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Bhattacharya, Suchandra. "New catalytic applications of functionalized graphenes and metal embedded organic polymer." Thesis, University of North Bengal, 2020. http://ir.nbu.ac.in/handle/123456789/4363.
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Haberer-Gehrmann, Danny. "Electronic Properties of Functionalized Graphene Studied With Photoemission Spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-97417.
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Graphene, a two dimensional single layer of graphite, attracts a lot of attention of researchers around the globe due to its remarkable physical properties and application potential. The origin can thereby be found in the peculiar electronic structure since graphene is a zero gap semi-conductor with a linear energy dispersion in the vicinity of the Fermi level. Consequently, the charge carriers in graphene mimic massless Dirac Fermions which brings principles of quantum electrodynamics and exotic effects like Klein tunneling into a bench-top experiment. Modifying the electronic and/or crystal structure structure by functionalization might therefore as well lead to new tantalizing physical properties, novel compound materials based on graphene like graphane (fully hydrogenated graphene) or flourographene (fluorinated graphene), and ultimately new applications.
In this work, the influences on the electronic structure of graphene are investigated with photoemission spectroscopies after covalent functionalization by atomic hydrogen and ionic functionalization with potassium. Regarding hydrogenation, the formation of tunable bandgap is observed along with a full recovery of the electronic properties of graphene upon removing the hydrogen by thermal annealing. Using high resolution x-ray photoemission and molecular dynamics simulations, the formation of a C4H structure is predicted for substrate supported graphene at a saturation H-coverage of 25%, due to a preferential para- arrangement of hydrogen atoms. In fully electron doped, hydrogenated graphene the formation of dispersionless hydrogen impurity state is observed with angle-resolved photoemission spectroscopy. This flat state is extended over the whole Brillouin zone and according to calculations not localized. Potassium-doped graphene shows a similar doping level as its 3D parent component, the graphite intercalation compound KC8. Investigating the electron-phonon coupling in doped graphene, by direct derivation of the Eliashberg-function, shows an asymmetric coupling strength along the high-symmetry directions in the Brillouin Zone of graphene. In the K-M direction additional low energetic contributions could be identified which may originate from out-of-plane phonon modes. Regarding the electron-phonon-coupling strength of the high energy in-plane phonon modes a reasonable agreement with theoretical predictions is found.
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Bointon, Thomas H. "Graphene and functionalised graphene for flexible and optoelectric applications." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/17620.
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The landscape of consumer electronics has drastically changed over the last decade. Technological advances have led to the development of portable media devices, such as the iPod, smart phones and laptops. This has been achieved primarily through miniaturisation and using materials such as Lithium and Indium Tin Oxide (ITO) to increase energy density in batteries and as transparent electrodes for light emitting displays respectively. However, ten years on there are now new consumer demands, which are dictating the direction of research and new products are under constant development. Graphene is a promising next-generation material that was discovered in 2004. It is composed of a two-dimensional lattice made only from carbon. The atoms are arranged in a two atom basis hexagonal crystal structure which forms a fundamental building block of all sp2 hybrid forms of carbon. The production of large area graphene has a high cost, due to the long growth times and the high temperatures required. This is relevant as graphene is not viable compared to other transparent conductors which are produced on industrial scales for a fraction of the cost of graphene growth. Furthermore, graphene has a high intrinsic resistivity (2KW/_) which is three orders of magnitude greater than the current industry standard ITO. This limits the size of the electrodes as there is dissipation of energy across the electrode leading to inefficiency. Furthermore a potential drop occurs across the electrode leading to a non-uniform light emission when the electrode is used in a light emitting display. I investigate alternative methods of large area graphene growth with the aim of reducing the manufacturing costs, while maintaining the quality required for graphene human interface devices. Building on this I develop new fabrication methods for the production of large-area graphene devices which are flexible and transparent and show the first all graphene touch sensor. Focusing on the reducing the high resistivity of graphene using FeCl3 intercalation, while maintaining high optical transmission, I show low resistivity achieved using this process for microscopic graphene flakes, large-area graphene grown on silicon carbide and large-area graphene grown by CVD. Furthermore, I explore the stability of FeCl3 intercalated graphene and a process to transfer a material to arbitrary flexible substrates.
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Sapkota, Indra Prasad. "Tunable band gap in functionalized epitaxial graphene." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2013. http://digitalcommons.auctr.edu/dissertations/709.
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Graphene is a two-dimensional system consisting of a single planar layer of carbon atoms with hexagonal arrangement. Various approaches have been proposed to control its physical and electronic properties. Graphite intercalation compounds are materials formed by inserting molecular layers of compounds between stacked sheets of graphene. We have studied the physical and electronic responses of two graphene layers intercalated with gold cluster. Quasi free-standing graphene with Dirac fermion behavior has been recently demonstrated through gold intercalated epitaxial graphene. Herein, we investigate the electronic characteristics of gold-intercepted epitaxial graphene under a perpendicularly applied electric field. Evolution of the band structure of intercalated epitaxial graphene as a function of the bias is investigated by means of density-functional theory including interlayer van der Waals interactions. Our results indicate that goldintercalated epitaxial graphene can lead to tunable band gap with the applied bias, which is important for future device.
Hexagonal boron-nitride (fc-BN) is an ideal substrate for graphene due to its dielectric, insulating, and polarizing features. Our first-principles investigation reveals that the interaction of the /i-BN substrate with graphene induces a band gap. The zigzagedged graphene and /i-BN nanoribbon possess intrinsic half-metalicity, whereas the reconstructed edges with heptagonal and pentagonal alterations yield metallic states. The application of a transverse electric bias to a graphene boron nitride nanoribbon (GBNNR) promotes a transition from exhibiting semiconducting states to half metallic properties while GBNNR with reconstructed edges undergo transition from metallic to semiconducting properties.
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Lin, Ziyin. "Functionalized graphene for energy storage and conversion." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51871.
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Graphene has great potential for energy storage and conversion applications due to its outstanding electrical conductivity, large surface area and chemical stability. However, the pristine graphene offers unsatisfactory performance as a result of several intrinsic limitations such as aggregation and inertness. The functionalization of graphene is considered as a powerful way to modify the physical and chemical properties of graphene, and improve the material performance, which unfortunately still being preliminary and need further knowledge on controllable functionalization methods and the structure-property relationships. This thesis aims to provide in-depth understanding on these aspects. We firstly explored oxygen-functionalized graphene for supercapacitor electrodes. A mild solvothermal method was developed for graphene preparation from the reduction of graphene oxide; the solvent-dependent reduction kinetics is an interesting finding in this method that could be attributed to the solvent-graphene oxide interactions. Using the solvothermal method, oxygen-functionalized graphene with controlled density of oxygen functional groups was prepared by tuning the reduction time. The oxygen-containing groups, primarily phenols and quinones, reduce the graphene aggregation, improve the wetting properties and introduce the pseudocapacitance. Consequently, excellent supercapacitive performance was achieved.
Nitrogen-doped graphene was synthesized by the pyrolysis of graphene oxide with nitrogen-containing molecules and used as an electrocatalyst for oxygen reduction reactions. We achieved the structural control of the nitrogen-doped graphene, mainly the content of graphitic nitrogen, by manipulating the pyrolysis temperature and the structure of nitrogen-containing molecules; these experiments help understand the evolution of the bonding configurations of nitrogen dopants during pyrolysis. Superior catalytic activity of the prepared nitrogen-doped graphene was found, due to the enriched content of graphitic nitrogen that is most active for the oxygen reduction reaction.
Moreover, we demonstrated a facile strategy of producing superhydrophobic octadecylamine-functionalized graphite oxide films. The long hydrocarbon chain in octadecylamine reduces the surface energy of the graphene oxide film, resulting in a high water contact angle and low hysteresis. The reaction mechanism and the effect of hydrocarbon chain length were systematically investigated. In addition to the researches on graphene-based materials, some results on advanced carbon nanomaterials and polymer composites for electronic packaging will also be discussed as appendix to the thesis. These include carbon nanotube-based capacitive deionizer and gas sensor, and hexagonal boron nitride-epoxy composites for high thermal conductivity underfill.
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Plachinda, Pavel. "Electronic Properties and Structure of Functionalized Graphene." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/585.
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The trend over the last 50 years of down-scaling the silicon transistor to achieve faster computations has led to doubling of the number of transistors and computation speed over about every two years. However, this trend cannot be maintained due to the fundamental limitations of silicon as the main material for the semiconducting industry. Therefore, there is an active search for exploration of alternate materials. Among the possible candidates that can may [sic] be able to replace silicon is graphene which has recently gained the most attention. Unique properties of graphene include exceedingly high carrier mobility, tunable band gap, huge optical density of a monolayer, anomalous quantum Hall effect, and many others. To be suitable for microelectronic applications the material should be semiconductive, i.e. have a non-zero band gap. Pristine graphene is a semimetal, but by the virtue of doping the graphene surface with different molecules and radicals a band gap can be opened. Because the electronic properties of all materials are intimately related to their atomic structure, characterization of molecular and electronic structure of functionalizing groups is of high interest. The ab-inito (from the first principles) calculations provide a unique opportunity to study the influence of the dopants and thus allow exploration of the physical phenomena in functionalized graphene structures. This ability paves the road to probe the properties based on the intuitive structural information only. A great advantage of this approach lies in the opportunity for quick screening of various atomic structures. We conducted a series of ab-inito investigations of graphene functionalized with covalently and hapticly bound groups, and demonstrated possible practical usage of functionalized graphene for microelectronic and optical applications. This investigation showed that it is possible [to] produce band gaps in graphene (i.e., produce semiconducting graphene) of about 1 eV, without degrading the carrier mobility. This was archived by considering the influence of those adducts on electronic band structure and conductivity properties.
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Hewa-Bosthanthirige, Mihiri Shashikala. "Structural and electronics properties of noncovalently functionalized graphene." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2013. http://digitalcommons.auctr.edu/dissertations/1286.
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Recent experimental work has demonstrated production of quasi free-standing graphene by methane intercalation. The intercalation weakens the coupling of adjacent graphene layers and yields Dirac fermion behaviour of monolayer graphene. We have investigated the electronic characteristics of methane intercepted graphene bilayer under a perpendicularly applied electric field. Evolution of the band structure of intercalated graphene as a function of the bias is studied by means of density-functional theory including interlayer van der Waals interactions. The implications of controllable band gap opening in methane-intercalated graphene for future device applications are discussed.
Noncovalent functionalization provides an effective way to modulate the electronic properties of graphene. Recent experimental work has demonstrated that hybrids of dipolar phototransductive molecules tethered to graphene are reversibly tunable in doping. We have studied the electronic structure characteristics of chromophore/graphene hybrids using dispersion-corrected density functional theory. The Dirac point of noncovalently functionalized graphene shifts upward via cis-trans isomerism, which is attributed to a change in the chromophore's dipole moment. Our calculation results reveal that the experimentally observed reversible doping of graphene is attributed to the change in charge transfer between the light-switchable chromophore and graphene via isomerization. Furthermore, we show that by varying the electric field perpendicular to the supramolecular functionalized graphene, additional tailoring of graphene doping can be accomplished.
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Pham, Van Dong. "STM characterization of functionalized carbon nanotubes and graphene." Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC245.
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Dans cette thèse, nous avons étudié l'interaction entre des molécules organiques et des nanomatériaux de carbone. En utilisant un microscope à effet tunnel (STM) à basse température et sous ultra-vide, nous avons mesuré les propriétés de molécules de porphyrine physisorbées sur du graphène ou des nanotubes de carbone. Nous avons d'abord étudié l'injection d'électrons dans le graphène sur des défauts (joints de grains et atomes d'azote insérés). Une étude d'états image résonants nous a également permis de mettre en évidence une variation locale du travail de sorite dans le graphène dopé. Nous avons ensuite étudié les propriétés de molécules de porphyrine (H2TPP) adsorbées sur une surface Au(111). En utilisant la pointe du microscope nous avons induit des réactions de tautomérisation et de déshydrogénation et montré comment cela modifie les états moléculaires et l'interaction molécule-surface. Nous avons ensuite étudié l'interaction du graphène avec des molécules de porphyrine. Nous avons montré que le couplage électronique est faible entre les molécules et le graphène. Nous avons ensuite montré comment un atome d'azote inséré dans le réseau de carbone du graphène modifie l'interaction molécule-surface. Une diminution de l'énergie des états moléculaires au niveau des sites dopants révèle un transfert de charge partiel entre les sites d'azote et les molécules. Dans la dernière partie, nous avons étudié les propriétés de nanotubes de carbone monoparois fonctionnalisés par un polymère de porphyrine. Les mesures ont révélé que le polymère couvre partiellement les nanotubes. La spectroscopie locale a indiqué que la densité d'états locale est modifiée au niveau du polymèreIn this thesis we studied the interaction between organic molecules and carbon nanomaterials. Using scanning tunneling microscopy (STM) at low temperature and in ultra-high vacuum, we measured the properties of porphyrin molecules at the surface of graphene and single-walled carbon nanotubes. We first studied electron injection in graphene at defect sites (grain boundaries and nitrogen doping atoms). Using image-potential states, we evidenced the variation of local work function in doped graphene. Secondly, we investigated the properties of free-base porphyrin (H2TPP) molecules adsorbed on a Au(111) surface. We performed tip-induced tautomerization and dehydrogenation of the molecules, and revealed how these operations modify the molecular states and molecule-substrate interaction. Following these two preliminary studies, we studied the interaction of graphene with porphyrin molecules. We evidenced a weak electronic coupling between the molecules and graphene. We then showed how a nitrogen dopant on doped graphene can tune the molecule-surface interaction. The comparison between molecules adsorbed on nitrogen doping sites with those adsorbed on carbon sites clearly reveals a downshift of the energy of the molecular states at the doping sites. This downshift reveals a partial electron transfer from the nitrogen sites of graphene to the adsorbed molecules. In the last part of this thesis, we studied the properties of single-walled carbon nanotubes functionalized with a porphyrin polymer. The STM measurements revealed that the polymer is partially covering the nanotubes. Local spectroscopy indicated that the local density of states are modified at the polymer location
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Arbuzov, A. A., V. E. Muradyan, B. P. Tarasov, and E. A. Sokolov. "Preparation of Amino-Functionalized Graphene Sheets and their Conductive Properties." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35639.
