Surface plasmon coupling in end-to-end linked gold nanorod dimers and trimers.

Colloidal gold nanorods were aligned end-to-end via dithiol coupling. The scattering properties of the resultant nanostructures were investigated at the single particle level by combining dark-field microscopy and high resolution scanning electron microscopy. The longitudinal surface plasmon resonance of end-to-end coupled Au nanorods exhibited a red-shift as the number of rods in the chain increased. The nanostructures exhibited polarization-dependent optical properties, due to selective excitation of collective bonding and anti-bonding modes. The surface plasmon peak energy was not strongly dependent on the angle of rod-sphere-rod trimers. The experimental scattering spectra were compared with the results obtained from theoretical calculations using the Finite Element Method (FEM) and found to be in good agreement.