Color-tunable Upconversion Properties of Tb~(3+)/Er~(3+)/Yb~(3+) Tri-doped Na_5Gd(WO_4)_4 Crystals

In this work, novel phosphors Na5Gd(WO4)4: Tb^3+/Yb^3+ and Na5Gd(WO4)4: Tb^3+/Er^3+/Yb^3+ phosphors were synthesized by the solid state reaction method. The photoluminescence properties were investigated. The introduction of Er^3+ to NGW: Tb^3+/Yb^3+ was used to modify the chromaticity coordinates, then providing a good color tunable property. The change in the chromaticity coordinates induces the shift of emission color from yellow-green to blue-green for NGW: Tb^3+/Er^3+/Yb^3+ as the temperature increases. All the results indicate that the NGW: Er^3+/Tb^3+/Yb^3+ phosphors may be used as optical temperature sensing materials.     

Efficient Near-infrared Down-conversion Phosphor of Ce~(3+)/Yb~(3+) Co-doped La_3Ga_5SiO_(14) and Its Spectral Structural Modulation

A series of near-infrared(NIR) down-conversion phosphors of La_3 Ga_5 SiO_(14)(LGS):Ce~(3+)/Yb~(3+)were synthesized via high-temperature solid-state reaction. Under excitation at 345 nm, the phosphors show strong NIR emission around 978 nm, which matches well with the optimal spectral response of crystalline silicon(c-Si)solar cells. The emission spectra and decay curves were used to demonstrate the energy transfer from Ce~(3+) to Yb~(3+).The energy transfer mechanism was discussed in detail, indicating that the energy transfer from Ce~(3+) to Yb3+ is dominated by a single photon process, and the energy transfer efficiency is up to 51%. In addition, La3 Ga5-zAlzSiO_(14)(z = 0, 1, 2, 3):Ce3+/Yb~(3+) were also synthesized. The NIR emission intensity of La3 Ga2 Al3 SiO14:1%Ce~(3+)/5%Yb~(3+) is 4.6 times that of LGS:1%Ce~(3+)/5%Yb~(3+), and the thermal relaxation was used to explain this phenomenon. The results show that La_3 Ga_(5-z)AlzSiO_(14)(z = 0, 1, 2, 3):1%Ce~(3+)/5%Yb~(3+) phosphors have the potential to increase the conversion efficiency of c-Si solar cells.     

980 nm LD激发下稀土掺杂Gd_2Ti_2O_7粉末上转换发光

用高温固相法分别合成了Er~(3+)/Yb~(3+),Ho~(3+)/Yb~(3+),Tm~(3+)/Yb~(3+)离子共掺杂的Gd_2Ti_2O_7粉末,X射线衍射结果表明所制备的粉体为立方相烧绿石结构,TEM电镜照片显示其颗粒平均粒径为3μm.该粉末在980 nm LD激发下,分别发射出中心波长为553 nm绿色和662 nm红色(掺Er~(3+)样品)、545 nm绿色和652 nm红色(掺Ho~(3+)样品)、482 nm蓝色和653 nm红色(掺Tm~(3+)样品)的上转换荧光.上转换发光强度和激发功率的关系研究表明,能量传递和激发态吸收是上转换发光的主要机制.同时对Yb~(3+)-Er~(3+),Yb~(3+)-Tm~(3+)共掺体系的上转换发光强度"过饱和"现象进行了分析,认为是样品的被激发点的温度升高导致了荧光猝灭现象.     

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.     

Spectroscopy and Energy Transfer in Yb3＋ and Tm3＋ Co-doped Gd3Ga5O12 Crystal

Yb3+/Tm3+ co-doped Gd3Ga5O12 single crystal with a dimension of Φ30mm×20mm was grown successfully by Czochralski method.The absorption spectrum was recorded at room temperature and used to calculate the absorption cross-section.Based on the Judd-Ofelt(J-O) theory,we obtained the three intensity parameters and spectral parameters of this crystal,such as the line strengths,oscillator strengths,radiative probabilities and radiative lifetimes as well as the fluorescent branching ratios.Room temperature fluorescence spectra and luminescence decay curves were recorded.The energy transfer between Yb3+-Tm3+ was observed and the mechanism was discussed.The stimulated emission cross-section of the 3F4→3H6 transition was calculated by the Füchtbauer-Ladenburg(F-L) equation.The potential laser gains for this transition were also investigated.This crystal is promising as a tunable infrared laser crystal at 2.0 μm.     

