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Synthesis and characterization of aqueous quantum dots for biomedical applications /Li, Hui. Shih, Wei-Heng. Shih, Wan Y. January 2008 (has links)
Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 154-177).
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Magnetic nanocrystals : synthesis and properties of diluted magnetic semiconductor quantum dots /Norberg, Nicholas S. January 2006 (has links)
Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 163-175).
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Hydrophob/hydrophil schaltbare Nanoteilchen für die BiomarkierungDubavik, Aliaksei 15 July 2011 (has links)
There is a demand for new straightforward approaches for stabilization and solubilization of various nanoparticulate materials in their colloidal form, that pave way for fabrication of materials possessing compatibility with wide range of dispersing media. Therefore in this thesis a new general method to form stable nanocrystals in water and organics using amphiphilic polymers generated through simple and low cost techniques is presented and discussed. Amphiphilic coating agents are formed using thiolated or carboxylated polyethylene glycol methyl ether (mPEG-SH) as a starting material. These materials are available with a wide variety of chain lengths.
The method of obtaining of amphiphilic NPs is quite general and applicable for semiconductor CdTe nanocrystals as well as nanoscale noble metal (Au) and magnetic (Fe3O4) particles. This approach is based on anchoring PEG segment to the surface of a nanoparticle to form an amphiphilic palisade. Anchoring is realized via interaction of –SH (for CdTe and Au) or –COOH (in the case of magnetite) functional groups with particle’s surface. The resulting amphiphilicity of the nanocrystals is an inherent property of their surface and it is preserved also after careful washing out of solution of any excess of the ligand. The nanocrystals reversibly transfer between different phases spontaneously, i.e. without any adjustment of ionic strength, pH or composition of the phases. Such reversible and spontaneous phase transfer of nanocrystals between solvents of different chemical nature has a great potential for many applications as it constitutes a large degree of control of nanocrystals compatibility with technological processes or with bio-environments such as water, various buffers and cell media as well as their assembly and self-assembly capabilities.
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Sistemas de análises químicas em fluxo explorando mecanismos de re-alimentação, calibração multivariada e outras abordagens para melhoria em desempenho / Flow systems exploiting feed-back mechanisms, multivariate calibration and other strategies for improving the analytical performanceFortes, Paula Regina 30 June 2010 (has links)
Estudos foram conduzidos relativamente ao desempenho dos sistemas de análises em fluxo quando configurados como sistemas inteligentes, associados às técnicas de calibração multivariada ou empregando nanocristais como sensibilizadores. Ainda, melhorias relacionadas às modificações dos fluxos foram avaliadas, especialmente no que se refere à diálise em linha. Neste sentido, foi proposta uma nova estratégia para implementar determinações simultâneas de ferro e vanádio em ligas metálicas envolvendo cinética diferencial. O método baseava-se nas diferentes influências exercidas por Fe2+ e por V4+ na taxa de oxidação de íons iodeto por íons Cr6+ sob condições ácidas. Três diferentes alíquotas de amostra eram inseridas em um fluxo transportador / reagente de KI, confluindo posteriormente com um fluxo de K2Cr2O7. A sobreposição entre as três zonas de amostra estabelecidas resultava em uma zona de amostra complexa com diversos valores de absorbância. Medidas realizadas nos pontos de máximos e minímos do sinal registrado eram mais precisas e continham informações acerca dos diferentes estágios de desenvolvimento da reação e de diferentes condições de concentrações. Em outra estratégia, um sistema MPFS inteligente foi proposto para a determinação turbidimétrica sequencial de sulfato e cloreto em águas naturais. Ambos os métodos foram implementados no mesmo módulo de análises, proporcionando facilidades relativas ao: preparo de amostra em linha; adição de íons sulfato ou cloreto ao meio reacional para melhoria das condições de supersaturação; decisão em tempo real acerca da necessidade ou não da próxima análise. Inicialmente, determinava-se a concentração de cloreto presente na amostra, e este resultado era comparado com um valor pré-determinado. Se este fosse superior, a amostra era analisada novamente visando à determinação de sulfato. Caso contrário, uma nova amostra era analisada. A estratégia resultou em aumento da velocidade analítica e em boas figuras de mérito analítico. Estudos relativos à natureza do fluxo foram conduzidos avaliando-se o desempenho