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Synthesis of Nanoparticles and Nanostructured Materials by Self-AssemblyVarón Izquierdo, Miriam 31 May 2012 (has links)
L’aparició de noves propietats químiques i físiques dins l’escala nanomètrica és un dels motius principals que fa necessari l’estudi de nanopartícules de diferents metalls, del seus òxids i dels seus aliatges, pel disseny de les seves futures aplicabilitats. Aquesta tesi estudia dos blocs temàtics: i) la síntesi i ii) l’autoensamblatge de nanopartícules metàl·liques.
En el primer bloc, s’estudien els aspectes més rellevants de la preparació de nanopartícules metàl·liques (constituïdes per un o dos metalls diferents) de mida i forma controlada. Es desenvolupa les síntesis de diferents partícules magnètiques, i s’obtenen dispersions col·loïdals de nanopartícules de cobalt (Co) i alguns del seus òxids, així com d’ or (Au), platí (Pt) i alguns dels seus aliatges.
Les nanopartícules de Co estan rebent un interès creixent degut a les propietats magnètiques que presenta el material, la qual cosa les fa molt interessants per a un nombre elevat d’aplicacions tecnològiques. Però la sensibilitat del material en front l’oxidació (la qual produeix canvis en les seves propietats magnètiques) requereix que es faci un estudi profund d’aquests processos. En aquest treball, s’han sintetitzat nanopartícules de Co de diferents mides i s’han estudiat els paràmetres que afecten les seves propietats magnètiques. A més, s’han estudiat els processos d’oxidació de les nanopartícules de Co, que han generat tant nanopartícules core/shell (nucli/recobriment) Co/CoO com nanopartícules “hollow” (buides) d’òxid de Co.
Les nanopartícules de Pt també són de gran interès degut a que presenten propietats òptiques i catalítiques úniques. Les seves propietats catalítiques depenen fortament dels seus àtoms superficials i, per tant, de la mida i de la forma de les nanopartícules. En aquesta tesi s’ha dut a terme la síntesi de nanopartícules de Pt de diferent mida i forma mitjançant el control de diferents paràmetres durant el procés sintètic (com la temperatura, els lligands i els temps de reacció). En particular, s’ha determinat la incorporació de traces metàl·liques durant la síntesis i el seu efecte en el control de la forma final de la nanopartícula.
Finalment, l’or es un dels materials més estudiats en l’escala nanomètrica degut a les seves propietats òptiques i el seu caràcter inert, que fa que sigui un dels materials més utilitzats en aplicacions biològiques. Les propietats òptiques són especialment importants en materials amb “aspect ratios” (relació longitud/amplada). En aquesta tesi s’han sintetitzat Au “rods” (barres) de gran llargada utilitzant nanopartícules de Pt com a catalitzador de la reacció, i se n’ha explorat la llargada que poden aconseguir, relacionades amb les seves possibles aplicacions.
En el segon bloc, s’estudia l’ús de les nanopartícules en la preparació de materials nanoestructurats mitjançant autoensamblatge. S’ha observat com depenent de la naturalesa i la forma de les nanopartícules, es creen diferents patrons. En particular, aquesta part es centra principalment en la utilització de nanopartícules de Co com a unitats de construcció de estructures autoensamblades, degut a les seves propietats magnètiques. S’ha estudiat l’autoensamblatge de nanopartícules de Co a sobre de diferents substrats d’interès tecnològic i les forces que intervenen en el procés. En particular, en destaquem: l’estudi de l’autoensamblatge de les partícules de Co sobre grafit i sobre substrats de silici.
