bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen evolution reaction on Co-Ni core-shell nanoclusters in different sizes: A DFT investigation from geometric structures to electronic structures
Authors: Xu Hengyue
Published: February 2022

Nanoclusters have broad prospects in the application of hydrogen evolution reaction (HER) electrocatalysis. Its high specific surface area, surface geometry effect, electronic properties, and quantum size effect often make the nanoclusters have higher activity than ordinary electrocatalytic materials. However, it is still challenging to design and regulate nanoclusters and make them have better HER performance. In this work, through first-principle calculations from geometric structures to electronic structures, we try to understand the basic physical and chemical properties and HER performance of nanoclusters composed of transition metals Co and Ni. We optimize the electronic structure and promote effective charge transfer by adjusting the size of nanoclusters and constructing core-shell alloying. First-principle studies reveal that the geometric size and electronic structure of Co-Ni nanoclusters can significantly affect the performance of the hydrogen evolution reaction. We found that Co@Ni12 (|ΔGH*|=0.01eV) shows the best HER performance. The Gibbs free energy of hydrogen adsorption of Co-Ni nanoclusters is positively related to the size of the clusters, and the ΔGH* can be adjusted within a certain range by changing the electronic structure of the clusters. Our research helps to understand and design high-efficiency nanocluster electrocatalysts, paving the way for the rational design and synthesis of advanced electrocatalysts for HER.
Hydrogen evolution reaction on Co-Ni core-shell nanoclusters in different sizes: A DFT investigation from geometric structures to electronic structures
Authors: Xu Hengyue
Published: February 2022

Nanoclusters have broad prospects in the application of hydrogen evolution reaction (HER) electrocatalysis. Its high specific surface area, surface geometry effect, electronic properties, and quantum size effect often make the nanoclusters have higher activity than ordinary electrocatalytic materials. However, it is still challenging to design and regulate nanoclusters and make them have better HER performance. In this work, through first-principles calculation from geometric structures to electronic structures, we try to understand the basic physical and chemical properties and HER performance of nanoclusters composed of transition metals Co and Ni. We optimize the electronic structure and promote effective charge transfer by adjusting the size of nanoclusters and constructing core-shell alloying. First-principles studies reveal that the geometric size and electronic structures of Co-Ni nanoclusters can significantly affect the performance of the hydrogen evolution reaction. We found that Co@Ni12 (|ΔGH*|=0.01eV) shows the best HER performance. The Gibbs free energy of hydrogen adsorption of Co-Ni nanoclusters is positively related to the size of the clusters, and the ΔGH* can be adjusted within a certain range by changing the electronic structures of the clusters. Our research helps to understand and design high-efficiency nanocluster electrocatalysts, paving the way for the rational design and synthesis of advanced electrocatalysts for HER.
A Simple Route to Aqueous Suspensions of Degradable Copolymer Nanoparticles from Radical Ring-Opening Polymerization-Induced Self-Assembly (rROPISA)
Authors: Zhu Chen , Denis Stephanie , Nicolas Julien
Published: February 2022

Degradable polymer nanoparticles are almost exclusively obtained by formulation of preformed degradable polymers, such as aliphatic polyesters, thus resulting is very low nanoparticle concentrations and limited structural diversity. On the other hand, many different vinyl polymers can be obtained by polymerization in aqueous dispersed media, but their non-degradability limits their use especially in the biomedical field. Herein, we combined the best of both worlds by developing a two-step radical ring-opening copolymerization-induced self-assembly (rROPISA) process, allowing to generate aqueous suspensions of narrowly dispersed, degradable vinyl copolymer nanoparticles at 15 wt.% solid contents, containing cyclic ketene acetal (CKA) units in the nanoparticle core. This strategy relied on rROPISA in DMF, followed by a simple transfer step to water. It was successfully applied to the three main CKAs used in rROP and yielded nanoparticles of ~80–215 nm in diameter with tunable amount of CKA up to 21 mol.%. Successful incorporation of ester groups in the copolymers was demonstrated by hydrolytic degradation of both the copolymers and the nanoparticles. The nanoparticles’ cytocompatibility was then established by cell viability assays and cell morphology observation with three representative healthy cell lines. Not only this synthetic strategy could be of great potential for drug delivery applications, but it can also be beneficial to other research fields to yield more environmentally friendly materials involving the use of latexes, such as paints or coatings.
Natural Products-based drug design from Bahia Semi-Arid region against SARS-CoV-2 Mpro (3Clpro)
Authors: Silva Rai , Freitas Humberto , Kimani Njogu , Santos Cleydson , Pita Samuel Silva da
Published: February 2022

