BaLn2Se4 (Ln = Er,Tm and Yb)

The compounds BaLn₂Se₄ (Ln = rare‐earth metal = lanthanide = Er, Tm and Yb), namely barium di(erbium/thulium/ytterbium) tetraselenide, crystallize in the orthorhombic space group Pnma in the CaFe₂O₄ structure type. In this structure type, all atoms possess m symmetry. The Ln atoms are octahedrally coordinated by six Se atoms. A three‐dimensional channel structure is formed by the corner‐ and edge‐sharing of these LnSe₆ octahedra. The Ba atoms are coordinated to eight Se atoms in a bicapped trigonal–prismatic arrangement, and they occupy the channels of the three‐dimensional framework.     

Coordination polyhedra LnOn (Ln = Er, Tm, Yb, Lu) in crystal structures

The Voronoi-Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to analyze crystal structures of 728 compounds containing 976 crystallographically non-equivalent sorts of LnO_n polyhedra (Ln = Er, Tm, Yb, Lu). The Ln C.N. vary from 3 to 10, and 14 sorts of coordination polyhedra are present in the structures. Despite the great diversity of C.N., the volume of the VDP was found to depend only on the nature of the Ln atom and its valence state.     

Preparation and crystal structure of the Isotypic Carbides Ln4Ni2C5 (Ln = Er,Tm, Yb and Lu)

The title compounds were prepared from the elemental components in a lithium flux. Their crystal structure was determined for the ytterbium compound from single-crystal X-ray data. It is orthorhombic, Pmm2, a = 352.88(6) pm, b = 1 143.0(3) pm, c = 366.16(6) pm, Z = 1, R = 0.020 for 1 261 structure factors and 29 variable parameters. The structure may be viewed as an intergrowth of slabs consisting of the CeNiC₂ and the ScC (NaCl type) structures. It thus contains C₂ pairs with a C? C distance of 138(1) pm and isolated carbon atoms. Together with the nickel atoms the C₂ pairs form one-dimensionally infinite building elements [Ni₂C₄]_n. The fifth carbon atom is octahedrally coordinated by ytterbium atoms. Accordingly the compound may be rationalized to a first approximation with the formula (Yb³⁺)₄[Ni₂C₄^8?]C^4?. Yb₄Ni₂C₅ shows Curie-Weiss behaviour with a magnetic moment of μ_exp = 4.44 μ_B per ytterbium atom in good agreement with the theoretical moment of μ_eff = 4.53 μ_B for Yb³⁺.     

Ordered phases in Ln-S systems (Ln = Tm, Yb)

The structures of known defect ordered phases present in Ln-X systems (50-60 at.% X) are analyzed and systematized according to the concentration of cation vacancies as cubic and trigonal phases. The structures of the defect phases present in Ln-X systems (X = S, Se, Te) are modeled by ordering the cation vacancies along (111) in the basic NaCl structure (ao~5.6 A). The following structures were derived: α-NaFeO₂ and defect structures on its basis Sc_I.37[]_0.62S₂, CaHo₂Se₄ (a_hex = 2a₀√2/4, Chex = 2a₀√3 a_R = 2a₀√6/4, α_R = 33?), CaY₂Se₄ ( a_hex = 2a₀√2/2, c_hex = 2a₀√3: a_R = 2a₀√2/2, α_R = 60?), and EuEr₂Te₄ ( a_hex = a₀√6/2, c_hex = a₀√3 ). All these phases except the last one may be obtained from NaCl by using direct rhombohedral distortion, and the last phase is a superstructure of a rhombohedral cell with parameters a_R ~ 2a₀√2/2, α_R ~ 60?. The solutionmelt method (eutectic mixture 1.86NaCl-NiCl₂ with Tm(Yb):S from 1:3 to 1:10) was used to synthesize poly crystalline samples containing two new trigonal defect phases of possible composition Ln_1+x+[]_1-xS² with cell parameters a = 3.835(7), c = 18.89(4) Å and a = 3.83(3), c= 18.78(1) A (I) and also a = 7.749(7), c = 18.46(3) Å and a = 7.74(1), c = 18.41(3) A (II) in Tm-S and Yb-S systems, respectively. It is maintained that the crystal structure of phase I with x ~ 0.37 (space group R3m) is derived from the NaCl structure and is close to Sc_1.37[]_0.63S₂ and the crystal structure of phase II with x~0.34 (space group P3cl) is derived from the Ni As structure. Possible ordering of cations with different formal charges accompanied by variation of symmetry is discussed.     

