Academic literature on the topic 'Points quantiques – Synthèse (chimie)'
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Dissertations / Theses on the topic "Points quantiques – Synthèse (chimie)":
Mabrouk, Salima. "Synthèse par voie colloïdale et étude des propriétés optiques et structurales de nanocristaux ternaires ZnSeS dopés." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0169.
In recent years, ternary QDs have experienced an exponential development thanks to their properties, especially their photoluminescence, which can be controlled not only by their size but also by their composition. As part of this thesis, we developed a new "green" synthesis in aqueous media of ZnSeS-doped ternary QDs and we studied the effect of the variation of the dopant (Mn2+, Cu2+, or Cu2+/Al3+) as well as its localization (in the core or in the shell) on their optical and structural properties. The first part of this work describes the synthesis of ZnSeS:Mn ternary QDs and ZnSeS:Mn/ZnS core/shell using 2-MPA as a ligand. The results obtained show that these nanocrystals can be prepared with quantum yields of 22% and 41%, respectively. These QDs have shown excellent photostability under UV irradiation and can easily be transferred to the organic phase using the hydrophobic octanethiol ligand without altering their optical properties. Subsequently, core/shell ZnSeS/ZnS:Cu/ZnS QDs for which the Cu dopant is introduced into the first shell were prepared using 3-MPA as a ligand. Excellent (photo)stability in the presence of air and oxygen was observed. ZnSeS/ZnS:Cu/ZnS core/shell QDs have a 20% photoluminescence quantum yield and have been used as photoluminescent probes for the detection of Pb2+ ions in aqueous media. A selective extinction of the photoluminescence emission in the presence of Pb2+ ions was observed. Finally, Cu and Al co-doped QDs, ZnSeS/ZnS:Cu/ZnS:Al/ZnS (first shell doped with Cu2+ and second shell doped with Al3+) were prepared. Co-doping allows the improvement of the optical properties, including quantum efficiency (up to 32%) as well as the photoluminescence lifetime of Cu-doped QDs
Mrad, Maroua. "Nouveaux procédés de synthèse en milieu aqueux de quantum dots ternaires AgInS₂ (AIS) et quaternaires AgInS₂/ZnS (AIZS). Dopage de ces nanocristaux par Ni²⁺ ou Co²⁺. Application à la photocatalyse hétérogène." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0119.
Quantum dots (QDs) have high potential for biological detection, photovoltaics and catalysis due to their unique photophysical properties. The most studied semiconductors contain heavy metals such as cadmium and lead and their fields of application are very limited. As part of this thesis, we developed new aqueous synthesis processes for ternary QDs AgInS₂ and quaternary AgInS₂/ZnS and studied their doping by the Ni(+2) and Co(+2) cations to prepare nanocrystals with fluorescent and magnetic properties. We first optimized the synthesis of AIZS QDs in aqueous media using 3-MPA as ligand and produced nanocrystals with a fluorescence quantum yield of 65%. Then, the doping of these nanocrystals by cations Ni(2+) and Co(2+) was studied. A drop in quantum fluorescence efficiency is observed after doping. The best magnetic properties were observed at low temperature (10 K) and the magnetization values increase with the dopant concentration. The AIZS QDs have been associated with the ZnO nanorods by heterojunction to form a good photocatalyst ZnO/AIZS(10%) which degrades 98% of the Orange II in visible during 90 min under intensity 40 W/cm². This material can be reused, its photocatalytic activity only slightly decreases after 8 cycles (91% photodegradation)
Alterary, Seham. "Synthèse, caractérisation et fonctionnalisation de CdS et de suspensions magnétiques collïdales en vue d'application biomolécules." Paris 7, 2008. http://www.theses.fr/2008PA077230.
