Effect of alkali and alkaline earth fluoride introduction on thermal stability and structure of fluorophosphate glasses

The thermal stability and structure of RF-RF2-AIF(3)-Al(PO3)(3) fluorophosphate glasses were investigated. Analyses of infrared absorbance spectra and Raman spectra reveal that with increasing number of alkali and alkaline earth fluoride components, the sum of P-O-P bond and O-P-O bond increases and glass network is strengthened. Consequently, the inhibition to nucleation and crystallization processes is improved, which is proved by the increment of thermal stability factors AT and S determined by differential scanning calorimetry. In addition, it was found that LiF has poor ability to form glass in univalent alkali fluorides and MgF2 has comparative strong ability to form glass in bivalent alkaline earth fluorides. (c) 2006 Published by Elsevier B.V.

Growth, characterization and optical quality of CaF2 single crystals grown by the temperature gradient technique

The CaF2 single crystals with diameters up to 200 mm were successfully grown by modified temperature gradient technique (TGT), which are suitable for application as optical elements in the ultraviolet range. The optimizations of various growth parameters were systematically studied. Properties of as-grown CaF2 crystals were characterized by the nature of inclusions, dislocations, crystallinity, and impurities contents. The results showed that the dislocations and multinucleation were mostly constrained in the conical part of the crystals with the cylindrical parts having the best crystalline quality and lowest impurity contents. The high optical quality of TGT-grown CaF2 single crystals was also confirmed to have excellent optical transmission in 190-2500 nm and refractive index homogeneity. (c) 2005 Elsevier Ltd. All rights reserved.

Sites structure and spectroscopic properties of Yb-doped and Yb, Na-codoped CaF2 laser crystals

For the first time, the effect of Na+ on crystal structure, valence state of Yb ions, spectroscopic properties of YbF3-doped CaF2 system was systematically studied. Na+ can greatly suppress the deoxidization of Yb3+ to Yb2+. Absorption and emission spectra showed codoping Na+ with different Na:Yb ratios can modulate the spectroscopy and photoluminescence properties of Yb3+ ions in CaF2 lattice in a large scope. The emission lifetime and quantum efficiency of Yb3+ in CaF2 were greatly enhanced by the codopant of Na+. The potential laser performances of the new Yb, Na-codoped CaF2 crystals were predicted. (c) 2005 Elsevier B.V. All rights reserved.

稀土氟化物和钨酸盐纳米/微米材料的合成和发光性质研究

在现代化学和材料科学中，纳米/微米材料的尺寸和形貌控制引起了学术界的广泛关注，如何合理控制材料的定向生长，调节其组成、形貌、尺寸以及维度，进而更好的理解晶体生长的复杂现象、揭示其潜在的基本理论和原理并最终实现按照人们的设计合成功能材料具有十分重要的意义。本论文在稀土氟化物和钨酸盐纳米/微米材料的设计合成、形貌控制、形成机制以及发光性质等方面进行了一些探索性的研究。 发展了一种简单、整体、没有模板、环境友好的水热方法合成系列稀土氟化物。用有机添加剂柠檬酸钠(Na3C6H5O7•2H2O)作为配位剂和形貌控制剂，通过改变氟源(NaF, NH4F或NaBF4)和最初溶液的pH值，得到了具有不同成分、晶体结构、尺寸和形貌的稀土氟化物，包括二元氟化物LnF3 (Ln = La-Lu)和三元氟化物NaREF4 (RE = Y, Yb, Lu)；首次研究了具有各种晶体结构和形貌的含镱(Yb)和镥(Lu)的二元和三元氟化物的可控合成；对各种产物可能的形成机理进行了合理、系统的讨论；并对各种基质中Eu3+, Tb3+掺杂的下转换和Yb3+/Er3+, Yb3+/Ym3+共掺杂的上转换发光性质进行了详细的研究。由于具有优良的荧光性质和可控的形貌和尺寸，这些发光材料可能在光显示、光发射二级管(LEDs)、固体激光器等领域有着潜在的应用价值。这些研究结论不仅丰富了稀土氟化物化学的内容，而且探索了纳米/微米材料的晶体生长规律和形成机理。 采用超声化学途径合成了CaWO4, CaWO4:Eu3+和CaWO4:Tb3+亚微米尺寸的球形荧光粒子，详细讨论了合成材料的结构、形成机理、光致发光、阴极射线发光性质以及能量传递现象，为其它钨酸盐的合成提供了新的思路。

