Spherical Carbon Nanoparticles Research Articles

A facile and environmentally friendly biomass-assisted stӧber method to fabricate dispersed carbon nanospheres

Mesoporous carbon nanospheres (MCs) with high dispersity, specific surface area (~ 1045 m2/g) and large pore volume (0.92 cm3/g) were fabricated through a facile biomass-assisted stӧber method. In this process, tetraethylorthosilicate (TEOS) not only acted as a pore-forming agent but also as a dispersant to reduce the cross-linking of particles, which has never been reported before. Inspiringly, the particle morphologies and mesoporous structures of the obtained MCs could be facilely tuned by varying the NH3·H2O concentration. Compared with previously reported method, the present strategy affords a convenient, inexpensive and environmentally friendly biomass-assisted stӧber method as well as proposes a possible route to prepare spherical carbon nanoparticles with mesoporous structures.

The fabrication of size-tunable nitrogen-doped dual-mesoporous carbon nanospheres with excellent thermal stability via colloidal silica driving co-assembly strategy

The synthesis of nitrogen-doped dual-mesoporous carbon nanospheres (N-DMCNs) with tunable sizes remains a great challenge due to the high cross-linking rate of carbon precursors and the weak interactions among the carbon precursors, inorganic components and templates. Herein, we demonstrated a colloidal silica nanoparticles (SN) driving co-assembly strategy for the first time to fabricate such N-DMCNs with hydrochloric acid (HCl) as a catalyst. Interestingly, SN not only acted as a pore-forming agent but also as a driving agent to induce the co-assembly of F127, carbon precursors and SN. The affinity between carbon precursor and template was enhanced by the Coulombic interaction originating from the I+X−S+ mechanism driven by the protonation under highly acidic conditions. Furthermore, the mesoporous structure and particle sizes could be facilely tuned by varying the HCl concentration, which was elucidated by both reversible reaction and nuclei growth mechanism. The as-prepared N-DMCNs could be potentially used as drug carrier for poorly water-soluble drug carbamazepine by improving its aqueous release rate. Compared with previously reported method, the present strategy has striking features such as convenient, inexpensive and environmentally friendly, especially affording a paradigm for the preparation of spherical mesoporous carbon nanoparticles through driving-induced assembly engineering.

Three-Dimensional Cyclic Voltammetry Simulations of EDLC Electrodes Made of Ordered Carbon Spheres

This study aims to investigate the effect of electrode nanoarchitecture on the performance of electric double layer capacitor (EDLC) porous electrodes consisting of highly-ordered monodisperse spherical carbon nanoparticles. To do so, cyclic voltammograms, reproducing three-electrode measurements, were numerically generated for electrodes with different thicknesses and nanoparticle diameters arranged in either simple cubic (SC) or face-centered cubic (FCC) packing structure. The transient three-dimensional simulations of interfacial and transport phenomena in the porous electrodes were based on a continuum model accounting for (1) binary symmetric electrolytes with finite ion size, (2) electric field-dependent dielectric constant of the electrolyte, (3) the Stern layer at the electrode/electrolyte interface, along with (4) Ohmic potential drop in the electrode. For both FCC and SC packing structures, the areal capacitance (in μF/cm2) increased with decreasing sphere diameter. In addition, for a given sphere diameter, FCC packing featured larger equilibrium capacitance than SC packing. These observations were attributed to larger electric field at the carbon sphere surface for smaller spheres and/or FCC packing. In all cases, the areal capacitance remained constant at low scan rates but decreased beyond a critical scan rate. The latter rate-dependent regime was reached at lower scan rates for thicker electrodes due to resistive losses across the electrode. Interestingly, limitation due to ion diffusion through the porous electrode was not observed. Finally, dimensional analysis was performed by scaling the CV cycle period by the time scale for electron transport in the electrode. This study illustrates powerful numerical simulation tools that can be used to select materials and electrolytes and to design and optimize EDLC electrodes.

