Carbon Nano-onions Research Articles

Synthesis of Hollow Carbon Nano-Onions Using the Pulsed Plasma in Liquid

We synthesized carbon nano-onions (CNOs) using a low-voltage spark discharge in a liquid and studied the effects of liquid type and pulse duration. By the pulsed electric discharge between two graphite rods of 120 mm length and 6 mm diameter submerged into a 200 ml toluene or ethanol, hollow CNOs with diameters ranging from 10 to 30 nm were produced. CNOs produced using toluene grew more carbon shells than does the sample produced using ethanol. The sample that was synthesized using pulsed plasma with pulse duration of 5 μs showed more carbon shells (10-30) than the sample prepared by 12 μs (2 to 10). High performance liquid chromatography (HPLC) and high resolution transmission electron microscopy analyses confirmed that the sample produced at 12 μs pulsed plasma contains fullerene C60, while the sample prepared at 5 μs does not.

Microwave-Assisted Solvothermal Synthesis of Pd-MnO2 Hybrid at Onion-like Carbons: Electrocatalytic Oxidation of Alcohols in Alkaline Media

The use of less toxic glycerol, (a non-flammable, volatile, and little-valued residue of biodiesel production), ethanol as well as ethylene glycol (EG) as fuel may be an interesting alternatives to methanol for Direct Alcohol Fuel Cell (DAFC) technology. The volumetric energy densities of glycerol, ethanol and EG are 5.80, 6.31 and 5.97 kW h L-1 compared to 5.81 kW h L-1for methanol makes them good fuel cell candidates [1-2]. The secret to the efficient electrocatalysis of alcohols is the use of efficient nanocatalyst. Palladium-based catalysts have emerged as the most viable electrocatalysts for alcohol in alkaline electrolytes. To harness the great catalytic potential offered by Pd, and to reduce cost, Pd-based alloys supported on different carbon supports are constantly used in direct alcohol fuel cells (DAFCs). In this work, palladium-manganese oxide nanoparticles supported on carbon nano onions (Pd-MnO2/OLC) were synthesized using the microwave-assisted solvothermal technique. Palladium-manganese oxide nanoparticles supported on Vulcan carbon (Pd@MnO2/XC–72) were also synthesized using the same technique for comparison. The catalysts were characterized using XRD, XPS, FESEM and HRTEM techniques. Electroxidation of the alcohols was performed in 0.5 M alcohol / 0.5 M KOH via cyclic and linear sweep voltammetry, chronoamperometric and elelctrochemical impedance spectroscopy. Results obtained show that the catalyst supported on OLC exhibited the highest current density and least charge transfer resistance relative to the catalyst supported on XC–72. Pd-MnO2/OLC gave the best result amongst the catalyst synthesized with respect to the current density, and electrochemical stability as well as exhibited the least charge transfer resistance in all the alcohols studied. For instance, the onset oxidation potential and current density of the glycerol oxidation process were -0.5386 V and 5.58mAcm-2, respectively. The implications of these results relative to methanol oxidation using the best catalyst system synthesized are discussed.

Chemical versus electrochemical synthesis of carbon nano-onion/polypyrrole composites for supercapacitor electrodes.

The development of high-surface-area carbon electrodes with a defined pore size distribution and the incorporation of pseudo-active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano-onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission- and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g(-1) for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g(-1) for the CNOs/Ppy bilayer (electrochemical deposition).

Surface analysis of zinc-porphyrin functionalized carbon nano-onions.

Multishell fullerenes, known as carbon nano-onions (CNOs), are an interesting class of carbon-based nanomaterials. They display several unique properties, such as a large surface area to volume ratio, a low density, and a graphitic multilayer morphology, which have made them appealing for several applications in many fields, including biology. Chemical functionalization of CNOs dramatically enhances their solubility and attenuates their inflammatory properties, thereby increasing their applicability especially in the fields of biology and medicine. CNOs functionalized with fluorescent probes can be used for cellular imaging. In this article, detailed surface characterization of CNOs functionalized with a zinc porphyrin (ZnTPP) as the fluorescent probe is presented. In particular, time-of-flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy provide a detailed surface characterization of the organic functionalities introduced via "click chemistry" and clearly demonstrate the success of the CNOs functionalization process. XPS data reveal the presence of Zn and N, whilst ToF-SIMS is able to identify specific fragments related to the presence of the ZnTPP, such as the quasimolecular mass peak [C32N4H20Zn](+) and the molecular mass peak [C44N4H28Zn](+). Moreover, ions fragments deriving from the triazole ring formed by the click chemistry reaction have been identified by ToF-SIMS analysis, proving unambiguously the covalent binding of the fluorescent molecules to the CNOs surfaces.