微/纳米结构氟化物溶剂热合成及其光学性质研究

本文主要利用Liquid-Solid-Solution（LSS）方法合成了一系列的碱土金属氟化物纳米粒子, 具有微米结构的Ba2ClF3体系以及复合金属氟化物NaMgF3纳米晶。利用X－射线衍射（XRD）、透射电镜（TEM）、扫描电镜（FE-SEM）、红外光谱（IR）等技术对合成材料的结构、形貌、组成等进行表征，采用紫外-可见吸收光谱、荧光光谱（PL）、荧光寿命等手段评价合成材料的光致发光性能；探讨了油酸作为表面活性剂在纳米晶形成过程中的作用，并阐述了纳米晶的生长过程及可能的生长机理。对氟化物的胶体溶液的发光性质作了研究，并提出了可能的发光机理。 采用LSS方法制备的一系列碱土金属氟化物（CaF2，SrF2，BaF2）纳米晶结晶完好，具有碱土金属氟化物体材料的立方相结构。制备所得的碱土金属氟化物纳米晶分别具有被截的八面体，立方体和立方片形貌，粒子尺寸较均匀，分布范围较窄。制备的纳米晶由于表面被油酸的长烷基链所包覆，可以溶于非极性溶剂如环己烷形成稳定透明的胶体溶液。三种纳米晶的环己烷胶体溶液在光致发光光谱中在400nm左右出现了一个较强的发射峰。这可能是由在纳米晶的形成过程中产生的缺陷和电子中心所造成的。 采用LSS方法在较低的温度下（160oC）成功地制备了一维Ba2ClF3六方微米棒。制备的Ba2ClF3微米晶结晶完好，具有其相应体材料的斜方六面体结构。由于斜方六面体相晶胞表现出六方相的特性，因此具有各向异性。在包覆剂油酸的作用下，生成一维的六方微米棒。制备的六方微米棒具有较好的分散性，光滑的棒表面以及清晰的棱。同时，油酸的加入，氢氧化钠量，反应物加入量以及反应时间均对形貌和尺寸有所影响。通过调节合成参数，我们成功了具有不同尺寸和长宽比的微米棒。 采用LSS方法制备了复合氟化物NaMgF3纳米晶。制备的NaMgF3纳米晶结晶完好，具有正交晶相的结构。粒子平均尺寸约为38.6 nm。所得的纳米晶可溶于环己烷溶剂形成稳定透明的胶体溶液，其胶体溶液在400 nm左右有一个强的发射峰。

几种稀土氟化物和氧化物纳米发光材料的制备、性能及其应用探索研究

目前，纳米材料已经应用于很多医药和生物领域，诸如临床诊断、药物传送、体内体外荧光标记等。稀土离子掺杂的纳米材料因其独特的发光性质已被认为是有前景的生物荧光标记，二氧化硅作为环境友好发光材料也受到越来越多的重视。本论文合成稀土离子掺杂的下转换和上转换发光纳米材料，并进行表面功能化，使之连接生物药物小分子，以期作为荧光标记。同时采用不同方法制备不同大小的二氧化硅球，并研究其发光性质。 采用多醇法成功地制备出结晶程度高的CeF3:Tb3+纳米粒子。氧化硅和胺基硅烷包覆使纳米粒子具有胺基功能化，然后通过SOCl2成功地活化生物素使之连接到纳米粒子上并随之与亲合素键合。胺基功能化的CeF3:Tb3+ 纳米粒子发光产生严重的猝灭，而生物分子与纳米粒子结合后发光得到很大程度上的恢复。生物功能化的CeF3:Tb3+ 纳米粒子能很好地分散在水中，为这些CeF3:Tb3+ 纳米粒子作为生物荧光探针奠定了基础。同时以P123为结构导向剂，介孔氧化硅成功地包覆CeF3:Tb3+ 纳米粒子。介孔氧化硅层存在部分有序的六方介孔体系和部分微孔结构，该复合物保持绿色荧光性质并具有相当大的孔容和大的表面积。布洛芬能载入复合物的孔道中，在24 h内释放完全。因此，这类复合物可以在靶向的药物传送体系中具有潜在的应用价值。 利用多醇法制备出NaYF4:Yb3+, Er3+ 纳米粒子。NaYF4:Yb3+, Er3+ 纳米粒子进行胺基功能化，并通过氧化寡糖链成功地活化亲合素，使之连接到胺基功能化的纳米粒子上。生物功能化的 NaYF4:Yb3+, Er3+纳米粒子仍保持较好的上转换发光性质，可以作为生物体系的荧光探针。另外用 P123作为结构导向剂和助表面活性剂PVP 或 TMB 成功地使NaYF4:Yb3+, Er3+ 纳米粒子包覆介孔氧化硅。外层氧化硅层有介孔结构。该复合物保持红色荧光性质，并具有大的孔容、表面积。布洛芬能载入复合物的孔道中，在12 h内完全释放。 通过高温溶剂法合成出YVO4:Eu3+ 纳米粒子。粒子结晶程度高，为椭球形状，长轴为80 nm，短轴为43 nm。YVO4:Eu3+ 纳米粒子的荧光发射跃迁主要源于5D0能级。FT-IR 谱和 XPS 谱表明纳米粒子表面的配体为油酸和油胺分子。Eu3+ (5D0 level) 寿命因表面有机配体的存在比体材料的寿命短。 成功地制备出不同大小的纳米至亚微米尺度且具有发光性能的单分散二氧化硅球，其尺寸随胺基浓度的增加而增大。烧结后粒子仍保持单分散性，但其尺寸缩小。烧结后的二氧化硅球含有C杂质。亚微米尺度的二氧化硅球的发射带最大值随氨丙基三乙氧基硅烷（APTES）浓度的增加而红移，但是纳米尺度的二氧化硅球的发射带最大值红移更大。单分散二氧化硅球发光原因归于二氧化硅结构中存在的碳和氧缺陷。

