Carbon Nano-onions Research Articles

Electrochemical Synthesis of Conductive Polymers to Enhance Carbon Supports for Metal Catalysts

In this project is based on the synthesis of electrically conductive polymers as supports for metal catalysts using the rotating disk slurry electrode (RoDSE) technique, in which isolated atoms, clusters and metal nanoparticles are deposited on an unsupported nanocarbon material. The aim of the research is the use of RoDSE to electrochemically synthesize nanoparticles based on polypyrrole as support for metallic catalysts. This technique will also be used to produce coatings of polypyrrole-based conducting polymers on nanocarbon supports to increase their surface. The first step is the synthesis of nanodiamonds to carbon nano-onions (CNO) using a thermal process. Once the product was obtained, it was characterized using the Raman and XRD technique. In the Raman, the signals are observed approximately 1300 cm-1 and 1700 cm-1, whereas in the X-ray diffraction diffractograms the peaks are observed approximately at 25° and 40°. Second, a synthesis was performed with the CNO to oxidize the layers of CNO particles with sulfuric acid. The follow step will be using RoDSE to deposit polypyrrole as support. To confirm these results, infrared Fourier transform spectroscopy and Raman techniques will be used to identify support materials. The techniques of cyclic voltammetry and electrochemical impedance spectroscopy will be used to identify the conductive polymers for their electrochemical properties. The dynamic light scattering technique will also be used to determine the size of the particles and the interactions with the polymers. Finally, the scanning electron microscopy technique will be used to obtain images of the analyzed surface.

Novel Nanocomposites for High-Performance Supercapacitors

The use of renewable energy with unsteady supply has been gradually increased, requiring energy storage for steady supply of energy. Carbonaceous materials such as graphene, carbon nanotubes, and carbon fibers have been studied for capacitive energy storage purposes. On the other hand, materials based on metal oxides/sulfides have been studied for electrochemical charge storage. Though the carbonaceous materials carry large surface area and high electrical conductivity, they have limited energy density. However, the metal oxides/sulfides perform electrochemical reactions, resulting in high energy density. Composites of carbonaceous materials and metal oxides/sulfides exhibit the synergistic effects on energy density and power density, improving the supercapacitor performances tremendously. We have tried several different carbon materials, metals, and particle sizes, synthetic methods, morphologies, etc., for better performances up to 4000 F g-1. Recently, we have developed carbon nano-onions and doped carbon nano-onions in inexpensive way for making remarkably capacitive materials. Figure 1

(Invited) Ammonia Oxidation Reaction Under Microgravity Conditions

Ammonia oxidation is an important electrochemical reaction needed in urine purification processes for water reclamation in the International Space Station (ISS). The objective of the microgravity experiment was to compare the ammonia oxidation capabilities of different catalysts at a half cell and in an alkaline fuel cell. Different Pt catalysts were studied, from nanoparticles on carbon supports to platinum nanocubes with preferential crystalline (100) sites. Under microgravity conditions the performance of a fuel cell was diminished by the absence of buoyancy since nitrogen gas was produced, blocking the catalytic sites. The following catalysts were studied: platinum nanocubes (ca. 10nm in diameter), platinum nanocubes on carbon Vulcan and platinum on carbon nanoonion support prepared by the RoDSE method [1]. This research has shown the difference between the performance of the catalysts in an ammonia fuel cell under microgravity and ground experimental conditions, in terms of normalized current densities [1]. In the case of a fuel cell with platinum black at the anode there is a reduction in the produced mass-normalized current densities of around 7.5% between the hypergravity and microgravity experimental episodes. This decrease was shown to be reversed when gravity effects were once again applied to the fuel cell, confirming the direct influence from microgravity on the electrochemical oxidation of ammonia. For the half cell, a decrease in performance of 20-65% over ground-based controls for the electrochemical oxidation of ammonia was found [2,3]. This decrease in current is theorized to be due to the lack of buoyancy driven mixing that occurs in microgravity. In microgravity only diffusional mixing occurs and, therefore, molecules may be unable to reach the nanocatalyst interface at the same rate as on the ground. During the first oxidation peak at ca. 0.7 V vs. Ag QRE, the formation of N2 molecule, during microgravity, conditions creates a stagnant gas-surface interaction that avoids ammonia molecules to reach the Pt surface. This situation leads to a significant peak current decrease compared to the ground experiments. On the other hand, during the second oxidation peak an oxynitride layer is formed at the interface of the electrode without the formation of N2 molecule. This latter peak does not have the effect of microgravity due to the surface chemistry reaction and the oxide adsorbates are no readily desorbed. Therefore, no major differences between the microgravity and ground conditions are observed in such an oxynitride layer region. These findings indicate that significant reductions in electrode performance for ammonia electrooxidation may occur if catalyst design measures are not taken in consideration to mitigate these microgravity effects. This conclusion is applicable specifically to electrochemical processes, but also may be relevant to all process constrained by nanoscale mixing of diffusion limited structures such as thermal catalysts, separation membranes, microbial growth and human cellular functions. For these microgravity experiments, a tailored electrochemical lab was designed and constructed that would handle 2g and 0g gravitational conditions (see Figure 1) [2,3]. References Poventud-Estrada, C. M.; Acevedo, R.; Morales, C.; Betancourt, L.; Diaz, D. C.; Rodriguez III, M. A.; Larios, E.; José-Yacaman, M.; Nicolau, E.; Flynn, M.; and Cabrera, C. R., “Microgravity Effect on Chronoamperometric Ammonia Oxidation at Platinum Nanoparticles Modified Mesoporous Carbon Supports”, Microgravity Science and Technology 2017, 29(5), 381-389. https://doi.org/10.1007/s12217-017-9558-5Acevedo, R.; Poventud-Estrada, C.M; Morales-Navas, C.; Martinez-Rodriguez, R.A.; Ortiz-Quiles, E.; Vidal-Iglesias, F.; Sollá-Gullón, J.; Nicolau, E.; Feliu, J.M.; Echegoyen, L.; Cabrera, C.R., “Chronoamperometric Study of Ammonia Oxidation in a Direct Ammonia Alkaline Fuel Cell under the Influence of Microgravity”, Microgravity Science and Technology 2017, 29(4),253–261. http://dx.doi.org/10.1007/s12217-017-9543-zNicolau, E., Poventud-Estrada, C.M., Arroyo, L., Fonseca, J., Flynn, M., Cabrera, C.R.: Microgravity effects on the electrochemical oxidation of ammonia: A parabolic flight experiment. Electrochim. Acta 2012, 75, 88-93. doi:10.1016/j.electacta.2012.04.079 Figure 1

