Tb3+掺杂CePO4花状团簇的控制合成及发光性能

在无模板条件下,通过调节Tb3+的浓度水热法控制合成了CePO₄∶Tb花状团簇。花状团簇由直径为80～90 nm、长度约为1 μm的纳米线组成。利用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)和荧光光谱分析了产物的相结构、晶粒尺寸、形貌及发光性能。当Ce3+/Tb3+摩尔比为0.850∶0.150时,Tb3+在过量的磷酸体系中诱导纳米线组装生长成花状团簇。发现反应物Ce3+/Tb3+摩尔比和磷酸浓度影响产物形貌的控制合成。并推测了花状团簇的生长机制。产物CePO₄∶Tb的荧光性质测试表明,当Ce3+/Tb3+摩尔比为0.850∶0.150时,所合成的花状团簇的发射强度达到最大值,Tb3+的掺入量继续增加其发光强度迅速降低。     

基于Ce4+/Ce3+转换的氧化还原荧光开关

通过简便的水热合成的方法,以稀土硝酸盐和三聚磷酸钠为原料,CePO4∶Tb3荧光纳米晶被成功制备.该纳米晶具有良好的稳定性和分散性.利用氧化还原反应诱导实现Ce4+/Ce3+之间的转换,能够有效地控制CePO4∶Tb3+荧光纳米晶的荧光“开”或“关”.在此文中,Fe3+作为氧化剂、抗坏血酸作为还原剂实现Ce4+/Ce3...     

LaF3∶Ce3+纳米晶的制备及荧光性质

采用水热法制备了掺杂Ce3+的LaF3的纳米粒子,分别用X射线粉末衍射(XRD)和荧光光谱(PL)对样品的结构和性质进行了表征.XRD的结果表明:LaF3∶Ce3+纳米晶标准卡为JCPDS 73-2192,且颗粒平均尺寸为18.7nm,掺入Ce3+杂质后晶格结构没有变化.荧光光谱结果表明:Ce3+呈现其宽带发射,激发峰在245nm处,发射峰在444nm处,随着Ce3+的摩尔浓度比的增加,样品的荧光强度先增大后减小,且Ce3+的掺杂量为4％(摩尔比)时,纳米粒子的荧光强度最强,但更高的掺杂浓度将导致荧光猝灭.     

空心半球形SrWO4和SrWO4∶Tb3+/Eu3+球形颗粒的合成及发光性能

采用水热法制备了空心半球形SrWO4及Tb3+、Eu3+掺杂的SrWO4球形颗粒,利用XRD、SEM、荧光光谱等研究其物相、形貌及发光性能。未掺杂的SrWO4具有空心半球形形貌,属四方晶系。SrWO4∶Tb3+及SrWO4∶Eu3+为球形颗粒,其相结构与未掺杂样品类似,形貌从空心半球形转变为球形颗粒。随着Tb3+掺杂浓度的增加,SrWO4∶Tb3+的形貌从球状变成由纳米棒构成的花状;随着Eu3+掺杂浓度的增加,样品中出现了单斜相的Eu2WO6,其形貌也发生了明显的变化。在紫外光激发下,SrWO4∶Tb3+及SrWO4∶Eu3+的发射光谱由钨酸根的宽带发射和掺杂离子的特征发射组成,分别表现出绿光和红光发射。Tb3+的最佳掺杂摩尔分数为3%,Eu3+的最佳掺杂摩尔分数为25%。     

六方相TbPO_4·nH_2O的控制合成及发光性能研究

通过控制PO3-4/Tb3+的量比,在低温水热条件下合成了不同形貌的TbPO4·nH2O纳米晶体。采用X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)及光致发光光谱(PL)等分析手段对所制备的样品进行了表征。研究了溶液中PO3-4/Tb3+比值变化对产物晶型结构、形貌、晶粒尺寸及发光性能的影响,给出了TbPO4·nH2O纳米粉体的生长机理。实验发现,当PO3-4/Tb3+比值达到60∶1时,产物在过量的磷酸根体系中生长成直径为100~200 nm的TbPO4·nH2O茧状微球,且产物的发光强度最大。PO3-4/Tb3+比值对TbPO4·nH2O形貌和发光性能有重要影响。     

