Otimização das propriedades estruturais e ópticas de nanofluoretos (CaF2, SrF2, LaF3, NaYF4 e SrYF5) e aplicações em nanotermomentria óptica

Abstract

In this work, we present the results of several studies involving the synthesis of fluorine-based nanoparticles (NPs) doped with the rare earth ions oErbium (Er3+) and Ytterbium (Yb3+), until the characterization and the use of these doped with Tullium (Tm3+) and Ytterbium (Yb3+) ions as luminescent thermometers in the infrared region. Initially we investigated the influence of some synthesis parameters (temperature and reaction time) on the structural and luminescent properties of LaF3 NPs co-doped with Er3+ and Yb3+ ions under heat treatment at 500 °C. From this initial study, NPs of different fluoride matrices (CaF2, SrF2, LaF3, NaYF4 and SrYF5) co-doped with Er3+ and Yb3+ ions were prepared to investigate the influence of the host matrices, without and undergoing thermal treatments at different temperatures, on the structural and luminescent properties. In addition to inducing modifications in the morphology and phase, the thermal treatment in each matrix allowed the elimination of surface defects, such as unsaturated bonds, surface adsorbed ions/molecules (H2O, CO2), impurities and binders. The success in the synthesis of each matrix was investigated observing the phase, the morphology, the size and the luminescence of the NPs in each temperature of thermal treatment, by means of measurements of X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and luminescence. Luminescent properties were observed through the use of Er3+ and Yb3+ ions, as combined and under laser excitation at 976 nm, these ions present, by energy upconversion , the generation of three main bands in the visible region located at 520, 550 and 660 nm. Finally, we investigated the use of different fluoride matrices (CaF2, SrF2, LaF3, NaYF4 and SrYF5) co-doped with Tm3+ and Yb3+ as luminescent nanothermometers in the infrared region, through the use of the emission intensity ratio in 810 nm, from Tm3+, and in 1000 nm, from Yb3+, both obtained by excitation of the Tm3+ at 690 nm.