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+).     

Uniform hollow Lu2O3:Ln (Ln = Eu3+, Tb3+) spheres: facile synthesis and luminescent properties

Uniform hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) phosphors have been successfully prepared via a urea-assisted homogeneous precipitation method using carbon spheres as templates, followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, kinetic decays, quantum yields (QY), and UV-visible diffuse reflectance spectra were employed to characterize the samples. The results show that hollow Lu(2)O(3):Ln spheres can be indexed to cubic Gd(2)O(3) phase with high purity. The as-prepared hollow Lu(2)O(3):Ln phosphors are confirmed to be uniform in shape and size with diameter of about 300 nm and shell thickness of approximate 20 nm. The possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow Lu(2)O(3):Ln microspheres has been proposed. Upon ultraviolet (UV) and low-voltage electron beams excitation, the hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) spheres exhibit bright red (Eu(3+), (5)D(0)-(7)F(2)) and green (Tb(3+), (5)D(4)-(7)F(5)) luminescence, which may find potential applications in the fields of color display and biomedicine.     

Synthesis and single-crystal x-ray diffraction examination of a structurally homologous series of tetracoordinate heteroleptic anionic lanthanide complexes: Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(L)3 (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb; (L)3 =(THF)3, (Et2O)3, (THF)2(Et2O)

Anhydrous lanthanide(III) chlorides (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) react with 3 equiv of lithium 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentanide, Li[N[Si(CH3)2CH2Ch2Si(CH3)2]], in THF or Et(2)O to afford the monomeric four-coordinate heteroleptic ate complexes Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(THF/Et2O)3 (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), Tm (8), Yb (9)), whose solid-state structures were determined by the single-crystal X-ray diffraction technique. All complexes additionally were characterized by melting point determination, elemental analyses, and mass spectrometry.     

Monodisperse lanthanide fluoride nanocrystals: synthesis and luminescent properties

Three types of high-quality, monodisperse lanthanide fluoride colloidal nanocrystals (NCs) including LnF(3) (Ln = La-Pr), NaLnF(4) (Ln = Sm-Er), and Na(5)Ln(9)F(32) (Ln = Tm-Lu) with two crystal phases (hexagonal and cubic) and a rich variety of morphologies have been synthesized in high boiling organic solvents oleic acid and 1-octadecene, via a thermal decomposition pathway. The as-synthesized NCs were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra, respectively. It is found that the as-synthesized NCs consist of monodisperse nanoparticles with diverse shapes and narrow size distribution, which can easily disperse in nonpolar cyclohexane solvent. Additionally, a possible mechanism of NC nucleation and growth has been proposed. The results reveal that the formation of monodisperse NCs closely correlates with the inherent nature of lanthanide series from La to Lu. Under 980 nm NIR excitation, as-synthesized Yb(3+)/Ln(3+) (Ln = Er, Tm, Ho)-doped NaGdF(4) and Na(5)Lu(9)F(32) colloidal NCs show the respective characteristic up-conversion (UC) emissions of Er(3+), Tm(3+), and Ho(3+), which are promising for applications in biolabels, bioimaging, displays, and other optical technologies.     

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.     

Novel heterometal-organic complexes as first single source precursors for up-converting NaY(Ln)F4 (Ln = Yb, Er, Tm) nanomaterials