NaZnLa(PO_4)_2中Ce~(3+)和Tb~(3+)的发光

采用高温固相反应合成了NaZnLa(PO4 ) 2 中掺杂Ce3 +、Tb3+的荧光体 ,对其晶体结构、发光行为进行了研究 ,并尝试对NaZnLa(PO4 ) 2 ∶Ce ,Tb荧光体进行调制。NaZnLa(PO4 ) 2 是LaPO4 的同构物 ,为单斜晶系独居石结构 ,从XRD谱数据得到NaZnLa(PO4 ) 2 基质的晶胞参数为a =0 6 82 3nm ,b =0 70 45nm ,c =0 6 497nm ,β =10 3 9° ,V =0 30 3nm3,其晶胞参数与单斜LaPO4 的晶胞参数相似。在NaZnLa(PO4 ) 2 ∶Ce ,Tb荧光体中 ,Ce3 +对Tb3+有良好的敏化作用 ,掺杂适量的BO3 -3 、Al3 +、Dy3 +,可以增强发光亮度     

单一基质白色荧光粉Ca_9Al(PO_4)_7:Ce~(3+),Dy~(3+)的制备与发光性能

采用高温固相法在还原气氛下合成了Ca9(1-x-y)Al(PO4)7:xCe3+,yDy3+荧光材料,并对其发光特性进行了研究。XRD测试表明所合成样品为纯相Ca9Al(PO4)7晶体。在268 nm紫外光激发下,Ca9Al(PO4)7:Ce3+呈现峰值位于363 nm的宽带发射。在350 nm近紫外光激发下,Ca9Al(PO4)7:Dy3+发射光谱为窄带谱,主峰分别位于483 nm和574 nm,对应Dy3+的4F9/2→6H15/2和4F9/2→6H13/2特征跃迁,呈黄白光发射。荧光光谱表明:Ce3+,Dy3+共掺之后,Ce3+不仅对Dy3+的特征发射有明显的敏化作用,而且通过调节Ce3+和Dy3+的掺杂比例,可实现从黄白光到白光的颜色变化。研究发现:Ca9(1-x-y)Al(PO4)7:xCe3+,yDy3+样品中,掺杂离子的最佳摩尔分数为x=0.02,y=0.02,此时色坐标为(0.306,0.313)。     

不同Te源和表面活性剂对水热法合成Bi_2Te_3纳米粉体形貌的影响（英文）

采用水热法合成了具有不同形貌的热电合金材料Bi_2Te_3纳米粉体.讨论了不同Te源和表面活性剂对Bi_2Te_3纳米粉体形貌的影响.纳米粉体通过XRD衍射仪分析物相,扫描电镜分析其表面形貌.通过改变Te源和表面活性剂得到了了纳米颗粒、纳米线、纳米片和花状团簇等不同的形貌.讨论了不同Te源和表面活性剂下Bi_2Te_3纳米结构可能的成核和生长机理.     

水溶性β-NaY(Gd)F4:Yb3+/Er3+纳米棒的水热合成及生物偶联

以聚乙烯亚胺(PEI)为表面活性剂,采用水热合成法,制得了表面氨基修饰的水溶性β-NaY(Gd)F₄:Yb³⁺/Er³⁺纳米棒,并对β-NaY(Gd)F₄:Yb³⁺/Er³⁺上转换纳米棒的制备方法、条件等进行了考察.结果表明,当Gd³⁺的引入摩尔分数为40%时,200 ℃下反应8 h即可获得纯β-NaY(Gd)F₄:Yb³⁺/Er³⁺纳米棒.利用X射线粉末衍射仪(XRD)、扫描电子显微镜 (SEM)、透射电子显微镜(TEM)、荧光光谱(PL)对样品的结构、形貌及光谱特性进行了表征.结构和形貌分析结果表明,制得的样品为单相β-NaY(Gd)F₄:Yb³⁺/Er³⁺纳米棒,纳米棒的截面粒径约为40 nm,平均长度约为210 nm.在980 nm波长激发下,样品的上转换发光光谱中出现了4个发射中心位于407,529,546,660 nm的发射带,分别对应于Er³⁺离子的²H_9/2→⁴I_15/2、²H_11/2→⁴I_15/2、⁴S_3/2→⁴I_15/2和⁴F_9/2→⁴I_15/2跃迁.采用戊二醛法,使β-NaY(Gd)F₄:Yb³⁺/Er³⁺上转换纳米棒表面的氨基与牛血清蛋白(BSA)分子中的氨基成功偶连在一起.利用紫外光谱分析(UV)和考马斯亮蓝法,对二者的偶联进行了证明.     

