透明β-NaYF4：Yb,Tm/PMMA 纳米复合材料的制备及其光学性能

采用高温溶剂热法制备了一系列不同Yb³⁺掺杂浓度的上转换发光纳米粒子β-NaYF₄：Yb,Tm和核壳结构的β-NaYF₄：Yb,Tm@β-NaYF₄：Yb纳米粒子。采用X射线衍射（XRD）、场发射扫描电镜（FESEM）、光致发光（PL）谱对材料的物相结构、形貌特征和发光性质进行了表征和研究,并特别研究了温度对材料发光性能的影响。结果表明：保持Tm³⁺浓度不变,随着Yb³⁺掺杂浓度的增加,β-NaYF₄：Yb,Tm的发光强度先增大后减小。当Yb³⁺掺杂摩尔分数为30%时,474 nm和645 nm处的发光强度达到最大值;当Yb³⁺掺杂摩尔分数为50%时,450 nm和692 nm处的发光强度达到最大值。在β-NaYF₄：Yb（30%）,Tm上包裹一层β-NaYF₄：Yb壳层后,其发光显著增强,随壳层Yb³⁺摩尔分数的增加,发光强度也是先增大后减小。当壳层Yb³⁺摩尔分数为10%时,核壳结构纳米粒子的发光强度达到最大值;当壳层Yb³⁺摩尔分数达到40%时,核壳结构纳米粒子的发光强度已经低于未包裹时。将样品进行热处理后,荧光增强。样品的发光强度随环境温度的升高,红光变弱,蓝光增强。采用原位聚合法将β-NaYF₄：Yb,Tm纳米粒子与PMMA制成复合材料后,仍能保持较好的透明度和发光强度。     

水溶性NaYF_4∶Yb/Tm纳米粒子的制备及其上转换发光性质

利用溶剂热法合成了NaYF4:20%Yb,0.5%Tm上转换发光纳米粒子(UCNPs),用扫描电子显微镜、X射线衍射分析、发光光谱测量等手段对水溶性纳米颗粒进行了形貌和发光性质表征。结果表明,UCNPs是纯立方相的NaYF4,尺寸均匀分布在30nm左右。在980nm红外光的激发下,UCNPs能够发出肉眼可见的明亮的蓝紫色光。发射光谱中最强发射峰在479nm,来源于Tm3+离子的1G4→3H6发射,并且给出了UCNPs的上转换发光机制。利用聚乙烯吡咯烷酮(PVP)作为表面活性剂所制备的上转换发光纳米颗粒具有良好的水溶性,尺寸较小,在生物荧光标记领域具有潜在的应用价值。     

微乳液-水热结合法制备光色可调的α-NaYF4:Yb,Er,Tm纳米材料

采用微乳液-水热结合法制备了NaYF4:Yb3+,Er3+,Tm3+纳米粒子,利用X射线衍射(XRD)、扫描电镜(SEM)等手段对样品的物相、结构和形貌进行了分析与表征。产物的X射线衍射峰与标准卡片PDF#77-2042完全一致,属于立方相NaYF4;SEM图片显示所制备的纳米粒子形貌和粒径都比较均一,为120nm左右的棉花状小球,由纳米微粒聚集而成;在980nm光的激发下,纳米粒子能够同时发出蓝光(438和486nm)、绿光(523和539nm)和红光(650nm);通过调节Tm3+:Er3+的比例(0,0.5,0.8,1,2,3,5,7),由色度坐标图(CIE)可以看出当Tm3+和Er3+的比例从0增加到2时,样品的整体发光光色是向绿光方向移动;当Tm3+和Er3+的比例为1:1时,得到伪白光;Tm3+和Er3+的比例从2到7时,样品整体的发光向红光方向移动。     