First heterometal-organic single source precursors for NaYF(4) nanomaterials as a host matrix for up-conversion emission are reported. These novel heterobimetallic derivatives NaY(TFA)(4)(diglyme) (1), [Na(triglyme)(2)][Y(2)(TFA)(7)(THF)(2)] (2) and Na(2)Y(TFA)(5)(tetraglyme) (3) (TFA = trifluoroacetate), which were fully characterized by elemental analysis, FT-IR and (1)H NMR spectroscopy, TG-DTA data as well as single crystal X-ray structures, are advantageous in terms of being anhydrous and having lower decomposition temperatures in comparison to the homometallic precursor Y(TFA)(3)(H(2)O)(3). In addition, they also contain chelating glyme ligands, which act as capping reagents during decomposition to control the NaYF(4) particle size and render them monodisperse in organic solvents. On decomposition in 1-octadecene, the molecular derivatives 1 and 3 are converted, in the absence of any surfactant or capping reagent, to cubic NaYF(4) nanocrystals at significantly lower temperatures (below 250 °C). At higher temperature, a mixture of the cubic and hexagonal phases was obtained, the relative ratio of the two phases depending on the reaction temperature. A pure hexagonal phase, which is many folds more efficient for UC emission than the cubic phase, was obtained by calcining nanocrystals of mixed phase at 400 °C. In order to co-dope this host matrix with up-converting lanthanide cations, analogous complexes NaLn(TFA)(4)(diglyme) [Ln = Er (4), Tm (5), Yb (6)] and Na(2)Ln(TFA)(5)(tetraglyme) [Ln = Er (7), Yb (8)] were also prepared and characterized. The decomposition in 1-octadecene of suitable combinations and appropriate molar ratios of these yttrium, ytterbium and erbium/thulium derivatives gave cubic and/or hexagonal NaYF(4): Yb(3+), Er(3+)/Tm(3+) nanocrystals (NCs) capped by diglyme or tetraglyme ligands, which were characterized by IR, TG-DTA data, EDX analysis and TEM studies. Surface modification of these NCs by ligand exchange reactions with poly acrylic acid (PAA) and polyethyleneglycol (PEG) diacid 600 was also carried out to render them water soluble. The THF solutions of suitable combinations of the diglyme derivatives were also used to elaborate the thin films of NaYF(4):Yb(3+), Er(3+)/Tm(3+) on a glass or Si wafer substrate by spin coating. The multicolour up-conversion fluorescence was successfully realized in the Yb(3+)/Er(3+) (green/red) and Yb(3+)/Tm(3+) (blue/violet) co-doped NaYF(4) nanoparticles and thin films, which demonstrates that they are promising UC nanophosphors of immense practical interest. The up-conversion excitation pathways for the Er(3+)/Yb(3+) and Tm(3+)/Yb(3+) co-doped materials are discussed.     

Bifunctional Mixed-Lanthanide Cyano-Bridged Coordination Polymers Ln(0.5)Ln'(0.5)(H(2)O)(5)[W(CN)(8)] (Ln/Ln' = Eu(3+)/Tb(3+), Eu(3+)/Gd(3+), Tb(3+)/Sm(3+))

A new family of mixed-lanthanide cyano-bridged coordination polymers Ln(0.5)Ln'(0.5)(H(2)O)(5)[W(CN)(8)] (where Ln/Ln' = Eu(3+)/Tb(3+), Eu(3+)/Gd(3+), and Tb(3+)/Sm(3+)) containing two lanthanide and one transition metal ions were obtained and characterized by X-ray diffraction, photoluminescence spectroscopy, magnetic analyses, and theoretical computation. These compounds are isotypical and crystallize in the tetragonal system P4/nmm forming two-dimensional grid-like networks. They present a magnetic ordering at low temperature and display the red Eu(3+) ((5)D(0) → (7)F(0-4)) and green Tb(3+) ((5)D(4) → (7)F(6-2)) characteristic photoluminescence. The Tb(0.5)Eu(0.5)(H(2)O)(5)[W(CN)(8)] compound presents therefore green and red emission and shows Tb(3+)-to-Eu(3+) energy transfer.     

Synthesis and characterization of heterodinuclear Ln(3+)-Fe3+ and Ln(3+)-Co3+ complexes,bridged by cyanide ligand (Ln3+ = lanthanide ions). Nature of the magnetic interaction in the Ln(3+)-Fe3+ complexes

