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1
Hogg, Charles R. III. "Pattern Transfer from Nanoparticle Arrays." Research Showcase @ CMU, 2010. http://repository.cmu.edu/dissertations/14.
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This project contributes to the long-term extensibility of bit-patterned media (BPM), by removing obstacles to using a new and smaller class of self-assembling materials: surfactant-coated nanoparticles. Self-assembly rapidly produces regular patterns of small features over large areas. If these patterns can be used as templates for magnetic bits, the resulting media would have both high capacity and high bit density. The data storage industry has identified block copolymers (BCP) as the self-assembling technology for the first generation of BPM. Arrays of surfactant-coated nanoparticles have long shown higher feature densities than BCP, but their patterns could not previously be transferred into underlying substrates. I identify one key obstacle that has prevented this pattern transfer: the particles undergo a disordering transition during etching which I have called “cracking”. I compare several approaches to measuring the degree of cracking, and I develop two novel techniques for preventing it and allowing pattern transfer. I demonstrate two different kinds of pattern transfer: positive (dots) and negative (antidots). To make dots, I etch the substrate between the particles with a directional CF4-based reactive ion etch (RIE). I find the ultrasmall gaps (just 2nm) cause a tremendous slowdown in the etch rate, by a factor of 10 or more — an observation of fundamental significance for any pattern transfer at ultrahigh bit densities. Antidots are made by depositing material in the interstices, then removing the particles to leave behind a contiguous inorganic lattice. This lattice can itself be used as an etch mask for CF4-based RIE, in order to increase the height contrast. The antidot process promises great generality in choice of materials, both for the antidot lattice and the particles themselves; here, I present lattices of Al and Cr, templated from arrays of 13:7nm-diameter Fe3O4 or 30nm-diameter MnO nanoparticles. The fidelity of transfer is also noticeably better for antidots than for dots, making antidots the more promising technique for industrial applications. The smallest period for which I have shown pattern transfer (15:7nm) is comparable to (but slightly smaller than) the smallest period currently shown for pattern transfer from block copolymers (17nm); hence, my results compare favorably with the state of the art. Ultimately, by demonstrating that surfactant-coated nanoparticles can be used as pattern masks, this work increases their viability as an option to continue the exponential growth of bit density in magnetic storage media.
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Torki, Amir. "Mechanical Transfer of Optically Trapped Nanoparticle." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200901.
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In this project, a mechanical system for transferring a silica nanoparticle is designedand implemented. This system is based on a mobile optical trap which enables 3Dmanipulation of a nanoparticle in high vacuum condition. The silica nanoparticle withdiameter 177nm is trapped at ambient pressure in first chamber called loading chamberat wavelength 1565nm. Then the pressure of loading chamber is reduced by vacuumpump to 10−5−10−6mbar. The second chamber is always kept in high vacuum. There isa vacuum valve between two chambers which isolates them from each other. As we openthe valve, the pressure inside the both chambers would be equilibrated. The trappednanoparticle is transferred to the second chamber with the distance around 20-25cm inless than 20-30 seconds with macroscopic scale resolution. During this long range transfer,we are able to perform microscopic transfer due to the presence of three nanopositionersaligned with three axes. No feedback system is used to stabilize particle motion for lowerpressure.I detta master examensarbete ett mekaniskt system för överflyttning av en kiselnanopartikelär utformad och implementerad. Detta system bygger på en mobil optisk fälla sommöjliggör 3D manipulering av en nanopartikel i högt vakuumtillstånd. Kiselnanopartikelmed 177nm diameter fångas vid omgivningsryck och vid våglängden 1565nm i förstakammaren såkallad laddningskammaren. Sedan reduceras trycket i laddningskammarenmed vakuumpump till 10−5−10−6mbar. Den andra kammaren hålls alltid i högvakuum.I syfte att isolera dessa tvåkammare ifrån varandra finns det en vakuumventil emellankammarna. När ventilen öppnas trycket inne i båda kamrarna hålls i jämvikt ochden fångade nanopartikel överförs till den andra kammaren på en avståndet runt 20-25cm, på mindre än 20-30 sekunder med makroskopisk skala upplösning. Under dennalånga överföringsintervall, har vi möjlighet att utföra mikroskopisk överföring pågrundav närvaron av tre nanopositioners inriktade med tre axlar. Inget återkopplingssystem används för att stabilisera partikelrörelse för lägre tryck.
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Pradhan, Sulolit. "Solid state charge transfer in nanoparticle solids /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.
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Luongo, Kevin. "Nanoparticle-Based Spintronic Computer Logic Switch." FIU Digital Commons, 2019. https://digitalcommons.fiu.edu/etd/3962.
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Spintronics is a rapidly growing research field due to scalability, integrablility within existing VLSI architecture, significantly reduced switching energy and latency while maintaining stable bit orientation (Spin-up, Spin-down). For the first time sub-5nm Spin Transfer Torque –Magnetic Tunneling Junctions (STT-MTJ) were investigated utilizing various Integrated Circuit (IC) fabrication techniques to evaluate novel concepts in logic switches.
Tunneling Magnetoresistance (TMR) was measured in STT-MTJ stacks of Ta/CoFeB/MgO/CoFeB/Ta with differing diameter ferrimagnetic CoFe2O4 nanoparticles (10nm, 4nm and 2nm) embedded in the MgO layer. MR was detected in the 2nm and 4nm particle devices and demonstrated evidence of single electron transport.
Tri-layer STT-MTJ devices were fabricated using a thin film stack of Ta/Ru/Ta/CoFeB(M1)/MgO/CoFeB(M2)/MgO/CoFeB(M3)/Ta. The overall diameter of the stack was reduced to sub-20nm using Focused Ion Beam (FIB) to mill away extra material. The coercivities of the ferrimagnetic CoFeB layers were modified during thin film deposition by altering sputter conditions. Field Applied- Magnetic Force Microscopy (FA-MFM) was used to detect four different magnetic intensities corresponding to three discreet resistances in the singly addressed device, making this architecture a candidate for neuromorphic computational applications.
Lastly a lithographic-less architecture was developed to mass fabricate and electo-mechanically probe multi-layered, single point, sub-5nm particle based STT-MTJ devices using off-the-shelf anodized nanoporous alumina. Once fabricated, the devices were probed to measure their IV characteristics and magnetoresistance (MR). The unprecedented MR changes on the order of 50,000% at room temperature suggest quantum mechanical behavior.
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Booker, Annette Casandra. "Optical Characterization and Evaluation of Dye-Nanoparticle Interactions." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/36370.
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Surface plasmon resonance has become a widely investigated phenomenon in the past few years. Initially descriptive of light interactions with metallic films, research has branched out to encompass the nanoparticles as well. Generation of the maximum surface plasmon resonance for nanostructures is based on the resonance condition that the oscillatory behavior of the 'free' electrons on the surface of the particle become equivalent to the frequency of the excitation light; for films this required a specific geometry.
Metallic nanoparticles have also interested researchers because of their unique optical properties. Depending on the metal, observations of quenching as well as fluorescence enhancement have been reported. Based on the phenomenon of surface plasmon resonance as well as the properties of metallic nanoparticles, this research reports the interaction of gold and silver nanoparticles in an aqueous dye solution. Our research is the basis for developing an optical sensor used for water treatment centers as an alarm mechanism. Due to the inefficiency of the fluorophore used in similar optodes, sufficient fluorescence was not obtained. With the addition of the nanoparticles, we hoped to observe the transfer of energy from the nanoparticle to the fluorophore to increase the overall intensity, thereby creating a sufficient signal.
Using the excitation theories discovered by Raman, Mie, and Forster and Dexter as our foundation, we mixed a strongly fluorescent dye with gold nanoparticles and aagain with silver nanoparticles. After taken measurements via fluorescence spectroscopy, absorption spectroscopy, and photoluminescence excitation, we observed that the silver nanoparticles seemed to enhance the fluorescence of the dye while the gold nanoparticles quenched the fluorescence.Master of Science
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Jenei, István Zoltán. "Nanoparticle assisted tribofilm formation and material transfer studied with SEM and TEM." Doctoral thesis, Stockholms universitet, Fysikum, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-114745.
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The discovery and subsequent synthesis of metal containing fullerenes- IFS (Inorganic Fullerene-like Structures) by R. Tenne et al. has generated considerable scientific interest with great potential impact in many industrial application areas such as lubrication. The lubrication mechanism (tribofilm formation) via exfoliation and deposition of the atomic layers from this cage-like IF-particles was revealed and demonstrated first by this research group. The incorporation of the nanoparticles into lubricants (oils, greases) is however not straightforward. When two surfaces are sliding against each other and a lubricant is used, a thin layer (tribofilm) is formed on the contact area. The friction reducing effects of the nanoparticles can be altered or hindered by certain additives that are used in lubricative oils. The effects of such additives on the tribological behavior of the nanoparticles are investigated by analyzing the tribofilms formed on the worn surfaces using energy-dispersive X-ray spectroscopy in a scanning electron microscope. Another challenge of nanoparticles in lubricants is the penetration of the nanoparticles into the contact zone. A possible solution of this problem is briefly discussed. A modified burnishing technique can be used to coat sliding metallic surfaces with a friction reducing tribofilm. The morphology and composition of these tribofilms was investigated with analytical electron microscopy techniques. In the second part of the thesis electron microscopy was used to investigate the material transfer. Titanium is an elements with high adhesive ability to the counter surface, it displays poor tribological properties in sliding metallic contacts. This can lead to material transfer and consequently severe surface damage. The cold formation and machining of titanium, thus can lead rapid tool wear and poor surface finish. Electron microscopy techniques were used to study the mechanism of titanium transfer to different counter surfaces.
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Park, Sunho 1976. "Control of oligonucleotide conformation on nanoparticle surfaces for nanoscale heat transfer study." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27120.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 77-82).
Metal nanoparticles can be used as antennae covalently linked to biomolecules. External alternating magnetic field can turn on and off the biological activity of the molecules due to induction heating from the particles that changes the temperature around the molecules. Here an experimental scheme towards direct temperature probing is proposed to predict the behavior of the antenna. Oligonucleotides modified with photosensitive molecules are conjugated with gold nanoparticles and report the temperature at their positions within some nanometers' distance from the particles. However, oligos have a known tendency to stick to gold surfaces. To locate the probes at desired position, 6-mercapto-1-hexanol (MCH) is used to reduce oligonucleotides' adsorption to the surface of gold. The experimental result shows that oligos on particle's surface can be stretched radially without any reduction of coverage ratio. Optimal MCH concentration and reaction time highly depend on the concentration of MCH and the conjugates as well as reaction time and the size of the molecules.
by Sunho Park.
S.M.
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Fermi, Andrea. "Polysulfurated aromatic compounds : Préparation and photophysical properties." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4124.
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Durant mon Doctorat de Sciences Chimiques, effectué en cotutelle entre l'Université de Bologne et l'Université de Aix-Marseille, j'ai pris en charge la synthèse et la caractérisation d'une série de composés aromatiques soufrés qui bénéficient de propriétés photophysiques intéressantes. Ce travail de thèse a été concentré sur deux classes de composés : la première s'apparente à des astérisques moléculaires contenant un coeur benzénique persoufré, fonctionnalisé avec des unités périphériques aromatiques. Dans chaque cas, des groupes stériquement encombrants ont été greffés sur les unités aromatiques situées à la périphérie des molécules. Ces molecules offrent la capacité de fonctionner comme luminophore AIE (Emission Induite par l'Agrégation) à l'état solide ou dans des milieux à haute rigidité. La deuxième famille de molécule est basée sur la même géométrie en astérisque. Cependant, chaque ligand de cette série utilise des unités terpyridyles comme unité périphérique, capables d'interagir avec des métaux de transition comme le fer(III) et le zinc. Suite à la complexation du zinc les propriétés photophysiques peuvent être modulées en fonction de la rigidité du système. Enfin, on a synthetisé un troisième type de système qui a été obtenu par le remplacement du coeur benzénique des astérisques par une fonction pyrene polysoufrée, en conservant les mêmes unités périphériques. Ce composé a montré des propriétés photophysiques intéressantes mais aussi des capacités de coordinations vers les ions métalliques (Fe(III), Zn(II) et le Nd(III)), ce qui a permis la génération d'émission dans le domaine du proche infrarougeThe aim of this thesis was the synthesis and photophysical characterization of some new polysulfurated aromatic compounds: this class of molecules can offer intriguing properties, potentially useful for the construction of new materials for optoelectronic devices. Two main families of compounds have been synthesized: the first is represented by a series of small molecular asterisks, with peripheral aromatic units, showing luminescence in solid phase or in highly rigid conditions. All compounds with peripheral substituents display an AIE behavior (Aggregation Induced Emission) with radiative deactivation of the triplet states. Taking inspiration from these smaller asterisks, a larger molecule with the same geometry has been designed, decorated with terpyridyl moieties as the outermost units: this compound shows great affinity for the coordination of several transition metal ions, changing luminescence properties after the interaction with zinc ions. With the same intentions, a tetrasulfurated pyrene-core molecule with terpyridyl external units has been synthesized and isolated: this ligand exhibits good coordination capabilities towards transition metal ions, giving rise to luminescent nanoaggregates upon addition of zinc(II), characterized by DLS and AFM microscopy. In addition a NIR emission is recorded after coordination of neodymium(III), showing evidence of an intramolecular energy transfer process
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Holladay, Robert Tyler. "Incorporating Magnetic Nanoparticle Aggregation Effects into Heat Generation and Temperature Profiles for Magnetic Hyperthermia Cancer Treatments." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/64507.
