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Дисертації з теми "Quantum dots ternaires":
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
Kauffer, Florence-Anaïs. "Synthèse, stabilité et toxicité de quantum dots à coeur CdSe." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0006/document.
Due to their unique properties compared to their bulk counterparts, nanomaterials have gained considerable attention, especially in industry and medicine. Their fast development has generated many public concerns, especially because of a lack of knowledge regarding their toxicity. Our project aims to use cadmium selenide (CdSe) as a model material in order to initiate a research aiming at establishing a correlation between the nanoparticles chemical structure, their surface reactivity, their stability and their toxicity. CdSe and alloyed CdSe(S) quantum dots (QDs) were prepared in aqueous phase either at 100°C or under hydrothermal conditions in order to differ solely by their core chemical structure (ternary alloy vs binary semiconductor), while other parameters such as the size, the surface charge or the surface ligand, have been kept constant. Cytotoxicity studies carried out on Escherichia coli have shown that release of Cd2+ played a key role in the toxicity for both QDs. However, alloyed CdSe(S) QDs were also found more stable and less toxic than CdSe nanocrystals. Without disregarding the importance of Cd2+ ions release by the nanoparticles, a correlation between the stability and the production of reactive oxygen species (ROS) showed that toxicity was dependent on QDs photostability. Our study highlights a relationship between the core reactivity, stability and the photo-induced toxicity QD nanoparticles
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)
Gourgon, Cécile. "Fabrication et caractérisation optique de fils et boites quantiques CdTe/CdZnTe." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10145.
Widmann, Frédéric. "Epitaxie par jets moléculaires de GaN, AlN, InN et leurs alliages : physique de la croissance et réalisation de nanostructures." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10234.