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MANGADLAO, JOEY DACULA. "Multifunctional Materials from Nanostructured Graphene and Derivatives." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1448279230.
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Zedan, Abdallah. "GRAPHENE-BASED SEMICONDUCTOR AND METALLIC NANOSTRUCTURED MATERIALS." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/457.
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Exciting periods of scientific research are often associated with discoveries of novel materials. Such period was brought about by the successful preparation of graphene which is a 2D allotrope of carbon with remarkable electronic, optical and mechanical properties. Functional graphene-based nanocomposites have great promise for applications in various fields such as energy conversion, opteoelectronics, solar cells, sensing, catalysis and biomedicine. Herein, microwave and laser-assisted synthetic approaches were developed for decorating graphene with various semiconductor, metallic or magnetic nanostructures of controlled size and shape. We developed a scalable microwave irradiation method for the synthesis of graphene decorated with CdSe nanocrystals of controlled size, shape and crystalline structure. The efficient quenching of photoluminescence from the CdSe nanocrystals by graphene has been explored. The results provide a new approach for exploring the size-tunable optical properties of CdSe nanocrystals supported on graphene which could have important implications for energy conversion applications. We also extended this approach to the synthesis of Au-ceria-graphene nanocomposites. The synthesis is facilely conducted at mild conditions using ethylenediamine as a solvent. Results reveal significant CO conversion percentages between 60-70% at ambient temperatures. Au nanostructures have received significant attention because of the feasibility to tune their optical properties by changing size or shape. The coupling of the photothermal effects of these Au nanostructures of controlled size and shape with GO nanosheets dispersed in water is demonstrated. Our results indicate that the enhanced photothermal energy conversion of the Au-GO suspensions could to lead to a remarkable increase in the heating efficiency of the laser-induced melting and size reduction of Au nanostructures. The Au-graphene nanocomposites are potential materials for photothermolysis, thermochemical and thermomechanical applications. We developed a facile method for decorating graphene with magnetite nanocrystals of various shapes (namely, spheres, cubes and prisms) by the microwave-assisted-reduction of iron acetylacetonate in benzyl ether. The shape control was achieved by tuning the mole ratio between the oleic acid and the oleyamine. The structural, morphological and physical properties of graphene-based nanocomposites described herein were studied using standard characterization tools such as TEM, SEM, UV-Vis and PL spectroscopy, powder X-ray diffraction, XPS and Raman spectroscopy.
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Risley, Mason J. "Surfactant-assisted exfoliation and processing of graphite and graphene." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48980.
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Surfactant assisted solution exfoliation of expanded graphite by means of sonication was carried out in an attempt to produce non-covalent charge functionality on the surface of graphene for the directed self assembly of graphene films on patterned substrates via electrostatic interactions. This thesis includes the results of experimental research associated with: 1) quantifying the effectiveness of various di-functionalized dithienothiophene surfactant small molecules, 2) further understanding the surface affinity and interaction mechanism between these surfactant molecules and the surface of expanded graphite and graphene and 3) experimentally testing the feasibility of the directed self-assembly of graphene films by means of charge functionalization of graphene by the surfactant molecules adsorbed onto the surface of exfoliated graphene.
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Li, Yanguang. "Nanostructured Materials for Energy Applications." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275610758.
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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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Gnanaprakasa, Tony Jefferson. "Surface Engineering and Synthesis of Graphene and Fullerene Based Nanostructures." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/605216.
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Graphene is a two-dimensional carbon structure that exhibits remarkable structure-property relations. Consequently, there has been immense effort undertaken towards developing methods for graphene synthesis. Chemical vapor deposition (CVD) and chemical exfoliation from colloidal suspensions are two common methods used for obtaining graphene films. However, the underlying experimental conditions have to be carefully optimized in order to obtain graphene films of controllable thickness and morphology. In this context, a significant part of this dissertation was devoted towards developing and improving current CVD-based and chemical exfoliation based methods for synthesizing high quality graphene films. Specifically, in the CVD based procedure for growing graphene on copper, the effect of surface pretreatment of copper was investigated and the quality of graphene grown using two different pretreatment procedures was compared and analyzed. In particular, graphene grown on electropolished copper (EP-Cu) was analyzed with respect to its surface morphology, surface roughness and thickness, and compared with graphene grown on as cold-rolled acetic acid cleaned copper (AA-Cu). It was shown that electropolishing of the Cu substrates prior to graphene growth greatly enhanced the ability to obtain flat, uniform, predominantly single layer graphene surface coverage on copper. The reported surface roughness of the graphene on EP-Cu was found to be much lower than for previously reported systems, suggesting that the electropolishing procedure adopted in this work has great promise as a pretreatment step for Cu substrates used in CVD growth of graphene. Obtaining graphene from colloidal suspensions of graphitic systems was also examined. In this work, an acid (H₂SO₄ + HNO₃) treatment process for intercalating natural graphite flakes was examined and the ability to reversibly intercalate and deintercalate acid ions within graphitic galleries was investigated. More importantly, a rapid-thermal expansion (RTP) processing was developed to thermally expand the acid-treated graphite, followed by exfoliation of predominantly bilayer graphene as well as few layer graphene flakes in an organic solvent (N, N-Dimethylformamide - DMF). The developed method was shown to provide bilayer and few layer graphene flakes in a reliable fashion. Fullerene is another carbon nanostructure that has garnered attention due to unique structure and chemical properties. Recently, there has been increased focus towards harnessing the properties of fullerenes by synthesizing fullerene self-assemblies in the form of extended rods, tubes and more complex shapes. Current methods to synthesize these self-assemblies are either cumbersome, time consuming or expensive. In this context, an alternate, straightforward dip-coating procedure technique to self-assemble equal-sized, faceted, polymerized fullerene nanorods on graphene-based substrates in a rapid fashion was developed. By suitably modifying the kinetics of self-assembly, the ability to reliably control the spatial distribution, size, shape, morphology and chemistry of fullerene nanorods was achieved.
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Nagelli, Enoch A. "CONTROLLED FUNCTIONALIZATION AND ASSEMBLY OF GRAPHENE NANOSTRUCTURES FOR SENSING AND ENERGY STORAGE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1402278821.
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CURCIO, DAVIDE. "Growth and Properties of Graphene-Based Materials." Doctoral thesis, Università degli Studi di Trieste, 2017. http://hdl.handle.net/11368/2908114.
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In this thesis, I have focused on graphene-based nanostructures as a versatile means of manipulating the electronic properties of graphene, while working with objects perfect at the atomic level. This is the nanotechnological approach, where we exploit the infinite possibilities of making small things with new materials. For these reasons, I concentrated my research efforts to graphene-based nanomaterials, because graphene is one of the most exciting materials we have to date, and because manipulation of surfaces at the nano-level is what allows us to make new materials today. In this thesis, I will show how we have created and studied new graphene-based nanostructures by employing cutting-edge surface science techniques. Most of the experimental data we have acquired has been given a new light by powerful Density Functional Theory calculations, that allow for an approach where hardly accessible data (experimentally) becomes indirectly known through numerical calculations, while providing valuable feedback for further aimed calculations. I will show how we have undertaken a route that takes us from a detailed study of how carbon monomers, the building blocks of graphene, come to exist on an Ir(1 1 1) surface after ethylene dissociation. Next, simple nanostructures have been ex- ploited, so that the properties of a preexisting graphene layer are manipulated by intercalating different metals between graphene and the substrate. Then I will discuss an experiment where graphene was grown on a highly anisotropic substrate, Ru(1 0 1 0), which proved to be an extremely rich system, giving rise to several self-assembled graphene nanostructures, including nanoribbons and one-dimensional quasi free-standing graphene waves. Then, we will progress to what are commonly perceived as being proper graphene-based nanostructures. We have, in fact, managed to create size selected graphene nanodomes on Ir(1 1 1) using coronene as a precursor, and we have understood many details of the dynamics in the formation of these carbon-based nanostructures, discovering that in certain steps of the reaction they lift from the surface and rotate, before settling in the definitive adsorption position. Furthermore, while performing similar experiments on pentacene (a semiconducting molecule, used the fabrication of molecular FETs) on Ir(1 1 1), we have discovered that the molecules exhibit a reversible dehydrogenation, allowing for a switch between semiconducting molecules and minimalistic graphene nanoribbons, only one aromatic ring wide.
Finally, a size-selected nanocluster source system will be described. In parallel with my research activity, I have been profoundly involved in the commissioning of such a machine that is currently capable of producing size selected nanoclusters.
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Wu, Yimin A. "Towards large area single crystalline two dimensional atomic crystals for nanotechnology applications." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:bdb827e5-f3fd-4806-8085-0206e67c7144.
