Nanoparticle assembly: Solvent-tuned structures

Eugenia Kumacheva and co-researchers have reported that conversion of hydrophilic gold nanorods into amphiphiles by selective replacement of surface ligands results in two-dimensional solvent-dependent organization of the nanorods. These ligands can also strongly influence the shape of the nanoparticles when they initially grow from precursors by stabilizing specific crystalline face and thereby promoting growth on others. For the amphiphilic nanorods that Kumacheva and colleagues describe, interdomain interactions become less important, as the rigidity of the nanorod becomes more important in determining self-assembly. They show the self-assembly of their gold nanorod amphiphiles to be dependent on the solvent quality in mixtures of N,N-dimethylformamide and tetrahydrofuran. These assemblies demonstrate an example of a synthetic system where assembly at the molecular level, through segregation of different ligands to spatially defined regions of a nanoparticle, translates into control over structure at larger length scales.