Bi3+掺杂对YVO4:Yb3+近红外发光的敏化作用

用主温固相法合成了Yb³⁺、Bi³⁺共掺的YVO₄,研究了Bi³⁺的掺入对YVO₄:Yb³⁺发光光谱的影响和近红外发光的敏化作用.X射线衍射图谱研究表明:掺入Yb³⁺、Bi³⁺之后,基质YVO₄的晶格结构没有发生明显变化.Bi³⁺的掺入不仅显著增强了样品中Yb³⁺的特征远红外发光强度,还使YVO₄:Yb³⁺激发光谱的范围红移,当Bi³⁺掺入的摩尔分数从0增加到0.05时,样品的最强激发峰位置从335nm红移至352 nm,激发光谱范围由300-360 nm扩宽至300-430 nm.优化的Bi³⁺掺入量为0.03.初步讨论了VO₄^3-,Bi³⁺Yb³⁺间的能量传递机理.结果表明Bi^3-的共掺使YVO₄:Yb³⁺样品对长波紫外光的响应性能大大改善,作为一种基于量子剪裁的光谱转换材料,可以更好地匹配太阳光的能量谱,有助于提高硅太阳能电池的光电转换效率.     

Preferential suppression of high-energy upconverted emissions of Tm3+ by Dy3+ ions in Tm3+/Dy3+/Yb3+-doped LiYF4 colloidal nanocrystals

The intensity of high energy UV and blue upconverted emissions of Tm(3+) ions in Tm(3+)/Yb(3+) co-doped LiYF(4) colloidal nanocrystals was selectively reduced compared to the NIR emission at 802 nm. This was achieved by doping a small amount of Dy(3+) ions into the host matrix.     

Shape Control,Crystalline Conversion and Pseudocapacitance Properties of Mn_3O_4: Effects of Yb~(3+) Doping

We report a facile method for the synthesis of manganese oxide(Mn_3O_4) nanorods via the direct reaction of MnCl2 and H_2 O2 by doping Yb~(3+) ions at room temperature and air atmosphere. The Mn_3O_4:Yb~(3+) samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), cyclic voltammetry(CVs), electrochemical impedance spectroscopy(EIS), and charging-discharging test(CD). The results show that trace Yb~(3+) doping(6 at%) could effectively induce crystalline transformation of Mn_3O_4 from cubic system(space group Fd-3 m) to tetragonal system(space group I41/amd) and incite the morphology changing from irregular particles to uniform nanorods. When Yb~(3+) doping amount is 3%, the capacitance of Mn_3O_4 reaches the maximum, 246 F/g, which is related to the morphology change and the corresponding decrease of impedance.     

Facile synthesis and multicolor luminescent properties of uniform Lu2O3:Ln (Ln=Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanospheres

Multicolor Lu(2)O(3):Ln (Ln=Eu(3+), Tb(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) nanocrystals (NCs) with uniform spherical morphology were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and photoluminescence (PL) spectra as well as kinetic decays were employed to characterize these samples. The XRD results reveal that the as-prepared nanospheres can be well indexed to cubic Lu(2)O(3) phase with high purity. The SEM images show the obtained Lu(2)O(3):Ln samples consist of regular nanospheres with the mean diameter of 95 nm. And the possible formation mechanism is also proposed. Upon ultraviolet (UV) excitation, Lu(2)O(3):Ln (Ln=Eu(3+) and Tb(3+)) NCs exhibit bright red (Eu(3+), (5)D(0)→(7)F(2)), and green (Tb(3+), (5)D(4)→(7)F(5)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu(2)O(3):Ln (Ln=Yb(3+)/Er(3+), Yb(3+)/Tm(3+), and Yb(3+)/Ho(3+)) NCs display the typical up-conversion (UC) emissions of 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-green (Ho(3+), (5)F(4), (5)S(2)→(5)I(8)), respectively.     

