Amino acid mediated linear assembly of Au nanomaterials

Nanoparticles possess unique properties that are enhanced due to their small size and varied shapes. These properties can be directly manipulated by controlling the aggregation state, which can further be exploited for applications in bio/chemical sensing, plasmonics, and as supports for catalysts. While the advantages of controlled aggregates of nanomaterials are great, synthetic strategies to achieve such structures with precision over the final arrangement of the materials in three-dimensional space remain limited. We have shown that ligand exchange reactions on Au nanomaterials of various shapes using simple amino acids can induce the formation of linear aggregates of the materials. The assembly process is mediated by partial ligand exchange on the particle surface, followed by the surface segregation of the two ligands that produces an electric dipole across the nanomaterial from which alignment occurs in solution via dipole-dipole interactions. This linear-based assembly can be used to tune the optical properties of the materials and could represent new pathways to study the interactions between biological molecules and inorganic nanomaterials.