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Amino-functionalized graphene sheets were prepared through chemical reduction by hydrazine hy-drate, amination or amidation of graphite oxide. For amination of graphite oxide were used polyamine such as ethylenediamine, diethylenetriamine and triethylenetetramine. Addition of amine groups to graphene is identified by Fourier transform infrared spectroscopy, Raman spectroscopy, elemental analysis and ther-mogravimetry. Scanning electron microscopy data indicate that the organic amine is not only as nitrogen sources to obtain the nitrogen-doped graphene but also as an important modification to control the assem-bly of graphene sheets in the 3D structures. The electrical conductivity of the materials obtained by amina-tion and amidation of graphene is much smaller than that of reduced graphite oxide.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35639
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Jeon, Intak. "Synthesis of functionalized few layer graphene via electrochemical expansion." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101797.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 59-62).
Single layer graphene is a nearly transparent two-dimensional honeycomb sp2 hybridized carbon lattice, and has received immense attention for its potential application in next-generation electronic devices, composite materials, and energy storage devices. This attention is a result of its desirable and intriguing electrical, mechanical, and chemical properties. However, mass production of high-quality, solution-processable graphene via a simple low-cost method remains a major challenge. Recently, electrochemical exfoliation of graphite has attracted attention as an easy, fast, and environmentally friendly approach to the production of high-quality graphene. This route solution phase approach complements the original micromechanical cleavage production of high quality graphite samples and also involved a chemically activated intermediate state that facilitates functionalization. In this thesis we demonstrate a highly efficient electrochemical exfoliation of graphite in organic solvent containing tetraalkylammonium salts, avoiding oxidation of graphene and the associated defect generation encountered with the broadly used Hummer's method. The expansion and charging of the graphite by intercalation of cations facilitates the functionalization of the graphene basal surfaces. Electrochemically enhanced diazonium functionalization of the expanded graphite was performed. The exfoliated graphene platelets were analyzed by Raman spectroscopy, to quantify defect states and the degree of exfoliation. Additional microscopy techniques provided additional insight into the chemical state and structure of the graphene sheets.
by Intak Jeon.
S.M.
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Nanayakkara, Tharanga Ranjan. "Electronic properties of nitrophenyl functionalized graphene and boron nanotubes." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2015. http://digitalcommons.auctr.edu/dissertations/3105.
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We have studied the electronic characteristics of covalently functionalized graphene by nitrophenol groups using first-principles density-functional theory calculations. The nitrophenyl functionalization leads to a band gap opening in graphene and transition from a semi-metallic to semiconducting state. The induced gap is shown to be attributed to the modification of the π-conjugation that depends on the configuration for a pair of monovalent adsorption. A detailed analysis reveals that this intriguing magnetism modulation by strain stems from the redistribution of spin-polarized electrons induced by local lattice distortions. A detailed analysis suggests a sensitive and effective way to tailor properties of graphene for future applications in nanoscale devices.
The quest for low-dimensional boron structures has been motivated by the potential applications of light-weight materials. Recently, a semi-metallic two-dimensional boron allotrope was predicted via ab initio evolutionary structure search, which is markedly lower in energy than the planar structures composed of triangular motifs and hexagonal holes. The emergence of a Dirac cone in the band structure demonstrates an intriguing perspective for quasiplanar counterpart of graphene. We studied the corresponding single walled boron nanotubes derived from the quasiplanar boron structure. In particular, our results are identified to have a Dirac cone, as well. The buckling and coupling between the two sublattices not only enhance the stability, but also are key factors to the emergence of the Dirac cone.
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Zhao, Mali. "Electronic Properties of Graphene Functionalized with 2D Molecular Assemblies." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS013.
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Le graphène a des propriétés électroniques et mécaniques extraordinaires en raison de sa structure de bande linéaire. Toutefois, l'absence d’une bande interdite limite l’utilisation du graphène dans les dispositifs électroniques. Ajuster la bande interdite de graphène permettrait un contrôle précis des porteurs de charge. Une solution prometteuse consiste à modifier le graphène par des briques élémentaires de molécules organiques. Les molécules organiques avec un ion métallique (métal-porphyrine et métal-phtalocyanine) sont des candidats potentiels en raison de leur structure robuste et de leurs propriétés de charge et de spin qui peuvent être modulées. Dans cette thèse, le graphène a été préparé par la sublimation d’atomes de Si sur les faces de Si et de C- du substrat SiC. Trois molécules qui transportent l'information de spin différents ont été étudiés avec le STM. A travers des collaborateurs les calculs DFT, nous apporte des informations complémentaires. La première molécule utilisée dans notre expérience est la phtalocyanine de Ni (NiPc). L'ion Ni²⁺ a une configuration d'électrons 3d⁸ avec au état de spin de 0. La seconde molécule est la tétraphénylporphyrine de Pt (PtTPP (CO₂Me)₄). L'ion Pt²⁺ montre également une configuration d'électrons 3d8 à un état de spin de zéro. Cependant, l'atome Pt est plus lourd que celui du Ni. Promettant des effets spin orbite plus importants. La troisième molécule est tétraphénylporphyrine de fer (III) chlorure (FeTPPCl). Le Fe³⁺ est dans l'état haut spin (S = 5/2). Chacune de ces trois molécules forment un réseau moléculaire carré bien ordonné sur le graphène. Les directions de réseau moléculaires sont dominées par la symétrie du graphène, tandis que les orientations moléculaires dépendent des interactions inter moléculaires. Les couplages électroniques entre chaque molécule et le graphène sont transmis par la force de Van der Waals, qui donne lieu à des interfaces capacitifs entre la couche de graphène et les molécules. Les interactions électroniques entre les molécules FeTPP et graphène sont plus fortes que celles entre NiPc ou PtTPP et le graphène. Les études des molécules organiques avec adsorbées sur le graphène des spins différents a le potentiel d’ouvrir la voie à l'application de l'interface organométallique molécules/ graphène dans les dispositifs de spintroniqueGraphene has extraordinary properties because of its linear band structure and zero band gap. However, the lack of a band gap hinders the implementation of graphene in electronics; tuning the band gap of graphene would enable a precise control of the charge carriers. One of the promising solutions is to modify graphene with organic molecular building blocks. Organic molecules with a metal ion (metal- porphyrin, metal- phthalocyanine) are potential candidates, because of their robust structure and the fact that their charge and spin properties can be tuned. In this thesis, graphene was prepared by sublimating Si atoms from both Si and C- terminated SiC substrates. Three molecules which carry different spin information were studied by STM experiments. Through collaborations, DFT calculations were used to improve our understanding of the molecule- graphene interaction.The first molecule used in our experiment is Ni- phthalocyanine (NiPc). The Ni²⁺ ion has a 3d⁸ electron configuration, giving a spin- state of 0. The second molecule is Pt- tetraphenylporphyrin (PtTPP(CO₂Me)₄). The Pt²⁺ ion also shows a d8 electron configuration with a spin state of zero. However, the Pt atom is heavier than Ni, which should increase the spin- orbit effects. The third molecule is tetraphenylporphyrin iron(III) chloride (Fe(TPP)Cl). The Fe³⁺ in Fe(TPP)Cl is stable in the high spin state (S=5/2). These three molecules each form well- ordered nearly square lattice molecular networks on graphene. The molecular lattice directions are dominated by the graphene symmetry, while the molecular orientations depend on the molecule- molecule interactions. The electronic couplings between each of three molecules and graphene are via the Van der Waals forces, which gives rise to the capacitive molecular- layer/ graphene interfaces. The electronic interactions between FeTPP molecules and graphene are stronger than those between NiPc or PtTPP molecules and graphene. The studies of the organic molecules with different spin information on the graphene has the potential to pave the way for the application of organometallic molecules/graphene interface in spintronic devices
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Penmatsa, Varun. "Functionalized Carbon Micro/Nanostructures for Biomolecular Detection." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/739.
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Advancements in the micro-and nano-scale fabrication techniques have opened up new avenues for the development of portable, scalable and easier-to-use biosensors. Over the last few years, electrodes made of carbon have been widely used as sensing units in biosensors due to their attractive physiochemical properties. The aim of this research is to investigate different strategies to develop functionalized high surface carbon micro/nano-structures for electrochemical and biosensing devices.
High aspect ratio three-dimensional carbon microarrays were fabricated via carbon microelectromechanical systems (C-MEMS) technique, which is based on pyrolyzing pre-patterned organic photoresist polymers. To further increase the surface area of the carbon microstructures, surface porosity was introduced by two strategies, i.e. (i) using F127 as porogen and (ii) oxygen reactive ion etch (RIE) treatment. Electrochemical characterization showed that porous carbon thin film electrodes prepared by using F127 as porogen had an effective surface area (Aeff 185%) compared to the conventional carbon electrode.
To achieve enhanced electrochemical sensitivity for C-MEMS based functional devices, graphene was conformally coated onto high aspect ratio three-dimensional (3D) carbon micropillar arrays using electrostatic spray deposition (ESD) technique. The amperometric response of graphene/carbon micropillar electrode arrays exhibited higher electrochemical activity, improved charge transfer and a linear response towards H2O2 detection between 250μM to 5.5mM.
Furthermore, carbon structures with dimensions from 50 nano-to micrometer level have been fabricated by pyrolyzing photo-nanoimprint lithography patterned organic resist polymer. Microstructure, elemental composition and resistivity characterization of the carbon nanostructures produced by this process were very similar to conventional photoresist derived carbon. Surface functionalization of the carbon nanostructures was performed using direct amination technique.
Considering the need for requisite functional groups to covalently attach bioreceptors on the carbon surface for biomolecule detection, different oxidation techniques were compared to study the types of carbon–oxygen groups formed on the surface and their percentages with respect to different oxidation pretreatment times.
Finally, a label-free detection strategy using signaling aptamer/protein binding complex for platelet-derived growth factor oncoprotein detection on functionalized three-dimensional carbon microarrays platform was demonstrated. The sensor showed near linear relationship between the relative fluorescence difference and protein concentration even in the sub-nanomolar range with an excellent detection limit of 5 pmol.
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Moraes, Ana Carolina Mazarin de 1983. "Graphene oxide and graphene oxide functionalized with silver nanoparticles : antibacterial activity and polymeric composites applications." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249034.
