(6ch) Single-Molecule Organometallic Catalysis, and Fluorescent Materials Preparation and Application

The chemical industry relies on catalytic processes, which are multibillion-dollar industry and involve heterogeneous and homogeneous catalysts. Combining the advantages of heterogeneous catalyst and homogeneous catalyst, surface organometallic chemistry attaches molecular catalysts to heterogeneous supports, and endows the efficacy and selectivity of homogeneous molecular catalysts with the reusability of heterogeneous catalysts. Interactions between the surface and the supported molecular catalyst add new functionality, and these supported molecular catalysts have become important tools in catalysis technology, particularly for in-flow reactors and electrochemical transformations. It is essential to comprehend activity species, active sites, dynamic order and static order of organometallic catalysts, so we can understand how molecular catalysts work during catalysis reactions and further rational design molecular catalysts.

My research objective is to investigate surface organometallic catalysts through novel fluorogenic reactions in single-molecule (SM) level. Palladium (Pd) organometallic catalysts are chosen as my target system due to their extensive applications in modern organic synthesis such as Suzuki, Negishi, Heck, Sonogashira, and Stille coupling or cross-coupling reactions, etc. Utilizing these reactions, I thus propose three research directions: (1) Single-molecule Pd catalysis of Heck-fluorogenic reactions, (2) Pd and Cu co-catalysis of Liebeskind-Srogl cross-coupling fluorogenic reactions in single molecule level, and (3) Fluorophore tagged alkene living polymerization in single molecule level using Pd catalysts.

My research will combine organic synthesis, catalysis, fluorescent materials and single-molecule imaging techniques. At the University of Connecticut, I developed a series of fluorescent nanomaterials (including polymer doped fluorophore materials and carbon dots with different emission colors) for sensing nitro-explosives. Following that, I synthesized small molecule fluorophores with green, yellow and red emissions at Cornell University. These molecules were used as monomers for living polymerization in both ensemble and single molecule level using Grubbs’ molecular catalysts. Total internal reflection fluorescence (TIRF) microscopy has been extensively applied to investigate single nanoparticle catalysis by Peng Chen et al. and also for single molecular polymerization studies in my research. Now I propose apply these approaches to make significant advancements and to lead new research directions in catalysis field.

Biological structure and dynamics have been extensively explored using single molecule techniques, while abiotic applications are mostly limited to studies of heterogeneous catalysts such as gold and copper nanoparticles, platinum silica core-shell particles, and inorganic nanocrystals. The reactive behavior of individual molecules is rarely observed.

Average properties of billions of molecules are usually measured, however, the catalytic activity of a few percent of molecules in homogeneous catalysis or active sites in heterogeneous catalysis can dominate the outcome of a chemical reaction in ensemble level, and even stoichiometric chemical reaction mechanisms must be determined by indirect methods that potentially miss competing pathways. Study of molecular catalysts by SM fluorescence microscopy promises to improve our understanding of chemical reactions by providing insights into catalyst kinetics and heterogeneity within catalyst populations. Catalytic polymerization is a key process in making synthetic polymers, which are one of the most important materials of our modern world. Living polymerization through molecular catalysts in single-molecule level is helpful to understand the relation between the macroscopic properties and microscopic structure and dynamics, to identify the origin of polymer heterogeneities, and to better polymer properties.

One big challenge in using SM fluorescence imaging to visualize molecular catalysts is the so-called “concentration barrier” for fluorescent species. There is currently no satisfactory way to probe chemical systems with commercial fluorophores, thus design and synthesis of novel fluorophore is highly necessary. Besides the fluorophore, the type of chemical reactions that could be studied by SM fluorescence method is still in infancy or discovery stage. I will design and develop a series of fluorogenic reactions to investigate molecular catalysts through Heck Reactions, Liebeskind-Srogl cross-coupling reactions and living polymerizations in single-molecule level.

My research utilizing new analytical tools that provide a microscopic, molecular-level understanding of molecular catalysis will lead new theories and research dimensions in catalysis. This research approach can ultimately provide a roadmap to develop high efficient catalysts for different applications with great stability and low cost and to obtain (polymeric) materials with well-controlled and improved properties.

Teaching Interests:

One reason why I want to be a faculty and to teach is to share my knowledge and to interact with students. I will teach by connecting the lecture to cutting-edge research and to practice. I will share my learning, industrial and research experiences that closely to chemical engineering field to educate students the attitude, the approaches and the core to learn in each course. I believe that caring for students and engaging them as collaborative authors of classes can improve their performance.

I have had extraordinary teachers throughout my education, especially in U.S. as a graduate student. During these classes, I was always wondering, if I were a teacher, which kind of methods could be taken and applied in my classroom. At the University of Connecticut, I was a teaching assistant in two courses (Transfer Operations and Chemical Engineering Analysis), to grade the students’ homework and exams, to explain the problem solution for their homework, and to answer the students’ questions. I also tutored several undergraduates for lab research, and even guided one undergraduate to present his scientific research under my supervision in AIChE national conference. I assigned research work to them, encouraged them to read scientific papers, let them express and try their research ideas in the lab, etc. Two undergraduates got co-authored scientific papers with me. I found these experiences enjoyable and gratifying.

For an engineering class, it is especially important and necessary to keep lessons relevant and to link the scientific concept to the outside world. I will design course projects, which will be either closed related to real life examples, my research and industrial experiences or projects. Some course projects are delicately decomposed and prototyped from my ongoing research projects. My research will be integrated into my teaching, because this could provide a vision of relationship between the knowledge imparted in courses and practical problems, update students the latest advance in the field and cultivate their interest in pursuing advanced study. These could help students understand that they work to solve problems in “real world”, not spending their time on something useless.

If I teach, various teaching methods could be combined and applied, such as projectors for powerpoint presentations with handwriting on blackboard; images, and videos with classic textbooks. Students have different background and learning styles. Teaching style and speed should be adjusted to the needs of students. A variety of methods could help examine and know the speed and progress of the class, such as quizzes, homework, surveys, in-class discussions, projects, writing, presentations, etc.

I would like to develop three courses, one introductory course – Introduction to Chemical Engineering, one advanced course for senior undergraduates – Separation Processes, and the third one for graduates – Chemical Kinetics.