title: Colloidal metal oxide nanocrystal catalysis by sustained chemically driven ligand displacement.
abstract: Surface chemistry is a key enabler for colloidal nanocrystal applications. In this respect, metal oxide nanocrystals (NCs) stand out from other NCs as carboxylic acid ligands adsorb on their surface by dissociation to carboxylates and protons, the latter proving essential in electron transfer reactions. Here, we show that this binding motif sets the stage for chemically driven ligand displacement where the binding of amines or alcohols to HfO2 NCs is promoted by the conversion of a bound carboxylic acid into a non-coordinating amide or ester. Furthermore, the sustained ligand displacement, following the addition of excess carboxylic acid, provides a catalytic pathway for ester formation, whereas the addition of esters leads to NC-catalysed transesterification. Because sustained, chemically driven ligand displacement leaves the NCs-including their surface composition-unchanged and preserves colloidal stability, metal oxide nanocrystals are thus turned into effective nanocatalysts that bypass the tradeoff between colloidal stability and catalytic activity.
authors.affiliation: Sol-gel Center for Research on Inorganic Powders and Thin films Synthesis, Ghent University, B-9000 Gent, Belgium.|NMR and Structure Analysis Unit, Ghent University, B-9000 Gent, Belgium.|Physics and Chemistry of Nanostructures group, Ghent University, B-9000 Gent, Belgium.
authors.forename: Jonathan
authors.initials: J
authors.lastname: De Roo
authors.affiliation: Sol-gel Center for Research on Inorganic Powders and Thin films Synthesis, Ghent University, B-9000 Gent, Belgium.
authors.forename: Isabel
authors.initials: I
authors.lastname: Van Driessche
authors.affiliation: NMR and Structure Analysis Unit, Ghent University, B-9000 Gent, Belgium.
authors.forename: José C
authors.initials: JC
authors.lastname: Martins
authors.affiliation: Physics and Chemistry of Nanostructures group, Ghent University, B-9000 Gent, Belgium.|Center for Nano and Biophotonics, Ghent University, B-9000 Gent, Belgium.
authors.forename: Zeger
authors.initials: Z
authors.lastname: Hens