A New T-Matrix Solvable Model for Nanorods: TEM-Based Ensemble Simulations Supported by Experiments

At present, the discrete dipole approximation (DDA) is the most popular technique to simulate optical responses from various nanoparticles, including gold nanorods with a complex morphology. However, the DDA code demands considerable computer resources and computation time if one needs orientation and ensemble averaging. Here, we introduce a new T-matrix-solvable and flexible geometrical model for nanorods that can be implemented on a usual office PC to calculate the optical properties of a statistical nanorod ensemble with random orientations. The model is used for accurate calculations of the orientation-averaged extinction spectra for transmission electron microscopy (TEM) based ensembles of gold nanorods with account taken of statistical variations in their shape and size. The simulated spectra are in good agreement with experimental measurements provided that the surface electron scattering constant A(s) is about 0.3. Our ensemble-based estimation of the surface-scattering constant is close to A(s) evaluations from single-rod scattering (Novo et al. Phys. Chem. Chem. Phys. 2006, 8, 3540-3546) and single-sphere absorption (Berciaud et al. Nano Lett. 2005, 5, 515-518) experiments.