Upconversion emission tuning from green to red in Yb³⁺/Ho³⁺-codoped NaYF₄nanocrystals by tridoping with Ce³⁺ions

Abstract

Upconversion (UC) emission tuning from green to red in monodisperse NaYF(4):Yb(3+)/Ho(3+) nanocrystals was successfully achieved by tridoping with Ce(3+) ions under diode laser excitation of 970 nm. It is proposed that two efficient cross-relaxation processes, 5S2/5F4(Ho) + 2F(5/2)(Ce) --> 5F5(Ho) + 2F(7/2)(Ce) and 5I6(Ho) + 2F(5/2)(Ce) --> 5I7(Ho) + 2F(7/2)(Ce)between Ho(3+) and Ce(3+) ions, have been employed to select UC pathways to tune the UC radiation. Theoretical investigations based on steady-state equations demonstrate the proposed UC mechanisms and explain well the observed linear increase of the UC red-to-green intensity ratio with the increment of Ce(3+) ion concentrations.

A sequential two-step near-infrared quantum splitting in Ho3+ singly doped NaYF4

“…On the other hand, the corresponding visible PL spectra are recorded for the 448 nm excitation, as shown in the inset of Fig. 3 23 Fig . 4 shows the diffuse reflection spectrum of the NaYF 4 :1%Ho 3+ phosphor.…”

Excitation energy migration dynamics in upconversion nanomaterials

“…7b), the existence of Mn 2+ ions was considered to disturb the transition possibilities between the green and red emissions of Er 3+ , with the Er 3+ -Mn 2+ energy transfer leading to depopulation of the green emitting 2 H 11/2 and 4 S 3/2 energy levels, and the consequent Mn 2+ -Er 3+ back energy transfer increases the population of the red emitting energy level ( 4 F 9/2 ), resulting in an enhanced red to green emission ratio by Er 3+ . Additionally, doping Ce 3+ into the Yb 3+ -Ho 3+ system could increase the red to green emission ratio by tuning the energy transfer process between Ce 3+ and Ho 3+ , 25 and the deep-ultraviolet upconversion emission of Gd 3+ View Article Online ions could be enhanced by doping in Ho 3+ , serving as a ''bridging ion'' in the Yb 3+ -Ho 3+ -Gd 3+ energy transfer process. 26 3.2.2.…”

Lanthanide upconversion luminescence at the nanoscale: fundamentals and optical properties

“…If this is not the case, there can still be promotion of desired wavelengths as long as the desired wavelength energy is lower (e.g. red vs green) and low energy phonon relaxation results in population of this state 142 . Both strategies have only been demonstrated for purifying red emission.…”