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Orientador: Oswaldo Luiz AlvesTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: O óxido de grafeno (GO) é uma forma quimicamente modificada de grafeno que possui grupos funcionais contendo oxigênio (epóxi, carboxila, carbonila, e hidroxila) distribuídos sobre a base e as bordas de suas folhas. Devido à abundância dos grupamentos oxigenados, o GO tem sido usado como uma plataforma para suportar e estabilizar nanoestruturas metálicas, tais como nanopartículas de prata (NPAgs), visando aplicações biológicas. Além disso, devido à sua excelente capacidade de dispersão e elevada área superficial, o GO tem sido considerado uma carga promissora para a construção de compósitos poliméricos. Neste trabalho, relatamos a síntese do GO e dos nanocompósitos de óxido de grafeno funcionalizado com NPAgs (GO-Ag) os quais podem ser utilizados como agentes antibacterianos de amplo espectro. O GO foi sintetizado por meio do método de Hummers modificado, e o GO-Ag foi preparado através da redução in situ dos íons de prata por citrato de sódio. As folhas de GO foram funcionalizadas com NPAgs esféricas de diâmetro médio de 9,4 nm. Estes nanocompósitos exibiram excelente atividade antimicrobiana contra as principais bactérias em ambiente hospitalar, tais como Escherichia coli, Enterococcus faecalis, Acinetobacter baumannii, e Staphylococcus aureus resistente à meticilina. Os nanocompósitos GO-Ag também foram aplicados como eficazes agentes antimicrobianos a fim de evitar a proliferação bacteriana em membranas de micro e ultrafiltração. Neste sentido, membranas antimicrobianas de acetato de celulose (CA) foram fabricadas a partir da incorporação de GO e GO-Ag na matriz polimérica (CA-GOAg). Após a funcionalização, as membranas permeáveis modificadas com GO-Ag foram capazes de inativar cerca de 90% das células de E. coli em comparação com as membranas de CA não modificadas. Os resultados sugerem que a incorporação de nanocompósitos GO-Ag é uma abordagem promissora para controlar o desenvolvimento da adesão bacteriana em membranas de purificação de água. Com relação à demanda de novos materiais com elevada estabilidade e com capacidade de proteção contra radiação ultravioleta (UV), foram fabricados filmes compósitos transparentes a partir de acetato de celulose e óxido de grafeno. A caracterização físico-química revelou que as folhas de GO estão bem dispersas por toda a matriz polimérica, proporcionando filmes compósitos lisos e homogêneos. Em comparação com os filmes pristinos de CA, os filmes compósitos exibiram melhor capacidade de proteção contra radiação UV combinado com transparência óptica à luz visível, o que reforça a sua aplicação como revestimentos transparentes com proteção UV para alimentos, produtos farmacêuticos, biomédicos, e produtos eletrônicos
Abstract: Graphene oxide (GO) is a chemically modified form of graphene that possesses oxygen-containing groups (epoxy, carboxyl, carbonyl, and hydroxyl) distributed on the plane and edges of the sheets. Owing to the abundance of oxygenated groups, GO has been used as a platform to support and stabilize metallic nanostructures such as silver nanoparticles (AgNPs), aiming biological applications. In addition, GO has been considered a promising material for building polymeric composites because of its excellent dispersibility and high surface area. In this work, we report the synthesis of GO and GO functionalized with AgNPs (GO-Ag) for use as a broad-spectrum antibacterial agent. GO was synthesized through the modified Hummers method, and the GO-Ag was prepared through the in situ reduction of silver ions by sodium citrate. Spherical AgNPs with average size of 9.4 nm were found well-dispersed throughout the GO sheets. This nanocomposite exhibited excellent antimicrobial activity against common nosocomial bacteria such as Escherichia coli, Enterococcus faecalis, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus. GO-Ag nanocomposites were also applied as an effective antimicrobial agent in order to prevent the bacterial proliferation on micro and ultrafiltration membranes. Cellulose acetate (CA) membranes were then fabricated from the incorporation of GO and GO-Ag into the polymeric matrix (CA-GOAg). After functionalization, the permeable CA membranes modified with GO-Ag were able to inactivate mostly 90% of E. coli cells compared to the non-modified CA membranes. The results suggest that the incorporation of GO-Ag nanocomposites is a promising approach to control biofouling development in water purification membranes. Concerning the demand for novel ultraviolet shielding materials with high stability, transparent and UV-shielding composite films were fabricated by casting a mixture of GO with cellulose acetate (CA). The physicochemical characterization revealed that GO sheets were well-dispersed throughout the polymeric matrix, providing smooth and homogeneous composite films. By comparison with pristine CA films, the composite films displayed an improved UV-shielding capacity combined with optical transparency under visible light, which underscores their application as transparent UV-protective coatings for food, pharmaceutical, biomedical, and electronic products
Doutorado
Quimica Inorganica
Doutora em Ciências
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Woo, Heechul. "The selective low cost gas sensor based on functionalized graphene." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX050/document.
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Les progrès récents dans les nanomatériaux présentent un fort potentiel pour la réalisation de capteurs de gaz avec de nombreux avantages tels que : la grande sensibilité de détection de molécule unique, le faible coût et la faible consommation d'énergie. Le graphène, isolé en 2004, est l'un des meilleurs candidats prometteurs pour le développement de futurs nanocapteurs en raison de sa structure à deux dimensions, sa conductivité élevée et sa grande surface spécifique. Chaque atome de la monocouche de graphène peut être considéré comme un atome de surface, capable d'interagir même avec une seule molécule de l'espèce gazeuse ou de vapeur cible, ce qui conduit finalement à un capteur ultrasensible.Dans cette thèse, des composants à base de graphène ont été fabriqués et caractérisés. Les films de graphène ont été synthétisés par dépôt chimique à phase vapeur (CVD) sur des substrats de verre. La spectroscopie Raman a été utilisée pour analyser la qualité et le nombre de couches de graphène. La microscope à force atomique (AFM) et la microscopie électronique à balayage (MEB) ont été également réalisées pour analyser la qualité du graphène. Après la caractérisation de couches de graphène, des dispositifs résistifs à base de graphène ont été fabriquées : quatre électrodes identiques ont été évaporées thermiquement et directement sur le film de graphène comme des électrodes métalliques. La caractérisation électrique a été réalisée à l'aide de Keithley-4200.La réponse de dispositif Intrinsèque a été étudiée sous différents conditions (pression, humidité, exposition à la lumière). Le dispositif a été fonctionnalisé de manière non covalente avec le complexe organométallique (Ru (II) trisbipyridine) et son effet sous exposition à la lumière a été étudié. La réponse de dispositif était reproductible même après de nombreux cycles en présence et en absence de la lumière. Les approches théoriques et expérimentales ainsi que les résultats obtenus au cours de cette thèse ouvrent un moyen de comprendre et de fabriquer des futurs dispositifs de détection de gaz à base du graphène fonctionnalisé de manière non covalenteRecent advances in nanomaterials provided a strong potential to create a gas sensor with many advantages such as high sensitivity of single molecule detection, low cost, and low power consumption. Graphene, isolated in 2004, is one of the best promising candidate for the future development of nanosensors applications because of its atom-thick, two-dimensional structures, high conductivity, and large specific surface areas. Every atom of a monolayer graphene can be considered as a surface atom, capable of interacting even with a single molecule of the target gas or vapor species, which eventually results in the ultrasensitive sensor response.In this thesis work, graphene films were synthesized by Chemical Vapor Deposition (CVD) on the glass substrate. Raman spectroscopy was used to analyze the quality and number of layers of graphene. Atomic Force Microscope (AFM) and Scanning Electron Microscopy (SEM) were also performed to analyze the quality of graphene. After the characterization of graphene films, graphene based resistive devices (four identical electrodes are thermally evaporated directly onto the graphene film as metal electrodes) were fabricated. The electrical characterization has been carried out using Keithley-4200.Intrinsic device response was studied with different external condition changes (pressure, humidity, light illumination). The device was non-covalently functionalized with organometallic complex (Ru(II) trisbipyridine) and the its light exposure response was studied. The observed device response was reproducible and similar after many cycles of on and off operations. The theoretical and experimental approaches and the results obtained during the thesis are opening up a way to understand and fabricate future gas sensing devices based on the non-covalentely functionalized graphene
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Tobias, Völkl [Verfasser], and Jonathan [Akademischer Betreuer] Eroms. "Spin-Orbit Coupling in Functionalized Graphene / Völkl Tobias ; Betreuer: Jonathan Eroms." Regensburg : Universitätsbibliothek Regensburg, 2021. http://d-nb.info/1240901801/34.
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Suggs, Kelvin L. "Tunable Electronic Properties of Chemically Functionalized Graphene and Atomic-Scale Catalytics." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2015. http://digitalcommons.auctr.edu/cauetds/17.
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In this dissertation we discuss the electronic properties, structural configurations, and reaction mechanisms of chemically functionalized graphene and charged atomic metals. In general, we analyze fundamental atomic scale and nanoscale systems with density functional theory in order to investigate chemical reaction energetics for peroxide synthesis as well as methanol production without carbon emission. These systems were found to be tunable via the addition of cationic and anionic charges, change in transition metal type, and modification through chemical functionalization. Furthermore, transition state theory was used to predict an optimal configuration for chemically functionalized graphene, efficient use of anionic atomic gold and palladium for synthesis of water to peroxide, and clean conversion of methane to methanol without carbon dioxide emission utilizing anionic gold.
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Li, Yuan. "New functionalized graphene nanocomposites for applications in energy storage and catalysis." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN025.
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Matériaux à base de graphène et d’oxyde de graphène ont attiré une grande attention depuis sa découverte. Cependant, comme la feuille de graphène a une surface spécifique élevée, il tend à former un agglomérat irréversible ou même empiler pour former le graphite par π-π empilage et Van-der Waals interactions. Les modifications doivent être faites pour séparer les feuilles de graphène sans apporter trop de dégâts dans sa structure aromatique. Dans cette thèse, nous avons lancé deux méthodes pour faire la modification du graphène, réaction de substitution nucléophile pour l’oxyde de graphène avec un C/O ~ 2 (FGS2), tandis que la demande électronique inverse réaction de Diels-Alder pour l’oxyde de graphène avec un très faible teneur en oxygène C/O ~ 20 (FGS20). Comme dans le second cas, FGS20 fonctionnalisés par tetrazine possède une excellente conductivité, il a été en outre combiné avec un polypyrrole pour fabriquer un matériau de supercondensateur.Dans le chapitre 2, nous avons greffé de manière covalente des dérivés de tétrazine à l'oxyde de graphène par substitution nucléophile. Comme l'unité de tétrazine est électroactif et riche en azote, avec un potentiel de réduction sensible du type de substituant et degré de substitution, nous avons utilisé l'électrochimie et la spectroscopie de photoélectrons X pour démontrer des preuves claires pour le greffage par liaison covalente. La modification chimique a été soutenue par spectroscopie infrarouge à transformée de Fourier et analyse thermique. Tétrazines greffé sur l'oxyde de graphène affichent différentes pertes de masse par rapport à graphène non modifiée et sont plus stables que les précurseurs moléculaires. Enfin, un dérivé de pontage tétrazine a été greffée entre des feuilles d'oxyde de graphène pour démontrer que la distance de séparation entre les feuilles peut être maintenue lors de la conception de nouveaux matériaux à base de graphène, y compris les structures d'oxydo-réduction chimiquement liés, les structures d'oxydoréduction.Dans le chapitre 3, des molécules modèles de graphène ont été sélectionnés afin de déterminer les conditions optimales de réaction entre graphène et tétrazine dérivés. Toutes les molécules de tétrazine ont d'abord été étudiés par électrochimie et ensuite mis à réagir avec le graphène par la demande électronique inverse Diels-Alder (DAinv) réaction dans un réacteur à micro-ondes, la XPS a été réalisée pour étudier sa composition chimique et de prouver la modification avec succès du graphène. Ensuite, le matériau de graphène tétrazine fonctionnalisé a été appliqué sur une électrode en acier inoxydable et ses performances électrochimiques ont été évaluées par voltamétrie cyclique et les tests de charge-décharge. La plupart des tétrazine modifié matériaux de graphène a montré de très bonnes performances électrochimiques et une faible résistance due à une bonne accessibilité des ions, ce qui en fait l'un des matériaux d'électrodes les plus prometteuses pour les supercondensateurs jusqu'à présent. Dans le chapitre 4, polypyrrole (PPy)-graphène nanocomposites ont été synthétisés par polymérisation de PPy sur les feuilles de graphène fonctionnalisés par tétrazine. Le matériau de graphène modifié contient des unités pyridazine tel que démontré par XPS. Puis PPy a été déposé sur ce matériau de graphène fonctionnalisé soit par polymérisation chimique ou électrochimique. Cellules de pièces symétriques ont été faites pour mesurer la capacité dans une configuration à deux électrodes. Les nanocomposites de polypyrrole-graphène avec 40% PPy présentent les meilleures performances électrochimiques et une faible résistance en raison d'une bonne accessibilité des ions, ce qui en fait l'un des meilleurs matériaux d'électrodes pour supercapacitor jusqu'à présentGraphene and graphene oxide based materials have attracted great attention since its discovery. However, as graphene sheet has a high specific surface area, it tends to form an irreversible agglomerates or even restack to form graphite through π–π stacking and van-der Waals interactions. Modifications need to be done to separate graphene sheets without bringing too much damage in its aromatic structure.In this thesis, two methods have been introduced to do the modification of graphene, nucleophilic substitution reaction for graphene oxide with a C/O~2 (FGS2), while inverse electron demand Diels-Alder reaction for graphene oxide with a very low oxygen content C/O~20 (FGS20). As in the latter case, tetrazine functionalized FGS20 has excellent conductivity, it has been further combined with polypyrrole to fabricate supercapacitor material.In chapter 2, we have covalently grafted tetrazine derivatives to graphene oxide through nucleophilic substitution. Since the tetrazine unit is electroactive and nitrogen-rich, with a reduction potential sensitive to the type of substituent and degree of substitution, we used electrochemistry and X-ray photoelectron spectroscopy to demonstrate clear evidence for grafting through covalent bonding. Chemical modification was supported by Fourier transform infrared spectroscopy and thermal analysis. Tetrazines grafted onto graphene oxide displayed different mass losses compared to unmodified graphene and were more stable than the molecular precursors. Finally, a bridging tetrazine derivative was grafted between sheets of graphene oxide to demonstrate that the separation distance between sheets can be maintained while designing new graphene-based materials, including chemically bound, redox structures.In chapter 3, model molecules of graphene were selected to determine the optimal reaction conditions between graphene and tetrazine derivatives. All tetrazine molecules were firstly studied by electrochemistry and then reacted with graphene through inverse electron demand Diels-Alder (DAinv) reaction in microwave reactor, X-ray photoelectron spectroscopy was carried out to study its chemical composition and prove the successfully modification of graphene. Then the tetrazine functionalized graphene material was coated on a Stainless Steel electrode and its electrochemical performances were assessed by cyclic voltammetry and charge-discharge experiments. Most of the tetrazine modified graphene materials showed very good electrochemical performance and a small resistance due to a good ion accessibility, which makes it one of the most promising electrode materials for supercapacitors so far.In chapter 4, polypyrrole (PPy)-graphene sheet nanocomposites have been synthesized by both chemical and in situ electrochemical polymerization of PPy on tetrazine derivatives functionalized graphene sheets. The modified graphene material contains pyridazine units as demonstrated by XPS. Then PPy was deposited on this functionalized graphene material either by chemical or electrochemical polymerization. Symmetrical coin cells were made to measure the capacitance in a two-electrode configuration. Polypyrrole-graphene nanocomposites with 40% PPy show the best electrochemical performances, with a very large capacitance per weight (326 F g-1 at 0.5 A g-1 and 250 F g-1 at 2 A g-1) and a small resistance due to a good ion accessibility, which makes it one of the best electrode materials for supercapacitors so far
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Shah, Rakesh K. "Enhancements of Mechanical, Thermal Stability, and Tribological Properties by Addition of Functionalized Reduced Graphene Oxide in Epoxy." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699889/.
