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 protons1,2, the latter proving essential in electron transfer reactions3. 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.
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Acknowledgements
This work was financially supported by the Research Foundation Flanders (FWO). We are grateful to P. Van Der Voort and E. De Canck for scientific discussions regarding the catalytic properties. The NMR equipment used in this work was financed through a grant from the Hercules Foundation (AUGE09006). Z.H. acknowledges funding from the European Commission via the Marie-Sklodowska Curie action Phonsi (H2020-MSCA-ITN-642656), BelSPo (IAP 7.35, photonics@be), the Research Foundation Flanders (research project G.0760.12) and Ghent University (GOA 01G01513).
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J.D.R. designed and carried out the experiments, interpreted the data, made the figures and wrote the manuscript. I.V.D. and Z.H. initiated the research and supervised the experiments. Z.H. also wrote the manuscript. J.C.M. supervised the research, provided the NMR instrumentation and aided in interpretation and discussions regarding the NMR data. All authors commented on the manuscript.
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De Roo, J., Van Driessche, I., Martins, J. et al. Colloidal metal oxide nanocrystal catalysis by sustained chemically driven ligand displacement. Nature Mater 15, 517–521 (2016). https://doi.org/10.1038/nmat4554
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DOI: https://doi.org/10.1038/nmat4554
