N-Heterocyclic Carbene-Based Copolymers for Templated Synthesis and Stabilization of Gold Nanoparticles

Surface functionalization and colloidal stability are pivotal for numerous applications of gold nanoparticles (Au-NPs). Over the past decade, N-heterocyclic carbenes (NHCs) have emerged as promising ligands for stabilizing Au-NPs owing to their ease of synthesis, structural diversity, and strong metal-ligand bonds. Here, we introduce Au(I)-NHC copolymer scaffolds as novel precursors to multidentate NHC-protected Au-NPs. Ring-opening metathesis copolymerization of a norbornene-appended Au(I)-NHC complex with another functionalized norbornene comonomer provides a diverse array of Au(I)-NHC copolymers with modular compositions and structures. Upon reduction, these copolymers yield multidentate polyNHC-coated Au-NPs with varied properties and corona functionalities dictated by the secondary monomer. These nanoparticles exhibit greater size homogeneity compared to those prepared using existing methods for the bottom-up synthesis of polyNHC-Au-NPs and demonstrate exceptional stability against aggregation in various buffers, cell culture media, and under exposure to electrolytes, oxidants, and exogenous thiols over extended periods. Moreover, we showcase the first example of post-synthetic surface functionalization reactions of polyNHC-Au-NPs while maintaining colloidal stability, highlighting their robustness and potential for applications such as bioconjugation. Overall, these findings underscore the potential of our ROMP-derived NHC-containing copolymers as highly tunable and versatile multidentate ligands that may be suitable for other inorganic colloids and flat surfaces with a wide array of applications.