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C, Volume 5, Issue 3 (September 2019)

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Open AccessFeature PaperReview
Porphyrinoid–Fullerene Hybrids as Candidates in Artificial Photosynthetic Schemes
C 2019, 5(3), 57; https://doi.org/10.3390/c5030057 - 18 Sep 2019
Viewed by 218
Abstract
Natural photosynthesis inspired the scientific community to design and synthesize molecular assemblies that possess advanced light-harvesting and electron-transfer features. In this review, we present the preparation and the photophysical investigation of novel porphyrin–fullerene hybrids acting as artificial photosynthetic systems. Porphyrinoids stand as chlorophyll [...] Read more.
Natural photosynthesis inspired the scientific community to design and synthesize molecular assemblies that possess advanced light-harvesting and electron-transfer features. In this review, we present the preparation and the photophysical investigation of novel porphyrin–fullerene hybrids acting as artificial photosynthetic systems. Porphyrinoids stand as chlorophyll analogues and have emerged as suitable photosensitizers in supramolecular electron donor–acceptor hybrids. Fullerenes (C60) are versatile electron acceptors with small reorganization energy and low reduction potentials. The novel derivatives presented herein mimic the fundamental features of the photosynthetic reaction center, namely, light harvesting, charge separation, and charge transport. To this end, a comprehensive analysis on these key processes that occur in various porphyrin–fullerene entities is illustrated in this work. Full article
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Open AccessReview
Structure and Properties of Chained Carbon: Recent Ab Initio Studies
C 2019, 5(3), 56; https://doi.org/10.3390/c5030056 - 11 Sep 2019
Viewed by 329
Abstract
Carbon chains or carbyne-like structures represent the next generation of 1D materials whose properties can be tuned by the chain length, doping, and the type of termination. Currently inaccessible technology of the macroscopic carbyne synthesis and characterization makes theoretical work especially valuable. The [...] Read more.
Carbon chains or carbyne-like structures represent the next generation of 1D materials whose properties can be tuned by the chain length, doping, and the type of termination. Currently inaccessible technology of the macroscopic carbyne synthesis and characterization makes theoretical work especially valuable. The state of the art methods being applied in the field are density functional theory and molecular dynamics. This paper provides a review of the current state of research on modeling linear carbon structures and related materials. We show that even though the “static” properties of carbon chains (mechanical strength, thermal conduction, band gaps, and phonon spectra) are extensively described, there are only a few simulations of the synthesis processes that constitute the next challenge in 1D research. Full article
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Open AccessArticle
Macroscopic Behavior and Microscopic Factors of Electron Emission from Chained Nanocarbon Coatings
C 2019, 5(3), 55; https://doi.org/10.3390/c5030055 - 09 Sep 2019
Viewed by 240
Abstract
The carbyne-containing films based on linear-chain carbon are promising materials for the manufacture of electronic equipment components. These carbyne-containing materials can be used as active elements of computational electronics and as ultra-miniature sensors of gaseous environment. The temperature studies of the electrical characteristics [...] Read more.
The carbyne-containing films based on linear-chain carbon are promising materials for the manufacture of electronic equipment components. These carbyne-containing materials can be used as active elements of computational electronics and as ultra-miniature sensors of gaseous environment. The temperature studies of the electrical characteristics of carbyne-containing films by most of the scientific groups are limited to the low temperature range in which the quantum properties of nanostructures are most pronounced. We studied carbyne-containing films with a thickness of 20 and 400 nm on copper and silicon substrates using optically stimulated electron emission (OSEE) in the temperature range from room temperature (RT) to 400 °C. Theoretical modeling explains the dependence of work function on termination groups and substrate lattice. Experimental data revealed a relationship between the spectral characteristics of electron emission and temperature. The spectral contributions of both surface states and bulk interband transitions were clearly distinguishable. Full article
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Open AccessArticle
Polycondensation of Hexamethylenetetramine in Anhydrous Acid Media as a New Approach to Carbyne-Like Materials and Its Application as Dispersant of Carbon Materials
C 2019, 5(3), 54; https://doi.org/10.3390/c5030054 - 06 Sep 2019
Viewed by 267
Abstract
Aminocumulene (AC), a technical name that results from the hexamethylenetetramine polycondensation in anhydrous sulfuric acid, was successfully performed toward the synthesis of oligomeric cumulenic compounds made up of carbyne-like (=C=C)x fragments as a main moiety together with amino endcapping groups. The tentative [...] Read more.