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In treating cancer, a primary consideration is the target specificity of the treatment. This is a measure of the treatment dose that the cancerous (target) tissue receives compared to the dose that healthy tissue receives. Nanoparticle (NP) based treatments offer many advantages for target specificity compared to other forms of treatment due to their ability to selectively target tumors. One benefit of using magnetic NPs is their ability to release heat, which can both sensitize tumors to other forms of treatment as well as damage the tumor. The work here aims to incorporate a broad range of relevant physics into a comprehensive model.
NP aggregation is known to be a large source of uncertainty in these treatments, thus a framework has been developed that can incorporate the effects of aggregation on NP diffusion, NP heat release, temperature rise, and overall thermal damage. To quanitify thermal damage in both healthy tissue and tumor tissue, the Cumulative Equivalent Minutes at 43 textcelsius~model is used. The Pennes bioheat equation is used as the governing equation for the temperature rise and included in it is a source heating term due to the NPs. NP diffusion and aggregation are simulated via a random walk process, with a probability of aggregation determining if nearest neighbor particles aggregate at each time step. Additionally, models are developed that attempt to incorporate aggregation effects into NP heat dissipation, though each proves to only be accurate when there is little aggregation occurring.
In this work, verification analyses are done for each of the above areas and, at minimum, qualitatively accurate results have been achieved. Verification results of this work show that aggregation can be neglected at concentrations on the order of $100~nM$ or less. This however only serves as a rough estimation and further work is needed to gain a better quantitative understanding of the effects of NP concentration on aggregation. Using this concentration as a limitation, results are presented for a variety of tumor sizes and concentration distributions.
Because this work incorporates a variety of physics and numerical methods into a single encompassing model, depth and physical accuracy in each area (bio-heat transfer, diffusion via random walk, NP energy dissipation, and aggregation) have been somewhat limited. This does however provide a framework in which each of the above areas can be further developed and their effects examined in the overall course of treatment.Master of Science
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Syed, Lateef Uddin. "Nanoelectrode and nanoparticle based biosensors for environmental and health monitoring." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13701.
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Doctor of PhilosophyDepartment of Chemistry
Jun Li
Reduction in electrode size down to nanometers dramatically enhances the detection sensitivity and temporal resolution. Here we explore nanoelectrode arrays (NEAs) and nanoparticles in building high performance biosensors. Vertically aligned carbon nanofibers (VACNFs) of diameter ~100 nm were grown on a Si substrate using plasma enhanced chemical vapor deposition. SiO[subscript]2 embedded CNF NEAs were then fabricated using techniques like chemical vapor deposition, mechanical polishing, and reactive ion etching, with CNF tips exposed at the final step. The effect of the interior structure of CNFs on electron transfer rate (ETR) was investigated by covalently attaching ferrocene molecules to the exposed end of CNFs. Anomalous differences in the ETR were observed between DC voltammetry (DCV) and AC voltammetry (ACV). The findings from this study are currently being extended to develop an electrochemical biosensor for the detection of cancerous protease (legumain). Preliminary results with standard macro glassy carbon electrodes show a significant decrease in ACV signal, which is encouraging. In another study, NEA was employed to capture and detect pathogenic bacteria using AC dielectrophoresis (DEP) and electrochemical impedance spectroscopy (EIS). A nano-DEP device was fabricated using photolithography processes to define a micro patterned exposed active region on NEA and a microfluidic channel on macro-indium tin oxide electrode. Enhanced electric field gradient at the exposed CNF tips was achieved due to the nanometer size of the electrodes, because of which each individual exposed tip can act as a potential DEP trap to capture the pathogen. Significant decrease in the absolute impedance at the NEA was also observed by EIS experiments. In a final study, we modified gold nanoparticles (GNPs) with luminol to develop chemiluminescence (CL) based blood biosensor. Modified GNPs were characterized by UV-Vis, IR spectroscopy and TEM. We have applied this CL method for the detection of highly diluted blood samples, in both intact and lysed forms, which releases Fe[superscipt]3[superscript]+ containing hemoglobin to catalyze the luminol CL. Particularly, the lysed blood sample can be detected even after 10[superscript]8 dilution (corresponding to ~0.18 cells/well). This method can be readily developed as a portable biosensing technique for rapid and ultrasensitive point-of-care applications.
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Mayilo, Sergiy. "Exploiting Energy Transfer in Hybrid Metal and Semiconductor Nanoparticle Systems for Biosensing and Energy Harvesting." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-102229.
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Person, Vernecia. "Structure Properties of Heterophase Hairy-Nanoparticles: Organic vs. Inorganic." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2015. http://digitalcommons.auctr.edu/cauetds/59.
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Substances that consist of nano-scale fillers dispersed in a polymer matrix are known as polymer-nanocomposites (PNCs). These materials are appealing since they have high potentials for applications, due to their mechanical, electrical, and thermo electrical properties. A common problem associated with PNCs is that the nano-fillers have a tendency to aggregate into clusters and form phase separated domains, which cause the desired properties of the system to either diminish or vanish all together. Hairy nanoparticles (HNPs) can avoid the issue of agglomeration that is commonly encountered by conventional PNCs. When polymer chains are grafted to a nanoparticle, and the coverage is high, the nanoparticles have decreased inter-particle interactions which allows for enhanced dispersion and mixing into a polymer matrix. By tailoring the architecture (functionalization of polymer chains, degree of polymerization, grafting density) of HNPs, it is possible to control the final properties of the system. An in depth study was carried out to investigate the effects of hairy-nanoparticle architecture on the resulting properties of the material itself. Atom transfer radical polymerization and living anionic polymerization were used to synthesize the polymer chains, of the HNP systems, while various instrumental methods including differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were utilized to study the physical ageing affects and self-assembly of these systems.
#88ABW-2015-4971
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Baker, Antony James. "Bioaccumulation, biological effects and trophic transfer of metal (oxide) nanoparticles in marine invertebrates." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/33183.
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The production and use of manufactured metal (oxide) nanoparticles has exploded in recent years as they are exploited for their novel physical and chemical properties. Cerium oxide NPs (CeO2NPs) help increase combustion in diesel engines and their reported ability to scavenge free radicals has been exploited in therapeutic treatments. Silver NPs (AgNPs) are now used in consumer products such as socks and sticking plasters due to their antibacterial properties. Once released into the environment, their ultimate fate is predicted to be the oceans The aims of this thesis are to investigate the bioaccumulation and biological effects (oxidative stress and lipid peroxidation) of CeO2NPs and AgNPs on the mussel Mytilus edulis, and to understand the potential for trophic transfer of CeO2NPs to the crab Carcinus maenas, and subsequent induced biological effects. It was found in acute exposures that, at the suggested regulatory limit of 3mg/l, less than 5% of a CeO2NP dose will be accumulated by the digestive gland of M. edulis within 4 hours, before being depurated over at least 56 hours. There were no significant biological effects of CeO2NPs, yet larger, micron-size particles had significant anti-oxidant effects. Most effects were transitory, returning to normal levels after 24 hours. In uptake comparisons between AgNPs and Ag-nanorods (AgNRs) at 10μg/l (towards the regulatory limit of 1.9μg/l), AgNRs were accumulated in the digestive gland within 2 hours, but were depurated by 4 hours. Similarity in accumulation between AgNPs and ionic Ag – including continuous accumulation in the gills over 48 hours – suggested dissolution was mostly responsible for this. Both nanoforms instigated isolated oxidative stress responses over 4-24 hours, yet none were significantly worse than AgNO3, which instigated the greatest suite of significant oxidative stress responses. In trophic transfer experiments C. maenas accumulated CeO2NPs in the hepatopancreas at less than 1% of the fed dose. Stomach accumulation was high but transitory, with most particles removed in the faeces. Gills were also a site of accumulation and it was thought that the haemolymph provided a route of transit between the digestive organs and the respiratory organs. This novel experiment used NPs crafted from 140Ce; changes in isotopic ratios of Ce in the crab following trophic transfer could therefore be used to determine absolute increases in concentration against high, and highly variable, background concentrations. There were no significant biological effects following trophic transfer of these 140CeO2NPs. It was found that the current regulatory limits are predicted to be sufficient to protect M. edulis and C. maenas from acute exposure to CeO2NPs and AgNPs, yet chronic exposures should be investigated since the relationship between the uptake and elimination rate of NPs will determine the extent of bioaccumulation and biological effects.
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Edwards, Bronwyn K. "Effect of combined nanoparticle and polymeric dispersions on critical heat flux, nucleate boiling heat transfer coefficient, and coating adhesion." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53288.
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Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-126).
An experimental study was performed to determine thermal performance and adhesion effects of a combined nanoparticle and polymeric dispersion coating. The critical heat flux (CHF) values and nucleate boiling heat transfer coefficients (HTC) of nickel wires pre-coated using 1.0% alumina, 0.1% alumina, 500ppm polyallylamine hydrochloride (PAH), and 0.1% alumina combined with 500ppm PAH dispersions were determined using the pool-boiling method. The adhesion of 0.1% alumina and combined 0.1% alumina and 500ppm PAH coatings was evaluated using the tape and modified bend test methods. Results of the pool boiling experiments showed that the wire heaters pre-coated with combined 0.1% alumina and 500ppm PAH dispersion increase the CHF in water by -40% compared to bare wire heaters, compared to an enhancement of -37% with a 0.1% alumina coating. The combined 0.1% alumina and 500ppm PAH dispersion degrades the wire HTC by less than 1%, compared to a degradation of over 26% with a 0.1% alumina coating. Results from the tape test indicate qualitatively that the combined 0.1% alumina and 500ppm PAH dispersion coating adheres better than the 0.1% alumina nanoparticle coating. Results from the modified bend test showed that the combined 0.1% alumina and 500ppm PAH dispersion coating did not fail at the failure strain of the 0.1% alumina nanoparticle coating (8.108x 10-4). The addition of PAH to alumina nanofluid for creating a nanoparticle coating through boiling deposition was found to improve both coating thermal performance and adhesion over the pure alumina nanofluid.
by Bronwyn K. Edwards.
S.M.and S.B.
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Kirez, Oguz. "A Numerical Forced Convection Heat Transfer Analysis Of Nanofluids Considering Performance Criteria." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615167/index.pdf.
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A nanofluid is a new heat transfer fluid produced by mixing a base fluid and solid nano sized particles. This fluid has great potential in heat transfer applications, because of its increased thermal conductivity and even increased Nusselt number due to higher thermal conductivity, Brownian motion of nanoparticles, and other various effects on heat transfer phenomenon.
In this work, the first aim is to predict convective heat transfer of nanofluids. A numerical code is created and run to obtain results in a pipe with two different boundary conditions, constant wall temperature and constant wall heat flux. The results for laminar flow for thermally developing region in a pipe are obtained for Al2O3/water nanofluid with different volumetric fraction and particle sizes with local temperature dependent conductivity approach. Various effects that influence nanofluid heat transfer enhancement are investigated. As a result, a better heat transfer performance is obtained for all cases, compared to pure water. The important parameters that have impact on nanofluid heat transfer are particle diameter of the nanoparticles, nanoparticle volumetric fraction, Peclet number, and viscous dissipation.
Next, a heat transfer performance evaluation methodology is proposed considering increased pumping power of nanofluids. Two different criteria are selected for two boundary conditions at constant pumping power. These are heat transfer rate ratio of the nanofluid and the base fluid for constant wall temperature boundary condition and difference between wall temperature of the pipe at the exit and inlet mean temperature of the fluid ratio for constant wall heat flux case. Three important parameters that influence the heat transfer performance of nanofluids are extracted from a parametric study. Lastly, optimum particle size and volumetric fraction values are obtained depending on Graetz number, Nusselt number, heat transfer fluid temperature, and nanofluid type.
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Joshi, Chakra Prasad. "Understanding Fundamentals of Plasmonic Nanoparticle Self-assembly at Liquid-air Interface." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1387306468.
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Green, Andrew J. "Heat Transfer from Optically Excited Gold Nanostructures into Water, Sugar, and Salt Solutions." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1376498592.
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Vazquez, Diane Marie. "Experimental studies of the heat transfer characteristics of silica nanoparticle water-based dispersion in pool boiling using nichrome flat ribbons and wires." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4575.
