Haut PDF Production of graphene based materials and their potential applications

Production of graphene based materials and their potential applications

Production of graphene based materials and their potential applications

Graphene is commonly produced by either bottom-up techniques, such as chemical vapor deposition (CVD) on metal substrates [11] and epitaxial growth on SiC [12] or by top-down approaches where graphene sheets are isolated from graphite by mechanical exfoliation using Scotch tape [3], chemical exfoliation methods, such as graphite oxide [13] and liquid phase exfoliation [14] routes. Among these methods, mechanical exfoliation gives the highest-quality graphene when the best-quality graphite is used; however, this method has extremely low yield; therefore, it can only be used for fundamental research. Bottom-up techniques, especially CVD, enable one to produce large area, planar graphene films with relatively low defect density and are well-suited for flexible transparent electrodes and electronic applications where the growth can be patterned precisely in combination with lithographical methods. However, the CVD-synthesized graphene film is mostly transferred from the grown substrate onto arbitrary (dielectric) substrates for further applications. The mobility of the CVD- synthesized graphene is limited by disorders, defects and impurities originating from both the synthesis process and the transfer technique. Therefore, it is required to enhance the transport properties of CVD graphene while growing it uniformly at a large-area. On the other hand, chemical exfoliation methods, e.g., liquid phase exfoliation (LPE) of graphite, are promising for large-scale production of graphene-based materials (lower quality compared to CVD- graphene) at low cost for applications where accurate positioning of the layers is not required, such as composite materials, conductive inks and energy storage. However, obtaining high quality few-layer (5 layers) graphene materials in a large scale and with a reasonable lateral size is the main challenge of LPE routes.
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Analysis of the materials and energy cost to manufacture graphene by roll-based chemical vapor deposition

Analysis of the materials and energy cost to manufacture graphene by roll-based chemical vapor deposition

One of the most alluring properties is the aforementioned room temperature electron mobility of approximately 2.5×10 5 cm 2 V -1 s -1 . Electron mobility is essentially a measure of how fast charge, and therefore signals, can be sent through semiconductors. Graphene could hold answers on how to make circuits faster. There are a few catches though; namely that, unlike silicon, graphene is a zero-bandgap material. [6] Chemical doping with nitrogen or boron has had some promising results, but it is not an exact science as of yet. [8] An additional wrinkle is that the substrates that graphene is typically put on after production, such as polymethyl methacrylate or polyethylene terephthalate, can contaminate the graphene and alter its electrical properties. [10] Thermal annealing and additional post-processing is occasionally required. Once reliable doping strategies are known, graphene will quickly be of use in circuits as a transistor, or as a supercapacitor. The monolayer aspect of graphene means that any component that it is made into will likely be smaller than any competitor material. The potential application of graphene in circuits is probably the best known, however, there are many other viable ways of using this material. Graphene has been proposed as a semi-permeable membrane for use in water desalination. Fluorinated graphene monolayer membranes have been found to have a 10000 times higher water flux than cellulose triacetate membranes currently in used. [8] Graphene with pores is also a good salt rejector, thanks to its consistent tight-knit atomic structure. These two facts in concert mean that graphene has tremendous opportunity as a primary membrane in forward osmosis processes.
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Safety assessment of graphene-based materials: focus on human health and the environment

Safety assessment of graphene-based materials: focus on human health and the environment

