Among the multitude of recently synthesized non-spherical colloids, hollow silica cubes distinguish themselves by their charged surface and the strong influence of van der Waals forces on their behaviour. While their self-assembly has been observed in experiment, it has not yet been fully studied and characterized. Using MD simulations, we investigate the electric double layer surrounding the cubes, then compute their interaction potential at different orientations to understand the influence of their anisometry. In combination with experimental observations and calculated trajectories, we show how the self-assembly of the cubes is driven by the competition between electrostatic and van der Waals forces. We then examine the microstructures formed by small clusters of cubes, which differ significantly from those exhibited by comparable spheres. These investigations give us a multifaceted understanding of the behaviour observed in these systems and pave the way for future applications.

 

 

 

 

Anisotropic and Anisometric Particles

Anisotropic Magnetic Particles

Magnetic colloids have evolved into an independent branch of dipolar soft matter. Not only have the carrier liquids been tuned to sustain low temperatures or meet medical requirements, but also the particles have been modified in various ways. We are especially interested in colloids with  magnetic caps and in magnetic Janus particles. Particles with shifted dipoles represent a toy model of magnetically capped colloids. It is a spherical particle with a dipole moment shifted outwards radially. As for magnetic Janus particles, they are half made of a magnetic material, and half of a non-magnetic one. We propose a simple toy model in which the spherical particle is divided into two hemispheres, one of which contains a point dipole parallel to the division plane. We employ molecular dynamics simulations and theoretical methods of ground-sate calculations to understand the influence of the dipolar position and dipole-external field coupling on the cluster topology and cluster-size distributions. 

 

  • Particles with Shifted Dipoles
  • Magnetic Janus Particles

Anisometric Magnetic Particles

New techniques in colloidal synthesis allow access to a vast array of particles with non-spherical shapes. These particles, for example cubesspheroids and rods, interact with each other in a manner whereby the orientation of particles is a crucial parameter. This anisotropy is in stark contrast to the simple isotropic interactions of spherical particles. The presence of this effect allows new phases to form with interesting and useful properties. Within our group, we study non-spherical particles constructed of magnetic compounds. These magnetic particles are approximated as single domain systems and treated as point-like dipoles. The resulting dipole interaction is inherently anisotropic. As such, there is competition and interplay between the magnetic and geometric origins of anisotropy. Our studies of these systems involve both theory and computer simulation. We have developed procedures to predict the microstructure of these systems: in bulk, in confined geometries and at low temperatures. Knowledge of their structure on the microscopic level then allows us to predict the thermodynamic properties of these colloids and in particular their magnetic properties and response.

 

  • Ellipsoids
  • Cubes