bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Electrocatalytic Oxygen Evolution by Chiral Molecular Functionalization of Hybrid 2D Electrodes
Authors: Liang Yunchang , Banjac Karla , Martin Kévin , Zigon Nicolas , Lee Seunghwa , Vanthuyne Nicolas , Garcés Felipe Andrés , Galan-Mascaros José R. , Hu Xile , Avarvari Narcis , Lingenfelder Magalí
Published: February 2022

A sustainable future requires highly efficient energy conversion and storage processes, where electrocatalysis plays a crucial role. The activity of an electrocatalyst is governed by the binding energy towards the reaction intermediates, while the scaling relationships prevent the improvement of a catalytic system over its volcano-plot limits. To overcome these limitations, unconventional methods that are not fully determined by the surface binding energy can be helpful. Here, we use organic chiral molecules, i.e., hetero-helicenes, to boost the oxygen evolution reaction (OER) by ca. 131.5 % (at the potential of 1.65 V vs. RHE) at state-of-the-art 2D catalysts via a spin-polarization mechanism. Our results show that chiral molecule-functionalization is able to increase the OER activity of catalysts beyond the volcano limits. A guideline for optimizing the catalytic activity via chiral molecular functionalization of hybrid 2D electrodes is given.
Hidden Lewis acidity: Studies on the medium and structure dependent fluorescence of zinc(II) complexes
Authors: Kurz Hannah , Hörner Gerald , Weser Oskar , Li Manni Giovanni , Weber Birgit
Published: February 2022

Three new zinc(II) coordination units [Zn(1–3)] based on planar-directing tetradentate Schiff base-like ligands H2(1–3) were synthesized. Their solid-state structures were investigated by single crystal X-ray diffraction, showing the tendency to overcome the square-planar coordination sphere by axial ligation. Affinity in solution towards axial ligation has been tested by extended spectroscopic studies, both in the absorption and emission mode. The electronic spectrum of the pyridine complex [Zn(1)(py)] has been characterized by multiconfiguration pair-DFT to validate the results of extended TD-DFT studies. Green emission of fluorescence-silent solutions of [Zn(1–3)] in chloroform could be switched on in the presence of potent Lewis-bases. While interpretation in terms of an equilibrium of stacked/non-fluorescent and destacked/fluorescent species is in line with precedents from literature, the sensitivity of [Zn(1–3)] was greatly reduced. Results of a computation-based structure search allow to trace the hidden Lewis acidity of [Zn(1–3)] to a new stacking motif, resulting in a strongly enhanced stability of the dimers.
Excited-State Intramolecular Hydrogen Transfer of Compact Molecules Controls Amyloid Aggregation Profiles
Authors: Hong Mannkyu , Kim Mingeun , Yoon Jiwon , Lee Seung-Hee , Baik Mu-Hyun , Lim Mi Hee
Published: February 2022

Designing new chromophores by tuning their molecular structures and optimizing their photophysical properties leads to suitable photochromic features. Herein, we report a series of anthraquinone (AQ)-based photosensitizers that undergoes excited-state intramolecular hydrogen transfer and effectively oxidizes amyloidogenic peptides, which significantly affects the subsequent aggregation pathways. DFT calculations showed that the appropriate position of the hydroxyl groups in the AQ backbone and the consequent intramolecular hydrogen transfer can facilitate the energy transfer to triplet oxygen. Biochemical and biophysical investigations confirmed that these photoactive chemical reagents are able to oxidatively modify both metal-free amyloid-β (Aβ) and metal-bound Aβ, thereby redirecting their on-pathway aggregation into off-pathway as well as disassembling their pre-formed aggregates. Moreover, the in vivo histochemical analysis of Aβ species produced upon photoactivation of the most promising candidate demonstrated that they do not aggregate into toxic oligomeric or fibrillar aggregates in the brain. Overall, our combined computational and experimental studies validate a light-based approach for designing small molecules as chemical reagents targeting and controlling amyloidogenic peptides associated with neurodegenerative disorders.
Navigate flying molecular elephants safely to the ground: mass-selective soft landing up to the Mega-Dalton range by Electrospray Controlled Ion-Beam Deposition
Authors: Walz Andreas , Stoiber Karolina , Huettig Annette , Schlichting Hartmut , Barth Johannes V
Published: February 2022

The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultra-high vacuum (UHV) is presented, along with encouraging performance data obtained on four model species which are thermolabile or not sublimable. The test panel comprises two small organic compounds, a protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMS) and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated Electrospray Controlled Ion Beam Deposition (ES-CIBD). Full control is achieved by i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMS allowing for investigation, purification and deposition of a virtually unlimited m/z range, ii) the adjustable landing energy of ions down to ~2 eV/z enabling integrity-preserving soft-landing, iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and iv) direct coverage control via the deposited charge. The maximum resolution of R=650 and overall efficiency up to T_total=4.4% calculated from solution to UHV deposition are remarkable as well, while the latter is mainly limited by the not yet optimized ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigation of the deponents demonstrating a selective, structure-preserving process and atomically clean layers.
Classifying Natural Products from Plants, Fungi or Bacteria in the COCONUT Database
Authors: Capecchi Alice , Reymond Jean-Louis
Published: February 2022