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), receives global attention due to the serious threat that affect public health. Since December 2019, its incidence affecting millions of patients and its rapid dissemination on a worldwide scale have led the searching for its treatment. To discover hit compounds that can be used alone or in combination with repositioned drugs, we initiated a structure-assisted drug design program including Virtual Screening, Docking, pharmacokinetic and toxicological analysis (ADMET) and Molecular Dynamics Simulation (MD) from Natural Products Database of the Bahia Semi-Arid region (NatProDB). We also aimed to identify novel scaffolds that target the SARS-CoV-2 Main Protease (Mpro, 3Clpro) since this protein plays a pivotal role in mediating viral replication and transcription, which makes it an attractive drug target for coronaviruses. Here, we selected 10 molecules that could be studied in vitro to lead discovery in response to this infectious diseases. The best SARS-CoV-2 Mpro complexes interactions revealed that some enzyme sites were accessed thereby confirming that this method can be employed as a suitable starting method for the identification of novel SARS-CoV-2 Mpro inhibitors. Two compounds (b01 and b02) suggest a better potential for interaction with SARS-CoV-2 main protease (Mpro) and could be further studied.
Highly Regio-, Enantio-, and Exo-selective Diels–Alder Reactions Enabled by a Bispyrrolidine Diboronate
Authors: Li Yuan-He , Zhang Su-Lei , Xiao Bo , Sun Tian-Yu , Chen Jia-Hua , Wu Yun-Dong , Yang Zhen
Published: February 2022

Catalytic asymmetric Diels−Alder reaction is one of the most powerful reactions in organic chemistry. It is still a challenge to achieve high and general exo-selectivity. A novel bispyrrolidine diboronate compound has been derived from the reaction of two molecules of oxazaborolidine with one molecule of water. Upon activation, it effectively catalyzes (0.4-5 mol % loading) the Diels–Alder reaction between a variety of mono- and di-carbonyl activated dienophiles and dienes with better than 20:1 regioselectivity, up to >99:1 enantioselectivity, and better than 20:1 exo/endo selectivity. Mechanistic studies show a remarkable nonlinearity in enantioselectivity, and a second-order kinetics with respect to the catalyst concentration. A model is proposed to rationalize the above observations. The reaction is expected to find wide applications in organic synthesis.
Mild and Chemoselective Phosphorylation of Alcohols Using a PSI-Reagent
Authors: baran phil , Ociepa Michał , Knouse Kyle , He David , Vantourout Julien , Flood Dillon , Padial Natalia , Chen Jason , Sanchez Brittany , Sturgell Emily , Zheng Bin , Qiu Shenjie , Schmidt Michael , Eastgate Martin
Published: February 2022

An operationally simple, scalable, and chemoselective method for the direct phosphorylation of alcohols using a P(V)-approach based on the PSI-reagent platform is disclosed. The method features a broad substrate scope of utility in both simple and complex settings and provides access to valuable phosphorylated alcohols that would be otherwise difficult to access.
Surface and Volumetric Phenomena on Polyaniline Supported Electrocatalysts
Authors: Ferreira Graziela , Khalid Mohmmad , Napporn Teko , Torresi Roberto , Varela Hamilton
Published: February 2022

Conducting polymers have been used as support for catalysts towards distinct electrocatalytic reactions. The overall activity of the modified interfaces critically depends on both the processes on the catalyst surface and of the charge compensation within the polymer matrix. Therefore, understand the coupling between surface and volumetric processes in such systems is of utmost importance. In this contribution we report on the experimental investigation of the interplay between surface and volumetric processes during the electro-oxidation of formic acid (and also formaldehyde) on platinum modified polyaniline electrodes. The study was performed through in situ nanogravimetry, with the Electrochemical Quartz Crystal Nanobalance (EQCN). We have explored the dynamics of charge and mass changes along several experimental conditions, including the self-organized potential oscillations. The systematic study included the analysis of several configurations: gold electrodes covered with a PANI film and dispersed platinum (Au/PANI/Pt); platinum electrodes covered with PANI (Pt/PANI); and bare platinum electrodes. The methodology introduced includes the detailed analysis of the charge compensation process and of the time-derivative of the mass variations. Typical results for the electro-oxidation of formic acid on PANI supported platinum indicate that the electrocatalysis itself is reflected in the current profile, whereas the charge compensation rules the gravimetric response. This general observation also holds for the oscillatory electro-oxidation of formic acid. The physicochemical description of the support/catalyst systems described here opens interesting perspectives for the investigation of parent systems.
Cationic yet Stronger Donor: A Surprising Partner Effect and the Partner Strategy in Accelerating a Pincer-Co Catalyzed Nitrile Hydroboration Reaction
Authors: Ma Yumiao
Published: February 2022

A strategy to tune the catalytic behavior of a organometallic catalysts rather than ligand engineering is suggested in this work, by computationally studying the effect of (18-crown-6)K+, W(CO)3 and W(PMe3)3 on the reactivity of a Pincer-Co catalyzed nitrile hydroboration reaction through π-coordination to the ligand aromatic ring. These extra additives, as called by the partners, binds the central phenyl ring of the ligand by either dispersion or chemical bonding. The electron-richness of the cobalt center is tuned by the partner, and follows the order (18-crown-6)K+ > W(PMe3)3 > no partner > W(CO)3. While the influence of covalent W-containing partners parallels the electron-richness of W, the non-covalent partner, (18-crown-6)K+, surprisingly increases the donor ability of the Pincer ligand, through polarization effect. All the elementary steps involved in the nitrile hydroboration reaction are influenced by the partner, and the overall barrier is lowered by a surprisingly large extent of 4.9 kcal/mol in the presence of (18-crown-6)K+, suggesting a charming partner effect to be explored by experimentalists that the reactivity of a catalyst can be consecutively tuned without ligand modification.
Membrane Composition and Raf[CRD]-Membrane Attachment Are Driving Forces for K-Ras4B Dimer Stability
Authors: Cournia Zoe , Andreadelis Ioannis , Kiriakidi Sofia , Lamprakis Christos , Theodoropoulou Anastasia , Doerr Stefan , Chatzigoulas Alexios , Manchester John , Velez-Vega Camilo , Duca José
Published: February 2022

