Zhang Hongxin, Jia Tianqing, Shang Xiaoying, Zhang Shian, Sun Zhenrong, Qiu Jianrong
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China.
Phys Chem Chem Phys. 2016 Oct 7;18(37):25905-14. doi: 10.1039/c6cp04413a. Epub 2016 Sep 7.
A thorough understanding of energy transfer and upconversion (UC) processes between trivalent lanthanide (Ln(3+)) ions is essential and important for improving UC performance. However, because of the abundant energy states of Ln(3+) ions, UC mechanisms are very complicated, which makes it a challenge to exclusively verify and quantitatively evaluate the dominant process. In this study, the fundamental excitation processes of Tm(3+)-doped NaYF4 nanocrystals under 800 nm continuous wave (CW) laser excitation were experimentally investigated on the basis of the quantum transition principle. An 800 nm CW laser combined with other wavelength CW lasers, including 471 nm, 657 nm, 980 nm, and 1550 nm lasers, were designed to study in-depth the excitation processes of UC luminescence via simultaneous two-wavelength laser excitation. The results indicate that the excited state absorption of (3)H6→(3)H4∼∼(3)H5→(1)G4 is the dominant pathway of the 481 nm and 651 nm emission bands, and two kinds of energy transfer UC pathways, uniformly expressed as (1)G4 + (3)H4→(1)D2 + (3)F4, play the primary roles in the 456 nm emission band.
深入理解三价镧系（Ln(3+)）离子之间的能量转移和上转换（UC）过程对于提高上转换性能至关重要。然而，由于Ln(3+)离子丰富的能态，上转换机制非常复杂，这使得专门验证和定量评估主导过程成为一项挑战。在本研究中，基于量子跃迁原理，对800 nm连续波（CW）激光激发下掺Tm(3+)的NaYF4纳米晶体的基本激发过程进行了实验研究。设计了800 nm CW激光与其他波长的CW激光（包括471 nm、657 nm、980 nm和1550 nm激光）相结合，通过同时双波长激光激发深入研究上转换发光的激发过程。结果表明，(3)H6→(3)H4∼∼(3)H5→(1)G4的激发态吸收是481 nm和651 nm发射带的主导途径，两种能量转移上转换途径，统一表示为(1)G4 + (3)H4→(1)D2 + (3)F4，在456 nm发射带中起主要作用。
