Dirk Zahn

Mixed antimony chalcogenides (Sb ₂ E ₃ , E = S, Se) as solar light absorbers offer bandgap tunability with favorable optical and electrical properties. However, depositing continuous films of thickness adjusted to the high optical absorption coefficients (2 Se ₃ , nucleation chemistry effects can render the substrate inert. Using tris(dimethylamido)antimony (Sb(NMe ₂ ) ₃ ) and bis(trimethylsilyl)selenide ((Me ₃ Si) ₂ Se) as precursors, we demonstrate that undesirable silylation of surface hydroxyl groups can be minimized by a pretreatment with Sb(NMe ₂ ) ₃ . The near‐saturation of nucleation sites on a metal oxide surface is demonstrated by scanning transmission electron microscopy and X‐ray reflectometry. Density functional theory highlights the importance of thermodynamics for surface inhibition and reactivation. The insight gained is applied to establishing a Sb ₂ Se ₃ ALD process which delivers smooth, continuous, ultrathin (2 Se ₃ ALD also provides a perspective on adjusting chemical bonding at the interface between an oxide and a heavier chalcogenide.

How molecular architecture is translated through intermolecular association into film structure and mechanical behavior remains a central question in conjugated-polymer self-assembly. Here, we compare two luminescent polymers with distinct backbone and side-chain structures: poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly(2,5-di(3′,7′-dimethyloctyl)phenylene-1,4-ethynylene) (PPE). Langmuir–Blodgett processing provides a controlled two-dimensional environment at the air–water interface, while the intrinsic fluorescence of both polymers allows interfacial organization to be followed from the earliest stages of spreading. PFO rapidly forms discrete domains. PPE instead develops a laterally interconnected network. Molecular dynamics simulations relate these morphologies to different modes of intermolecular association. In PFO, fluorene units associate more locally, favoring compact aggregation. PPE instead forms more spatially distributed contacts along the phenylene–ethynylene backbone. This distinction persists during mechanical deformation. Compression brings pre-existing PFO domains into contact, but decompression rapidly fragments the film. PPE remains laterally connected and undergoes extensive expansion. Deformation is accommodated predominantly through the ethynylene linkages of the conjugated backbone. Beyond the monolayer stability limit, both polymers develop anisotropic semicrystalline structures. PFO forms isolated needle-like domains, whereas PPE develops an interconnected fibrillar network. The results thus establish a hierarchical link between local intermolecular association and the subsequent evolution of monolayer structure and mechanical behavior. This relationship remains reflected in the ordered structures formed after monolayer collapse and provides a basis for designing ultrathin conjugated-polymer films with controlled lateral connectivity and anisotropic organization.

We report on tensile testing of atomistic simulation models mimicking silicone resins. To this end, we extend previous studies on silicone hardening and network formation (Polymers 2025, 17, 2619) to molecular dynamics simulations of the atomic-scale processes that account for elastic behavior, visco-elastic and plastic deformation. This encompasses Si–O bond scission and reformation, thus giving rise to siloxane network reorganization upon yielding, which implies both slipping of molecular chains and chemical modifications in terms of changing siloxane cross-linking. Based on graph theory, we discriminate percolating siloxane strands and elucidate the interplay of large per-atom stress in these load-bearing parts of the polymer network and heterogeneity of atomic displacements to dissipate local stress. On this basis, findings from atomic-scale characterization are discussed in the context of bulk polymer mechanical characteristics such as maximum stress, plasticity and fracture energy (4.7 ± 0.9 J/m²).

We present a combined molecular simulation and experimental study of the mechanisms of calcium oxalate monohydrate formation within a biomimetic matrix. Using a double‐diffusion approach to feed calcium and oxalate ions into an agarose gel, we show how selective ion association to different crystal faces may guide the morphogenesis and surface charge of the precipitates. Our analyses rationalize two conceptually different growth mechanisms leading to the aggregation of crystallites in terms of negatively charged needles and positively charged platelets, respectively, whereas embedding organic macromolecules are related to the hosting of counterions. We argue that this reflects a key characteristic of renal stone formation, while benefiting from drastic reduction of system complexity. Hence, the biomimetic setup is suggested for both, ex situ formation of (much simplified) proxies to kidney/urinary stones and steps toward the understanding of growth factors for tailoring inner structure, size, and dispersion in water.

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.

The accurate prediction of electronically excited states is essential for the computational design of molecular photoswitches but remains challenging for thioindigoid chromophores owing to their complex excited‐state electronic structure. In this work, we establish theoretical best estimates for the two lowest singlet and three lowest triplet vertical excitation energies of a chemically diverse set of hemithiophenindigo (HTPI) derivatives using high‐level coupled cluster methods (CC3 and CCSDT). The selected model systems retain the characteristic chromophoric core of thioindigo and hemithioindigo photoswitches while remaining accessible to benchmark calculations. Analysis of electron‐rich and electron‐poor derivatives reveals pronounced position‐dependent effects on the low‐lying excited states that closely resemble trends reported for larger thioindigoid chromophores. Based on this reference data, we benchmark 65 semiempirical and quantum‐chemical methods, including density functional approximations across multiple rungs of Jacob's ladder as well as single‐ and multireference wave function approaches. To identify computationally efficient workflows for future virtual screening studies, we additionally assess 25 combinations of ground state geometry optimization and excitation‐energy methods. The resulting recommendations for singlet‐singlet and singlet‐triplet excitation energies provide a validated methodological foundation for large‐scale in silico exploration of thioindigo and hemithioindigo dyes, thus enabling the screening of tens of thousands of candidate chromophores while retaining high overall accuracy.

