Ho^(3+)-Yb^(3+)掺杂β-NaYF_(4)纳米晶的近红外荧光与能量传递

Energy Transfer Analysis and Near-infrared Luminescence of Ho^(3+)-Yb^(3+) Doped β-NaYF_(4) Nanocrystals

用共沉淀法制备了Ho^(3+),Yb^(3+)掺杂的β-NaYF_(4)纳米晶,测量并分析了不同Yb^(3+)掺杂浓度下NaYF_(4)∶Ho^(3+),Yb^(3+)的荧光光谱与荧光衰减曲线。结果表明,在447 nm泵浦光激发下,较强的近红外光发射主要来源于Ho^(3+)-Yb^(3+)之间高效的能量传递过程。被泵浦光激发的Ho^(3+)通过^(5)F_(4),^(5)S_(2)能级与5F5能级将能量传递给Yb^(3+),使Yb^(3+)从基态2F7/2能级跃迁到^(2)F_(5/2)能级。同时,处于^(2)F_(5/2)能级的Yb^(3+)可以将能量再传递给Ho^(3+)的^(5)I_(6)能级从而增强Ho^(3+)离子^(5)I_(6)→^(5)I_(8)的跃迁发光。在所研究的样品中,NaYF_(4)∶3%Ho^(3+),3%Yb^(3+)表现出最强的近红外荧光发射,其980 nm附近的荧光强度是NaYF_(4)∶3%Ho^(3+)样品的18倍。较强的近红外光发射使得NaYF_(4)∶Ho^(3+),Yb^(3+)材料在提高太阳能电池的光电转换效率以及进行荧光标记等方面有潜在的应用价值。

Ho^(3+)-Yb^(3+) co-doped β-NaYF_(4) nanocrystals were prepared by co-precipitation method. The fluorescence spectra and decay curves of NaYF_(4)∶Ho^(3+),Yb^(3+) were measured and analyzed at different Yb^(3+) doping concentrations. The results confirm that, under the excitation of 447 nm pump light, the strong near-infrared light emission mainly came from the efficient energy transfer process between Ho^(3+)-Yb^(3+). The Ho^(3+) ions excited by the pump light could transfer energy to the Yb^(3+) ions through the ^(5)F_(4), ^(5)S_(2) and 5F5 levels, so that the Yb^(3+) ions would jump from the ground state 2F7/2 to the ^(2)F_(5/2) level. Meanwhile, the Yb^(3+) ions at the ^(2)F_(5/2) level can return the energy to the ^(5)I_(6) level of Ho^(3+) to enhance the emission of Ho^(3+)∶^(5)I_(6)→^(5)I_(8) transition. NaYF_(4)∶3% Ho^(3+), 3% Yb^(3+) shows the strongest near-infrared emission, and its emission intensity around 980 nm was 18 times than that of NaYF_(4)∶3% Ho^(3+) samples. The strong near-infrared emission capability makes NaYF_(4)∶Ho^(3+),Yb^(3+) materials have potential application value in improving the photoelectric conversion efficiency of solar cells and conducting fluorescence labeling.