Publications

We study the geometric structure of the drift dynamics of Irreversible port-Hamiltonian systems. This drift dynamics is defined with respect to a product of Poisson brackets, reflecting the interconnection structure and the constitutive relations of the irreversible phenomena occuring in the system. We characterise this product of Poisson brackets using a covariant 4-tensor and an associated function. We derive various conditions for which this 4-tensor and the associated function may be reduced to a product of almost Poisson brackets.

The activation step of Vaska-type Rh(I) complexes, such as the photocleavage of the Rh‑CO bond, plays an important role in the subsequent C-H activation. To elucidate the details of the photochemistry of Vaska-type Rh(I) complexes, such as trans-Rh(PMe3)2(CO)(Cl), we here present a computationally derived picture as obtained at the density functional level of theory (DFT) in combination with multireference wavefunction-based methods. We have identified that the photocleavage of CO proceeds via the metal-centered excited state, which is populated through intersystem crossing (ISC) from the dipole-allowed excited state S1. Moreover, the present study unraveled the reasons for the low C-H activation efficiency when using Rh featuring the bidentate ligand 1,2-bis(dimethylphosphino)ethane (dmpe), namely due to its unfavorable photochemical properties, i.e., the small driving force for light-induced CO loss and the fast deactivation of 3MC state back to the singlet ground state. In this study, we provide theoretical insight into mechanistic details underlying the light-induced CO dissociation process, for Rh complexes featuring PMe3 and dmpe ligands.

Platelets are activated immediately when contacting with non-physiological surfaces. Minimization of surface-induced platelet activation is important not only for platelet storage but also for other blood-contacting devices and implants. Chemical surface modification tunes the response of cells to contacting surfaces, but it requires a long process involving many regulatory challenges to transfer into a marketable product. Biophysical modification overcomes these limitations by modifying only the surface topography of already approved materials. The available large and random structures on platelet storage bags do not cause a significant impact on platelets because of their smallest size (only 1-3 μm) compared to other cells. We have recently demonstrated the feasibility of the mask-free nanoprint fluid force microscope (FluidFM) technology for writing dot-grid and hexanol structures. Here, we demonstrated that the technique allows the fabrication of nanostructures of varying features. Characteristics of nanostructures including height, width, and cross-line were analyzed and compared using atomic force microscopy imaging. Based on the results, we identified several technical issues, such as the printing direction and shape of structures that directly altered nanofeatures during printing. We confirmed that FluidFM is a powerful technique to precisely fabricate a variety of desired nanostructures for the development of platelet/blood-contacting devices if technical issues during printing are well controlled.

Scanning tunneling microscopy and spectroscopy experiments on surface-localized electron states confined to nanometer-scaled resonators are reviewed from the first observations to the recently discovered novel reflection mechanism of electron de Broglie waves. The focus of the presented work is on lateral confinement and on processes leading to finite decay rates of the confined states.

With the development of the energy system transformation the quality and efficiency of the rechargeable batteries, particularly the Li ion technology, gain major importance. In spite of the enormous advances, along with many other technological challenges corrosion of the metallic battery parts is often a difficult obstacle for producers and researchers. Li-metal batteries and especially the “anode-free” battery concept could significantly increase the energy density. However, contact corrosion of the Li anode, can occur in this cell configuration since there is a high probability of a three-phase contact between Li-metal, current collector and electrolyte, a condition triggering an intensive Li corrosion. In this work, a new in-situ analytical methodology based on combining electrochemical (ZRA) and microgravimetric (QCM) techniques is proposed for studying the galvanic corrosion. The applicability of this approach is explored in three different electrolyte compositions. Beside the analysis of the conventional electrochemical parameters an in-situ gravimetric detection of the deposited electrolyte decomposition products on the cathode surface is demonstrated. Adsorbed polymer layer on the Cu surface is applied for cathodic inhibition of the galvanic corrosion process, which is studied by means of the novel ZRA-QCM approach.