Physical and optical studies of Gd₂ O₂ S:Eu³⁺ nanophosphors by microwave irradiation and γ-irradiation methods

Gd₂ O₂ S:Eu³⁺ nanophosphors have been successfully synthesized using microwave irradiation and γ-irradiation methods with polyvinyl pyrrolidone as a stabilizer. The physical and luminescence spectra were compared. The morphologies of both Gd₂ O₂ S:Eu³⁺ nanophosphors were in the hexagonal phase and mainly consisted of spherical nanostructures with diameters of ~90 nm and ~50 nm for both microwave irradiation and γ-irradiation methods. Upon 325 nm of ultraviolet (UV) light excitation, strong red emissions (626 nm) were observed for both methods; these emissions corresponded to the ⁵ D₀ →⁷ F₂ transition of Eu³⁺ ions. However, Gd₂ O₂ S:Eu³⁺ nanophosphors following microwave treatment showed better luminescence intensity than Gd₂ O₂ S:Eu³⁺ nanophosphors treated with γ-irradiation. This difference was attributed to the crystallinity phase and surface quenching effects of Gd₂ O₂ S:Eu³⁺ nanophosphors. The reaction mechanisms of Gd₂ O₂ S:Eu³⁺ nanophosphors in both methods are discussed in detail.