Inert gamma degradation of 46 organic hole transport materials reveal a high average ionizing dose tolerance of more than 10 kGy, with BODIPY molecules exceeding 100 kGy.

Amorphous calcium carbonate (ACC) is a central precursor in biomineralization, paleoclimate archives, and functional carbonate materials. Yet, how foreign ions regulate ACC nucleation and composition remains unclear. Here, we show that Mg-2(+), Sr-2(+), and Ba-2(+) modulate ACC formation through ion-specific mechanisms that defy simple solubility and classical nucleation arguments. All three ions incorporate into supra-ionic coordination clusters that act as compositional gatekeepers from which ACC forms by aggregation. Integration of Ba into clusters stabilizes the solution entropically, leading to progressive nucleation inhibition with increasing Ba/Ca ratios- counterintuitive, given the lower solubility of Ba- vs. Ca-carbonate. Sr exhibits retrograde behavior, inhibiting nucleation at low Sr/Ca ratios but promoting it at higher ratios. Mg is distinct: Mg shows formation of two cluster populations, and ACC nucleation proceeds presumably mainly from Mg-depleted clusters. Mg acts hereby as a two-stage regulator, first delaying nucleation through cluster integration and subsequently being expelled from clusters during cluster phase separation. Together, these findings reveal a spectrum of ion-specific nucleation interferences that challenge classical nucleation concepts: entropic nucleation inhibition (Ba), ratio-sensitive induction/inhibition (Sr), and nucleation-induced compositional change (Mg). Beyond fundamental insight, they provide chemical levers to program nucleation pathways, tune material composition, and decode biomineralization control mechanisms.

Atomare Kontrolle über lösungsprozessierte hybride Halogenid‐Perowskite wird experimentell durch Atomlagenabscheidung aus der Lösung (Engl. solution atomic layer deposition , sALD) erreicht. Diese Methode überträgt die oberflächenchemischen Prinzipien der Gasphasen‐ALD (gALD) auf in der Flüssigphase gelöste Präkursoren. Durch das Umgehen der Einschränkungen, die mit der für die gALD nötige Flüchtigkeit der Präkursoren verbunden sind, erweitert die sALD das Spektrum nutzbarer Reaktions‐Chemien und zugänglicher Materialklassen. Wir demonstrieren ihre Anwendbarkeit für die Abscheidung ultradünner Filme ionischer Halbleiter, indem wir ein sALD‐Verfahren für den prominentesten Halogenid‐Perowskit, Methylammonium‐Triiodidoplumbat (CH 3 NH 3 PbI 3 , „MAPI“) entwickeln. Der Prozess zeigt bei Variation der Präkursordosierung ein sättigendes, selbstlimitierendes Wachstum, wie es für ALD typisch ist, was sowohl ex‐situ als auch in‐situ nachgewiesen wird. Die durch sALD abgeschiedenen MAPI‐Filme sind hochrein, stöchiometrisch und polykristallin. Werden MAPI‐Filme paarweise und in jeweils identischer Dicke durch sALD und durch ein modernes Spin‐Coating‐Verfahren hergestellt, so übertreffen die sALD‐Filme ihre Spin‐Coating Gegenstücke deutlich hinsichtlich der Ladungsträgerlebensdauer und der Stabilität. Sie weisen zudem eine hohe Ladungsträgermobilität auf und bilden funktionale lichtabsorbierende Schichten in Solarzellen.

We demonstrate the application of the ‘instantaneous p K ’ approach to the molecular dynamics simulation of crystallite models exposed to an acidic solvent environment.

