Carbon Nano-onions Research Articles

Simulations of graphitic nanoparticles at air-water interfaces.

The free energy associated with transferring a set of fullerene particles through a finite water layer is calculated using explicit solvent molecular dynamic simulations. Each fullerene particle is a carbon network of one or more spheroidal shells of graphitic carbon, and include single-shell (single-wall) or nested multi-shelled (nano-onions) structures ranging from 6 to 28 Å in radius. Corresponding changes in energy suggest a stronger affinity of carbon nano-onions for water compared to their single-shelled analogues. In the case of multi-shelled structures, the free energy profiles display a global minimum only in the bulk liquid indicating a high affinity of multi-shelled fullerene for complete hydration. Single-wall particles however, display a minimum at the air-water interface and for particles larger than 2 nm this minimum is a global minimum possessing a lower energy compared to the particle's state of complete hydration. While the propensity for single-shell particles to adsorb to the air-interface may increase with increasing particle size, there is an indication based on line tension calculations that larger single-shell particles may actually exhibit enhanced wetting compared to their smaller analogues.

Designing binder-free, flexible electrodes for high-performance supercapacitors based on pristine carbon nano-onions and their composite with CuO nanoparticles

Binder-free flexible CNO–CuO composite electrodes delivering an energy density of 58.33 W h kg−1 at less than 1 $.

Pressure induced structural transition of small carbon nano-onions

Small carbon nano-onions (S-CNOs) were prepared by annealing nanodiamonds (ND) in an argon atmosphere.

Multi-Functionalized Carbon Nano-onions as Imaging Probes for Cancer Cells.

Carbon-based nanomaterials have attracted much interest during the last decade for biomedical applications. Multimodal imaging probes based on carbon nano-onions (CNOs) have emerged as a platform for bioimaging because of their cell-penetration properties and minimal systemic toxicity. Here, we describe the covalent functionalization of CNOs with fluorescein and folic acid moieties for both imaging and targeting cancer cells. The modified CNOs display high brightness and photostability in aqueous solutions and their selective and rapid uptake in two different cancer cell lines without significant cytotoxicity was demonstrated. The localization of the functionalized CNOs in late-endosomes cell compartments was revealed by a correlative approach with confocal and transmission electron microscopy. Understanding the biological response of functionalized CNOs with the capability to target cancer cells and localize the nanoparticles in the cellular environment, will pave the way for the development of a new generation of imaging probes for future biomedical studies.

Electrochemical sensing performance of nanodiamond-derived carbon nano-onions: Comparison with multiwalled carbon nanotubes, graphite nanoflakes, and glassy carbon

Carbon nano-onions (CNOs) are emerging carbon nanomaterials with unique microstructure and electronic properties. CNOs are 0-D carbon analogs of 1-D carbon nanotubes (CNTs) and 2-D graphenes. CNOs are composed of sp2-bonded, concentric nanographene shells surrounding a hollow core. Microstructure, electrochemical properties, and biosensing performances of nanodiamond-derived CNOs (N–CNOs) were studied in comparison with other popular carbon electrodes: multiwalled carbon nanotubes (MWCNTs), graphite nanoflakes (GNFs), and glassy carbon (GC). First, morphology and microstructure of N–CNOs were characterized by scanning and transmission electron microscopies (SEM, TEM), X-ray diffraction (XRD), and Raman spectroscopy. Chemical composition and chemical functional groups were probed by X-ray photoelectron spectroscopy (XPS). Raman spectra of N–CNOs showed a large value of ID/IG, indicating that N–CNOs include defects, i.e., exposed edge planes. Second, electrocatalytic activity of N–CNOs toward oxygen reduction reaction was tested in comparison with MWCNTs, GNFs, and GC. Last, biosensing performances of N–CNOs were studied. Cyclic voltammetric and differential pulse voltammetric measurements were carried out for the detection of redox-active biomolecules such as dopamine, epinephrine, and norepinephrine. The results showed remarkable electrochemical activities of N–CNOs with high sensitivity, high selectivity, and stable electrode responses for the detection of biologically important molecules.

