NSF Award
2404203
With the support of the Chemical Structure and Dynamics (CSD) Program in the Division of Chemistry of the National Science Foundation (NSF) and the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG) Lead Agency Activity in Measurements of Interfacial Systems at Scale with In-situ and Operando Analysis, Professor Franz Geiger of Northwestern University and Professors Braunschweig and Ravoo of the University of Muenster are studying molecular aspects of photoswitchable surfaces comprised of self-assembled monolayers of arylazopyrazole (AAP) derivatives.The wetting of solid surfaces by liquids is known from everyday experience and is surprisingly easy to observe - just consider a bathroom mirror fogging and clearing up with changing relative humidity. Yet, changing the surface properties of a material with spatially and temporally directed external stimuli such as relative humidity, light, or applied potential in a controlled and reversible way is a formidable challenge. This project addresses this challenge by quantifying, under operando conditions, key molecular and structural properties of the "on" and "off" states of a molecular switch. Their studies could contribute to the fundamental understanding that is needed to predict and control the wettability of surfaces for applications in microfluidics and green energy technologies. The project will offer opportunities for graduate student training in an international, cross-Atlantic research environment and interdisciplinary training across organic synthesis, nanotechnology, thin film measurements, and advanced nonlinear optical spectroscopy. Trainees will participate in 2 month-long laboratory exchanges each year and participate in outreach opportunities through science blogging and high school outreach in Germany and the U.S.<br/> <br/>The team will use a unique combination of surface-specific spectroscopies (vibrational sum frequency generation and electronic second harmonic generation) to study the mechanism of AAP isomerization and the resulting changes in wetting properties of the surface. Self assembled monolayers (SAMs) of AAP derivatives will be studied in contact with electrolyte solutions as well as humid air. Changes in surface group orientations will be correlated with applied voltages and solvent exposure to gain molecular insights into the role of water dynamics on reactions at the interface. Patterning of the SAMs by microcontact printing will allow for the study of edges and defects Iin their structural order. While focus is placed on fundamental studies of switchable surfaces, this research will also provide new insights into the dynamics of solvents at electrodes surfaces, the structure of Stern layers, and the distribution of surface potentials in operando.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
