Enhancing Room Temperature Phosphorescence from Organic Molecules by Internal Heavy Atom Effect and External Agents by Jaehun Jung A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Macromolecular Science and Engineering) in The University of Michigan 2018 Doctoral Committee: Professor Jinsang Kim, Chair Professor Theodore Goodson III Professor L. Jay Guo Professor John Kieffer @Jaehun Jung [email protected] ORCID ID: 0000-0002-5859-3027 2018 Acknowledgement First, I would like to thank Professor Kim. When I was visiting scholar, he gave me not only insightful advice but also passion on research. After I joined in his group, he always encouraged me and suggested to learn knowledge of a variety of research fields which is helpful to develop my research careers. Although I was trouble to my health during Ph.D. study, I could finish the study thanks for him. I really can’t thank enough for his professional and personal supports. Secondly I must thank my friend and colleague, Dr Minsang Kwon. As senior and Post.doc, he taught me organic chemistry and chemical synthesis. It was the happiest moment in my Ph.D. that we studies and taught each other about photochemistry. Without him, I cannot imagine that I am graduated. Thanks Minsang. I would like to express my gratitude to my collaborators, Jialiu Ma, Dr. Daniel Hashem, Dr. Huan Wang and Dr Johannes Gierschner. During the collaboration, I got research achievements as well as the opportunities to work with them could expand research into other knowledge arenas. Of course, I thank the members of our research group. In particular, Dr Dongwook Lee, Dr. Kyeongwoon Chung, Dr Sungbaek Seo and Deokwon Seo helped me to adapt my life to a new school. I thank Dr. David Bilby, Dr Apoorv Shanker for their contribution. I learned great ownership from Dr. David Bilby and Dr Apoorv Shanker and thank their sacrifice of time for lab maintenance. I own thanks to Da Seul Yang and JoonKoo Kang. Also I thank other group members and visiting members for kind assistance. I would like to add a word of gratitude to my family. I am most grateful to my parents and my sister for supports and encouragement. My wife, Anna Jo, sacrificed a lot of times and just supported me to spend much time for experiments. I Know she felt lonely in Ann Arbor life. I feel sorry and thank her sacrifice. I could finish my Ph.D due to her support and patience. Thanks Anna. ii Table of Contents Acknowledgements .................................................................................................................... ii List of Figures ............................................................................................................................ v List of Tables ............................................................................................................................. ix List of Schemes .......................................................................................................................... x Abstract ..................................................................................................................................... xi Chapter 1: Introduction and background ................................................................................... 1 1.1 Phosphorescence and fluorescence ...................................................................... 1 1.1.1 Triplet state .......................................................................................... 1 1.1.2 Photoluminescence pathways.............................................................. 2 1.1.3 Phosphorescence quantum yield, lifetime and kinetic constants ........ 6 1.2 Oxygen quenching ............................................................................................... 7 1.2.1 Quantum chemistry of oxygen ............................................................ 7 1.2.2 Energy transfer mechanism ................................................................. 8 1.2.3 Singlet oxygen generation and phosphorescence quenching ............ 9 1.2.4 Applications of phosphorescent molecules : bio-imaging ................ 10 1.2.5 Applications of phosphorescent molecules : oxygen Indicator......... 12 1.3 Rate of intersystem crossing from singlet to triplet ........................................... 13 1.3.1 El-Sayed’s rules ................................................................................. 14 1.3.2 Heavy atom effect ............................................................................. 16 1.3.3 Metal-to-ligand charge transfer (MLCT) ........................................ 17 1.3.4 The energy difference between singlet and triplet state .................... 18 1.4 The theoretical explanation of non-radiative decay via vibration between T1 to S0 ........................................................................................................................ 19 1.4.1 The “Loose Bolt” effect : The effect of molecular rigidity on non- radiative decay by intramolecular vibration ...................................... 20 1.4.2 Non-radiative decay by intramolecular vibration, intersystem crossing from between T1 to S0 ......................................................... 21 1.4.3 Non-radiative decay by intermolecular vibration from T1 to S0 ....... 25 1.5 Recent progress about metal-free organic phosphors ........................................ 27 1.5.1 Polymer as host and metal-free phosphors as guest system for room temperature phosphorescence ........................................................... 28 1.5.2 Persistent phosphorescence in organic crystal .................................. 31 1.6 Conclusion ......................................................................................................... 33 1.7 References .......................................................................................................... 35 Chapter 2: Molecular design for fluorene based metal-free phosphors in amorphous polymer matrices .................................................................................................................................... 38 2.1 Introduction........................................................................................................ 39 2.2 Experiments ....................................................................................................... 41 2.2.1 General methods................................................................................ 41 2.2.2 Synthesis of molecules ...................................................................... 42 2.3 Results and discussion ....................................................................................... 49 2.3.1 Effect of structural rigidity on phosphorescence .............................. 49 iii 2.3.2 Effect of modifiying halide and functional group on phosphorescence radiative decay(kp) ............................................................................ 51 2.3.3 The Correlation between the molecular structure and type of polymer relaxation to quench phosphorescence .............................................. 57 2.3.4 Conclusion......................................................................................... 60 2.3.5 References ......................................................................................... 61 Chapter 3: Optimization of coupled plasmonic effects for viable phosphorescence of metal- free phosphor ........................................................................................................................... 65 3.1 Introduction........................................................................................................ 66 3.2 Background knowledge ..................................................................................... 67 3.2.1 Surface Plasmons .............................................................................. 67 3.2.2 Interaction of fluorophores with Surface plasmons .......................... 69 3.3 Experiments ....................................................................................................... 70 3.3.1 Synthesis of AuNP (~55 nm) and AgNP (~7 and ~70 nm) ............. 70 3.3.2 Fabrication of plasmon-mediated Br6A/Br6 crystals ....................... 71 3.3.3 Characterization techniques .............................................................. 72 3.4 Results and discussion ....................................................................................... 72 3.5 Conclusion ......................................................................................................... 85 3.6 References .......................................................................................................... 86 Chapter 4: Metal organic phosphors frameworks .................................................................... 90 4.1 Introduction........................................................................................................ 91 4.2 Experiments ....................................................................................................... 91 4.2.1 General methods................................................................................ 91 4.2.2 Synthesis of molecules and fabrication of MOFs and MOFs-PS composite .......................................................................................... 92 4.3 Results and discussion ....................................................................................... 94 4.3.1