Y2O3:Tm,Yb nanophosphors for correlative upconversion luminescence and cathodoluminescence imaging

We present a phosphor nanoparticle that shows both upconversion luminescence (UCL) and cathodoluminescence (CL). With this particle, low-autofluorescence, deep-tissue and wide-field fluorescence imaging can be achieved with nanometer-order high-spatial-resolution imaging. We synthesized Y₂O₃:Tm,Yb nanophosphors that emit visible and near-infrared UCL under 980 nm irradiation and blue CL via electron beam excitation. The phosphors were applied to fluorescent imaging of HeLa cells. The photostability of the phosphors was superior to that of a conventional organic dye. We show that after uptake by HeLa cells, the particles can be imaged with SEM and CL contrast in a cellular section. This indicates that correlative UCL and CL imaging of biological samples could be realized.     

KLa(MoO_4)_2∶Yb~(3+),Ho~(3+),Tm~(3+)白光荧光粉的制备及性能研究

采用水热法成功制备了Yb~(3+),Ho~(3+),Tm~(3+)三掺的多晶KLa(Mo O4)2荧光粉。在980 nm激光激发下,KLa(MoO_4)_2∶Yb~(3+),Ho~(3+),Tm~(3+)发出裸眼可见的明亮白光,这其中包括Tm~(3+)离子发出的蓝光(~475 nm)、Ho~(3+)离子发出的绿光(~540 nm)和红光(~651 nm)。根据色度坐标系计算得出的坐标点可以看出,随着Ho~(3+)/Tm~(3+)掺杂浓度之比的增加,KLa(Mo O_4)_2∶Yb~(3+),Ho~(3+),Tm~(3+)所发出的白光呈现从冷白光到暖白光的变化。最后详细讨论了KLa(Mo O_4)_2∶Yb~(3+),Ho~(3+),Tm~(3+)荧光粉可能的发光机制。     

Tailoring red-green-blue emission from Er3+, Eu3+ and Tb3+ doped Y2O3 nanocrystals produced via PVA-assisted sol-gel route

Y₂O₃ luminescent nanoparticles were synthesized via PVA-assisted sol-gel method and their structural and optical properties were investigated. Effects of rare earth (Er³⁺, Eu³⁺ and Tb³⁺) doping on luminescence properties of the produced nanophosphors have been investigated under NIR (800 nm) and UV (240–300 nm) excitation. Intense infrared to red and green emissions were observed and a weak blue upconverted luminescence was also detected. Moreover, it was observed that changing the doping ions, the color emitted by the samples could be modified and different combinations of UV excitation and doping produced effective white light emissions. The obtained results demonstrate that PVA-assisted sol-gel is an effective methodology for the synthesis of rare-earth doped Y₂O₃ nanophosphors.     

YLiF4: Er3+, Tm3+, Yb3+中Tm3+浓度对上转换发光的影响

利用水热法合成了YLiF4: Er3 , Tm3 , Yb3 , 其中Er3 和Yb3 的浓度保持固定不变, 分别为1 mol%和1.5 mol%, Tm3 浓度变化范围是2 mol%～8 mol%. 在这种共掺杂体系中, 同时观察到了Er3 , Tm3 和Yb3 的吸收, 且Tm3 的吸收随着其浓度的增强而增强. 在980 nm光的激发下, 当Tm3 浓度很小时, 这种材料的上转换发光为白光. 其中蓝光主要来源于Tm3 的激发态1G4到基态3H6的跃迁, 绿光来源于Er3 的4S3/2和2H11/2到基态4I15/2的跃迁, 红光既来源于Tm3 的1G4→3F4的跃迁, 也来源于Er3 的4F9/2→4I15/2的跃迁. 并且这种上转换发光强度随着Tm3 浓度的增强而降低, 但对应不同能级跃迁的发光强度降低的幅度不同, 这是因为Er3 和Tm3 之间的相互作用.     

