YVO_4∶Eu~(3+)@SiO_2核壳结构纳米复合材料的合成与表征

用沉淀法制备了尺寸约为8 nm的YVO4∶Eu3+纳米粒子,然后用反相微乳液法在YVO4∶Eu3+纳米粒子的表面包覆了一层Si O2壳。利用XRD、TEM、UV-Vis吸收光谱和光致发光光谱对合成的样品进行了表征。得到的复合物具有较好的核壳结构,通过改变硅酸四乙酯的用量可以改变Si O2壳的厚度。研究了Si O2壳对YVO4∶Eu3+发光性质的影响,结果表明:包覆和未包覆的样品在紫外光激发下都有Eu3+的特征发射;随着Si O2壳厚度的增加,发光强度和量子效率越来越低,Eu3+格位对称性越来越高。

Synthesis and Characterization of Core-shell Structured YVO4:Eu3+@SiO2 Nanocomposites

YVO₄ :Eu³⁺ nanoparticles of about 8 nm were synthesized by precipitation reactions and coated with SiO₂ by a reverse microemulsion method. Powder X-ray diffraction (XRD) patterns indicate that these nanoparticles are purely tetragonal phase. Transmission electron microscope (TEM) images show that YVO₄ :Eu³⁺ nanoparticles are successfully coated with silica to form core-shell structured nanocomposites. The thicknesses of SiO₂ shells can be altered by changing the volume of tetraethoxysilane (TEOS) used in the reaction. The ultraviolet-visible (UV-Vis) absorption spectra of YVO₄ :Eu³⁺@SiO₂ nanocomposites agree well with that of the YVO₄ :Eu³⁺ nanoparticles colloid. Both the excitation and emission spectra are the same for YVO₄ :Eu³⁺ nanoparticles and the nanocomposites. With the increasing of the thickness of SiO₂ shell, the intensity ratio of ⁵D₀-⁷F₂/⁵D₀-⁷F₁ decreases, indicating that SiO₂ shells can increase the local symmetry of Eu³⁺. All samples can emit bright red light under ultraviolet irradiation. The photoluminescence quantum yield decreases after SiO₂ coating. With the increasing of the thickness of SiO₂ shell, the photoluminescence quantum yield becomes lower and lower.