Collaborative Research: Characterization and Optimization of N-Heterocyclic Carbene Functionalized Nanoparticle Systems

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Dr. David Jenkins of the University of Tennessee and Drs. Jon Camden and Gina Navoa Svarovsky of the University of Notre Dame explore the use of N-heterocyclic carbenes (NHCs) chemistry for the surface modification of gold nanoparticles.

Gold nanoparticles, which are typically stabilized by charged molecules such as citrate or monolayers with thiol anchoring groups, are used in wide-ranging chemical, biological, and environmental technologies but use is limited by the inherent instability of the nanoparticles in water. Drs. Jenkins and Camden are identifying ways to overcome this limitation by using NHC ligands.

To do so, they are using a top-down method that involves the initial coordination of these ligands to coinage metal ions before being transferred to gold nanoparticle surfaces. They are using a variety of characterization tools to evaluate this chemistry and to better understand what NHC ligands promote enhanced stability of the functionalized gold nanoparticles.

Drs. Jenkins, Camden, and Svarovsky are pursuing a Teaching Fellows Residency program to create an immersive research experience in the research laboratories and a Student Engagement in Authentic Science (SEAS) program that engages middle school students with original scientific data.

The research involves the synthesis, characterization, and transfer of metal NHC complexes to gold nanoparticle surfaces, the characterization of the resulting bonding and close packing of a library of NHC ligands on gold nanoparticles, and the subsequent evaluation of NHC-functionalized gold stability and longevity. All of these studies utilize a top-down approach wherein the gold nanoparticles are functionalized after isolated coinage metal NHC complexes have formed in solution.

This universal, top-down strategy is expected to be broadly applicable to gold nanoparticles of varying shapes and sizes. This approach has the potential to overcome limitations associated with bottom-up functionalization steps where each individual reaction is typically optimized for a specific system. Gold nanoparticles functionalized with heterocyclic carbenes hold promise in the quest to overcome challenges faced by conventional surface chemistries.

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.