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Nanomaterials have attracted great interest due to the unique physical properties and great potential in the applications of nanoscale devices. Two dimensional atomic crystals, which are atomic thickness, especially graphene, have triggered the gold rush recently due to the fascinating high mobility at room temperature for future electronics. The crystal structure of nanomaterials will have great influence on their physical properties. Thus, this thesis is focused on developing the methods to control the crystal structure of nanomaterials, namely quantum dots as semiconductor, boron nitride (BN) as insulator, graphene as semimetal, with low cost for their applications in photonics, structural support and electronics. In this thesis, firstly, Mn doped ZnSe quantum dots have been synthesized using colloidal synthesis. The shape control of Mn doped ZnSe quantum dots has been achieved from branched to spherical by switching the injection temperature from kinetics to thermodynamics region. Injection rates have been found to have effect on controlling the crystal phase from zinc blende to wurtzite. The structural-property relationship has been investigated. It is found that the spherical wurtzite Mn doped ZnSe quantum dots have the highest quantum yield comparing with other shape or crystal phase of the dots. Then, the Mn doped ZnSe quantum dots were deposited onto the BN sheets, which were micron-sized and fabricated by chemical exfoliation, for high resolution imaging. It is the first demonstration of utilizing ultrathin carbon free 2D atomic crystal as support for high resolution imaging. Phase contrast images reveal moiré interference patterns between nanocrystals and BN substrate that are used to determine the relative orientation of the nanocrystals with respect to the BN sheets and interference lattice planes using a newly developed equation method. Double diffraction is observed and has been analyzed using a vector method. As only a few microns sized 2D atomic crystal, like BN, can be fabricated by the chemical exfoliation. Chemical vapour deposition (CVD) is as used as an alternative to fabricate large area graphene. The mechanism and growth dynamics of graphene domains have been investigated using Cu catalyzed atmospheric pressure CVD. Rectangular few layer graphene domains were synthesized for the first time. It only grows on the Cu grains with (111) orientation due to the interplay between atomic structure of Cu lattice and graphene domains. Hexagonal graphene domains can form on nearly all non-(111) Cu surfaces. The few layer hexagonal single crystal graphene domains were aligned in their crystallographic orientation over millimetre scale. In order to improve the alignment and reduce the layer of graphene domains, a novel method is invented to perform the CVD reaction above the melting point of copper (1090 ºC) and using molybdenum or tungsten to prevent the balling of the copper from dewetting. By controlling the amount of hydrogen during the growth, individual single crystal domains of monolayer over 200 µm are produced determined by electron diffraction mapping. Raman mapping shows the monolayer nature of graphene grown by this method. This graphene exhibits a linear dispersion relationship and no sign of doping. The large scale alignment of monolayer hexagonal graphene domains with epitaxial relationship on Cu is the key to get wafer-sized single crystal monolayer graphene films. This paves the way for industry scale production of 2D single crystal graphene.
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Luo, Qinmo. "Interfacial-Active Graphene Oxide-based Materials for Ionic Liquid Encapsulation." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1575900447161884.
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Barabanova, Liudmyla. "Frictional Anisotropy of Graphene and Graphene Based Materials." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461941753.
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Rodier, Bradley J. "Modification of Graphene Oxide for Tailored Functionality." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1515509392532651.
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Liu, Yiyang. "PHOTOLUMINESCENCE MECHANISM AND APPLICATIONS OF GRAPHENE QUANTUM DOTS." UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/78.
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Graphene quantum dots (GQDs) are small pieces of graphene oxide whose physical dimensions are so confined (a few to a few tens nm) that they have a finite bandgap due to a quantum confinement effect. The finite bandgap of GQDs grants them pronounced absorption bands and a substantial photoluminescence. These optical properties are rarely observed in traditional carbon materials, since most of carbon materials are metallic with a near-zero bandgap and thus have broad absorption spectra with no photoluminescence. The unique optical properties of GQDs, along with GQDs’ inherited advantages from carbon material family (cheap, abundant, non-toxic), make GQDs an attractive material for various applications such as bio-imaging, photoinduced therapy, chemical and metal ion sensors, and photovoltaic devices. Despite of their great potential, several great challenges need to be overcome to enable wider applications. One challenge is the fact that GQDs prepared by typical chemical methods possess significant inhomogeneity, so the precise control of the dimension and surface functionalities is very difficult. Due to the inhomogeneity of GQDs in terms of dimensions and surface functionalities, it is challengeable to establish a precise structure-property relationship. As of today, it is still under debate how surface functional groups of GQDs are responsible for the photoluminescence mechanism, photophysics, and photochemistry. This dissertation is mainly to provide a dedicated study about the photoluminescence mechanism and structure-property relations of GQDs.
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Rice, Philip Zachary. "The Effect of Nanostructure on the Electrical Properties of Metal Oxide Materials." Thesis, State University of New York at Albany, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3568291.
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Resistive random access memory (ReRAM) is a potential replacement technology for Flash and other memory implementations. Advantages of ReRAM include increased scalability, low power operation, and compatibility with silicon semiconductor manufacturing. Most of the ReRAM devices described to date have utilized thin film based metal oxide dielectrics as a resistive switching matrix. The goal of this dissertation project has been to investigate the resistive switching behavior of nanoparticulate metal oxides and to develop methods to utilize these materials in ReRAM device fabrication. To this end, nanoparticles of TiO2 and HfO2 were synthesized under a variety of conditions resulting in various size, shape, and crystallinity. Electrical measurements of individual nanoparticles, as well as composite films of nanoparticles, were performed with limited success. To improve the stability of nanoparticle films, a spin on glass, hydrogen silsesquioxane (HSQ), was incorporated into the film stack. Addition of HSQ prevented electrical shorting and stabilized the nanoparticle films. In addition to serving as a stabilizer for nanoparticle films, HSQ was also found to have its own resistive switching properties. Composite films consisting of HSQ and nanoparticles yielded modified switching behavior which was tunable based upon nanoparticle composition and the thickness of the nanoparticle film. Our results demonstrate that both VSET and VRESET of HSQ switching can be increased when nanoparticles are incorporated with HSQ, without any significant changes to the device's high and low resistance states. We conclude that metal oxide nanoparticles can function as the dielectric material for ReRAM and can also be used to modulate the switching properties of composite ReRAM devices.
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Rodner, Marius. "Towards a versatile gas sensing platform with epitaxial graphene." Licentiate thesis, Linköpings universitet, Sensor- och aktuatorsystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-160482.
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The work presented in this thesis focuses on how to utilize epitaxially grown graphene on SiC as a basis for ultra-sensitive gas sensor. Several approaches have been tested and evaluated to increase the sensitivity, selectivity, speed of response and stability and of the graphene based gas sensors with a focus on air quality monitoring applications. The graphene surfaces have been functionalized with different metal oxide nanoparticles and nanolayers using hollow-cathode sputtering and pulsed laser deposition. The modified surface was investigated towards its topography, integrity and chemical composition with characterization methods such as AFM, Raman and XPS. Moreover, the binding energy was calculated with density functional theory for benzene and formaldehyde when reacting with pristine epitaxial graphene and iron oxide nanoparticle decorated graphene to verify the usefulness of this approach. The impact of environmental influences such as operating temperature, relative humidity and UV irradiation towards sensing properties was investigated as well. To further decrease time constants, the first-order time-derivative of the sensor’s resistance is introduced as an alternative sensor signal and evaluated towards its applicability. Applying these methods in laboratory conditions, sensors with a quantitative readout of single ppb benzene and formaldehyde were developed and time constants of less than one minute could be achieved with the first-order time-derivative signal. These results show promise to fill the existing gap of low-cost but highly sensitive and fast gas sensors for air quality monitoring.
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Srivastava, Devesh. "Fabrication of nanostructures and nanostructure based interfaces for biosensor application." Diss., Connect to online resource - MSU authorized users, 2008.
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Lin, Andrew. "Metal-Organic Frameworks and Graphene-Based Support Materials for Heterogeneous Catalysis." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5574.
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Nanoparticles are involved in a broad range of applications, including heterogeneous catalysis. Nanoparticles tend to quickly lose their well-defined shapes and facets due to aggregation under duress such as heat.
A series of highly studied materials are explored as support materials for nanoparticle supports. These supports include metal-organic frameworks (MOF), graphene oxide (GO), and a MOF-PRGO (partially reduced graphene oxide) hybrid. The inclusion of a support with the palladium increased lifespan of the catalyst by separation of nanoparticles. The choice of support material not only allowed for supporting of palladium nanoparticles, but allowed for rational catalyst synthesis in order to design catalysts with improved catalytic activity.
CO oxidation, vanillin hydrogenation, and Suzuki cross coupling were studied. For the CO oxidation reaction, a cerium-based MOF, Ce-MOF, is shown to increase activity of palladium nanoparticles by capturing reactant gases and acting as an oxygen reservoir that cycles between (III) and (IV) states while transferring oxygen to palladium nanoparticles at the Pd/Ce-MOF interface. A hybrid Ce-MOF-PRGO was synthesized to increase the surface area and acidity of Ce-MOF materials and was shown to be active for vanillin hydrogenation. Smaller rod-like Ce-MOF crystals were observed, indicating intercalation of crystals on GO. Zirconium-based MOF UiO-66-NH2 was acidified via incorporation of tungstophosphoric acid (HPW), which increased the selectivity of products by adjusting the mechanistic pathway. GO was partially functionalized with aromatic amines to improve the coupling of bromobenzene and phenylboronic acid. Small amounts of aromatic amines increased the Pd(0) content and decreased nanoparticle size.
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Zhang, Guohui. "Electrochemistry and applications of sp2 carbon materials : from graphite to graphene." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/89303/.
