SYNTHESIS AND INVESTIGATION OF OPTICAL PROPERTIES AND NEUTRON SENSITIVITIES OF BORATE COMPOUNDS CONTAINING BORON-10 ISOTOPE

Date

2024-5-09

Author

HIZAL, ÖZDE CEREN

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This dissertation presents a comprehensive study on the synthesis, structural characterization, and multifunctionality of pure and rare-earth doped alkaline earth tetraborates, specifically focusing on calcium, magnesium, and strontium tetraborates. The synthesis and multifaceted applications of alkaline-earth tetraborates represent a significant advancement, particularly in developing multifunctional materials. These compounds, consisting of calcium, magnesium, and strontium, have gained attention due to their structural, optical, and neutron-capturing properties, which were further enhanced by doping with rare-earth elements. The versatility of these materials is evident in their wide range of applications, from photodynamic therapy and biomedical imaging to sensing and energy conversion. This study investigated the synthesis of pure and rare-earth doped alkaline-earth tetraborates using three distinct methods: solution combustion, combustion, and solid-state synthesis. Each method brought its own advantages in terms of particle size, purity, and crystallinity, which in turn affect the material's properties. Structural characterization through X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed notable changes in unit cell volumes correlating with the dopant and host sizes, indicating successful incorporation of the dopants into the host lattice. Optical properties were thoroughly investigated, showing that undoped hosts and those doped only with terbium (Tb) or erbium (Er) did not exhibit up-conversion emissions. However, co-doping with ytterbium (Yb) resulted in very pronounced emissions via cooperative energy transfer. This highlighted the role of dopants in tailoring the optical responses of these materials. In addition, the results also showed the strong role played by ytterbium as a sensitizer in the up-conversion process. The incorporation of Boron-10 isotope further expanded the utility of these tetraborates, enhancing their boron neutron capturing capabilities under thermal neutron irradiation. In this study, the tetraborate structures of alkaline earth elements were specifically chosen due to their high boron densities. This property is particularly promising for applications in cancer therapy, where targeted neutron capture can be used to destroy malignant cells without harming surrounding healthy tissue. The study also explored the cytotoxicity of these particles, with calcium and magnesium tetraborates demonstrating non-toxicity, making them suitable for biomedical applications. The non-toxic nature of these materials, combined with their multifunctionality, positions them as ideal candidates for a variety of uses, including imaging, and as agents in photodynamic therapy. In conclusion, novelty of this study is the synthesis and investigation of the neutron sensitivity and upconversion behaviors of the Yb3+/Tb3+ co-doped Ca, Mg, and Sr tetraborates for the first time. It is not only contributed to the understanding of alkaline-earth tetraborates but also paved the way for the development and usage in interdisciplinary areas through the comprehensive investigation of their structural, optical, and toxic properties.

Subject Keywords

Alkaline earth tetraborates, upconversion emission, neutron sensitivity, Ytterbium, Terbium

URI

https://hdl.handle.net/11511/109866

Collections

Graduate School of Natural and Applied Sciences, Thesis