RAS proteins are membrane-anchored GTPases that regulate key cellular signaling networks. It has been recently shown that different anionic lipid types can affect the properties of RAS in terms of dimerization/clustering on the cell membrane. To understand the effects of anionic lipids on key spatiotemporal properties of dimeric K-Ras4B, we perform all-atom molecular dynamics simulations of the dimer K-Ras4B in the presence and absence of Raf[CRD/RBD] effectors on two model anionic lipid membranes: one containing 78% mol. DOPC, 20% mol. DOPS, 2% mol. PIP2 and another one with enhanced concentration of anionic lipids containing 50% mol. DOPC, 40% mol. DOPS, 10% mol. PIP2. Analysis of our results unveils the orientational space of dimeric K-Ras4B, and shows that the stability of the dimer is enhanced on the membrane containing a high concentration of anionic lipids in the absence of Raf effectors. This enhanced stability is also observed in the presence of Raf[CRD/RBD] effectors although it is not influenced by the concentration of anionic lipids in the membrane, but rather on the ability of Raf[CRD] to anchor to the membrane. We generate dominant K-Ras4B conformations by Markov State Modeling and yield the population of states according to the K-Ras4B orientation on the membrane. For the membrane containing anionic lipids, we observe correlations between the diffusion of K-Ras4B and PIP2 and anchoring of anionic lipids to the Raf[CRD] domain. We conclude that the presence of effectors with the CRD domain anchoring on the membrane as well as the membrane composition both influence the conformational stability of the K-Ras4B dimer enabling the preservation of crucial interface interactions.
Predicting Phosphorescence Energies and Inferring Wavefunction Localization with Machine Learning
Authors: Sifain Andrew E. , Lystrom Levi , Messerly Richard A. , Smith Justin , Nebgen Benjamin , Barros Kipton , Tretiak Sergei , Lubbers Nicholas , Gifford Brendan J.
Published: February 2022

Phosphorescence is commonly utilized for applications including light-emitting diodes and photovoltaics. Machine learning (ML) approaches trained on ab-initio datasets of singlet-triplet energy gaps may expedite the discovery of phosphorescent compounds with the desired emission energies. However, we show that standard ML approaches for modeling potential energy surfaces inaccurately predict singlet-triplet energy gaps due to the failure to account for spatial localities of spin transitions. To solve this, we introduce localization layers in a neural network model that weight atomic contributions to the energy gap, thereby allowing the model to isolate the most determinative chemical environments. Trained on the singlet-triplet energy gaps of organic molecules, we apply our method to an out-of-sample test set of large phosphorescent compounds and demonstrate the substantial improvement that localization layers have on predicting their phosphorescence energies. Remarkably, the inferred localization weights have a strong relationship with the ab-initio spin density of the singlet-triplet transition, and thus infer localities of the molecule that determine the spin transition, despite the fact that no direct electronic information was provided during training. The use of localization layers is expected to improve the modeling of many localized, non-extensive phenomena and could be implemented in any atom-centered neural network model.
Effect of storage conditions on the performance of nitrocellulose test strips used in lateral flow assays
Authors: Kaur Navjot , Kaimal Mridul , Toley Bhushan
Published: February 2022

The effect of long-term storage of membrane materials on the performance of lateral flow assays (LFAs) has never been studied. We experimentally examined the impact of common lab storage conditions on the performance of different types of membrane materials typically used to fabricate LFAs, e.g. cellulose source pads, glass fiber conjugate pads, and nitrocellulose test membranes. Changes in flow properties, protein affinity, fluid imbibition/hydrophobicity, and LFA signal development were measured after storage under varied temperatures, humidity levels, and light and particulate matter exposure, for 1, 2 and 7 months. At the end of 7 months, the lateral imbibition rates decreased by 6±0.41x for nitrocellulose membranes exposed to light and dust, and 4.5±1.15x for nitrocellulose membranes stored at 37°C, in comparison to control membranes. These results shed light upon the significant shift in performance parameters of diagnostic membranes with long term storage.
Selective cellular probes for mammalian thioredoxin reductase TrxR1: rational design of RX1, a modular 1,2-thiaselenane redox probe
Authors: Zeisel Lukas , Felber Jan G. , Poczka Lena , Scholzen Karoline , Maier Martin S. , Cheng Qing , Arnér Elias S. J. , Thorn-Seshold Julia , Thorn-Seshold Oliver
Published: February 2022

