Real-time monitoring for the morphological variations of single gold nanorods.

The morphological characteristics of metal nanoparticles, particularly the shape, play an essential role in the optical, physical and chemical properties. In this work, we reported a transverse etching process to investigate the morphological variations of single gold nanorods (GNRs). Dark-field microscopy and Rayleigh scattering spectroscopy were used as complementary technologies to track the transverse etching process. Dark-field imaging with high spatial and temporal resolution could easily monitor the transverse etching process of GNRs in situ and in real time. Interactions between the scattering spectrum and the morphological variations were judiciously calculated within the dipole approximation by the Drude function. The calculated peak shift of GNRs (Δλmax = 17 nm) was obtained via the ratio of the long axis and short axis (aspect ratio) of GNRs from transmission electron microscopy. The average scattering peak shift (Δλmax = 22 nm) from Rayleigh scattering spectroscopy was in good agreement with the calculated peak shift. Monitoring the morphological variations of single GNRs enables us to track the transverse etching of GNRs at arbitrary time. This promises to be a useful method for the study of different nanomaterials and their spectral properties.