Heat transfer nanofluid based on curly ultra-long multi-wall carbon nanotubes

The main challenge in the use of multi-wall carbon nanotube (MWCNT) as key components of nanofluids is to transfer excellent thermal properties from individual nanotubes into the bulk systems. We present studies on the performance of heat transfer nanofluids based on ultra-long (~2 mm), curly MWCNTs – in the background of various other nanoC-sp2, i.e. oxidized MWCNTs, commercially available Nanocyl™ MWCNTs and spherical carbon nanoparticles (SCNs). The nanofluids prepared via ultrasonication from water and propylene glycol were studied in terms of heat conductivity and heat transfer in a scaled up thermal circuit containing a copper helical heat exchanger. Ultra-long curly MWCNT (1 wt.%) nanofluids (stabilized with Gum Arabic in water) emerged as the most thermally conducting ones with a 23–30%- and 39%-enhancement as compared to the base-fluids for water and propylene glycol, respectively. For turbulent flows (Re = 8000–11,000), the increase of heat transfer coefficient for the over-months stable 1 wt.% ultra-long MWCNT nanofluid was found as high as >100%. The findings allow to confirm that longer MWCNTs are promising solid components in nanofluids and hence to predict their broader application in heat transfer media.

Continuous and catalyst free synthesis of graphene sheets in thermal plasma jet

Herein we present a continuous and catalyst free method for the synthesis of graphene sheets from aliphatic alcohols in a radiofrequency thermal plasma jet. Nine aliphatic linear alcohols (ethanol-decanol) were tested as possible precursors for the massive production of graphene sheets. Moreover, additional tests were also carried out with the inclusion of gaseous oxygen in order to promote the formation of graphene and to eliminate the unwanted carbon byproducts. The obtained materials were investigated by electron microscopy, Raman and infrared spectroscopy. The thermal stability of products was also evaluated using thermogravimetry. The surface chemistry features were analyzed using acid-base titration and X-ray photoelectron and IR spectroscopy. Finally, the adsorption performance of graphene sheets was tested in the removal of 4-chlorophenol from aqueous solutions. The highest content of graphene sheets was found in the product obtained from ethanol with the production rate of ca. 1.5g/h. The plasma processing of higher alcohols yielded a mixture of graphene sheets and spherical carbon nanoparticles.

Fe-carbon nitride “Core-shell” electrocatalysts for the oxygen reduction reaction

In this report, the preparation of Fe-carbon nitride (CN)-based electrocatalysts (ECs) with a “core-shell” morphology for the oxygen reduction reaction (ORR) is described. The ECs consist of spherical XC-72R carbon nanoparticles, the “cores”, that are covered by a CN matrix, the “shell”, that embeds Fe species in “coordination nests”. The latter consist of hollow cavities in the CN matrix, whose internal surface is covered by N- and C-ligands able to stabilize alloy nanoparticles or active sites. Two families of CN-based ECs are prepared, which are grouped on the basis of the concentration of N atoms in the CN “shell”. Each group comprises of both a “pristine” and an “activated” EC; the latter is obtained from the “pristine” EC by a suitable series of treatments (A) devised to improve the ORR performance. The chemical composition of the CN-based ECs is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and microanalysis. The thermal stability under both inert and oxidizing atmospheres is gauged by High-Resolution Thermogravimetric Analysis (HR-TGA). The structure is probed by powder X-ray diffraction, and the morphology is inspected by Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM). The surface area of the CN-based ECs is determined by nitrogen physisorption techniques, and the surface composition is probed by X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and reaction mechanism of the CN-based ECs in the ORR is investigated in both acid and alkaline environments by cyclic voltammetry with the Thin-Film Rotating Ring-Disk Electrode setup (CV-TF-RRDE). The influence of the preparation parameters and of the treatments on the physicochemical properties, the ORR performance, and reaction mechanism is studied in detail. In the alkaline environment the FeFe2-CNl 900/CA“core-shell” EC shows a remarkable ORR onset potential of 0.908V vs. RHE which, with respect to the value of 0.946V vs. RHE of the Pt/C ref., classifies the proposed materials as very promising “Platinum Group Metal-free” ECs for the ORR.