Determination of the Hansen solubility parameters of carbon nano-onions and prediction of their dispersibility in organic solvents

Carbon nano-onions (CNOs) are the least studied allotropes of carbon despite their discovery before nanotubes and fullerenes. CNOs are multilayered fullerenes concentrically arranged one inside the other resembling the structure of an onion. Typically, their size average ranges from 2 to 50 nm in diameter. Recently, CNOs have gained attention in different fields because of their interesting chemical and physical properties. However, their lack of dispersibility in common solvents due to strong intermolecular interactions limits their applications. Here, we studied the dispersion behavior of CNOs prepared by nanodiamond annealing in 20 solvents of different polarities. Dynamic light scattering and transmission electron microscopy were used to study the dispersion of CNOs in the different solvents. The solvents were classified as “good” or “bad” solvents to determine the Hansen solubility parameters (HSP) of the CNOs using various optimization approaches. The calculated HSPs (δD, δP and δH) were further used to predict the CNO dispersion behavior in other solvents with a very good agreement between expected and observed dispersibilities. Our results will be helpful to estimate the behavior of CNOs in other solvents or their interaction with other materials with known HSPs.

Detonation synthesis of carbon nano-onions via liquid carbon condensation

Transit through the carbon liquid phase has significant consequences for the subsequent formation of solid nanocarbon detonation products. We report dynamic measurements of liquid carbon condensation and solidification into nano-onions over ∽200 ns by analysis of time-resolved, small-angle X-ray scattering data acquired during detonation of a hydrogen-free explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts a direct liquid to solid graphite phase transition for DNTF products ~200 ns post-detonation. Solid detonation products were collected and characterized by high-resolution electron microscopy to confirm the abundance of carbon nano-onions with an average diameter of ∽10 nm, matching the dynamic measurements. We analyze other carbon-rich explosives by similar methods to systematically explore different regions of the carbon phase diagram traversed during detonation. Our results suggest a potential pathway to the efficient production of carbon nano-onions, while offering insight into the phase transformation kinetics of liquid carbon under extreme pressures and temperatures.