Landscape Compila- tion reports (see https://publications.europa.eu/en/ ). These reports o ffer a snapshot of the environment for nanotechnology in di fferent application fields. In the report on “health”, GBMs are hardly mentioned, whereas in the report on “environment”, the authors have stated that “based on the scarce available evidence, it cannot be excluded that some forms of graphene will be as potent a toxicant as carbon nanotubes ”. This statement raises the spectre of asbestos-like properties of carbon nanotubes, 5 but according to a recent report published by the International Agency for Research on Cancer (IARC), only certain types of rigid, multiwalled carbon nanotubes can be classi fied as being possibly carcinogenic to humans. 344 More- over, as we have discussed at length in the present review, GBMs cannot be grouped together as one material. Indeed, GBMs di ffer with respect to three key parameters: the number of graph- ene layers, average lateral dimensions, and carbon-to-oxygen atomic ratio. 22 Furthermore, GBMs can be functionalized in a multitude of di fferent ways, thereby changing their properties and, in all likelihood, their biological behavior. The fact that GO 140 and FLG 345 can be digested by cells of the immune sys- tem implies that these materials are not necessarily biopersistent. Notably, research conducted in the context of the Graphene Flagship and by other investigators in the past several years has shown that the hazard potential for di fferent members of the GBM family may vary considerably, and it is not a valid state- ment that all GBMs are as hazardous as carbon nanotubes, nor is it true that all carbon nanotubes are hazardous. In fact, the devil is in the details, and careful characterization of material properties is of critical importance. Furthermore, it is equally important that the material properties are reported in full in papers dealing with (eco)toxicity assessment of GBMs. Can the information that has
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Safety Assessment of Graphene-Based Materials: Focus on Human Health and the Environment

Safety Assessment of Graphene-Based Materials: Focus on Human Health and the Environment

Landscape Compila- tion reports (see https://publications.europa.eu/en/). These reports o ffer a snapshot of the environment for nanotechnology in di fferent application fields. In the report on “health”, GBMs are hardly mentioned, whereas in the report on “environment”, the authors have stated that “based on the scarce available evidence, it cannot be excluded that some forms of graphene will be as potent a toxicant as carbon nanotubes ”. This statement raises the spectre of asbestos-like properties of carbon nanotubes, 5 but according to a recent report published by the International Agency for Research on Cancer (IARC), only certain types of rigid, multiwalled carbon nanotubes can be classi fied as being possibly carcinogenic to humans. 344 More- over, as we have discussed at length in the present review, GBMs cannot be grouped together as one material. Indeed, GBMs di ffer with respect to three key parameters: the number of graph- ene layers, average lateral dimensions, and carbon-to-oxygen atomic ratio. 22 Furthermore, GBMs can be functionalized in a multitude of di fferent ways, thereby changing their properties and, in all likelihood, their biological behavior. The fact that GO 140 and FLG 345 can be digested by cells of the immune sys- tem implies that these materials are not necessarily biopersistent. Notably, research conducted in the context of the Graphene Flagship and by other investigators in the past several years has shown that the hazard potential for di fferent members of the GBM family may vary considerably, and it is not a valid state- ment that all GBMs are as hazardous as carbon nanotubes, nor is it true that all carbon nanotubes are hazardous. In fact, the devil is in the details, and careful characterization of material properties is of critical importance. Furthermore, it is equally important that the material properties are reported in full in papers dealing with (eco)toxicity assessment of GBMs. Can the information that has
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Fennel oil and by-products seed characterization and their potential applications

Fennel oil and by-products seed characterization and their potential applications

1. Introduction ABSTRACT The implementation of renewable resources in the industrial production processes appears to be the most ef. fective way to achieve sustainable development. However, in order to tacl<le the lœy issues of shifting to re­ newable resources, a full exploitation of biomass resources and efficient utilization of complex organic macro­ molecules and a1so other chemical constituents such as antioxidants in bio-refinery system will be crucial. In this regard, fennel (Poeniculum wl,gare) seeds could be a promising bio-resource with significant interest as a rich source ofboth vegetable oil (VO) and essential oil (EO), in addition to rare phytochemicals. Thus, in the present paper, a trans-disdplinary assessment of a new bio-refinery process from fennel seeds was established: the development of an integrated valorization of fennel seeds, allowing the extraction of VO and EO and their exploitation in cosmetic applications as well as the valorization of residual by-products as a source of biologi­ cally active compounds, these processes constituted the basis of this bio-refinery concept. Laboratory obtained results and pilot«ale levels with fennel seeds reported extraction of high yield of both VO and EO (19.8% and 1.8%, respectively) with significant amounts of valuable components, petroselinic add and trans--anethole (74.8% and 70.7%, respectively). Further, the valorization of these oils as functional ingredients in moisturizing cream formulas showed a positive impact on the overall emulsions structure and quality. Next to this, fennel oilseeds by-products exhibited a remarkable antioxidant potential with high phenols and flavonoids contents and exhibited good antimicrobial properties depending on the extract type. These promising findings are of great economic interest as they can lead to a wild range of nove!, bio-based industrial applications from fennel seeds.
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Development of Polymer Nanocomposite Films and their Potential for Photovoltaic Cell Applications