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The effects of octadecylamine-functionalized reduced graphene oxide (FRGO) on the frictional and wear properties of diglycidylether of bisphenol-A (DGEBA) epoxy are studied using a pin-on-disk tribometer. It was observed that the addition of FRGO significantly improves the tribological, mechanical, and thermal properties of epoxy matrix. Graphene oxide (GO) was functionalized with octadecylamine (ODA), and then reduction of oxygen-containing functional groups was carried out using hydrazine monohydrate. The Raman and x-ray photoelectron spectroscopy studies confirm significant reduction in oxygen-containing functional groups and formation of ODA functionalized reduced GO. The nanocomposites are prepared by adding 0.1, 0.2, 0.5 and 1.0 wt % of FRGO to the epoxy. The addition of FRGO increases by more than an order of magnitude the sliding distance during which the dynamic friction is ≤ 0.1. After this distance, the friction sharply increases to the range of 0.4 - 0.5. We explain the increase in sliding distance during which the friction is low by formation of a transfer film from the nanocomposite to the counterface. The wear rates in the low and high friction regimes are approximately 1.5 x 10-4 mm3/N·m and 5.5 x 10-4 mm3/N·m, respectively. The nanocomposites exhibit a 74 % increase in Young’s modulus with 0.5 wt. % of FRGO, and an increase in glass transition and thermal degradation temperatures.
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Xia, Chao. "Characterizations of as grown and functionalized epitaxial grapheneg rown on SiC surfaces." Doctoral thesis, Linköpings universitet, Halvledarmaterial, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120893.
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The superior electronic and mechanical properties of Graphene have promoted graphene to become one of the most promising candidates for next generation of electronic devices. Epitaxial growth of graphene by sublimation of Si from Silicon Carbide (SiC) substrates avoids the hazardous transfer process for large scale fabrication of graphene based electronic devices. Moreover, the operation conditions can potentially be extended to high temperatures, voltages and frequencies. This thesis is focused on characterizations of as grown and functionalized epitaxial graphene grown on both Si-face and C-face SiC. Synchrotron radiation-based techniques are employed for detailed investigations of the electronic properties and surface morphology of as grown and functionalized graphene. Large area and homogeneous monolayer (ML) graphene has been possible to grow on SiC(0001) substrates by sublimation, but efforts to obtain multilayer graphene of similar quality have been in vain. A study of the transport behavior of silicon atoms through carbon layers was therefore performed for the purpose to gain a better understanding of the growth mechanism of graphene on Si-face SiC. It showed that a temperature of about 800°C is required for Si intercalation into the interface to take place. Intercalation of Si was found to occur only via defects and domain boundaries which probably is the reason to the limited growth of multilayer graphene. Annealing at 1000-1100°C induced formation of SiC on the surface and after annealing above 1200°C Si started to de-intercalate and desorb/sublimate. Different alkali metals were found to affect graphene grown in SiC quite differently. Li started to intercalate already at room temperature by creating cracks and defects, while K, Rb and Cs were found unable to intercalate into the graphene/SiC interface. Effects induced by the alkali metal Na on graphene grown on both Si-face and C-face SiC were therefore studies. For the Si-face, partial intercalation of Na through graphene was observed on both 1 ML and 2 ML areas directly after Na deposition. Annealing at a temperature of about 75°C strongly promoted Na intercalation at the interface. The intercalation was confirmed to start at domain boundaries between 1 ML and 2 ML areas and at stripes/streaks on the 1 ML areas. Higher annealing temperature resulted in desorption of Na from the sample surface. Also for C-face graphene, a strong n-type doping was observed directly after Na deposition. Annealing at temperatures from around 120 to 300 °C was here found to result in a considerable π-band broadening, interpreted to indicate penetration of Na in between the graphene layers and at the graphene SiC interface. The thermal stability of graphene based electronic devices can depend on the choice of contact material. Studies of the stability and effects induced by two commonly used metals (Pt and Al) on Si-face graphene were carried out after deposition and after subsequent annealing at different temperatures. Both Al and Pt were found to be good contact materials at room temperature. Annealing at respectively ~400 ºC and ~ 800 ºC was found to trigger intercalation of Al and Pt into the graphene/SiC interface, and induce quasi-free-standing bilayer electronic properties. Contacts of Pt can thus withstand higher temperatures than Al contacts. For Al inhomogeneous islands of different ordered phases were observed to form on the surface during annealing, while this was not the case for Pt. The initial single π-band structure was in the Al case restored after annealing at ~1200 ºC although some Al remained detectable from the sample. For Pt, the bilayer graphene electronic properties induced by intercalation were thermally stable up to 1200ºC. In the case of Al the stability and effects induced on C-face graphene were also investigated for comparison, and significant differences were revealed. An ordered Al-Si-C compound was found to form after annealing at temperatures between ca. 500ºC and 700ºC. Formation of this compound was accompanied with a large reduction of graphene in the surface region. Annealing at temperatures above 800°C resulted in a gradual decomposition of this compound and regrowth of graphene. No Al signal could be detected after annealing C-face graphene at 1000°C. Graphene grown on C-face SiC has attracted high interest since its mobility has been reported to be one order of magnitude higher compared to Si-face graphene. C-face graphene has moreover been claimed to be fundamentally different compared to Si-face graphene. A rotational disorder between adjacent graphene layers has been suggested that effectively decouples the graphene layers and result in monolayer electronic properties of multilayer C-face graphene. The domain/grain size is typically much smaller for C-face graphene and the number of graphene layers less uniform than on Si-face graphene. Using LEEM and micro-LEED we showed that there is no rotational disorder between adjacent layers within the domains/grains but that they had different azimuthal orientations. Using nano-APRES, we recently also revealed that multilayer Cface graphene show multiple π-bands and Bernal stacking, similar to multilayer Si-face graphene.
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Morelli, Laura. "Study of graphene-based gas sensors functionalized with gold nanoparticles for NO2 detection." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17577/.
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Obiettivo della tesi è la ricerca di un metodo volto a migliorare le attuali prestazioni dei sensori di gas realizzati in grafene. Negli ultimi anni il grafene ha attirato particolare attenzione nel campo dei sensori di gas. Tuttavia, l’utilizzo del grafene presenta limitazioni che rendono difficile lo sviluppo di sensori utilizzabili commercialmente. Tra queste, la mancanza di selettività, nonché la difficoltà del segnale a raggiungere la saturazione e a ritornare al livello iniziale durante la fase di ripristino, rappresentano i maggiori ostacoli. La funzionalizzazione del grafene risulta essere tra i metodi più promettenti per rimediare alle predette limitazioni. Nella tesi, l’oggetto della ricerca è un resistore chimico, il cui materiale sensibile è costituito da grafene multi-strato realizzato tramite deposizione chimica da fase vapore. Il processo di funzionalizzazione scelto si basa sulla deposizione di nanoparticelle di oro sulla superficie del grafene multi-strato. Le caratteristiche fisiche ed elettriche del materiale e le prestazioni del sensore vengono analizzate e confrontate prima e dopo il processo di funzionalizzazione. In particolare, la tesi sviluppa i seguenti punti:
Nel Capitolo 1 vengono introdotte le caratteristiche fisiche ed elettriche del grafene, e le sue potenzialità nelle applicazioni di tipo "gas-sensing".
Nel Capitolo 2 viene presentato lo stato dell’arte sul processo di funzionalizzazione.
Il Capitolo 3 contiene le analisi delle caratteristiche fisiche ed elettriche del materiale, esaminando le differenze riscontrate dopo la funzionalizzazione.
I risultati dei test su gas, prima e dopo la funzionalizzazione, sono presentati nel Capitolo 4. SI usa NO2 come "target gas", N2 come gas portante. Per alcuni test, una percentuale di umidità relativa viene aggiunta al flusso di gas.
Infine, i risultati vengono confrontati e discussi in dettaglio.
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Rodner, Marius [Verfasser]. "Functionalized epitaxial graphene as versatile platform for air quality sensors / Marius Rodner." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2021. http://d-nb.info/123726877X/34.
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Zhao, Jie. "The application of functionalized nanocarbon materials as bio-interfaces in early diagnosis support." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13314.
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The aim of this study is to design and develop novel carbon nanotube and graphene based platforms as biosensors for electrochemically detecting dopamine. The use of such novel nanostructure, which was introduced with functional groups or bio-recognizition molecular, will enable the development of affinity-based biosensors for disease diagnostics and therapy monitoring. The electrical devices are extremely useful for dopamine determination in a fast and simple way. In this study, a Nafion/MWCNT chip prepared by inkjet printing was developed for rapid dopamine determination in human serum. A well dispersed Nafion/MWCNT composite was investigated with homogeneous double layers which increased the efficiency of dopamine detection, producing a measurable current change at the underlying sensor electrode. This platform as described successfully demonstrated detection of dopamine concentrations (0.1 M to 10 M, R=0.999) using DPV and amperometry methods. This direct measurement of dopamine in serum samples without pretreatment and dilution is reported for the first time in a Nafion/MWCNT system. In addition, to improve the specificity of the detecting probe, the direct electrochemical detection of antibody-antigen recognition was developed. Graphene can be used as an electrode surface for sensitive detection of a label. Graphene sheets were modified with gold nanoparticles or the dopamine antibody fragments (Fab’) loaded with sulphur binding with gold. Unfortunately, such bio-sensing systems did not perform sensitively and selectively for detection of the neurotransmitters/neurochemicals by utilizing certain nanostructure and introducing various functional groups. Further study will be conducted on analysing fragments’ and the whole antibodies’ activity and affinity of specific recognition.
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Tu, Zhaoxu [Verfasser]. "Functionalized Graphene Sheets as Multivalent 2D Platforms and Their Antitumor Applications / Zhaoxu Tu." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1196806098/34.
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Kalil, Haitham Fawzy Mohamed. "NANOMATERIALS-BASED SENSORS FOR PEROXYNITRITE DETECTION AND QUANTIFICATION." Cleveland State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu151336709631904.
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Halbig, Christian Eberhard [Verfasser]. "Fundamental Aspects on the Formation, Structure and Functionalisation of oxo-functionalised Graphene and thereout derived Graphene / Christian Eberhard Halbig." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1181788684/34.
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Sreeramoju, Mahendra K. "PREPARATION, CHARACTERIZATION AND APPLICATIONS OF FUNCTIONALIZED CARBON NANO-ONIONS." UKnowledge, 2013. http://uknowledge.uky.edu/chemistry_etds/20.
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Carbon nano-onions (CNOs) discovered by Ugarte in 1992 are multi-layered fullerenes that are spherical analogs of multi-walled carbon nanotubes with diameters varying from 6 nm to 30 nm. Among the various methods of synthesis, CNOs prepared by graphitization of nanodiamonds (N-CNOs) and underwater electric arc of graphite rods (A-CNOs) are the subject of our research. N-CNOs are considered as more reactive than A-CNOs due to their smaller size, high curvature and surface defects.
