(552j) The Hindered Translational and Rotational Dynamics of Nano-Rods Diffusing Near a Solid-Liquid Interface in Aqueous Solution

We discuss a new method for measuring the three-dimensional translational and rotational dynamics of ZnO nanorods diffusing in aqueous solution above a solid-liquid interface. We simultaneously record the spatially correlated scattering of multiple evanescent light sources by isolated anisotropic particles, and use this data to reconstruct instantaneous positions and orientations at millisecond time-intervals. By observing diffusion in each spatial mode over time we are able to quantify each translational and rotational diffusion coefficient as a function of interfacial separation, and show an asymptotic approach to the expected constant value in the bulk. These same data can also be used to measure equilibrium particle-interface interaction potentials with orientation and position effects optionally decoupled, completing a rich set of tools for probing anisotropic interactions. Aside from fundamental applications, this approach will be particularly useful for understanding and tuning the self-assembly of films and other structures incorporating anisotropic nanoparticles.