Finalment, s’ha estudiat la influència de les propietats en el procés d’autoensamblatge de nanopartícules de Co, així com l’estructura magnètica dels assemblats, mitjançant holografia electrònica i microscopia Lorentz. S’ha estudiat la variació de l’estructura magnètica dels diferents assemblats en funció de la seva mida total, i també en funció de la temperatura. L’estudi de les propietats individuals de les nanopartícules de Co dins l’assemblat és possible mitjançant les dues tècniques mencionades prèviament, i s’han observat els efectes col·lectius entre totes les partícules integrants de les estructures. Els resultats obtinguts indiquen que l’ordenació ferromagnètica dipolar és molt persistent en les estructures, fins i tot amb un elevat grau de desordre a la xarxa de partícules. / The emergence of new chemical and physical properties at the nanoscale is one of the main reasons that make necessary the study of nanoparticles of different metals, their oxides and alloys for different applications. In this thesis, two thematic blocks are studied: i) the synthesis and ii) the self- assembly of metallic nanoparticles.
In the first block, the more relevant aspects in the preparation of metallic and bimetallic nanoparticles of controlled size and shape are studied. The syntheses of different metal nanoparticles are developed, and monodisperse colloidal suspensions of Co metal particles and some of their oxides, as well as Au, Pt and some alloy nanoparticles are obtained.
Co particles are receiving much interest due to their magnetic properties of the material, which turn them interesting for a number of technological applications. On the other
hand, the sensitivity of the material to oxidation (with a consequent change in its properties) makes necessary a deeper study of these processes. In this work, Co magnetic nanoparticles of different sizes have been synthesized and the parameters that affect the variation of their magnetic properties have been studied. Moreover, the oxidation processes of the Co nanoparticles have been also studied, generating both Co/CoO core/shell and CoO hollow nanoparticles.
Pt nanoparticles are also a subject of interest due to their unique optical and catalytic properties. Their catalytic properties strongly depends on their surface atoms and, therefore, on the size and shape of the particles. During this thesis, different size and shape Pt nanoparticles have been synthesized by controlling different parameters during the synthetic process (i.e. temperature, surfactants, and reaction times). In particular, the incorporation of metal “traces” during the synthesis process, and their effect on the control of the shape are determined.
Finally, Au is one of the most studied materials at the nanometer scale due to its optical properties and its inertness, making it one of the most used materials in biological applications. The optical properties are particularly important in materials with aspect ratios (length/width). In this thesis, the synthesis of extra long Au rods (bars) using Pt nanoparticles as the reaction catalyst have been synthesized, and the length that they can reach have been also explored for its potential applications (e.g. as connections between electrodes).
In the second block, the use of nanoparticles for the preparation of nanostructured materials via self-assembly processes is studied. It is observed how, depending of both the nature and the shape of the nanoparticle, different patterns are created. In particular, this part focuses mainly on the use of Co nanoparticles as building block units for construction of self-assembled structures, due to their magnetic properties. The self-assembly of Co nanoparticles onto different substrates with technological interest and the forces involved in the process have been studied. Particularly, the works to be highlighted are the study of the self-assembly of Co on graphite and on silicon substrates due to dipolar interactions.
Finally, the influence of the magnetic properties in the self-assembly process of Co nanoparticles, and the magnetic structure of the formed assemblies, are studied by electron holography and Lorentz microscopy. The variation of the magnetic structure of the different self-assembled structures has been studied as a function of both the assembly total size and the temperature. The study of the individual and collective behavior of the Co nanoparticles on the assembly is possible with these techniques, and collective effects among the whole NPs forming the structures have been observed. The obtained results showed that dipolar ferromagnetism order is extremely persistent even under a high degree of lattice disorder.
