Charge exchange dynamics of ions for structural studies of short-range ordered molecular nanosheet

• Applicants: Professor Dr. Jürgen Schnack; Professor Dr. Andrey Turchanin
• Subject Area: Experimental Condensed Matter Physics ; Synthesis and Properties of Functional Materials ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552519713

The main goal of this proposal is to develop a quantifiable method to probe and discriminate the structure in the sub-nm regime for organic, short-range ordered freestanding molecular nanosheets, with particular focus on their porosity. Since nearly all mechanical, chemical, and electronic properties of materials ultimately follow from their internal atomistic structure, we need to clarify this structure for the very promising material class of CNMs. We propose highly charged ion (HCI) scattering as the method of choice and therefore need to achieve a deeper understanding of the scattering process, and particularly the pre-equilibrium stage of the charge state evolution in ion-solid interaction for slow highly charged ions. Therefore, we intent to focus our investigations on three major objectives: 1. Systematic measurements of the scattering-angle-dependent charge exchange of slow HCIs passing through molecular nanosheets (Carbon Nanomembranes (CNM)). Charge exchange will be determined from the measurements. Subsequent modeling, based on recent work at TU Wien, will allow us to determine the mean porosity of molecular nanosheets. 2. Tailored synthesis of CNMs by tuning molecular precursors and understanding the crosslinking mechanisms enabling to adjust their porosity. CNMs will be synthesized from various molecular precursors to adjust their porosity. The crosslinking mechanisms will be investigated as a function of the electron energy used to convert these precursors into the CNMs. To this end, a combination of complementary electron spectroscopy, microscopy and diffraction techniques (XPS, UPS, LEEM, μLEED, SEM) together with high resolution AFM will be employed. Complementary, the porosity of CNMs will be estimated from precise permeation measurements of gases with various kinetic diameters. These results will be compared and analyzed together with the data obtained from slow HCI spectroscopy measurements and theoretical modelling. 3. Development of structure models for CNMs. The development of models based on classical carbon structures and classical molecular dynamics aims at a deeper understanding of the internal structure of the CNMs. In particular, we want to develop effective procedures to simulate the formation of pores, to understand a possible correlation of properties, in particular porosity with precursor molecules as well as to model permeation of molecules through CNMs. Links to experimental results of spectroscopy and AFM in view of, e.g., aromaticity and character of the carbon-carbon bonds shall be derived. Large efforts will be made to model highly charged ion scattering; this includes a further development of the effective dynamical description and a benchmarking with alternative thin structures.

• DFG Programme: Research Grants
• International Connection: Austria
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partner: Professor Dr. Richard Wilhelm