Dispersing and stabilizing silicon nanoparticles in a low-epsilon medium

One possible approach to prevent the oxidation of silicon nanoparticles during a dispersing process is to use a dispersing medium, which does not contain any oxygen atoms in its structure, e.g. toluene. However, dispersing nanoparticles in such a non-polar organic medium is a major challenge, because the particles tend to aggregate very easily. The attempt of wet-grinding non-stabilized SiNP in toluene with a stirred media mill results in μm-sized aggregates that precipitate rapidly. In order to achieve stable suspensions with regard to aggregation a suitable additive, added during the process of dispersion, is necessary. The stabilizing efficiency of several different additives, mostly oligo- and polymeric compounds, was evaluated by investigating the aggregate formation via dynamic light scattering, complemented by scanning electron micrographs. This work demonstrates that the stability of the particulate system and therefore the formation of aggregates can be adjusted selectively by the choice of the additive towards well-dispersed or densified particles. The attachment of the additives upon the surface of the SiNP was examined by diffuse reflectance infrared Fourier transform spectroscopy and the surface coverage was quantified by a combination of thermogravimetric analysis and gas sorption experiments.