Characterization of Light-Emitting Inorganic Nanomaterials using Synchrotron Radiation Spectroscopy

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Light-emitting materials have a wide range of applications such as optoelectronics, optical detection, biomedical imaging, and sensing. Materials with desired optical properties are being synthesized through morphology control, composition tuning, and surface modifications. Finding the connection between structure and luminescence mechanism is crucial for improving the optical properties and developing novel materials. Synchrotron radiation spectroscopy is a fast-advancing technology that can provide key information that cannot be obtained through laboratory techniques. In my proposed research program, I will develop synchrotron-based characterization techniques to gain a thorough understanding of the luminescence mechanism in existing and newly synthesized inorganic light-emitting materials. I will use X-ray absorption fine structure (XAFS) and X-ray excited optical luminescence (XEOL) as my primary methods. My research program focuses on three themes, and each featuring one type of material. Theme 1. I will investigate the luminescence mechanism of lead halide perovskite (LHP) and develop controlled synthesis of LHP with desired optical properties. I will apply XAFS-XEOL to analyze the role of doping ions on the luminescence of LHP. By monitoring the phase transformation in a ternary CsxPbyBrz compound using nanoprobe XEOL and in situ XAFS-XEOL, I will develop strategies to tune the phase of CsxPbyBrz to achieve higher luminescence. Theme 2. I will investigate the role of doping on the composition and luminescence of bioactive calcium phosphate (CaP). I will study the correlation between luminescence and the structure of doped CaP, and develop a characterization technique to track composition evolution of CaP species using their optical properties. Theme 3. I will perform a systematic study on gold nanoclusters (AuNCs) using XAFS-XEOL analysis to gain a deeper understanding on how the luminescence of AuNCs are affected by metal-ligand, ligand-ligand, nanocluster-cellular interactions. I will design and perform in situ XAFS-XEOL study to track the formation of Au-based bimetallic alloy NCs. Bright light-emitting AuNCs will be designed based on fundamental knowledge obtained through these, and explored as new biomedical sensors and imaging agents. There has been significant investment worldwide in building new synchrotron facilities and in updating older ones. The synchrotron spectroscopy user community has greatly expanded, and the number of potential users is drastically increasing. Using the materials mentioned above as research platforms, I will develop synchrotron techniques with the aim of making them accessible to a wider community. I will pay particular attention to opportunities for presenting XAFS+XEOL as a quantitative materials characterization tool that may be used for product development by industry in the fields of optoelectronics, petrochemicals, alternative energy, green mining, or green chemistry.