NSF-BSF: Quantifying the Nature of N-Heterocyclic Carbene-Gold Nanoparticle Interactions

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Richard Brutchey of the University of Southern California, in collaboration with Professors Elad Gross and Uri Banin of the Hebrew University of Jerusalem, will investigate new strategies to enhance the stability and performance of colloidal gold nanoparticles, which are widely used in medical diagnostics, cancer therapies, and chemical catalysis. Although gold nanoparticles have been employed for decades—such as in immunoassay-based diagnostic tests—their surfaces are typically coated with sulfur-containing organic molecules called thiols, which are prone to degradation when exposed to heat, light, or air. This project will explore a more durable class of organic molecules known as N-heterocyclic carbenes (NHCs), aiming to understand how these molecules bind to gold surfaces and contribute to the development of more robust, stable, and customizable nanoparticles. Beyond laboratory research, the team will conduct immersive nanochemistry workshops for community college students at Cerritos College in Los Angeles County, fostering interest and retention in STEM fields while promoting international collaboration and increasing transfer rates to four-year institutions. This research effort will focus on elucidating the binding behavior of NHCs on gold nanoparticle surfaces in comparison with traditional thiol-based ligands, particularly in terms of binding strength and crystal facet specificity. The team will experimentally quantify the thermodynamics of ligand binding—measuring enthalpy, entropy, and free energy—using variable-temperature solution nuclear magnetic resonance spectroscopy and isothermal titration calorimetry. Additionally, high-resolution infrared nanospectroscopy will be employed to investigate how NHCs and thiols competitively interact with distinct gold nanoparticle facets at the atomic scale. These findings will provide crucial insights into the mechanisms of NHC–gold surface binding, helping enable the rational design of more stable gold nanoparticle systems for targeted applications. 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.