Types Of Carbon Nanomaterials Research Articles

Vegetable-extracted carbon dots and their nanocomposites for enhanced photocatalytic H2production

In this work, we describe a facile construction of eco-friendly and effective nanocomposites from carbon dots (CDs), a novel type of carbon nanomaterial, for photocatalytic purposes. A series of benign CDs with favourable photoluminescence (PL) features were initially obtained from the hydrothermal treatment of natural vegetables including guava, red pepper, peas and spinach. The spinach-extracted CDs, with the highest PL emission intensity, were integrated with versatile TiO2 ensembles, i.e. nanoparticles (NPs) and nanotubes (NTs), to form desirable nanocomposites by further hydrothermal synthesis. TEM images, coupled with XPS spectra, confirm that the CDs are well decorated on the surfaces of TiO2. Due to the favourable electron transfer property of CDs, the H2 generation rates are enhanced to 75.5 and 246.1 μmol g−1 h−1 for TiO2 NP/CD and NT/CD nanocomposites, which are 21.6 and 3.3 times the rates of bare NPs and NTs, respectively. The strategy reported here may contribute to the fabrication of green and efficient nanocomposites for diverse applications.

탄소나노튜브 및 그래핀 나노플레이트 폴리프로필렌 복합재 필름 압출 및 물성 평가

본 연구에서는 폴리프로필렌과 다양한 탄소나노소재를 사용하여 제조한 복합재의 압출방향 및 권취속도에 따른 기계적 물성과 결정화도에 대한 연구를 수행하였다. 폴리프로필렌에 탄소나노소재를 균일하게 분산시키기 위해 미분쇄기에 폴리프로필렌 분말(<700 <TEX>${\mu}m$</TEX>)과 탄소나노소재를 혼합한 후 나노복합재 필름 제조를 위해 압출기를 사용하였다. 나노복합재 필름의 결정화도를 분석하기 위해 differential scanning calorimetry를 이용하였다. 기계적 물성을 인장시험을 통해서 측정한 후 순수 폴리프로필렌 물성과 비교하였고, 압출 시 필름 권취속도에 대한 나노복합재 결정화도의 차이를 확인하였다. 탄소나노소재를 첨가함으로써 고분자 필름의 기계적 물성이 향상됨을 확인하였고, 그에 따른 결정화도 역시 증가하는 것을 확인하였다. 반면, 권취속도가 증가 할수록 압출물의 냉각속도도 역시 증가함으로써 결정화도가 오히려 감소함을 확인하였다. Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of <TEX>$750m^2/g$</TEX> showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.

Transmission Electron Microscopy and the Science of Carbon Nanomaterials

Carbon is a unique and versatile element that is capable of forming different architectures at nanoscale. The element has become a key component in nanoscience and nanotechnology. Transmission electron microscopy (TEM) acts as "our eyes" enabling us not only to reveal the morphology, but also to provide structural, chemical and electronic information of nanocarbon on the atomic level. In fact, except for fullerene, nearly all types of carbon nanomaterials were discovered by TEM, such as carbon nanotubes, carbon nanocones, and graphene-like nanocarbon. It cannot be imagined what nanoscience and nanotechnology would be without the contributions of TEM. Herein, the "interaction" between TEM and the science of carbon nanomaterials is reviewed and it is demonstrated for some selected examples that TEM provides a dramatic driving force for the development of nanocarbon science.

Preface to the Focus Issue on Nanocarbons for Energy Harvesting and Storage

We are pleased to present a Focus Issue of the ECS Journal of Solid State Science and Technology (JSS) on nanocarbons for energy harvesting and storage. Fullerenes, carbon nanotubes and graphene have taken a solid place in modern science and technology, as demonstrated by the awarding of two Nobel Prizes – the first, in Chemistry, was given in 1996 to Robert F. Curl Jr., Sir Harold Kroto and Richard E. Smalley for the discovery of fullerenes. The second, in Physics, was awarded in 2010 to Andre Geim and Konstantin Novoselov for the isolation of graphene. Since 1985, more than 115,000 scientific papers have been published on topics devoted to fullerenes, carbon nanotubes, graphene and related materials and there is no doubt that these types of carbon nanomaterials, with their unique structures and properties, will continue to find many new applications in all areas of science, medicine and technology, including electrochemical science and technology.