Atomic-level control of solution-processed hybrid halide perovskites is achieved experimentally by solution atomic layer deposition (sALD). This method transfers the surface chemical principles of gas-phase ALD (gALD) to precursors dissolved in the liquid phase. Circumventing limitations associated with precursor volatility, sALD broadens the portfolio of reaction chemistries usable and material classes accessible. We establish its applicability to depositing ultrathin films of ionic semiconductors by developing an sALD procedure for the most prominent halide perovskite, methylammonium triiodoplumbate (CH3NH3PbI3, 'MAPI'). The process saturates upon precursor dosage variation to self-limiting growth typical for ALD, as analyzed by ex-situ and in-situ techniques. sALD-deposited MAPI is highly pure, stoichiometric, and polycrystalline. When MAPI films are prepared in congruent pairs by sALD and by a state-of-the-art spin-coating method, sALD-grown films clearly outperform their spin-coated counterparts in terms of charge carrier lifetimes and stability. They exhibit high carrier mobility and yield functional light absorbing layers in solar cells.

Atomic‐level control of solution‐processed hybrid halide perovskites is achieved experimentally by solution atomic layer deposition (sALD). This method transfers the surface chemical principles of gas‐phase ALD (gALD) to precursors dissolved in the liquid phase. Circumventing limitations associated with precursor volatility, sALD broadens the portfolio of reaction chemistries usable and material classes accessible. We establish its applicability to depositing ultrathin films of ionic semiconductors by developing an sALD procedure for the most prominent halide perovskite, methylammonium triiodoplumbate (CH 3 NH 3 PbI 3 , ‘MAPI‘). The process saturates upon precursor dosage variation to self‐limiting growth typical for ALD, as analyzed by ex‐situ and in‐situ techniques. sALD‐deposited MAPI is highly pure, stoichiometric, and polycrystalline. When MAPI films are prepared in congruent pairs by sALD and by a state‐of‐the‐art spin‐coating method, sALD‐grown films clearly outperform their spin‐coated counterparts in terms of charge carrier lifetimes and stability. They exhibit high carrier mobility and yield functional light absorbing layers in solar cells.

Emerging photovoltaics for outer space applications are one of the many examples where radiation hard molecular semiconductors are essential. However, due to a lack of general design principles, their resilience against extra-terrestrial high-energy radiation can currently not be predicted. In this work, the discovery of radiation hard materials is accelerated by combining the strengths of high-throughput, lab automation and machine learning. This way, a large material library of more than 130 organic hole transport materials is automatically processed, degraded, and measured. The materials are degraded under ultraviolet-C (UVC) light in a nitrogen atmosphere, serving as the conditions for electromagnetic radiation hardness tests. A value closely related to the differential quantum yield for photodegradation is extracted from the evolution of the UV-visible (UV-vis) spectra over time and used as a stability target. Following this procedure, a stability ranking spanning over 3 orders of magnitude was obtained. Combining Gaussian Process Regression based on predictors from structural fingerprints and manual filtering of the materials by features, structure-stability relations for UVC stable materials could be found: Fused aromatic ring clusters are beneficial, whereas thiophene, methoxy and vinylene groups are detrimental. Comparing the UV-vis spectra of the degraded material in film and solution, bond cleavage could be made out as the leading degradation mechanism. Even though UVC light can in principle break most organic bonds, the stable materials are able to distribute and dissipate the energy well enough so that the chemical structures remain stable. The established predictive model quantifies the effect of specific molecular features on UVC stability, allowing chemists to consider UVC stability in their molecular design strategy. In the future, a larger data set will allow to inversely design molecular semiconductors which show high performance and radiation hardness at the same time.

