Selective Processing, Structural Characterization, and Photoluminescence Behaviors of Single Crystalline (Gd1-xEux)2O3 Nanorods and Nanotubes

This study presents a simple yet effective hydrothermal route for selective generation of (Gd1-xEux)2O3 (x=0.03-0.13) redphosphor nanorods and nanotubes. Detailed characterizations of the products were achieved by combined means of XRD, FT-IR, TGA/DSC, BET, FE-SEM, HR-TEM, PL/PLE, fluorescence decay analysis, and transient techniques. The precursors are of hexagonal (Gd1-xEux)(OH)3, whose morphology (nanotube or nanorod) is largely affected by the final pH of the hydrothermal reaction. A minimum annealing at 600 °C is needed to crystallize solid-solution oxides of desirable photoluminescence, while at 1000 °C the polycrystalline precursors mostly transform into single-crystalline oxides. The two types of phosphors exhibit nearly identical positions of the PLE/PL bands and similar asymmetry factors of luminescence [I(5D0→7F2)/I(5D0→7F1)], but the nanotubes show a significantly stronger red emission at ~613 nm (~2.3 times that of the nanorods) upon UV excitation into the charge transfer band at ~250 nm. The quenching concentration of Eu3+ was found to be ~8 at% and the quenching mechanism is dominantly exchange interaction. Luminescent properties of the nanorod and nanotube phosphors, in terms of PL/PLE intensity, fluorescence lifetime and asymmetry factor of luminescence, have been successfully correlated to the phase evolution process, annealing temperature, Eu3+ content, and particle morphology