bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyrimidoquinxoalinophenanthroline opens next chapter in design of bridging ligands for artificial photosynthesis
Authors: Brückmann Jannik , Müller Carolin , Maisuradze Tamar , Mengele Alexander , Nauroozi Djawed , Fauth Sven , Gruber Andreas , Gräfe Stefanie , Leopold Kerstin , Kupfer Stephan , Dietzek-Ivansic Benjamin , Rau Sven
Published: February 2022

Using a dehydrogenative chemistry on the complex approach, a new polypyridine bridging ligand that bridges the gap of already existing systems is synthesized. By the usage of versatile cross-coupling reactions two different coordination spheres are included in the ligand architecture. Due to the twisted geometry of the novel ditopic ligand, the resultant division of the ligand in two distinct subunits leads to steady state as well as excited state properties of the corresponding mononuclear Ru(II) polypyridine complex resembling those of prototype [Ru(bpy)3]2+ (bpy = 2,2´-bipyridine). The localization of the initially optically excited and the nature of the long-lived excited states on the Ru-facing ligand spheres is evaluated by resonance Raman and fs-TA spectroscopy, respectively, and supported by DFT and TDDFT calculations. Coordination of a second metal (Zn or Rh) to the available bis-pyrimidyl-like coordination sphere strongly influences the frontier molecular orbitals apparent by e.g., luminescence quenching. Thus, the new bridging ligand motif offers electronic properties which can be adjusted by the nature of the second metal center. Using the heterodinuclear Ru-Rh complex, visible light-driven reduction of NAD+ to NADH was achieved, highlighting the potential of this system for photocatalytic applications.
Effect of Silicone Coating on Atomic Oxygen Reactivity with Carbon Fiber Preform and Phenolic Impregnated Carbon Ablator
Authors: Chen David , Xu Chenbiao , Minton Timothy
Published: February 2022

We have conducted a comparative study on how the presence of the anti-dust CV-1144-0 silicone coating from NuSil Technology LLC affects the atomic oxygen oxidation and ablation of heat shields, specifically phenolic-impregnated carbon ablator (PICA) and its carbon fiber preform substrate, FiberForm. Using an atomic oxygen beam-surface scattering apparatus, we measured the scattered products from the surface of the materials at temperatures from 1000 K to 1800 K. Results showed higher nonreactive vs. reactive scattering flux on coated materials compared to their uncoated counterparts up to 1500 K, around which point the silicon-oxide layer decomposed. Upon the breakdown of the oxide layer, the reactivity of the sample reverted to that of its underlying substrate, either that of FiberForm or charred PICA. In addition, a subtle influence of underlying impurities, specifically calcium, was observed in the oxidation of both PICA and FiberForm. PICA appeared to retain the presence of these impurities after ablation at 1800 K, which was attributed to a shielding effect that the phenolic resin matrix provides to the material. The data should be useful for the development of an improved PICA ablation model.
Directing both the Morphology and Packing of Chiral Metal-Organic Frameworks by Cation Exchange Mediated by Nanochannels
Authors: Nasi Hadar , di Gregorio Maria Chiara , Wen Qiang , Shimon Linda J. W. , Kaplan-Ashiri Ifat , Bendikov Tatyana , Lahav Michal , van der Boom Milko E.
Published: February 2022

Crystals are among the most challenging materials to design, both at the molecular and macroscopic levels. We show here that metal-organic frameworks, based on tetrahedral pyridyl ligands, can be used as a morpho-logical and structural mold to form a series of other isostructural crystals having different metal ions. The cati-on exchange is versatile, based on the use of diverse first-row metals; it occurs with retention of the morpholo-gy. Different morphologies were obtained by a direct reaction between the ligand and metal salts. An iterative crystal-to-crystal conversion has also been demonstrated by two consecutive cation exchange processes. The primary manganese-based crystals have a complex connectivity characterized by a rare space group (P622). The molecular structure generates two types of homochiral channels that span longitudinally the entire hex-agonal prism. These channels mediate the cation exchange, as indicated by energy-dispersive X-ray spectros-copy combined with scanning electron microscopy measurements on microtome-sectioned crystals. The occur-rence of the observed cation exchange is in excellent agreement with the Irving-Williams series (Mn < Fe < Co < Ni < Cu > Zn) that are associated with the relative stability of the resulting coordination nodes. The overall approach allows for the predictability of the structural properties of rare metal-organic frameworks based on tetrahedral pyridyl ligands at different hierarchies: from elemental composition, molecular packing, and mor-phology to the bulk properties.
The Anomalies and Local Structure of Liquid Water from Many-Body Molecular Dynamics Simulations
Authors: Gartner III Thomas E. , Hunter Kelly M. , Lambros Eleftherios , Caruso Alessandro , Riera Marc , Medders Gregory R. , Panagiotopoulos Athanassios Z. , Debenedetti Pablo G. , Paesani Francesco
Published: February 2022