Synthesis of carbon nanostructures from corn stalk using mechano-thermal method

Millions of tons of nuts are produced every year in the world (e.g. hazelnut shell, corn stalk, walnut shell) and these vegetal wastes create serious environmental problems. It is crucial that these wastes are converted into valuable products using simple and industrially applicable methods. The products obtained are widely used as adsorbents. Some studies utilizing these wastes as raw materials have obtained activated carbon using chemical methods, and employed this activated carbon as an adsorbent. In this study, a product containing carbon nanostructures was synthesized from corn stalk using mechno-thermal method. This product consists of many structures such as carbon nanotubes, carbon fibers, carbon nano-onion and amorphous carbon. We think that this synthesized product is an effective adsorbent. First, corn stalks were carbonized. The carbonized structure was milled for 20 h using a high-energy mill and the particle size was reduced to nano-scale. At the last stage of production, the milled sample was subjected to thermal treatment at 1400 °C. Analyses showed that the product is composed of graphitic carbon structures such as carbon nanotubes, nano-onion, and amorphous carbons. Very thin layers of graphite were also observed in some parts of the product. This study aimed to produce a structure containing carbon nanostructures from corn stalk and achieved this goal. Further research on the use of the product as an adsorbent is in progress.

Generation of carbon nano-onions by laser irradiation of gaseous hydrocarbons for high durability catalyst support in proton exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFC) are promising zero emission power sources that typically use precious noble metals such as platinum as catalysts. Due to the expensive catalyst material costs, the durability of catalyst support material is vital PEMFC systems. Carbon nano-onions (CNOs) are spherical multi-shelled fullerenes that have higher quality graphitic layers with less defects, leading to better resistance to carbon corrosion. Here, we show that CNOs produced by laser pyrolysis can be used instead of commonly used carbon black, Vulcan XC-72, as the catalyst support material. Both cells have similar initial performance, but CNO based cell is better able to maintain power output in harsh operating conditions.

Carbon Nano-Onions as Non-Cytotoxic Carriers for Cellular Uptake of Glycopeptides and Proteins.

Carbon nano-onions (CNOs) possess favorable properties that make them suitable for biomedical applications, including their small size, ready surface modification, and good biocompatibility. Here, we report the covalent immobilization of a synthetic glycopeptide and the protein bovine serum albumin (BSA) onto the surface of carbon nano-onions using the maleimide–thiol “addition reaction”. The glycopeptide and BSA are readily transported inside different cell lines, together with carbon nano-onions, through the endocytosis pathway. Our results show that carbon nano-onions are excellent scaffolds for glycopeptides and proteins immobilization and act as intracellular carriers for these biomolecules. These findings open new perspectives in the application of carbon nano-onions as intracellular transporters in diverse biomedical applications.

Amperometric biosensor for glyphosate based on the inhibition of tyrosinase conjugated to carbon nano-onions in a chitosan matrix on a screen-printed electrode.

Glyphosate [N-(phosphonomethyl)glycine] is the most frequently used herbicide to date. Due to its indiscriminate use, it has become a globally occurring pollutant of surface waters. A biosensor for glyphosate is described here that consists of a carbon nano-onion/tyrosinase conjugate immobilized in a chitosan matrix on a screen-printed electrode. The analytical principle is based on the inhibition of the enzyme tyrosinase by glyphosate. L-DOPA is used as the enzyme substrate. The presence of the carbon nano-onions has a beneficial effect on the sensitivity of the assay. Glyphosate can be amperometrically quantified in the 0.015 to 10μM concentration range and with a 6.5nM (1.1μgL-1) detection limit. The biosensor is stable more than 2months at 4°C. It was applied to the detection of glyphosate in waterand soil samples taken from irrigation of a rice field after aerial application. Results were in good agreement with data obtained by a commercial ELISA. Graphical abstract A highly sensitive amperometric biosensor for glyphosate is reported, based on the covalent immobilization of a carbon nano-onion/tyrosinase conjugate on a chitosan matrix.

Carbon Nano‐Onions Made Directly from CO2 by Molten Electrolysis for Greenhouse Gas Mitigation

AbstractA high yield, low energy synthesis of carbon nano‐onions (CNOs) by electrolysis of CO2 in molten carbonate is presented. Carbon nano‐onions are a recently recognized, less studied morphology of carbon nanomaterials consisting of nested concentric carbon spheroids. Previously, a high yield growth of carbon nanotubes by CO2 electrolysis in molten carbonate was achieved through transition metal nucleation points on the electrolysis cathode. Here, effective low energy CNO synthesis from CO2 is achieved instead by excluding those nucleating agents from the molten carbonate growth medium resulting in a profusion of uniform CNOs, with an increasing diameter correlated to increasing growth time. CO2 transformation to valuable materials, such as CNOs, adds value to CO2 to incentivize consumption of this greenhouse pollutant. For example, CNOs are currently valued 20 000 times higher than coal.

