bluuebunny/crossref_metadata_2025 huggingface dataset:
From operando Raman mechanochemistry to "NMR crystallography": understanding the structures and interconversion of Zn-terephthalate networks using selective 17O-labelling.
Authors: Leroy César , Métro Thomas-Xavier , Hung Ivan , Gan Zhehong , Gervais Christel , Laurencin Danielle
Published: February 2022

The description of the formation, structure and reactivity of coordination networks and MOFs remains a real challenge in a number of cases. This is notably true for compounds composed of Zn2+ ions and terephthalate ligands (benzene 1,4-dicarboxylate, BDC), because of the difficulties in isolating them as pure phases and/or because of the presence of structural defects. Here, using mechanochemistry in combination with operando Raman spectroscopy, the observation of the formation of various zinc-terephthalate compounds was rendered possible, allowing the distinction and isolation of three intermediates during the ball-milling synthesis of Zn3(OH)4(BDC). An “NMR crystallography” approach was then used, combining solid-state NMR (1H, 13C and 17O) and DFT calculations, in order to refine the poorly described crystallographic structures of these phases. Particularly noteworthy are the high-resolution 17O NMR analyses, which were made possible in a highly efficient and cost-effective way, thanks to the selective 17O-enrichment of either hydroxyl or terephthalate groups by ball-milling. This allowed the presence of defect sites to be identified for the first time in one of the phases, and the nature of the H-bonding network of the hydroxyls to be established in another. Lastly, the possibility of using deuterated precursors (e.g. D2O and d4-BDC) during ball-milling is also introduced, as a means for observing specific transformations during operando Raman spectroscopy studies, that would not have been possible with hydrogenated equivalents. Overall, the synthetic and spectroscopic approaches developed herein are expected to push forward the understanding of the structure and reactivity of other complex coordination networks and MOFs.
Multiple Resonance TADF Sensitizers Enable Green-to-Ultraviolet Photon Upconversion: Application in Photochemical Transformations
Authors: Wei Yaxiong , Pan Ke , Li Yuanming , Cao Xiaosong , Zhou Xiaoguo , Yang Chuluo
Published: February 2022

Efficient visible-to-ultraviolet (UV) triplet-triplet annihilation upconversion (TTA-UC) with large anti-Stokes shift is highly promising in solar-powered and indoor applications. Nonetheless, the excitation wavelength is confined to the blue region (< 450 nm) mainly due to large energy loss during triplet sensitization. Herein, a series of multiple resonance thermal activated delayed fluorescence (MR-TADF) compounds are constructed as pure organic sensitizers for the purpose of energy-loss reduction, which also feature intense absorbance at visible region, high intersystem crossing efficiencies, and long triplet lifetimes. By pairing the MR-TADF sensitizers with appropriate UV-emissive acceptors, green-to-UV TTA-UC systems were realized with anti-Stokes shift up to 1.05 eV, upconversion quantum yield up to 7.6% and threshold excitation intensity as low as 9.2 mW cm-2 in solution. Proof-of-concept demonstrations suggest the TTA-UC pairs could be applied as internal or external source of UV photons to trigger energy-demanding photopolymerization and photoligation reactions even under excitation of low-power-density green LED light, suggesting the broad utility of these molecular upconverters.
Improvement of poly(3-hexylthiophene-2,5-diyl) electron mobility through complete elimination of regioregularity defects
Authors: Nawaz Ali , Koehler Marlus , Kumar Anil , Merces Leandro , B. R. Abreu Anne , C. B. Bufon Carlos , P. M. Serbena Jose , A. Hummelgen Ivo
Published: February 2022

The improvement of electron transport in polymer semiconductors is highly desirable for realizing robust, large-area and low-cost organic integrated circuits. This work investigates the effect of regioregularity on the intrinsic hole and electron transport characteristics of poly(3-hexylthiophene-2,5-diyl) (P3HT) using current-voltage (I-V) measurements in metal/polymer/metal sandwich structures. Through a direct comparison between 93% regioregular P3HT (EG-P3HT) and 100% regioregular defect-free poly(3-hexylthiophene-2,5-diyl) (DF-P3HT), it is found that the elimination of regioregularity defects improves the electron mobility of DF-P3HT (1.05 × 10-7 cm2 V-1 s-1) by three orders of magnitude compared to the 93% regioregular EG-P3HT sample (1.82 × 10-10 cm2 V-1 s-1). Quantum chemical calculations indicate that the improvement of electron mobility in DF-P3HT can be associated to the lower degree of disorder in these samples that tends to increase the transfer angle between the lowest unoccupied molecular orbitals of adjacent chains. At the same time, the lower dipole moments produced by the defect-free polymer molecules also appears to play an important role in decreasing the susceptibility of charge transport to environment-induced electron traps. The obtained results provide a strong evidence that the elimination of regioregularity defects is an effective technique to improve electron transport and restore the symmetry between hole and electron mobility in P3HT as well as other thiophene-based polymers.
Kinetic Effects of Temperature on Fe-N-C Catalysts for 2e- and 4e-Oxygen Reduction Reactions
Authors: Yang Jie , Li Junfen , Ding Ruimin , Liu Chang , Yin Xi
Published: February 2022

