Mechanisms of the blue emission of NaYF4:Tm(3+) nanoparticles excited by an 800 nm continuous wave laser.
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.
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China. tqjia@phy.ecnu.edu.cn.
Hongxin
H
Zhang
Tianqing
T
Jia
Xiaoying
X
Shang
Shian
S
Zhang
Zhenrong
Z
Sun
Jianrong
J
Qiu