Navegando por Palavras-chave "Luminescent"
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- ItemAcesso aberto (Open Access)Filmes ultrafinos luminescentes de Acetato de Celulose com complexos de íons Eu3+ E Tb3+ obtidos por Langmuir-Blodgett(Universidade Federal de São Paulo, 2022-06-20) Figueiredo, Mayara Macedo [UNIFESP]; Molina, Celso [UNIFESP]; Caseli, Luciano [UNIFESP]; http://lattes.cnpq.br/8929162910172931; http://lattes.cnpq.br/3819814458216651; http://lattes.cnpq.br/5976241386554063A técnica de Langmuir-Blodgett (LB) permite a obtenção de filmes ultrafinos, organizados na forma de mono ou multicamadas a partir da transferência para suportes sólidos de monocamadas de anfifílicos organizados na interface ar-água, com potencial para várias aplicações tais como sondas luminescentes para bioaplicações e camadas ativas em dispositivos emissores de luz. Visando a obtenção de filmes com viés sustentável, foi utilizado neste trabalho um polímero derivado de fonte renovável (acetato de celulose) e que possua alta transparência na região do visível, juntamente com fosfolipídio ácido dimiristoilfosfatídico (DMPA), anfifílico insolúvel em água e formador de filmes de Langmuir. Foram também incorporados os complexos luminescentes Eu(tta)3(H2O)2 e Tb(acac)3(H2O)3. Assim, estudou-se o efeito da incorporação dos complexos, à monocamada mista formada por acetato de celulose e DMPA na interface ar-água. Os filmes de Langmuir foram caracterizados por isotermas de pressão e potencial superficial-área, microscopia no ângulo de Brewster e espectroscopia de absorção-reflexão no infravermelho para investigação das propriedades termodinâmicas, elétricas, morfológicas e estruturais das monocamadas. Os filmes são mais estáveis quando os componentes acetato de celulose e DMPA são misturados previamente e coespalhados na interface ar-água. As monocamadas foram comprimidas lateralmente e transferidas para suportes sólidos pela técnica LB e caracterizados por espectroscopia no infravermelho e de fotoluminescência. Os filmes LB apresentaram luminescência e apresentaram as principais emissões características dos íons Eu3+ e Tb3+ quando excitados via efeito antena. Além disso, parâmetros como tempo de vida do estado excitado foram obtidos, viabilizando os filmes como possível camada ativa para dispositivos emissores de luz.
- ItemSomente MetadadadosNanopartículas e filmes luminescentes - magnéticos de complexos de íons lantanídeos Eu3+ e Tb3+ e óxido de ferro para bioaplicações(Universidade Federal de São Paulo (UNIFESP), 2020-03-19) Espindola, Ariane De [UNIFESP]; Molina, Celso [UNIFESP]; Universidade Federal de São PauloLuminescent nanoparticles containing complexes of Eu3+ and Tb3+ ions have been used in a range of applications in the field of photonics, attracting special attention to bioapplications in therapy and diagnosis (theranostics). Superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with biomolecules are also commonly used for biomedical applications. Aiming these applications, nanoparticles of magnetite (Fe3O4) functionalized with silica and biocompatible ligands such as polyethylene glycol (PEG), Glutathione (GSH) and Chitosan (CS) and lanthanide ion complexes [Eu(tta)3(H2O)2] and [Tb(acac)3(H2O)3] were synthesized and characterized. SPIONs with chitosan and europium complex were also incorporated in biopolymer derived from cellulose, hydroxypropylmethylcellulose (HPMC), to obtain magnetic - luminescent films. The nanoparticles (NPs) were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), magnetic measurements (SQUID), photoluminescence (PL), dynamic light scattering (DLS) and cytotoxicity assays in mononuclear cells. The structural and magnetic studies showed that the crystalline structure and the superparamagnetic properties of the magnetite were preserved with an increasement in the hydrodynamic size after the functionalization of NPs with biopolymers, silica and complexes. All functionalized nanoparticles, as well as the film, are luminescent, presenting the main emissions of Eu3+ and Tb3+ ions by excitation in the ultraviolet region via antenna effect. From the cytotoxicity, EC50 values were found showing that NPs have potential for biological applications, as they can be magnetically guided and monitored by luminescence.
- ItemAcesso aberto (Open Access)Síntese e propriedades de nanocompósitos luminescentes de terras raras e SBA-15(Universidade Federal de São Paulo, 2017-08-17) Takamori, Dante Yugo [UNIFESP]; Martins, Tereza da Silva [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Currently the elements known as rare earths are the object of much research due to their unique properties, amongst them, the possibility of producing luminescent materials. However, the direct excitation of rare earths is inefficient due to its low molar absortivity, making it necessary to employ other species, called matrixes, which have the purpose of absorbing electromagnetic radiation and transfering energy to luminescent ions, forming nanocrystals. A virtually unexplored method for controlling the properties of this kind of material is the use of ionic liquids (IL), which modify the reaction medium and influence the particle size, morphology and crystalline phase, consequently altering the luminescent properties. Nanocomposites that combine those luminescent materials and mesoporous silica are of great interest as they provide better stability and resistence besides having the ability of adsorbing other species. This work aimed to prepare and characterize nanocomposites made from SBA-type ordered mesoporous silica and nanocrystals (sodium yttrium fluoride (NaYF4) and yttrium oxide (Y2O3)) doped with erbium and europium rare earths, using for the latter the IL 1-butyl-3-methylimidazolium bromide (BMIBr), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4), 1-dodecyl-3-methylimidazolium bromide (DMIBr) and 1-dodecyl-3-methylimidazolium tetrafluoroborate (DMIBF4) in the reactium medium. The influence of the IL’s cations and anions on the properties of the material was studied, as well as the regular fluorescence phenomena (downshifting) in materials with europium and the upconversion phenomena in erbium doped samples preared with different matrixes, incorporated or not into SBA-15 (nanocrystal/nanocomposite mass proportion 0.2). It was possible to obtain luminescent materials for both matrixes, both with erbium and europium, even when incorporated into silica. Distinct morphologies were obtained for Y2O3 prepared with different IL, also resulting in different quantum yield for each morphology, although displaying the same cubic crystalline phase. For the composite prepared with BMIBr, the quantum yield was comparable to the unincorporated material. Obtaining a nanocomposite as luminescent as the pure crystal is interesting for its applicability, for its properties, stability and the possibility of its functionalization with drugs, allowing to track or photoactivate them in vivo using infrared excitation luminescence, as for the erbium doped material.