Master of Science
Tremendous interest in increasing the control over surface properties has led to high demand for new efficient methods for chemical surface modifications. In this work, several approaches toward surface functionalization are explored, and modified surfaces are subsequently characterized using uniquely suited spectroscopic techniques. In the first part of this thesis, strain-promoted alkyne-azide cycloaddition (SPAAC) reactions are investigated for their potential to precisely tune the surface properties of gold substrates at the monolayer level. The utility of SPAAC reactions in preparing biorecognition interfaces for cell adhesion is then examined. Polarization modulation infrared reflection-absorption spectroscopy is used to characterize adsorbed monolayers and probe the progress of surface SPAAC reactions. In the second section of this thesis, novel plasmonically active metallic substrates are fabricated. These substrates are used to catalyze the plasmon-mediated grafting of diazonium salts onto gold nanoparticle surfaces and are also employed as platforms for surface-enhanced Raman spectroscopy.
Summary for Lay Audience
The ability to tune the surface properties of materials through chemical modifications is an essential field of study that plays an indispensable role in many applications ranging from nanoelectronics to bioengineering. Fine control over surface chemistry is vital, as the properties and interactions of surfaces on the microscale directly dictate the nature and function of material surface interfaces at the macroscopic level. Thus, there is considerable demand for new and improved surface modification techniques that allow for precise tailoring of material surfaces. Currently, there exists a host of methodologies to manipulate surface chemistry. In this thesis, select surface modification strategies of interest are investigated in detail.
One reaction that has been examined for the development of chemically modified surfaces is a “click” reaction called the strain-promoted alkyne-azide cycloaddition (SPAAC) reaction. Click chemistry, a class of reactions characterized by rapid kinetics, mild reaction conditions, high selectivity, and high efficiency, is well established as a means of surface modification. One of the aims of this research is to employ a variety of SPAAC reactions designed to specifically alter the surface properties of metal substrates, and to explore the applicability of SPAAC reactions in the preparation of surfaces for biochemical applications. Polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), a specialized type of infrared spectroscopy developed for the study of monolayers on reflective surfaces, is used to detect and characterize the modified substrates.
Localized surface plasmon resonance (LSPR) occurs when a collective oscillation of free electrons in a metallic nanoparticle (NP) is excited by electromagnetic radiation, often in the range of visible light. As the LSPR decays, high energy electrons are generated at the NP surface. These electrons can participate in and contribute to chemical reactions between organic species on the NP surface. Activation of chemical reactions via plasmon-driven pathways is a relatively new concept that remains largely unexplored. The second portion of this thesis focuses on designing and creating LSPR-supporting substrates and using these substrates to activate chemical reactions via plasmonic catalysis. The substrates are then used to perform surface-enhanced Raman spectroscopy measurements for surface characterization.
Legge, Sydney, "Chemical Reactions at Metal Surfaces: Functionalization Strategies and Spectroscopic Characterization" (2020). Electronic Thesis and Dissertation Repository. 7373.