Unique Spectral Overlap and Resonant Energy Transfer between Europium(II) and Ytterbium(III) Cations: No Quantum Cutting

Samples of the Ca₃Sc₂Si₃O₁₂ (CSS) host singly doped with Eu²⁺ or Yb³⁺, doubly doped with Eu²⁺ and Yb³⁺, and triply doped with Ce³⁺, Eu²⁺ and Yb³⁺ were synthesized by a sol–gel combustion process under reducing conditions. Unlike previous reports of Eu²⁺→Yb³⁺ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb³⁺ is further enhanced by co‐doping with Ce³⁺ in addition to Eu²⁺. The quantum efficiencies of the doped materials range between 9 % and 93 %.     

Radioisotopic tracing of lanthanide uptake in erythrocyte, using ytterbium (169Yb3+) and mouse erythrocytes

This study describes a highly sensitive and simple method of ¹⁶⁹Yb tracing to investigate the uptake of Yb³⁺ in mouse erythrocyte. The amounts of Yb³⁺ absorbed by erythrocyte, membrane and cytoplasm at different time were determined after erythrocytes were incubated with 1.0^.10^-6mol^.l^{-1 169}Yb³⁺ solution at 37^°C. The results indicated that Yb³⁺ absorbed on the membrane was transferred promptly to the cytoplasm during the separation process. The observation of a very low level of Yb³⁺ in the cytoplasm could not lead to a verdict that Yb³⁺ could travel across the erythrocyte membrane This revised version was published online in July 2006 with corrections to the Cover Date.     

EPR and optical study of coupled Yb<Superscript>3+</Superscript> ion pairs in weakly doped LiNbO<Subscript>3</Subscript>:Yb single crystal

The results of electron paramagnetic resonance and optical spectroscopy studies of Yb³⁺ ions in LiNbO₃:1% Yb host crystal are reported. Also some results of Raman spectra measurements are presented. The observed features are assigned to single Yb³⁺ ions and pairs of dissimilar ions (with different g value) of the type of ^evenYb³⁺-^evenYb³⁺. The values of the components of the g-tensor for both ions and interaction exchange tensors are estimated. The value of J = ?0.0283 cm^?1 shows that the exchange interactions are of antiferromagnetic nature. The most probably the ^evenYb³⁺-^evenYb³⁺ pairs substitute for neighborhood Li⁺-Nb⁵⁺ positions what induces gain of distance between ions of about 1 Å. There are no observed dissimilar ion pairs of the type ^oddYb³⁺-^oddYb³⁺.     

Yb/Er掺杂Y2O3纳米核壳颗粒的荧光性能及体内标定研究

为改善无机Y2O3上转换纳米粒子(UCNPs)的荧光性能,且同步实现其在生物体内的成像标定,通过共沉淀法及梯度合成工艺,制备出各组不同壳层厚度的Y2O3:Yb³⁺,Er³⁺@Y2O3:Yb³⁺ UCNPs。利用透射电子显微镜(TEM)扫描、X射线衍射(XRD)、上转换荧光(UCL)光谱、UCL寿命等对样品的形貌、结构及荧光性能进行了表征。结果表明：利用共沉淀法制得小尺寸Y2O3:Yb³⁺,Er³⁺@Y2O3:Yb³⁺纳米核壳颗粒,平均粒径范围在25.57~26.24 nm之间。通过调整Yb³⁺浓度和水浴时间优化合成工艺,获得高发射强度、长荧光寿命方案(80% Yb掺杂,8 h水浴)。高红绿比的荧光发射特征,决定其在小动物体内荧光标定检测时更宜采用红色信道。     

Up-converted luminescence in Yb,Tm co-doped LaGaO3 phosphors by high-energy ball milling and solid state reaction