Electrochemical properties of arc-black and carbon nano-balloon as electrochemical capacitor electrodes

In this study, we used two types of carbon nanomaterials, arc-black (AcB) which has an amorphous structure and carbon nano-balloon (CNB) which has a graphitic structure as electrochemical capacitor electrodes. We made a coin electrode from these carbon materials and fabricated an electric double-layer capacitor (EDLC) that sandwiches a separator between the coin electrodes. On the other hand, RuO2 was loaded on these carbon materials, and we fabricated a pseudo-capacitor that has an ion insertion mechanism into RuO2. For comparison with these carbon materials, activated carbon (AC) was also used for a capacitor electrode. The electrochemical properties of all the capacitors were evaluated in 1M H2SO4 aqueous solution. As a result of EDLC performance, AcB electrode had a higher specific capacitance than AC electrode at a high scan rate (≥ 100 mV/s). In the evaluation of pseudo-capacitor performance, RuO2-loaded CNB electrode showed a high specific capacitance of 734 F/g per RuO2 weight.

Progress in graphene-based photoactive nanocomposites as a promising class of photocatalyst

Carbon nanomaterials based nanocomposites have gained increasing interest owing to their potential applications in many aspects, such as photocatalysis, solar cells, solar fuel, etc. Graphene, as a new type of carbon nanomaterial, has attracted consideration attention due to its unique two-dimensional conjugated structure and electronic properties. In this feature article, we cover recent advances in the applications of graphene-based photoactive nanocomposites in environmental remediation and energy conversion, including photocatalytic degradation of organic contaminants, photoelectrochemical solar cells, and solar fuel production. Finally, the perspectives of the challenges and opportunities in this emerging area are also discussed.

Synthesis of various carbon nanomaterials (CNMs) on powdered activated carbon

Carbon nanomaterials (CNMs) are promising in many potential applications for their attractive physical and chemical properties. Chemical vapor deposition technique (CVD) is used to synthesize CNMs on fixed substrate. Powdered activated carbon (PAC) was used as a successful substrate for CNMs growth in CVD reaction process. Iron clustered nano particles Fe3+ was impregnated successfully on PAC surface under sonication. EDX characterization results showed the evidence of impregnation and growth of CNMs on PAC surface. The optimum weight percentage of Fe3+ impregnation on PAC was found to be 5%. The CVD reactor used in thisstudy was locally fabricated and modified to reduce the process time and cost. CNMs were synthesized at different temperatures (850, 750, 650 and 550°C) and the maximum yield was obtained at 550°C with majority of CNFs. Various types of CNMs were grown: carbon nanotubes (CNTs), carbon nanofibers (CNFs), CN spheres and CN-coils. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images were studied for all the samples to investigate the nanostructures for CNMs. Key words: Carbon nanomaterials, carbon nanotube, carbon nanofibers, nanotechnology, chemical vapor deposition, catalyst impregnation, activated carbon

Raman Spectroscopy and Field Emission Scanning Electron Microscopic Studies on Carbon Nanomaterials

Raman analysis is one of the main methods use to investigate type of graphitized carbon nanomaterials. It provides information on the vibration of crystal lattice, electron structure and regularity of crystal structure of the graphitized carbon materials. In this work the single step chemical vapour deposition (CVD) method was introduced for the direct growth of all as-synthesized carbon nanomaterials; carbon nanotubes (CNTs), carbon nanofiber (CNF), carbon nanosphere chain (CNSC) and CNT heterojunctions (HJCNTs). Series of metal catalysts were formulated from Ni, Fe, Cr and Cu, and were used in the synthesis of the respected carbon nanomaterials (CNMs). By introducing the right combination of the reaction conditions consisting of the formulated catalyst, reaction temperature and flow rate as well as type of carbon source resulted in the formation of different types of carbon nanomaterials. Raman spectra analysis revealed that the used of acetylene and ethanol as the carbon precursors are proficient to produce different form of carbon nanomaterials as depicted by the evolution of the G-band and D-band intensities. The FESEM micrographs obtained confirmed the morphology and types of the respected carbon nanomaterials synthesized in this study.

