Gold nanoparticles with reversible colloidal aggregation mediated with Cu(II) ions

Abstract

Gold nanoparticle (AuNPs) colloidal assemblies mediated with auxiliary components can lead to intricate response-triggered functional materials with many practical applications. Herein, we report the synthesis and characterization of gold nanoparticles that form reversible colloidal assemblies mediated with Cu(II) ions. The synthesis and characterization of the ligand 11-(diethylenetriamine) undecanethiolate is reported and comprises dual binding modes. One side of the ligand binds to AuNPs via a thiolate group and the other side binds to transition metals such as Cu(II) ions via the tridentate diethylenediamine group. The tridentate ligand can form bis-adduct complexes with Cu(II), thus forming bridges between the AuNPs that lead to the coordination-driven AuNP assemblies. The Cu(II) ion concentrations determined the size range of the AuNP assemblies, which can be from nm to microns. The Cu-AuNP assemblies can revert to individual AuNPs upon metal sequestration via ligand-exchange reactions in solution. This type of coordination-directed control of nanoparticle aggregation can play an essential role in developing response-triggered nanomaterials with a wide range of applications.