Controllable multicolor upconversion luminescence of lanthanide doped NaGdF4 nanocrystals through single laser excitation at 980 nm

Room temperature multicolor Upconversion (UC) luminescence in Yb3+, Tm3+, Er3+ ions doped NaGdF4 nanocrystals have been successfully synthesized by a hydrothermal method. As-prepared nanocrystals are highly crystalline and well-dispersed in cyclohexane to form stable and clear colloidal solutions, which demonstrates strong emission properties with a single laser excitation at 980 nm. The multicolor light consists of blue, green, and red UC radiations that correspond to transitions 1G4 --> 3H6 of Tm3+, 2H(11/2)/4S(3/2) --> 4I(15/2), and 4F(9/2) --> 4I(15/2) of Er3+ ions, respectively. The UC mechanisms were proposed based on spectral, kinetic, and pump power dependence analyses.     

Up-conversion emissions characteristics of non-aqueous sol-gel derived RE3Al5O12 nanocrystals

The RE3Al5O12 (REAG:Er3Al5O12, Er:Y3Al5O12 and Er:Yb3Al5O12) up-conversion (UC) nanocrystals have been prepared by the non-aqueous sol-gel method. The green and red UC emissions are attributed to the 2H(11/2), 4S(3/2) --> 4I(15/2) and 4F(9/2) --> 4I(15/2) transitions of Er3+, respectively, were obtained for all samples with a 975 nm semiconductor LD excitation. For Er3Al5O12 nanocrystals, the green and red UC emissions have similar intensities. Y and Yb ions have no evident effect on the peak positions, but strongly affected the intensities of the green and red UC emissions of the Er. A much higher intensity of the green relative to red UC emission was observed for Er:Y3Al5O12 nanocrystals, however, the red UC emission became predominant for Er:Yb3Al5O12 nanocrystals. It was suggested that the two-photon process was responsible for the green and red UC emissions mechanism for all the samples.     

Er3+/Yb3+掺杂NaGd(WO4)2粉体的制备与发光性能

采用水热法成功制备了Er~(3+)/Yb~(3+)双掺杂的NaGd(WO_4)_2纳米粉体,研究了不同络合剂、水热温度对样品形貌和结构的影响。测量了不同Er~(3+)掺杂浓度样品的可见上转换和近红外发射光谱。结果表明:在980nm LD激发下,可观测到样品强烈的绿色上转换发光,对应Er~(3+)的~2H_(11/2)→~4I_(15/2)(530nm)和~4S_(3/2)→~4I_(15/2)(552nm)跃迁,以及较弱的红色上转换和近红外发光,分别对应Er~(3+)的~4F_(9/2)→4I15/2(656nm)和~4I_(13/2)→~4I_(15/2)(1 532nm)跃迁。且随着Er~(3+)掺杂浓度的增加,样品的上转换红绿光和1.54μm附近的近红外光均呈现出先增大后减小的趋势。样品的激发和发射光谱显示,在378nm处的激发峰最强,对应Er~(3+)的~4I_(15/2)→~4 G_(11/2)能级跃迁,最强发射峰位于552nm。根据泵浦功率与发光强度的关系可以得出,红光和绿光的发射主要为双光子吸收过程,但红光还包含了一定的单光子吸收成分。     

P2O3-B2O3-Al2O3-SrO-BaO玻璃中Yb3+非辐射能量转移下Er3+离子的增强发射

本文研究了共掺Er3 +/Yb3 +P2 O3 -B2 O3 -Al2 O3 -SrO -BaO玻璃的能量转移过程。实验中制备了高掺杂Yb3 +离子的双掺Er3 +/Yb3 +的磷酸盐玻璃样品。在Er3 +/Yb3 +掺杂比率 >1 :1 8(mol% )时 ,观测到了基于Yb3 +离子至Er3 +离子能量转移下Er3 +( 4 I13 / 2 →4I15 / 2 )的增强发射和Yb3 +( 2 F7/ 2 →2 F5 / 2 )发射的减弱 ,当Yb3 +离子掺杂浓度超过 2 .1× 1 0 2 1ions/cm3 时 (Er3 +/Yb3 +≤ 1 :1 8,mol% ) ,由于Yb3 +离子的自淬灭效应 ,Er3 +离子的发射强度降低。实验中得到了Yb3 +离子的最佳掺杂浓度为1 .74× 1 0 2 1ions/cm3     