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Synthesis, Characterization, and Biological uses of Carbon NanoparticlesMarcano Quevedo, Daniela 24 July 2013 (has links)
Many diseases have been associated with oxidative stress (OS) which is caused when the production of reactive oxygen species (ROS), such as superoxide (O2•-) and hydroxyl radical (•OH), overcome the scavenging efficiency of living organisms. It is known that ROS production is worsened during traumas related to ischemic events and subsequent reperfusion in which the treatment with fast and effective antioxidants is critical to prevent cell and tissue damage. PEG-HCCs are carbon nanoparticles that showed O2•- and •OH scavenging properties according to electron paramagnetic resonance (EPR) experiments and peroxyl scavenging properties based on oxygen radical absorbance capacity (ORAC) assays. The O2•- quenching capability was also examined in vivo using a mild traumatic brain injury (mTBI) model complicated with hypotension. As result of the PEG-HCCs treatment, the cerebral blood flow (CBF) was restored while normalizing O2•- and nitric oxide (NO•) levels, primarily in the cerebral vasculature
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Creation of bifunctional particles with spatially segregated proteinsTang, Jennifer L 06 April 2012 (has links)
We present a fabrication process to create bifunctional microparticles displaying two different proteins have been spatially segregated onto hemispheres. Silica and polystyrene microparticles with 2.0 m, 4.08 m, and 4.74 m diameters are processed with metal deposition to form two chemically distinct and segregated hemispheres. The surface of each hemisphere is then separately derivatized with proteins using different chemical conjugation strategies. These bifunctional Janus particles possess biologically relevant, native conformation proteins attached to a biologically-unreactive and safe substrate. They also display high densities of two types of spatially segregated proteins which may enable a range of capabilities that monofunctional particles cannot, such as improved targeting of drug carriers and bioimaging agents.
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The effects of multi-walled carbon nanotube exposure on soil organismsMartin, William J. January 2012 (has links)
With the rapid proliferation of carbon nanotube technologies and consumer products comes a need to research the toxicological and ecotoxicological effects of these materials. This research attempted to develop a baseline knowledge of the effects of bulk, unmodified multi-walled carbon nanotubes on commonly studied soil toxicology test organisms: earthworms, springtails, and agricultural plants. In order to minimize confounding factors in the study, a slurry composed of bulk multi-walled carbon nanotubes, silica sand, and water was used to amend test soil without the use of surfactants or functionalization.
Analysis of data produced by these experiments showed no significant trends resulting from the exposure of the test organisms to artificial soil amended by the multi- walled carbon nanotube slurry. It was observed, however that carbon nanotubes accumulated in the gut of the earthworm Eisenia andrei and were expelled as castings in the test soil.
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Iron Nanoparticles for In Situ Chemical OxidationAl-Shamsi, Mohammed 31 July 2013 (has links)
Recently, metal nanoparticles have attracted the attention of researchers in several fields of study due to their high surface area and other unique properties. Using metal nanoparticles as a component of an in situ chemical oxidation (ISCO) system is emerging and hence very little information is available.
In this research, nano zero valent iron (nZVI) particles and iron-based bimetallic zero valent nanoparticles (BZVNs) were employed to activate some common peroxygens (hydrogen peroxide (H2O2), persulfate (S2O82-), and peroxymonosulfate (HSO5-)) to degrade hazardous organic compounds. Aqueous and soil slurry batch systems were used along with a one-dimensional physical model.
The results from the aqueous batch systems showed that nZVI is a promising activator for S2O82- compared to other conventional iron activators (e.g., granular-ZVI and Fe2+). For example, the initial trichloroethylene (TCE) reaction rate by nZVI activated S2O82- was 1.11 x 10-4 M L-1 min-1 compared to an initial reaction rate of 6.25 x 10-5 M L-1 min-1, 5.18 x 10-6 M L-1 min-1, and 1.8 x 10-7 M L-1 min-1 for Fe2+ activated S2O82-, granular-ZVI activated S2O82-, and non-activated S2O82-, respectively. However, the surfaces of nZVI particles were passivated quickly following exposure to S2O82-, causing the reaction rate to reduce to a magnitude representative of an un-activated S2O82- system. An iron-sulfate (FeSO4) complex was formed on the surfaces of the nZVI particles following exposure to S2O82- compared to the iron oxyhydroxide (FeOOH) layer that was present on fresh nZVI surfaces.
