Physics Of Luminescence Nanomaterials
Woo, Boon Kuan
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Luminescence oxide nanoparticles have tremendous potential in revolutionizing many interesting applications in today's emerging cutting-edge optical technology such as solid state lighting, biomedical labeling, imaging, photodynamic activation and radiation detection. In the early parts of this thesis, we synthesized two types of luminescence oxide nanoparticles, namely zinc oxide and gadolinium oxide in the hope of investigating their optical properties and to gain a deeper understanding in determining the relationship in between the ZnO's surface defect emission and its excitonic emission. We also investigated the luminescence properties of rare-earth dopants such as Ce³⁺ and Eu³⁺ doped into the host gadolinium oxide nanoparticles, in the hope of utilizing them as multi-color phosphor for radiation detection with fast response time, high energy resolution and sensitivity.Fluorescence and phosphorescence or persistent luminescences are two fascinating optical phenomena that have attracted the attention of many optical scientists and material researchers world-wide. The most puzzling of them all, the persistent luminescence phenomena remains a mystery unsolved since the mechanism to explain them remain unclear. Of so many vast research publications available on persistent luminescence materials, little attention has been given to the role of the host phosphor material. In the later parts of this thesis, we studied deeply the roles of luminescence oxide nanoparticles such as ZnO nanoparticles in preparing luminescence material or long afterglow phosphor material. The host phosphor chosen in our study is CaZnGe₂O₆, in which we measured their optical properties under UV and X-ray illuminations. Our extensive investigations cover a wide variety of dopants from rare-earth elements, transition metals and cations from group IIA, IIIA and VA. A whole myriad of interesting optical observations have been uncovered ranging from UVA, visible light and infra-red emission as we seek to uncover the deepest truth about the electrons migration between the host phosphor and the dopants' luminescence centers that have been elusively hidden and guarded by the internal lattice structure of this phosphor material.