Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Dissertation_Adams_V3.pdf (21.6 MB)

ETD Abstract Container

Abstract Header

Spectroscopic Studies of Atmospherically- and Biologically-Relevant Interfaces: Lipids, Ions, and Interfacial Water Structure

Adams, Ellen M.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1480608026126993

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Chemistry.
Sea spray aerosols (SSA) impact Earth’s climate directly and indirectly by scattering and absorbing solar radiation and influencing cloud formation, respectively. SSA are formed through the wind-drive wave action at the ocean surface, and their chemical composition is impacted by the biological activity in the sea surface microlayer (SSML), the thin organic layer present at the air-ocean interface. Physical and optical properties of SSA are influenced by the structure and organization of their surfaces. Organic films are known to form at the surface of SSA, and therefore a molecular-level understanding of the organic species that make up these films and their subsequent impact on interfacial properties is necessary to gain insight into climate change. In this dissertation Langmuir monolayers are utilized as proxies for organic-coated SSA. Phase behavior, rigidity, and stability of monolayers are assessed with surface pressure-area isotherms. Surface morphology of monolayers was imaged with Brewster angle microscopy (BAM). Infrared reflection-absorption spectroscopy (IRRAS) and vibrational sum frequency generation (VSFG) spectroscopy were used to examine the molecular-level structure and intermolecular interactions of the monolayers. VSFG was additionally used to probe the organization and structure of water molecules in the interfacial region. As SSA are chemically complex, several different types of atmospherically-relevant lipid-aqueous interfaces are investigated. The effect of ion enrichment for marine-relevant cations (Na+, Mg2+, Ca2+, and K+) on the interfacial properties of the phospholipid dipalmitoylphosphatidylcholine (DPPC) was investigated. All cations were found to impact monolayer properties, with divalent cations having a greater effect than monovalent ions. Refractive index of the monolayer was found to decrease with increasing cation concentration. In the case of Ca2+, significant dehydration of the phosphate headgroup was observed. Binding affinity followed the trend Ca2+ > Mg2+ > Na+ ˜ K+. Investigation of cation enrichment was extended to concentrated solutions of Zn2+ and Sr2+. Sr2+ was found to have weak interactions with the DPPC monolayer, and impacted properties of the monolayer in a manner similar to a monovalent ion. In contrast, Zn2+ interacted strongly with the monolayer, and altered the phase behavior and surface morphology. Increased hydration of the phosphate headgroup was observed with increasing Zn2+ concentration. Probing of the interfacial water structure near the monolayer revealed that the hydrogen-bonding network was significantly perturbed by Zn2+. Water molecules preferentially solvate the PC-Zn2+ complex, leading to a reduced hydrogen-bonding network. Sr2+ also impacted the hydrogen-bonding network through charge screening effects, but to a lesser extent than Zn2+. The impact of carbohydrates and glycolipids on the organization of interfacial water molecules was also investigated. Glucose was found to have a concentration-dependent influence on the hydrogen-bonding network. The soluble glycolipid lipopolysaccharide (LPS) was found to impact the hydrogen-bonding network similar to glucose, and had a much greater effect than the insoluble lipids cerebroside and ceramide. The effect of pH on a palmitic acid (PA) monolayer was studied as well. When PA molecules became deprotonated in the high pH regime, dissolution of lipid molecules into bulk solution occurred. Addition of NaCl to the bulk solution increased the surface propensity of PA molecules, but restoration of a full monolayer did not occur. Probing of interfacial water structure revealed that the hydrogen-bonding network near the monolayer was not perturbed until the majority of the monolayer was deprotonated. The impact of lipid composition within the monolayer on interfacial properties was probed through the investigation of stratum corneum lipids extracted from four different lark species. Results revealed that phase behavior, surface morphology, and conformation of alkyl chains depended upon the relative abundance of lipid classes in the monolayer. Interfacial water structure was correlated to surface morphology of the monolayer, where a porous morphology lead to an increased population of less coordinated water molecules. The studies conducted in this dissertation show that interfacial properties of organic-coated SSA are impacted by complexation of lipids with ions, solubility of the lipid, pH, and chemical composition of the organic species. As SSA are complex systems, all of these factors must be considered in attempting to predict their effects on climate change.
Heather Allen (Advisor)
202 p.
Chemistry
sea spray aerosols; Langmuir monolayers; Brewster angle microscopy; infrared reflection-absorption spectroscopy; sum frequency generation spectroscopy

Recommended Citations

Citations

  • Adams, E. M. (2016). Spectroscopic Studies of Atmospherically- and Biologically-Relevant Interfaces: Lipids, Ions, and Interfacial Water Structure [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480608026126993

    APA Style (7th edition)

  • Adams, Ellen. Spectroscopic Studies of Atmospherically- and Biologically-Relevant Interfaces: Lipids, Ions, and Interfacial Water Structure. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1480608026126993.

    MLA Style (8th edition)

  • Adams, Ellen. "Spectroscopic Studies of Atmospherically- and Biologically-Relevant Interfaces: Lipids, Ions, and Interfacial Water Structure." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480608026126993

    Chicago Manual of Style (17th edition)

osu1480608026126993
164
© 2016, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.