One-step solvothermal synthesis, a worm-shaped morphology and luminescence properties of green-emitting Y₂O₂S:Tb³⁺ nanophosphors

The worm-shaped Y₂O₂S:Tb³⁺ nanophosphors have been successfully prepared via one-step solvothermal synthesis, using ethanediamine as the main solvent and sublimed sulfur powder as the source of sulfur without adding additional structure-directing reagents. XRD, FT-IR, FESEM, PL and CIE chromaticity diagram were used to characterize the obtained products. XRD results demonstrate that all diffraction peaks of the sample can be well indexed to pure hexagonal phase of Y₂O₂S with optimal condition, i.e. the molar ration of S/Y³⁺ m = 10, solvothermal temperature T = 220 °C and synthetic time t = 24 h. When t varies from 2 h to 24 h, the morphology of Y₂O₂S transforms from cauliflower-like structure to worm-shaped nanoparticles with the length of ∼80 nm. The formation mechanism depending on t has also been proposed. Upon 250 nm ultraviolet (UV) light excitation, the worm-shaped Y₂O₂S:Tb³⁺ nanophosphors exhibit green emissions, corresponding to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ions. The quenching concentration is 7% and its corresponding lifetime is 1216 μs. The CIE chromaticity coordinates show the tuneable emission shifting from yellow green to yellowish green with increasing concentration of Tb³⁺ions from 1% to 7%. Those results suggest that the worm-shaped Y₂O₂S:Tb³⁺ nanophosphors may have potential applications in X-ray intensifying screens, fluorescence and biomedical fields.