Graphite Arc Discharge Research Articles

Carbon nano-onion as next-generation functional nanomaterial: Synthesis methods and practical applications

Carbon nano-onion (CNO) (also known as onion-like carbon, OLC), exhibiting multiple enclosed fullerene shell structures, as one of the most promising nanoforms, has attracted worldwide attention during the past decades due to its exceptional chemical and physical properties such as non-toxicity, high chemical stability, large sufficient surface area with low density, and superior high electronic and thermal conductivities, visible photoluminescence, etc. Nowadays, functional CNOs have been applied in energy storage devices, supercapacitors, photovoltaics, light-emitting diodes and bio-imaging technology. Since the first observation of CNOs by transmission electron microscopy as a byproduct in the synthesis of carbon black in 1980, numerous experimental and theoretical studies including expressive practical applications of CNOs have been intensively developed in modern chemistry. With respect to synthetic techniques, the high-temperature annealing of nano diamond, detonation of high explosive molecules, arc discharge of graphite, chemical vapor deposition, laser ablation, thermal pyrolysis, hydrothermal carbonization, and microwave pyrolysis have been reported. It has been addressed that the synthesis approach plays a key role in determining the structure of CNOs and resultant properties. This paper reviewed the developments of CNOs through major synthesis methods utilized for a selected wide spectrum of applications, by covering both the past and current progress. The contents outlined in the current review will offer readers comprehensive insights into the design and development of CNO materials.

Graphene and graphene oxide with anticancer applications: Challenges and future perspectives.

Graphene‐based materials have shown immense pertinence for sensing/imaging, gene/drug delivery, cancer therapy/diagnosis, and tissue engineering/regenerative medicine. Indeed, the large surface area, ease of functionalization, high drug loading capacity, and reactive oxygen species induction potentials have rendered graphene‐ (G‐) and graphene oxide (GO)‐based (nano)structures promising candidates for cancer therapy applications. Various techniques namely liquid‐phase exfoliation, Hummer's method, chemical vapor deposition, chemically reduced GO, mechanical cleavage of graphite, arc discharge of graphite, and thermal fusion have been deployed for the production of G‐based materials. Additionally, important criteria such as biocompatibility, bio‐toxicity, dispersibility, immunological compatibility, and inflammatory reactions of G‐based structures need to be systematically assessed for additional clinical and biomedical appliances. Furthermore, surface properties (e.g., lateral dimension, charge, corona influence, surface structure, and oxygen content), concentration, detection strategies, and cell types are vital for anticancer activities of these structures. Notably, the efficient accumulation of anticancer drugs in tumor targets/tissues, controlled cellular uptake properties, tumor‐targeted drug release behavior, and selective toxicity toward the cells are crucial criteria that need to be met for developing future anticancer G‐based nanosystems. Herein, important challenges and future perspectives of cancer therapy using G‐ and GO‐based nanosystems have been highlighted, and the recent advancements are deliberated.

SYNTHESIS OF CARBON NANOTUBES BY THE ELECTRIC ARC-DISCHARGE METHOD

The paper presents the synthesis of carbon nanotubes (CNTs) by the method of electric arc-discharge. To obtain CNTs, the process of an electric arc-discharge of graphite was carried out; the current strength at a constant voltage of 50 V was 120, 150, 170, 200 A (inert medium - argon). Using the methods of electron microscopy, BET and Raman scattering, the chemical composition, specific surface area were determined, and the surface morphology of the obtained samples was studied. The results of determining the specific surface area and pore volume show that with increasing current strength, the specific surface area and specific pore volume increase from 25.450 to 159.737 m2/g and from 0.011 cm3/g to 0.068 cm3/ g, respectively. Electron microscopic images show CNT particles with a diameter of 58 to 370 nm, which are rolled into a single, seamless, cylindrical shape.