Dynamically driven cellular redox networks power a broad range of physiological cellular processes, and additionally are often dysregulated in various pathologies including cancer and inflammatory diseases. Therefore it is vital to be able to image and to respond to the turnover of the key players in redox homeostasis, to understand their physiological dynamics and to target pathological conditions. However, selective modular probes for assessing specific redox enzyme activities in cells are lacking. Here we report the development of cargo-releasing chemical probes that target the mammalian selenoprotein thioredoxin reductase (TrxR) while being fully resistant to thiol reductants in cells, such as the monothiol glutathione (GSH). We used a rationally oriented cyclic selenenylsulfide as a thermodynamically stable and kinetically reversible trigger that matches the chemistry of the unique TrxR active site, and integrated this reducible trigger into modular probes that release arbitrary cargos upon reduction. The probes' redox biochemistry was evaluated over a panel of thiol-type oxidoreductases, particularly showing remarkable, selenocysteine-dependent sensitivity of the "RX1" probe design to cytosolic TrxR1, with little response to mitochondrial TrxR2. The probe was cross-validated in cells by TrxR1 knockout, selenium starvation, TrxR1 knock-in, and use of TrxR-selective chemical inhibitors, showing excellent TrxR1-dependent cellular performance. The RX1 design is therefore a robust, cellularly-validated, modular probe system for mammalian TrxR1. This sets the stage for in vivo imaging of TrxR1 activity in health and disease; and the thermodynamic and kinetic considerations behind its selectivity mechanism represent a significant advance towards rationally-designed probes for other key players in redox biology.
Unexpected reactivity related to support effects during xylose hydrogenation over ruthenium catalysts
Authors: Vilcocq Léa , Paez Ana Maria , Freitas Victoria , Veyre Laurent , Fongarland Pascal , Philippe Régis
Published: February 2022

Xylose is a major component of hemicelluloses. In this paper, its hydrogenation to xylitol in aqueous medium was investigated with two Ru/TiO2 catalysts prepared with two commercial TiO2 supports. A strong impact of support on catalytic performances was evidenced. Ru/TiO2-R led to fast and selective conversion of xylose (100 % conversion in 2 h at 120°C with 99 % selectivity) whereas Ru/TiO2-A gave a slower and much less selective transformation (58 % conversion in 4 h at 120°C with 17 % selectivity) with the formation of several by-products. Detailed characterization of catalysts with ICP, XRD, FTIR, TEM, H2 chemisorption, N2 porosimetry, TPR and acid-base titration were performed to elucidate the role of each support. TiO2-R has a small specific surface area with large ruthenium nanoparticles in weak interaction with TiO2 support and no acidity, whereas TiO2-A is a mesoporous material with a large specific surface area, mildly acidic, and bears small ruthenium particles in strong interaction with TiO2 support. The former was very active and selective for xylose hydrogenation to xylitol whereas the latter was less active and poorly selective. Moreover, careful analysis of reaction products also revealed that TiO2 anatase can catalyze undesired side-reactions such as xylose isomerisation to various pentoses, and therefore the corresponding unexpected polyols (arabitol, ribitol) were produced during xylose conversion by hydrogenation. In a first approach of the kinetics, a simplified kinetic model was built to compare quantitatively intrinsic reaction rates of both catalysts. The kinetic constant for hydrogenation was 20 times higher for Ru/TiO2-R at 120°C.
Polydopamine coated CdSe@CdS dot-in-rod heterostructures with Rhodium-based catalysts for stable photocatalytic NAD+ reduction
Authors: Boecker Marcel , Micheel Mathias , Mengele Alexander K. , Neumann Christof , Herberger Tilmann , Marchesi D'Alvise Tommaso , Liu Bei , Undisz Andreas , Rau Sven , Turchanin Andrey , Synatschke Christopher V. , Wächtler Maria , Weil Tanja
Published: February 2022

We report on a photocatalytic system consisting of CdSe@CdS nanorods, coated with a polydopamine (PDA) shell functionalized with molecular rhodium catalysts. The PDA shell was implemented to enhance photostability of the photosensitizer, to improve charge carrier separation and to offer multiple options for stable covalent functionalization, allowing for spatial proximity and efficient shuttling of charges between sensitizer and reaction center. The activity of the photocatalytic system was demonstrated by light-driven reduction of nicotinamide adenine dinucleotide (NAD+) to its reduced form NADH. This work shows that PDA coated nanostructures present an attractive platform for covalent attachment of reduction and oxidation reaction centers for photocatalytic applications.
Boosting the in situ encapsulation of proteins with MIL-100(Fe): the role of strong Lewis acid centers
Authors: Cases Jesús , Giménez-Marqués Mónica
Published: February 2022

Encapsulation of biomolecules using Metal-Organic Frameworks (MOFs) to form stable biocomposites has been demonstrated a valuable strategy for their preservation and controlled release, which has been however restricted to specific electrostatic surface conditions. We present a general in situ strategy that promotes the spontaneous MOF growth onto a broad variety of proteins, for the first time, regardless of their surface nature. We demonstrate that MOFs based on cations exhibiting considerable inherent acidity such as MIL-100(Fe) enable biomolecule encapsulation, including alkaline proteins previously inaccesible by the welldeveloped in situ encapsulation with azolate-based MOFs. In particular, MIL-100(Fe) scaffold permits effective encapsulation of proteins with very distinct surface nature, retaining their activity and allowing triggered release under biocompatible conditions. This general strategy will enable an ample use of biomolecules in desired biolotechnological applications.
Vacancy-Stabilized Superionic State in Na3 – xSb1 – xWxS4
Authors: Nishimura Shin-ichi , Hayashi Akitoshi , Sakuda Atsushi , Yamada Atsuo
Published: February 2022

