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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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19 pages, 2186 KiB  
Review
Recent Advances in Carbon Nanotube Technology: Bridging the Gap from Fundamental Science to Wide Applications
by Zhizhi Tao, Yuqiong Zhao, Ying Wang and Guojie Zhang
C 2024, 10(3), 69; https://doi.org/10.3390/c10030069 - 6 Aug 2024
Cited by 1 | Viewed by 3773
Abstract
Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption [...] Read more.
Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption capacity, and a substantial specific surface area, rendering them superb catalyst supports. Particularly in electrochemical energy storage, CNTs are extensively employed in supercapacitor electrodes owing to their elevated electrical conductivity, mechanical robustness, and electrocatalytic prowess, which facilitate significant energy storage capabilities. Their intricate pore architecture and reactive sites make functionalized carbon nanotubes well suited for synthesizing composite materials with diverse components, which are ideal for sequestering carbon dioxide from both atmospheric and indoor environments. This review presents a comprehensive examination of carbon nanotube synthesis methodologies, encompassing chemical vapor deposition, arc discharge, and laser ablation, and evaluates their impacts on the structural and functional properties of carbon nanotubes. Furthermore, this article underscores the applications of carbon nanotubes in fields such as fuel cells, photocatalysis, ammonia synthesis, dry methane reforming, Fischer–Tropsch synthesis, and supercapacitors. Despite the considerable potential of carbon nanotubes, their manufacturing processes remain intricate and costly, impeding large-scale industrial production. This review concludes by addressing the challenges in fabricating carbon nanotube composites and outlining future development prospects. Full article
(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)
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17 pages, 6455 KiB  
Article
Indirect Voltammetry Detection of Non-Electroactive Neurotransmitters Using Glassy Carbon Microelectrodes: The Case of Glutamate
by Sandra Lara Galindo, Surabhi Nimbalkar, Alexis Oyawale, James Bunnell, Omar Nunez Cuacuas, Rhea Montgomery-Walsh, Amish Rohatgi, Brinda Kodira Cariappa, Abhivyakti Gautam, Kevin Peguero-Garcia, Juyeon Lee, Stephanie Ingemann Bisgaard, Carter Faucher, Stephan Sylvest Keller and Sam Kassegne
C 2024, 10(3), 68; https://doi.org/10.3390/c10030068 - 31 Jul 2024
Viewed by 1302
Abstract
Glassy carbon (GC) microelectrodes have been successfully used for the detection of electroactive neurotransmitters such as dopamine and serotonin through voltammetry. However, non-electroactive neurotransmitters such as glutamate, lactate, and gamma-aminobutyric acid (GABA) are inherently unsuitable for detection through voltammetry [...] Read more.
Glassy carbon (GC) microelectrodes have been successfully used for the detection of electroactive neurotransmitters such as dopamine and serotonin through voltammetry. However, non-electroactive neurotransmitters such as glutamate, lactate, and gamma-aminobutyric acid (GABA) are inherently unsuitable for detection through voltammetry techniques without functionalizing the surface of the microelectrodes. To this end, we present here the immobilization of the L-glutamate oxidase (GluOx) enzyme on the surface of GC microelectrodes to enable the catalysis of a chemical reaction between L-glutamate, oxygen, and water to produce H2O2, an electroactive byproduct that is readily detectable through voltammetry. This immobilization of GluOx on the surface of bare GC microelectrodes and the subsequent catalytic reduction in H2O2 through fast-scan cyclic voltammetry (FSCV) helped demonstrate the indirect in vitro detection of glutamate, a non-electroactive molecule, at concentrations as low as 10 nM. The functionalized microelectrodes formed part of a four-channel array of microelectrodes (30 μm × 60 μm) on a 1.6 cm long neural probe that was supported on a flexible polymer, with potential for in vivo applications. The types and strengths of the bond between the GC microelectrode surface and its functional groups, on one hand, and glutamate and the immobilized functionalization matrix, on the other hand, were investigated through molecular dynamic (MD) modeling and Fourier transform infrared spectroscopy (FTIR). Both MD modeling and FTIR demonstrated the presence of several covalent bonds in the form of C-O (carbon–oxygen polar covalent bond), C=O (carbonyl), C-H (alkenyl), N-H (hydrogen bond), C-N (carbon–nitrogen single bond), and C≡N (triple carbon–nitrogen bond). Further, penetration tests on an agarose hydrogel model confirmed that the probes are mechanically robust, with their penetrating forces being much lower than the fracture force of the probe material. Full article
(This article belongs to the Special Issue Micro/Nanofabrication of Carbon-Based Devices and Their Applications)
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17 pages, 5721 KiB  
Article
Insights into the Electrocatalytic Activity of Fe,N-Glucose/Carbon Nanotube Hybrids for the Oxygen Reduction Reaction
by Rafael G. Morais, Natalia Rey-Raap, José L. Figueiredo and Manuel F. R. Pereira
C 2024, 10(2), 47; https://doi.org/10.3390/c10020047 - 17 May 2024
Viewed by 1081
Abstract
Glucose-derived carbon hybrids were synthesized by hydrothermal treatment in the presence of oxidized carbon nanotubes. Additionally, iron and nitrogen functionalities were incorporated into the carbon structure using different methodologies. The introduction of iron and nitrogen in a single step under a H2 [...] Read more.
Glucose-derived carbon hybrids were synthesized by hydrothermal treatment in the presence of oxidized carbon nanotubes. Additionally, iron and nitrogen functionalities were incorporated into the carbon structure using different methodologies. The introduction of iron and nitrogen in a single step under a H2 atmosphere favored the formation of quaternary nitrogen and oxidized nitrogen, whereas the incorporation of nitrogen under an N2 atmosphere after doping the hybrids with iron mainly produced pyridinic nitrogen. The samples were characterized by scanning electron microscopy, X-ray spectroscopy, adsorption isotherms, inductively coupled plasma optical emission spectrometry, and Raman spectroscopy. The presence of iron and nitrogen in the carbons increases the onset potential toward oxygen reduction in KOH 0.1 mol L−1 by 130 mV (0.83 V), in comparison to carbonized glucose, whereas the reaction mechanism shifts closer to a direct pathway and the formation of HO2− decreases to 25% (3.5 electrons). The reaction rate also increased in comparison to the carbonized glucose, as observed by the decrease in the Tafel slope value from 117 to 61 mV dec−1. Furthermore, the incorporation of iron and nitrogen in a single step enhanced the short-term performance of the prepared electrocatalysts, which may also be due to the higher relative amount of quaternary nitrogen. Full article
(This article belongs to the Special Issue Nanoporous Carbons for Hydrogen Sorption and Electrochemical Energy Storage)
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16 pages, 6377 KiB  
Article
Effect of Carbon Nanoparticles on the Porous Texture of ι-Carrageenan-Based N-Doped Nanostructured Porous Carbons and Implications for Gas Phase Applications
by Samantha K. Samaniego Andrade, Alfréd Menyhárd, Szilvia Klébert, Miklós Mohai, Balázs Nagy and Krisztina László
C 2023, 9(3), 68; https://doi.org/10.3390/c9030068 - 12 Jul 2023
Cited by 2 | Viewed by 2042
Abstract
S and N double-doped high surface area biomass-derived carbons were obtained from marine biomass-derived ι-carrageenan. Adding carbon nanoparticles (CNPs), namely graphene oxide (GO) or carbon nanotubes (CNTs), in the early stage of the synthesis leads to a modified porous texture and surface chemistry. [...] Read more.
S and N double-doped high surface area biomass-derived carbons were obtained from marine biomass-derived ι-carrageenan. Adding carbon nanoparticles (CNPs), namely graphene oxide (GO) or carbon nanotubes (CNTs), in the early stage of the synthesis leads to a modified porous texture and surface chemistry. The porous textures were characterized by N2 (−196.15 °C) and CO2 (0 °C) isotherms. The best GO- and CNT-added carbons had an apparent surface area of 1780 m2/g and 1170 m2/g, respectively, compared to 1070 m2/g for the CNP-free matrix. Analysis of the Raman spectra revealed that CNT was more efficient in introducing new defects than GO. Based on XPS, the carbon samples contain 2–4.5 at% nitrogen and 1.1 at% sulfur. The Dubinin–Radushkevich (DR) and Henry models were used to assess the strength of the interactions between various gases and the surface. The N2/H2 and CO2/CH4 selectivities were estimated with ideal adsorbed solution theory (IAST). While the CNPs, particularly GO, had a remarkable influence on the porous texture and affected the surface chemistry, their influence on the separation selectivity of these gases was more modest. Full article
(This article belongs to the Special Issue Carbons for Health and Environmental Protection)
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15 pages, 2833 KiB  
Article
Nanocomposites Produced with the Addition of Carbon Nanotubes Dispersed on the Surface of Cement Particles Using Different Non-Aqueous Media
by Vanessa Vilela Rocha, Bruno Athaíde Bacelar, Isabela Domingues Coelho and Péter Ludvig
C 2023, 9(1), 36; https://doi.org/10.3390/c9010036 - 22 Mar 2023
Cited by 2 | Viewed by 2002
Abstract
The inclusion of carbon nanotubes (CNTs) in cementitious composites has been studied due to their electrical, thermal, and mechanical enhancing properties. Considering the hydrophobic characteristics of CNTs, these nanomaterials need to be well dispersed in the aqueous media in which they are inserted [...] Read more.