980 nm LD 激发下Yb3+,Er3+:Y2O3纳米晶粉体的上转换发光

用共沉淀法合成出Yb^3＋,Er^3＋离子双掺杂的Y2O3粉体,X射线衍射结果表明所制备粉体为立方Y2O3结构。场发射扫描电镜照片显示其颗粒形状为球形,粒径为60～80nm;该粉体在波长为980nm的半导体激光器激发下发射出中心波长为562nm的绿色和660nm的红色上转换荧光,分别对应于Er^3＋离子的^4S3/2H11／2→^415/2跃迁和^4F6/2→^415/2跃迁。发光强度和激发功率关系的研究揭示其均为双光子过程,能量传递和激发态吸收是上转换发光的主要机制。由于其高效的上转换发光性能,这种材料有可能应用于荧光标记和红外探测方面。     

Photoluminescence in Gd2O3: Er3+, Yb3+ upconversion inverse opal

Photoluminescence properties of Gd₂O₃: Er³⁺, Yb³⁺ upconversion inverse opal photonic crystals were investigated. The photoluminescence spectra of the inverse opal show strong dependence on upconversion emission intensity and the corresponding photonic band-gaps of the inverse opal. Significant suppression of the green or red upconversion emission was observed if the photonic band-gap overlaps with the Er³⁺ ions emission band. The color purity of the red or green emission was improved in the inverse opal by the suppression of green or red UC emission. We believe that the present work will be valuable for not only the foundational study of upconversion emission modification but also new optical devices in upconversion lighting and display.     

氧化物纳米材料Y2O3:(Yb3+,Er3+)上转换发光性质的研究

以Y2O3,Yb2O3,Er2O3为原料,利用燃烧法分别制备了Y2O3:Er3 和Y2O3:(Yb3 ,Er3 )两种纳米材料和相应的体材料Y2O3:(Yb3 ,Er3 ).用发射波长为978 nm的半导体激光器和日立F-4500荧光分析仪测量了它们的上转换发光,得到纳米材料Y2O3:Er3 的上转换发光主要为绿色上转换发射而纳米材料Y2O3:(Yb3 ,Er3 )主要为红色上转换发射,而后者与激活离子掺杂浓度相同的体材料Y2O3:(Yb3 ,Er3 )的上转换发射相比较,体材料以绿色上转换发射为主、红色上转换发射很弱.     

Enhanced white light emission in Er/Tm/Yb/Li codoped Y2O3 nanocrystals

Er/Tm/Yb codoped Y₂O₃ nanocrystals and Er/Tm/Yb/Li codoped Y₂O₃ nanocrystals have been synthesized by sol-gel method, bright white light emission has been observed at 976 nm excitation. The blue, green, and red emissions, respectively, arise from the transitions ¹G₄ → ³H₆ of Tm³⁺, ²H_11/2/⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 of Er³⁺ ion. Moreover, after doping Li⁺ ions into Er/Tm/Yb codoped Y₂O₃ nanocrystals, the white light emission increase greatly. CIE coordinate of Er/Tm/Yb/Li codoped Y₂O₃ nanocrystals is X = 0.32 and Y = 0.36 at 10 W/cm² excitation, which is very close to the standard equal energy white light illuminate (X = 0.33, Y = 0.33).     

Er3+/Yb3+共掺杂铋酸盐玻璃的上转换发光和能量传递

用高温熔融法制备了Er³⁺/Yb³⁺共掺杂的45Bi₂O₃-45GeO₂-10PbO玻璃,对玻璃样品进行了光谱测试,分析了上转换发光机制和Yb³⁺→Er³⁺的能量传递效率。通过Yb³⁺离子浓度对Er³⁺离子在铋酸盐玻璃中的上转换荧光强度影响的研究,得到Er³⁺质量分数为0.5%以及Yb³⁺质量分数为2.5%时上转换发光强度最大。研究结果表明,在970nm泵浦激发下,Er³⁺/Yb³⁺共掺杂B₄₅G₄₅P₁₀玻璃在532,545,673nm处产生较强的上转换绿光和红光,是一种较为理想的上转换发光基质材料。     

Highly efficient infrared-to-visible energy upconversion in Er(3+):Y(2)O(3)

Very intense green and red emission was observed at room temperature from the (4)S(3/2) and (4)F(9/2) levels of Er(3+):Y(2)O(3). A cw diode laser at 975 nm was used as a pump for resonant sequential excitation of the (4)I(11/2) and (4)F(7/2) levels. The fluorescence was easily visible to the naked eye, even with 27 mW of excitation power. It was found that at 850 mW of cw excitation power the total luminance was 39,000 cd/m(2). This corresponds to ~100 muW of green emission and 270 muW of red emission.     

