Debye Institute for Nanomaterials Science

118
Physical and Colloid Chemistry
Cubic colloids and their applications
Laura Rossi, L.Rossi@uu.nl, phone: 030 - 253 39 81
Sponsor: Senter Novem, since June 2008
Supervisors: Prof. dr. Albert P. Philipse and Prof. dr. Willem K. Kegel
TEM, SEM, Optical microscopy, Confocal fluorescence microscopy
A fundamental issue in condensed matter science is the relation between particle shape and the
symmetry and structure of the crystals they form. The simplest (but rare) crystal structure in nature
is cubic and its natural building block is the cube. We have prepared micron-sized silica hollow cubic
colloids using hematite cubic particles as template. To induce the particles self-assembly we made
use of the well-known depletion forces that arise when the colloids are dispersed in the presence
of a non-adsorbing polymer. These attraction forces surprisingly arrange the particles in a registered
configuration (Figure 1) yielding simple cubic crystals, a direct consequence of the shape of the
cubes that have slightly rounded edges.
In this project, we are currently busy investigating the effect of the polymer size on the crystal
structure.
The colloidal cubes presented in the figure below are also studied for their use as micro-capsules for
the preparation of a variety of inorganic and organic colloids, which is very useful for the control
of the particle shape, size and stability during synthesis.
Application of the particles as delivery carriers for food nutraceuticals is also under investigation.
Figure 1: Schematic picture of the self-assembly of micron size hollow colloidal cubes (imaged by TEM and SEM, left) to
simple cubic crystals (imaged by optical –top-, and confocal –bottom- microscopy).