超细YF_3与GdF_3纳米晶的合成及其上转换发光

当使用液固溶法(LSS法)制备分散性纳米晶时,将传统油酸/油酸钠/酒精反应体系中的NaOH用氨水取代时,氨水将会与油酸形成新的表面活性剂油酸铵,这样就可以合成各种超细分散性的REF3纳米晶(RE代表稀土元素)。在这种新的反应体系中,合成了平均直径小于10 nm的YF3和GdF3超细颗粒,X射线与透射电镜测试表明YF3是正交相,而GdF3是面心立方结构,空间群为Fm3m,晶格常数为0.582 9 nm。在980 nm半导体激光器激发下,可检测到YF3∶Yb/Er在515~570 nm处有较强的绿色发光峰、645~675 nm处有较强的红色发光峰,呈橙色发光。YF3∶Yb/Tm和GdF3∶Yb/Tm样品在460~490 nm处有较强的蓝色发光峰,而在800 nm附近有更强的近红外发光峰。由于其超细的尺寸及红外上转换发光特性,合成的样品在生物成像、生物标签等方面有潜在的应用价值。     

低温凝胶燃烧法合成Y2O3∶Er3+，Yb3+纳米晶上转换发光材料

分别以柠檬酸和甘氨酸为燃烧剂,采用低温凝胶燃烧法合成了Er³⁺、Yb³⁺共掺Y₂O₃纳米晶粉体。通过TG-DSC、XRD、SEM等分析手段对两种燃烧剂所对应的反应过程及纳米晶粉体的物理性能进行了分析,结果表明甘氨酸法具有更高的反应效率、更好的粉体分散性及粒径均匀性。在980 nm激光二极管(LD)激发下,对甘氨酸法所得样品的上转换发光性能分析表明,绿光和红光发射谱带分别来自于Er³⁺的⁴S_3/2/ ²H_11/2→ ⁴I_15/2和⁴F_9/2→ ⁴I_15/2跃迁。此外,对Er³⁺和Yb³⁺掺杂浓度、粉体煅烧温度对纳米晶样品上转换发光性能的影响进行了讨论。     

WO3/YF3:Eu3+复合纳米材料的制备与发光性能

采用直接沉淀法制备了WO_3/YF_3∶Eu~(3+)复合纳米材料,并对其结构、组成、形貌和发光性能进行了研究。XRD分析表明:复合纳米材料由纳米粒子WO3和结晶良好的正交晶系的YF3∶Eu~(3+)组成。SEM照片表明:片状WO3颗粒表面沉积了分散性较好、粒径均匀(尺寸为10~50 nm)的YF3∶Eu3纳米颗粒。荧光光谱分析表明:该复合纳米材料具有良好的发光性,以593 nm附近的5D0→7F1磁偶极跃迁为最强发射峰,与纯的YF3∶Eu~(3+)相比WO_3/YF_3∶Eu~(3+)发光强度明显增强,表明具有表面等离子共振效应的WO3纳米粒子对壳层的YF3∶Eu~(3+)起到发光增强作用。     

球形La2O3∶Eu纳米晶的制备及其发光特性

The spheric La₂O₃∶Eu nanocrystals were prepared using NH₃·H₂O-NH₄HCO₃ mixture as precipitant. The material was characterized by FTIR, XRD and TEM techniques. The luminescence properties of Eu³⁺ in spheric La₂O₃ were measured by three dimension spectra, emission and excitation spectra. The results indicate that the La₂O₃∶Eu nanocrystals are in hexagonal phase by annealing at 800 ℃, the crystal size is about 30 nm. The maximum emission and excitation wavelength were determined by three dimensional spectroscopy to be at 591 nm and 394 nm, respectively. In emission spectrum the band at 591 nm and 612 nm are corresponding to ⁵D₀-⁷F₁ and ⁵D₀-⁷F₂ transition of Eu³⁺ ions. With increasing in annealing temperature the differences of intensity of the two transitions are increased. This phenomenon shows that the luminescence intensity of La₂O₃∶Eu nanocrystals can be tuned by changing annealing temperature.     

