Size and shape controllable synthesis and luminescent properties of BaGdF5:Ce3+/Ln3+ (Ln = Sm, Dy, Eu, Tb) nano/submicrocrystals by a facile hydrothermal process

In this paper, we present a facile and environmentally-friendly hydrothermal process to synthesize BaGdF(5): 2.5 mol% Ce(3+)/2.5 mol% Ln(3+) (Ln = Sm, Dy, Eu and Tb) nano/submicroparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), as well as photoluminescence (PL) spectra are used to characterize the resulting samples. The size, shape, and composition of the products could be tuned just by varying the organic additives and the pH values of the initial reaction solutions. The morphologies for the products include nanospheres, submicrospheres, peanut-like particles, as well as the spindle-like and star-like aggregates. Moreover, the size of the samples can be tuned from 50 nm to 150 nm. Additionally, we systematically investigate the luminescence properties of different lanthanide ions in BaGdF(5) host. Under single-wavelength excitation at 260 nm, the samples doped with different lanthanide ions show intensive multicolor visible emissions depending on the doped Ln(3+) ions. The luminescence process can be attributed to the strong absorption of UV irradiation by Ce(3+) ions, followed by energy transfer to Gd(3+) ions, from which the energy is transferred to Ln(3+), resulting in the emission from the luminescent Ln(3+) centers. The Gd(3+) ions play an intermediate role in this process.     

稀土离子(Gd~(3+),Ce~(3+)/Ce~(4+),Eu~(3+))对Tb~(3+)掺杂硅酸盐玻璃发光性能的影响

研究了(Gd3+,Ce3+/Ce4+,Eu3+)对Tb3+掺杂硅酸盐玻璃发光性能的影响.结果表明:Tb3+掺杂硅酸盐玻璃可以发出弱蓝光(400～460 mm)和较强的绿光(480～600mm).Gd3+对Tb3+的发光起敏化作用,可提高TB3+掺杂硅酸盐玻璃的发光强度.在空气中熔制的玻璃中Ce3+和Ce4+同时存在,Ce3+对Tb3+发光起敏化作用;而Ce4+对Tb3+发光起淬灭作用.由于Ce4+比例比较高,CeO2加入导致TB3+发光强度降低,同时也缩短了Tb3+发光余辉.加入Eu2O3时,Eu3+自身发光分散了激发Tb3+发光的能量,使Tb3+的特征发射强度降低.     

四元混配配合物[Ln(x-MBA)2(NO3)(Phen)]2的合成及表征

在酸性介质,乙醇／水混合溶剂中合成得到了三个系列的四元混配配合物[Ln(x-MBA)2(NO3)(Phen)]2(Ln=La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Er;MBA=CH3C6H4COO^-）。用元素分析、IR、UV、DTA－TG和^1H NMR等方法对配合物进行了表征,测量了三个Eu配合物的荧光光谱和三个Gd配合物的ESR谱。     

Controlled synthesis and optical spectroscopy of lanthanide-doped KLaF₄ nanocrystals

KLaF(4), as a good host matrix for trivalent lanthanide (Ln(3+)) ions to fabricate upconversion (UC) or downconversion (DC) phosphors, has been rarely reported. Herein, monodisperse (～10 nm) cubic-phase Ln(3+)-doped KLaF(4) nanocrystals (NCs) were synthesized via a facile thermal decomposition method. Upon excitation at 980 nm, UC luminescence properties of KLaF(4):Ln(3+)/Yb(3+) (Ln = Tm, Ho, Er) NCs were comprehensively surveyed. Particularly, after coating an inert KLaF(4) shell, the green and red UC luminescence intensity of KLaF(4):Er(3+)/Yb(3+) NCs was enhanced ～35 times, and the corresponding UC lifetimes of (4)S(3/2) and (4)F(9/2) levels of Er(3+) were observed significantly prolonged from 42 and 68 μs in core-only NCs to 87 and 136 μs in core/shell counterparts. Furthermore, intense DC luminescence was also achieved in Ce(3+)/Tb(3+) and Eu(3+) doped KLaF(4) NCs, with absolute quantum yields of 39.8% (Tb(3+)) and 17.3% (Eu(3+)). The luminescence lifetimes of (5)D(0) (Eu(3+)) and (5)D(4) (Tb(3+)) were determined to be 4.2 and 4.7 ms, respectively. Water-soluble Ln(3+)-doped KLaF(4) NCs featuring excellent monodispersion, long luminescence lifetime, and high UC/DC efficiency may have versatile and promising applications as luminescent nano-biolabels.     

