Rotation in suspension of a rod-shaped colloid.

The simple strategy of coating a closely packed colloid monolayer with a nanometer-thick metal film to connect colloidal spheres and then gently sonicating produces a series of colloid metastructures, including rods and planar sheets. These structures can be fluorescently labeled, which can serve as a probe to monitor their dynamics in complex environments. The metal coating modulates fluorescence emission as these structures rotate in suspension. By analyzing the time sequence of fluorescence images using single-particle tracking techniques, here we measure the rotational dynamics of a rodlike tetramer, quantifying rotation along the long axis.