For the last 50 years, researchers have sought molecular models that can accurately reproduce water’s microscopic structure and thermophysical properties across broad ranges of its complex phase diagram. Herein, molecular dynamics simulations with the many-body MB-pol model are performed to monitor the thermodynamic response functions and local structure of liquid water from the boiling point down to deeply supercooled temperatures at ambient pressure. The isothermal compressibility and isobaric heat capacity show maxima at ~223 K, in excellent agreement with recent experiments, and the liquid density exhibits a minimum at ~208 K. Furthermore, a local tetrahedral arrangement, where each water molecule accepts and donates two hydrogen bonds, is the most probable hydrogen-bonding topology at all temperatures. This work suggests that MB-pol may provide predictive capability for studies of liquid water’s physical properties across broad ranges of thermodynamic states.
Spatial reactant distribution in CO2 electrolysis: Balancing CO2 utilization and Faradaic Efficiency
Authors: Subramanian Siddhartha , Middelkoop Joost , Burdyny Thomas
Published: February 2022

The production of value added C1 and C2 compounds within CO2 electrolyzers has reached sufficient catalytic performance that system and process performance – such as CO2 utilization – have come more into consideration. Efforts to assess the limitations of CO2 conversion and crossover within electrochemical systems have been performed, providing valuable information to position CO2 electrolyzers within a larger process. Currently missing, however, is a clear elucidation of the inevitable trade-offs that exist between CO2 utilization and electrolyzer performance, specifically how the Faradaic Efficiency of a system varies with CO2 availability. Such information is needed to properly assess the viability of the technology. In this work, we provide a combined experimental and 3D modelling assessment of the trade-offs between CO2 utilization and selectivity at 200 mA/cm2 within a membrane-electrode assembly CO2 electrolyzer. Using varying inlet flow rates we demonstrate that the variation in spatial concentration of CO2 leads to spatial variations in Faradaic Efficiency that cannot be captured using common ‘black box’ measurement procedures. Specifically, losses of Faradaic efficiency are observed to occur even at incomplete CO2 consumption (80%). Modelling of the gas channel and diffusion layers indicated at least a portion of the H2 generated is considered as avoidable by proper flow field design and modification. The combined work allows for a spatially resolved interpretation of product selectivity occurring inside the reactor, providing the foundation for design rules in balancing CO2 utilization and device performance in both lab and scaled applications.
New Insights on the Self-Assembly of Bio-sourced Block Copolymer MH-b-PS in Aqueous Solutions: Nanocorals, Cubosomes & Nanocubes
Authors: Atassi Yomen , Borsali Redouane
Published: February 2022

Polymer self-assembly in solution still constitutes a simple methodology for the preparation of elegant yet sophisticated nanomaterials. This work aims at presenting how the fine tuning of the experimental parameters of the nanoprecipitation process can lead to a variety of novel morphologies ranging from nanocorals through cubosomes to nanocubes. A carbohydrate dibloc copolymer with a simple and linear structure MH1.2k-b-PS2.3 has been used as a model to illustrate the formation of these new self-assemblies. This is the first time that nanocube morphology has been generated using this type of bio-sourced co-polymer in aqueous solution and at room temperature.
MoleGuLAR: Molecule Generation using Reinforcement Learning with Alternating Rewards
Authors: Goel Manan , Raghunathan Shampa , Laghuvarapu Siddhartha , Priyakumar U. Deva
Published: February 2022

Design of new inhibitors for novel targets is a very important problem especially in the current scenario with the world being plagued by COVID-19. Conventional approaches undertaken to this end, like, high-throughput virtual screening require extensive combing through existing datasets in the hope of finding possible matches. In this study we propose a computational strategy for de novo generation of molecules with high binding affinities to the specified target. A deep generative model is built using a stack augmented recurrent neural network for initially generating drug like molecules and then it is optimized using reinforcement learning to start generating molecules with desirable properties--primarily the binding affinity. The reinforcement learning section of the pipeline is further extended to multi-objective optimization showcasing the model's ability to generate molecules with a wide variety of properties desirable for drug like molecules, like, LogP, Quantitative Estimate of Drug Likeliness etc.. For multi-objective optimization, we have devised a novel strategy in which the property being used to calculate the reward is changed periodically. In comparison to the conventional approach of taking a weighted sum of all rewards, this strategy shows enhanced ability to generate a significantly higher number of molecules with desirable properties.
Elucidating the Role and Interplay of Nickel and Molybdenum Carbide Particles Supported on Zeolite Y in Methane-Steam Reforming
Authors: Zhang Xianghui , Ha Su , Wu Di
Published: February 2022

Methane steam reforming (MSR) reaction is a mature industrial process that has been applied for large-scale hydrogen production. Here, we report the synthesis and characterization, reaction kinetics, and deactivation mechanism of a series of catalysts with metallic nickel (Ni) clusters and molybdenum carbide (Mo2C) particles supported on zeolite Y (Ni-Mo2C/FAU) in MSR reaction at 850 oC. Despite low Ni loading less than 2.4 wt%, MSR on Ni-Mo2C/FAU exhibits high activity and stability, yet deactivation of Ni-FAU (the sample without Mo2C) is significant. Further investigations elucidate that the catalyst deactivation is caused by Ni particle sintering via Ostwald ripening instead of coking, and steam induces hydroxylated Ni surface that accelerates sintering. Moreover, encapsulated Mo2C boosts the activity and stability of Ni on zeolite Y by enhancing CH4 activation rather than activating H2O. The interplays among Mo2C and Ni particles dynamically balance the carbon formation and consumption rates, and inhibit Ni sintering. This study enables insights into an alternative design principle of transition metal carbide – Ni catalysts with high activity and stability for effective MSR by tuning the compositional, structural, and interfacial factors.
Moisture-assisted Near-UV Emission Enhancement of Lead-free Cs4CuIn2Cl12 Double Perovskite Nanocrystals
Authors: Liu Maning , Matta Sri Kasi , Matuhina Anastasia , Grandhi G. Krishnamurthy , Ali-Löytty Harri , Russo Salvy P. , Vivo Paola
Published: February 2022

