University of Kentucky UKnowledge Theses and Dissertations--Chemistry Chemistry 2018 CARBON QUANTUM DOTS: BRIDGING THE GAP BETWEEN CHEMICAL STRUCTURE AND MATERIAL PROPERTIES Timothy J. Pillar-Little Jr. University of Kentucky, [email protected] Author ORCID Identifier: https://orcid.org/0000-0001-6365-9417 Digital Object Identifier: https://doi.org/10.13023/ETD.2018.108 Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Pillar-Little, Timothy J. Jr., "CARBON QUANTUM DOTS: BRIDGING THE GAP BETWEEN CHEMICAL STRUCTURE AND MATERIAL PROPERTIES" (2018). Theses and Dissertations--Chemistry. 94. https://uknowledge.uky.edu/chemistry_etds/94 This Doctoral Dissertation is brought to you for free and open access by the Chemistry at UKnowledge. It has been accepted for inclusion in Theses and Dissertations--Chemistry by an authorized administrator of UKnowledge. For more information, please contact [email protected]. STUDENT AGREEMENT: I represent that my thesis or dissertation and abstract are my original work. Proper attribution has been given to all outside sources. I understand that I am solely responsible for obtaining any needed copyright permissions. I have obtained needed written permission statement(s) from the owner(s) of each third-party copyrighted matter to be included in my work, allowing electronic distribution (if such use is not permitted by the fair use doctrine) which will be submitted to UKnowledge as Additional File. I hereby grant to The University of Kentucky and its agents the irrevocable, non-exclusive, and royalty-free license to archive and make accessible my work in whole or in part in all forms of media, now or hereafter known. I agree that the document mentioned above may be made available immediately for worldwide access unless an embargo applies. I retain all other ownership rights to the copyright of my work. I also retain the right to use in future works (such as articles or books) all or part of my work. I understand that I am free to register the copyright to my work. REVIEW, APPROVAL AND ACCEPTANCE The document mentioned above has been reviewed and accepted by the student’s advisor, on behalf of the advisory committee, and by the Director of Graduate Studies (DGS), on behalf of the program; we verify that this is the final, approved version of the student’s thesis including all changes required by the advisory committee. The undersigned agree to abide by the statements above. Timothy J. Pillar-Little Jr., Student Dr. Doo Young Kim, Major Professor Dr. Mark A. Lovell, Director of Graduate Studies CARBON QUANTUM DOTS: BRIDGING THE GAP BETWEEN CHEMICAL STRUCTURE AND MATERIAL PROPERTIES DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Arts and Sciences at the University of Kentucky By Timothy James Pillar-Little Jr. Lexington, Kentucky Director: Dr. Doo Young Kim, Professor of Chemistry Lexington, Kentucky 2017 Copyright © Timothy James Pillar-Little Jr. 2017 ABSTRACT OF DISSERTATION CARBON QUANTUM DOTS: BRIDGING THE GAP BETWEEN CHEMICAL STRUCTURE AND MATERIAL PROPERTIES Carbon quantum dots (CQDs) are the latest generation of carbon nanomaterials in applications where fullerenes, carbon nanotubes, and graphene are abundantly used. With several attractive properties such as tunable optical property, edge-functionalization, and defect-rich chemical structure, CQDs have the potential to revolutionize optoelectronics, electro- and photocatalysis, and biomedical applications. Chemical modifications through the addition of heteroatoms, chemical reduction, and surface passivation are found to alter the band gap, spectral position, and emission pathways of CQDs. Despite extensive studies, fundamental understanding of structure-property relationship remains unclear due to the inhomogeneity in chemical structure and a complex emission mechanism for CQDs. This dissertation outlines a series of works that investigate the structure-property relationship of CQDs and its impact in a variety of applications. First, this relationship was explored by modifying specific chemical functionalities of CQDs and relating them to differences observed in optical, catalytic, and pharmacological performance. While a number of scientific articles reported that top-down or bottom-up synthesized CQDs yielded similar properties, the results herein present dissimilar chemical structures as well as photoluminescent and metal sensing properties. Second, the role of nitrogen heteroatoms in top-down synthesized CQD was studied. The effect of nitrogen atoms on spectral position and fluorescence quantum yield was considerably studied in past reports; however, thorough investigation to differentiate various nitrogen related chemical states was rarely reported. By finely tuning both the quantity of nitrogen doping and the distribution of nitrogen-related chemical states, we found that primary amine and pyridine