- Spectroscopy and upconversion mechanisms of CsCdBr3:Dy3+
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The upconversion luminescence of a Dy3+-doped system is presented and analyzed. CsCdBr3:x% Dy3+ (x = 0.2,1,5) was synthesized and grown as crystals using the Bridgman technique. Dy3+ ions preferentially enter this host as charge-compensated dimers. Due to the low-phonon energy the efficiency of multiphonon-relaxation processes is significantly reduced in this host compared to oxides and fluorides. Yellow-green upconversion luminescence originating from 4F9/2 can be induced upon excitation into 6F5/2 or 6F3/2 in the near infrared (NIR). Depending on the excitation wavelength, upconversion occurs by an energy-transfer or excited-state absorption mechanism. The two are distinguished by their temporal behavior after an excitation pulse. Analysis of the upconversion-luminescence transient of CsCdBr3:0.2% Dy3+ at 10 K leads to a rate constant Wt = 165 s-1 for the energy-transfer step. This is very small, and thus upconversion based on one excitation wavelength is inefficient. In addition, the intermediate NIR level 6F5/2 is significantly depopulated by multiphonon relaxation at room temperature.
- Wermuth, Markus,Riedener, Toni,Guedel, Hans U.
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- Lanthanide containing ionic liquid crystals: EuBr2, SmBr 3, TbBr3 and DyBr3 in C12mimBr
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Doping the ionic liquid crystal C12mimBr with various lanthanide halides yields interesting novel liquid crystalline and luminescent materials. The thermal phase behavior of all compounds was investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry and the photophysical properties were determined by luminescence spectroscopy. C 12mimBr itself is an ionic liquid crystal that shows bluish-white emission upon excitation with UV light due to transitions in the imidazolium p-system. Doping lanthanide bromides into C12mimBr with concentrations of about 1 mol-% does not affect the liquid crystalline behavior of the host materials to a great extent and room temperature liquid crystals are obtained. All materials show an appreciable luminescence. EuBr2 in C12mimBr yields a material, which shows a blue emission originating from 4f-5d-transitions. SmBr3-doped samples show a red and TbBr 3 samples a green luminescence. Upon doping C12mimBr with DyBr3 an orange luminescent liquid crystalline material is obtained. Most interestingly the emission color for the TbBr3 and DyBr 3 containing materials can be tuned from bluish-white (mainly C 12mimBr emission) to green (for TbBr3) and orange-yellow (for DyBr3) depending on the wavelength of the excitation light used.
- Getsis, Anna,Mudring, Anja-Verena
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p. 1726 - 1734
(2011/01/07)
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- Structural characterization of methanol substituted lanthanum halides
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The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]-0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4-6 were slightly higher in comparison to their hydrated counterparts.
- Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
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p. 1784 - 1795
(2010/07/03)
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- Systematics and anomalies in rare earth/aluminum bromide vapor complexes: Thermodynamic properties of the vapor complexes LnAl3Br12 from Ln = Sc to Ln = Lu
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Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by the phase equilibrium-quenching experiments. The measurements suggest that the LnAl3Br12 complexes are the predominant vapor compl
- Wang, Zhi-Chang,Yu, Jin
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p. 4248 - 4255
(2008/10/09)
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- M3NS3 (M = La - Nd, Sm, Gd - Dy): Structure and magnetism of 3:1:3-type nitride sulfides of trivalent lanthanides