Natural products (NPs) represent one of the most important resources for discovering new drugs. Here we asked whether NP origin can be assigned from their molecular structure in a subset of 60,171 NPs in the recently reported Collection of Open Natural Products (COCONUT) database assigned to plants, fungi, or bacteria. Visualizing this subset in an interactive tree-map (TMAP) calculated using MAP4 (MinHashed atom pair fingerprint) clustered NPs according to their assigned origin (https://tm.gdb.tools/map4/coconut_tmap/), and a support vector machine (SVM) trained with MAP4 correctly assigned the origin for 94% of plant, 89% of fungal, and 89% of bacterial NPs in this subset. An online tool based on an SVM trained with the entire subset correctly assigned the origin of further NPs with similar performance (https://np-svm-map4.gdb.tools/). Origin information might be useful when searching for biosynthetic genes of NPs isolated from plants but produced by endophytic microorganisms.
NEW MODULAR ORGANIC PLATFORM FOR UNDERSTANDING THE EFFECT OF STRUCTURAL CHANGES ON SLOW MAGNETIC RELAXATION IN MONONUCLEAR OCTAHEDRAL COPPER(II) COMPLEXES
Authors: Marcinkowski Dawid , Adamski Ariel , Kubicki Maciej , Consiglio Giuseppe , Patroniak Violetta , Ślusarski Tomasz , Açıkgöz Muhammed , Szeliga Daria , Vadra Nahir , Karbowiak Mirosław , Stefaniuk Ireneusz , Rudowicz Czesław , Gorczyński Adam , Korabik Maria
Published: February 2022

Current advances in molecular magnetism are aimed at the construction of molecular nanomagnets and spin qubits for their utilization as high-density data storage materials and quantum computers. Mononuclear coordination compounds with low spin values of S=½ are excellent candidates for this endeavour, but their construction via rational design is limited. This particularly applies to the single copper(II) spin center, having been only recently demonstrated to exhibit slow relaxation of magnetisation in the appropriate octahedral environment. We have thus prepared a novel, modular organic scaffold that would allow one to gain general insight into how purposeful structural differences affect the slow magnetic relaxation in monometallic, transition metal complexes. As a proof-of-principle, we demonstrate how one can construct two, structurally very similar complexes with isolated Cu(II) ions in an octahedral ligand environment, the magnetic properties of which differ significantly. The differences in structural symmetry effects and in magnetic relaxation are corroborated with a series of experimental and theoretical techniques, showing how symmetry distortions affect the relaxation behaviour in these isolated Cu(II) systems. Our highly modular organic platform can be efficiently utilized for the construction of various transition-metal ion systems in the future, effectively providing a model system for investigation of magnetic relaxation via targeted structural distortions.
Self-supervised Clustering of Mass Spectrometry Imaging Data Using Contrastive Learning
Authors: Hu Hang , Padmakumar Bindu Jyothsna , Laskin Julia
Published: February 2022

Mass spectrometry imaging (MSI) is widely used for the label-free molecular mapping of biological samples. The identification of co-localized molecules in MSI data is crucial to the understanding of biochemical pathways. However, complex MSI data are too large for manual annotation but too small for training deep networks. Herein, we introduce a self-supervised clustering approach based on contrastive learning, which shows an excellent performance in clustering of small MSI data. We train a deep convolutional neural network (CNN) using MSI data from a single experiment without manual annotations to effectively learn high-level spatial features from ion images and classify them based on molecular colocalizations. We demonstrate that contrastive learning generates ion image representations that form well-resolved clusters. Subsequent self-labeling is used to fine-tune both the CNN encoder and linear classifier based on confidently classified ion images. This new approach enables autonomous and high-throughput identification of co-localized species in MSI data, which will dramatically expand the application of spatial lipidomics, metabolomics, and proteomics in biological research.
The role of hydrophobic hydration in the free energy of chemical reactions at the gold/water interface: size and position effects
Authors: Serva Alessandra , Havenith Martina , Pezzotti Simone
Published: February 2022

Metal/water interfaces catalyze a large variety of chemical reactions, which often involve small hydrophobic molecules. In the present theoretical study we show that hydrophobic hydration at the Au(100)/water interface actively contributes to the reaction free energy by up to several hundreds of meV. This occurs either in adsorption/desorption reaction steps, where the vertical distance from the surface changes in going from reactants to products, or in addition and elimination reaction steps, where two small reactants merge into a larger product and viceversa. We find that size and position effects cannot be captured by treating them as independent variables. Instead, their simultaneous evaluation allows to map the important contributions, and we provide examples of their combinations for which interfacial reactions can be either favoured or disfavoured. By taking a N2 and a CO2 reduction pathway as test cases, we show that explicitly considering hydrophobic effects is important for the selectivity and rate of these relevant interfacial processes.
The zwitterion isomer of orthosilicic acid and its role in neutral pH dimerization from density functional theory.
Authors: Felipe Mihali
Published: February 2022

Using density functional theory, the plausible existence of the zwitterion isomer of orthosilicic acid is proposed to account for some of the properties of silica in water. Explicit hydration and explicit addition of salt are used in modeling the zwitterion and the dimerization reaction. Paths between orthosilicic acid, the zwitterion and the autoionization products are presented. The pK for the formation of the aqueous zwitterion species is calculated to be 7.78 in dilute silica solutions and the activation energy for the dimerization reaction ranges from 59.8 kJ/mol to 70.7 kJ/mol depending on salt concentration.
Optimization of a Pyrimidinone Series for Selective Inhibition of Ca2+/Calmodulin-Stimulated Adenylyl Cyclase 1 Activity for the Treatment of Chronic Pain
Authors: Scott Jason , Soto-Velasquez Monica , Hayes Michael , Lavigne Justin , Miller Heath , Kaur Jatinder , Ejendal Karin , Watts Val , Flaherty Daniel
Published: February 2022