Lead-based halide perovskite nanocrystals (NCs) are recognized as emerging emissive materials with superior photoluminescence (PL) properties. However, the toxicity of lead and the swift chemical decomposition under atmospheric moisture severely hinder their commercialization process. Herein, we report the first colloidal synthesis of lead-free Cs4CuIn2Cl12 layered double perovskite NCs via a facile moisture-assisted hot-injection method stemming from relatively nontoxic precursors. While moisture is typically detrimental to NC synthesis, we demonstrate that the presence of water molecules in Cs4CuIn2Cl12 synthesis enhances the PL quantum yield (mainly in the near-UV range), induces a morphological transformation from 3D nanocubes to 2D nanoplatelets, and converts the dark transitions to radiative transitions for the observed self-trapped excitons relaxation. This work paves the way for further studies on the moisture-assisted synthesis of novel lead-free halide perovskite NCs for a wide range of applications.
Mind the Gap! Tailoring Sol-gel Ceramic Mesoporous Coatings on Labile Metal-organic Frameworks through Kinetic Control.
Authors: Bindini Elisa , Lüdtke Tanja , Otaegui Dorleta , Möller Marco , Haddad Ryma , Boissière Cédric , Moya Sergio
Published: February 2022

Surface engineering of metal-organic frameworks (MOFs) with a mesoporous silica coating can improve MOF mechanical properties and provide an easy way to decorate MOF nanoparticles with organic or biological molecules though silane chemistry or electrostatic interactions, while retaining open access to MOF porosity. Silica coating would be highly beneficial for employing MOFs in a wide range of applications such as catalysis or drug delivery. However, obtaining a stable, controlled core-shell structure using MOF nanoparticles as seed is challenging because of their intrinsic chemically labile nature. Here we analyze the factors that destabilize the core of the Zeolitic Imidazolate Framework-8 (ZIF-8) MOFs during the sol-gel deposition of a mesoporous silica shell causing a partial or total etching of the MOF material. Silicates in solution are found to scavenge Zn2+ ions removing them from the ZIF structure and causing a partial or complete dissolution of the ZIF seed. By carefully tuning the silicate concentration in solution simultaneous control can be obtained over both the ZIF-8 dissolution and the silica condensation kinetics, resulting in the growth of a uniform mesoporous silica shell while preserving the integrity of ZIF-8. The core-shell nanoparticles obtained show a compact core shell structure with no gap between the MOF core and the silica shell, even after calcination, while the crystalline ZIF-8 structure is retained. Overall, a general synthetic approach is presented for producing nanocomposite core-shell materials which can be applied to other MOF labile seed to design new hierarchical materials.
Novel transformation products from the glucosinolate breakdown products isothiocyanates and thioglucose formed during cooking
Authors: Hoffmann Holger , Andernach Lars , Kanzler Clemens , Hanschen Franziska S.
Published: February 2022

Glucosinolates are secondary plant metabolites occurring in Brassicaceae plants. Upon tissue disruption these compounds can be enzymatically hydrolyzed into isothiocyanates. The latter are very reactive and can react with nucleophiles during food processing such as cooking. Here, a novel type of glucosinolate degradation product was identified resulting from the reaction of the isothiocyanates sulforaphane and allyl isothiocyanate with thioglucose during aqueous heat treatment. The cyclic compounds were isolated and their structure elucidated by NMR spectroscopy and high resolution mass spectrometry as 4-hydroxy-3-(4-(methylsulfinyl)butyl)thiazolidine-2-thione and 3-allyl-4-hydroxythiazolidine-2-thione. Based on experiments with isotope-labeled reagents, the determination of the diastereomeric ratio and further reactions, a reaction mechanism was proposed. Finally, the formation of the two 3-alk(en)yl-4-hydroxythiazolidine-2-thiones was quantified in boiled cabbage samples with contents of 92 pmol/g respectively 19 pmol/g fresh weight using standard addition method.
A Favorable Path to Domain Separation in the Orange Carotenoid Protein
Authors: Sharawy Mahmoud , Pigni Natalia B. , May Eric R. , Gascón José A.
Published: February 2022

The Orange Carotenoid Protein (OCP) is responsible for nonphotochemical quenching (NPQ) in cyanobacteria, a defense mechanism against potentially damaging effects of excess light conditions. This soluble two-domain protein undergoes profound conformational changes upon photoactivation, involving translocation of the ketocarotenoid inside the cavity followed by domain separation. Domain separation is a critical step in the photocycle of OCP because it exposes the N-terminal domain (NTD) to perform quenching of the phycobilisomes. Many details regarding the mechanism and energetics of OCP domain separation remain unknown. In this work, we apply metadynamics to elucidate the protein rearrangements that lead to the active, domain-separated, form of OCP. We find that translocation of the ketocarotenoid canthaxanthin has a profound effect on the energetic landscape and that domain separation only becomes favorable following translocation. We further explore, characterize, and validate the free energy surface (FES) using equilibrium simulations initiated from different states on the FES. Through pathway optimization methods, we characterize the most probable path to domain separation and reveal the barriers along that pathway. We find that the free energy barriers are relatively small (<5 kcal/mol), but the overall estimated kinetic rate is consistent with experimental measurements (>1 ms). Overall, our results provide detailed information on the requirement for canthaxanthin translocation to precede domain separation and an energetically feasible pathway to dissociation.
Control and Monitoring of Temperature in 3D-Printed Circular Disk Reactors for Continuous Flow Photochemistry using Raspberry Pi Based Software
Authors: Walmsley Lee , Hilton Stephen , Sellier Emilie , Penny Matthew , Maddox Daniel
Published: February 2022

