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Добірка наукової літератури з теми "Nanocristaux de diamant"
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Дисертації з теми "Nanocristaux de diamant"
Adam, Marie-Pierre. "Développements de microscopies optiques pour l'imagerie super-résolue de nanocristaux de diamant fluorescents comme rapporteurs d'anomalies fonctionnelles du neurone." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00975895.
Повний текст джерелаAdam, Marie-Pierre. "Développements de microscopies optiques pour l’imagerie super-résolue de nanocristaux de diamant fluorescents comme rapporteurs d’anomalies fonctionnelles du neurone." Thesis, Cachan, Ecole normale supérieure, 2013. http://www.theses.fr/2013DENS0040/document.
Повний текст джерелаSuper resolution microscopy techniques are a useful tool to understand some biomolecular mechanisms, particularly in neurons. We have built such a STED (STimulated Emission Depletion) microscope for observing Nitrogen-Vacancy (NV) fluorescent defect in diamond, and have reached a resolution of 50 nm. In the longer term, this instrument will study the macromolecular organization of proteins involved in synaptic plasticity and marked with fluorescent nanodiamonds (ND). In this context, we studied the resolution limit of STED for ND of subwavelength size. Our experiments, conducted with the team of Stefan Hell (Max Planck Institute for Biophysical Chemistry) showed that the STED spot size of an NV in ND could reach 10 nm, which is similar to performances obtained in a macroscopic diamond. We can also resolve several NV centers, which are separated from only ~15 nm in the same ND. These results are in agreement with numerical simulations carried out by the team of Jean-Jacques Greffet (Laboratoire Charles Fabry). In parallel, we have demonstrated the spontaneous internalization of fluorescent ND in primary culture of cortical neurons from mouse embryos, and studied their colocalization with vesicles of the trans-Golgi network. Finally, we started the study of trafficking vesicles containing ND and showed that it depends on the microtubule network. The motion parameters are compatible with those of molecular motors, but we expect them to be different in the case of overexpression of proteins involved in traffic (work in progress)
Beveratos, Alexios. "Réalisation expérimentale d'une source de photons uniques par fluorescence de centres colorés dans le diamant : application à la cryptographie quantique." Phd thesis, Paris 11, 2002. http://www.theses.fr/2002PA112236.
Повний текст джерелаSecure key distribution between two persons is a complicated task. In a classical world, it is impossible to guarantee that an eavesdropper doesn't create a copy of the key during the exchange. In 1984 has been proposed a protocol based on the properties of quantum mechanics that assures an unconditionally secure exchange of secret keys. Ideally, the protocol uses single photon sources, the information being coded on the polarisation of the photons. The security is guaranteed by choosing randomly the polarisation base (Linear, Circular). In this context, this work describes the realisation of a single photon source, and it's application to quantum cryptography. A single photon source is obtained by pulsed excitation of a single dipole. The dipole studied in this work, is the NV center in diamond. It is composed of a Nitrogen atom and a Vacancy substituting two carbon atoms. Under continuous excitation the center has been studied with a confocal microscope and an intensity autocorrelation set-up. It has turned out to be a very good candidate for a single photon source since it is easy to manipulate and photostable. Under pulsed excitation, we show that this single photon source has great production efficiency, and a very low number of two-photon pulses. Finally, this source has been used in a quantum cryptography prototype. After a description of the experimental set-ups of the emitter and the receiver, we describe the realisation of a quantum cryptography experiment. The achieved performances show a quantitative advantage in the maximum tolerated tosses, compared to prototypes using faint laser pulses
Bernard, Romain. "Nanocristaux et nanobâtonnets de CdSe déposés sous ultra-vide sur des sufaces de silicium hydrogénée, diamant hydrogénée et graphite résolues à l'échelle atomique." Paris 11, 2005. http://www.theses.fr/2005PA112183.
