03 Fakultät Chemie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/4
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Item Open Access Identification of the first sulfobetaine hydrogel‐binding peptides via phage display assay(2023) Ihlenburg, Ramona B. J.; Petracek, David; Schrank, Paul; Davari, Mehdi D.; Taubert, Andreas; Rothenstein, DirkUsing the M13 phage display, a series of 7- and 12-mer peptides which interact with new sulfobetaine hydrogels are identified. Two peptides each from the 7- and 12-mer peptide libraries bind to the new sulfobetaine hydrogels with high affinity compared to the wild-type phage lacking a dedicated hydrogel binding peptide. This is the first report of peptides binding to zwitterionic sulfobetaine hydrogels and the study therefore opens up the pathway toward new phage or peptide/hydrogel hybrids with high application potential.Item Open Access The Hartree-Fock exchange for crystalline systems : the Implementation with an (all-electron) Gaussian-type basis set and numerical evidence with reference to perovskites(2026) Dovesi, Roberto; Doll, Klaus; Causà, Mauro; Rérat, Michel; D’Arco, PhilippeThe treatment of the Hartree-Fock exchange (HFX) series in periodic systems is described when a Gaussian-type basis set is adopted, and its performance is documented with reference to the KCrF3 perovskite. The computational scheme for the exchange, implemented in the CRYSTAL code in its general lines more than 35 years ago (Causà et al., J. Chem. Phys. 92, 909 (1988)), is here documented for the first time with reference to the variables essential for the description of many properties of periodic systems: truncation of the exchange series, reduction of point symmetry, change of space group, and dimension of the unit cell: these features are involved in the calculation of the total energy, the equilibrium geometry, the relative stability of phases, the Jahn-Teller splitting and orbital ordering, the ferromagnetic versus antiferromagnetic energy difference, the vibrational frequencies, and the IR and Raman intensities, to quote the most important properties of interest. The same computational scheme is used for both pure HF and for full-range or range-separated hybrid functionals, in which a variable percentage X of HFX is used. To document the role of X, a very recently defined functional is employed, PBE(X), such that PBE(0) = PBE and PBE(25) = PBE0. The high efficiency of the algorithms implemented in CRYSTAL permits to perform calculations for supercells of KCrF3 containing, for example, 3430 atoms (7 × 7 × 7 supercell of the monoclinic cell, containing 10 atoms), when an all-electron basis set of triple-ζ quality is adopted.Item Open Access Enhanced representation-based sampling for the efficient generation of data sets for machine-learned interatomic potentials(2026) Schäfer, Moritz R.; Kästner, JohannesIn this work, we present enhanced representation-based sampling (ERBS), a novel enhanced sampling method designed to generate structurally diverse training data sets for machine-learned interatomic potentials. ERBS automatically identifies collective variables by dimensionality reduction of atomic descriptors and applies a bias potential inspired by the On-the-Fly probability enhanced sampling framework. We highlight the ability of Gaussian moment descriptors to capture collective molecular motions and explore the impact of biasing parameters using alanine dipeptide as a benchmark system. We show that free energy surfaces can be reconstructed with high fidelity using only short biased trajectories as training data. Further, we apply the method to the iterative construction of a liquid water data set and compare the quality of simulated self-diffusion coefficients for models trained with molecular dynamics and ERBS data. Further, we active-learn models for liquid water with and without enhanced sampling and compare the quality of simulated self-diffusion coefficients. The self-diffusion coefficients closely match those simulated with a reference model at a significantly reduced data set size. Finally, we compare the sampling behavior of enhanced sampling methods by benchmarking the mean squared displacements of BMIM+BF4 - trajectories simulated with uncertainty-driven dynamics and ERBS and find that the latter significantly increases the exploration of configurational space.Item Open Access A reflection on ‘A hydrazone-based covalent organic framework for photocatalytic