In this communication we report our investigations into the control and monitoring of temperature in a 3D printed circular disk reactor (CDR) for continuous flow photochemistry using datalogging via a Raspberry Pi microprocessor. A lamp base and holder were designed and realised using 3D printing to enable efficient monitoring of temperature using a temperature probe and the photo-CDR was cooled using a constant controlled flow of compressed air. We demonstrated that temperature gains under commercial LED light sources are significant and that the design of our suitably designed low-cost air-cooled holder could control and stabilise the temperature of the photo-CDR over sustained time-periods.
Multifunctional Polyoxometalate-Platforms for Supramolecular Light-driven Hydrogen Evolution
Authors: Maloul Salam , van den Borg Matthias , Müller Carolin , Zedler Linda , Mengele Alexander , Gaissmaier Daniel , Jacob Timo , Rau Sven , Dietzek-Ivansic Benjamin , Streb Carsten
Published: February 2022

Multifunctional supramolecular systems are a central research topic in light-driven solar energy conversion. Here, we report a polyoxometalate (POM)-based supramolecular dyad, where two platinum-complex hydrogen evolution catalysts are covalently anchored to an Anderson polyoxomolybdate anion. Supramolecular electrostatic coupling of the system to an iridium photosensitizer enables visible light-driven hydrogen evolution. Combined theory and experiment demon-strate the multifunctionality of the POM, which acts as photosensitizer / catalyst-binding-site and facilitates light-induced charge-transfer and catalytic turnover. Chemical modification of the Pt-catalyst site leads to increased hydrogen evolution reactivity. Mechanistic studies shed light on the role of the individual components and provide a molecular understanding of the interactions which govern stability and reactivity. The system could serve as a blueprint for multifunctional polyoxometalates in energy conversion and storage.
Structure and Surface Passivation of Ultrathin Cesium Lead-Halide Nanoplatelets Revealed by Multilayer Diffraction
Authors: Toso Stefano , Baranov Dmitry , Giannini Cinzia , Manna Liberato
Published: February 2022

The research on bidimensional colloidal semiconductors has received a boost from the emergence of ultrathin lead-halide perovskite nanoplatelets. While the optical properties of these materials have been widely investigated, their accurate structural and compositional characterization is still challenging. Here, we exploited the natural tendency of the platelets to stack into highly ordered films, which can be treated as single crystals made of alternating layers of organic ligands and inorganic nanoplatelets, to investigate their structure by Multilayer Diffraction. Using X-ray diffraction alone, this method allowed to refine the structure of ∼12 Å thick Cs-Pb-Br perovskite and ∼25 Å thick Cs-Pb-Cl-I Ruddlesden-Popper nanoplatelets by precisely measuring their thickness, stoichiometry, surface passivation type and coverage, as well as deviations from the crystal structures of the corresponding bulk materials. It is noteworthy that a single, readily available experimental technique, coupled with proper modeling, provides access to such detailed structural and composition information.
Docking Ligands into Flexible and Solvated Macromolecules. 8. Forming New Bonds – Challenges and Opportunities.
Authors: Moitessier Nicolas , Labarre Anne , Stille Julia , Patrascu Mihai Burai , Martins Andrew , Pottel Joshua
Published: February 2022

Over the years, structure-based design programs and specifically docking small molecules to proteins have become prominent in drug discovery. However, many of these computational tools have been developed to primarily dock enzyme inhibitors (and ligand to other protein classes) relying heavily on hydrogen bonds, electrostatic and hydrophobic interactions. In reality, many drug targets either feature metal ions, can be targeted covalently, or are simply not even proteins (e.g., nucleic acids). Herein, we describe several new features that we have implemented into FITTED to broaden its applicability to a wide range of covalent enzyme inhibitors, and to metalloenzymes, where metal coordination is essential for drug binding. We also report new datasets that were essential demonstrate areas of success and those where additional efforts are required. This resource could be used by other program developers to assess their own
Watching Paint Dry: I/VOC Emissions from Architectural Coatings and their Impact on SOA Formation
Authors: Tanzer-Gruener Rebecca , Dugan Liam , Bier Mark , Robinson Allen , Presto Albert
Published: February 2022