Controllable synthesis and up-conversion properties of tetragonal BaYF5:Yb/Ln (Ln=Er, Tm, and Ho) nanocrystals

The nanocrystals (NCs) of tetragonal barium yttrium fluoride (BaYF(5)) doped 1 mol% Ln(3+) (Ln=Er, Tm, Ho) and 20 mol% Yb(3+) with different morphologies and sizes have been successfully synthesized through a facile hydrothermal method. The influences of pH values of the initial solution and fluorine sources on the final structure and morphology of the products have been well investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the size, structure and morphology of these samples prepared at different conditions. And it is found that BaYF(5):Yb/Ln NCs prepared at pH value of 10 using NaBF(4) as F(-) source have a uniform spherical morphology with average diameter of 25 nm. Additionally, the up-conversion (UC) properties of Yb/Er, Yb/Tm, and Yb/Ho doped BaYF(5) nanoparticles were also discussed. Under 980 nm laser excitation, the BaYF(5):Yb/Er, BaYF(5):Yb/Tm, and BaYF(5):Yb/Ho NCs exhibit green, whitish blue, and yellow green UC luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

Controllable synthesis and tunable luminescence properties of Y2(WO4)3:Ln3+ (Ln = Eu, Yb/Er, Yb/Tm and Yb/Ho) 3D hierarchical architectures

Yttrium tungstate precursors with novel 3D hierarchical architectures assembled from nanosheet building blocks were successfully synthesized by a hydrothermal method with the assistance of sodium dodecyl benzenesulfonate (SDBS). After calcination, the precursors were easily converted to Y(2)(WO(4))(3) without an obvious change in morphology. The as-prepared precursors and Y(2)(WO(4))(3) were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra, respectively. The results reveal that the morphology and dimensions of the as-prepared precursors can be effectively tuned by altering the amounts of organic SDBS and the reaction time, and the possible formation mechanism was also proposed. Upon ultraviolet (UV) excitation, the emission of Y(2)(WO(4))(3):x mol% Eu(3+) microcrystals can be tuned from white to red, and the doping concentration of Eu(3+) has been optimized. Furthermore, the up-conversion (UC) luminescence properties as well as the emission mechanisms of Y(2)(WO(4))(3):Yb(3+)/Ln(3+) (Ln = Er, Tm, Ho) microcrystals were systematically investigated, which show green (Er(3+), (4)S(3/2), (2)H(11/2)→(4)I(15/2)), blue (Tm(3+), (1)G(4)→(3)H(6)) and yellow (Ho(3+), (5)S(2)→(5)I(8)) luminescence under 980 nm NIR excitation. Moreover, the doping concentration of the Yb(3+) has been optimized under a fixed concentration of Er(3+) for the UC emission of Y(2)(WO(4))(3):Yb(3+)/Er(3+).     

Highly uniform and monodisperse beta-NaYF(4):Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln3+ (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu3+ (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to 5D0-3 --> 7FJ (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively. When doped with 5% Tb3+ ions, the strong DC fluorescence corresponding to 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions with 5D4 --> 7F5 (green emission at 544 nm) being the most prominent group that has been observed. In addition, under 980 nm laser excitation, the Yb3+/Er3+- and Yb3+/Tm3+-codoped beta-NaYF4 samples exhibit bright green and whitish blue up-conversion (UC) luminescence, respectively. The luminescence mechanisms for the doped lanthanide ions were thoroughly analyzed.     

Microwave synthesis and photoluminescent properties of Sr2CeO4/Ln3+ (Ln = Er, Ho, Tm)

Sr₂CeO₄/Ln³⁺ (Ln = Er, Ho, Tm) phosphors were synthesized with the microwave radiation method for the first time. The luminescent properties of the samples were investigated and the up-conversion luminescence of Er³⁺, Ho³⁺ and Tm³⁺ doped Sr₂CeO₄ phosphors was observed. The spectra indicate that the energy transfer takes place from the triplet excited state of MLCT (metal-to-ligand charge transfer) state for Sr₂CeO₄ (sensitizer) to the rare earth ions (activator). __________ Translated from Journal of Hebei Normal University (Natural Science Edition), 2007, 31(2): 212–216 [译自: 河北师范大学学报 (自然科学版)]     

系列Ln(Ⅲ)配位聚合物的合成、结构及光物理性能(Ln(Ⅲ)=Yb、Ho、Er)

