Surfactant Removal for Colloidal Nanocrystal Catalysts Mediated by N-Heterocyclic Carbenes

Abstract

We report the facile removal of surfactants from colloidally synthesized nanocrystals via ligand exchange with N-heterocyclic carbenes (NHCs). Subsequent protonation of the NHC ligands in acid efficiently cleans the nanocrystals' surface while preserving their uniform morphology and structure for catalysis. The broad efficacy of this strategy is validated using monodisperse Pt, Pd, and Au nanocrystals, each prepared with strongly bound phosphine stabilizers. The surface-activated nanocrystals exhibit significantly improved catalytic activities, superior to those obtained with other surface cleaning methods, as demonstrated in two centrally important electrochemical reactions (glycerol oxidation and CO₂ reduction). This work highlights a new surface activation strategy for catalysis and other applications that enables the efficient use of well-defined nanocrystal libraries prepared by colloidal chemistry.