Sequence lasing in a gain-switched Yb3+,Er(3+)-doped silica double-clad fiber laser

Experimental results relating to the gain-switched operation of a double-clad Yb3+,Er(3+)-doped silica fiber laser that is pulse pumped with the output from a flash-lamp-pumped Ti:sapphire laser are presented. For all the configurations of the fiber laser that we studied, the 2F5/2-->2F7/2 laser transition of the Yb3+ ion lased prior to laser emission from the 4I13/2-->4I15/2 transition of the Er3+ ion. To the best of our knowledge, this is the first reported operation of sequence lasing in the Yb3+,Er(3+)-codoped system. This succession of laser pulses deduced from the measurements of this investigation is a consequence of both the short intense pump pulse and the short 900-nm wavelength of the pump that does not overlap with any important excited-state absorption transitions. We believe that the predominant interionic interaction during the course of the pump pulse is the double-energy transfer to the Er3+ ion acting twice from the 2F5/2 energy level of the Yb3+ donor ion. A maximum total output of 1.65 mJ is obtained (1.38 mJ from the 2F5/2-->2F7/2 transition of Yb3+ and 0.27 mJ from the 4I13/2-->4I15/2 transition of Er3+) from a nonoptimized configuration of the fiber laser. The wavelength of the output from the fiber laser was measured to vary approximately linearly with fiber length from 1040 to 1046 nm for the Yb(3+)-based laser and 1535 to 1541 nm for the Er(3+)-based laser.     

Fabrication and up-conversion luminescence of Er3+:Y2O3 nanoparticles

Y2O3 nanoparticles doped with different concentrations of Er3+ were prepared by the co-precipitation method. X-ray diffraction and transmission electron microscopy results show that Er3+ dissolves completely in the Y2O3 cubic phase. The Er3+:Y2O3 nanoparticles are homogeneous in size and nearly spherical, and the average diameter of the particles after being calcined at 1,000 degrees C for 2 h is in the range of 40-60 nm. When Er3+:Y2O3 nanoparticles are excited under a 980 nm diode laser, there are two main emission bands: green emission centered at 562 nm corresponding to the 4S3/2/2H11/2 --> 4115/2 radiative transitions and red emission centered at 660 nm corresponding to the 4F9/2 --> 4I15/2 radiative transitions. By changing the doping concentration of Er3+ ions, the up-conversion luminescence can be gradually tuned from green to red.     

Broadband downconversion in Bi3+, Yb3+-Co-doped YVO4 phosphor

Yttrium vanadate phosphors co-doped with Bi3+ and Yb3+ ions have been prepared via the solid-state reaction. The phosphors were characterized by various methods including X-ray diffraction, photoluminescence excitation and photoluminescence spectra. Upon ultraviolet (UV) light excitation, an intense near-infrared (NIR) emission of Yb3+ corresponding to the transition of 2F(5/2) --> 2F(7/2) peaking at 985 nm was observed as a result of energy transfer from O2(-)-V5+ or Bi3+-V5+ charge transfer state (CTS) to Yb3+. A broad excitation band ranging from 250 to 375 nm was recorded when the Yb3+ emission was monitored, which suggests an efficient energy transfer from CTS to Yb3+ ions. The dependence of Yb3+ doping concentration on the visible emission, the NIR emission and decay lifetime has been investigated. The results of visible and NIR spectral evolution with temperature indicate that the mechanism for the NIR-emission is mainly phonon-assisted energy transfer at room temperature, while the mechanism is mainly cooperative energy transfer at low temperature. The YVO4:Bi3+, Yb3+ phosphor has prospects for realizing high efficiency crystalline Si solar cells by converting broadband UV energy into NIR light.     