Optical Spectroscopic Properties of Yb~(3+)-Doped MgMoO_4 Crystal Grown by the TSSG Method

This paper reports the growth and spectral assessments of Yb~(3+) ion doped MgMoO_4(Yb~(3+):MgMoO_4) crystal grown by the TSSG method. Polarized spectral properties of Yb~(3+):MgMoO_4 crystal, including absorption and emission cross-sections, absorption FWHM and fluorescence lifetime, have been investigated. The laser performance parameters bmin, Isat and Iminhave also been evaluated. All the investigated results show the Yb~(3+)-doped MgMoO_4 crystal is expected as a promising candidate for ultrashort pulse and tunable lasers.     

沉淀法合成纳米晶上转换发光材料Y_2O_2S:Yb,Er

采用沉淀法在不同温度下合成了纳米上转换发光材料Y2O2S∶Yb,Er,运用XRD、TEM和上转换发光光谱对其进行表征。结果表明,使用该法在700℃即能合成纳米上转换发光材料Y2O2S∶Yb,Er,随着合成温度的升高,产物的粒径从60到120nm逐渐增大。上转换发光光谱显示该材料主要有2个发射带,其中红光发射的中心波长位于668nm,绿光发射的中心波长位于525和550nm。此外,对材料的上转换发光过程进行了探讨。     

Target-responsive DNAzyme hydrogel for portable colorimetric detection of lanthanide(Ⅲ) ions

Lanthanide elements(Ln)play an important role in industry and agriculture.As a result of the increasing consumption of lanthanides,environmental emission of Ln has become detrimental to the health of flora and fauna.Current methods for trace lanthanides detection mainly rely on sophisticated instruments.In this article,a Ln~(3+)dependent DNAzyme was incorporated into a hydrogel to generate Ln~(3+)sensitive DNAzyme hydrogel for portable colorimetric detection.The enzyme strand and its substrate strand act as crosslinker and functional unit of the hydrogel with polyacrylamide chains as the scaffold and gold nanoparticles(AuNPs)as the indicator of hydrogel stability.Any ions in the Ln~(3+)series can trigger the cleavage of substrate strand by activating the enzyme strand,thereby decreasing the crosslink ratio and leading to collapse of the hydrogel.The release of the encapsulated AuNPs turns the supernatant wine red.Using this colorimetric method,Ln~(3+)can be detected with high sensitivity,with a limit of detection(LOD)of 20 nM for Ce~(3+).The hydrogel responds specifically to any Ln~(3+)ion and works well with the spiked lake sample without the need of instruments and skilled operators.Our results suggest that the lanthanide responsive hydrogel can be used for portable and sensitive detection of Ln~(3+)contamination in the field.     

静电纺丝技术制备Y_2O_3∶Yb~(3+),Er~(3+)上转换纳米纤维及其表征

采用静电纺丝技术制备了PVA/[Y(NO3)3+Yb(NO3)3+Er(NO3)3]复合纳米纤维,将其在适当的温度下进行热处理,得到Y2O3∶Yb3+,Er3+上转换纳米纤维.XRD分析表明,复合纳米纤维为无定形,Y2O3∶Yb3+,Er3+上转换纳米纤维属于体心立方晶系,空间群为Ia3.SEM分析表明,复合纳米纤维的平均直径约为150nm;随着焙烧温度的升高,纤维直径逐渐减小.经过600℃焙烧后,获得了直径约60nm的Y2O3∶Yb3+,Er3+上转换纳米纤维.TG-DTA分析表明,当焙烧温度高于600℃时,复合纳米纤维中水分、有机物和硝酸盐分解挥发完毕,样品不再失重,总失重率为83%.FTIR分析表明,复合纳米纤维与纯PVA的红外光谱一致,当焙烧温度高于600℃时,生成了Y2O3∶Yb3+,Er3+上转换纳米纤维.该纤维在980nm的半导体激光器激发下发射出中心波长为521,562nm的绿色和656nm的红色上转换荧光,分别对应于Er3+离子的2H11/2/4S3/2→4Il5/2跃迁和4F9/2→4Il5/2跃迁.对Y2O3∶Yb3+,Er3+上转换纳米纤维的形成机理进行了讨论.     