The discovery of numerous superionic conductors has accelerated the development of solid-state energy storage systems. Among all alkaline-ionic conductors known thus far, Na3 – xSb1 – xWxS4 exhibits the highest ionic conductivity of > 30 mS cm–1 at ambient temperature, even surpassing the conductivity of the best lithium superionic conductor. The origin of the peculiar high Na+ diffusivity was investigated by the in-depth crystallographic analysis of Na3 – xSb1 – xWxS4 through combined X-ray diffraction and molecular dynamics simulations, emphasizing the accurate three-dimensional disordered nature of sodium in the crystalline matrix. The important features induced by the aliovalent tungsten substitution were (i) tetragonal to cubic transformation, (ii) the creation of sodium vacancies that are evenly distributed throughout the crystal without the local condensation around W, and (iii) the effective formation of sodium positional disordering by sodium vacancy. These features inherent to the best alkaline-ion conducting phase reported thus far would provide invaluable insights toward the further development of superionic conductors.
Molecular docking and ADMET based study to identify potential phytochemical inhibitors for papain-like protease of SARS-CoV-2
Authors: Wadanambi Padmika , Mannapperuma Uthpali , Jayathilaka Nimanthi
Published: February 2022

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen for the novel COVID-19 disease. SARS-CoV-2 papain-like protease (PLpro) is responsible for viral replication and host innate immunity suppression. Thus, this study aimed to explore potential phytochemical inhibitors against this dual therapeutic target using virtual screening methods. Thirty-one phytochemicals with reported anti-SARS-CoV-1 PLpro activity were used to construct the phytochemical library along with two positive controls. Molecular docking using AutoDock 4.2 was employed to calculate binding affinity and inhibition constant of each compound within the S3/S4 binding pocket of SARS-CoV-2 PLpro. Based on the docking results, twelve compounds were subjected to non-covalent interaction analysis utilizing the Discovery Studio Visualizer software. Further, their physicochemical, pharmacokinetics and toxicity descriptors were evaluated using molinspiration and pkCSM web servers, respectively. Hirsutenone from Alnus japonica and broussoflavan A from Broussonetia papyrifera, displayed the strongest binding affinity (-8.23 kcal/mol and -8.13 kcal/mol), lowest inhibition constant (920.39 nM and 1.1 μM) and highest ligand efficiency (0.34 and 0.26) among all phytochemicals towards the binding pocket of SARS-CoV-2 PLpro, demonstrating superiority to PLpro inhibitors, 3k and GRL0617 which were used as positive controls. Additionally, hirsutenone, broussoflavan A and broussochalcone A (from Broussonetia papyrifera) possessed favorable physicochemical properties for oral drug development, satisfying Lipinski’s and Veber’s rules. Furthermore, in silico pharmacokinetics and toxicity predictions revealed that the three aforementioned phytochemicals are water soluble, non-mutagenic, non-hepatotoxic and biologically safe. Hence these lead compounds might be exploited to accelerate the drug discovery process against the ongoing COVID-19 infection.
Photoinduced Hydrocarboxylation via Thiol-Catalyzed Delivery of Formate Across Alkenes
Authors: Alektiar Sara , Wickens Zachary
Published: February 2022

Herein we disclose a new photochemical process to prepare carboxylic acids from formate salts and alkenes. This redox-neutral hydrocarboxylation proceeds in high yields across diverse functionalized alkene substrates with excellent regioselectivity. This operationally simple procedure can be readily scaled with low photocatalyst loading (0.01% photocatalyst) without the need for a flow reactor or any precautions to exclude air or moisture. Furthermore, this new reaction can leverage commercially available formate carbon isotologues to enable the direct synthesis of isotopically labeled carboxylic acids. Mechanistic studies support the working model involving a thiol-catalyzed radical chain process wherein the atoms from formate are delivered across the alkene substrate via CO2•– as a key reactive intermediate.
Formation Mechanism and Porosity Development in Porous Boron Nitride
Authors: L'Hermitte Anouk , Dawson Daniel M. , Ferrer Pilar , Roy Kanak , Held Georg , Tian Tian , Ashbrook Sharon E. , Petit Camille
Published: February 2022

In the past decade, porous boron nitride (BN) has proven promising as a novel class of inorganic materials in the field of separations and particularly adsorption. Owing to its high surface area and thermal stability, porous BN has been researched for CO2 capture and water cleaning, for instance. However, most research remains at laboratory scale due to a lack of understanding of the formation mechanism of porous BN, which is still largely a ‘black box’ and prevents scale-up. Partial reaction pathways have been unveiled, but they omit critical steps in the formation, including the porosity development, which is key to adsorption. To unlock the potential of porous BN at a larger scale, we have investigated its formation from the perspective of both chemical formation and porosity development. We have characterised reaction intermediates obtained at different temperatures with a range of analytical and spectroscopic tools. Using these analyses, we propose a mechanism that highlights the key stages of BN formation and its porosity, including the intermediates and gaseous species formed in the process. We identified that the formation of non-porous carbon nitride is crucial to form porous BN with release of porogens, such as HCN and CO2. This work paves the way for scaled-up processes to use porous BN to its full potential at industrial level for gas and liquid separations.
Identifying the true origins of selectivity in chiral phosphoric acid catalyzed N-acyl-azetidine desymmetrizations
Authors: Champagne Pier Alexandre
Published: February 2022

