Cr^(3+)掺杂F^(-)修饰BaScO_(2)F钙钛矿结构宽带近红外荧光粉

Cr^(3+)掺杂的近红外荧光材料,因具有高量子效率、可调的宽带发射及在蓝色光谱范围内的强吸收特性而备受关注。通过晶体场工程,可以调节Cr^(3+)掺杂的近红外荧光材料的发射范围,但常规的阳离子取代对发射范围的调节通常限制在近红外Ⅰ区(波长<1000 nm)。在生物医学成像领域,由于生物组织的吸收、散射和自发荧光较低,在近红外Ⅱ区,能够实现更高的穿透深度及无创或微创的深部组织成像。采用高温固相法,以Ba_(2)Sc_(2)O_(5)类钙钛矿型氧化物为基体,合成了一系列基于F^(-)修饰的近红外荧光粉BaSc_(1-x)O_(2)F:xCr^(3+)(x=0.001—0.01)。通过XRD图谱和容差因子计算,证明了合成的样品具有立方钙钛矿结构。另外,通过漫反射光谱(DRS)和X射线光电子能谱(XPS)等表征手段,确认了Cr离子的价态为Cr^(3+)。利用电子顺磁共振(EPR)对Cr^(3+)周围的晶体环境进行检测分析发现,样品在波长700—1400 nm范围内表现出近红外宽带发射,发射中心约在1040 nm处,半峰宽(FWHM)高达250 nm。表明,Cr^(3+)的发射有效覆盖了近红外Ⅱ区。同时,也证明了通过阴离子掺杂调节晶体场强度是可行的。由于PLE光谱和PL光谱在波长700—850 nm范围内存在重叠,随着Cr^(3+)掺杂浓度的增加,发射部分被重吸收,导致发射中心出现明显的红移现象。由于BaSc_(1-x)O_(2)F:xCr^(3+)近红外荧光粉的吸收峰与蓝光LED芯片能够匹配,表明其具有商业化潜力。本研究为生物医学成像领域的近红外Ⅱ区荧光粉转换LED器件提供了优异的宽带近红外光源材料。

Broadband near-infrared luminescence and energy trans-fer in Bi singly-doped and Bi/Yb co-doped titanate glasses

Super-broadband near-infrared(NIR)emission from 1100 nm to 1600 nm is observed in Bi-doped titanate glasses at the excitation of 808 nm laser diode(LD).The effects of Bi content on the optical spectra are investigated.It is also found that the Bi-related emission intensity can be enhanced by Yb3+co-doping at the excitation of 980 nm LD.It should be ascribed to the energy transfer from Yb3+to active Bi ions.The energy transfer processes are studied based on the Inokuti-Hirayama(I-H)model,and the energy transfer of electric dipole-dipole interaction is confirmed to be dominant in Bi/Yb co-doped glasses.