Double functionalization of a fullerene in drastic arc-discharge conditions: synthesis and formation mechanism of C2v(2)-C78Cl6(C5Cl6)

Arc-discharge of graphite is the most prevalent technique for synthesis of novel fullerenes, but the extreme conditions of the carbon arc prevent any currently available instrument from detecting the reaction species inside. To detour the difficulties for probing the derivatization mechanism in the drastic arc-discharge conditions, C78Cl6(C5Cl6) with prototypical C2v(2)-C78 cage has been isolated and characterized in the products of the chlorine-involving carbon arc. The structure of C2v(2)-C78Cl6(C5Cl6), featuring with fullerene C2v(2)-C78 doubly functionalized by chlorine atoms and perchlorinated cyclopentadiene, has been identified by X-ray crystallography. Confirmed by standard Density Functional Theory (DFT) calculations and Car-Parrinello simulations as well as mass spectrometry, the fullerene core has been revealed to form firstly followed then by reaction with chlorine atoms and afterwards with perchlorinated cyclopentadiene, with implication about stepwise reaction temperatures and sequences for the formation of fullerenes and their derivatives in the otherwise inaccessible extreme conditions of the carbon arc.

Catalyst Support on Carbon Nanoballoon and Evaluation of Its Catalytic Activity in Direct Methanol Fuel Cells

The reduction of CO2 emissions from cars has recently become an important issue, and the development of fuel cell vehicle (FCV) is now in progress. Two problems to be solved for its wide commercial use of fuel cells are the efficient use of platinum (Pt) and ruthenium (Ru) catalysts and the improvement of power density. Carbon black, nanometer-size carbon particles, is commercially used as a catalyst support in fuel cells owing to its high surface area, porosity, electric conductivity, low density, and low cost. Carbon nanomaterials have unique characteristics. In the previous work, we supported PtRu catalysts on various carbon nanomaterials with different geometry and evaluated the catalytic activity of the supported catalysts for direct methanol fuel cell (DMFC) [1]. In this study, we used carbon nanoballoon (CNB) as a catalyst support and measured the catalytic activity of CNB-supported PtRu catalysts. Arc black (AcB) was produced by an arc discharge of graphite in N2 atmosphere as the precursor of CNB. The twin-torch arc discharge apparatus was used for AcB synthesis. AcB is mainly composed of cocoon-shaped carbon nanoparticles with a lot of amorphous ingredients. CNB was prepared by a heat treatment of AcB in Ar gas at 2600°C for 2 h [2]. AcB and CNB comprised spherical particles of 50 nm in diameter. The particle shape of CNB is hollow. CNB is graphitic and is expected to have high conductivity. Carbon nanocoil (CNC) was synthesized using an automatic chemical vapor deposition system with consecutive substrate transfer mechanism [1]. The fiber diameters of the CNCs was ~300 nm, and the coil diameters of the CNCs was ~1000 nm. We prepared PtRu catalysts for the DMFC anode. The PtRu catalysts were loaded onto CNB by the reduction method using sodium boron hydrate (NaBH4), and counterparts employing the commercial Vulcan-supported PtRu catalyst and CNC-supported PtRu catalyst were also prepared. Hydrogen hexachloroplatinate (IV) hexahydrate (H2PtCl6·6H2O) and ruthenium trichloride (RuCl3) were used as the Pt and Ru precursors, respectively. The molar ratio of Pt and Ru was set at 1:1. Each of the carbon nanomaterials (200 mg) was dispersed in 500 mL of deionized water by sonication for 20 min. H2PtCl6·6H2O and RuCl3 were stirred in 50 mL of deionized water at 60 rpm for 10 min. The solutions were mixed and stirred at 600 rpm for 10 min. Next, a 30-fold molar excess of NaBH4 with respect to the metal precursors was added to 400 mL deionized water. This NaBH4 solution was added to the metal precursor and carbon nanomaterial mixture and stirred. The solution was then filtered, washed and dried to obtain the supported catalyst. The carbon nanomaterials were characterized using scanning electron microscopy (SEM), a laser Raman spectroscopy, Brunauer–Emmet–Teller (BET) measurements, and compressive resistivity measurements. The morphological characteristics and crystalline structure of the prepared catalysts were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The amounts of catalyst loaded on the carbon nanomaterials were analyzed by thermo-gravimetric analysis (TGA). We measured the electrochemical property of the PtRu catalysts supported on the carbon nanomaterials with different shapes, size, and electrical properties. The same amounts of catalyst were loaded on each carbon nanomaterial. The catalyst amount was measured to be 30 wt.% by TGA. Their catalytic activities were measured by cyclic voltammetry (CV) in H2SO4 and CH3OH/H2SO4 electrolytes. The highest methanol oxidation reaction (MOR) current densities were observed for the PtRu catalysts supported on CNB. The catalyst activity of the CNB-supported catalysts was higher than that of the Vulcan-supported catalysts. This is mainly due to the higher electrical conductivity benefiting from the structure of CNB.