This dissertation focuses on structural analysis and surface functionalization of N- CNOs with diameters ranging from 6—10 nm. Synthetic approaches such as oleum- assisted oxidation, Freidel-Crafts acylation and Billups reductive alkylation were used to functionalize N-CNOs to improve their dispersion properties in aqueous and organic solvents. Functionalized N-CNOs were characterized using various techniques such as TGA, TG-MS, Raman spectroscopy and pH-titrimetry. We designed an experimental method to isolate polycyclic aromatic adsorbates formed on the surface of oleum oxidized N-CNOs (ON-CNOs) and characterized them.
A-CNOs, on the other hand are bigger than N-CNOs with diameters ranging from 20—40 nm. In this dissertation, we discuss the preparation of graphene structures by unzipping of A-CNOs using KMnO4 as oxidizing agent. These graphene structures were characterized using powder X-ray diffraction, TGA, BET nitrogen adsorption/desorption studies and compressed powder conductivity.
This dissertation also focuses on lithiation/delithiation studies of N-CNOs, A- CNOs and A-CNO-derived graphene structures to use them as negative electrode materials in lithium-ion batteries. The cycling performances of these materials at a charge/discharge rate of C/10 were discussed. The cycling performance of N-CNOs was tested at faster charge/discharge rate of C.
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Pirondelli, Andrea. "Production and Electrical Characterization of Low Density Polyethylene-based Micro- and Nano-dielectrics containing Graphene Oxide, Functionalized Graphene and Carbon Black additives." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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Oggigiorno la ricerca di nuovi materiali per gradatori di campo da impiegarsi in accessori di cavi ha iniziato a studiare alcuni materiali nano dielettrici con proprietà elettriche non lineari con la tensione ed aventi proprietà migliorate rispetto al materiale base. Per questo motivo in questo elaborato si sono studiati materiali nanostrutturati a base di polietilene a bassa densità (LDPE) contenenti nano polveri di grafene funzionalizzato (G*), ossido di grafene (GO) e carbon black (CB). Il primo obiettivo è stato quello di selezionare e ottimizzare i metodi di fabbricazione dei provini. La procedura di produzione è suddivisa in due parti. Nella prima parte è stata utilizzatala tecnica del ball-milling, mentre nella seconda un pressa termica (thermal pressing). Mediante la spettroscopia dielettrica a banda larga (BDS) si sono misurate le componenti reali e immaginarie della permettività e il modulo della conducibilità del materiale, in tensione alternata. Il miglioramento delle proprietà rispetto al provino di base composto dal solo polietilene si sono ottenute quando il quantitativo delle nanopolveri era maggiore. Le misure sono state effettuate sia a 3 V che a 1 kV. Attraverso misurazioni di termogravimetria (TGA) si è osservato l’aumento della resistenza termica di tutti i provini, soprattutto nel caso quando la % di nanopolveri è maggiore. Per i provini LDPE + 0.3 wt% GO e LDPE + 0.3 wt% G* si è misurata la resistenza alle scariche parziali attraverso la valutazione dell’erosione superficiale dei provini. Per il provino contenente G* è stato registrato una diminuzione del 22% del volume eroso, rispetto al materiale base, mentre per quello contenente GO non vi sono state variazioni significative. Infine si è ricercata la resistenza al breakdown di questi ultimi tre provini sopra citati. Per la caratterizzazione si è fatto uso della distribuzione di Weibull. Lo scale parameter α risulta aumentare solo per il provino LDPE + 0.3 wt% G*.
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Wang, Zhenping [Verfasser]. "Investigation of electrical properties of monolayer oxo-functionalized graphene-based two-dimensional materials / Zhenping Wang." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1212031997/34.
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Nordlund, Michael. "Carbon Nanostructures – from Molecules to Functionalised Materials : Fullerene-Ferrocene Oligomers, Graphene Modification and Deposition." Doctoral thesis, Uppsala universitet, Organisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-327189.
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The work described in this thesis concerns development, synthesis and characterisation of new molecular compounds and materials based on the carbon allotropes fullerene (C60) and graphene. A stepwise strategy to a symmetric ferrocene-linked dumbbell of fulleropyrrolidines was developed. The versatility of this approach was demonstrated in the synthesis of a non-symmetric fulleropyrrolidine-ferrocene-tryptophan triad. A new tethered bis-aldehyde, capable of regiospecific bis-pyrrolidination of a C60-fullerene in predominantly trans fashion, was designed, synthesised and reacted with glycine and C60 to yield the desired N-unfunctionalised bis(pyrrolidine)fullerene. A catenane dimer composed of two bis(pyrrolidine)fullerenes was obtained as a minor co-product. From the synthesis of the N-methyl analogue, the catenane dimer could be separated from the monomeric main product and fully characterised by NMR spectroscopy. Working towards organometallic fullerene-based molecular wires, the N-unfunctionalised bis(pyrrolidine)fullerene was coupled to an activated carboxyferrocene-fullerene fragment by amide links to yield a ferrocene-linked fullerene trimer, as indicated by mass spectrometry from reactions carried out at small scale A small library of conjugated diarylacetylene linkers, to be coupled to C60 via metal-mediated hydroarylation, was developed. Selected linker precursors were prepared and characterised, and the hydroarylation has been adapted using simple arylboronic acids. Few-layer graphene was prepared and dip-deposited from suspension onto a piezoelectric polymer substrate. Spontaneous side-selective deposition was observed and, from the perspective of non-covalent interaction, rationalised as being driven by the inbuilt polarization of the polymer. Aiming for selectively edge-oxidized graphene, a number of graphitic materials were treated with a combination of ozone and hydrogen peroxide under sonication. This mild, metal-free procedure led to edge-oxidation and exfoliation with very simple isolation of clean materials indicated by microscopy, spectroscopy, and thermogravimetric analysis.
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Irmer, Susanne [Verfasser], Jaroslav [Akademischer Betreuer] Fabian, and John [Akademischer Betreuer] Schliemann. "Theoretical investigations of orbital and spin-orbital effects in functionalized graphene / Susanne Irmer ; Jaroslav Fabian, John Schliemann." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1161606777/34.
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Li, Rui. "Theoretical investigation of electronic properties of atomic clusters in their free forms and adsorbed on functionalized graphene support." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3018/document.
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Les (sub)nanoclusters sont des agrégats d’atomes ou de molécules composés de quelques unités à quelques centaines d’unités. En raison de leur petite taille, ils peuvent avoir des propriétés électroniques, optiques, magnétiques et catalytiques très différentes par rapport au solide correspondant . D'un point de vue expérimental, il est encore très difficile de synthétiser des agrégats de taille calibrée. D'un point de vue théorique, le développement des puissances de calcul, des méthodes de calcul de structure électronique et des algorithmes de recherches globales de structures stables, permettent un calcul toujours plus précis de leurs propriétés physico-chimiques. L’étude théorique permet alors de déterminer de façon fiable les structures stables de ces systèmes qui président aux calculs de leurs propriétés . L’exemple qui illustre ce travail s’inspire du processus observé au sein des piles à combustible dans lequel le Platine (Pt) est couramment utilisé pour produire de l’énergie par oxydation du dihydrogène en favorisant notamment sa dissociation . L’objet de ce travail consiste à comparer la capacité des clusters de Platine de différentes tailles à adsorber la molécule de dihydrogène sous leur forme libre et adsorbée sur substrat. Le graphène , matériaux bidimensionnel cristallin formé de carbone est choisi dans ce travail en tant que substrat en raison de sa grande résistance mécanique et chimique. La première partie de ce travail est consacrée à la recherche d’éléments dopants qui vont permettent à la fois d’améliorer la capacité d’adsorption des clusters de Platine sur la surface et éviter leur migration. L’objectif est ici de proposer un substrat sur lequel peuvent être empêchés les phénomènes d’agglomération, de dissolution et de détachement du cluster qui ainsi limiteraient son efficacité catalytique . Des dopages de la surface, tel qu’ils sont réalisables expérimentalement , par l’Azote, le Bore et le Nitrure de Bore, par substitution atomique et avec ou sans considération préalable de lacunes, ont été étudiés. La seconde partie correspond à l’implémentation dans le code GSAM (Global Search Algorithm of Minima - algorithme de recherche globale de minima) développé au laboratoire , , des éléments qui permettent la recherche de structures de plus basse énergie de clusters moléculaires adsorbés sur substrat, tels que les systèmes [H2-Ptn-Graphène dopé] de cet exemple. La troisième partie concerne l’illustration de la fiabilité de la méthode de recherche globale employée et de la qualité de quelques méthodes de calcul de l’énergie moléculaire (DFT et GUPTA) vis-à-vis de résultats mentionnés dans la littérature sur les clusters de Platine. La dernière partie comporte l’investigation structurale des systèmes [H2-Ptn] et [H2-Ptn-Graphène dopé] pour différentes tailles de clusters allant de n=6 à n=20. La variation de l’énergie d’adsorption de H2 sur les clusters libres et supportés ainsi que celle du cluster moléculaire sur le substrat en fonction de la taille est reportéeA sub-nanometer sized metal cluster consists of only several to tens of atoms. Due to its small size and quantum effects, it can have very specific electronic, optical, magnetic and catalytic properties as compared with their bulk behaviors . From an experimental point of view, it is still a big challenge to realize size-controlled synthesis for (sub) nanoclusters. From a theoretical point of view, benefiting from the development of faster high-performance computational sources, more efficient electronic structure modelling software and more reliable global search methods for the determination of the most stable structures, the chemical and physical properties of clusters can be determinate more accurately. As it is experimentally a big challenge to realize size-controlled synthesis for (sub) nanoclusters, theoretical studies can provide detailed information on their geometric structure, electronic structure, as well as adsorption and reaction properties . The example chosen to be treated in this study is inspired by the fuel cell, in which the Platinum (Pt) is a typical and most commonly used precious metal catalyst for the production of energy by the oxidation of dihydrogene . Graphene is a recently discovered 2D carbon net structure, has several special properties, such as: low weight, high strength, high surface area, high electrical conductivity, etc. With these properties and their novel combinations, graphene might prove a promising candidate to be used as catalyst supports. The first part of this study is devoted to the search of the doping elements which permit both enhance the adsorption capacity of Pt clusters on the surface and prevent their migration. The aim here is propose one substrate which can avoid the problems of cluster agglomeration, dissolution and detachment, which reduce the performance of the catalysts . The ways of doping of the surface, which have already been experimentally realized , such as Nitrogen, Boron, and N-B patches substitution of Carbon atoms with or without introducing the vacancy on the pristine graphene, are studied. The second part corresponds to the implementation of some new features into the code GSAM (Global Search Algorithm of Minima) developed in our laboratory , , , which permit the search of the most stable structures of the molecular clusters adsorbed on substrate, such as the complex systems of [H2-Ptn-doped Graphene]. The third part is to evaluate the reliabilities of the global search method used, as well as the DFT and the empirical (GUPTA) potential energy surface. Thus, the main discussion appears as a comparison with the results of the literature concerning the Pt clusters. The fourth part consists of the structural investigation of [H2-Ptn] and [H2-Ptn-doped Graphene] systems for different sizes of Pt clusters with n=6 to n=20. The variation of the adsorption energy of H2 on the free and supported Ptn clusters, and the adsorption energy of (H2+Ptn) system on the surface with respect to the size of the cluster is discussed
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Mathumba, Penny. "Aluminium and gold functionalized graphene quantum dots as electron acceptors for inverted Schottky junction type rainbow solar cells." University of Western Cape, 2020. http://hdl.handle.net/11394/7232.
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Philosophiae Doctor - PhDThe main aim of this study was to prepare band gap-engineered graphene quantum dot (GQD) structures which match the different energies of the visible region in the solar spectrum. These band gap-engineered graphene quantum dot structures were used as donor materials in rainbow Schottky junction solar cells, targeting all the energies in the visible region of the solar spectrum for improved solar-to-electricity power conversion efficiency. Structural characterisation of the prepared nanomaterials under solid-state nuclear magnetic resonance spectroscopy (SS-NMR) showed appearance of bands at 40 ppm due to the presence of sp3 hybridised carbon atoms from the peripheral region of the GQD structures. Other bands were observed at 130 ppm due to the presence of polycyclic aromatic carbon atoms from the benzene rings of the GQD backbone, and around 180 ppm due to the presence of carboxylic acid carbons from oxidation due to moisture. Fourier-transform infrared resonance (FTIR) spectroscopy further confirmed the presence of aromatic carbon atoms and oxidised carbons due to the presence of C=O, C=C and -OH functional groups, concurrent with SS-NMR results.
2023-12-01
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Ventura, Espinosa David. "Development of New Hybrid Materials Based on Graphene Functionalised with Molecular Complexes. Evaluation of Properties and Catalytic Applications." Doctoral thesis, Universitat Jaume I, 2020. http://hdl.handle.net/10803/669305.