Highly surface functionalized carbon nano-onions for bright light bioimaging

Carbon-based nanomaterials functionalized with fluorescent and water-soluble groups have emerged as platforms for biological imaging because of their low toxicity and ability to be internalized by cells. The development of imaging probes based on carbon nanomaterials for biomedical studies requires the understanding of their biological response as well as the efficient and safety exposition of the nanomaterial to the cell compartment where it is designed to operate. Here, we present a fluorescent probe based on surface functionalized carbon nano-onions (CNOs) for biological imaging. The modification of CNOs by chemical oxidation of the defects on the outer shell of these carbon nanoparticles results in an extensive surface functionalization with carboxyl groups. We have obtained fluorescently labelled CNOs by a reaction involving the amide bond formation between fluoresceinamine and the carboxylic acids groups on the surface of the CNOs. The functionalized CNOs display high emission properties and dispersability in water due to the presence of high surface coverage of carboxylic acid groups that translate in an efficient fluorescent probe for in vitro imaging of HeLa cells, without significant cytotoxicity. The resulting nanomaterial represents a promising platform for biological imaging applications due to the high dispersability in water, its efficient internalization by cancer cells and localization in specific cell compartments.

A One-Step Synthesis Method for Hollow Carbon Nano-Onions

Carbon nano-onions with hollow/shell structures were directly synthesized by a combustion synthesis process, using poly (tetrafluoroethylene) powders and ferrous chloride as raw materials. The growth of an intermediate FeF2 core template which is a dynamic-controlled process is demonstrated to be the key factor to prepare hollow carbon nano-onions. Raman spectroscopy revealed that the as-synthesized product was mainly composed of amorphous carbon. Such unique process suggests a new method for controlling the growth of an intermediate core to prepare different hollow carbon nanostructures.

A review on the use of carbon nanostructured materials in electrochemical capacitors

Sustainable and renewable energy resources, as well as energy storage systems (ESSs), are amongst the current and critical global requirements. A comparative discussion on batteries, fuel cells and electrochemical capacitors (ECs) is presented. The mechanisms involved in various classes of ECs are also elaborated. Additionally, a historical background highlighting some of the major steps associated with EC development over the years is discussed in this review. In particular, carbon nanostructured materials have high potential in the development of ESSs, and hence this review presents an insight on the current ESSs with a strong bias towards these materials as ECs. The current status of carbon nanomaterials, such as carbon nanotubes, nanofibers, nano-onions, nanorods, fullerenes and graphene nanosheets, in ECs is reviewed. The associated effects of nanostructural parameters, such as pore sizes and specific electro-active areas, amongst others, in terms of energy storage capabilities are also discussed. Typical physicochemical characterisation techniques, which enrich understanding of their characteristics, are also reviewed. The discussion views set platforms for a variety of unique carbon nanomaterial designs with high prospective specific capacitance. Key porosity tailoring protocols, such as chemical activation, introduction of heteroatoms in carbon nanostructures and template synthesis methods, are also reviewed. The effects of other device components, such as electrolyte ion size and solvent system, electrode design and use of binders, to the overall capability of EC, are also discussed. Copyright © 2015 John Wiley & Sons, Ltd.

Activated Carbon Nanochains with Tailored Micro-Meso Pore Structures and Their Application for Supercapacitors

Carbon nanochains (CNCs) were synthesized by a facile chemical vapor deposition process consisting of a 1D chain of interconnected carbon nano-onions for potential application in supercapacitors. In this study, the CNCs were further activated by a chemical method using potassium hydroxide (KOH) as the activation agent to obtain micro-meso pore structures. To improve the specific surface area (SSA) and optimize the pore size distribution (PSD) to enhance the capacitance performance, we investigated the activation parameters, including the KOH content, temperature and duration. The results indicated that CNCs with a hierarchical pore structure and high SSA could be achieved using an activation process with a KOH-to-CNC ratio of 2 at 900 °C for 20 h. The mechanism is also discussed. The activation temperature and duration affect the promotion of the carbon graphitization and exaggeration of the carbon etching. The CNCs activated using the optimal parameters exhibited a high capacitance performance of 112.7 F...

ChemInform Abstract: Carbon Nano‐Onions (Multi‐Layer Fullerenes): Chemistry and Applications

AbstractReview: 83 refs.