Aminocumulene (AC), a technical name that results from the hexamethylenetetramine polycondensation in anhydrous sulfuric acid, was successfully performed toward the synthesis of oligomeric cumulenic compounds made up of carbyne-like (=C=C)x fragments as a main moiety together with amino endcapping groups. The tentative mechanism for the synthesis of the soluble and insoluble AC likely included the participation of carbene species as an intermediate. Spectral properties obtained from UV-Vis, infrared, and Raman spectroscopies, and surface chemistry analysis through X-ray photoelectron spectroscopy of the soluble AC confirmed the presence of a mixture of linear and branched aminocumulene-based oligomers. AC displayed high performance as a dispersant and stabilizer agent of both multi-walled carbon nanotubes and graphene in aqueous solutions after powerful insonation treatment under controlled temperature compared to the most commonly used dispersant agents. Thereby, AC is vitally important for the preparation of carbonaceous materials based on nanoinks in a wide variety of fields. Full article
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Open AccessReview
Recent Advances in Seeded and Seed-Layer-Free Atomic Layer Deposition of High-K Dielectrics on Graphene for Electronics
C 2019, 5(3), 53; https://doi.org/10.3390/c5030053 - 02 Sep 2019
Viewed by 278
Abstract
Graphene (Gr) with its distinctive features is the most studied two-dimensional (2D) material for the new generation of high frequency and optoelectronic devices. In this context, the Atomic Layer Deposition (ALD) of ultra-thin high-k insulators on Gr is essential for the implementation of [...] Read more.
Graphene (Gr) with its distinctive features is the most studied two-dimensional (2D) material for the new generation of high frequency and optoelectronic devices. In this context, the Atomic Layer Deposition (ALD) of ultra-thin high-k insulators on Gr is essential for the implementation of many electronic devices. However, the lack of out-of-plane bonds in the sp2 lattice of Gr typically hinders the direct ALD growth on its surface. To date, several pre-functionalization and/or seed-layer deposition processes have been explored, to promote the ALD nucleation on Gr. The main challenge of these approaches is achieving ultra-thin insulators with nearly ideal dielectric properties (permittivity, breakdown field), while preserving the structural and electronic properties of Gr. This paper will review recent developments of ALD of high k-dielectrics, in particular Al2O3, on Gr with “in-situ” seed-layer approaches. Furthermore, recent reports on seed-layer-free ALD onto epitaxial Gr on SiC and onto Gr grown by chemical vapor deposition (CVD) on metals will be presented, discussing the role played by Gr interaction with the underlying substrates. Full article
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Open AccessFeature PaperArticle
Changing Contents of Carbon Hybridizations in Amorphous Hydrogenated Carbon Layers (a-C:H) on Sustainable Polyhydroxybutyrate (PHB) Exhibit a Significant Deterioration in Stability, Depending on Thickness
C 2019, 5(3), 52; https://doi.org/10.3390/c5030052 - 30 Aug 2019
Viewed by 288
Abstract
PHB is a biodegradable polymer based on renewable raw materials that could replace synthetic polymers in many applications. A big advantage is the resulting reduction of the waste problem, as well as the conservation of fossil resources. To arrange it for various applications, [...] Read more.
