Berlin 2015 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 5: Nanoparticles and Composite Materials I (joint CPP/BP)
BP 5.1: Vortrag
Montag, 16. März 2015, 09:30–09:45, C 243
Iron Oxide Nancube Monolayers at the Air/Water Interface: Self-Organization on Nano- and Mikroscale — •Heiko Ahrens1, Sarah Mehdizadeh Taheri2, Thomas Ortmann1, Andreas Gröning1, Stephan Förster2, and Christiane A. Helm1 — 1Physik, Uni Greifswald, 17487 Greifswald, Germany — 2Physikalische Chemie I, Uni Bayreuth, 95440 Bayreuth, Germany
Monodisperse Cubic Iron Oxide nano particles (5-8 nm) covered in oleic acid form stable films on the air water interface. Isotherms exhibit a plateau at 18 - 20 mN/m, then the pressure increases steeply. At zero surface pressure, Brewster angle microscopy(BAM)shows micrometer sized domains consisting of nanocubes immersed in a matrix of excess oleic acid. These small domains show Brownian motion. Then linear and mesh-like rigid domains (size 100 *m) are observed. The 5.5nm nanocubes form a homogenous monolayer in the plateau region, on further pressure increase large (100 *m) homogenous domains of bi- and even multilayer appear. The films of the larger 8 nm nanocubes remain heterogeneous at all surface pressures. Large (100 *m) patches of oleic acid monolayers coexist with medium sized (50*m) domains of particle monolayer and small domains (10 *m) of bi- and multilayers. All aggregation is irreversible.
These observations are confirmed by X-ray reflectivity and Grazing Incidence X-ray diffraction.