Optical characterization and rotational dynamics observation of colloidal gold nanorods based on polarized light scattering microscopy

Gold nanorods have a strongly polarized light at their longitudinal plasmon frequency that can be utilized to characterize colloidal gold nanorods and monitor their rotational dynamics in a bulk sample by polarized light scattering microscopy. By monitoring the time trace of the scattering polarization contrast, we could measure the polarization anisotropy of nanorods and their aspect ratio. More, we could gain insights into the rotational dynamics of nanorods and measure the rotational diffusion time on the microsecond time scale, which is an important parameter for various biological phenomena. The effects of aspect ratio and solution viscosity on the rotational time were determined. To carry out the measurements in a robust way, two-color laser illumination schemes were used and the correlation between both results was figured out. Results demonstrate the possibility of using polarized light scattering from gold nanorods to analyze the diffusion dynamics/conformations of biomolecules on the nanoscale.