Hydrogen peroxide (H2O2) formed via the two-electron oxygen reduction reaction (2e-ORR) on Fe-N-C catalysts at elevated temperatures can cause catalyst degradation in fuel cells. In this work, we studied the effects of temperature on the selectivity of Fe-N-C catalysts for the 2e- and 4e-ORRs in acidic electrolytes. The results showed that the H2O2 yield increased with increasing temperature, and prolonged high-temperature exposure under ORR polarization conditions led to catalyst degradation and higher H2O2 yield. These effects were further explained by means of a kinetic model describing the competitive reactions and the thermodynamics of the system.
Mechanistic investigation and free energies of the reactive adsorption of ethanol at the alumina/water interface
Authors: Clabaut Paul , Rey Jérôme , Réocreux Romain , Steinmann Stephan , Michel Carine
Published: February 2022

Controlling the adsorption/desorption of molecules at the solid/water interface is central to a diversity of fields from catalysis to batteries. Preventing the desorption of alcohol at the gamma-Al2O3/water interface is key to increase the stability of this catalyst support to perform reactions in water. Taking ethanol as a typical example, we investigate here the mechanism of desorption of two adsorption modes, namely chemisorbed ethanol and ethoxy, from the interface to the bulk water using three DFT-based simulations. Our 3D well-tempered metadynamics simulations include a bias in solvation, which triggers possible proton transfers with water. They evidence that solvation needs to be increased prior to desorption in both cases. Comparison with static approaches and thermodynamic integration simulations unambiguously identifies ethoxy as the more stable adsorption mode. It is more stable by at least 40 kJ/mol when considering adsorption at the gas/solid interface. And the presence of liquid water yields to a desorption barriers ranging from 89 kJ/mol (thermodynamic integration) to 149 kJ/mol (well-tempered metadynamics). The observed difference between the two biased ab initio molecular dynamics methods can be ascribed to the intrinsic difficulty of sampling the desorbed state vs. the adsorbed state.
Electrochemical oscillatory baffled reactors fabricated with additive manufacturing for efficient continuous-flow oxidations
Authors: Alvarez Elena , Romero-Fernandez Maria , Iglesias Diego , Martinez-Cuenca Raul , Okafor Obinna , Delorme Astrid , Conradie Alex , Lozano Pedro , Licence Peter , Goodridge Ruth , Chiva Sergio , Paradisi Francesca , Walsh Darren A. , Sans Víctor
Published: February 2022

Electrochemical oscillatory baffled reactors fabricated with additive manufacturing for efficient continuous-flow oxidations
Capturing the Transient Microstructure of a Physically Assembled Gel Subjected to Temperature and Large Deformation
Authors: Badani Prado Rosa Maria , Mishra Satish , Ahmad Humayun , Burghardt Wesley R. , Kundu Santanu
Published: February 2022