水热法制备LaF3:Ce,Tb纳米荧光粉及发光性质研究

利用水热法制备了LaF3∶Ce,Tb纳米荧光粉,分别用XRD,TEM和发光光谱等测试手段对粉末的物相、形貌、发光性质进行了研究.XRD和TEM结果表明:所得的纳米荧光粉粒度均匀、结晶完好,呈规则的六边形形状,颗粒平均尺寸为30 nm,掺人Ce3 和Tb3 ,杂质后晶格结构没有变化.发光光谱的测试表明:Ce3 呈现其宽带发射;Tb3 呈现其特征绿色发射,最强峰位于544 nm处.Ce3 的掺入有效敏化了Tb3 的发光,通过进一步光谱分析证实了在LaF3∶Ce,Tb体系中存在Ce3 →Tb3 的能量传递过程.当Ce3 和Tb3 掺杂摩尔浓度分别为35 mol%和5 mol%时具有最强荧光发射.制备的样品无需煅烧即可获得比体相材料高2倍的荧光,也高于优化条件下煅烧样品的荧光.     

Synthesis and optical properties of flower-like ZnO nanorods by thermal evaporation method

Flower-like ZnO nanorods have been synthesized by heating a mixture of ZnO/graphite powders using the thermal evaporation and vapor transport on Si (1 0 0) substrates without any catalyst. The structures, morphologies and optical properties of the products were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The synthesized products consisted of large quantities of flower-like ZnO nanostructures in the form of uniform nanorods. The flower-like ZnO nanorods had high purity and well crystallized wurtzite structure, whose high crystalline quality was proved by Raman spectroscopy. The as-synthesized flower-like ZnO nanorods showed a strong ultraviolet emission at 386 nm and a weak and broad yellow-green emission in visible spectrum in its room temperature photoluminescence (PL) spectrum. In addition, the growth mechanism of the flower-like ZnO nanorods was discussed based on the reaction conditions.     

Interconfigurational 5d?→?4f luminescence of Ce(3+) and Pr(3+) in Ca(9)Lu(PO(4))(7)

Ca(9)Lu(PO(4))(7):Ce (3+) and Ca (9)Lu (PO (4))(7):Pr (3+) polycrystalline materials were synthesized by solid state reaction at high temperature. The materials were characterized by powder x-ray diffraction (XRPD). The luminescence spectroscopy and the excited state dynamics of these compounds were investigated upon excitation with UV/VUV synchrotron radiation. Both materials showed efficient and fast 5d-4f emission upon direct VUV excitation into the 5d levels but only Ca(9)Lu(PO(4))(7):Ce (3+) revealed luminescence upon excitation across the bandgap. The decay kinetics of the 5d-4f emission upon VUV intra-center excitation is characterized by a decay time of 29?ns for Ce (3+) and 17 ns for Pr (3+) with no significant build-up after the excitation pulse. For the both compounds, no significant temperature dependence of the 5d-4f emission lifetime was observed within the range 8-300?K.     

Controlled synthesis and luminescence properties of LaPO4:Eu phosphors

Uniform single crystal LaPO₄ phosphors were selectively synthesized using a facile hydrothermal method without the aid of templates or catalysts. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra were used to characterize the nanocrystal materials. The morphological evolution from nanorods to nanoparticles was brought about by altering the pH. In addition, the crystal structure was changed from hexagonal phase to monoclinic one by increasing the hydrothermal temperature. We propose a possible growth mechanism for LaPO₄ nanorods based on the results of our analyses. Furthermore, we compared the photoluminescence properties of LaPO₄:Eu with different morphologies. The results showed that the fluorescence intensity of monoclinic LaPO₄:Eu nanorods is stronger than that of nanoparticles.     

A novel strong green phosphor： K3Gd（PO4）2：Ce^3＋, Tb^3＋ for a UV-excited white light-emitting-diode

A series of K3Gd1-x-y（PO4）2：xCe^3＋, yTb^3＋ phosphors are synthesized by the solid-sate reaction method. X-ray diffraction and photoluminescence spectra are utilized to characterize the structures and luminescence properties of the as-synthesized phosphors. Co-doping of Ce^3＋ enhances the emission intensity of Tb^3＋ greatly through an efficient energy transfer process from Ce^3＋ to Tb^3＋. The energy transfer is confirmed by photoluminescence spectra and decay time curves analysis. The efficiency and mechanism of energy transfer are investigated carefully. Moreover, due to the non- concentration quenching property of K3Tb（PO4）2, the photoluminescence spectra of K3Tb1-x（PO4）2：xCe^3＋ are studied and the results show that when x = 0.11 the strongest Tb^3＋ green emission can be realized.     