基于KMnF_3∶Yb~(3+),Er~(3+)纳米晶的红光聚合物平面光波导放大器

制作了基于KMnF_3∶Yb~(3+),Er~(3+)纳米晶材料的工作波长655 nm的聚合物平面光波导放大器。材料的吸收光谱表明,KMnF_3∶Yb~(3+),Er~(3+)纳米晶在980 nm附近有很强的吸收。在980 nm激光的激发下,由于Er~(3+)和Mn2+能级之间的能量传递,KMnF_3∶Yb~(3+),Er~(3+)纳米晶产生了很强的红色上转换发光。根据KMnF_3∶Yb~(3+),Er~(3+)纳米粒子的发光特性,制备了KMnF_3∶Yb~(3+),Er~(3+)NCs-PMMA复合材料,用其作为芯层设计了掩埋形结构光波导放大器,利用传统的半导体工艺完成器件制备。器件测试结果表明,当655 nm信号光功率为0.1 m W、980 nm泵浦功率为260 m W时,器件获得了2.7 d B的相对增益。     

基于NaYF_4:Yb~(3+),Er~(3+)上转换发光材料的色彩设计

采用共沉淀法制备β-NaYF4:Yb3+,Er3+。X射线衍射图谱结果表明退火有利于β相生长。样品在970nm处有一强烈吸收峰,利用980nm激光激发样品,实现红、绿、蓝三色上转换发光;其中蓝光相对较弱,红、绿光的发射峰分别为521,539,659nm。速率方程表明红、绿发射对应跃迁均是双光子过程,实验结果与理论分析相符。此外,对红、绿发射带面积比的研究表明激发功率和Yb3+掺杂量影响发光颜色;进而可实现简便的色彩设计。     

共沉淀法制备Y2SiO5∶Er3+ ,Yb3+ ,Tm3+及其上转换发光性能研究

采用化学共沉淀法制备了系列Y_1.98-2xYb_2x Er_0.02SiO₅(0.00≤x≤0.15)以及Y_1.736Yb_0.24Er_0.02Tm_0.004SiO₅上转换发光材料,比较了室温下Y_1.98-2xYb_2x Er_0.02 SiO₅ (x=0.00,0.08)样品在400—1600 nm范围内的吸收光谱,测量了所有样品在976 nm OPO激光器激发下的上转换发射光谱,以及Er³⁺离子⁴S_3/2(⁴F_9/2)→⁴I_15/2,Tm³⁺离子¹G₄→³H₆荧光衰减曲线和不同激发功率下的上转换蓝光发射强度,从而分析讨论了Er³⁺,Tm³⁺在Y₂SiO₅中的上转换发光机理.研究结果表明:在1250 ℃相对较低的温度下合成了X2型单斜晶系Y₂SiO₅ ∶Ln³⁺(Ln³⁺=Er³⁺,Yb³⁺,Tm³⁺),Yb³⁺的敏化显著增强了样品在976 nm附近的吸收能力,并大幅度加宽了该处的吸收带.分析上转换发射光谱发现:上转换绿光和红光强度都随着Yb³⁺浓度的增加先增强后减弱,但红光的猝灭浓度较高,归因于Er³⁺→Yb³⁺反向能量传递ETU4和Yb³⁺→Er³⁺正向能量传递ETU3过程的发生;上转换蓝光发射是三光子吸收过程,是通过Yb³⁺,Tm³⁺之间三次声子辅助的能量转移方式实现的. 关键词： 上转换 共沉淀 2SiO₅∶Er³⁺')" href="#">Y₂SiO₅∶Er³⁺ 3+')" href="#">Yb³⁺ 3+')" href="#">Tm³⁺     

镱铥共掺杂的氟化镧纳米粒子的亮蓝色上转换发光

采用反胶束法合成镱铥共掺杂的氟化镧纳米粒子.这种反胶束是由微乳液作为合成媒介,这些分散的纳米粒子在化学成分、尺寸分布上是可控的.产物形貌经场发射扫描电镜和透射电镜表征.固态样品分散在乙醇中,在未经超声处理时,样品表现为玉米棒样的聚集.棒的平均直径和长度分别为110,575nm.我们认为这种大量纳米粒子聚集成良好超结构是由于溶剂挥发,分子交叉链接或者表面活性剂分子附着于纳米粒子特殊晶面造成的.当样品经过超声处理后,由于超声振动破坏了上述因素,玉米棒形貌的聚集体转为大量纳米粒子.单个粒子的高分辨电镜显示出该纳米粒子的单晶结构.并且晶面间距约为0.366nm,与纯氟化镧六角相[002]晶面相一致.样品在300℃退火30min后的透射电镜照片显示纳米粒子的平均直径大约为35nm,这与XRD结果相吻合.并且,这些纳米粒子表现出了良好的单分散性,并且在978nm二极管激发下,纳米粒子呈现出亮蓝色上转换发光,这种上转换荧光粉在光电子或生物检测中有潜在的应用前景.     