The microstructure of physically assembled gels depends on mechanical loading and environmental stimuli such as temperature. Here, we report the real-time change in the structure of physically assembled triblock copolymer gels that consist of 10 wt% and 20 wt% of poly(styrene)-poly(isoprene)-poly(styrene) [PS-PI-PS] triblock copolymer in mineral oil (i) during the gelation process with decreasing temperature, (ii) subjected to large oscillatory deformation, and (iii) during the stress-relaxation process after the application of a step-strain. The presence of loosely bounded PS-aggregates at temperatures higher than the rheologically determined gelation temperature (Tgel) captures the progressive gelation process spanning over a broad temperature range. However, the microstructure fully develops at temperatures sufficiently lower than Tgel. The microstructure orients in the stretching direction with the applied strain. In an oscillation strain cycle, such oriented structure has been observed at low-strain. But, at large-strain, because of strain-localization the oriented structure splits, and only a fraction of midblock participates in load-bearing. Both microstructure recovery and time-dependent moduli during the stress-relaxation process after the application of a step-strain have been captured using a stretched-exponential model. However, the microstructure recovery time has been found to be two orders of magnitude slower than the stress-relaxation time at room temperature, indicating a complex nature of stress-relaxation and microstructure recovery processes involving midblock relaxation, endblock pullout and reassociation. Due to their viscoelastic nature, these gels' mechanical responses are sensitive to strain, temperature, and rate of deformation. Therefore, insights into the microstructural information as a function of these parameters will assist these gels' real-life applications and design new gels with improved properties.
Organic Photovoltaic Efficiency Predictor: Data-Driven Predictions of Power Conversion Efficiencies of Non-Fullerene Acceptor Organic Solar Cells
Authors: Greenstein Brianna , Hutchison Geoffrey
Published: February 2022

In the fabrication of organic solar cells, there has been a need for materials with high power conversion efficiencies (PCE). Scharber’s model is commonly used to predict efficiency, however it exhibits poor performance with new non-fullerene acceptor (NFA) devices (RMSE=2.53%). In this work, an empirical model is proposed that can be a more accurate alternative for NFA organic solar cells. Additionally, many screening studies use computationally expensive methods. A model based on using the semi-empirical simplified time-dependent density functional theory (sTD-DFT) as an alternative method can accelerate the calculations and yields similar accuracy. The models presented in this paper, referred to as Organic Photovoltaic Efficiency Predictor (OPEP) models, have shown significantly lower errors than previous models, with OPEP/B3LYP yielding errors of 1.53% and OPEP/sTD-DFT of 1.55%. The proposed computational models can be utilized for fast and accurate screening of new high-efficiency NFAs and donor polymer pairs.
Modulated Self-Assembly of an Interpenetrated MIL-53 Sc Metal-Organic Framework with Excellent Volumetric H2 Storage and Working Capacity
Authors: Thom Alexander , Madden David , Bueno-Perez Rocio , Al Shakhs Ali , Lennon Ciaran , Marshall Ross , Wilson Claire , Murray Claire , Thompson Stephen , Turner Gemma , Bara Dominic , Moggach Stephen , Fairen-Jimenez David , Forgan Ross
Published: February 2022

To achieve optimal performance in gas storage and delivery applications, metal-organic frameworks (MOFs) must combine high gravimetric and volumetric capacities. One potential route to balancing high pore volume with suitable crystal density is interpenetration, where identical nets sit within the void space of one another. Herein, we report an interpenetrated MIL-53 topology MOF, named GUF-1, where one-dimensional Sc(µ2-OH) chains are connected by 4,4’-(ethyne-1,2-diyl)dibenzoate linkers into a material that is an unusual example of an interpenetrated MOF with a rod-like secondary building unit. A combination of modulated self-assembly and grand canonical Monte Carlo simulations are used to optimise the porosity of GUF-1; H2 adsorption isotherms reveal a very high Qst for H2 of 7.6 kJ mol-1 and a working capacity of 41 g L-1 in a temperature-pressure swing system, which is comparable to benchmark MOFs. These results show that interpenetration is a viable route to high performance gas storage materials comprised of relatively simple building blocks.
Modular Synthesis of Azabicyclohexanes and Cyclobutenyl Amines
Authors: Dhake Kushal , Woelk Kyla , Becica Joseph , Un Andy , Jenny Sarah , Leitch David
Published: February 2022

The development of two divergent and complementary Lewis acid catalyzed additions of bicyclobutanes to imines is described. Microscale high-throughput experimentation was integral to the discovery and optimization of both reactions. N-arylimines undergo formal (3+2) cycloaddition with bicyclobutanes to yield azabicyclo[2.1.1]hexanes in a single step; in contrast, N-alkylimines undergo an addition/elimination sequence to generate cyclobutenyl methanamine products with high diastereoselectivity. These new products contain a variety of synthetic handles for further elaboration, including many functional groups relevant to pharmaceutical synthesis. The divergent reactivity observed is attributed to differences in basicity and nucleophilicity of the nitrogen atom in a common carbocation intermediate, leading to either nucleophilic attack (N-aryl) or E1 elimination (N-alkyl).
Controlled aggregation properties of modified single amino acids
Authors: Gour Nidhi , Koshti Bharti , Naskar Soumick , Kshtriya Vivekshinh , Narode Hanuman
Published: February 2022