PHB is a biodegradable polymer based on renewable raw materials that could replace synthetic polymers in many applications. A big advantage is the resulting reduction of the waste problem, as well as the conservation of fossil resources. To arrange it for various applications, the surface is arranged by plasma-enhanced chemical vapor deposition (PECVD) with amorphous hydrogenated carbon layers (a-C:H). Here, on a 50 µm thick PHB-foil, a-C:H layers of different thicknesses (0–500 nm) were deposited in 50 nm steps. Surface topography was investigated by scanning electron microscopy (SEM), chemical composition by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and wettability checked by contact angle. In addition, layers were examined by synchrotron supported X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS), which revealed thickness dependent changes of the sp2/sp3 ratio. With increasing thickness, even the topography changes show internal, stress-induced phenomena. The results obtained provide a more detailed understanding of the predominantly inorganic a-C:H coatings on (bio)polymers via in situ growth. Full article
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Open AccessArticle
Insights into the Electrochemical Behavior of Mercury on Graphene/SiC Electrodes
C 2019, 5(3), 51; https://doi.org/10.3390/c5030051 - 22 Aug 2019
Viewed by 359
Abstract
Fast and real time detection of Mercury (Hg) in aqueous solutions is a great challenge due to its bio-accumulative character and the detrimental effect on human health of this toxic element. Therefore, development of reliable sensing platforms is highly desirable. Current research is [...] Read more.
Fast and real time detection of Mercury (Hg) in aqueous solutions is a great challenge due to its bio-accumulative character and the detrimental effect on human health of this toxic element. Therefore, development of reliable sensing platforms is highly desirable. Current research is aiming at deep understanding of the electrochemical response of epitaxial graphene to Mercury exposure. By performing cyclic voltammetry and chronoamperometry measurements as well as density functional theory calculations, we elucidate the nature of Hg-involved oxidation-reduction reactions at the graphene electrode and shed light on the early stages of Hg electrodeposition. The obtained critical information of Hg behavior will be helpful for the design and processing of novel graphene-based sensors. Full article
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Open AccessArticle
Atom Probe Tomography (APT) Characterization of Organics Occluded in Single Calcite Crystals: Implications for Biomineralization Studies
C 2019, 5(3), 50; https://doi.org/10.3390/c5030050 - 22 Aug 2019
Viewed by 344
Abstract
Occlusion of organic components in synthetic calcite crystals has been recently used as a model to understand the role of intra-crystalline organics in biominerals. However, the characterization of the distribution of both types of organics inside these calcite crystals is very challenging. Here, [...] Read more.
Occlusion of organic components in synthetic calcite crystals has been recently used as a model to understand the role of intra-crystalline organics in biominerals. However, the characterization of the distribution of both types of organics inside these calcite crystals is very challenging. Here, we discuss the potential of using the technique of atom probe tomography (APT) for such characterization, focusing on the analysis of chitin incorporation in single crystals. Additionally, APT has at least the same spatial resolution as TEM tomography, yet with the advantage of obtaining quantitative chemical data. Results show that chitin, either after degradation with yatalase or in the form of nanofibers, forms discrete clusters (2 to 5 nm) in association to water and hydronium molecules, rather than forming a 3D network inside crystals. Overall findings indicate that APT can be an ideal technique to characterize intra-crystalline organic components in abiogenic and biogenic carbonates to further advance our understanding of biomineralization. Full article
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Open AccessArticle
Growing Cities and Mass Participant Sport Events: Traveling Behaviors and Carbon Dioxide Emissions
C 2019, 5(3), 49; https://doi.org/10.3390/c5030049 - 20 Aug 2019
Viewed by 335
Abstract
Fast-growing cities are expected to become a key contributor to the global climate crisis. A key characteristic of those urban districts is the accommodation of mass participant sport events. Sport entities, in collaboration with city governments, plan annually active participation sport events to [...] Read more.
Fast-growing cities are expected to become a key contributor to the global climate crisis. A key characteristic of those urban districts is the accommodation of mass participant sport events. Sport entities, in collaboration with city governments, plan annually active participation sport events to promote their cities as tourism destinations. Mass participant sport events aim to attract more visitors to the cities and to establish a successful social and economically sustainable future to those places. Given the fact that transportation is a critical factor of the residents and the visitors’ behavior, it is crucial to research the quantity of CO2 emissions generated to those places in association with the travel behaviors of the active sport event participants. Data collected from an annual mass participant running event in a highly ranked growing city in the United States. Findings showed that most of the active sport event participants traveled more than 150 miles to participate in the race and they used their vehicles. The largest quantity of CO2 emissions derived from those participants who traveled a round trip of, on average, 500 miles. The long-distance travelers alone generated 338 million kg of CO2 emissions. The conclusions recommend that growing cities and sport events should target long-distance travelers for promotions concerning sustainable transportation. Consequently, mass participant sport events could play a crucial role in the development of growing cities, and, in turn, growing cities that control long-distance traveling behaviors can reduce the global amount of greenhouse gas emissions and their impact on the global environmental destruction. Full article
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Open AccessArticle
Preparation, Stability and Local Piezoelectrical Properties of P(VDF-TrFE)/Graphene Oxide Composite Fibers
C 2019, 5(3), 48; https://doi.org/10.3390/c5030048 - 13 Aug 2019
Viewed by 391
Abstract
The unprecedented attributes such as biocompatibility and flexibility of macromolecular piezoelectric polymer has triggered an immense interested in scientific society for their potential exploitation in implantable electronic devices. In the present article, a theoretical and experimental investigation is done to explore the polarization [...] Read more.