Emissions from volatile chemical products (VCPs) are emerging as a major source of anthropogenic secondary organic aerosol (SOA) precursors. Paints and coatings are an important class of VCPs that emit both volatile and intermediate volatility organic compounds (VOCs and IVOCs). In this study, we directly measured I/VOC emissions from representative water-based (latex) and oil paints used in the U.S. Paint I/VOC emissions vary over several orders of magnitude by both solvent and gloss level. Oil paint had the highest emissions (>10^5 microgram/g-paint) whereas low-gloss interior paints (Flat, Satin, and Semigloss) all emitted ~10^2 microgram/g-paint. Emissions from interior paints are dominated by VOCs, whereas exterior-use paints emitted a larger fraction of IVOCs. Extended emissions tests showed that most I/VOC emissions occur within 12-24 hours after paint application, though some IVOC-dominated paints continue to emit for 48 hours or more. We used the emissions measurements to estimate paint I/VOC emissions and subsequent SOA production in the U.S. Total annual paint I/VOC emissions are 168 +/- 15 Mg. This amounts to 291 g/kg of paint used and 0.51 kg/person, which are significantly larger than comparable emissions factors from combustion systems. These emissions contribute to the formation of 8 Mg of SOA annually. Oil paints contribute ~90% of the I/VOC emissions and SOA formation, even though it only accounts for ~20% of paint usage.
Fast, accurate and non-empirical determination of the lattice thermal conductivities of I-III-VI2 chalcopyrite semiconductors
Authors: Plata Jose J. , Posligua Victor , Marquez Antonio , Fernández Sanz Javier , Grau-Crespo Ricardo
Published: February 2022

The use of computer simulation to predict the lattice thermal conductivity of materials has the potential to accelerate the discovery of new thermoelectric materials. However, the accurate prediction of this property from first principles, without input from experiment, is very computationally demanding, which limits the use of high-throughput strategies in thermoelectric materials design. We present here an accurate, fast, and non-empirical determination of the lattice thermal conductivities of a large family of semiconductors, with composition ABX2 (I-III-VI2), with A=Cu, Ag; B=Al, Ga, In, Tl; and X=S, Se, Te. We solve the Boltzmann transport equation with force constants derived from density functional theory calculations and machine-learning-based regression algorithms, reducing between one and two orders of magnitude the computational cost with respect to conventional approaches of the same accuracy. The results are in good agreement with available experimental data and allow us to rationalize the role of chemical composition, temperature and nanostructuring on the thermal conductivities across this important family of semiconductors.
A Computational Study on the Ca2+ Solvation, Coordination Environment, and Mobility in Electrolytes for Calcium Ion Batteries
Authors: Biria Saeid , Pathreeker Shreyas , Hosein Ian
Published: February 2022

Calcium (ion) batteries are promising next-generation energy storage systems, owing to their numerous benefits in terms of performance metrics, low-cost, mineral abundance, and economic sustainability. A central and critical area to the advancement of the technology is the development of suitable eletrolytes that allow for good salt solubility, ion mobility, electrochemical stability, and reversible redox activity. At this time, the study of different solvent-salt combinations is very limited. Here, we present a computational study on the coordination environment, solvation energetics, and diffusivity of calcium ions over a range of pertinent ionic liquids, cyclic and acylic alkyl carbonates, and specific alkyl nitriles and alkyl formamides, using the salts calcium bis(trifluoromethylsulfonyl)imide (Ca(TFSI)2) and calcium perchlorate (Ca(ClO4)2). Key findings are that several solvents from different solvent classes present comparable solvation environments and mobilities. Ca(TFSI)2 is prefered over Ca(ClO4)2 owing to the former’s mix coordination of Ca2+ to O and N atoms. Ionic liquids with alkyl sulfonate anions provide better coordation over TFSI, which leads to greater diffusivity. Binary organic mixtures (carbonates) provide the best solvation of Ca2+, however, single organic solvents also provide good solvation, such as EC, THF and DMF, as well as some acyclic carbonates. Ion pairing with the salt anion is always present, but can be mitigated through solvent selection, which also correlates to greater mobility; however, there are examples in which strong ion pairing is not significantly adverse to diffusivity. The solvent incorporate into the solvation structure with binary organic mixtures correlates well with the solvation capabilities of the individual solvents. Finally, we show that ionic liquids (specifically alkyl imidazole (cation) alkyl sulfonate (anion) ionic liquids) do not decompose when coordinating at a Ca metal interface, which indicates its promising stability. Overall, this study contributes further generalized understanding of the correlation between solvent and salt and the resultant Ca2+ complexes and Ca2+ mobility in a range of electrolytes, and reveals a range of possible solvents suitable for exploration in calcium (ion) batteries.
Elucidating Effects of Orbital Delocalization on Electrochemiluminescent Efficiency for Carbon Nitrides
Authors: Fang Yanfeng , Hou Yuhua , Yang Hong , Li Wang , Ma Jin , Han Dan , Cao Xuwen , Liu Songqin , Shen Yanfei , Zhang Yuanjian
Published: February 2022

Electrochemiluminescence (ECL), an emission of light excited by electrochemical reactions, has drawn attention as tools across diverse fields, ranging from clinical disease diagnosis to photo-/electro-catalysts development. Nonetheless, the ECL efficiency of most luminophores in aqueous solutions is low, which significantly hamper their broad applications; thus, understanding the intrinsic factors for ECL efficiency is highly envisioned. Herein, taking emerging carbon nitride (CN) with unique electronic structures and rigid 2D backbone as a model luminophore, we report that the orbital delocalization was a promising unifying factor for its ECL efficiency. Behind the complicated transformation of molecular structures regarding cyano-terminal groups and triazine/heptazine basal frameworks, the orbital delocalization of the as-prepared CN was found to be generally improved at an elevated condensation temperature. Such intrinsic evolution in electronic structure favored the electron injection in excitation and photon emission afterward in ECL of CN. As a result, the cathodic ECL efficiency of CN was remarkably improved to a new milestone of 170-fold greater than benchmark Ru(bpy)3Cl2.
Synthesis and characterization of lithium-conducting composite polymer-ceramic membranes for use in nonaqueous redox flow batteries
Authors: Ashraf Gandomi Yasser , Krasnikova Irina , Akhmetov Nikita , Ovsyannikov Nikolay , Pogosova Mariam , Matteucci Nicholas , Mallia Christopher , Neyhouse Bertrand , Fenton Jr. Alexis , Brushett Fikile , Stevenson Keith
Published: February 2022

