溴氧镧铽镝的发光特性及能量传递机理

使用高温常压方法合成了稀土发光材料ＬａＯＢｒ２Ｄｙ＾３＋，Ｔｂ＾３＋，研究了其结构，紫外４主阴极射线激发下的激发与发射光谱，Ｄｙ＾３＋的掺杂可将Ｔｂ＾３＋的＾５Ｄ３能级激光能有地弛豫到＾５Ｄ４能级，从而使５Ｄ４－Ｆ（Ｊ＝０，１）的发射，尤其是＾５Ｄ４－＾７Ｆ５的发射增强，发光亮度提高。     

Photoluminescence and energy transfer study of Er3+ and Dy3+ codoped tellurite glasses

Photoluminescence properties of the Er(3+)-Dy3+ codoped tellurite glasses were studied by absorption and visible emission spectra, which revealed luminescence bands of both Er3+ and Dy3+ when pumping with the wavelength of 325 nm. The concentration quenching occurred as Dy3+ concentration increased beyond 3 mol%. The dependence of Er3+ characteristic emission on Dy3+ concentration indicated energy transfer process between Er3+ and Dy3+. The chromaticity coordinates of these glasses are close to white light, which implies that these glasses might be potential candidates for white lighting through an appropriate combination.     

Luminescent properties of rare earth ions in one-dimensional oxide nanowires

Rare-earth doped one-dimensional oxide nanowires including LaPO4, La2O3, and Gd2O3 were synthesized by the hydrothermal method. Their luminescent properties including local environments, electronic transitions, energy transfer, and frequency up-conversion luminescence processes were systematically studied. In LaPO4:Eu and La2O3:Eu nanowires, different symmetry sites of Eu3+ ions were identified, which obviously differed from those of the corresponding micrometer-sized particles. This was attributed to crystal field degeneration in the fringe along the length axis. In LaPO4:Eu nanowires, the electronic transition rate of 5D1-sigmaJ7FJ increased approximately 2 times over that of the zero-dimensional nanoparticles and micrometer-sized particles, which was related to the variation of dipole field induced by shape anisotropy. Considering the nonradiative relaxations, meanwhile, the luminescent quantum efficiency for 5D1-sigmaJ7FJ transitions of Eu3+ in nanowires increased 100% over that in nanoparticles and 20% over that in micrometer particles. In Gd2O3:Eu3+, LaPO4:Ce3+, and LaPO4:Tb3+ nanowires and micrometer-sized particles, the electronic transition rate of rare earths had only a little variation. In LaPO4:Ce3+/Tb3+ nanowires, the energy transfer rate of Ce3+--> Tb3+ decreased 3 times compared to that in micrometer rods. Despite this, the brightness for the 5D4-7F5 green emissions of Tb3+ increased several times due to decreased energy transfer from the excited states higher than 5D4 to some defect levels. In Gd2O3:Er3+/Yb3+ nanocrystals, as the shape varied from nanopapers to nanowires, the relative intensity of up-conversion luminescence of 2H(11/2)/4S(3/2)-4I(15/2) and 4F(9/2)-4I(15/2) to the infrared down-conversion luminescence of 4I(13/2)-4I(15/2) increased remarkably, indicating efficient up-conversion luminescence. Our present results indicate that rare-earth-doped oxide nanowires is a type of new and efficient phosphors.     

Study on luminescence behavior of BaAl12O19:Tb, Eu

BaAl12O19:Tb, Eu phosphors were prepared by sol-gel technique. The luminescence properties and the energy transfer between Eu2+ and Tb3+ were investigated. For BaAll2O19:Tb phosphor, the strongest excitation peak and emission peak produced from Tb3+ transition of 5D4-7F5 were at 240 nm and at 550 nm respectively, while the peak shape was narrow and peak intensity was large. The Eu2+ added in the BaAl12O19:Tb induced energy transfer to Tb3+ and different color luminescence from blue (400 nm) to green (570 nm) was obtained by changing the ratio of Tb3+/Eu2+ with excitation at 240 nm.     

