Carbon Capsules Research Articles

Anisotropic polydopamine capsules with an ellipsoidal shape that can tolerate harsh conditions: efficient adsorbents for organic dyes and precursors for ellipsoidal hollow carbon particles

Ellipsoidal PDA capsules with enhanced mechanical rigidity can be directly carbonized into ellipsoidal carbon capsules and used as efficient adsorbents for organic dyes in water.

Multifunctional Mesoporous Carbon Capsules and their Robust Coatings for Encapsulation of Actives: Antimicrobial and Anti-bioadhesion Functions.

We present the synthesis and applications of multifunctional hollow porous carbon spheres with well-ordered pore architecture and ability to encapsulate functional nanoparticles. In the present work, the applications of hollow mesoporous carbon capsules (HMCCs) are illustrated in two different contexts. In the first approach, the hollow capsule core is used to encapsulate silver nanoparticles to impart antimicrobial characteristics. It is shown that silver-loaded HMCCs (concentration ∼100 μg/mL) inhibit the growth and multiplication of bacterial colonies of Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) up to 96% and 83%, respectively. In the second part, the fabrication of hierarchical micro- and nanostructured superhydrophobic coatings of HMCCs (without encapsulation with silver nanoparticles) is evaluated for anti-bioadhesion properties. Studies of protein adsorption and microorganism and platelet adhesion have shown a significant reduction (up to 100%) for the HMCC-based superhydrophobic surfaces compared with the control surfaces. Therefore, this unique architecture of HMCCs and their coatings with the ability to encapsulate functional materials make them a promising candidate for a variety of applications.

FeS2 nanocrystals prepared in hierarchical porous carbon for lithium-ion battery

FeS2 nanocrystals are successfully prepared in the carbon capsules of pre-prepared hierarchical porous carbon (HPC). The absorbed Fe ions in HPC are first calcined into Fe3O4 and then react with sulfur under vacuum conditions to synthesize FeS2. HPC, with micro-porous shells and inter-connected macro-porous carbon capsules, shows highly ionic/electrical conductivities and efficient buffer effect on the volume change of FeS2. FeS2@HPC exhibits a high specific capacity of 907 mAh·g−1 in the first cycle and remains 720 mAh·g−1 after 100 cycles at the rate of 1 C.

RAPET (Reaction under Autogenic Pressure at Elevated Temperatures) Technique Assisted Synthesis of Encapsulated CdE@C [E= S, Se and Te] Nanocrystallites

We present an easy synthetic method for the fabrication of encapsulated nanosized semiconductor CdE [E [Formula: see text] S, Se and Te] within the core of carbon capsule. We also discuss the growth of CdSC and neat CdS nanocrystals on stainless steel coupons (SSC) by a reaction under autogenic pressure at elevated temperature (RAPET) technique. The thermal decomposition of mixture of Cd(acetate)2 and sulfur, selenium and tellurium was carried out at 750[Formula: see text]C under air for 3[Formula: see text]h. The synthesized products were systematically characterized by X-ray powder diffraction, scanning electron microscopy (SEM) and transmission electron microscopy. Carbon matrix, with an average diameter of 250[Formula: see text]nm, encapsulated several nanometric-sized CdS nanocrystals, as evidenced from high resolution SEM (HRSEM). We examined the optical properties of this core/shell CdS@C and nonencapsulated CdS nanocrystals and found that both core shell and neat CdS nanocrystals show emission in the pohotoluminescence (PL) spectrum.

ChemInform Abstract: Hollow Carbon Spheres, Synthesis and Applications ‐ A Review

AbstractReview: 151 refs.

Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

Topographical modifications of spherical surfaces are imprinted on National Ignition Facility target capsules by extending the capabilities of a recently developed full-surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density, and long reach of a focused laser beam to preimpose sinusoidal modulations on the outside surface of high-density carbon capsules and the inside surface of glow discharge polymer capsules. Sinusoidal modulations described in this paper have submicron to tens of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulated patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as the laser beam intensity profile, the material removal function, the starting surface figure, and the desired surface figure. The patterns are optimized to minimize surface roughness. In this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.

Catalytically Active Bimetallic Nanoparticles Supported on Porous Carbon Capsules Derived From Metal-Organic Framework Composites.