LaGaO₃:Tm³⁺, Yb³⁺ powder was synthesized by a high-energy ball milling (HEB) and a conventional solid state reaction (SSR). The X-ray diffraction patterns confirmed the LaGaO₃:Tm³⁺, Yb³⁺ powder phosphors to have an orthorhombic structure. The spectrum consisted of ¹G₄ → ³H₆, weak ¹G₄ → ³F₄, and intense ³H₄ → ³H₆ transition bands within the f¹² configuration of Tm³⁺, together with the ²F_5/2 → ²F_7/2 transition of Yb³⁺. Up-converted emission of the LaGaO₃:Tm³⁺, Yb³⁺ powders were observed under laser diode excitation of 975 nm. The PL intensity of the HEB-LaGaO₃:Tm³⁺, Yb³⁺ powders sintered at 1300 °C were higher than those of all LaGaO₃:Tm³⁺, Yb³⁺ powder samples examined. The energy transition probability of HEB-LaGaO₃:Tm³⁺, Yb³⁺ powders are higher than that of the SSR-LaGaO₃:Tm³⁺, Yb³⁺ powders. Compared to the solid state reaction method, synthesis by high-energy ball milling is simple and provides improved crystallinity of the host.     

Synthesis and characterization of nanoporous NaYF4:Yb3+, Tm3+@SiO2 nanocomposites

Novel upconversion nanocomposites with nanoporous structure were presented in this paper. Silica-coated cubic NaYF₄:Yb³⁺, Tm³⁺ nanoparticles were first prepared. After annealing, monodisperse cubic/hexagonal mixed phases NaYF₄:Yb³⁺, Tm³⁺@SiO₂ nanoparticles were obtained, and the NaYF₄:Yb³⁺, Tm³⁺ cores became nanoporous. To the best of our knowledge, the nanoporous structure in NaYF₄:Yb³⁺, Tm³⁺@SiO₂ nanocomposites was observed for the first time. They demonstrate increased upconversion emission compared with unannealed dense NaYF₄:Yb³⁺, Tm³⁺ nanoparticles due to the appearance of the hexagonal NaYF₄:Yb³⁺, Tm³⁺. The silica shell not only makes the nanocomposites possess bio-affinity but also protects the NaYF₄:Yb³⁺, Tm³⁺ cores from aggregating and growing up. Thus the upconversion, nanoporous and bio-affinity properties were combined into one single nanoparticle. The nanocomposites have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), small angle X-ray diffraction (SAXRD) and emission spectroscopy. These multifunctional nanocomposites are expected to find applications in biological fields, such as biolabels, drug storage and delivery.     

Vacuum ultraviolet and near-infrared excited luminescence properties of Ca3(PO4)2:RE, Na (RE=Tb, Yb, Er, Tm, and Ho)

Tb³⁺, Yb³⁺, Tm³⁺, Er³⁺, and Ho³⁺ doped Ca₃(PO₄)₂ were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb³⁺-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb³⁺ content is comparable with that of the commercial Zn₂SiO₄:Mn²⁺ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb³⁺, Tm³⁺, Er³⁺, and Ho³⁺ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb³⁺-Ho³⁺, Yb³⁺-Er³⁺, and Yb³⁺-Tm³⁺ in Ca₃(PO₄)₂, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb³⁺-Tm³⁺-Er³⁺-Ho³⁺ in Ca₃(PO₄)₂, in which the cross-relaxation process between Er³⁺ and Tm³⁺, producing the ¹D₂-³F₄ transition of Tm³⁺, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.     

Nd3+ and Yb3+ germanate and tellurite glasses for fluorescent solar energy collectors

The features of fluorescent glass solar collectors are discussed. Combination of Nd³⁺ and Yb³⁺ in high refractive index glasses is suggested as concentration material. Energy absorbed by Nd³⁺ is transferred with high efficiency to Yb³⁺ emitting at 970 nm. The self-absorption of Nd³⁺ is eliminated and long-wavelength emission at 1.06 μm decreased as a result of energy transfer.     

Impact of High Ytterbium(III) Concentration in the Shell on Upconversion Luminescence of Core–Shell Nanocrystals

After coating 20 Yb/2 Er:NaGdF₄ core nanocrystals with a NaYbF₄ shell, upconversion emission of the rare earth ions weakens. So far, the exact reason for this phenomenon is still unclear due to lack of the direct evidence. In this report, a core@shell@shell sandwich‐like structure is designed and fabricated to investigate this phenomenon. We find that high Yb³⁺ concentration in the shell has mainly two adverse impacts: it promotes not only the deleterious back energy transfer from Er³⁺ in the core to Yb³⁺ in the shell but also the energy transfer from Yb³⁺ in the core to Yb³⁺ in the shell. To obtain nanocrystals with high upconversion efficency, appropriate Yb³⁺ concentration should be introduced into the shell or the transition layer.     