Tb~(3+)和Ce~(3+)在Sr_7Zr(PO_4)_6基质中能量传递及发光特性研究

用高温固相法制备了Sr_7Zr(PO_4)_6∶Tb~(3+)、Sr_7Zr(PO_4)_6∶Ce~(3+)及Sr_7Zr(PO_4)_6∶Tb~(3+),Ce~(3+)一系列荧光粉,并通过X射线衍射仪及荧光光谱仪分析了其结构和发光性质。结果表明,Sr_7Zr(PO_4)_6∶Tb~(3+)呈现特征绿色发射,最强发射峰位于543 nm,属于Tb~(3+)的5D4→7F5跃迁,激发峰位于226 nm处,但激发带较窄。为拓宽其激发带的宽度,在Sr_7Zr(PO_4)_6∶Tb~(3+)中掺入了Ce~(3+),观察到掺入Ce~(3+)后激发带变宽,且在Ce~(3+)的激发波长处激发得到了Tb~(3+)的发射,表明存在Ce~(3+)到Tb~(3+)的能量传递。     

Electrochemical performances of nano-Co3O4 with different morphologies as anode materials for Li-ion batteries

Three kinds of Co₃O₄ nanomaterials with different morphologies were synthesized controllably by a post-anneal-assisted hydrothermal method in this study. X-ray diffraction and scanning electron microscopy indicated that all three kinds of samples were pure cubic phase of Co₃O₄ with morphologies of nanorods, nanoclusters, and nanoplates. Moreover, the transmission electron microscopy (TEM) and high-resolution TEM showed that the Co₃O₄ nanorods were bamboo-like and highly crystalline structures. When these materials were applied to the lithium-ion batteries (LIBs) as anode materials, the Co₃O₄ of nanorods demonstrated the best performance. It has a stable reversible capacity of 954 mAh g^?1 as the anode of a LIB, much higher than the other two kinds of Co₃O₄ of rod-like nanoclusters and nanoplates, even after 35 cycles. All results showed that the morphology and microstructure take very important roles in the performance of Co₃O₄ as the anode materials in LIBs.     

Additive-free controllable fabrication of bismuth vanadates and their photocatalytic activity toward dye degradation

Bismuth vanadates (BiVO₄) with various crystal structures (tetragonal scheelite, monoclinic scheelite, and tetragonal zircon) and morphologies (sphere-, nanosheet-, dendrite-, and flower-like) were controllably fabricated by using a mild additive-free hydrothermal treatment process under the different preparation conditions. The crystal structures, morphologies, and photophysical properties of the products were well-characterized. Subsequently, their UV- as well as visible-light photocatalytic performance was evaluated via dyes rhodamine B (RB) and methylene blue (MB) degradation. Special attention was paid to evaluate the correlation of the reactivity with crystal structure, morphology, and electronic structure of as-prepared BiVO₄ samples.     

Temperature-dependent structures of proton-conducting Ba(Zr(0.8-x)Ce(x)Y(0.2))O(2.9) ceramics by Raman scattering and x-ray diffraction

In situ temperature-dependent micro-Raman scattering and x-ray diffraction have been performed to study atomic vibration, lattice parameter and structural transition of proton-conducting Ba(Zr(0.8-x)Ce(x)Y(0.2))O(2.9) (BZCY) ceramics (x = 0.0-0.8) synthesized by the glycine-nitrate combustion process. The Raman vibrations have been identified and their frequencies increase with decreasing x as the heavier Ce(4+) ions are replaced by Zr(4+) ions. The main Raman vibrations of Ba(Ce(0.8)Y (0.2))O(2.9) appear near 305, 332, 352, 440 and 635 cm(-1). The X-O ( X=Ce, Zr, Y) stretching modes are sensitive to the variation of Ce/Zr ratio. A rhombohedral-cubic structural transition was observed for x = 0.5-0.8, in which the transition shifts toward higher temperature as cerium increases, except for Ba(Ce(0.8)Y(0.2))O(2.9). A minor monoclinic phase possibly coexists in the rhombohedral matrix for x = 0.5-0.8. The lower-cerium BZCYs (x = 0.0-0.4) ceramics do not exhibit any transition in the region of 20-900?°C, indicating a cubic phase at and above room temperature.