Impact of Co/Mo ratio on the activity of CoMo/MgO catalyst for production of high-quality multi-walled carbon nanotubes from polyethylene waste

A simple two-stage method was used to produce multiwalled carbon nanotubes (MWCNTs) from low-density polyethylene (LDPE) plastic waste using a group of CoMo/MgO catalysts with several Co/Mo molar ratios (14.5, 6.5, 2.5, 1 and 0.4). The catalytic degradation of LDPE waste was performed using the HZSM-5 catalyst at a low temperature of 400 °C to form non-condensable gases, which were subsequently used as a carbon source for the production of MWCNTs at 700 °C. The influence of Co/Mo ratio on the yield, morphological structure, thermal stability, purity, and quality of MWCNTs was studied. The freshly calcined catalysts were characterized using BET surface area, XRD, FTIR, and H2-TPR techniques. On the other hand, Raman spectroscopy, TEM, XRD, and TGA analyses were performed for full characterization of the as-deposited carbon materials. The TPR and FTIR profiles of the fresh catalysts illustrated that the interaction between Co, Mo, and MgO increased by decreasing the Co/Mo ratio from 14.5 to 0.4. Also, the CoMo(6.5)/MgO catalyst displayed the highest surface properties compared to the other catalysts with different Co/Mo ratios. The CoMo(6.5)/MgO catalyst was the most active in terms of MWCNTs production. Moreover, the morphology, purity, and quality of the produced MWCNTs were strongly associated with the catalyst composition. TEM images illustrated that pure MWCNTs were obtained using the CoMo(14.5)/MgO catalyst, while a mixture of MWCNTs, carbon nanofibers (CNFs) and carbon nano-onions (CNOs) was produced using the CoMo(0.4)/MgO catalyst. Raman spectroscopy and TGA results proved that MWCNTs with the best quality and purity were obtained using the catalysts with Co/Mo ratios of 14.5 and 6.5.

Biological Responses of Onion-Shaped Carbon Nanoparticles.

Nanodiamonds are emerging as new nanoscale materials because of their chemical stability, excellent crystallinity, and unique optical properties. In this study, the structure of nanodiamonds was engineered to produce carbon nano-onion particles (CNOs) with multiple layers. Following a series of physicochemical characterizations of the CNOs, various evaluations for biological responses were conducted for potential biotechnological applications of the CNOs. The possibility of biological applications was first confirmed by assessment of toxicity to animal cells, evaluation of hemolysis reactions, and evaluation of reactive oxygen species. In addition, human immune cells were evaluated for any possible induction of an immune response by CNOs. Finally, the toxicity of CNOs to Escherichia coli present in the human colon was evaluated. CNOs have the chemical and physical properties to be a unique variety of carbon nanomaterials, and their toxicity to animal and human cells is sufficiently low that their biotechnological applications in the future are expected.

Diversity-oriented synthesis of blue emissive nitrogen heterocycles and their conjugation with carbon nano-onions

The search for new fluorescent molecules for possible applications as functional π-electron systems and their conjugation with different nanomaterials is nowadays of paramount importance to broaden the availability of materials with different properties. Herein we present a diversity-oriented approach to heterocyclic luminophores based on a multicomponent Ugi reaction followed by a Pd-mediated cascade sequence. The new molecules are coupled to carbon nano-onions, and hybrid systems represent the first example of blue emitters conjugated with these carbon nanoparticles.

Synthesis of carbon nano-onion embedded metal-organic frameworks as an efficient adsorbent for cadmium ions: kinetic and thermodynamic studies.

Carbon nano-onions (CNOs), metal-organic frameworks (MOF-199), and carbon nano-onion embedded metal-organic frameworks (CMOF-199) were synthesized from garlic peels as a green source of carbon atoms while MOF-199 was prepared by solvothermal interaction between 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate. All the prepared solid materials were characterized by nitrogen adsorption/desorption isotherm, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), point of zero charge (pHPZC), and Fourier transform infrared spectroscopy (FTIR). Adsorption of cadmium ions from aqueous solution was investigated onto all prepared solid materials considering different application conditions such as adsorbent dosage, pH, contact time, initial concentration of Cd+2, and temperature. Adsorption of Cd+2 was investigated by Langmuir, Freundlich, Temkin, and Dubinin-Radhushkevich adsorption isotherm models. Maximum adsorption capacity (113.3mgg-1) was achieved by CMOF-199 at 40°C. The adsorption of Cd+2 obeys pseudo-second-order kinetic model. Thermodynamic studies confirmed that the adsorption process is spontaneous, favorable, endothermic, and physisorption. Adsorption results proved that carbon nano-onion embedded metal-organic frameworks are promising solid adsorbents for cadmium ion adsorption.