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En la presente tesis doctoral se ha descrito la síntesis de nuevos materiales híbridos basados en complejos organometálicos anclados mediante interacciones no covalentes sobre materiales derivados del grafeno. Los nuevos materiales son activos en diferentes reacciones catalíticas como la deshidrogenación de alcoholes y aminas, el acoplamiento de silanos y alcoholes y la hidratación e hidroaminación de alquinos. Los resultados muestran que el grafeno empleado como soporte tiene una importante influencia sobre el proceso catalítico, obteniéndose siempre mejores actividades con los materiales híbridos que con los complejos moleculares. En global este trabajo establece una nueva metodología para la obtención de catalizadores mejorados que, además se pueden reciclar fácilmente.
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Ries, Lucie. "Functionalized two-dimensional (2D) MoS2 nanosheets as building blocks for water purification membranes." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2019. http://www.theses.fr/2019ENCM0009.
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Les technologies de séparation par membranes jouent un rôle important dans divers domaines tels que le traitement de l’eau, la séparation de produits chimiques et de gaz dans de nombreux domaines industriels ou encore l’industrie alimentaire. L’accent a récemment été mis sur les matériaux bidimensionnels(2D) pour les applications membranaires, car leur épaisseur atomique et leur espacement limité entre les couches pourraient théoriquement améliorer les performances de séparation. Les nanofeuillets eux-mêmes ou l’empilement de plusieurs feuillets peuvent former des membranes sélectives. L’empilement multicouche de monofeuillets sous forme de membrane nanolaminée crée des capillaires 2D (ou nanocanaux) capables de tamiser efficacement les espèces chimiques en fonction de leur taille. Des exemples récents ont été rapportés dans la littérature démontrant le potentiel des matériaux 2D en tant que membranes multicouches ou monocouches pour le tamisage moléculaire (222; 260; 466; 204), la séparation de gaz (219; 246; 190),la production d’énergie (467) et le dessalement de l’eau de mer (198; 194). Parmi les différentes membranes 2D nanolaminées, l’oxyde de graphène (GO) est le matériau le plus étudié, et le tamisage moléculaire au sein de sa structure est principalement dicté par la taille de ses capillaires 2D (222). Malheureusement,l’hydrophilie importante des nanofeuillets rend les membranes de GO instables en milieu aqueux, et la difficulté de contrôler la largeur des capillaires entre les nanofeuillets limite l’utilisation de ces membranes pour le traitement des eaux. D’autres matériaux 2D tels que les nanofeuillets exfoliées de dichalcogénures de métaux de transition (TMD) constituent des plateformes attrayantes pour la réalisation de membranes nanolaminées.Des travaux récents menés sur des membranes nanolaminées en disulfure de molybdène (MoS2) ont montré sa stabilité améliorée (3). Dans le cadre de cette thèse, nous avons étudié les performances d’un nouveau type de membranes nanolaminées en MoS2 pour lesquelles la chimie de surface des feuillets est précisément contrôlée (14). Afin d’évaluer le rôle de la chimie de surface,nous avons exploré l’impact de la fonctionnalisation covalente sur le tamisage moléculaire pour la purification de l’eau (plus particulièrement le dessalement et l’élimination des micropolluants) (14). Nos résultats ouvrent de nouvelles voies pour ajuster avec précision les capacités de séparation des membranes à base de matériaux 2DMembrane separation technology plays an important role in various fields including water treatment, chemicals and gas separation for numerous industrial fields, and food processing. There has been a renewed focus on two-dimensional(2D) materials for membrane application since their atomic thicknessand confined interlayer spacing could theoretically lead to enhanced separative performances. Either the single nanosheets themselves, or the stackingof multiple sheets can form selective membranes. The multilayer assembly of single nanosheets – forming nanolaminate membranes – creates 2D capillaries(or nanochannels) that can efficiently sieve chemical species depending ontheir size.Recent examples have been reported in the literature demonstrating the potential of 2D materials as multi- or single-layer membranes for molecular sieving(222; 260; 466; 204), gas separation (219; 246; 190), energy harvesting (467)and water desalination (198; 194).Among the different building blocks of nanolaminate membranes made of two-dimensional materials (2D), graphene oxide (GO) has been studied as a candidate for molecular sieving via size-limited diffusion in the 2D capillaries (222). Unfortunately the high hydrophilicity of GO nanosheets makes GO membranes unstable in water, while the poor control of the capillary width between the nanosheets limits the water permeance of the membranes. Other 2D materials such as exfoliated nanosheets of transition metal dichalcogenides (TMDs)constitute attractive platforms for the realization of nanolaminate membranes.Recent works carried out on nanolaminate membranes made of molybdenum disulfide (MoS2) have demonstrated improved stability (3). Within this thesis we have studied the performance of a novel type of MoS2 nanolaminate membranes with well-controlled surface chemistry of the nanosheets (14). Inorder to assess the role of surface chemistry, we explored the impact of covalent functionalization on molecular sieving toward water purification (i.e. desalination and micropollutant removal) (14). Our results open novel directions to finely tune the sieving behavior of membranes based on 2D materials
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Macêdo, Lucyano Jefferson Alves de. "Microespectroscopia IR para o estudo de folhas de grafeno funcionalizadas e eletroquímica in-situ." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-22052018-142915/.
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Esta dissertação de mestrado aborda dois estudos que foram desenvolvidos utilizando a técnica de microscopia FTIR (micro-FTIR): a reatividade do grafeno funcionalizado e a eletroquímica in-situ com micro-FTIR para avaliação de reações redox. A reatividade e a distribuição de cargas em materiais 2D, mais especificamente em folhas individuais de grafeno, têm sido alvo de muita investigação na última década. No entanto, ainda não é conhecido como elas se apresentam em grafeno com grandes áreas, uma vez que a maioria dos estudos utilizam áreas muito pequenas (~μm2). Neste estudo, investigou-se experimentalmente como um eletrodo formado por uma única folha de grafeno se comporta quando sua estrutura é alterada por funcionalização covalente. Utilizando microespectroscopia na região do infravermelho, avaliou-se a funcionalização de grafeno com unidades de ácido benzoico no grafeno ancorados eletroquimicamente. O mapeamento químico mostrou que a distribuição espacial dessas unidades não ocorre uniformemente, ao invés disso, existem pontos específicos de ancoramento. Por fim, observou-se que a funcionalização ocorre mais intensamente na borda da folha de grafeno, alterando as propriedades óticas e eletroquímicas deste material, reduzindo o ganho ótico proporcionado pelos plásmons e aumentando a resistência de transferência heterogênea de elétrons. Para o segundo capítulo dessa dissertação, aplicou-se a microespectroscopia FTIR multiplex ao estudo da mudança química de um eletrodo de ouro modificado com azul da prússia (AP). Para isso, observou-se que uma etapa limitante era a confecção de um porta-amostra que reduzisse a camada de eletrólito ao mínimo de forma que a água não mais absorvesse a radiação de forma majoritária. Logo, foi possível o estudo vibracional de vários pontos da superfície do eletrodo, observando-se a influência do potencial aplicado, onde tem-se uma grande dependência dos sinais referentes ao estiramento C≡N do AP com a condição de potencial imprimida no eletrodo.This Masters dissertation approaches two studies developed using the FTIR microspectroscopy technique (micro-FTIR): the activity of graphene functionalized and the in-situ electrochemistry with micro-FTIR for the evaluation of redox reactions. Reactivity and charge distribution in 2D materials, especially in single graphene sheets, have been the focus of extensive investigation during the last decade. However, there is still no knowledge on how large-area graphene behaves, since most of the studies utilize too small areas (~μm2). In this study, we aim to investigate experimentally how an electrode composed of only one single sheet of graphene behaves when its structure is changed by covalent functionalization. Using infrared microspectroscopy, the electrochemically induced covalent functionalization of graphene with benzoic acid unities was evaluated. The chemical mapping showed that the spatial distribution of these unities does not occur uniformly, instead, there are specific anchoring points. Lastly, it was observed that the functionalization occurs more intensely on the edges of the graphene sheet and that the covalent, affecting its optical and electrochemical properties, reducing the optical gain provided by the plasmons and increasing the resistance of heterogeneous electron transfer. In the second chapter of this dissertation, multiplex FTIR microspectroscopy was applied to the study of the chemical changes of a gold electrode modified with Prussian blue (PB). It was observed that the limiting step for this type of analysis was the building of a sample holder that reduces the electrolyte layer to the minimum in a way that water did not absorb the radiation in majority. Therefore, a vibrational study of several points of the electrode surface was possible evaluating the influence of the applied potential, where there is a dependence of the signals related to the C≡N stretching mode from PB on the potential condition applied to the electrode.
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Haberer-Gehrmann, Danny [Verfasser], Bernd [Akademischer Betreuer] Büchner, and Thomas [Akademischer Betreuer] Pichler. "Electronic Properties of Functionalized Graphene Studied With Photoemission Spectroscopy / Danny Haberer-Gehrmann. Gutachter: Bernd Büchner ; Thomas Pichler. Betreuer: Bernd Büchner." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://d-nb.info/1068148195/34.
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BAKRY, AYYOB MOHAMMED A. "Applications of Chemically Modified Nitrogen Doped Carbon, Zirconium Phosphate, Metal Organic Frameworks, and Functionalized Graphene Oxide Nanostructured Adsorbents in Water Treatment." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6105.
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Water contaminations by many pollutants, especially heavy metals such as Pb(II), Hg(II), Cu(II), Cd(II), and Cr(VI) pose many public health and environmental concerns as reported in the list of hazardous substances compiled by the US Environmental Protection Agency due to their high toxicity, refractory degradation, and ease of entering food chain. Adsorption by chelating resins is proven to be the most effective method for the extraction of metal ions from polluted and wastewater. However, traditional absorbents such as activated carbon, activated alumina, clay, zeolite, etc., show limited adsorption abilities for these heavy metal ions. The major goal of this thesis is to develop efficient and cost-effective adsorbents for the extraction of heavy metals from wastewater. This dissertation will focus on the development of four chemically modified high surface area adsorbents with accessible chelating sites for capturing and retaining toxic metal ions from polluted water.
The first adsorbent, Nitrogen Doped Carboxylated Activated Carbon (ND-CAC), is prepared by a polymerization reaction between melamine and formaldehyde to form the melamine formaldehyde resin (MF-R) followed by carbonization at 800 oC under nitrogen atmosphere to form nitrogen doped carbon (ND-C), and finally oxidation to form the ND-CAC adsorbent. The ND-CAC adsorbent shows high adsorption capacities of 750.5, 250.5, 98.2 mg/g for the extraction of Pb(II), Hg(II), and Cr(VI), respectively from aqueous solutions with a high selectivity to Pb(II).
The second adsorbent, Melamine Zirconium Phosphate (M-ZrP) is prepared by a precipitation reaction between Melamine Phosphate (MP) and ZrCl4 in an aqueous solution. The M-ZrP adsorbent is used for the removal of Pb(II), Hg(II), and Cd(II) with maximum adsorption capacities of 680.4, 119.0, and 60.0 mg/g, respectively with a high selectivity to Pb(II).
The third adsorbent is chemically functionalized metal organic framework (UIO-66-IT) was prepared by post-synthetic modification using the chelating ligand 2-Imino-4-Thioburit. The adsorbent was used to extract Hg(II) and (HPO4)- ions from aqueous solutions and the results revealed exceptionally high adsorption capacities toward mercury and phosphate ions of 700 and 160 mg/g, placing it among the top functionalized MOF known for the high capacity of Hg(II) removal from aqueous solutions.
The fourth adsorbent, Melamine Thiourea Partially Reduced Graphene Oxide (MT-PRGO) prepared by the amidation reaction between chemically modified graphene oxide and melamine thiourea, is used for the effective extraction of Hg(II), Co(II) and Cu(II) from polluted water. The MT-PRGO adsorbent shows exceptional selectivity for the extraction of Hg(II) with a capacity of 651 mg/g, placing it among the top of carbon-based materials known for the high capacity of Hg(II) removal from aqueous solutions.
Desorption studies demonstrate that the new adsorbents ND-CAC, M-ZrP, UIO-66-IT, and MT-PRGO are easily regenerated with the desorption of the heavy metal ions Hg(II), Pb(II), Cd(II), and Cr(VI) reaching 99 % - 100 % recovery from their maximum sorption capacities using different eluents. Moreover, all prepared adsorbents showed tremendous abilities to clean contaminated water from toxic heavy metals at trace concentrations. That prove the ability of using them at water contamination level when the concentration of heavy metals is very low. The new adsorbents ND-CAC, M-ZrP, UIO-66-IT, and MT-PRGO are proposed as top performing remediation adsorbents for the extraction of the heavy metals Pb(II), Hg(II), Cd(II), Cr(VI), and (HPO4)- from waste and polluted water.