X-ray photoelectron spectroscopy studies of Yb14MnSb11 and Yb14ZnSb11

Measurements of core and valence electronic states of single crystals of the rare earth transition metal Zintl phases Yb₁₄MnSb₁₁ and Yb₁₄ZnSb₁₁ were performed using the X-ray photoelectron spectroscopy station of Beamline 7 at the Advanced Light Source. Sample surfaces of Yb₁₄MnSb₁₁ and Yb₁₄ZnSb₁₁ were measured as received, after Ar⁺ ion bombardment, and after cleaving in situ. The single crystal structure of Yb₁₄ZnSb₁₁ is also reported. Both compounds are air-sensitive and show Yb³⁺ due to surface oxidation. In the case of Yb₁₄MnSb₁₁, there is no evidence for Yb³⁺ that would be intrinsic to the sample, consistent with previously reported X-ray magnetic circular dichroism studies. Detailed analyses of the Yb₁₄ZnSb₁₁ surfaces reveal a significant contribution of both Yb³⁺ and Yb²⁺ 4f states in the valence band region. This result is predicted for the Zn analog by Zintl counting rules and support the mixed valency of Yb for Yb₁₄ZnSb₁₁. Further detailed analysis of the core and valence band structure of both Yb₁₄MnSb₁₁ and Yb₁₄ZnSb₁₁ is presented.     

Preparation of upconversion Yb3+ doped microspherical BiOI with promoted photocatalytic performance

Bismuth oxychloride (BiOI) has a good visible light responsive property due to their relatively narrow band gap, and its photocatalytic performance was further improved by doping ytterbium ions (Yb³⁺). This may be due to strong optical absorption in UV–visible light, effective separation of the photoinduced electron-hole pairs, and the capacity to up-convert Near-IR light into visible-light of Yb³⁺ ions. In this study, a facile solvothermal method was adopted to synthesize Yb³⁺ ions doped BiOI photocatalysts. The doped photocatalysts with molar ratios of 0, 0.5, 1, 1.5, 2 and 2.5% Yb³⁺ ions were prepared. The 2% Yb³⁺ ions doped BiOI exhibited the highest photocatalytic degradation efficiency on degrading Rhodamine B, which was two times higher than that of pure BiOI. Also Yb³⁺ ions doped BiOI showed high photocatalytic degradation on herbicide isoproturon. The prepared photocatalysts were characterized by SEM, XRD, UV–vis DRS. It indicated that the doping ions entered the lattice of BiOI crystals and improved the photocatalytic performance. The photocatalytic mechanism was also studied. This work provided the potential application of Yb³⁺ doped BiOI for the degradation of organic contaminants.     

Redox reaction Yb(III) + <Emphasis Type="Italic">e</Emphasis> = Yb(II) in a molten eutectic mixture NaCl-2CsCl

Potentiometric method was used to measure the redox potentials of Yb³⁺/Yb²⁺ in a eutectic melt of sodium and cesium chlorides relative to a chlorine reference electrode in the temperature range 823–973 K. The basic thermodynamic characteristics of the redox reaction YbCl₂(s.) + 1/2Cl₂(g.) ai YbCl₃(s.) were calculated from the conditional standard potentials E*(Yb³⁺/Yb²⁺).     

A general approach for selective enhancement of green upconversion emissions in Er3+ doped oxides by Yb3+–MoO4 2− dimer sensitizing

In this paper, we report a general approach to enhance the upconversion (UC) luminescence of Er³⁺ doped oxides phosphors by Yb³⁺–MoO₄ ^2? dimer sensitizing, which induced strong green UC emissions under the 976 nm laser diode excitation. By codoping of Yb³⁺ and Mo⁶⁺ in the Er³⁺ doped TiO₂ and ZnO, the green UC emissions intensity can be selectively increased about 10 and 500 times than those of Er³⁺–Yb³⁺ codoped TiO₂ and ZnO, respectively. The high excited state energy transfer between |²F_7/2, ³T₂> state of Yb³⁺–MoO₄ ^2? dimer and ⁴F_7/2 level of Er³⁺ significantly avoids the nonradiative decay processes happened at lower energy levels of Er³⁺, and then increases the green UC emissions efficiently. The proposed Yb³⁺–MoO₄ ^2? dimer sensitizing has been realized as an efficient way to enhance the green UC emissions in other Er³⁺ doped oxides phosphors. It is expected that the selective enhanced green UC emissions sensitized by Yb³⁺–MoO₄ ^2? dimer in Er³⁺ doped oxides phosphors can greatly extend their scope of applications.     

