Morphological evolution of zinc oxide originating from zinc hydroxide carbonate

Zinc oxide can be obtained by thermal decomposition of hydrozincite, a topochemical reaction. This work reports the relation between zinc oxide morphology and the precursor zinc hydroxide carbonate precipitation time. The morphological evolution was monitored by SEM, IR and XRD. Zinc oxide obtained from initially precipitated hydrozincite consists of porous spherical aggregates and shows a single Zn-O IR vibrational band. At longer periods of precipitation time the aggregates were transformed into spherulitic-shaped zinc oxide particles showing the Zn-O split vibrational band. X-ray patterns show that the hexagonal zinc oxide phase is substantially increased as a function of hydrozincite precipitation time. © 1997 Elsevier Science S.A

Pechini's solution as precursor for Eu(III)-containing ZnO films

The flat-panel-display's (FPD) market and demand for highly efficient and colored luminescent films have been growing quickly. In this work, thin films were obtained from Pechini's solution by dip-coating. The green films were thermally treated at 873 K in order to get ZnO:Eu 1 at% thin film. A Schott(R) glass plate hydrothermally treated was used as substrate. The films have a mosaic shaped feature that was observed by optical microscopy. That feature is a result of substrate thermal treatment. The film deposition decreases the substrate transmittance in the visible range. When the F-7(0) -->L-5(6) (392nm) Eu3+ transition is excited, it is possible to detect emission from D-5(0) --> F-7(J) (J = 1, 2, 3 and 4) transitions. The D-5(0) --> F-7(2) transition is also observed by using ZnO excitation wavelengths indicating energy transfer from ZnO to Eu3+ ion. (C) 2003 Elsevier B.V. (USA). All rights reserved

Europium(III)-containing zinc oxide from Pechini method

ZnO:Eu3+ (0.1 and 3 at%) with average particle size of 500 nm were prepared by the Pechini method. Photoluminescence spectroscopy evidences that there is no energy transfer between ZnO and Eu3+ ion. The emission spectrum at 77 K shows that Eu3+ ions occupy at least three different sites in ZnO:Eu 3 at% sample. The experimental intensity parameter Omega(2) indicates that Eu3+ ions in the sample doped with 3 at% occupy sites where 4-configurational levels can better mix with opposite-parity states than those in the sample doped with 0.1 at%. (C) 2002 Elsevier B.V. B.V. All rights reserved

Phase separation in pyrex glass by hydrothermal treatment: evidence from micro-Raman spectroscopy

In this work, we investigated the formation of porous silica matrix obtained by hydrothermal treatment under saturated steam condition from Pyrex (R) glass. This investigation was carried out by scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray powder diffractometry (XRD) and Raman microscopy. We observed the presence of connected and homogeneously distributed pores in a non-crystalline silica phase and a detectable interface between silica and remnant glass phases resulting in a framework similar to asymmetric membranes. The results indicate that the process of phase separation takes place at lower temperature than that of glass-transition on the surface of the glass phase. Essential reaction between water and silica at supercritical condition together with the formation and leaching of soluble phase contribute to obtain porous silica matrix, (C) 2001 Elsevier B.V. B.V. All rights reserved

Luminescence of Eu(III) beta-diketone complex supported on functionalized macroporous silica matrix

This work reports on the photoluminescent properties of the complex diequatris(thenoyltrifluoroacetonate) europium(III), which was adsorbed or supported on tubes of modified surface silica matrix. The luminescence data and the experimental intensity parameter results evidence the existence of high interactions between the complex [Eu(tta)(3)(H2O)(2)] and the modified surface matrix. The anchored complex on macroporous silica shows higher intensity parameter values suggesting that the Eu-0 bond becomes more covalent than the adsorbed one. Therefore, the hypersensitive character of the D-5(0) --> F-7(2) transition increases evidencing a high contribution of the dynamic coupling mechanism possibly due to highly polarizable chemical environments occupied by europium(III) ion. The lifetimes of the complex on silica matrices were measured. (C) 2001 Elsevier B.V. Ltd. All rights reserved

Controlling dimensionality via a dual ligand strategy in Ln-thiophene-2,5-dicarboxylic Acid-terpyridine coordination polymers

Eleven new lanthanide (Ln = Nd-Lu)-thiophene-2,5-dicarboxylic acid (25-TDC)-2,2':6',2 ''-terpyridine (terpy) coordination polymers (1-11) which employ a dual ligand strategy have been synthesized hydrothermally and structurally characterized by single crystal and powder X-ray diffraction. Two additional members of the series (12 and 13) were made with Ce3+ and Pr3+ and characterized via powder X-ray diffraction only. The series is comprised of three similar structures wherein differences due to the lanthanide contraction manifest in Ln(3+) coordination number as well as the number of bound and solvent water molecules within the crystal lattice. Structure type I (Ce3+-Sm3+) contains two nine-coordinate Ln(3+) metal centers each with a bound water molecule. Structure type II (Eu3+-Ho3+) features a nine and an eight coordinate Ln(3+) metal along with one bound and one solvent water molecule. Structure type III (Er3+-Lu3+) includes two eight-coordinate Ln(3+) metal centers with both water molecules residing in the lattice. Assembly into supramolecular 3D networks via p-p interactions is observed for all three structure types, whereas structure types II and III also feature hydrogen-bonding interactions via the well-known C-H center dot center dot center dot O and O-H center dot center dot center dot O synthons. Visible and near-IR luminescence studies were performed on compounds 1, 2, 10, and 13 at room temperature. As a result characteristic near-IR luminescent bands of Pr3+, Nd3+, Sm3+, and Yb3+ as well as visible bands of Sm3+ were observed44361584315854COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP46711202009/54066-7United States Department of Energy (DOE); George Washington Universit