We report a new methodology for producing monometallic or bimetallic nanoparticles confined within hollow nitrogen-doped porous carbon capsules. The capsules are derived from metal-organic framework (MOF) crystals that are coated with a shell of a secondary material comprising either a metal-tannic acid coordination polymer or a resorcinol-formaldehyde polymer. Platinum nanoparticles are optionally sandwiched between the MOF core and the shell. Pyrolysis of the MOF-shell composites produces hollow capsules of porous nitrogen-doped carbon that bear either monometallic (Pt, Co, and Ni) or alloyed (PtCo and PtNi) metal nanoparticles. The Co and Ni components of the bimetallic nanoparticles are derived from the shell surrounding the MOF crystals. The hollow capsules prevent sintering and detachment of the nanoparticles, and their porous walls allow for efficient mass transport. Alloyed PtCo nanoparticles embedded in the capsule walls are highly active, selective, and recyclable catalysts for the hydrogenation of nitroarenes to anilines.

Fabrication of Nitrogen-Doped Hollow Mesoporous Spherical Carbon Capsules for Supercapacitors.

A novel "dissolution-capture" method for the fabrication of nitrogen-doped hollow mesoporous spherical carbon capsules (N-HMSCCs) with high capability for supercapacitor is developed. The fabrication process is performed by depositing mesoporous silica on the surface of the polyacrylonitrile nanospheres, followed by a dissolution-capture process occurring in the polyacrylonitrile core and silica shell. The polyacrylonitrile core is dissolved by dimethylformamide treatment to form a hollow cavity. Then, the polyacrylonitrile is captured into the mesochannel of silica. After carbonization and etching of silica, N-HMSCCs with uniform mesopore size are produced. The N-HMSCCs show a high specific capacitance of 206.0 F g(-1) at a current density of 1 A g(-1) in 6.0 M KOH due to its unique hollow nanostructure, high surface area, and nitrogen content. In addition, 92.3% of the capacitance of N-HMSCCs still remains after 3000 cycles at 5 A g(-1). The "dissolution-capture" method should give a useful enlightenment for the design of electrode materials for supercapacitor.

Fe-N-Doped Carbon Capsules with Outstanding Electrochemical Performance and Stability for the Oxygen Reduction Reaction in Both Acid and Alkaline Conditions.

High surface area N-doped mesoporous carbon capsules with iron traces exhibit outstanding electrocatalytic activity for the oxygen reduction reaction in both alkaline and acidic media. In alkaline conditions, they exhibit more positive onset (0.94 V vs RHE) and half-wave potentials (0.83 V vs RHE) than commercial Pt/C, while in acidic media the onset potential is comparable to that of commercial Pt/C with a peroxide yield lower than 10%. The Fe-N-doped carbon catalyst combines high catalytic activity with remarkable performance stability (3500 cycles between 0.6 and 1.0 V vs RHE), which stems from the fact that iron is coordinated to nitrogen. Additionally, the newly developed electrocatalyst is unaffected by the methanol crossover effect in both acid and basic media, contrary to commercial Pt/C. The excellent catalytic behavior of the Fe-N-doped carbon, even in the more relevant acid medium, is attributable to the combination of chemical functions (N-pyridinic, N-quaternary, and Fe-N coordination sites) and structural properties (large surface area, open mesoporous structure, and short diffusion paths), which guarantees a large number of highly active and fully accessible catalytic sites and rapid mass-transfer kinetics. Thus, this catalyst represents an important step forward toward replacing Pt catalysts with cheaper alternatives. In this regard, an alkaline anion exchange membrane fuel cell was assembled with Fe-N-doped mesoporous carbon capsules as the cathode catalyst to provide current and power densities matching those of a commercial Pt/C, which indicates the practical applicability of the Fe-N-carbon catalyst.

High Hydrophilic Mesoporous Carbon As Support of Pd Electrocatalyst for Ethanol Oxidation