The epithelial sodium channel (ENaC) mediates Na+ absorption in several epithelia. Its impaired function leads to severe disorders, like pseudohypoaldosteronism type 1 and respiratory distress. Interestingly, a small molecule ENaC activator, the peptidomimetic S3969, stimulates human but not mouse αβγ-ENaC (Lu et al. 2008, J Biol Chem). Our aim was to identify and characterize the S3969 binding site in human ENaC. ENaC was heterologously expressed in Xenopus laevis oocytes, amiloride-sensitive whole-cell currents (ΔIami) were measured using the two-electrode voltage clamp technique. A putative S3969 binding site was predicted by using molecular docking and molecular dynamics (MD) simulations based on a recently published ENaC structure (Noreng et al. 2020, Elife). In addition, the effect of S3969 on endogenously expressed ENaC was studied in human airway epithelial cells (H441) using transepithelial measurements in Ussing chambers. We confirmed that in oocytes S3969 activated human αβγ-ENaC by ~2-fold with an EC50 of ~0.3 μM (n=25). As reported, murine αβγ-ENaC was insensitive to S3969 in concentrations up to 10 μM (n=19). Using mouse-human chimeric ENaC, we found that a portion of the extracellular loop of the β-subunit (residues 256-404), which includes parts of the thumb, palm and β-ball domains, is critical for channel stimulation by S3969. Computer simulations predicted a putative S3969 binding pocket in this area, with βR388, βF391, and βY406 as key residues coordinating S3969. Mutating these residues strongly reduced (βR388A) or nearly abolished (βY406A; βF391G) the stimulatory effect of S3969 on ΔIami (n=12-18), without altering the effect of an alternative ENaC activator chymotrypsin (n=5). MD simulations also suggested that the binding of S3969 to ENaC increased the distance between the β-thumb and the γ-palm domain. Consistent with this, the stimulatory effect of S3969 was abolished when the β-thumb domain was covalently attached to the γ-palm domain following the introduction of two cysteine residues (βR437C, γS298C) to form a disulfide bridge (n=15). Importantly, reducing the disulfide bond with DTT partially rescued the effect of S3969 on ΔIami (relative stimulation 31±1%, n=15, p<0.001). We also showed that S3969 stimulated endogenously expressed human ENaC in H441 cells. In conclusion, we demonstrated that S3969 activates ENaC by interacting with a specific binding pocket in β-ENaC which probably increases the β-γ-intersubunit distance. These results may help to identify novel ENaC modulators with potential physiological or therapeutic implications. Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), project number 509149993, TRR 374 (subproject A4 to A.I. and C.K.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The epithelial sodium channel (ENaC) is essential for mediating sodium absorption in several epithelia. Its impaired function leads to severe disorders, including pseudohypoaldosteronism type 1 and respiratory distress. Therefore, pharmacological ENaC activators have potential therapeutic implications. Previously, a small molecule ENaC activator (S3969) was developed. So far, little is known about molecular mechanisms involved in S3969-mediated ENaC stimulation. Here, we identified an S3969 binding site in human ENaC by combining structure-based simulations with molecular biological methods and electrophysiological measurements of ENaC heterologously expressed in Xenopus laevis oocytes. We confirmed a previous observation that the extracellular loop of β-ENaC is essential for ENaC stimulation by S3969. Molecular dynamics (MD) simulations predicted critical residues in the thumb domain of β-ENaC (Arg388, Phe391, and Tyr406) that coordinate S3969 within a binding site localized at the β-γ-subunit interface. Importantly, mutating each of these residues reduced (R388H; R388A) or nearly abolished (F391G; Y406A) the S3969-mediated ENaC activation. MD simulations also suggested that S3969-mediated ENaC stimulation involved a movement of the α5 helix of the thumb domain of β-ENaC away from the palm domain of γ-ENaC. Consistent with this, the introduction of two cysteine residues (βR437C – γS298C) to form a disulfide bridge connecting these two domains prevented ENaC stimulation by S3969 unless the disulfide bond was reduced by DTT. Finally, we demonstrated that S3969 stimulated ENaC endogenously expressed in cultured human airway epithelial cells (H441). These new findings may lead to novel (patho-)physiological and therapeutic concepts for disorders associated with altered ENaC function.