dos fluxos pulsados provenientes de bombas solenóide em relação à eficiência do transporte de massas, dispersão da zona de amostra relacionada com a mudança de sentido do fluxo e eficiência do processo de diálise quando comparados aos fluxos tipicamente laminares. Embora fosse observada a presença de vórtices, o número de Reynolds experimentalmente obtido demonstrou que o fluxo resultante não era turbulento. Porém seu perfil exibia características de mescla turbulenta, melhorando assim o desempenho relativo ao transporte de massas e redução da dispersão da zona de amostra. Entretanto, beneficios relativos a melhorias no processo de diálise foram ausentes devido provavelmente à alta pressão exercida dentre da câmara de diálise, com consequente deformação dos poros da membrana. Nestas situações, um sistema de análises híbrido (com fluxo laminar e mescla turbulenta) seria fortemente recomendado. Finalmente, a implementação de nanocristais quantum dots (QDs) como sensibilizadores em um sistema MPFS envolvendo reação quimioluminescente foi proposta para a determinação de glipizida e gliclazida em formulaçoes farmacêuticas. O método fundamentava-se na oxidação dos íons S2- por Ce4+ em meio ácido. Na presença dos analitos, a intensidade da radiação emitida era inibida. A influência do diâmetro médio dos nanocristais foi avaliada, e os critérios utilizados para o dimensionamento do sistema foram a repetibilidade, a reprodutibilidade e a sensibilidade analítica. Os analitos foram quantificados no mesmo módulo de análises, e boas figuras de mérito analítico foram verificadas. Os resultados obtidos se apresentaram concordantes com aqueles obtidos pela Farmacopéia Britânica / Studies focusing on performance of intelligent analytical flow systems, association with multivariate calibration or use of nanocrystals as sensitizers were carried out. Moreover, improvements related to modifications in flow pattern were evaluated with emphasis to in-line dialysis. To this end, a strategy for implementing simultaneous determinations of iron and vanadium in alloys relying on differential kinetics was proposed. The method was based on the influence of Fe2+ and V4+ on the rate of iodide oxidation by Cr6+ under acidic conditions. Three different plugs of the sample were sequentially inserted into an acidic KI reagent carrier stream, and a confluent K2Cr2O7 solution was added downstream. Overlap between the established plugs led to a complex sample zone with several regions of maximal and minimal absorbance values. Measurements performed on these regions were more precise and revealed the different degrees of reaction development. In another strategy, an intelligent MPFS was proposed for sequential turbidimetric determination of sulphate and chloride in natural waters. Both methods were implemented in the same manifold, providing facilities for: in-line sample cleanup; addition of low amounts of sulphate or chloride ions to the reaction medium for improving supersaturation conditions and real-time decision on the need for next assay. The sample was initially run for chloride determination, and the analytical signal was compared with a preset value. If higher, the sample was run again, now for sulphate determination. Otherwise, next sample was assayed. The strategy led to an increased sample throughput and good analytical figures of merit. Studies focusing on the flow pattern were carried out aiming at the evaluation of the influence of the pulsed flows delivered by solenoid pumps in relation to the efficiency of mass transfer, dispersion related to changes in flow direction of the sample zone and dialysis process as compared with typical laminar flow. Although the establishment of vortices were noted, the experimentally obtained Reynolds number showed that a turbulent flow was not established. Its pattern exhibited characteristics which improved the performance due to the enhanced radial mass transport inherent in turbulent mixing. Comparatively to laminar flow, beneficial aspects were noted in relation to sample dispersion and mass transfer. In relation to dialysis efficiency however process the benefits were not noted probably due to the high pressure inside the dialysis chamber, with consequent membrane pore deformation. In this situation, a hybrid flow analysis system (with laminar flow and turbulent mixing) might be recommended. Implementation of quantum dots nanocrystals (QDs NC) as sensitizers in a MPFS with chemiluminometric detection was proposed for the determinations of gliclazide and glipizide in pharmaceutical formulations. The method relied on the oxidation of sulphite by Ce4+ in acidic medium and, in the presence of the analytes, the emitted radiation of the Ce4+-SO3 2--CdTe QDs system was inhibited. Influence of crystal size was investigated, and the criteria for system optimization were the analytical repeatability, reproducibility and sensitivity. Both analytes were quantified in the same manifold, resulting in good analytical figures of merit. The results were in fairly good agreement with those obtained by the British Pharmacopoeia reference method
