Exploiting Selective Surface Activation for Surface Enhanced Spectroscopy Measurements

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This research at the University of Iowa is supported by an award from the Chemical Theory, Models and Computational Methods Program in the Division of Chemistry to exploit non-covalent intermolecular and molecule-surface interactions to expand the utility of surface-enhanced Raman scattering (SERS) of molecules that directly adsorb to gold nanostars. SERS is a powerful detection method that depends on the optical properties of metal nanoparticles and chemical effects arising from molecule-surface interactions. The Iowa team will pursue methods to understand how zwitterionic surface ligand charge differences influence their affinity to gold. By partially weakening the surface stabilizing agents, small pockets are generated on the metal for subsequent molecular binding, including molecules that do not traditionally bind readily to gold thus increasing the analytical utility of this sensitive and specific detection method. The research team will focus on the professional development and training of students who pursue this research. To aid in generating an equitable environment, the group will maintain a living document that summarizes expectations for communication, ethics, experiment planning and documentation, respect, and safety. The group also plans to perform outreach activities with K-12 students in person and virtually that focus on chemistry as well as on nanoscale objects and properties.This University of Iowa team will address challenges associated with the reproducible and quantitative capabilities of SERS by exploiting the roles of intermolecular interactions, solvation, and chemical effects arising from molecule-substrate interactions. Tuning the binding affinity of surface-stabilizing zwitterions on gold nanostars using cations, protons, and solvent facilitates the formation of hydrophobic binding pockets on gold nanostar surfaces. By locally modulating the electron density in the surface ligands, the hydrophobicity and dimensions of these active sites are probed using SERS and other surface sensitive detection methods. The group subsequently tunes molecular solubility and SERS excitation conditions to quantify and understand the chemical interactions between molecules and the gold interface. By developing a mechanistic understanding of how electron distribution in surface stabilizing agents impact molecule-metal chemical interactions, the utility of SERS and other spectroscopic techniques will be achieved.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.