采用水热方法合成了3个Ln(Ⅲ)配位聚合物：[Ln(NH₂-C₆H₄-COO)₂DMF(HCOO)(H₂O)]_n(Ln=Yb 1,Ho 2,Er 3);通过X-单晶衍射、红外光谱(IR)、紫外吸收光谱(UV-Vis-NIR)、发射光谱(紫外可见荧光光谱和近红外发射光谱)等方法对化合物进行了表征。结果表明,化合物1、     

Synthesis and thermal decomposition of CH3NH3Ln(SO4)2.4H2O (Ln=Tm,Yb OR Lu)

The double sulfates of Tm, Yb and Lu with monomethylammonium were obtained by evaporation of an aqueous mixture of rare earths(III) sulfate and monomethylammonium sulfate at room temperature and treatment of the concentrated mixture with ethanol. After identification of the double sulfates, they were examined by means of TG, DTG and DTA analysis, from 20 to 700°. Two clearly separated stages of thermal decomposition were evident. It was possible to determine the stoichiometry of the obtained compounds from the TG curves.

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Zusammenfassung Die Doppelsulfate von Tm,Yb und Lu mit Monomethylammonium wurden durch Verdampfen eines wäßrigen Gemisches aus Seltenerden(III)-sulfaten und Monomethylammoniumsulfate bei Raumtemperatur und durch Behandlung des konzentrierten Gemisches mit Ethanol erhalten. Nach Identifizierung der Doppelsulfate wurden diese im Temperaturbereich 20–700° mittels TG, DTG und DTA- Analyse untersucht. Zwei eindeutig separate thermische Zersetzungsschritte wurden deutlich. Anhand der TG-Kurven war eine Bestimmung der Stöchiometrie der erhaltenen Verbindungen möglich.

     

Synthesis and characterization of Ln,Yb:BaGdF5 (Ln = Er,Ho) nanocrystals by hydrothermal method

The Er,Yb: BaGdF₅ and Ho,Yb: BaGdF₅ nanocrystal materials with the narrow particle size distribution was synthesized by a hydrothermal method at 180°C for 24 h. The phase structure and fluorescence properties were investigated by X-ray diffraction, scanning electron microscopy and up-conversion spectroscopy, respectively. The phase composition does not change with increasing the pH value, leading to the formation of a pure phase BaGdF₅, while the solution was turbid state. The products show a good crystallinity, dispersion and uniform particle size distribution. Under the LD excitation at 980 nm, Er,Yb: BaGdF₅ and Ho,Yb: BaGdF₅ nanocrystal materials were researched in the visible range of the fluorescence spectrum. Er,Yb: BaGdF₅ nanocrystals were achieved the launch of green, blue, and red. Ho,Yb: BaGdF₅ nanocrystal with green and red light output were realized. The light-emitting belong to the two-photon transition process. And the possible mechanism for the corresponding up-conversion luminescence was also discussed. The Er,Yb: BaGdF₅ and Ho,Yb: BaYbF₅ nanocrystals with the narrow particle size distribution have potential applications in biological field as luminescence probes.

     

Preparation and up-conversion luminescence of hollow La2O3:Ln (Ln = Yb/Er, Yb/Ho) microspheres

Hollow La(2)O(3):Ln (Ln = Yb/Er, Yb/Ho) microspheres with up-conversion (UC) luminescence properties were successfully synthesized via a facile sacrificial template method by employing carbon spheres as hard templates followed by a subsequent heating process. The structure, morphology, formation process, and fluorescent properties are well investigated by various techniques. The results indicate that the hollow La(2)O(3):Ln microspheres can be well indexed to the hexagonal La(2)O(3) phase. The hollow La(2)O(3):Ln microspheres with uniform diameter of about 270 nm maintain the spherical morphology and good dispersion of the carbon spheres template. The shell of the hollow microspheres consists of numerous nanocrystals with the thickness of approximately 40 nm. Moreover, the possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow La(2)O(3):Ln microspheres has also been proposed. The Yb/Er and Yb/Ho codoped La(2)O(3) hollow spheres exhibit bright up-conversion luminescence with different colors derived from different activators under the 980 nm NIR laser excitation. Furthermore, the doping concentration of the Yb(3+) is optimized under fixed concentration of Er(3+)/Ho(3+). This material may find potential applications in drug delivery, hydrogen and Li ion storage, and luminescent displays based on the uniform hollow structure, dimension, and UC luminescence properties.     