Adenylyl cyclase type 1 is an emerging target for the treatment of chronic pain that is downstream on the analgesic pathway from the traditional µ-opioid receptor. AC1 is expressed in the central nervous system and critical for signaling in pain sensitization. Behavioral studies have revealed AC1 knockout mice exhibit reduced behavioral pain sensitization responses similar to morphine administration. AC1, and a closely related isoform AC8, are also implicated to have a role in learning and memory signaling processes. However, reports suggest selectively targeting AC1 over AC8 may be a viable strategy to eliminate potential deleterious effects on learning and memory. Our team has carried out cellular screening for inhibitors of AC1 that yielded a pyrazolyl-pyrimidinone scaffold with potency comparable to previously published AC1 inhibitors, selectivity versus AC8, and improved drug-like physicochemical properties. Structure-activity relationship (SAR) studies produced 36 analogs that balanced improvements in potency with cellular IC50 values as low as 0.25 µM and selectivity versus AC8. Prioritized analogs were selective for AC1 compared to other AC isoforms and other common neurological targets. A representative analog was assessed for efficacy in a mouse model of inflammatory pain and displayed modest anti-allodynic effects. This series of compounds represents the most potent and selective inhibitors of Ca2+/Calmodulin-stimulated AC1 activity to date with reduced off-target liabilities and improved drug-like physicochemical properties making them promising lead compounds for the treatment of inflammatory pain.
Electrically fueled active supramolecular materials
Authors: Guan Zhibin , Selmani Serxho , Schwartz Eric , Mulvey Justin , Wei Hong , Grosvirt-Dramen Adam , Gibson Wyeth , Hochbaum Allon , Patterson Joseph , Ragan Regina
Published: February 2022

Fuel-driven dissipative supramolecular assemblies in biology, such as actin filaments and microtubules contribute to the formation of complex, dynamic structures in living organisms and give rise to emergent functions such as motility, homeostasis, self-healing, and camouflage. Several synthetic dissipative supramolecular materials have been created using chemicals or light as fuel, with the goal of furthering our understanding of biological systems and creating synthetic materials that have life-like dynamic properties. However, electrical energy, one of the most common energy sources, has remained mostly unexplored for such purposes. Here we demonstrate the use of electrically fueled dissipative assembly as a new platform for creating active supramolecular materials. Through an electrochemical redox reaction network operating in mild aqueous buffers, a transient and highly active supramolecular assembly based on a redox-sensitive cysteine derivative is achieved by applying an electric potential. The dissipative self-assembly as well as its emergent properties can be spatiotemporally controlled by modulation of electrical signals on patterned microelectrodes. Using electrical energy as a readily available and clean fuel, we are able to create dissipative supramolecular materials rapidly (in seconds to minutes) and repetitively under mild conditions with directional and spatiotemporal control. As electronic signals are the default information carriers in modern technology, the described approach offers a promising opportunity to integrate active materials into electronic devices for bioelectronics applications.
Communication: Effect of Oxidation on Excited State Dynamics of Neutral TinO2n-x (n<10, x<4) Clusters
Authors: Garcia Jacob , Heald Lauren , Shaffer Ryan , Sayres Scott
Published: February 2022

Excited state lifetimes of neutral titanium oxide clusters (TinO2n-x, n < 10, x < 4) were measured using a sequence of 400 nm pump and 800 nm probe femtosecond laser pulses. Despite large differences in electronic properties between the closed shell stoichiometric TinO2n clusters and the suboxide TinO2n-x (x = 1-3) clusters, the transient responses for all clusters contain a fast response of 35 fs followed by a sub-picosecond excited state lifetime. In this non-scalable size regime, subtle changes in the sub-ps lifetimes are attributed to variations in the coordination of Ti atoms and localization of charge carriers following UV photoexcitation. In general, clusters exhibit longer lifetimes with increased size and also with addition of O atoms. This suggests that removal of O atoms develops stronger Ti-Ti interactions as the system transitions from a semiconducting character into a fast metallic electronic relaxation mechanism.
Conversational Artificial Intelligence/Natural Language Processing Algorithms for Modeling and Research Summarization of Friction Stir Welded Aluminum Joints
Authors: Mishra Akshansh
Published: February 2022

Natural Language Processing (NLP) is the sub-division of Artificial Intelligence that narrows down the gap between technology and human cognition by extracting the relevant information from the pile of data. In the present work, scientific information regarding the Friction Stir Welding of Aluminum alloys was collected from the abstract of 20 scholarly research papers. For extracting the relevant information from these research abstracts four Natural Language Processing based algorithms i.e. Latent Semantic Analysis (LSA), Luhn Algorithm, LexRank Algorithm, and KL-Algorithm were used. In order to evaluate the accuracy score of these algorithms, Recall-Oriented Understudy for Gisting Evaluation (ROUGE) was used. The results showed that the Luhn Algorithm resulted in the highest f1-Score of 0.413 in comparison to other algorithms.
Electron spin resonance resolves intermediate triplet states in delayed fluorescence
Authors: Drummond Bluebell , Aizawa Naoya , Zhang Yadong , Myers William , Xiong Yao , Cooper Matthew , Barlow Stephen , Gu Qinying , Weiss Leah , Gillett Alexander , Credgington Dan , Pu Yong-Jin , Marder Seth , Evans Emrys
Published: February 2022

