ZrO2：Er^3＋，Yb^3＋纳米晶的制备及Er^3＋离子能级在晶体场中的分裂

采用1，3-丁二醇低热结晶法制备了ZrO2：Er^3 ，Yb^3 纳米晶．常温下，用980nm的红外激光激发可以观察到很强的ZrO2：Er^3 ，Yb^3 纳米晶红光发射，用荧光光谱仪记录了该上转换光谱．X射线粉末衍射(XRD)结果表明，ZrO2：Er^3 ，Yb^3 纳米晶属于立方晶系．研究了纳米晶的上转换发光机理，根据晶体场理论对Er^3 的2个上转换能级进行了Stark分裂计算，对2个能级之间的谱线进行了归属，进一步证实了980nm激发Er^3 离子的上转换经历两个过程：一是连续吸收2个980nm光子的过程，二是吸收980nm光子，电子转移到亚稳态能级后，再吸收980nm光子的过程．     

MgAl2O4∶Er^3+,Yb^3+荧光粉的制备及其上转换发光性能

以尿素为沉淀剂,采用低温水热法结合煅烧过程制备出MgAl2O4∶Er^3+,Yb^3+上转换荧光粉,并对样品的结构、微观形貌及上转换发光性能予以表征。结果表明,随尿素加入量的增大,产物主形貌由六角片状结构向纳米棒状转变,经1100℃煅烧可得纯相镁铝尖晶石结构,且Er^3+和Yb^3+能有效进入MgAl2O4晶格并占据Mg^2+位置形成均匀固溶体。在980 nm光激发下,MgAl2O4∶1.0%(n/n)Er^3+,x%(n/n)Yb^3+(x=0~8.0)荧光粉表现出在524、545 nm处绿光以及658 nm处的强红光发射,红绿光强度均在5.0%(n/n)Yb^3+掺杂时达到最大,但红绿光强度比却在7.0%(n/n)Yb^3+掺杂时达到最大值5.2,这归因于Er^3+-Er^3+之间交叉弛豫(CR)在红光发射过程中所起的重要作用。通过控制荧光粉中Yb^3+的掺杂量,能初步实现对于黄绿光色度的有效调控。     

GdF3∶Er^3＋,Yb^3＋的合成和上转换发光特性

采用水热法制备了Er^3＋离子浓度为3%,Yb^3＋离子浓度分别为10%,20%的GdF3∶Er^3＋,Yb^3＋。XRD结果表明：合成的样品均为正交结构的GdF3,Gd0.87Yb0.10Er0.03F3和Gd0.77Yb0.20Er0.03F3样品的晶粒尺寸分别为28和26nm。研究了980nm红外光激发的上转换发射光谱。结果表明：红光和绿光发射分别来自于Er^3＋离子的2H11/2,4S3/2→4I15/2和4F9/2→4I15/2跃迁。样品的绿光发射强度较红光发射强。但绿光和红光发射的相对强度比例与Yb^3＋离子浓度有关。对Gd0.87Yb0.10Er0.03F3和Gd0.77Yb0.20Er0.03F3样品中可能的上转换发光机制进行了讨论。     

用于1．54μm微片激光器的高Er^3＋／Yb^3＋共掺杂的氟铝酸盐玻璃

本文系统制备了980nm半导体崩浦的应用于1．54μm波段微片激光器的高Er^3 ／Yb^3 共掺杂的氟铝酸盐玻璃。通过玻璃的吸收光谱，发射光谱和上转换荧光光谱的测试，对其光学性质、浓度淬灭及其淬灭机制进行了分析和讨论。当玻璃中Er^3 离子掺杂浓度低于10mol％的情况下，浓度淬灭现象较弱，Er^3 ／Yb^3 共掺杂的氟铝酸盐玻璃在由于Er^3 离子^4 I13／2→4^I 15／2跃迁所引起的1．54μm波段的发射强度比Er^3 单掺杂的氟铝酸盐玻璃中的荧光强度要强。在Er^3 离子掺杂浓度高于10mol％的情况下，由于Er^3 与Yb^3 之间的反能量转移过程，Er^3 ／Yb^3 共掺杂的氟铝酸盐玻璃的1．54μm波段的荧光浓度淬灭效应比Er^3 离子单掺杂的情况下明显。在Er^3 离子掺杂浓度小于10mol％的情况下，实验中发现可获得1．54μm波段高发射效率的Er^3 与Yb^3 离子最佳摩尔浓度掺杂比例约为1：1。     