无氨湿法制备纳米晶In2O3及表征

Preparation of In₂O₃nano-scale powders by ultrasonic and homogeneous precipitation, using metal In and urea as raw materials, was reported for the first time, while the effects of reaction temperature, the ratio of the materials and the pH etc. on the preparation was dicussed. This method can be operated and industrialized easily with very low cost． The structural properties of precursor and In₂O₃were characterized by TG-DTA, XRD, ESCA and TEM. The results show that In₂O₃produced are very pure, monophase and spherical nano-scale powders with average size of 25 nm.     

Er3+/Yb3+共掺杂SrF2纳米晶的合成及上转换发光特性

利用水热法以聚乙二醇作为分散剂合成了Er3+和Yb3+共掺的SrF2纳米晶.在980 nm半导体激光器激发下.研究了不同Er3+离子掺杂浓度对发光性能的影响,确定了最佳掺杂浓度比,讨论了退火温度对样品发光的影响及样品的协作敏化和声子辅助共振能量传递的上转换发光机制.用X射线衍射和透射电镜对样品的结构和粒度进行了分析.研究结果表明:用水热法在180℃保温13 h下,合成的样品粒径约为50 nm;当CYb3+CEr3+=4:1,而对Er3+掺杂浓度为1.3mol%时,样品上转换发光强度达到最强.     

(ZrO2)0.92(Gd2O3)0.08纳米晶的水热合成及其烧结体的电性能

用新制备的(Gd，Zr)(OH)_x·yH₂O共沉淀作前驱体，在强碱性介质中用水热法合成了(ZrO₂)_0.92(Gd₂O₃)_0.08纳米立方晶，考察了反应温度、pH值等水热反应条件对纳米晶粒大小的影响。将(ZrO₂)_0.92(Gd₂O₃)_0.08     

超细ZnFe2O4纳米晶与蛋白质的相互作用

水热法制备了超细ZnFe₂O₄纳米晶,并通过高分辨透射电镜(HRTEM)、XRD和EDX技术对其进行了表征。以牛血清白蛋白(Bovine Serum Albumin,BSA)和牛血红蛋白(Hemoglobin)为模式蛋白,研究了纳米晶在不同pH条件下对蛋白质分子的吸附及其与ζ电势的关系。通过动态光散射(Dynamic Light Scattering,DLS)和傅立叶变换红外光谱(Fourier Transform Infrared,FTIR)技术分别研究了纳米晶吸附蛋白后流体力学直径的变化以及蛋白质构象的变化。结果表明,ZnFe₂O₄纳米晶对牛血红蛋白的吸附符合静电吸附的规律,而对BSA的吸附则不符合静电吸附的规律。纳米晶吸附牛血红蛋白后主要以单体和三聚体的形式存在,仅存在少量的团聚体,而吸附BSA后完全以团聚体的形式存在。FTIR光谱则显示纳米晶对牛血红蛋白构象的影响大于对BSA构象的影响。在合适的pH条件下,纳米晶对BSA及牛血红蛋白的吸附容量均超过380mg·g^-1,有望应用于蛋白质的高效分离。     

LaF_3∶Yb~(3+),Er~(3+)纳米晶:溶剂热法合成及上转换发光性质

利用溶剂热合成方法,分别以油酸和油胺为表面有机配体,合成了具有六角结构,颗粒尺寸分别为19和23nm单分散的LaF3:Yb3+,Er3+纳米晶。在980nm红外激光照射下,LaF3:Yb3+,Er3+纳米晶发射出肉眼可观察的绿色和红色上转换荧光,而且其发光过程均符合双光子过程。结合红外光谱与上转换光谱分析了表面有机配体对LaF3:Yb3+,Er3+纳米晶上转换发光的影响,结果显示,以油酸分子为表面配体的纳米晶具有较高的上转换发射强度,但以油胺为表面配体的纳米晶的红光发射相对增强。     

(ZrO2)1-x(Yb2O3)x纳米晶的水热法合成及其烧结体的电性能

(ZrO₂)_1-x(Yb₂O₃)_x (x=0.07, 0.09, 0.11) nanocrystallites were hydrothermally prepared in basic media by using co-precipitated Zr(OH)₄ and Yb(OH)₃ as precursor. The nanocrystallites have small particle sizes of 5.8~7.5 nm, narrow size distribution, less agglomeration and high sinterability. The oxide-ionic conduction properties of the prepared ceramics were investigated by means of AC impedance spectroscope, oxygen concentration cell at 600~1 000 ℃. The results show that the ceramic with x=0.09 is superior to the ceramics with x=0.07 and 0.11 in oxide-ionic conduction.     