Повний текст джерелаThis thesis is the first step of a project aiming to use a single isolated nanocristal as a photon nano-source, excited by the electrons of a stm. We have developped a way to synthesize very pure solutions of cdse nanocrystals and nanorods. At the same time, we have developped a deposition method by pulsed injection under uhv, allowing to deposit these nano-objects on clean and reconstructed hydrogenated silicon, hydrogenated diamond and graphite surfaces. With the stm, we verified that these surfaces remain clean and were reconstructed after the deposition and we performed tunneling spectroscopy measurements in order to characterise the double barrier tunnel junction formed by the surface-nanocrystal-tip. Thanks to this deposition method which preserves the surface structure, we have shown that the nanorods are spontaneously orientated (with respect to the surface structure) when they are deposited on the hydrogenated silicon and graphite surfaces. We concluded from the estimation of the different interaction energies between the nanorod and the surface that this spontaneous orientation is due to the anisotropic interaction of the nanorod's ligands with these surfaces. This phenomenon shows that the deposition of such objects on atomically structured surfaces can be used to control their organisation through the ligand-surface interaction
Henry, Killian. "Nanodiamants et graphite fluorés pour des réflecteurs de neutrons nouvelle génération." Electronic Thesis or Diss., Université de Lorraine, 2024. http://www.theses.fr/2024LORR0067.
Повний текст джерелаThe aim of this PhD work was to synthesize highly scattering nanomaterials with low neutron absorption, consisting solely of carbon and fluorine, in order to close the slow neutron reflectivity gap in the 90-600 m/s neutron velocity range (between the best supermirror and graphite). The materials selected were nanodiamonds with a calibrated diameter (5 nm) and fluorinated graphites. Among fluorinated graphites, the (C2F)n phase has the highest interplanar distance (9 Å), enabling reflectivity of up to 220 m/s. Despite the difficulty of obtaining this (C2F)n phase, due to its restricted fluorination temperature range (350-400°C), the tendency to over-fluorinate and the risk of exfoliation, we successfully synthesized fluorinated graphite powders with a high (C2F)n content, with a maximum content of 96 % (C2F)n and an interplanar distance of around 9 Å. Neutron reflectivity measurements of these samples revealed that (C2F)n-rich fluorinated graphite can be used as an effective reflector for slow neutrons. Graphite foils have also been fluorinated to overcome the impossibility of densifying fluorinated graphite powders, an essential criterion for the creation of neutron reflectors. High levels of (C2F)n were also obtained, i.e. ~75%, and no exfoliation was observed. All these characteristics make fluorinated graphite foils very promising as slow neutron reflectors. The detonation nanodiamonds are chosen for the purpose of developing new slow neutron reflectors because they are available in industrial quantities. They unfortunately contain a sp2 carbon shell on their surface and hydrogenated and oxygenated neutron-absorbing impurities, as well as metallic impurities that can be activated under neutron flux. It was shown in this study that the use of chlorine effectively eliminates metallic impurities from detonation nanodiamonds, and that the combination with molecular fluorine converts the hydrogenated and oxygenated groups present on the surface of these nanoparticles into C-F bonds, providing a hydrophobic character that prevents any subsequent adsorption of water molecules. A method for concentrating metallic impurities was developed during the course of this PhD work, which made it possible to overcome the detection limit of the characterization equipment used. It also proved that the combustion temperature of detonation nanodiamonds was a good indicator of their purity. In addition, the combination of chlorination and fluorination treatments increased the thermal stability of these compounds by 200 °C
Corcuera, Valerie Cecile. "Filmes de DLC com nanocristais de diamante para aplicações espaciais." Instituto Nacional de Pesquisas Espaciais (INPE), 2016. http://urlib.net/sid.inpe.br/mtc-m21b/2016/06.23.18.37.
Повний текст джерелаDue to agglomeration tendency the development of functionalization and subsequent dispersion of detonation nanodiamond (ND) powder can become a challenge. ND powder was purified by heat treatment and two types of functionalizations were achieved ND-H and ND-COOH. Purification and functionalizations were successfully achieved and were verified by TGA and FT-IR. AFM analysis showed that the thermal oxidation treatment which provides ND-COOH functionalization reduces the agglomerates in about 74\% of the original size. The average size of ND-COOH agglomerates as measured by dynamic light scattering has been significantly reduced by 95\% of its original size after functionalization and mechanical shearing of the powder in a liquid medium. The stability of ND dispersion in polar solvent tetrahydrofuran increased considerably having a zeta potential of -31 mV. Development of a new method for the dispersion of agglomerated nano diamond (ND) in a liquid medium was included in this thesis. Diamond-Like Carbon (DLC) films with nano diamand particles were deposited on flat samples of titanium alloy Ti6Al4V by pulsed DC Plasma Enhanced Chemical Vapor Deposition (PECVD). Precursor solutions for DLC films deposition were presented. DLC and DLC-ND films were produced from different polar and nonpolar solvents and their properties were evaluated. Comparative analyzes profilometry, friction coefficient, Raman spectroscopy have been addressed. SEM and AFM analysis revealed the presence of ND in the film.