复合氟化物的合成及掺杂稀土离子的光谱性质

本论文通过水热、溶剂热、高温固相以及单晶生长法合成了复合氟化物及部分稀土离子激活的氧化物。运用近年来兴起的温和水热和溶剂热法探索了MAIF5（M＝Ca、Sr、Ba）和LIMAIFa（M＝Ca、Sr）系列复合氟化物的合成条件。以水作为溶剂，合成了CaAIF、SrAIF、BaA作ICaAIF6和L诏rAI凡化合物，从起始反应物、反应温度、反应时间及酸度儿方面考察了几种化合物的合成条件。对于溶剂热反应，选择了五种不同的溶剂作为反应介质，分别为乙二醇、乙醇、甲苯、毗咙、四氢「臾喃。以乙二醇和甲苯为溶剂，可以合成SrAlF5和LiSrAlF6民复合氟化物，而乙醇、毗咙、四氢「归喃作为反应介质没有得到l；l标产物。在五种汽半剂中均不能合成CoAIF6、BaAlF5和LiCaAlF6复合氟化物。通过水热、高温固相以及单晶生民法介成了KMgF3:Eu体系。水热合成的产，物具有氧含员低、物相纯等优点，同时该伙合成的多移，体存在史多的色心。比较三种方法合成的KMgFa:EU的光谱，发现水热和单晶样品中除了6P7/2→8S7/2的线发则外，还明显出现址火峰位置位于420nm处的带发射。结合退火实验，相刃刁又热样品的带发射是由于色心所致，而单晶样l界，的带峰则源于晶体中存在的色心、和少量氧所致，但以色心为主。在高温样品中，只有特征的线发射，没有观察到类似的带发射。结合退火前后线带发射弧度的变化及色心激发谱和翻”．6P7/2-8S7/2发射潜的乘补程度，得出Eu3+→色心的能址传递。通过高温固相反应合成Gd，Eu单掺、双掺的KMgFa、BaLiF3、BaY2F8三种磷光体，考察了Gd2+，Eu2+的光学性质，发现了双掺体系中（Gd3+→Eu2+的能里传递以生象，分析了能墩传递方式，并计算了前两个体系中Gd3+→Eu2+能最传递儿率。考察了Pr内+ 在KMgF2、LiYF4、BaY2F8基质中的光谱情况，指认了发射峰所对应的跃迁光潜项，具体讨论了KMgFa:Pr3+激发潜中352nm处的宽带激发峰。考察了Pr3+的发射弧度在KMg1-xCaxF3体系中的咨隋况，发现随枷含嫩的增加，Pr3+的在各发射区的发射强度显著增弧，分析了可能的原因。此外本论文也通过旋转试域熔融法生长了Ca2MgSi2O2单晶，详细讨论了生长品体的彩响因索，并以该化合物为纂质，考察了Eu的掺杂行为。在空气氛围下，没有发生Eu3+→Eu2+的还原，而是形成Ca2Eu8Si6O26化合物，这借助X-ray粉末衍射、组分分析及光谱分析得到证实。

Preparation and Characterization of BaLiF3:Er3+ Nanoparticles by the Hydrothermal Microemulsion Synthesized Method

Nanoparticles of BaLiF3:Er3+ were prepared from the quaternary microemulsions of Cetyltrim-Enthyl Ammonium Bromide (CTAB), n-butanol, n-octane, and water, using the hydrothermal-microemulsion technique. The complex fluorides were characterized by means of X-ray power diffraction, Environmental Scanning Electron Microscopy (ESEM), and fluorescence spectra.