We present a molecular simulation approach to studying the role of local and momentary molecular environment for potential acid-base reactions. For this, we combine thermodynamic considerations on the pK of ionic species with rapid sampling of energy changes related to (de)protonation. Using dispersed carbonate ions in water as a reference, our approach aims at the fast assessment of the momentary protonation energy, and thus the 'instantaneous pK', of calcium-carbonate ion aggregates. The latter include transient complexes that are elusive to long sampling runs. This motivated the elaboration of approximate, yet particularly fast assessable sampling strategies. Along this line, we were able to characterize instantaneous pK values at a statistical accuracy of 0.4 pK units within sampling runs of only 10 ps duration, whereas statistical errors reduce to 0.1 pK units in 75 ps sampling runs, respectively. This readily enabled the required time resolution for the characterization of [Cax (CO3 )y ]2(x-y) aggregates with x=1,2 and y=1,2,3, respectively. In turn, the analysis of the pH-dependent nature of calcite-water interfaces and dynamically ordered liquid-like oxyanion polymers (dollop) domains is outlined at 10 ps resolution.

Amorphes Kalziumcarbonat (ACC) ist ein wichtiger Vorläufer in der Biomineralisierung und von zentraler Bedeutung für die geologische und industrielle Kalzifizierung. Einige kleine organische Moleküle haben die Fähigkeit, die Bildung, Zusammensetzung und Stabilität von ACC stark zu beeinflussen. In ihrem Forschungsartikel (e202208475) entschlüsseln Asher Schmidt, Dirk Zahn, Stephan E. Wolf et al. die zugrundeliegenden molekularen Mechanismen, die sowohl die Pränukleation als auch die Zusammensetzung der Lösung regulieren. Amorphes Kalziumcarbonat (ACC) ist ein wichtiger Vorläufer in der Biomineralisierung und von zentraler Bedeutung für die geologische und industrielle Kalzifizierung. Einige kleine organische Moleküle haben die Fähigkeit, die Bildung, Zusammensetzung und Stabilität von ACC stark zu beeinflussen. In ihrem Forschungsartikel (e202208475) entschlüsseln Asher Schmidt, Dirk Zahn, Stephan E. Wolf et al. die zugrundeliegenden molekularen Mechanismen, die sowohl die Pränukleation als auch die Zusammensetzung der Lösung regulieren. Organische Halbleiter Photokatalyse Polymere Heterogene Katalyse

Abstract We present the convenient synthesis and characterization of the new ternary thiostannate Na4SnS4 (space group I41/acd ) by directed removal of crystal water molecules from Na4SnS4⋅14 H2O. The compound represents a new kinetically stable polymorph of Na4SnS4, which is transformed into the known, thermodynamically stable form (space group P4‾21c ) at elevated temperatures. Thermal co‐decomposition of mixtures with Na3SbS4⋅9 H2O generates solid solution products Na4−x Sn1−x Sb x S4 (x=0.01, 0.10) isostructural to the new polymorph (x=0). Incorporation of Sb5+ affects the bonding and local structural situation noticeably evidenced by X‐ray diffraction, 119Sn and 23Na NMR, and 119Sn Mössbauer spectroscopy. Electrochemical impedance spectroscopy demonstrates an enormous improvement of the ionic conductivity with increasing Sb content for the solid solution (σ 25°C=2×10−3, 2×10−2, and 0.1 mS cm−1 for x=0, 0.01, and 0.10), being several orders of magnitude higher than for the known Na4SnS4 polymorph.