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Sistemas de análises químicas em fluxo explorando mecanismos de re-alimentação, calibração multivariada e outras abordagens para melhoria em desempenho / Flow systems exploiting feed-back mechanisms, multivariate calibration and other strategies for improving the analytical performancePaula Regina Fortes 30 June 2010 (has links)
Estudos foram conduzidos relativamente ao desempenho dos sistemas de análises em fluxo quando configurados como sistemas inteligentes, associados às técnicas de calibração multivariada ou empregando nanocristais como sensibilizadores. Ainda, melhorias relacionadas às modificações dos fluxos foram avaliadas, especialmente no que se refere à diálise em linha. Neste sentido, foi proposta uma nova estratégia para implementar determinações simultâneas de ferro e vanádio em ligas metálicas envolvendo cinética diferencial. O método baseava-se nas diferentes influências exercidas por Fe2+ e por V4+ na taxa de oxidação de íons iodeto por íons Cr6+ sob condições ácidas. Três diferentes alíquotas de amostra eram inseridas em um fluxo transportador / reagente de KI, confluindo posteriormente com um fluxo de K2Cr2O7. A sobreposição entre as três zonas de amostra estabelecidas resultava em uma zona de amostra complexa com diversos valores de absorbância. Medidas realizadas nos pontos de máximos e minímos do sinal registrado eram mais precisas e continham informações acerca dos diferentes estágios de desenvolvimento da reação e de diferentes condições de concentrações. Em outra estratégia, um sistema MPFS inteligente foi proposto para a determinação turbidimétrica sequencial de sulfato e cloreto em águas naturais. Ambos os métodos foram implementados no mesmo módulo de análises, proporcionando facilidades relativas ao: preparo de amostra em linha; adição de íons sulfato ou cloreto ao meio reacional para melhoria das condições de supersaturação; decisão em tempo real acerca da necessidade ou não da próxima análise. Inicialmente, determinava-se a concentração de cloreto presente na amostra, e este resultado era comparado com um valor pré-determinado. Se este fosse superior, a amostra era analisada novamente visando à determinação de sulfato. Caso contrário, uma nova amostra era analisada. A estratégia resultou em aumento da velocidade analítica e em boas figuras de mérito analítico. Estudos relativos à natureza do fluxo foram conduzidos avaliando-se o desempenho dos fluxos pulsados provenientes de bombas solenóide em relação à eficiência do transporte de massas, dispersão da zona de amostra relacionada com a mudança de sentido do fluxo e eficiência do processo de diálise quando comparados aos fluxos tipicamente laminares. Embora fosse observada a presença de vórtices, o número de Reynolds experimentalmente obtido demonstrou que o fluxo resultante não era turbulento. Porém seu perfil exibia características de mescla turbulenta, melhorando assim o desempenho relativo ao transporte de massas e redução da dispersão da zona de amostra. Entretanto, beneficios relativos a melhorias no processo de diálise foram ausentes devido provavelmente à alta pressão exercida dentre da câmara de diálise, com consequente deformação dos poros da membrana. Nestas situações, um sistema de análises híbrido (com fluxo laminar e mescla turbulenta) seria fortemente recomendado. Finalmente, a implementação de nanocristais quantum dots (QDs) como sensibilizadores em um sistema MPFS envolvendo reação quimioluminescente foi proposta para a determinação de glipizida e gliclazida em formulaçoes farmacêuticas. O método fundamentava-se na oxidação dos íons S2- por Ce4+ em meio ácido. Na presença dos analitos, a intensidade da radiação emitida era inibida. A influência do diâmetro médio dos nanocristais foi avaliada, e os critérios utilizados para o dimensionamento do sistema foram a repetibilidade, a reprodutibilidade e a sensibilidade analítica. Os analitos foram quantificados no mesmo módulo de análises, e boas figuras de mérito analítico foram verificadas. Os resultados obtidos se apresentaram concordantes com aqueles obtidos pela Farmacopéia Britânica / Studies focusing on performance of intelligent analytical flow systems, association with multivariate calibration or use of nanocrystals as sensitizers were carried out. Moreover, improvements related to modifications in flow pattern were evaluated with emphasis to in-line dialysis. To this end, a strategy for implementing simultaneous determinations of iron and vanadium in alloys relying on differential kinetics was proposed. The method was based on the influence of Fe2+ and V4+ on the rate of iodide oxidation by Cr6+ under acidic conditions. Three different plugs of the sample were sequentially inserted into an acidic KI reagent carrier stream, and