02/26/18 - 4:00 PM to 5:00 PM
Special Seminar: Professor Shelley A. Claridge
"Standing, Lying, and Sitting: Noncovalent Ligand Layers on 2D Materials as a Foundation for 3D Interface Design from sub-10-nm to mm Scales"
Designing interfaces to control material structure down to sub-10-nm scales is a challenge central to applications including next-generation electronics, energy conversion, and human health. Creating interfaces that organize two very different chemistries on this scale is a significant challenge, in part due to physical properties such as line tension and disjoining pressure that increase in importance at very short length scales. However, biology routinely addresses a related challenge in the lipid bilayer, using precise nanometer-scale hydrophilic/hydrophobic orthogonality to spatially organize and gate processes including ion transport, adhesion, and recognition, through self-assembly of polyfunctional phospholipid building blocks. Conventional standing phases of phospholipids such as those in cell membranes do not directly meet the requirement to display orthogonal surface chemistry at few-nm scales for synthetic materials. However, polymerizable amphiphiles can be self-assembled into lying down or ‘sitting’ phases on 2D materials such as graphite and graphene, exposing both polar heads and nonpolar tails to the environment. In this conformation, the headgroups represent ~1-nm-wide functional patterns separated by ~5-nm stripes of lying-down alkyl chains. The monolayer is noncovalently adsorbed to the substrate, enabling useful dynamics that are very different from the behavior of tightly packed standing phase monolayers. We examine physical consequences of this bioinspired chemical orthogonality for a variety of applications, using 1-nm-wide rows of headgroups to template synthesis of metallic nanowires, crystallization of aromatic small molecules, and anisotropic interfacial wetting near the molecular scale. Additionally, we develop strategies for controlling and characterizing noncovalent monolayer structure across length scales from <10 nm up to macroscopic scales.
A central theme in Professor Claridge's research group is the development of new self-assembly and integrated imaging strategies that advance the limits of interfacial ordering complexity and structural analysis, mirroring the structural diversity and functional precision achieved in biology. These include:
- reenvisioning design principles of the cell membrane as strategies for developing precise control over synthetic material interfaces, addressing emerging needs in areas ranging from nanoscale optoelectronics to human health;
- development of custom nanoscale surface analytical instrumentation to enable molecular-scale chemical imaging and characterization of dynamic self-assembly processes at hydrophilic-hydrophobic interfaces relevant to nanoscopic materials and biology;
- synthesis of novel polymerizable amphiphiles and other molecules (e.g. peptides) useful for noncovalent functionalization of layered materials;
- unconventional applications of bioanalytical techniques to address problems including characterization of nanoscale anisotropic wetting phenomena similar to those occurring in biological water and ion transport (e.g. through aquaporins); and
- integrating molecular modeling and advanced interfacial characterization to develop detailed predictive understanding of noncovalently assembled interfaces with technologically important layered materials such as graphene.
Professor Claridge earned her Bachelor of Science degree in mathematics, biochemistry, and genetics from Texas A&M University, and her doctorate in chemistry from the University of California, Berkeley. She was a National Institutes of Health post-doctoral fellow and Merkin Family Foundation post-doctoral Fellow at Penn State and University of California, Los Angeles.