Hydrophobic assembly of gold nanoparticles into plasmonic oligomers with Langmuir-Blodgett film

Hydrophobic effect was utilized to self-assemble gold nanoparticles into oligomer structures, or plasmonic dimers, trimers, and so on. Langmuir-Blodgett film of n-octadecanamine was prepared on a glass substrate. Citrate-stabilized gold nanoparticles were adsorbed onto the film, resulting hydrophobic point decoration. The gold nanoparticles with the point decoration were removed from the substrate and self-assembled into plasmonic dimers in ethanol. The products were observed by an atomic force microscope, where not only dimers but also trimers and other aggregates were found. The yield of the plasmonic dimer was ∼13% without any purifications. We measured the scattering spectrum of the single plasmonic dimer, exhibiting the optical anisotropy.