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This work deals with a study of enhanced critical heat flux (CHF) and burnout heat flux (BHF) in pool boiling of water with suspended silica nanoparticles using ribbon-type and wire heaters. Previously our group and other researchers have reported three-digit percentage increase in critical heat flux in silica nanofluids. This study investigates the effect of various heater surface dimensions and cross-sectional shapes on pool boiling heat transfer characteristics of water and water-based nanofluids. CHF and BHF were analyzed for circular and rectangular cross-section nichrome wires and ribbons of increasing sizes in the range of 0.32mm to 2.38mm width, approaching a flat-plate scenario. Experimental trends showed that the CHF and BHF in water pool boiling decrease as heater surface area increases, and for similar surface area, the wire had a 25% higher CHF than that of the ribbon. For concentrations from 0.1vol% to 2vol%, various properties such as viscosity, pH, and surface tension as well as silica deposition on surface and glowing length of ribbon were measured in order to study the possible factors in the heat transfer behavior of nanofluids. The deposition of the particles on the wire allows high heat transfer through inter-agglomerate pores, resulting in a nearly 3-fold increase in burnout heat flux at very low concentrations. Results have shown a maximum of up to 340% CHF enhancement for ribbon-type heaters, and the relationship of CHF with respect to nanoparticle concentration has been found to be non-monotonic with a peak around 0.2vol% to 0.4vol%. Visualization of boiling experiments aided with determination of relative bubble sizes, nucleation, and flow regimes. The surface morphology of the heater was investigated using SEM and EDS analyses, and it was inferred that the 2vol% concentration deposition coating had higher porosity and rate of deposition compared with 0.2vol% case.ID: 028916806; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.E.)--University of Central Florida, 2010.; Includes bibliographical references (p. 79-83).
M.S.M.E.
Masters
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
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Chen, Po Chih. "Design and synthesis of small molecules and nanoparticle conjugates for cell type-selective delivery." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28111.
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Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Oyelere, Adegboyega; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Lobachev, Kirill; Committee Member: Tolbert, Laren.
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Ziemann, Dirk. "Theory of Excitation Energy Transfer in Nanohybrid Systems." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/22142.
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Im Folgenden werden Transferprozesse in Nanohybridsystemen theoretisch untersucht.
Diese Hybridsysteme sind vielversprechende Kandidaten für neue optoelektronische Anwendungen und erfahren daher ein erhebliches Forschungsinteresse.
Jedoch beschränken sich Arbeiten darüber hauptsächlich auf experimentelle Untersuchungen und kaum auf die dazugehörige theoretische Beschreibung.
Bei den theoretischen Betrachtungen treten entscheidende Limitierungen auf.
Es werden entweder Details auf der atomaren Ebene vernachlässigt oder Systemgrößen betrachtet, die wesentlich kleiner als im Experiment sind.
Diese Thesis zeigt, wie die bestehenden Theorien verbessert werden können und erweitert die bisherigen Untersuchungen durch die Betrachtung von vier neuen hoch relevanten Nanohybridsystemen.
Das erste System ist eine Nanostruktur, die aus einem Au-Kern und einer CdS-Schale besteht.
Beim zweiten System wurde eine ZnO/Para-Sexiphenyl Nanogrenzfläche untersucht.
Die zwei anderen Systeme beinhalten jeweils einen CdSe-Nanokristall, der entweder mit einem Pheophorbide-a-Molekül oder mit einem röhrenförmigen Farbstoffaggregat wechselwirkt.
In allen Systemen ist der Anregungsenergie-Transfer ein entscheidender Transfermechanismus und steht im Fokus dieser Arbeit.
Die betrachteten Hybridsysteme bestehen aus zehntausenden Atomen und machen daher eine individuelle Berechnung der einzelnen Subsysteme sowie deren gegenseitiger Wechselwirkung notwendig.
Die Halbleiter-Nanostrukturen werden mit der Tight-Binding-Methode und der Methode der Konfigurationswechselwirkung beschrieben.
Für das molekulare System wird die Dichtefunktionaltheorie verwendet.
Die dazugehörigen Rechnungen wurden von T. Plehn ausgeführt.
Das metallische Nanoteilchen wird durch quantisierte Plasmon-Moden beschrieben.
Die verwendeten Theorien ermöglichen eine Berechnung von Anregungsenergietransfer in Nanohybridsystemen von bisher nicht gekannter Systemgröße und Detailgrad.In the following, transfer phenomena in nanohybrid systems are investigated theoretically. Such hybrid systems are promising candidates for novel optoelectronic devices and have attracted considerable interest. Despite a vast amount of experimental studies, only a small number of theoretical investigations exist so far. Furthermore, most of the theoretical work shows substantial limitations by either neglecting the atomistic details of the structure or drastically reducing the system size far below the typical device extension. The present thesis shows how existing theories can be improved. This thesis also expands previous theoretical investigations by developing models for four new and highly relevant nanohybrid systems. The first system is a spherical nanostructure consisting of an Au core and a CdS shell. By contrast, the second system resembles a finite nanointerface built up by a ZnO nanocrystal and a para-sexiphenyl aggregate. For the last two systems, a CdSe nanocrystal couples either to a pheophorbide-a molecule or to a tubular dye aggregate. In all of these systems, excitation energy transfer is an essential transfer mechanism and is, therefore, in the focus of this work. The considered hybrid systems consist of tens of thousands of atoms and, consequently, require an individual modeling of the constituents and their mutual coupling. For each material class, suitable methods are applied. The modeling of semiconductor nanocrystals is done by the tight-binding method, combined with a configuration interaction scheme. For the simulation of the molecular systems, the density functional theory is applied. T. Plehn performed the corresponding calculations. For the metal nanoparticle, a model based on quantized plasmon modes is utilized. As a consequence of these theories, excitation energy transfer calculations in hybrid systems are possible with unprecedented system size and complexity.
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Albero, Sancho Josep. "Photo-induced charge transfer reactions in quantum dot based solar cells." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/81717.
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En esta tesis doctoral se han estudiado procesos fundamentales de reacciones de transferencia de carga en películas mesoporosas de dióxido de titanio sensitivizado con puntos cuánticos, en películas finas de mezclas polímero:puntos cuánticos y en dispositivos completos de mezclas del polímero PCPDTBT y puntos cuánticos de CdSe en operaciones de trabajo reales.
Los resultados obtenidos permiten abordar la fabricación de dispositivos fotovoltaicos con un conocimiento de los procesos de recombinación que limitan la eficiencia de las celdas más amplio. Y por tanto, se demuestra la posibilidad de fabricar celdas solares basadas en puntos cuánticos con eficiencias iguales o superiores a los dispositivos fotovoltaicos orgánicos.The fundamental processes of the charge transfer reactions between titania dioxide mesoporous films and quantum dots, in blend films of the semiconductor polymer P3HT and CdSe quantum dots and in complete devices fabricated with the polymer PDPCTBT and CdSe quantum dots in working conditions have been studied in this doctoral thesis. The obtained results allow the fabrication of photovoltaic devices with a deeper and wider knowledge of the recombination processes that limit the device efficiency. Therefore, it is demonstrated the possibility of fabrication of quantum dot based solar cells with efficiencies similar or higher than the organic photovoltaic devices.
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Pavageau, Corentin. "Molécules et Nanosystèmes Multi-émissifs et Photocommutables." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN026/document.
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Ce projet de thèse consiste dans un premier temps à synthétiser des systèmes moléculaires multifonctionnels possédants un grand nombre d’entités fluorescentes et photochromes. De telles architectures nécessitent ensuite une étude photophysique poussée pour caractériser leurs propriétés d’émission photo-activée pour jouer le rôle de sondes moléculaires fluorescentes super-résolutives en imagerie de fluorescence. En effet, l’accès aux observations nanométriques par microscopie optique est actuellement un domaine de recherche extrêmement actif et prometteur. Ici, la combinaison astucieuse de molécules photochromes (de type diaryléthène) et fluorescentes (de type dicyanométhylène pyranes ou benzophénoxazines) à l’échelle nanométrique, grâce à des plateformes moléculaires telles que des oligosaccharides et des peptides fonctionnalisés par “chimie click”, doit permettre d’obtenir des structures aux géométries variées avec des distances et orientations inter-chromophores diverses, dont l’optimisation doit conduire à des interactions efficaces menant à l’émergence d’effets collectifs coopératifs. Pour ces assemblages moléculaires mixtes, il est attendu que la présence d’une unité photochrome puisse engendrer l’extinction de fluorescence de plusieurs fluorophores lorsque ces entités sont situées à une distance appropriée pour que le transfert d’énergie ait lieu de manière amplifiée. Par ailleurs, même une faible conversion des photochromes doit permettre d’atteindre un contraste de fluorescence extrêmement efficace avoisinant 100% et ainsi obtenir des super-molécules dont la photo-commutation serait rapide et économe en photons. Il s’agira enfin de démontrer que les systèmes moléculaires multichromophoriques ainsi optimisés présentent le comportement souhaité à l’échelle de la molécule unique pour l’imagerie de fluorescence super-résolutionThe synthesis of photoswitchable emissive molecular system still represents a challenge, in order to develop fluorescence-based devices for nanotechnologies. In the last decade, excitation energy transfer processes (EET) have been advantageously employed to design photoswitchable fluorescent molecular systems between a photochromic dye and an appropriate fluorescent molecule. More recently, photochromic dyes of particular interest, showing no emission in the open-form (P-OF) but a strong emission signal in the closed-form (P-CF), have been developed. Such molecules allow a multi-emission switch when combined with a fluorescent moiety. In this project, we will design and synthesize fluorescent photochromic diarylethene covalently linked to different fluorophores, such as benzothiadiazole (BTD) and BODIPY derivatives. By choosing a fluorophore moiety with blue/green emission (F) and a photochromic moiety with orange/red emission in closed-form (P-CF), EET can occur between F and P-CF leading to photoswitchable multi-emission properties. Photophysical characteristics of dyads will be studied by spectroscopy with the aim of presenting their light-controllable optical properties and the intramolecular EET processes between fluorescent and photochromic moieties
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Chirra, Dinakar Hariharasudhan. "NANOSCALE FUNCTIONALIZATION AND CHARACTERIZATION OF SURFACES WITH HYDROGEL PATTERNS AND BIOMOLECULES." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/60.
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The advent of numerous tools, ease of techniques, and concepts related to nanotechnology, in combination with functionalization via simple chemistry has made gold important for various biomedical applications. In this dissertation, the development and characterization of planar gold surfaces with responsive hydrogel patterns for rapid point of care sensing and the functionalization of gold nanoparticles for drug delivery are highlighted.
Biomedical micro- and nanoscale devices that are spatially functionalized with intelligent hydrogels are typically fabricated using conventional UV-lithography. Herein, precise 3-D hydrogel patterns made up of temperature responsive crosslinked poly(N-isopropylacrylamide) over gold were synthesized. The XY control of the hydrogel was achieved using microcontact printing, while thickness control was achieved using atom transfer radical polymerization (ATRP). Atomic force microscopy analysis showed that to the ATRP reaction time governed the pattern growth. The temperature dependent swelling ratio was tailored by tuning the mesh size of the hydrogel. While nanopatterns exhibited a broad lower critical solution temperature (LCST) transition, surface roughness showed a sharp LCST transition. Quartz crystal microbalance with dissipation showed rapid response behavior of the thin films, which makes them applicable as functional components in biomedical devices.
The easy synthesis, relative biocompatibility, inertness, and easy functionalization of gold nanoparticles (GNPs) have made them useful for various biomedical applications. Although ATRP can be successfully carried out over GNPs, the yield of stable solution based GNPs for biomedical applications prove to be low. As an alternative approach, a novel method of ISOlating, FUnctionalizing, and REleasing nanoparticles (ISOFURE) was proposed. Biodegradable poly(β-amino ester) hydrogels were used to synthesize ISOFURE-GNP composites. ATRP was performed inside the composite, and the final hydrogel coated GNPs were released via matrix degradation. Response analysis confirmed that the ISOFURE method led to the increased stability and yield of the hydrogel coated ISOFURE-GNPs. The ISOFURE protocol was also utilized in functionalizing GNPs with enzyme catalase in the absence of a stabilizing reagent. Biotin-streptavidin affinity was used as the bioconjugation method. Activity analysis of the conjugated enzyme showed that the ISOFURE-GNPs showed enhanced biomolecular loading relative to solution based stabilizing reagent passivated GNPs.
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Césard, Vincent. "Étude des Mécanismes de Transfert des Nanoparticules au travers d'une Barrière de Confinement Dynamique." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0190/document.