Semiconductor quantum dots (QDs) are a new generation of inorganic probes with advantageous properties over traditional organic probes for biological applications. A major hurdle in the use of QDs for biology is the inability of the hydrophobically synthesized QDs to interface with aqueous environments. In the first part of this dissertation we describe the synthesis of water-soluble CdS QDs end-capped with N-hydroxysuccinimide ester groups, with narrow size distribution. These CdS QDs are synthesized in polyol medium using terthiophene dicarboxylic acid as a stabilizer. The structure of the hybrid product was investigated by TEM, XRD, optical and FTIR spectroscopy. The modifîed nanoparticles consist of a few tens of oligothiophène units attached to the CdS core. The free carboxylic end groups were transformed into 7V-hydroxysuccinimidyl ester and were further cross-linked with biotin and avidin. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results indicate successful modification of CdS QD surfaces. The second part, describes the synthesis and the characterization of hybrid magnetic core-shell structures. The Stöber method bas been adopted to prepare hybrid core-shell particles by coating the surfaces of monodisperse magnetic emulsion with uniform silica shells. The Stöber method has been adopted to prepare hybrid core-shell particles by coating the surfaces of monodisperse magnetic emulsion with uniform silica shells. The coated particles have been characterized by electron microscopy (TEM), XPS spectroscopy and IR and showing a core shell structure with a uniform layer of silica
Henry, Étienne. "Auto-assemblages nanostructurés à base de lipides, d'actine et de quantum dots : synthèse, structure et propriétés photophysiques." Rennes 1, 2007. http://www.theses.fr/2007REN1S166.
Two nanostructured self-assemblies, with and without quantum dots, were obtained by the synchronization of the growth of actin filaments and the layer stacking of lipidic membranes. A broad panel of techniques (X-rays diffraction, transmission electronic microscopy and optical microscopy) and an important instrumental development allowed to study and understand the growing dynamic of these matrices, in order to control their nanostructuration. A fluorescence micro-spectrometer has been developed to study the fluorescence of the matrix decorated by quantum dots. New photophysic properties has been characterized and are due to the nanostructuration. The new feature of the structures and their biochemical mechanism of organization, open new features in the field of self-assembled materials and nano-photonic
Galiyeva, Perizat. "Doped Ag-In-Zn-S and Ag-In-Ga-Zn-S QDs : synthesis and potential as dual-modality probes for magnetic resonance and fluorescence imaging of cells." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0118.
Since fluorescence imaging (FI) and magnetic resonance imaging (MRI) are among the most effective diagnostic tools, QDs with fluorescent and magnetic properties are of great interest as dual-modal probes. In this work, undoped and doped Ag-In-Zn-S (AIZS) and Ag-In-Ga-Zn-S (AIGZS) QDs were synthesized and investigated as bimodal probes for FI and MRI. Highly fluorescent AIZS QDs were prepared in organic media using DDT and OAm as capping ligands. Mn:AIZS QDs showed paramagnetic and superparamagnetic properties. AIZS and Mn:AIZS QDs were also transferred into aqueous phase using the amphiphilic PMAO polymer. Further, Mn, Gd or Fe-doped AIZS QDs were prepared in aqueous media, showed low cytotoxicity toward KB cells, and demonstrated potential as fluorescent probes for FI. Finally, AIGZS and Mn:AIGZS QDs, synthesized via a novel single precursor thermal decomposition method, showed high fluorescence and paramagnetic/superparamagnetic properties. Mn-doped aqueous transferred AIGZS QDs increased contrast in both T1-weighted and T2-weighted images with increasing in Mn loading
Loczechin, Aleksandra. "Les nanomatériaux en carbone : des alternatives antibactériennes et antivirales." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I117.
Increasing antibiotic resistance and limited development of new drugs necessitate the search for alternative strategies to eradicate bacterial infections. Similar problems are faced in the development of antiviral therapeutics, due to the constant emergence of new viruses and their ability to escape therapy by genetic mutations. This work investigates the potential antibacterial and/or antiviral activity of carbon-based nanostructures such as diamond nanoparticles and carbon quantum dots (CQDs) as well as reduced graphene oxide (rGO) in combination with cryogels. CQDs formed by hydrothermal synthesis from 4-aminophenylboronic acid as the carbon precursor showed to be efficient in the inhibition of the viral attachment of human coronavirus HCoV-229E-Luc to cells with an EC50 of 5.2±0.7 µg mL-1. Mechanistic studies suggest that the CQDs are acting at the early stage of virus infection as well at the viral replication step. In parallel, we took advantage of the multivalent character of CQDs as well as nanodiamonds and modified them with short synthetic antimicrobial peptides (AMPs). Tests of these nanostructures against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli pathogens showed increased antibacterial activity when compared to AMPs alone. In the case of rGO combined with cryogels loaded with AMPs, bacterial eradication was achieved efficiently and on-demand using near-infrared light as external trigger to release AMPs
Bogicevic, Alexandra. "Synthèse colloïdale de structures hybrides or/quantum dots." Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLS092.