Redox flow batteries (RFBs) are a burgeoning electrochemical platform for long-duration energy storage, but present embodiments are too expensive for broad adoption. Nonaqueous redox flow batteries (NAqRFBs) seek to reduce system costs by leveraging the large electrochemical stability window of organic solvents (> 3 V) to operate at high cell voltages and to facilitate the use of redox couples that are incompatible with aqueous electrolytes. However, a key challenge for emerging nonaqueous chemistries is the lack of membranes/separators with suitable combinations of selectivity, conductivity, and stability. Single-ion conducting ceramics, integrated with polymeric fillers to make flexible composites, may offer a pathway to the performance attributes needed for competitive nonaqueous systems. Here, we explore composite polymer-inorganic binder-filler membranes for lithium-based NAqRFBs, investigating two different ceramic compounds with NASICON-type (NASICON: sodium (Na) Super Ionic CONductor) crystal structure, Li1.3Al0.3Ti1.7(PO4)3 (LATP) and Li1.4Al0.4Ge0.2Ti1.4(PO4)3 (LAGTP), blended with a polyvinylidene fluoride (PVDF) polymeric matrix. We characterize the physicochemical and electrochemical properties of the synthesized membranes as a function of processing conditions and formulation using a range of microscopic, spectroscopic, and electrochemical techniques. We then integrate select composite membranes into a single electrolyte flow cell configuration and perform polarization measurements with different redox electrolyte compositions. We find that mechanically robust, chemically stable LATP/PVDF composites can support > 40 mA cm−2 at 400 mV cell overpotential, but further improvements are needed in selectivity. The insights gained through this work begin to establish the foundational knowledge needed to advance composite polymer-inorganic membranes/separators for NAqRFBs.
Solar-thermal production of graphitic carbon and hydrogen via methane decomposition
Authors: Abuseada Mostafa , Wei Chuyu , Spearrin Mitchell , Fisher Timothy
Published: February 2022

This work reports a process in which concentrated irradiation from a simulated solar source converts methane to high-value graphitic carbon and hydrogen gas. Methane flows within a photo-thermal reactor through the pores of a thin substrate irradiated by several thousand suns at the focal peak. The methane decomposes primarily into hydrogen while depositing highly graphitic carbon that grows conformally over ligaments in the porous substrate. The localized solar heating of the porous substrate serves to capture the solid carbon into a readily extractable and useful form while maintaining active deposition site density with persistent catalytic activity. Results indicate a strong temperature dependence with high decomposition occurring in the central heating zone with concentration factors and temperatures above 1000 suns and 1300 K, respectively. Even with a large flow area through regions of lower irradiation and temperature, methane conversion and hydrogen yields of approx. 70\% are achieved, and 58\% of the inlet carbon is captured in graphitic form.
A Dual CuH- and Pd-Catalyzed Stereoselective Synthesis of Highly Substituted 1,3-Dienes
Authors: Hou Chuan-Jin , Schuppe Alexander , Knippel James Levi , Ni Anton , Buchwald Stephen
Published: February 2022

Conjugated dienes are versatile building blocks and prevalent substructures in synthetic chemistry. Herein, we report a method for the stereoselective hydroalkenylation of alkynes, utilizing readily available enol triflates. We leveraged an in situ generated and geometrically pure vinyl-Cu(I) species to form the Z,Z- or Z,E-1,3-dienes in excellent stereoselectivity and yield. This approach allowed for the synthesis of highly substituted Z-dienes, including pentasubstituted 1,3-dienes, which are difficult to prepare by existing approaches.
Multi-Wavelength Photopolymerization of Stable Poly(Catecholamines)-DNA Origami Nanostructures
Authors: Winterwerber Pia , Whitfield Colette J. , Ng David Y. W. , Weil Tanja
Published: February 2022

Orthogonality is pivotal yet chemically challenging in the bottom-up synthesis of multicomponent nanostructures. Here, we leverage the fidelity of the DNA origami technique to install a multi wavelength responsive photopolymerization system with nanometer resolution. By precisely immobilizing various photosensitizers on the origami template, which are only activated at their respective peak wavelength, we can control sequential polymerization processes. In particular, the triggered photosensitizers generate reactive oxygen species that in turn initiate the polymerization of the catecholamines dopamine and norepinephrine. We imprint polymeric layers at designated positions on DNA origami, which modifies the polyanionic nature of the DNA objects, thus, promoting their uptake into living cells while preserving their integrity. Our herein proposed methodology provides a rapid platform to access complex 3D nanostructures by customizing material and biological interfaces.
”Copper Effect” in Migita–Kosugi–Stille Coupling Revisited
Authors: Tanaka Hideya , Nakamoto Masaaki , Yoshida Hiroto
Published: February 2022

