In3+共掺杂诱导NaY0.95-xYb0.03Er0.02F4相转变与上转换发光增强研究

引入In³⁺作为新的掺杂离子通过水热法合成了In³⁺与Er³⁺,Yb³⁺共掺杂的NaYF₄上转换发光材料. 通过XRD表征及Rietveld精修,SEM以及TEM研究了In掺杂引起的NaYF₄形貌与晶体结构的变化. 通过发射光谱与发光衰减曲线表征了掺杂NaYF₄的上转换发光性能,以研究晶体微观结构与上转换发光性能之间的关系. 结果表明随着In掺杂量的增加,立方相NaYF₄的晶格畸变不断增强且发生由立方相向六方相的转变. 对于六方相NaYF₄,其上转换发光强度随着In含量的提高不断增强并当In含量为3%时达到最大值. 该研究结果可以有助于设计与合成具有优良上转换发光性能的材料.     

La0.789Yb0.20Ho0.001Tm0.01F3纳米立方体的溶剂热合成及白色上转换发光性质

采用溶剂热方法制备了La0.789Yb0.20Ho0.001Tm0.01F3纳米立方体,并利用粉末X射线衍射仪、透射电子显微镜和X射线能谱仪表征了其组成、结构和形貌,用荧光分光光度计测量了样品的室温上转换发射光谱,结果表明,样品具有红、绿和蓝色3个发射带,其辐射跃迁分别归属于Tm3+的1G4→3H6(蓝色)和1G4→3...     

水热合成稀土氟化物材料YLiF4∶Yb,Tm的上转换发光特性

利用水热法合成了掺杂Tm3 和Yb3 的YLiF4材料, 并研究了Tm3 和Yb3 在材料中的光吸收, 以及980 nm红外光激发下不同Tm3 浓度掺杂下的上转换发光特性. 实验发现, 在980 nm激光激发下, 材料可发出可见光. 上转换发光光谱中包括蓝光和红光. 与蓝光相比, 红光强度要弱1～2个数量级. 上转换发光强度和浓度关系研究显示, 当Tm3 浓度为0.3% (摩尔分数)时上转换发光达到最强, 大于0.3% (摩尔分数)后发光开始减弱. 通过分析输出光强与泵浦功率的双对数曲线, 发现Tm3 的蓝光发射和红光发射均属于双光子过程.     

YVO_4:Eu~(3+)纳米晶的水热合成与发光特性

采用水热法在不同温度下制备了系列YVO4:Eu3+纳米晶。利用X射线衍射、电镜和荧光光谱对前驱体和系列样品的结构、形貌和发光性能进行了研究。XRD研究结果表明:合成的样品均为四方相YVO4,纳米晶的一次性粒径分布在13~44 nm。发射光谱和激发光谱的研究表明:特征发射峰来自于5D0-7FJ跃迁,激发带主要来自于Eu-O和V-O的电荷迁移带,发射强度和激发强度随样品结晶度的提高而增强。对样品5D0-7F2跃迁中来自于不同态的发射峰的相对强度进行了比较和讨论。     

Hf4+共掺NaYF4:Yb/Tm提高上转换发光性能研究

利用X射线多晶衍射仪、场发射扫描电镜、场发射透射电镜、X射线光电子能谱和荧光光谱仪对相近半径离子Hf⁴⁺和Zr⁴⁺共掺六方NaYF₄:Yb³⁺/Tm³⁺的结构、形貌和上转换发光性能进行研究.结果表明Hf⁴⁺和Zr⁴⁺离子共掺六方NaYF₄:Yb³⁺/Tm³⁺可有效调控晶场的不对称性, Hf⁴⁺相对于Zr⁴⁺是个更好的掺杂离子,它在调控晶场的同时还参与Tm³⁺离子上转换发光的能量传递过程,明显提高了短波500 nm以下发射带的荧光强度;而Zr⁴⁺离子仅扮演晶场调控角色而未能参与稀土离子Tm³⁺的上转换发光过程, Tm³⁺离子小于500 nm短波发射带的荧光强度没有得到明显的提高,仅提高802 nm发射带的荧光强度.该研究发现Hf⁴⁺可作为蓄能离子参与稀土离子的上转换发光过程,有助于将Hf⁴⁺作为蓄能离子和晶格操纵工具用于设计和制备其它高性能的稀土上转换发光材料.     

