Controlled preparation of Gd2O2SO4:Eu3+ monospheres via hydrothermal precursor engineering for enhanced photoluminescence.

[Display omitted] • (Gd 0.95 Eu 0.05) 2 O 2 SO 4 monospheres and nanoplates were selectively synthesized from a new type of precursor. • The mechanism and kinetics of composition/phase/morphology evolution were clarified. • The monosphere phosphor emits ∼ 1.35 times as strong as nanoplates. • The monosphere phosphor has a high thermal stability of luminescence (∼81% at 150 °C) Rare-earth oxysulfates (RE 2 O 2 SO 4) attracted attention for large-capacity oxygen storage, low-temperature magnetism and luminescence, whose preparation mostly involves toxic SO x gases and/or complicated procedures. In the phosphor field, monospheres are preferred for a number of applications due to their better luminescence and high packing density. With the simple reactants of RE(NO 3) 3 , Na 2 CO 3 and (NH 4) 2 SO 4 for hydrothermal reaction, dispersed monospheres and nanoplates were selectively synthesized for the recently discovered RE 2 (OH) 2 CO 3 SO 4 · n H 2 O (RE = Gd 0.95 Eu 0.05 , REOCSH) layered compound precursor, from which RE 2 O 2 SO 4 phosphors mostly retaining their precursor morphologies were facilely derived via calcination in air at 800 °C, without involving SO x. Solution pH was found to decisively determine the chemical composition and crystallization kinetics of the initial precipitate, and the possible mechanisms of phase/morphology evolution during hydrothermal treatment were proposed by comparatively investigating the temperature-course and time-course of REOCSH formation under the typical pH values of 6 and 7. It was revealed that (Gd 0.95 Eu 0.05) 2 O 2 SO 4 monospheres emit ∼1.35 times as strong as nanoplates (λ ex = 257 nm, λ em = 617 nm) and may retain as high as ∼81% of the room-temperature intensity at 150 °C. The phosphor monospheres were also analyzed to have a fluorescence lifetime of ∼1.32 ms at room temperature and an activation energy of ∼0.19 eV for the thermal quenching of luminescence. [ABSTRACT FROM AUTHOR]