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Les travaux de thèse ont permis de quantifier l'efficacité de confinement de deux dispositifs distincts (un poste de sécurité microbiologique et une sorbonne classique) lors de la production simultanée de nanoaérosols et d'un gaz traceur (SF6). Deux techniques de mesure différentes ont été exploitées : la première basée sur la mesure de la distribution granulométrique de l'aérosol s'échappant (SMPS-C), l'autre reposant sur la détection de fluorescence d'échantillons prélevés (fluorescéine sodée utilisée comme marqueur des nanoparticules). Les résultats ont permis d'établir une forte corrélation entre le comportement d'un nanoaérosol et celui d'un gaz traceur lorsqu'ils sont émis simultanément dans une enceinte ventilée. Plus encore, on a observé une rétrodiffusion gazeuse quasiment deux fois plus importante pour le gaz traceur que pour les nanoparticules testées dans différentes configurations. Le dépôt ainsi que l'agglomération présents dans le cas du transport d'un nuage de nanoparticules peuvent expliquer ces écarts dans le niveau global de confinement obtenu. Cependant, ce constat n'est pas un gage de protection suffisante dans la mesure où il n'existe pas de valeur spécifique de référence lors de l'exposition à des nanoparticules. Il est alors utile de respecter les règles de bonne conduite qui ont été définies dans de nombreux guides INRS ou au travers de multiples études de l'IRSN. En plus de ces études expérimentales, le banc d'essai développé à l'INRS a fait l'objet d'une simulation numérique permettant de valider un modèle eulérien de transport et de dépôt implémenté dans un code de CFD destiné à modéliser le comportement d'un nanoaérosol. Les résultats numériques/expérimentaux sont concordants ; les ordres de grandeur des niveaux de confinement atteints sont comparablesThe thesis works have enabled us to quantify the containment efficiency of two devices (a microbiological safety cabinet and classical fume hood) during the simultaneous production of nanoaerosols and a tracer gas (SF6). Two different measurement techniques were used: the first based on the measurement of particle size distribution of the escaping aerosol (SMPS-C), the other based on the detection of fluorescence of samples (sodium fluorescein used as marker of nanoparticles). The results have established a strong correlation between the behavior of a nanoaerosols and the tracer gas when they are emitted simultaneously in a ventilated enclosure. More, we observed that tracer gas back diffusion was almost twice greater than for nanoparticles back diffusion in all the tested configurations. The deposit and the agglomeration present in the case of transport of a cloud of nanoparticles can explain these differences in the overall level of containment. However, this observation does not guarantee sufficient protection since there is no specific reference value for nanoparticle exposure. It is useful to observe the guidelines that have been defined in many INRS publications or through IRSN studies. In addition to these experimental studies, the test-rig developed at INRS has been numerically simulated to validate an eulerian transport and deposition model implemented in a CFD code for modeling the behavior of a nanoaerosol. Numerical and experimental results are concordant; orders of magnitude for the achieved containment levels are comparable
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Trofymchuk, Kateryna. "Controlled switching of fluorescent organic nanoparticles through energy transfer for bioimaging applications." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ121/document.
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Les performances des techniques de bioimagerie et de biodétection peuvent être améliorées grâce aux nanoparticules fluorescentes (NPs) permettant un transfert d’énergie résonante de type Förster (FRET) efficace. Le but de mon projet de thèse est le développement de NPs polymériques brillantes et ultrastables encapsulant des fluorophores, capables de produire un FRET au-delà du rayon de Förster. Il a été montré que les groupements encombrés sont essentiels pour minimiser l’auto-extinction et le blanchiment des fluorophores encapsulés. Par ailleurs, la matrice polymérique joue un rôle crucial dans le contrôle de l’effet collaboratif entre fluorophores du au transfert d’énergie d’excitation. Puis, en utilisant cet effet collaboratif entre fluorophores, nous avons conçu des NPs présentant une photocommutation efficace, ainsi qu'un phénomène de "light harvesting" très important. Enfin, de très petites NPs avec un FRET efficace à leur surface ont été élaborées et appliquées pour la détection ultra-sensible de protéines. Les résultats obtenus fournissent de nouvelles perspectives dans le développement des nanoparticules brillantes avec un transfert d'énergie efficace, ainsi que des nano-sondes pour la détection de molécules uniquesPerformance of biosensing and bioimaging techniques can be improved by fluorescent nanoparticles (NPs) capable of efficient Förster resonance energy transfer (FRET). The aim of my PhD project is to develop bright and photostable dye-loaded polymer NPs capable to undergo efficient FRET beyond the Förster radius. We showed that bulky groups are essential for minimizing self-quenching and bleaching of encapsulated dyes. Moreover, polymer matrix plays a crucial role in controlling the inter-fluorophore communication by excitation energy transfer. Then, by exploiting communication of dyes, we designed NPs exhibiting efficient photoswitching as well as giant light-harvesting. Finally, very small NPs with efficient FRET to their surface were developed and applied for ultra-sensitive molecule detection of proteins. The obtained results provide new insights in the development of bright nanoparticles with efficient energy transfer as well as nano-probes for single-molecule detection
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Reinhardt, Nora Maria Elisabeth. "Modification chimique de surface de nanoparticules de silice pour le marquage d'ADN dans des lipoplexes." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14820/document.
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Les nanoparticules de silice sont des plateformes idéales pour la conception d’outils de bioimagerie afin d’étudier les mécanismes de transfert de gènes par des lipoplexes. L’objectif de notre étude est le développement d’une modification chimique de surface permettant d’obtenir des colloïdes de silice chargés positivement susceptible de lier de l’ADN par des interactions électrostatiques. Deux stratégies pour la génération de groupements ammonium quaternaires sur des nanoparticules de silice sont présentées a) une silanisation directe par l’utilisation d’un agent de couplage silanique contenant un groupement ammonium quaternaire et b) un procédé en deux étapes mettant en jeu une modification de surface chimique par des aminosilanes primaires et secondaires suivie d’une alkylation des amines par l’iodomethane. Différentes méthodes physico-chimiques (essais de cosédimentation, des expériences de microbalance à cristal de quartz avec mesure de dissipation et d’imagerie MET et Cryo-MET) ont été utilisées pour mettre en évidence et caractériser les interactions entre les biomolécules et les surfaces quaternisées. Des études préliminaires ont montrées les capacités de marquage de lipoplexes par de telles nanoparticulesSilica nanoparticles are ideal platforms for the conception of bioimaging tools serving for the elucidation of the mechanisms of gene transfection via lipoplex structures. The purpose of the present study is the development of a chemical surface modification for the generation of quaternary ammonium groups on silica nanoparticles permitting the obtainment of highly positively charged silica colloids which strongly attract DNA by electrostatic interactions. Two modification strategies to generate quaternary ammonium groups on silica are presented a) a direct silanization using quaternary ammonium groups containing silane derivatives and b) a modification of silica nanoparticles via a first modification with an amine group containing silane derivative and a subsequent quaternization of the amine groups via an alkylation with iodomethane. Different physicochemical methods were employed (cosedimentation assays, quartz crystal microbalance with dissipation monitoring measurements, TEM and Cryo-TEM imaging) to analyze interactions between quaternized surfaces, DNA and lipids. A preliminary study was carried out which shows the capacity of the synthesized nanoparticles to label DNA in lipoplexes
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Kroschwald, Felix. "Prozessintegrierter Transfer von Nanopartikeln auf Polycarbonatoberflächen beim Spritzgießen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-202485.
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Im Rahmen dieser Arbeit werden die Nanopartikel mittels verschiedener Beschichtungsverfahren auf eine Zwischenoberfläche (Substrat) appliziert. Diese wird anschließend in die Kavität einer Spritzgießmaschine eingelegt, wobei es während des Spritzgießprozesses zur Übertragung der Nanopartikel auf das PC-Formteil kommt. Als Modellsystem werden dafür Goldnanopartikel (AuNP) verwendet, da diese charakteristische optische, chemische und physikalische Eigenschaften aufweisen. Im weiteren Verlauf wurde die Übertragung von Kohlenstoffnanoröhren (CNT) und Siliziumdioxidnanopartikeln (SiO2-NP) untersucht. Die Oberflächen der SiO2-NP wurden außerdem mithilfe funktioneller Alkoxysilane modifiziert, um den Einfluss der Nanopartikeloberfläche auf die Übertragung zu untersuchen.
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Mongin, Denis. "Spectroscopie ultrarapide de nanoparticules métalliques et hybrides." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10129/document.
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L'utilisation d'un montage expérimental pompe-sonde a permis l'étude de différentes propriétés physiques typiques de différentstypes de nano-objets. Tout d'abord, l'étude sélective d'un transfert d'électron dans un nano-hybride semi-conducteur/métal composé d'un nano-bâtonnet de CdS et d'une nanoparticule d'or en contact direct avec le semi-conducteur, a prouvé l'existence du transfert de charge entre les deux composants du nano-hybride et montré que ce phénomène intervient pour des temps caractéristiques inférieurs à 15 femtosceondes. L'étude des propriétés optiques des nanoparticules d'or ayant reçu les charges transférées a montré que l'ajout de quelques charges négatives à de petites nanoparticules d'or provoque un décalage de la résonance palsmon dans le rouge du spectre. Ensuite, la mesure des modes de vibrations fondamentaux de nano-objets métallique (spériques ou sphéroïdaux) encapsulés par une couche encapsulés par une couche diélectrique ou métallique nous a permis d'obtenir des informations sur les épaisseurs relatives des différentes couches composants les nano-objets étudiés ainsi que sur les la qualité du contact entre ces couches. Enfin, l'étude du temps typique d'interaction électron-phonon dans des nanoparticules métalliques a mis en évidence que deux méthodes de mesure optique de ce temps par spectroscopie ultrarapide sont pôssibles, et que des effets de transitions entre un comportement type "peti solide" et un comportement moléculaire sont observable pour des nanoparticules de moins de 250 atomesThe usse of a pump-probe experimental setup allowed the study of different specific physical properties of different types of nano-objects. First, the selective study of an hybrid nanoparticles comosed of a CdS nanostick and a particle directly groxwn on the semiconductor part proved the existence of a transfer between the two part of the hybrid nanoparticle and showed that this phenomenon occurs in less than 15 femtosecondes. The study of optical propertie of gold nanoparticles with an extra charge due to the transfer showed that adding few electrons to a small gold nanoparticles leads to a red shift of the plasmon resonance. Secondly, measurment of the period of fundamental vibration modes of a bilayer nano-object (spheric or elongated) composed of a metallic core and a dielectric or metallic shell lead to information on the relative thickness of the layers and the contact quality between them. LAstly, the study of the characteristic time of electron-phonon interactions in metallic nanoparticles has proven that there are two different methods of measuring this characteristic time, and its investigation for small nanoparticles (less than 250 atoms) leads to the observation of a transition form a "bulk" to a molecular behaviour
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Vivien, Anthony. "Complexes de cobalt(I) : synthèse raisonnée de nanocristaux mono- ou bimétalliques et applications catalytiques." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS235.
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L’univers de la nanocatalyse reste encore un domaine peu exploré notamment à cause de la difficulté de pouvoir synthétiser de manière simple et contrôlée les nanoparticules et de la mise en place d’un système réactionnel adaptable à ce type de catalyse hétérogène. Dans ces travaux de thèse nous montrons qu’il est possible d’obtenir des nanoparticules de cobalt hc en partant du complexe CoCl(PPh3)3 facile d’accès et en le chauffant simplement dans l’oléylamine. Le mécanisme de synthèse basé sur la dismutation de ce complexe de cobalt(I) a été prouvé par des études expérimentales et théoriques. Nous montrons également qu’il est possible de contrôler la taille et la forme de ces nanoparticules en changeant certains paramètres de réactions comme la durée ou la nature du précurseur métallique. De plus, en appliquant ce protocole à d’autres métaux (notamment le nickel) nous avons réussi à obtenir des nanoparticules et également à former des alliages bimétalliques CoxNi1-x. Nos nanoparticules ont été utilisées dans des réactions d’hydrogénations et de transferts d’hydrogène en présence de NH3BH3 (principalement sur des alcynes) et ont montré leur efficacité tant au niveau des conversions que sur la sélectivité. Nous avons pu comparer ces résultats avec ceux obtenus en phase homogène en partant de différents complexes de cobalt. Une étude approfondie de cette catalyse homogène a été faite, montrant une fois encore l’efficacité du cobalt (tant sous la forme de nanoparticules que de complexes) sur les réactions d’hydrogénation et de transfert d’hydrogène. Ces résultats ouvrent de grandes perspectives quant à l’utilisation des métaux non nobles pour le stockage et l’utilisation du dihydrogène, permettant un accès plus simple vers des applications dans le domaine de l’énergieNanocatalysis universe is a field which is yet to be explored, especially because of the difficult access to simple and well-controlled nanoparticles and their uses in heterogeneous catalyzed reactions. In this work, we show that it is possible to obtain hcp cobalt nanoparticles starting from the easily accessible CoCl(PPh3)3 and by simply heating it in oleylamine. The mechanism of this reaction based on the disproportionation of the cobalt(I) was proved by experimental and theoretical studies. We also demonstrate that it is possible to control the size and the shape of those nanoparticles by changing some parameters like the reaction time or the nature of the organometallic precursor. Moreover, by using the same protocol with other metals (especially nickel) we were able to obtain nanoparticles and then to form CoxNi1-x bimetallic alloys. Our nanoparticles were used for hydrogenation and hydrogen transfer reactions in presence of NH3BH3 (mainly on alkynes) giving good conversions and selectivities. We then compare those results with homogeneous catalysis, using different cobalt complexes. We made an in-depth study of this homogeneous catalysis which shows once again the efficiency of cobalt (as nanoparticles or organometallic complexes) on hydrogenations and hydrogen transfers. Those results offer new opportunities concerning the use of non-noble metals for the storage and the use of dihydrogen, allowing easier access towards energy applications
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Prédélus, Dieuseul. "Rôle des hétérogénéités texturale et structurale du sol sur le transfert et la rétention des nanoparticules dans la zone non saturée : Expérimentation et modélisation." Thesis, Vaulx-en-Velin, Ecole nationale des travaux publics, 2014. http://www.theses.fr/2014ENTP0006/document.