两种基质中Er^3＋的上转换发光特性

合成了一种新型共掺杂Er^3 和Yb^3 的氟氧化物（ZnF2-SiO2基质）材料,研究了Er^3 在这种基质材料中的吸收和在980nm激发下的上转换发光,并对比了同等激发条件下Er^3 离子在ZBLAN玻璃和这种氟氧化物中的上转换发光特性。实验发现两种基质中Er^3 离子吸收峰位置基本相同,但吸收强度明显不同。氟氧化物中Er^3 离子的上转换发光强度要低于ZBLAN基质中Er^3 离子的上转换发光强度,不同的是Er^3 离子在氟氧化物基质中红光发射强度要强于绿光强度。分析了两种基质中Er^3 的上转换发光机制,氟氧化物基质中Er^3 离子红绿光发射均为双光子过程,ZBLAN基质中Er^3 离子绿光发射为双光子过程,而红光发射为双光子和三光子混合过程。     

用脉冲激光溅射法制备的Yb^3＋和Er^3＋共掺杂氟化物薄膜的上转换发光

脉冲激光溅射法（PLD），作为一种制备高质量薄膜的方法，被广泛地用于制备超导、铁电等薄膜。用PLD法制备的Yb^3 和Er^3 共掺杂氟化物薄膜的上转换发光性质。在978nm LD激发下，薄膜发出强烈的橙色光，用日立－F4500光谱仪测量了其上转换发光光谱，观测到了Er^3 很强的^2H9/2→^4I15/2(408nm),^2H11/2→^4I15/2(520nm),^4S3/2→^4I15/2(550nm)和^4F9/2→^4I15/2(650nm)跃迁发射峰。给出了上转换发光强度随激发强度的关系，分析了其上转换发光机制及紫色上转换发光增强的原因。     

温度对YLiF∶Er3+上转换发光的影响

研究了用水热法合成的YLiF4:Er^3 的上转换发光特性，用980nm的光激发样品时，得到了很强的绿光554nm和红光666nm，对应Er^3 离子不同能级的上转换发射为双峰发射，表明基质中Er^3 离子处于两种不同的格点上，改变测试温度时，样品的上转换发光强度随着温度的升高而下降，室温下，绿光的上转换机制是双光子和三光子混合过程，红光为双光子过程。     

Yb^(3+)/Er^(3+)双掺杂的NaYF_(4)上转换纳米功能材料的制备与设计优化北大核心CSCD

为合成单分散、形貌尺寸均一、高上转换发光的稀土上转换纳米功能材料,本文以稀土氯化物为反应前驱体,采用溶剂热法合成Yb^(3+)/Er^(3+)双掺杂的NaYF_(4)上转换发光纳米材料,并对稀土元素掺杂比例、反应时间、反应温度、油酸体积分数等影响材料结构、形貌和发光性能的条件进行了优化。结果表明,最佳稀土元素掺杂比例为78%Y^(3+)∶20%Yb^(3+)∶2%Er^(3+),反应时间90 min,反应温度300℃,油酸体积分数15.5%。在最佳条件下,本研究合成的NaYF_(4)∶Yb^(3+),Er^(3+)纳米材料形貌呈六方晶型,直径约为30 nm,与标准卡片匹配良好;在980 nm近红外光激发下,该纳米材料在529 nm、542 nm以及657 nm处均可以观察到Er^(3+)的特征发射峰,且发射出明亮的绿色荧光。本研究为后续制备修饰有不同功能基团的NaYF_(4)∶Yb^(3+),Er^(3+)纳米材料及其应用奠定了基础。     

Er~(3+)∶Yb~(3+)∶Tm~(3+)共掺硼硅酸盐玻璃光致发光温度特性和能级劈裂

高温固相烧结法制备了Er^3＋：Yb^3＋：Tm^3＋共掺硼硅酸盐玻璃．在978nm半导体激光器抽运下,测量了样品在300～573K下光致发光谱强度随温度的变化,讨论了室温时上转换绿光和红光等波段的光谱劈裂．分析了Er^3＋：Yb^3＋和Tm^3＋之间的能量传递机制．研究结果表明,当温度升高时,Er^3＋：Yb^3＋：Tm^3＋共掺硼硅酸盐玻璃的481nm蓝光、517和534nm绿光、以及657nm红光等光致发光强度单调下降,在490K时几乎消失．但900nm左右的近红外光谱则随温度的升高而持续增强,而且其中心波长向短波方向移动．在室温时,光谱劈裂明显,高温时劈裂逐渐消失．     

Studies on Upconversion Mechanism of ZrO2 ： Er^3＋, Yb^3＋ Nanocrystals Under Excitation at 488 and 980 nm

Erbium, Ytterbium-codoped ZrO2 nanoparticles(ZrO2:Er^3 ,Yb^3 ) were prepared by the sol-emulsiongel technique. The purpose of the present study is the application of upconversion phosphor in the biological label. In order to make out the mechanism of upconversion under 980 nm excitation the 488 nm pump was used. The influence of temperature on the crystallite phase was studied. The results confirm the upconverted mechanism in ZrO2:Er^3 ,Yb^3 nanocrystals is due to an energy transfer upconversion(ETU).     