Heterogenized molecular catalysts commonly rely on covalent grafting to solid supports. Cleavage of these linkages under catalytic conditions, however, can compromise structural definition and control at the interface. Here, we introduce a ligand‐encoded anchoring strategy in which a platinum(II) bis(NHC) complex is immobilized on mesoporous silica (SBA‐15) exclusively through directional, non‐covalent F–Si interactions. The molecular pre‐catalyst trans ‐[Pt(L ^F ) ₂ Cl ₂ ] was structurally characterized by single‐crystal X‐ray diffraction and multinuclear solution‐state NMR spectroscopy. Advanced solid‐state MAS NMR experiments, including ¹⁹ F{ ²⁹ Si} REDOR, combined with molecular dynamics simulations, establish well‐defined F–Si contacts with internuclear distances on the Å‐scale and reveal the organization of the pre‐catalyst at the silica interface. A model hydrosilylation reaction demonstrates catalytic activity and retention of the molecular species on the support during turnover. This work establishes non‐covalent interface engineering as a viable strategy for structurally defined heterogenized catalysis.

Phthalate esters (PAEs) are human-made pollutants of omnipresent concern due to their extensive use as polymer plasticizers and their endocrine-disruptive effects. Although the use of certain compounds has been restricted, PAEs continue to accumulate in aquatic environments through ongoing direct release or leaching from polymeric materials. In this study, we report functionalized superparamagnetic iron oxide nanoparticles (SPIONs) designed to bind various PAEs via noncovalent interaction motifs. The SPION surface is tailored via self-assembled monolayers (SAMs) while the SPION core enables magnetic collection. Systematic remediation experiments demonstrate the broad-range removal of highly concerning PAEs. Molecular dynamics simulations provide insights into the key interaction features between PAE pollutants and SAM. With regard to potential sources of emissions, PAEs leaching from commercially available soft polyvinyl chloride children’s toys are identified and efficiently removed. Cost-efficient and recyclable functionalized SPIONs provide a sustainable approach for the removal of PAEs from water.

Pyrenylimidazolyl-functionalized free-base phthalocyanines (H2Pc) and their zinc complexes (ZnPc) constitute multifunctional building blocks for realizing heterostructures with liquid phase exfoliated transition-metal dichalcogenides (LPE-TMDs). Here, we report the synthesis, optical features, and excited-state characterization of three different phthalocyanines, namely H2Pc 4, ZnPc 5, and ZnPc 6, which we designed to test how π-extended anchoring groups and metalation modulate interfacial charge transfer (iCT) with LPE-TMDs. Clean isosbestic behavior and the emergence of an interfacial Q-band at ∼720 nm as seen in steady-state titrations with LPE-TMDs, namely s-WS2 and s-MoS2, underline strong ground-state electronic coupling. In the excited state, femtosecond transient absorption spectroscopy corroborates ultrafast formation of interfacial charge-separated states (iCSS) with characteristic signatures in the short-wave infrared (SWIR) and multiphasic decay kinetics. The direction of iCSS depends on the alignment of the phthalocyanine orbitals with respect to the TMDs band structure. Pyrenylimidazolyl groups enhance immobilization onto s-TMD and foster spin-conversion between iCSS of singlet and triplet multiplicities. Responsible are the rigid phthalocanine-to-pyrenylimidazolyl linkage as well as the charge transfer transition from pyrene to the phthalocyanine core. Overall, these results establish how the molecular design impacts interfacial interactions and processes in phthalocyanine@s-TMD and provide key design rules for tailoring excitonic and electronic processes in mixed-dimensional optoelectronic systems.

We present an all-atom model mimicking superparamagnetic iron oxide nanoparticles functionalized by alkyl phosphonic acids and demonstrate the prediction of grafting density, X-ray diffraction profiles, and solvent-dependent particle radii. The inherent complexity of this nanosystem calls for careful model preparation to avoid bias from human intuition. We suggest a cascade of simulated annealing steps for (i) providing reasonable starting points for the iron oxide particle and (ii) grafting by self-assembled monolayers. The latter was performed as a function of the number of phosphonic acid molecules deposited, thus offering an unbiased assessment of the grafting density and structural alignment of the tail groups that define the outer shell of the nanoparticle. The overall protocol is widely transferable and implies moderate computational costs as compared to the explicit modeling of phosphonic acid association from solution. In turn, solvent effects on the surface structure of the nanoparticle model initially prepared in the gas phase were considered using hexane, propanol, and water, respectively. Voronoi analyses clearly demonstrated the solvent-dependent bundling of the terminal alkyl groups of the phosphonic acids grafted onto iron oxide nanoparticles. To this end, the nanoparticle-solvent interface gives rise to nanometer-scale patterns of differently oriented monolayer structures.