”Copper effect” in Migita–Kosugi–Stille coupling (MKSC) has been well known as acceleration effect by a copper cocatalyst, which has thus far been ascribed to two different actions of copper depending on polarity of solvents, i.e., Sn/Cu transmetalation (in polar solvent such as DMF and NMP) and scavenging of ligands (in less polar ethereal solvent). Herein, we report on reconsideration of the copper effect; MKSC is markedly accelerated based on the Sn/Cu transmetalation in ethereal solvents. In particular, perfluorophenyl- and heteroaryl-stannanes were found to undergo the Sn/Cu transmetalation with excellent site-selectivity in the presence of other Ar–Sn bonds under the ethereal conditions, leading to highly chemoselective, sequential MKSC without masking/unmasking process on a tin center. Moreover, we have also demonstrated that a combination of 119Sn NMR chemical shifts (experimental) and computed FIA (theoretical) provides a quantitative criterion estimating tin-Lewis acidity that is strongly linked to activity toward the present MKSC.
The Flexible Microtube Plasma as Post-Ionization Source for Cholesterol in nano-Electrospray Mass Spectrometry
Authors: Foest Daniel , Knodel Alexander , Ahrends Robert , Coman Cristina , Franzke Joachim , Brandt Sebastian
Published: February 2022

Cholesterol serves as a biomarker in clinical- and life-sciences. The determination of abnormal levels can indicate several types of human diseases. However, the low polarity of free cholesterol makes it hardly accessible by (nano) electrospray ionization mass spectrometry (nESI-MS). As novel approach, the flexible microtube plasma (FμTP) for post-ionization allows the determination of low-polar compounds like cholesterol in combination with nESI-MS. Focusing on the analytical performance, the activated post-ionization leads to an increased cholesterol signal by a factor of 22. The repeatability and long-term stability could be successful evaluated by using a complex liver extract. Via the method of standard addition, a linear dynamic range of 1.7 orders of magnitude, a minimum detectability of 3.71 mg/L and a high accuracy (deviation: − 8.11 %) is demonstrated proofing the FμTP-nESI-MS as an excellent approach for a derivatization-free determination of cholesterol without the necessity of high-resolution Orbitrap devices or enhanced MS acquisition-methods.
Adding colour to mass spectra: Charge Determination Analysis (CHARDA) assigns charge state to every ion peak
Authors: Lyutvinskiy Yaroslav , Nagornov Konstantin O. , Kozhinov Anton N. , Gasilova Natalia , Menin Laure , Meng Zhaowei , Zhang Xuepei , Saei Amir Ata , Tsybin Yury O. , Makarov Alexander , Zubarev Roman
Published: February 2022

Traditionally, mass spectrometry (MS) output is the ion abundance plotted versus ionic mass-to-charge ratio m/z. While employing only commercially available equipment, Charge Determination Analysis (CHARDA) adds a third dimension to MS, estimating for individual peaks their charge states z, starting from z=1, and colour-coding z in m/z spectra. CHARDA combines the analysis of ion signal decay rates in the time-domain data (transients) in Fourier transform (FT) MS with the interrogation of mass defects of biopolymers. Being applied to individual isotopic peaks in a complex protein tandem (MS/MS) dataset, CHARDA facilitates charge state deconvolution of large ionic species in crowded regions, estimating z even in the absence of isotopic distribution (e.g., for monoisotopic mass spectra). CHARDA is fast, robust and consistent with conventional FT MS and FT MS/MS data acquisition procedures. An effective charge state resolution Rz≥6 is obtained, with potential for further improvements.
Speeding up quantum dissipative dynamics of open systems with kernel methods
Authors: Ullah Arif , Dral Pavlo O.
Published: February 2022

The future forecasting ability of machine learning (ML) makes ML a promising tool for predicting long-time quantum dissipative dynamics of open systems. In this Article, we employ nonparametric machine learning algorithm (kernel ridge regression as a representative of the kernel methods) to study the quantum dissipative dynamics of the widely-used spin-boson model. Our ML model takes short-time dynamics as an input and is used for fast propagation of the long-time dynamics, greatly reducing the computational effort in comparison with the traditional approaches. Presented results show that the ML model performs well in both symmetric and asymmetric spin-boson models. Our approach is not limited to spin-boson model and can be extended to complex systems.
Experimental and Computational Investigations into Trivalent Phosphorous-Mediated Radical Thiol Desulfurization
Authors: Lopp John , Schmidt Valerie
Published: February 2022

Radical-mediated thiol desulfurization processes using tricoordinate phosphorous reagents are used in a range of applications from small molecule synthesis to peptide modification. A combined experimental and computational examination of the mechanism and kinetics of the radical desulfurization of alkyl thiyl radicals using trivalent phosphorus reagents was performed. Primary alkyl thiols undergo desulfurization between 10^6 to 10^9 M-1s-1 depending on the phosphorus component with either an H-atom transfer step or β-fragmentation of the thiophosphoranyl intermediate may be rate-controlling. While the desulfurization of primary aliphatic thiols showed a marked dependence on the identity of phosphorous reagent used with either a rate-controlling H-atom transfer or -fragmentation, thiols yielding stabilized C-centered radicals showed much less sensitivity. Support for a stepwise S-atom transfer process progressing via a distorted trigonal bipyramidal thiophosphoranyl radical intermediate was obtained from DFT calculated energetics and hyperfine splitting values.
The Impact of Surface Chemistry on Gold Nanorods Uptake in Stem Cell-derived Therapeutic Cells
Authors: Mackiewicz Marilyn , Marquart Grant , Stoddard Jonathan , McGill Trevor , Kinnison Karen , Hugo Richard , Ryals Renee , Schubert Scott , Zhou Felicia
Published: February 2022