Influence of oxygen concentration, fuel composition, and strain rate on synthesis of carbon nanomaterials

This paper investigates the influence of flame parameters including oxygen concentration, fuel composition, and strain rate on the synthesis of carbon nanomaterials in opposed-jet ethylene diffusion flames with or without rigid-body rotation. In the experiments, a mixture of ethylene and nitrogen was introduced from the upper burner; meanwhile, a mixture of oxygen and nitrogen was supplied from the lower burner. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. With non-rotating opposed-jet diffusion flames, carbon nanotubes (CNTs) were successfully produced for oxygen concentrations in the range of 21–50 % at a fixed ethylene concentration of 20 %, and for ethylene concentrations ranging from 14 to 24 % at a constant oxygen concentration of 40 %. With rotating opposed-jet diffusion flames, the strain rate was varied by adjusting the angular velocities of the upper and lower burners. The strain rate governed by flow rotation greatly affects the synthesis of carbon nanomaterials [i.e., CNTs and carbon nano-onions (CNOs)] either through the residence time or carbon sources available. An increase in the angular velocity lengthened the residence time of the flow and thus caused the diffusion flame to experience a decreased strain rate, which in turn produced more carbon sources. The growth of multi-walled CNTs was achieved for the stretched flames experiencing a higher strain rate [i.e., angular velocity was equal to 0 or 1 rotations per second (rps)]. CNOs were synthesized at a lower strain rate (i.e., angular velocity was in the range of 2–5 rps). It is noteworthy that the strain rate controlled by flow rotation greatly influences the fabrication of carbon nanostructures owing to the residence time as well as carbon source. Additionally, more carbon sources and higher temperature are required for the synthesis of CNOs compared with those required for CNTs (i.e., about 605–625 °C for CNTs and 700–800 °C for CNOs).

Pt-nanoparticle functionalized carbon nano-onions for ultra-high energy supercapacitors and enhanced field emission behaviour

In the present work, we have investigated the charge storage capacitive response and field emission behaviour of platinum (Pt) nanoparticles decorated on carbon nano onions (CNOs) and compared them with those of pristine carbon nano onions.

Facile synthesis of electrochemically active Pt nanoparticle decorated carbon nano onions

Well dispersed platinum nanoparticles (∼2 nm) on carbon nano-onions are accessible using a simple and scalable one-step batch method.

Ultraviolet and blue emitting graphene quantum dots synthesized from carbon nano-onions and their comparison for metal ion sensing.

Ultraviolet and blue emitting graphene quantum dots (GQDs) were synthesized by chemical oxidation of carbon nano-onions. TEM, AFM, XPS, and optical characterization techniques showed that different optical properties of UV- and blue-emitting GQDs originate from their unique structure and chemical functionalities. UV- and blue-emitting GQDs were also compared for heavy metal ion sensing.

Non-covalent functionalization of carbon nano-onions with pyrene–BODIPY dyads for biological imaging

We report a novel approach based on non-covalent interactions for the functionalization of carbon nano-onions (CNOs) with fluorophores.

Perylenetetracarboxylic anhydride as a precursor of fluorescent carbon nanoonion rings.

Thermal annealing at 400 °C of perylenetetracarboxylic anhydride in low molecular mass PEG gives rise to the formation of well defined nanoobjects of 2.5 nm height and size distribution from 10 to 65 nm (average 40 nm) after purification of the raw mixture with silicagel chromatography. TEM reveals that the flat nanoobjects are constituted of concentric graphenic rings (0.34 nm interlayer distance). The morphology of the nanoparticles resembles onion rings of nanometric dimensions (nanoonion rings C-NOR). C-NOR particles have an excitation dependent emission with λem from 430 to 570 nm and a maximum emission quantum yield of 0.49. C-NOR particles can be internalized into Hep3B human hepatoma cells as determined by confocal fluorescence microscopy and are remarkably biocompatible affecting slightly cell viability according to the MTT test.

