Li^+/Er^3+:Y2O3上转换发光增强机制研究

采用溶胶凝胶法合成了Li^+/Er^3+∶Y2O3粉体.随着Li+掺杂浓度的增加,Li^+/Er^3+∶Y2O3粉体的上转换发光明显增强.实验结果表明:小半径、低价态的Li+掺杂可以降低Er3+周围局部晶体场对称性,提高Er^3+的辐射跃迁几率、影响Er^3+的能级寿命.同时,Li^+掺杂能够增大晶粒尺寸,减少表面高能悬键,降低无辐射跃几率.因此,掺杂Li^+后Er^3+发光强度明显提高.

低温凝胶燃烧法合成Y_2O_3:Er^(3+),Yb^(3+)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4S3/2/2H11/2→4I15/2和4F9/2→4I15/2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。

Y_2O_3:Er^(3+):Yb^(3+)纳米材料的制备及其上转换发光特性

以水热法合成了Yb3+,Er3+共掺杂的Y2O3纳米材料,并通过X射线粉末衍射、扫描电子显微镜及荧光分光光度计对样品的物相结构、微观形貌及粒度、光谱性质等进行分析表征.结果表明,样品结构属于纯立方晶系,样品形貌为棒状,其直径约100 nm,长度达到微米级,并且无明显团聚,分散性较好.样品在980 nm LD激发下,发蓝(408 nm)、绿(520~570 nm)和红色光(650~670 nm),与之对应的辐射跃迁分别属于2H9/2→4I15/22、H11/2,4S3/2→4I15/2和4F9/2→4I15/2.

Yb^(3+),Er^(3+)和Tm^(3+)三掺YF_3/Y_2O_3纳米粉未的白色上转换发光研究

采用溶胶凝胶法,合成YF_3/Y_2O_3:Yb^(3+),Er^(3+),Tm^(3+)样品.通过TEM,XRD,Raman及荧光分光光度计对样品的形貌、物相及上转换发光进行表征.结果表明,在980nm激光激发下,Y_2O_3:Yb^(3+),Er^(3+),Tm^(3+)样品在Tm^(3+)掺杂浓度较低时,因Y_2O_3基质具有较大的声子能量,能够实现白色上转换发光.Y_2O_3:Yb^(3+),Er^(3+),Tm^(3+)纳米粒子有望在白色激光器、白色荧光粉及生物医学荧光标记等方面发挥更大的作用.

Y_2O_3:Yb^(3+)/Er^(3+)纳米片的制备及其上转发光性能研究

采用共沉淀法制备了Yb^(3+)/Er^(3+)共掺的Y_2O_3上转换荧光材料,利用X-射线衍射仪(XRD)、扫描电镜(SEM)、荧光光谱仪(以980 nm激光器作为光源)对合成样品的结构、形貌、发光性能进行了表征。分析结果表明:所制备的样品物相与Y_2O_3基质的物相基本一致;在扫描电子显微镜观察下,Y_2O_3:Yb^(3+)/Er^(3+)呈片状;当用980 nm激光激发样品时,可以观测到波长位于525 nm、550 nm处的绿色发射和波长位于660 nm处的红色发射光谱,分别对应于Er^(3+)的2H11/2,4S3/2→4I15/2和4F9/2→4I15/2特征跃迁。

Upconversion Luminescence Dynamics in Er^3＋/Yb^3＋ Codoped Nanocrystalline Yttria

The upconversion luminescence and dynamics in Er^3＋ /Yb^3＋ codoped nanocrystalline yttria （7-65 nm） are studied under 980-nm pulsed laser excitation, It is found that the red emission of ^4F9/2-^4I15/2 and the green emission of ^2H11/2/^4S3/2 in nanoparticles with lower concentration of Yb^3＋ result from a two-photon excitation, In nanocrystals with higher Yb^3＋ concentration, the red emissions from a two-photon excitation, while the green emissions from a three-photon excitation, The luminescence dynamics indicates that as the particle size decreases, both the rise and the decay time constants become shorter, As the size decreases to several nanometres, the rise process nearly disappears, suggesting that the upconversion luminescence originates mainly from self-excitation of Er^3＋, instead of the energy transfer of Yb^3＋→ Er^3＋.

Er^(3+)/Yb^(3+)共掺Y_2O_3纳米薄膜的制备及上转换光谱的研究

利用电沉积方法制备了Er^(3+)/Yb^(3+)共掺杂的Y_2O_3上转换荧光薄膜,采用X-射线衍射,扫描电子显微镜等技术对纳米颗粒进行表征.结果显示,Y_2O_3∶Er^(3+)/Yb^(3+)薄膜由均匀纳米薄片组成,纳米片厚度为30 nm左右.在980 nm激光激发Y_2O_3∶Er^(3+)/Yb^(3+)共掺纳米体系时,观测到了因此而产生的上转换荧光辐射.应用激光光谱学的方法,分析了Er^(3+)/Yb^(3+)共掺杂Y_2O_3荧光光谱的性质,研究了离子浓度对上转换辐射荧光的跃迁强度和弛豫速率的影响,通过对相关能级的分析阐明了上转换辐射荧光产生的机理.

高比表面积Y_2O_3:Er^(3+)+TiO_2的制备及上转换发光特性研究

采用共沉淀法和sol-gel法制备了Y2O3:Er3+,Y2O3:Er3+/Yb3+和Y2O3:Er3++TiO2三种样品.通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、比表面积仪、紫外可见分光光度计及荧光光谱仪分析和测试了样品的表面形貌、比表面积、孔隙度、紫外可见吸收光谱和室温下的荧光光谱.SEM和TEM测试表明共沉淀法制备的样品发光离子分散性很好;sol-gel法制备的Y2O3:Er3++TiO2表面分布着许多的介孔,颗粒直径在10nm左右.对3种样品的孔径分布和表面积测试表明,Y2O3:Er3+和TiO2复合后的性质不是两种物质性质的简单叠加,其比表面积高达135.991m2/g,是纯Y2O3:Er3+的4.8倍,是纯Degussa P25 TiO2的2.5倍,如此高的比表面积有利于提高TiO2的光催化性能.样品的荧光光谱显示其在388,500和570nm的可见光激发下分别对应在237,395和467nm处各有一个上转换发光峰.

Combustion synthesis and enhanced 1.5 μm emission in Y_2O_3:Er^(3+) powders codoped with La^(3+) ions

Er3+ and La3+ codoped Y2O3 nanocrystalline powders were synthesized by gel combustion method and characterized with thermal analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) techniques and fluorescence spectroscopy. After being calcined at 1200 oC, the (Y1–xLax)2O3:Er3+ powders were confirmed to be cubic Y2O3 phase with the crystalline grain size in the range of 20–40 nm. The Er3+ emission at 1.53μm from the4I13/2→4I15/2 transition was observed, which was found to be enhanced by introducing La3+ ions. Such enhancement could be attributed to the adjustment of Er3+ ions’ local environment by the codoping of La3+ ions, leading to the increased ground state absorption cross section of Er3+ ions.