CeO2∶Er3+纳米晶的合成及上转换发光特性研究

采用燃烧法制备得到CeO2∶Er3+纳米晶粉末.用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)和荧光分光光度计等对CeO2∶Er3+纳米晶的结构、形貌和上转换发光特性进行了研究.结果表明:所得到的纳米晶粒度均匀、结晶完好,属于立方萤石结构.上转换发光光谱的研究表明:在980nm红外光激发下,可以发现上转换荧光,分别来自于Er3+离子的2H11/2,4S3/2→4 I15/2和4 F9/2→4I15/2跃迁.     

Emission Properties of Yb3+/Er3+ Doped TeO2-WO3-ZnO Glasses for Broadband Optical Amplifiers

The YbS /Er3 doped TeO2-WO3-ZnO glasses were prepared. The absorption spectra, emission spectra and fluorescence lifetime of Era at 1.5μm, excited by 970 nm were measured. The influence of Er2Oa, Yb2Oa and Ohcontents on emission properties of Era at 1.5 μm was investigated. The optimum doping concentrations for Era and Yba is around 3.34× 1020 ions/cma and 6.63×1020 ions/cma, respectively. The peak emission cross section is 0.83～0.87 pm2. With the increasing concentration of Yba , the FWHM of Era emission at 1.5 μm in the glass increases from 77 nm to 83 nm. The results show that Yba /Era doped meO2-Woa-ZnO glasses are promising candidate for Era -doped broadband optical amplifier.     

Emission properties of hydrothermal Yb(3+), Er(3+) and Yb(3+), Tm(3+)-codoped Lu2O3 nanorods: upconversion, cathodoluminescence and assessment of waveguide behavior

Yb(3+) and Ln(3+) (Ln(3+) = Er(3+) or Tm(3+)) codoped Lu(2)O(3) nanorods with cubic Ia3 symmetry have been prepared by low temperature hydrothermal procedures, and their luminescence properties and waveguide behavior analyzed by means of scanning near-field optical microscopy (SNOM). Room temperature upconversion (UC) under excitation at 980 nm and cathodoluminescence (CL) spectra were studied as a function of the Yb(+) concentration in the prepared nanorods. UC spectra revealed the strong development of Er(3+) (4)F(9/2) → (4)I(15/2) (red) and Tm(3+) (1)G(4) → (3)H(6) (blue) bands, which became the pre-eminent and even unique emissions for corresponding nanorods with the higher Yb(3+) concentration. Favored by the presence of large phonons in current nanorods, UC mechanisms that privilege the population of (4)F(9/2) and (1)G(4) emitting levels through phonon-assisted energy transfer and non-radiative relaxations account for these observed UC luminescence features. CL spectra show much more moderate development of the intensity ratio between the Er(3+) (4)F(9/2) → (4)I(15/2) (red) and (2)H(11/2), (4)S(3/2) → (4)I(15/2) (green) emissions with the increase in the Yb(3+) content, while for Yb(3+), Tm(3+)-codoped Lu(2)O(3) nanorods the dominant CL emission is Tm(3+) (1)D(2) → (3)F(4) (deep-blue). Uniform light emission along Yb(3+), Er(3+)-codoped Lu(2)O(3) rods has been observed by using SNOM photoluminescence images; however, the rods seem to be too thin for propagation of light.     

Improved infrared emissions of Er(3+)-Tm3+ co-doped Al2O3 thin films: the role of cross relaxation among rare earth ions

We report the infrared emissions of Er(3+)-Tm3+ co-doped amorphous Al2O3 thin films pumped at 791 nm by a Ti:sapphire laser. The as-deposited films were annealed to improve the photoluminescence performance. Three cross relaxation channels among Er(3+)-Tm3+ and Tm(3+)-Tm3+ ions incorporated in the films were investigated as annealing temperature increases especially from 800 to 850 degrees C. In order to understand the Stark effect and cross relaxations, the photoluminescence spectra were deconvoluted by Gaussian fittings. Our results indicate that the luminescence intensity of 1.62 microm in comparison to 1.5 microm can be enhanced by the cross relaxation process [Er3+ (4I13/2) + Tm3+ (3H6) --> Er3+ (4I15/2) + Tm3+ (3F4)], and the longer-wavelength side of Er3+ emission can be improved by the CR process [Er3+ (4I15/2) + Tm3+ (3H4) --> Er3+ (4I3/2) + Tm3+ (3F4) at expense of the Tm3+ 1.47 microm emission which is also maybe quenched by the CR effect between themselves. These results suggest one possible approach to achieve broadband infrared emissions at the wavelength region of 1.45-1.65 microm from the Er(3+)-Tm3+ co-doped systems.     

