Part II projects
In our group we study colloidal suspensions, where particles on the
order of a micrometer (the colloids) are dispersed in a solvent.
systems are highly interesting
and relevant, as they find numerous applications in several industrial
such as coatings, food, cosmetics but also in more technical
photonic crystals and data storage devices. In addition, colloids are
widely accepted as a versatile
model system for atoms and molecules as their phase behaviour is
that of atomic and molecular systems; they display rich
phase behaviour involving colloidal ‘crystal’, ‘liquid’ and ‘gas’
phases. The typical colloidal length and time scales, i.e. micrometers
and seconds, make it possible to directly observe colloidal particles
in real-space and real-time using video- and/or confocal microscopy.
Advanced colloid chemistry techniques are available to tune the
chemical and physical properties of the particles or even to develop
completely new and unique colloidal model systems. In addition,
colloidal systems are easily deformed and manipulated using external
fields such as optical
Please find below some examples of possible part II research projects.
If you are interested, please contact Roel Dullens for more
detailed information. These projects will be carried out in close
collaboration with the group of Dirk Aarts. Please click
to find out more about Part II projects in the Aarts group.
and charaterisation of new colloidal model
Well defined colloidal model
systems are of upmost importance in the study of colloidal dispersions.
Using colloid chemistry the chemical and physical properties of the
colloidal model system can be precisely adjusted to the physical
experiments in mind. Therefore, the synthesis and characterisation of
colloidal model systems plays a central role in our research.A wide
variety of chemical techniques is available to synthesize many
different colloidal particles with very specific properties. For
example, very monodisperse silica or latex spheres can be made, bit
also rods, magnetic and fluorescent colloids can be prepared. Also the
specific interactions between colloids can be controlled using surface
chemistry. To characterise the particles several techniques such as
light scattering, optical (confocal) microscopy and electron microscopy
will be used.
- Alfons van
Blaaderen, Colloids get complex, Nature (News and Views) 439, 545 (2006)
P.A. Dullens, Colloidal hard spheres: Cooking and Looking, Soft
Matter, 2, 805 (2006
- Roel P.A.
Dullens, E.M. Claesson and W.K. Kegel, Preparation and Properties
of Crosslinked Fluorescent Poly(methyl methacrylate) Latex Colloids,
Langmuir, 20, 658 - 664 (2004)
P.A. Dullens, Maria Claesson, Didi Derks, Alfons van Blaaderen and
Willem Kegel, Monodisperse core-shell Poly(methyl methacrylate)
latex colloids, Langmuir, 19, 5963 - 5966 (2003)
optical tweezer is a strongly focussed laser beam that can trap small
objects, such as colloids, using the forces that are exerted by the
light. The scattering
forces push the particles down and the gradient forces pull the
particle towards the center of the beam. Combining
optical tweezers and colloidal systems facilitates the ability to
manipulate and deform colloidal systems on the microscopic, i.e.
single-particle level (see MOVIE
on the right!).
- D. G. Grier, Nature 424, 810 (2003)
- D. L. J. Vossen et al, Rev. Sci. Instrum. 78, 2960
- M. J. Lang, S. M.
Block, Am. J. Phys. 71, 201 (2003)
boundaries and frustrated crystallisation
The strength of materials
is closely related to the grain size of the
material. However, grain boundary stability is still far from
understood. Using geometrical frustration, crystals which are rich in
grain boundaries can be prepared. By studying the
structural and dynamical behaviour of both colloidal single
crystals and crystal imperfections insight will
be gained into the relation between frustration and the stability of
- Roel P.A. Dullens
and Andrei V. Petukhov, Second-type disorder in colloidal crystals,
Europhysics Lett., 77, 58003 (2007)
- Roel P.A.
Dullens, Maurice C.D. Mourad, Dirk G.A.L. Aarts, Jacob P. Hoogenboom
and W.K. Kegel, Shape-induced frustration of hexagonal order in
polyhedral colloids, Phys. Rev. Lett., 96, 028304 (2006)
W.A. de Villeneuve, Roel P.A. Dullens, Dirk G.A.L. Aarts, Esther
Groeneveld, Johannes H. Scherff, Willem K. Kegel and Henk N.W.
Lekkerkerker, Colloidal hard sphere crystal growth frustrated by
large spherical impurities, Science, 309, 1231 (2005)
- A.V. Pethukov, D.
van der Beek, R.P.A. Dullens, I. Dolbnya and H.N.W. Lekkerkerker, Observation
of a hexatic columnar liquid crystal of polydisperse colloidal disks,
Phys. Rev. Lett., 95, 077801 (2005)
of hard-sphere colloids display an entropy-driven
fluid-crystal transition. This remarkable phenomenon widely serves as a
simple model of crystallization in atomic systems. Detailed knowledge
of the structure and dynamics of the solid-fluid interface is of
central importance for processes such as crystal nucleation and growth.
Using specially developed ‘core-shell’ colloidal hard spheres and
confocal microscopy the equilibrium and non-equilibrium properties of
the interface can be studied at the single particle, model atomic