Colloids are small particles with dimensions in the range 1-1000 nm and are therefore much larger than molecules. Since they are still small enough to exhibit thermal motion (Brownian motion) the properties of colloidal solutions (dispersions) are similar to molecular systems; for example both exhibit diffusion, gas-liquid condensation and crystallisation. Contrary to molecules, however, the interactions between colloids can be tuned to the desired strength. Furthermore, due to their relatively large size, colloids are suitable for study with a wide variety of characterisation techniques. For example, the particles can be directly imaged with transmission electron microscopy or light microscopy, and studied (indirectly) by light diffraction, light scattering and/or sedimentation experiments. In addition, magnetic colloids can be further characterised by determining the magnetic properties, as for instance by measuring the magnetic dynamic susceptibility.

Electron microscope image
Cryo-TEM image of magnetite (Fe3O4) spheres, showing chains due to strong dipolar attractions

One important aspect of the research in our section is the interplay between chemistry and physics; experimental research is conducted to establish the effect of particle shape and interaction on the macroscopic (physical) behaviour of the colloids. To obtain a comprehensive view on the macroscopic features of colloidal systems, the thermodynamics (phase transitions), rheology (fluid dynamics), and diffusion and sedimentation properties are studied. To perform such studies, well-defined model particles with appropriate shape and tunable interactions are required. Consequently, the synthesis and characterisation of colloids is also an important topic within our section.

Electron microscope image
Hematite (Fe2O3) rods

The van 't Hoff laboratory has developed extensive expertise on the synthesis of inorganic colloids (spherical SiO2, needle-like AlOOH, platelet-like AL(OH)3, and magnetic Fe3O4). Recently, also much attention has been paid to organic polymer colloids as for example polymethylmethacrylate. (Several electron microscope images are shown on this page).

Electron microscope image
TEM image of gibbsite (Al(OH)3) platelets

Besides experimental work, also computer simulations and (statistical mechanics) theory form part of our research activities. The combination of chemical synthesis, physical experiments and theory makes colloid chemistry an attractive and interdisciplinary research area, in which people with different interest work.

Electron microscope image
Boehmite (AlOOH) rods

Our laboratory is located in the Kruyt building on the seventh floor. You can visit our permanent colloid exhibition, which gives an impression of our research (come around 10:30 or 15:15 and coffee and tea will be available). If you would like to hear more about student projects please contact a member of our group or have a look at the research proposals.