Control and Switching of Charge-Selective Catalysis on Nanoparticles by Counterions

It is known that when catalytic nanoparticles are functionalized with charged ligands, the polarity of these ligands can selectively control the approach of either (+) or (-) charged substrates, effectively rendering the particles' catalytic activity charge-selective. In such experiments, however, the role of the counterions surrounding the charged ligands is generally not considered. The present work demonstrates that counterions - despite being only loosely bound - can have a dramatic effect on the on-particle catalysis. In particular, with the same charged ligands but with counterions of different sizes, catalysis can be allowed or completely blocked. Moreover, when counterions are exchanged, the same particles can be reversibly toggled between catalytically active and inactive states.