Oxidative Elimination and Reductive Addition of Thiol-Terminated Polymer Ligands to Metal Nanoparticles.

Metal nanoparticles (NPs) stabilized with thiol- (HS-) terminated polymers have applications in medicine, optoelectronics, and catalysis. It is assumed that upon exposure to oxidants or even air, these NPs lose colloidal stability, due to the oxidation of the HS-end-group and elimination of polymer ligands from the NP surface, however, this mechanism does not explain the unsuccessful recovery of the NP stability by adding fresh HS-terminated polymers. Here we propose the oxidation of the surface metal atoms as a mechanism for the oxidative elimination of polymer from the NP surface. Based on this mechanism, we reversed NP aggregation by reducing the oxidized metal surface and re-attaching HS-terminated polymer ligands. This mechanism is general for various metal NPs and different HS-terminated polymers. We show that oxidative elimination and reductive addition reactions can improve the colloidal stability of polymer-capped metal NPs and control their redox stimuli-responsive self-assembly.