Removing PAHs from urban runoff water by combining ozonation and carbon nano-onions

Ozone (O3) is a chemical oxidant capable of transforming polycyclic aromatic hydrocarbons (PAHs) in urban runoff within minutes but complete oxidation to CO2 can take days to weeks. We developed and tested a flow-through system that used ozone to quickly transform PAHs in a runoff stream and then removed the ozone-transformed PAHs via adsorption to carbon nano-onions (CNOs). To quantify the efficacy of this approach, 14C-labeled phenanthrene and benzo(a)pyrene, as well as a mixture of 16 unlabeled PAHs were used as test compounds. These PAHs were pumped from a reservoir into a flow-through reactor that continuously ozonated the solution. Outflow from the reactor then went to a chamber that contained CNOs to adsorb the ozone-transformed PAHs and allowed clean water to pass. By adding a microbial consortium to the CNOs following adsorption, we observed that bacteria were able to degrade the adsorbed products and release more soluble, biodegradable products back into solution. Control treatments confirmed that parent PAH structures (i.e., non-ozonated) were not biologically degraded following CNO adsorption and that O3-transformed PAHs were not released from the CNOs in the absence of bacteria. These results support the combined use of ozone, carbon nano-onions with subsequent biological degradation as a means of removing PAHs from urban runoff or a commercial waste stream.

Impact of Carbon Nano-Onions on Hydra vulgaris as a Model Organism for Nanoecotoxicology.

The toxicological effects of pristine and chemically modified carbon nano-onions (CNOs) on the development of the freshwater polyp Hydra vulgaris were investigated in order to elucidate the ecotoxicological effects of CNOs. Chemical modifications of the CNOs were accomplished by surface functionalization with benzoic acid, pyridine and pyridinium moieties. thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy confirmed the covalent surface functionalization of CNOs. Hydra specimens were exposed to the carbon nanomaterials by prolonged incubation within their medium. Uptake was monitored by optical microscopy, and the toxicological effects of the CNOs on Hydra behavior, morphology, as well as the long-term effects on the development and reproductive capability were examined. The obtained data revealed the absence of adverse effects of CNOs (in the range 0.05–0.1 mg/L) in vivo at the whole animal level. Together with previously performed in vitro toxicological analyses, our findings indicate the biosafety of CNOs and the feasibility of employing them as materials for biomedical applications.

Reinforcement with in-situ synthesized carbon nano-onions in aluminum composites fabricated by flake powder metallurgy

Bulk aluminum matrix composites reinforced with carbon nano-onions (CNOs) were fabricated by a flake powder metallurgy route. Homogenous dispersion of CNOs (with an average size of ∼20 nm) was guaranteed by in situ polymer pyrolysis chemical vapor deposition of the precursor on Al nanoflakes with high specific surface area, followed by consolidating the CNO/Al nanoflake powders and then hot extrusion. The uniformly dispersed CNOs in ultrafine grained Al matrix exhibited remarkable strengthening efficiency: the 1.2 wt.% CNO/Al composite had a yield strength of 268 MPa and an ultimate tensile strength of 384 MPa, improved by 77% and 56% as compared to the Al matrix without CNOs, respectively. The strength enhancement with the in-situ CNOs is mainly attributed to a combined mechanism of grain boundary strengthening and Orowan strengthening.

ChemInform Abstract: Recent Applications of Carbon Nanomaterials in Fluorescence Biosensing and Bioimaging

AbstractReview: 215 refs.

Enhanced Synthesis of Carbon Nanomaterials Using Acoustically Excited Methane Diffusion Flames.

Acoustically modulated methane jet diffusion flames were used to enhance carbon nanostructure synthesis. A catalytic nickel substrate was employed to collect the deposit materials at sampling position z = 10 mm above the burner exit. The fabrication of carbon nano-onions (CNOs) and carbon nanotubes (CNTs) was significantly enhanced by acoustic excitation at frequencies near the natural flickering frequency (ƒ = 20 Hz) and near the acoustically resonant frequency (ƒ = 90 Hz), respectively. At these characteristic frequencies, flow mixing was markedly enhanced by acoustic excitation, and a flame structure with a bright slender core flame was generated, which provided a favorable flame environment for the growth of carbon nanomaterials. The production rate of CNOs was high at 20 Hz (near the natural flickering frequency), at which the gas temperature was about 680 °C. Additionally, a quantity of CNTs was obtained at 70–95 Hz, near the acoustically resonant frequency, at which the gas temperature was between 665 and 830 °C. However, no carbon nanomaterials were synthesized at other frequencies. The enhanced synthesis of CNOs and CNTs is attributed to the strong mixing of the fuel and oxidizer due to the acoustic excitation at resonant frequencies.