The reaction of Ln(NO3)3.aq with K3[Fe(CN)6] or K3[Co(CN)6] in N,N'-dimethylformamide (DMF) led to 25 heterodinuclear [Ln(DMF)4(H2O)3(mu-CN)Fe(CN)5].nH2O and [Ln(DMF)4(H2O)3(mu-CN)Co(CN)5].nH2O complexes (with Ln = all the lanthanide(III) ions, except promethium and lutetium). Five complexes (Pr(3+)-Fe3+), (Tm(3+)-Fe3+), (Ce(3+)-Co3+), (Sm(3+)-Co3+), and (Yb(3+)-Co3+) have been structurally characterized; they crystallize in the equivalent monoclinic space groups P21/c or P21/n. Structural studies of these two families show that they are isomorphous. This relationship in conjunction with the diamagnetism of the Co3+ allows an approximation to the nature of coupling between the iron(III) and the lanthanide(III) ions in the [Ln(DMF)4(H2O)3(mu-CN)Fe(CN)5].nH2O complexes. The Ln(3+)-Fe3+ interaction is antiferromagnetic for Ln = Ce, Nd, Gd, and Dy and ferromagnetic for Ln = Tb, Ho, and Tm. For Ln = Pr, Eu, Er, Sm, and Yb, there is no sign of any significant interaction. The isotropic nature of Gd3+ helps to evaluate the value of the exchange interaction.     

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.     

Electrospinning synthesis and luminescence properties of one-dimensional La(9.33)(SiO4)6O2: Ln3+ (Ln = Ce, Eu, Tb) microfibers

One-dimensional La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and low voltage cathodoluminescence (CL) as well as kinetic decay were used to characterize the resulting samples. SEM and TEM results indicated that the diameter of the microfibers annealed at 1000 °C for 3 h was 200-245 nm. The microfibers were further composed of fine and closely linked nanoparticles. La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors showed the characteristic emission of Ce(3+) (5d → 4f), Eu(3+) ((5)D(0)→(7)F(J)) and Tb(3+) ((5)D(3,4)→(7)F(J)) under ultraviolet excitation and low-voltage electron beams (3-5 kV) excitation. An energy transfer from Ce(3+) to Tb(3+) was observed in the La(9.33)(SiO(4))(6)O(2): Ce(3+), Tb(3+) phosphor under ultraviolet excitation and low-voltage electron beam excitation. Luminescence mechanisms were proposed to explain the observed phenomena. Blue, red and green emission can be realized in La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers by changing the doping ions. So the La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors have potential applications in full-color field emission displays.     

Luminescence properties and quenching mechanisms of Ln(Tf2N)3 complexes in the ionic liquid bmpyr Tf2N

The emission properties, including luminescence lifetimes, of the lanthanide complexes Ln(Tf(2)N)(3) (Tf(2)N = bis(trifluoromethanesulfonyl)amide); Ln(3+) = Eu(3+), Tm(3+), Dy(3+), Sm(3+), Pr(3+), Nd(3+), Er(3+)) in the ionic liquid bmpyr Tf(2)N (bmpyr = 1-n-butyl-1-methylpyrrolidinium) are presented. The luminescence quantum efficiencies, η, and radiative lifetimes, τ(R), are determined for Eu(3+)((5)D(0)), Tm(3+)((1)D(2)), Dy(3+)((4)F(9/2)), Sm(3+)((4)G(5/2)), and Pr(3+)((3)P(0)) emission. The luminescence lifetimes in these systems are remarkably long compared to values typically reported for Ln(3+) complexes in solution, reflecting weak vibrational quenching. The 1.5 μm emission corresponding to the Er(3+) ((4)I(13/2)→(4)I(15/2)) transition, for example, exhibits a lifetime of 77 μs. The multiphonon relaxation rate constants are determined for 10 different Ln(3+) emitting states, and the trend in multiphonon relaxation is analyzed in terms of the energy gap law. The energy gap law does describe the general trend in multiphonon relaxation, but deviations from the trend are much larger than those normally observed for crystal systems. The parameters determined from the energy gap law analysis are consistent with those reported for crystalline hosts. Because Ln(3+) emission is known to be particularly sensitive to quenching by water in bmpyr Tf(2)N, the binding properties of water to Eu(3+) in solutions of Eu(Tf(2)N)(3) in bmpyr Tf(2)N have been quantified. It is observed that water introduced into these systems binds quantitatively to Ln(3+). It is demonstrated that Eu(Tf(2)N)(3) can be used as a reasonable internal standard, both for monitoring the dryness of the solutions and for estimating the quantum efficiencies and radiative lifetimes for visible-emitting [Ln(Tf(2)N)(x)](3-x) complexes in bmpyr Tf(2)N.     

