The Synthesis Of Core-Shell Structured Micro-Nnano Particles SiO₂@Y₂O₃:Eu³⁺ And Their Luminescent Properties

The core-shell structured micro-nano particles SiO2@Y2O3:Eu3+ were successfully synthesized by hydrothermal method and precipitation method under different reaction conditions. Several factors affecting the luminescent properties of micro-nano particles SiO2@Y2O3:Eu3+ were further studied. X-ray diffraction (XRD), were used to characterize the phase composition. The scanning electron microscope (SEM), transmission electron microscope (TEM) and infrared spectra (IR) were used to characterize the morphology and structure of samples, and the luminescent properties were further studied on a spectrophotometer.The main results are as follows:(1) The nano silica spheres were prepared by a certain amount of TEOS, ammonia, ethanol, and water as reaction raw materials. The as-obtained silica spheres were prepared for further core-shell samples. Monodisperse SiO2 was used to synthesize monodisperse core-shell materials by template method. On one hand, its chemical properties is stable, and its particle size distribution is narrow, it could not act with other materials; On the other hand, it can control the SiO2 nanosphere particle size to regulate the size of core-shell materials.(2) Using Y2O3 and Eu2O3 as reactants, and urea as precipitating agent, the core-shell structured micro-nano particles SiO2@Y2O3:Eu3+ were prepared by hydrothermal method successfully. Several conditions affecting on the morphology of the product were studied. The factors such as the particle size of SiO2, the amount of SiO2, the coating number of layers, the annealing temperature, the doping concentration of Eu3+ and other factors on the luminescent properties were further studied. The XRD analysis showed that the core-shell structured micro-nano particles SiO2@Y2O3:Eu3+ synthesized successfully under conditions of 180℃ reaction temperature for 20 h, followed 800℃ annealing temperature for 2 h showed pure cubic phase structure of Y2O3. The SEM and TEM showed that the as-obtained samples present obvious core-shell structure with good dispersion and no agglomeration. The surface of the core-shell structured particles was not smooth, and the shell thickness can be controlled through multiple coating. The fluorescence analysis showed that under the excitation at 240 nm, the samples present strong red emission corresponding to the 5D0â†'7F2 transition of the Eu3+ions at 613 nm. The size of SiO2 is an important factor influencing the luminescent properties of the as-obtained samples. The luminescent properties increase with the size of SiO2 decreasing. The reason may be due to nano size and small size effect, smaller SiO2 particles can be better coated by Y2O3:Eu3+ phosphor, resulting in less the surface crystal defects.(3) Using Y2O3 and EU2O3 as reactants, and urea as precipitating agent, the core-shell structured micro-nano particles SiO2@Y2O3:Eu3+ were prepared by precipitation method successfully. Some reaction conditions such as reaction time, reaction temperature, amount of precipitation agent affecting on the morphology were studied. The factors such as the doping concentration of Eu3+, reaction temperature, reaction time, the amount of urea on the luminescent properties of the as-obtained samples were further investigated. The results showed that under conditions of 80℃ reaction temperature for 3 h, followed 800℃ annealing temperature the core-shell structured micro-nano particles SiO2@Y2O3:Eu3+ showed pure cubic phase structure of Y2O3. It should be noted that the Y2O3 presents good crystallinity, the SiO2 did not act with the Y2O3:Eu3+. Fluorescence analysis showed that, the doping concentration of Eu34 is an important factor influencing the luminescent properties of the micro-nano particles, due to concentration quenching effect, when the doping concentration of Eu3+ was 5%, the as-obtained samples present the best luminescence performance.