Mn2+掺杂水溶性NaBiF4:Yb/Er上转换微米晶的制备及其上转换发光性能

NaBiF₄作为一种新型的上转换发光基质材料,具有优异的发光性能。本文以聚乙烯吡咯烷酮(PVP)作为表面活性剂,通过溶剂热法成功制备出水溶性NaBiF₄:Yb³⁺/Er³⁺/Mn²⁺上转换微米晶,并对其晶相、形貌及发光性能进行了表征。在980 nm激发光条件下,NaBiF₄:Yb³⁺/Er³⁺/Mn²⁺可发射出强烈的绿色发光,且发光强度随Mn²⁺掺杂浓度的提高呈现先增强后减弱的趋势,表现出优异的上转换发光性能。同时,NaBiF₄:Er³⁺/Yb³⁺/Mn²⁺上转换发光对温度具有良好的依赖性,有望成为潜在的温度传感器材料。     

热解法制备KY3F10: Yb, RE(RE=Er, Ho, Tm)纳米晶及其特性研究

有机染料和量子点等荧光标记材料存在发射光谱宽、 光热稳定性差和细胞毒性等缺陷, 限制了其在生物学研究中的应用. 镧系掺杂上转换发光材料不存在"自发荧光"和"光漂白"现象, 灵敏度高, 长期稳定性好, 利于活体检测. 论文首次采用热解法, 以油酸和十八烯为表面活性剂和溶剂, 制备了KY₃F₁₀: Yb, RE(RE=Er, Ho, Tm) 纳米晶. 研究了油酸含量对产物形貌和粒径尺寸的影响, 当油酸与十八烯的比例为3:1时, 为制备类球形单分散纳米晶体的最佳工艺条件, 在980 nm半导体激光器激发下, 样品KY₃F₁₀: Yb, RE(RE=Er, Ho, Tm) 分别发射出较强的黄绿、 绿色和蓝色光, 这些结果显示KY₃F₁₀: Yb, RE(RE=Er, Ho, Tm) 纳米粒子作为生物探针在多重荧光标记方面具有优异的特性.     

NaYF_4∶Yb,Er上转换荧光纳米颗粒的共沉淀法合成及表征

以二乙二胺五乙酸(DTPA)为络合剂,采用共沉淀法合成了单分散的NaYF_4:Yb,Er上转换荧光纳米颗粒.通过X射线衍射(XRD)、透射电子显微镜(TEM)、荧光(FL)光谱、热重-差示扫描量热分析(TG-DSC)对合成的样品进行了表征.所合成纳米颗粒的粒径均一,通过改变络合剂DTPA的用最可使颗粒的平均粒径在20～120 nm范围内可调.纳米颗粒经煅烧后发生了由立方品型向六方晶型的转变,并伴随着荧光强度的大幅提升.还探讨了络合剂DTPA的用量、煅烧温度对纳米颗粒粒径、晶型及荧光性能的影响.研究结果表明:络合剂DTPA的加入虽然在一定程度上阻碍纳米颗粒由立方晶型向六方晶型的转变,但可获得单分散的小粒径纳米颗粒,其荧光强度仍能满足生物标记的要求.     

Ca2+掺杂对NaYF4:Yb,Er微米晶上转换发光性能的影响

采用柠檬酸钠辅助的水热方法制备了一系列不同Ca²⁺含量的Ca²⁺/Yb³⁺/Er³⁺共掺的NaYF₄微米片。利用透射电子显微镜(TEM)、X射线衍射分析(XRD)、发光光谱等测量手段对样品进行了形貌、晶相、发光性质的表征。样品在980 nm激光泵浦下,可以观察到强的上转换绿色荧光。在Ca²⁺的摩尔分数从0增加到8%的过程中,紫外到可见的上转换发光随着Ca²⁺浓度的增加而显著增强。这是由于Ca²⁺的掺杂导致了晶体内部的不对称性,同时也提高了晶体的结晶性。     

纳米SrMoO4∶Yb,Er上转换发光粉的合成及其性质

以柠檬酸为络合剂,用溶胶-凝胶法制备出纳米级上转换发光粉SrMoO4∶Yb,Er。XRD、TEM确定了样品SrMoO4∶Yb,Er是四方晶系,其粒径约为70nm,属于多晶。实验表明:用980nmLD对其进行激发,在室温下观察到了526,548nm附近的绿光发射和652nm附近微弱的红光发射,分别对应于Er3 离子2H11/2→4I15/2,4S3/2→4I15/2和4F9/2→4I15/2的跃迁;当n(Yb)/n(Er)为7∶1时,上转换发光强度最强。由激发功率与发光强度的关系得出绿光和红光发射均为双光子过程。     

