Gold nanorods as novel nonbleaching plasmon-based orientation sensors for polarized single-particle microscopy

By monitoring the polarized light scattering from individual gold nanorods in a darkfield microscope, we are able to determine their orientation as a function of time. We demonstrate time resolution of milliseconds and observation times of hours by observing the two-dimensional rotational diffusion of gold rods attached to a glass surface. The observed orientational diffusion shows a fast component of about 60 ms and "sticky times" of seconds. The large signal-to-noise ratio, chemical and photochemical stability, fast time response, and small size of these gold nanorods make them an ideal probe for orientation sensing in material science and molecular biology.