Understanding the characteristics of interfaces between materials and solvent media such as structure, chemistry, and charge remains crucial to determining the properties and performance of numerous systems and technologies. This thesis focuses specifically on characterizing the interactions of water at oxide interfaces. A large collection of questions remains unanswered about these phenomena despite decades of study surrounding these particular systems. This is due to the undeniable complexity of the interfacial environment and the multiscale levels of interactions that occur within its proximity. Furthermore, the chemistries that occur in this region dictate pathways of adsorption, reactivity, and transport in the fundamental operation of various environmental and technological processes. As such, developing a deeper understanding of molecular and mesoscale phenomena at oxide surfaces that arise from the solvent environment remains essential for driving the direction of research for applications related to the field.This thesis focuses on the development and application of second order nonlinear spectroscopies, namely heterodyne second harmonic generation (HD-SHG) and sum frequency generation (SFG) to elucidate structural and electrostatic information from charged interfaces. Additionally, the work attempts to answer longstanding questions about the origin of the optical response and its sampling range of the electrical double layer and interfacial properties. Previous models are revisited in order to accomplish this, and we report an additional term that is present in the nonresonant HD-SHG response that accounts for the rise of previously unaccounted for contributions to the imaginary portion of the spectroscopic signal. After obtaining information about this term, we also explore more aspects of the different portions of the electrical double layer. We report decoupled dynamics between Stern and diffuse layers at the silica/water interface by mapping and over changing ionic strength conditions. Moreover, we quantify the magnitude of these changes across different salt concentrations and take steps towards providing a chemical origin for hysteresis at oxide/water interfaces. Finally, we examine iron oxide surfaces under aqueous phase to begin understanding water structure and specific ion effects with an eye towards electrochemical applications.

Creator

• Ma, Emily

DOI

• https://doi.org/10.21985/n2-q7cx-sf17

Subject

• Chemistry

Language

• en

Alternate Identifier

• etdadmin_upload_968387
• http://dissertations.umi.com/northwestern:16438

Date created

• 2023-01-01

Resource type

• Dissertation

Rights statement

• In Copyright