Molecular organic fluorophores are currently used in organic light-emitting diodes, though non-emissive triplet excitons generated in devices incorporating conventional fluorophores limit the efficiency. This limit can be overcome in materials that have intramolecular CT excitonic states and associated small singlet-triplet energy; triplets can be converted to emissive singlet excitons resulting in efficient delayed fluorescence. However, the mechanistic details of the spin interconversion have not yet been fully resolved. We report transient ESR studies that allow direct probing of the spin conversion in a series of delayed fluorescence fluorophores with varying energy gaps between LE and CT triplets. The observation of distinct triplet signals, unusual in transient ESR, suggests that multiple triplets mediate the photophysics for efficient light emission in delayed fluorescence emitters. We reveal that as the energy separation between LE and CT triplets decreases, spin interconversion changes from a direct, singlet-triplet mechanism to an indirect mechanism involving intermediate states.
Transition metal-free photodecarboxylative amination of redox-active esters with diazirines
Authors: Maharaj Vishala , Chandrachud Preeti , Che Wen , Wojtas Lukasz , Lopchuk Justin
Published: February 2022

Due to the prevalence of nitrogen-containing compounds in medicine, materials, and related fields, the search for general, mild methods for electrophilic amination remains an area of intense research. Diazirines have been recently demonstrated to serve as electrophilic amination reagents that afford diaziridines, versatile heterocycles that are readily transformed into amines, hydrazines, and a variety of nitrogen-containing heterocycles. Here we report the phosphine-mediated, photodecarboxylative amination of redox-active esters with diazirines. This method is transition metal-free, uses inexpensive photoactivators under mild conditions, and offers a significantly enhanced scope and yields for primary redox-active esters. Furthermore, the stability of diazirines to blue light (456 nm) is demonstrated, paving the way for further research into other photochemical amination methods with these unique heterocycles.
Core/Shell Magic-Sized Semiconductor Nanocrystals
Authors: Pun Andrew , Mule Aniket , Held Jacob , Norris David
Published: February 2022

Magic-sized semiconductor nanocrystals (MSNCs) grow via discrete jumps between specific sizes. Despite their potential to offer atomically precise structures, their use has been limited by poor stability and trap-dominated photoluminescence. Recently, syntheses have been reported that produce CdSe MSNCs over a larger size series. We exploit such particles and demonstrate a method to grow shells on CdSe MSNC cores. Thin CdS shells lead to dramatic improvements in the emissive properties of the MSNCs, narrowing their fluorescence linewidths, enhancing photoluminescence quantum yields, and eliminating trap emission. While thicker CdS shells lead to decreased performance, CdxZn1-xS alloyed shells maintain efficient and narrow fluorescence lines. These alloyed core/shell crystallites also exhibit a tetrahedral shape, in agreement with a recent model for MSNC growth. Our results indicate that MSNCs can compete with other state-of-the-art semiconductor nanocrystals. Furthermore, these core/shell structures will allow further study of MSNCs and their potential for atomically precise growth.
Process parameter optimization of 6061AA Friction Stir Welded Joints using Supervised Machine Learning Regression-based Algorithms
Authors: Mishra Akshansh , Meseele Sefene Eyob , Asmare Tsegaw Assefa
Published: February 2022

The highest strength-to-weight ratio criterion has fascinated curiosity increasingly in virtually all areas where heft reduction is indispensable. Lightweight materials and their joining processes are also a recent point of research demands in the manufacturing industries. Friction Stir Welding (FSW) is one of the recent advancements for joining materials without adding any third material (filler rod) and joining below the melting point of the parent material. The process is widely used for joining similar and dissimilar metals, especially lightweight non-ferrous materials like aluminum, copper, and magnesium alloys. This paper presents verdicts of optimum process parameters on attaining enhanced mechanical properties of the weld joint. The experiment was conducted on a 5 mm 6061 aluminum alloy sheet. Process parameters; tool material, rotational speed, traverse speed, and axial forces were utilized. Mechanical properties of the weld joint are examined employing a tensile test, and the maximum joint strength efficiency was reached 94.2%. Supervised Machine Learning based Regression algorithms such as Decision Trees, Random Forest, and Gradient Boosting algorithms were used. The results showed that the Random Forest algorithm yielded highest coefficient of determination value of 0.926 which means it gives a best fit in comparison to other algorithms.
Ligand-Metal Cooperation Enables C–C Activation Cross-Coupling Reactivity of Cyclopropyl Ketones
Authors: Gilbert Michael , Trenerry Michael , Longley Victoria , Berry John , Weix Daniel
Published: February 2022

