纳米NaYF4:Er3+,Yb3+上转换材料的合成及其性质研究

采用溶胶-凝胶法在水相合成了纳米NaYF_4:Er~(3 ),Yb~(3 )上转换材料,980nm红外激光照射下,肉眼可观察到明亮的上转换发光。实验研究了铒、镱掺杂浓度及焙烧温度对材料合成的影响。所合成的纳米材料呈圆球形、颗粒均匀、分散性好,平均粒径70nm,可应用于生物标记。     

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.     

Ultraviolet upconversion fluorescence of Er3+ in Yb3+/Er3+-codoped Gd2O3 nanotubes

Under 980 nm excitation, room-temperature ultraviolet (UV) upconversion (UC) emissions of Er3+ from the 4G(9/2), 2K(13/2), and 2P(3/2) states were observed in Gd2O3:Yb3+/Er3+ nanotubes, which were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 degrees C. The experimental results exhibited that these UV emissions came from four-photon UC processes. In the Gd2O3:Yb3+/Er3+ nanocrystals, the energy transfers (ETs) from Yb3+ to Er3+ played important roles in populating the high-energy states of Er3+ ions. This material provides a possible candidate for building UV compact solid-state lasers or fiber lasers.     

Up-conversion fluorescence of Tm3+ and Gd3+ in Yb3+/Tm3+ co-doped Gd2O3 nanocrystals

Through a co-precipitation method Gd(OH)3:20%Yb3+, 1%Tm3+ nanorods were synthesized. After sintered at 900 degrees C for 1 h in air, the as-prepared Gd(OH)3:20%Yb3+, 1%Tm3+ nanorods were converted into Gd2O3:20%Yb3+, 1% Tm3+ nanocrystals. Crystalline phases, sizes, and morphologies of the two samples were characterized by X-ray diffraction and field emission scanning electron microscope. The up-conversion (UC) fluorescence spectra of the Gd2O3:20%Yb3+, 1%Tm3+ nanocrystals were recorded by using a fluorescence spectrophotometer with a 980 nm continuous wave laser diode as excitation source. The nanocrystals not only present characteristic blue and ultraviolet (UV) UC emissions of activated Tm3+, but also show UV UC emissions of host Gd3+. The experimental study suggests that the excitation power has great effects on UC fluorescence properties and the energy transfer from Tm3+ to Gd3+ is very efficient.     

Up-conversion luminescence properties of Y2O2S:Yb3+,Er3+ nanophosphors

Up-converting yttrium oxysulfide nanomaterials doped with ytterbium and erbium (Y₂O₂S:Yb³⁺,Er³⁺) were prepared with the flux method. The precursor oxide materials were prepared using the combustion synthesis. The morphology of the oxysulfides was characterized with transmission electron microscopy (TEM). The particle size distribution was 10–110 nm, depending on the heating temperature. According to the X-ray powder diffraction (XPD), the crystal structure was found hexagonal and the particle sizes estimated with the Scherrer equation agreeded with the TEM images. Upon the 970 nm infrared (IR) laser excitation, the materials yield moderate green ((²H_11/2, ⁴S_3/2) → ⁴I_15/2 transition) and strong red (⁴F_9/2 → ⁴I_15/2) luminescence. The green luminescence was enhanced with respect to the red one by an increase in both the crystallite size and erbium concentration due to the cross-relaxation (CR) processes. The most intense up-conversion luminescence was achieved with x_Yb and x_Er equal to 0.10 and 0.005, respectively. Above these concentrations, concentration quenching occurred.     

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.     

In vitro and in vivo investigations of upconversion and NIR emitting Gd2O3:Er3+,Yb3+ nanostructures for biomedical applications

The use of an “over 1000-nm near-infrared (NIR) in vivo fluorescence bioimaging” system based on lanthanide containing inorganic nanostructures emitting in the visible and NIR range under 980-nm excitation is proposed. It may overcome problems of currently used biomarkers including color fading, phototoxicity and scattering. Gd₂O₃:Er³⁺,Yb³⁺ nanoparticles and nanorods showing upconversion and NIR emission are synthesized and their cytotoxic behavior is investigated by incubation with B-cell hybridomas and macrophages. Surface modification with PEG-b-PAAc provides the necessary chemical durability reducing the release of toxic Gd³⁺ ions. NIR fluorescence microscopy is used to investigate the suitability of the nanostructures as NIR–NIR biomarkers. The in vitro uptake of bare and modified nanostructures by macrophages is investigated by confocal laser scanning microscopy. In vivo investigations revealed nanostructures in liver, lung, kidneys and spleen a few hours after injection into mice, while most of the nanostructures have been removed from the body after 24?h.     