Yb3+、Er3+和Eu3+共掺杂TiO2纳米带的制备与表征

通过离子交换和水热两步合成过程简单制备了Yb3+、Er3+和Eu3+共掺杂锐钛矿型TiO2纳米带。该3种离子共掺杂未导致TiO2结构和形貌发生变化。光学特性测试结果表明,由于稀土离子掺杂浓度低,Eu3+掺杂未改变由Yb3+和Er3+产生的上转换发射峰位,但可观察到因上转换发光激发的Eu3+荧光发射峰;Eu3+荧光光谱也未受到Yb3+和Er3+掺杂的影响。通过对掺杂样品上转换发光机理的考察证实,上转换发光过程是双光子过程,但TiO2和Eu3+掺杂对此发光过程有明显影响。     

Synthesis of colloidal upconverting NaYF4: Er3+/Yb3+ and Tm3+/Yb3+ monodisperse nanocrystals

The synthesis, characterization, and spectroscopy of upconverting lanthanide-doped NaYF4 nanocrystals (NCs) is presented. The monodisperse cubic NaYF4 NCs were synthesized via a thermal decomposition reaction of trifluoroacetate precusors in a mixture of technical grade chemicals, octadecene and the coordinating ligand oleic acid. In this straightforward method, the dissolved precursors are added slowly to the reaction solution through a stainless-steel canula resulting in highly luminescent nanocrystals with an almost monodisperse particle size distribution. The NCs were characterized through the use of transmission electron microscopy, selected area electron diffraction, 1H NMR, powder X-ray diffraction, and high-resolution luminescence spectroscopy. The NaYF4 NCs are capable of being of dispersed in nonpolar organic solvents thus forming colloidally stable solutions. The colloids of the Er3+, Yb3+ and Tm3+, Yb3+ doped NCs exhibit green/red and blue upconversion luminescence, respectively, under 980 nm laser diode excitation with low power densities.     

Upconversion luminescence properties of YF3:Yb3+, Er3+ nanoclusters

The synthesis, characterization, and spectroscopy of upconverting Yb3+/Er3+ codoped YF3 rod-like nanoclusters are presented. The YF3 nanoclusters were synthesized by a simple hydrothermal method. The clusters structure was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Under 978 nm laser excitation, stronger blue (4F(5/2) --> 4I(15/2) and 2p(3/2) --> 4I(11/2)) and green (4S(3/2), 2H(11/2) --> 4I(15/2)) upconversion luminescence were observed at 978 nm. The measured intensity of upconversion luminescence was different when pump power changed, which shows that the blue and green upconversion luminescence come from three-photon and two-photon energy transfer processes, respectively.     

Preparation and luminescent properties of YVO4:Eu3+ nanofibers by electrospinning

This paper describes a procedure based on electrospinning for generating europium-doped yttrium vanadate (YVO4:Eu3+) nanofibers with diameters ranging from 30 to 50 nm. The YVO4:Eu3+ nanofibers were obtained through calcining precursory nanofibers, which were prepared through the electrospinning method. Suitable electrospinning parameters, such as concentration of PVP in solution, spinneret tip-to-collector plate distance (TCD), and applied voltage between spinneret and collector plate, are used to obtain thinner and more uniform precursory nanofibers of YVO4:Eu3+, which is important for preparing smaller diameter pure YVO4:Eu3+ nanofibers. The luminescent properties of the YVO4:Eu3+ nanofibers including excitation and emission spectra and fluorescence lifetime were studied. The excitation spectrum shows a broad band extending from 200 to 350 nm, which corresponds to the strong vanadate absorption in YVO4:Eu3+. The emission spectrum is dominated by the red 5D0 --> 7F2 hypersensitive transition of Eu3+. The fluorescence lifetime of Eu3+ 5D0 --> 7F2 (619 nm) is determined to be 493 micros at room temperature, which is basically in accordance with that in the bulk (521 micros).     

