Using light scattering to resolve Brownian rotation dynamics of optically trapped Au nanorods

Optically trapped Au nanorods are known to adopt a preferential orientation when trapped in three dimensions at the focus of linearly polarised optical tweezers. Trapped nanorods experience both translational and rotational perturbations due to Brownian motion that are governed by the strength of the trap and associated shape-dependent hydrodynamic properties. In this study, we make use of the strong angular dependent light scattering of the localised surface plasmon resonances to interrogate the rotational dynamics of trapped nanorods principally aligned along the propagation axis of the trapping laser. Our measurements reveal that significant rotational dynamics can be observed whilst maintaining stable translational trapping at low powers.