试验优化设计GdTaO4:RE/Yb(RE=Tm,Er)荧光粉制备及上转换发光特性研究

为得到GdTaO₄:RE/Yb(RE=Tm, Er)系列最大特征发光强度的上转换荧光粉,通过试验优化设计建立了980 nm激光激发下荧光粉发光强度与其稀土掺杂浓度的回归方程,其中Tm³⁺/Yb³⁺样品结合均匀设计和二次通用旋转组合设计, Er³⁺/Yb³⁺样品则利用均匀设计和三次正交多项式回归设计分步寻优.检验并求解回归方程,分析浓度与发光强度关系,结果表明RE³⁺(RE=Tm, Er)和Yb³⁺浓度变化均对发光强度影响显著,且在试验空间中存在光强极值点.同条件下再次通过高温固相法制备最优发光样品.分析最优样品X射线衍射(XRD)图谱,结果表明样品均为纯相, Li+助熔剂掺杂会抑制反应杂相的产生,稀土的掺入使衍射峰向高角度偏移,且不改变峰形.分析激发功率与发光强度的关系,结果表明Tm³⁺/Yb³⁺共掺的蓝光发射为三光子过程, Er³⁺/Yb³⁺共掺...     

3d~5金属离子共掺杂NaYF_4:Yb,Er纳米晶的上转换发光

采用水热法制备了Mn~(2+)/Fe~(3+)共掺杂的NaYF_4上转换纳米晶,通过改变掺杂浓度来调控晶相、晶粒尺寸以及上转换荧光发射强度。以Fe~(3+)共掺杂的上转换纳米晶为晶核,通过改变反应时间来调控SiO_2壳厚度,观察到上转换荧光发射强度在反应4 h的条件下出现最大值。Mn~(2+)/Fe~(3+)共掺杂的上转换纳米晶样品整体上转换荧光强度分别提高到3.7倍和4.5倍,同时Fe~(3+)共掺样品的红色上转换荧光增强近7倍。基于近红外980 nm激光激发下的稳态光谱研究,提出Yb~(3+)-过渡族离子和Er~(3+)之间的能量传递以及晶场对称性的改变引起了这种增强效应,随着过渡族离子掺杂浓度的增加,过渡族离子之间的交换相互作用导致上转换荧光的猝灭。     

Up-conversion white light of Tm/Er/Yb tri-doped CaF2 phosphors

Tm³⁺/Er³⁺/Yb³⁺ tri-doped CaF₂ phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980 nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20-260 W/cm², the chromaticity coordinates of the UC light of the phosphor Ca_0.885Tm_0.005Er_0.01Yb_0.1F₂ fell well in the white region of the 1931 CIE diagram. For the proportion of red, green and blue (RGB) in white light is strict, key factors for achieving UC white light, such as host materials, rare earth ions doping concentrations, annealing temperatures, as well as the excitation power densities, were investigated and discussed.     

Up-conversion emission in triply-doped Ho/Yb/Tm KGd(WO4)2 single crystals

Detailed spectroscopic studies of the triply doped KGd(WO₄)₂:Ho³⁺/Yb³⁺/Tm³⁺ single crystals (which exhibit multicolor up-conversion fluorescence) are reported for the first time. The absorption spectra of crystals were measured at 10 and 300 K; the room temperature luminescence spectra were excited at 980 nm wavelength. The dependence of the intensity of luminescence on the excitation power for three different concentration of Ho³⁺, Yb³⁺ and Tm³⁺ ions was investigated. Efficient green and red up-converted luminescence of Ho³⁺ ions and weak blue up-conversion luminescence of Tm³⁺ ions were observed in spectra. The red emission of Ho³⁺ ions is more intensive than their green emission. Dependence of the up-conversion luminescence intensity on the excitation power and impurities concentration was also studied; the number of phonon needed for efficient up-conversion was determined for each case. All possible energy transfer processes between different pairs of the impurity ions' energy levels are also discussed.     