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This thesis can be divided into three themes: (i) the electrochemistry of sp2 carbon materials, with a focus on graphite and graphene, where electron transfer (ET) kinetics and surface functionalisation were considered; (ii) methodology development for graphene transfer, to facilitate the fabrication of versatile tools for microscopy research and allow the properties of supported and suspended graphene to be readily assessed and compared; (iii) the electrowetting of graphite, providing a new mechanism for droplet actuation on a conducting surface with an applied electric field. There is a large body of literature that the basal plane of highly oriented pyrolytic graphite (HOPG) is inert or has little electroactivity for outer-sphere redox couples and adsorbed species. Here, the model is revisited with the macroscopic ET kinetics studies of three classical (outer-sphere) redox couples on different grades of HOPG using a droplet-cell setup. It is shown that the ET kinetics for all of the redox species studied is fast on all grades of HOPG (comparable to metal electrodes), despite the low density of electronic states (DOS) on graphite. This is in line with the results where the ‘special’ redox couple, Fe3+/2+, associated with a slow kinetics, is tested. Moreover, localised surface mapping measurements of HOPG using scanning electrochemical cell microscopy (SECCM), reveal a relatively uniform activity on basal plane and step edges of HOPG towards Fe3+/2+, highlighting that the basal plane is electroactive and the major site for the ET kinetics of Fe3+/2+. The next goal is to elucidate whether adsorbed electroactive anthraquinone-2,6-disulfonate (AQDS) can be used as a marker of step edges, previously regarded as the main electroactive sites of graphite. Step edges are shown to have little effect on the extent of adsorbed electroactive AQDS in macroscopic studies. The amount of adsorbed electroactive AQDS and the ET kinetics are independent of the step edge coverage, as determined by fast scan cyclic voltammetry-SECCM. Further, SECCM reactive patterning shows essentially uniform and high activity across the basal surface of HOPG, indicative of the dominance of basal plane in HOPG electroactivity. Regarding the close relation between graphene and graphite, effort is put to introduce a polymer-free method for transferring chemical vapour deposition (CVD)-grown graphene, to arbitrary substrates, using an organic/aqueous biphasic configuration. Avoiding any polymeric contamination, graphene is coated on arbitrary substrates, such as atomic force microscopy (AFM) tips and transmission electron microscopy (TEM) grids, generating tools for conductive AFM and high resolution TEM imaging. Furthermore, electrochemical and wetting measurements at either a freestanding graphene film or a copper-supported graphene area, are readily made and compared. As an example of the myriad potential applications of graphite, electrowetting is demonstrated at HOPG, using cyclic voltammetry, with significant changes in contact angle and relative contact diameter seen. These are comparable to the widely studied electrowetting-on-dielectric (EWOD) system, but over a much lower voltage range. Electrowetting is found to be due to the intercalation/de-intercalation of anions between the graphene layers of graphite, driven by the applied potential, providing a new mechanism for electrowetting and diversifying the means by which electrowetting can be controlled and applied.
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Baltazar, Jose A. "Polycyclic aromatic hydrocarbons: exploring new processes and materials for electronics." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51787.
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Graphene is a two-dimensional sp2 hybridized carbon lattice that is also the fundamental building block of graphite. Graphene has attracted significant interest recently due to its distinctive electrical, optical and mechanical properties. These properties have spurred research directed at modifying graphene for use in a variety of electronic, optoelectronic, and sensor technologies. However, before graphene can be used in products, it is necessary to find methods to tune, modify, grow and integrate graphene features while substantially boosting device performance and maintaining current processing compatibility and ease of integration with existing manufacturing infrastructure.
This dissertation focuses on developing techniques for controllably doping the graphene layer through scalable, industry friendly and simple chemical doping; using self-assembled monolayer compounds, photo-acid and photo-base generators, polymers and metal-organic species. We have, in fact, demonstrated simple p-n junctions fabricated in this manner. Characteristic I-V curves indicate the superposition of two separate Dirac points from the p and n regions, confirming an energy separation of neutrality points within the complementary regions; Raman studies of these methods have shown that these processes result in extremely low defect levels in the graphene. Our simple methods for producing patterned doping profiles in graphene films and devices open up a variety of new possibilities for forming complex doping profiles in a simple manner in graphene. This work can enable rapid testing, such as controlled work function tuning, complex doping profiles and simple post-fabrication tuning, of concepts for graphene that may be useful in both interconnect and transparent conductor applications.
In addition to graphene doping, we also investigated approaches to the synthesis of few-layer graphene flakes, since current techniques still produce inferior materials. Exfoliation of Graphene Sheets by an Electron Donor Surfactant was demonstrated to generate few-layers graphene flakes that rival the electrical quality of reduce graphene-oxide (rGO) flakes. Last but not least, Diels-Alder adducts on silica were explored as a controllable carbon precursor for pristine graphene; these allow for a rational direct-growth-of-graphene-on-surface reaction mediated by copper catalyst, without the use of flammable precursors, such as methane, that are used in current methods of chemical vapor deposition synthesis of graphene.
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Petroski, Janet Marie. "Platinum metal nanoparticles : investigation of shape, surface, catalysis and assembly." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/30961.
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Tran, Hoang Anh. "One-Dimensional Nanostructure and Sensing Applications: Tin Dioxide Nanowires and Carbon Nanotubes." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2689.
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The key challenge for a nanomaterial based sensor is how to synthesize in bulk quantity and fabricate an actual device with insightful understanding of operational mechanisms during performance. I report here effective, controllable methods that exploit the concepts of the "green approach" to synthesize two different one-dimensional nanostructures, including tin oxide nanowires and carbon nanotubes. The syntheses are followed by product characterization and sensing device fabrications as well as sensor performance understanding at the molecular level. Sensor-analyte response and recovery kinetics are also presented.
The first part of the thesis describes bulk-scale synthesis and characterization of tin oxide nanowires by the molten salt synthetic method and the nanowire doping with antimony (n-types) and lithium. The work builds on the success of using n-doped SnO2 nanoparticles to selectively detect chlorine gas at room temperature. Replacing n-doped nanoparticles with n-doped nanowires reduces the number of inter-particle electron hops between sensing electrodes. The nanowire based sensors show unprecedented 5 ppb detectability of corrosive Cl2 gas concentration in air. At the higher range, 10 ppm of Cl2 gas leads to a 250 fold increase in the device resistance. During sensor recovery, FT-IR studies show that dichlorine monoxide (Cl2O) and chlorine dioxide (ClO2) are the desorbing species. Long term stability of devices is affected by lattice oxygen vacancies replaced by chlorine atoms.
Bulk-scale synthesis of multiwall carbon nanotube (MWCNTs) was achieved by a novel inexpensive synthetic method. The green chemistry method uses the non-toxic and easy to handle solid carbon source naphthalene. The synthesis is carried out by simply heating naphthalene and organometallic precursors as catalysts in a sealed glass tube. Synthesis at 610º C leads to MWCNTs of 50 nm diameter and lengths exceeding well over microns. MWCNT doping is attempted with nitrogen (n-type) and boron (p-type) precursors. Palladium nanoparticles decorated on as-synthesized MWCNTs are employed for specific detection of explosive hydrogen gas with concentrations far below the explosive concentration limits. During performance, the sensor exhibits abnormal response behaviors at hydrogen gas concentrations higher than 1%. A model of charge carrier inversion, brought about by reduction of MWCNT by hydrogen molecules dissociated by Pd nanoparticles is proposed.
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Guday, Guy [Verfasser]. "Surface Chemistry of Low-Dimensional Carbon Materials : Synthesis and Functionalization of Graphene / Guy Guday." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/120573645X/34.
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Cheekati, Sree Lakshmi. "GRAPHENE BASED ANODE MATERIALS FOR LITHIUM-ION BATTERIES." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1302573691.
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Rhoads, Daniel Joseph. "A Mathematical Model of Graphene Nanostructures." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1438978423.
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Kubo, Shiori. "Nanostructured carbohydrate-derived carbonaceous materials." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5315/.
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Nanoporous carbon materials are widely used in industry as adsorbents or catalyst supports, whilst becoming increasingly critical to the developing fields of energy storage / generation or separation technologies. In this thesis, the combined use of carbohydrate hydrothermal carbonisation (HTC) and templating strategies is demonstrated as an efficient route to nanostructured carbonaceous materials. HTC is an aqueous-phase, low-temperature (e.g. 130 – 200 °C) carbonisation, which proceeds via dehydration / poly-condensation of carbon precursors (e.g. carbohydrates and their derivatives), allowing facile access to highly functional carbonaceous materials. Whilst possessing utile, modifiable surface functional groups (e.g. -OH and -C=O-containing moieties), materials synthesised via HTC typically present limited accessible surface area or pore volume. Therefore, this thesis focuses on the development of fabrication routes to HTC materials which present enhanced textural properties and well-defined porosity.
In the first discussed synthesis, a combined hard templating / HTC route was investigated using a range of sacrificial inorganic templates (e.g. mesoporous silica beads and macroporous alumina membranes (AAO)). Via pore impregnation of mesoporous silica beads with a biomass-derived carbon source (e.g. 2-furaldehyde) and subsequent HTC at 180 oC, an inorganic / carbonaceous hybrid material was produced. Removal of the template component by acid etching revealed the replication of the silica into mesoporous carbonaceous spheres (particle size ~ 5 μm), representing the inverse morphological structure of the original inorganic body. Surface analysis (e.g. FTIR) indicated a material decorated with hydrophilic (oxygenated) functional groups. Further thermal treatment at increasingly elevated temperatures (e.g. at 350, 550, 750 oC) under inert atmosphere allowed manipulation of functionalities from polar hydrophilic to increasingly non-polar / hydrophobic structural motifs (e.g. extension of the aromatic / pseudo-graphitic nature), thus demonstrating a process capable of simultaneous control of nanostructure and surface / bulk chemistry.
As an extension of this approach, carbonaceous tubular nanostructures with controlled surface functionality were synthesised by the nanocasting of uniform, linear macropores of an AAO template (~ 200 nm). In this example, material porosity could be controlled, showing increasingly microporous tube wall features as post carbonisation temperature increased. Additionally, by taking advantage of modifiable surface groups, the introduction of useful polymeric moieties (i.e. grafting of thermoresponsive poly(N-isopropylacrylamide)) was also demonstrated, potentially enabling application of these interesting tubular structures in the fields of biotechnology (e.g. enzyme immobilization) and medicine (e.g. as drug micro-containers).
