Building block magneto-luminescent nanomaterials of iron-oxide/ZnS@LaF3:Ce3+,Gd3+,Tb3+ with green emission

Abstract

The preparation of novel triply-doped bifunctional Fe₃O₄/ZnS@LaF₃:xCe³⁺,xGd³⁺,yTb³⁺ (x = 5; y = 5, 10 and 15 mol%) nanocomposites with efficient optical and magnetic features has been reported. The ZnS semiconductor functionalized Fe₃O₄ particles were coated with LaF₃:RE³⁺ materials via a chitosan-assisted co-precipitation method. The size of iron oxide ∼7.2 nm and trigonal structures of bifunctional nanostructures were confirmed through X-ray diffraction and high-resolution transmission electron microscopy. The static magnetic measurements supported and manifested the superparamagnetic behavior of the materials at 300 K. A broad emission band was observed in the blue region (400–550 nm) due to the sulphur vacancy on the surface of the Fe₃O₄/ZnS nanocomposite. For a triply doped bifunctional nanostructure, the excitation spectra revealed broad absorption bands centered at around 270 nm, which were attributed to the 4f(⁷F_7/2) → 5d interconfigurational transition of the Ce³⁺ ion accompanied by narrow absorption lines arising from the 4f–4f intraconfigurational transitions of the Tb³⁺ ion. The emission spectra of the nanocomposites showed characteristic narrow emission lines assigned to the ⁵D₄ → ⁷F_J transitions (J = 6–0) of the Tb³⁺ ion. The energy transfer process from the Ce³⁺ → Gd³⁺ → Tb³⁺ ions has also been presented and discussed. Furthermore, the structural, photoluminescence and magnetic properties of Fe₃O₄/ZnS@LaF₃:RE³⁺ suggested that it may be an efficient candidate for magnetic light-converting molecular devices (MLMCDs) and high energy radiation detection.