Eu3+/Tb3+和Eu3+/Pr3+共掺杂P(MMA-co-St)的荧光性能的研究

将不同荧光性能的铽(Tb)、镨(Pr)离子分别与铕(Eu)离子混合，以三异丙氧基稀土的形式掺杂P(MMA-CO-St)共聚物，研究Eu^3 ／Tb^3 和Eu^3 ／pr^3 共掺杂P(MMA-CO-St)的荧光性能的变化情况．结果表明，Eu^3 ／Tb^3 掺杂的P(MMA-CO-St)中，Tb^3 作为能量给予体，Eu^3 作为能量接受体，能量转移的结果使Eu^3 特征荧光显增强；Eu^3 ／pr^3 掺杂的P(MMA-CO-St)中，Eu^3 的能量向pr^3 转移，致使Eu^3 的特征荧光猝灭，pr^3 的荧光略为增强．     

相位可控的氟钪纳米晶的合成及其上转换发光性能

控制反应条件如表面活性剂的组成、加入量或反应时间,可以制得不同形态、相结构且具有上转换发光(UCL)的氟钪纳米晶(NCs)。改变表面活性剂油酸(OA)/油胺(OM)的比例有利于晶体结构从立方相ScF_3∶Yb,Er转变为具有上转换发光性能增强的正交相KSc_2F_7∶Yb,Er纳米晶,而纳米晶的形态会发生从小到大的转变。改变掺杂元素的种类及含量,在980 nm光激发下,KSc_2F_7纳米晶的上转换发光可以从蓝色变到白色,再到主要发射紫色光。     

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.     

纳米晶LaAlO3掺Eu3+的复合沉淀法制备及发光性质

以NH₃·H₂O-NH₄HCO₃混合溶液为复合沉淀剂,制备了LaAlO₃:Eu³⁺纳米晶体.通过X射线衍射、扫描电镜和透射电镜对产物进行了表征,用荧光光度计测试了样品的三维荧光光谱、激发光谱和发射光谱.结果表明:前驱沉淀物经800℃焙烧处理2h,制备出球型形貌,颗粒分散性好、尺寸约为40nm的立方相LaAlO₃纳米晶.由三维荧光光谱确定了LaAlO₃:Eu³⁺的最佳监测波长和激发波长,在395nm波长光的激发下观察到纳米LaAlO₃中Eu³⁺的591nm(⁵D₀-⁷F₁)和613nm(⁵D₀-⁷F₂)特征发射谱,磁偶极跃迁⁵D₀-⁷F₁的发射峰强度要比电偶极跃迁⁵D₀-⁷F₂更强,而且这种趋势随着焙烧温度的升高明显增强,说明由该法制备的纳米LaAlO₃中Eu³⁺离子占据的位置具有高的对称性.     

Energetics of Ce and Pu incorporation into zirconolite waste-forms

The General Utility Lattice Program (GULP) has been used to model the zirconolite lattice, calculate the energies of substituting Ce(3+), Ce(4+), Pu(3+), Pu(4+) and Fe(3+) into the lattice both as single and multi-defect systems and model the formation of Ce(3+), Ce(4+), Pu(3+) and Pu(4+) doped zirconolite lattices. These results have been compared against experimental observations, with particular emphasis on those Ce containing solid solutions that exhibit Ce(3+)/Ce(4+) mixed valence characteristics. It is found that the Ce(3+)/Ce(4+) mixed valence is as a result of reduction within the lattice, with the Ce(3+) being stabilised on the Ca site, and that this behaviour would not be expected for the corresponding Pu solid solutions.     

Luminescence interference-free lifetime nanothermometry pinpoints in vivo temperature

Luminescence nanothermometry makes non-invasive and real-time temperature readings possible in living animals. However,the spectral fluctuation in tissues and fluids, as well as the interaction between fluorophores and environment hinders accuracy of the thermometry. Here, we report a luminescence lifetime-based nanothermometry which specifically addresses this problem. A temporal based calibration(lifetime sensing) in the NIR range, an endogenous thermal response as well as a polymer encapsulation evading environmental factors, altogether help to pinpoint temperature in vivo. Thanks to the highly condensed NdYb ions in a well-protected tiny core-shell nanocrystal(overall 11 nm), a temperature sensitivity about 2.07% K~(-1)(with 5% Yb~(3+) doped nanoparticles) and an accuracy of 0.27 K(with 25% Yb~(3+) doped nanoparticles) in biological fluids are achieved.Hopefully, combining thermally activated energy transfer nanothermometer with anti-interference lifetime thermometry would provide a more accurate temperature measurement for biological and preclinical studies.     

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+).