The study of diffusion in complex confined environments has received great attention in the field of condensed matter physics. The emergence of colloidal systems provides an excellent experimental model system for the quantitative study of the confined diffusion of microscopic particles. When the shape of colloidal particles changes from spherical to ellipsoidal, the system exhibits anisotropic diffusion dynamics. Recent studies have found that rough surfaces, another important physical parameter of colloids, can lead to unusual rotational dynamics in spherical colloidal systems. However, due to the lack of a suitable experimental system, little is known about the effect of rough surfaces on the confined diffusion of ellipsoidal colloidal particles. In this paper, rough colloidal sphere, rough colloidal ellipsoid and smooth colloidal ellipsoid are prepared, and then monolayer colloidal samples are prepared to study the confined diffusion of these two types of ellipsoids in a dense packing of the rough sphere colloids. By calculating the mean square displacement, intermediate self-scattering function, and orientation correlation function of the ellipsoids, we quantitatively characterized the diffusion dynamics of rough and smooth ellipsoids in varying concentrations of rough spheres. The results indicate that the translational and rotational diffusion of both rough and smooth ellipsoids slow down as the concentration of rough spheres increases. This is due to the confinement of the ellipsoid by the surrounding spheres. At low stacking fractions of spheres, smooth and rough ellipsoids show similar translational and rotational diffusion. However, as the stacking fraction of spheres increases, the advection diffusion of rough and smooth ellipsoids differs significantly. The advection diffusion of rough ellipsoids is significantly slower than that of smooth ellipsoids. This is because the rough surface strongly inhibits rotation, meaning that the rotational diffusion of the rough ellipsoid is significantly slower than that of the smooth ellipsoid. By extracting the diffusion coefficients for translation and rotation from the ellipsoid's long-time mean-square displacements, we found that at Φ = 0.60 and 0.65, the diffusion coefficients of rough ellipsoids are smaller than those of smooth ellipsoids. The translational diffusion coefficient of the rough ellipsoid is notably smaller than that of the smooth ellipsoid. However, the rotation diffusion coefficient of the rough ellipsoid does not significantly differ from that of the smooth ellipsoid. This suggests that rough surfaces primarily impact translational diffusion, strongly suppressing the translational diffusion of the ellipsoid. By calculating the displacement probability distribution for ellipsoidal motion, we found that at Φ = 0.65, the rough ellipsoid's translational displacements have a relatively narrow distribution. This suggests that the particles' translational motion is suppressed by the rough surface. However, the distributions of rotation displacement for both are very similar, indicating that the rough surface has less impact on particle rotation. At Φ = 0.74, the rough surface suppresses both the translation and rotation of the ellipsoid, resulting in a narrower displacement distribution compared to the smooth ellipsoid.
These findings suggest that rough surfaces significantly impede ellipsoidal diffusion, with effects on translational and rotational motions not occurring simultaneously. This study marks a significant advancement in understanding the role of rough surfaces of colloidal particles in confined diffusion and provides an experimental basis for explaining the diffusion laws of rough materials.