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La production croissante des nanoparticules issues du développement des nanotechnologies et leur incorporation dans des produits de consommation vont inévitablement conduire à leur introduction dans l’environnement. Ces particules peuvent constituer un vecteur de substances polluantes en raison du transport facilité des contaminants organiques ou inorganiques potentiellement adsorbés sur leurs surfaces ou représentent elles-mêmes un risque pour l’environnement et la santé humaine. La zone non saturée joue une fonction importante de filtration naturelle des eaux de recharge des nappes. Les mécanismes de transport et de rétention des nanoparticules à travers cette zone sont complexes du fait des hétérogénéités de type structural et textural de celle-ci. Ces hétérogénéités sont à l'origine des écoulements préférentiels et d’un grand nombre de facteurs d'interaction physico-chimiques liés aux propriétés des nanoparticules et de la zone non saturée elle-même. L'objectif de la thèse est de mieux comprendre les effets de ces hétérogénéités sur le transport des nanoparticules dans un milieu non saturé hétérogène afin de mieux prévenir le devenir des nanoparticules dans le sol. Dans ce contexte, trois matériaux granulaires (un sable et des mélanges sable-gravier) ont été mis en place en colonne (10 cm de diamètre x 30 cm de hauteur) et dans le lysimètre LUGH du LEHNA (100 x 160 x 100 cm3) pour simuler le transport des nanoparticules dans le sol. Le but est de déterminer le rôle des hétérogénéités texturale (différentes granulométries) et structurale (barrière capillaire) du sol, en prenant en compte les effets de la force ionique de la solution et de la vitesse d’écoulement sur le transfert des nanoparticules en conditions non saturées. Des nanoparticules de silice marquées par des molécules organiques fluorescentes ont été développées en tant que nanotraceur particulaire dans le cadre de cette étude, l’ion bromure a été utilisé pour caractériser l’écoulement de l’eau. Le modèle de transfert de non équilibre hydrodynamique à fractionnement de l'eau en deux phases mobile et immobile, MIM, incluant un terme de rétention et de relargage des nanoparticules, décrit correctement les courbes d'élution de nanoparticules, pour les expériences en colonne. Cette étude a permis de caractériser les effets liés aux différentes tailles des grains du sol et à la barrière capillaire sur la rétention des nanoparticules. Les expériences réalisées avec différentes forces ioniques montrent que pour les forces ioniques comprises entre 1 et 50 mM, la rétention est croissante comme prédit la théorie DLVO ; cependant à partir d’une force ionique supérieure à 100 mM il se produit une inversion de la rétention. Lorsque la vitesse d’écoulement diminue, la rétention augmente, probablement en partie à l’interface air-eau. Le lysimètre LUGH a permis d’identifier le rôle de la barrière capillaire sur la rétention des nanoparticules. Un modèlenumérique 3D basé sur l’équation de Richards pour l’écoulement et les équations convection dispersion couplées avec un module de rétention pour les nanoparticules a été dévelopé. Les résultats montrent que la rétention a augmenté à l’interface sable-milieu bimodal. Le profil de rétention de nanoparticules indique qu’elles sont majoritairement retenues en surface du sol, puis la rétention diminue avec la profondeur, pour les expériences réalisées en colonne. Le nanotraceur constitue un outil puissant pour l’étude du rôle des hétérogénéités dans le transfert des particules dans un sol non saturéIncreasing production of nanoparticles from nanotechnology development and incorporation into consumer products will inevitably lead to their introduction into the environment. These particles can be a vector of pollutants due to the facilitated transport of organic and inorganic contaminants potentially adsorbed on their surfaces or represent a risk to the environment and human health themselves. The unsaturated zone plays an important function of natural water filtration recharge. The transport and retention mechanisms of nanoparticles through this zone are complex due to the structural and textural soil heterogeneities. These heterogeneities are causing preferential flows and are responsible a large number of physical and chemical interaction related to the nanoparticles properties. The aim of the thesis is to better understand effects of soil heterogeneities on the transport of nanoparticles in a heterogeneous unsaturated media to better prevent the fate of nanoparticles in the vadose zone. In this context, three granular materials (sand and sand - gravel mixtures) were introduced in column (10 cm diameter x 30 cm high) and the lysimeter LUGH of Lehna (100 x 160 x 100 cm3) to simulate the transport of nanoparticles in the soil. The goal is to determine the role of heterogeneous textural (different sizes) and structural (barrier capillary) heterogeneities of the soil, taking into account the effects of the ionic strength of the solution and the flow rate on the transfer of the nanoparticles in unsaturated conditions. Silica nanoparticles labeled with fluorescent organic molecules have been developed as particulate v in this study, the bromide ion has been used to characterize the flow of water. The transfer model of non-equilibrium hydrodynamic fractionation of water and two mobile and immobile phases, MIM, including a retention and release term of the nanoparticles, properly described breakthrough curves of nanoparticles on column experiments. This study allowed to characterize the effects related of different grain sizes of soil and capillary barrier on the nanoparticle retention. Experiments with different ionic strengths show for the ionic strength between 1 and 50 mM, the retention increased as predicted by the DLVO theory. However, from an ionic strengh greater than 100 mM an inversion retention occurs. When the flow rate decreases, retention increases, air - water interface increases and trapps probably the nanoparticles. Lysimeter LUGH allowed to identify the role of the capillary barrier on the retention of nanoparticles. A 3D numerical model based on Richards equation for flow and the convection dispersion equations coupled with a mechanical module for nanoparticle trapping was developed. Results show retention increased in the sand-bimodal interface. The retention profile indicates that nanoparticles are predominantly retained at the soil surface, then the retention decreases with depth, for the column experiments. The nanotracer is a powerful tool for studying the role of heterogeneous in the transfer of particles in an unsaturated soil
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Laszewski, Henryk. "Transfert thermique photo-induit par des nanoparticules d’or appliqué à la thérapie génique." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN003/document.
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La thérapie génique est probablement une des approches la plus ambitieuse de l'histoire de l'humanité pour éliminer des maladies résistantes à tout autre traitement. Cependant, c'est une approche qui doit encore être développée afin d'obtenir un meilleur contrôle du processus de délivrance des médicaments et aussi de réduire les coûts. À cette fin, ce projet de thèse est axé sur l’optimisation et le contrôle de la délivrance d’oligonucléotides basée sur l'utilisation de nanobâtonnets d'or (Gold NanoRods, GNRs). De telles nanoparticules (40 nm de long et 10 nm de diamètre) sont internalisées par les cellules et grâce à leurs propriétés physiques extraordinaires permettent de délivrer les médicaments dans le cytoplasme de manière contrôlée. En effet, leur absorption très élevée dans le proche infrarouge du spectre électromagnétique permet de convertir l’énergie lumineuse en chaleur à l’intérieur et autour des nanobâtonnets, sans affecter la cellule. L’avantage d’une absorption dans l’infrarouge est qu’à cette longueur d’onde la lumière pénètre profondément dans les tissus humains (3 cm). Le contrôle de la température autour des nanoparticules permet la libération d'oligonucléotides par simple dénaturation du duplex à un instant donné.L’obtention de nanoparticules pouvant être considérées comme un « cargo » implique de remplir les conditions suivantes : stabilité de la forme colloïdale en milieu complexe, conservation des propriétés physiques et chimiques une fois administrées et possibilité d’immobiliser et de libérer le médicament de manière contrôlée.La première étape de mon projet a consisté à établir un protocole de synthèse de nanobâtonnets d’or afin d’obtenir une solution colloïdale mono-disperse et dont la bande d’absorption de plasmon longitudinal soit dans le proche infrarouge. L'étape suivante était d’optimiser un protocole de fonctionnalisation de la surface des GNRs. Le défi ici est associé à l'agrégation des GNRs lorsque le surfactant (CTAB) nécessaire au maintien des GNRs en solution est remplacé par des biomolécules (oligonucléotides). Cependant, après une étude systématique et détaillée, la déstabilisation de la couche protectrice de surfactant sur la surface métallique et l’ajout d’oligonucléotides ayant une fonction thiol à une des deux extrémités dans un rapport approprié ont permis une bio-fonctionnalisation efficace des nanobâtonnets. En conséquence, les nanoparticules fonctionnalisées, après redispersion dans la solution, ont les propriétés physico-chimiques nécessaires. En outre, l’immobilisation des oligonucléotides sur la surface des nanoparticules est spécifique (via la liaison thiol-Au) et permet leur transfert dans des solutions tamponnées ou dans des milieux complexes sans affecter leur stabilité. Après hybridation entre le simple brin immobilisé sur la surface des nanobâtonnets et le brin complémentaire, j’ai démontré que les oligonucléotides étaient stables et que le nombre de doubles brins qui se forment par hybridation peut être contrôlé. L’analyse des propriétés des nanomatériaux a constitué la seconde étape clé de mon travail, car elle revêt une importance cruciale pour la délivrance contrôlée de médicaments. J'ai décidé d'appliquer des méthodes uniquement optiques couvrant l'absorption des nanobâtonnets et l'analyse de la fluorescence des oligonucléotides marqués et des images TEM.Au cours du projet, il a donc été possible d’établir une nouvelle approche de fonctionnalisation et de créer un protocole de caractérisation efficace, axé sur les oligonucléotidesGene therapy is probably one of the most ambitious approaches in human history that aims to eliminate diseases, often those completely resistant to other treatments. However, this approach requires further development in order to obtain better control over the process of drug delivery and reduce costs. For this purpose, this project has focused on delivery of oligonucleotides using gold nanorods (GNRs). Such nanoparticles, (40 mm in length and 10 nm in diameter) can be internalized by cells and their extraordinary physical properties allow the delivery of drugs to the cytoplasm of cells in a controlled manner. Indeed, their strong absorption in the near-infrared part of the electromagnetic spectrum allows conversion of the energy of light into heat around the nanorods without affecting the cells. The advantage of absorption in the infrared is that at this wavelength the light can penetrate human tissues (3 cm). Control of the temperature around the nanoparticles allows the release of oligonucleotides by simple denaturation of the duplex at a given time.Obtaining nanoparticles that can be considered as a "cargo ship" implies fulfilling the following conditions: stability of the colloidal form in a complex medium, preservation of the physical and chemical properties once administered and the ability to immobilize and release the drug in a controlled manner.The first step of my project was to establish a nanorods synthesis protocol in order to obtain a monodisperse colloidal solution whose longitudinal absorption band is in the near infrared. The next step was to optimize the functionalisation protocol of the surface of the GNRs. The challenge here is associated with the aggregation of GNRs when the surfactant (CTAB) needed to maintain the GNRs in solution is replaced by biomolecules (oligonucleotides). However, after a systematic and detailed study, the destabilisation of the surfactant protective layer on the metal surface and the addition of oligonucleotides having a thiol function at one of the two extremities in a suitable ratio allowed an efficient bio-functionalisation of the nanoparticles. As a consequence, the functionalised nanoparticles, after redispersion in solution, possess the necessary physicochemical properties. In addition, the immobilisation of oligonucleotides on the surface of the nanoparticles is specific (via the thiol-Au bond) and allows their transfer into buffered solutions or in complex media without affecting their stability. After hybridisation between the single strand immobilized on the surface of the nanorods and the complementary strand, I demonstrated that the oligonucleotides were stable and that the number of double strands that are formed by hybridization can be controlled. The analysis of the properties of nanomaterials was the next important part of the work, as it is of crucial importance for the controlled delivery of drugs. I decided to apply only optical methods covering nanorods absorption and fluorescence analysis of labeled oligonucleotides and TEM images.In summary, during the project it was possible to establish a new functionalization approach and create a protocol for efficient characterization, focused on oligonucleotides. We expect that these observations will aid further research in the field of gene delivery based on gold nanoparticles
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Stuart, Dale. "Heat Transfer Enhancement using Iron Oxide Nanoparticles." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/425.
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Two different iron oxide nanofluids were tested for heat transfer properties in industrial cooling systems. The nanofluids either had 30 nm particles with a wide size distribution to include particles greater than 1 micrometer or 15 nm particles with greater than 95% of the particles less than 33 nm. Calorimetry and thermal circuit modeling indicate that the 15 nm particle ferrofluid enhanced heat capacity. The smaller particle ferrofluid also demonstrated up to a 39% improvement in heat transfer, while the larger particle ferrofluid degraded the heat transfer performance. Particles from the larger particle ferrofluid were noted as settling out of a circulating system and therefore not participating in the bulk fluid properties. Application of 0.32% 15nm particles in an open cooling system improved cooling tower efficiency by 7.7% at a flow rate of 11.4 liter per minute and improved cooling tower efficiency by 3.3% at a flow rate of 22.7 liter per minute, while applying 0.53% 15 nm particles also improved cooling tower efficiency but was less effective than the lower concentration.
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Lerond, Thomas. "Etude des interactions nanoparticules métalliques-émetteurs quantiques." Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0030/document.
