Colloidal deposition will be investigated for charged silica cubes, driven out of stable aqueous dispersions to glass substrates primarily by polymer-induced depletion forces. Our recently developed, hollow silica cubes are expected to have the unique feature of forming ordered dense layers ('mosaics') with crystal symmetries set by the polymer/cube size ratio. Tailoring of optical and wetting properties of the colloidal mosaics will be investigated employing internal and external functionalization of cube surfaces. Three-dimensional cube deposition into multi-layers will be monitored via ellipsometry and confocal laser scanning microscopy. The fundamental incentive for this project is to calculate and understand the interaction (double-layer repulsion plus depletion attraction) between silica cubes, and to demonstrate that depletion-driven cube deposition may occur from a bulk of non-aggregated cubes that itself remains in stable regions of the phase diagram.

• prof. dr. ir. R. (Remco) Tuinier

Chirality is abundant in nature and plays an important role in biology, chemistry and physics. Symmetry breaking and handedness establishment lead to essentially novel phenomena such as coupling of the translational degrees of freedom and self-propelling.
Within the proposed research, we shall develop novel synthesis methods to fabricate colloids with chiral shape resembling that of DNA. To this end we shall use the molecular/colloidal co-assembly method recently discovered by us. In this approach molecular self-assembly of surfactant (SDS) and cyclodextrin (β-CD) complexes yields hollow tubes of a well-defined size, which confine colloidal particles in their interior. The chiral assemblies are then formed due to simple geometrical restrictions. The co-assembly approach will be further optimised to increase the yield of chiral assemblies and to gain better control of their geometrical parameters. This will be achieved by varying details of the SDS@2β-CD system as well as by testing other molecular tube-forming systems. The crucial step of this proposal is to develop synthesis methods to fix the generated dynamic colloidal assemblies in order to fabricate chiral colloidal particles, which will be stable after the cylindrical confinement is removed.
The synthesised particles will then be used to study the effects of chirality on their anisotropic Brownian and induced motion, self-propelling, etc. We shall subsequently develop separation techniques to yield monodisperse fractions with well-defined handedness. We shall study the interactions of chiral colloids with liquid-crystalline chiral media such as the cholesteric phase, which can provide new means to influence the latter with possible novel applications in the display technology and photonics. Furthermore, we shall investigate the effects of the particle chirality on their pair-wise interactions such as excluded volume, hydrodynamic and screened electrostatic, which can play a role for biological macromolecules. Finally, studies of the self-assembly of chiral colloids will be initiated.

• dr. Andrei Petoukhov

• drs. B.W.M. (Bonny) Kuipers