Chemical pressure effects on the spectroscopic properties of Nd3+-doped gallium nano-garnets

[EN] Nd3+-doped RE3Ga5O12 (RE = Gd, Y, and Lu) nano-crystalline garnets of 40-45 nm in size have been synthesized by a sol-gel method. With the decrease of the RE atom size, the chemical pressure related to the decreasing volumes of the GaO4 tetrahedral, GaO6 octahedral and REO8 dodecahedral units drive the nano-garnets toward a more compacted structure, which is evidenced by the change of the vibrational phonon mode frequencies. The chemical pressure also increases the crystal-field strength felt by the RE3+ ions while decreases the orthorhombic distortion of the REO8 local environment. These effects alter the absorption and emission properties of the Nd3+ ion measured in the near-infrared luminescence range from 0.87 to 1.43 ¿m associated with the 4 F3/2¿4 IJ (J = 9/2, 11/2, 13/2) transitions. The 4 F3/2 luminescence decay curves show non-exponential behavior due to dipole-dipole energy transfer interactions among Nd3+ ions that increases with pressure.Authors are grateful to The Governments of Spain and India for the Indo-Spanish Joint Programme of Bilateral Cooperation in Science and Technology (PRI-PIBIN-2011-1153/DST-INT-Spain-P-38-11). Dr. Venkatramu is grateful to DAE-BRNS, Government of India for the award of DAE Research Award for Young Scientist (No. 2010/20/34/5/BRNS/2223). This work have been partially supported by MINECO under The National Program of Materials (MAT2013-46649-C4-2-P/-3-P/-4-P), The Consolider-Ingenio 2010 Program (MALTA CSD2007-00045), by Fundacion CajaCanarias (ENER-01), and by the EU-FEDER funds. V. Monteseguro wishes to thank MICINN for the FPI grant (BES-2011-044596). Authors also thank Agencia Canaria de Investigacion, Innovacion y Sociedad de la Informacion for the funds given to Universidad de La Laguna, co-financed by The European Social Fund by a percentage of 85%.Monteseguro, V.; Rathaiah, M.; Linganna, K.; Lozano-Gorrin, AD.; Hernandez-Rodriguez, MA.; Martin, IR.; Babu, P.... (2015). Chemical pressure effects on the spectroscopic properties of Nd3+-doped gallium nano-garnets. Optical Materials Express. 5(8):1661-1673. https://doi.org/10.1364/OME.5.001661S1661167358Pollnau, M., Hardman, P. ., Clarkson, W. ., & Hanna, D. . (1998). Upconversion, lifetime quenching, and ground-state bleaching in Nd3+:LiYF4. Optics Communications, 147(1-3), 203-211. doi:10.1016/s0030-4018(97)00524-5Brandle, C. D., & Barns, R. L. (1974). Crystal stoichiometry of Czochralski grown rare-earth gallium garnets. Journal of Crystal Growth, 26(1), 169-170. doi:10.1016/0022-0248(74)90223-1Venkatramu, V., Giarola, M., Mariotto, G., Enzo, S., Polizzi, S., Jayasankar, C. 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Synthesis and evaluation of antimitotic activity of alkylated 2-amino-1,3,4-oxadiazole derivatives

Series of N-alkylated-2-amino-1,3,4-oxadiazoles (2) were synthesized via alkylation of 2-amino-1,3,4-oxadiazoles (1) under phase transfer condition. This paper also describes the study of antimitotic activity of these molecules by onion root tip method. (C) 2000 Elsevier Science S.A. All rights reserved

<span style="font-size:12.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-ansi-language: EN-IN;mso-fareast-language:EN-IN;mso-bidi-language:AR-SA" lang="EN-IN">Synthesis of bishydrazones (aldazines)¹ </span>

1126-1128<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">Bishydrazones have been prepared by thermolysis of aldehyde hydrazone under reduced pressure in a sealed tube at 120-30°C. The possible mass spectral fragementation mode of bishydrazones have also been discussed.</span