Esteves, Diogo António da Costa e. Veiga. "Termistores de diamante para aplicações biomédicas." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7404.
Повний текст джерелаO presente trabalho consistiu no desenvolvimento de um termistor de diamante CVD (chemical vapour deposition) dopado com boro, através da deposição de um filme por deposição química em fase de vapor assistida por filamento quente (HFCVD) num substrato cerâmico de nitreto de silício (Si3N4). O objectivo deste termistor é a sua aplicação na biomedicina, nomeadamente na medicina dentária, funcionando como um sensor de temperatura na ajuda ao diagnóstico à vitalidade dos dentes. A adição de boro foi realizada através da dissolução de B2O3 em etanol, sendo o transporte da mistura realizado com árgon através de um borbulhador. Os substratos de nitreto de silício foram produzidos através de uma mistura de pós comerciais de 89,3% α – Si3N4 (Starck Grade C) + 7,0% Y2O3 (Starck Grade M11) + 3,7% Al2O3 (ALCOA CT-3000SG) em um meio de isopropanol. A suspensão resultante foi seca e peneirada, de seguida foi sujeita a uma maquinação através de pressão uniaxial isostática, sendo sinterizada sem pressão aplicada numa atmosfera de nitrogénio. Este tipo de substrato apresenta-se como um candidato ideal para deposição de diamante, devido á sua elevada dureza, mas sobretudo devido ao seu coeficiente de expansão térmica ser bastante próximo do diamante. Os substratos sofreram um tratamento superficial prévio através de dois métodos: riscagem mecânica (ou manual) com um pó de diamante monocristalino com granolumetria entre 0,5-1 μm, e de seguida uma riscagem em ultrasons numa suspensão de diamante em etanol com a granolumetria de 15μm, com o objectivo de ajudar à nucleação do filme no substrato. Através do método de análise de Taguchi criou-se uma matriz de ensaios através de uma tabela L9, com o objectivo de saber as condições ideias de deposição HFCVD para obter o comportamento eléctrico desejado. Foram variadas condições como a razão CH4/H2 e Ar/H2, a pressão, a distância do substrato ao filamento. A caracterização dos filmes foi feita por microscopia electrónica de varrimento (SEM), difracção de raios-X, e espectroscopia Raman. Através de SEM foi observado que existe uma grande variedade a nível morfológico e de tamanho de grão. Também foi possível medir a espessura de filme a sua taxa de crescimento. Através de DRX (LIBAD) foi analisada a cristalinidade dos filmes e o tamanho de cristalite, e de espectroscopia Raman a sua qualidade e fases de carbono (sp2/sp3). Foram também realizados testes eléctricos com o objectivo de saber o comportamento eléctrico dos filmes, nomeadamente a sua variação da resistência com a temperatura, e calculando o valor de B, um factor que avalia a variação da resistência em função da temperatura, para um dado um material. Através do método Taguchi foram conseguidas as condições óptimas e foram construídos dois termistores com contactos ohmicos de WC. O seu comportamento foi comparado com o de um termistor comercial de 10k . O seu comportamento quando sujeito a ciclos contínuos de aquecimento e arrefecimento, revelou tempos de resposta bastante mais rápidos do que o termistor comercial. Decréscimos na ordem dos 31% e 67% foram conseguidos para os termistores T1 e T2 respectivamente em ciclos de aquecimento, ao passo que no arrefecimento foram conseguidos decréscimos na ordem dos 77% e 46% para T1 e T2. Os ciclos foram feitos num intervalo de temperatura entre os 24ºC e os 32ºC. Estes resultados suportam a aplicabilidade de termistores de diamante na medicina dentária com melhorias significativas no diagnóstico.
