31.12.06 - Self-Assembled Nanostructures Prepared by Colloidal Chemistry. Thèse EPFL, n° 3399 (2005). Dir.: Prof. H. Hofmann.

The thesis combines fundamental colloidal chemistry approach with standard processing technologies for the successful manufacturing of unique nanosized structures with a high potential for further applications.

Self-Assembled Nanostructures Prepared by Colloidal Chemistry.

The use of nanomaterials has been shown to be promising in potential applications such as magnetic storage devices, nano-optical devices and sensors, amongst others. Such applications require the disposition of nanoparticles, of a wide variety of materials and with a narrow size distribution, into large and ordered arrays. Such aim has been shown to be achievable by controlling and possibly modifying the forces present in the self-assembly process of colloidal particles.

In the present work, silica, gold, iron oxide and zinc sulphide monodisperse and spherical nanoparticles were first deeply investigated in their suspending medium and then assembled into various ordered structures. Three-dimension colloidal crystals and two-dimension ordered monolayers of nanoparticles were first produced by adapting pH, ionic strength and particle concentration, and by evaporating the suspending medium. The forces involved during such self-assembly processes were evaluated and shown to arise from dispersion, capillary and adhesion forces. Furthermore, dip-coating of topographically nanopatterned substrates, prepared by Extreme-UV Interference Lithography, allowed the production of micrometers-long chains of nanoparticles and ordered arrays of isolated dots. Electrical and optical property measurements were finally performed on such chains of gold particles, to show the great potential of such nanostructures.