Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 75: Particles and clusters

O 75.3: Talk

Thursday, March 29, 2012, 16:30–16:45, MA 041

The size-dependent agglomeration of nanoparticles in solvents — Gediminas Galinis, Gauthier Torricelli, Hanieh Yazdanfar, Atea Akraiam, Mark Watkins, and •Klaus von Haeften — Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, United Kingdom

Nanoparticles suspended in solvents usually tend to agglomerate by mutual physisorption. We have investigated this phenomenon by depositing silicon clusters with a broad size distribution (peak size 40 to 60 nm) into water. Drops of the cluster-water suspension were then placed on highly oriented pyrolitic graphite (HOPG) and dried in vacuum. AFM measurements in UHV revealed a height distribution peaking at 1 to 2 nanometers, which was much smaller than the original size distribution. We explain this observation as being due to size-dependent agglomeration in water caused by the balance of thermal energy and van der Waals attraction. The maximum height of 3 nm diameter was consistent with the prediction of the Hamaker theory [1]. While single clusters where identified most clusters were laterally agglomerated and for high densities a distinct second layer was identified. In addition, the clusters showed various forms of self-organisation such as rings or gratings depending on the wetting behaviour of the solvents.

[1] G. Torricelli, A. Akraiam, K. von Haeften, Nanotechnology 22, 315711 (2011).