Three-Dimensional High-Resolution Rotational Tracking with Superlocalization Reveals Conformations of Surface-Bound Anisotropic Nanoparticles

The ability to directly follow three-dimensional rotational movement of anisotropic nanoparticles will greatly enhance our understanding of the way nanoparticles interact with surfaces. Herein, we demonstrate dual-color total internal reflection scattering microscopy as a tool to probe the interactions of plasmonic gold nanorods with functional surfaces. By taking advantage of both the short and long axis surface plasmon resonance scattering enhancement, we are able to decipher both in-plane and out-of-plane gold nanorod motion relative to the sample surface with equally high resolution. In combination with superlocalization through point spread function fitting, we overcome the four-quadrant angular degeneracy of gold nanorods in the focal plane of the objective and resolve conformations of surface-bound anisotropic nanoparticles in unprecedented detail