Mono-, di- and trimetallic coinage nanoparticles prepared via the Brust-Schiffrin method

The Brust-Schiffrin two-phase method is a facile way to prepare thiolate-protected metal nanoparticles, but its mechanism remains controversial. In this work, we demonstrate the use of the Brust-Schiffrin method based on coordination compound theory. We confirmed that the formation of stable complexes is the driving force for a series chemical reaction in the organic phase. We found that the stable Cu(I)-thiolate complex decreased the half-cell reduction potential of Cu(I)/Cu(0). Thus, when thiol ligands were in excess, thiolate-protected Cu(I) clusters formed rather than Cu(0)-cored nanoparticles. The thiolate-protected metal-hydride nanoclusters were the intermediate between the metal complexes and nanoparticles. The "metallophilic" interactions of the d¹⁰ closed-shell electronic configuration of the metal coordination centers were proposed as the driving force for nanocluster and nanoparticle formation. To confirm this mechanism, we synthesized Au, Ag, and Cu monometallic nanoparticles and bi- and trimetallic nanoparticles. We found that although thiolate-protected Cu(I) nanoclusters are not easily reduced, they can combine with Au and/or Ag nanoclusters to form nanoparticles. The proposed mechanism is expected to provide deeper insight into the Brust-Schiffrin method and further extend its application to metals other than Au, Ag and Cu.