Preparation of carbon nano-onions by the low-temperature unfolding of MWCNTs via interaction with theraphthal

Ultrasonic treatment of theraphthal and MWCNT dispersions resulted in the formation of nano-onion structures in mild conditions.

Supramolecular solubilization of cyclodextrin-modified carbon nano-onions by host-guest interactions.

Small carbon nano-onions (CNOs, 6-12 shells) were prepared in high yields and functionalized with carboxylic groups by chemical oxidation and reacted with βCD-NH2 to yield CNOs decorated with βCDs. A biocompatibile dextran polymer with graphted ferrocene groups was employed for the supramolecular self-assembly on the βCD-CNO surfaces. The βCDs act as hosts and the polymer ferrocene groups as guests (Fc-Dex) by the formation of inclusion complexes. After their assembly these nanostructures were soluble in aqueous solutions. The resulting product was characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and FT-IR and Raman spectroscopies. Moreover, the deposition of successive layers on the surface of the particles was monitored using DLS measurements and zeta potentials. Through-space interactions between the Fc moieties and the CNO cores and the influence of an additional dextran-βCD outer layer were measured electrochemically.

Fabrication and purification of carbon nano onions

Carbon nano onions (CNOs) with diameters of 70–100 nm were fabricated by chemical vapor deposition at 800 °C, using methane as carbon source and high-temperature steam treated 316 stainless steel mesh as catalyst. The CNOs were isolated from the substrate by HNO3 refluxing, calcination in air at 500 °C and magnetic separation. The morphology, microstructures and magnetic properties of the CNOs were characterized by SEM, TEM, XRD, Raman spectroscopy, FT-IR spectroscopy and vibration sample magnetometer tests. Results showed that the surface-attached catalyst particles and amorphous carbon can be effectively removed from raw CNOs through HNO3-refluxing and calcination. Magnetic separation can selectively remove the CNOs encapsulating a [Ni, Fe] magnetic catalyst from the CNOs that are hollow. [New Carbon Materials 2014, 29(5): 398–403]

Carbon nano-onions (multi-layer fullerenes): chemistry and applications.

This review focuses on the development of multi-layer fullerenes, known as carbon nano-onions (CNOs). First, it briefly summarizes the most important synthetic pathways for their preparation and their properties and it gives the reader an update over new developments in the recent years. This is followed by a discussion of the published synthetic procedures for CNO functionalization, which are of major importance when elucidating future applications and addressing drawbacks for possible applications, such as poor solubility in common solvents. Finally, it gives an overview over the fields of application, in which CNO materials were successfully implemented.

Electric field-oriented growth of carbon nanotubes and Y-branches in a needle-pulsed arc discharge unit: mechanism of the production

Carbon nano-onions, multiwall carbon nanotubes and Y-branched nanotubes are synthesised in a simple production apparatus. A pulsed plasma is generated by discharging a high voltage needle pulse between two graphite electrodes. A strong electric field is presented along anode and cathode electrodes. The pulse width is 0.3 μs. Acetone vapour, as a precursor, is introduced to the plasma through a graphite nozzle in the cathode assembly. A magnetic field, perpendicular to the plasma path, is provided. The possibility of carbon nanotube production through a short-pulsed arc discharge technique is investigated in this article. The results show that adding an electric field between electrodes prevents carbon ions’ dispersion, facilitates charge transferring between ions and electrodes, orients the growth of carbon nanotubes along the applied electric field and finally makes it possible to produce functionalised carbon nanoparticles such as Y-branch nanotubes and nanoknees. In this work, the growth mechanism of carbon nanotubes in a needle-pulsed arc-discharge reactor is discussed. And a possible explanation is provided for the synthesis of Y-branch carbon nanotubes. The products are examined by using scanning probe microscopy technique.

