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Lijia Liu

Education

B.Sc. University of Science and Technology of China
Ph.D. Western University

RESEARCH

My research group studies the fundamental properties of advanced light-emitting materials. These materials are commonly used in optoelectronics, bioimaging, and sensing. We use modern spectroscopy techniques, such as steady-state photoluminescence, time-resolved photoluminescence, absorption spectroscopy to analyze the luminescence mechanism of the materials. The information obtained provides a guideline toward designing new synthesis strategies in order to precisely control the luminescence property of the material and ultimately achieve performance enhancement in practical applications. Synchrotron-based spectroscopy is another major tool which will be regularly utilized to gain in-depth information on the correlation between the observed luminescence and the electronic structure of the material. We also work on developing new synchrotron radiation-based spectroscopy techniques for their use in material analysis. Techniques based on X-ray absorption fine structure (XAFS) and X-ray excited optical luminescence (XEOL) will be advanced in both time-domain (i.e., in situ study) and space domain (i.e., nanoscale imaging).

Current ongoing projects are:

Lead halide perovskite. Lead halide perovskite ABX₃ has recently become an attractive material in research fields like solar cells, light-emitting diodes, optical detectors, and even catalysis. It contains a large family of compounds of similar structure: A monovalent cation (Cs⁺, or organic CH₃NH₃⁺), a divalent Pb²⁺, and three halide ions (Cl^-, Br^-, or I^-). The color of the luminescence can also be tuned throughout the visible wavelength by composition tuning. Research along this direction involves (1) synthesis of ABX3 nanocrystals of stable, bright and color-tunable luminescence, and (2) spectroscopy characterization using PL, XAFS and XEOL. We aim to discover the key factors that control the luminescence properties of ABX₃ nanocrystals and to develop synthesis strategies of ABX₃ for practical applications.

Calcium hydroxyapatite. Calcium hydroxyapatite (HAp) is the main component in human calcified tissue (i.e. bones and teeth). Synthetic HAp plays an extremely important role in tissue engineering, such as bioimplant and coating. Other than HAp, the calcium orthophosphate family contains several stable species of different chemical formula, which either co-exists with HAp, or transforms to HAp reversibly under controlled environment. We have found that different calcium phosphate species have their unique contributions to the bioactivity of an implant coating. Research along this direction aims to study (1) the crystallization process of synthetic HAp and its interaction with biomolecules, (2) the structure transformation among calcium orthophosphate species under various conditions, (3) dissolution of synthetic HAp in simulated body fluid. Our approach is to develop a strategy which is able to track the evolvement of structure and composition of calcium phosphate implant by monitoring its luminescence.

Collaborative projects. We are collaborating with several research groups in China and Canada who are specialising in material synthesis. We use these materials as test candidates to develop novel in situ, in operando spectroscopy/microscopy techniques at synchrotron research facilities in Canada, Taiwan, and US.

Students in the group will have opportunity to develop skills in both material synthesis and spectroscopy analysis. Training includes wet-chemical synthesis (mostly inorganic), standard characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence, UV-visible spectroscopy. Students will also visit synchrotron radiation research facilities to perform hands-on experiments. The three mostly visited facilities are the Canadian Light Source (CLS, Canada), Advanced Photon Source (APS, US), and Taiwan Photon Source (TPS, Taiwan).

TEACHING

• 9546 - Optical Spectroscopy of Solid-State Materials

SELECTED PUBLICATIONS

• Jinjin Ma, Qianting Yao, John A. McLeod, Lo-Yueh Chang, Chih-Wen Pao, Jiatang Chen, Tsun-Kong Sham and Lijia Liu. Investigating the Luminescence Mechanism of Mn-doped CsPb(Br/Cl)₃Nanocrystals. Nanoscale 11 (2019) 6182-6191.
• Meihua Wu, Jia Zhao, Daniel M. Chevier, Peng Zhang, and Lijia Liu. Luminescent Au(I)-Thiolate Complexes through Aggregation-Induced Emission: The Effect of pH during and Post Synthesis. J. Phys. Chem. C 123 (2019) 6101-6107.
• Lijia Liu, Jitao Li, John A. McLeod. Influence of Eu-substitution on Luminescent CH₃NH₃PbBr₃Quantum Dots. Nanoscale 10 (2018) 11452-11459.
• Linju Yang, Jeremy Bourque, John A. McLeod, Pengfei Shen, Kim Baines, and Lijia Liu Beyond Oxidation States: Distinguishing Chemical States of Gallium in Compounds with Multiple Gallium Centers. Chem. 56 (2017) 2985-2991.
• Weidong Xu, John A. McLeod, Yingguo Yang, Yimeng Wang, Zhongwei Wu, Sai Bai, Zhongcheng Yuan, Tao Song, Yusheng Wang, Junjie Si, Rongbin Wang, Xingyu Gao, Xinping Zhang, Lijia Liu and Baoquan Sun Iodomethane-Mediated Organometal Halide Perovskite with Record Photoluminescence Lifetime, ACS Appl. Mater. Interfaces 8 (2016) 23181-23189.