Long, Needle-like Carbon Nanotubes and Asbestos Activate the NLRP3 Inflammasome through a Similar Mechanism

Carbon nanomaterials (CNM) are targets of great interest because they have multiple applications in industry but also because of the fear of possible harmful heath effects of certain types of CNM. The high aspect ratio of carbon nanotubes (CNT), a feature they share with asbestos, is likely the key factor for reported toxicity of certain CNT. However, the mechanism to explain this toxicity is unclear. Here we investigated whether different CNM induce a pro-inflammatory response in human primary macrophages. Carbon black, short CNT, long, tangled CNT, long, needle-like CNT, and crocidolite asbestos were used to compare the effect of size and shape on the potency of the materials to induce secretion of interleukin (IL) 1-family cytokines. Our results demonstrated that long, needle-like CNT and asbestos activated secretion of IL-1β from LPS-primed macrophages but only long, needle-like CNT induced IL-1α secretion. SiRNA experiments demonstrated that the NLRP3 inflammasome was essential for long, needle-like CNT and asbestos-induced IL-1β secretion. Moreover, it was noted that CNT-induced NLRP3 inflammasome activation depended on reactive oxygen species (ROS) production, cathepsin B activity, P2X(7) receptor, and Src and Syk tyrosine kinases. These results provide new information about the mechanisms by which long, needle-like materials may cause their harmful health effects. Furthermore, the techniques used here may be of use in future risk assessments of nanomaterials.

Acute toxicity of carbon-based nanomaterials to Escherichia coli is partially dependent on the presence of process impurities

Using inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy, we perform a compositional analysis of ten commercially available and laboratory carbon nanomaterials (CNMs). It is found that, depending on the type of CNMs and applied purification technology, they can contain 20 to 50 out of the 62 identified chemical elements, totally amounting to 0.03 to 23.1% of the weight of the sample under analysis. It is shown that the acute toxicity of CNMs, which is determined according to the effect on the luminescence intensity of a sensor Escherichia coli strain carrying cloned luxCDABE genes of Photobacterium leiognathi, is partially dependent on the presence of process impurities of Ni, Y, Zn, Sm, Gd, Ho, and Fe. With an increase in the time of contact between the sensor microorganism and the CNM, the latter develop intrinsic biotoxicity, which decreases the significance of the impurity composition in determining this activity within the dynamics of the experiment.

Functionalized carbon nanomaterials: exploring the interactions with Caco-2 cells for potential oral drug delivery

Although carbon nanomaterials (CNMs) have been increasingly studied for their biomedical applications, there is limited research on these novel materials for oral drug delivery. As such, this study aimed to explore the potential of CNMs in oral drug delivery, and the objectives were to evaluate CNM cytotoxicity and their abilities to modulate paracellular transport and the P-glycoprotein (P-gp) efflux pump. Three types of functionalized CNMs were studied, including polyhydroxy small-gap fullerenes (OH-fullerenes), carboxylic acid functionalized single-walled carbon nanotubes (f SWCNT-COOH) and poly(ethylene glycol) functionalized single-walled carbon nanotubes (f SWCNT-PEG), using the well-established Caco-2 cell monolayer to represent the intestinal epithelium. All three CNMs had minimum cytotoxicity on Caco-2 cells, as demonstrated through lactose dehydrogenase release and 3-(4,5-dimethyliazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Of the three CNMs, f SWCNT-COOH significantly reduced transepithelial electrical resistance and enhanced transport of Lucifer Yellow across the Caco-2 monolayer. Confocal fluorescence microscopy showed that f SWCNT-COOH treated cells had the highest perturbation in the distribution of ZO-1, a protein marker of tight junction, suggesting that f SWCNT-COOH could enhance paracellular permeability via disruption of tight junctions. This modulating effect of f SWCNT-COOH can be reversed over time. Furthermore, cellular accumulation of the P-gp substrate, rhodamine-123, was significantly increased in cells treated with f SWCNT-COOH, suggestive of P-gp inhibition. Of note, f SWCNT-PEG could increase rhodamine-123 accumulation without modifying the tight junction. Collectively, these results suggest that the functionalized CNMs could be useful as modulators for oral drug delivery, and the differential effects on the intestinal epithelium imparted by different types of CNMs would create unique opportunities for drug-specific oral delivery applications.