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Nitride sulfides of the trivalent lanthanides with the composition M 3NS3 (M = La - Nd, Sm, Gd - Dy) can be prepared by the oxidation of the respective lanthanide metal with sulfur, sodium azide (NaN 3), and the corresponding lanthanide tribromide (MBr3) when an additional flux (NaBr) is used. Temperature ranges from 800 to 900 °C for the thermal treatment of the reaction mixtures in evacuated silica tubes secure the formation of bright to dark brown, transparent, lath shaped single-crystals. The orthorhombic crystal structure (Pnma, Z = 4) was determined from single-crystal X-ray diffraction data (La3NS3: a = 1215.13(5), b = 415.90(2), c = 1322.12(5) pm, Ce3NS3: a = 1206.28(4), b = 410.16(1), c = 1307.18(5) pm, Pr3NS3: a = 1205.45(7), b = 405.35(2), c = 1297.58(8) pm, Nd3NS3: a = 1207.82(5), b = 401.31(1), c = 1295.20(4) pm, Sm3NS3: a = 1201.58(6), b = 394.84(2), c = 1285.63(7) pm, Gd3NS3: a = 1197.17(7), b = 388.22(3), c = 1286.92(8) pm, Tb3NS3: a = 1191.62(7), b = 385.07(3), c = 1282.44(8) pm, and Dy3NS3: a = 1187.66(7), b = 382.55(3), c = 1276.77(8) pm). There are three crystallographically different M3+ cations present in coordination of both the N3- and the S2- anions. However, [NM 4]9+ tetrahedra connected via two common corners (c) to form linear chains ∞1{[N(M1)1/1 t(M2)1/1t(M3)2/2c] 6+} along [010] build up the main structural feature. A non-linear behaviour for the decreasing lattice constants of the pseudo-isotypic series from La3NS3 to Dy3NS3 concerning the a- and c-axes is observed along with the lanthanoid contraction caused by the diminishing coordination sphere of (M1)3+ (CN = 7) and (M3) 3+ (CN = 7) moving from the light to the heavier lanthanides. Curie-Weiss-type magnetic behaviour for Dy3NS3 with μeff = 10.3(1) μB for DyN1/3S corresponding to a 6H15/2 groundstate for Dy3+ at higher temperatures and antiferromagnetic ordering of the Dy3+ moments below 5 K is observed.
- Lissner, Falk,Meyer, Monika,Kremer, Reinhard K.,Schleid, Thomas
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p. 1995 - 2002
(2008/10/09)
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- Synthesis and crystal structure of (NH4)3Cu4Ho2Br13. Further bromides of the (NH4)3Cu4M2Br13 Type (M = Dy-Lu, Y) and on Rb3Cu4Ho2Br13
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Single crystals of (NH4)3Cu4Ho2Br13 were obtained for the first time from the reaction of CuBr with HoBr3 which was contaminated with NH4Br: cubic, space group Pn3, Z = 2, a = 1101.71(5) pm. The crystal structure may be considered as a variant of the fluorite type according to [(HoBr6)4] [(NH4)6Cu4Br)2] ≡ Ca4F8. Pure products can be prepared from the binary halides in glass ampoules at 350°C. The bromides (NH4)3Cu4M2Br13 (M = Dy-Lu, Y) and Rb3Cu4Ho2Br13 are isotypic with (NH4)3Cu4Ho2Br13. Johann Ambrosius Barth 1996.
- Wickleder, Mathias S.,Bohnsack, Andreas,Meyer, Gerd
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p. 675 - 678
(2008/10/09)
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- COMPLEXES OF YTTRIUM AND LANTHANIDE BROMIDES WITH 4-N-(2'-HYDROXYBENZYLIDENE)AMINOANTIPYRINEY
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Ten new complexes of bromides of yttrium and lanthanides with 4-N-(2'-hydroxybenzylidene)aminoantipyrine (HBAAP) having the formula [Ln(HBAAP)2Br2]Br, where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er have been prepared and characterized. Molar conductance studies indicate 1:1 electrolytic behaviour for these complexes. Their infrared spectra show that HBAAP acts as a neutral tridentate ligand coordinatin throuhg the carbonyl oxzgen, azomethine nitrogen and phenolic oxygen. Electronic spectra showthe week covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to about 170.degree .C and undergo decomposition in two stages forming the respective metal bromides as the final products.
- Joseph, M.,Nair, M. K. M.,Radhakrishnan, P. K.
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p. 1331 - 1344
(2008/10/09)
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