Size-dependent upconversion luminescence in YF3:Yb/Tm nanobundles

The upconversion luminescent properties of YF₃:Yb³⁺(20%)/Tm³⁺(1%) nanobundles with different sizes (240-500 nm in length) were studied under 980-nm excitation. Ultraviolet (¹I₆ → ³F₄/³H₆ and ¹D₂ → ³H₆), blue (¹D₂ → ³F₄ and ¹G₄ → ³H₆), red (¹D₂ → ³H₄, ¹G₄ → ³F₄, and ³F₃ → ³H₆), and near infrared (³H₄ → ³H₆) emissions were observed. The results indicated that the relative intensity of the ultraviolet to the blue as well as the blue to the near infrared increased with decreasing the size of nanobundles. Especially, the position of the dominant red emission peak varied with the size of nanobundles. As the length of nanobundles increased to 500 nm, unusual ³F₃ → ³H₆ transition was observed, which was theoretically explained considering the decrease of the nonradiative transition rate of ³F₃ → ³H₄.     

Enhanced ultraviolet up-conversion emissions of Tm/Yb codoped YF3 nanocrystals

Tm³⁺/Yb³⁺ codoped rod-like YF₃ nanocrystals were synthesized through a facile hydrothermal method. After annealing in an argon atmosphere, the nanocrystals emitted bright blue and intense ultraviolet (UV) light under a 980-nm continuous wave diode laser excitation. Up-conversion emissions centered at ∼291 nm (¹I₆ → ³H₆), ∼347 nm (¹I₆ → ³F₄), ∼362 nm (¹D₂ → ³H₆), ∼452 nm (¹D₂ → ³F₄), ∼476 nm (¹G₄ → ³H₆), ∼642 nm (¹G₄ → ³F₄), and ∼805 nm (³H₄ → ³H₆) were recorded using a fluorescence spectrophotometer. Especially, enhanced UV emissions were studied by changing Yb³⁺/Tm³⁺ doping concentrations, the annealing temperatures, and the excitation power densities. A possible mechanism, energy transfer-cross relaxation-energy transfer (ET-CR-ET), was proposed based on a simple rate-equation model to elucidate the process of the enhanced UV emissions.     

GdF3∶Eu3+/NaGdF4∶Eu3+纳米晶的水热合成及发光性质

采用水热法,以聚乙二醇(400)为分散剂,以NaOH和HNO3溶液调节初始溶液pH值,合成GdF3∶Eu3+和NaGdF4∶Eu3+纳米晶。XRD和SEM结果表明:在酸性溶液(pH=3,5)、中性溶液(pH=7)和碱性溶液(pH=9)中,分别获得具有正交结构的GdF3∶Eu3+纳米晶,GdF3∶Eu3+和NaGdF4∶Eu3+混合晶,六方结构NaGdF4∶Eu3+棒状微米晶。根据Scherrer公式估算pH=3和pH=5时制备纳米晶的一次性粒径分别为49和28 nm。样品的发射光谱结果表明:特征发射峰来自于5D2、5D1、5D0到7FJ跃迁。在主晶相为GdF3样品中,主发射峰来自于Eu3+的5D0→7F1的磁偶极跃迁;晶相为NaGdF4样品的主发射峰来自于Eu3+的5D0→7F2电偶极跃迁。5D0→7F1和5D0→7F2跃迁发射相对强度比值显示:Eu3+在NaGdF4晶体中的格位对称性下降。激发光谱显示出Gd3+和Eu3+具有较好的能量传递。     