Development of Polymer Nanocomposite Films and their Potential for Photovoltaic Cell Applications

1.8 Problem Identification and Originality of the Work As it was summarized in the preceding sections of literature review, reducing the costs of mass production of solar cells is one of the main approaches to find reliable cost-effective renewable energy sources. Although simplicity and inexpensive materials of DSSCs have made them very interesting, the high temperature treatment of the TiO2 layer brings a limitation in their cost- effectiveness and making light and durable flexible DSSCs based on plastic substrates. Therefore, developing a novel process to produce the photoelectrode at relatively low temperatures is necessary. In this PhD thesis, it is aimed to develop a porous composite film structure containing TiO2 nanoparticles which can be used as the photoelectrode of DSSC. To the best of our knowledge, it is the first work on using polymer melt processing methods to produce a flexible polymer composite layer at relatively low temperatures that makes it possible to use plastic substrates. In the first stage, it is important to investigate electrical properties of the polymer composite containing TiO2 because it is necessary to have a TiO2 network to collect the photogenerated charges. Relation among composition, morphology and electrical properties of the blend of the thermoplastic polymer and TiO2 nanoparticle is one of the most interesting subject that has not been well studied. Moreover, processability of the compound is a critical factor in polymer melt processing. Accordingly, it is essential to investigate the relation among morphology, rheology, and electrical properties with an emphasis on percolation of the TiO2 phase in the thermoplastic matrix. As it was reviewed, stretching is an efficient route in generating pores in filled polymer films. However, the relation between stretching process conditions and final properties of the porous films should be extensively studied for the composite films containing TiO2. Finally, the functionality of such composite film as photoelectrodes for DSSC should be examined.
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Defects and impurities in graphene-like materials

Defects and impurities in graphene-like materials

Fig. 10 Charge distribution, projected potentials and TEM simulations for nitrogen-doped graphene. (a) The relaxed atomic configuration for a nitrogen impurity substitution in graphene. Bond lengths are given in angstroms. (b) Projected potential based on the IAM (independent atom model), with the periodic components of the graphene lattice removed, and bandwidth-limited to their experimental resolution (about 1:8 Å). Dark contrast corresponds to higher projected potential values, in accordance with conventional TEM imaging conditions. (c) TEM simulation based on the IAM potential, for two different defocus parameters f1 and f2, where the condition f2 stands for a more defocused situation. Filters are: (i) unfiltered, (ii) periodic components removed by a Fourier filter, and (iii) low-pass filtered. (d) Atomic structure (using the same bond lengths), with the changes in the projected electron density due to bonding shown in colour. Blue corresponds to a lower, red to a higher electron density in the DFT result as compared with the neutral-atom (IAM) case. (e) Projected potential, filtered as in (b), based on the all-electron DFT calculation. (f) TEM simulations using the DFT-based potentials. The grey-scale calibration bar applies to columns (ii) and (iii), which are all shown on the same grey-scale range for direct comparison. The scale bars are 5 Å. Reprinted from 36 by permission from Macmillan Publishers Ltd, © 2011.
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Complex Mode Spectra of Graphene-Based Planar Structures for THz Applications

Complex Mode Spectra of Graphene-Based Planar Structures for THz Applications

by a coherent THz source) in order to excite a pair of weakly attenuated leaky modes that propagate along the structure and mainly determine its radiation features through their complex propagation constants [13]-[15]. In this work we deal with a complete dispersion analysis of a GPW within the band of 0.25-2.0 THz. For the sake of simplicity we start from an ideal struc- ture [3] consisting of a dielectric-filled parallel-plate waveguide (PPW) whose upper plate is made of graphene. A detailed dispersion analysis is performed by numerically solving the relevant dispersion equation obtained through the transverse-resonance technique [16]-[19]. The main result of this analysis is rep- resented by the fact that for suitably high values of the chemical potential the first higher-order modes exhibit leaky regimes with low attenuation constant, hence they may be employed to achieve scannable directive beams in graphene- based tunable FPCAs [20].
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Nanocellulose, a Versatile Green Platform: From Biosources to Materials and Their Applications