Gold nanorods (AuNRs) hold tremendous potential to improve the diagnosis and therapeutic options across the blood-retinal barrier to treat retinal diseases. For clinical ophthalmological translation, a fundamental understanding of how their physicochemical properties such as size, shape, charge, surface chemistry, and concentration, impact their stability biological environments, mechanism and efficiency of uptake, and toxicity is a necessity. Here we interrogated the uptake efficiency, biocompatibility, and stability of two subtypes of AuNRs with different types of surface coatings and varying charges, including a commercially available set of AuNRs with a 5 nm mSiO2-polymer coating and hybrid lipid-coated AuNRs developed in-house. Confocal and bright field microscopy images showed uptake of both subtypes of AuNRs in retinal pigment epithelium (RPE), neural progenitor (NP), and baby hamster kidney (BHK) cells. Transmission electron microscopy (TEM) confirms both types of AuNRs are taken up into the cytoplasm of the cells; however, larger aggregates of AuNRs are observed with the more positive and “sticky” AuNRs with a 5 nm mSiO2-polymer coating than the slightly negative hybrid lipid-coated AuNRs. Inductively Coupled Mass Spectroscopy (ICP-MS) confirm that ~3,000 of the slightly negative hybrid lipid-coated AuNRs cells and ~5,400 of the positively charged AuNRs with a 5 nm mSiO2-polymer coating (+35 mV) are taken up into RPE and BHK cell lines. Stability studies in a variety of cellular media showed that hybrid lipid-coated AuNRs are stable and disaggregated in water, 10 mM PBS buffer pH 7, and BHK media except for NP media. In contrast, the positively charged AuNRs with a 5 nm mSiO2-zeta polymer coating aggregated in all media, indicating more interactions with each other and components of the media. Bright-field and TEM confirm the presence of large aggregates of AuNRs on the surface and within the cytoplasm. Cytotoxicity studies both subtypes of AuNRs have an 80 ± 8 % cell viability, indicating mild toxicity. The hybrid lipid-coated AuNR with the cell-penetrating peptide had the least toxicological impact with a > 92 ± 7 % cell viability. Our study highlights the importance of evaluating the impact of the physicochemical features of each new nanoparticle design on their stability in biologically relevant environments and their impact on cellular uptake and toxicity in stem cell-derived therapeutic cells. Here we also provide a simple design strategy for tuning the surface chemistry of robust hybrid lipid-coated AuNRs to enhance cellular uptake to label stem cells with minimal aggregation and toxicity.
Photo Rechargeable Li-Ion Batteries using Nanorod Heterostructure Electrodes
Authors: Tharangattu Narayanan Narayanan , Kumar Amar , Thakur Pallavi , Sharma Rahul , Puthirath Anand , Pulickel Ajayan
Published: February 2022

New ways of directly using solar energy to charge electrochemical energy storage devices such as batteries would lead to exciting developments in energy technologies. Here, a two-electrode photo-rechargeable Li-ion battery is demonstrated using nanorod of type II semiconductor heterostructures with in-plane domains of crystalline MoS2 and amorphous MoOx. The staggered energy band alignment of MoS2 and MoOx limits the electron holes recombination and cause holes to be retained in the Li intercalated MoS2 electrode. The holes generated in the MoS2 pushes the intercalated Li+ ions and hence, charge the cell. Low band gap, high efficiency photo-conversion and efficient electron-hole separation help the battery to fully charge within a few hours with a low power light. The proposed concept and materials could enable next generation stable solar chargeable battery electrodes, in contrast to the reported materials.
A Generalized Kinetic Model for Compartmentalization of Organometallic Catalysis
Authors: Jolly Brandon , Co Nathalie , Davis Ashton , Diaconescu Paula , Liu Chong
Published: February 2022

Compartmentalization is an attractive approach to enhance catalytic activity by retaining reactive intermediates and mitigating deactivating pathways. Such a concept has been well explored in biochemical and more recently, organometallic catalysis to ensure high reaction turnovers with minimal side reactions. However, a scarcity of theoretical framework towards confined organometallic chemistry impedes a broader utility for the implementation of compartmentalization. Herein, we report a general kinetic model and offer design guidance for a compartmentalized organometallic catalytic cycle. In comparison to a non-compartmentalized catalysis, compartmentalization is quantitatively shown to prevent the unwanted intermediate deactivation, boost the corresponding reaction efficiency (γ), and subsequently increase catalytic turnover frequency (TOF). The key parameter in the model is the volumetric diffusive conductance (F_V) that describes catalysts’ diffusion propensity across a compartment’s boundary. Optimal values of F_V for a specific organometallic chemistry are needed to achieve maximal values of γ and TOF. As illustrated in specific reaction examples, our model suggests that a tailored compartment design, including the use of nanomaterials, is needed to suit a specific organometallic catalytic cycle. This work provides justification and design principles for further exploration into compartmentalizing organometallics to enhance catalytic performance. The conclusions from this work are generally applicable to other catalytic systems that need proper design guidance in confinement and compartmentalization.