Synthesis And Characterization Of α-NaYF₄:Yb, Er Upconversion Nano-particles And Its Silica Coated Particles

In this paper, we used of CTAB- Hexanol - n-Heptane– water, which was water/oil microemulsion system as chemical reaction vessels, rare earth salt solution Ln(NO3)3 as precursors to syntheticα-NaYF4:Yb,Er (Cubic) up-conversion nanoparticles, and its morphology and phase structure was conformed by XRD,SEM. Upconversion fluorescence was analyzed through 980nmNIR diode laser excited from 2H11/2,4S3/2---4I15/2 fluorescence 525nm and 550nm for the green light, 4F9/2---4I15/2 for the 660nm of the red fluorescence. Excitation process analyzed through analysis of power dependent relationship from the 2H11/2, 4S3/2---4I15/2 and 4F9/2---4I15/2 of the 4f electron transformation were 3-photon process. Preparation of Cubic NaYF4:Yb,Er @ SiO2 core-shell structure through TEOS decomposition. In my experiment, upconversion fluorescence intensity has been enhanced by silica-coated surface nano-particle NaYF4:Yb,Er. And the mechanism of silica-coated surface and its impact on the luminescence mechanism was studied. Through power dependent relationship the experiment confirmed the SiO2-coatedα-NaYF4:Yb,Er luminescence enhancement of the NPs that contributed from the reducing surface defects in pure NPs, increase the luminescence center of surface. Besides, it increased 4f electron 2H11/2 and 4S3/2 energy level amount. At the end of my thesis, my experiment introduced the process to produceα-NaYF4:Yb,Er@SBA-15. First, we use of P123 solute Lyotropic Liquid Crystal as soft-template to synthesis a two-dimensional hexagonal structure (P6mm) of SBA-15 powder, and then nanocasted unorganic salt precursors in the pore of SBA-15. Through the hydrothermal treatment make precursors synthesizedα-NaYF4:Yb,Er in the channel and pore door. However, the P6mm structure of host-material SBA-15 was partly damaged.