Reversible Electrochemical Modulation of a Catalytic Nanosystem

A catalytic system based on monolayer-functionalized gold nanoparticles (AuNPs) that can be electrochemically modulated and reversibly activated is reported. The catalytic activity relies on the presence of metal ions (Cd2+ and Cu2+), which can be complexed by the nanoparticle-bound monolayer. This activates the system towards the catalytic cleavage of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNPP), which can be monitored by UV/Vis spectroscopy. It is shown that Cu2+ metal ions can be delivered to the system by applying an oxidative potential to an electrode on which Cu-0 was deposited. By exploiting the different affinity of Cd2+ and Cu2+ ions for the monolayer, it was also possible to upregulate the catalytic activity after releasing Cu2+ from an electrode into a solution containing Cd2+. Finally, it is shown that the activity of this supramolecular nanosystem can be reversibly switched on or off by oxidizing/reducing Cu/Cu2+ ions under controlled conditions.