Up-conversion photoluminescence emissions of CaMoO4：Pr3＋/Yb3＋ powder

CaMoO_4：Pr^（3＋）/Yb^（3＋） powder was successfully synthesized by a facile hydrothermal method. X-ray diffraction（XRD） patterns of samples confirmed tetragonal structure and morphology and sizes were confirmed by scanning electron microscopy（SEM） analyses. Particles consisted of regular micro-spheres with uniform sizes, the diameter of each sphere lay in the range of 3 to 4 μm. The up-conversion photoluminescence emission and its concentration dependence were investigated under infrared excitation at 980 nm. All the UC micro-particles exhibited the typical blue, green and red emissions. Dominant blue emissions originated from ~3P_0→~3H_4 and intense red emissions originated from ~3P0→~3F_2 transitions, and they both belonged to two-photon excitation processes in CaMoO_4： Yb^（3＋）/Pr^（3＋） powder. The optimum doping concentrations of Pr^（3＋） and Yb^（3＋） for the highest UC luminescence were 0.1 mol.% and 16 mol.%, respectively. The possible up-conversion mechanisms were discussed in detail. It was found that the UC emission could be well controlled from blue to green to white color by adjusting the concentration of Pr^（3＋） ions in CaMoO_4：Pr^（3＋）/Yb^（3＋） microcrystal. So it is a candidate material for solid-state lasers, biological imaging, solar cells, and optical communications.

Effects of different ligands on luminescence properties of LaF_3:Nd nanoparticles

A series of neodymium-doped lanthanum fluoride nanoparticles （NPs） were synthesized with hydrothermal method, and the effects of several ligands on the luminescence properties of the NPs were investigated. The X-ray diffraction （XRD） results indicated that the crystal phases of the modified NPs coincided with the standard spectrum. The transmission electron microscopy （TEM） showed that the samples were of similar size, shape and dispersibility. The infi＇ared spectra suggested that the content of-OH groups as quenchers on the NPs surfaces decreased after modification. Compared with NPs modified by branched paraffin ligands, NPs conjugating ring-contained modifiers had less quenching effect and possessed stronger fluorescence intensity and longer fluorescence lifetime.

Sm^(3+)掺杂LaOF荧光粉的制备及光学性能

以LaOF晶体为基质,利用水热辅助固相法制备出一系列Sm^(3+)掺杂LaOF荧光粉。采用XRD、TEM、荧光光谱仪等测试手段对所制得的样品的相结构、微观形貌及光学性能进行表征。结果表明,LaOF在不同煅烧温度下会产生四方相和斜方六面体两种不同晶相。此外,由于受跃迁概率和局域对称性的影响,Sm^(3+)掺杂四方相LaOF发光强度更大,其各浓度样品在405 nm光激发下,于567 nm、605 nm、651 nm和710 nm等处均出现了Sm^(3+)的特征发射峰,并且随着Sm^(3+)掺杂量的增加,其发光强度呈现先增大后减小的趋势,且当Sm^(3+)掺杂量为3.0%(摩尔分数,下同)时,La_(1-x)Sm_(x)OF样品发光强度达最大值。此外,所得样品的色纯度极高,其多个激发峰均位于商用近紫外和蓝光LED芯片的发射波长附近,可实现多种波长激发下的可见橙光发射。

稀土Eu掺杂的NaYF_4发光材料的制备及性能研究

稀土离子因其独特的电子结构,使稀土掺杂发光材料具有光化学稳定、荧光寿命长、发射光谱窄等优点。本文采用水热合成法制得六方相Na YF4:Eu3+发光材料;采用XRD、SEM、荧光光谱仪等测试技术手段对物相组成、颗粒尺寸、形貌、荧光强度进行了分析。

Ca_3(PO_4)_2:Dy^(3+)纳米荧光粉的制备及发光性能研究

采用水热法制备出Ca_3(PO_4)_2:Dy^(3+)纳米荧光粉,通过XRD、SEM和荧光光谱对样品进行了分析,主要研究了制备工艺以及Dy^(3+)离子掺杂浓度对材料发光性能的影响规律。研究结果表明:初始溶液pH值为7,反应釜填充度为80%,在180℃条件下反应24 h所得的Ca_3(PO_4)_2:0.02 Dy^(3+)纳米荧光粉发光性能最佳。SEM分析表明荧光粉颗粒的平均粒径为100 nm,分散性好。

稀土掺杂Ba_(2)GdF_(7)纳米材料的合成和温度传感性能

PEG-Ba_(2)GdF_(7):Yb^(3+),Er^(3+)已成为一种重要的稀土掺杂上转换纳米材料,不过其在温度传感领域应用的可能性尚需进一步研究。采用水解法制备PEG-Ba_(2)GdF_(7):Yb^(3+),Er^(3+)纳米材料,通过改变氟源以及PEG的修饰与否,研究了该纳米材料的光学性质,并探究了其在温度传感领域的应用潜力。结果发现:NaF作为氟源制备的PEG-Ba_(2)GdF_(7):Yb^(3+),Er^(3+)纳米材料具有最佳的发光效果,并且在303~373 K范围内,该纳米材料的相对灵敏度(S_(r))可达1.12%K^(-1),高于同领域多数研究。因此,该纳米材料有望成为一种新型的无创纳米温度计,在细胞和生物医学温度传感领域具有广泛的前景。

YVO4:Eu3+球形荧光粉的合成与发光性能优化

采用水热法合成了YVO4:Eu3+红色荧光粉。通过X射线粉末衍射(XRD)、扫描电镜(SEM)以及荧光光谱(PL)对荧光粉的晶体结构、形貌和发光性能进行表征。结果表明,在水热条件下合成了一系列四方锆石结构的Y1-xEuxVO4纳米晶,一次性粒径约为7nm,组装成球形形貌、分散性好、尺寸均一的颗粒,其平均粒径约为80nm。在316nm波长激发下,YVO4:Eu3+荧光粉最强发光峰位于619nm处,对应于Eu3+的5 D0→7F2电偶极跃迁,且Eu3+最佳摩尔分数为11%。

CeO_2:Eu^(3+)纳米晶的水热合成和光学性能

以硝酸铈(Ce(NO3)3·6H2O)、硝酸铕(Eu(NO3)3·6H2O)、氨水(NH3·H2O)为原料和十六烷基三甲基溴化铵(CTAB)为分散剂,采用水热法制备了CeO2:Eu3+纳米晶,用X射线衍射(XRD)、X射线光电子能谱分析(XPS)、透射电镜(TEM)、傅立叶红外(FT-IR)、拉曼光谱和荧光(FL)等手段对产品的结构和光学性能进行分析和表征。测试结果表明:CeO2:Eu3+是立方萤石结构的纳米晶体,铕以Eu3+形式进入CeO2晶格中致使其晶胞参数略增,晶粒尺寸减小。相比纯CeO2,CeO2:Eu3+的紫外-可见光吸收边发生些许红移,其中CeO2:Eu3+(9.0%)纳米晶的能带隙为2.84 e V。CeO2:Eu3+纳米晶在593,612和632 nm处发橙红光,其中非直接激发(356 nm)的CeO2:Eu3+(1.0%)的磁偶极跃迁(5D0→7F1)占主导,而直接激发(468 nm)的CeO2:Eu3+(5.0%)的电偶极跃迁(5D0→7F2)强度更大,两者均随焙烧温度升高而增强。