The unprecedented attributes such as biocompatibility and flexibility of macromolecular piezoelectric polymer has triggered an immense interested in scientific society for their potential exploitation in implantable electronic devices. In the present article, a theoretical and experimental investigation is done to explore the polarization behavior of composite fibers based on copolymer poly-trifluoroethylene P(VDF-TrFE) and graphene oxide (GO) with varying composition of the components is explored for its possible application in bioelectronic devices. Electromechanical properties of the PVDF/GO nanofibers were investigated using piezoresponse force microscopy (PFM) method. The switching behavior, charge states, and piezoelectric response of the fibers were found to depend on the concentration of GO up to 20%. Theoretical models of PVDF chains, interacting with Graphene/GO layers has been used to explore the evolution of piezoresponse in the composite fibers. In order to compute piezoelectric coefficients, the behavior of composite in electrical fields has been modeled using software HyperChem. The experimental results are qualitatively correlated with a computed theoretical model. Full article
(This article belongs to the Special Issue Carbon Nanostructures for Biological Applications)
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Open AccessArticle
Macadamia Nutshell Biochar for Nitrate Removal: Effect of Biochar Preparation and Process Parameters
C 2019, 5(3), 47; https://doi.org/10.3390/c5030047 - 08 Aug 2019
Viewed by 388
Abstract
Agricultural runoff is a major cause of degradation to freshwater sources. Nitrate is of particular interest, due to the abundant use of nitrogen-based fertilizers in agricultural practices globally. This study investigated the nitrate removal of biochar produced from an agricultural waste product, macadamia [...] Read more.
Agricultural runoff is a major cause of degradation to freshwater sources. Nitrate is of particular interest, due to the abundant use of nitrogen-based fertilizers in agricultural practices globally. This study investigated the nitrate removal of biochar produced from an agricultural waste product, macadamia nutshell (MBC). Kinetic experiments and structural analyses showed that MBC pyrolsed at 900 °C exhibited inferior NO3 removal compared to that pyrolsed at 1000 °C, which was subsequently used in the column experiments. Concentrations of 5, 10 and 15 mg/L, with flowrates of 2, 5 and 10 mL/min, were examined over a 360 min treatment time. Detailed statistical analyses were applied using 23 factorial design. Nitrate removal was significantly affected by flowrate, concentration and their interactions. The highest nitrate removal capacity of 0.11 mg/g MBC was achieved at a NO3 concentration of 15 mg/L and flowrate of 2 mL/min. The more crystalline structure and rough texture of MBC prepared at 1000 °C resulted in higher NO3 removal compared to MBC prepared at 900 °C. The operating parameters with the highest NO3 removal were used to study the removal capacity of the column. Breakthrough and exhaustion times of the column were 25 and 330 min respectively. Approximately 92% of the column bed was saturated after exhaustion. Full article
(This article belongs to the Special Issue Carbon Materials for Water Treatment)
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Open AccessArticle
Synthesis of Carbon Nanotubes by Plasma-Enhanced Chemical Vapor Deposition Using Fe1−xMnxO Nanoparticles as Catalysts: How Does the Catalytic Activity of Graphitization Affect the Yields and Morphology?