Carbon dots coated with vitamin B12 as selective ratiometric nanosensor for phenolic carbofuran

A carbon quantum dots (CQDs) based ratiometric nanosensor exhibiting dual emission fluorescence was developed. The spherical fluorescent carbon nanoparticles were obtained from lactose using a hydrothermal method. Under a single excitation at 355nm they showed the typical blue emission at 417nm and a red emission at 550nm attributed to the coating effect of vitamin B12. The latter is explained by the fluorescence resonance energy transfer (FRET) and it consists of 61% of total emission. Upon the presence of carbofuran phenol 3-Keto, a phenolic metabolite of carbofuran, the red emission was quenched, resulting in a ratiometric fluorescence response in the blue range. This ratiometric nanosensor exhibited a good selectivity to carbofuran phenol 3-Keto. The ratio of I417/I550 linearly decreased with an increasing carbofuran phenol 3-Keto concentration in the range 9.8μM–1.40×10−4M. A detection limit for carbofuran phenol 3-Keto pesticide was 12.2μM. The pesticide tested was extracted from soy sauce. Recovery values ranged from 98% to 114% with RSD values from 1.50% to 6.50%.

Transport Phenomena in Electrical Double Layer Capacitors with Highly Ordered 3D Porous Carbon Electrodes

Electric double layer capacitors (EDLCs) store energy via ion adsorption in the electric double layer forming at the electrode/electrolyte interfaces in highly porous carbon electrodes. This charge storage mechanism is very fast and highly reversible resulting in large power density and long cycle life. Applications range from regenerative breaking for hybrid electric vehicles to the smart grid. The architecture of the carbon electrodes is known to have a significant effect on the performance of EDLCs. Unfortunately, experimental optimization can be time consuming and challenging due to the large number of design parameters. Numerical simulations could offer a faster and less costly alternative. This study aims to demonstrate the use of numerical tools to simulate transient three-dimensional interfacial and transport phenomena in EDLCs with realistic electrode architecture. It also aims to derive design rules for EDLC porous electrodes. To do so, cyclic voltammograms were numerically generated for EDLCs consisting of electrodes with highly-ordered spherical carbon nanoparticles arranged in simple cubic (SC) or face-centered cubic (FCC) packing in LiClO4/propylene carbonate electrolyte. Simulations were performed for different carbon nanoparticles diameter, electrode thickness, and scan rate. The continuum model was based on the modified Poisson-Nernst-Planck model and accounted for (i) the Stern layer at the electrode/electrolyte interface, (ii) finite ion size, (iii) binary and symmetric electrolyte, and (iv) three-dimensional electrode morphologies. In all cases, the areal capacitance was independent of scan rate at low scan rate but decreased beyond a critical scan rate corresponding to the diffusion-limited regime when ion transport cannot follow the rapid changes in electric potential. The results indicate that the areal capacitance (in F/m2) increased with decreasing sphere diameter below 40 nm due to the increasing surface curvature resulting in larger surface electric field. In addition, FCC packing featured larger capacitance that SC packing thanks to larger surface electric field for given sphere diameter and low scan rate . However, the ion diffusion regime was reached at lower scan rates in FCC packing because of the higher turtuosity limiting the ion transport in the electrode.

Graphite to ultrafine nanocrystalline diamond phase transition model and growth restriction mechanism induced by nanosecond laser processing

To have a clear insight into nanocrystal growth from graphite to diamond upon high energy pulsed laser irradiation of graphite suspension, synthesis of ultrafine nanocrystalline diamonds with laser energy set up from 0.3 J to 12 J, repetition rate of 10 Hz has been studied. The method allows synthesizing ultrafine nanocrystalline particles continuously at the ambient temperature and normal pressure. The particle size is shown independent of laser energy, which is ultrafine and ranges in 2–6 nm. The theoretical grown size of nano-diamonds is found in well agreement with the experiment results. Four kinds of production were found: nano-diamond, spherical carbon nano-particles, flocculent amorphous carbon, and graphene nano-ribbon rolls. A solid-vapor-plasma-liquid coexistence model describing phase transition from graphite to diamond induced by nanosecond laser processing was proposed. Graphene nano-ribbon rolls might be the intermediate phase in the conversion from graphite to diamond.