Complimentary to these hard templating routes, a combined HTC / soft templating route for the direct synthesis of ordered porous carbonaceous materials was also developed. After selection of structural directing agents and optimisation of synthesis composition, the F127 triblock copolymer (i.e. ethylene oxide (EO)106 propylene oxide (PO)70 ethylene oxide (EO)106) / D-Fructose system was extensively studied. D-Fructose was found to be a useful carbon precursor as the HTC process could be performed at 130 oC, thus allowing access to stable micellular phase. Thermolytic template removal from the synthesised ordered copolymer / carbon composite yielded functional cuboctahedron single crystalline-like particles (~ 5 μm) with well ordered pore structure of a near perfect cubic Im3m symmetry. N2 sorption analysis revealed a predominantly microporous carbonaceous material (i.e. Type I isotherm, SBET = 257 m2g-1, 79 % microporosity) possessing a pore size of ca. 0.9 nm. The addition of a simple pore swelling additive (e.g. trimethylbenzene (TMB)) to this system was found to direct pore size into the mesopore size domain (i.e. Type IV isotherm, SBET = 116 m2g-1, 60 % mesoporosity) generating pore size of ca. 4 nm. It is proposed that in both cases as HTC proceeds to generate a polyfuran-like network, the organised block copolymer micellular phase is essentially “templated”, either via hydrogen bonding between hydrophilic poly(EO) moiety and the carbohydrate or via hydrophobic interaction between hydrophobic poly(PO) moiety and forming polyfuran-like network, whilst the additive TMB presumably interact with poly(PO) moieties, thus swelling the hydrophobic region expanding the micelle template size further into the mesopore range.Nanoporöse kohlenstoffbasierte Materialien sind in der Industrie als Adsorbentien und Katalysatorträger weit verbreitet und gewinnen im aufstrebenden Bereich der Energiespeicherung/erzeugung und für Trennverfahren an wachsender Bedeutung. In der vorliegenden Arbeit wird gezeigt, dass die Kombination aus hydrothermaler Karbonisierung von Zuckern (HTC) mit Templatierungsstrategien einen effizienten Weg zu nanostrukturierten kohlenstoffbasierten Materialien darstellt. HTC ist ein in Wasser und bei niedrigen Temperaturen (130 - 200 °C) durchgeführter Karbonisierungsprozess, bei dem Zucker und deren Derivate einen einfachen Zugang zu hochfunktionalisierten Materialien erlauben. Obwohl diese sauerstoffhaltige Funktionalitäten auf der Oberfläche besitzen, an welche andere chemische Gruppen gebunden werden könnten, was die Verwendung für Trennverfahren und in der verzögerten Wirkstofffreisetzung ermöglichen sollte, ist die mittels HTC hergestellte Kohle für solche Anwendungen nicht porös genug. Das Ziel dieser Arbeit ist es daher, Methoden zu entwickeln, um wohldefinierte Poren in solchen Materialien zu erzeugen. Hierbei führte unter anderem der Einsatz von anorganischen formgebenden mesoporösen Silikapartikeln und makroporösen Aluminiumoxid-Membranen zum Erfolg. Durch Zugabe einer Kohlenstoffquelle (z. B. 2-Furfural), HTC und anschließender Entfernung des Templats konnten poröse kohlenstoffbasierte Partikel und röhrenförmige Nanostrukturen hergestellt werden. Gleichzeitig konnte durch eine zusätzliche Nachbehandlung bei hoher Temperatur (350-750 °C) auch noch die Oberflächenfunktionalität hin zu aromatischen Systemen verschoben werden. Analog zur Formgebung durch anorganische Template konnte mit sog. Soft-Templaten, z. B. PEO-PPO-PEO Blockcopolymeren, eine funktionelle poröse Struktur induziert werden. Hierbei machte man sich die Ausbildung geordneter Mizellen mit der Kohlenstoffquelle D-Fructose zu Nutze. Das erhaltene Material wies hochgeordnete Mikroporen mit einem Durchmesser von ca. 0,9 nm auf. Dieser konnte desweiteren durch Zugabe von Quell-Additiven (z. B. Trimethylbenzol) auf 4 nm in den mesoporösen Bereich vergrößert werden. Zusammenfassend lässt sich sagen, dass beide untersuchten Synthesewege nanostrukturierte kohlenstoffbasierte Materialien mit vielfältiger Oberflächenchemie liefern, und das mittels einer bei relativ niedriger Temperatur in Wasser ablaufenden Reaktion und einer billigen, nachhaltigen Kohlenstoffquelle. Die so hergestellten Produkte eröffnen vielseitige Anwendungsmöglichkeiten, z. B. zur Molekültrennung in der Flüssigchromatographie, in der Energiespeicherung als Anodenmaterial in Li-Ionen Akkus oder Superkondensatoren, oder als Trägermaterial für die gezielte Pharmakotherapie.
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Shukr, Delan. "Carbon nanomaterials as electrical conductors in electrodes." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85056.
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In this project, different molecules have been investigated with the purpose of creating anohmic contact between metals and carbon nano materials. In particular, we considered simplemolecules connecting a graphene layer and a copper-slab. In order to determine the capability of such systems, the electronic structure was computedusing Density Functional Theory (DFT). Structural relaxation was performed in order to findcandidates where the metal and the graphene binds chemically with the hypothesis that thehybridization of the states will induce more states at the Fermi level. Six different molecularchains were tested and three of them were found to chemisorb to the graphene sheet and thecopper surface simultaneously. The electronic properties for these systems were then furtherinvestigated using the density of states (DOS). An overlap density of states (ODOS) wasdefined in order to evaluate the respective contribution of the graphene, metal and molecule. From the DOS analysis, we report that these systems did not form ohmic contacts as the resultshows too few states close to the Fermi level. The most interesting case was using a hexanolchain which had some partially overlapping states seen from the ODOS of the graphenemoleculeand graphene-Cu at the Fermi level. However, these were only small contributions.Further research is crucial in order to find a more suitable molecular chain between thegraphene and the copper for an ohmic contact.
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Hos, James Pieter. "Mechanochemically synthesized nanomaterials for intermediate temperature solid oxide fuel cell membranes." University of Western Australia. School of Mechanical Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0016.
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[Truncated abstract] In this dissertation an investigation into the utility of mechanochemically synthesized nanopowders for intermediate temperature solid oxide fuel cell components is reported. The results are presented in the following parts: the synthesis and characterisation of precursors for ceramic and cermet components for the fuel cell; the physical and electrical characterisation of the electrolyte and electrodes; and the fabrication, operation and analysis of the resulting fuel cells. Samarium-doped (20 mol%) ceria (SDC) nanopowder was fabricated by the solid-state mechanochemical reaction between SmCl3 with NaOH and Ce(OH)4 in 85 vol% dilution with NaCl. A milling time of 4 hours and heat treatment for 2 hours at 700°C yielded a material with equivalent particle and crystallite sizes of 17 nm. The existence of a complete solid solution was affirmed by electron energy loss spectroscopy and x-ray diffraction analysis. Doped-ceria compacts were sintered for 4 hours at 1350°C forming ceramics of 88% theoretical density. The ionic conductivity in flowing air was 0.009 S/cm, superior to commercially supplied nanoscale SDC. Anode precursor composite NiO-SDC nanopowder was synthesized by milling Ni(OH)2 with the previously defined SDC formulation ... Anode-supported fuel cells were fabricated on a substrate of at least 500 'm 55wt%NiO-SDC with 17vol% graphite pore formers. Suspensions of SDC were deposited by aerosol on the sintered bilayer at a thickness around 5 'm. A cathode of 10% SDC (SmSr)0.5CoO3 was deposited onto the sintered electrolyte and after firing had a thickness of around 25 'm. Operation of fuel cells in single-chamber mixtures of CH4 and air diluted in argon were successful and gave power outputs of 483 'W/cm2. Operation in undiluted 25 vol% CH4:air gave a power output of 5.5 mW/cm2. It was shown that a large polarisation resistance of 4.1 Ω.cm2 existed and this was assigned to losses in the anode, namely mass transport limitation associated with the catalytic combustion of methane and insufficient porosity. The large surface area of Ni appeared to allow more methane to combust and hence prevented its electrochemical reaction from occurring, thus limiting the performance of the cell. The synthesis procedures, ceramic processing and fabrication techniques and testing methods are discussed and contribute significant understanding to the fields of ceramic science and fuel cell technology.
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Chalangar, Ebrahim. "Graphene-based nanocomposites for electronics and photocatalysis." Licentiate thesis, Linköpings universitet, Fysik, elektroteknik och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-157095.
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The development of future electronics depends on the availability of suitable functional materials. Printed electronics, for example, relies on access to highly conductive, inexpensive and printable materials, while strong light absorption and low carrier recombination rates are demanded in photocatalysis industry. Despite all efforts to develop new materials, it still remains a challenge to have all the desirable aspects in a single material. One possible route towards novel functional materials, with improved and unprecedented physical properties, is to form composites of different selected materials. In this work, we report on hydrothermal growth and characterization of graphene/zinc oxide (GR/ZnO) nanocomposites, suited for electronics and photocatalysis application. For conductive purposes, highly Al-doped ZnO nanorods grown on graphene nanoplates (GNPs) prevent the GNPs from agglomerating and promote conductive paths between the GNPs. The effect of the ZnO nanorod morphology and GR dispersity on the nanocomposite conductivity and GR/ZnO nanorod bonding strength were investigated by conductivity measurements and optical spectroscopy. The inspected samples show that growth in high pH solutions promotes a better graphene dispersity, higher doping and enhanced bonding between the GNPs and the ZnO nanorods. Growth in low pH solutions yield samples characterized by a higher conductivity and a reduced number of surface defects. In addition, different GR/ZnO nanocomposites, decorated with plasmonic silver iodide (AgI) nanoparticles, were synthesized and analyzed for solar-driven photocatalysis. The addition of Ag/AgI generates a strong surface plasmon resonance effect involving metallic Ag0, which redshifts the optical absorption maximum into the visible light region enhancing the photocatalytic performance under solar irradiation. A wide range of characterization techniques including, electron microscopy, photoelectron spectroscopy and x-ray diffraction confirm a successful formation of photocatalysts. Our findings show that the novel proposed GR-based nanocomposites can lead to further development of efficient photocatalyst materials with applications in removal of organic pollutants, or for fabrication of large volumes of inexpensive porous conjugated GR-semiconductor composites.