Nanocellulose, a Versatile Green Platform: From Biosources to Materials and Their Applications

89 polyurethane) as well as thermoplastic polymers (PE, PP, PPC, PVA, PLA, and PEO) have been reinforced with nanocellulosic materials to obtain quality products 180 . Previously we discussed the interest of nanocellose-polyaniline-graphene related materials composites, but the simple nanocellose-polyaniline composite is also interesting as a conductive material. Polyaniline alone is brittle, rigid, has poor processability, and easily aggregates into large particles 298,299 . Nanocellulose is an ideal candidate to reinforce polyaniline. It can provide greater interfacial area and strong interactions with the matrix. These tunable electrically conducting biocomposites have potential applications in anti-static, electrochromic devices, electromagnetic interference shielding, sensors, electrodes, and storage devices. Relatively, high specific capacitance of about 161.9 F/g could be achieved for the NC/polyaniline composite, benefitting from the large electrochemical activity of polyaniline and a good range of structural stability due to the synergistic effects in the bionanocellulose. Chen and co-workers have published a series of papers on the in situ preparation, and the electro-analytical studies of polyaniline-nanocellulose composites 300-303 . In general, the thermal stability and conductivity of nanocellulose increased upon loading with polyaniline. The significant increase in conductivity results from the dense coverage of tiny polyaniline particles on the surface of cellulose nanowhiskers and the formation of an interconnected network. The high conductivity of the NC/polyaniline composite attributes to the homogenous formation of a polyaniline layer on the surfaces of the cellulose nanowhiskers.
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Electrochemical biosensors for foodborne contaminants based on aptamers and graphene materials.

Electrochemical biosensors for foodborne contaminants based on aptamers and graphene materials.

ABSTRACT Food safety is a global health goal and food quality control is essential for authorities and professional players in the food supply chain . The presence of unsafe levels of foodborne contaminants such as allergens and toxins in food represents a growing public health problem that necessitates the development of efficient tools for their detection. Despite the relatively high sensitivity of some of the currently used detection methods, they are highly laborious, time consuming, require highly trained personnel and are expensive. These limitations encourage the research for alternative tools to be applied in a regulatory monitoring regime in order to guarantee a high level of consumer protection. Therefore, biosensors have appeared recently as interesting alternatives that exhibited potential applications for food quality analysis. Particularly, electrochemical biosensors have become an attractive choice due to their very low cost, high sensitivity, ease of use and capability of miniaturization. However, two main challenges are facing the wide applicability of the available electrochemical biosensors for the detection of food contaminants today. First, the sophisticated detection strategies which are used to obtain the required sensitivity, usually include a time consuming, costly labelling process and multiple reagents and washing steps. Second, the poor specificity of the available recognition receptors, their high cost as well as their limited stability are major disadvantages. To address these challenges, this work describes the development of novel, simple, sensitive, specific and low cost biosensing platforms for the detection of some foodborne contaminants, particularly allergens and toxins.
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Resonant Edge Magnetoplasmons and Their Decay in Graphene

Resonant Edge Magnetoplasmons and Their Decay in Graphene

We obtained the quality factor of the resonator Q ¼ 8.5 and 15.4 at T ¼ 4 K using Q ¼ πfτ with measured f and τ for the 200-μm and 1000-μm samples, respectively. Note that consistent values can be obtained from the peak width of the fundamental mode in frequency domain [23] . These values are larger than Q ∼ 3.8 obtained by similar time domain measurements using two-dimensional elec- tron systems in GaAs/AlGaAs heterostructures with much higher mobility of 6.2 × 10 6 cm 2 =V s at f ∼ 300 MHz and T ¼ 0.3 K [21] . We suggest that the smaller decay is an intrinsic property of graphene. Larger cyclotron gap arising from lighter effective mass suppresses the resistive coupling to the localized states. At the same time, it reduces the size of the localized states, reducing the capacitive coupling. Atomically sharp edge potential would also contribute to the smaller decay: narrower w at the sharp edge potential prevents EMPs from being excited inside ECs to acoustic charge modes [33] . Our results indicate that graphene ECs provides a platform for robust quantum effects, stimulating the use of gra- phene for quantum transport experiments and plasmonic applications.
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Nanoarchitectured Graphene-Based Supercapacitors for Next-Generation Energy-Storage Applications