The inclusion of carbon nanotubes (CNTs) in cementitious composites has been studied due to their electrical, thermal, and mechanical enhancing properties. Considering the hydrophobic characteristics of CNTs, these nanomaterials need to be well dispersed in the aqueous media in which they are inserted to guarantee those gains. Among the methods applied to produce such composites is the dispersion of CNTs on the surface of anhydrous cement particles using non-aqueous suspensions such as acetone, ethanol, or isopropanol. Even though those non-aqueous media have been individually studied by researchers, comparisons of the efficiency of CNTs dispersion was not found in the literature. Therefore, as a novelty, the present article aims to analyze the influence of the addition of the multi-walled CNTs dispersed in the cited three types of non-aqueous suspensions on the cement paste’s electrical and mechanical properties. Pastes containing 0%, 0.5%, and 1.0% of CNTs were prepared on the surface of anhydrous cement particles using a pre-dispersion technique based on simultaneous sonication and mechanical agitation in the three cited media. Tests to determine electric-volumetric resistivity, compressive strength, and splitting tensile strength were performed. It was observed that acetone dispersion decreases the cement paste’s electrical resistivity, even without the addition of CNTs. The cementitious composites with CNTs demonstrated increased mechanical strength (both compressive and tensile) using all three dispersion media. Statistical analysis (analysis of variance—ANOVA—and Tukey’s Test) was performed to evaluate the significance of the results. Full article
(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)
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30 pages, 8911 KiB  
Review
Carbon Fibers: From PAN to Asphaltene Precursors; A State-of-Art Review
by Hossein Bisheh and Yasmine Abdin
C 2023, 9(1), 19; https://doi.org/10.3390/c9010019 - 4 Feb 2023
Cited by 11 | Viewed by 9197
Abstract
Due to their outstanding material properties, carbon fibers are widely used in various industrial applications as functional or structural materials. This paper reviews the material properties and use of carbon fiber in various applications and industries and compares it with other existing fillers [...] Read more.
Due to their outstanding material properties, carbon fibers are widely used in various industrial applications as functional or structural materials. This paper reviews the material properties and use of carbon fiber in various applications and industries and compares it with other existing fillers and reinforcing fibers. The review also examines the processing of carbon fibers and the main challenges in their fabrication. At present, two main precursors are primarily utilized to produce carbon fibers, i.e., polyacrylonitrile (PAN) and petroleum pitch. Each of these precursors makes carbon fibers with different properties. However, due to the costly and energy-intensive processes of carbon fiber production based on the existing precursors, there is an increasingly growing need to introduce cheaper precursors to compete with other fibers on the market. A special focus will be given to the most recent development of manufacturing more sustainable and cost-effective carbon fibers derived from petroleum asphaltenes. This review paper demonstrates that low-cost asphaltene-based carbon fibers can be a substitute for costly PAN/pitch-based carbon fibers at least for functional applications. The value proposition, performance/cost advantages, potential market, and market size as well as processing challenges and methods for overcoming these will be discussed. Full article
(This article belongs to the Special Issue Carbon and Related Composites for Sensors and Energy Storage: Synthesis, Properties, and Application)
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12 pages, 2363 KiB  
Article
Reduced Graphene Oxide—Polycarbonate Electrodes on Different Supports for Symmetric Supercapacitors
by Olena Okhay, Alexandre Cunha Bastos, Kateryna Andreeva, Sampo Tuukkanen and Alexander Tkach
C 2022, 8(1), 12; https://doi.org/10.3390/c8010012 - 2 Feb 2022
Cited by 2 | Viewed by 3462
Abstract
Electrode materials for electrochemical capacitors or supercapacitors (SCs) are widely studied, as they are needed for the development of energy storage devices in electrical vehicles and flexible electronics. In the current work, a self-supported paper of reduced graphene oxide (rGO) with polycarbonate (PC) [...] Read more.
Electrode materials for electrochemical capacitors or supercapacitors (SCs) are widely studied, as they are needed for the development of energy storage devices in electrical vehicles and flexible electronics. In the current work, a self-supported paper of reduced graphene oxide (rGO) with polycarbonate (PC) (as rGO-PC composite) was prepared by simple vacuum filtration and low-temperature annealing. rGO-PC as a freestanding single electrode was studied in a three-electrode system and presented a capacitive energy storage mechanism. To fabricate SCs based on rGO-PC, flexible polyethylene terephthalate (PET) with layers of both Cu tape (Cu tape) and carbon tape (C tape) (PET/Cu/C), as well as PET covered by graphene ink (PET/GrI), were used as supports. Fabricated flexible symmetric SCs have shown similar behavior with a higher areal capacitance value than that on PET/Cu/C substrate. Full article
(This article belongs to the Collection Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)
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19 pages, 3725 KiB  
Article
The X-ray, Raman and TEM Signatures of Cellulose-Derived Carbons Explained
by Petros Kasaira Mubari, Théotime Beguerie, Marc Monthioux, Elsa Weiss-Hortala, Ange Nzihou and Pascal Puech
C 2022, 8(1), 4; https://doi.org/10.3390/c8010004 - 3 Jan 2022
Cited by 23 | Viewed by 4871
Abstract
Structural properties of carbonized cellulose were explored to conjugate the outcomes from various characterization techniques, namely X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy. All these techniques have evidenced the formation of graphene stacks with a size distribution. Cellulose carbonized at [...] Read more.
Structural properties of carbonized cellulose were explored to conjugate the outcomes from various characterization techniques, namely X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy. All these techniques have evidenced the formation of graphene stacks with a size distribution. Cellulose carbonized at 1000 and 1800 °C at a heating rate of 2 °C/min showed meaningful differences in Raman spectroscopy, whereas in XRD, the differences were not well pronounced, which implies that the crystallite sizes calculated by each technique have different significations. In the XRD patterns, the origin of a specific feature at a low scattering angle commonly reported in the literature but poorly explained so far, was identified. The different approaches used in this study were congruous in explaining the observations that were made on the cellulose-derived carbon samples. The remnants of the basic structural unit (BSU) are developed during primary carbonization. Small graphene-based crystallites inherited from the BSUs, which formerly developed during primary carbonization, were found to coexist with larger ones. Even if the three techniques give information on the average size of graphenic domains, they do not see the same characteristics of the domains; hence, they are not identical, nor contradictory but complementary. The arguments developed in the work to explain which characteristics are deduced from the signal obtained by each of the three characterization techniques relate to physics phenomena; hence, they are quite general and, therefore, are valid for all kind of graphenic materials. Full article
(This article belongs to the Collection Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)
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28 pages, 4895 KiB  
Review
sp2 Carbon Stable Radicals
by Elena F. Sheka
C 2021, 7(2), 31; https://doi.org/10.3390/c7020031 - 26 Mar 2021
Cited by 7 | Viewed by 4636
Abstract
sp2 Nanocarbons such as fullerenes, carbon nanotubes, and graphene molecules are not only open-shell species, but spatially extended, due to which their chemistry is quite specific. Cogently revealed dependence of the final products composition on size and shape of the carbons in [...] Read more.
sp2 Nanocarbons such as fullerenes, carbon nanotubes, and graphene molecules are not only open-shell species, but spatially extended, due to which their chemistry is quite specific. Cogently revealed dependence of the final products composition on size and shape of the carbons in use as well as on the chemical prehistory is accumulated in a particular property—the stabilization of the species’ radical efficiency, thus providing the matter of stable radicals. If the feature is highly restricted and rarely available in ordinary chemistry, in the case of sp2 nanocarbons it is just an ordinary event providing, say, tons-in-mass stable radicals when either producing such widely used technological products as carbon black or dealing with deposits of natural sp2 carbons such as anthracite, shungite carbon, and other. Suggested in the paper is the consideration of stable radicals of sp2 nanocarbons from the standpoint of spin-delocalized topochemistry. Characterized in terms of the total and atomically partitioned number of effectively unpaired electrons as well as of the distribution of the latter over carbon atoms and described by selectively determined barriers of different reactions exhibiting topological essence of intermolecular interaction, sp2 nanocarbons reveal a peculiar topokinetics that lays the foundation of the stability of their radical properties. Full article
(This article belongs to the Collection Feature Papers in the Science and Engineering of Carbons)
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14 pages, 5922 KiB  
Article
Anisotropic Magnetism in Gradient Porous Carbon Composite Aerogels
by Jochen Bahner, Nicolas Hug and Sebastian Polarz
C 2021, 7(1), 22; https://doi.org/10.3390/c7010022 - 13 Feb 2021
Cited by 3 | Viewed by 2815
Abstract
Porosity is of high importance for functional materials, as it allows for high surface areas and the accessibility of materials. While the fundamental interplay between different pore sizes and functionalities is quite well understood, few studies on gradually changing properties in a material [...] Read more.
Porosity is of high importance for functional materials, as it allows for high surface areas and the accessibility of materials. While the fundamental interplay between different pore sizes and functionalities is quite well understood, few studies on gradually changing properties in a material exist. To date, only a few examples of such materials have been synthesized successfully. Herein, we present a facile method for synthesizing macroscopic carbon aerogels with locally changing pore sizes and functionalities. We used ultracentrifugation to fractionate differently functionalized and sized polystyrene nanoparticles. The assembly into gradient templates was conducted in a resorcinol–formaldehyde (RF) sol, which acted as a liquid phase and carbon precursor. We show that the modification of nanoparticles and a sol–gel precursor is a powerful tool for introducing dopants (sulfur and phosphorous) and metal nanoparticles (e.g., Ni) into gradient porous carbons formed during the carbonization of the RF sol. Understanding the underlying interactions between particles and precursors will lead to a plethora of possibilities in the material design of complex functionally graded materials. We showed this by exchanging parts of the template with magnetite–polystyrene composites as templating nanoparticles. This led to the incorporation of magnetite nanoparticles in the formed gradient porous carbon aerogels. Finally, gradually increasing concentrations of magnetite were obtained, ultimately leading to macroscopic carbon aerogels with locally changing magnetic properties, while the graded porosity was maintained. Full article
(This article belongs to the Special Issue Carbon-Rich Compounds: From Molecules to Materials)
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12 pages, 4784 KiB  
Article
A Comparative Study of Aromatization Catalysts: The Advantage of Hybrid Oxy/Carbides and Platinum-Catalysts Based on Carbon Gels
by Luisa M. Pastrana-Martínez, Sergio Morales-Torres and Francisco J. Maldonado-Hódar
C 2021, 7(1), 21; https://doi.org/10.3390/c7010021 - 12 Feb 2021
Cited by 5 | Viewed by 2651
Abstract
This manuscript is focused on the relationship between sol-gel synthesis processes and the development of new active phases with fitted morphology, porosity and surface chemistry. The influence of the above parameters on the catalytic performance of the prepared materials for the aromatization of [...] Read more.