Synergistic effect of zero-dimensional spherical carbon nanoparticles and one-dimensional carbon nanotubes on properties of cement-based ceramic matrix: microstructural perspectives and crystallization investigations

In the present investigation, hybrid effect of spherical carbon nanoparticles and carbon nanotubes as zero- and one-dimensional entities, respectively (synthesized by novel CVD route), on properties of cement ceramic matrix was studied. Ceramic matrix composites were fabricated using different dosages (% by wt. of cement) of as-synthesized nanoadditive (labeled as rCNTs) and tested for their resistance to compression at increasing hydration curing times of 7, 14, and 28 days. Evolution of different inorganic crystalline phases in composites was examined using X-ray diffraction (XRD). Improvement in mechanical behavior of composites was explained on the basis of microstructural observations using field emission scanning electron microscopy (FE-SEM). Electrical behavior was evaluated using four-probe method and it was observed that addition of nanoadditive had a semiconducting influence on ceramic matrix composites. Thermal behavior of composites was investigated using thermogravimetric analysis (TGA) and compared with that of unreinforced counterpart. All the properties of rCNT composites were compared with carbon black (pCB) cement mortar nanocomposites. Obtained results indicated a maximum improvement of 13.5% in strength in case of 0.125% rCNT cement mortar composite. Electrical and thermal properties were improved with incorporation of rCNTs indicating significant potential for the practical application of low-cost novel rCNT in the preparation of cement-based materials of high strength and smart functionality.

Green synthesis of fluorescent carbon nanoparticles from lychee (Litchi chinensis) plant

Fluorescent carbon nanoparticles (CNPs) were prepared from waste lychee peel by hydrothermal process using green chemistry. These CNPs were characterized by UV-vis absorption, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. Their morphology was analyzed by field emission scanning electron microscopy. Spherical carbon nanoparticles with a particle size ranging from 40–70 nm were observed. FTIR data indicated that these CNPs were functionalized with hydroxyl and carboxylic or carbonyl group. The maximum fluorescence intensity for these CNPs was observed on the excitation wavelength at 365 nm with emission maxima centered at 450 nm. These particles exhibited excitation wavelength dependent fluorescence emission spectra. CNPs were found to be highly fluorescent and exhibited high water solubility. The band gap was estimated to be 3.8 eV. Therefore, as prepared CNPs would be useful in bioimaging, biolabeling and in the other applications of nanobiotechnology.

Micro-porous layer stochastic reconstruction and transport parameter determination

The Micro-Porous Layer (MPL) is a porous, thin layer commonly used in fuel cells at the interfaces between the catalyst layers and gas diffusion media. It is generally made from spherical carbon nanoparticles and PTFE acting as hydrophobic agent. The scale and brittle nature of the MPL structure makes it challenging to study experimentally. In the present work, a 3D stochastic model is developed to virtually reconstruct the MPL structure. The carbon nanoparticle and PTFE phases are fully distinguished by the algorithm. The model is shown to capture the actual structural morphology of the MPL and is validated by comparing the results to available experimental data. The model shows a good capability in generating a realistic MPL successfully using a set of parameters introduced to capture specific morphological features of the MPL. A numerical model that resolves diffusive transport at the pore scale is used to compute the effective transport properties of the reconstructed MPLs. A parametric study is conducted to illustrate the capability of the model as an MPL design tool that can be used to guide and optimize the functionality of the material.