Sonochemical synthesis of monodispersed KY3F10 : Eu3+ nanospheres with bimodal size distribution

Monodispersed KY3F10:Eu3+ nanospheres with bimodal size distribution have been successfully synthesized via a facile and efficient sonochemical method in a surfactant-free system. Rare-earth nitrate (Y, Eu)(NO3)(3) and potassium fluoborate (KBF4) were used as precursors. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and photoluminescence (PL) spectra were used to characterize the samples.

Facile EG/ionic liquid interfacial synthesis of uniform RE3+ doped NaYF4 nanocubes

Uniform multicolor upconversion luminescent RE3+ doped NaYF4 nanocubes are fabricated through a facile ethylene glycol (EG)/ionic liquid interfacial synthesis route at 80 degrees C, with the ionic liquids acting as both reagents and templates.

Solvothermal synthesis of well-dispersed NaMgF3 nanocrystals and their optical properties

Complex metal fluoride NaMgF3 nanocrystals were successfully synthesized via a solvothermal method at a relatively low temperature with the presence of oleic acid, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra, photoluminescence (PL) excitation and emission spectra, respectively. fit the synthetic process, oleic acid as a Surfactant played a Crucial role in confining the growth and solubility of the NaMgF3 nanocrystals. The as-prepared NaMgF3 nanocrystals have quasi-spherical shape with a narrow distribution. A possible formation mechanism of the nanocrystals was proposed based on the effect of oleic acid. The as-prepared NaMgF3 nanocrystals are highly crystalline and well-dispersed in cyclohexane to form stable and clear colloidal Solutions, which demonstrate a strong emission band centered at 400 nm in photoluminescence (PL) spectra compared with the cyclohexane solvent.

Shape-controllable synthesis and upconversion properties of lutetium fluoride (doped with Yb3+/Er3+) microcrystals by hydrothermal process

Lutetium fluorides with different compositions, crystal phases, and morphologies, such as beta-NaLuF4 hexagonal microprisms, microdisks, mirotubes, alpha-NaLuF4 submicrospheres, LuF3 octahedra, and NH4Lu2F7 icosahedra, prolate ellipsoids and spherical particles have been successfully synthesized via a facile hydrothermal route. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, and photoluminescence spectra were used to characterize the samples. The intrinsic structural feature of lutetium fluorides, the solution pH values, F- sources, and organic additives (Cit(3-) and EDTA) account for the ultimate shape evolutions of the final products. The possible formation mechanisms for products with various architectures have been presented. Additionally, we investigated the upconversion luminescence properties of beta-NaLuF4: 20% Yb3+/2% Er3+ with different morphologies.

Electronic structures and chemical bonding in 4d transition metal monohalides

Bond distances, vibrational frequencies, dipole moments, dissociation energies, electron affinities, and ionization potentials of NIX (XM = Y-Cd, X = F, Cl, Br, I) molecules in neutral, positively, and negatively charged ions were studied by density functional method, B3LYP. The bonding patterns were analyzed and compared with both the available data and across the series. It was found that besides ionic component, covalent bonds are formed between the 4d transition metal s, d orbitals, and the p orbital of halogen. For both neutral and charged molecules, the fluorides have the shortest bond distance, iodides the longest. Although the opposite situation is observed for vibrational frequency, that is, fluorides have the largest value, iodides the smallest. For neutral and anionic species, the dissociation energy tends to decrease with the increasing atomic number from Y to Cd, suggesting the decreasing or weakening of the bond strength. For cationic species, the trend is observed from Y to Ag.

Growth and vibrational spectra of doped KMgF3 single crystal

The different ions doped KMgF3 single crystals are prepared by the vertical Bridgman method. The near-infrared absorption spectra for different parts of all as-growth crystals indicate that there is the best transparency in middle part. The correlation between the vibronic frequencies of Eu2+ and the site displacement of Cu+ co-doped ions is firstly studied, which indicates that Cu+ ions replace the site of the Mg2+ ions. The co-doped Eu2+ counteracts the charge misfit causing by the replacement of Mg2+ with Cu+. The overlapping of the emission spectra of the Eu2+ and the excitation spectra of the Cu+ results in the energy transfer from Eu2+ to Cu+.