The new form of carbon materials such as onion-like carbon, flower-like carbon, straw-like carbon and nanorods carbon have been of continuous research interest, since fullerenes in 1985 and carbon nanotube in 1991 were be found. They have a wide range of applications including conductive and high-strength composites, gas/energy storage, nano devices supports of catalytic systems, and adsorbents because of their intrinsic properties involving large BET surface area, low weight, self-sinter, chemical inertia and excellent conduction of electricity and heat and so on. As we know, as supports of electrocatalyst, it is necessary that carbons have an enough conductivity and a large surface area because it is able to improve the catalytic activity through fasting the charge transportation and increasing the gas/liquid interfacial area. In the previous reports, it was found that the material with hollow structure and large micropores as electrocatalyst support can effectively improve the performance of electrocatalyst [1-4]. Several different carbon materials such as spherical carbon capsules [5] carbon hollow nanosphere [6], active fiber carbon (AFC) [7], mesoporous structured carbon materials [8] were used as supports of Pt or Pd electrocatalyst due to their large surface area and high stability, especially functional mesoporous structures. Recently, various approaches have been developed for the chemical modification of carbon surface. The most widely used technique to functionalize the carbon surface involves oxidizing it with acid or ozone, which oxygenated functionalities, such as carboxylic acid, esters is generated. However, the drawbacks of this method lie in the low bonding densities, and damage to the pore structure during oxidative treatment [9]. Though some functional methods retained the carbon structure, it needed two separated synthesis steps, which makes the process quite complex. We report here on a promising novel and one-step synthesis of highly hydrophilic ordered mesoporous carbon-organic polymer composites with larger specific surface area by a rapid intermittent microwave heating technique (IMH). The resulting composite materials have the bifunctionality of both mesoporous carbon and organic polymer, and retain the ordered pore structure of the carbon. The synthesis strategy can be extended to various compositions of hydrophilic and hydrophobic mesoporous materials-organic polymer. The resultant materials, exhibiting chemical properties of the polymers as well as the electric conductivity of the mesoporous carbon, were used as Pd based electrocatalyst support for ethanol oxidation in alkaline media. Mesoporous carbon (MC) with high surface area, high hydrophilic and high conductivity has been synthesized by a mixed soft template Poly vinyl alcohol (PVA) and hard template SBA-15 route and investigated as an electrocatalystic support for ethanol oxidation. There are four times higher activity of Pd/MC-PVA for ethanol oxidation than Pd/MC with the same Pd loading in alkaline media. The enhanced activity is attributed to a better Pd dispersion and utilization on mesoporous carbon support because of its high hydrophilic and conductivity. Both cyclic voltammetric and chronoamperametric measurements of the Pd based mesoporous carbon indicate that the performance of this catalyst modified by PVA can be significantly improved for ethanol oxidation. Cyclic voltammograms of ethanol oxidation on Pd/MC and Pd/MC-PVA were shown in Figure 1. The onset potential, peak potential and peak current density of the ethanol oxidation on Pd/MC and Pd/MC-PVA electrodes are -0.49 V, -0.151 V, 10.0 mA/cm-2 and -0.55 V, -0.185 V, 27.1 mA/cm-2, respectively. The performance of the similar onset potential and peak potential on two electrodes are due to the same structure of carbon supports. However, the peak current density of Pd/MC-PVA electrocatalyst is 2.7 times higher than that of Pd/MC, just due to the better hydrophilic and conductivity on Pd/MC-PVA. According to the insert in Figure 1(a), we can sure that the improvement of catalystic activity was owed to the good hydrophilic and conductivity of MC modified by PVA which was able to give the more active center for the electrocatalysic reaction and species transportation.

Fabrication and Applications of Tailored Carbon Capsules

Recently, diverse carbon materials with elegant structures such as fullerene, nanotube, and graphene have been realized and thus tailoring those elaborate structures has become a challenging research task. In addition, various emerging carbon materials have been demonstrated such as capsules, tubes, and vesicles. Among these candidates, carbon capsules are particularly interesting owing to their interesting characteristics such as relatively high surface area, structural stability, chemical inertness, mechanical durability, and potential applications. They can be incorporated to the energy storage/conversion, electronic and magnetic devices, biocompatible components, nanocomposite, and environment friendly systems. In addition, they have acted as reaction media and sacrificial scaffolds to generate intriguing micro and nanostructures. Therefore, herein, it is worthwhile to summarize the previous research works on fabrication and applications of carbon capsules (micro and nano). It is expected that this article can provide essential information for future research activities. Keywords: Carbon, carbon nanostructure, capsule, energy storage/conversion, nanocarbon.

The Ignition Physics Campaign on NIF: Status and Progress

We have made significant progress in ICF implosion performance on NIF since the 2011 IFSA. Employing a 3-shock, high adiabat CH (“High-Foot”) design, total neutron yields have increased 10-fold to 6.3 x1015 (a yield of ∼ 17 kJ, which is greater than the energy invested in the DT fuel ∼ 12kJ). At that level, the yield from alpha self-heating is essentially equivalent to the compression yield, indicating that we are close to the alpha self-heating regime. Low adiabat, 4-shock High Density Carbon (HDC) capsules have been imploded in conventional gas-filled hohlraums, and employing a 6 ns, 2-shock pulse, HDC capsules were imploded in near-vacuum hohlraums with overall coupling ∼ 98%. Both the 4- and 2-shock HDC capsules had very low mix and high yield over simulated performance. Rugby holraums have demonstrated uniform x-ray drive with minimal Cross Beam Energy Transfer (CBET), and we have made good progress in measuring and modelling growth of ablation front hydro instabilities.