Transmetalation in a Ce(III)‐phosphoester Crystalline Coordination Polymer with an Exceptionally High Selectivity for Yb(III) and Lu(III)

A novel crystalline coordination polymer containing Ce³⁺ and bis(4‐nitrophenyl) phosphate (L), CeL₃, was synthesized and its unique transmetalation selectivities toward Yb³⁺ and Lu³⁺ in the lanthanide series were evaluated. The relatively large difference in transmetalation selectivity between the neighboring Tm³⁺ and Yb³⁺ species is noteworthy because the reactivities of heavy lanthanides are generally considerably similar. The structural strain of the polymeric framework is likely responsible for this unusual trend. Powder X‐ray diffraction analysis indicated that, in the cases of only Yb³⁺ and Lu³⁺, large differences in their ionic sizes compared to that of Ce³⁺ in the parent framework may induce a structural strain after solid solution formation, while cleavage of the relatively weak Ce?O bond allows the formation of new Yb?O and Lu?O bonds with the incoming Yb³⁺ and Lu³⁺, respectively. Structural phase transitions likely caused by the heterogeneous nucleation of the Yb‐ (or Lu‐) type phase were also observed.     

Upconversion Luminescence through Cooperative and Energy-Transfer Mechanisms in Yb3+-Metal-Organic Frameworks

Lanthanide-doped metal–organic frameworks (Ln-MOFs) have versatile luminescence properties, however it is challenging to achieve lanthanide-based upconversion luminescence in these materials. Here, 1,3,5-benzenetricarboxylic acid (BTC) and trivalent Yb³⁺ ions were used to generate crystalline Yb-BTC MOF 1D-microrods with upconversion luminescence under near infrared excitation via cooperative luminescence. Subsequently, the Yb-BTC MOFs were doped with a variety of different lanthanides to evaluate the potential for Yb³⁺-based upconversion and energy transfer. Yb-BTC MOFs doped with Er³⁺, Ho³⁺, Tb³⁺, and Eu³⁺ ions exhibit both the cooperative luminescence from Yb³⁺ and the characteristic emission bands of these ions under 980 nm irradiation. In contrast, only the 497 nm upconversion emission band from Yb³⁺ is observed in the MOFs doped with Tm³⁺, Pr³⁺, Sm³⁺, and Dy³⁺. The effects of different dopants on the efficiency of cooperative luminescence were established and will provide guidance for the exploitation of Ln-MOFs exhibiting upconversion.     

Determination of trace amounts of Eu3+ and Yb3+ ions at Nafion-coated thin mercury film electrodes

The use of Nafion-coated thin mercury film electrodes (NCTMFE) for determining trace amounts of Eu³⁺ and Yb³⁺ ions was examined. Ion-exchange preconcentration of submicromolar levels of the two rare earths was achieved efficiently at a rotating NCTMFE, while the use of “classical” Nafion-coated glassy carbon electrodes is restricted to the determination of Eu³⁺ alone. Differential-pulse voltammetry was used to quantify the accumulated ions. The influence of variables such as rotation rate, preconcentration time and scan parameters was assessed. A preconcentration -voltammetry-regeneration scheme suitable for multiple analysis with the same modified electrode was developed. Calibration graphs with a linearity range extending up to 2 μM and detection limits of 0.03 and 0.08 μM for Eu³⁺ and Yb³⁺, respectively, were obtained. For Yb³⁺, the detection limit can be lowered to 0.02 μM by electrocatalytic amplification of the signals achieved by operating in the presence of ammonium nitrate as supporting electrolyte. However, in this instance a more restricted linearity range is observed. The effect of competing incorporation caused by the presence in solution of an excess of La³⁺ is also discussed, together with the competition between Eu³⁺ and Yb³⁺ when one of the two is present in large excess over the other.     

