Structure and percolation of one-patch spherocylinders.

When the volume fraction exceeds the threshold, the colloidal particles would form a spanning cluster to realize percolation, which is affected by the shape of the particles, interaction between particles, etc. In this paper, we use the Monte Carlo method to study the structure and percolation of a system of one-patch spherocylinders which have been fabricated recently [Chaudhary et al., J. Am. Chem. Soc., 2012, 134, 12901]. With strong adsorption, one-patch spherocylinders self-assemble into multipods which further make contact with each other to form a percolation network at a high volume fraction, while the percolation network is inhibited by the local structures in a system of one-patch spheres. The main multipods are dipods when the patch angle equals π/3, while they are tetrapods and pentapods when the patch angle equals 2π/3. With enhancing the adsorption, the bigger the patch angle, the more the percolation threshold drops. The orientational order parameter, the distribution of the relative orientation between the nearest neighbors and the probabilities of a spherocylinder owning n adsorbing neighbors have been calculated to analyze the formation and transition of the structures.

Ring formation in the quasi-two-dimensional system of the patchy magnetic spheres.

Fabricating new functional materials has always been at the center of colloidal science, and how to form circular rings is a meaningful challenge due to their special electronic, magnetic and optical properties. Magnetic colloidal spheres can self-assemble into rings, but these rings have an uncontrollable length and shape and also have to coexist with chains and defected clusters. To make the most of magnetic spheres being able to self-assemble into rings, a patch is added to the surface of the sphere to form a chiral link between particles. The structural transition in the system of patchy magnetic spheres is studied using the Monte Carlo simulation. When the patch angle is in the interval 60° to 75°, rings become the dominant structure if the strength of patchy interaction exceeds a particular threshold and the shape of these rings is close to the circle. With an increase in the patch angle, the threshold of patchy interaction decreases and the average length of the circular ring increases approximately from 5 to 8.5.