The fabrication of one-dimensional Ca4Y6(SiO4)6O: Ln3+ (Ln=Eu, Tb) phosphors by electrospinning method and their luminescence properties

One-dimensional Ca(4)Y(6)(SiO(4))(6)O: Ln(3+) (Ln=Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD) pattern and high-resolution transmission electron microscopy (HRTEM) confirmed that the fibers were composed of hexagonal Ca(4)Y(6)(SiO4)(6)O phase. Thermogravimetric and differential scanning calorimetry (TG-DSC) results showed that the Ca(4)Y(6)(SiO4)(6)O phase began to crystallize at 740°C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicated that the diameter of as-prepared microfibers ranged from 390 to 900 nm and the diameter of the microfibers annealed at 1000°C ranged from to 120 to 260 nm. Under ultraviolet and low-voltage electron beams (3-5 kV) excitation, the Ca(4)Y(6)(SiO(4))(6)O: Ln(3+) (Ln=Eu, Tb) samples showed the red and green emission, corresponding to (5)D(0)→(7)F(2) transition of Eu(3+) and (5)D(4)→(7)F(5) transition of Tb(3+), respectively.     

Azulene-moiety-based ligand for the efficient sensitization of four near-infrared luminescent lanthanide cations: Nd3+, Er3+, Tm3+, and Yb3+

The ML(4) complexes formed by reaction between the bidentate azulene-based ligand diethyl 2-hydroxyazulene-1,3-dicarboxylate (HAz) and several lanthanide cations (Pr(3+), Nd(3+), Gd(3+), Ho(3+), Er(3+), Tm(3+), Yb(3+), and Lu(3+)) have been synthesized and characterized by elemental analysis, FT-IR vibrational spectroscopy and electrospray ionization mass spectroscopy. Spectrophotometric titrations have revealed that four Az(-) ligands react with one lanthanide cation to form the ML(4) complex in solution. Studies of the luminescence properties of these ML(4) complexes demonstrated that Az(-) is an efficient sensitizer for four different near-infrared emitting lanthanide cations (Nd(3+), Er(3+), Tm(3+), and Yb(3+)); the resulting complexes have high quantum yield values in CH(3)CN. The near-infrared emission arising from Tm(3+) is especially interesting for biologic imaging and bioanalytical applications since biological systems have minimal interaction with photons at this wavelength. Hydration numbers, representing the number of water molecules bound to the lanthanide cations, were obtained through luminescence lifetime measurements and indicated that no molecules of water/solvent are bound to the lanthanide cation in the ML(4) complex in solution. The four coordinated ligands protect well the central luminescent lanthanide cation against non-radiative deactivation from solvent molecules.     

CO activation on the late lanthanide dimers: matrix infrared spectra of the Ln2[eta2(mu2-C, O)]x (Ln = Tb, Dy, Ho, Er, Lu; x = 1, 2) molecules

Reactions of laser-ablated late lanthanide atoms (Tb, Dy, Ho, Er, Tm, Yb, and Lu) with dilute carbon monoxide molecules in solid argon have been investigated using matrix-isolation infrared spectroscopy. The Ln2[eta2(mu2-C, O)]x (Ln = Tb, Dy, Ho, Er, Lu; x = 1, 2) molecules are observed upon sample annealing, whereas no product is observed for Tm and Yb. The C-O stretching frequencies in these dilanthanide carbonyls range from 1100 to 1300 cm-1, far below the value of free CO in the gas phase (2143.5 cm-1), implying that the C-O bonds are highly activated. Density functional theory calculations have been performed on these products. These Ln2[eta2(mu2-C, O)]x molecules are predicted to have planar structures, which carry asymmetrically bridging CO moieties that are tilted to the side.     