Sensitized upconversion emissions of Tb3+ by Tm3+ in YF3 and NaYF4 nanocrystals

Yb3+-Tm3+-Tb3+-codoped YF3 and NaYF4 nanocrystals (NCs) were synthesized using a simple hydrothermal method. Under 980 nm excitation, violet and ultraviolet upconversion (UC) emissions of 5D3 --> 7FJ (J = 6, 5, 4) and 5D4 --> 7FJ (J = 6, 5, 4, 3) of Tb3+ ions were observed with the fluoride NCs. In the Yb-Tm-Tb codoped NCs, energy transfer (ET) processes from Tm3+ to Tb3+ were proposed to be the main mechanisms for the UC emissions of Tb3+ ions. They are more efficient than the phonon assisted cooperative sensitization of the Yb3+ couple proposed previously for similar material system. The analysis of power dependence indicated that populating the 5D4 level of the Tb3+ ions was a four photon UC process, which demonstrated the existence of the two step ET process of Yb3+ --> Tm3+ --> Tb3+. It was also found that UC luminescence properties of Tb3+ ions were sensitive to crystal structures.     

铒单掺和铒/镱共掺氟氧玻璃的上转换发光性质研究

研究了室温下掺不同摩尔分数Er3+单掺和Er3+/Yb3+双掺的20GaF3-15InF3-17CdF2-15ZnF2-10SnF2-3P2O5-(20-x-y)PbF2-xErF3-yYbF3(x=0.1~0.4,y=1~4)氟氧玻璃的上转换发光性质。755nm激发下,在Er3+单掺系列玻璃中观察到紫色(410nm)、蓝色(465nm)和绿色(522nm、544nm)上转化发光,随着掺杂Er3+浓度的增大,各荧光强度增幅有变缓的趋势。980nm激发下,由于Yb3+的敏化作用,在Er3+/Yb3+双掺系列玻璃中观察到绿色(548nm、527nm)和红色(661nm)上转换发光,固定Er3+浓度,随着Yb3+浓度的增大,各荧光强度先增大后减小,当Yb3+、Er3+掺杂浓度比为15时发光强度最大。该氟氧玻璃具有比氟化物玻璃更好的抗析晶稳定性,掺稀土离子后在不同波长激发下可观察到明亮的红、绿色上转换荧光,是一种有潜质用于红、绿色上转换发光的材料。     

Investigations of Ce3+ co-doped SbPO4:Tb3+ nano-ribbons and nanoparticles by vibrational and photoluminescence spectroscopy

Nano-ribbons and very small nanoparticles (size 2-5 nm) of SbPO4 doped with lanthanide ions (Ce3+ and Tb3+) are prepared at a relatively low temperature of 120 degrees C based on a solution method. Detailed vibrational and luminescence studies on these samples establish that these lanthanide ions are incorporated at Sb3+ site of the SbPO4 lattice. The excitation spectrum corresponding to the Tb3+ emission and the excited state lifetime of the 5D4 level of Tb3+ ions in the sample confirm the energy transfer from Ce3+ to Tb3+ ions in the SbPO4 host. The extent of energy transfer from Ce3+ to Tb3+ in these samples is found to be around 60%. Dispersion of these nanomaterials in silica matrix effectively shields the lanthanide ions at the surface of the nano-ribbons/nanoparticles from the stabilizing ligands resulting in the reduction in the vibronic quenching of the excited state. Our results show significant reduction in the surface contribution in the decay curve corresponding to the 5D4 level of the Tb3+ ions after incorporating the nano-ribbons/nanoparticles in silica. These nanomaterials incorporated in silica matrix can have potential applications in bio-assays and bio-imaging.     

Study on energy transfer and energy migration of Ca2Gd8(SiO4)6O2:Dy3+ phosphor films

Being a kind of rare-earth-metal silicate with oxidapatite structure, Ca2R8(SiO4)6O2 (R = Y, Gd, La) is a promising material doped with rare earth, and widely used as phosphors. In this thesis, Ca2Gd8(SiO4)6O2:Dy3+ films were prepared by the sol-gel method. X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting films. AFM study indicated that the phosphor films consisted of 120 nm homogeneous particles. By combining the model of Burshtein for donor-donor migration and the V-F-B model for donor-acceptor energy transfer, the experimental luminescence decay curve of 6P(J) state of Gd3+ was re-simulated. It is found that concentration quenching of Gd3+ can be due to the result of the joint action of donor-donor (Gd3+-Gd3+) energy migration and donor-acceptor (Gd3+-Dy3+) energy transfer.     

