R F. magnetron sputtering followed with argon ion beam bombardment to enhance the adhere strength of the substrate and then were introduced hydrogen by using hydrogen ion irradiation or high pressure permeation techniques. XPS was used to investigate the sub-surface of these C-SiC films. The results show that, apart from carbon adsorbing hydrogen, carbon-hydrogen, SiC and Si_1−xC_x, contamination by oxygen reacting with Si and C in the films was apparent. Further reaction with hydrogen to form C_y-Si-O-H on the sub-surface of the C-SiC films was also shown. Calculation of the concentrations of the different configurations based on Ghosh model shows that different x values in Si_1−xC_x and different y values in C_y-Si-O-H can be obtained due to different hydrogen introduction methods.     

Numerical simulation of soot formation in pulverized coal combustion with detailed chemical reaction mechanism

A two-dimensional unsteady numerical simulation with a detailed chemical reaction mechanism that considers 158 species and 1804 reactions is applied to pulverized coal combustion in a mixing layer and the soot formation behavior is investigated in detail. The computational conditions and ignition process are the same as those in our previous work (Muto et al., 2017). The results show that the peak of the mass density of the soot is distributed in the region where the gas temperature is higher than the unburned gas temperature of the mixture of volatile matter and air (1300–1400?K) and lower than the flame temperature (2000?K $～$). This is due to the fact that soot formation from the precursors (C₂H₂ and C₆H₆) is enhanced as the gas temperature increases, whereas the quantities of the precursors and the produced soot are reduced due to oxidation at the higher gas temperature condition that exists close to the flame. The peak value of the mass density of the soot is also distributed in the region between the peak values of the gas temperature and the probability density function of the number of coal particles.     

Synthesis of boron-doped diamond films by DC plasma CVD using a CH4+CO2+H2 gas mixture at lower substrate temperature and formation of an n-Si/p-diamond heterojunction

Diamond films were synthesized by direct current plasma chemical vapour deposition using a CH₄+CO₂+H₂ gas mixture on Si substrates. The optimum deposition conditions were determined. It was found that 0.4 A/cm² current density, at applied voltage of 1 kV, resulted in good-quality diamond films. The substrate temperature was 750 K which is considerably lower than the conventional requirement of ∼1100 K. Boron doping was achieved by passing a portion of the gas mixture through boric acid dissolved in methanol. The boron-doped p-type diamond films were deposited on an n-type single crystalline Si substrate and an n-Si/p-diamond heterojunction was fabricated. The p-n junction was characterized in terms of current-voltage (I-V) and capacitance-voltage (C-V) measurements.     

Formation of High Mass Cn clusters (n > 100) by Laser Ablation/Desorption Coupled with Mass Spectrometry

Abstract

The “in-situ” formation of high mass carbon C_n clusters (n>100) is studied by laser irradiation of the fullerenes C₆₀, C₇₀, C76 and C₈₄ in a Laser Microprobe coupled with Mass Spectrometry (LMMS).The fragmentation of the fullerene by loss of C₂ units and the distribution of the obtained coalescence products are strongly depending on the laser power density and the wavelength. This phenomenum is correlated to the reactivity of the C₂ fragments.     

Photocatalytic degradation of methylene blue by C<Subscript>3</Subscript>N<Subscript>4</Subscript>/ZnO: the effect of the melamine/ZnO ratios

The C₃N₄/ZnO composite photocatalysts were synthesized by mechanical milling combined with a calcination process. Various ratios of melamine and ZnO powders were milled by a planetary ball mill for 10 h. After heating at 540^°C for 3 h in air, melamine was converted to C₃N₄ but the formation of C₃N₄ depended on the ratios of the melamine and ZnO (M/Z) powders. From the experimental results, the conversion of melamine to C₃N₄ could be inhibited by ZnO particles; as there was no detectable C₃N₄ in the sample at low M/Z values or high ZnO contents. The photocatalytic activities of prepared samples were investigated under the illumination of blacklight and fluorescent lamps as the low wattage light source. The C₃N₄ /ZnO showed a better photocatalytic activity than ZnO to degrade a methylene blue (MB) dye solution using blacklight lamps, but there is no significant difference in photocatalytic activities between ZnO and prepared C₃N₄/ZnO under visible light by the fluorescent lamps. However, the prepared C₃N₄/ZnO can well function under illumination by Xe lamp as the high power light source. Ecotoxicities of MB solutions before and after photocatalytic process were also studied through growth inhibition of the alga Chlorella vulgaris.     

The preparation of carbon-coated iron nanocrystals produced from Fe2O3-containmg composite anode in arc discharge

Using an Fe₂O₃-containing composite anode instead of an Fe-containing composite anode in the Kratschmer-Huffman carbon arc method, carbon-coated Fe (not Fe₂O₃) nanocrystals are produced both in the soot on the reactor walls and in the cathode deposits. The encapsulates also contain a little iron carbide, but do not contain iron oxides, as identified by transmission electron microscopy ( TEM ) and X-ray diffraction (XRD). As compared with Ni₂O₃- and Co₂O₃-containing composite anodes, the action of the Fe₂O₃-containing composite anode is unique. When the Fe₂O₃ contents in the composite graphite rod for the carbon arc nanocrystal production are increased in the range 5-33 wt.%, the effect on the structure and diameter distribution of the iron nanocrystals is investigated. The diameter distribution of iron nanocrystals is about 1–30 nm. The effect of helium pressure in the range 80–680 torr on the yield of C_60/70 in carbon soot produced from the composite graphite rod has also been examined. We present a novel result about the relationship of C_60/70 yields and helium gas pressure using a composite anode differing remarkably from the result using a homogeneous graphite anode in arc discharge.     

Mechanisms of increased wear resistance of composites based on PTFE doped with fullerene soot

We have studied the effect of small additives of a fullerene soot (FS) on the linear wear intensity I _h of poly(tetrafluoroethylele) (PTFE) in sliding friction on steel with water lubrication. The introduction of only 1% FS into PTFE leads to a sharp drop in I _h . The investigation of FS samples by means of small-and wide-angle X-ray scattering showed that FS contains C₆₀ fullerene and graphite nanocrystals with an average size of 20–25 nm and ultrafine carbon particles 2–3 nm in size. The presence of dispersed nanoscopic particles probably imparts the FS-doped PTFE samples the properties of nanocomposites. The possible mechanism of microcrack healing in PTFE by nanoparticles representing fullerene fragments is considered.     

Study of some physical properties of biodegradable films based on blends of gelatin and poly(vinyl alcohol) using a response-surface methodology

The aim of this work was to study the effect of the hydrolysis degree (HD) and the concentration (C_PVA) of two types of poly(vinyl alcohol) (PVA) and of the type (glycerol and sorbitol) and the concentration (C_P) of plasticizers on some physical properties of biodegradable films based on blends of gelatin and PVA using a response-surface methodology. The films were prepared with a film forming solutions (FFS) with 2 g of macromolecules (gelatin+PVA)/100 g de FFS. The responses analyzed were the mechanical properties, the solubility, the moisture content, the color difference and the opacity. The linear model was statistically significant and predictive for puncture force and deformation, elongation at break, solubility in water, moisture content and opacity. The C_PVA affected strongly the elongation at break of the films. The interaction of the HD and the C_P affected this property. Moreover, the puncture force was affected slightly by the C_PVA. Concerning the solubility in water, the reduction of the HD increased it and this effect was greater for high C_PVA values. In general, the most important effect observed in the physical properties of the films was that of the plasticizer type and concentration. The PVA hydrolysis degree and concentration have an important effect only for the elongation at break, puncture deformation and solubility in water.