Preparation of raspberry-like γ-Fe2O3/crackled nitrogen-doped carbon capsules and their application as supports to improve catalytic activity.

In this manuscript, we have introduced a novel method to improve the catalytic activity of metal nanoparticles via optimizing the support structure. To this end, raspberry-like γ-Fe2O3/crackled nitrogen-doped carbon (CNC) capsules were prepared by a two-step method. Compared with traditional magnetic capsules, in γ-Fe2O3/CNC capsules, the γ-Fe2O3 nanoparticles were embedded in a CNC shell; therefore, they neither occupied the anchoring sites for metal nanoparticles nor came into contact with them, which was beneficial for increasing the metal nanoparticle loading. Numerous tiny cracks appeared on the porous CNC shell, which effectively improved the mass diffusion and transport in catalytic reactions. Additionally, the coordination interaction could be generated between the precursor metal ions and doped-nitrogen atoms in the capsule shell. With the help of these structural merits, γ-Fe2O3/CNC capsules were ideal supports for Pd nanoparticles, because they were beneficial for improving the Pd loading, reducing the nanoparticle size, increasing their dispersity and maximizing the catalytic performance of Pd nanoparticles anchored on the inner shell surface. As expected, γ-Fe2O3/CNC@Pd catalysts exhibited a dramatically enhanced catalytic activity towards hydrophilic 4-nitrophenol and hydrophobic nitrobenzene. The reaction rate constant k was compared with recent work and the corresponding reference samples. Moreover, they could be easily recycled by using a magnet and reused without an obvious loss of catalytic activity.

Egg yolk-derived phosphorus and nitrogen dual doped nano carbon capsules for high-performance lithium ion batteries

Egg yolk-derived P and N dual doped nano carbon capsules (PNCCs) have been synthesized and used as lithium ion battery anodes. The application of egg yolk as the carbon source is a new and environmental-friendly approach for biomass recycling. The reversible capacity of half cells made of PNCCs is as high as ~770mAhg−1 at a current density of 0.5Ag−1 with considerable rate capacity and cycling stability. PNCCs show a capsule-like structure, which provide extra edges and active sites for lithium intercalation. The heteroatom doping also introduce defects and disorder, which increases the electrochemical activity and creates more active sites for lithium insertion.

PEGylated Carbon Nanocapsule: A Universal Reactor and Carrier for In Vivo Delivery of Hydrophobic and Hydrophilic Nanoparticles.

We have developed PEGylated mesoporous carbon nanocapsule as a universal nanoreactor and carrier for the delivery of highly crystalline hydrophobic/hydrophilic nanoparticles (NPs) which shows superior biocompatibility, dispersion in body fluids, good biodistribution and NPs independent cellular uptake mechanism. The hydrophobic/hydrophilic NPs without surface modification were synthesized in situ inside the cavities of mesoporous carbon capsules (200-850 nm). Stable and inert nature of carbon capsules in a wide range of reaction conditions like high temperature and harsh solvents, make it suitable for being used as nano/microreactors for the syntheses of a variety of NPs for bioimaging applications, such as NaYF4:Eu(3+)(5%), LaVO4:Eu(3+)(10%), GdVO4:Eu(3+)(10%), Y2O3:Eu(3+)(5%), GdF3:Tb(3+)(10%), Mo, Pt, Pd, Au, and Ag. Multiple types of NPs (Y2O3:Eu(3+)(5%) (hydrophobic) and GdF3:Tb(3+)(10%) (hydrophilic)) were coloaded inside the carbon capsules to create a multimodal agent for magneto-fluorescence imaging. Our in vivo study clearly suggests that carbon capsules have biodistribution in many organs including liver, heart, spleen, lungs, blood pool, and muscles.