The first catalytic intermolecular desymmetrization of azetidines was reported by Sun and coworkers in 2015 using a BINOL-derived phosphoric acid catalyst (J. Am. Chem. Soc. 2015, 137, 5895-5898). To uncover the mechanism of the reaction and the origins of the high enantioselectivity, Density Functional Theory (DFT) calculations were performed at the B97D3 / 6-311+G(2d,2p) / SMD(toluene) // B97D3 / 6-31G(d,p) / CPCM(toluene) level of theory. Comparison of four possible activation modes confirms that this reaction proceeds through the bifunctional activation of the azetidine nitrogen and the thione tautomer of the 2-mercaptobenzothiazole nucleophile. Upon thorough conformational sampling of the enantiodetermining transition structures (TSs), a free energy difference of 2.0 kcal mol-1 is obtained, accurately reproducing the experimentally measured 88% e.e. at 80 °C. This energy difference is due to both decreased distortion and increased non-covalent interactions in the pro-(S) TS. To uncover the true origins of selectivity, the TSs optimized with the full catalyst were compared to those optimized with a model catalyst through steric maps. It is found that the arrangements displayed by the substrates are controlled by strict primary orbital interaction requirements at the transition complex, and their ability to fit into the catalyst pocket drives the selectivity. A general model of selectivity for phosphoric acid-catalyzed azetidine desymmetrizations is proposed, which is based on the preference of the nucleophile and benzoyl group to occupy empty quadrants of the chiral catalyst pocket.
Poly(thioether phenyl acrylate) Based Micelles Show Exclusively ROS-triggered Breakdown
Authors: Piergentili Irene , Bouwmans Pepijn R. , Reinalda Luuk , Lewis Reece W. , Klemm Benjamin , Liu Huanhuan , de Kruijff Robin M. , Denkova Antonia G. , Eelkema Rienk
Published: February 2022

In certain tumor and diseased tissues, reactive oxygen species (ROS), such as H2O2, are produced in higher concentrations than in healthy cells. To date, only few examples of drug delivery and release systems responds selectively to these small but significantly elevated ROS concentrations. In addition, assuring the stability of the polymer-based carrier in “healthy” biological conditions is still a challenge in the field of oxidation-sensitive materials. Here, we present ROS-responsive block copolymer micelles capable of achieving micellar disruption over days in the presence of 2 mM H2O2 and within hours under higher concentrations of H2O2 (60 – 600 mM). At the same time, these micelles are stable for over two weeks in oxidant-free physiological (pH = 7.4, 37°C) and for at least six days in mildly acidic (pH = 5.0 and pH = 6.0, 37°C) conditions. The observed selectivity is programmed into the material using a 4-(methylthio)phenyl ester based logic gate. Here, oxidation of the thioether moiety results in a large increase in ester hydrolytic lability, effectively switching the ester hydrolysis from off to on. The concept represents a step forward to realize signal responsive drug delivery materials capable of selective action in biological environments.
Increased Performance of an all-Organic Redox Flow Battery model by Nitration of the [4]Helicenium Ion Electrolyte
Authors: Moutet Jules , Mills David , Hossain Md Mubarak , Gianetti Thomas L.
Published: February 2022

Redox Flow Batteries (RFBs) through their scalable design and virtually unlimited capacity, are promising candidates for large-scale energy storage. While recent advances in the development of redox-active bipolar organic molecules satisfy the prerequisites for the pioneering Symmetrical all-Organic Redox Flow Batteries (SORFBs) emerging, problems of low durability or low energy density remain a bottleneck for their wide-spread application. The present work reports that nitration of the [4]helicenium ion core (DMQA+) result in a significant enhancement of the electrochemical performance of DMQA as electrolyte for SORFBs. The physical and kinetic properties of NO2C+ were evaluated by cyclic voltammetry (CV) and UV-visible spectroscopy in acetonitrile and compared to those of its precursor HC+. The electrons storage ability of NO2C+ was investigated in three differents type of static H-cell experiments. In the first experiment, NO2C+ provided an open circuit voltage (OCV) of 2.24 V and demonstrated good stability, as well as high coulombic (>98%) efficiencies, over more than 200 charge/discharge cycles. In the second experiment, a charge-discharge cycling over the entire redox window of NO2C+ (OCV > 3 V) resulted in 80 cycles at a potential energy density above 12 Wh/L. During the last epxeriment, a bipolarization stress-test was performed during which NO2C+ demonstrated a remarkable durability of 90 cycles at 100% load with a perfect retention of capacity and coulombic efficiency. The electrochemical performance results of this enhanced redox material highlights that DMQA+ ions are robust and versatile materials for the emergence of symmetrical all-Organic ORFB
Using Graphene Encapsulated Ni and Pd Catalysts with Solvent Effect to Achieve Highly Chemo-Selective Hydrogenation of 4-Nitrostyrene to Different Products
Authors: Liu Jianguo , Sun Jiangmin , Lin Shanshan , Ma Longlong
Published: February 2022