Rotating Disk Slurry Electrochemically Modified Platinum Carbon Nano-Onion Anode Material for Polymer Electrolyte Membrane Fuel Cells

Platinum modified carbon nano-onion anode materials (Pt-CNO) with 18.5% metal loading were prepared by the Rotating Disk Slurry Electrode (RoDSE) technique for Polymer Electrolyte Membrane Fuel Cell applications. The Pt-CNO was characterized and tested in direct ethanol, methanol, and hydrogen polymer electrolyte membrane fuel cells at 55°C. Platinum particles showed an average size of (9±1) nm according to XRD data and applying the Scherrer equation. However, high-resolution transmission electron microscopy images showed well-dispersed Pt nanoparticles, clusters, and atoms on the carbon based support material. The 5 cm2 fuel cell studies were done with commercial Pt black and Pt-CNO catalysts anode electrode loadings of 4 mg/cm2. Pt-CNO exhibited enhanced maximum power density compared to Pt black, when normalized by the Pt anode loading, i.e. 20mg and 3.7mg for Pt black and Pt-CNO, respectively. For ethanol, methanol, and hydrogen the anode Pt mass normalized power densities showed increments of 32%, 66%, and 353%, respectively.

Raman spectroscopy of polyhedral carbon nano-onions

The Raman spectra of polyhedral carbon nano-onions (PCO), obtained by underwater arc discharge of graphite electrodes, are studied. While the general Raman spectrum of PCO is very similar to those of other carbon nanostructures, including spherical nano-onions, the fine structure of the G and 2D bands gives valuable information that allows using Raman spectroscopy for differentiating the PCO from other carbon structures. The interpretation of the features of the fine structure of the spectra is supported by evidences obtained by TEM.

Reactive Carbon Nano-Onion Modified Glassy Carbon Surfaces as DNA Sensors for Human Papillomavirus Oncogene Detection with Enhanced Sensitivity.

Glassy carbon electrodes were modified with small carbon nano-onions (CNOs) and activated by electrografting of diazonium salts bearing terminal carboxylic acid and maleimide groups. The CNO-modified surfaces were characterized by ESEM and AFM microscopy as well as by electrochemical techniques. The modified electrodes were used for the amperometric detection of a model DNA target sequence associated with the human papillomavirus by immobilizing short recognition sequences by amidation or thiol-maleimide reactions. The analytical parameters of the developed biosensors were compared with glassy carbon electrodes without CNOs. In both cases, the incorporation of CNOs resulted in an enhancement in sensitivity and a decrease in detection limits ascribed to a combination of large surface areas and enhanced electron transfer properties of the CNO-modified electrodes. These results offer promise for the construction of other CNO-based biomolecule detection platforms with enhanced sensitivities.

Influence of the Synthetic Conditions on the Structural and Electrochemical Properties of Carbon Nano-Onions.

Thermal annealing of nanodiamonds with diameters of a few nanometers (in an inert atmosphere and at temperatures in the range: 1500-1800 °C) leads to the formation of carbon nano-onions (CNOs) with diameters between 5 and 6 nm, which correspond to nanostructures with six to eight graphitic layers. The resulting spherical CNO structures were thermally modified under different atmospheres and characterized by SEM, TEM, thermogravimetric analysis and spectroscopic (Raman and diffuse reflectance infrared Fourier transform/FTIR) spectroscopy. The electrochemical properties of the CNOs prepared under different conditions were determined and compared. The results reveal that the CNOs show different structures with predominant spherical "small" carbon nano-onions. The aim of this article is to investigate the impact of the CNO's synthesis conditions on the resulting structures and study the effect of further thermal modifications on the sizes, shapes and homogeneity of these carbon nanostructures.

Synthesis and Characterization of Far-Red/NIR-Fluorescent BODIPY Dyes, Solid-State Fluorescence, and Application as Fluorescent Tags Attached to Carbon Nano-onions.

A series of π-extended distyryl-substituted boron dipyrromethene (BODIPY) derivatives with intense far-red/near-infrared (NIR) fluorescence was synthesized and characterized, with a view to enhance the dye's performance for fluorescence labeling. An enhanced brightness was achieved by the introduction of two methyl substituents in the meso positions on the phenyl group of the BODIPY molecule; these substituents resulted in increased structural rigidity. Solid-state fluorescence was observed for one of the distyryl-substituted BODIPY derivatives. The introduction of a terminal bromo substituent allows for the subsequent immobilization of the BODIPY fluorophore on the surface of carbon nano-onions (CNOs), which leads to potential imaging agents for biological and biomedical applications. The far-red/NIR-fluorescent CNO nanoparticles were characterized by absorption, fluorescence, and Raman spectroscopies, as well as by thermogravimetric analysis, dynamic light scattering, high-resolution transmission electron microscopy, and confocal microscopy.