Intense ultraviolet upconversion luminescence from hexagonal NaYF_4:Yb^3+/Tm^3+ microcrystals

Abstract

Under 980 nm excitation, unusual 3P2-->3H6 (approximately 264 nm) and 3P2-->3F4 (approximately 309 nm) emissions from Tm3+ ions were observed in hexagonal NaYF4:Yb3+ (20%)/Tm3+ (1.5%) microcrystals. In comparison with the strong emissions from 1D2 and 1I6, the emissions from 1G4 and 3H4 almost vanished due to the efficient cross-relaxation of 1G4 + 3H4-->3F4 + 1D2(Tm3+). Double logarithmic plots of the upconversion emission intensity versus the excitation power are neither straight lines nor typical saturation curves. Theoretical analysis indicated that the complicated dependent relationships were mainly caused by phonon-assisted energy transfers and nonradiative relaxation.

Lanthanide‐Doped Upconversion Nanoparticles: Emerging Intelligent Light‐Activated Drug Delivery Systems

“…In particular, it should be emphasized that the anti‐Stokes emission efficiency of ETU route is strongly dependent on the distance between ions, which is determined by the concentrations of ion dopants 40, 52, 54, 55, 56. To date, monodispersed core–shell UCNPs comprising of NaYF 4 nanocrystals doped with lanthanides, such as Tm 3+ and Yb 3+ (NaYF 4 :TmYb) have been reported as promising candidates for the upconversion process 11, 57, 58. The proposed ETU mechanism of the most thoroughly investigated UCNPs with NaYF 4 : Yb 3+ /Er 3+ (Tm 3+ ) structure and also highly efficient Nd 3+ ‐sensitized UCNPs are illustrated in Figure 2 a,b respectively and explained in detail in the literature 59, 60, 61…”

Energy transfer efficiency in YF3 nanocrystals: Quantifying the Yb3+ to Tm3+ infrared dynamics

“…As it can be seen, 16,[29][30][31] As it can be deduced from Figure 2(c), the probability of the second and third upconversion processes depends on the probability of the first IR energy transfer from Yb 3þ ions to Tm 3þ ions, which triggers all the subsequent steps. Therefore, the first energy transfer mechanism is the key process to allow the upconversion, and any change in that process will strongly affect the intensity of the visible and UV emissions.…”

Strong tunability of cooperative energy transfer in Mn2+-doped (Yb3+, Er3+)/NaYF4 nanocrystals by coupling with silver nanorod array

“…This has been demonstrated using a specially designed Au pyramid array that enables further adjustment of the emission spectra due to the metal-mediated quenching of the green fluorescence on flat metal surfaces [39][40][41][42]. The power-dependent and nonlinear plasmon-enhanced upconversion process has also attracted considerable attention, and effective manipulation and utilization of the upconversion nanocrystals have been the focus of research [43][44][45][46][47][48][49][50][51]. However, a key issue of plasmonenhanced cooperative energy transfer in Mn 2+ -doped (Yb 3+ , Er 3+ )/NaYF 4 has not been addressed.…”