Hans-Georg Steinrück

Micropollution is an ever‐increasing concern to human health and wildlife caused by population growth, industrialization, and intensive agriculture. An example of such micropollutants are natural and synthetic estrogen hormones. They are found everywhere in the aquatic environment at very low but dangerous concentrations. In this article, we demonstrate a supramolecular design principle for adsorption of such low‐concentrated estrogens onto tailored superparamagnetic iron oxide nanoparticles (SPIONs) enabling efficient magnetic water cleaning. We facilitate the adsorption by tuning the SPION surface with a binary self‐assembled monolayer (SAM) composed of two phosphonic acid derivatives: one serving as hydrophobic interaction site and the other improving water dispersibility of the system. Next to validating the concept in real river water, we conclude the demonstration of our nanomaterials by unveiling the estrogen‐SAM interaction at dilute conditions via synergistic combination of model systems, characterization techniques, and simulation. We experimentally deduce tight binding of estrogens combined with simulations that identify different, dynamic adsorption motifs at molecular space and time scale including a rare intercalation state, in which the hydrophobic pollutants minimize their contact to water. We believe that beyond our materials, these insights on the pollutant‐adsorbent interface underline the importance and potential of rational, molecular‐scale design of nano‐adsorbents.

Zeolite flexibility triggered by ion-exchange tuning pore geometry impacts the responsive interactions with guest species in selective adsorption and industrial catalysis. However, direct observation of their local atomic structure deformation and subsequent fundamental flexibility correlation between ions and atomic microenvironment remains elusive. Here, we report atomic-resolution imaging of the microscopic ring flexibility in ion-exchanged MFI zeolites, revealing how ion-induced electric field alterations drive the framework distortions. Specifically, extra-framework Ba²⁺ ions confined within the 10-membered rings (10-MRs) trigger a 0.5 Å channel expansion, which exceeds the 0.2 Å expansion induced by Na⁺ ions while maintaining the framework’s macroscopic rigidity. Using differential phase contrast imaging, we visualize the local coupling of the internal electric field between confined ions and the MFI framework. The combination of our theoretical analysis, which is based on the structure and the charge distribution, demonstrates that the electric field generated by the Ba²⁺ results in an 8° deformation in the nearby T–O–T bond angles, thereby distorting the 10-MR. The ion-exchange-driven 10-MR flexibility was further experimentally verified by the adsorption and separation of CO₂, as this molecular size matches the expanded rings. This work resolves a long-term unsettled issue on the ion-exchange effect of pore size deformation in zeolites, offering insights into electric field-driven framework dynamics and introducing the intrinsic behavior of ions confined in zeolites.

Electrochemical systems are important for a sustainable and defossilized energy system of the future. While accurate and precise, the corresponding electrochemical measurements, in which many reactions may occur simultaneously, often do not contain enough information to understand the underlying mechanism and processes. This information, however, is crucial toward rational materials and devices as well as process development and for inventing innovative concepts. In this perspective, we introduce explicitly the concept of “X-ray Coulomb Counting”, in which X-ray methods are used to quantify on an absolute scale how much charge is transferred into which reactions during the electrochemical measurements. This allows one to interpret the electrochemical measurements in detail and obtain the desired phenomenological and mechanistic understanding. We show a few recent examples from the Li-ion battery literature in which the concept of X-ray Coulomb Counting was employed to obtain foundational understanding.

Self-discharge and chemically induced mechanical effects degrade calendar and cycle life in intercalation-based electrochromic and electrochemical energy storage devices. In rechargeable lithium-ion batteries, self-discharge in cathodes causes voltage and capacity loss over time. The prevailing self-discharge model centers on the diffusion of lithium ions from the electrolyte into the cathode. We demonstrate an alternative pathway, where hydrogenation of layered transition metal oxide cathodes induces self-discharge through hydrogen transfer from carbonate solvents to delithiated oxides. In self-discharged cathodes, we further observe opposing proton and lithium ion concentration gradients, which contribute to chemical and structural heterogeneities within delithiated cathodes, accelerating degradation. Hydrogenation occurring in delithiated cathodes may affect the chemo-mechanical coupling of layered cathodes as well as the calendar life of lithium-ion batteries.

Due to the hydrolytic instability of LiPF₆ in carbonate-based solvents, HF is a typical impurity in Li-ion battery electrolytes. HF significantly influences the performance of Li-ion batteries, for example by impacting the formation of the solid electrolyte interphase at the anode and by affecting transition metal dissolution at the cathode. Additionally, HF complicates studying fundamental interfacial electrochemistry of Li-ion battery electrolytes, such as direct anion reduction, because it is electrocatalytically relatively unstable, resulting in a LiF passivation layer. Methods to selectively remove ppm levels of HF from LiPF₆-containing carbonate-based electrolytes are limited. We introduce and benchmark a simple yet efficient electrochemical method to selectively remove ppm amounts of HF from LiPF₆-containing carbonate-based electrolytes. The basic idea is the application of a suitable potential to a high surface-area metallic electrode upon which only HF reacts (electrocatalytically) while all other electrolyte components are unaffected under the respective conditions.

Bacterial colonization and biofilm formation on abiotic surfaces are initiated by the adhesion of peptides and proteins. Understanding the adhesion of such peptides and proteins at a molecular level thus represents an important step toward controlling and suppressing biofilm formation on technological and medical materials. This study investigates the molecular adhesion of a pilus‐derived peptide that facilitates biofilm formation of Pseudomonas aeruginosa, a multidrug‐resistant opportunistic pathogen frequently encountered in healthcare settings. Single‐molecule force spectroscopy (SMFS) was performed on chemically etched ZnO surfaces to gather insights about peptide adsorption force and its kinetics. Metal‐free click chemistry for the fabrication of peptide‐terminated SMFS cantilevers was performed on amine‐terminated gold cantilevers and verified by X‐ray photoelectron spectroscopy (XPS) and polarization‐modulated infrared reflection absorption spectroscopy (PM‐IRRAS). Atomic force microscopy (AFM) and XPS analyses reveal stable topographies and surface chemistries of the substrates that are not affected by SMFS. Rupture events described by the worm‐like chain model (WLC) up to 600 pN were detected for the non‐polar ZnO surfaces. The dissociation barrier energy at zero force ΔG(0), the transition state distance x_b and bound‐unbound dissociation rate at zero force k_off(0) for the single crystalline substrate indicate that coordination and hydrogen bonds dominate the peptide/surface interaction.