BZVNs showed better treatment effectiveness than nZVI particles as activators for H2O2, S2O82-, and HSO5-. For example, the TCE reaction rate constant for nano-Ag-Fe0 activated H2O2 was 9 to 18 fold higher than that for nZVI activated H2O2. Of the nine different BZVNs investigated as activators, the greatest TCE degradation was achieved by nano-Pd-Fe0 and nano-Zn-Fe0 activated S2O82- system, nano-Co-Fe0 activated HSO5- system, and nano-Ag-Fe0 activated H2O2 system. For all of these systems, an increase in the dosage of nanoparticles and peroxygens increased TCE degradation. The activated H2O2 system showed a lower TCE degradation rate compared to either the activated S2O82- or the activated HSO5- systems, suggesting that a bridged group complex is formed between the activators and H2O2.
The dissolved TCE concentration remaining in the soil slurry batch systems after using the nano-Pd-Fe0 activated S2O82- system was two to three fold higher than that in an aqueous batch system. Furthermore, for five different aquifer materials used, the higher mass of aquifer materials the lower the TCE degradation, indicating that the aquifer materials compete with a target organic compound in the presence of activated S2O82-. A linear relationship was observed between the organic carbon (OC) content and the initial TCE decomposition rate. Although there is no direct evidence of the effect of OC on the treatment system, it is suggested that the OC may result in scavenging the generated free radicals or by directly consuming persulfate.
In the one-dimensional physical model systems, bimetallic nanoparticles were mobile in a non-geological porous medium and relatively immobile in a geological porous medium. In the non-geological porous medium, we found that adding a second metal (e.g., Pd) to nano-Fe0 particles significantly improved their functionality and performance (e.g., mobility and suspension). For example, the results from mobility experiments using columns packed with glass beads showed that the effluent iron concentration was <6 % of the influent iron concentration for the nano-Fe0 particles, while it was ~100 % for the nano-Pd-Fe0 particles. In the geological porous medium, based on visual inspection, nano-Pd-Fe0 particles could not travel more than a few centimeters into columns packed with CFB Borden sand, and no iron was detected in the effluent.
To overcome the delivery issue in porous media, nano-Pd-Fe0 particles were injected to create a zone of activation to activate S2O82- for the treatment of TCE source zone. However, we found that the TCE mass destruction was only 9 % higher in the nano-Pd-Fe0 activated S2O82- system compared to the non-activated S2O82- system as revealed by the effluent chloride concentration. In addition, the activation zone composed of nano-Pd-Fe0 particles was rapidly deactivated after exposure to persulfate as visually observed by color change, indicating that the longevity of the activation zone is limited.
This research effort provides a contribution to the field of ISCO by evaluating the potential utility and applicability of a new class of activators for some common peroxygens.
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An investigation into bimetallic hollow nanoparticles in catalysisSnyder, Brian 03 April 2013 (has links)
Nanocatalysis, catalysis using particles on the nanoscale, is an emerging field that has tremendous potential. Nanoparticles have different properties than bulk material and can be used in different roles. Macro sized precious metals, for example, are inert, but nanoparticles of them are becoming more widely used as catalysts. Understanding the manner in which these particles work is vital to improving their efficacy.
This thesis focuses on two aspects of nanocatalysis. Chapter 1 begins with a brief introduction into nanotechnology and some of the areas in which nanoparticles are different than bulk particles. It then proceeds into an overview of catalysis and nanocatalysis more specifically. Focus is brought to the definitions of the different types of catalysis and how those definitions differ when applied to nanoparticles. Chapter 2 is in finding an inert support structure to more easily assist in recycling the nanoparticles. Polystyrene microspheres were studied and found to prevent platinum nanoparticles from aggregating in solution and possibly aid in recycling of the nanoparticles. These nanoparticles were used in catalysis, aiding in the reduction of 4-nitrophenol in the presence of sodium borohydride. While the rate decreased by a factor of ~ 7 when using the polystyrene, the activation energy of the reaction was unaltered, thus confirming the inactivity of the polystyrene in the reaction.