Highly zone-dependent synthesis of different carbon nanostructures using plasma-enhanced arc discharge technique

Three kinds of carbon nanostructures, i.e., graphene nanoflakes (GNFs), multi walled carbon nanotubes (MWCNTs), and spherical carbon nanoparticles (SCNPs) were comparatively investigated in one run experiment. These carbon nanostructures are located at specific location inside the direct current plasma-assisted arc discharge chamber. These carbon nanomaterials have been successfully synthesized using graphite as arcing electrodes at 400 torr in helium (He) atmosphere. The SCNPs were found in the deposits formed on the cathode holder, in which highly curled graphitic structure are found in majority. The diameter varies from 20 to 60 nm and it also appears that these particles are self-assembled to each other. The MWCNTs with the diameter of 10–30 nm were obtained which were present inside the swelling portion of cathode deposited. These MWCNTs have 14–18 graphitic layers with 3.59 A interlayer spacing. The GNFs have average lateral sizes of 1–5 μm and few of them are stacked layers and shows crumpled like structure. The GNFs are more stable at low temperature (low mass loss) but SCNPs have low mass loss at high temperature.

J1130106 カーボンオニオン微粒子の固体潤滑特性に及ぼすその添加量および基材表面粗さの影響

CO(carbon onion particles) are spherical carbon nanoparticles that have a mechanical strength and a reducing effect of friction. By these properties, CO are expected as a new lubricant materials to lead frictional parts to a high function and a lifelong duration. But the problem is shown that CO on sliding surfaces are come off just after sliding. To solve this, these were carried out so far that surface modification of OC and addition of nanometer structure onto sliding surface. These studies have problems that are degeneration of friction property of OC and high fabrication cost. Thus, this paper focuses on fine grooves which can trap lubricant on sliding surfaces with easy techniques. And when I identify surface roughness as fine grooves, the ball-on-disk tribology test to sliding surfaces that CO dispersed was carried out due to investigating effects of additive amount of CO and surface roughness of a substrate on its tribological performance. As results, small roughness of sliding surface was better in terms of minimum friction coefficient, and large one was in terms of stability of friction coefficient. Wear track observation after the friction tests revealed that OC were confirmed along grooves on the surface having large roughness but few CO confirmed on small roughness. Therefore, this revealed that tribological performance of CO maybe affected by interrelationship of additive amount of CO and the depth of fine grooves.

Influence of the Concentration and Shape of Carbon Fillers on the Mechanical Properties of Polypropylene Fibers

Polypropylene fibers containing various concentrations of spherical (technical carbon) and anisotropic (nanofibers, nanotubes) carbon nanoparticles were prepared under laboratory conditions. The mechanical properties of the composite fibers were determined. It was shown that their strength and elasticity modulus increased by ~1.5 times only upon adding small concentrations (1-5 mass%) of anisotropic particles. Adding technical carbon at all concentrations decreased the fiber strength and fracture bending with an insignificant increase of elasticity modulus. The development of nanocomposites based on polymeric matrices is a promising area of contemporary materials science. Electrically conductive additives such as soot, graphite, chopped fibers, and metal powders are used to decrease charging during processing of synthetic materials and use of items made of them. However, synthetic composites with stable anti-static properties can be produced only by adding large concentrations (10-20 mass%) of these fillers [1-3]. It is worth noting that filled samples are weaker than the starting polymer. Fillers with particle sizes from several nanometers to tens of nanometers, i.e., carbon nanofibers and nanotubes, are beginning to play an increasingly important role. Such fillers can produce polymer composites with controlled mechanical, electrical, and other transport properties. It was shown [4] that the threshold concentrations of electrically conductive fillers that were required for stable anti-static protection of the polymer matrix could be reduced considerably from 15 mass% for technical carbon (TC) to 0.5 mass% for nanotubes by increasing the axial ratio of the nanoparticles. It was also demonstrated [5-7] that the mechanical properties of nanocomposites with anisotropic nanoparticles could be increased by preliminary orientation of carbon nanofibers (CNF) along the fiber axis during spinning of the composite from the melt. The literature on the strength of composites containing carbon nanotubes (CNT) and CNF [8-12] indicates that the strength of nanocomposites can be increased only with small (<5 mass%) additions of nanofillers. Increasing the concentration further does not affect the strength or even lowers it. The elasticity modulus of such materials can be increased by ~1.5 times with the same low nanoparticle concentrations and then almost does not change. As a rule, blocks or films were investigated in many publications focused on the physical-mechanical properties of nanocomposites with anisotropic nanoparticles [5, 6, 13-15]. Nevertheless, industrial manufacturing of polymers used to fabricate textiles is often accompanied by additional oriented drawing at elevated temperatures [16, 17]. This can improve the mechanical and operating properties of the final products. The influence of the type, shape, and concentration of dispersed nanoparticles on the bending and tensile properties of a single polymeric matrix subjected to oriented drawing is practically unstudied.

