铒镱共掺磷酸镧纳晶的合成和近红外荧光性质

以磷酸三丁酯作为配体,使用高温溶液法合成了掺铒磷酸镧纳米晶体,高分辨电镜和XRD结果表明产物尺寸均一,直径4nm左右,具有高度的结晶性,在甲苯等有机溶剂中分散性良好.近红外发光光谱表明,产物在1535 nm处有发光峰,半高全宽为50 nm,高于目前掺铒光纤放大器(EDFA)的增益带宽.通过IR、元素分析研究发现,使用真空干燥等方法不能有效去除纳晶表面的羟基.为了进一步消除表面缺陷和猝灭基团对纳晶发光性质的影响,我们尝试在其外围生长一层LaPO₄壳做成核壳粒子以消除表面缺陷和隔离猝灭基团,结果表明,新的纳晶的发光强度得到了显著提高.

Synthesis and Characterization of Er-Yb Codoped LaPO_4 Nanocrystals Possessing Near-IR Fluorescence

Rare earth ions (Er~(3+), Eu~(3+) and Yb~(3+)) doped LaPO_4 and YbPO_4 nanocrystals were synthesized by a coordinate precipitation method. In a high temperature organic solution the LaCl_3 and tributyl phosphate form a complex and react with H_3PO_4 to yield LaPO_4 nanocrystals. The structural properties of LaPO_4 nanocrystals were studied by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM),Fourier transform infrared spectrometer (FT-IR). HRTEM measured the size about 4 nm and showed the clear lattice fringe image of the nanocrystals which validated the high crystallinity. XRD patterns show that the samples crystallized in monazite structure. The emission of the nanocrystals under 975 nm excited was measured and the peak was at 1535 nm. Elemental analysis result revealed that the common desiccation in vacuum was failed to remove the residual quenching group such as O-H and C-H. When coated by a LaPO_4 shell the fluorescence intensity was obviously enhanced. It validated the conclusion that the core/shell structure could enhance the emission of nanocrystals.