Si(OCH2Fc)4: Synthesis, Electrochemical Behavior, and Twin Polymerization

AbstractThe preparation and twin polymerization of the twin monomer Si(OCH2Fc)4 [Fc = Fe(η5‐C5H4)(η5‐C5H5)] (2) by the reaction of FcCH2OH (1) with SiCl4 in the presence of pyridine was explored. The electronic properties of 2 were investigated by cyclic voltammetry, square‐wave voltammetry, and UV/Vis/near‐IR spectroelectrochemistry, which showed a redox separation caused by electrostatic repulsion. Thermally induced condensation of 2 is characteristic, as evidenced by differential scanning calorimetry (DSC) and thermogravimetry coupled mass spectrometry (TG–MS). Upon heating 2 to 210 °C, twin polymerization occurred and a hybrid material was formed that showed similarities with known systems derived from 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] (SBS), such as the nanopatterning of the formed silicon dioxide, which is characteristic for twin polymerization. Electron microscopy of this material revealed the absence of typical microstructuring found for other twin polymers, and hence, the herein presented system can be characterized as a borderline system if compared to known twin monomers such as SBS. The copolymerization of 2 and SBS afforded a hybrid material from which porous carbon or silica materials containing iron oxide nanoparticles could be obtained. The oxidation state of the incorporated particles was examined by Mössbauer experiments, which confirmed that only FeIII was incorporated within the porous carbon and silica materials, respectively. The preparation of iron oxide containing porous carbon capsules was achieved by applying a mixture of 2 and SBS to silicon dioxide spheres (d = 200 nm). After twin polymerization and carbonization, porous carbon capsules with incorporated iron oxide nanostructures were obtained.

Zinc disrupts central carbon metabolism and capsule biosynthesis in Streptococcus pyogenes.

Neutrophils release free zinc to eliminate the phagocytosed bacterial pathogen Streptococcus pyogenes (Group A Streptococcus; GAS). In this study, we investigated the mechanisms underpinning zinc toxicity towards this human pathogen, responsible for diseases ranging from pharyngitis and impetigo, to severe invasive infections. Using the globally-disseminated M1T1 GAS strain, we demonstrate that zinc stress impairs glucose metabolism through the inhibition of the glycolytic enzymes phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase. In the presence of zinc, a metabolic shift to the tagatose-6-phosphate pathway allows conversion of D-galactose to dihydroxyacetone phosphate and glyceraldehyde phosphate, partially bypassing impaired glycolytic enzymes to generate pyruvate. Additionally, zinc inhibition of phosphoglucomutase results in decreased capsule biosynthesis. These data indicate that zinc exerts it toxicity via mechanisms that inhibit both GAS central carbon metabolism and virulence pathways.

First high-convergence cryogenic implosion in a near-vacuum hohlraum.

Recent experiments on the National Ignition Facility [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] demonstrate that utilizing a near-vacuum hohlraum (low pressure gas-filled) is a viable option for high convergence cryogenic deuterium-tritium (DT) layered capsule implosions. This is made possible by using a dense ablator (high-density carbon), which shortens the drive duration needed to achieve high convergence: a measured 40% higher hohlraum efficiency than typical gas-filled hohlraums, which requires less laser energy going into the hohlraum, and an observed better symmetry control than anticipated by standard hydrodynamics simulations. The first series of near-vacuum hohlraum experiments culminated in a 6.8 ns, 1.2 MJ laser pulse driving a 2-shock, high adiabat (α∼3.5) cryogenic DT layered high density carbon capsule. This resulted in one of the best performances so far on the NIF relative to laser energy, with a measured primary neutron yield of 1.8×10(15) neutrons, with 20% calculated alpha heating at convergence ∼27×.

High-density carbon ablator ignition path with low-density gas-filled rugby hohlraum

A recent low gas-fill density (0.6 mg/cc 4He) cylindrical hohlraum experiment on the National Ignition Facility has shown high laser-coupling efficiency (>96%), reduced phenomenological laser drive corrections, and improved high-density carbon capsule implosion symmetry [Jones et al., Bull. Am. Phys. Soc. 59(15), 66 (2014)]. In this Letter, an ignition design using a large rugby-shaped hohlraum [Amendt et al., Phys. Plasmas 21, 112703 (2014)] for high energetics efficiency and symmetry control with the same low gas-fill density (0.6 mg/cc 4He) is developed as a potentially robust platform for demonstrating thermonuclear burn. The companion high-density carbon capsule for this hohlraum design is driven by an adiabat-shaped [Betti et al., Phys. Plasmas 9, 2277 (2002)] 4-shock drive profile for robust high gain (>10) 1-D ignition performance and large margin to 2-D perturbation growth.

High-density carbon capsule experiments on the national ignition facility.

Indirect-drive implosions with a high-density carbon (HDC) capsule were conducted on the National Ignition Facility (NIF) to test HDC properties as an ablator material for inertial confinement fusion. A series of five experiments were completed with 76-μm-thick HDC capsules using a four-shock laser pulse optimized for HDC. The pulse delivered a total energy of 1.3 MJ with a peak power of 360 TW. The experiment demonstrated good laser to target coupling (∼90%) and excellent nuclear performance. A deuterium and tritium gas-filled HDC capsule implosion produced a neutron yield of 1.6×10^{15}±3×10(13), a yield over simulated in one dimension of 70%.