Engineering the Optical Properties of Gold Nanorods: Independent Tuning of Surface Plasmon Energy, Extinction Coefficient, and Scattering Cross Section

The future integration of plasmonic nanoparticles, such as gold nanorods (Au NRs), into applications requires the ability to tune the components of their optical properties to optimize performance for the underlying technology. Verifying techniques that model the resonance energy and associated extinction, scattering, and absorption cross sections necessitate experimental data from series of Au NRs where structural features are independently tuned. Here, the extinction cross section and scattering efficiency are presented for Au NR series with high compositional and structural purity where effective volume, aspect ratio, length, and diameter are independently varied by factors of 25, 3, 2, and 4, respectively. The extinction cross sections quantitatively agree with prior calculations, confirming that the volume of the rod is the dominant factor. Comparisons of the scattering efficiency however are less precise, with both quantitative and qualitative differences between the role of rod volume and aspect ratio. Such extensive experimental data sets provide a critical platform to improve quantitative structure-property correlations, and thus enable design optimization of plasmonic nanoparticles for emerging applications.