Dye stabilised nanoemulsions as powerful platform for the synthesis of nanoparticles

• Applicant: Professor Dr. Ulrich Ziener
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Solid State and Surface Chemistry, Material Synthesis
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431859640

Small, narrowly distributed silica nanoparticles (ca. 6–30 nm diameter) can be prepared with high precision in dye stabilized nanoemulsions via a sol-gel process. Alternatively, very homogeneous capsules can be generated in the nanoemulsions depending on the dyes. There are assumptions on the mechanism of the process but detailed data on a molecular level is missing. In the beginning of the project investigations on the mechanism of formation of the silica particles and capsules shall be performed with the help of various characterization methods (1H-, 13C-, 29Si-NMR-, Raman-, IR-spectroscopy, SAXS/WAXS, TEM, SEM) and modelling with molecular dynamics. SAXS/WAXS will play a pivotal role because in preliminary work structural information on the arrangement of the dye molecules as well as on the inorganic particles at the interface could be obtained. Those shall be refined and combined with time dependent measurements at the synchrotron to gather important data on the kinetics of the sol-gel process. Through the gained information, the concept shall be extended in terms of a universal platform. Copolymerizations and postfunctionalizations of the particles’ surface will be carried out. The mild reaction conditions (pH ca. 7, no further additives) shall also allow to employ sensitivesurface modificators like peptides or proteins. Because of the reaction at the interface particles with Janus morphology are expected. Furthermore, core-shell morphologies and colloidosomes should be accessible by this process. In addition, it is planned to substitute the silica precursors by titanium containing monomers to obtain small and uniform TiO2 nanoparticles. Caused by the precuorsors' hydrolytic lability there might be the necessity to fall back on non-aqueoussystems. A striking advantage of the dyes over classical surfactants is that the former can be easily removed by washing which is followed without problems visually or spectroscopically. From the methodical viewpoint, there will be a strong focus of the project on static lightscattering experiments. They shall help to elucidate the mechanism of formation of the nanoparticles and –capsules without laborious sample preparation and to control (online) the process of their formation. The project focuses on the synthesis of new materials with strong methodical support in order to better understand and control the synthesis. The selection of the materials is made by application aspects but the direct realization of applications would gobeyond the scope of the project.The project focusses on three key issues: 1) mechanism of stabilization by the dyes, 2) role of the dyes in the sol-gel process and 3) extension of the concept to further morphologies and materials.Summarizing, the project’s versatility, flexibility and high potential of dye stabilized nanoemulsions as interfacial reactors for sol-gel processes shall be demonstrated.

• DFG Programme: Research Grants
• International Connection: Austria
• Co-Investigators: Professor Dr. Axel Groß; Professor Dr. Mika Lindén
• Cooperation Partner: Professor Dr. Heinz Amenitsch