Syntheses,structures, and properties of the bis(cyclopentadienyl) rare-earth imidodiphosphinochalocogenido compounds Cp2Ln[N(QPPh2)2] (Ln = La,Gd, Er,or Yb for Q = Se; Ln = Yb for Q = S)

The compounds Cp2Ln[N(QPPh2)2] (Ln = La (1), Gd (2), Er (3), or Yb (4) for Q = Se, Ln = Yb (5) for Q = S) have been synthesized from the corresponding rare-earth tris(cyclopentadienyl) compound and H[N(QPPh2)2]. The structures of compounds 1, 2, 3, and 5, as determined by X-ray crystallography, consist of a Cp2Ln fragment, coordinated eta 3 through two chalcogen atoms and an N atom of the imidodiphosphinochalcogenido ligand [N(QPPh2)2]-. In compound 4, the Cp2Yb moiety is coordinated eta 2 through the two Se atoms of the [N(SePPh2)2]-ligand. 31P and 77Se (for 1) NMR spectroscopies lend insight into the solution nature of these species. Crystal data: 1, C34H30LaNP2Se2, triclinic, P1, a = 9.7959(10) A, b = 12.4134(13) A, c = 13.9077(14) A, alpha = 88.106(2) degrees, beta = 88.327(2) degrees, gamma = 68.481(2) degrees, V = 1572.2(3) A3, T = 153 K, Z = 2, and R1(F) = 0.0257 for the 5947 reflections with I > .2 sigma(I); 2, C34H30GdNP2Se2, triclinic, P1, a = 9.7130(14) A, b = 12.2659(17) A, c = 13.953(2) A, alpha = 88.062(2) degrees, beta = 87.613(2) degrees, gamma = 69.041(2) degrees, V = 1550.7(4) A3, T = 153 K, Z = 2, and R1(F) = 0.0323 for the 5064 reflections with I > 2 sigma(I); 3, C34H30ErNP2Se2, triclinic, P1, a = 9.704(2) A, b = 12.222(3) A, c = 13.980(4) A, alpha = 88.230(4) degrees, beta = 87.487(4) degees, gamma = 69.107(4) degrees, V = 1547.4(7) A3, T = 153 K, Z = 2, and R1(F) = 0.0278 for the 6377 reflections with I > 2 sigma(I); 4, C34H30NP2Se2Yb.C4H8O, triclinic, P1, a = 12.087(4) A, b = 12.429(4) A, c = 23.990(7) A, alpha = 89.406(5) degrees, beta = 86.368(5) degrees, gamma = 81.664(5) degrees, V = 3558.8(18) A3, T = 153 K, Z = 4, and R1(F) = 0.0321 for the 11,883 reflections with I > 2 sigma(I); and 5, C34H30NP2S2Yb, monoclinic, P21/n, a = 13.8799(18) A, b = 12.6747(16) A, c = 17.180(2) A, beta = 91.102(3) degrees, V = 3021.8(7) A3, T = 153 K, Z = 4, and R1(F) = 0.0218 for the 6698 reflections with I > 2 sigma(I).     

Syntheses,Crystal Structures,and Optical and Magnetic Properties of Some CsLnCoQ3 Compounds (Ln = Tm and Yb,Q = S; Ln = Ho and Yb,Q = Se)

The four new compounds CsTmCoS₃, CsYbCoS₃, CsHoCoSe₃, and CsYbCoSe₃ have been synthesized at 1123 K. These black‐colored isostructural compounds crystallize in the KZrCuS₃ structure type with four formula units in space group Cmcm of the orthorhombic system. The structure of these compounds is composed of layers separated by Cs atoms. Because there are no Q–Q bonds, the formal oxidation states of Cs/Ln/Co/Q are 1+/3+/2+/2?, respectively. CsHoCoSe₃ shows paramagnetic behavior with μ_eff = 11.9(1) μ_B, whereas CsYbCoS₃ displays an antiferromagnetic‐like transition at ～2.7 K with μ_eff = 5.85(1) μ_B. Both CsYbCoS₃ and CsYbCoSe₃ exhibit optical band gaps in the near infrared region and broad absorption bands at lower energies.     

