| Nanocomposites have been playing important roles in modern science andtechnology.Dual-functional nanocomposites combined with magnetism andluminescence have potential applications in bio-and nano-technology drugs.In thisarticle, we synthesis a series of magnetic fluorescent compound through chemicalcoprecipition, where Fe3O4, Y2O3doped with rare-earth and SiO2were fabricated asmagnetic cores, shells and coupling agents.We tried to explain the influence ofdifferent interacting time to the fluorescence in the magnetic field. The couplingagents of carbon and TiO2were investigated effects to the magnetism andfluorescence. We also discussed the roles of Eu3+as single activator, Eu3+and Tb3+dual-activators to dual-functional applications, showing the possible mechanism ofenergy transferred from Tb3+to Eu3+ions. We speculate from excitation spectrum thatthere exists energy transfer from Tb3+to Eu3+ions.In order to broaden the applicationsof these bifunctional compounds, we also prepared hollow mesoporous compounds,which had large specific surface area, good magnetic and fluorescent properties viasacrificing template. Details were as follows:In summary, we demonstrated a solvothermal synthesis of multifunctionalFe3O4@SiO2@Y2O3:Eu3+nanocomposites with well-defined core-shell nanostructures,magnetic and luminescent properties, which had superior performances thanFe3O4@Y2O3:Eu3+nanocomposites in magnetism and fluorescence by variouscharacterizationtechniques. The SiO2on the surface of magnetic core was the base tothe sandwich-structured materials, which was important to good magnetic andluminescent properties. The luminescence gradually increased in3h when the sampleswere in magnetic field for different time, then decreased，indicating tunable opticalproperties, good magnetic respondence and chemical stability.We demonstrated a successful synthesis ofmultifunctional Fe3O4@SiO2/C/TiO2@Y2O3:Eu3+nanocomposites with the magnetic and luminescence properties in a core/shell frame. The Y2O3:Eu3+could easily grow on the coupling agents‘layercoating the Fe3O4microsphere.Compared with three different coupling agentnanocomposites, it was obvious that the chemical bonds in activated carbon layerpromoted to combine these two different crystalline structures, which made theFe3O4@C@Y2O3:Eu3+nanocomposites,had better proformance than Fe3O4@SiO2@Y2O3:Eu3+and Fe3O4@TiO2@Y2O3:Eu3+nanocomposites in magnetic andluminescent properties by various characterization techniques. However, differentcoupling agents all shown good magnetic respondence, unique luminescence and highsolubility in ethanol.By usingcarbon as a sacrificial template, silica as coupling agent and CTAB asstructure-directingagent, we synthesized multifunctional Fe3O4@HM-SiO2@Y2O3:Eu3+nanocomposites via a multi-step. The results revealed that materials showtypical ordered mesoporous characteristics, havemonodisperse spherical morphologywith smooth surface and narrow size distribution. The multifunctionalnanocomposites show the characteristic emission of Eu3+（5D0-7F1-4）. Magnetismmeasurement revealed the paramagnetic feature of the samples. Besides we alsocompared the magnetic and fluorescent properties of solid Fe3O4@SiO2@Y2O3:Eu3+and Fe3O4@HM-SiO2@Y2O3:Eu3+.The nanocomposites with good dispersion and core–shellstructures weresynthesized via a facile two-step co-precipitation process in the fabrication ofFe3O4@SiO2@Y2O3:Eu3+,Tb3+. XRD spectra showed that Fe3O4core has crystallizedin a good face-centered cubic structure; SiO2layer is amorphous and Y2O3layer iscubic. Nanocomposites excitated by UV irradiation, Fluorescence spectroscopyshown that there is a strong emission at around610nm corresponding to the forcedelectric dipole5D0–7F2transition of Eu3+and at around545nm corresponding to5D4-7F5transition of Tb3+. We speculated from excitation spectrum that there existedenergy transfer from Tb3+to Eu3+ions. |
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