The Direct Decomposition of Nitric Oxide Over Fe/CNOs (CNOs: Carbon Nano Onions)

The decomposition of NO was studied over carbon nano onions (CNOs) supported Fe catalyst made in a facility of spinning disc process (SDP). At the temperature of 500°C, 83% NO was decomposed to N2 with 93% of selectivity (N2 formation rate: 3.44 µmol N2·s–1·gcatalyst–1). The rest are the by-products of NO2 and N2O. X-ray diffraction study demonstrated that the iron carbide was generated in the catalyst. Thermogravimetric analysis indicated that CNOs were stable below 600°C under air atmosphere. In situ diffuse reflectance infrared Fourier transformation spectroscopy study detected the NO2 and N2O2 species during NO adsorption.

Purification of Carbon Nano-Onions Fabricated by Arc Discharge

Soot containing carbon nano-onions was synthesized by traditional electric arc-discharge method with nickel powder as catalyst. After heating at 400°C for 2 h, the arc discharged soot was soaked in hydrochloric acid solution 8 h, and then ultrasonically dispersed into sodium cholate solution. Such obtained dispersion was filtrated with a medium-speed filter paper, and the filtrate was further filtered with a 0.2 μm polytetrafluoroethylene membrane to collect the purified carbon nano-onions. SEM (scanning electron microscope) and TEM (transmission electron microscope) observation showed that carbon nano-onions with hollow or nickel-encapsulated cavities were observed and they had a wide size distribution with an averaged diameter of 24.4 nm. XRD (X-ray diffraction) and Raman scattering investigations evidenced a high degree graphitization of such obtained carbon nano-onions. The XPS (X-ray photoemission spectroscopy) analysis, survey to surface chemistry, demonstrated that oxygen-containing and nitrogen-containing functional groups and the metal catalyst were removed from the surface of carbon nano-onions after purification.

Pulse laser ablation system for carbon nano-onions fabrication

A new laser ablation chamber design for KrF excimer laser synthesis of carbon nanomaterials, including nano-onions, is reported. The conditions for carbon nano-onions deposition, using excimer laser to ablate a commercial pure graphite target, were investigated. The transmission electron microscopy analysis of the collected deposits indicates that mainly nano-onions are obtained when pure graphite targets are ablated. Raman spectroscopy identified without doubt production of carbon nano-onions.

Synthesis of Carbon Nanotubes and Nano-onions Using Electric Field Induced Needle-Pulsed Arc Discharge Plasma

Carbon nano-onions and multi-walled carbon nanotubes (MWCNTs) are synthesized by needle-pulsed arc discharge plasma. In a simple production apparatus, a needle pulsed plasma is applied between two graphite electrodes in the presence of an electric field between anode and cathode. The possibility of carbon nanotube production by short pulsed arc discharge technique is investigated in this article. The pulse width is 0.3 μsec. Acetone vapor as carbon source is introduced to plasma. A magnetic field, perpendicular to the plasma path, is provided. The advantages of using short pulsed plasma are studied in this work. The results show that applying a DC electric field between electrodes, increases plasma tendency toward cathode, enhances the chance of plasma-hydrocarbon interaction, prevents carbon ions from dispersion and finally makes it possible to produce CNTs by low-power short pulses in an arc-discharge plasma reactor. The products are examined using SPM techniques. In this work, adding an electric field to the pulsed plasma techniques, suggests a new method to produce carbon nano particles (CNPs) by short current pulses with lifetime of below one microsecond.

Hollow carbon nano-onions with hierarchical porosity derived from commercial metal organic framework

We report on the synthesis of new metal–organic framework derived carbons using a two-step process employing for the first time a commercially available iron-containing metal–organic framework. The resulting carbons consist mainly of highly graphitic shells due to the highly dispersed iron in the precursor structure which catalyzes the formation of graphitic carbon. In addition, a distinct onion-like morphology is observed, with high total pore volumes of up to 1cc/g and a hierarchically structured porosity in which the hollow cores of the carbon onions are accessible via smaller micro- and mesopores. As a proof of concept we furthermore demonstrate the inherent structure of this carbon being advantageous for the application in lithium–sulfur batteries as a both confining and contacting host for the active material, yielding capacities of up to 550mAh/g after 40 cycles.