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Avec un monde industriel dont l’un des enjeux est la miniaturisation, l’échelle nanométrique est la prochaine étape à maîtriser. Les nanosources optiques, basées sur un fort confinement de la lumière, devraient permettre d’alimenter les futurs dispositifs nanophotoniques. Depuis que Purcell a démontré que les propriétés d’émission de lumière ne sont pas intrinsèques aux luminophores, la communauté scientifique vise à comprendre et contrôler ces propriétés. Les nanoparticules ou structures métalliques permettent de modifier ces propriétés de luminescence en influant sur l’efficacité d’émission, l’efficacité d’excitation ou encore la redirection de l’émission des émetteurs de lumière. Dans le cadre de ce travail de thèse, nous nous sommes focalisés sur l’étude de ce couplage au travers de structures simples composées de nanoparticules entourées de fluorophores, afin de discriminer l’effet de ce couplage à différentes distances séparant le métal de l’émetteur. Nous dégageons trois processus principaux : une forte inhibition de luminescence lors d’une grande proximité entre les émetteurs et le métal, une exaltation de luminescence à distances légèrement plus élevées, et une exaltation de l’excitation. Nous montrons par la suite qu’il est possible d’utiliser cette exaltation de l’excitation pour augmenter les effets d’absorption multiphotonique. Enfin nous ouvrons sur une nouvelle possibilité pour les travaux futurs : l’utilisation de l’aluminium pour utiliser ses possibilités plasmonique dans l’ultra-violet pour réfléchir à des nanosources UVIn an industrial world where one of the most important issues is miniaturization the next step is to master nanometric scale. Optical nanosources, which are based on a strong light confinment, should allow to supply the next nanophotonic devices. Since Purcell demonstrate that light emission properties are not inhérent to optical emitters, scientists search to understand and control these properties. Metallic nanoparticles or nanostructures allow to modify these luminescence properties by changing emission and excitation rates or redirect the emitted light.In this study, we focus on this coupling with simple structures made from nanoparticles and quantum emitters in order to discriminate the effect of this coupling at different distances between metal and emitter. We observe three different processes: a strong quenching of the luminescence at the viscinity of the metal, an enhancement at longer distances, and an excitation enhancement. Then we show that it is possible to use this amplified excitation to obtain multiphoton absorption. Finally, we prospect a new way for future works: using aluminium plasmonic properties in UV to search on UV nanosources
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Goetz, Joan. "Biocompatible luminescent probes for imaging and inhibition of cancer." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF004.
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Cette thèse s’inscrit dans le cadre d’une collaboration entre Hong Kong Baptist University (Dr. Gary K-L Wong) et le Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse (LIMAA - Dr. Loïc Charbonnière) financé par la région Alsace afin de synthétiser des nouvelles nanosondes pour la détection, l’imagerie et le traitement du cancer. Le premier travail a été de synthétiser des nouvelles nanoparticules ultrabrillantes hybrides. Elles ont été obtenues à partir d’un noyau La0.9Tb0.1F3 et recouvertes de différents ligands. Grâce au mécanisme d’effet d’antenne, la brillance des nanoparticules a été considérablement améliorée. Le deuxième travail a été de synthétiser un nouveau ligand pour photosensibiliser les nanoparticules La0.90Eu0.1F3 hydrosolubles afin d’améliorer l’émission de l’europium. Un second ligand et des nouvelles nanoparticules hétérométalliques ont été synthétisées dans le but de favoriser le transfert d’énergie des ions Tb(III) à la surface des NPs vers les ions Eu(III) dans le noyau des nanoparticules pour obtenir des temps de vie très longs et un rendement quantique exceptionnel en solution aqueuse. Le dernier travail a été de fonctionnaliser des nanoparticules de g-C3N4 (graphitic-carbon nitride) par des porphyrines. Les porphyrines ont été synthétisées pour générer de l’oxygène singulet (1O2), pour accueillir un ion Ga3+ dans sa cavité et deux espaceurs différents pour être couplés aux nanoparticules. Ce système a pour objectif d’être sensible au pH, être un agent théranostique pour l’imagerie TEP et la thérapie PDTThis joint PhD program is part of a collaboration between Hong Kong Baptist University (Dr. Gary K-L Wong) and Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse (LIMAA - Dr. Loïc Charbonnière) funded by the Alsace region to synthesize new nanoprobes for sensing, imaging, and inhibiting cancer diseases. The first work was to synthesize new hybrid ultrabright nanoparticles. They have been obtained from a La0.9Tb0.1F3 core and coated by different ligands. Thanks to a mechanism of antenna effect, the brightness of the nanoparticles has been significantly improved. The second work was to synthesize a new ligand to photosensitize water-soluble La0.90Eu0.1F3 nanoparticles in order to improve the emission of europium. A second ligand and new heterometallic nanoparticles have been synthesized with the aim to promote the energy transfer from Tb(III) ions on the surface of the NPs to Eu(III) ions in the core of the nanoparticles and to get a very long excited-state lifetime and an exceptional quantum yield in aqueous solution. The last work was to functionalize water-soluble graphitic-carbon nitride (g-C3N4) nanoparticles by porphyrins. The porphyrins have been synthesized to generate singlet oxygen (1O2), to host a Ga3+ ion inside their cavity and with two different linkers to be coupled to nanoparticles. This system aims to be a pH sensor, and a PDT and PET theranostic agent
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Carle, Florian. "Flow motion in sessile droplets : evaporation and nanoparticles assembly." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4726/document.
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L'évaporation d'une goutte reposant sur un support plat semble être un système relativement simple à étudier et a fait l'objet d'études scientifiques depuis plus d'un siècle. Cependant, l'étude de l'évaporation de gouttes sessiles est toujours d'actualité aujourd'hui avec l'essor de nouvelles techniques de visualisation ou de l'apparition de nouveaux types de fluides complexes.Cette étude expérimentale sera focalisée sur deux aspects distincts :- L'étude sur l'évaporation de fluides purs permettra d'étudier la dynamique d'évaporation et les ondes hydrothermales qui apparaissent dans les gouttes de fluides volatils lors du changement de phase. L'influence du type de fluide (différents alcools et alcanes) et du niveau de gravité (terrestre, lunaire et martienne) seront étudiés. De plus, l'utilisation de différents niveaux de gravité permet de développer un modèle empirique afin de prendre en compte dans le modèle quasi-stationnaire limité par diffusion de la vapeur la convection naturelle qui augmente fortement le débit d'évaporation.- Si les fluides complexes présentent une dynamique de séchage similaire à celle des fluides purs, d'autres mécanismes entrent en jeux, comme la gélification, l'organisation des particules et l'apparition de craquelures (voir Figure 2). Le mouillage et les différents groupes fonctionnels graphés sur les particules seront étudiés en regard du motif final de craqueluresSessile droplets are widely found in day to day life: it might be a coffee spilt, rain onto a waterproof raincoat or again, water falling onto a cooking plate. However, despite the vast number of studies devoted to droplets for almost half a century, the fundamental phenomenon of the evaporation of sessile droplets is still a field that attracts a high level of interest due to its wide applicability and the development of new visualisation techniques or new types of complex fluids. This experimental study is focused two distinct aspects:- The evaporation of pure fluids has allow to study hydrothermal waves that appear in the droplets of volatile fluids during phase change. The influence of the type of fluid ---different alcohols and alkanes--- and the gravity levels ---Terrestrial, Lunar and Martian--- is investigated to have a better understanding of the flow motion inside droplet. Moreover, the use of different gravity levels allows to experimentally evidence the contribution of the atmospheric convective transport to sessile droplet evaporation. This investigation has allowed to develop an empirical model to take account of natural convection which greatly increases the evaporation rate in the quasi-steady diffusion-controlled evaporation model.- If complex fluids exhibit an evaporation dynamic similar to pure fluid, other mechanisms come into play, such as gelation, particles organisation and cracks formation. Wetting and different functional groups on the particles graphs will be studied in relation to the final pattern of cracks
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Heimburger, Doriane. "Synthèse de nanoparticules fluorescentes ultra-brillantes à base de polymères et leur application pour la bio-imagerie." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF065.
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Les nanoparticules polymériques fluorescentes apparaissent comme des outils importants pour l'imagerie en temps réel des processus biologiques au niveau moléculaire et cellulaire. L’objectif de mon projet de doctorat a été d’optimiser les nanoparticules polymériques fluorescentes pour l’imagerie biologique. Premièrement, nous avons pu, en faisant varier la chimie des polymères, obtenir un très bon contrôle de leur taille. Ceci a permis de mettre en évidence l’importance de la taille des NPs pour des applications intracellulaires avec une taille maximale de 23 nm pour une distribution dans tout le cytosol. Deuxièmement, nous avons pu montrer que la simple adsorption d’un amphiphile PEGylé de type Pluronic permet la stabilisation des nanoparticules dans des milieux biologiques. Le nombre de molécules incorporées et leur stabilité ont été étudiés en combinant des techniques de FRET et de FCS. Les meilleures formulations résultent en une stabilité des nanoparticules in vivo, ce qui a permis leur imagerie en tant que particules individuelles dans les vaisseaux sanguins du cerveau de souris. Troisièmement, le transfert d’énergie entre différents fluorophores encapsulés dans les NPs a été étudié et optimiséFluorescent polymeric nanoparticles appear as important tools for real-time imaging of biological processes at the molecular and cellular level. The objective of my PhD project was to optimize fluorescent polymeric nanoparticles for biological imaging. First, by varying the chemistry of the polymers, we have been able to obtain a very good control of their size. This made it possible to highlight the importance of NPs size for intracellular applications with a maximum size of 23 nm for optimal distribution throughout the cytosol. Secondly, we have shown that simple adsorption of a PEGylated amphiphiles pluronic family allows the stabilization of nanoparticles in biological media. The number of incorporated molecules and their stability has been studied by combining FRET and FCS techniques. The best formulations result in nanoparticle stability in vivo, which allowed their imaging as individual particles in the blood vessels of the mouse brain. Third, energy transfer among different fluorophores encapsulated in NPs has been studied and optimized
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Deng, Fengjun. "Single electron transfer of organized assemblies of gold nanoparticles /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2006. http://uclibs.org/PID/11984.
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Alkurdi, Ali. "Transport Thermique aux Interfaces : Angle Critique des Phonons, Transfert à Travers un Gap; Transfert Autour d'une Nanoparticule Colloïdale Cœur-Coquille." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1197.
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Cette thèse s'inscrit dans le domaine de la nanothermique, c'est à dire, l'étude des transferts de chaleur à l'échelle du nanomètre, pour lesquels la loi de Fourier n'est plus valide. A cette échelle, l'interface domine le transport thermique par sa résistance au flux d'énergie thermique. Cetterésistance se manifeste par une discontinuité de la température aux interfaces. Il est important de pouvoir la prédire afin de contrôler et aménager les flux thermiques dans les application en microélectroniques où la taille des transistors modernes devient nanomètrique. Le but de cette thèse est d'une part, d'étudier la transmission angulaire des phonons et prédire la résistance de Kapitza aux interfaces entre solides, de quantifier le transfert d'énergie assuré par les phonons au travers d'un gap de vide nanométrique, et d'autre part d'étudier le transfert thermique dans un système nanoparticule cœur-coquille immergé dans l'eau. Nous avons développé une nouvelle méthode de dynamique de réseau couplée à l'utilisation de constantes de force issus des calculs ab-initio. Cette méthode permet d'obtenir la transmission des phonons entre deux solides, en fonction de leur fréquence et vecteur d'onde, en tenant comptede la dispersion des phonons en volume dans les deux milieux. Nous avons également appliqué la méthode pour décrire le transfert thermique à travers un gap de vide entre deux solides. Enfin, nous nous sommes intéressés au transfert thermique autour d'une nanoparticule (NP) immergée dans l'eau et chauffée par un faisceau laser. Nous avons comparé l'efficacité de chauffage des NPs homogènes d'or à celles de type cœur-coquille or-siliceThis thesis is devoted to the study of interfacial thermal transport at the nanoscale where Fourier’s law is not valid. This is because, at this scale, phonon mean free path becomes smaller to the characteristic length of the system, thus the heat transfer is no longer diffusive but rather ballistic. As a consequence, the thermal boundary resistance (TBR) becomes a determinant factor in heat transfer. The goal of this thesis is, firstly, to study phonon transmission and predict the thermal boundary conductance at interface between two solids. To this end, we have developed a new approach, which combines lattice dynamics calculations and inputs from ab initio, and we have applied our LD model to two types of solid structures: the face-centered cubic (FCC) crystal solid and the diamond-like crystal solid.Secondly, we aim to quantify the phononic contribution in heat transfer across a nanometric vacuum gap that separates two solids. We have used this ab initio LD model to predict the contribution of phonons in the heat transfer across a vacuum gap in two systems: the Au/vacuum-gap/Au and the Si/vacuum-gap/Si. Our results indicate that phonons do contribute significantly to heat transfer across a nanometric/subnanometric vacuum gap. Finally, we have investigated heat transfer in a system made of a core-shell nanoparticle (NP) immersed in water and heated by a laser pulse. We have used the four temperatures model, we have solved numerically the heat transfer equations in the system, taking into account the thermal boundary resistance (TBR) and the interfacial electron-phonon coupling
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Patel, Sandeep A. "Photophysics of fluorescent silver nanoclusters." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28110.
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Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Dickson, Robert; Committee Member: Brown, Ken; Committee Member: Curtis, Jennifer; Committee Member: Payne, Christine; Committee Member: Perry, Joseph.
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Long, Wei. "Designing immobilized catalysts for chemical transformations: new platforms to tune the accessibility of active sites." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/49017.
