Luminescência em sistemas coloidais polifosfato-polioxometalatos
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Data
2009-08-11
Autores
Barbosa, Anne Jacqueline [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Novos sistemas coloidais polifosfato-tungstato:Eu3+ em meio aquoso, coacervatos polifosfato-cálcio/tungstato:Eu3+ e sistemas híbridos polifosfato-niobato/3- aminopropiltrietoxisilano:Eu3+ foram preparados e caracterizados quanto as suas propriedades estruturais e de luminescência. Os sistemas polifosfato-tungstato:Eu3+ foram caracterizados para diferentes concentrações relativas polifosfato:tungstato. Em soluções de polifosfato os íons Eu3+ ocupam sítios onde o íon é encapsulado pelas cadeias de metafosfato. O número médio de moléculas de água coordenadas aos íons Eu3+ é de 0,5 moléculas e a eficiência quântica de emissão do estado excitado do Eu3+ 5D0 é igual a 0,22. Com o aumento da concentração relativa de tungstato há uma forte interação do tungstato-Eu3+ levando a uma maior proteção dos ions em relação as moléculas do solvente. Imagens de Microscopia Eletrônica de Transmissão mostraram nanopartículas ricas em tungstênio com tamanhos entre 5-10 nm. Os resultados obtidos a partir da análise de espectroscopia de luminescência para amostras contendo altas concentrações relativas de tungstato (acima de 30 mol%) mostraram a presença do Eu3+ em estruturas do tipo polioxometalatos (POM) (decatungstatoeuropato- [EuW10O36]9-. A eficiência quântica de emissão é de 0,8, semelhante a observada para o polioxometalato no estado sólido. Coacervatos polifosfato-cálcio/tungstato:Eu3+ foram preparados utilizando-se diferentes concentrações de tungstato. Os resultados obtidos mostraram que a adição de tungstato aos coacervatos não quebram as cadeias de polifosfato e os espectros de excitação mostraram a transferência de carga tungstato-Eu3+. A presença da espécie [Eu(PW11O39]11- pôde ser sugerida pela comparação com resultados da literatura. Amostras altamente luminescentes foram preparadas pela adição do ligante orgânico tenoiltrifuloracetonato...
New aqueous colloidal systems poliphosphate-tungstate:Eu3+, coacervates poliphosphate-calcium/tungstate:Eu3+ and hybrids poliphosphate-niobate/3- aminopropyltrietoxisilane:Eu3+ have been prepared and characterized. Polyphosphate-tungstate-Eu3+ systems were characterized for different polyphosphate:tungstate relative contents. In aqueous solutions Eu3+ ions occupy cagelike sites where metal ions are encapsulated by the polyphosphate chains. The number of water molecules in the Eu3+ coordination shell is 0.5 and the quantum efficiency is 0.22. With the increase in the tungstate content an additional interactions is observed and the quantum efficiency is 0.8. Transmission electron microscopy and spectroscopic measurements lead to the identification of the decatungstoeuropate ([EuW10O36]9-) nanocrystals. Polyphosphate-calcium-tungstate:Eu3+ coacervates were also obtained and the highly luminescent specie [Eu(PW11O39]11 could be identified. The addition of the betadiketonate ligand tenoyltrifluoroacetonate (tta) lead to enhanced emission and by comparing the spectroscopic results with the ones obtained for the well known complex [Eu(tta)3(H2O)2] the tta-Eu3+ energy transfer process could be identified. Low temperature glasses were prepared by mixing polyphosphate coacervates and carboximethylcellulose. Transparent monoliths were obtained displaying the same spectroscopic properties of the colloidal systems suggesting these new systems for special optical applications. Polyphosphate-niobate-3-aminopropyltriethoxisilane-Eu3+ hybrids were also prepared. The formation of (Na8Nb6O19.13H2O) rod crystals was putforward. Preliminary results suggest that these anisotropic crystals could align in the suspension leading to intricate optical phenomena.
New aqueous colloidal systems poliphosphate-tungstate:Eu3+, coacervates poliphosphate-calcium/tungstate:Eu3+ and hybrids poliphosphate-niobate/3- aminopropyltrietoxisilane:Eu3+ have been prepared and characterized. Polyphosphate-tungstate-Eu3+ systems were characterized for different polyphosphate:tungstate relative contents. In aqueous solutions Eu3+ ions occupy cagelike sites where metal ions are encapsulated by the polyphosphate chains. The number of water molecules in the Eu3+ coordination shell is 0.5 and the quantum efficiency is 0.22. With the increase in the tungstate content an additional interactions is observed and the quantum efficiency is 0.8. Transmission electron microscopy and spectroscopic measurements lead to the identification of the decatungstoeuropate ([EuW10O36]9-) nanocrystals. Polyphosphate-calcium-tungstate:Eu3+ coacervates were also obtained and the highly luminescent specie [Eu(PW11O39]11 could be identified. The addition of the betadiketonate ligand tenoyltrifluoroacetonate (tta) lead to enhanced emission and by comparing the spectroscopic results with the ones obtained for the well known complex [Eu(tta)3(H2O)2] the tta-Eu3+ energy transfer process could be identified. Low temperature glasses were prepared by mixing polyphosphate coacervates and carboximethylcellulose. Transparent monoliths were obtained displaying the same spectroscopic properties of the colloidal systems suggesting these new systems for special optical applications. Polyphosphate-niobate-3-aminopropyltriethoxisilane-Eu3+ hybrids were also prepared. The formation of (Na8Nb6O19.13H2O) rod crystals was putforward. Preliminary results suggest that these anisotropic crystals could align in the suspension leading to intricate optical phenomena.
Descrição
Palavras-chave
Química inorgânica, Luminescencia, Niobatos, Coacervatos, Inorganic chemistry
Como citar
BARBOSA, Anne Jacqueline. Luminescência em sistemas coloidais polifosfato-polioxometalatos. 2009. 144 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Química, 2009.