Analytical Modeling of Effective Diffusivity in Micro-Porous Layers

The membrane electrode assembly (MEA) used in polymer electrolyte fuel cells consists of a membrane, two electrodes (anode and cathode), and two gas diffusion layers (GDLs). The GDL is responsible for providing the pathways for transport of the reactant gases from the flow channels to the catalyst layers. Hence, the mass transport resistance of this layer should be minimized for high performance operation. The GDL is typically a dual-layer carbon-based material composed of a macro-porous substrate, which usually contains carbon fibers, binder, and PTFE, and a thin delicate micro-porous layer (MPL), which is usually made of carbon nano-particles and PTFE. Spherical carbon nano-particles of 20-100 nm in diameter construct the complex structure of MPL. Small pore sizes and highly hydrophobic characteristics are the two main specifications of the MPL. The effective diffusivity of the MPL is a key property in determining the fuel cell performance. However, since the MPL is a recently developed material, the number of published works with focus on its diffusivity is limited. Measuring the MPL diffusivity is a challenging task since the MPL needs a physical support and cannot be analyzed as a separate object. Similar to its measurements, modeling the MPL diffusivity is also a difficult task (Nanjundappa et al., Electrochimica Acta 110:349-57), since it involves the reconstruction of the complex structure numerically and solving the diffusion equations in the nano-scale pores where the continuum assumption may be invalid and Knudsen diffusion may prevail. Usually, complex numerical algorithms are employed to reconstruct a small portion of the MPL. This step is followed by a computationally intensive stage to solve the diffusion equations inside the void spaces of the reconstructed domain. Although this approach leads to reliable and accurate results, an analytical relationship that correlates certain design parameters to the MPL diffusivity could be helpful. A fully analytical solution of the mass transport equation inside a randomly structured porous material is however not feasible. Simplifying assumptions are therefore required to derive an analytical model for predicting the transport properties of porous structures. The unit cell approach is one way of simplifying the structure. A unit cell is a hypothetical, periodic domain that represents the entire structure. Hence, optical observations can aid the selection of the optimal unit cell arrangement. In this work a unit cell is chosen based on cross-sectional SEM images of a standard MPL material. Generally, two main regions can be observed in the MPL: i) clusters of spherical particles; and ii) pores. The considered unit cell, which is devised based on these observations, is shown in Figure 1. The analogy between the heat and mass transfer is employed to solve the diffusion equation in the unit cell and a relationship is proposed to calculate the effective MPL diffusivity. The obtained values from this relationship are compared with the experimental data available in the literature and another stochastic model which is under development in our group. The proposed relationship is able to predict the MPL diffusivity with an acceptable accuracy, i.e., with less than 10% deviation. The required input parameters of the model are particle diameter, MPL porosity, and average pore size. A parametric study is then performed to examine the effects of these parameters on the MPL diffusivity. The proposed relationship is expected to be useful to the fuel cell community, especially for the purposes of performance modeling. Furthermore, the results from the parametric study c provide valuable information on the effects of carbon particle size, the MPL porosity, and the MPL pore size distribution on its effective diffusivity. Acknowledgments:This research was supported by Ballard Power Systems and the Natural Sciences and Engineering Research Council of Canada.