Li+掺杂对TeO2:Tm3+/Er3+/Yb3+纳米材料上转换发光的增强作用

采用水热法制备了发白光的Li+掺杂α-TeO2∶Tm3+/Er3+/Yb3+和β-TeO2∶Tm3+/Er3+/Yb3+纳米上转换发光材料。采用X射线衍射、透射电镜和上转换发光光谱对制备的TeO2∶Tm3+/Er3+/Yb3+/Li+纳米材料进行表征,结果显示:Li+的掺入基本不改变纳米材料的晶型和结构;在980 nm近红外光的激发下,纳米材料发射出中心波长476 nm的蓝光,525 nm及545 nm的绿光和659 nm及675nm的红光,分别对应于Tm3+的1G4→3H6能级跃迁,Er3+的2H11/2→4I15/2和4S3/2→4I15/2能级跃迁,Er3+的4F9/2→4I15/2能级跃迁和Tm3+的3F2→3H6能级跃迁;Li+的掺入能够增大白光体系的发光强度,基本不改变纳米材料的白光颜色。此外,探讨了纳米材料的上转换发光机理。     

MgAl2O4∶Er^3+,Yb^3+荧光粉的制备及其上转换发光性能

以尿素为沉淀剂,采用低温水热法结合煅烧过程制备出MgAl2O4∶Er^3+,Yb^3+上转换荧光粉,并对样品的结构、微观形貌及上转换发光性能予以表征。结果表明,随尿素加入量的增大,产物主形貌由六角片状结构向纳米棒状转变,经1100℃煅烧可得纯相镁铝尖晶石结构,且Er^3+和Yb^3+能有效进入MgAl2O4晶格并占据Mg^2+位置形成均匀固溶体。在980 nm光激发下,MgAl2O4∶1.0%(n/n)Er^3+,x%(n/n)Yb^3+(x=0~8.0)荧光粉表现出在524、545 nm处绿光以及658 nm处的强红光发射,红绿光强度均在5.0%(n/n)Yb^3+掺杂时达到最大,但红绿光强度比却在7.0%(n/n)Yb^3+掺杂时达到最大值5.2,这归因于Er^3+-Er^3+之间交叉弛豫(CR)在红光发射过程中所起的重要作用。通过控制荧光粉中Yb^3+的掺杂量,能初步实现对于黄绿光色度的有效调控。     

Eu3+掺杂的LaBO3荧光粉制备及发光性能

采用水热法合成前驱体,后经热处理方式制备不同晶相的LaBO3∶Eu^3+荧光粉。通过X射线衍射(XRD)、电子扫描电镜(SEM)、红外光谱和荧光光谱对样品的结构、形貌和发光性能进行了研究。并研究了硼酸用量、热处理温度及初始溶液pH等对晶相结构和发光性能的影响。XRD研究结果表明:合成样品具有单斜结构、正交结构及单斜和正交两相混合结构。适当的硼酸用量、较高的热处理温度及较高的初始溶液pH值易于获得正交结构的荧光粉。红外光谱显示:pH值和硼酸用量影响前驱体成分,热处理温度影响晶相的转变。SEM结果显示:LaBO3∶Eu^3+荧光粉的晶粒尺寸随着pH值的增加逐渐减小,与XRD计算结果相一致。荧光光谱结果表明:正交结构的LaBO3∶Eu^3+发光粉具有较高的紫外吸收和较为纯正的红色发射强度。     

Yb3+/Tm3+掺杂的NaY(WO4)2纳米晶的制备及发光特性

以聚乙二醇为配位剂,用水热法制备出纳米级上转换发光粉Yb3+和Tm3+共掺杂的NaY(WO4)2。研究了不同cYb/cTm对上转换发光强度的影响,实验表明当cYb/cTm=5∶1时,上转换发光强度最强。用XRD,SEM确定了Yb3+和Tm3+共掺杂的NaY(WO4)2是四方晶系,其粒径在25~35 nm范围,且分散均匀。用980 nm半导体激光器(LD)对其进行激发,在室温下观察到了365 nm附近紫外发射峰、456 nm,476 nm附近的蓝光发射峰和648 nm附近的红光发射峰,分别对应于Tm3+离子的1D2→3H6,1D2→3F4,1G4→3H6和1G4→3F4的跃迁。根据泵浦功率与发光强度的关系得出紫外发射峰、蓝光和红光发射均为双光子过程。