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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 48: Nanoparticles and Composite Materials II

CPP 48.7: Talk

Friday, March 18, 2011, 12:00–12:15, ZEU 114

Truly two-dimensional colloidal nanocrystals — •Christian Klinke — Institute of Physical Chemistry, University of Hamburg

Controlled assembly leading to anisotropic nanostructures poses a conceptual challenge in materials research. Oriented attachment of nanocrystal, a self-assembly of particles into larger single crystalline objects, is one of the most promising approaches in nanotechnology to synthesize anisotropic materials. One-dimensional assemblies of oriented attachment have been reported, and in most cases the anisotropy during self-assembly is caused by crystal planes with preferred reactivity and dipole moments in the crystallites. Systems with cubic crystal symmetry, however, like PbS and PbSe, where beautiful one-dimensional oriented attachment occurs, are somewhat more difficult to explain. In a new approach we synthesized truly two-dimensional nanocrystals by oriented attachment with lateral dimensions on the micrometer scale. We show that the formation of ordered and densely packed ligand surface layers of oleic acid on {100} PbS surfaces can drive the normally isotropic crystal growth into a two-dimensional oriented attachment of nanocrystals. Hereby the presence of chlorine containing co-solvents during the initial nucleation and growth process of the nanocrystals plays a prominent role. In the talk the synthesis and the formation mechanism will be discuss and detailed characterizations will be introduced. The obtained two-dimensional structures can be readily integrated in a photo-detector device without further treatment.

Literature: Schliehe et al., Science 329 (2010) 550.