This manuscript is focused on the relationship between sol-gel synthesis processes and the development of new active phases with fitted morphology, porosity and surface chemistry. The influence of the above parameters on the catalytic performance of the prepared materials for the aromatization of n-hexane to benzene is also evaluated. Different series of catalysts were prepared, either using noble metals (i.e., Pt) or metal oxides (i.e., Mo, W), as active phases. In both cases, the catalytic performance and stability of classical aromatization catalysts was significantly improved. Interesting one-pot carboreduction process of the metal oxide during carbonization is suggested as a real alternative for the preparation of high-performance aromatization catalysts, leading to the formation of less acidic and non-stoichiometric oxides and carbides. Full article
(This article belongs to the Collection Carbon-Derived Materials from Bioresources for Advanced Applications)
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13 pages, 3833 KiB  
Article
Energy Absorption in Carbon Fiber Composites with Holes under Quasi-Static Loading
by Omar Alhyari and Golam Newaz
C 2021, 7(1), 16; https://doi.org/10.3390/c7010016 - 1 Feb 2021
Cited by 7 | Viewed by 3633
Abstract
Composite tubular structures have shown promise as energy absorbers in the automobile industry. This paper investigates the energy absorption characteristics of carbon fiber reinforced plastic (CFRP) tubes with pre-existing holes. Holes may represent an extreme case of impact damage that perforates the tube, [...] Read more.
Composite tubular structures have shown promise as energy absorbers in the automobile industry. This paper investigates the energy absorption characteristics of carbon fiber reinforced plastic (CFRP) tubes with pre-existing holes. Holes may represent an extreme case of impact damage that perforates the tube, e.g., stones from road surface impacting the tubes. Tubes with holes represent more conservative performance characteristics, since impact damage of the same size will have residual material, which may carry some load. Tubes with holes can provide the lower limit of CFRP tube performance under axial crushing relative to impact damaged tubes with perforation diameter close to the hole diameter. In this study, tubes with lay-up of [05/902/04] with one and two holes in defined locations and different diameters are experimentally studied under quasi-static loading. It was found that specific energy absorption (SEA) reduces by 50% with one or two holes of 15 mm size, 100 mm from top of the tube. The SEA reduction is about 60% lower than the regular tube when the diameter of the hole is 20 mm located at 100 mm from top. The most severe reduction occurs if the location of single or double holes are 75 mm from the top. In this case, a SEA reduction of 75% can be expected. Results indicate that holes can significantly alter the energy absorption capability of the tubes. It is also clear that in axial crushing of composite tubes, the location of the hole (100 to 75 mm) appears to create more pronounced effect than the size of the hole itself (15 vs. 20 mm) for the cases investigated. The failure modes for tubes with holes seem to preserve similar damage modes with delamination, frond creation, and brittle fracture, which is typically observed in regular composite tubes under axial crushing load. This is due to primarily front end crushing, which dominates the failure modes, while hole induced damage occurs later. Full article
(This article belongs to the Collection Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)
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16 pages, 3530 KiB  
Review
Citric Acid Derived Carbon Dots, the Challenge of Understanding the Synthesis-Structure Relationship
by Junkai Ren, Luca Malfatti and Plinio Innocenzi
C 2021, 7(1), 2; https://doi.org/10.3390/c7010002 - 22 Dec 2020
Cited by 56 | Viewed by 11807
Abstract
Carbon dots (CDs) are highly-emissive nanoparticles obtained through fast and cheap syntheses. The understanding of CDs’ luminescence, however, is still far from being comprehensive. The intense photoluminescence can have different origins: molecular mechanisms, oxidation of polyaromatic graphene-like layers, and core-shell interactions of carbonaceous [...] Read more.
Carbon dots (CDs) are highly-emissive nanoparticles obtained through fast and cheap syntheses. The understanding of CDs’ luminescence, however, is still far from being comprehensive. The intense photoluminescence can have different origins: molecular mechanisms, oxidation of polyaromatic graphene-like layers, and core-shell interactions of carbonaceous nanoparticles. The citric acid (CA) is one of the most common precursors for CD preparation because of its high biocompatibility, and this review is mainly focused on CA-based CDs. The different parameters that control the synthesis, such as the temperature, the reaction time, and the choice of solvents, were critically described. Particular attention was devoted to the CDs’ optical properties, such as tunable emission and quantum yields, in light of functional applications. The survey of the literature allowed correlating the preparation methods with the structures and the properties of CA-based CDs. Some basic rules to fabricate highly luminescent nanoparticles were selected by the metanalysis of the current literature in the field. In some cases, these findings can be generalized to other types of CDs prepared via liquid phase. Full article
(This article belongs to the Special Issue Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots)
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28 pages, 7844 KiB  
Review
Carbon Allotropes as ITO Electrode Replacement Materials in Liquid Crystal Devices
by Ingo Dierking
C 2020, 6(4), 80; https://doi.org/10.3390/c6040080 - 10 Dec 2020
Cited by 8 | Viewed by 4151
Abstract
Indium tin oxide (ITO)-free optoelectronic devices have been discussed for a number of years in the light of a possible indium shortage as demand rises. In particular, this is due to the largely increased number of flat panel displays and especially liquid crystal [...] Read more.
Indium tin oxide (ITO)-free optoelectronic devices have been discussed for a number of years in the light of a possible indium shortage as demand rises. In particular, this is due to the largely increased number of flat panel displays and especially liquid crystal displays (LCDs) being produced for home entertainment TV and mobile technologies. While a shortage of primary indium seems far on the horizon, nevertheless, recycling has become an important issue, as has the development of ITO-free electrode materials, especially for flexible liquid crystal devices. The main contenders for new electrode technologies are discussed with an emphasis placed on carbon-based materials for LCDs, including composite approaches. At present, these already fulfil the technical specifications demanded from ITO with respect to transmittance and sheet resistance, albeit not in relation to cost and large-scale production. Advantages and disadvantages of ITO-free technologies are discussed, with application examples given. An outlook into the future suggests no immediate transition to carbon-based electrodes in the area of LCDs, while this may change in the future once flexible displays and environmentally friendly smart window solutions or energy harvesting building coverings become available. Full article
(This article belongs to the Special Issue Carbon Based Electrochemical Devices)
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32 pages, 8356 KiB  
Article
A Study on the Effect of Carbon Nanotubes’ Distribution and Agglomeration in the Free Vibration of Nanocomposite Plates
by D. S. Craveiro and M. A. R. Loja
C 2020, 6(4), 79; https://doi.org/10.3390/c6040079 - 30 Nov 2020
Cited by 7 | Viewed by 3667
Abstract
The present work aimed to characterize the free vibrations’ behaviour of nanocomposite plates obtained by incorporating graded distributions of carbon nanotubes (CNTs) in a polymeric matrix, considering the carbon nanotubes’ agglomeration effect. This effect is known to degrade material properties, therefore being important [...] Read more.
The present work aimed to characterize the free vibrations’ behaviour of nanocomposite plates obtained by incorporating graded distributions of carbon nanotubes (CNTs) in a polymeric matrix, considering the carbon nanotubes’ agglomeration effect. This effect is known to degrade material properties, therefore being important to predict the consequences it may bring to structures’ mechanical performance. To this purpose, the elastic properties’ estimation is performed according to the two-parameter agglomeration model based on the Eshelby–Mori–Tanaka approach for randomly dispersed nano-inclusions. This approach is implemented in association with the finite element method to determine the natural frequencies and corresponding mode shapes. Three main agglomeration cases were considered, namely, agglomeration absence, complete agglomeration, and partial agglomeration. The results show that the agglomeration effect has a negative impact on the natural frequencies of the plates, regardless the CNTs’ distribution considered. For the corresponding vibrations’ mode shapes, the agglomeration effect was shown in most cases not to have a significant impact, except for two of the cases studied: for a square plate and a rectangular plate with symmetrical and unsymmetrical CNTs’ distribution, respectively. Globally, the results confirm that not accounting for the nanotubes’ agglomeration effect may lead to less accurate elastic properties and less structures’ performance predictions. Full article
(This article belongs to the Collection Feature Papers in the Science and Engineering of Carbons)
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14 pages, 2737 KiB  
Article
Electrochemical Aspects of a Nitrogen-Doped Pseudo-Graphitic Carbon Material: Resistance to Electrode Fouling by Air-Aging and Dopamine Electro-Oxidation
by Kailash Hamal, Jeremy May, Haoyu Zhu, Forrest Dalbec, Elena Echeverria, David N. McIlroy, Eric Aston and I. Francis Cheng
C 2020, 6(4), 68; https://doi.org/10.3390/c6040068 - 27 Oct 2020
Cited by 5 | Viewed by 3454
Abstract
The nitrogen-doped form of GUITAR (pseudo-Graphite from the University of Idaho Thermalized Asphalt Reaction) was examined by X-ray photoelectron, Raman, and X-ray diffraction spectroscopies and cyclic voltammetry (CV). Electrochemical studies indicate that N-GUITAR exhibits significant resistance to fouling by adsorption and by passivation. [...] Read more.
The nitrogen-doped form of GUITAR (pseudo-Graphite from the University of Idaho Thermalized Asphalt Reaction) was examined by X-ray photoelectron, Raman, and X-ray diffraction spectroscopies and cyclic voltammetry (CV). Electrochemical studies indicate that N-GUITAR exhibits significant resistance to fouling by adsorption and by passivation. Unlike other carbon materials, it maintains fast heterogenous electron transfer (HET) kinetics with Fe(CN)63−/4− with exposure to air. The CV peak potential separation (ΔEp) of 66 mV increased to 69 mV in 3 h vs. 67 to 221 mV for a highly oriented pyrolytic graphite (HOPG) electrode. Water contact angle measurements indicate that N-GUITAR was able to better maintain a hydrophilic state during the 3-h exposure, going from 55.8 to 70.4° while HOPG increased from 63.8 to 80.1°. This indicates that N-GUITAR better resisted adsorption of volatile organic compounds. CV studies of dopamine also indicate N-GUITAR is resistant to passivation. The ΔEp for the dopamine/o-dopaminoquinone couple is 83 mV indicating fast HET rates. This is reflected in the peak current ratios for the oxidation and reduction processes of 1.3 indicating that o-dopaminoquinone is not lost to passivation processes. This ratio along with the minimal signal attenuation is the best reported in literature. Full article
(This article belongs to the Collection Feature Papers in the Science and Engineering of Carbons)
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12 pages, 2963 KiB  
Article
Electrically Conductive MXene-Coated Glass Fibers for Damage Monitoring in Fiber-Reinforced Composites
by Christine B. Hatter, Asia Sarycheva, Ariana Levitt, Babak Anasori, Latha Nataraj and Yury Gogotsi
C 2020, 6(4), 64; https://doi.org/10.3390/c6040064 - 16 Oct 2020
Cited by 14 | Viewed by 6242
Abstract
Multifunctional fiber-reinforced composites play a significant role in advanced aerospace and military applications due to their high strength and toughness resulting in superior damage tolerance. However, early detection of structural changes prior to visible damage is critical for extending the lifetime of the [...] Read more.