C 2019, 5(3), 46; https://doi.org/10.3390/c5030046 - 08 Aug 2019
Viewed by 444
Abstract
The choice of a catalyst for carbon nanotube (CNT) growth is critical to controlling the morphology and chirality of the final product. Plasma-enhanced chemical vapor deposition (PECVD) can alleviate the requirements of the catalyst, i.e., they must be active for both the decomposition [...] Read more.
The choice of a catalyst for carbon nanotube (CNT) growth is critical to controlling the morphology and chirality of the final product. Plasma-enhanced chemical vapor deposition (PECVD) can alleviate the requirements of the catalyst, i.e., they must be active for both the decomposition of the source gas and graphitization in the conventional thermal CVD. However, it is still not well understood how the catalytic activity of the graphitization affects the yield and quality of CNTs. In this paper, we systematically investigated the influence of the catalytic activity of graphitization by tuning the composition of Fe1−xMnxO (x = 0–1) nanoparticles as catalysts. As the Mn component increased, the number of CNTs decreased because Mn has no catalytic function of the graphitization. The quality of CNTs also affected by the inclusion of the Mn component. Our study may provide useful information to develop a new catalyst for CNT growth in PECVD. Full article
(This article belongs to the Special Issue Plasma Processing for Carbon-based Materials)
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Open AccessArticle
Fluence Enhanced Optical Response of Ag Implanted Amorphous Carbon Thin Films
C 2019, 5(3), 45; https://doi.org/10.3390/c5030045 - 05 Aug 2019
Viewed by 399
Abstract
Silver nanoparticles (NPs) are known to exhibit strong interaction with light photons because their surface conduction electrons undergo collective oscillations once photo-excited at specific wavelengths; the so-called surface plasmon resonance (SPR). Their incorporation into carbon-based material is shown to greatly influence the overall [...] Read more.
Silver nanoparticles (NPs) are known to exhibit strong interaction with light photons because their surface conduction electrons undergo collective oscillations once photo-excited at specific wavelengths; the so-called surface plasmon resonance (SPR). Their incorporation into carbon-based material is shown to greatly influence the overall optical response of the matrix due to aggregation. In this paper, we studied the optical response of silver-irradiated amorphous carbon films due to varying fluence of 25 keV Ag ions in the range 2.5–3.4 × 1016 ions/cm2. Raman spectroscopy provided an insight into the microstructural details of the Ag:a-C nanocomposites such that access to bond characteristics of the films is enabled by directly linking the Raman information with sp2/sp3 configurations. Atomic force microscopy (AFM) analysis show significant increase in particle grain size and surface roughness of the films with increasing fluence while transmission electron microscopy (TEM) confirmed fluence-induced particle aggregation due to irradiation. Optical absorption studies revealed that the SPR of Ag NPs occurs in the wavelength range 418–395 nm in the irradiated films. The blue shift in plasmonic wavelength response is explained with respect to the fluence-induced increase in the particulate grain size and particle density as confirmed by AFM and TEM. The optical band gap energy ( E g ) of the pristine carbon film decreased from 1.79 eV to 1.41 eV while Urbach parameter ( E u ) increased from 0.01 eV to 12.0 eV, respectively with increasing fluence. These tunable optical parameters can be tailored into applications in surface coatings and as functional materials for solar cell efficiency enhancement. Full article
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Open AccessArticle
Waste Coffee Management: Deriving High-Performance Supercapacitors Using Nitrogen-Doped Coffee-Derived Carbon
C 2019, 5(3), 44; https://doi.org/10.3390/c5030044 - 01 Aug 2019
Viewed by 622
Abstract
In this work, nitrogen-doped activated carbon was produced from waste coffee powder using a two-step chemical activation process. Nitrogen doping was achieved by treating the coffee powder with melamine, prior to chemical activation. The produced nitrogen-doped carbon resulted in a very high surface [...] Read more.