induce a red- shift in emission while pyrrolic and graphitic nitrogen produced a blue-shift in emission. The investigation of nitrogen chemical states was extended to bottom-up synthesized CQDs with similar results. Finally, top-down, bottom-up, nitrogen-doped and chemically reduced CQDs were separately tested for their ability to act as photodynamic anti-cancer agents. This series of experiments uncovered the distribution of reactive oxygen species produced during light exposure which elucidated the photodynamic mechanisms of cancer cytotoxicity. The results presented in this dissertation provide key insight into engineering finely-tailored CQDs as the ideal nanomaterial for a broad range of applications. KEYWORDS: Materials Chemistry, Carbon Nanomaterials, Structure-Property Relationship, Optoelectronics, Electrocatalysis, Biophotonics Timothy James Pillar-Little Jr. 3/9/2018 CARBON QUANTUM DOTS: BRIDGING THE GAP BETWEEN CHEMICAL STRUCTURE AND MATERIAL PROPERTIES By Timothy James Pillar-Little Jr. Dr. Doo Young Kim ______________________________ Director of Dissertation Dr. Mark A. Lovell ______________________________ Director of Graduate Studies 3/9/2018 ______________________________ Date I dedicate this work to the people who supported me in this dream of mine: my parents, Timothy Little Sr. and Wendy Little; my wife, Elizabeth Pillar-Little; and my many friends. Thank you everyone for your words of encouragement, your advice, and your love. ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Doo Young Kim, for telling me to keep pushing forward throughout my Ph. D. studies – even when forward is out of my comfort zone. Though he is always busy working to get funding for our research and unable to spend time doing hands-on advising; I am grateful for his kindness and patience towards me and my work. Even if he couldn’t make much time during the week to talk about data, he would make the time at his own personal expense. I am also thankful of the skills I have learned both inside and outside of the lab. There will always be a special place in my heart for CP-38/40 at the University of Kentucky. I feel lucky to have such a kind advisor who allows me to do the work I feel is important and worth pursuing. I am proud of this work and I hope that you can find pride in it as well. To my committee members: Drs. Yang-Tse Cheng, Beth Guiton, and Dong-Sheng Yang; thank you for serving on my doctoral committee all these years and asking me the tough questions. If I can be half the scientist in my career as you all are in yours; I will be doing pretty well in life. I want to thank my labmates (both past and present): Rosemary Calabro, Dr. Yiyang Liu, Allen Reed, Josiah Roberts, Namal Wanninayake, Yan Zhang, and Sin Hea Yeom. I will always appreciate the many talks and discussions we have had in group meetings and our time working together. We have seen each other grow into the people we are now and will become. I could not ask for better co-workers during my time here who just happen to be some of my best friends. You are all great scientists and I wish you the best in life. I want to thank Art Sebesta for providing electronics support in our lab. Your work is scarcely recognized and you are a true master of your craft. Thank you for your assistance, your advice, and reminding me what day of the week it is. Aside from the wonderful people I have worked with at the University of Kentucky, I must make a special acknowledgement to my parents: Timothy Little Sr. and Wendy Little. You two are the foundation of my passion for this work and are, without a doubt, iii my two greatest role models in my life. Dad, you always set out to meet or exceed your goals no matter the cost or uphill battle you face. I have learned so much from you over all these years and you have taught me the skills that have helped me be the person I am today. Mom, you are absolutely the strongest person I know with your determination and fighting spirit. Thank you for being the rock I cling to in the storm. Your words of encouragement, those long phone calls listening to my complaints, and those big hugs I get when we see each other have helped me to get to this point. I know that I will go very far in life if I am one-tenth the person you are daily. Thank you both for everything: your laughter, your love, and your example. I am proud to have you two as parents and I love you both very much. I would also like to acknowledge my wife, Dr. Elizabeth Pillar-Little, for so much that I can’t scratch the surface of what positive impact you have in my life. To put it simply (if there is such a thing), I am thankful that you are my best friend, my biggest supporter and ever-present lifeline when I get lost.
Details
-
File Typepdf
-
Upload Time-
-
Content LanguagesEnglish
-
Upload UserAnonymous/Not logged-in
-
File Pages205 Page
-
File Size-