Cationic Polymer Coating Increases the Catalytic Activity of Gold Nanoparticles toward Anionic Substrates

Organiccoatings on catalytic metal nanoparticles (NPs) typicallyhinder their activity due to the blocking of active sites. Therefore,considerable effort is made to remove organic ligands when preparingsupported NP catalytic materials. Here, cationic polyelectrolyte coatingsare shown to increase the catalytic activity of partially embeddedgold nanoislands (Au NIs) toward transfer hydrogenation and oxidationreactions with anionic substrates compared to the activity of identicalbut uncoated Au NIs. Any potential steric hindrance caused by thecoating is countered by a decrease in the activation energy of thereaction by half, resulting in overall enhancement. The direct comparisonto identical but uncoated NPs isolates the role of the coating andprovides conclusive evidence of enhancement. Our findings show thatengineering the microenvironment of heterogeneous catalysts, creatinghybrid materials that cooperatively interact with the reactants involved,is a viable and exciting path to improving their performance.