Nanoarchitectured Graphene-Based Supercapacitors for Next-Generation Energy-Storage Applications

2 , MnO 2 , NiO, and In 2 O 3 ) have been shown to exhibit high pseu- docapacitance but poor stability during charge–discharge cy- cling with the exception of RuO 2 - and MnO 2 -based materials. [9] Nickel and cobalt hydroxides with various shapes also exhibit high potential as novel electrochemical pseudocapacitors. [10] It is generally known that the typical charge–discharge times for pseudocapacitors are significantly longer than those of EDLCs. Carbon materials, such as activated carbons (ACs) and carbon nanotubes (CNTs), usually exhibit good stability but limited ca- pacitance values. It is clear that EDLCs processes are surface phenomena, and hence the CD performance greatly depends on the electrolyte-accessible surface area. The micropores in carbon materials are inaccessible by the electrolyte, resulting in the inability of the double layer to form in the pores. This result leads to a decrease in the capacitance value (10–20 % of the ‘theoretical’ capacitance) of ACs. Good electrical conductiv- ity, high chemical and mechanical stability, and an optimized nanostructure are also other important factors that are respon- sible for achieving high capacitance values. In spite of the type of the charge storage mechanism, carbon-based materials are the most common materials for supercapacitor applications because of their outstanding properties such as their nontoxic nature, high electrical, chemical, and strong mechanical prop- erties, and environmental friendliness, etc. The potential win- dows in nonaqueous electrolytes are generally larger than those obtained in aqueous media, although the overpotential of hydrogen evolution on carbons is high, especially in neutral electrolytes.
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Revealing the materials and production techniques of european historical copper-based seal matrices

Revealing the materials and production techniques of european historical copper-based seal matrices

e ambre.vilain@gmail.com, f pierre.chastang@uvsq.fr, g etienne.anheim@ehess.fr Seal matrices have been used in many civilizations across the globe since several millenniums. In Europe, during late medieval and early modern periods, they were made of a resistant material such as metal, most of the time copper-based alloys, and were an essential item of official documents, acting as personal signatures. The matrices accompanied the sigillants throughout his life, as they carried it often on their belt, visible for everyone (Vilain 2015). Those objects remained totally undocumented until very recently. Our work contributes to lift the fog on the technical landscape of seal matrices production by looking at materials and techniques in presence. Our study brings his attention to the collections kept at the French National Archives institution and at the Fine Arts Museum of Lyon which constitute a unique corpus of objects from the 13th c. to the 17th c., mostly French, but also Italian.
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Bottom-up synthesis of porphyrin based graphene nanoribbons and nanomeshes

Bottom-up synthesis of porphyrin based graphene nanoribbons and nanomeshes

a CEA, IRAMIS, NIMBE, LICSEN, F-91191 Gif sur Yvette, France b CNRS, UMR 6242, Aix-Marseille Université, Centrale Marseille, IM2NP, F-13397 Marseille Cedex 20, France c CEA, IRAMIS, NIMBE, LCMCE, F-91191 Gif sur Yvette, France d CNRS, UMR 7313 Aix Marseille Université, Centrale Marseille, iSm2, F-13397 Marseille Cedex 20, France The outstanding properties of graphene strongly inspire the scientific community at both the fundamental and applicative levels for high performance electronics, low power spintronics, renewable energy, composites materials and biomedicine. However, along this way several key scientific issues have to be addressed and one of the main challenges is the control and modification of graphene electronic properties, and notably the controlled opening of a sizable bandgap. This can be achieved by quantum confinement, by means of the fabrication of nano-objects with a precise control of the topology, edge-effects... As a consequence, two main graphene forms have emerged for electronic applications, Graphene NanoRibbons (GNR) and Graphene NanoMeshes (GNM). For the last decade, a great attention has been paid to the fabrication of GNRs [1] and GNMs [2] using conventional top-down approach (lithography, etching, thermal treatments). However, this approach does not allow manipulating the material at the atomic scale. In order to truly control the morphology and the composition of the materials and of its edges, the bottom-up approach is the relevant way to proceed.[3] Recently, graphene incorporating porphyrin molecules have been designed either by the groups of Barth [4] and Fischer.[5]
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A comparative study on few-layer graphene production by exfoliation of different starting materials in a low boiling point solvent

