y Environmental Impact on the Excitation Path of the Red Upconversion Emission of Nanocrystalline NaYF4:Yb3+,Er3+

: Hyppanen I, Hoysniemi N, Arppe R, Schaferling M, Soukka T

Publisher: AMER CHEMICAL SOC

: 2017

: Journal of Physical Chemistry B

: JOURNAL OF PHYSICAL CHEMISTRY C

: J PHYS CHEM C

: 121

: 12

: 6924

: 6929

: 6

: 1932-7447

DOI: https://doi.org/10.1021/acs.jpcc.7b01019

The mechanism for red upconversion luminescence of Yb-Er codoped materials is not generally agreed on in the literature. Both two-photon and three-photon processes have been suggested as the main path for red upconversion emission. We have studied beta-NaYF4:Yb-3,Er3+ nanoparticles in H2O and D2O, and we propose that the nanoparticle environment is a major factor in the selection of the preferred red upconversion excitation pathway. In H2O, efficient multiphonon relaxation (MPR) promotes the two-photon mechanism through green emitting states, while, in D2O, MPR is less effective and the three-photon path involving back energy transfer to Yb3+ is the dominant mechanism. For the green upconversion emission, our results suggest the common two-photon path through the F-4(9/2) energy state in both H2O and D2O.