We report the self-assembled structure formed by Fmoc protected charge single amino acid Fmoc-L-glutamic acid 5-tert-butyl ester (Fmoc-Glu(OtBu)-OH), Fmoc-L-aspartic acid 4-tert-butyl ester (Fmoc-Asp(OtBu)-OH), and Na-Fmoc-Ne-Boc-L-lysine (Fmoc-Lys(Boc)-OH). The self-assembled architecture formed by the charge aliphatic amino acids were assessed under different conditions such as concentration, temperature and pH. Fmoc-Glu(OtBu)-OH assembled to spheres at both lower and higher concentration under room temperature condition. However, it forms a broom stick like morphology at both lower and higher concentration on heating. Fmoc-Asp(OtBu)-OH on the other hand formed rod like at both both low and high concentration and also on hhealing. Fmoc-Lys(Boc)-OH also self-assemble to sphere like morphology in all conditions irrespective of concentration and heating. Since these structure are very intriguing, our future endevorous is to study these structure through different microscopic techniques such as scanning electron microscopy (SEM), Transmission Electron microscopy (TEM). The mechanisms of the structure formation by these amino acids will be characterized by using solution state NMR, FTIR and TGA in future. The self-assembled structures formed by modified amino acids are easy and facile route to design novel nanoarchitectures which may be potentially useful in future for various type of applications in the field of material chemistry, bioscience, biomedical.
A Template for the Validation of DART-MS for Qualitative Seized Drugs Analysis
Authors: Sisco Edward , Burns Amber , Schneider Elizabeth , Bobka Laurel , Ikpeama Ikeanna
Published: February 2022

Direct analysis in real time mass spectrometry (DART-MS) is an increasingly employed tool for a wide range of forensic applications including seized drug analysis. A significant body of research surrounds DART-MS for the analysis of seized drugs and how it can be used to address many of the challenges caused by the increased presence of emerging drugs and novel psychoactive substances. A lack of available resources to help address validation, operation, training, and data interpretation needs is just one of the hurdles that laboratories face when adopting new technologies, such as DART-MS. To provide additional resources to assist in validation development, this work provides a template that can be adopted or adapted for DART-MS or other ambient ionization mass spectrometry techniques for qualitative seized drug analysis. The template, which was created as a result of recent implementation efforts, provides a description of validation studies with a focus on understanding the potential challenges and limitations caused by the prevalence of novel psychoactive substances and other emerging drugs. The studies address accuracy and precision, reproducibility, specificity, sensitivity, environmental factors, use in casework, and robustness. In addition to providing a template for validation, the results obtained from completing these studies on two high-resolution DART-MS systems are also presented. This work, and the corresponding supplemental information, was created to add to the available resources that laboratories can leverage to assist in overcoming the adoption hurdles of ambient ionization mass spectrometry methods such as DART-MS.
Bioorthogonal Photo-Catalytic Activation of an Anti-Cancer Prodrug by Riboflavin
Authors: Yang Xin , Ma Limin , Shao Hongwei , Ling Xia , Yao Mengyu , Luo Guowen , Mazzone Gloria , Gao Meng , Tang Ben Zhong
Published: February 2022

Chemotherapies for cancer treatment usually suffer from poor targeting ability and serious side-effects. To improve the treatment efficiency and reduce side effects, photoactivatable chemotherapy has been recently proposed for precise cancer treatment with high spatiotemporal resolution. However, most photoactivatable prodrugs require decoration by stoichiometric photo-cleavable groups, which are only responsive to ultraviolet irradiation and suffer from low reaction efficiency. To tackle these challenges, we herein propose a bioorthogonal photo-catalytic activation strategy with riboflavin as the catalyst for in situ transformation of prodrug dihydrochelerythrine (DHCHE) prodrug into anti-cancer drug chelerythrine (CHE), which can efficiently kill cancer cells and inhibit in vivo tumor growth under light irradiation. Meanwhile, the photo-catalytic transformation from DHCHE into CHE can be in situ monitored by green-to-red fluorescence conversion, which can be used for precise control of the therapeutic dose. We believe this imaging-guided bioorthogonal photo-catalytic strategy is promising for cancer treatment in clinical applications.
Star-Polymer-DNA Gels Showing Highly Predictable and Tunable Mechanical Responses
Authors: Ohira Masashi , Katashima Takuya , Naito Mitsuru , Aoki Daisuke , Yoshikawa Yusuke , Iwase Hiroki , Takata Shinichi , Miyata Kanjiro , Chung Ung-il , Sakai Takamasa , Shibayama Mitsuhiro , Li Xiang
Published: February 2022