ChemInform Abstract: Graphene Oxide: Strategies for Synthesis, Reduction and Frontier Applications

AbstractReview: 263 refs.

Retrieving Precursors Toward Endohedral Metallofullerenes

A series of intermediates such as C6, C1 0 and C16 have been retrieved by chlorination from the crude soot of carbon arc, affording insight into endofullerene formation. Identified by HPLC-MS and UV/Vis, production of perchlorinated polycyclic aromatic hydrocarbons (PAHs) such as C6Cl6, C1 0C8, and C16Cl10 from the reaction involving ICl with the crude soot of carbon arc heavily depends on formation of endofullerenes, as exemplified by the arc-discharge synthesis of metallofullerenes encapsulating with lanthanum or dysprosium. The perchlorinated PAHs reduce dramatically in chlorination of the pristine soot in the control trials with arc-discharge of graphite in absence of the typical encapsulated metals, with implication about the polycyclic carbon skeletons (i.e. C6, C1 0, C16) originating from the precursors toward endohedral metallofullerens. The work facilitates the understanding of how and what metals encapsulatable in the fullerene cage.

Improving the characteristic of electric double layer capacitors using oxidized carbon nanoballoon

Carbon nanomaterials are used as an electrode of electric double layer capacitors (EDLCs). In this research, we used arc black (AcB) and carbon nanoballoon (CNB) as the electrode material. AcB was produced by an arc discharge of graphite in N2 atmosphere, and CNB was formed by a heat treatment of AcB. CNB is graphitic, and the particle shape is hollow. CNB has a higher specific capacitance than AcB at a high scan rate. In order to increase the specific capacitance of EDLC, CNB was oxidized at 625°C in the air. By oxidization, the outer shell of CNB forms wrinkle. We call this material oxidized CNB (Ox-CNB). AcB, CNB, and Ox-CNB were used for the EDLC electrodes and were compared with commercially available activated carbon (AC). Cyclic voltammetry and electrochemical impedance spectroscopy of the EDLC electrodes were measured by an electrochemical measurement system. The specific capacitance of Ox-CNB (29 F/g) was larger than that of AC (16 F/g) at a scan rate of 500mV/s. Furthermore, Ox-CNB had a high conductivity as a result of impedance measurement. Ox-CNB is an excellent electrode material of EDLC when using at a high charge/discharge rate.

Strategies for the Synthesis of Graphene, Graphene Nanoribbons, Nanoscrolls and Related Materials

Single-layer graphene (SLG), the 3.4 Å thick two-dimensional sheet of sp(2) carbon atoms, was first prepared in 2004 by mechanical exfoliation of graphite crystals using the scotch tape technique. Since then, SLG has been prepared by other physical methods such as laser irradiation or ultrasonication of graphite in liquid media. Chemical methods of synthesis of SLG are more commonly used; the most popular involves preparation of single-layer graphene oxide followed by reduction with a stable reagent, often assisted by microwave heating. This method yields single-layer reduced graphene oxide. Other methods for preparing SLG include chemical vapour deposition over surfaces of transition metals such as Ni and Cu. Large-area SLG has also been prepared by epitaxial growth over SiC. Few-layer graphene (FLG) is prepared by several methods; arc discharge of graphite in hydrogen atmosphere being the most convenient. Several other methods for preparing FLG include exfoliation of graphite oxide by rapid heating, ultrasonication or laser irradiation of graphite in liquid media, reduction of few-layer graphene oxide, alkali metal intercalation followed by exfoliation. Graphene nanoribbons, which are rectangular strips of graphene, are best prepared by the unzipping of carbon nanotubes by chemical oxidation or laser irradiation. Many graphene analogues of inorganic materials such as MoS(2), MoSe(2) and BN have been prepared by mechanical exfoliation, ultrasonication and by chemical methods involving high-temperature or hydrothermal reactions and intercalation of alkali metals followed by exfoliation. Scrolls of graphene are prepared by potassium intercalation in graphite or by microwave irradiation of graphite immersed in liquid nitrogen.