Fabrication,Structure and Optical Properties of Zr~(4+) Doped Ba(Mg,Ta) O_3 Transparent Ceramics with High Refractive Index

Novel transparent ceramics of Zr4+ doped Ba(Mg,Ta)O3(BMT)with a high refractive index of 2.037 at 587.56 nm were successfully fabricated via high temperature solid-state-reaction sintering method.To make it transparent,the pure cubic Ba(Zr,Mg,Ta)O3 phases(BZMT)were realized in advance by skillfully modulating the lattice structure of BMT from trigonal symmetric to cubic symmetric through doping Zr4+ into the lattice of BMT crystal.Highly optical transmittance of 74% at 650 n,,which hit the upper limit of the theory,was achieved for BZMT.Both abbe number of 23.4 and the bandgap Eg of 3.22 eV have been calculated.     

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.     

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.     

Sr_2SiO_4:Eu~(3+)荧光粉的燃烧法制备及其发光性能的研究

利用H3BO3作为助熔剂、尿素为燃料,采用燃烧法成功制备了发光性能良好的Sr2SiO4:Eu3+红色荧光粉,通过X射线衍射和荧光分光光度计对样品进行了表征。实验结果表明:Sr2SiO4:Eu3+荧光粉的衍射峰发生了偏移,晶格常数减小,Eu3+的加入使得晶格发生了收缩;同时发现H3BO3的加入有利于α′-Sr2SiO4纯相的形成和(211)晶面的生长;选择H3BO3(1%,2%,3%,5%(质量分数))做助熔剂,有效地提高了Sr2SiO4:Eu3+荧光粉的发光强度;H3BO3用量从1%增加到3%时,位于5D1→7F3跃迁的587 nm的发射峰和5D0→7F2跃迁的622 nm的发射峰逐渐增强。     

Structure and Photocatalytic Performance of Zr~(4+) Doped Bi_2WO_6 Synthesized by Fast Microwave-assisted Hydrothermal Method

Zr~(4+) doped Bi_2WO_6 was prepared by a fast microwave-assisted hydrothermal method and used for photocatalytic degradation of organic dyes. The as-prepared samples were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and UV-Vis spectroscopy. The results indicate that cell volume of Bi_2WO_6 has a slight increase dependent on the substitution of W6+ by Zr~(4+) with increasing the Zr doping amount. The photocatalytic performance of Zr~(4+) doped Bi_2WO_6 was evaluated by the photodegradation of MO under visible light irradiation. Compared with samples obtained with traditional hydrothermal method as well as pure Bi_2WO_6, an obviously improved photocatalytic efficiency of Zr~(4+) doped Bi_2WO_6 is achieved by this microwave-assisted hydrothermal way. The 3% Zr doped Bi_2WO_6 sample exhibited the best photocatalytic activity, which is probably because of the appropriate proportion of components and optimum amount of oxygen vacancies of the sample.     