Understanding the underlying processes of biomineralization is crucial to a range of disciplines allowing us to quantify the effects of climate change on marine organisms, decipher the details of paleoclimate records and advance the development of biomimetic materials. Many biological minerals form via intermediate amorphous phases, which are hard to characterize due to their transient nature and a lack of long-range order. Here, using Monte Carlo simulations constrained by X-ray and neutron scattering data together with model building, we demonstrate a method for determining the structure of these intermediates with a study of amorphous calcium carbonate (ACC) which is a precursor in the bio-formation of crystalline calcium carbonates. We find that ACC consists of highly ordered anhydrous nano-domains of approx. 2 nm that can be described as nanocrystalline. These nano-domains are held together by an interstitial net-like matrix of water molecules which generate, on the mesoscale, a heterogeneous and gel-like structure of ACC. We probed the structural stability and dynamics of our model on the nanosecond timescale by molecular dynamics simulations. These simulations revealed a gel-like and glassy nature of ACC due to the water molecules and carbonate ions in the interstitial matrix featuring pronounced orientational and translational flexibility. This allows for viscous mobility with diffusion constants four to five orders of magnitude lower than those observed in solutions. Small and ultra-small angle neutron scattering indicates a hierarchically-ordered organization of ACC across length scales that allow us, based on our nano-domain model, to build a comprehensive picture of ACC formation by cluster assembly from solution. This contribution provides a new atomic-scale understanding of ACC and provides a framework for the general exploration of biomineralization and biomimetic processes.

Small-molecular-weight (MW) additives can strongly impact amorphous calcium carbonate (ACC), playing an elusive role in biogenic, geologic, and industrial calcification. Here, we present molecular mechanisms by which additives regulate stability and composition of both CaCO3 solutions and solid ACC. Potent antiscalants inhibit ACC precipitation by interacting with prenucleation clusters (PNC); they specifically trigger and integrate into PNCs or feed PNC growth. Only PNC-interacting additives are traceable in ACC, considerably stabilizing it against crystallization. The selective incorporation of potent additives in PNCs is a reliable chemical label that provides conclusive chemical evidence that ACC is a molecular precipitate derived PNCs. Our results reveal additive-cluster interactions beyond established mechanistic conceptions. They reassess the role of small-MW molecules in crystallization and biomineralization, while breaking grounds for new sustainable antiscalants.

Here, we approach the issue of ACC ultrastructure by applying a method for determining atomically resolved structures of amorphous materials using Monte Carlo simulations constrained by both X-ray and neutron scattering data. This structural analysis approach allows us to develop a detailed model for ACC at the atomic level. Our findings reveal that synthetic ACC, rapidly precipitated at high pH, consists of two-nanometer sized units containing a high degree of near range order similar to partially disordered nano-crystals. Small-angle scattering analyses show a multi-scale hierarchical organisation of the structure, supportive of a multi-step colloid self-assembly process. Computer simulations and high-resolution transmission electron microscopy show that the mesostructure of ACC resembles that of a glassy gel with crystalline material in domains. Our findings support the formation of ACC by a nanoparticle aggregation process that likely starts from prenucleation clusters in solution.

Strontium-substituted apatite-(CaF)-gelatin composites have been synthesized within a gelatin gel using the double-diffusion technique. All experimental parameters were kept constant while systematically varying the strontium/calcium molar ratio in solution. The effect of the presence of strontium ions in the growth solution on composition, morphogenesis, and morphology as well as pyroelectric properties of synthetic aggregates was systemically analyzed. It was shown that strontium ions significantly inhibit the growth process of composite aggregates and increase growth anisotropy along [0001], which were also confirmed and explained using molecular dynamic simulations. Furthermore, the promotion of the crystal branching processes and spherulite formation were observed. Pyroelectric microscopy (SPEM) measurements on mixed substituted apatite-(CaSrF)-gelatin composite aggregates showed an increase in polar properties, suggesting a lowering of the crystal symmetry. This was verified by Rietveld refinement of synchrotron powder X-ray diffraction, which revealed the noncentrosymmetric P6(3) apatite crystal structure. These data could shed new light on understanding piezoelectric and pyroelectric properties of apatite-based biological hard tissues.

Conjugate Sn(iv)(pyropheophorbide a)dichloride-(peptide nucleic acid) catalyzes reduction of azobenzene derivatives in the presence of complementary nucleic acid (NA) upon irridiation with red light (660 nm). This is the first red light-induced NA-templated photoreduction. It is highly sensitive to single mismatches in the NA-template and can detect down to 5 nM NAs.