Activation of C–C bonds has the potential to revolutionize how molecules are made by altering the carbon skeleton and enabling new synthetic routes. Stereodefined cyclopropyl ketones have become readily available and would be an ideal source of linear 3-carbon fragments, but this reactivity is unknown. In this study we show how a new type of C–C activation catalyst, that relies upon a different, metalloradical mechanism, can enable new subsequent reactivity: the cross- coupling of cyclopropyl ketones with organozinc reagents and chlorotrimethylsilane to form 1,3- difunctionalized, ring-opened products. A mixture of experiment and theory sheds light on how cooperation between the redox-active ligand and the nickel catalyst enables the C–C bond activation step, suggesting how this approach could be applied in other systems.
Ultra-high sensitivity measurement of DNA sequences with conducting polymer-modified electrodes: mechanism, large-scale manufacture, and prospects for rapid polymerase chain reaction measurement (e-PCR)
Authors: Zhu Bicheng , Kerr-Philips Thomas , Al-Ghaus Zahraa , Chan Eddie , Barker David , Evans Clive , Travas-Sejdic Jadranka , Williams David
Published: February 2022

At low copy number, sequence detection by polymerase chain reaction (PCR) requires up to 30 cycles (amplification by a factor of 109) to produce a reliably detectable concentration of fluorescently-labelled amplicons. The cycle number and hence detection time is determined by the analytical sensitivity of the detector. Hybridisation of complementary DNA strands to oligonucleotide-modified conducting polymer electrodes yields an increase in the charge transfer resistance for the ferri-ferrocyanide redox couple. Sensors using this technology for e-PCR offer a label-free method with detector sensitivity in the pM range, potentially decreasing the required cycle number from 30 to 10 and offering a much simplified instrument construction. We demonstrate sensors using screen-printed carbon electrodes modified with a conducting polymer formed from a monomer pre-functionalised with complementary oligonucleotide. Off-chip pre-functionalisation of the conducting polymer precursor is a key step towards practical manufacture and the method is potentially a general one for sensors which require a capture probe-functionalised surface. We demonstrate reliable sensitivity of the interfacial resistance change at the pM scale for short (20-mer) sequences and at the aM scale for bacterial lysate, with dynamic range extending to μM scale and response time-scale 5 min. Donnan exclusion of the redox couple from the surface, as previously proposed, seems unlikely as a mechanism for such ultra-high sensitivity. We demonstrate that the most important element in the response at the lowest concentrations is due to variation of an electrical resistance within the polymer film. We develop a mechanism based on repulsion from the solution interface of dopant anions and attraction towards and trapping at the interface of radical cations (polarons) by the charge associated with surface-bound DNA. With results for >160 single-use sensors, we formulate a response model based on percolation within a random resistor network and highlight challenges for large-scale manufacture of such sensors. We propose a PCR device concept for rapid use at point-of-sampling.
Elevating Density Functional Theory to Chemical Accuracy for Water Simulations through a Density-Corrected Many-Body Formalism
Authors: Dasgupta Saswata , Lambros Eleftherios , Perdew John , Paesani Francesco
Published: February 2022

Kohn-Sham density functional theory (DFT) has been extensively used to model the properties of water. Albeit maintaining a good balance between accuracy and efficiency, no density functional has so far achieved the degree of accuracy necessary to correctly predict the properties of water across the entire phase diagram. The recent development of the strongly constrained and appropriately normed (SCAN) functional has renewed the interest in ab initio simulations of liquid water, yielding promising results that are, however, still unable to reproduce all the experimental data. Here, we present density-corrected SCAN (DC-SCAN) calculations for water which, minimizing density-driven errors, elevate the accuracy of the SCAN functional to that of coupled cluster theory, the “gold standard” for chemical accuracy. Building upon the accuracy and efficiency of DC-SCAN within a many-body formal- ism, we introduce a data-driven many-body potential energy function, the MB-SCAN(DC) PEF, that is able to quantitatively reproduce coupled cluster reference values for interaction, binding, and individual many-body energies of water clusters. Importantly, the properties of liquid water calculated from molecular dynamics simulations carried out with the MB- SCAN(DC) PEF are found to be in excellent agreement with the experimental data, which thus demonstrates that MB-SCAN(DC) is effectively the first DFT-based model that correctly describes water from the gas to the condensed phase. Since the many-body formalism adopted by the present MB-SCAN(DC) PEF for water is general, we believe it can open the door to the routine development of data-driven many-body PEFs for predictive simulations of generic (small) molecules in the gas, liquid, and solid phases.
Overhaul of the reducing ability of Breslow-type derivatives and implications for carbene-catalyzed radical reactions.
Authors: Delfau Ludivine , Nichilo Samantha , Molton Florian , Broggi Julie , Tomás-Mendivil Eder , Martin David
Published: February 2022

We report the synthesis of acyl azolium salts stemming from thiazolylidenes CNS, triazolylidenes CTN, mesoionic carbenes CMIC and the generation of their corresponding radicals and enolates, covering about 60 Breslow-type derivatives. This study highlights the role of additives in the redox behavior of these compounds and unveils several critical misconceptions about radical transformations of aldehyde derivatives under N-heterocyclic carbene catalysis. In particular, the reducing ability of enolates has been dramatically underestimated in the case of biomimetic CNS. In contrast with previous electrochemical studies, we show that these catalytic intermediates can transfer electrons to iodobenzene within minutes at room temperature. Enols derived from CMIC are not the previously claimed super electron donors, although enolate derivatives of CNS and CMIC are powerful reducing agents.
Data Synchronization in Operando Gas and Heating TEM
Authors: Zhang Fan , Pen Merijn , Spruit Ronald G. , Perez Garza Hugo , Liu Wei , Zhou Dan
Published: February 2022