Tm3+,Yb3+共掺钨酸钙多晶材料的上转换发光及荧光温度特性

采用高温固相法制备了Tm³⁺,Yb³共掺CaWO₄多晶材料. 980 nm二极管激光器激发下,在可见区获得了¹G₄→³H₆,¹G₄→³H₄,³H₂,³H₃→³H₆ 跃迁产生的上转换荧光. 讨论了Yb³⁺ 离子浓度的变化对Tm³⁺ 的上转换发光强度的影响,同时根据荧光强度比的方法研究了689 和705 nm 红色上转换荧光在313–773 K 范围内的温度特性. 结果表明：基于Tm³⁺,Yb³⁺ 共掺CaWO₄ 多晶材料的红色上转换荧光可以实现温度监测,其测温的最大灵敏度值为5.7×10^-4 K^-1,相应的测量温度为458 K. 关键词： 上转换发光 3+')" href="#">Tm³⁺ 钨酸钙 荧光温度传感     

超薄金壳包覆NaYF4:Yb,Er@SiO2纳米结构的可控合成与表面增强上转换荧光

利用原位还原法成功制备了尺寸均一、超薄完整金壳包覆的NaYF₄:Yb,Er@SiO₂@Au（NSA）纳米结构,其XRD、TEM、EDX、HRTEM-HAADF、Mapping及吸收光谱表征结果表明,SiO₂壳及纳米金壳的平均厚度分别约为5 nm和2 nm。在980 nm连续激光激发下,系统研究了核壳结构的上转换荧光强度与氯金酸浓度的依赖关系。稳态光谱结果显示,NSA与仅SiO₂包覆样品（NS）相比Er³⁺的红绿荧光强度均增强了~2.8倍。通过分析上转换荧光动力学过程及利用FDTD方法模拟,讨论了表面等离激元增强上转换荧光的机制。     

Hydrothermal synthesis of hexagonal-phase NaYF4: Er, Yb with different shapes for application as photovoltaic up-converters

Hexagonal β-NaYF4 co-doped with Yb3+ and Er3+ is directly synthesized under mild conditions using a hydrothermal method.The variation of the ratio of Ln3+ to F-and ethylenediaminetetraacetic acid(EDTA) causes the shape of the microcrystal to change from microplate to microcolumn.The NaYF4 powder is mixed with polydimethylsiloxane(PDMS) to create an up-converter for thin film amorphous silicon solar cells so as to evaluate the effectiveness of the synthesized material as an up-converter.In order to overcome the difficulty in measuring the effectiveness of up-conversion material,a new method of using near infrared illumination to measure the short circuit current densities of solar cells both with and without up-converters is developed.An up-converter with pure hexagonal NaYF4:Yb3+/Er3+ microcrystal produces a high current output.Emission intensity data obtained by photoluminescence suggest that pure hexagonal NaYF4:Yb3+/Er3+ microcrystals are more efficient than nanocrystals when used as up-converting phosphors.     

A series of new compounds A3+Fe2 O4 (A = Ho,Er, Tm,Yb, and Lu)

A series of new compounds A Fe₂ O₄ (A = Ho, Er, Tm, Yb, and Lu) have been successfully synthesized under the lower oxygen partial pressures at 1200°C and their unit cell dimensions were determined.     

Preparation of NaYF4:,Er3+/TiO2 composite and up-conversion luminescence properties under visible light excitation

The up-conversion luminescence composite NaYF 4:Er 3+ /TiO 2 is prepared using the sol-gel method.The specimen has good crystallinity and two shapes,i.e.,viereck and round,while the sizes of viereck and round particles are both micron-sized.The TiO 2 has an anatase structure,while the NaYF 4 has a hexagonal phase,which can be hardly obtained through the common sol-gel method.Due to the big particle size and the high crystallinity of pure NaYF 4:Er 3+,the composite has a small specific surface area that is less than Degussa P25 TiO 2.The NaYF 4:Er 3+ /TiO 2 composite shows several emission peaks at 211,237,and 251 nm under the excitation of 388 nm,at 395 nm and 411 nm under the excitation of 500 nm,and at 467,481,492,and 508 nm under the excitation of 570 nm.