Multifunctional fiber-reinforced composites play a significant role in advanced aerospace and military applications due to their high strength and toughness resulting in superior damage tolerance. However, early detection of structural changes prior to visible damage is critical for extending the lifetime of the part. MXenes, an emerging class of two-dimensional (2D) nanomaterials, possess hydrophilic surfaces, high electrical conductivity and mechanical properties that can potentially be used to identify damage within fiber-reinforced composites. In this work, conductive Ti3C2Tx MXene flakes were successfully transferred onto insulating glass fibers via oxygen plasma treatment improving adhesion. Increasing plasma treatment power, time and coating layers lead to a decrease in electrical resistance of MXene-coated fibers. Optimized uniformity was achieved using an alternating coating approach with smaller flakes helping initiate and facilitate adhesion of larger flakes. Tensile testing with in-situ electrical resistance tracking showed resistances as low as 1.8 kΩ for small-large flake-coated fiber bundles before the break. Increased resistance was observed during testing, but due to good adhesion between the fiber and MXene, most connective pathways within fiber bundles remained intact until fiber bundles were completely separated. These results demonstrate a potential use of MXene-coated glass fibers in damage-sensing polymer-matrix composites. Full article
(This article belongs to the Special Issue Carbide Derived Carbons)
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15 pages, 5052 KiB  
Article
Effect of Cellulose Nanocrystals on the Coating of Chitosan Nanocomposite Film Using Plasma-Mediated Deposition of Amorphous Hydrogenated Carbon (a–C:H) Layers
by Torben Schlebrowski, Zineb Kassab, Mounir El Achaby, Stefan Wehner and Christian B. Fischer
C 2020, 6(3), 51; https://doi.org/10.3390/c6030051 - 30 Jul 2020
Cited by 3 | Viewed by 3017
Abstract
The substitution of petroleum-based polymers with naturally derived biopolymers may be a good alternative for the conservation of natural fossil resources and the alleviation of pollution and waste disposal problems. However, in order to be used in a wide range of applications, some [...] Read more.
The substitution of petroleum-based polymers with naturally derived biopolymers may be a good alternative for the conservation of natural fossil resources and the alleviation of pollution and waste disposal problems. However, in order to be used in a wide range of applications, some biopolymers’ properties should be enhanced. In this study, biocompatible, non-toxic, and biodegradable chitosan (CS) film and CS reinforced with 10 wt% of cellulose nanocrystals (CN–CS) were coated with amorphous hydrogenated carbon layers (a–C:H) of different thickness. To investigate the effect of the nano-reinforcement on the a–C:H layer applied, mild radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) was used to coat the CS and its CN–CS bio-nanocomposite film. Both the surface characteristics and the chemical composition were analyzed. The surface morphology and wettability were examined by ex-situ atomic force microscopy (AFM) and contact angle measurements (CA), respectively. Hereby, the relationship between sp2/sp3 ratios on a macroscopic scale was also evaluated. For the investigation of the chemical composition, the surface sensitive synchrotron X-ray radiation techniques near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) as well as diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) were used. Full article
(This article belongs to the Special Issue Characterization of Disorder in Carbons)
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11 pages, 443 KiB  
Article
Evidence for Glass Behavior in Amorphous Carbon
by Steven Best, Jake B. Wasley, Carla de Tomas, Alireza Aghajamali, Irene Suarez-Martinez and Nigel A. Marks
C 2020, 6(3), 50; https://doi.org/10.3390/c6030050 - 30 Jul 2020
Cited by 8 | Viewed by 4151
Abstract
Amorphous carbons are disordered carbons with densities of circa 1.9–3.1 g/cc and a mixture of sp2 and sp3 hybridization. Using molecular dynamics simulations, we simulate diffusion in amorphous carbons at different densities and temperatures to investigate the transition between [...] Read more.
Amorphous carbons are disordered carbons with densities of circa 1.9–3.1 g/cc and a mixture of sp2 and sp3 hybridization. Using molecular dynamics simulations, we simulate diffusion in amorphous carbons at different densities and temperatures to investigate the transition between amorphous carbon and the liquid state. Arrhenius plots of the self-diffusion coefficient clearly demonstrate that there is a glass transition rather than a melting point. We consider five common carbon potentials (Tersoff, REBO-II, AIREBO, ReaxFF and EDIP) and all exhibit a glass transition. Although the glass-transition temperature (Tg) is not significantly affected by density, the choice of potential can vary Tg by up to 40%. Our results suggest that amorphous carbon should be interpreted as a glass rather than a solid. Full article
(This article belongs to the Special Issue Characterization of Disorder in Carbons)
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28 pages, 4985 KiB  
Review
Characterization of Carbon Materials for Hydrogen Storage and Compression
by Giuseppe Sdanghi, Rafael L. S. Canevesi, Alain Celzard, Matthias Thommes and Vanessa Fierro
C 2020, 6(3), 46; https://doi.org/10.3390/c6030046 - 9 Jul 2020
Cited by 41 | Viewed by 7131
Abstract
Carbon materials have proven to be a suitable choice for hydrogen storage and, recently, for hydrogen compression. Their developed textural properties, such as large surface area and high microporosity, are essential features for hydrogen adsorption. In this work, we first review recent advances [...] Read more.
Carbon materials have proven to be a suitable choice for hydrogen storage and, recently, for hydrogen compression. Their developed textural properties, such as large surface area and high microporosity, are essential features for hydrogen adsorption. In this work, we first review recent advances in the physisorption characterization of nanoporous carbon materials. Among them, approaches based on the density functional theory are considered now standard methods for obtaining a reliable assessment of the pore size distribution (PSD) over the whole range from narrow micropores to mesopores. Both a high surface area and ultramicropores (pore width < 0.7 nm) are needed to achieve significant hydrogen adsorption at pressures below 1 MPa and 77 K. However, due to the wide PSD typical of activated carbons, it follows from an extensive literature review that pressures above 3 MP are needed to reach maximum excess uptakes in the range of ca. 7 wt.%. Finally, we present the adsorption–desorption compression technology, allowing hydrogen to be compressed at 70 MPa by cooling/heating cycles between 77 and 298 K, and being an alternative to mechanical compressors. The cyclic, thermally driven hydrogen compression might open a new scenario within the vast field of hydrogen applications. Full article
(This article belongs to the Collection Carbon-Based Materials for Hydrogen Production, Storage and Conversion)
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25 pages, 5166 KiB  
Review
Review on Activated Carbons by Chemical Activation with FeCl3
by Jorge Bedia, Manuel Peñas-Garzón, Almudena Gómez-Avilés, Juan J. Rodriguez and Carolina Belver
C 2020, 6(2), 21; https://doi.org/10.3390/c6020021 - 10 Apr 2020
Cited by 104 | Viewed by 17322
Abstract
This study reviews the most relevant results on the synthesis, characterization, and applications of activated carbons obtained by novel chemical activation with FeCl3. The text includes a description of the activation mechanism, which compromises three different stages: (1) intense de-polymerization of [...] Read more.
This study reviews the most relevant results on the synthesis, characterization, and applications of activated carbons obtained by novel chemical activation with FeCl3. The text includes a description of the activation mechanism, which compromises three different stages: (1) intense de-polymerization of the carbon precursor (up to 300 °C), (2) devolatilization and formation of the inner porosity (between 300 and 700 °C), and (3) dehydrogenation of the fixed carbon structure (>700 °C). Among the different synthesis conditions, the activation temperature, and, to a lesser extent, the impregnation ratio (i.e., mass ratio of FeCl3 to carbon precursor), are the most relevant parameters controlling the final properties of the resulting activated carbons. The characteristics of the carbons in terms of porosity, surface chemistry, and magnetic properties are analyzed in detail. These carbons showed a well-developed porous texture mainly in the micropore size range, an acidic surface with an abundance of oxygen surface groups, and a superparamagnetic character due to the presence of well-distributed iron species. These properties convert these carbons into promising candidates for different applications. They are widely analyzed as adsorbents in aqueous phase applications due to their porosity, surface acidity, and ease of separation. The presence of stable and well-distributed iron species on the carbons’ surface makes them promising catalysts for different applications. Finally, the presence of iron compounds has been shown to improve the graphitization degree and conductivity of the carbons; these are consequently being analyzed in energy storage applications. Full article
(This article belongs to the Special Issue Porous Carbon: Synthesis, Modification and Applications)
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10 pages, 2504 KiB  
Article
Hydrogen Sorption and Reversibility of the LiBH4-KBH4 Eutectic System Confined in a CMK-3 Type Carbon via Melt Infiltration
by Filippo Peru, SeyedHosein Payandeh, Georgia Charalambopoulou, Torben R. Jensen and Theodore Steriotis
C 2020, 6(2), 19; https://doi.org/10.3390/c6020019 - 31 Mar 2020
Cited by 8 | Viewed by 2906
Abstract
Metal borohydrides have very high hydrogen densities but their poor thermodynamic and kinetic properties hinder their use as solid hydrogen stores. An interesting approach to improve their functionality is nano-sizing by confinement in mesoporous materials. In this respect, we used the 0.725 LiBH [...] Read more.
