Template-free hydrothermal synthesis of Gd2O2SO4:Eu3+ hollow spheres based on urea-ammonium sulfate (UAS) system

Gd2O2SO4:Eu3+ hollow spheres were successfully synthesized through a template free hydrothermal synthesis routine from commercially available Gd2O3, Eu2O3, HNO3, (NH4)(2)SO4 and CO(NH2)(2) (urea) as the starting materials. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric and differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and photoluminescence (PL) spectra. The XRD, FT-IR and TG-DSC results demonstrate that the precursor is composed of Gd-2(OH)(2)CO3SO4 center dot xH(2)O and could be converted into pure Gd2O2SO4 phase at 800 degrees C for 2 h. in air. SEM and FESEM observations show that the obtained Gd2O2SO4 particles possess hollow sphere structure, which has a typical size of about 10 mu m in diameter and about 1.5 mu m in shell thickness. The formation mechanism of the Gd2O2SO4 hollow spheres is related to the Ostwald ripening process. PL spectroscopy reveals that the strongest red emission peak is located at 619 nm under 275 nm UV light excitation for the Gd2O2SO4:Eu3+ hollow spheres, which corresponds to the D-5(0) -> F-7(2) transition of Eu3+ ions. Decay study demonstrates that the D-5(0) -> F-7(2) transition of Eu3+ ions has a single exponential decay behavior and its corresponding fluorescence lifetime is 1.50 ms according to the linear fitting result. (C) 2016 Elsevier GmbH. All rights reserved.