Synthesis and luminescence properties of Sr2SiO4: Eu3+, Dy3+ phosphors by the sol-gel method

The Sr2SiO4:Eu3+, Dy3+ phosphors for white light emitting diodes (LEDs) were synthesized by the sol-gel method. The microstructure and luminescent properties of the obtained Sr2SiO4:Eu3+, Dy3+ particles were well characterized. The results demonstrate that the Sr2SiO4:Eu3+, Dy3+ particles, which have spherical morphology, emitted an intensive white light emission under excitation at 386 nm. The phosphors show three emission peaks: the blue emission at 486 nm corresponding to the 4F(9/2)-6H(15/2) transition of Dy3+, the yellow emission at 575 nm corresponding to the 4F(9/2)-6H(13/2) transition of Dy3+, and the red emission at 615 nm corresponding to the 5D0-7F2 transition of Eu3+. At the same time, the effect of Eu3+ concentration on the emission intensities of Sr2SiO4:Eu3+, Dy3+ was investigated in detail. The phosphors used for white LEDs were obtained by combining near ultraviolet (NUV) light (386 nm) with Sr2SiO4:0.04Dy3+, 0.01Eu3+ phosphors with the characteristic of Commission Internationale de l'Eclairage (CIE) chromaticity coordinate (x, y) of (0.33, 0.34), and color temperature Tc of 5,603 K. In addition, the effect of the charge compensators (Li+, Na+, and K+ ions) on the photoluminescence (PL) emission intensities were studied.     

Dy3+掺杂CaWO4荧光粉体的制备及发光性能

采用固相陶瓷方法制备了Dy3+掺杂的CaWO4∶Dyx3+荧光粉体。采用XRD、SEM和FT-IR对制备粉体的微观结构进行了表征;采用荧光分析法研究了制备的荧光体的室温光致发光性能;探讨了掺杂剂Dy3+浓度对CaWO4∶Dyx3+荧光粉体的微结构和光致发光性能的影响。结果表明,制备的CaWO4∶Dyx3+荧光粉体为白钨矿结构,Dy3+的掺入会抑制CaWO4∶Dy3x+晶粒的生长。当Dy3+的掺入量为1%(摩尔分数)时,其在480nm(蓝)和575nm(黄)的发射强度达到最大;随着Dy3+浓度的增加,其特征发射峰(480nm和575nm)强度反而逐渐下降。     

Polyol-mediated synthesis and photoluminescent properties of Ce3+ and/or Tb3+-doped LaPO4 nanoparticles

Rare-earth ion (Ce3+, Tb3+) doped LaPO4 nanoparticles were prepared by the polyol method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, and lifetimes. The results of XRD indicate that the as-prepared nanoparticles are well-crystallized at 160 degrees C and assigned to the monoclinic monazite structure of the LaPO4 phase. The obtained LaPO4:Ce3+, Tb3+ nanoparticles are spherical with narrow size distribution and average size of 20 nm. The doped rare-earth ions show their characteristic emission in LaPO4 nanoparticles, i.e., Ce3+ 5d-4f and Tb3+ 5D4-7FJ (J = 6-3) transitions, respectively. The optimum doping concentration for Tb3+ in La(0.8-x)Ce0.2TbxPO4 nanoparticles is determined to be 15 mol% (x = 0.15). The luminescence decay curves of Ce3+ in LaPO4:Ce3+ and LaPO4:Ce3+, Tb3+ nanoparticles present a single-exponential behavior, and the lifetimes (tau) of Ce3+ decrease with increasing Tb3+ concentrations (at the constant Ce3+ concentration) in LaPO4:Ce3+, Tb3+ nanoparticles due to the energy transfer from Ce3+ to Tb3+. The energy-transfer efficiency from Ce3+ to Tb3+ was calculated, which depends on the doping concentrations of Tb3+ if the concentration of Ce3+ is fixed.     

Spherical SiO2 @ GdPO4: Eu3+ core-shell phosphors: sol-gel synthesis and characterization

Nanocrystalline GdPO4 : Eu3+ phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by Pechini sol-gel method, resulting in the formation of core-shell structured SiO2 @ GdPO4 : Eu3+ particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), time-resolved PL spectra and lifetimes were used to characterize the core-shell structured materials. Both XRD and FT-IR results indicate that GdPO4 layers have been successfully coated on the SiO2 particles, which can be further verified by the images of FESEM and TEM. Under UV light excitation, the SiO2 @ GdPO4 : Eu3+ phosphors show orange-red luminescence with Eu3+ 5D0-7F1 (593 nm) as the most prominent group. The PL excitation and emission spectra suggest that an energy transfer occurs from Gd3+ to Eu3+ in SiO2 @ GdPO4 : Eu3+ phosphors. The obtained core-shell phosphors have potential applications in FED and PDP devices.     