Colloidal semiconductor nanocrystals, also known as quantum dots (QDs), have exceptional optical properties, such as high absorption cross section and quantum yield. Their emission spectra can be tuned by changing their size, their shape or composition. Recently, our group reported the plasmonic coupling of unique QD emitters embedded in silica coated with a gold nanoshell with a Purcell factor of 6. The resulting emitters showed enhanced photostability and reduced blinking rates.In this thesis, we explore synthesis and optical properties of similar objects containing not one but hundreds of QDs in their core (superparticles).We first synthesize CdSe/CdS/ZnS core/multishell QDs and assemble them into aggregates of controlled sizes by emulsion/evaporation. The aggregates are then coated with a silica shell (Stöber process) and with a gold nanoshell using a deposition process.The optical properties of QD aggregates with and without gold shells are addressed. These objects exhibit high quantum efficiency, as well as stable and Poissonian emission at room temperature. In addition, we demonstrate a Förster-type resonance energy transfer (FRET) between neighboring QDs inside the aggregates. We also prove that polyvinylpyrrolidone (PVP) can be used to regulate both the reduction rate of gold and the morphology of the gold nanoshell.The second objective is to transpose this synthesis onto 2D semiconductor nanocrystals called nanoplatelets (NPLs) which exhibit particular emission polarization properties thanks to their anisotropic shape. To preserve this anisotropy throughout the synthesis process of the gold nanoshells, a supplementary extension step has to be conducted on these NPLs
Merheb, Melissa. "Une approche universelle d'assemblage dirigé de nanoparticules dans des microstructures polymères 1D, 2D et 3D." Electronic Thesis or Diss., Troyes, 2022. http://www.theses.fr/2022TROY0013.
The controlled assembly of nanoparticles (NPs) on 3D micropatterns and over a large surface is a promising method for the creation of structured materials with new properties. In this context, the combination of lithography with colloidal deposition has attracted much attention during the last decade due to the advantages offered by both approaches. In this thesis, we have developed a versatile method allowing the control of the assembly of NPs whatever their nature, size and shape. This approach is based on the functionalization of a photopolymer in order to give it positive charges allowing it, after two photon photopolymerization (2PP) step, to attract negatively charged NPs, due to electrostatic interactions. Studying the reactivity of the photopolymer and both optical and structural properties of the assemblies enabled us to optimize the photochemical stability in 2PP, improve the reproducibility of the process, extend the functionalization technique to a large number of amines and acrylic monomers and provide a better understanding of the functionalization mechanism. At the same time, we have proposed a new functionalization approach that consists of treating the polymerized surface with amines. The advantage of this approach is the possibility of obtaining an assembly of NPs on large surfaces produced by photopolymerization at 1 or 2 photons which overcomes the constraints associated with the prior functionalization of the monomer
Parola, Stéphanie. "Synthèse et caractérisations de matériaux composites à base de nanocristaux de Ge pour des applications optroniques." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00762352.
Kharin, Alexander. "Group IV nanoparticles for cell imaging and therapy." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1032/document.
Biomedicine and biophotonics related businesses are currently growing at a breathtaking pace, thereby comprising one of the fastest growing sectors of innovative economy. This sector is truly interdisciplinary, including, very prominently, the development of novel nanomaterials, light sources, or novel device/equipment concepts to carry out photon conversion or interaction. The great importance of disease diagnosis at a very early stage and of the individual treatment of patients requires a carefully targeted therapy and the ability to induce cell death selectively in diseased cells. Despite the tremendous progress achieved by using quantum dots or organic molecules for bio-imaging and drug delivery, some problems still remain to be solved: increased selectivity for tumor accumulation, and enhancement of treatment efficiency. Other potential problems include cyto- and genotoxicity, slow clearance and low chemical stability. Significant expectations are now related to novel classes of inorganic materials, such as silicon-based or carbon-based nanoparticles, which could exhibit more stable and promising characteristics for both medical diagnostics and therapy. For this reason, new labeling and drug delivery agents for medical application is an important field of research with strongly-growing potential.The 5 types of group IV nanoparticles had been synthesized by various methods. First one is the porous silicon, produced by the electrochemical etching of bulk silicon wafer. That well-known technique gives the material with remarkably bright photoluminescence and the complicated porous structure. The porous silicon particles are the agglomerates of the small silicon crystallites with 3nm size. Second type is 20 nm crystalline silicon particles, produced by the laser ablation of the bulk silicon in water. Those particles have lack of PL under UV excitation, but they can luminesce under 2photon excitation conditions. 3rd type of the particles is the 8 nm nanodiamonds