Navegando por Palavras-chave "Emission"

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    CaTiO3 and Ca1-3xSmxTiO3: Photoluminescence and morphology as a result of Hydrothermal Microwave Methodology
    (Elsevier Sci Ltd, 2016) Pinatti, Ivo Mateus; Mazzo, Tatiana Martelli [UNIFESP]; Goncalves, Rosana de Fatima [UNIFESP]; Varela, Jose Arana; Longo, Elson; Rosa, Ieda Lucia Viana
    Calcium titanate (CaTiO3 - CT) and samarium doped calcium titanate (CaTiO3:Sm3+ - CT:Sm) powders in different Sm3+ concentrations (0.5-5.0% molar ratio of Sm3+) were obtained by the Hydrothermal Microwave Methodology at 140 degrees C for 16 min. These crystals were structurally characterized by X-ray diffraction (XRD) and micro-Raman (MR) spectroscopy. Field emission scanning electron microscopy images were employed to observe the shape and size of the crystals. The optical properties were investigated by ultraviolet visible (UV Vis) absorption and photoluminescence (PL) measurements. The XRD indicated structural organization at long range while MR revealed short range order for all undoped and Sm-doped samples. Morphological analysis revealed a new cubic morphology for CT:Sm, presenting an average size of 3.0 mu m. Further, the ultraviolet visible absorption spectra indicated the existence of intermediary energy levels within the band gap. The maximum intensity PL emission occurred due to (4)G(5/2) -> H-6(7/2) and (4)G(5/2) -> H-6(9/2), transitions of Sm3+. CIE chromaticity coordinates of the samples were determined and support these materials are promising candidates for applications as phosphors in the visible orange range. This research concluded that the methodology employed here was responsible for the presence of unusual and interesting properties for these new luminescent materials. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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    CaTiO3 and Ca1-3xSmxTiO3: Photoluminescence and morphology as a result of Hydrothermal Microwave Methodology
    (Elsevier Sci Ltd, 2016) Pinatti, Ivo Mateus; Mazzo, Tatiana Martelli [UNIFESP]; Gonçalves, Rosana de Fátima [UNIFESP]; Varela, Jose Arana; Longo, Elson; Rosa, Ieda Lucia Viana
    Calcium titanate (CaTiO3 - CT) and samarium doped calcium titanate (CaTiO3:Sm3+ - CT:Sm) powders in different Sm3+ concentrations (0.5-5.0% molar ratio of Sm3+) were obtained by the Hydrothermal Microwave Methodology at 140 degrees C for 16 min. These crystals were structurally characterized by X-ray diffraction (XRD) and micro-Raman (MR) spectroscopy. Field emission scanning electron microscopy images were employed to observe the shape and size of the crystals. The optical properties were investigated by ultraviolet visible (UV Vis) absorption and photoluminescence (PL) measurements. The XRD indicated structural organization at long range while MR revealed short range order for all undoped and Sm-doped samples. Morphological analysis revealed a new cubic morphology for CT:Sm, presenting an average size of 3.0 mu m. Further, the ultraviolet visible absorption spectra indicated the existence of intermediary energy levels within the band gap. The maximum intensity PL emission occurred due to (4)G(5/2) -> H-6(7/2) and (4)G(5/2) -> H-6(9/2), transitions of Sm3+. CIE chromaticity coordinates of the samples were determined and support these materials are promising candidates for applications as phosphors in the visible orange range. This research concluded that the methodology employed here was responsible for the presence of unusual and interesting properties for these new luminescent materials. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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    Pf/clay hybrid materials: a simple method to modulate the optical properties
    (Assoc brasil polimeros, 2016) Chen Em, Marcio Chao [UNIFESP]; Barbosa, Camila Gouveia [UNIFESP]; Peres, Laura Oliveira [UNIFESP]; Faez, Roselena
    The aim of this work was modulate the emission properties and improve thermal stability of a conjugated polymer incorporated into an inorganic matrix. Hybrid material was prepared based on poly(9,9-dioctylfluorene-co-phenylene (PF) and montmorillonite (Na(+)Mt) clay using wet impregnation of 10, 30 and 50 wt.% of PF into Na(+)Mt and Na(+)Mt intercalated with ammonium quaternary salts (hexadecyltrimethylammonium - HDTMA) in a different proportions (OMt-1 and OMt-2). The materials were characterized by infrared and UV-Vis spectroscopy, fluorescence, X-ray diffratometry and thermogravimetry analysis. The results show that the presence of the clay alters the photoluminescent and thermal properties. Nevertheless, the degree of the clay organophilization and the clay content influences the luminescent properties due to the diverse interaction behavior between the polymer and clay. The sodium clay acted only as dispersing agent since no intercalation process occurs and the emission displacement is assigned to this behavior. In this case the PF emission displace from 402 to 395 nm. A nonlinear displacement is observed for PF/OMt-2 due the difficulties to conclude if the intercalation of the polymer occurs (379, 403 and 412 for hybrid with 10, 30 and 50%, respectively). For PF/OMt-1 a higher displacements for lower wavelength is observed due to intercalation of polymer chains and subsequent isolation in the interlamellar space, especially with material with 10 and 30% of PF in the hybrid material, whose displacement reached to 360 nm. All these results show that is possible to try to control the emission of the conjugated hybrid material changing the rate of the material.