A comparative study on few-layer graphene production by exfoliation of different starting materials in a low boiling point solvent

Comprehensive reviews were published on exfoliation of gra- phite powders into single- and few-layer graphene sheets in vari- ous liquids, including organic solvents, ionic liquids, and water/surfactant solutions [1–4] . The qualities, yields and electri- cal properties of exfoliated graphene samples are also reviewed in these papers. Zhong et al. [5] have recently reviewed wet chem- ical graphite exfoliation routes highlighting their progress and challenges in terms of graphene commercialization. There have been several attempts to produce graphene-based materials at a large-scale. Exfoliation of graphite in aqueous solutions with aid of surfactants yielded graphene concentrations of mostly <1 mg/ ml [6] . Concentration was further increased up to 15 mg/ml by continuous addition of surfactant throughout the sonication pro- cess [7] . Ager et al. [8] demonstrated complete exfoliation of up to 5 wt% graphene in water by using triblock copolymers and copolymeric nanolatexes based on a reactive ionic liquid acrylate surfactant for extended time periods of sonication. Ayán-Varela et al. [9] recently reported very high graphene concentrations (up to 50 mg ml 1 ) in aqueous dispersions by using the sodium salt of flavin mononucleotide biomolecule as a surfactant in an exfoli- ation process which was carried out in an ultrasonic bath for 5 h. However, most surfactants are insulating compounds that should
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A comparative study on few-layer graphene production by exfoliation of different starting materials in a low boiling point solvent

A comparative study on few-layer graphene production by exfoliation of different starting materials in a low boiling point solvent

Comprehensive reviews were published on exfoliation of gra- phite powders into single- and few-layer graphene sheets in vari- ous liquids, including organic solvents, ionic liquids, and water/surfactant solutions [1–4] . The qualities, yields and electri- cal properties of exfoliated graphene samples are also reviewed in these papers. Zhong et al. [5] have recently reviewed wet chem- ical graphite exfoliation routes highlighting their progress and challenges in terms of graphene commercialization. There have been several attempts to produce graphene-based materials at a large-scale. Exfoliation of graphite in aqueous solutions with aid of surfactants yielded graphene concentrations of mostly <1 mg/ ml [6] . Concentration was further increased up to 15 mg/ml by continuous addition of surfactant throughout the sonication pro- cess [7] . Ager et al. [8] demonstrated complete exfoliation of up to 5 wt% graphene in water by using triblock copolymers and copolymeric nanolatexes based on a reactive ionic liquid acrylate surfactant for extended time periods of sonication. Ayán-Varela et al. [9] recently reported very high graphene concentrations (up to 50 mg ml 1 ) in aqueous dispersions by using the sodium salt of flavin mononucleotide biomolecule as a surfactant in an exfoli- ation process which was carried out in an ultrasonic bath for 5 h. However, most surfactants are insulating compounds that should
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Development of graphene-based composite materials for electrochemical storage applications

Development of graphene-based composite materials for electrochemical storage applications

