Oriented and Yellow-Emitting Nano-Phosphor Films of High Transparency Assembled from Exfoliated Nanosheets of Layered Rare-Earth Hydroxide (LRH).

Abstract

(Y0(.975− x)) Gd(x)Dy(0.025)(2)(OH)(5)NO(3) · nH2O (0 ≤ x ≤ 0.975) LRH crystals with tens of micron sized laterals have been hydrothermally synthesized by adding mineralizer NH(4)NO(3). Smaller LRHs particles, expanded main layer, and shorter interlayer distance were found at a higher Gd incorporation. Free anions NO− 3 at the interlayer of LRHs have been completely replaced by oleate anions with the help of hydrothermal processing, thus weakening the interaction of layers. Therefore, tens of micron sized LRH nanosheets can be easily exfoliated from the oleate-intercalated LRHs in toluene. Highly [111] oriented and transparent films of (Y0975− x Gd x Dy0.025)2O3 (0 ≤ x ≤ 0.975), with thicknesses of ~12 nm, have been constructed through spin-coating the colloidal suspension of exfoliated nanosheets on quartzs, followed by calcination at 800 °C. Under excitation at 270 nm, the oxide films exhibit typical yellow emission at 576 nm, whose intensity shows a clear dependence on Gd3+ concentration. Increasing the Gd content from 0 to 97.5 at.% yielded a 450% increase in the yellow emission intensity, owing to the energy transfer from Gd(3+) to Dy(3+). Because Gd(3+) content has little influence on fluorescence lifetime, fluorescence decay analysis yields similar lifetimes of ~1.45 ± 0.30 ms for all the samples.