Comparison of laser generation in thermally bonded and unbonded Er3+,Yb3+:glass/Co2+:MgAl2O4 microchip lasers

Pulse laser generation in several Er³⁺,Yb³⁺:glasses thermally bonded with Co²⁺:MgAl₂O₄ was achieved. Peak power in the range of 1.83–7.68 kW with pulse duration between 2.9 and 4.2 ns and energy up to 24 μJ was obtained. The output characteristics for different transmissions of the output couplers were investigated. To show the improvements gained by the thermal bonding procedure, a comparison of thermally bonded and unbonded samples was done in terms of generation efficiency, peak power, beam quality, generated spectra and pulse to pulse jitter.     

络合沉淀法合成纳米Y2O3:Yb,Er及其上转换发光性能

以EDTA为螯合剂,采用络合沉淀法合成了纳米级Yb、Er共掺杂的Y2O3上转换发光粉.通过X射线衍射(XRD)、透射电子显微镜(TEM)、光致发光(PL)光谱和红外(IR)光谱对微晶进行了表征.结果表明,经980℃焙烧后的粒子为单一的立方晶相,其颗粒基本为球形,并且其粒径约为30nm.PL谱和IR谱分析结果表明:纳米粒子的表面效应使得表面原子更易吸附空气中的水和二氧化碳,从而增强了4S3/2→4F9/2的无辐射弛豫过程,使得样品所发红光与体材料相比具有更高的荧光分支比.另外,本文还对样品的发光性能作了详细的讨论.     

Photoluminescence of transparent glass-ceramics based on ZnO nanocrystals and co-doped with Eu3+, Yb3+ ions

Glasses of the K₂OZnOAl₂O₃SiO₂ system co-doped with Eu₂O₃ and Yb₂O₃ were prepared by the melt-quenching technique. Transparent zincite (ZnO) glass–ceramics were obtained by secondary heat-treatments at 680–860 °C. At 860 °C, traces of Eu oxyapatite appeared in addition to ZnO nanocrystals. The average crystal size obtained from the X-ray diffraction data was found to range between 14 and 35 nm. Absorption spectra of the initial glasses are composed of an absorption edge and absorption bands due to electronic transitions of Eu³⁺ ions. With heat-treatment, the absorption edge pronouncedly shifts to the visible spectral range. The luminescence properties of the glass and glass-ceramics were studied by measuring their excitation and emission spectra at 300, 78, and 4.2 K. Strong red emission of Eu³⁺ ions dominated by the ⁵D₀–⁷F₂ (612 nm) electric dipole transition was detected. Changes in the luminescence properties of the Eu³⁺-related excitation and emission bands were observed after heat-treatments at 680 °C and 860 °C. The ZnO nanocrystals showed both broad luminescence (400–850 nm) and free-exciton emission near 3.3 eV at room temperature. The upconversion luminescence spectrum of the initial glass was obtained under excitation of the 976 nm laser source.     

Controllable synthesis of tetragonal LiScF4:Yb3+, Er3+ nanocrystals and its upconversion photoluminescence properties: Lithium scandium fluoride nanocrystals

Tetragonal rare-earth ions codoped LiScF₄ nanocrystals have been synthesized by a modified solvothermal method. The results revealed that the phase and morphology can be tailored through varying the synthesis conditions, such as reaction temperature and time. Meanwhile, the UC fluorescence emission spectra were measured. It turned out that the UC emission intensity can be significantly influenced by reaction temperature and time. Different from the NaYF₄:20%Yb³⁺,2%Er³⁺ nanocrystals that usually emit green emission, yellow color emission can be observed in the LiScF₄:20%Yb³⁺,2%Er³⁺ samples under 980 nm excitation, which illustrates that the obtained new phase LiScF₄ is suitable as a promising host for efficient UC fluorescence generation and tunable UC emission spectra. Moreover, the UC mechanism was investigated in detail.     

Synthesis and luminescence of ultrafine Er3+- and Yb3+-doped Gd11SiP3O26 and Gd14B6Ge2O34 particles for cancer diagnostics

In search of new contrast materials for NMR and fluorescence diagnostics and neutron capture therapy of cancer, we have synthesized ultrafine Er³⁺- and Yb³⁺-doped Gd₁₁SiP₃O₂₆ and Gd₁₄B₆Ge₂O₃₄ particles and studied their luminescence properties. We measured the Er³⁺ upconversion luminescence spectra of the gadolinium erbium ytterbium phosphosilicates and borate germanates in the visible range and evaluated the absolute quantum yield of their luminescence. The quantum yield of luminescence in the gadolinium phosphosilicate Gd₁₁SiP₃O₂₆ doped with 5.0 at % Yb and 2.5 at % Er is comparable to that in known Yb³⁺/Er³⁺ codoped fluorides. The nonradiative Yb³⁺ ?? Er³⁺ energy transfer efficiency is evaluated.     