In this work, nitrogen-doped activated carbon was produced from waste coffee powder using a two-step chemical activation process. Nitrogen doping was achieved by treating the coffee powder with melamine, prior to chemical activation. The produced nitrogen-doped carbon resulted in a very high surface area of 1824 m2/g and maintained a high graphitic phase as confirmed by Raman spectroscopy. The elemental composition of the obtained coffee-derived carbon was analyzed using X-ray photoelectron spectroscopy (XPS). The supercapacitor electrodes were fabricated using coffee-waste-derived carbon and analyzed using a three-electrode cell testing system. It was observed that nitrogen-doping improved the electrochemical performance of the carbon and therefore the charge storage capacity. The nitrogen-doped coffee carbon showed a high specific capacitance of 148 F/g at a current density of 0.5 A/g. The symmetrical coin cell device was fabricated using coffee-derived carbon electrodes to analyze its real-time performance. The device showed the highest specific capacitance of 74 F/g at a current density of 1 A/g. The highest energy and power density for the device was calculated to be 12.8 and 6.64 kW/kg, respectively. The stability test of the device resulted in capacitance retention of 97% after 10,000 cycles while maintaining its coulombic efficiency of 100%. These results indicate that the synthesized nitrogen-doped coffee carbon electrode could be used as a high-performance supercapacitor electrode for energy storage applications, and at the same time manage the waste generated by using coffee. Full article
(This article belongs to the Special Issue Carbon Nanomaterials for Energy Conversion and Storage Technologies)
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Open AccessArticle
Innovative Activated Carbon Based on Deep Eutectic Solvents (DES) and H3PO4
C 2019, 5(3), 43; https://doi.org/10.3390/c5030043 - 30 Jul 2019
Viewed by 420
Abstract
In this present work, a novel method for synthesis of palm kernel shell activated carbon was established using DES (choline chloride/urea)/H3PO4 as the activating agent. The pore characterization, morphology, and adsorption properties of the activated carbons were investigated. The activated [...] Read more.
In this present work, a novel method for synthesis of palm kernel shell activated carbon was established using DES (choline chloride/urea)/H3PO4 as the activating agent. The pore characterization, morphology, and adsorption properties of the activated carbons were investigated. The activated carbon samples made from the same feedstock at two pyrolysis temperatures (500 and 600 °C) were compared for their ability to adsorb Pb(II) in aqueous solution. The results demonstrated that the production of the activated carbon and adsorptive properties were significantly influenced by the pyrolysis temperature and the ratio of precursor to activating agent. DES/H3PO4 activated carbon (having surface area 1413 m2/g and total pore volume 0.6181 cm3/g) demonstrated good Pb(II) removal. Although all the tested activated carbon samples adsorbed Pb(II) from aqueous solution, they demonstrated different adsorption capabilities according to their various properties. The pyrolysis temperature, however, showed little influence on the activated carbon adsorption of Pb(II) when compared to the impregnation ratio. Their good desorption performance perhaps resulted from the porous structure. Full article
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Open AccessReview
Mechanism of Catalytic CNTs Growth in 400–650 °C Range: Explaining Volcano Shape Arrhenius Plot and Catalytic Synergism Using both Pt (or Pd) and Ni, Co or Fe
C 2019, 5(3), 42; https://doi.org/10.3390/c5030042 - 29 Jul 2019
Viewed by 454
Abstract
The Arrhenius plot of catalytic carbon formation from olefins on Ni, Co, and Fe has a volcano shape in the range 400–550 °C with reaction orders 0 (at lower T: Below ~500 °C) and one (at higher T: Above ~500 °C) [...] Read more.