hydrogen production’ : teaching sponges new tricks(2026) Rodríguez-Camargo, Andrés; Lotsch, Bettina V.Covalent organic frameworks (COFs) are a unique class of porous materials built entirely from organic building blocks. As such, COFs unite the tunability of molecules with the robustness and optoelectronic functionality of extended solids-key requisites for (photo)catalysis. This LEGO®-like design of crystalline “molecular sponges” has captivated the imagination of chemists and inspired the first COF photocatalyst: a hydrazone-linked COF capable of harnessing visible light to drive the evolution of hydrogen from water. This commentary revisits that seminal contribution, published 11 years ago in Chemical Science (L. Stegbauer, K. Schwinghammer, B. V. Lotsch, Chem. Sci. , 2014, 5 , 2789-2793, https://doi.org/10.1039/C4SC00016A ), and reflects on its lasting impact. We survey the major advances that have shaped COF photocatalysis over the past decade and outline emerging opportunities and challenges, offering a forward-looking perspective on the role of COFs in solar energy conversion.Item Open Access Adsorption of heavy metals from low concentration solutions onto dried Chlamydomonas reinhardtii(2024) Genduso, Maria Giuseppina; Guagliano, Marianna; Finocchio, Elisabetta; Cristiani, Cinzia; Dotelli, Giovanni; Santomauro, GiuliaHeavy metals, such as Pb(II), Cr(III), and Cd(II), are frequently discharged into the environment, resulting in a threat for the health of living organisms. Microalgae represent an ecological method for the removal of these pollutants. The capture capability of active and dried Chlamydomonas reinhardtii towards both mono-ionic and multi-ionic solutions is evaluated to study the bioremediation in low-polluted wastewaters. Several characterization techniques have been performed to study morphology, composition, and the interaction between the metals and the microalgal functional groups of the wall. The effect of the operating conditions, such as contact time and pH, is assessed; an increased contact time of 4 days did not influence the adsorption yields of Pb and Cr, but it had a negative effect on Cd adsorption, while the impact of pH was mainly affecting the chemical speciation, rather than the adsorption capability. The microalga showed a larger affinity for Pb and Cd, respectively, 80 and 76% ( w / w ) of adsorption, while only the 65% ( w / w ) of the total Cr was adsorbed, suggesting a preferential biosorption.Item Open Access Designing covalent organic framework‐based light‐driven microswimmers toward therapeutic applications(2023) Sridhar, Varun; Yildiz, Erdost; Rodríguez‐Camargo, Andrés; Lyu, Xianglong; Yao, Liang; Wrede, Paul; Aghakhani, Amirreza; Akolpoglu, Birgul M.; Podjaski, Filip; Lotsch, Bettina V.; Sitti, MetinWhile micromachines with tailored functionalities enable therapeutic applications in biological environments, their controlled motion and targeted drug delivery in biological media require sophisticated designs for practical applications. Covalent organic frameworks (COFs), a new generation of crystalline and nanoporous polymers, offer new perspectives for light‐driven microswimmers in heterogeneous biological environments including intraocular fluids, thus setting the stage for biomedical applications such as retinal drug delivery. Two different types of COFs, uniformly spherical TABP‐PDA‐COF sub‐micrometer particles and texturally nanoporous, micrometer‐sized TpAzo‐COF particles are described and compared as light‐driven microrobots. They can be used as highly efficient visible‐light‐driven drug carriers in aqueous ionic and cellular media. Their absorption ranging down to red light enables phototaxis even in deeper and viscous biological media, while the organic nature of COFs ensures their biocompatibility. Their inherently porous structures with ≈2.6 and ≈3.4 nm pores, and large surface areas allow for targeted and efficient drug loading even for insoluble drugs, which can be released on demand. Additionally, indocyanine green (ICG) dye loading in the pores enables photoacoustic imaging, optical coherence tomography, and hyperthermia in operando conditions. This real‐time visualization of the drug‐loaded COF microswimmers enables unique insights into the action of photoactive porous drug carriers for therapeutic applications.Item Open Access Evaluation of process parameters for integrated CO2 electrolysis to produce