Dynamically crosslinked gels are appealing materials for applications that require time-dependent mechanical responses. DNA duplexes are ideal crosslinkers for building such gels because of their excellent sequence addressability and flexible tunability in bond energy. However, the mechanical responses of most DNA gels are complicated and unpredictable despite the high potential of DNA. Here, we demonstrate a DNA gel with a highly homogeneous gel network and well-predictable mechanical behaviors by using a pair of star-polymer-DNA precursors with presimulated DNA sequences showing the two-state transition. The melting curve analysis of the DNA gels reveals the good correspondence between the thermodynamic potentials of the DNA crosslinkers and the presimulated values by DNA calculators. Stress-relaxation tests and dissociation kinetics measurements show that the macroscopic relaxation time of the DNA gels is approximately equal to the lifetime of the DNA crosslinkers over four orders of magnitude from 0.1-2,000 sec. Furthermore, a series of durability tests find the DNA gels are hysteresis-less and self-healable after the applications of repeated temperature and mechanical stimuli. These results demonstrate the great potential of star-polymer-DNA precursors for building gels with predictable and tunable viscoelastic properties, suitable for applications such as stress-response extracellular matrices, injectable solids, and soft robotics.
CH-π interaction boosts photocatalytic CO2 reduction activity in a noble-metal-free system with a molecular cobalt catalyst anchored on carbon nitride
Authors: Wang Jia-Wei , Gil Sepulcre Macros , Huang Hai-Hua , Solano Eduardo , Mu Yan-Fei , Llobet Antoni , Ouyang Gangfeng
Published: February 2022

The construction of efficient noble-metal-free systems for visible-light-driven CO2 reduction still remains a key challenge. Here we report an efficient molecular hybrid system composed of a Co-PYN5 catalyst that contains a pyrene functionality that anchors on g-C3N4 dye surface via CH-π interactions. This hybrid material achieves high TONs and TOFs for visible light reduction of CO2 to CO of 533 and 95 h-1, that are within the best reported up to now. The exceptional performance is rationalized in terms of the electronic coupling that takes place with the π-system of the pyrene group with both the g-C3N4 surface and the Co-pyridyl moiety of the catalysts.
Low scaling excited state calculation using block interaction product state
Authors: Wang Ke , Ma Haibo
Published: February 2022

We develop an automatic and efficient scheme for the accurate construction of the bases for excitonic models, which can enable "black-box" excited state structure calculations for large molecular systems. These new and optimized bases, which are named as block interaction product state (BIPS), can be expressed as the direct products of the local states for each chromophore. Each chromophore's local states are selected by diagonalization of its reduced density matrix (RDM), which is obtained by quantum chemical calculation of the small subsystem composed of the chromophore and its nearest neighbors. We implemented BIPS framework with fragment-based calculations considering 2-body and 3-body interactions. Test calculations for 8 different molecular aggregates demonstrate that this framework provides accurate description of not only the excitation energies, but also the first-order wavefunction properties (dipole moment and transition dipole moment) of the low-lying excited states at a low-scaling computational cost.
In-Silico Structural prediction and functional annotation of uncharacterized protein Q7TLC7 (Y14_SARS) presence in SARS-COV2
Authors: Rahman MD. Ashiqur , Rumi Rumana Akter
Published: February 2022

Protein structure prediction strategies point to predict the structures of proteins from their amino acid sequences, utilizing different computational calculations. Basically, the prediction of 3D structure of a protein from its amino acid sequence is one of the foremost critical indecisive issues in computational biology. This paper endeavors to grant a comprehensive presentation of the foremost later exertion and advance on protein structure prediction. Taking after the common flowchart of structure prediction, related concepts and strategies are displayed and experimentally established. In addition, brief presentations are made to a few widely-used prediction methods and the community-wide basic appraisal of protein structure prediction experiments. Here we can see Unknown proteins exist but have not been characterized or connected to known qualities. Domains of unknown function are experimentally distinguished proteins with no known functional or structural domain. In this paper, the examination and characterization of the likely useful perspectives of a hypothetical protein: coronavirus Q7TLC7 (Y14_SARS) was performed utilizing different computational strategies and tools. As the protein tertiary structure not accessible within the Protein Data Bank, the basic demonstrate expectation with its structural and functional annotation is well explained in this paper which consequently, gives an understanding into this hypothetical protein ( Q7TLC7) .In this manner, unleashes an opportunity for medicate and immunization focusing on against the disease by COVID19 investigation will be of significance in understanding the mechanism of the infections and will demonstrate to be advantageous within the revelation of new drugs
Machine-Learned Functionals for Strongly Correlated Systems
Authors: King Daniel , Gagliardi Laura , Truhlar Donald
Published: February 2022

