  Real time visualization and tracking of colloidal particles with 3D
resolution is essential for probing the local structure and dynamics in complex
fluids. Although tracking translational motion of spherical colloids is
well-known, accessing rotational dynamics of such particles remains a great
challenge. Here, we report a novel approach of using fluorescently labeled
raspberry-like colloids with an optical anisotropy to concurrently track
translational and rotational dynamics in 3 dimensions. The raspberry-like
particles are coated by a silica layer of adjustable thickness, which allows
tuning the surface roughness. The synthesis and applicability of the proposed
method is demonstrated by two types of probes: rough and smoothened. The
accuracy of measuring Mean Squared (Angular) Displacements are also
demonstrated by using these 2 probes dispersed in 2 different solvents. The
presented 3D trackable colloids offer a high potential for wide range of
applications and studies, such as probing crystallization dynamics, phase
transitions and the effect of surface roughness on diffusion.