Luminescence and decay characteristics of Tb3+-doped fluorophosphate glasses

Tb3+-doped fluorophosphate glasses with the composition of P2O5–K2O–SrF2–Al2O3–x Tb4O7 (where x = 0.1, 0.5, 1.0, 2.0 and 4.0 mol%) were prepared by a conventional high temperature melt quenching technique and characterized through absorption, emission, excitation and decay measurements. From the emission studies, a strong green emission at around 546 was observed, which corresponds to the 5D4 → 7F5 transition of Tb3+ ion. Green/blue intensity ratios (IG/IB) were evaluated as a function of Tb3+ concentration and vice versa. Higher IG/IB intensity ratio confirms the higher covalency between Tb–O bond and higher asymmetry around the Tb3+ ions in the present fluorophosphate glasses. The decay curves for the 5D4 level of Tb3+ ion were measured and found that they exhibited single exponential nature irrespective to the dopant concentration. The experimental lifetime was determined using single exponential fitting and found that it increased from 2.65 to 2.95 ms when Tb3+ concentration increased from 0.1 mol% to 4.0 mol%. The derived properties were compared to the other Tb3+-doped glasses in order to see the potentiality of the material for visible laser gain media at 546 nm

Effect of WO3 on physical and magneto-optical properties of TeO2–La2O3–WO3 glasses for magneto-optics application

The ternary TeO2–La2O3–WO3 glasses with a formula of (100 − y − x)TeO2–yLa2O3–xWO3 (y = 5 and 10 mol%; x  = 10 to 25 mol%) were made by the melting and casting method for high Verdet constant diamagnetic magneto-optical (MO) materials in the application of MO devices operating at 1550 nm. The compositional effects of WO3 and La2O3 contents on key glass properties of thermal stability, Knoop hardness, optical transmission, and Verdet constant, were systematically studied for both series of glasses. High transparency level (T: >70 %) in the region from 0.4 to 5.2 μm and a high refractive index (n: 2.05 at 1550 nm) were obtained in the studied glasses. The tellurite glasses with 5 mol% of La2O3 exhibited higher thermal stability and refractive indices than those with 10 mol% La2O3. The 85TeO2–5La2O3–10WO3 glass exhibited a large Verdet constant value of 3.95 rad/(T·m) at 1550 nm among the studied glasses. These results show that the presented TeO2–La2O3–WO3 glasses have considerable potential as diamagnetic MO materials for MO device applications operating at 1550 nm

Synthesis, Structural Properties and Upconversion Emission of Er3+ and Er3+/Yb3+ Doped Nanocrystalline NaNbO3

Nanocrystalline sodium niobate (NaNbO3) powders doped with Er3+ and Er3+/Yb3+ ions have been successfully synthesized via Pechini sol\u2013gel method for the first time. The prepared NaNbO3 nanocrystalline compounds are single phase, with orthorhombic structure, and have an average particle size of 60 nm. The Raman investigation reveals a disorder nature of the host. Upon near infrared excitation with an 970 nm radiation, an intense green and a weaker red upconversion emission was observed from the 2H11/2, 4S3/2 4I15/2 and 4F9/2 4I15/2 transitions respectively, along with 1.55 !m emission from 4F13/2 !4I15/2 transition for both Er3+ doped and Er3+/Yb3+ codoped NaNbO3. A two photon process is found to be the origin of the upconverted emission. An enhancement of nearly 30 times of the upconverted emission is observed in the Er3+/Yb3+ codoped than the Er3+ doped NaNbO3, suggesting a possible use of the present materials in field where the upconversion properties can be useful, such as in solar cells or biomedical applications

Spectroscopic properties of tellurite glasses co-doped with Er3+ and Yb3+

Spectroscopic characterization of Er3+/Yb3+ co-doped tellurite glasses 70.8TeO2-5Al2O3-13K2O-(11-x)-BaO-0.2Er2O3-xYb2O3, where x=0, 0.4, 0.8, 1.2 and 2 mol% has been carried out through X-ray diffraction, Raman, absorption and luminescence spectra. The Judd-Ofelt intensity parameters were calculated for 0.2 mol% Er3+-doped glass and are used to evaluate radiative properties such as transition probabilities, branching ratios and radiative lifetime. The emission cross-section of the 4I13/2→4I15/2 transition has been calculated from the absorption data using McCumber's theory. The emission intensity of both, visible and infrared signals as a function of Yb2O3, have been studied under 980 nm and 375 nm laser excitation. The physical mechanisms responsible for both, visible and infrared signals in the tellurite samples have been explained in terms of the energy transfer and excited state absorption process. The FWHM of the 4I13/2→4I15/2 transition as a function of Yb2O3 mol% and distance (δ) between the laser focusing point and the end-face of the glass has been reported. It was observed both, experimentally and numerically, a change in the FWHM with variations of δ less than 8 mm. The latter was attributed to the radiation trapping effect. © 2015 Elsevier B.V. All rights reserved