In Chapter 3, nanocatalysis was studied by examining bimetallic hollow nanoparticles with specific attention to the effect of altering the ratios of the two metals. Ten different bimetallic nanocages were tested in an electron transfer reaction between hexacyanoferrate and thiosulfate. Five PtAg nanocages and five PdAg with varying metal ratios were prepared and studied. It was found that while silver cubes immediately precipitate out of solution when combined with thiosulfate, a small amount of either platinum or palladium allows the particles to remain in solution and function as a substantially more effective catalyst. However, as additional Pt was added the activation energy increased. To obtain a better understanding of the catalysis using bimetallic cages, the evolution of these cages was studied as the 2nd metal was added. Initially the particle edge length increased and then slowly decreased back to the size of the template cubes. The increase in edge length suggests of addition of material to the nanoparticles. This indicated the 2nd metal is on the outside of the cage, which was confirmed using UV-Vis spectroscopy and EDS mapping. By understanding how these bimetallic particles evolve, we may be able to manipulate these synthetic methods to more precisely design nanoparticles for catalysis.
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MRI Contrast Enhancement using Gd2O3 NanoparticlesKlasson, Anna January 2008 (has links)
There is an increasing interest for nanomaterials in biomedical applications and in this work, nanoparticles of gadolinium oxide (Gd2O3) have been investigated as a novel contrast agent for Magnetic Resonance Imaging (MRI). Relaxation properties have been studied in aqueous solutions as well as in cell culture medium and the nanoparticles have been explored as cell labeling agents. The fluorescent properties of the particles were used to visualize the internalization in cells and doped particles were also investigated as a multimodal agent that could work as a fluorescent marker for microscopy and as a contrast enhancer for MRI. Results show that in aqueous solutions, there is a twofold increase in relaxivity for Gd2O3 compared to commercial agent Gd-DTPA. In cell culture medium as well as in cells, there is a clear T1 effect and a distinct increase in signal intensity in T1-mapped images. Fluorescent studies show that the Gd2O3 nanoparticles doped with 5% terbium have interesting fluorescent properties and that these particles could work as a multimodal contrast agent. This study shows that Gd2O3 nanoparticles possess excellent relaxation properties that are retained in more biological environments. Gd2O3 particles are suitable as a T1 contrast agent, but seem also be adequate for T2 enhancement in for instance cell labeling experiments.
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Electrochemically deposited metal nanostructures for application in genosensorsSoreta, Tesfaye Refera 17 December 2009 (has links)
Las señales de los biosensores se pueden mejorar mediante el diseño de superficies transductoras. En este sentido, se han investigado diversos métodos para la nanoestructuración de superficies. El primero de ellos se basó en la formación inicial de monocapas autoensambladas (SAM) de alcanotioles sobre sustratos bimetálicos, seguida de la desorción reductiva selectiva (SRD) de las SAM de determinados metales. Se consiguió la SRD de 2-mercaptoetanol de dominios de paladio desde una superficie de platino-oro. El segundo método para preparar superficies nanoestructuradas que se investigó fue la nucleación electroquímica secuencial de las nanopartículas metálicas (oro y paladio) sobre electrodos de carbón vidrio para las SAM de alcanotiol y para aumentar la densidad de las nanopartículas sin permitir la formación de agregados. Con este método, las señales redox de las SAM alcanotiol ferrocenil eran seis y cincuenta veces mejores que los electrodos de oro y paladio, respectivamente. Finalmente, se demostró la nanoestructuración de las superficies de los electrodos para mejorar la señal de un biosensor de ADN. / Biosensor signals can be enhanced by specifically designing transducer surfaces. In this thesis, several surface nanostructuring approaches have been investigated. The first approach studied was based on the initial formation of self-assembled monolayers (SAM) of alkanethiols on bi-metallic substrates, followed by the selective reductive desorption (SRD) of the SAM from one of the metals. SRD of 2-mercaptoethanol from palladium domains of a palladium-gold surface was achieved. The second nanostructured surface preparation method investigated was the sequential electrochemical nucleation of metal nanoparticles (gold and palladium) on glassy carbon electrode and SAM formation on the NPs to prevent aggregation and by that increasing the number densities. With this method, a six-fold and a fifty fold enhancement in the ferrocenyl alkanethiol SAM redox signal was achieved in comparison to plain gold and palladium electrodes, respectively. Finally, electrode surface nanostructuring using sequentially nucleated gold nanoparticles for signal enhancement of DNA biosensor was demonstrated.
