The preferred upconversion pathway for the red emission of lanthanide-doped upconverting nanoparticles, NaYF4:Yb(3+),Er(3.).
Lanthanide-doped upconverting nanoparticles (UCNPs, NaYF4:Yb(3+),Er(3+)) are well known for emitting visible photons upon absorption of two or more near-infrared (NIR) photons through energy transfer from the sensitizer (Yb(3+)) to the activator (Er(3+)). Of the visible emission bands (two green and one red band), it has been suggested that the red emission results from two competing upconversion pathways where the non-radiative relaxation occurs after the second energy transfer (pathway A, (4)I15/2 → (4)I11/2 → (4)F7/2 → (2)H11/2 → (4)S3/2 → (4)F9/2 → (4)I15/2) or between the first and the second energy transfer (pathway B, (4)I15/2 → (4)I11/2 → (4)I13/2 → (4)F9/2 → (4)I15/2). However, there has been no clear evidence or thorough analysis of the partitioning between the two pathways. We examined the spectra, power dependence, and time profiles of UCNP emission at either 980 nm or 488 nm excitation, to address which pathway is preferred. It turned out that the pathway B is predominant for the red emission over a wide range of excitation powers.
Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea. ktlee@gist.ac.kr hohjai@gist.ac.kr.
Taeyoung
T
Jung
Hong Li
HL
Jo
Sang Hwan
SH
Nam
Byeongjun
B
Yoo
Youngho
Y
Cho
Jongwoo
J
Kim
Hyung Min
HM
Kim
Taeghwan
T
Hyeon
Yung Doug
YD
Suh
Hohjai
H
Lee
Kang Taek
KT
Lee