Phosphine-catalyzed annulations of azomethine imines: allene-dependent [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] pathways

In this paper we describe the phosphine-catalyzed [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] annulations of azomethine imines and allenoates. These processes mark the first use of azomethine imines in nucleophilic phosphine catalysis, producing dinitrogen-fused heterocycles, including tetrahydropyrazolo-pyrazolones, -pyridazinones, -diazepinones, and -diazocinones. Counting the two different reaction modes in the [3 + 3] cyclizations, there are five distinct reaction pathways-the choice of which depends on the structure and chemical properties of the allenoate. All reactions are operationally simple and proceed smoothly under mild reaction conditions, affording a broad range of 1,2-dinitrogen-containing heterocycles in moderate to excellent yields. A zwitterionic intermediate formed from a phosphine and two molecules of ethyl 2,3-butadienoate acted as a 1,5-dipole in the annulations of azomethine imines, leading to the [3 + 2 + 3] tetrahydropyrazolo-diazocinone products. The incorporation of two molecules of an allenoate into an eight-membered-ring product represents a new application of this versatile class of molecules in nucleophilic phosphine catalysis. The salient features of this protocol--the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates--suggest that it might find extensive applications in heterocycle synthesis.     

Bi3+-Er3+ and Bi3+-Yb3+ Codoped Cs2AgInCl6 Double Perovskite Near-Infrared Emitters

Bi³⁺ and lanthanide ions have been codoped in metal oxides as optical sensitizers and emitters. But such codoping is not known in typical semiconductors such as Si, GaAs, and CdSe. Metal halide perovskite with coordination number 6 provides an opportunity to codope Bi³⁺ and lanthanide ions. Codoping of Bi³⁺ and Ln³⁺ (Ln=Er and Yb) in Cs₂AgInCl₆ double perovskite is presented. Bi³⁺-Er³⁺ codoped Cs₂AgInCl₆ shows Er³⁺ f-electron emission at 1540 nm (suitable for low-loss optical communication). Bi³⁺ codoping decreases the excitation (absorption) energy, such that the samples can be excited with ca. 370 nm light. At that excitation, Bi³⁺-Er³⁺ codoped Cs₂AgInCl₆ shows ca. 45 times higher emission intensity compared to the Er³⁺ doped Cs₂AgInCl₆. Similar results are also observed in Bi³⁺-Yb³⁺ codoped sample emitting at 994 nm. A combination of temperature-dependent (5.7 K to 423 K) photoluminescence and calculations is used to understand the optical sensitization and emission processes.     

Strong visible up-conversion emission in Tb3+, Tm3+ and Tb3+-Tm3+ co-doped tellurite glasses sensitized by Yb3+

Up-conversion luminescence characteristics under 975 nm excitation have been investigated with Tb3+/Tm3+/Yb3+ triply doped tellurite glasses. Here, green (547 nm: (5)D(4)-->(7)F(4)) and red (660 nm: (5)D(4)-->(7)F(2)) up-conversion (UC) luminescence originating from Tb3+ is observed strongly, because of the quadratic dependences of emission intensities on the excitation power. Especially, the UC luminescence was intensified violently with the energy transfer from the Tm3+ ions involves in the Tb3+ excitation. To the Tb3+/Tm3+/Yb3+ triply doped glass system, a novel up-conversion mechanism is proposed as follows: the energy of (3)G(4) level (Tm3+) was transferred to (5)D(4) (Tb(3+)) and the 477-nm UC luminescence of Tm3+ was nearly quenched.     

Pseudorotational dynamics of H3+ and Li3+

The origin of the pseudoprecession phenomenon is investigated through a computational study of the time evolution of H₃⁺ and Li₃⁺ by electron nuclear dynamics theory. In particular, the pseudorotation of both molecules is shown to induce a spatial rotation, which in turn leads to Coriolis coupling of the two orthogonal nuclear shape deformation modes. This effect is rooted in an anisotropy of the molecular ground state potential energy surface that is caused by the interaction between the D_3h ground state and a twofold degenerate first excited state. Computations are performed for a variety of vibrational energies. In addition, the impact of the anharmonicity of the ground state potential surface on the shape deformation modes and the coupling between them is discussed. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Spectroscopic properties of Er3+, Yb3 + and Er3 + /Yb3+ doped metaphosphate glasses

