Modification of Bi6Fe1.9Co0.1Ti3O18/SiO2/NaGdF4:Yb3+,Er3+ nanocomposites with different SiO2 thicknesses for tunable upconversion luminescent and ferromagnetic properties

Abstract

The coexistence of luminescent and magnetic properties in nanocomposites has attracted the interest of many researchers to study nanocomposites due to their unique properties. In this study, we present a convenient synthesis of Bi₆Fe_1.9Co_0.1Ti₃O₁₈/SiO₂/NaGdF₄:Yb³⁺,Er³⁺ (BFCTO/SiO₂/NGF) core/shell/satellite nanocomposites with precise control over the thickness of the SiO₂ shell. By adjusting the amount of tetraethyl orthosilicate (TEOS), we obtained BFCTO/SiO₂/NGF samples with different SiO₂ thicknesses (0 nm, 8 nm, 13 nm, 18 nm, 25 nm and 36 nm). On account of the SiO₂ spacer effectively reducing the absorption intensity around the green and red regions, the optimal upconversion luminescence intensity of BFCTO/SiO₂/NGF was observed at a separation distance of 36 nm. Moreover, at room temperature, the hysteresis loop of BFCTO/∼13 nm SiO₂/NGF obtained the maximum remnant magnetization (2Mr) of 0.13 emu g⁻¹. Also, the BFCTO/∼36 nm SiO₂/NGF sample reached the maximum coercive field (2Hc) of 1200 Oe. Besides, the BFCTO/∼8 nm SiO₂/NGF sample had the best ferromagnetism with a saturated magnetization Ms of 0.63 emu g⁻¹.