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Chemical catalysts are divided into two traditional categories: homogeneous and heterogeneous catalysts. Although homogeneous (molecular) catalysts tend to have high activity and selectivity, their wide application is hampered by the difficulties in catalyst separation. In contrast, the vast majority of industrial scale catalysts are heterogeneous catalysts based on solid materials. Immobilized catalysts, combining the advantages of homogeneous and heterogeneous catalysts, have developed into an important field in catalysis research. This dissertation presents synthesis, characterization and evaluation of several novel immobilized catalysts. In the first part, MNP supported aluminum isoproxide was developed for ROP of Є-caprolactone to achieve facile magnetic separation of catalysts from polymerization system and reduce toxic metal residues in the poly(caprolactone) product. Chapter 3 presents a silica coated MNP supported DMAP catalyst that was synthesized and displayed good activity and regio-selectivity in epoxide ring opening reactions. In Chapter 4, hybrid sulfonic acid catalysts based on polymer brush materials have been developed. The unique polymer brush architecture permits high catalyst loadings as well as easy accessibility of the active sites to be achieved in this catalytic system. In Chapter 5, aminopolymer-silica composite supported Pd catalysts with good activity and selectivity were developed for the selective hydrogenation of alkynes. In this case, the aminopolymer composite works as a stabilizer for palladium nanoparticles, as well as a modifier to tune the catalyst selectivity. All in all, the general theme of the thesis is developing new immobilized catalysts with improved activity/selectivity as well as easy separation via rational catalyst design.
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Jouanin, Anthony. "Extraction de la lumière par des nanoparticules métalliques enterrées dans des films minces." Phd thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://pastel.archives-ouvertes.fr/pastel-01061272.
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L'essor des procédés de micro et nano-fabrications rend aujourd'hui accessible la synthèse contrôlée de nanoparticules métalliques (typiquement de 3 à 200nm) offrant de larges résonances d'absorption et de diffusion dont les fréquences peuvent être contrôlées finement en variant judicieusement leur géométrie et leur composition. Dans ce travail de thèse relevant de l'électrodynamique classique établit par Maxwell, nous étudions numériquement l'intérêt de ces particules pour la problématique du (dé)couplage de la lumière piégée dans un film mince diélectrique - une géométrie de référence permettant de rendre compte du phénomène de piégeage qui limite considérablement l'efficacité de dispositifs électroluminescents et de certaines cellules solaires. Pour ce faire, nous proposons quelques règles de conception de nanoparticules capables d'extraire efficacement la lumière piégée. Pour un émetteur seul, environ 20% de la lumière émise est rayonnée hors du guide (rad~0.2). L'ajout d'une monocouche (~50nm d'épaisseur) composée d'un ensemble de particules " optimisées " et aléatoirement positionnées autour de l'émetteur permet d'accroître cette efficacité jusqu'à 70% en moyenne statistique sur le désordre. D'intéressants effets de cohérences liés à la nature du désordre au sein de ladite couche sont également mis en évidence.
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López-Millán, Alejandra, Paul Zavala-Rivera, Reynaldo Esquivel, Roberto Carrillo, Enrique Alvarez-Ramos, Ramón Moreno-Corral, Roberto Guzmán-Zamudio, and Armando Lucero-Acuña. "Aqueous-Organic Phase Transfer of Gold and Silver Nanoparticles Using Thiol-Modified Oleic Acid." MDPI AG, 2017. http://hdl.handle.net/10150/623868.
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The handling of metallic nanoparticles often requires their dispersion into several polar and nonpolar solvents. Solid-phase stages or polymer-based ligands are commonly required to complete the transfer. The construction of a thiol ligand based in oleic acid, and its ability to efficiently assist in gold and silver nanoparticle aqueous-organic phase transfer is reported. After the transfer, the particles are completely dispersed in an organic solvent, preserving their diameter and morphology, as confirmed by ultraviolet-visible spectroscopy and scanning transmission electron micrographs.
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Dacosta, Fernandes Benoit. "Etude des propriétés électroniques et vibrationnelles de nano-objets métalliques et hybrides par spectroscopie femtoseconde." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0047/document.
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Ce travail a porté sur l’étude expérimentale de la dynamique électronique et vibrationnelle de nano-objets métalliques et hybrides par spectroscopie pompe-sonde femtoseconde. L’étude de la dynamique des échanges d’énergie électrons-réseau dans des systèmes métalliques bidimensionnels nous a permis de mettre en évidence une accélération du transfert d’énergie entre électrons et phonons due au confinement. Cette accélération est gouvernée par la plus petite dimension des nano-objets étudiés (nano-triangles d’argent 2D) lorsque celle-ci devient inférieure à environ 10 nm. Nous avons aussi étudié la dynamique vibrationnelle de nanoparticules métalliques, bimétalliques et métal diélectrique. Nous nous sommes intéressés aux modes de vibration longitudinaux et radiaux de bipyramides d’or en fonction de leurs dimensions, et à leurs évolutions consécutives à un dépôt d’argent. Une forte sensibilité des périodes et des amplitudes de vibration à de faibles dépôts a été mise en évidence. L’étude de l’évolution des modes de vibration de nano-objets de type coeur-coquille (argent-silice et or-silice) nous a permis d’obtenir des informations sur la qualité du contact mécanique à l’interface métal-diélectrique. Enfin, nous avons étudié les interactions électroniques dans des nano-systèmes hybrides métal/semi-conducteur (ZnO-Ag), et plus particulièrement les transferts de charge et les échanges d’énergie entre les deux composants.Nous avons montré la forte influence de l’environnement sur la dynamique électronique du ZnO et mis en évidence un transfert d’électron, photo-induit par une impulsion infrarouge, de la particule métallique vers la bande de conduction du semi-conducteurElectronic and vibrational dynamics have been studied in metallic and hybrid nano-object using femtosecond timeresolved spectroscopy. The study of electron-lattice energy exchanges in two-dimensional metallic systems showed an acceleration of the energy transfer between electrons and phonons due to confinement. This acceleration is governed by the smallest dimension of the nano-objects (2D-silver nano triangles ) when it becomes smaller than 10 nm. We also studied the vibrational dynamics of metallic nanoparticles, bimetallic and metal-dielectric. We investigated the longitudinal and radial modes of vibration of gold bipyramids which depend on their size, and studied their evolution under silver deposition. A high sensitivity of periods and amplitudes for small deposition were demonstrated. Our work on the evolution of acoustic vibrations of core-shell nano-objects (silver-silica and goldsilica) allowed us to obtain information on the quality of mechanical contact at the metal-dielectric interface. Finally, we studied the electronic interactions in hybrid metal / semiconductor (ZnO-Ag) nano-systems, and especially the charge transfer and energy exchanges between the two components. We showed a strong influence of the environment on the electron dynamics of ZnO and proved the existence of an electron transfer, photoinduced by an infrared pulse, from the metal particle to the semiconductor conduction band
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Krishnamoorthy, Mahentha. "Developing cationic nanoparticles for gene delivery." Thesis, Queen Mary, University of London, 2016. http://qmro.qmul.ac.uk/xmlui/handle/123456789/23193.
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Gene delivery can potentially treat acquired and genetic diseases such as cystic fibrosis, haemophilia and cancer. Non-viral gene delivery vectors are attractive candidates over viral vectors such as recombinant viruses, due to their lower cytotoxicity and immunogenicity, despite significantly lower transfection efficiencies. To improve efficiency of non-viral vectors, the investigation of the various parameters influencing DNA transfection is essential. The present study developed a versatile gene delivery system with tailored physicochemical and biological properties. The system used polymer brushes synthesised via atomic transfer radical polymerisation (ATRP), grafted from silica nanoparticles, whose charge density, grafting density, chemistry, length of brush, the size and shape can be altered. The primary focus of the study was poly(2-dimethylaminoethyl methacrylate) (PDMAEMA), known for its positive charge and DNA condensation. The ability of PDMAEMA to interact with DNA was characterised using dynamic light scattering, electrophoretic light scattering methods, surface plasmon resonance and in situ ellipsometry whilst its interaction with cells was studied via cell viability assays. The brush behaviour in response to pH and ionic strength was also studied. The charge density was altered by copolymerising with poly[oligo(ethylene glycol) methyl ether methacrylate](POEGMA) and the effect of such modification on DNA interaction was studied. PDMAEMA-grafted nanoparticles gave the highest transfection efficiency compared to other synthesised polymer brushes, but still displaying almost 2-fold lower transfection efficiency than the commercially available reagent jetPEI®. Different brush chemistries were also investigated. Poly(glycidyl methacrylate) (PGMA) decorated with oligoamines: allylamine, diethylenetriamine and pentaethylene hexamine, and PDMAEMA quaternized with alkyl halides: methyl iodide, allyl iodide and ethyl iodoacetate did not show any significant transfection, despite their performance reported in the literature. The robust system developed is a promising platform for further investigation of parameters influencing cellular uptake and gene expression, and important milestone to develop non-viral gene delivery systems.
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Wang, Ying. "Electrocatalytic nanoeffect at gold nanoparticles." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:daa430c1-ecb1-496f-9744-d3f58ba16dc6.
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Nanoelectrochemistry explores the differences in chemical behaviour at the nanoscale as compared to the macro-scale. This thesis is concerned with nanoelectrochemistry and aims to develop and apply novel experiments for the unambiguous identification of changed electrode kinetics at the nanoscale. This is challenging since electrochemical responses are controlled by diverse factors like enhanced mass transport and adsorption as well as electron transfer kinetics. A joint computational and experimental strategy is employed. Chapter 1, 2 and 3 cover essential introductory material and basic experimental details relevant to all experiment. Fuller descriptions and details are given in the following chapters as and when needed. Chapter 4 reports the development of an electrochemical characterization method, to achieve a fast and simple quantification of the average particle size and the number of nanoparticles deposited on a glassy carbon electrode. The method consists of surface area characterization by underpotential deposition of lead particles and the determination of the amount of gold from anodic stripping in HCl. This method is also proven to be effective by comparing the results with SEM measurements. Next, in chapter 5, a generic strategy combining computation and experimental approach is developed in order to study the electron transfer kinetics of gold nanoparticles. The modelling part considers the kinetics of the electrochemical process on the bulk materials for different regions in the electrode, that is, the substrate (glassy carbon) and the nanoparticles (gold). Comparison of experimental and theoretical results enables the detection of changes in the electrode kinetics at the nanoscale. This approach is applied into the electro-oxidations of nitrite and L-ascorbic acid for gold nanoparticles from 20 - 90 nm. In the former, analysing the system shows that no change in electron transfer kinetics is involved in the process, even though a decrease of the over-potential and an increase in the peak current are observed. But these changes reflect mass transport effects, not electrocatalysis. A case where an authentic enhanced electron transfer kinetic change occurs is shown for the ascorbic acid system. Finally, in chapter 6 , the above strategy is exploited further to apply a quantitative study of electron transfer kinetics for various sizes of gold nanoparticles in the oxygen reduction reaction system in sulphuric acid at 298 K. The latter is at the heart of energy transformation techniques (fuel cells, battery and so on). Compared with the electron transfer kinetics on macro gold electrodes, there is no change at gold nanoparticles from size 5 nm to 40 nm. However, in the presence of Pb(II), a strong enhancement of electron transfer kinetics is observed on 5 nm citrate capped gold nanoparticles for ORR. On the other hand, a significant decrease of electron transfer kinetics has been found for gold nanoparticles of size 2 nm for ORR. The latter observation of strong negative electrocatalysis is also observed for the hydrogen evolution reaction (HER). This represents the first report of such effects with the HER system. Overall the thesis has established a rigurous, theoretical basis for evaluating electrocatalysis in nanoparticulate system.
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Le, Bihan Olivier. "Etude par microscopie électronique des mécanismes d'action de vecteurs synthétiques pour le transfert de gènes." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13972/document.
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La grande majorité des essais cliniques de transfert de gènes in vivo utilise des vecteurs viraux. Si ces derniers sont efficaces, ils présentent des risques immunogènes, toxiques, voire mutagènes avérés. Les vecteurs synthétiques (non viraux), par leur grande modularité et leur faible toxicité représentent une alternative très prometteuse. Le principal frein à leur utilisation est leur manque d’efficacité. L’objectif majeur de ce travail de thèse a été de comprendre le mécanisme de transfert de gènes associé à différents complexes vecteurs synthétiques/ADN plasmidique, ce qui est indispensable pour une conception rationnelle de nouveaux vecteurs. Nous avons étudié, sur cellules en culture, le mécanisme de transfert de gènes associé à deux lipides cationiques ; le BGTC (bis(guanidinium)-tren-cholesterol) et la DOSP (DiOleylamine A-Succinyl-Paromomycine) qui sont connus pour être des vecteurs efficaces in vitro. Nous avons ainsi pu visualiser par microscopie électronique leurs voies d’entrée, leurs remaniements structuraux ainsi que leur échappement endosomal qui représente une étape clé du processus de transfert de gènes. L’identification non ambigüe des lipoplexes tout au long de leur trafic intracellulaire a été rendue possible grâce au marquage de l’ADN par des nanoparticules de silice dotées d’un cœur de maghémite (Fe2O3) dense aux électrons. Cette stratégie de marquage a également été appliquée à l’étude du mécanisme d’action d’un autre vecteur synthétique de type polymère, le copolymère à blocs non ionique P188 ou Lutrol. Contrairement à la plupart des vecteurs synthétiques, celui-ci présente une efficacité de transfection in vivo chez la souris par injection in situ pour le tissu musculaire ou en intra trachéale dans le poumon. En revanche, il est totalement inefficace in vitro. Nous avons montré que le Lutrol permet une augmentation de l’internalisation d’ADN par les cellules mais n’induit pas son échappement endosomal, ce qui expliquerait son absence d’efficacité in vitro. D’autres voies d’entrée sont alors à envisager in vivo pour comprendre son mécanisme d’actionThe vast majority of clinical trials of gene transfer in vivo use viral vectors. Although they are effective, they induce immunogenic, toxic or mutagenic risks. Due to their high modularity and low toxicity, synthetic vectors (non viral), represent a promising alternative despite their lack of effectiveness. The major objective of this work was to understand the mechanism of gene transfer using two prototypic synthetic vectors, in the context of a rational design of new vectors. We studied on cultured cells, the mechanism of action of two cationic lipids; BGTC (bis(guanidinium)-tren-cholesterol) and DOSP (DiOleylamine A-Succinyl-Paromomycine) formulated with plasmid DNA (lipoplexes) which are in vitro efficient vectors. We have been able to visualize by electron microscopy, their intracellular pathways, their structural alterations and their endosomal escape, the latter being a key step in the process of gene transfer. The unambiguous identification of lipoplexes throughout their intracellular trafficking has been made possible thanks to the labelling of DNA by core-shell silica nanoparticles with an electron dense maghemite core (Fe2O3). The labeling strategy has also been applied to study the mechanism of action of a nonionic block copolymer (P188 or Lutrol). Interestingly, these synthetic vectors have an in vivo transfection efficiency in mice lung and muscle tissue while they are totally inefficient in vitro. We have shown that Lutrol induces an increase of DNA internalization into cells and fails to trigger endosomal escape, which would explain the lack of in vitro efficacy. These findings suggest that the in vivo mechanism of action of Lutrol would involve other internalization pathways
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Meng, Xiangyin. "Coupling of nanofluid flow, heat transfer and nanoparticles sedimentation using OpenFOAM." Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/17350/.
