Preparation of novel composite materials by means of magnetically controlled self-assembly of colloidal nanoparticles

The aim of this project is the preparation of composite materials via self-assembling properties of magnetic nanoparticles in the presence of magnetic fields.

Magnetic nanoparticles are investigated because of their unique properties. One of the most striking is superparamagnetism,  i.e. the ability to respond to the application to an external magnetic field by developing a strong magnetic dipolar moment, which is lost upon field removal. In the presence of a magnetic field, these particles have the ability to self-assemble into chains co-aligned with the field. This ability has been used in the literature to prepare rod-like materials. The goal of this project is instead to use magnetic nanoparticles as shape-directing agents and modify the structure of other materials, such as silica-gels. Typically, silica gels are random materials with high porosity, the structure of which is governed by their composition. By adding magnetic nanoparticles to solution undergoing a sol-gel transition, the structure of the resulting gel can be controlled by the application of magnetic fields. Static magnetic fields lead to the formation of materials with a long needle-like structure, while the application of more complex field patterns can induce the formation of platelets and other exotic structures. The silica gels obtained this way can be used as a skeleton for the preparation of composite materials and can also be selectively broken to create functional components, such as magnetic rods or platelets.

Involved people

Adolphe Merkle Institute - Chemin des Verdiers 4 - CH-1700 Fribourg - Phone +41 26 300 9254