Tunable dual-mode photoluminescences from SrAl2O4: Eu/Yb nanofibers by different atmospheric annealing

Abstract One-dimensional Eu/Yb co-doped SrAl2O4 nanofibers were successfully synthesized via an electrospinning technique. The morphologies, crystal structures, and chemical valences were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The results revealed that the valence of Eu ions was primary trivalent (Eu3+) after annealing in oxygen ambient (air), and the red up-conversion (UC) luminescence was observed which was derived from 5D0–2 to ground state 7FJ (J = 0–6) of Eu3+ ions. While they evolved to bivalent (Eu2+) after annealing in a reduced (H2/Ar) ambient, showing green down-conversion (DC) luminescence under the exposure of 365 nm, which was ascribed to Eu2+ 4f-5d allowed transition. The mixed valence of Eu2+/Eu3+ could be realized through a partially oxidation in air again, strikingly, resulting in dual-mode UC and DC. Herein, we demonstrate the tunable dual-mode UC and DC emission performance in SrAl2O4: Eu/Yb nanofibers through selective annealing processes. Consequently, the synthesized SrAl2O4: Eu/Yb nanofibers may offer potentials applications towards multifunctional luminescent occasion.