Time-resolved correlations between the environment, the reaction products, the energy transfer and the material structures during the reaction processes make operando gas and heating TEM more and more attractive in recent years. The intrinsic time delays that exist among parameter measurement locations need to be calibrated for valid correlations. Otherwise, erroneous conclusions would be drawn, such as over-estimating the critical temperatures, or mismatching the structure and composition relationships to activities. Herein, we report on a method measuring and calibrating the time delays involved in operando TEM. This method relies on the unique capability of on-chip calorimetry of the gas Nano-Reactor. It is shown that the time delay depends on the gas flow rate and pressure, and has little dependence on the gas type. A functional relationship fitted between the time delay and the gas flow rate can automize the time delay calibration and thus synchronize the data from different locations. Based on the investigations, we developed algorithms and scripts to enable the automatic data synchronization in operando gas and heating TEM in both real time experiments and post experiments.
Surfactant-assisted synthesis of titanium nanoMOFs for thin film fabrication
Authors: Romero-Angel María , Castells-Gil Javier , Rubio-Giménez Víctor , Ameloot Rob , Tatay Sergio , Martí-Gastaldo Carlos
Published: February 2022

We use dodecanoic acid as a modulator to yield titanium MOF nanoparticles with good control of size and colloid stability and minimum impact to the properties of the framework to enable direct fabrication of crystalline, porous thin films
Atmospheric Nitrogen Fixation via a Porous Coordination Polymer Platform with Bridging Dinitrogen Anions
Authors: Xiong Yan , Li Bang , Gu Yuming , Yan Tong , Ni Zhigang , Li Shuhua , Zuo Jing-Lin , Ma Jing , Jin Zhong
Published: February 2022

The design of highly electron-active and stable heterogeneous catalysts for ambient nitrogen reduction reaction is challenging due to the inertness of N2 molecule. Herein, we designed and synthesized the first zinc-based coordination polymer with bridging dinitrogen anion ligand, namely NJUZ-1, which is an efficient photocatalyst for atmospheric nitrogen fixation, exhibiting an outstanding ammonia conversion rate of 140 μmol g−1 h−1 and functioning well even with unpurified air as feeding gas. Experimental and theoretical studies revealed that the active “Zn2+-(N≡N)−1-Zn2+” sites can promote the formation of NH3, and the detachment of the yielded NH3 creates unsaturated “Zn2+···Zn+” intermediates, which can be replenished again by external N2 sequestration and fast intermolecular electron migration. The “Zn2+···Zn+” intermediates stabilized by the sandwiched cage-like donor-acceptor-donor framework can sustain continuous catalytic cycles via a pathway analogous to the Mars-van Krevelen process. This work presents a conceptually new strategy for nitrogen fixation via molecular active site catalysts based on metal complexes under mild conditions.
Dynamic Role of the Correlation Effect Revealed in the Exceptionally Slow Autodetachment Rates of the Vibrational Feshbach Resonances in the Dipole-Bound State
Authors: Kang Do Hyung , Kim Jinwoo , Kim Sang Kyu
Published: February 2022

Real-time autodetachment dynamics of the loosely-bound excess electron from the vibrational Feshbach resonances of the dipole-bound states (DBS) of 4-bromophonoxide (4-BrPhO-) and 4-chlorophenoxide (4-ClPhO-) anions have been thoroughly investigated. The state-specific autodetachment rate measurements obtained by the picosecond time-resolved pump-probe method on the cryogenically cooled anions, exhibit the exceptionally long lifetime (τ) of ~ 2.5  0.6 ns (as the upper bound) for the 11’1 vibrational mode of the 4-BrPhO- DBS. Strong mode-dependency in the wide dynamic range has also been found, giving τ ~ 5.3 ps for the 10’1 mode, for instance. Though it is nontrivial to get the state-specific rates for the 4-ClPhO- DBS, the average autodetachment lifetime of the 19’120’1/11’1 mode has been estimated to be ~ 548  108 ps. Observation of these exceptionally slow autodetachment rates of vibrational Feshbach resonances strongly indicates that the ‘correlation effect’ may play a significant role in the DBS photodetachment dynamics. The Fermi’s golden rule has been invoked so that the correlation effect is taken into account in the form of the interaction between the charge and the induced dipole where the latter is given by the polarizable counterparts of the electron-rich halogenated compound and the diffuse non-valence electron. This report suggests that one may measure, from the real-time autodetachment dynamics, the extent of the correlation effect contribution to the stabilization and/or dynamics of the excess non-valence electron among many different types of the long-range interactions of the DBS.
Spin-component-scaled and dispersion-corrected second-order Møller-Plesset perturbation theory: A path toward chemical accuracy
Authors: Greenwell Chandler , Rezac Jan , Beran Gregory
Published: February 2022