Ln4(CH2)4 cubane-type rare-earth methylidene complexes consisting of "(C5Me4SiMe3)LnCH2" units (Ln = Tm, Lu)

Tetranuclear cubane-type rare-earth methylidene complexes consisting of four "Cp'LnCH(2)" units, [Cp'Ln(μ(3)-CH(2))](4) (4-Ln; Ln = Tm, Lu; Cp' = C(5)Me(4)SiMe(3)), have been obtained for the first time through CH(4) elimination from the well-defined polymethyl complexes [Cp'Ln(μ(2)-CH(3))(2)](3) (2-Ln) or mixed methyl/methylidene precursors such as [Cp'(3)Ln(3)(μ(2)-Me)(3)(μ(3)-Me)(μ(3)-CH(2))] (3-Ln). The reaction of the methylidene complex 4-Lu with benzophenone leads to C═O bond cleavage and C═C bond formation to give the cubane-type oxo complex [Cp'Lu(μ(3)-O)](4) and CH(2)═CPh(2), while the methyl/methylidene complex 3-Tm undergoes sequential methylidene addition to the C═O group and ortho C-H activation of the two phenyl groups of benzophenone to afford the bis(benzo-1,2-diyl)ethoxy-chelated trinuclear complex [Cp'(3)Tm(3)(μ(2)-Me)(3){(C(6)H(4))(2)C(O)Me}] (6-Tm).     

Palladium(II)-selenoether complexes as new single source precursors: first synthesis of Pd4Se and Pd7Se4 nanoparticles

Pd(4)Se and Pd(7)Se(4) nanoparticles (size 38-104 nm), protected by TOP, have been obtained for the first time using Pd(II) ligated with selenated primary and secondary amines (see 1 and 2) as single source precursors respectively. TEM, SEM, powder XRD and photoluminescence have been used to characterize them. 1 and 2 are also the first Pd(II)-selenoether complexes used for the synthesis of nanoparticles containing palladium and selenium.     

Crystal-chemical features of monoclinic lanthanide oxobromotungstates of composition LnWO4Br (Ln = Eu, Gd, Dy, Er, Yb)

The crystal-chemical properties of lanthanide oxobromotungstates of composition LnWO₄Br (Ln = Eu, Gd, Dy, Er, Yb) are studied. The crystal system and space group for the oxobromotungstates are determined. The unit cell parameters are refined. The parameters a, b, c, and V of the LnWO₄Br compounds are studied as functions of the atomic number of the lanthanide. Analytical equations are derived to predict unit cell parameters for unsynthesized lanthanide oxobromotungstates of the class in question.     

Syntheses, structures and properties of seven isomorphous 1D Ln3+complexes Ln(BTA)(HCOO)(H2O)3 (H2BTA = bis(tetrazoly)amine, Ln = Pr, Gd, Eu, Tb, Dy, Er, Yb) and two 3D Ln3+ complexes Ln(HCOO)3 (Ln = Pr, Nd)

Seven isomorphous 1D chain Ln3+ complexes Ln(BTA)(HCOO)(H2O)3 (Ln = Pr (1), Gd (2), Eu (3), Tb (4) Dy (5), Er (6) and Yb (7)), and two formate coordinating and bridging 3D Ln3+ complexes Ln(HCOO)3 (Ln = Pr (8) and Nd (9)) have been synthesized and characterized by single crystal X-ray diffraction analysis. Although the Ln3+ ions in 1-7 have different radius, the trivalent lanthanide ions in 1-7 show the same coordinated environment. The well-defined single crystal structures of 8 and 9 are first samples for formate-bridged Ln3+ metallic complexes. The luminescent properties of solid samples of 2-5 at room temperature and the magnetic property of 2 have been also reported and discussed in this paper.     

Near-infrared luminescent hybrid materials doped with lanthanide (Ln) complexes (Ln = Nd, Yb) and their possible laser application

The crystal structures of ternary Ln(DBM)(3)phen complexes (DBM = dibenzoylmethane, phen = 1,10-phenanthroline, and Ln = Nd, Yb) and their in situ syntheses via the sol-gel process are reported. The properties of the Ln(DBM)(3)phen complexes and their corresponding Ln(3+)/DBM/phen-co-doped luminescent hybrid gels obtained via an in situ method (Ln-D-P gel) have been studied. The results reveal that the lanthanide complexes are successfully in situ synthesized in the corresponding Ln-D-P gels. Both Ln(DBM)(3)phen complexes and Ln-D-P gels display sensitized near-infrared (NIR) luminescence upon excitation at the maximum absorption of the ligands, which contributes to the efficient energy transfer from the ligands to the Ln(3+) ions (Ln = Nd, Yb), an antenna effect. The radiative properties of the Nd(3+) ion in a Nd-D-P gel are discussed using Judd-Ofelt analysis, which indicates that the (4)F(3/2) --> (4)I(11/2) transition of the Nd(3+) ion in the Nd-D-P gel can be considered as a possible laser transition.