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Walz, Michael Steffen [Verfasser], and F. [Akademischer Betreuer] Evers. "Ab initio simulations of local current densities in mesoscopic films: Current vortices in functionalized graphene nanoribbons / Michael Steffen Walz. Betreuer: F. Evers." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1079594876/34.
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Pavlásková, Lucie. "Biosenzory na bázi funkcionalizovaného grafenu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443227.
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V této práci byl demonstrován grafenový polem řízený transistor (GFET) jako platforma pro detekci glukózy. Sukcinimidyl ester pyrenbutanové kyseliny (PSE) sloužící jako nosič a enzym glukóza oxidáza (GOx) byly úspěšně použity k funkcionalizaci grafenového kanálu ve FE transistoru. Enzym GOx byl imobilizován na kanálu pro glukózovou detekci, jelikož indukuje selektivní katalytickou reakci glukózy. Proces funkcionalizace byl charakterizován pomocí Ramanovy spektroskopie a Atomární silové mikroskopie (AFM). Vyrobený biosenzor na bázi grafenu umožnil elektrickou detekci glukózy ve dvou různých uspořádáních. V uspořádní FET prostřednictvím posunu Diracova bodu ve voltampérové charakteristice, jakož i v nastavení pro kotinuální monitorování v reálném čase prostřednictvím změny odporu grafenového kanálu. Tato studie naznačuje, že grafen je slibným materiálem pro vývoj nanoelektronických biosenzorů včetně aplikací pro monitorování hladiny glukózy.
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Rosenzweig, Shirley Ferreira. "Adsorption of Copper (II) on Functionalized Carbon Nanotubes (CNT): A study of adsorption mechanisms and comparative analysis with Graphene Nanoplatelets (GNP) and Granular Activated Carbon (GAC) F-400." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368026548.
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Shah, Priyal. "Computational Analysis of Elastic Moduli of Covalently Functionalized Carbon Nanomaterials, Infinitesimal Elastostatic Deformations of Doubly Curved Laminated Shells, and Curing of Laminates." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77034.
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We numerically analyze three mechanics problems described below. For each problem, the developed computational model is verified by comparing computed results for example problems with those available in the literature.
Effective utilization of single wall carbon nanotubes (SWCNTs) and single layer graphene sheets (SLGSs) as reinforcements in nanocomposites requires their strong binding with the surrounding matrix. An effective technique to enhance this binding is to functionalize SWCNTs and SLGSs by covalent attachment of appropriate chemical groups. However, this damages their pristine structures that may degrade their mechanical properties. Here, we delineate using molecular mechanics simulations effects of covalent functionalization on elastic moduli of these nanomaterials. It is found that Young's modulus and the shear modulus of an SWCNT (SLGS), respectively, decrease by about 34% (73%) and 43% (42%) when 20% (10%) of carbon atoms are functionalized for each of the four functional groups of different polarities studied.
A shell theory that gives results close to the solution of the corresponding 3-dimensional problem depends upon the shell geometry, applied loads, and initial and boundary conditions. Here, by using a third order shear and normal deformable theory and the finite element method (FEM), we delineate for a doubly curved shell deformed statically with general tractions and subjected to different boundary conditions effects of geometric parameters on in-plane and transverse stretching and bending deformations. These results should help designers decide when to consider effects of these deformation modes for doubly curved shells.
Composite laminates are usually fabricated by curing resin pre-impregnated fiber layers in an autoclave under prescribed temperature and pressure cycles. A challenge is to reduce residual stresses developed during this process and simultaneously minimize the cure cycle time. Here, we use the FEM and a genetic algorithm to find the optimal cycle parameters. It is found that in comparison to the manufacturer's recommended cycle, for a laminate with the span/thickness of 12.5, one optimal cycle reduces residual stresses by 47% and the total cure time from 5 to 4 hours, and another reduces the total cure time to 2 hours and residual stresses by 8%.Ph. D.
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Sunday, Christopher Edozie. "The design of ultrasensitive immunosensors based on a new multi-signal amplification gold nanoparticles-dotted 4-nitrophenylazo functionalised graphene sensing platform for the determination of deoxynivalenol." Thesis, University of Western Cape, 2014. http://hdl.handle.net/11394/3361.
Full textAbstract:
Philosophiae Doctor - PhDA highly dispersive gold nanoparticle-dotted 4-nitrophenylazo functionalised graphene nanocomposite (AuNp/G/PhNO2) was successfully synthesised and applied in enhancing sensing platform signals. Three label-free electrochemical immunosensors for the detection of deoxynivalenol mycotoxin (DON) based on the systematic modification of glassy carbon electrodes (GCE) with AuNp/G/PhNO2 was effectively achieved. General electrochemical impedance method was employed for the sensitive and selective detection of DON in standard solutions and reference material samples. A significant increase in charge transfer resistance (Rct) of the sensing interface was observed due to the formation of insulating immune-complexes by the binding of deoxynivalenol antibody (DONab) and deoxynivalenol antigen (DONag). Further attachments of DONab and DONag resulted in increases in the obtained Rct values, and the increases were linearly proportional to the concentration of DONag. The three immunosensors denoted as GCE/PDMA/AuNp/G/PhNH2/DONab, GCE/Nafion/[Ru(bpy)3]2+/AuNp/G/PhNH2/DONab and GCE/Nafion/[Ru(bpy)3]2+/G/PhNH2/DONab have detection range of 6 – 30 ng/mL for DONag in standard samples. Their sensitivity and detection limits were 43.45 ΩL/ng and 1.1 pg/L; 32.14ΩL/ng and 0.3 pg/L; 9.412 ΩL/ng and 1.1 pg/L respectively. This result was better than those reported in the literature and compares reasonably with Enzyme Linked Immunosorbent Assay (ELISA) results. The present sensing methodology represents an attractive alternative to the existing methods for the detection of deoxynivalenol mycotoxin and other big biomolecules of interest due to its simplicity, stability, sensitivity, reproducibility, selectivity, and inexpensive instrumentation. And they could be used to develop high-performance, ultra-sensitive electrochemiluminescence, voltammetric or amperometric sensors as well.
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Rubrice, Kevin. "Matériaux composites commandables pour applications hyperfréquences dans les structures navales." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S127.
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Les matériaux composites prennent une place de plus en plus importante dans la conception et la fabrication des moyens de transport et notamment dans le domaine naval où ils sont particulièrement privilégiés. En effet, ces matériaux sont utilisés pour leur légèreté, insensibilité à la corrosion et leurs caractéristiques mécaniques. Dans le domaine militaire, où l'optimisation des moyens de communication et de protection électromagnétique est primordiale, le développement de matériaux composites dotés de propriétés de reconfigurabilité sous commande(s) externe(s), présente un atout opérationnel majeur pour les parois structurales exploitant ces matériaux. Afin d'explorer cette voie, DCNS et l'Institut d’Électronique et de Télécommunications de Rennes (IETR, UMR-6164) se sont associés. Les travaux de thèse engagés ont pour objectif d'étudier et de développer des matériaux composites présentant des fonctions de reconfigurabilité applicables aux systèmes navals tels que les radômes, les antennes et exploitables pour répondre aux problématiques de furtivité (SER). Une première étude a permis d'explorer les matériaux à base de carbone, présentant une potentielle agilité de leurs caractéristiques diélectriques sous actuateur électrique. Ces matériaux présentent également un fort pouvoir absorbant électromagnétique, tributaire des propriétés diélectriques, elles-mêmes potentiellement reconfigurables. La seconde étude engagée a étudié l'impact des matériaux ferroélectriques, c'est-à-dire des matériaux reconfigurables sous champ électrique, lorsqu'ils sont intégrés comme charge dans une résine d'imprégnation. Ce nouveau matériau composite présente alors une reconfigurabilité de ses caractéristiques diélectriques, rendant commandable en fréquence sa structure hôte. Une troisième étude, exploitant aussi le matériau ferroélectrique a permis l'obtention d'une reconfigurabilité des caractéristiques de réflectivité de panneaux composites grâce au développement de surfaces sélectives en fréquence reconfigurables. De nouvelles propriétés ont ainsi été mises en évidence en hyperfréquences. Enfin, les matériaux d'âmes et spécifiquement les nids d'abeilles diélectriques ont fait l'étude d'une fonctionnalisation pour des applications DC et hyperfréquencesComposite materials are used for their lightness, high resistance to corrosion and high mechanical properties over large application areas, such as naval, ground and aerial. Collaboration between DCNS group and the Institute of Electronics and Telecommunications of Rennes (IETR, UMR-6164) has been initiated to develop smart composite materials with tunable properties at microwaves. Three different routes have been investigated during the thesis work. The first one is based on carbon composite material, its electromagnetic absorbing ability and its potential dielectric tunability. For this, we develop composite materials loaded with various carbon particles (carbon nanotube, graphene, black carbon). Next, to elaborate smart composite materials, a ferroelectric material has been used as filler. The dielectric characteristics of such materials can be tuned under external biasing for example. Thus we develop an active composite material under various external actuators for naval application, and especially for new reconfigurable frequency selective surface (RFSS). Finally dielectric honeycomb materials have been specifically elaborated and studied to develop smart properties for DC and microwave applications. During this work, three different prototypes improving composite materials in naval area have been performed: reconfigurable radome, RCS reduction, and antenna isolation
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Wang, Jing-shiuan, and 王靜萱. "Innovative Solid-State Polymer Nanocomposite Electrolytes: Enhancement of Ionic Conductivity by Polymer- Functionalized Graphenes." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/2652x8.
Full textAbstract:
碩士國立臺灣科技大學
化學工程系
100
There is a growing shift from liquid electrolytes toward solid polymer electrolytes, in energy storage devices, due to the many advantages of the latter such as enhanced safety, flexibility, and manufacturability. The main issue with polymer electrolytes is their lower ionic conductivity compared to that of liquid electrolytes. Nanoscale fillers such as silica and alumina nanoparticles are known to enhance the ionic conductivity of polymer electrolytes. Although graphene have been used as fillers for polymers in various applications, they have not yet been used in polymer electrolytes as they are conductive and can pose the risk of electrical shorting. In this study, we show a powerful and reliable strategy to synthesis covalently functionalize graphene. The polymer electrolytes whose ion-conducting channels are physically and chemically modulated by the polymer functionalize graphene. We show that such hybrid nanofillers increase the lithium ion conductivity of PEG electrolyte by almost 2 orders of magnitude. Furthermore, the lithium ion transference number was tLi+ of PEG/PILB-G/LiClO4 at 60 ◦C was as high as 0.68 , which was also three times higher than that of PEG/LiClO4.
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HSIEH, YU-HUN, and 謝宇涵. "Epoxy/Functionalized Graphene Nanocomposites." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/se2hcr.
Full textAbstract:
碩士東海大學
化學工程與材料工程學系
105
The research purpose of this thesis was to investigate the effect of graphene nanoplatelets on the epoxy/graphene composites. Dicyandiamide (DICY), milled with different particle sizes, was used as the hardener for epoxy curing, then vacuum mixed with different accelerators. Methanol was the solvent for dissolving both the handener and the accelerators. Morphological and property characterization was performed on the cured samples. The original graphite surface does not have any ionic or reactive groups. Therefore, oxidation is necessary to introduce the reactive groups onto the graphite surface. The graphite oxide was then functionalized with ODA. Epoxy nanocomposites was prepared by adding functionalized graphene oxide, using ultrasonication to achieve uniform mixing. The particle size of milled DICY was determined by Dynamic Light Scattering (DLS). The dispersibility of graphene nanoplatelets in composites and their effect on thermal conductivity and mechanical properties was examined. The composite morphology was observed with SEM. The composition and the degradation of the composites were investigated with TGA. DSC was used to analyze the curing behavior and thermal conductivity. The mechanical properties of the composite were examined with DMA. Finally, TMA was used to determine the linear thermal expansion of the composites. The results showed that the addition of trace graphene has improved the composite physical properties and thermal conductivity. Dissolvion of DICY and 2-MI by methanol helped improve the physical properties of composite materials.
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Chen, Yan-Ru, and 陳演儒. "Functionalized graphene for supercapacitor." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/61356142398451451721.