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Vijapur, Santosh H. "Engineering Graphene Films from Coal." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1449157836.
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Kisurin, Vitaly Mr. "Laser Vaporization Controlled Condensation and Laser Irradiation in Solution for the Synthesis of Supported Nanoparticle Catalysts." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4636.
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Solid catalyst supports of SiOx-RGO (Reduced Graphene Oxide) and UiO-67 (Universitet i Oslo) have been successfully synthesized and were loaded with palladium nanoparticles to test for a series of heterogeneous reactions. The SiOx/RGO catalysts were synthesized through laser ablation of silicon and graphite oxide micron powder and UiO-67 metal-organic framework (MOF) was synthesized through mixing of precursors with DMF/HCl solution and washing the resultant powder from impurities. The SiOx/RGO supports were later impregnated with palladium precursors which were then subject to Microwave Irradiation (MWI). The UiO-67 framework was impregnated with palladium precursors and was irradiated with pulsed Nd:YAG 532 nm laser and was purified through washing and centrifugation. The resulting catalyst supports were characterized with UV-Vis, FTIR, Raman, XRD and XPS techniques and the UiO-67 framework was subject to Brunauer-Emmet-Teller (BET) surface area measurements before and after the catalytic reactions. The catalytic activity of palladium nanoparticles supported on SiOx/RGO and UiO-67 framework was tested in carbon cross-coupling reactions of Suzuki-Miyaura, Sonogashira reactions and oxidation of benzyl alcohol respectively. The catalysts have demonstrated excellent performance and have yielded a promising future for the catalytic supports in the previously stated reactions.
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Chou, Tammy Ping-Chun. "Effects of the nanostructure and the chemistry of various oxide electrodes on the overall performance of dye-sensitized solar cells /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10580.
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McCausland, Jeffrey A. "Select Applications of Scanning Probe Microscopy to Group XIV Surfaces and Materials." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510327417528433.
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Pfau, Michaela R. "Toward High Performance Nanocarbon Fibers." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1578.
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High performance carbon fibers (CFs) have been a commercially available since their commercial boom in the 1970s, and are generally produced via carbonization of poly (acrylonitrile) (PAN). More recently, carbon nanomaterials like graphene and carbon nanotubes (CNTs) have been discovered and have shown excellent mechanical, thermal, and electrical properties due to their sp2 carbon repeating structure. Graphene and CNTs can both be organized into macroscopic fibers using a number of different techniques, resulting in fibers with promising mechanical performance that can be readily multifunctionalized. In some cases, the two materials have been combined, and the resulting hybrid fibers have been shown to display synergistically enhanced mechanical properties. The incredible intrinsic properties of graphene and CNTs has never been fully realized in their fiber assemblies, so part of the aim of this work is to discover methods to improve upon the performance of nanocarbon based fibers. Carbon nanomaterials can be difficult to work with because of the difficulty in processing them into commercially viable materials, and the challenges associated with scalable production techniques. So, the main goal of this work is to prepare hybrid graphene and CNT based fibers with optimal mechanical performance using simple, cost-effective methods.
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Daggag, Dalia. "Computational Study on Binding of Naturally Occurring Aromatic and Cyclic Amino Acids with Graphene." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2019. http://digitalcommons.auctr.edu/cauetds/203.
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The knowledge on the conformations of amino acids is essential to understand the biochemical behaviors and physical properties of proteins. Comprehensive computational study is focused to understand the conformational landscape of three aromatic amino acids (AAAs): tryptophan, tyrosine, and phenylalanine. Three different density functionals (B3LYP, M06-2X and wB97X-D) were used with two basis sets of 6-31G(d) and 6-31+G(d,p) for geometry optimizations of the conformers of AAAs followed by the vibrational frequencies. The goal was to identify the right choice of density functional theory (DFT) level for conformational analysis of amino acids by comparing the computational data against the available experimental results. Calculated infrared (IR) frequency values indicated that wB97X-D/6-31+G(d,p) level is less favorable than other DFT levels in case of O-H and N-H stretching frequencies for the conformers of AAAs. The C=O stretching frequencies at different computational levels were in good agreement with the experimental results.
Interactions of AAAs (tryptophan, tyrosine, and phenylalanine) and two cyclic amino acids (histidine and proline) individually with two finite-sized graphene sheets (C62H20 and C186H36) were explored using M06-2X/6-31G(d) level. Computational investigations of the binding of amino acids with graphene provide knowledge for designing of new graphene-based biological/biocompatible materials. Selected conformers for each amino acid with different orientations on the surface of graphene were examined. The purpose of computational study on graphene-amino acids interactions was to identify the preferred conformer of amino acid to bind on graphene as well as to find the influence of amino acid binding on the band gap of graphene. Different conformers of AAAs generally prefer parallel orientation through π-π interactions to bind with graphene. However, bent orientation is more preferred over parallel to bind on the surface of graphene in case of conformer having relative energy approximately equal to 5 kcal/mol for all three AAAs. Histidine generally exhibits higher binding affinity than proline to form complex with graphene. The binding energies in the aqueous medium were slightly lower than those obtained in the gas phase with some exceptions. The adsorption of amino acids did not affect the band gap of graphene.
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Wisetsuwannaphum, Sirikarn. "Electrochemical studies of carbon-based materials." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b18b808e-c517-4b18-9cf7-6f2a6714f8d4.
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Graphene, as a recently discovered carbon allotrope, possesses with it many outstanding properties ranging from high electrical conductivity to great mechanical strength. Single layer graphene can be prepared by mechanical cleavage of graphite or by a more sophisticated method, CVD. However, the scale-up process for these preparation techniques is still unconvincing. Solution-processed graphene from exfoliation of graphite oxide on the other hand provides an alternative prospect resulting in the formation of graphene nanoplatelets (GNPs), which can be readily manipulated to tailor-suit various application demands. The main aim of the thesis is to explore the possibility and availability of this versatile method to produce graphene nanoplatelet and its composites with good all-round performance in energy and bioanalytical applications. A range of physical and chemical characterisation techniques were utilised including SEM, TEM, AFM, XPS, XRD, DLS, FTIR, Raman and UV-Vis spectroscopy in order to investigate the structural and chemical information of the graphene-based materials prepared. Functionalisation of graphene oxide with polyelectrolyte polymer could facilitate deposition of platinum nanoparticles in the formation of Pt-GNPs composites. The resultant composite was employed for bioanalytical application in the detection of an important neurotransmitter, glutamate, based on glutamate oxidase enzyme. The performance of Pt-GNPs based glutamate sensor exhibited enhanced sensitivity and prolonged stability compared to the sensors based on Pt decorated diamond or glassy carbon electrodes. The significant interfering effect from concomitant electrochemically active biological compounds associated with Pt-GNPs electrode however could be alleviated via opting for Prussian blue deposited GNPs electrode instead. The oppositely charged Pt-GNPs due to different functionalising polymers were also subject to self-assembly, which was enabled by the electrostatic interaction of the opposite charges of Pt-GNPs. The self-assembled film showed enhanced mechanical stability than the conventional drop-casted film and provided reasonably good activity towards oxidation of hydrogen peroxide. Three-component composite of graphene, nanodiamond and polyaniline was prepared via in-situ polymerisation for usage as an electrode material in electrochemical capacitors ("supercapacitors"). The addition of graphene was shown to significantly enhance specific capacitance while nanodiamond could improve the stability of the electrode by strengthening the polymer core. Another approach to produce a supercapacitor was via electrodeposition of nickel and cobalt hydroxides on graphene oxide film corporated with bicarbonate salt. The film was then subject to thermal reduction of GO and expansion of graphene layers within the film was observed. This leavening process enhanced the surface area of graphene film and thus the higher specific capacitance was obtained. The decoration of nickel and cobalt hydroxides onto the film also boosted the specific capacitance further however the poor cycling stability of the heated film still remained an issue. Graphene nanoplatelets were also used as a support for electrodeposition of Pt nanoparticles for methanol oxidation in acidic media. The preferential phase of the Pt deposited and large surface area of graphene in comparison to other carbon supports studied led to good catalytic activity being observed.
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Yang, Xiangwen, Xiaodong Zhuang, Yinjuan Huang, Jianzhong Jiang, Hao Tian, Dongqing Wu, Fan Zhang, Yiyong Mai, and Xinliang Feng. "Nitrogen-enriched hierarchically porous carbon materials fabricated by graphene aerogel templated Schiff-base chemistry for high performance electrochemical capacitors." Royal Society of Chemistry, 2015. https://tud.qucosa.de/id/qucosa%3A36425.
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This article presents a facile and effective approach for synthesizing three-dimensional (3D) graphenecoupled Schiff-base hierarchically porous polymers (GS-HPPs). The method involves the polymerization of melamine and 1,4-phthalaldehyde, yielding Schiff-base porous polymers on the interconnected macroporous frameworks of 3D graphene aerogels. The as-synthesized GS-HPPs possess hierarchically porous structures containing macro-/meso-/micropores, along with large specific surface areas up to 776 m² g⁻¹ and high nitrogen contents up to 36.8 wt%. Consequently, 3D nitrogen-enriched hierarchically porous carbon (N-HPC) materials with macro-/meso-/micropores were obtained by the pyrolysis of the GS-HPPs at a high temperature of
800 °C under a nitrogen atmosphere. With a hierarchically porous structure, good thermal stability and a high nitrogen-doping content up to 7.2 wt%, the N-HPC samples show a high specific capacitance of 335 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH, a good capacitance retention with increasing current density, and an outstanding cycling stability. The superior electrochemical performance means that the N-HPC materials have great potential as electrode materials for supercapacitors.
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Ying, Chen. "Visible-Light-Responsible Co-Catalysts Enhanced by Graphene for Solar Energy Harvesting." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1614.