Photophysical properties of asymmetric and water-soluble dinuclear lanthanide complexes of poly glycol chain functionalized-benzoic acid derivative: experimental and theoretical approaches

New water-soluble lanthanide complexes with a poly glycol chain (–OEtOEtOEtOMe) functionalized benzoic acid derivative ligand were synthesized and photophysically characterized. The results indicate a formation of an asymmetric dinuclear lanthanide complexes. The [Eu2(mee)6(H2O)2] complex shows emission in water solution and it was noted that after 48 h part of the ligands are replaced by water molecules resulting on quenching of the emission and decreasing of lifetimes by O–H oscillators from water molecules. The average Judd–Ofelt intensity parameters were determined experimentally from emission spectra of the europium(III) complex. Additionally, the contribution of each asymmetric europium(III) center to the JO intensity parameters were calculated independently using time resolved spectroscopy and the LUMPAC software helping the proposition of the polyhedral coordination sphere determined by the ground state geometry using the Sparkle/PM3 model. The transfer and back energy transfer rates were also calculated. The values obtained for energy transfer rates are lower than previous values obtained for europium(III) complexes with benzoic acid derivative ligands, indicating the role of the poly glycol chain on photophysical properties of the [Eu2(mee)6(H2O)2] complex.6103101133101141CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP159249/2014-7Sem informação2015/22426-5; 2013/22127-

Study of optical absorption, visible emission and NIR-vis luminescence spectra of Tm3+/Yb3+, Ho3+/Yb3+ and Tm3+/Ho3+/Yb3+ doped tellurite glasses

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOTm3+/Yb3+, Ho3+/Yb3+ co-doped and Tm3+/Ho3+/Yb3+ triply doped TeO2-Bi2O3-ZnO-Li2O-Nb2O5 (TBZLN) tellurite glasses were prepared by melt quenching method. Judd-Ofelt intensity parameters (Omega(lambda), lambda=2, 4 and 6), radiative transition probabilities, branching ratios and radiative lifetimes of Tm3+, Ho3+ ions in co-doped TBZLN glasses were calculated from the optical absorption spectra. Excitation, visible luminescence and decay lifetimes in visible region were also investigated. The stimulated emission and gain cross-sections for the Tm3+:F-3(4) -> H-3(6) (1700 nm) and Ho3+:I-5(7) -> I-5(8) (1956 nm) transitions in co-doped TBZLN glasses have been analyzed and compared with those of other reported glasses. Up-conversion luminescence was observed in TBZLN glasses under 980 nm laser excitation and energy transfer mechanisms have been discussed. Finally, CIE color co-ordinates were calculated and it is observed that the color co-ordinates fall in blue and green regions for Tm3+/Yb3+ and Ho3+/Yb3+ co-doped TBZLN glasses, respectively. A subsequent shift in color co-ordinates from green to greenish-yellow region has been observed with an increase in the concentration (0.1, 0.5 and 1.0 mol%) of Tm3+ ions in Tm3+/Ho3+/Yb3+ triply doped TBZLN glasses. (C) 2015 Elsevier B.V. All rights reserved.Tm3+/Yb3+, Ho3+/Yb3+ co-doped and Tm3+/Ho3+/Yb3+ triply doped TeO2-Bi2O3-ZnO-Li2O-Nb2O5 (TBZLN) tellurite glasses were prepared by melt quenching method. Judd-Ofelt intensity parameters (Omega(lambda), lambda=2, 4 and 6), radiative transition probabilities, branching ratios and radiative lifetimes of Tm3+, Ho3+ ions in co-doped TBZLN glasses were calculated from the optical absorption spectra. Excitation, visible luminescence and decay lifetimes in visible region were also investigated. The stimulated emission and gain cross-sections for the Tm3+:F-3(4) -> H-3(6) (1700 nm) and Ho3+:I-5(7) -> I-5(8) (1956 nm) transitions in co-doped TBZLN glasses have been analyzed and compared with those of other reported glasses. Up-conversion luminescence was observed in TBZLN glasses under 980 nm laser excitation and energy transfer mechanisms have been discussed. Finally, CIE color co-ordinates were calculated and it is observed that the color co-ordinates fall in blue and green regions for Tm3+/Yb3+ and Ho3+/Yb3+ co-doped TBZLN glasses, respectively. A subsequent shift in color co-ordinates from green to greenish-yellow region has been observed with an increase in the concentration (0.1, 0.5 and 1.0 mol%) of Tm3+ ions in Tm3+/Ho3+/Yb3+ triply doped TBZLN glasses.166816FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP [12/50480-6]FAPESP [2009/54066-7]2009/54066-7, 12/50480-6This work is financially supported by FAPESP, Grant # 12/50480-6. The authors would like to thank the Group of ultrafast phenomena and Optical Communications (GFURCO) and the Laboratory of Advanced Optical Spectroscopy (LMEOA//FAPESP Grant # 2009/54066-7) for providing lab facilities

Controlling dimensionality via a dual ligand strategy in Ln-thiophene-2,5-dicarboxylic acid-terpyridine coordination polymers

Eleven new lanthanide-2,5-TDC-terpyridine coordination polymers which employ a dual ligand strategy have been synthesized and characterized by single crystal and powder X-ray diffraction as well as luminescence spectroscopy.</p