Energy transfer and luminescent properties of Eu3+, Tb3+, Eu3+-Yb3+and Tb3+-Yb3+ doped α-NaYF4 nanophosphors prepared by coprecipitation route

Abstract

Cubic α-NaYF 4 nanometer-sized crystals doped with Eu 3+ , Tb 3+ , Yb 3+-Eu 3+ or Yb 3+-Tb 3+ were synthesized by an original coprecipitation route. The obtained nanoparticles exhibited primary particles showing cubic shape with sizes ranging between 35 and 65 nm. The singlyor co-doped nanophosphors exhibited strong red (Eu 3+) or green (Tb 3+) fluorescence upon ultraviolet (UV) or near infrared (NIR) excitation, which resulted respectively from down-or up-conversion processes occurring in their structure. Spectroscopic properties were investigated on the basis of emission spectra as well as luminescence decays. From the emission spectra of Eu 3+ doped samples, the Ω 2 and Ω 4 Judd-Ofelt intensity parameters were calculated. The concentration quenching of the Eu 3+ or Tb 3+ ion emissions in singly-doped or Yb 3+ co-doped α-NaYF 4 were ascribed to resonant cross-relaxations. The main derived interaction between the active ions was evidenced as an electric dipole-dipole one through fitting the decays curves with the Inokuti-Hirayama model. The critical distances and energy transfer microparameters for the transfer processes were given showing very short range interaction. The dependence of integral up-conversion intensity on the NIR energy of the beam power was measured. The results indicated a two-photon process based on a cooperative energy transfer.

Efficient down-shifting and up-conversion emission dual-mode in RE3+-doped NaTbF4-based nano-glass ceramics

“…Taking into account these energy transfer efficiencies, the PLQY ( ϕ ) can be calculated through the well-known equation ϕ = η ET ·ϕ f−f where ϕ f−f represents the Eu 3+ 4f−4f emission quantum yield, estimated by the following equation 44 where A MD being equal to 14.65 s −1 is the spontaneous emission probability of magnetic dipole ( 5 D 0 → 7 F 1 ) transition, n is the refractive index of the media (1.432 and 1.460 for nanocrystalline and glassy environments 45–47 ), τ obs are Eu 3+ decay lifetimes previously described and ( I tot / I MD ) is the ratio of the total integrated emission intensity from 5 D 0 → 7 F J levels to the integrated intensity of the 5 D 0 → 7 F 1 transition, obtained from emission spectra exciting at 351 nm with 16 ms of delay and exciting at 463 nm (partially shown in Fig. 5(c) and in left inset of Fig.…”

A multi-color persistent luminescent phosphor β-NaYF4:RE3+ (RE = Sm, Tb, Dy, Pr) for dynamic anti-counterfeiting

“…For NaYF 4 :Sm 3+ , the RL spectrum shows the characteristic emission of Sm 3+ : 562 nm ( 4 G 5/2 / 6 H 5/2 ), 601 nm ( 4 G 5/2 / 6 H 7/2 ), 645 nm ( 4 G 5/2 / 6 H 9/2 ) and 700 nm ( 4 G 5/2 / 6 H 11/2 ), with the orange emission ( 4 G 5/2 / 6 H 7/2 transition) being the most signicant. 40,42,43 For NaYF 4 :Dy 3+ , the blue (480 nm) and yellow (572 nm) emission bands are attributed to the ( 4 F 9/2 / 6 H 15/2 ) and ( 4 F 9/2 / 6 H 13/2 ) transitions of Dy 3+ , respectively. It is observed that NaYF 4 :Pr 3+ shows characteristic purple emission upon X-rays irradiation, the multi-peaks are due to the f-f transitions of Pr 3+ .…”

Design of Eu3+-Doped Fluoride Phosphor with Zero Thermal Quenching Property Based on Density Functional Theory

“…Therefore, fluoride phosphors have drawn much attention from researchers, especially the NaYF 4 -based and NaGdF 4 -based phosphors. Unfortunately, Previous reports show that NaYF 4 :Eu 3+ and NaYF 4 :Eu 3+ ,Tb 3+ red-light phosphors did not have zero thermal quenching (ZTQ) properties. − The Eu 3+ -doped NaGdF 4 -based red light phosphors are reported by Mech et al, Gui et al, and Luo et al − It is regretful that these studies failed to obtain red-light phosphors with ZTQ properties.…”