Synthesis and Selected Properties of Graphene and Graphene Mimics

Graphene has generated great excitement in the last few years because of its novel properties with potential applications. Graphene exhibits an ambipolar electric field effect, ballistic conduction of charge carriers, and the quantum Hall effect at room temperature. Some of the other interesting characteristics of graphene include high transparency toward visible light, high elasticity and thermal conductivity, unusual magnetic properties, and charge transfer interactions with molecules. In this Account, we present the highlights of some of our research on the synthesis of graphene and its properties. Since the isolation and characterization of graphene by micromechanical cleavage from graphite, several strategies have been developed for the synthesis of graphene with either a single or just a few layers. The most significant contribution from our laboratory is the synthesis of two to four layer graphene by arc-discharge of graphite in a hydrogen atmosphere. Besides providing clean graphene surfaces, this method allows for doping with boron and nitrogen. UV and laser irradiation of graphene oxide provides fairly good graphene samples, and laser unzipping of nanotubes produces graphene nanoribbons. We have exploited Raman spectroscopy to investigate the charge-transfer interactions of graphene with electron-donor and -acceptor molecules, as well as with nanoparticles of noble metals. Graphene quenches the fluorescence of aromatics because of electron transfer or energy transfer. Notable potential applications of the properties of graphene are low turn-on field emission and radiation detection. High-temperature ferromagnetism is another intriguing feature of graphene. Although incorporation of graphene improves the mechanical properties of polymers, its incorporation with nanodiamond or carbon nanotubes exhibits extraordinary synergy. The potential of graphene and its analogues as adsorbents and chemical storage materials for H(2) and CO(2) is noteworthy.

GRAPHENE: SYNTHESIS, FUNCTIONALIZATION AND PROPERTIES

Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arcdischarge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS2and WS2have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.

GRAPHENE: SYNTHESIS, FUNCTIONALIZATION AND PROPERTIES

Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arc-discharge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS2and WS2have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.

Synthesis of Carbon Nanomaterials in Flames

<p>Usage of combustion processes for production of target products is less common than the application of catalytic processes. However, there are known examples of production of carbon black, HCl, TiO<sub>2</sub> etc. Some research work was done at the Institute of Combustion Problems (Almaty, Kazakhstan) consider the synthesis in flame of carbon nanomaterials: fullerenes, nanotubes and soot nanobeads with superhydrophobic surface. An alternative of fullerenes and nanotubes synthesis in arc discharge of graphite is the method using stationary hydrocarbon flames. Flame is a self-sustaining system in which the hydrocarbons can be precursors of carbon nanomaterials, and the heat released during combustion, is a parameters of the process control. It is known that PAH are nucleation centers of forming soot i.e. PAH can be converted into either soot or fullerenes. The formation of CNTs occurs in diffusion flames from the fuel side and is initiated by transition metals particles. The paper presents data on the formation of fullerenes and carbon nanotubes as well as soot with the superhydrophobic surface, obtained on nickel and silicon supports in benzene-oxygen and propane-oxygen diffusion flames. New results regarding the synthesis of superhydrophobic surface with a contact angle 135-175° have great practical interest as anti-corrosion additives to various materials.</p>

Photoluminescence, white light emitting properties and related aspects of ZnOnanoparticles admixed with graphene and GaN

ZnO nanoparticles exhibit a broad band centred around 530 nm in the photoluminescence(PL) spectrum due to the presence of oxygen vacancies. Composites of ZnO nanoparticleswith graphenes show marked changes in the PL spectrum with broad bands covering theentire visible region, making them candidates for solid state lighting, while grapheneprepared by arc discharge of graphite in a hydrogen atmosphere (HG) containing 2–3 layersas well as boron-doped (BHG) and nitrogen-doped (NHG) samples of HG give white lightwhen admixed with ZnO nanoparticles; excellent results are obtained with the addition ofjust 7 wt% of BHG to the ZnO nanoparticles. Mixtures of ZnO and GaN nanoparticles alsoexhibit white light emission. The quantum yields of these ZnO nanoparticle based whitelight sources are in the 4–6% range. Photoconductivity characteristics of ZnOnanoparticles are affected by the addition of even a small amount of graphene (<0.5 wt%).