Synthesis and characterization of Y2O3:Er3+ upconversion materials with nanoporous structures

Y2O3:Er3+ upconversion materials with nanoporous structures were prepared by a hydrothermal method following a post-thermal treatment. The structure and morphology of the materials were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results indicated that the as-obtained Y2O3:Er3+ powders were of cubic-phase structure, and the nanoporous structure was formed in the annealing process. The optical results indicated that high annealing temperature could improve the upconversion properties, but it could destroy the nanoporous structure. Under 980 nm excitation, red (4F(9/2) --> 4I(15/2) and green (2H(11/2), 4S(3/2) --> 4I(15/2)) upconversion luminescence was observed. The studies on the intensity dependence of upconversion emission indicated that two-photon processes were responsible for the green and red upconversion luminescence. This kind of multifunctional material has potential applications in nanocontainers for use as biomolecule and drugs carriers.     

铋锗酸盐玻璃中铒离子的上转换光谱特性

研究了由重金属氧化物Bi2O3-GeO2-PbO组分高温融熔而成的铋锗酸盐玻璃中稀土掺杂铒离子(Er3+)的吸收光谱、上转换发光谱以及玻璃基质的红外吸收谱,着重分析了975 nm和800 nm泵浦光激励下Er3+离子的上转换发光机理.结果表明,在975 nm或800 nm泵浦光激励下,观察到了绿光(529 nm、552...     

Synthesis and characterization of upconverting NaYF4:Er3+, Yb3+ nanocrystals via thermal decomposition of stearate precursor

Er3+-Yb3+ codoped hexagonal NaYF4 nanocrystals were prepared via a method of thermal decomposition of stearate precursor. Their crystal structure, morphologies and photoluminescence (PL) properties were characterized by XRD, SEM, and fluorescence spectra. The hexagonal NaYF4:Er3+, Yb3+ nanocrystals could be well dispersed in cyclohexane to form a clear solution. Under 980 nm excitation, the solution of Er3+-Yb3+ codoped NaYF4 nanocrystals emits bright green upconversion fluorescence.     

Energy transfer mechanisms in Yb3+-doped GdVO4 near-infrared downconversion nanophosphor

Yb3+-doped GdVO4 nanophosphor was prepared by the co-precipitation method. Under ultraviolet (UV) light excitation, strong near-infrared (NIR) emission of Yb3+ (2F(5/2) --> 2F(7/2)) around 980 nm was observed. Owing to the host absorption of GdVO4, a broad excitation band ranging from 250 to 350 nm was recorded when the Yb3+ emission was monitored, which suggests an efficient energy transfer from the host to the Yb3+ ions. The concentration dependence of the visible vanadate emission and the Yb3+ emission was investigated. The decay curve of the vanadate emission was measured under the excitation of a 266 nm pulsed laser. The decay time of the vanadate emission at 500 nm was remarkably reduced by introducing Yb3+, further verifying that the energy transfer from the vanadate host to the Yb3+ ions was very efficient. Cooperative energy transfer (CET) is discussed as the possible energy transfer process. The temperature dependence of the emission intensity and decay time were also investigated for our further discussion.     

Structural and optical properties of NaY(WO4)2:Tm3+,Yb3+ and NaY(WO4)2:Tm3+,Er3+,Yb3+ powders synthesized by the high-temperature solid-state method

Journal of Materials Science: Materials in Electronics - The NaY(WO4)2:Tm3+,Yb3+ (NYW:Tm3+,Yb3+) and NaY(WO4)2:Tm3+,Er3+,Yb3+ (NYW:Tm3+,Er3+,Yb3+) powders have been synthesized by the...