Chemo-selective hydrogenation of challenging nitrostyrene to the corresponding product of vinylaniline, ethylbenzenamine, and ethylnitrobenzene separately in high yield is difficult since there exists competitive activation of the C=C double bond and the –NO2 group over most supported metal catalysts. Also, the currently reported catalysts still have some disadvantages of high cost, catalyst reusability and separation problem, catalyst stability and leaching during harsh reaction conditions, waste generation, which disagree with the requirements of low cost, highly active and selective, sustainable, environmentally friendlier, and industrially applicable. Herein we report thin graphene layer encapsulated Ni and Pd nanoparticles core-shell structures as highly active, chemo-selective, and reusable catalysts for hydrogenation of 4-nitrostyrene in both batch reactor and industrially applicable flow reactor. In the standard hydrogenation of 4-nitrostyrene, the optimized catalysts Ni/NiO@-700-200-1-H2O and Pd@NC-2 yield a selectivity to every single product of 4-vinylaniline 99%, 4-ethylbenzenamine 99%, 1-ethyl-4-nitrobenzene 99% through simple changing reaction conditions, the best achieved over Ni and other group metals and higher than the best result reported in the literature. In non-polar solvent toluene, in contrast to traditional catalysts, the Ni@C catalyst is inert for the C=C and is only active about the -NO2, while the N-doped Pd@NC-2 has opposite hydrogenation ability and can hydrogenate the C=C without touching -NO2 in non-polar solvent cyclohexane, which rarely reported in the previous literature. In addition, the catalysts show excellent stability and the 4-nitrostyrene’s hydrogenation can be successfully applied in industrially applicable flow reactors for each of the three product syntheses separately with excellent yield. These discoveries may extend the design of non-noble catalysts with excellent chemoselectivity for use in fine chemicals’ synthesis.
Stacked Ensemble Machine Learning for Range-Separation Parameters
Authors: Ju Cheng-Wei , French Ethan , Geva Nadav , Kohn Alexander , Lin Zhou
Published: February 2022

High-throughput virtual materials and drug discovery based on density functional theory has achieved tremendous success in recent decades, but its power on organic semiconducting molecules suffered catastrophically from the self-interaction error until the optimally tuned range-separated hybrid (OT-RSH) exchange-correlation functionals were developed. The accurate but expensive �first-principles OT-RSH transitions from a short-range (semi-)local functional to a long-range Hartree-Fock exchange at a distance characterized by the inverse of a molecule-specific, non-empirically-determined range-separation parameter (ω). In the present study, we proposed a promising stacked ensemble machine learning (SEML) model that provides an accelerated alternative of OT-RSH based on system-dependent structural and electronic configurations. We trained ML-ωPBE, the first functional in our series, using a database of 1,970 organic semiconducting molecules with sufficient structural diversity, and assessed its accuracy and efficiency using another 1,956 molecules. Compared with the �first-principles OT-ωPBE, our ML-ωPBE reached a mean absolute error of 0:00504a_0^{-1} for the optimal value of ω, reduced the computational cost for the test set by 2.66 orders of magnitude, and achieved comparable predictive powers in various optical properties.
Comparative study between adsorbents based on magnetic nanoferrite. Application to the removal of methyl orange from wastewater
Authors: Saad Sabrine , Ben Amor Sarra , Ben Slimane Amel
Published: February 2022

Magnetic ferrite (Mg-doped bismuth ferrite) and its clay-based composite (Mg-doped bismuth ferrite-bentonite) were prepared by self-combustion method utilizing glycine as fuel and served for the removal of methyl orange (MO) from aqueous solutions. The ferrite-based adsorbents were characterized by the measurement of specific surface area (BET), scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD). The different experimental parameters that affect the performance of this reaction such as: temperature, contact time, initial dye concentration and mass of adsorbent were investigated. The point of zero charge pH (pHPZC) was determined for the two adsorbents. Langmuir and Freundlich adsorption models were employed to provide a description of the equilibrium isotherms. Adsorption tests showed that the equilibrium time is a function of the initial concentration of dye. The adsorption kinetic study indicated that the equilibrium adsorption is established after 300 minutes for Mg-doped bismuth ferrite, while it is established after 180 minutes for Mg-doped bismuth ferrite-bentonite composite. Furthermore, this suggests that the adsorption of MO on both adsorbents can be perfectly described by pseudo-second order kinetics. The maximum adsorption capacity determined by the mathematical model of Langmuir is equal to 181.8 mg.g-1 for Mg-doped bismuth ferrite and to 188.7 mg.g-1 for its composite, at 298 K. Adsorption isotherms shows that the Freundlich model perfectly represents adsorption of methyl orange to the prepared Mg-doped bismuth ferrite. The ferrite/bentonite composite has 2-50 nm-sized pores and is indeed a mesoporous material. The small pores observed on the surface of the adsorbents are in line with type IV isotherm, with possible capillary condensation of the adsorbate. Moreover, Langmuir model seems to be the most suitable model for the absorption of methyl orange on the Mg-doped bismuth ferrite-bentonite composite. The thermodynamic parameters related to the sorbent/adsorbate system indicate that adsorption is spontaneous and exothermic. The determination of isosteric heat of adsorption suggested that it is indeed a physisorption characterized by weak intermolecular forces between MO and the surface.
Polyallylamine assisted synthesis of 3D branched AuNPs with plasmon tunability in the vis-NIR region modification.
Authors: Lodeiro Carlos , Nuti Silvia , Fernández-Lodeiro Carlos , Fernández-Lodeiro Javier , Fernández-Lodeiro Adrián , Perez-Juste Jorge , Pastoriza Santos Isabel , LaGrow Alec P. , Schraidt Olivier , Capelo-Martínez José Luis
Published: February 2022

