Plasmonic coupling in nondipolar gold colloidal dimers

Nanoscale Gold colloidal dimers are built thanks to the convective capillary force assembly (CFA) technique. CFA efficiently demonstrates precise dimer localization, particle separation control, and object reproducibility. Darkfield microspectroscopy measurements combined with numerical modeling exhibit a redshift in the dimer surface plasmon resonance as the interdistance decreases. The study points out that metallic particles, which are not in the dipolar approximation (diameter similar to 150 nm), present a similar optical behavior than that of smaller particles for the first resonance mode. Finally, local electric field simulations indicate that these dimers are valid candidates for sensing applications in the near-infrared regime. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3560456]