The Arrhenius plot of catalytic carbon formation from olefins on Ni, Co, and Fe has a volcano shape in the range 400–550 °C with reaction orders 0 (at lower T: Below ~500 °C) and one (at higher T: Above ~500 °C) at each side of the maximum rate. The reaction follows a catalytic route with surface decomposition of the gas (olefin) on the catalyst nanoparticle, followed by the bulk diffusion of carbon atoms and carbon nanotube growth on the opposite side. At the higher temperature region (500–550 °C), the initial surface reaction step controls the rate and the reaction order is one, both in olefins and hydrogen (H). This confirms that H is essential for the surface reaction to occur. This is very valuable information to get faster CNT growth rate at relatively low temperatures. The apparent activation energy observed must correspond with the surface reaction Ea corrected for the temperature dependence of the two molecules involved (olefin and H). Adding a noble metal (Pt, Pd) to the carbon formation catalyst is frequently found to increase the reaction rate further. This effect has been described as an H spillover since 1964. However, there is evidence that the bulk diffusion of H atoms prevails and does not “spillover” the surface diffusion. Diffusion of H atoms through the solids involved is easy, and the H atoms remain single (“independent”) until emerging on a surface. Full article
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Open AccessEditorial
Recent Advances in Carbon Dots
C 2019, 5(3), 41; https://doi.org/10.3390/c5030041 - 22 Jul 2019
Viewed by 490
Abstract
It is unequivocally true that in recent years, carbon-based nanomaterials such as graphene, carbon nanotubes, and fullerenes, have attracted tremendous interest and an increasing number of applications have reaped their numerous benefits [...] Full article
(This article belongs to the Special Issue Recent Advances in Carbon Dots)
Open AccessFeature PaperArticle
Atmospheric Pressure Plasma-Treated Carbon Nanowalls’ Surface-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (CNW-SALDI-MS)
C 2019, 5(3), 40; https://doi.org/10.3390/c5030040 - 18 Jul 2019
Viewed by 500
Abstract
Carbon nanowalls (CNWs), vertically standing highly crystallizing graphene sheets, were used in the application of a surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS). The CNW substrates solved the issues on interferences of matrix molecules and alkali metal addition ions in low-weight molecule detection. [...] Read more.
Carbon nanowalls (CNWs), vertically standing highly crystallizing graphene sheets, were used in the application of a surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS). The CNW substrates solved the issues on interferences of matrix molecules and alkali metal addition ions in low-weight molecule detection. Before SALDI sample preparations, the hydrophobic CNW was treated by atmospheric pressure plasma for exposing hydrophilicity to the CNWs’ surface. Detection of water soluble amino acids, arginine, was demonstrated. Full article
(This article belongs to the Special Issue Plasma Processing for Carbon-based Materials)
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Open AccessArticle
A Rational Investigation of the Lewis Acid-Promoted Coupling of Carbon Dioxide with Cyclohexene Oxide: Towards CO2-Sourced Polycyclohexene Carbonate under Solvent- and Cocatalyst-Free Conditions
C 2019, 5(3), 39; https://doi.org/10.3390/c5030039 - 16 Jul 2019
Viewed by 483
Abstract
We report a rational investigation of the selective synthesis of poly(cyclohexene carbonate) from CO2 and cyclohexene oxide by using commercially available Lewis acids with nontoxic metal centers. After a preliminary screening, we focused on the use of zinc salts, and the effect [...] Read more.
We report a rational investigation of the selective synthesis of poly(cyclohexene carbonate) from CO2 and cyclohexene oxide by using commercially available Lewis acids with nontoxic metal centers. After a preliminary screening, we focused on the use of zinc salts, and the effect of the pressure, the temperature, the catalyst loading, and the presence of cocatalyst or a solvent on the reaction yields, selectivity, and molar masses was evaluated for selected catalytic platforms. Thus, we found that ZnTosylate in catalytic amounts under solvent- and cocatalyst-free conditions enables the selective synthesis of poly(cyclohexene carbonate) with a molecular weight of about 62.1 kg/mol with about 70% yields at 343 K and 4 MPa. To the best of our knowledge, this is a rare example of high molar mass polycyclohexene carbonates that are moreover obtained under solvent- and cocatalyst-free conditions. The high selectivity of ZnTos towards the formation of poly(cyclohexene carbonate) was interpreted, thanks to in situ FTIR spectroscopy and DFT calculations, as resulting from its ability to coactivate CO2. Full article
(This article belongs to the Special Issue From CO2 to High-Added-Value Products through Carbon-Based Materials)
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Open AccessArticle
Electrodeposition of Cu–SWCNT Composites
C 2019, 5(3), 38; https://doi.org/10.3390/c5030038 - 13 Jul 2019
Viewed by 476
Abstract
Single walled carbon nanotubes (SWCNTs) are used as a component of a plating solution of CuSO4 for direct current electrodeposition of Cu–SWCNT composites with varying nanotube proportions without the use of either a surfactant, a dispersing agent, or functionalization of the SWCNTs. [...] Read more.
