| Author: | Lu, Lu |
| Title: | Native point defect tuned lanthanide persistent luminescence materials for theragnostic and photocatalysis |
| Advisors: | Huang, Bolong (ABCT) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Laser materials Rare earths Imaging systems in medicine Photocatalysis Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Biology and Chemical Technology |
| Pages: | 198 pages : color illustrations |
| Language: | English |
| Abstract: | Exploring long afterglow imaging agents that can be excited under lower radiation energy or pre-excited in vitro before injection has been one of the criticalities for avoiding high-dose radiation caused tissue damage in image-guided surgery and radiographic diagnose. To screen out the suitable electron trapping states for near-infrared (NIR) afterglow-based imaging, we have investigated the electronic properties of native point defects in LaAlO3 (LAO) band gap via DFT + Hubbard U based computational method within CASTEP codes. Biomedical imaging in higher detecting window (NIR-II/III) can afford deeper tissue penetrability due to declined photon scattering/absorption and auto-fluorescence interference. Then we figure out the possible defect-state based electron transition paths for emission wavelength modulation to resolve the authentic structures of target organs/tissues with improved imaging depth and resolution. Due to the additional trap states offered by Cr3+dopants for the storage of electrons, the luminescent intensity and decay time can be remarkably enhanced, and the synergy between Cr3+-dopant states and LAO-defect states can further tune the emission wavelength from red light (Cr3+ states as recombination center) to NIR-II/III (native defect states as recombination center) via energy transfer process. Our work offers a reliable theoretical reference on the innovation of super-long lifetime PL contrast agents for in-vivo deep tissue NIR biomedical imaging with in-vitro pre-excitation. Compared to NIR laser, high-energy X-rays have much stronger penetrability in animal tissues, so it is more powerful excitation source for probing the inner structure of target organs under nondestructive situation with a nearly unlimited penetration depth in human bodies. So, X-rays exhibit great potential for the imaging-based diagnosis and photodynamic therapy (PDT) toward deep-site tumor. To further improve the optical performance for existing scintillation materials and give new thoughts for future scintillators design, firstly we have a deep study on scintillation mechanism. Then we conducted a comprehensive data analysis focusing on both the defect and dopant states of perovskite-structured LAO scintillator. And we further made a deep analysis on these results to find out potential electron transition levels involved in visible emissions that matching the photoactive window of popular PDT photosensitizers. In recent decades, due to the energy crisis caused by the contest for fossil fuels, the continuable photocatalytic H2 production has attracted intense research interests. The typical photocatalytic material (PCM) TiO2, it can be activated by sunlight and give out H2 by photocatalytic water splitting, enabling the conversion from solar energy to hydrogen energy source. In this work, for shifting the photocatalytic window to visible/NIR range, we have applied a systematic investigation on the electronic properties of various defect types in anatase TiO2 to predict their performance for water splitting under sunlight. For the modulation of persistent luminescence materials (PLMs), both defects- and dopants- modulations are applied for prolonging the afterglow lifetime and the tuning of emission wavelength. These systematic simulation data and the reaction mechanisms built in this work will provide a reliable theoretical reference to guide the design of novel PLMs-based overnight photocatalytic platform for H2 production. |
| Rights: | All rights reserved |
| Access: | open access |
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