126 6. Further Conclusions & perspectives This extensive study performed on reduced pillared graphene materials (RPs) synthesized using three different alkyl diamines has shown that the alkyl diamines could indeed facilitate pillaring of graphene sheets and allow precise tuning of the d-spacing. XRD analyses allowed a direct characterization of the newly formed cross-linked galleries (CL) with direct determination of their d-spacing values. Additionally, the relative shapes and intensities of the CL peaks among various RPs has shown that with increasingly longer diamines the CL peaks get sharper and more intense. This observation along with the pore size distributions of the RPs have suggested that increasing length of the alkyl diamine may facilitate repetitive cross- linking of GO sheets with diamines and result in larger crystallite sizes. This observation was also noted in the previous chapter among the GH-ED and GH-DB synthesized with 1,2- diaminoethane and 1,4-diaminobutane. Overall, choosing longer alkyl diamines over the shorter ones from the previous chapter has provided the materials with required architecture. The well-defined d-spacing values of RPs (0.78 – 0.86 nm) have allowed electrochemical ion sieving analyses with a class of TAABF 4 electrolytes that offer varying cation sizes (0.68 - 0.95 nm) and a constant anion size (0.48 nm). Cyclic voltammograms performed under positive and negative polarizations (with respect to OCV) showed a definitive evidence of ion sieving in these pillared graphene materials. This first observation that the electrolyte ions can enter the inter-layer graphene galleries has thus showed great potential of the pillared graphene materials for enhanced charge storage in SCs. Despite the promising fundamental observations of ions entering the galleries, the specific capacitances calculated from RPs were only marginally better than that of RGO which has extensive restacking with no pillared structures. 5 RP exhibited a charge storage of 130 F.g -1 at 20 mV.s -1 whereas RGO stored ~ 110 F.g -1 in a 1 M TEABF
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Classification framework for graphene-based materials

Classification framework for graphene-based materials

Graphene is the enabling material of the 21st century and there are high expectations for its potential applications. A clear and consistent system describing the various derivatives of graphene promotes a precise vocabulary for the family of graphene-based materials. This will be a prerequisite, for example, to understand structure–activity relationships in the context of human health and safety and to avoid general- izations about the capabilities and limitations of graphene- based materials. Within the European Unions GRAPHENE Flagship project, three physical-chemical descriptors specific for graphene were defined to assist in the classification of graphene-based materials.
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Bimetallic salen-based compounds and their potential applications

Bimetallic salen-based compounds and their potential applications

were refined anisotropically. Hydrogen atoms were refined where possible, and otherwise added using the riding model position parameters. Powder X-ray spectra were collected on a Stoe STADIP using Cu-Kα1 radiation (1.5406 Å) using a Mythen detector. TGA were recorded on a Mettler Toledo TGA7SDTA851. The structures were solved and refined using full-matrix least- squares on F 2 with the SHELX-2014 package. All atoms (except hydrogen atoms) were refined anisotropically. Hydrogen atoms were refined when possible, and otherwise added using the riding model position parameters. Crystallographic data can be found in the Supporting Information (see Table S1). CIF files can be obtained from the Cambridge Crystallographic Data Centre, CCDC-1860979 (1), CCDC-1861009 (2), CCDC-1860982 (3), CCDC-1860981 (4), CCDC-1860983 (5), CCDC-1860980 (6), CCDC-1861005 (“LCuMn Cl 2 ”), CCDC-1861004
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Two dimensional materials (graphene and MXenes) for supercapacitor applications

Two dimensional materials (graphene and MXenes) for supercapacitor applications

32 b) Supercapacitors Graphene was first investigated as supercapacitor electrode material by Ruoff and co-workers in 2008 [117]. Chemically modified graphene was used and exhibited specific capacitance of 135 F g -1 and 99 F g -1 in aqueous and organic electrolytes, respectively. Since then, intensive research efforts have been made to characterize graphene and graphene-based materials in supercapacitors applications [116, 130- 132]. Specific capacitance beyond 200 F g -1 has been achieved in both aqueous and organic electrolytes [131, 133-136], which is similar or even better to many carbon materials like porous activated carbon [137]. However, the low density of graphene limits the volumetric capacitance (F cm -3 ) which is a concern in most of applications, including micro devices [15]. Besides, restacking of graphene film still remains an issue limits the capacitance [138, 139]. Accordingly, efforts have been devoted to synthesize more compact but non-restacked graphene films. In 2013, D. Li’s group [134] proposed a method to develop dense graphene films by capillary compression of graphene gel film in the presence of a nonvolatile liquid electrolyte, where the presence of electrolyte between the layers prevents the restacking of graphene layers. As shown in Figure I – 22a, a flexible electrolyte-containing graphene film can be prepared by vacuum filtration and electrolyte immersion. The SEM images of the cross- sectional of the film (Figure I – 22b and c) presents a layer-by-layer structure, resulting in a high mass density (with a maximum density more than 1 g/cm 3 as shown in Figure I – 22d). Meanwhile, the
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