Single walled carbon nanotubes (SWCNTs) are used as a component of a plating solution of CuSO4 for direct current electrodeposition of Cu–SWCNT composites with varying nanotube proportions without the use of either a surfactant, a dispersing agent, or functionalization of the SWCNTs. The Cu–SWCNT composites are characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The composites are comprised of metallic Cu and SWCNTs with minor oxide impurities, as well as the residual (Fe) catalyst from the unpurified SWCNTs, in addition to displaying nanotube-mediated morphological differences. EDX analysis of carbon (wt%) is close to quantitative with respect to the wt% of SWCNTs added to the electrolysis solution. The presence of SWCNTs decreases the oxidation of the copper, as well as changing the identity of the oxide from CuO, for electrolysis of Cu, to Cu2O. Hard adherent Cu–SWCNT coatings are prepared by the addition of Cu powder to the electrolysis solution. The approach described in this paper will enable controlled synthesis of metal-nanomaterial composites that can potentially be processed further into high ampacity electrical conductors. Full article
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Open AccessArticle
Mechanical Desensitization of an Al/WO3 Nanothermite by Means of Carbonaceous Coatings Derived from Carbohydrates
C 2019, 5(3), 37; https://doi.org/10.3390/c5030037 - 01 Jul 2019
Viewed by 554
Abstract
Nanothermites show great developmental promise in the near future in civilian, military and aerospace applications due to their tuneable reactive properties (ignition delay time, combustion velocity and pressure release). However, the high mechanical sensitivities of some of these energetic nanocomposites can make transportation [...] Read more.
Nanothermites show great developmental promise in the near future in civilian, military and aerospace applications due to their tuneable reactive properties (ignition delay time, combustion velocity and pressure release). However, the high mechanical sensitivities of some of these energetic nanocomposites can make transportation and handling of them hazardous. Here, a mechanical desensitization (shock and friction) of an Al/WO3 nanothermite is successfully obtained by means of carbon adding through the pyrolysis of naturally occurring molecules (carbohydrates). The combustion behaviour of the carbon-based energetic mixtures were also evaluated and a respectable reactivity has been evidenced. Full article
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Open AccessCommunication
Handling and Risk Mitigation of Nanoscale Graphene and Related Materials: Some Considerations and Recommendations
C 2019, 5(3), 36; https://doi.org/10.3390/c5030036 - 01 Jul 2019
Viewed by 455
Abstract
The purpose of this communication is to put forward some considerations and recommendations while handling nanomaterials, especially graphene and its derivatives. A large graphene sheet is generally stable and inert; thus, graphene and its derivatives are not considered hazardous, but good laboratory practices [...] Read more.
The purpose of this communication is to put forward some considerations and recommendations while handling nanomaterials, especially graphene and its derivatives. A large graphene sheet is generally stable and inert; thus, graphene and its derivatives are not considered hazardous, but good laboratory practices should be taken seriously for the safe handling and use of such materials. This article provides some insights about nanoscale graphene handling and some important considerations. Full article
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Open AccessArticle
A Simple Two-Step Process for Producing Strong and Aligned Carbon Nanotube-Polymer Composites
C 2019, 5(3), 35; https://doi.org/10.3390/c5030035 - 27 Jun 2019
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Abstract
In this paper, we present the results of a study related to fabrication of polymer-aligned carbon nanotube (CNT) composites made with different thermoplastic polymers. These composites have been manufactured by employing a simple two-step process using the internal resistive heating approach. The resulting [...] Read more.
In this paper, we present the results of a study related to fabrication of polymer-aligned carbon nanotube (CNT) composites made with different thermoplastic polymers. These composites have been manufactured by employing a simple two-step process using the internal resistive heating approach. The resulting composites have shown improved tensile strength, load, and elastic modulus compared to pristine CNT sheets. Poly (methyl methacrylate) (PMMA)-CNT, UltemTM-CNT and thermoplastic polyurethane (TPU)-CNT composites showed an increase in tensile strength by as much as 41%, 77% and 86% respectively over pristine CNT sheets. The improvement in tensile strength is the result of a good adhesion achieved between the aligned CNTs and polymer as observed with transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Full article
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