Metal borohydrides have very high hydrogen densities but their poor thermodynamic and kinetic properties hinder their use as solid hydrogen stores. An interesting approach to improve their functionality is nano-sizing by confinement in mesoporous materials. In this respect, we used the 0.725 LiBH4–0.275 KBH4 eutectic mixture, and by exploiting its very low melting temperature (378 K) it was possible to successfully melt infiltrate the borohydrides in a mesoporous CMK-3 type carbon (pore diameter ~5 nm). The obtained carbon–borohydride composite appears to partially alleviate the irreversibility of the dehydrogenation reaction when compared with the bulk LiBH4-KBH4, and shows a constant hydrogen uptake of 2.5 wt%–3 wt% for at least five absorption–desorption cycles. Moreover, pore infiltration resulted in a drastic decrease of the decomposition temperature (more than 100 K) compared to the bulk eutectic mixture. The increased reversibility and the improved kinetics may be a combined result of several phenomena such as the catalytic action of the carbon surface, the nano-sizing of the borohydride particles or the reduction of irreversible side-reactions. Full article
(This article belongs to the Collection Carbon-Based Materials for Hydrogen Production, Storage and Conversion)
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12 pages, 3377 KiB  
Article
Pulling Simulations and Hydrogen Sorption Modelling on Carbon Nanotube Bundles
by Anastasios Gotzias and Andreas Sapalidis
C 2020, 6(1), 11; https://doi.org/10.3390/c6010011 - 4 Mar 2020
Cited by 9 | Viewed by 3569
Abstract
Recent progress in molecular simulation technology has developed an interest in modernizing the usual computational methods and approaches. For instance, most of the theoretical work on hydrogen adsorption on carbon nanotubes was conducted a decade ago. It should be insightful to reinvestigate the [...] Read more.
Recent progress in molecular simulation technology has developed an interest in modernizing the usual computational methods and approaches. For instance, most of the theoretical work on hydrogen adsorption on carbon nanotubes was conducted a decade ago. It should be insightful to reinvestigate the field and take advantage of code improvements and features implemented in contemporary software. One example of such features is the pulling simulation modules now available in many molecular dynamics programs. We conduct pulling simulations on pairs of carbon nanotubes and measure the inter-tube distance before they dissociate in water. We use this distance to set the interval size between adjacent nanotubes as we arrange them in bundle configurations. We consider bundles with triangular, intermediate and honeycomb patterns, and armchair nanotubes with a chiral index from n = 5 to n = 10. Then, we simulate low pressure hydrogen adsorption isotherms at 77 K, using the grand canonical Monte Carlo method. The different bundle configurations adsorb great hydrogen amounts that may exceed 2% wt at ambient pressures. The computed hydrogen capacities are considered large for physisorption on carbon nanostructures and attributed to the ultra-microporous network and extraordinary high surface area of the configured models. Full article
(This article belongs to the Collection Carbon-Based Materials for Hydrogen Production, Storage and Conversion)
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15 pages, 5207 KiB  
Article
Fluorescence and Physico-Chemical Properties of Hydrogenated Detonation Nanodiamonds
by Giannis Thalassinos, Alastair Stacey, Nikolai Dontschuk, Billy J. Murdoch, Edwin Mayes, Hugues A. Girard, Ibrahim M. Abdullahi, Lars Thomsen, Anton Tadich, Jean-Charles Arnault, Vadym N. Mochalin, Brant C. Gibson and Philipp Reineck
C 2020, 6(1), 7; https://doi.org/10.3390/c6010007 - 7 Feb 2020
Cited by 8 | Viewed by 4242
Abstract
Hydrogenated detonation nanodiamonds are of great interest for emerging applications in areas from biology and medicine to lubrication. Here, we compare the two main hydrogenation techniques—annealing in hydrogen and plasma-assisted hydrogenation—for the creation of detonation nanodiamonds with a hydrogen terminated surface from the [...] Read more.
Hydrogenated detonation nanodiamonds are of great interest for emerging applications in areas from biology and medicine to lubrication. Here, we compare the two main hydrogenation techniques—annealing in hydrogen and plasma-assisted hydrogenation—for the creation of detonation nanodiamonds with a hydrogen terminated surface from the same starting material. Synchrotron-based soft X-ray spectroscopy, infrared absorption spectroscopy, and electron energy loss spectroscopy were employed to quantify diamond and non-diamond carbon contents and determine the surface chemistries of all samples. Dynamic light scattering was used to study the particles’ colloidal properties in water. For the first time, steady-state and time-resolved fluorescence spectroscopy analysis at temperatures from room temperature down to 10 K was performed to investigate the particles’ fluorescence properties. Our results show that both hydrogenation techniques produce hydrogenated detonation nanodiamonds with overall similar physico-chemical and fluorescence properties. Full article
(This article belongs to the Special Issue Functionalized Nanodiamond: Properties, Characterization and Applications)
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17 pages, 2467 KiB  
Article
Application of Experimental Design to Hydrogen Storage: Optimisation of Lignin-Derived Carbons
by Jemma L. Rowlandson, James Coombs OBrien, Karen J. Edler, Mi Tian and Valeska P. Ting
C 2019, 5(4), 82; https://doi.org/10.3390/c5040082 - 7 Dec 2019
Cited by 6 | Viewed by 4424
Abstract
Lignin is a significant by-product of the paper pulping and biofuel industries. Upgrading lignin to a high-value product is essential for the economic viability of biorefineries for bioethanol production and environmentally benign pulping processes. In this work, the feasibility of lignin-derived activated carbons [...] Read more.
Lignin is a significant by-product of the paper pulping and biofuel industries. Upgrading lignin to a high-value product is essential for the economic viability of biorefineries for bioethanol production and environmentally benign pulping processes. In this work, the feasibility of lignin-derived activated carbons for hydrogen storage was studied using a Design of Experiments methodology, for a time and cost-efficient exploration of the synthesis process. Four factors (carbonisation temperature, activation temperature, carbonisation time, and activation time) were investigated simultaneously. Development of a mathematical model allowed the factors with the greatest impact to be identified using regression analysis for three responses: surface area, average pore size, and hydrogen uptake at 77 K and 1 bar. Maximising the surface area required activation conditions using the highest settings, however, a low carbonisation temperature was also revealed to be integral to prevent detrimental and excessive pore widening. A small pore size, vital for efficient hydrogen uptake, could be achieved by using low carbonisation temperature but also low activation temperatures. An optimum was achieved using the lowest carbonisation conditions (350 °C for 30 min) to retain a smaller pore size, followed by activation under the severest conditions (1000 °C for 60 min) to maximise surface area and hydrogen uptake. These conditions yielded a material with a high surface area of 1400 m2 g−1 and hydrogen uptake of 1.9 wt.% at 77 K and 1 bar. Full article
(This article belongs to the Collection Carbon-Based Materials for Hydrogen Production, Storage and Conversion)
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14 pages, 2669 KiB  
Review
Interstellar Carbon Dust
by Emmanuel Dartois
C 2019, 5(4), 80; https://doi.org/10.3390/c5040080 - 2 Dec 2019
Cited by 10 | Viewed by 3897
Abstract
In the ranking of cosmic abundance of the elements, carbon is the second element, after oxygen, able to form multiple bonds propagating the formation of a network, thus playing an essential role in the formation of nanometer- to micrometer-sized interstellar dust grains. Astrophysical [...] Read more.
In the ranking of cosmic abundance of the elements, carbon is the second element, after oxygen, able to form multiple bonds propagating the formation of a network, thus playing an essential role in the formation of nanometer- to micrometer-sized interstellar dust grains. Astrophysical spectroscopic observations give us remote access to the composition of carbonaceous and organic interstellar grains. Their presence and abundances from spectroscopic observations and the phases of importance for the Galactic carbon budget are considered in this article. Full article
(This article belongs to the Special Issue Characterization of Disorder in Carbons)
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20 pages, 3077 KiB  
Article
Analyzing the Raman Spectra of Graphenic Carbon Materials from Kerogens to Nanotubes: What Type of Information Can Be Extracted from Defect Bands?
by Pascal Puech, Mariem Kandara, Germercy Paredes, Ludovic Moulin, Elsa Weiss-Hortala, Anirban Kundu, Nicolas Ratel-Ramond, Jérémie-Marie Plewa, Roland Pellenq and Marc Monthioux
C 2019, 5(4), 69; https://doi.org/10.3390/c5040069 - 1 Nov 2019
Cited by 124 | Viewed by 9823
Abstract
Considering typical spectra of a broad range of carbonaceous materials from gas-shale to nanotubes, various ways by which defects show up in Raman spectra are exampled and discussed. The position, resonance behavior, and linewidth of both the D and G bands are compared, [...] Read more.
Considering typical spectra of a broad range of carbonaceous materials from gas-shale to nanotubes, various ways by which defects show up in Raman spectra are exampled and discussed. The position, resonance behavior, and linewidth of both the D and G bands are compared, even if in some cases obtaining accurate information on the materials from the fitting parameters is a difficult task. As a matter of fact, even if a full picture is unreachable, defining parameter trends is one acceptable option. Two ways to determine the linewidth, either graphically and or by fitting are proposed in order to be able to compare literature data. The relationship between the crystallite size obtained from the linewidth and from X-ray diffraction, which is complementary to the Tuinstra and Koenig law, is examined. We show that a single approach is not possible unless modeling is performed and therefore that analysis of Raman spectra should be adapted to the specificities of each sample series, i.e., a minimum of knowledge about the materials is always required. Full article
(This article belongs to the Special Issue Characterization of Disorder in Carbons)
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10 pages, 1949 KiB  
Article
Effect of Halogen Ions on the Photocycle of Fluorescent Carbon Nanodots
by Alice Sciortino, Roberto Pecorella, Marco Cannas and Fabrizio Messina
C 2019, 5(4), 64; https://doi.org/10.3390/c5040064 - 24 Oct 2019
Cited by 2 | Viewed by 2875
Abstract
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, [...] Read more.