The absorption and emission spectroscopies of Er3+ doped and Er3+/Yb3+ codoped Ca(PO3)2, Sr(PO3)2 and Ba(PO3)2 glasses have been studied. From the Judd-Ofelt intensity parameters, the spontaneous emission probabilities of some relevant transitions and the radiative lifetimes of several excited states of Er3+ have been calculated. The decay curves of the Er3+ emission at 1.5 microm have been measured at different temperatures. The data have been fitted using a stretched exponential function and the obtained experimental lifetimes have been compared with the calculated radiative lifetimes. The difference between the experimental and calculated lifetimes is attributed to the presence of traces of OH groups in the host glasses. The absolute OH content in some glasses has been determined from the infrared spectra. The emission spectra at 1.5 microm of the Er3+ ion in the codoped glasses have been measured at different temperatures. The integrated emission intensities decrease significantly on passing from room temperature to 13 K, suggesting a temperature dependence of the rate of the energy transfer process between Yb3+ and Er3+.     

Energy transfer between Gd3+ and Sm3+ the effect of Gd3+ on quenching of Sm3+ and intensity parameters of Sm3+ in borate glasses

Intensity parameters of Sm³⁺ in borate glasses were obtained by fitting the oscillator strengths to the Judd-Ofelt formula and a study of energy transfer from gadolinium to samarium was performed. An increase of samarium fluorescence originating from the ${}^4\text{G}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ level was observed in the presence of gadolinium, in the concentration range of 0.1–3 wt% samarium with gadolinium constant at 3 wt%. The intensity of samarium fluorescence on excitation at 273 nm increased by one order of magnitude in the presence of gadolinium. From the excitation spectrum of the double-doped glasses (Gd + Sm), it was deduced that energy absorbed by gadolinium is transferred from ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ gadolinium levels to the ${}^4\text{P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and ${}^4\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ samarium levels.The mechanism of this energy transfer was obtained by plotting the energy transfer probabilities as a function of samarium concentration. A linear dependence of $\text{η}{}_0\text{η}$ (η intensity of gadolinium in the presence of samarium) versus square of concentration of Sm + Gd is obtained. From this it is concluded that the transfer is of electric-multipolar type, mainly dipole-dipole. A small increase (about 10%) of fluorescence of samarium in the presence of gadolinium excited at levels where no energy transfer can take place is attributed to the fact that the quenching of samarium occurring by the cross relaxation $\text{(}{}^4\text{G}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{→}{}^6\text{F}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{) (}{}^6\text{H}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{→}{}^6\text{F}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}$ is suppressed by the presence of gadolinium as seen from concentration dependence of samarium doped glasses compared to double-doped glasses.     

Er3+-Tm3+-Yb3+ tri-doped CaMoO4 upconverting phosphors in optical devices applications

The structural and optical properties of the Er³⁺-Tm³⁺-Yb³⁺codoped CaMoO₄ phosphors prepared by chemical route have been explored. The crystalline structures of the prepared phosphors have been investigated with the help of X-ray diffraction analysis. The presence of different vibrational modes and absorption bands arising due to the transitions from the ground state to different excited states of rare earth ions have been identified using the Raman and UV-VIS-NIR absorption spectra of the developed phosphor, respectively. The concentration quenching effect on the luminescence property of the prepared materials has been explained in detail. The upconversion luminescence property of the Er³⁺-Tm³⁺-Yb³⁺codoped CaMoO₄ phosphor annealed at different temperatures under 980 nm and 808 nm excitations have been reported. The energy transfer Er³⁺ → Tm³⁺, Yb³⁺ → Er³⁺ and Tm³⁺ has been found to be responsible for efficient UC emission. The dipole-dipole interaction is observed to be responsible for the concentration quenching of the luminescence intensity. The effect of annealing temperature on the upconversion luminescence property has been explained in detail. The results suggest that the developed tri-doped phosphor may be suitable in making the efficient NIR to visible upconverter and lighting based optical devices.     

沉淀法制备Sm3+,Er3+与Nd3+一次共掺杂的BaTiO3基半导体陶瓷电容器

在共沉淀法的基础上,通过双施主不同浓度的Nd3+和Sm3+,Er3+(4.0%～5.0%)掺杂,研究了BaTiO3基表面型陶瓷电容器的电性能,结果表明,Sm3+和Er3+的掺杂可以提高居里温度,但使介电常数降低,其含量为25%时可获得绝缘电阻500 MΩ左右,C/S为0.5895μf·cm-2电性能参数.     

Tb~(3+)在YAG中的发光及Tb~(3+)与Tm~(3 +)间的能量传递

采用溶胶 -凝胶方法合成了系列化合物 (Y1 -x- yTbxTmy) 3Al5O1 2 ,研究了Tb3+在该化合物中的发光及其浓度对发光性质的影响 ,以及Tb3+与Tm3+间的能量传递现象。