Study on optical properties of rare-earth ions in nanocrystalline monoclinic SrAl2O4: Ln (Ln = Ce3+, Pr3+, Tb3+)

SrAl(2)O(4): Ln (Ln = Ce(3+), Pr(3+), Tb(3+)) nanocrystals have been synthesized by the combustion method. The results of XRD indicated that the resulting SrAl(2)O(4): Ln (Ln = Ce(3+), Pr(3+), Tb(3+)) nanocrystals have a reduced and distorted monoclinic lattice compared with bulk materials. The spectral properties are measured, and it is found that the excitation peaks of 5d energy levels red shift in nanocrystals in contrast to that in bulk crystals. The mechanism of spectra and energy changes is investigated. The order of the degree of red shift for nano SrAl(2)O(4): Ln (Ln = Ce(3+), Pr(3+), Tb(3+)) crystals is Pr(3+) > Ce(3+) > Tb(3+), which is in good agreement with our predicted results.     

Highly uniform and monodisperse Gd(2)O(2)S:Ln(3+) (Ln = Eu, Tb) submicrospheres: solvothermal synthesis and luminescence properties

Gd(2)O(2)S:Ln(3+) (Ln = Eu, Tb) submicrospheres were successfully prepared through a facile and mild solvothermal method followed by a subsequent heat treatment. X-ray diffraction (XRD) results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure hexagonal phase of Gd(2)O(2)S. The energy dispersive spectroscopy (EDS), element analysis, and FT-IR results show that the precursors are composed of the Gd, Eu, O, S, C, H, and N elements. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that these spheres are actually composed of randomly aggregated nanoparticles. The formation mechanism for the Gd(2)O(2)S:Ln(3+)(Ln = Eu, Tb) spheres has been proposed on an isotropic growth mechanism. Under ultraviolet excitation, Gd(2)O(2)S:Ln(3+)(Ln = Eu, Tb) spheres show red and green emission corresponding to the (5)D(0)→(7)F(2) transition of the Eu(3+) ions and the (5)D(4)→(7)F(5) transition of the Tb(3+) ions. Furthermore, this synthetic route may have potential applications for fabricating other lanthanide oxysulfides.     

Coordination polymers based on inorganic lanthanide(II) sulfate skeletons and an organic isonicotinate N-oxide connector: segregation into three structural types by the lanthanide contraction effect

Fourteen three-dimensional coordination polymers of general formula [Ln(lNO)(H2O)(SO4)]n, where Ln = La, 1.La; Ce, 2.Ce; Pr, 3.Pr; Nd, 4.Nd; Sm, 5.Sm; Eu, 6.Eu; Gd, 7.Gd; Tb, 8.Tb; Dy, 9.Dy; Ho, 10.Ho; Er. 11.Er; Tm, 12.Tm; Yb, 13.Yb; and Lu, 14.Lu; INO = isonicotinate-N-oxide, have been synthesized by hydrothermal reactions of Ln3+, MnCO3, MnSO4 x H2O, and isonicotinic acid N-oxide (HINO) at 155 degrees C and characterized by single-crystal X-ray diffraction, IR, thermal analysis, luminescence spectroscopy, and the magnetic measurement. The structures are formed by connection of layer, chain, or dimer of Ln-SO4 by the organic connector, INO. They belong to three structural types that are governed exclusively by the size of the ions: type I for the large ions, La, Ce, and Pr; type II for the medium ions, Nd, Sm, Eu, Gd, and Tb; and type III for the small ions, Dy, Ho, Er, Tm, Yb, and Lu. Type I consists of two-dimensional undulate Ln-sulfate layers pillared by INO to form a three-dimensional network. Type II has a 2-fold interpenetration of "3D herringbone" networks, in which the catenation is sustained by extensive pi-pi interactions and O-H...O and C-H...O hydrogen bonds. Type III comprises one-dimensional chains that are connected by INO bridges, resulting in an alpha-Po network. The progressive structural change is due to the metal coordination number decreasing from nine for the large ions via eight to seven for the small ions, demonstrating clearly the effect of lanthanide contraction. The sulfate ion acts as a micro4- or micro3-bridge, connecting two, three, or four metals, and is both mono- and bidentate. The INO ligand acts as a micro3- or micro2-bridge with carboxylate group in syn-syn bridging or bidentate chelating mode. The materials show considerably high thermal stability. The magnetic properties of 4.Nd, 6.Eu, 7.Gd, and 13.Yb and the luminescence properties of 6.Eu and 8.Tb are also investigated.     