Bi_4Ge_3O_(12):TR(TR=Pr,Eu,Ce)晶体的吸收和发光光谱

测量了Bi_4Ge_3O_(12)(BGO):Pr、Eu和Ce的吸收、激发和发光光谱。掺杂BGO吸收和激发带相应于pr~(3+)、Eu~(3+)和Ce~(3+)离子特征跃迁。Xe灯中不同波长激发所得到掺杂BGO的发光光谱可通过Bi~(3+)心和掺杂材料之间能量传输过程加以解释。Bi~(3+)心400—600mm发射强度因受到Ce杂质影响变弱,这现象在高Ce浓度晶体里更为显著。     

Electrospinning-derived Tb2(WO4)3:Eu(3+) nanowires: energy transfer and tunable luminescence properties

One-dimensional Tb(2)(WO(4))(3) and Tb(2)(WO(4))(3):Eu(3+) nanowires have been prepared by a combination method of sol-gel process and electrospinning. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. The as-obtained precursor samples present fiber-like morphology with uniform size, and Tb(2)(WO(4))(3) and Tb(2)(WO(4))(3):Eu(3+) nanowires were formed after annealing. Under ultraviolet excitation and low-voltage electron beams excitation into WO(4)(2-) and the f-f transition of Tb(3+), the Tb(2)(WO(4))(3) samples show the characteristic emission of Tb(3+) corresponding to (5)D(4)-(7)F(6, 5, 4, 3) transitions due to an efficient energy transfer from WO(4)(2-) to Tb(3+), while Tb(2)(WO(4))(3):Eu(3+) samples mainly exhibit the characteristic emission of Eu(3+) corresponding to (5)D(0)-(7)F(0, 1, 2) transitions due to an energy transfer occurs from WO(4)(2-) and Tb(3+) to Eu(3+). The increase of Eu(3+) concentration leads to the increase of the energy transfer efficiency from Tb(3+) to Eu(3+). The PL color of Tb(2)(WO(4))(3):x mol% Eu(3+) phosphors can be tuned from green to red easily by changing the doping concentration (x) of Eu(3+), making the materials have potential applications in fluorescent lamps and color display fields.     

Influence of Gd content on the structural,Raman spectroscopic and magnetic properties of CoFe2O4 nanoparticles synthesized by sol-gel route

The structural and magnetic properties of sol-gel synthesized Gd doped (x = 0.00 to 0.15) CoFe₂O₄ nanoparticles (NPs) have been studied. The x-ray diffraction (XRD) and FTIR spectroscopy along with Raman spectra confirmed the formation of face centered cubic inverse spinel structure. TEM images showed the NPs are well-dispersed with average particle size 30 nm. Room temperature magnetic measurement showed the value of coercivity fluctuates from 353 Oe to 1060 Oe for different % of Gd content. The maximum coercivity, saturation magnetization, magnetic moment, magnetic anisotropy, remnant magnetization found for 0.03% Gd content are 1060.19 Oe, 77.53 emu/gm, 3.29 μ, 4.11 × 10⁴ erg/cm³, 32.38 emu/gm, respectively. The large value of coercivity indicated that the interparticle interactions and crystalline anisotropy are high. Thus CoFe_2-xGd_xO₄ magnetic NPs might be a potential candidate for data processing, automotive and telecommunications.     

