Formation and characterization of asymmetrical nanoparticle-superstructures

• Applicant: Professor Dr. Joachim Koetz
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2016 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 313068956

The aim of the project is to synthesize and characterize asymmetric nanoparticle superstructures on basis of triangular/hexagonal gold nano-platelets. Anionic vesicles are transformed into a tube-like network structure by adding PalPhBisCarb, i.e. Poly(N,N-diallyl-N,N-dimethylammonium-alt-3,5-bis-carboxyphenylmaleamincarboxylate). The resulting network structure is used as a template phase for the formation of gold-nanoplatelets. The specific tube-like network of the template phase enables the growth of asymmetric flat hexagonal/triangular platelets. Due to the presence of the polyampholyte, i.e. PalPhBisCarb, the gold nanoplatelets show a negatively charged surface. Therefore, the adsorption of oppositely charged cationic nanoparticles in a size range of 2-20 nm (Ag, Au, CdS, Fe3O4) becomes possible. These spherical particles have been formed in a separate nucleation process and their stability is achieved by covering their surface with a polycation, i.e. poly(ethylenimine). Due to predominantly electrostatic interactions between negatively charged gold nano-platelets and positively charged spherical nanoparticles, but also by a conjugation via DNA strands or mercapto groups supramolecular architectures can be created in a next step. The advantage of this strategy is to create tuneable special optical and magnetic properties of the highly ordered architectures in dependence on the adsorbed spherical nanoparticles. Therefore, highly ordered anisotropic structures on the nanometerscale with antibacterial, magnetic or opto-electronical properties becomes available. Because the size range for spherical particles in the order of 2-20 nm is tuneable in dependence on the template used, e.g. polyelectrolyte-modified microemulsions, a variation of the properties of the assemblies is not only possible by the kind of the adsorbed nanoparticle but also by their particle size. Asymmetric Flow - Field Flow Fractionation (AF-FFF), dynamic and electrophoretic light scattering measurements in combination with UV-vis spectroscopy are applied for characterizing size and charge of the particles. For a morphological characterization of the triangular and supramolecular architectures High Resolution Transmission Electron Microscopy (HRTEM) will be applied. Because of the state-of-the-art equipment in the research group Koetz (EELS, EDX elemental analysis, tomography) of HRTEM, the adsorption of single nanoparticles at the surface of the matrix is directly provable. Finally, it has to be stated here that the project is exceeding the state of present knowledge because a unique monodisperse distribution in asymmetric assemblies could not be realized until now. Therefore, the project opens a door to further activities in the field of multifunctional nano-assemblies with extraordinary properties.

• DFG Programme: Research Grants
• Cooperation Partner: Privatdozent Dr. Dietmar Appelhans