The present work aimed at the development of a diamond based termistor, using the Hot Filament Chemical Vapour Deposition (HFCVD) technique. The boron doped diamond coatings were deposited on silicon nitride based ceramics. This devices were developed bearing in mind biomedical applications, namely in dentistry, working as a temperature sensor to help in the teeth vitality diagnose. Boron addition in the gas mixture was accomplished by the dissolution of B2O3 in ethanol, carried along with argon trough a bubbler. Silicon nitride (Si3N4) based ceramic substrates were obtained by mixing commercial powders α -Si3N4 (Starck grade C), Y2O3 (Starck grade M11) and Al2O3 (ALCOA CT-3000SG) in a 89,3%/7,0%/ 3,7% weight proportion, in a isopropyl alcohol media. The resulting suspension was dried and sieved, consolidated by uniaxial and isostatic pressing and finally pressureless sintered in a nitrogen atmosphere. The Si3N4 substrates are an ideal candidate for diamond deposition, due to their high hardness and toughness, but specially for possessing a thermal expansion coefficient close to that of diamond. Prior to diamond deposition the ceramic surface was pretreated with a manual scratching with a 0,5-1 μm diamond powder and then sonicated in a 15μm diamond suspension in ethanol, to increase the diamond nucleation density. A Taguchi matrix was designed to study the HFCVD diamond deposition parameters, using a L9 orthogonal array, where CH4/H2 and Ar/H2 gas ratios, the pressure and the substrate-filament distance were used as controllable factors. The characterization of the coatings was performed by SEM, XRD and μ- Raman spectroscopy. SEM allowed the evaluation of the coatings morphology and thickness (cross-sectional micrographs), thus the determination of the growth rate. XRD (LIBAD) allowed the determination of the grain size for nanocrystalline diamond, as well as the crystallographic orientation. μ-Raman spectroscopy allowed the evaluation of the carbon phase content (sp2/sp3) in the coatings. The electrical behavior of the films was accessed, namely the dependence of the resistance with the temperature, allowing the calculation of the B parameter, which is a set parameter of each material, for a given range of temperature. Using the Taguchi Method the optimal Diamond deposition conditions were achieved and two diamond termistors were built with WC ohmic contacts. Their electrical behavior was compared to that of a commercial termistor with resistances of the order of 10k . However, their electrical response to cyclic heating and cooling steps evidence much fasters response times. Decreases in response time on the order of 31% and 67% were achieved respectively for T1 and T2 upon heating, and 77% and 46% for respectively T1 and T2 termistors during cooling in the temperature range of 24-32ºC. These results support the applicability of diamond based termistors in the field of dentistry with significant improvements in the diagnose accuracy.
Marciano, Fernanda Roberta. "Estudo de crescimento de filmes de DLC com nanocristais de diamante para aplicações tecnológicas e industriais." Instituto Tecnológico de Aeronáutica, 2011. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1150.
Повний текст джерелаCarvalho, Alexandre Faia. "Simultaneous synthesis of diamond on graphene for electronic application." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14801.
Повний текст джерелаNeste trabalho é descrito o estudo de estruturas híbridas de grafeno e diamante nano-cristalino (GDH) sintetizadas por deposição química em fase vapor por plasma de micro-ondas (MPCVD) em cobre. Foram investigadas técnicas de controlo da nucleação do diamante nano-cristalino, tendo sido encontrados dois processos com sucesso. Procedeu-se ainda à caracterização estrutural, morfológica e ótica das amostras por análise de SEM, TEM, AFM, EFM, medidas de transmitância UV-Vis e espetroscopia de Raman. A avaliação das propriedades de transporte destes materiais foi efetuada pela medição da curva de transferência de transístores de efeito de campo produzidos para o efeito, sendo os GDHs produzidos o material ativo do canal. Foram observadas baixas mobilidades devido à hidrogenação do grafeno. Em linha com resultados teóricos da literatura, foram encontradas evidências de abertura do hiato energético do grafeno, um potencial desenvolvimento para a aplicação em dispositivos de comutação lógica.
In this work, hybrid structures of graphene and nano-crystalline diamond (GDH) produced by microwave plasma chemical vapor deposition (MPCVD) in copper substrates are studied. The control of the diamond clusters nucleation was investigated, having two different approaches been identified as promising. Structural, morphological and optical characterization was carried out by SEM, TEM, AFM, EFM, UV-Vis transmittance, and Raman spectroscopy. The transport properties of this material were analyzed through the transfer curve of field-effect transistors with GDH channels. Low mobilities were found due to graphene hydrogenation. In line with theoretical studies, evidences were found of graphene band gap opening, a potential breakthrough for the development of logical switching devices.