YAG：Ce,Ln体系中Ce~（3＋）的荧光寿命的研究

采用高温固相法合成了一系列的（Y0.95Ln0.01Ce0.04）3Al5O12（简称YAG∶Ce,Ln）,系统地研究了此体系中Ln3＋对Ce3＋的荧光寿命的影响。结果表明,荧光寿命数值能够较好地说明双掺杂晶体中除Ce3＋以外的其它三价稀土离子（Ln3＋）对Ce3＋的发光强度的增强或者猝灭现象。     

Preparation, Characterization, and Microwave Properties of RETiNbO6 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, and Yb) Dielectric Ceramics

Microwave ceramic dielectric resonators (DRs) based on RETiNbO₆ (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, and Yb) have been prepared using the conventional solid-state ceramic route. The DR samples are characterized using XRD and SEM methods. The microwave dielectric properties are measured using resonant methods and a net work analyzer. The ceramics based on Ce, Pr, Nd, and Sm have dielectric constants in the range 32–54 and positive coefficient of thermal variation of resonant frequency (τ_f). The ceramics based on Gd, Tb, Dy, Y, and Yb have dielectric constants in the range 19–22 and negative τ_f.     

Synthesis and electrochemistry of acetylacetonatolanthanide(III)- phthalocyaninates

The synthesis and electrochemistry of acetylacetonatolanthanide(III)phthalocyaninates are reported. Two new kinds of lanthanide complexes Li[Pc]Ln(acac)₂] and (Pc)Ln(acac) were obtained where Ln is the trivalent ions of Eu, Gd, Dy, Tb, Ho, Er, Tm, Lu, and Pc is the dianion of phthalocyanine and acac is the acetylacetonate anion. These complexes were characterized by infrared and electronic absorption spectroscopy. An overall oxidation reduction mechanism at a platinum electrode in dimethyl sulfoxide is presented.     

Lanthanide ion-doped GdPO4 nanorods with dual-modal bio-optical and magnetic resonance imaging properties

Here, dual-modal bioprobes for combined optical and magnetic resonance (MR) imaging are reported. Gadolinium orthophosphate (GdPO(4)) nanorods co-doped with light-emitting lanthanide ions have been successfully prepared through a hydrothermal method. An efficient downconversion luminescence from Ce/Tb or Eu doped GdPO(4) nanorods and upconversion luminescence from Yb/Er co-doped GdPO(4) nanorods are observed, respectively, which offers the optical modality for the nanoprobes. Notably, we first report the upconversion phenomenon based on the GdPO(4) matrix under 980 nm near infrared irradiation. The possibility of using these nanoprobes with downconversion and upconversion luminescent emissions for optical cell imaging is also demonstrated. Furthermore, these Gd(3+)-containing nanophosphors show good positive signal-enhancement ability when performed under a 4.7 T MR imaging scanner, indicating they have potential as T(1) MR imaging contrast agents. Thus, nanoprobes based on GdPO(4) nanophosphors are shown to provide the dual modality of optical and MR imaging.     

Nanoscale coordination polymers exhibiting luminescence properties and NMR relaxivity

This article presents the first example of ultra-small (3-4 nm) magneto-luminescent cyano-bridged coordination polymer nanoparticles Ln0.33(3+)Gdx3+/[Mo(CN)8]3- (Ln=Eu (x=0.34), Tb (x=0.35)) enwrapped by a natural biocompatible polymer chitosan. The aqueous colloidal solutions of these nanoparticles present a luminescence characteristic of the corresponding lanthanides (5D0→7F0-4 (Eu3+) or the 5D4→7F6-2 (Tb3+)) under UV excitation and a green luminescence of the chitosan shell under excitation in the visible region. Magnetic Resonance Imaging (MRI) efficiency, i.e. the nuclear relaxivity, measurements performed for Ln0.33(3+)Gdx3+/[Mo(CN)8]3- nanoparticles show r1p and r2p relaxivities slightly higher than or comparable to the ones of the commercial paramagnetic compounds Gd-DTPA? or Omniscan? indicating that our samples may potentially be considered as a positive contrast agent for MRI. The in vitro studies performed on these nanoparticles show that they maybe internalized into human cancer and normal cells and well detected by fluorescence at the single cell level. They present high stability even at low pH and lack of cytotoxicity both in human cancer and normal cells.     