Synthesis and characterization of core–shell SiO2@(Er3+,Yb3+):Lu2O3

We synthesized crystalline Erbium Er³⁺ and Ytterbium Yb³⁺ codoped -Lu₂O₃ nanolayers on SiO₂ microspheres using the modified Pechini method. Two different kinds of precursors, nitrates and chlorides, have been used leading to a layer-to-layer morphology and necklaces structures, respectively. In both cases, the size of nanocrystallites constituting the optical active layer is around 5 nm. We performed X-ray powder diffraction to confirm the cubic crystalline structure of the sesquioxides layer. High resolution transmission electron microscopy analyses corroborate the crystalline nature of the layer. The optical emission of Er³⁺ in the visible range has been recorded.     

Er3+单掺与Er3+/Yb3+共掺Y2SiO5的上转换发光

报道了一种新的上转换发光材料X2型Y2SiO5:Er, Yb并研究了Yb3 浓度和泵浦功率对样品的上转换发光特性的影响:(1)随着Yb3 浓度的增加,绿、红光发射均呈先增强后减弱的变化,但相对于绿光发射,红光发射受Yb3 浓度的影响更剧烈,并且当12%(摩尔分数)Yb3 时,可以得到很纯的红光发射;(2)上转换发光强度与泵浦功率的关系表明,双光子吸收贡献样品的上转换发射.此外,讨论了可能的上转换机制.认为随着Yb3 浓度增加,Er3 的激发态吸收、Yb3 到Er3 的能量传递和Er3 的交叉弛豫对上转换发光的作用依次逐渐加强.     

Synthesis and two-color emission properties of BaGd2(MoO4)4:Eu3+,Er3+,Yb3+ phosphors

Eu³⁺, Er³⁺ and Yb³⁺ co-doped BaGd₂(MoO₄)₄ two-color emission phosphor was synthesized by the high temperature solid-state method. The structure of the sample was characterized by XRD, and its luminescence properties were investigated in detail. Under the excitation of 395 nm ultraviolet light, the BaGd₂(MoO₄)₄:Eu³⁺,Er³⁺,Yb³⁺ phosphor emitted an intense red light at 595 and 614 nm, which can be attributed to ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions of Eu³⁺, respectively. The phosphor will also show bright green light under 980 nm infrared light excitation. The green emission peaks centred at 529 and 552 nm, were attributed to ⁴H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions of Er³⁺, respectively. It indicated that the two-color emission can be achieved from the same BaGd₂(MoO₄)₄:Eu³⁺,Er³⁺,Yb³⁺ host system based on the different pumping source, 395 nm UV light and 980 nm infrared light, respectively. The obtained results showed that this kind of phosphor may be potential in the field of multi-color fluorescence imaging and anti-counterfeiting.     

The charge transfer excitation of trivalent rare earth ions Sm3+, Eu3+, Gd3+, Ho3+, Er3+ and Yb3+ emission in BaFC1 crystals

The charge transfer type excitation spectra of trivalent rare earth ions Sm³⁺, Eu³⁺, Gd³⁺, Ho³⁺, Er³⁺ and Yb³⁺ emission in BaFC1 crystals have been studied. The charge transfer type emissions of Ho³⁺, Er³⁺ and Yb³⁺ in BaFC1 have also been observed in addition to that of Eu³⁺. The energy of charge transfer band of these RE³⁺ ions were estimated experimentally and also calculated by Jørgensen's refined electron spin-pairing energy theory. Both the experimental and calculated values coincide well. The reductive enthalpy changes ΔH⁰_III−II of these RE ions were evaluated. Comparison of the variation of energy of the CT band maximum with that of the enthalpy change ΔH⁰_III−II shows a close agreement.     

Thermal analysis of a diffusion bonded Er3+,Yb3+:glass/Co2+: MgAl2O4 microchip lasers

The analysis of thermal effects in a diffusion bonded Er³⁺,Yb³⁺:glass/Co²⁺:MgAl₂O₄ microchip laser is presented. The analysis is performed for both wavelengths at 940 nm and at 975 nm as well as for two different sides of pumping, glass side and saturable absorber side. The heat sink effect of Co²⁺:MgAl₂O₄, as well as the impact of the thermal expansion and induced stress on the diffusion bonding are emphasised. The best configurations for reducing the temperature peaks, the Von Mises stresses on the diffusion bonding, and the thermal lensing are determined.     

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.