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, especially in view of their possible sensing applications, the existing works have mostly focused on the quenching of C-dot fluorescence induced by metal cations. In fact, these latter easily bind to C-dots surfaces, which are negatively charged in most cases, promoting an electron transfer from the surface to them. Much less is known from the literature on the effect induced on C-dots by prototypical negative species in solutions, motivating more systematic studies on this different class of interactions. Here, we analyzed the effect of halogen ions on the fluorescence of C-dots, by combining steady-state optical absorption and photoluminescence, time-resolved fluorescence and femtosecond pump/probe spectroscopy. We demonstrate a quenching effect of C-dots fluorescence in the presence of halogen ions, which becomes more and more pronounced with increasing atomic number of the halogens, being negligible for chloride, appreciable for bromide and stronger for iodide. We find that quenching is mostly static, due to the binding of halogen ions on suitable surface sites at C-dots surfaces, while collisional quenching becomes obvious only at very high iodide concentrations. Finally, nanosecond and femtosecond time-resolved spectroscopies provide information on the quenching mechanism and time scales. Based on these data, we propose that the fluorescent state is deactivated by intersystem crossing to a dark triplet state, induced by close-range interactions with the heaviest halogen ions. Full article
(This article belongs to the Special Issue Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites)
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13 pages, 1621 KiB  
Article
Near-Infrared, Light-Triggered, On-Demand Anti-Inflammatories and Antibiotics Release by Graphene Oxide/Elecrospun PCL Patch for Wound Healing
by Nicolò Mauro, Salvatore Emanuele Drago, Gennara Cavallaro and Gaetano Giammona
C 2019, 5(4), 63; https://doi.org/10.3390/c5040063 - 23 Oct 2019
Cited by 30 | Viewed by 3688
Abstract
Very recently, significant attention has been focused on the adsorption and cell adhesion properties of graphene oxide (GO), because it is expected to allow high drug loading and controlled drug release, as well as the promotion of cell adhesion and proliferation. This is [...] Read more.
Very recently, significant attention has been focused on the adsorption and cell adhesion properties of graphene oxide (GO), because it is expected to allow high drug loading and controlled drug release, as well as the promotion of cell adhesion and proliferation. This is particularly interesting in the promotion of wound healing, where antibiotics and anti-inflammatories should be locally released for a prolonged time to allow fibroblast proliferation. Here, we designed an implantable patch consisting of poly(caprolactone) electrospun covered with GO, henceforth named GO–PCL, endowed with high ibuprofen (5.85 mg cm−2), ketoprofen (0.86 mg cm−2), and vancomycin (0.95 mg cm−2) loading, used as anti-inflammatory and antibiotic models respectively, and capable of responding to near infrared (NIR)-light stimuli in order to promptly release the payload on-demand beyond three days. Furthermore, we demonstrated the GO is able to promote fibroblast adhesion, a key characteristic to potentially provide wound healing in vivo. Full article
(This article belongs to the Special Issue Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites)
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12 pages, 2033 KiB  
Review
Porphyrinoid–Fullerene Hybrids as Candidates in Artificial Photosynthetic Schemes
by Vasilis Nikolaou, Asterios Charisiadis, Christina Stangel, Georgios Charalambidis and Athanassios G. Coutsolelos
C 2019, 5(3), 57; https://doi.org/10.3390/c5030057 - 18 Sep 2019
Cited by 20 | Viewed by 4569
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
(This article belongs to the Special Issue Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites)
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14 pages, 3100 KiB  
Article
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
by Torben Schlebrowski, Lucas Beucher, Hadi Bazzi, Barbara Hahn, Stefan Wehner and Christian B. Fischer
C 2019, 5(3), 52; https://doi.org/10.3390/c5030052 - 30 Aug 2019
Cited by 14 | Viewed by 3235
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
(This article belongs to the Special Issue Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites)
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10 pages, 4550 KiB  
Article
Atmospheric Pressure Plasma-Treated Carbon Nanowalls’ Surface-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (CNW-SALDI-MS)
by Takayuki Ohta, Hironori Ito, Kenji Ishikawa, Hiroki Kondo, Mineo Hiramatsu and Masaru Hori
C 2019, 5(3), 40; https://doi.org/10.3390/c5030040 - 18 Jul 2019
Cited by 6 | Viewed by 4077
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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16 pages, 4598 KiB  
Article
A Multifunctional Wearable Device with a Graphene/Silver Nanowire Nanocomposite for Highly Sensitive Strain Sensing and Drug Delivery
by Ge Shi, Tianqing Liu, Zlatko Kopecki, Allison Cowin, Ivan Lee, Jing-Hong Pai, Sean E. Lowe and Yu Lin Zhong
C 2019, 5(2), 17; https://doi.org/10.3390/c5020017 - 4 Apr 2019
Cited by 30 | Viewed by 6666
Abstract
Advances in wearable, highly sensitive and multifunctional strain sensors open up new opportunities for the development of wearable human interface devices for various applications such as health monitoring, smart robotics and wearable therapy. Herein, we present a simple and cost-effective method to fabricate [...] Read more.
Advances in wearable, highly sensitive and multifunctional strain sensors open up new opportunities for the development of wearable human interface devices for various applications such as health monitoring, smart robotics and wearable therapy. Herein, we present a simple and cost-effective method to fabricate a multifunctional strain sensor consisting of a skin-mountable dry adhesive substrate, a robust sensing component and a transdermal drug delivery system. The sensor has high piezoresisitivity to monitor real-time signals from finger bending to ulnar pulse. A transdermal drug delivery system consisting of polylactic-co-glycolic acid nanoparticles and a chitosan matrix is integrated into the sensor and is able to release the nanoparticles into the stratum corneum at a depth of ~60 µm. Our approach to the design of multifunctional strain sensors will lead to the development of cost-effective and well-integrated multifunctional wearable devices. Full article
(This article belongs to the Special Issue Biomedical Applications of Carbon Materials)
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35 pages, 4280 KiB  
Review
Carbon Nanodots: A Review—From the Current Understanding of the Fundamental Photophysics to the Full Control of the Optical Response
by Alice Sciortino, Andrea Cannizzo and Fabrizio Messina
C 2018, 4(4), 67; https://doi.org/10.3390/c4040067 - 13 Dec 2018
Cited by 166 | Viewed by 19686
Abstract
Carbon dots (CDs) are an emerging family of nanosystems displaying a range of fascinating properties. Broadly speaking, they can be described as small, surface-functionalized carbonaceous nanoparticles characterized by an intense and tunable fluorescence, a marked sensitivity to the environment and a range of [...] Read more.
Carbon dots (CDs) are an emerging family of nanosystems displaying a range of fascinating properties. Broadly speaking, they can be described as small, surface-functionalized carbonaceous nanoparticles characterized by an intense and tunable fluorescence, a marked sensitivity to the environment and a range of interesting photochemical properties. CDs are currently the subject of very intense research, motivated by their possible applications in many fields, including bioimaging, solar energy harvesting, nanosensing, light-emitting devices and photocatalyis. This review covers the latest advancements in the field of CDs, with a focus on the fundamental understanding of their key photophysical behaviour, which is still very debated. The photoluminescence mechanism, the origin of their peculiar fluorescence tunability, and their photo-chemical interactions with coupled systems are discussed in light of the latest developments in the field, such as the most recent results obtained by femtosecond time-resolved experiments, which have led to important steps forward in the fundamental understanding of CDs. The optical response of CDs appears to stem from a very complex interplay between the electronic states related to the core structure and those introduced by surface functionalization. In addition, the structure of CD energy levels and the electronic dynamics triggered by photo-excitation finely depend on the microscopic structure of any specific sub-type of CD. On the other hand, this remarkable variability makes CDs extremely versatile, a key benefit in view of their very wide range of applications. Full article
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9 pages, 2467 KiB  
Article
Investigation of Nanographene Produced by In-Liquid Plasma for Development of Highly Durable Polymer Electrolyte Fuel Cells
by Vladislav Gamaleev, Kengo Kajikawa, Keigo Takeda and Mineo Hiramatsu
C 2018, 4(4), 65; https://doi.org/10.3390/c4040065 - 23 Nov 2018
Cited by 11 | Viewed by 4263
Abstract
Recently, polymer electrolyte fuel cells (PEFCs) are attracting a lot of attention owing to their small size and relatively low working temperature (below 80 °C), which enables their usage in automobiles and household power generation. However, PEFCs have a problem with decreased output [...] Read more.
Recently, polymer electrolyte fuel cells (PEFCs) are attracting a lot of attention owing to their small size and relatively low working temperature (below 80 °C), which enables their usage in automobiles and household power generation. However, PEFCs have a problem with decreased output caused by corrosion of amorphous carbon, which is commonly used as a catalytic carrier. This problem could be solved by the usage of carbon nanostructures with a stronger crystal structure than amorphous carbon. In this work, nanographene supported by Pt nanoparticles was synthesized and examined for possible applications in the development of PEFCs with increased durability. Nanographene was synthesized by in-liquid plasma generated in ethanol using alternating current (AC) high voltage. A membrane electrode assembly (MEA) was constructed, where Pt nanoparticle-supported nanographene was used as the catalytic layer. Power generation characteristics of the MEA were evaluated and current density for the developed MEA was found to be approximately 240 mA/cm2. From the electrochemical evaluation, it was found that the durability of Pt nanoparticle-supported nanographene was about seven times higher than that of carbon black. Full article
(This article belongs to the Special Issue Plasma Processing for Carbon-based Materials)
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22 pages, 3532 KiB  
Perspective
Crucial Factors for the Application of Functional Nanoporous Carbon-Based Materials in Energy and Environmental Applications
by Martin Oschatz and Ralf Walczak
C 2018, 4(4), 56; https://doi.org/10.3390/c4040056 - 17 Oct 2018
Cited by 14 | Viewed by 5808
Abstract
This special issue of C—Journal of Carbon Research is dedicated to “Functional Nanoporous Carbon-Based Materials”. It contains contributions reporting on the synthesis of nanoporous carbons for the adsorption of proteins, their applications in electrochemical energy storage/conversion, and on the characterization/modification of their surface [...] Read more.