Trap Levels in Eu-Doped SrAl2O4 Phosphor Crystals Co-Doped with Rare-Earth Elements

SrAl₂O₄:Eu²⁺ phosphor crystals co-doped with auxiliary activators such as La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y have been grown by the floating zone (FZ) technique. Photoluminescence spectrum (PL), time-resolved PL, and thermally stimulated luminescence (TSL) are evaluated to clarify the long-duration phosphorescence mechanism of SrAl₂O₄, Eu, and Ln phosphors. TSL spectra were measured in the temperature range from RT to 600 K to evaluate the depth and densities of the traps generated by the doping of auxiliary activators that are responsible for the long-duration phosphorescence. The peak wavelength of PL does not vary with auxiliary activator elements, while decay curves vary greatly with the auxiliary activators. The trap depth and the densities of the trapped carriers estimated based on the hole trap model also vary with the auxiliary activator elements. The traps generated at around E =0.5 eV by the auxiliary activators, Nd, Dy, and Tm, with sufficient densities are effective for the long-duration phosphorescence.     

Lanthanide coordination polymers constructed from 5-(4-pyridyl)-isophthalic acid: Synthesis,structure and photoluminescent properties

Nine lanthanide coordination polymers [Ln₂(pyip)₃(H₂O)₄·DMF·3H₂O]_n (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) based on the pyip^2 − ligand {H₂pyip = 5-(4-pyridyl)-isophthalic acid} have been synthesized under solvothermal conditions. X-ray crystallographic studies reveal that 1–9 are isostructural and crystallize in the triclinic system, space group P2₁/c, and exhibit a 3D framework. Topological analysis reveals that the 3D framework can be simplified to a uninodal 6-connected pcu alpha-Po primitive cubic type structure. Meanwhile, the luminescent properties of these nine coordination polymers in the solid state are also investigated. Especially the Eu and Tb compounds show bright red and green luminescence with luminescence lifetimes of 0.39 and 0.80 ms, respectively.     

Crystal structure of rare-earth silicon-oxynitride J-phases,Ln4Si2O7N2

Rare-earth silicon-oxynitride J-phases, Ln₄Si₂O₇N₂ (Ln=Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), were prepared by the N₂ gas-pressured sintering method at 1 MPa of N₂ and 1500–1700 °C. The Rietveld analysis was carried out for X-ray powder diffraction data measured at room temperature. The crystal structures of Ln₄Si₂O₇N₂ were refined with the structure model of La₄Si₂O₇N₂ for Ln=La, Pr, Nd, and Sm, and with that of Lu₄Si₂O₇N₂ for Ln=Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The refined monoclinic unit-cell parameters (lengths a, b, c, angles β, and volume V) increased linearly in their two series of Ln with increasing ionic radii of rare-earth atoms. Discontinuities of the unit-cell parameters were found between the two Ln series.     

Enhanced emission of ultra-small-sized LaF(3):RE(3+) (RE = Eu, Tb) nanoparticles through 1,2,4,5-benzenetetracarboxylic acid sensitization

