Caracterização óptica de estruturas core-shell à base de conversores N aY F4 e nanoestruturas à base de T iO2

Abstract

Sodium yttrium fluoride (N aY F4) is widely recognized for its remarkable physical and chemical properties, which include a high refractive index, low phonon energy, excellent transparency in the ultraviolet and visible regions, and high photochemical stability with minimal light dispersion. These characteristics make N aY F4 an ideal host matrix for co-doping with rare earth ions such as Yb and Er, facilitating ecient upconversion processes that convert infrared radiation into visible light. This study focuses on the detailed optical characterization of N aY F4 : Y b, Er nanoparticles synthesized via the co-precipitation method. The nanoparticles exhibited uniform morphology and controlled nanoscale size. Through comprehensive analytical techniques, such as optical absorption, photoluminescence, and lifetime analysis, an in-depth characterization of the nanostructures was achieved. Results indicated that partially hexagonal samples, obtained under specific synthesis conditions, display intense luminescent emissions, highlighting their eciency in capturing and emitting light energy. Furthermore, samples were coated with T iO2 incorporated with acetylacetonate (acac) and characterized to assess their potential in photocatalytic processes. It was observed that the coating reduced emission intensities due to energy transfer to the semiconductor, suggesting promising applications in photocatalysis for atmospheric pollutant degradation. Thus, it is concluded that uncoated nanoparticles are promising candidates for optical devices, such as lasers for biomedical imaging, due to their high sensitivity and safety, minimizing the risk of photodegradation in biological tissues. Conversely, the coated structures show strong potential for use in environmental applications, particularly in treating atmospheric pollutants through photocatalysis. The findings of this study provide a solid foundation for the development of new materials with advanced applications in photonics and environmental sustainability.