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This study focuses on the visible light response of hetero-structures of TiO2-graphene- MoS2 for solar energy harvestings. The commercial P25 TiO2 nano-particles, and selfprepared layered reduced graphene oxides (RG) and MoS2 were assembled for the targeted hetero-structure materials as visible-light responsible solar harvesting cocatalysts. The hydrothermal method was applied for nano-material synthesis, the reduction of graphene oxides, and bonding formation. Multiple characterization methods (SEM-TEM, XRD, XPS, UV-VIS, PL, FT-IR, TGA) have been applied to understand the electron-hole pair separation and recombination, and performance tuning in their visible-light photo-catalysis rhodamine B (Rh.B) degradations process
Compared to TiO2, an obvious red shift of light absorption (from 3.1 eV to 2.6 eV) of the as-prepared RG-TiO2 was observed by UV-vis analysis, and an enhanced photocatalytic degradation of the Rhodamine B (Rh.B) using the as-prepared RG-TiO2 was also observed in a Xe lamp exposure test. The explication of these two approaches to photocatalytic improvements were concluded as the energy gap changing, the formation of Ti-O-C chemical bonds between TiO2 and RG for charge transfer and the reduction of the band gap, as well as a likelihood of up-conversion photoluminescence mechanism (UCPL). The synthesis temperature was found to be critical factor to control binding formation and agglomeration of nano-materials. The lower and higher temperatures induced ineffective formations of preferable bonding structures and the significant agglomeration. The optimal synthesis temperature was found to be within 120 ℃-150 ℃ in the TiO2-RG system. For better understanding of the Ti-O-C bonding, a heterostructure of TiO2 nanotube arrays with GO (TNA-GO) was synthesized using the Langmuir-Blodgett (LB) assembly method. The band gap of this assemble was very close to the previous TiO2-RG synthesized below 120 ℃, which is very close to that of TiO2 nano-particles. This lead to the conclusion on the significance of the Ti-O-C bonding in the visible-light-responsible photo-catalysis solar harvestings.
This study revealed the fundamental mechanisms on the bonding formations and the significant visible-light-response of hetero-structcures between commercial-available, inexpensive and non-toxic TiO2 and layered materials, such as the zero-band-gap graphene and the smaller-band-gap MoS2. This mechanisms understanding will greatly sustain applications of economical-effective and environmental-safe TiO2.
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Jia, Tiantian. "Photocatalytic hydrogen production over layered materials." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6426c02b-f2b1-4326-a767-2384c303faf3.
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The technology of semiconductor-based photocatalytic water splitting to produce hydrogen using solar energy has been considered as one of the most important approaches to solve the world energy crisis. Therefore, the development of the effective semiconductor photocatalysts has undergone considerable research. However, the traditional photocatalysts suffer from the negative effects from rapid charge recombination, which reduces the excited charges by emitting light or generating phonons. Efficient charge separation and fast charge transport, avoiding any bulk/surface recombination, are fundamentally important for photocatalytic hydrogen generation through water splitting. Here, we have introduced assembled layered materials as photocatalyst systems with their unique physicochemical properties to realize the effective charge separation and high photocatalytic activity. Using graphene as a two-dimensional supporting matrix, we have succeeded in selective anchoring of semiconductor and metal nanoparticles as separate catalytically active sites on the graphene surface. The ability of graphene to capture, transfer and store electrons and its potential to serve as a conductive support are demonstrated. The TiO2 semiconductor/metals nanocrystals-graphene ensemble makes it possible to carry out selective catalytic processes at the separate sites and provides the potentials for applications in water splitting reactions. After demonstrating the positive role of graphene in such photocatalytic system, we then fabricate a simple but highly cooperative ensemble with CdS and MoS2 nanocrystals dispersed on graphene sheets. It is demonstrated that CdS nanocrystals can also capture visible light energy and facilitate excited electron transfer to MoS2 (as metal substituent) for catalytic hydrogen production via the 2-D graphene which plays a key role as an efficient electron mediator. Hexagonal multilayer MoS2 with a layered structure in this system serves to provide active sites for hydrogen evolution by its exposed Mo edges. Hence, multilayer MoS2 is an ideal cocatalyst of semiconductors for hydrogen generation. This crystalline-layered structure also shows semiconducting properties, however, its characteristic indirect band gap displays a poor light capture and emission ability with excited electrons and holes with different momentum. In contrast, single layer MoS2 shows a direct band gap behavior. Our studies have clearly shown that single layer MoS2 prepared with lithium intercalation indeed displays encouraging results in hydrogen evolution due to the direct band gap and quantum confinement effects. In addition, the exfoliated single layer MoS2 exhibits extraordinary enhanced activity and stability in combination with the Eosin Y sensitized system when compared to those of multilayer MoS2 and bulk MoS2 counterparts, which is attributed to the improvement of the density of surface active sites with stronger adsorption for the Eosin Y molecules on the single layer MoS2. In addition, this multifunctional catalyst on graphene sheet can also create adsorption sites on a defective basal surface of single layer MoS2 through adsorption of Eosin Y where electron transfer from photoexcited Eosin Y molecule to graphene via the 2-D MoS2 mainly takes place. Thus, the photo-generated electrons are then effectively transported to the exposed active sites of MoS2 for the proton reduction to hydrogen molecule. It is believed the above novel assembled molecular layered systems may be applicable for a wide range of catalytic,photocatalytic and electrocatalytic reactions.
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Watson, Venroy George. "Decoration of Graphene Oxide with Silver Nanoparticles and Controlling the Silver Nanoparticle Loading on Graphene Oxide." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1396879714.
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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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Botero, Carrizosa Sara C. "Synthesis, Characterization, and Properties of Graphene-Based Hybrids with Cobalt Oxides for Electrochemical Energy Storage and Electrocatalytic Glucose Sensing." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1941.
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A library of graphene-based hybrid materials was synthesized as novel hybrid electrochemical electrodes for electrochemical energy conversion and storage devices and electrocatalytical sensing namely enzymeless glucose sensing. The materials used were supercapacitive graphene-family nanomaterials (multilayer graphene-MLG; graphene oxide-GO, chemically reduced GO-rGO and electrochemical reduced GOErGO) and pseudocapacitive nanostructured transition metal oxides including cobalt oxide polymorphs (CoO and Co3O4) and cobalt nanoparticles (CoNP). These were combined through physisorption, electrodeposition, and hydrothermal syntheses approaches. This project was carried out to enhance electrochemical performance and to develop electrocatalytic platforms by tailoring structural properties and desired interfaces. Particularly, electrodeposition and hydrothermal synthesis facilitate chemically-bridged (covalently- and electrostatically- anchored) interfaces and molecular anchoring of the constituents with tunable properties, allowing faster ion transport and increased accessible surface area for ion adsorption. The surface morphology, structure, crystallinity, and lattice vibrations of the hybrid materials were assessed using electron microscopy (scanning and transmission) combined with energy dispersive spectroscopy and selected-area electron diffraction, X-ray diffraction, and micro-Raman Spectroscopy. The electrochemical properties of these electrodes were evaluated in terms of supercapacitor cathodes and enzymeless glucose sensing platforms in various operating modes. They include cyclic voltammetry (CV), ac electrochemical impedance spectroscopy, charging-discharging, and scanning electrochemical microscopy (SECM).
These hybrid samples showed heterogeneous transport behavior determining diffusion coefficient (4⨯10-8 – 6⨯10-6 m2/s) following an increasing order of CoO/MLG < Co3O4/MLG < Co3O4/rGOHT < CoO/ErGO < CoNP/MLG and delivering the maximum specific capacitance 450 F/g for CoO/ErGO and Co3O4/ rGOHT. In agreement with CV properties, these electrodes showed the highest values of low-frequency capacitance and lowest charge-discharge response (0.38 s – 4 s), which were determined from impedance spectroscopy. Additionally, through circuit simulation of experimental impedance data, RC circuit elements were derived. SECM served to investigate electrode/electrolyte interfaces occurring at the solid/liquid interface operating in feedback probe approach and imaging modes while monitoring and mapping the redox probe (re)activity behavior. As expected, the hybrids showed an improved electroactivity as compared to the cobalt oxides by themselves, highlighting the importance of the graphene support. These improvements are facilitated through molecular/chemical bridges obtained by electrodeposition as compared with the physical deposition.
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ALRASHED, MAHER M. "ORGANIC/INORGANIC HYBRID COATINGS FOR ANTICORROSION APPLICATIONS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491226580793534.
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Uddin, MD Hanif. "Polymeric Hairy Nanoparticles with Helical Hairs: Synthesis and Self-Assembly." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2018. http://digitalcommons.auctr.edu/cauetds/137.
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Nanoscale particles based on the nature of building blocks often self-assemble into superstructures with distinctive spatial arrangements which can be used as functional materials for different application. Micro-phase separated hairy nanoparticle with helical hair can self-assemble to form supramolecular material which may mimic the properties and functions of the natural polymers such as protein and cellulose. Beside this hairy/core-shell nanoparticles also may find many applications such as in asymmetric catalysis, nano-fillers in tire and rubbers, model systems for biology, lithography and as sensors. In this work, we have successfully synthesized two hairy nanoparticles both of which has cross-linked polystyrene core with helical poly (3- methyl 4- vinyl pyridine) and poly (2- methoxystyrene) brushes respectively by living anionic polymerization via one-pot synthesis. NMR spectroscopy was used to determine that polymerization was successful and compositions of HNPs have the agreement with the targeted HNPs structure. By tailoring the architecture (functionalization of polymer chains, the degree of polymerization, grafting density) of HNPs, it is possible to control the final properties of the system. Differential Scanning Calorimetry was used to demonstrate the thermal properties of the synthesized HNPs which corresponds to polymer composition. Dynamic light scattering, SEM and AFM images were recorded to measure the particle size and morphology of the particles. Circular dichroism spectroscopy was used to determine the induced chirality of helical polymer brushes by complexing it with the small chiral molecule. SEM and AFM imaging were recorded to find out the morphology and hierarchically self-assembly of the hairy nanoparticle system. The synthesized particles may have great potential to successfully generate self-assembled suprastructures which can further solve the chiral resolution problem and can also find different applications.