Uniform, ultra-small-sized and well-water-dispersible LaF(3) nanoparticles doped with trivalent rare earth (RE) ions (Eu(3+) or Tb(3+)) have been synthesized by a simple, low temperature synthesis route. The nanoparticles, with sizes of about 3.2 nm (for those doped with Eu(3+)) and 3.0 nm (for those doped with Tb(3+)), are roughly spherical and monodisperse. 1,2,4,5-Benzenetetracarboxylic acid (labeled as BA) as sensitizer has been bonded to the surface of the nanoparticles, which can sensitize the emission of RE(3+) in the LaF(3) nanoparticles. The BA-LaF(3):RE(3+) (RE = Eu or Tb) nanoparticles have a broad absorption band in the UV domain, and show enhanced luminescence of RE(3+) based on an energy transfer from BA ligands to RE(3+) ions (i.e. the so-called "antenna effect"). Due to the dual protection of organic ligands (BA) and inorganic matrices (LaF(3)), BA-LaF(3):RE(3+) (RE = Eu or Tb) nanoparticles have longer excited state lifetimes than LaF(3):RE(3+) (RE = Eu or Tb) nanoparticles as well as lanthanide coordination polymers of BA.     

Hydrothermal synthesis and luminescence properties of YF3:Ln (Ln=Sm,Dy, Tb and Pr) nano-/microcrystals

YF₃:Ln (Ln=Sm, Dy, Tb and Pr) nano-/microcrystals with uniform morphology and size have been successfully prepared by a facile, and environmentally friendly hydrothermal method. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) have been used to study the morphologies and crystal structure of the products. The effects of the molar ratio of EDTA to Y³⁺, and chelator on the crystal growth have been investigated in detail. The time-dependent experiments have been conducted to investigate the morphology evolution process. Based on the results, a possible growth mechanism is proposed. The photoluminescence spectra at room temperature show that the as-prepared YF₃:Ln (Ln=Sm, Pr, Tb and Dy) nano-/microcrystals show strong light emissions with different colors coming from different activator ions. It is noticed that morphology and size of the products have great influence on their emission intensity. Interestingly, in the YF₃:Sm system, we observed the Sm²⁺ emission peaks when excited at 323 nm. The results reveal that some of the Sm³⁺ ions should have been reduced to the divalent state during the hydrothermal process.     

Extraction of Lanthanides(III) from Aqueous Nitrate Media with Tetra‐(p‐tolyl)[(o‐Phenylene)Oxymethylene] Diphosphine Dioxide

A novel tridentate neutral organophosphorus compound, tetra‐(p‐tolyl)[(o‐phenylene)oxymethylene] diphosphine dioxide (I) has been synthesized and its extracting ability for microquantities of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO₃ and NH₄NO₃ aqueous solutions has been studied. The effect of HNO₃ concentration in the aqueous phase and that of the extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes and conditional extraction constants of Ln(III) have been determined. The extraction behavior of compound I is compared with that of the diglycolamide ligand TODGA. The potentialities of polymeric resin impregnated with compound I for the preconcentration of lanthanides(III) from nitric acid solutions are demonstrated.     

Defect centers of rare-earth metals in <Emphasis Type="Italic">a</Emphasis>-Si(H)

Electrical and photoelectric properties of a-Si(H) films doped by rare-earth metals were investigated. Nd, Sm, Gd, Tb, Dy, Ho, and Yb dopant atoms were shown to generate an acceptor type band near to the middle of the mobility gap of a-Si(H). Eu dopant atoms generate a donor-type band in the mobility gap of a-Si(H). Eu, Dy and Yb dopant atoms intensify photoconduction of a-Si(H) whereas Nd, Sm, Gd, Tb, and Ho dopes inhibit the photoconduction.     

A novel nitronyl nitroxide radical and its Gd(III), Tb(III), Dy(III) complexes: Synthesis,structure and magnetic properties

Three new lanthanide complexes based on a novel nitronyl nitroxide radical [Ln(hfac)₃(NITPhiPr)₂] (Ln = Gd(1), Tb(2), Dy(3); hfac = hexafluoroacetylacetonate, NITPhiPr = 4′-isopropyl-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been successfully synthesized, characterized structurally and magnetically, which all display radical-Ln(III)-radical tri-spin structures. The magnetic studies reveal the ferromagnetic interactions between the Gd(III) ion and radicals and the antiferromagnetic interaction between two radicals in the complex 1. And both Ln(III)–radical ferromagnetic interactions exist in complexes 2 and 3.