a confluent K2Cr2O7 solution was added downstream. Overlap between the established plugs led to a complex sample zone with several regions of maximal and minimal absorbance values. Measurements performed on these regions were more precise and revealed the different degrees of reaction development. In another strategy, an intelligent MPFS was proposed for sequential turbidimetric determination of sulphate and chloride in natural waters. Both methods were implemented in the same manifold, providing facilities for: in-line sample cleanup; addition of low amounts of sulphate or chloride ions to the reaction medium for improving supersaturation conditions and real-time decision on the need for next assay. The sample was initially run for chloride determination, and the analytical signal was compared with a preset value. If higher, the sample was run again, now for sulphate determination. Otherwise, next sample was assayed. The strategy led to an increased sample throughput and good analytical figures of merit. Studies focusing on the flow pattern were carried out aiming at the evaluation of the influence of the pulsed flows delivered by solenoid pumps in relation to the efficiency of mass transfer, dispersion related to changes in flow direction of the sample zone and dialysis process as compared with typical laminar flow. Although the establishment of vortices were noted, the experimentally obtained Reynolds number showed that a turbulent flow was not established. Its pattern exhibited characteristics which improved the performance due to the enhanced radial mass transport inherent in turbulent mixing. Comparatively to laminar flow, beneficial aspects were noted in relation to sample dispersion and mass transfer. In relation to dialysis efficiency however process the benefits were not noted probably due to the high pressure inside the dialysis chamber, with consequent membrane pore deformation. In this situation, a hybrid flow analysis system (with laminar flow and turbulent mixing) might be recommended. Implementation of quantum dots nanocrystals (QDs NC) as sensitizers in a MPFS with chemiluminometric detection was proposed for the determinations of gliclazide and glipizide in pharmaceutical formulations. The method relied on the oxidation of sulphite by Ce4+ in acidic medium and, in the presence of the analytes, the emitted radiation of the Ce4+-SO3 2--CdTe QDs system was inhibited. Influence of crystal size was investigated, and the criteria for system optimization were the analytical repeatability, reproducibility and sensitivity. Both analytes were quantified in the same manifold, resulting in good analytical figures of merit. The results were in fairly good agreement with those obtained by the British Pharmacopoeia reference method
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Characterization and Application of Colloidal Nanocrystalline Materials for Advanced PhotovoltaicsBhandari, Khagendra P. 22 October 2015 (has links)
No description available.
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Robust Polymer Matrix Based on Isobutylene (Co)polymers for Efficient Encapsulation of Colloidal Semiconductor NanocrystalsShiman, Dmitriy I., Sayevich, Vladimir, Meerbach, Christian, Nikishau, Pavel A., Vasilenko, Irina V., Gaponik, Nikolai, Kostjuk, Sergei V., Lesnyak, Vladimir 01 April 2021 (has links)
We introduce new oxygen- and moisture-proof polymer matrixes based on polyisobutylene (PIB) and its block copolymer with styrene [poly(styrene-block-isobutylene-blockstyrene), PSt-b-PIB-b-PSt] for the encapsulation of colloidal semiconductor nanocrystals. In order to prepare transparent and processable composites, we developed a special procedure of nanocrystal surface engineering including ligand exchange of parental organic ligands to inorganic species followed by the attachment of specially designed short-chain PIB functionalized with an amino group. The latter provides excellent compatibility of the particles with the polymer matrixes. As colloidal nanocrystals, we chose CdSe nanoplatelets (NPLs) because they possess a large surface and thus are very sensitive to the environment, in particular in terms of their limited photostability. The encapsulation strategy is quite general and can be applied to a wide variety of semiconductor nanocrystals, as demonstrated on the example of PbS quantum dots. All obtained composites exhibited excellent photostability, being tested in a focus of a powerful white-light source, as well as exceptional chemical stability in a strongly acidic media. We compared these properties of the new composites with those of widely used polyacrylate-based materials, demonstrating the superiority of the former. The developed composites are of particular interest for application in optoelectronic devices, such as color-conversion light-emitting diodes, laser diodes, luminescent solar concentrators, etc.
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