91福利

Tailored nano architectures:
Nanotubes, nanoparticles and composites for future electronic devices

Carbon nanotubes and inorganic nanoparticles are structures that exhibit extraordinary physical and chemical properties. In my talk I will discuss how such materials can be synthesized, combined, and assembled. In a first part, I will present a novel one pot synthesis approach in which semiconducting and metallic nanoparticles can be attached to non-functionalized and non-pretreated carbon nanotubes at a very high degree of coverage. They represent interesting systems with advanced crystallographic and electric properties. Such nano-materials can find applications e.g. as transistors, sensors, and in solar cells and fuel cells. In a second part, I will present recent results on truly two-dimensional colloidal nanocrystals which self-assemble by oriented attachment. One-dimensional colloidal structures 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. I will 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.