A biofuel cell with a single-walled carbon nanohorn-based bioanode operating at physiological condition

Single-walled carbon nanohorns (SWNHs), a new type of carbon nanomaterials, possess excellent catalytic properties, high-purity, and low toxicities, which make them suitable for bioelectrochemical application. Here a biofuel cell anode has been developed by using SWNHs as the support for redox mediator and biocatalyst for the first time. Cyclic voltammetric results show SWNHs promotes the electropolymerization of methylene blue (MB) and the resulted nanocomposite (poly MB–SWNHs) exhibits prominent catalytic ability to the oxidation of nicotinamide adenine dinucleotide. Glucose dehydrogenase was then immobilized on the poly MB–SWNHs modified electrode for the oxidation of glucose. Employing Pt nanoparticles supported on functionalized TiO 2 colloidal spheres with nanoporous surface as cathode catalyst, the as-assembled glucose/O 2 biofuel cell operate at the physiological condition with good performance.

Magnetic properties and transmission electron microscopy studies of Ni nanoparticles encapsulated in carbon nanocages and carbon nanotubes

Three types of carbon nanomaterials, including bamboo-shaped carbon nanotubes with Ni encapsulated and hollow and Ni catalytic particles filled carbon nanocages, have been prepared by methane catalytic decomposition at a relatively low temperature. Transmission electron microscopy observations showed that fascinating fullerene-like Ni–C (graphitic) core–shell nanostructures predominated. Detailed examination of high-resolution transmission electron microscopy showed that the walls of bamboo-shaped carbon nanotubes with quasi-cone catalytic particles encapsulated consisted of oblique graphene planes with respect to the tube axis. The Ni particles encapsulated in the carbon nanocages were larger than that encapsulated in carbon nanotubes, but the diameters of the cores of hollow carbon nanocages were less than that of Ni particles encapsulated in carbon nanotubes, suggesting that the sizes of catalyst particles played an important role during carbon nanomaterial growth. The magnetic properties of the carbon nanomaterials were measured, which showed relatively large coercive force ( H c = 138.4 O e) and good ferromagnetism ( M r/ M s = 0.325).

Structural analysis of conical carbon nanofibers

Conical carbon nanofibers are a relatively new type of carbon nanomaterial that has received considerable scientific and commercial interest due to its physical properties. However, its structure and growth mechanism have still not been determined conclusively. In this study the structure of these materials was investigated employing molecular models and structural analyses and compared with reported experimental observations, principally of cone apex angles. The results showed that stacked cone models could not explain the wide variety of apex angles observed for these nanofibers and related structures. Cone–helix models, originally proposed for other carbon conical structures, allow a variety of apex angle structures and were found to be applicable for nanofibers as well. An equation was developed that allows for prediction of cone–helix structures with good graphitic alignment. Such structures were also shown to be more compatible with the physical properties and growth mechanism of nanofibers than stacked cone structures. From these results a cone–helix structure, and a new cone–helical growth mechanism for the nanofibers based on heterogeneous nucleation on conical catalyst particles, are proposed.

Preparation of Pt nanoparticles on carbon nanotubes and graphite nanofibers via self-regulated reduction of surfactants and their application as electrochemical catalyst

An in situ synthetic method is reported for preparing and decorating metal nanoparticles at sidewalls of sodium dodecyl sulfate micelle functionalized single wall/multiwall carbon nanotubes and graphite nanofibers. The amount and morphology of Pt nanoparticles depend on the types of carbon nanomaterials (C NM). The results demonstrate for the attachment of metal nanoparticles to the carbon nanotubes’ (CN) surface via non-destructed surfactant modification. These nanocomposites are successfully used as catalysts for oxidation of methanol, the results of which reveal an increase of oxidizing power of Pt/C NM upon increasing the C NM diameter.

Formation of Carbon Nanotubes and Cubic and Spherical Nanocages

Three types of carbon nanomaterials, including bamboo-shaped carbon nanotubes and cubic and spherical carbon nanocages, have been prepared by an ethanol thermal reduction process. Scanning electron microscopy studies showed that carbon nanotubes predominated. Transmission electron microscopy investigations indicated that as-synthesized sample contained mostly bamboo-shaped carbon nanotubes, with some carbon cubic and spherical nanocages. Detailed examination of high-resolution transmission electron micrography showed that the walls of bamboo-shaped carbon nanotubes consisted of oblique graphene planes with respect to the tube axis, whose interlayer spacing was about 0.335 nm. The experimental results suggest that the growth mechanism of the bamboo-shaped carbon nanotubes follows the base growth model and the appearance of cubic and spherical carbon nanocages arises from the graphitic sheets bending in an attempt to eliminate the highly energetic dangling bonds present at the edge of the growing structure....