Second-order Møller-Plesset perturbation theory (MP2) provides a valuable alternative to density functional theory for modeing problems in organic and biological chemistry. However, MP2 suffers from known lim- itations in the description of van der Waals dispersion interactions and reaction thermochemistry. Here, a spin-component-scaled, dispersion-corrected MP2 model (SCS-MP2D) is proposed that addresses these weaknesses. The dispersion correction, which is based on Grimme’s D3 formalism, replaces the uncoupled Hartree-Fock dispersion inherent in MP2 with a more robust coupled Kohn-Sham treatment. The spin- component scaling of the residual MP2 correlation energy then reduces the remaining errors in the model. This two-part correction strategy solves the problem found in earlier spin-component-scaled MP2 models where completely different spin-scaling parameters were needed for describing reaction energies versus in- termolecular interactions. Results on 18 benchmark data sets and two challenging potential energy curves demonstrate that SCS-MP2D considerably improves upon the accuracy of MP2 for intermolecular interac- tions, conformational energies, and reaction energies. Its accuracy and computational cost are competitive with state-of-the-art density functionals such as DSD-BLYP-D3(BJ), revDSD-PBEP86-D3(BJ), ωB97X-V, and ωB97M-V for systems with ∼100 atoms.
Mechanochemical Ring-Opening Metathesis Polymerization: Development, Scope, and Mechano-Only Copolymer Synthesis
Authors: Lee Gue Seon , Lee Hyo Won , Lee Hyun Sub , Do Taeyang , Do Jean-Louis , Lim Jeewoo , Friščić Tomislav , Kim Jeung Gon
Published: February 2022

Ruthenium-alkylidene initiated ring-opening metathesis polymerization (Ru-ROMP) was realized under solid-state conditions employing a mechanochemical ball milling method, promoting greenness and broadening scope. High-speed ball milling provided sufficient mixing and energy to the reaction mixture comprised of the catalyst and solid monomers, thus eliminating the need for solvents. Studies on the catalytic species and ball milling parameters (liquid-assisted grinding, vibration frequency, and ball size) revealed that mechanical energy regulated solid-state Ru-ROMP and it follows similar mechanistic features of solution-phase reactions. The solubility and miscibility of monomer and Ru-initiator are not a limitation in solid-state ball milling. Without the use of a solvent, a wide spectrum of solid monomers, including ionomer, fluorous monomer, and macromonomers, were successfully polymerized. Finally, effective direct copolymerization of immiscible monomers such ionic/hydrophobic and ionic/fluorous monomers resulted in a set of copolymers that are difficult to make using traditional solution procedures.
Stable and Reversible Functionalization and Super-Resolution Microscopy of Live Cell Membranes
Authors: Hossain Ahad , Majumder Joydeb , Bi Cheng , Huang Fang , Chopra Gaurav
Published: February 2022

Live cell surface functionalization has been increasingly explored in recent years because of its emerging bio- medical and therapeutic applications. Known methods to functionalize live-cell surface includes time-consuming metabolic docking of non-natural functional groups on cell surfaces that are hard to use. Here, we report an easy and direct functionalization method for cell surface and cell-cell conjugation utilizing native phosphate groups on cell membranes. We used three-dimensional single-molecule localization microscopy to confirm that the chemical conjugate binds preferentially on the cell surface. We show an application of this method for live-cell imaging and enhancement of cell-cell interaction leading to increased T cell proliferation. Our simple and reversible cell-conjugation strategy would be widely useful to explore and optimize cell-cell contact-based proliferation for any cell-based therapeutic applications.
Electrosynthesis of Green Urea by co-reduction of N2 and CO2 Using Dual Active Sites of Copper Phthalocyanine Nanotube
Authors: Ghorai Uttam , Mukherjee Jit , Paul Sourav , Adalder Ashadul , Kapse Samadhan , Thapa Ranjit , Mandal Sumit , Ghorai Biswajit , Sarkar Sougata
Published: February 2022

Green synthesis of urea under ambient conditions by electrochemical co-reduction of N2 and CO2 gases using effective electrocatalyst essentially pushes the conventional two steps (N2 + H2 = NH3 & NH3 + CO2 = CO (NH2)2) industrial process at high temperature and high pressure, to the brink. The single step urea synthesis process has hit a roadblock due to the lack of efficient and economically viable electrocatalyst with multiple active sites for dual reduction of N2 and CO2 gas molecules to urea. Herein, CuPc nanotubes having multiple active sites (such as metal center, Pyrrolic-N3, Pyrrolic-N2, and Pyridinic-N1) are reported to exhibit urea yield of 143.47 µg h-1 mg-1cat and FE of 12.99% at –0.6 V vs RHE by co-reduction of N2 and CO2. Theoretical calculation suggests that Pyridinic-N1 and Cu centers are responsible to form C-N bonds for urea by reduction of N2 to NN* and CO2 to *CO respectively.
Using pH dependence for understanding mechanisms in electrochemical CO reduction
Authors: Kastlunger Georg , Wang Lei , Govindarajan Nitish , Heenen Hendrik H. , Ringe Stefan , Jaramillo Thomas , Hahn Christopher , Chan Karen
Published: February 2022