Visible upconversion emission of Pr3+ doped gadolinium gallium garnet nanocrystals

The luminescence properties of a Pr3+-doped gadolinium gallium garnet (GGG, Gd3Ga5O12) nanocrystalline host were investigated. Dominant blue/green emission was observed emanating from the 3P0 --> 3H4 transition after excitation using a wavelength of 457.9 nm. Continuous wave excitation into the 1D2 level of the Pr3+ ion at 606.9 nm transition produced blue upconversion luminescence spectra, ascribed to emission from the 3P1 --> 3H4 and 3P0 --> 3H4 transitions. The increase in the decay times of the observed transitions following excitation with 606.9 nm is indicative of the dominance of an energy transfer upconversion (ETU) mechanism relative to excited state absorption (ESA). Furthermore, blue, green and red upconversion emission was observed from the 3P0, 3P1 and 1D2 states following excitation into the 1G4 energy level with 980 nm. No change in the decay times of the emitting states was observed following excitation with a wavelength of 980 or 457.9 nm; hence, upconversion was determined to primarily occur through ESA. The luminescence properties of the nanocrystals are compared to a single crystal of GGG:Pr3+ (bulk) with an identical Pr3+ concentration (1%).     

Luminescence and energy transfer characteristics of Ce3+- and Tb3+-codoped nanoporous 12CaO 7Al2O3 phosphors

The novel green-emitting phosphors of 12CaO 7Al2O3:Ce3+ , Tb3+ (C12A7:Ce3+, Tb3+) were synthesized by a solid-state reaction. Upon the excitation of Ce3+ at 350 nm, the C12A7:Ce3+, Tb3+ phosphor shows intense green emissions located at 543 nm assigning to 5D4-7F5 transitions of Tb3+ ions, and weak blue emissions centered at 434 nm due to the transitions of Ce3+ 5d-4f. The photoluminescence (PL) intensity of Ce3+ decrease with increasing Tb3+ concentration, indicating the effective energy transfer (ET) occurred from Ce3+ to Tb3+ in C12A7:Ce3+, Tb3+. The ET efficiency between Ce3+ and Tb3+ in the optimum composition reaches to 99%. Based on Dexter's ET theory, we have demonstrated that the efficient ET is a resonant type via dipole-dipole mechanism with an energy transfer critical distance of 4.02 A. Our results suggested that C12A7:Ce3+, Tb3+ phosphor would be a promising green-emitting phosphor for UV-converting white light-emitting diodes.     

One-step synthesis and luminescent properties of nanocrystalline YVO4:Eu3+ powders

In this paper, nanocrystalline YVO4:Eu3+ powders have been successfully synthesized via high-temperature solution-phase synthesis process. The nanocrystalline YVO4:Eu3+ particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV/Nis absorption spectra and luminescence spectra, luminescence decay curve and Fourier transform infrared (FT-IR), X-ray photoelectron spectra (XPS) respectively. The as-prepared nanocrystalline YVO4:Eu3+ particles are well crystallized with ellipsoidal morphology. The emission of YVO4:Eu3+ particles show emission originating from the 5D0 level, with 5D0-7F2 at 616 nm as the most prominent group. The excitation spectrum fits basically with the absorption spectrum from the vanadate ions. FT-IR and XPS spectra indicate that the surface ligands of nanocrystalline particles were oleic acid and oleylamine. The lifetime for the luminescence of Eu3+ in the as-prepared YVO4:Eu3+ samples are shorter than that of the bulk material due to the absorption of organic ligands on the nanoparticle surface.     

Optical properties and luminescence dynamics of Eu3+-doped terbium orthophosphate nanophosphors

The development of luminescent inorganic nanocrystals (NCs) doped with rare-earth (RE) ions has attracted increasing interest owing to their distinct optical properties and versatile applications in time-resolved bioassays, multiplex biodetection, DNA hybridization and bioimaging. Hexagonal TbPO4:Eu3+ NCs (10-30 nm) were synthesized via a facile hydrothermal method assisted with oleic acid (OA) surfactants, which exhibit tunable emissions from green to red by varying the concentration of Eu3+. The Tb3+-to-Eu3+ energy transfer efficiency observed reaches up to 94%. Different from their bulk counterparts, a new interface-state band (316 nm) in addition to the commonly observed spin-forbidden 4f-5d transition band (265 nm) of Tb3+ was found to be dominant in the excitation spectrum of NCs due presumably to the formation of surface TbPO4/OA complexes, which provides an additional excitation antenna in practical utilization. Two kinds of luminescence sites of Eu3+ in TbPO4 NCs, with the site symmetry of C2 or C1, were identified based on the emission spectra at 10 K and room temperature. Furthermore, the photoluminescence (PL) dynamics of Tb3+ ions in pure TbPO4 NCs have been revealed. Compared to the exponential PL decay in bulk counterparts induced by very fast energy migration, the non-exponential decay from 5D4 of Tb3+ in TbPO4 NCs is mainly attributed to the diffusion-limited energy migration due to more rapid energy transfer from Tb3+ to defects than the energy migration among Tb3+.     