ethylene(2026) Hauf, Fabian; Kollmuß, Ricarda; Haufe, Stefan; Klemm, EliasElectrochemical CO2 reduction provides a promising strategy for reducing greenhouse gas emissions by converting CO2 into chemicals such as ethylene. Integrated CO2 electrolysis, using CO2‐enriched absorbent solutions, is a cost‐effective alternative to gas‐fed systems due to reduced process complexity. However, for industrial applications, the process parameters need to be optimized to enhance selectivity and efficiency. Despite advances in catalyst and cell design, the impact of operational factors like catholyte flow rate, pressure, and temperature on C2+ product selectivity remains largely unexplored. This study systematically investigates the effects of catholyte flow rate, overpressure, and temperature on ethylene selectivity in integrated CO2 electrolysis with a potassium carbonate absorbent. Our results show that increasing the catholyte flow rate enhances the Faraday efficiency for ethylene by mitigating mass transport limitations between the flow field and the catalyst layer, whereas increasing pressure or temperature does not yield similar improvements. This insight shifts the focus from stoichiometric availability of physically dissolved CO2 to mass transport limitations, suggesting that further advances in cell design could unlock higher conversion efficiencies. Our study provides a foundation for scaling up integrated CO2 electrolysis by highlighting the importance of improving mass transport, a key step toward industrial implementation of sustainable CO2 conversion technologies.Item Open Access CuCl-promoted β‑acylation of cyclopropanols with thioesters(2026) Ponomarev, Savva; Papińska, Sandra W.; Stier, Michael; Kästner, Johannes; Fleischer, IvanaCuCl-induced cyclopropyl alcohol ring-opening followed by β-acylation with thioester is reported. Cyclopropanols and thioesters with various substitution patterns were successfully subjected to the reaction, and a series of 1,4-dicarbonyl compounds were synthesized. The mechanistic investigation revealed the involvement of Cu(I)-homoenolate, which reacts with the thioester via oxidative addition. Both experimental and computational evidence were found. Operational simplicity, high chemo- and regioselectivity, and good to excellent yields are the core features of the presented approach.Item Open Access Polycondensation‐derived high‐molecular weight lignin as nonblended precursor for carbon fibers(2024) Clauss, Manuel M.; Frank, Erik; Bauch, Volker; Kuske, Lisa; Buchmeiser, Michael R.A new concept for the controlled chain‐extension of lignin has been developed. A mixture of trioxane as formaldehyde source, resorcinol as chain extender, and lignin allows to prepare high molecular weight precursor fibers by melt‐spinning, which can be spun on a semitechnical scale. Chain extension with resorcinol bridged by methylene groups is achieved during the stabilization process of the precursor fiber. After carbonization, carbon fibers (CFs) with an average diameter of 18 µm show an average tensile strength of 0.78 GPa and a Young's modulus of 106 GPa. A maximum tensile strength of 2.44 GPa and a Young's modulus of 294 GPa are reached with fibers 9.7 µm in diameter.Item Open Access Counterion effects on the mesomorphic and electrochemical properties of guanidinium salts(2024) Ebert, Max; Lange, Alyna; Müller, Michael; Wuckert, Eugen; Gießelmann, Frank; Klamroth, Tillmann; Zens, Anna; Taubert, Andreas; Laschat, SabineIonic liquid crystals (ILCs) combine the ion mobility of ionic liquids with the order and self-assembly of thermotropic mesophases. To understand the role of the anion in ILCs, wedge-shaped arylguanidinium salts with tetradecyloxy side chains were chosen as benchmark systems and their liquid crystalline self-assembly in the bulk phase as well as their electrochemical behavior in solution were studied depending on the anion. Differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS, SAXS) experiments revealed that for spherical anions, the phase width of the hexagonal columnar mesophase increased with the anion size, while for non-spherical anions, the trends were less clear cut. Depending on the anion, the ILCs showed different stability towards electrochemical oxidation and reduction with the most stable being the PF6 based compound. Cyclic voltammetry (CV) and density functional theory (DFT) calculations suggest a possible contribution of the guanidinium cation to the oxidation processes.