Enhanced up-conversion luminescence from NaYF₄:Yb,Er nanocrystals by Gd³⁺ ions induced phase transformation and plasmonic Au nanosphere arrays

Abstract

NaYF4:Yb,Er nanocrystals with different concentrations of Gd3+ ions are prepared via a hydrothermal method.

Gd3+-Doping Effect on Upconversion Emission of NaYF4: Yb3+, Er3+/Tm3+ Microparticles

“…Upconversion intensity enhancement by Gd 3+ co-doping of NaYF 4 : Yb, Er or NaYF 4 : Yb, Tm is usually explained by host phase transition from cubic to hexagonal, which would significantly improve luminescence intensity [ 17 , 35 ]. However, in our case, hexagonal phase formed even in the case of Gd 3+ -free powders.…”

“…All experimental decay curves displayed non-single exponential behavior and two exponential models were applied for fitting. Average luminescence lifetime ( τ av ) was calculated according to the following equation to simplify comparison [ 35 , 36 ]: where A 1 and A 2 are pre-exponential constants, and τ 1 and τ 2 are fitting lifetimes ( Table S1, Supplementary Materials ). The calculated lifetimes of NaYF 4 : Yb, Er, Gd and NaYF 4 : Yb, Tm, Gd powders are listed in Table 1 .…”

“…However, in our case, hexagonal phase formed even in the case of Gd 3+ -free powders. Introduction of Gd 3+ ions in the NaYF4 host leads to the formation of crystal lattice defects, as shown in Figure 2c,d, which change the symmetry of the surroundings of ytterbium, Upconversion intensity enhancement by Gd 3+ co-doping of NaYF 4 : Yb, Er or NaYF 4 : Yb, Tm is usually explained by host phase transition from cubic to hexagonal, which would significantly improve luminescence intensity [17,35]. However, in our case, hexagonal phase formed even in the case of Gd 3+ -free powders.…”

The gadolinium effect on crystallization behavior and luminescence of β‐NaYF4:Yb,Er phase

“…Strengthening the of the 4 F 9/2 → 4 I 15/2 transition is most intense with the time (rise of about 70 times is detected) due to a more homogeneous distributions of dopants in crystal matrix which directly build‐up energy transfer from Yb 3+ to Er 3+ ions. With further increasing of the Gd 3+ content to 30 mol% UC emission decreased as a consequence of the higher microstrain induced by the substitution of yttrium with bigger ion (Table ), as well as due to increased rate of the non‐radiative recombination which suppress the UC emission …”

Graphene Quantum Dots-Driven Multiform Morphologies of β-NaYF4:Gd3+/Tb3+ Phosphors: The Underlying Mechanism and Their Optical Properties

“…31 While Chen et al studied the influence of Gd 3+ ions on the phase transformation of NaYF 4 crystals from cubic to hexagonal phase and also observed decrease in luminescence intensity because of the decrease in the size of the nanorods with higher Gd 3+ doping. 32 Hitherto, numerous methods have been reported to fabricate the anisotropic nanoparticles such as rods, plates, prisms, tubes, spheres, disks, and spindles, and so forth. These methods include solvothermal, coprecipitation, thermal decomposition, combustion, and sol–gel process, among which hydro-/solvothermal method is considered a relatively environment-friendly method which provides high crystallinity and monodispersity to the material with diverse controllable morphologies and architectures.…”