Ultrafast laser-excited vibration and elastic modulus of individual gold nanorods

Ultrafast laser irradiation of single gold nanorods of various sizes is simulated for the investigation of the vibrations of the nanorods. The investigation uses a hybrid method that couples molecular dynamics (MD) with the two-temperature model (TTM). The extensional frequencies of the single gold nanorods are extracted from the atomic trajectories obtained by the MD simulations. In combination with continuum elasticity, the elastic moduli of the single gold nanorods are determined, along with the predicted extensional frequencies of the nanorods. It is shown that as the nanorod width increases, the modulus of the single gold nanorods also increases and approaches that of bulk gold. The notable softening of the elastic modulus is clearly shown for the smaller nanorods with widths of ∼8 and ∼12  nm.