Characteristics of field-effect transistors based on undoped and B- and N-doped few-layer graphenes

Field-effect transistor characteristics of few-layer graphenes prepared by several methods have been investigated in comparison with those of single-layer graphene prepared by the in situ reduction of single-layer graphene oxide. Ambipolar features have been observed with single-layer graphene and n-type behaviour with all the few-layer graphenes, the best characteristics being found with the graphene possessing 2–3 layers prepared by arc-discharge of graphite in hydrogen. FETs based on boron and nitrogen doped graphene show n-type and p-type behaviour respectively.

Semiconducting single-walled carbon nanotubes synthesized by S-doping

Abstract An approach was presented for synthesis of semiconducting single-walled carbon nanotubes (SWNTs) by sulfur (S) doping with the method of graphite arc discharge. Raman spectroscopy, UV-vis-NIR absorption spectroscopy and electronic properties measurements indicated the semconducting properties of the SWNTs samples. Simulant calculation indicated that S doping could induce convertion of metallic SWNTs into semiconducting ones. This strategy may pave a way for the direct synthesis of pure semiconducting SWNTs.

NO2 and humidity sensing characteristics of few-layer graphenes

Sensing characteristics of few-layer graphenes for NO2 and humidity have been investigated with graphene samples prepared by the thermal exfoliation of graphitic oxide, conversion of nanodiamond (DG) and arc-discharge of graphite in hydrogen (HG). The sensitivity for NO2 is found to be highest with DG. Nitrogen-doped HG (n-type) shows increased sensitivity for NO2 compared with pure HG. The highest sensitivity for humidity is observed with HG. Sensing characteristics of graphene have been examined for different aliphatic alcohols and the sensitivity is found to vary with the chain length and branching.

Production of magnetic iron oxide nanoparticles by using graphite arc discharge in Fe(OH)3 colloidal solution

AbstractIn this study, magnetic iron oxide nanoparticles were produced by thermal treatment of Fe(OH)3 colloidal solution after graphite arc discharge in the solution. The X‐ray diffraction (XRD) pattern of the heat‐treated powders showed that magnetic iron oxide nanoparticles (γ‐Fe2O3 or Fe3O4) were produced by the phase transformation from α‐Fe2O2 at the thermal treatment temperature over 500°C. The XRD pattern also indicated that the graphite powders produced by the arc discharge were contained in the Fe(OH)3 colloidal solution, suggesting that the graphite powders contributed to the reduction process of α‐Fe2O3. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(2): 55–62, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10024

Synthesis of fullerene by pyrolysis of acetylene in thermal HF-Plasma

Carbon soot containing fullerene was continuously produced in volume by pyrolyzing acetylene in thermal HF-Plasma. The characteristics of the carbon soot and C60 were analyzed by thtransmission electron microscopy, UV/visible, IR and Raman spectroscopy. The results show that the main ingredients of the carbon soot with size of about 25 nm are amorphous carbon, graphite and fullerene. The fullerene yield in carbon soot is about 2.5 g·h−. Compared with the graphite arc discharge method, the acetylene thermal plasma method is a preferential one for synthesis of fullerene.

Production of Magnetic Iron Oxide Nanoparticles by using Graphite Arc Discharge in Fe(OH)3 Colloidal Solution

In this study, magnetic iron oxide nanoparticles were produced by thermal treatment of Fe(OH)3 colloidal solution after graphite arc discharge in the solution. X-ray diffraction (XRD) pattern of the heat-treated powders showed that magnetic iron oxide nanoparticles (γ-Fe2O3 or Fe3O4) were produced by the phase transformation from α-Fe2O3 at the thermal treatment temperature over 500°C. The XRD pattern also indicated that the graphite powders produced by the arc discharge were contained in the Fe(OH)3 colloidal solution, suggesting that the graphite powders contributed to the reduction process of α-Fe2O3.