Preparation and characterization of upconversion luminescent Tm3+/Yb3+ co-doped Y2O3 nanophosphor

Tm³⁺/Yb³⁺ co-doped Y₂O₃ nanophosphor has been synthesized by the solution combustion technique. Heat treatment of the phosphor materials at higher temperatures modifies the structural and optical properties. At low concentration of Yb³⁺, an intense upconversion emission is observed in blue region (478?nm) on excitation with 976?nm radiations. Emission has also been observed in the ultraviolet (UV) region viz. at 300?nm. The intensity of blue emission initially increases with dopant concentration as well as with the annealing temperature. However, for higher concentrations of Yb³⁺ (10?mol%), emission in the blue region is greatly suppressed and NIR emission at 813?nm appears with a large intensity. Intensity ratio of NIR and blue emission (I _NIR/I _B) reaches 74, resulting in almost monochromatic light at 813?nm. To check the suitability of blue emission for display devices, CIE color coordinates (x,y), color purity and the dominant wavelength (?? _d) for the blue emission have been calculated and the resulting value is found to be close to the coordinates of available standard blue phosphors.     

激发功率、退火温度及Tm3+浓度对Tm3+/Er3+/Yb3+三掺YF3粉末上转换发光性质的影响

用水热法合成了Tm³⁺/Er³⁺/Yb³⁺三掺杂YF₃上转换发光粉末,并对其进行了结构和形貌表征.对上转换发射谱的研究表明,在相对低激发功率下,可以观察到比较明亮的近白色发光,且随着激发功率的增大,上转换发射强度迅速增大并达到饱和状态,继续增大激发功率,出现发光猝灭现象.退火温度对上转换发射强度的影响表明,随着退火温度的升高,Tm³⁺,Er³⁺的所有特征发射峰均相对增强.上转换发射谱随Tm³⁺浓度变化关系表明,在相对低Tm³⁺掺杂浓度下,Tm³⁺-Er³⁺相互作用占优势,Tm³⁺把能量传递给Er³⁺,Er³⁺发射相对增强;在相对高掺杂浓度下,Tm³⁺-Tm³⁺之间交叉弛豫过程占优势,Er³⁺发射相对减弱.从实验结果看出,该粉末的上转换发光非常丰富,从紫外到红外均有发射,是一种潜在的白色上转换发光及三维固体显示材料.     

Optical losses in YVO4: RE (RE = Nd3+, Er3+, Tm3+) laser crystals

The relevance of processes contributing to depletion of pump and upper laser levels has been assessed based on experimental data obtained during measurement of excited state absorption, steady state emission and dynamics of excited states as a function of excitation power and activator concentration. It has been concluded that the excited state absorption in YVO₄: Nd and YVO₄: Er is not significant except for that from the ⁴ I _11/2 level of Er³⁺. In these systems, the interionic processes are dominant. In particular, the reported decrease of the YVO₄: Er laser slope efficiency when the Er³⁺ concentration increased from 0.5 to 1 at % is due mainly to the up-conversion by energy transfer from the pump level and upper laser level. Excited state absorption cannot contribute to depletion of excited states involved in the ³ F ₄-³ H ₆ laser operation near 1800 nm in the YVO₄: Tm crystal. However, the heavy doping required to enhance the cross-relaxation process which feeds the upper laser level brings about the migration-accelerated energy transfer to energy sinks.     

Gd3+掺杂对NaYF4:Yb3+,Tm3+/Er3+ 纳米材料上转换荧光性能的影响

利用温和的溶剂热方法合成了具有上转换发光性能的Yb³⁺-Tm³⁺和Yb³⁺-Er³⁺共掺的纳米NaYGdF₄。在该体系中,通过调节Gd³⁺在基质中的掺杂量可以有效地控制产物的相变、尺寸以及上转换荧光性能。XRD和TEM分析结果表明,Gd³⁺的掺入在促进NaYF₄纳米颗粒由立方相到六方相转变的同时有助于减小其尺寸。上转换光谱研究表明,在Yb³⁺-Tm³⁺和Yb³⁺-Er³⁺共掺体系中,可通过优化Gd³⁺的掺杂量来有效提高产物的上转换荧光强度。同时,通过研究Tm³⁺和Er³⁺在不同可见光波段的发光强度与泵浦功率的关系探讨了上转换发光的机制。