This paper describes the synthesis of highly branched gold nanoparticles through a facile seeded growth approach using poly(allylamine hydrochloride) (PAH) as shape inducing agent. The obtained branched Au NPs present highly tunable optical properties in the Vis-NIR region from ca. 560 nm to 1260 nm. We controlled the morphology, and therefore the optical response, of the NPs by either changing the gold salt to seed ratio or fine-tuning the solution pH. We proposed that the formation of size-dependent PAH-AuCl4- aggregates as demonstrated by dynamic light scattering measurements, together with pH-dependent gold salt speciation, might be responsible for the branched morphology. Advanced electron microscopy techniques demonstrated the polycrystalline nature of the NPs and facilitated a better understanding of branched morphology. Additionally, the refractive index sensitivity estimated by the inflexion point of the Localized Surface Plasmon Resonance (LSPR) band can be controlled by tuning the nanoparticle branching. Furthermore, the versatility of the PAH chemistry allowed the easy functionalization of the synthesized NPs.
Accurate Prediction of Voltage of Battery Electrode Materials Using Attention Based Graph Neural Networks
Authors: Louis Steph-Yves , Siriwardane Edirisuriya , Joshi Rajendra , Omee Sadman , Kumar Neeraj , Hu Jianjun
Published: February 2022

Performing first principle calculations to discover electrodes’ properties in the large chemical space is a challenging task. While machine learning (ML) has been applied to effectively accelerate those discoveries, most of the applied methods ignore the materials’ spatial information and only use pre-defined features: based only on chemical compositions. We propose two attention-based graph convolutional neural network techniques to learn the average voltage of electrodes. Our proposed method, which combines both atomic composition and atomic coordinates in 3D-space, improves the accuracy in voltage prediction by 17% when compared to composition based ML models. The first model directly learns the chemical reaction of electrodes and metal-ions to predict their average voltage, whereas the second model combines electrodes’ ML predicted formation energy (Eform) to compute their average voltage. Our models demonstrates improved accuracy in transferability from our subset of learned metal-ions to other metal-ions.
Iron Complexes of a Proton-Responsive SCS Pincer Ligand with Sensitive Electronic Structure
Authors: Skubi Kazimer , Hooper Reagan , Mercado Brandon , Bollmeyer Melissa , MacMillan Samantha , Lancaster Kyle , Holland Patrick
Published: February 2022

SCS pincer ligands have an interesting combination of strong-field and weak-field donors that is also present in the nitrogenase active site. Here, we explore the electronic structures of iron(II) and iron(III) complexes with such a pincer ligand, bearing a monodentate phosphine, thiolate S donor, amide N donor, ammonia, or CO. The ligand scaffold features a protonresponsive thioamide site, and the protonation state of the ligand greatly influences the reduction potential of iron in the phosphine complex. The N–H bond dissociation free energy can be quantitated as 56 ± 2 kcal/mol. EPR spectroscopy and SQUID magnetometry measurements show that the iron(III) complexes with S and N as the fourth donors have an intermediate spin (S = 3/2) ground state with large zero field splitting, and X-ray absorption spectra show high Fe–S covalency. The Mössbauer spectrum changes drastically with the position of a nearby alkali metal cation in the iron(III) amido complex, and DFT calculations explain this phenomenon through a change between having the doubly-occupied orbital as dz2 or dyz, as the former is more influenced by the nearby positive charge.
A fluorinated 2D magnetic coordination polymer
Authors: Lopez-Cabrelles Javier , Mañas-Valero Samuel , Vitórica-Yrezábal Iñigo J. , Bereciartua Pablo J. , Coronado Eugenio , Minguez Espallargas Guillermo
Published: February 2022

Herein we show the versatility of coordination chemistry to design and expand a family of 2D materials by incorporating F groups at the surface of the layers. Through of use of a prefuntionalized organic linker with F groups, it is possible to achieve a layered magnetic material based on Fe(II) centers that are chemically stable in open air, contrary to the known 2D inorganic magnetic materials. The high quality of the single crystals and their robustness allow to fabricate 2D molecular materials by micromechanical exfoliation, preserving the crystalline nature of these layers together with the desired functionalization.
Development of Specially Reinforced Magnesium Composites Prepared by Squeeze Casting Process
Authors: Mishra Akshansh , Dixit Devarrishi , Al-Sabur Raheem
Published: February 2022

A wide range of opportunities in the field of automotive and structural applications are being offered by Magnesium matrix composites because of their enhanced mechanical properties. Magnesium alloys based Metal Matrix Composites (MMCs) are the best candidates for lightweight structural applications due to their improved creep properties. In the present study, three specimens of specially reinforced magnesium composites were manufactured by using the squeeze casting process. Specimen 1 has a composition of 7 % aluminum alloy in addition to 1% zinc and the composition of reinforcement is Titanium Carbide 0.3 % in addition to 1.5% Carbon nanotubes. Specimen 2 has a composition of 12 % aluminum alloy in addition to 1 % zinc and the composition of reinforcement is 2% B_4 C in addition to 2 % Carbon nanotubes. Specimen 3 has a composition of 14 % aluminum alloy in addition to 1 % zinc and the composition of reinforcement is 2 % B_4 C in addition to 2 % Carbon nanotubes. The mechanical properties analysis showed that specimen 2 has a higher hardness value in comparison to other manufactured specimens and it was also observed that specimen 2 possesses a higher tensile strength value in comparison to the other two specimens. Microstructure analysis shows that there was a uniform distribution of the reinforcements in the matrix. So it can be inferred that this uniform distribution causes higher hardness and higher tensile strength in the manufactured specimens.