Synthesis, structure, and thermally stable luminescence of Eu(2+)-doped Ba2Ln(BO3)2Cl (Ln = Y, Gd and Lu) host compounds

A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba(2)Ln(BO(3))(2)Cl:Eu(2+) (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln(3+) sites in Ba(2)Ln(BO(3))(2)Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba(2)Ln(BO(3))(2)Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P2(1)/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping. Ba(2)Ln(BO(3))(2)Cl:Eu(2+) phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba(2)Y(BO(3))(2)Cl:Eu(2+), Ba(2)Gd(BO(3))(2)Cl:Eu(2+), and Ba(2)Lu(BO(3))(2)Cl:Eu(2+), respectively. Furthermore, they possess a high thermal quenching temperature. With the increase of temperature, the emission bands show blue shifts with broadening bandwidths and slightly decreasing emission intensities. It is expected that this series of chloroborate phosphors can be used in white-light UV-LEDs as a good wavelength-conversion phosphor.     

重水溶液中稀土-吡啶-2,6-二羧酸配合物的第二配位圈^1HNMR顺磁位移

对稀土-吡啶-2,6-二羧酸(DPA)配合物Ln(DPA)3进行了NMR研究并观察到了由溶剂分子形成的第二配位圈的顺磁位移效应.     

General synthesis and structural evolution of a layered family of Ln8(OH)20Cl4 x nH2O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y)

The synthesis process and crystal structure evolution for a family of stoichiometric layered rare-earth hydroxides with general formula Ln(8)(OH)(20)Cl(4) x nH(2)O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y; n approximately 6-7) are described. Synthesis was accomplished through homogeneous precipitation of LnCl(3) x xH(2)O with hexamethylenetetramine to yield a single-phase product for Sm-Er and Y. Some minor coexisting phases were observed for Nd(3+) and Tm(3+), indicating a size limit for this layered series. Light lanthanides (Nd, Sm, Eu) crystallized into rectangular platelets, whereas platelets of heavy lanthanides from Gd tended to be of quasi-hexagonal morphology. Rietveld profile analysis revealed that all phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions. In-plane lattice parameters a and b decreased nearly linearly with a decrease in the rare-earth cation size. The interlamellar distance, c, was almost constant (approximately 8.70 A) for rare-earth elements Nd(3+), Sm(3+), and Eu(3+), but it suddenly decreased to approximately 8.45 A for Tb(3+), Dy(3+), Ho(3+), and Er(3+), which can be ascribed to two different degrees of hydration. Nd(3+) typically adopted a phase with high hydration, whereas a low-hydration phase was preferred for Tb(3+), Dy(3+), Ho(3+), Er(3+), and Tm(3+). Sm(3+), Eu(3+), and Gd(3+) samples were sensitive to humidity conditions because high- and low-hydration phases were interconvertible at a critical humidity of 10%, 20%, and 50%, respectively, as supported by both X-ray diffraction and gravimetry as a function of the relative humidity. In the phase conversion process, interlayer expansion or contraction of approximately 0.2 A also occurred as a possible consequence of absorption/desorption of H(2)O molecules. The hydration difference was also evidenced by refinement results. The number of coordinated water molecules per formula weight, n, changed from 6.6 for the high-hydration Gd sample to 6.0 for the low-hydration Gd sample. Also, the hydration number usually decreased with increasing atomic number; e.g., n = 7.4, 6.3, 7.2, and 6.6 for high-hydration Nd, Sm, Eu, and Gd, and n = 6.0, 5.8, 5.6, 5.4, and 4.9 for low-hydration Gd, Tb, Dy, Ho, and Er. The variation in the average Ln-O bond length with decreasing size of the lanthanide ions is also discussed. This family of layered lanthanide compounds highlights a novel chemistry of interplay between crystal structure stability and coordination geometry with water molecules.