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Bhatkar, Omkar S. "Facile Fabrication of Functionally Graded Graphene Films for Transient Electronics." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1544623828859207.
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Ludlow, James M. III. "Design and Synthesis of Terpyridine based Metallo-Supramolecular Architectures." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1444989836.
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Olson, Grant T. "Improving Hybrid Solar Cells: Overcoming Charge Extraction Issues In Bulk Mixtures of Polythiophenes and Zinc Oxide Nanostructures." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1257.
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Organic photovoltaics (OPVs) have received a great deal of focus in recent years as a possible alternative to expensive silicon based solar technology. Current challenges for organic photovoltaics are centered around improving their lifetimes and increasing their power conversion efficiencies. One approach to improving the lifetime of such devices has been the inclusion of inorganic metal oxide layers, but interaction between the metal oxides and common conjugated polymers is not favorable. Here we present two methods by which the interactions between polythiophenes and nanostructured ZnO can be made to be more favorable. Using the first method, direct side on attachment of polythiophene to ZnO nanowires via chemical grafting, we demonstrate chemical linkage between the polymer and ZnO phases. The attachment was confirmed to affect the morphological properties of the polymer layer as well, inducing highly ordered regions of the polymer at the ZnO surface via chemical attachment and physical adsorption. Using the second method to improve polythiophene ZnO interactions, we have functionalized ZnO nanowires with organic molecules that favorably interact with conjugated polymer and organic solvents. Photovoltaic devices were made using a blended active layer of functionalized ZnO nanowires and P3HT. Electrical analysis of the resultant devices concluded that the devices were functional photovoltaic cells and isolated the dominant loss mechanisms for further device improvement.
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Etmimi, Hussein Mohamed. "New approaches to the synthesis and exfoliation of polymer/functional graphene nanocomposites by miniemulsion polymerization." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20119.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: New methods are described for the synthesis of polymer/graphite nanocomposites using the miniemulsion polymerization process. Natural graphite was functionalized by oxidation to produce graphite oxide (GO) nanosheets. Poly(styrene-co-butyl acrylate) (poly(St-co-BA)) nanocomposite latices containing GO nanosheets were successfully synthesized using miniemulsion as a one-step nano-incorporation technique. The approach followed included expanding the GO nanosheets in situ during the miniemulsification step and then polymerizing the monomers in the presence of these expanded nanosheets. Styrene (St) and butyl acrylate (BA) were mixed with GO and then emulsified in the presence of a surfactant and a hydrophobe to afford pre-miniemulsion latex particles. The stable pre-miniemulsions were then polymerized to yield poly(St-co-BA)/GO nanocomposite latices. The polymerization proceeded with relatively high monomer conversion and produced stable nanocomposite latex particles. The nanocomposites exhibited mainly an intercalated morphology, irrespective of the percentage of GO filler loading. The synthesis of exfoliated polymer nanocomposites made with modified GO is described. GO was modified with a surfmer (reactive surfactant), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), which widened the gap between the GO nanosheets and facilitated monomer intercalation between its nanogalleries. The AMPS-modified GO was used for the synthesis of poly(St-co-BA)/GO nanocomposite latices using a similar miniemulsion procedure. The obtained nanocomposites had exfoliated morphologies and the GO nanosheets were largely exfoliated (about 2–5 nm thick) in the resultant films obtained from the synthesized nanocomposite latices. The synthesized nanocomposites had enhanced thermal and mechanical properties compared to pure polymer as a result of the presence of AMPSmodified GO. Furthermore, the nanocomposites made with AMPS-modified GO had better thermal and mechanical properties than the unmodified GO. The mechanical properties of the nanocomposites depended on the AMPS-modified GO loading in the nanocomposites. The synthesis of polystyrene/GO (PS-GO) nanocomposites using the reversible additionfragmentation chain transfer (RAFT) mediated polymerization method is also described. The GO was synthesized and immobilized with a RAFT agent to afford RAFT-functionalized GO nanosheets. The RAFT-immobilized GO was used for the synthesis of PS nanocomposites in a controlled manner using miniemulsion polymerization. The molar mass and dispersity of the PS in the nanocomposites depended on the amount of RAFT-grafted GO in the system, in accordance with the features of the RAFT-mediated polymerization. X-ray diffraction and transmission electron microscopy analyses revealed that the nanocomposites had exfoliated morphology, even at relatively high GO content. The thermal stability and mechanical properties of the PS-GO nanocomposites were better than those of the neat PS polymer. Furthermore, the mechanical properties were dependent on the modified-GO content (i.e., the amount of RAFT-grafted GO). The hydrophobicity and barrier properties of the resulting films prepared from the synthesized poly(St-co-BA)/GO nanocomposite latices to water and water vapor were also investigated. The hydrophobicity of the synthesized nanocomposite films was determined using contact angle measurements. The water permeability was determined by measuring the moisture vapor transmission rate of the films. The GO in the nanocomposites was reduced to its original form (i.e., graphite), and the barrier properties of the obtained nanocomposite films were determined and compared to films containing the unmodified GO (as-prepared GO). Results showed that reduction of GO had a significant impact on the water affinity of the resultant films prepared from the synthesized nanocomposite latices. The presence of reduced-GO (RGO) instead of unmodified GO in the miniemulsion formulation significantly improved the hydrophobicity and barrier properties of the final films to water. However, the barrier properties of the nanocomposites were unaffected by the amount of RGO in the nanocomposites.
AFRIKAANSE OPSOMMING: Nuwe metodes is beskryf vir die sintese van polimeer/grafiet nanosamestellings deur gebruik te maak van die miniemulsie polimerisasieproses. Natuurlike grafiet is gefunksionaliseer dmv oksidasie om grafietoksied (GO) nanovelle te vorm. Polistireen-ko-butielakrilaat (poli[St-ko- BA]) nanosamestellinglatekse wat GO nanovelle bevat is suksesvol gesintetiseer deur gebruik te maak van miniemulsie polimerisasie as ‘n een-stap nano-insluitingstegniek. Die benadering wat gevolg is het die uitbreiding van die GO nanovelle, in situ, gedurende die miniemulsifiseringstap behels, gevolg deur die polimerisasie van die monomere in die teenwoordigheid van hierdie uitgebreide nanovelle. Stireen (St) en butielakrilaat (BA) is met GO gemeng en daarna emulgeer in die teenwoordigheid van ‘n seepmiddel (surfactant) en ‘n hidrofoob om pre-miniemulsielateksdeeltjies te lewer. Die stabiele pre-miniemulsies is gepolimeriseer om poli(St-ko-BA)/GO nanosamestellinglatekse te vorm. Die polimerisasie het met redelike hoë monomeeromskakeling verloop en het stabiele nanosamestellinglateksdeeltjies gelewer. Hierdie nanosamestellings het hoofsaaklik geïnterkaleerde morfologie, onafhanklik van die persentasie GO vullers, getoon. Die sintese van afgeskilferde polimeernanosamestellings berei met gewysigde GO is beskryf. GO is gewysig met ‘n ‘surfmer’ (reaktiewe seepmiddel), 2-akrielamido-2-metiel-1- propaansulfoonsuur (AMPS), wat die gapings tussen die GO nanovelle vergroot het en die monomeer interkalering tusssen sy nanogange fasiliteer. Die AMPS-gewysigde GO is gebruik vir die sintese van poli(St-ko-BA)/GO nanosamestellinglatekse deur gebruik te maak van ‘n soortgelyke miniemulsie prosedure. Die nanosamestelling sό verkry het ‘n afgeskilferde morfologie getoon en die GO nanovelle was grootendeels afgeskilfer (ongeveer 2–5 nm dik) in die films wat berei is van die gesintetiseerde nanosamestellinglatekse. Laasgenoemde het verhoogde termiese en meganiese eienskappe gehad in vergelyking met die suiwer polimeer, as gevolg van die teenwoordigheid van die AMPS-gewysigde-GO. Die meganiese eienskappe van die nanosamestellings hang af van persentasie AMPS-gewysigde GO vullers in die nanosamestellings. Die sintese van PSt/GO nanosamestellings dmv die omkeerbare-addisie-fragmentasieoordrag- (OAFO-, Eng. RAFT-) bemiddelde polimerisasie metode is ook beskryf. Die GO is berei en geïmmobiliseer met ‘n RAFT verbinding om GO nanovelle met RAFT funksionaliteit te lewer. Die RAFT-geïmmobiliseerde GO is gebruik vir die sintese van PSt nanosamestellings in ‘n gekontrolleerde manier mbv miniemulsie polimerisasie. Die molêre massa en dispersie van die PSt in die nanosamestellings hang af van die hoeveelheid RAFTgeënte GO in die sisteem, in ooreenstmming met die kenmerke van RAFT-bemiddelde polimerisasie. X-straaldiffraksie en transmissie-elektronmikroskopie analises het bewys dat die nanosamestellings, selfs by relatiewe hoë GO inhoud, ‘n afgeskilferde morfologie gehad het. Die termiese stabiliteit en meganiese eienskappe van die PSt-GO nanosamestellings was beter as dié van die suiwer PSt polimeer. Verder was die meganiese eienskappe afhanklik van die gewysigde-GO-inhoud (dws, die hoeveelheid RAFT-geënte-GO). Die hidrofobisiteit en spereienskappe van die films berei vanaf die gesintetiseerde poli(St-ko- BA)/GO nanosamestellinglatekse teenoor water en waterdamp is ook ondersoek. Die hidrofobisiteit is ondersoek deur gebruik te maak van kontakhoekmeting. Die waterdeurlaatbaarheid is bepaal deur die waterdampoordragtempo van die films te bepaal. Die GO in die nanosamestellings is gereduseer tot sy eenvoudigste vorm (grafiet) en die spereienskappe van die nanosamestellingfilms is bepaal en vergelyk met die films wat die ongewysigde GO bevat het. Resultate het getoon dat reduksie van GO ‘n groot invloed gehad het op die wateraffiniteit van die films wat berei is vanaf die gesintetiseerde nanosamestellinglatekse. Die teenwoordigheid van die gereduseerde-GO (RGO) in plaas van die onveranderde GO in die miniemulsie formulasie het die hidrofobisiteit en spereienskappe van die finale films, teenoor water, baie verbeter. Die spereienskappe van die nanosamestellings is egter nie beïnvloed deur die hoeveelheid RGO in die nanosamestellings nie.