This special issue of C—Journal of Carbon Research is dedicated to “Functional Nanoporous Carbon-Based Materials”. It contains contributions reporting on the synthesis of nanoporous carbons for the adsorption of proteins, their applications in electrochemical energy storage/conversion, and on the characterization/modification of their surface chemistry. Nanoporous carbon-based materials are widely researched, but at the same time, the field is still full of unutilized potential. The atomic construction of the carbon framework, pore sizes, pore geometries, presence of heteroatoms, particle size and shape, and many other “internal screws” are available; in the end, the high potential of carbon-based materials will only be fully explored if the interplay of these crucial factors is precisely controlled. This article is a summary of what we consider important for future targeted improvement of porous carbon nanomaterials for energy and environmental applications. Full article
(This article belongs to the Special Issue Functional Nanoporous Carbon-Based Materials)
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16 pages, 3172 KiB  
Article
Activated Carbons Derived from High-Temperature Pyrolysis of Lignocellulosic Biomass
by Cristian I. Contescu, Shiba P. Adhikari, Nidia C. Gallego, Neal D. Evans and Bryan E. Biss
C 2018, 4(3), 51; https://doi.org/10.3390/c4030051 - 12 Sep 2018
Cited by 100 | Viewed by 9418
Abstract
Biomass pyrolysis to produce biofuel and hydrogen yields large amounts of charred byproducts with low commercial value. A study was conducted to evaluate their potential for being converted into higher value activated carbons by a low-cost process. Six chars derived from various lignocellulosic [...] Read more.
Biomass pyrolysis to produce biofuel and hydrogen yields large amounts of charred byproducts with low commercial value. A study was conducted to evaluate their potential for being converted into higher value activated carbons by a low-cost process. Six chars derived from various lignocellulosic precursors were activated in CO2 at 800 °C to 30–35% weight loss, and their surface area and porosity were characterized by nitrogen adsorption at 77 K. It was found that, in similar activation conditions, the surface area of the activated carbons correlates with the activation energy of the oxidation reaction by CO2, which in turn varies inversely with the carbon yield after thermolysis in nitrogen at 1000 °C. Since lignin is the most thermally-stable component of lignocellulosic biomass, these results demonstrate, indirectly, that robust, lignin-rich vegetal precursors are to be preferred to produce higher quality activated carbons. The chars derived from white pine (pinus strobus) and chestnut oak (quercus prinus) were converted to activated carbons with the highest surface area (900–1100 m2/g) and largest mesopores volume (0.85–1.06 cm3/g). These activated carbons have properties similar to those of commercially-available activated carbons used successfully for removal of pollutants from aqueous solutions. Full article
(This article belongs to the Special Issue Carbons from Biomasic Waste and Their Applications)
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17 pages, 7658 KiB  
Article
High-Performance Vanadium Redox Flow Batteries with Graphite Felt Electrodes
by Trevor J. Davies and Joseph J. Tummino
C 2018, 4(1), 8; https://doi.org/10.3390/c4010008 - 25 Jan 2018
Cited by 47 | Viewed by 9960
Abstract
A key objective in the development of vanadium redox flow batteries (VRFBs) is the improvement of cell power density. At present, most commercially available VRFBs use graphite felt electrodes under relatively low compression. This results in a large cell ohmic resistance and limits [...] Read more.
A key objective in the development of vanadium redox flow batteries (VRFBs) is the improvement of cell power density. At present, most commercially available VRFBs use graphite felt electrodes under relatively low compression. This results in a large cell ohmic resistance and limits the maximum power density. To date, the best performing VRFBs have used carbon paper electrodes, with high active area compression pressures, similar to that used in fuel cells. This article investigates the use of felt electrodes at similar compression pressures. Single cells are assembled using compression pressures of 0.2–7.5 bar and tested in a VRFB system. The highest cell compression pressure, combined with a thin Nafion membrane, achieved a peak power density of 669 mW cm−2 at a flow rate of 3.2 mL min−1 per cm2 of active area, more than double the previous best performance from a felt-VRFB. The results suggest that felt electrodes can compete with paper electrodes in terms of performance when under similar compression pressures, which should help guide electrode development and cell optimization in this important energy storage technology. Full article
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5791 KiB  
Article
Evaluation of Carbon-Coated Graphite as a Negative Electrode Material for Li-Ion Batteries
by Varvara Sharova, Arianna Moretti, Guinevere A. Giffin, Diogo Vieira Carvalho and Stefano Passerini
C 2017, 3(3), 22; https://doi.org/10.3390/c3030022 - 4 Jul 2017
Cited by 23 | Viewed by 12158
Abstract
Low-cost and environmentally-friendly materials are investigated as carbon-coating precursors to modify the surface of commercial graphite for Li-ion battery anodes. The coating procedure and final carbon content are tuned to study the influence of the precursors on the electrochemical performance of graphite. Thermogravimetric [...] Read more.
Low-cost and environmentally-friendly materials are investigated as carbon-coating precursors to modify the surface of commercial graphite for Li-ion battery anodes. The coating procedure and final carbon content are tuned to study the influence of the precursors on the electrochemical performance of graphite. Thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analysis are used to characterize the carbon coating content and the surface area, respectively, whereas X-ray diffraction (XRD) and Raman spectroscopy allow tracking of the graphite’s structural changes and surface amorphization. In general, the coating reduces the first cycle coulombic efficiency by 3%–10% compared to pristine graphite due to the increase of the surface area available for the continuous electrolyte decomposition. However, the use of citric acid as a carbon source (5 wt %) improves the rate capability of graphite, resulting in the specific delithiation capacity at 3C of 228 mAh g−1 vs. 211 mAh g−1 for the uncoated graphite. The attempt to reduce the coating amount from 5 wt % to 2 wt % results in a lower rate capability, but the first cycle coulombic efficiency is similar to that of pristine graphite. Full article
(This article belongs to the Special Issue Batteries: Recent Advances in Carbon Materials 2017)
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1988 KiB  
Review
Biosensors Based on Lipid Modified Graphene Microelectrodes
by Georgia-Paraskevi Nikoleli, Christina G. Siontorou, Dimitrios P. Nikolelis, Spyridoula Bratakou, Stephanos Karapetis and Nikolaos Tzamtzis
C 2017, 3(1), 9; https://doi.org/10.3390/c3010009 - 16 Mar 2017
Cited by 6 | Viewed by 5945
Abstract
Graphene is one of the new materials which has shown a large impact on the electronic industry due to its versatile properties, such as high specific surface area, high electrical conductivity, chemical stability, and large spectrum of electrochemical properties. The graphene material-based electronic [...] Read more.
Graphene is one of the new materials which has shown a large impact on the electronic industry due to its versatile properties, such as high specific surface area, high electrical conductivity, chemical stability, and large spectrum of electrochemical properties. The graphene material-based electronic industry has provided flexible devices which are inexpensive, simple and low power-consuming sensor tools, therefore opening an outstanding new door in the field of portable electronic devices. All these attractive advantages of graphene give a platform for the development of a new generation of devices in both food and environmental applications. Lipid-based sensors have proven to be a good route to the construction of novel devices with improved characteristics, such as fast response times, increased sensitivity and selectivity, and the possibility of miniaturization for the construction of portable biosensors. Therefore, the incorporation of a lipid substrate on graphene electrodes has provided a route to the construction of a highly sensitive and selective class of biosensors with fast response times and portability of field applications for the rapid detection of toxicants in the environment and food products. Full article
(This article belongs to the Special Issue Carbon-Based Sensors)
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4010 KiB  
Review
An Overview of Pesticide Monitoring at Environmental Samples Using Carbon Nanotubes-Based Electrochemical Sensors
by Ademar Wong, Tiago A. Silva, Fábio R. Caetano, Márcio F. Bergamini, Luiz H. Marcolino-Junior, Orlando Fatibello-Filho and Bruno C. Janegitz
C 2017, 3(1), 8; https://doi.org/10.3390/c3010008 - 15 Mar 2017
Cited by 25 | Viewed by 7296
Abstract
Carbon nanotubes have received enormous attention in the development of electrochemical sensors by promoting electron transfer reactions, decreasing the work overpotential within great surface areas. The growing concerns about environmental health emphasized the necessity of continuous monitoring of pollutants. Pesticides have been successfully [...] Read more.
Carbon nanotubes have received enormous attention in the development of electrochemical sensors by promoting electron transfer reactions, decreasing the work overpotential within great surface areas. The growing concerns about environmental health emphasized the necessity of continuous monitoring of pollutants. Pesticides have been successfully used to control agricultural and public health pests; however, intense use can cause a number of damages for biodiversity and human health. In this sense, carbon nanotubes-based electrochemical sensors have been proposed for pesticide monitoring combining different electrode modification strategies and electroanalytical techniques. In this paper, we provide a review of the recent advances in the use of carbon nanotubes for the construction of electrochemical sensors dedicated to the environmental monitoring of pesticides. Future directions, perspectives, and challenges are also commented. Full article
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3627 KiB  
Article
High-Bandwidth and Sensitive Air Flow Sensing Based on Resonance Properties of CNT-on-Fiber Hairs
by Keith Slinker, Corey Kondash, Benjamin T. Dickinson and Jeffery W. Baur
C 2017, 3(1), 6; https://doi.org/10.3390/c3010006 - 8 Mar 2017
Cited by 6 | Viewed by 4869
Abstract
Artificial hair flow sensors were fabricated using piezoresistive, radially grown carbon nanotube arrays on glass fibers and investigated for their dynamic aerodynamic response as measured within an instrumented plane-wave tube. The sensors were experimentally observed to provide both a large bandwidth of operation [...] Read more.
Artificial hair flow sensors were fabricated using piezoresistive, radially grown carbon nanotube arrays on glass fibers and investigated for their dynamic aerodynamic response as measured within an instrumented plane-wave tube. The sensors were experimentally observed to provide both a large bandwidth of operation below first resonance and a strong resonance response at selected frequencies above first resonance. The frequency of first resonance was easily tunable by adjusting the length of the exposed hair and could be made to vary from a few hundred hertz to over 13 kHz. Higher frequency bands were accessible for a given hair length using higher-order resonance modes, up to five of which were observed. All of the responses were understood and modeled using a vibrating Euler-Bernoulli beam analysis. Full article
(This article belongs to the Special Issue Carbon-Based Sensors)
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2261 KiB  
Review
Recent Progress in Design of Biomass-Derived Hard Carbons for Sodium Ion Batteries
by Joanna Górka, Cathie Vix-Guterl and Camelia Matei Ghimbeu
C 2016, 2(4), 24; https://doi.org/10.3390/c2040024 - 5 Dec 2016
Cited by 68 | Viewed by 13013
Abstract
Sodium ion batteries (SIBs) have attracted lots of attention over last few years due to the abundance and wide availability of sodium resources, making SIBs the most cost-effective alternative to the currently used lithium ion batteries (LIBs). Many efforts are underway to find [...] Read more.