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Nanochemistry on Si(100): Surface Biofunctionalization by Amino-containing Bifunctional Molecules, and Shape Control of Copper Core-Shell NanoparticlesRadi, Abdullah January 2009 (has links)
The present research involves two projects: a surface science study of the room-temperature adsorption and thermal evolution of allylamine and ethanolamine on Si(100)2×1, studied by using temperature-dependent X-ray photoelectron spectroscopy (XPS) and thermal desorption spectrometry (TDS), as well as Density Functional Theory (DFT) calculations; and a materials science study on the shape control of copper nanoparticles (Cu NPs) deposited on H-terminated Si(100) substrate with an extended size regime of 5-400 nm, by using a simple, one-step electrochemical method. The Cu NPs of three primary shapes were characterized with scanning-electron microscopy (SEM), glancing-incidence X-ray diffraction (GIXRD) and XPS.
In the first surface science study, the presence of broad N 1s XPS features at 398.9-399.1 eV, corresponding to N–Si bonds, indicates N–H dissociative adsorption for both allylamine and ethanolamine on Si(100)2×1. For allylamine, the presence of C 1s features at 284.6 eV and 286.2 eV, corresponding to C=C and C−N, respectively, and the absence of the Si−C feature expected at 283.5 eV show that the reactions involving the ethenyl group such as the [2+2] C=C cycloaddition or those producing the [N, C, C] tridentate adstructures do not occur at room temperature. For ethanolamine, the O 1s feature at 533.1 eV indicates the formation of Si−O bond and O−H dissociation, which confirms an [O, N] bidentate adstructure and excludes the N−H and O−H dissociation unidentate structures. These XPS data are consistent with the N−H unidentate, and N−H and O−H double dissociation [O, N] bidentate adstructures for allylamine and ethanolamine, respectively, as predicted by the DFT calculations. TDS and temperature-dependent XPS data further show the desorption of propene and ethylene at 580 K and of acetylene at 700 K for allylamine and the desorption of ethylene at 615 K for ethanolamine, while the lack of N- or O-containing desorbates suggests that the dissociated N and O species are likely bonded to multiple surface Si atoms or diffused into the bulk at elevated temperatures (as confirmed by the corresponding temperature-dependent XPS spectra). Unlike the multidentate allyl alcohol and allylamine adstructures that have been found to be not favored kinetically, the present [O, N] bidentate ethanolamine adstructure appears to be kinetically favored on Si(100)2×1.
In the second materials science study, Cu NPs of three primary shapes have been deposited on H-terminated Si(100) by a simple, one-step electrochemical method. By precisely manipulating the electrolyte concentration [CuSO4.5H2O] below their respective critical values, cubic, cuboctahedral, and octahedral Cu NPs of ranges of average sizes and number densities can be easily obtained by varying the deposition time. Combined GIXRD and depth-profiling XPS studies show that these Cu NPs have a crystalline core-shell structure, with a face-centered cubic metallic Cu core and a simple cubic Cu2O shell with a CuO outerlayer. The shape control of Cu NPs can be understood in terms of a progressive growth model under different kinetic conditions as dictated by different [CuSO4.5H2O] concentration regimes. The two studies in the present work lay the foundation for future investigation of surface biofunctionalization of these fascinating Cu NPs with different shapes and therefore different surface chemistries as controlled by the relative amounts of the (100) and (111) facets, and their boundaries.