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Nanofluid is a suspension containing a certain quantity of nanoscaled solid particles in a conventional cooling liquid. Compared to pure liquid in micro channels, nanofluid shows notably better heat transfer performance but without erosion and clogging problems as normal two-phase suspensions. Due to such advantages, nanofluid is increasingly applied as an ideal coolant in engineering. For a better understanding of nanofluid flow and heat transfer performance, many investigations have been carried out recently in both experimental and numerical ways. In numerical investigations, computational fluid dynamics (CFD) is playing a dominant role due to its maturity in the area of fluid flow and heat transfer research. However, in previous CFD studies, the problem of nanoparticles sedimentation is always ignored based on the assumption that nanofluid is stable with homogeneous properties throughout the simulation. To some extreme cases in which nanoparticles sedimentation would happen soon after nanofluid preparation, such assumption could induce inaccurate numerical results. To investigate the relationships between nanofluid flow, heat transfer and nanoparticles sedimentation, an open source CFD package, OpenFOAM is employed as the basis to develop several numerical solvers in multi-phase way for the first time. More specifically, nanofluid CFD simulations are carried out by several newly developed OpenFOAM solvers under both Eulerian-Langrangian and Eulerian-Mixture (a simplified Eulerian-Eulerian approach) frames. By comparing present numerical results to previous published experimental and numerical investigations, it can be concluded that the newly developed solvers under both Eulerian-Langrangian and Eulerian-Mixture frames are capable to investigate nanofluid flow and heat transfer performance coupling with nanoparticles sedimentation. However, with the considerations of computational resource requirement, Eulerian-Mixture approach is believed to be better to achieve the balance between accuracy and computational effort. With an assumption that no appropriate stabilizing treatments have been applied after nanofluid preparation, CFD simulations are carried out for 0.64% Al²O³/water nanofluid in three most typical geometries by the newly developed solver 'nanofluidMixtureFoam'. According to the present research, it can be confirmed that nanofluid heat transfer and nanoparticles sedimentation have considerable impacts to each other other in nanofluid natural convections (in both two- and three-dimensional cases). More specifically, temperature driven flow leads to ticker nanoparticles sedimentation layer than that in normal sedimentation case. On the other hand, nanoparticles sedimentation layer induces worse nanofluid natural convection heat transfer performance. Furthermore, for forced convection problems in a horizontal channel with an open cavity, nanoparticles sedimentation is likely to occur at cavity bottom and leads to higher temperature at heating surface. For better heat transfer performance of the cooling blocks with similar geometries, lower fins (cavity depths) in blocks are recommended to reduce possible nanoparticles sedimentation. In summary, the newly developed OpenFOAM solvers and numerical observations in this thesis are expected to guide future nanofluid CFD study and correlative practical applications.
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Rebstock, Jaclyn. "Structural And Dosage Dependence Of Electron Transfer From Conjugated Polymer Nanoparticles." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091699.
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Conjugated polymer nanoparticles (CPNs or Pdots) have become popular fluorophores for a variety of fluorescence imaging applications due to their brightness, photostability, and aqueous compatibility. Recently, their ability to generate charged species has begun to be exploited in applications ranging from photocatalysis to photovoltaic cells. Upon excitation, CPNs can eject an electron via photoinduced electron transfer (PET) to oxygen or other acceptors. The competition between fluorescence and PET is undesirable in redox-based applications. However, CPNs are capable of the simultaneous generation and detection of reactive oxygen species, expanding their use in photodynamic therapy (PDT). We seek to determine the dependence of PET on conjugated polymer structure and irradiation dosage. We will present studies of PET and fluorescent superoxide sensing in the most widely-used CPNs. These results will ultimately aid in the selection of polymers and irradiation conditions for PDT applications.
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Delecourt, Gwendoline. "Synthèse de nanoparticules monoplasmidiques pour le transfert de gènes." Electronic Thesis or Diss., Sorbonne université, 2021. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2021SORUS002.pdf.
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Depuis le XXème siècle, la thérapie génique ouvre la voie au traitement de maladies d’origine génétique et de maladies acquises. L’introduction d’un polynucléotide dans les cellules présentant une mutation génétique permet de moduler leur fonctionnement. Afin de passer les différentes barrières biologiques et de rejoindre le noyau des cellules ciblées, l’ADN doit être protégé par un vecteur. Divers vecteurs ont été développés tels que les vecteurs polymériques à base de PEI. Malgré leur efficacité, ces vecteurs montrent des réactions immunogènes. Des fonctionnalisations sont développées pour réduire cette toxicité notamment par la formation de vecteurs furtifs. La stratégie standard de PEGylation montre, cependant, des limites nécessitant l’utilisation de nouveaux polymères hydrophiles. Dans ce contexte, la POxylation a été étudiée comme alternative à la PEGylation pour le design de nouveaux polyplexes. Une nouvelle méthode de synthèse de copolymères PEI-b-POx par hydrolyse sélective de copolymères à blocs poly(2-R1-2-oxazoline-b-2-R2-2-oxazoline) a été mise au point ainsi que la fonctionnalisation par des résidus histidine pour améliorer l’efficacité de transfection et diminuer la toxicité du vecteur polymère. Un ligand galactose a été greffé en fin de chaîne hydrophile pour induire un ciblage cellulaire. Les polymères synthétisés ont été utilisés pour former des polyplexes avec l’ADN via une méthode de formulation « par extrusion » avant de réaliser des tests de transfection in vitro et in vivo. Une réduction de la cytotoxicité a été observée lors de l’utilisation des copolymères PEI-b-POx en comparaison aux PEI tout en conservant une efficacité de transfectionSince 20th century, breakthrough in gene therapy paves the way for new therapeutic strategies against genetic disorders, cancers and neurodegenerative diseases. Cells with genetic mutation may have their cellular machinery modulated via the introduction of polynucleotides in their nucleus. Nevertheless, DNA needs to be protected by a vector to cross biological barriers and to reach targeted cell nucleus. Various types of vectors have been developed like PEI-based vectors. However, those efficient polymeric vectors exhibit a toxicity which can be lowered by PEG functionalization. Nevertheless, the well-known PEGylation approach shows limits requiring news hydrophilic polymers. In this context, POxylation was studied as PEG alternatives in the design of new pDNA containing nanovectors. A new synthetic strategy was developed with a selective hydrolysis of block poly(2-R1-2-oxazoline-b-2-R2-2-oxazoline) copolymers. The functionalization of the synthetized PEI-b-POx copolymers with histidine moieties was achieved, along with galactose grafting to induce cellular targeting or histidine grafting to improve endosomal escape. These polymers were used to form polyplexes with DNA via extrusion method and further biological testing via in vitro and in vivo transfection essays were performed. An efficient transfection was obtained with a reduction of the cytotoxicity for PEI-b-POx copolymers compared to PEI
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Suleimanov, Iurii. "Nano-objets et nano-composites à transition de spin basés sur des complexes du fer(II) avec des ligands 1,2,4-triazoles." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30017.
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L'échelle moléculaire est de plus en plus considérée comme une solution alternative pour la miniaturisation des composants électroniques en vue de la construction de dispositifs fonctionnels. L'approche actuelle "top-down" basée sur la technologie du silicium force les chimistes du solide, les physiciens et les électroniciens à manipuler progressivement des quantités de matière de plus en plus faibles. Dans ce domaine, les dispositifs moléculaires offrent des perspectives remarquables avec des niveaux de sensibilité et de sélectivité qui ne peuvent pas être atteints avec les matériaux à semi-conducteurs conventionnels. Dans ce contexte, les complexes ou polymères de coordination représentent une classe importante de composés possédant des propriétés de commutation magnétiques, optiques et électrochimiques intéressantes. En particulier, les composés à transition de spin (transition intra-métallique de l'état haut spin vers l'état bas spin) des métaux de transition sont bien adaptés à cette stratégie car ils peuvent être le siège d'une transition réversible du premier ordre avec hystérésis sous l'effet d'une perturbation extérieure (température, pression ou éclairement) impliquant des modifications magnétique, optique et structurale. Dans ces travaux de thèse, des matériaux susceptibles de présenter des propriétés de bistabilité avec hystérésis autour de la température ambiante sont présentés et discutés. Un des objectifs est d'étudier l'évolution de leurs propriétés en fonction de la taille et de valoriser ces matériaux. Pour cela, ces composés ont été nano-structurés. Ainsi nous avons élaboré des nanoparticules à base de composé à transition de spin par différentes voies de synthèse et réalisé des films minces et des nanostructures de ces matériaux par des méthodes de lithographie douce et de lithographie électronique. Pour caractériser les propriétés de ces nouveaux objets, nous nous sommes orienté vers l'utilisation de nouvelles techniques de détection optiques et en particulier vers des techniques qui permettent la mesure de la variation du changement d'indice optique de ces matériaux, à savoir, des mesures de la variation des plasmons de surface lorsque des couches minces bistables de ces composés sont mises au contact de surface d'or et des mesures de variation de l'efficacité de diffraction à partir de réseaux de motifs de tailles micro- et nanométriques. Par ailleurs, une méthode basée sur la variation de l'intensité de fluorescence d'un fluorophore sélectionné et intégré au sein de composé mixte (composé à transition de spin - fluorophore) a également été développée. L'ensemble de ces méthodes concourt à pouvoir détecter un objet unique de taille nanométriqueThe thesis is devoted to the preparation of new nanoobjects and nanocomposites of spin crossover complexes [Fe(Htrz)2(trz)](BF4) and [Fe(NH2-trz)3](NO3)2 (where Htrz - 1,2,4-triazole, trz - 1,2,4-trazolato, NH2-trz - 4-amino-1,2,4-triazole) and investigation their properties. Nanoobjects of mixed-ligand complexes with different ratio of 4-amino-1,2,4-triazole to 1,2,4-triazole were synthesized in reverse emulsions. It was shown that the increasing of the of 4-amino-1,2,4-triazole quantity leads to the increasing of nanoparticles anisotropy while spin crossover temperatures decrease. Double-step spin transition was observed at 20% mol of 4-amino-1,2,4-triazole, while at concentrations over 50% mol. spin crossover properties of [Fe(Htrz)2(trz)](BF4) completely disappear. Investigations of their morpholgy, size and spin transition characteristics as well as investigations of mechanisms of the fluorescent properties change under the spin switching process are shown. We consider obtaining nanoobjects of mixed-ligand complexes of iron (II) based on 1,2,4-triazole and 4-amino-1,2,4-triazole. The ligands ratio influences the morphology, size and characteristics of the spin transition of nanoobjects obtained. New modification of the complex [Fe(NH2-trz)3](NO3)2 in the form of nanoobjects was obtained using ligand excess. High transition temperature of this form was evidenced by various methods of analysis. This form was found to be isostructural with a resolved structure of [Fe(NH2-trz)3](NO3)2 · 2H2O. Series of nanocomposites with plasmonic and luminescent properties were prepares. For the core-shell composite with gold nanoparticles higher efficiency of the spin state switching due to the photothermal effect was demonstrated in comparison to the control sample. Fluorescent spin crossover composites with quantum dots, organic luminophors and terbium complexes were described. For all these composites the luminescence intensity variation as a function of temperature have been found. The mechanisms responsable of the luminescence intensity variation at two spin state are discussed. These mechanisms include resonant energy transfer, mechanical strain and photon reabsorption. High photostability fort he terbium - spin crossover composite is demonstrated comparing to previously obtained similar spin crossover luminescetnt composites. An example of a practical application of obtained composites for manufacturing fluorescent thermosensitive paper is shown