Preparation and microwave absorption properties of magnetic carbon nano-onion matrix composites

Preparation and microwave absorption properties of magnetic carbon nano-onion matrix composites

Photoinduced Charge Shift in Li+-Doped Giant Nested Fullerenes

Over the last years, carbon nano-onions (CNOs) have been in focus in material science research. Their red-shifted absorption allows utilizing CNOs as promising photosensitizers. We report here a systematic study of excited state properties of six double-layered Li+-doped fullerenes of Ih symmetry: [Li@C60@C240]+, [Li@C60@C540]+, [Li@C60@C960]+, [Li@C240@C540]+, [Li@C240@C960]+, and [Li@C540@C960]+. On the basis of time-dependent density functional theory calculations, we show that the long-wave absorption by the Li+-doped species leads to charge transfer (CT) between the inner and the outer shells unlike their neutral double-layered precursors. The CT energy depends strongly on the size of the concentric fullerenes and it can easily be tuned by varying both the encapsulated metal ion and the size of the shells. Two types of low-lying excited states are identified: (1) capacitor-like structures, as Li+@C60–@C240+, with alternating positive and negative charges, and (2) states, where the positive charge is delocalized over the outer shell, as in Li@C240@C540+. We suggest a simple expression to estimate the energy difference of these excited states and to predict the type of the lowest CT state in nested fullerenes. The effect of nature of the encapsulated ion on the CT state energies is considered. The highest occupied molecular orbital–lowest unoccupied molecular orbital transition energy is found to vary significantly when going from [Li@C60@C240]+ to [Li@C540@C960]+.

Natural oil derived carbon nano-onions as a sensitive electrocatalyst for nitrite determination

In this communication, we report carbon nano-onions (CNOs) derived from natural oil as metal-free sensors for efficient nitrite determination. The pristine CNOs showed remarkable nitrite oxidation capability with a linear detection range of 1 μM–90 μM (R2 = 0.998), the sensitivity of 214.29 μA mM−1 cm−2 and detection limit as low as 0.75 μM. The performance of this material exceed many well studied materials used as active materials for nitrite sensor.

One-step gas-liquid detonation synthesis of carbon nano-onions and their tribological performance as lubricant additives

Carbon nano-onions (CNOs) were synthesized in a few milliseconds by a detonation method using a gas-liquid mixture as the precursor. The composition, morphology and microstructure of products were studied by TEM, XRD, Raman and XPS. Furthermore, the four-ball tests were carried out to investigate the tribological properties of CNOs as lubricant additives. The results showed that the CNOs consisting of spherically concentric graphitic shells with a narrow size distribution about 15.8 nm, which plays the role of “micro bearing” in mechanical lubrication. From the four-ball tests, the friction coefficient and wear scar diameter become slighter and uniform with the addition of CNOs to the base lubricant. When the content of CNOs is about 0.06 wt%, there are minimum frictional coefficient and wear scar diameter.

Stability of a Carbon Nano-Onion in Contact with a Graphite Substrate

A theoretical model describing the stability of a carbon nano-onion in the presence of a bulk catalytic graphite phase is constructed based on the continuum approximation of interatomic interaction potential and mechanics of deformed systems. It is shown that a carbon nano-onion becomes unstable when its radius exceeds double value of the radius of a fullerene C60 molecule.

Development of highly sensitive IgA immunosensors based on co-electropolymerized L-DOPA/dopamine carbon nano-onion modified electrodes

The development of versatile platforms to construct novel and sensitive immunosensors is nowadays an intense research field. Nanomaterials and polymers are often combined to fabricate new platforms to immobilize capture antibodies. Here we evaluate for the first time the co-electropolymerization of dopamine (DA) and L-3,4-dihydroxyphenylalanine (L-DOPA) on carbon nano-onion (CNO) modified electrodes as versatile platform to develop electrochemical immunosensors. Mixtures of DA and L-DOPA at different molar rations were co-electropolymerized on CNO-modified glassy carbon electrodes to form a poly(L-DOPA/DA) film. Immobilization of aminoferrocene was used to estimate the number of accessible carboxylic acid groups on the surface (11.3 nmol/cm2), a value comparable to three-dimensional matrices. This platform was applied to the electrochemical detection of IgA antibodies using both a HRP-based sandwich type assay and label-free detection based on [Fe(CN)6]3-/4- signal blocking. The sandwich and the label-free assays showed a wide linear response with LOD of 19 and 48 ng/mL, respectively, allowing the detection of serum IgA deficiency. Most remarkably, the incorporation of CNO layer led to a significant improvement (three-orders of magnitude) of the analytical performance of these immunosensors due to a combination of high surface area and increased electron transfer rates provided by the CNO layer.