Ba_3(PO_4)_2:Ce~(3+),Dy~(3+)荧光粉的组成与发光特性研究

在活性炭还原气氛下高温固相法合成了Ba3(PO4)2:Ce3+,Dy3+紫外发射荧光粉。XRD图谱表明,烧结温度为1100℃时保温处理3 h,样品为单相的Ba3(PO4)2型六方晶系结构。荧光光谱显示:单掺Ce3+样品中,Ce3+掺杂浓度为8%(摩尔分数)时样品的发光最强,发射峰的位置处在350 nm附近(Ce3+的2D→2F5/2和2D→2F7/2跃迁发射)。适量的Sr2+取代部分Ba2+离子,改变了基质晶格环境,使样品的发光强度得到提高且发射峰向长波方向红移。引入Dy3+作为敏化剂,样品发射峰红移到386 nm,亮度增强,主要是由于Dy3+和Ce3+之间发生了有效的能量传递过程。确定了Dy3+的最佳掺杂浓度为3%,发光强度提高了27%。     

水热合成稀土氟化物材料KZnF3∶Er, Yb的上转换发光特性

水热法合成了掺杂Er3+和Yb3+的 KZnF3材料, 研究了Er3+和Yb3+在这种基质材料中的吸收和在980 nm红外光激发下的上转换发光, 对比了不同Yb3+浓度(0%～4%)下的上转换发光特性.实验发现, 在同种材料中, Er3+的红光发光强度要明显强于绿光, 而且掺Yb3+后红光和绿光的光强比不掺Yb3+时都有了很明显地增强.当Yb3+浓度为2%时上转换发光光强达到最强, 大于2%后发光开始减弱.通过分析输出光强与泵浦光强的双对数曲线, 发现Er3+的红光和绿光的发射均属于双光子过程, 最后分析了红光和绿光上转换发光的具体过程和转换通道.     

水热法合成YLiF4∶Er3+的上转换发光

用水热法合成了YLiF4∶Er3+,Er3+浓度变化范围为 0%～5%.在室温下,测试了所有样品在200～1200 nm间的吸收光谱.当 Er3+浓度为2%(Er-2样品)时,由吸收光谱计算得到的J-O参数为Ω2=1.05×10-20 cm2,Ω4=1.25×10-20 cm2和Ω6=1.35×10-20 cm2.在980 nm激发下,测试了所有样品的上转换发光光谱,发光强度随Er3+ 浓度增加而增长.当Er3+ 浓度小于1.5%,激发态吸收是主要的上转换发光机制.当Er3+ 浓度高于1.5%时,上转换机制包括激发态吸收和能量传递.在室温下,Er-2样品的能级2H11/2的寿命是205 μs,4S3/2的是205 μs,4F9/2是188 μs.根据实验数据和计算所得的跃迁几率,计算了4S3/2能级和4F9/2能级的量子效率,分别是27.9%和10.7%,表明两者都具有很高的量子效率.     

Er~(3+)掺杂硼硅酸盐玻璃的近红外发射特性研究

利用高温熔融法合成了掺Er3+硼硅酸盐玻璃。测量了样品的吸收光谱,由J-O理论得到了强度参数Ωλ(λ=2,4,6)及一些相关参数。用970nm光激发测量了10～300K之间的近红外发射光谱。利用McCumber理论拟合得到了1.53μm发射的受激发射截面,并与测量得到的发射光谱线形符合较好。由受激发射截面和发射光谱得到的半高全宽分别为59和56nm。利用能级简化模型讨论了样品的红外变温发射光谱,提出了增大1.53μm发射带宽的途径。     

[Ru(bpy)_2tpphz]~(2+)与Zn~(2+)形成的双核配合物的荧光性质研究

近年来,钌多吡啶配合物与DNA的作用得到了比较广泛的研究,并且发展了一系列具有特定功能的钌配合物犤1犦。如传统的DNA分子光开关犤Ru(bpy)2dppz犦2+和犤Ru(phen)2dppz犦2+犤2,3犦(bpy=2,2'-联吡啶,phen=1,10-菲咯啉,dppz=二吡啶犤3,2-a:2',3'-c犦吩嗪)。这些配合物与DNA具有较强的结合力,在水溶液中几乎不发光,但在DNA存在下则有强烈荧光发出。这是由于配合物插入DNA的碱基对之后,保护了dppz的吡嗪环上的N原子,使其免受水分子的进攻从而导致配合物荧光的恢复。但是对于大多数的多吡啶钌配合物来讲,由于其自身较强的背景荧光或与DN…     