Towards large scale preparation of carbon nanostructures in molten LiCl

This study examines the preparation of graphitic carbon nanostructures, including carbon nanotubes (CNTs) with both cylindrical and bamboo-like morphology and spherical carbon nanoparticles by electrochemical erosion of graphite cathodes in molten LiCl on a scale of more than 10g which could easily be increased to a larger scale. A uniform erosion of graphite electrodes was achieved using bare electrodes immersed in molten salt. It was demonstrated that any shadow on the graphite cathode made by ceramic insulators impedes erosion of the electrode. Moreover, the carbon products obtained at different cathode current densities ranging from about 0.4 to 1Acm−2 were characterized by electron microscopy. Accordingly, a mechanism is proposed for the erosion of the graphite electrodes, based on the electrochemical peeling and etching of graphite flakes in negative electrodes, leading to the formation of CNTs and spherical nanoparticles, respectively.

Plasma dry reforming of methane in an atmospheric pressure AC gliding arc discharge: Co-generation of syngas and carbon nanomaterials

An alternating-current (AC) gliding arc reactor has been developed offering a new route for the co-generation of syngas and value-added carbon nanomaterials by plasma dry reforming of methane. Different carbon nanostructures including spherical carbon nanoparticles, multi-wall carbon nanotubes and amorphous carbon have been obtained as by-products of syngas generation in the plasma system. Optical emission spectra of the discharge demonstrate the formation of different reactive species (Al, CO, CH, C2, Hα, Hβ and O) in the plasma dry reforming reaction. The effect of different operating parameters (feed flow rate, input power and CH4/CO2 molar ratio) on the performance of the plasma process has been evaluated in terms of the conversion of feed gas, product selectivity and energy conversion efficiency. It is interesting to note that gliding arc plasma can be used to generate much cleaner gas products of which syngas is the main one. The results also show that the energy efficiency of dry reforming using gliding arc plasma is an order of magnitude higher than that for processing using dielectric barrier or corona discharges. Both of these can be attributed to the higher electron density in the order of 1023 m−3 generated in the gliding arc plasma.

Carbon-core silver-shell nanodots as sensitizers for phototherapy and radiotherapy

Spherical carbon nanoparticles (carbon nanodots) with a silver shell were investigated as potential sensitizing agents. The cytotoxicity of the combination of ultraviolet radiation or x-rays with the nanodots was examined in cancer cells in vitro. The cell viability decreased following the exposure to the radiation. The carbon nanodots enhanced the radiation effects by significantly reducing the amount of surviving cells compared to that of the cells exposed only to the radiation. Carbon-core silver-shell nanodots can be proposed as a bimodal sensitization platform for biological and medicinal applications employing non-ionizing or ionizing radiation.

Flame retardancy through carbon nanomaterials: Carbon black, multiwall nanotubes, expanded graphite, multi-layer graphene and graphene in polypropylene

Herein we investigate the influence of carbon additives with different particle sizes and shapes on the flame retardancy and mechanical properties of isotactic polypropylene. Thermally reduced graphite oxide (TRGO) and multi-layer graphene (MLG250), consisting of few graphene layers, are compared with spherical, tubular and platelet-like carbon fillers such as carbon black (CB), multiwall nanotubes (MWNT) and expanded graphite (EG). The different morphologies control the dispersion of the carbon particles in PP and play a key role in structure–property relationships. Uniformly dispersed CB, MLG250 and TRGO shift the onset temperature of PP decomposition to temperatures around 30 °C higher, induce a flow limit in the composites' melt viscosity and change drastically their fire behaviour. The prevented dripping and significantly increased heat absorption result in decreased time to ignition and hardly any change in the reaction to a small flame. Under forced-flaming conditions reductions in the peak heat release rate of up to 74% are achieved due to the formation of a protective layer of residue during combustion. The described effects of carbon nanomaterials on the properties of PP composites are most pronounced for well-exfoliated graphenes, making them preferable to less exfoliated, micron-sized expanded graphite or conventional spherical and tubular carbon nanoparticles.