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Del, Rosso Maria Girolama. "Exploring supramolecular Interactions in hybrid materials." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF028/document.
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Ce travail visait à explorer les interactions supramoléculaires comme un outil dans les domaines de la chimie hôte-invité, les nanomatériaux et les nanotechnologies en général, afin de parvenir à des objectifs différents. D'abord, une interaction classique hôte-invité a été étudiée, au moyen d'une technique innovante telle que l'ITC, puis nous avons exploité les interactions supramoléculaires afin de maitriser la production de graphène exfolié en phase liquide, en mettant un accent particulier sur l'amélioration de la qualité et la quantité du matériau produit. Enfin, nous avons étendu l'utilisation de la chimie supramoléculaire à un dispositif réel par la fonctionnalisation des électrodes d'or avec des molécules photochromiques, ouvrant alors la voie à des dispositifs organiques multifonctionnels, pouvant être contrôlés par la lumièreThis work was aimed at exploring supramolecular interactions as a tool in the fields of host-guest chemistry, nanomaterials and in general nanotechnology, in order to achieve different goals. First, a classical host-guest interaction was studied by means of the ITC technique, then we exploited supramolecular interactions in order to harness the production of liquid-phase exfoliated graphene, with a particular focus on improving the quality and quantity of material produced. Finally, we extended the use of supramolecular chemistry to a real device by functionalization of gold electrodes with photochromic molecules, hence paving the way towards multifunctional organic devices and in prospective to graphene based light-controlled multifunctional devices
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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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Mosconi, Dario. "Crashing flatland: defective and hybrid 2D-materials for (Electro) catalysis." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426844.
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This Ph.D. project is aimed to discover new strategies to develop materials to utilize in the fields of Green Energy and Green Chemistry and it was directed at the application of 2D Materials in particular. This thesis is divided into five main chapters where we presented five exemplary systems in which we focused our attention on different aspects of materials design. Each chapter comprises an introduction and a conclusion section, in which we tried to go into the details of each targeted application and of the specific design strategy employed. However, at the beginning and at the end of the thesis, the reader can find an Introduction and a Conclusion section where we tried to collocate the goals and challenges of this work within a broader context of materials science and catalysis/electrocatalysis.
In our studies in the Green Energy area, we focused on the use of MoS2-based materials in water splitting cathodic half-reaction in order to obtain the best possible performance in hydrogen generation in different conditions. To do that, different strategies were developed to drive the original material to adapt to specific application. In detail, in Chapter Two we investigated the design of three-dimensional MoS2 structures doped with different amount of Ni in order to activate MoS2 for the Hydrogen Evolution Reaction (HER) performed in alkaline environment, which typically hinder this reaction. We carried out an extensive structural characterization in order to establish the role of each type of active sites formed on the material in the HER activity and kinetics. In Chapter Three, we developed an electrodeposition method for preparing amorphous MoS2/Ag2S hybrid using recycled DVD as the support; this revealed as a viable opportunity to turn an abundant waste into an added-value material. After a suitable investigation to understand what kind of material was formed upon electrodeposition, MoS2/Ag2S/DVD was tested for HER in acidic medium. In Chapter Four another kind of hybrid was prepared by designing a one-pot solvothermal synthesis of MoS2(1-x)Se2x nanosheets grown on N-doped reduced Graphene Oxide (N-rGO). The goal was the control of the optoelectronic properties of the final material, since the combination of MoS2(1-x)Se2x and N-rGO allows to form p-n nanojunctions, which induce an enhancement of HER activity upon illumination with visible light. Then we used different techniques to prove what was the best Se:S ratio to optimize both the absolute performances in HER and the enhancement upon light irradiation.
Regarding Green Chemistry area, we used Graphene Acid (GA) as starting material and we exploited its uniform surface functionalization to prepare materials for heterogeneous catalysis for different reactions, comparing them with the benchmark Graphene Oxide (GO), modified with the same protocol. In Chapter Five, we synthesized a heterogeneous catalyst by covalently grafting Ferrocene (Fc) moieties to –COOH surface groups of GA and GO. The resulting Fc-modified graphene derivatives have been tested as heterogeneous catalysts for the C-H insertion of aryl diazonium salts into several arene substrates. The tests revealed a strong influence of the support, which we could attribute the intrinsic properties of GA. In Chapter Six, we have grown Pd nanoparticles on GA to prepare a catalyst for Suzuki-Miyaura cross coupling reaction. We have studied the effect of surface functionalization on the nanoparticles formation process and on the derived capability on the controlling the size distribution. The catalysts were tested in Suzuki cross coupling in green conditions and we could highlight the influence of nanoparticles size on activity. Moreover, we studied the same catalysts also for boronic acid homocoupling reaction, that can provide similar final products, but in a more atom economically way.Questo progetto di dottorato è mirato alla scoperta di nuove strategie per lo sviluppo di materiali da utilizzare nei campi della Green Energy e della Green Chemistry ed è rivolto all’applicazione dei materiali 2D in particolare. Questa tesi è divisa in cinque capitoli principali dove presentiamo cinque sistemi esemplificativi in cui ci siamo focalizzati su diversi aspetti del design del materiale. Ogni capitolo comprende una sezione di introduzione e una di conclusione, in cui abbiamo provato ad andare nel dettaglio di ogni applicazione e della specifica strategia di design utilizzata. In ogni caso, all’inizio e alla fine della tesi, il lettore può trovare una sezione di Introduzione e una di Conclusione dove abbiamo provato a collocare gli obbiettivi e le sfide di questo lavoro in un contesto più ampio della scienza dei materiali e della catalisi/elettrocatalisi. Nei nostri studi nell’area della Green Energy, ci siamo focalizzati sull’utilizzo di materiali a base MoS2 per la riduzione dell’acqua così da ottenere le migliori performance possibile nella generazione di idrogeno in diverse condizioni. Abbiamo sviluppato diverse strategie per indurre il materiale originale ad adattarsi alla specifica applicazione. Nel Capitolo Due abbiamo investigato il design di strutture 3D di MoS2 drogato con diverse quantità di Ni, con lo scopo di attivare il MoS2 per Hydrogen Evolution Reaction (HER) in ambiente alcalino, che di solito ostacola la reazione. Abbiamo eseguito un’estensiva analisi strutturale per stabilire il ruolo di ogni tipo di sito attivo formato sul materiale nell’attività e nella cinetica della HER. Nel Capitolo Tre, abbiamo sviluppato un metodo di elettrodeposizione per preparare un ibrido MoS2/Ag2S amorfo usando DVD riciclati come supporto, rivelandosi un’ottima strada per ridare valore a un materiale di scarto. Dopo un’adeguata analisi per capire il tipo di materiale formato, MoS2/Ag2S/DVD è stato testato per la HER in ambiente acido. Nel Capitolo Quattro abbiamo preparato un ibrido ottimizzando una sintesi solvotermale di nanofogli di MoS2(1-x)Se2x su Grafene Ossido ridotto drogato-N (N-rGO). L’obiettivo era il controllo delle proprietà optoelettroniche del materiale, dato che la combinazione di MoS2(1-x)Se2x e N-rGO permette di formare nanogiunzione p-n, che inducono un aumento dell’attività HER sotto illuminazione. Abbiamo utilizzato differenti tecniche per provare quale fosse il miglior rapporto Se:S per ottimizzare sia la performance assoluta in HER sia l’incremento dovuto all’irradiamento. Riguardo all’area della Green Chemistry, abbiamo utilizzato il Grafene Acido (GA) come materiale di partenza e abbiamo sfruttato la sua funzionalizzazione superficiale uniforme per preparare materiali per catalisi eterogenea di diverse reazioni, comparandoli con il riferimento Grafene Ossido (GO), modificato con la stessa procedura. Nel Capitolo Cinque, abbiamo sintetizzato un catalizzatore eterogeneo attaccando unità di Ferrocene (Fc) a GA e GO. I risultanti derivati grafenici modificati con Fc sono stati testati come catalizzatori eterogenei per l’inserimento di sali di diazonio aromatici in substrati arenici. I test hanno rivelato una forte incidenza del supporto, attribuibile alle proprietà intrinseche del GA. Nel Capitolo Sei, abbiamo cresciuto nanoparticelle di Pd sul GA per preparare un catalizzatore per la reazione di cross coupling Suzuki-Miyaura. Abbiamo studiato gli effetti della chimica superficiale sul processo di formazione delle nanoparticelle e sulla conseguente capacità di controllare la taglia. I catalizzatori sono stati testati nella Suzuki-Miyaura in condizioni green e abbiamo potuto evidenziare l’influenza della taglia delle nanoparticelle sull’attività. In aggiunta, abbiamo studiato gli stessi catalizzatori anche per la reazione di homocoupling di acidi boronici, la quale può fornire simili prodotti finali, ma con un migliore economia atomica.