正铌酸镧(LaNbO4)及其掺杂粉体的发光特性

采用化学共沉淀法和高温固相法合成制备得到纯的和掺杂Tb的LaNbO4超细粉体, 并对其发光性能进行了激发和发射光谱分析.测试表明, LaNbO4可被汞线激发, 发射波长处于蓝紫光区; 相比高温固相法, 化学共沉淀法制备的LaNbO4粉末相对发光强度增加3～4倍;Tb的掺杂使(La, Tb)NbO4粉体在汞线激发下发出黄绿色光, (La, Tb)NbO4的基质络离子NbO6发生淬灭, 并对有关机制进行了讨论.     

Luminescence of RE~(3+) and energy transfer from Gd~(3+) to RE~(3+) (RE = Dy, Eu) in SrGdAlO_4:RE~(3+)

Spectral properties of Gd3+, Dy3+ and Eu3+ ions in SrGdAlO4 are reported in detail. A cooperative vibronic transition of Gd3+ and the emission from the higher 5DJ (J=1, 2, 3) levels of Eu3+ were observed. Energy transfer occurs from Gd3+ to Dy3+ and to Eu3+. The influence of Gd3+ and Dy3+ concentrations on the luminescence intensity is discussed.     

Upconversion emission enhancement of Gd3+ ions induced by surface plasmon field in Au@NaYF4 nanostructures codoped with Gd(3+)-Yb(3+)-Tm(3+) ions

Au nanoparticles (NPs) attached β-NaYF(4) nanocrystals codoped with Gd(3+)-Yb(3+)-Tm(3+) were synthesized by a facial solution method. The UV-vis-near-infrared absorption spectrum shows typical surface plasmon resonance band of Au NPs in addition to the characteristic absorption peaks of Yb(3+) ion. X-ray diffraction and selected area electron diffraction results indicate the existence of Au NPs. The transmission electron microscopic image reveals the formation of Au@NaYF(4) nanostructures. Enhanced ultraviolet (UV) upconversion luminescence (UCL) was observed in the nanostructures under the excitation of 980-nm infrared laser. The largest enhancement factor was obtained as 76 for the (6)I(J)→(8)S(7/2) emission of Gd(3+) ions, which was much larger than those emission enhancement factors of Tm(3+). It is for the first time to our knowledge that the emission enhancement of Gd(3+) ions was obtained. Local field enhancement induced by Au NPs was found to be responsible for the UCL enhancement, which is the further experimental evidence of local field enhancement theory. Magnetic measurements of the Au@NaYF(4) nanostructure indicated it would have potential application in magnetic resonance imaging.     

在La_2Na_2Sr_6(PO_4)_6Br_2基质中Tb~(3+)的发光及Ce~(3+)对Tb~(3+)的敏化

用高温固相反应法合成了发光材料、研究了Tb~(3+)在La_2Na_2Sr_6(PO_4)_6Br_2基质中的光致发光性质及Ce~(3+)对Tb~(3+)的敏化作用.在254nm紫外光激发下,Tb~(3+)的发光较弱,但Ce~(3+)对Tb~(3+)有强的敏化作用,其能量传递机埋是偶极-偶极相互作用引起的共振能量传递,计算了传递效率。     

Enhanced anodic Ru(bpy)3(2+) electrogenerated chemiluminescence by polyphenols

Anodic Ru(bpy)₃²⁺ electrogenerated chemiluminescence (ECL) can be enhanced by polyphenols in alkaline solution. Spin trapping-electron spin resonance (ESR) experiments verified that reactive oxygen species (ROS) were generated during the electrolysis of Ru(bpy)₃²⁺ in alkaline solution, and oxidation of quercetin enhanced Ru(bpy)₃²⁺ ECL at anodic potential by producing additional ROS. This ECL enhancement can be used to analyze real sample and evaluate antioxidant activity of polyphenols.