Ernest van der Wee MSc

Ornstein Laboratory, room 14
Princetonplein 1, 3584 CC Utrecht
P.O. Box 80 000, 3508 TA Utrecht
The Netherlands
phone: +31(0)30 253 1287
secretariat: +31(0)30 253 2952


Promotor: Prof. dr. A. van Blaaderen
Employed since November 2013
Funded by EU-ERC Advanced Grant

Arresting colloidal self-assemblies and processes

Confocal fluorescence microscopy, Scanning electron
microscopy (SEM), Colloidal synthesis
Confocal fluorescence microscopy is commonly used to acquire 3D information of
a colloidal system. Although very useful for dense packed systems where the
particles are immobile [1], 3D data collected from systems with mobile particles
will be distorted. When scanning at high resolution, the mobile particles will move
during the scanning of the sample, resulting in an incorrect image of the
particles. This is a problem when studying, for instance, long range repulsive
colloidal systems (see figure 1). Although raising the scanning frequency and the
viscosity of the dispersion lower the distortion of the acquired data, we
investigate a complete arrest of the particles without distorting the configuration
of the dispersion.
By the addition of a monomer and initiator to the solvent in the dispersion and a
subsequent exposure to UV-light, we want to effectively arrest the colloidal
system. This procedure was developed in water by the Asher group [2]. By
extracting the 3D coordinates of the particles from the confocal fluorescence
microscopy images through particle identification software, we determine the
particles position prior to and after the polymerization of the solvent. With
quantitative analysis methods, such as radial distribution functions and bond
order parameters, we can determine whether the configuration of the colloidal
system has changed.
With this method we want to study colloidal assemblies and processes on a
fundamental level (e.g. structure and nucleation of crystals), as well as look for
interesting applications. For instance: the exposure of polymerized colloidal
crystals to electric fields, yielding tunable photonic crystals (see figure 1).
Figure 1: Confocal fluorescence microscopy image of a long range repulsive
colloidal crystal (left) and schematic representation of an polymerized
colloidal crystal array which can be manipulated by an electric field (right)
[1] A. van Blaaderen and P. Wiltzius, Science 270 , 1177-1179 (1995)
[2] J.H. Holtz and S.A. Asher, Nature 389 , 829-832 (1997)