Red-Emitting Magnetic Nanocomposites Assembled from Ag-Decorated Fe3O4@SiO2 and Y2O3:Eu~(3+): Impact of Iron-Oxide/Silver Nanoparticles on Eu3+ Emission

摘要

The new multistep approach for co-assembling magnetic iron oxide nanoflowers with red-emitting Y2O3:Eu~(3+) to form luminescent and magnetic nanocomposites was reported. The Fe3O4 core prepared by solvothermal method was layered by SiO2 shell and decorated with small size spherical Ag nanoparticles as well as further coated with Y2O3:Eu~(3+) luminophore. The nanoflower shape Fe3O4 core of size ~110 nm and crystalline cubic structure of bifunctional iron-oxide@Y2O3:Eu3+, Fe3O4@SiO2@Y2O3:Eu3+ and Fe3O4@SiO2-Ag@Y2O3:Eu3+ (1 mol%) nanomaterials were confirmed from X-rays diffraction, EDS spectra and transmission electron microscopy (TEM) images. The static magnetic measurements supported and manifested nonsuperparamagnetic behavior of the materials at 300 K. The iron oxides are usually luminescence quenchers. In order to rationalize this effect, their optical properties based on their emission spectral data and luminescence decay curves were studied. Experimental intensity parameters (Wl), lifetimes (t), intrinsic quantum yield (Q_(Ln) ~(Ln)) as well as radiative (Arad) and nonradiative (Anrad) decay rates were calculated to probe the local chemical environment of the Eu~(3+) ion and to better understand the phenomena of iron oxide induced luminescence quenching. The highest value of the intrinsic quantum yield (Q_(Ln) ~(Ln)= 74%) for the a-Fe2O3@Y2O3:Eu~(3+) (1 mol%) among all the luminescent and magnetic nanocomposites suggests that a- Fe2O3 phase induces a lower luminescence quenching then Fe3O4/γ-Fe2O3. The SiO2 thin layer leads to improve the luminescence efficiency, whereas the Ag nanoparticles act as luminescence quencher. These novel Eu~(3+) nanomaterials may act as a red emitting layer for magnetic and light converting molecular devices.