SrAl2O4:Eu2+,Dy3+光致发光搪瓷涂层的制备

稀土Eu^2 激活的铝酸盐发光材料是近年来新发展起来的新型长余辉光致发光材料，由于其发光亮度和发光余辉比传统的硫化物高许多，且无毒，无放射性，因而引起广泛关注，采用高温固相反应法制备了SrAl2O4:Eu^2 ,Dy^3 发光材料，并利用SrAl2O4:Eu^2 ,Dy^3 发光材料，参考普通搪瓷的制备工艺，制得了性能稳定的光致发光搪瓷涂层，余辉时间长达12h以上，这种发光搪瓷涂层可用于制造广告牌，交通标牌和建筑物标识牌等，在许多领域有应用前景。     

Study on luminescent properties of Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors prepared by co-precipitation

Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors with different concentrations have been prepared by co-precipitation. XRD (X-ray diffraction) and SEM (scanning electron microscopy) were used to investigate the structure and morphology. The emission spectra, excitation spectra and fluorescence decay curves were measured, and partial J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated. Furthermore, concentration quenching curves of Eu3+ in different hosts were drawn. The photoluminescent properties of Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors have been studied. The results indicate that Eu3+ 5D0-7F2 red luminescence can be effectively excited by 395 nm and 465 nm in Gd2WO6 and Gd2W2O9 hosts, similar to the familiar Gd2(WO4)3:Eu. Especially Gd2W2O9:Eu has strong red emission and high quenching concentration, so it has potential applications for trichromatic white LED as red fluorescent materials.     

Gd3+为敏化剂的掺Tb3+硅酸盐闪烁玻璃

实验制备了以Tb³⁺为激活剂、Gd³⁺为敏化剂的硅酸盐闪烁玻璃, 研究了Tb₂O₃和Gd₂O₃含量对玻璃密度和玻璃折射率, 以及对玻璃在紫外光激发和X射线激发条件下的光学光谱特性的影响. 通过研究Tb³⁺/Gd³⁺共掺闪烁玻璃的激发与发光特性、荧光寿命, 结合稀土离子能级结构, 分析了Gd³⁺→Tb³⁺离子之间的能量转移与传递机制. 结果表明：在紫外激发条件下, 大量引入Tb₂O₃和Gd₂O₃可提高Gd³⁺→Tb³⁺离子之间的能量传递效率, 有利于Tb³⁺离子的绿色发光; 但是在X射线激发条件下大量引入Tb³⁺离子, 由于缺陷数增加而弱化Tb³⁺离子荧光.     

Strong luminescence and efficient energy transfer in Eu3+/Tb3+-codoped ZnO nanocrystals

Single crystalline Eu³⁺/Tb³⁺-codoped ZnO nanocrystals have been synthesized by using a simple co-precipitation method. Successful doping is realized so that strong green and red luminescence can be efficiently excited by ultraviolet and near ultraviolet radiation, demonstrating an efficient energy transfer from ZnO host to rare earth ions. The energy transfer from the ZnO host to Tb³⁺ in ZnO: Tb³⁺ samples and ZnO host to Eu³⁺ in the ZnO: Eu³⁺ samples under UV excitation are investigated. It is found that the red ⁵D₀ → ⁷F₂ emission of Eu³⁺ ions decreases with increasing temperature but the green ⁵D₄ → ⁷F₅ emission of Tb³⁺ ions increases with increasing temperature, implying a different energy transfer processes in the two samples. Moreover, energy transfer from Tb³⁺ ions to Eu³⁺ ions in ZnO nanocrystals is also observed by analyzing luminescence spectra and the decay curves. By adjusting the doping concentration, the Eu³⁺/Tb³⁺-codoped ZnO phosphors emit green and red luminescence with chromaticity coordinates near white light region, high color purity and high intensity, indicating that they are promising light-conversion materials and have potential in field emission display devices and liquid crystal display backlights.