희토류 이온이 첨가된 CaTiO3 페로브스카이트 기반 다기능성 나노복합체 개발 및 광학적 특성

Abstract

Recently, rare-earth doped fluorescent materials have been attracting a lot of attention because of their high quantum yield, sharp emission bandwidth, photostability, low toxicity, and tunable optical properties by varying lanthanide dopants in the host matrix. Calcium titanate (CaTiO3) has been widely studied as a host material because of its good chemical and thermal stability, bio-ceramic with excellent biocompatibility, and low phonon energy among oxide materials. In this dissertation, we investigated the structural and optical properties of Eu3+ doped CaTiO3 (CaTiO3:Eu3+) perovskite phosphor powers obtained via the high-energy ball-milling (HEBM) method, and we examined the influence of ball-milling time, Eu3+ concentration, and annealing temperature on these properties. The highest photoluminescence (PL) emission intensity was observed at an annealing temperature of 1200 °C and a Eu3+ ion concentration of 6 mol%. The PL spectra showed strong characteristic peaks at 614 nm by the 5D0 → 7F2 electric dipole transition of Eu3+ at an excitation wavelength of 398 nm. These results suggest that the PL emission intensity of CaTiO3:Eu3+ perovskite phosphor powders can be controlled by Eu3+ concentration and annealing temperature. To develop of SERS-fluorescence bimodal nanocomposites, we synthesized Au-decorated CaTiO3:Eu3+ nanocomposites (CaTiO3:Eu3+@Au NCs). The SERS and PL emission intensities of CaTiO3:Eu3+@Au NCs were enhanced compared to those of CaTiO3:Eu3+ powders. The highest SERS and PL emission intensities were observed at an Au concentration of 0.08 mol/L. In recent years, rare-earth doped up-conversion nanoparticles (UC NPs) have been attracting attention because NIR excitation light causes minimal photo damage, induces practically no auto-fluorescence background, and can penetrate biological tissues to a much greater extent. The CaTiO3:Yb3+,Er3+ NPs were synthesized by HEBM, and their crystal structure and surface morphology were investigated by XRD and FE-SEM. The PL spectra of CaTiO3:Yb3+,Er3+ NPs under the excitation of a 980 nm diode laser consist of two characteristic emission bands from 4F9/2 → 4I15/2 (red) and 4S3/2, 2H11/2 → 4I15/2 (green) transitions. For biomedical applications, the surface of CaTiO3:Yb3+,Er3+ NPs was modified with SiO2, and cytotoxicity was examined. The MDA-MB-231 cell viability assay showed higher than 80 % cell viability in the presence of 5, 10, 20, and 40 μg/mL NPs. This study showed that the CaTiO3:Yb3+,Er3+@SiO2 NPs have the potential to be used in biomedical applications.