Utilizing electrochemical conversion of CO(2) into hydrocarbons and oxygenates is envisioned as a promising path towards closing the carbon cycle in modern technology. To this day, however, the exact reaction mechanisms towards the plethora of single and multi-carbon products on Cu electrodes are still disputed. This uncertainty even extends to the rate-limiting step of the respective reactions. Since multi-carbon products do not show a dependence on the electrolyte pH in neutral and alkaline media, CO dimerization on the Cu surface has been proposed as the rate-limiting step. However, other elementary steps would lead to the same pH dependence, namely the proton-electron transfer to *CO followed by subsequent coupling or the protonation of the *OCCO dimer. The pH dependence of methane production on the other hand suggests that the rate limiting step is located beyond the first proton-electron transfer to *CO. In order to conclusively identify the rate limiting steps in CO reduction, we analyzed the mechanisms on the basis of constant potential DFT calculations, CO reduction experiments on Cu at varying pH values (3 - 13) and fundamental rate theory. We find that, even in acidic media, the reaction rate towards multi-carbon products is nearly unchanged on an SHE potential scale, which indicates that its rate limiting step does not involve a proton donor. Hence, we deduce that the rate limiting step can indeed only consist of the coupling of two CO molecules on the surface, both in acidic and alkaline conditions. For methane, on the other hand, the rate-limiting step changes with the electrolyte pH from the first protonation step in acidic/neutral conditions to a later step in alkaline conditions. Finally, based on an in-depth kinetic analysis, we conclude that the pathway towards CH4 involving a surface combination of *CO and *H is unlikely, since it is unable to reproduce the measured current densities and Tafel slopes.
Quantitative spatiotemporal mapping of thermal runaway propagation rates in lithium-ion cells using cross-correlated Gabor filtering
Authors: Radhakrishnan Anand N. P. , Buckwell Mark , Pham Martin , Finegan Donal , Rack Alexander , Hinds Gareth , Brett Dan , Shearing Paul
Published: February 2022

Abuse testing of lithium-ion batteries is widely performed in order to develop new safety standards and strategies. However, testing methodologies are not standardised across the research community, especially with failure mechanisms being inherently difficult to reproduce. High-speed X-ray radiography is proven to be a valuable tool to capture events occurring during cell failure, but the observations made remain largely qualitative. We have therefore developed a robust image processing toolbox that can quantify, for the first time, the rate of propagation of battery failure mechanisms revealed by high-speed X-ray radiography. Using Gabor filter, the toolbox selectively tracks the electrode structure at the onset of failure. This facilitated the estimation of the displacement of electrodes undergoing abuse via nail penetration, and also the tracking of objects, such as the nail, as it propagates through a cell. Further, by cross-correlating the Gabor signals, we have produced practical, illustrative spatiotemporal maps of the failure events. From these, we can quantify the propagation rates of electrode displacement prior to the onset of thermal runaway. The highest recorded acceleration (≈ 514 mm s-2) was when a nail penetrated a cell radially (perpendicular to the electrodes) as opposed to axially (parallel to the electrodes). The initiation of thermal runaway was also resolved in combination with electrode displacement, which occurred at a lower acceleration (≈ 108 mm s-2). Our assistive toolbox can also be used to study other types of failure mechanisms, extracting otherwise unattainable kinetic data. Ultimately, this tool can be used to not only validate existing theoretical mechanical models, but also standardise battery failure testing procedures.
Combined use of total fluorine and oxidative fingerprinting for quantitative determination of side-chain fluorinated polymers in textiles
Authors: Liagkouridis Ioannis , Awad Raed , Schellenberger Steffen , Plassmann Merle , Cousins Ian , Benskin Jonathan
Published: February 2022

Given their extensive production volumes and potential to form persistent perfluoroalkyl acids (PFAAs), there is concern surrounding the ongoing use of side-chain fluorinated polymers (SFPs) in consumer products. Targeted SFP quantification relies on matrix assisted laser desorption ionization-time-of-flight mass spectrometry, which suffers from poor accuracy and high detection limits. Alternatively, total fluorine (TF)-based methods can be used, but these approaches report concentrations on a “fluorine equivalent” basis (e.g. F/m2 in the case of textiles) and are incapable of elucidating structure/chain length, which is critical for predicting the identity and quantity of degradation products. Here a new method for comprehensive characterization of SFPs is presented, which makes use of the total oxidizable precursors assay for fingerprint-based structural elucidation, and combustion ion chromatography for TF quantification. When used in parallel, quantitative determination of SFPs (in units of mass of CnF2n+1/m2 textile) is achieved. Expressing SFP concentrations in terms of mass of side-chain (as opposed to fluorine equivalents) facilitates estimation of both the structure and quantity of PFAA degradation products. As a proof-of-principle, the method was applied to six unknown SFP-coated medical textiles from Sweden. Four products contained C6-fluorotelomer-based SFPs (concentration range 36-188 mg C6F13/m2), one contained a C4-sulfonamide-based SFP (718 mg C4F9/m2), and one contained a C8-fluorotelomer-based SFP (249 mg C8F17/m2).
Chebyshev matrix product states with canonical orthogonalization for spectral functions of strongly correlated systems
Authors: Jiang Tong , Ren Jiajun , Shuai Zhigang
Published: February 2022

We propose a method to calculate the spectral functions of strongly correlated systems by Chebyshev expansion in the framework of matrix product states coupled with canonical orthogonalization (coCheMPS). The canonical orthogonalization can improve the accuracy and efficiency significantly because the orthogonalized Chebyshev vectors can provide an ideal basis for constructing the effective Hamiltonian in which the exact recurrence relation can be retained. In addition, not only the spectral function but also the excited states and eigen energies can be directly calculated, which is usually impossible for other MPS-based methods such as time-dependent formalism or correction vector. The remarkable accuracy and efficiency of coCheMPS over other methods are demonstrated by calculating the spectral functions of spin chain and ab initio hydrogen chain. We demonstrate for the first time that Chebyshev MPS can be used in quantum chemistry. We also caution the application for electron-phonon system with densed density of states.