Effect of crystal structure and ions concentration on luminescence in Yb and Tm codoped fluoride microcrystals

A facile hydrothermal method is used for the preparation of Tm³⁺/Yb³⁺ codoped fluoride microphosphors. The effect of crystal structure and ions concentration on the spectra and lifetimes of the radiative levels of Tm³⁺ ions in the different fluoride microcrystals is studied in detail. XRD analysis of Tm³⁺/Yb³⁺ codoped LaF₃ microcrystals shows that 20% Yb³⁺ doping is sufficient for hexagonal LaF₃ microparticles to crystallize completely in the orthorhombic phase. And lifetime analysis suggests that the average lifetimes of the radiative levels of Tm³⁺ ions increased when the matrix phase structure changing from orthorhombic phase to hexagonal phase with ytterbium dopant concentration changing.     

Preparation and up-conversion fluorescence of rare earth (Er or Yb/Er)-doped TiO2 nanobelts

Anatase TiO₂ nanobelts doped with rare earth (RE) ions Yb³⁺, Er³⁺ or Yb³⁺/Er³⁺ have been prepared using layered titanate nanobelts (LTO NBs) with RE ions as the precursor obtained by ion-exchange between LTO NBs and RE ions under hydrothermal process. Various measurement results demonstrate that the RE ions have doped into the lattice of TiO₂, and the Er³⁺ or Yb³⁺/Er³⁺ doped nanobelts show strong visible up-conversion (UC) fluorescence under 980 nm excitation. The UC emission intensity of LTO NBs embedded with Er³⁺ or Yb³⁺/Er³⁺ is slightly higher than that of the corresponding TiO₂ nanobelts doped with RE ions, whereas higher RE doping content leads to the decrease of UC emission intensity due to the concentration-quenching effect.     

ErxYb1-x(TPB)3Bath(x=0,0.218,0.799,0.896,0.987,1)配合物的近红外发光性能

采用4,4,4-三氟-1-苯基-1,3-丁二酮（TPB）为第一配体,4,7-二苯基-1,10-菲咯啉（Bath）为第二配体,分别制备了配合物Er（TPB）₃Bath和Yb（TPB）₃Bath,以及它们的混合配合物Er_xYb_1-x（TPB）₃Bath（x=0.218,0.799,0.896,0.987）,并对所制得配合物的发光性能进行了系统研究。研究结果表明,所有配合物均能发射所含稀土离子的近红外特征光,并且可以通过调节混合配合物中的n_Er/n_Yb来调控Yb³⁺/Er³⁺之间的能量传递,进而提高Er³⁺离子在1530 nm处的发光。     

Rare‐Earth‐Based Nanoparticles with Simultaneously Enhanced Near‐Infrared (NIR)‐Visible (Vis) and NIR‐NIR Dual‐Conversion Luminescence for Multimodal Imaging

Multifunctional NaGdF₄:Yb³⁺,Er³⁺,Nd³⁺@NaGdF₄:Nd³⁺ core–shell nanoparticles (called Gd:Yb³⁺,Er³⁺,Nd³⁺@Gd:Nd³⁺ NPs) with simultaneously enhanced near‐infrared (NIR)‐visible (Vis) and NIR‐NIR dual‐conversion (up and down) luminescence (UCL/DCL) properties were successfully synthesized. The resulting core–shell NPs simultaneously emitted enhanced UCL at 522, 540, and 660 nm and DCL at 980 and 1060 nm under the excitation of a 793 nm laser. The enhanced UCL and DCL can be explained by complex energy‐transfer processes, Nd³⁺→Yb³⁺→Er³⁺ and Nd³⁺→Yb³⁺, respectively. The effects of Nd³⁺ concentration and shell thickness on the UCL/DCL properties were systematically investigated. The UCL and DCL properties of NPs were observed under the optimal conditions: a shell Nd³⁺ content of 20 % and a shell thickness of approximately 5 nm. Moreover, the Gd:Yb³⁺,Er³⁺,Nd³⁺@Gd:20 % Nd³⁺ NPs exhibited remarkable magnetic resonance imaging (MRI) properties similar to that of a clinical agent, Omniscan. Thus, the core–shell NPs with excellent UCL/DCL/magnetic resonance imaging (MRI) properties have great potential for both in vitro and in vivo multimodal bioimaging.