Bridging of gold nanoparticles by functional polyphenylene dendrimers

We describe a protocol for the in-suspension bridging of gold particles with shape-persistent polyphenylene dendrimers, carrying multiple lipoic acid groups at their periphery. A solvent mixture is identified where both reactants are stable as individuals. Upon mixing, aggregates with stoichiometry-dictated size form rapidly. Initially, the spacing between individual gold colloids is large enough that their absorption spectrum is only slightly different from isolated particles. The aggregates rearrange within hours, leading to strong optical coupling between the gold particles and a corresponding spectral shift.