AP Seminar - Recent Advances in X-ray Imaging Scintillators
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Date
27 Jul 2023
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Organiser
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Time
11:00 - 12:00
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Venue
CD620, 6/F, Wing CD, PolyU Map
Speaker
Dr. Omar F. Mohammed
Summary
The high demand for ultralow detection limits of ionizing radiation in medical radiography, high-energy physics, and security screening has driven extensive research on X-ray imaging scintillators. While high-performance scintillators in the current X-ray imaging market made of ceramics that require harsh and costly preparation and engineering conditions, perovskites and their related structures, heavy-atom engineered thermally activated delayed fluorescence (TADF) and copper nanoclusters with their unique optical behaviors and high X-ray absorption cross section are promising competitors if not alternatives. In this talk, I will present the room-temperature synthesis of colloidal perovskite nanosheets with excellent scintillation performance due to efficient energy transfer processes between stacked thin and thick nanosheet. Additionally, I will present the efficient and ultrafast energy transfer strategies between perovskite nanosheets and TADF that successfully produced a reabsorption-free organic X-ray imaging scintillator with a low detection limit of 38.7 nGy/s and outstanding X-ray imaging resolution. Similarly, we found that perovskite related Cu and Ag halides as well as Cu-based halide consisting of Cu4I6 nanostructures showed high performance X-ray imaging. For instance, Cu4I6 nanostructures exhibit very low detection limits of 96.4 and 102.1 nGy/s, which are approximately 55 times lower than the dose required for standard medical diagnosis (5.5 μGy s–1) and extraordinary X-ray imaging resolutions exceeding 30 lp/mm, more than double those of the conventional CsI:Tl and Ga2O2S:Tb scintillators. Finally, the talk also discusses a novel top-filter-bottom sandwich structure scintillator for high-performance dual-energy X-ray imaging within a single exposure. Multi-energy X-ray imaging screens with unprecedented imaging capabilities will be presented and discussed for the first time. This breakthrough research enables clear resolution of different biological tissues based on their corresponding colors and paves the way for the development of new scintillator architectures for dual and multi-energy X-ray imaging with potential applications in medical imaging, industrial monitoring and security screenings.
Keynote Speaker
Dr. Omar F. Mohammed
Professor
Division of Physical Sciences and Engineering
King Abdullah University of Science and Technology
Dr. Mohammed is Professor of Chemistry and Materials Science & Engineering; and the principal investigator of ultrafast laser spectroscopy and four-dimensional (4D) electron imaging laboratory at KAUST. He earned a Ph.D in Physical and Theoretical Chemistry from Humboldt University of Berlin, Germany. Prior to joining KAUST, Dr. Mohammed was a senior research associate at Caltech, where he worked with Professor Zewail, a Nobel laureate, on developing innovative laser spectroscopic and time-resolved electron imaging techniques. During his time at Caltech, Dr. Mohammed made significant contributions to the profound understanding of the dynamics of photo-generated charge carriers in photoactive materials, and pioneered the development of advanced characterization techniques for studying surface and interfacial dynamics on nanometer and femtosecond scales. The current research activities of Dr. Mohammed are focused on the development of highly efficient solar cells, light-emitting diodes and X-ray imaging scintillators with the aid of ultrafast laser spectroscopy, 4D electron imaging and computational materials. Dr. Mohammed has published over 310 articles in international peer-reviewed journals including Science, Nature, Nature Materials, Nature Energy and Nature Photonics, large number of these papers are currently highly cited (> 39 papers). Dr. Mohammed has more than 32,000 citations and 84 h-index. In 2019 and 2020, 2021, 2022 Dr. Mohammed was identified as a Highly Cited Researcher by Web of Science. In January 2020, he joined the Editorial Advisory Board of the Journal of Physical Chemistry Letters. In February, 2021, he was named a Fellow of the Royal Society of Chemistry (FRSC). In March, 1, 2021, Dr. Mohammed was appointed an Associate Editor of ACS Applied Materials & Interfaces. In January 2023, he joined the Editorial Advisory Board of ACS Materials Letters and the Journal of Physical Chemistry A & B & C (American Chemical Society) – some of the leading journals of the field of Physical Chemistry and Materials Science. In July 2023, he was named a Fellow of the Institute of Physics (IOP). Finally, Dr. Mohammed is the recipient of several prestigious awards, including the Distinguished Scholar Award from Arab Fund for Economic and Social Development, Kuwait; Long-term Fellowship, Germany, the Japan Society for the Promotion of Science (JSPS) fellowship, Japan, the State Prize in Basic Sciences, Egypt, Shoman Prize in Photochemistry, Shoman Foundation, Jordan, and Kuwait Prize in Physics, Kuwait Foundation, Kuwait.