Sodium ion batteries (SIBs) have attracted lots of attention over last few years due to the abundance and wide availability of sodium resources, making SIBs the most cost-effective alternative to the currently used lithium ion batteries (LIBs). Many efforts are underway to find effective anodes for SIBs since the commercial anode for LIBs, graphite, has shown very limited capacity for SIBs. Among many different types of carbons, hard carbons—especially these derived from biomass—hold a great deal of promise for SIB technology thanks to their constantly improving performance and low cost. The main scope of this mini-review is to present current progress in preparation of negative electrodes from biomass including aspects related to precursor types used and their impact on the final carbon characteristics (structure, texture and composition). Another aspect discussed is how certain macro- and microstructure characteristics of the materials translate to their performance as anode for Na-ion batteries. In the last part, current understanding of factors governing sodium insertion into hard carbons is summarized, specifically those that could help solve existing performance bottlenecks such as irreversible capacity, initial low Coulombic efficiency and poor rate performance. Full article
(This article belongs to the Special Issue Batteries: Recent Advances in Carbon Materials)
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4986 KiB  
Review
Three-Dimensional Carbon Nanostructures for Advanced Lithium-Ion Batteries
by Chiwon Kang, Eunho Cha, Mumukshu D. Patel, H. Felix Wu and Wonbong Choi
C 2016, 2(4), 23; https://doi.org/10.3390/c2040023 - 26 Oct 2016
Cited by 6 | Viewed by 9135
Abstract
Carbon nanostructural materials have gained the spotlight as promising anode materials for energy storage; they exhibit unique physico-chemical properties such as large surface area, short Li+ ion diffusion length, and high electrical conductivity, in addition to their long-term stability. However, carbon-nanostructured materials [...] Read more.
Carbon nanostructural materials have gained the spotlight as promising anode materials for energy storage; they exhibit unique physico-chemical properties such as large surface area, short Li+ ion diffusion length, and high electrical conductivity, in addition to their long-term stability. However, carbon-nanostructured materials have issues with low areal and volumetric densities for the practical applications in electric vehicles, portable electronics, and power grid systems, which demand higher energy and power densities. One approach to overcoming these issues is to design and apply a three-dimensional (3D) electrode accommodating a larger loading amount of active anode materials while facilitating Li+ ion diffusion. Furthermore, 3D nanocarbon frameworks can impart a conducting pathway and structural buffer to high-capacity non-carbon nanomaterials, which results in enhanced Li+ ion storage capacity. In this paper, we review our recent progress on the design and fabrication of 3D carbon nanostructures, their performance in Li-ion batteries (LIBs), and their implementation into large-scale, lightweight, and flexible LIBs. Full article
(This article belongs to the Special Issue Batteries: Recent Advances in Carbon Materials)
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3343 KiB  
Article
Simple Process for Sidewall Modification of Multi-Walled Carbon Nanotubes with Polymer Side Chain Radicals Generated by Ultraviolet-Induced C–Cl Bond Dissociation of Polystyrene Derivatives
by Tomoya Takada, Takuma Baba and Shigeaki Abe
C 2016, 2(3), 20; https://doi.org/10.3390/c2030020 - 26 Jul 2016
Cited by 3 | Viewed by 7263
Abstract
In this work, we investigated a simple one-step process for the formation of chemical bonds between multi-walled carbon nanotubes (MWCNTs) and benzyl-type side chain radicals generated by UV photolysis of polystyrene derivatives containing the chloromethyl (–CH2Cl) group. Poly(4-chloromethyl)styrene, or styrene/4-(chloromethyl)styrene random [...] Read more.
In this work, we investigated a simple one-step process for the formation of chemical bonds between multi-walled carbon nanotubes (MWCNTs) and benzyl-type side chain radicals generated by UV photolysis of polystyrene derivatives containing the chloromethyl (–CH2Cl) group. Poly(4-chloromethyl)styrene, or styrene/4-(chloromethyl)styrene random copolymer, was mixed with MWCNTs in 1-methyl-2-pyrrolidone and irradiated with ultraviolet (UV) light. Films of polymer/MWCNT mixtures before and after UV irradiation were fabricated, and then examined by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. According to the XPS analysis, the amount of Cl atoms in the mixture was found to decrease upon UV irradiation, indicating that the Cl atoms generated by photolysis of chloromethyl groups escaped from the reaction system in the form of gaseous Cl2. The structural change of CNTs after UV irradiation was also observed by comparing the G/D ratios (the intensity ratio of the G to D bands) of the Raman spectra obtained before and after UV irradiation. Similar phenomena were also confirmed in the case of the polymer/MWCNT mixture containing hydroxylammonium chloride as a dispersant of MWCNTs. These results confirmed the UV-induced covalent bond formation between polymer side chains and MWCNTs. Full article
(This article belongs to the Special Issue Surface Modification of Carbon Nanotubes)
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2931 KiB  
Article
Thermochemistry of a Biomimetic and Rubisco-Inspired CO2 Capture System from Air
by Andrew Muelleman, Joseph Schell, Spencer Glazer and Rainer Glaser
C 2016, 2(3), 18; https://doi.org/10.3390/c2030018 - 1 Jul 2016
Cited by 6 | Viewed by 8463
Abstract
In theoretical studies of chemical reactions the reaction thermochemistry is usually reported for the stoichiometric reaction at standard conditions (ΔG°, ΔH°, ΔS°). We describe the computation of the equilibrium concentrations of the CO2-adducts for the [...] Read more.
In theoretical studies of chemical reactions the reaction thermochemistry is usually reported for the stoichiometric reaction at standard conditions (ΔG°, ΔH°, ΔS°). We describe the computation of the equilibrium concentrations of the CO2-adducts for the general capture reaction CO2 + Capture System ⇆ CO2-adduct (GCR) and the rubisco-type capture reaction CO2 + Capture System ⇆ CO2-adduct + H2O (RCR) with consideration of the reaction CO2(g) ⇆ CO2(aq) via Henry’s law. The resulting equations are evaluated and graphically illustrated as a function of atmospheric CO2 concentration and as a function of temperature. The equations were applied to the thermochemistry of small molecule rubisco-model reactions and series of additional model reactions to illustrate the range of the Gibbs free enthalpy for the effective reversible capture and of the reaction entropy for economic CO2 release at elevated temperature. A favorable capture of free enthalpy is of course a design necessity, but not all exergonic reactions are suitable CO2 capture systems. Successful CO2 capture systems must allow for effective release as well, and this feature is controlled by the reaction entropy. The principle of using a two-pronged capture system to ensure a large negative capture entropy is explained and highlighted in the graphical abstract. It is hoped that the presentation of the numerical examples provides useful guidelines for the design of more efficient capture systems. Full article
(This article belongs to the Special Issue Materials and Processes for Carbon Dioxide Capture and Utilisation)
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2681 KiB  
Review
Tuning CNT Properties for Metal-Free Environmental Catalytic Applications
by Raquel P. Rocha, Olívia S.G.P. Soares, José L. Figueiredo and Manuel Fernando R. Pereira
C 2016, 2(3), 17; https://doi.org/10.3390/c2030017 - 29 Jun 2016
Cited by 29 | Viewed by 8486
Abstract
The application of carbon nanotubes (CNTs) as metal-free catalysts is a novel approach for heterogeneous liquid phase catalytic systems. Textural and chemical modifications by liquid/gas phase or mechanical treatments, as well as solid state reactions, were successfully applied to obtain carbon nanotubes with [...] Read more.
The application of carbon nanotubes (CNTs) as metal-free catalysts is a novel approach for heterogeneous liquid phase catalytic systems. Textural and chemical modifications by liquid/gas phase or mechanical treatments, as well as solid state reactions, were successfully applied to obtain carbon nanotubes with different surface functionalities. Oxygen, nitrogen, and sulfur are the most common heteroatoms introduced on the carbon surface. This short-review highlights different routes used to develop metal-free carbon nanotube catalysts with enhanced properties for Advanced Oxidation Processes. Full article
(This article belongs to the Special Issue Surface Modification of Carbon Nanotubes)
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1611 KiB  
Article
Calculating the Emissions Impacts of Waste Electronics Recycling in Ontario, Canada
by Calvin Lakhan
C 2016, 2(2), 11; https://doi.org/10.3390/c2020011 - 11 Apr 2016
Cited by 4 | Viewed by 7968
Abstract
This study highlights the economic and environmental challenges of recycling in Ontario, specifically examining the effect of attempting to increase the emissions target for the province’s Waste Electronics (WEEE) program. The findings from the cost model analysis found that Ontario’s Electronic Stewardship program [...] Read more.
This study highlights the economic and environmental challenges of recycling in Ontario, specifically examining the effect of attempting to increase the emissions target for the province’s Waste Electronics (WEEE) program. The findings from the cost model analysis found that Ontario’s Electronic Stewardship program reduces overall carbon emissions by approximately 205 thousand tonnes every year. This study also found that targeting specific materials for recovery could result in a scenario where the province could improve emissions offsets while reducing material management costs. Under our modeled scenario, as the tonnes of greenhouse gases (GHGs) avoided increases, the system cost per tonne of GHG avoided initially declines. However, after avoiding 215 thousand tonnes of GHGs (the optimal point), the system cost/tonne GHG avoided increases. To achieve an emissions target in excess of 215 thousand tonnes, the province will have to have to start recycling higher cost difficult to recycle materials (display monitors, computer peripherals, etc.). Full article
(This article belongs to the Special Issue Materials and Processes for Carbon Dioxide Capture and Utilisation)
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