Functionalization with polymer ligands enhances the catalytic activity of surfactant-stabilized gold nanoparticles

Plasmonic nanoparticles are increasingly explored as catalytically active entities to affect (photo-)catalytic transformations. Synthesis methods are established for accessing such nanoparticles with defined dimension and shape, thereby controlling their plasmonic behavior, including the possibility of resonance engineering and the control of chiral plasmonic properties of single plasmonic nanoparticles that can be used to drive asymmetric photocatalytic transformations. However, the most productive nanoparticle synthesis procedures employ surfactants that lead to comparably dense surface layers and may limit surface accessibility. In this work, we demonstrate that functionalization of such surfactant-stabilized plasmonic gold nanoparticles with a brush-type polymer-ligand layer results in both significantly increased catalytic activity in the colloidal solution state (by a factor of ∼4) and excellent colloidal stability, enabling several catalytic cycles. Heterogeneous catalysis experiments performed after surface deposition allowed the comparison between polymer ligand-grafted and ligand-free gold nanoparticles, which show comparably weak differences in catalytic rate (a factor of ∼1.8). These results pave the way for efficient (photo-)catalysis driven by well-defined plasmonic nanoparticles in colloidal solution.