Full textAbstract:
博士國立臺灣大學
材料科學與工程學研究所
102
Abstract The high-rate performances of supercapacitors generally are limited by the polarization. As a result, the charge/discharge capacitances decay very dramatically with the increase of charge-discharge rates. Therefore, more effective additives with a much smaller mass fraction are needed in future supercapacitors, especially for the high-rate case where there must be a more efficient conducting network. Due to the fact that graphene exhibits exceptional electron transport properties and unique geometrical nature (a soft and ultrathin planar structure), graphene is introduced into supercapacitors as a conducting additive to improve the high rate charge/discharge performances. However, similar to other nanomaterials, a key challenge in synthesis and processing of graphenes sheets is aggregation. Due to the fact that graphenes possess high specific surface area, they tend to form irreversible agglomerates or even restack to form graphite through van der Waals interactions. In this study, a surface modification technology is used to change the surface of graphene and improve its dispersity. The dispersion stability of functionalized graphene is measured by zeta potential. Functionalized graphenes are used as conductive additive in the electrode of supercapacitor, and their electrochemical performances are compared by charge/discharge and AC impedence. With suitable functionalized graphene as conductive additive is important, therefore we will divide into two chapter to discussions. In chapter 4, graphene with oxygen (M-rGO and H-rGO) and nitrogen (N-rGO) related functional groups have been fabricated. Reduce graphenes including H-rGO, M-rGO and N-rGO were mixed with activated carbons as the composite electrodes and characterized for supercapacitors. The effects of the functional groups on graphenes as the conductive additive have been investigated. It was found that a suitable content of functional groups can improve the stability of dispersion, and therefore reduce the internal resistance (IR drop) and charge transfer resistance (Rct) resulting in higher rate capability. The supercapacitor with M-rGO and KS6 as additive at the activated carbon electrode can be operated at a rate as high as 6 A/g and exhibits a capacitance of 208 F/g, whereas the supercapacitor using only KS6 as additive shows a capacitance of only 107 F/g. The graphene contained supercapacitor has been cycled over 2000 times at 4 A/g with almost no capacitance fading. In the chapter 5, Sulfonated polyetheretherketone (SPEEK) has been synthesized by sulfonation process and used as the solid-state electrolyte, binder and surfactant for soild-state supercapacitors. The suspensions of M-rGO/SPEEK, H-rGO/SPEEK, N-rGO/SPEEK, M-rGO/PVDF, H-rGO/PVDF, and N-rGO/PVDF in organic solvents (DMSO) have been prepared and the surfactant effects of SPEEK and PVDF toward graphenes (M-rGO, H-rGO and N-rGO) have been investigated. Functionalized graphenes dispersed by SPEEK are used as high efficiency conducting additives in solid-state supercapacitors. It was found that SPEEK can dramatically improve the stability of graphene dispersion, and therefore the solid-state supercapacitors showed largely decrease of IR drop and charge transfer resistance (Rct), resulting in higher rate capability. The solid-state supercapacitors with M-rGO /SPEEK/activated carbon electrode can be operated from 1 to 8 A/g and exhibit capacity retention of 93%. The noteworthy is more than twice higher value for capacity retention by comparison with the solid-state supercapacitors using M-rGO/PVDF/activated carbon electrode (capacity retention is 36%). The cell of graphene with SPEEK has been cycled over 5000 times at 5 A/g with no capacitance fading.
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HUANG, WAN-YU, and 黃婉瑜. "Epoxy/Functionalized Graphene Nanocomposites." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8x5f6t.
Full textAbstract:
碩士東海大學
化學工程與材料工程學系
106
The research purpose of this study is to examine the effect of graphene nanoplatelets, which was added to the epoxy as a reinforcing agent, on the enhancement of the physical properties of the epoxy/graphene nanocomposites. Using different solvents mixed with the hardener dicyandiamide (DICY) and the accelerator 2-methylimidazole (2-MI), the stirred evenly with the epoxy and vacuum hot pressed to prepare the samples for characterization of morphological and physical properties. The original graphene surface does not have any ionic or reactive groups. Therefore, oxidization to produce the reactive groups on the graphene surface is necessary, and then coupling agents were used for modifiying the grapheme oxide. We studied the effects of with graphene oxide or functionalized graphene on the properties of the nanocomposites. Ultrasonication was employed to achieve uniform mixing. The dispersion of graphene nanoplatelets in composites and their effect on thermal conductivity and mechanical properties were examined. The composite morphology was observed with SEM. The composition and the degradation of the composites were investigated with TGA. DSC was used to analyze the curing behavior and thermal conductivity. The mechanical properties of the composite were examined with DMA. Finally, TMA was used to determine the linear thermal expansion of the composites. From the experimental results, the addition of organically modified graphene improved the thermal properties, mechanical properties and thermal conductivity. Methanol as a solvent effectively dissolved hardener and accelerator.
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Cunha, Eunice Paula Freitas. "Functionalized graphene for polymer composites." Doctoral thesis, 2017. http://hdl.handle.net/1822/45762.
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Tese de Doutoramento (Ciência e Engenharia de Polímeros e Compósitos)Along the past decade graphene has emerged as an exciting material revealing potential applications in various fields. The translation of the graphene outstanding properties observed at lab-scale into real-world applications at industrial scale, however, greatly depends on the capacity to produce good quality graphene at large scale. The typical large scale graphene production processes present disadvantages such as high cost, or the formation of graphene with structural defects, or contaminants which are difficult to remove. Recently, interesting approaches to produce graphene were proposed, based on graphite exfoliation in water using amphiphilic molecules such as pyrene derivatives with a polar moiety. Another approach consists in the production of graphene nanoribbons (GNR) by unzipping of carbon nanotubes. These methods allow the production of graphene sheets (GS) and GNR with negligible structural damage, using low boiling point solvents that are easy to remove. The present work investigated these two graphene production methods. The exfoliation of graphite into GS was achieved by interaction with two different water soluble pyrene derivatives, modified with a carboxylic acid moiety bonded to pyrene through semiflexible side arms of different lengths. The suspensions produced were formed by approximately 80 % of bi-layer and few-layer graphene. The GNR were produced from pyrrolidine-functionalized carbon nanotubes, through application of ultrasounds in ethanol. Multiwall carbon nanotubes of different diameters, namely with approximately 10 and 110 nm, were covalently functionalized using a simple, solvent free method, and the unzipping was observed to occur in both cases. The unzipping process was assigned to the type of functional groups bonded to the nanotubes. The graphene products were extensively characterized, and tested for polymer composite applications. Graphene has the potential to improve the mechanical, electrical, thermal and barrier properties of polymer-based nanocomposites. For that purpose graphene, or graphene derivative, has to be homogeneously distributed and dispersed into the polymer matrix, and establish good interfacial adhesion. Solution mixing is a good method to produce homogeneous graphene/polymer nanocomposites, particularly when using water as a solvent. This method is limited to water soluble polymers, however the development of waterborne polymer suspensions is an area of intense research. Waterborne polyurethane (WPU) is a good example of an eco-friendly synthetic polymer widely used in the coating industry. In this work nanocomposite films were produced incorporating GS formed in aqueous suspension. The composite films presented a large decrease of permeability to water vapor, of the electrical resistivity, and an increase of the mechanical properties. Melt mixing of reinforcing particles in thermoplastic polymers is probably the most environmentally and economically attractive technique, and a scalable method, for composite production. However, the dispersion of nanoparticles in high viscosity polymer melts is a complex process. Several studies reported in the literature used different mixing equipment (extruders, internal mixers, prototype mixers) to disperse carbon black, carbon nanofibers and carbon nanotubes, in polymer melts. They demonstrated that the nanoparticle dispersion varies with factors such as the intensity and type of hydrodynamic stresses, residence time, and interfacial adhesion. Few studies report the dispersion of graphite-derivatives in polymer melts. In the present work the dispersion in polypropylene of graphite nanoplates, with and without functionalization, was studied using a small-scale prototype mixer designed to generate high extensional flow. The dispersion of the nanoparticles was analyzed along the mixer length, demonstrating the initial agglomerated form of the graphite nanoplates and their dispersion into the original nanoplate size along the melt processing.
O grafeno tem sido apresentado como um nano material muito interessante com potenciais aplicações em várias áreas. Contudo, a extrapolação das suas excelentes propriedades, que são observadas à escala laboratorial, para uma escala industrial depende amplamente da capacidade de produção de grafeno em grandes quantidades e com boa qualidade. Os processos que normalmente são utilizados para produção de grafeno em grande quantidade apresentam algumas desvantagens, tais como, elevado custo de produção, a obtenção de grafeno com defeitos estruturais ou com contaminações cuja remoção é difícil. Recentemente foram reportadas abordagens interessantes para a produção de grafeno baseadas na exfoliação da grafite em meio aquoso utilizando moléculas anfifílicas, tais como derivados de pireno com grupos funcionais polares. Outra abordagem consiste na produção de nanofitas de grafeno através da abertura longitudinal de nanotubos de carbono. Estes métodos permitem a produção de folhas de grafeno e nanofitas de grafeno com poucos defeitos estruturais, utilizando solventes com pontos de ebulição baixos que são fáceis de remover. Neste trabalho foram estudadas estas duas abordagens para a produção de grafeno. A exfoliação da grafite para a formação de folhas de grafeno foi obtida através da interação com dois derivados de pireno solúveis em água, modificados com um grupo funcional ácido carboxílico ligado à molécula de pireno formando cadeias semi-flexíveis com comprimentos diferentes. As suspensões produzidas apresentaram cerca de 80% de grafeno bicamada e grafeno com poucas camadas. As nanofitas de grafeno foram produzidas a partir de nanotubos de carbono funcionalizados com um grupo pirrolidina, através da aplicação de ultrassons em etanol. Os nanotubos de carbono multicamada com diferentes diâmetros, nomeadamente, 10 e 110 nm, foram funcionalizados covalentemente através de uma metodologia simples, sem a utilização de solventes, e a abertura longitudinal dos nanotubos de carbono funcionalizados ocorreu em ambos os casos. O processo de abertura dos nanotubos de carbono funcionalizados foi desencadeado devido ao tipo de grupo funcionais ligados à superfície dos nanotubos. As nanofitas de grafeno bem como o grafeno obtido a partir da exfoliação da grafite foram caracterizados extensivamente e testados para aplicações em compósitos poliméricos. O grafeno tem potencial para melhorar as propriedades mecânicas, elétricas bem como propriedades de barreira em nanocompósitos poliméricos. Para tal, o grafeno ou derivados de grafeno têm que estar distribuídos e dispersos homogeneamente na matriz polimérica, e estabelecer uma boa adesão na interface com a matriz. A mistura em solução é uma boa técnica para a produção de nanocompósitos poliméricos com grafeno de uma forma homogénea, especialmente quando o solvente utilizado é a água. Este método é limitado à utilização de polímeros solúveis em água, contudo o desenvolvimento de polímeros que formam suspensões estáveis em água tem vindo a ser extensamente estudado. O poliuretano de base aquosa representa um bom exemplo de um polímero sintético e ecológico que é amplamente usado da industria dos revestimentos. Neste trabalho foram produzidos filmes nanocompósitos com a incorporação de folhas de grafeno produzidas em suspensão aquosa. Os filmes nanocompósitos apresentaram uma diminuição significativa na permeabilidade ao vapor de água, da resistividade elétrica bem como um melhoramento das propriedades mecânicas. A mistura de partículas de reforço em polímeros termoplásticos fundidos é provavelmente a técnica mais atrativa do ponto de vista económico e ecológico, e um método que pode ser utilizado para a produção de compósitos poliméricos em escala industrial. Todavia, a dispersão de nanopartículas em polímeros com viscosidade elevada é um processo complexo. Alguns estudos reportados na literatura usaram diferentes equipamentos de mistura (como por exemplo, extrusoras e misturadores protótipos) para dispersar nanopartículas de carbono, tais como, negro de fumo, nanofibras de carbono e nanotubos de carbono, em polímero fundido. Os estudos demonstraram que a dispersão das nanopartículas varia com fatores como a intensidade e o tipo de tensões hidrodinâmicas, o tempo de residência, e a adesão na interface entre o reforço e a matriz. Poucos estudos reportam a dispersão de derivados de grafite em polímero fundido. Neste trabalho foi estudada a dispersão em polipropileno fundido de nanoplaquetas de grafite, com e sem funcionalização, utilizando um misturador protótipo, que permite o estudo em pequenas quantidades de material, e que foi desenhado para gerar fluxos extensionais elevados. A dispersão das nanopartículas foi analisada ao longo do misturador, demonstrado que os aglomerados de nanoplaquetas de grafite formados evoluíram até às dimensões inicias destas ao longo do processamento em polímero fundido.
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JIN, TING-JHEN, and 金庭甄. "Polylactic Acid/Functionalized Graphene Nanocomposites." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/71296577222206442572.
Full textAbstract:
碩士東海大學
化學工程與材料工程學系
105
The research focused on solution blending for preparing the polylactic acid/functionalized graphene nanocomposites. Because the natural graphite was thick and inert, the first step was the oxidation process to convert the inert surface of graphite into hydroxyl, carboxyl, and epoxy functional groups. The next step was to modify the graphite oxide (GO) by octadecylamine (ODA). Subsequently, the nanocomposites of PLA filled with modified GO were prepared directly by solution blending. In the experiment, the GOAs grafted with functionalized polylactic acid of different molecular weight became well dispersed in the matrix, which improved significantly most of the physical properties of the composites. According to the experimental results, the addition of functionalized PLA improved the dispersion of GOA in the matrix, and accordingly mechanical, thermal, and conductive properties were enhanced.