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Enzymatic Electrode Design: a Systematic Approach to Enhanced Bioelectrocatalysis Ryan James Lopez

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Enzymatic Electrode Design: a Systematic Approach to Enhanced Bioelectrocatalysis Ryan James Lopez University of New Mexico UNM Digital Repository Nanoscience and Microsystems ETDs Engineering ETDs 6-9-2016 Enzymatic Electrode Design: A Systematic Approach to Enhanced Bioelectrocatalysis Ryan James Lopez Follow this and additional works at: https://digitalrepository.unm.edu/nsms_etds Recommended Citation Lopez, Ryan James. "Enzymatic Electrode Design: A Systematic Approach to Enhanced Bioelectrocatalysis." (2016). https://digitalrepository.unm.edu/nsms_etds/12 This Dissertation is brought to you for free and open access by the Engineering ETDs at UNM Digital Repository. It has been accepted for inclusion in Nanoscience and Microsystems ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Ryan Lopez Candidate Nanoscience and Microsystems Engineering Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: Plamen Atanassov, Ph.D., Chairperson Kateryna Artyushkova, Ph.D. Sofia Babanova, Ph.D. Andrew Shreve, Ph.D. i ENZYMATIC ELECTRODE DESIGN: A SYSTEMATIC APPROACH TO ENHANCED BIOELECTROCATALYSIS by RYAN JAMES LOPEZ B.S., Global Environmental Science, University of Hawaii at Manoa, 2011 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Nanoscience and Microsystems Engineering The University of New Mexico Albuquerque, New Mexico May 2016 ii ©2016, Ryan James Lopez iii DEDICATION This work is dedicated to my grandparents, Pedro and Aracely Lopez, James and Alice Hall, to my aunt Chely Guzman, and to my uncle Michael Hall. iv ACKNOWLEDGMENTS I would like to thank my wife Holly for being a constant while undertaking this endeavor, I never would have reached the end without your (and Rio’s) unwavering support. I also thank my parents Pete and Cindy Lopez for always allowing me to find my own way and providing encouragement as I ping-ponged in different directions throughout childhood and early adult life. Thank you to my older brother Peter and sister Amie for paving the way with their own successes and providing the comedic relief and perspective that is often lacking in a doctoral candidate’s life. I also want to thank my extended family for showing interest in my academic progress and sitting patiently as I try to explain “what exactly it is that I do.” I would like to thank my advisor Plamen Atanassov for giving me the opportunity to undergo cutting edge research in his group and guiding me whenever the roadblocks seemed insurmountable. His mentoring style and the dynamic of doing research within a large research group helped me grow as both an individual and a researcher. I would also like to thank Michael Cooney, for laying the groundwork of my career in research and providing the bridge that brought me to UNM. I thank the other members of my committee, Kateryna Artyushkova, Sofia Babanova, and Andrew Shreve for helping me construct this body of research through their constructive criticisms and expertise. I would also like to thank my fellow grad students and postdocs, for providing me with friendship and healthy competition through their own successes. v Enzymatic Electrode Design: A Systematic Approach to Enhanced Bioelectrocatalysis by Ryan James Lopez B.S., GLOBAL ENVIRONMENTAL SCIENCE, UNIVERSITY OF HAWAII AT MANOA, 2011 Ph.D., NANOSCIENCE AND MICROSYSTEMS ENGINEERING, UNIVERSITY OF NEW MEXICO, 2016 ABSTRACT Although they were first discovered more than a century ago, modern enzymatic electrodes used in enzymatic fuel cells and enzymatic amperometric sensors are a rapidly diversifying field, the applications of which have yet to be fully realized. The design parameters that guide the research and industry are also changing as the fundamental mechanisms at the core of the technology become clearer. One of the key design parameters is concerned with how the enzyme catalyst engages the underlying electrode current collector. This one design consideration has led to considerable branching of the field into different fundamental endeavors such as development of enzyme immobilization techniques, research in to the different interfacial electron transfer mechanisms, electrode material characteristics, enzyme orientation in relation to the electrode, and modifications to the electrode to mediate or promote the charge transfer. This work attempts to look at the overall picture of enzyme engagement of the electrode and the subsequent impact of these different characteristics on the overall performance of the electrode. The goal of this work vi is to develop immobilization, orientation, and electrode modification techniques and to characterize the impact on the electrode. To accomplish this, different bi-functional tethering agents are compared with covalent bonding of the enzyme to the electrode. Two different enzyme orientation techniques are developed, one involving the interaction between an enzyme and its natural substrate and the other involving the interaction of an electric field with the enzyme dipole moment. The internal electron transport chain of a specific group of redox enzymes is explored and then mimicked on the surface of the electrode to aid in the interfacial electron transfer. The mechanisms and techniques elucidated from the previous studies are then applied towards the development of an enhanced enzymatic fuel cell. Finally, the interaction of monochromatic electromagnetic radiation with immobilized metalloporphyrins and the subsequent promotion effect through photo-induced electron transfer is explored. vii Table of Contents DEDICATION .................................................................................................................. IV ACKNOWLEDGMENTS ................................................................................................. V ABSTRACT ...................................................................................................................... VI TABLE OF CONTENTS ............................................................................................... VIII LIST OF FIGURES ....................................................................................................... XIV LIST OF TABLES ........................................................................................................ XXII CHAPTER 1 - INTRODUCTION ............................................................................................. 1 1.1 Fundamentals of the Electrochemical Cell ................................................................. 1 1.1.1 The Electrochemical Basis .......................................................................... 1 1.1.2 Conduction .................................................................................................. 2 1.1.3 Electrode Potentials .................................................................................... 3 1.1.4 Electrode Polarization ................................................................................. 5 1.1.5 Electrocatalysis ........................................................................................... 8 1.2 Enzymatic Fuel Cells ............................................................................................... 10 1.2.1 Bioelectrocatalysis .................................................................................... 12 1.2.2 Mediated Electron Transfer ...................................................................... 14 1.2.3 Direct Electron Transfer ........................................................................... 14 1.2.4 Enzymes for Bioelectrocatalysis ............................................................... 18 1.2.4.1 Cathodic Enzymes ............................................................................ 19 1.2.4.2 Anodic Enzymes ............................................................................... 21 1.2.5 Electrode Material Surface Characteristics ............................................... 23 viii CHAPTER 2 - PROBLEM STATEMENT AND OBJECTIVES .................................................. 24 2.1 Problem Statement ................................................................................................... 24 2.1.1 Scientific Objectives ................................................................................. 24 2.1.2 Engineering Objectives ............................................................................. 25 2.2 Specific Objectives ................................................................................................... 25 2.2.1 Objective 1 - Explore the current state of the art of enzyme immobilization. …………………………………………………………………………....25 2.2.2 Objective 2 - Attempt to improve cathode performance by advantageously orienting bilirubin oxidase using its natural substrate. ......................................... 26 2.2.3 Objective 3 - Explore the possibility of using electric fields to orient PQQ- sGDH during immobilization of the enzyme on an electrode. ............................. 26 2.2.4 Objective 4 - Mimic the internal electron transfer chain of quinohemoproteins on the electrode surface to improve the interfacial electron transfer if PQQ-sGDH anodes. ............................................................................. 26 2.2.5 Objective 5 – Produce an enzymatic fuel cell with enhanced performance utilizing the new enzyme orientation and electrode modification techniques. ..... 27 2.2.6 Objective 6 - Characterize the impact of the photo-promotion effect
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