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Synthesis of Carbon Nanomaterials and Their Applications in the OilfieldLu, Wei 16 September 2013 (has links)
This dissertation explores the potential applications of nanotechnology in the oilfield including poly(vinyl alcohol) stabilized carbon black nanoparticles for oil exploration and temperature-responsive carbon black nanoparticles for enhanced oil recovery. Also, it describes the rational design of graphene nanoribbons via intercalating reactive metals into multi-walled carbon nanotubes followed by addition of vinyl monomers or haloalkanes. Efficient production and modification of these aforementioned nanomaterials will make them more attractive for applications in the oilfield and electronics materials.
A method is reported for detecting the hydrocarbon in the porous media with stabilized nanoparticles that are capable of efficiently transporting hydrophobic molecules through oil-containing rocks and selectively releasing them when a hydrocarbon is encountered. Nano-sized carbon black was oxidized and then functionalized with poly(vinyl alcohol) via a coupling reaction between the polymer's hydroxyl groups and the carboxylic groups on oxidized carbon black. Breakthrough curves show that poly(vinyl alcohol)-coated oxidized carbon black was stable in synthetic sea brine at room temperature and could carry the 14C-labeled radioactive tracer 2,2ˊ,5,5ˊ-tetrachlorobiphenyl through rocks and then released the tracer upon exposure to hydrocarbon.
Due to the temperature-sensitivity of hydrogen bonds, higher molecular weight poly(vinyl alcohol) was used to improve the stability of carbon black nanoparticles in synthetic sea brine at higher temperatures. After sulfation, high molecular weight poly(vinyl alcohol) could stabilized carbon black nanoparticles in American Petroleum Institute standard brine at high temperatures. Those nanoparticles could efficiently transport mass-tagged probe molecules through a variety of oil-field rock types and selectively released the probe molecules into the hydrocarbon-containing rocks. Those proof-of-concept chemical nanoreporters can potentially be used under conditions commonly observed in the reservoir, and aid in the recovery of oil that remains in place.
Amphiphilic carbon nanoparticles have been prepared that are capable of reversibly transferring across the water/oil interface in a temperature-controlled manner. Nano-sized carbon black was oxidized and then functionalized with amphiphilic diblock polyethylene-b-poly(ethylene glycol) copolymers that were water-soluble at low-to-moderate temperatures but oil-soluble at higher temperatures. The correlation between the phase transfer temperature and the melting temperature of the hydrophobic block of the copolymers and the weight percent of hydrophilic block were investigated. The amphiphilic nanoparticles were used to stabilize oil droplets for demonstrating potential applications in reducing the water/oil interfacial tension, a key parameter in optimizing crude oil extraction from downhole reservoirs.
Graphene nanoribbons free of oxidized surfaces can be prepared in large batches and 100% yield by splitting multi-walled carbon nanotubes with potassium vapor. If desired, exfoliation is attainable in a subsequent step using chlorosulfonic acid. The low-defect density of these GNRs is indicated by their electrical conductivity, comparable to that of graphene derived from mechanically exfoliated graphite. Additionally, cost-effective and potentially industrially scalable, in situ functionalization procedures for preparation of soluble graphene nanoribbons from commercially carbon nanotubes are presented. To make alkane-functionalized graphene nanoribbons, multi-walled carbon nanotubes were intercalated by sodium/potassium alloy under liquid-phase conditions, followed by addition of haloalkanes, while polymer-functionalized graphene nanoribbons were prepared via polymerizing vinyl monomers using potassium-intercalated graphene nanoribbons. The correlation between the splitting of MWCNTs, the intrinsic properties of the intercalants and the degree of graphitization of the starting MWCNTs has also been demonstrated. Those functionalized graphene nanoribbons could have applications in conductive composites, transparent electrodes, transparent heat circuits, and supercapcitors.
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