We introduce multiconfiguration data-driven functional theory (MC-DDFT) as a new approach to multiconfiguration nonclassical functional theory (MC-NCFT), in which the classical energy of a multiconfigurational wave function is combined with a machine-learned functional for the nonclassical exchange-correlation energy. We also present results obtained by a related approach, multiconfiguration energy-correcting functional theory (MC-ECFT), in which the total energy of a wave function method (e.g. CASSCF or NEVPT2) is corrected with a machine-learned functional. On a dataset of carbene singlet-triplet energy splittings, we demonstrate that these new multiconfiguration data-driven functional methods (MC-DDFMs) are able to achieve near-benchmark performance on systems not used for training while being less active-space dependent than multiconfiguration pair-density functional theory using currently available translated functionals.
Flexible boundary layer using exchange for embedding theories. I. Theory and implementation
Authors: Shen Zhuofan , Glover William
Published: February 2022

Embedding theory is a powerful computational chemistry approach to exploring the electronic structure and dynamics of complex systems, with QM/MM being the prime example. A challenge arises when trying to apply embedding methodology to systems with diffusible particles, e.g. solvents, if some of them must be included in the QM region, for example in the description of solvent supported electronic states or reactions involving proton transfer or charge-transfer-to-solvent: without a special treatment, inter-diffusion of QM and MM particles will lead eventually to a loss of QM/MM separation. We have developed a new method called Flexible Boundary Layer using Exchange (FlexiBLE) that solves the problem by adding a biasing potential to the system that maintains QM/MM separation. The method rigorously preserves ensemble averages by leveraging their invariance to exchange of identical particles. With a careful choice of the biasing potential, and the use of a tree algorithm to include only important QM and MM exchanges, we find the method has an MM-forcefield-like computational cost and thus adds negligible overhead to a QM/MM simulation. Furthermore, we show that molecular dynamics with the FlexiBLE bias conserves total energy and remarkably, dynamical quantities in the QM region are unaffected by the applied bias. FlexiBLE thus widens the range of chemistry that can be studied with embedding theory.
SEEKR2: Versatile Multiscale Milestoning Utilizing the OpenMM 7.5 Molecular Dynamics Engine
Authors: Votapka Lane , Stokely Andrew , Ojha Anupam , Amaro Rommie
Published: February 2022

We present SEEKR2 (Simulation-Enabled Estimation of Kinetic Rates Version 2) – the latest iteration in the family of SEEKR programs for using multiscale simulation methods to computationally estimate the kinetics and thermodynamics of molecular processes, in particular, ligand-receptor binding. SEEKR2 generates equivalent, or improved, results compared to the earlier versions of SEEKR, but with significant increases in speed and capabilities. SEEKR2 has also been built with greater ease of usability with extensible features to enable future expansions of the method. Now, in addition to supporting simulations using NAMD, calculations may be run with the fast and extensible OpenMM simulation engine. The Brownian dynamics portion of the calculation has also been upgraded to Browndye 2.
On-Board Reagent Storage and Release by Solvent-Selective, Rotationally Opened Membranes – A Digital Twin Approach
Authors: Ducrée Jens
Published: February 2022

Decentralized bioanalytical testing in resource-poor settings ranges among the prime applications of microfluidic systems. The high operational autonomy in such point-of-care / point-of-use scenarios requires on-board stored liquid reagents, which need to be safely contained during long-term storage, transport and handling, and reliably released prior to activation. Over the recent decades, centrifugal microfluidic technologies have demonstrated the capability of integrated, automated and parallelized sample preparation and detection of bioanalytical protocols. This paper introduces a novel concept for onboard storage of liquid reagents which can be delivered in a well-defined manner by a rotational stimulus of the system-innate spindle motor, while still aligning with the conceptual simplicity of such “Lab-on-a-Disc” (LoaD) concepts. The reagent storage technology is captured by a digital twin which allows making complex performance analysis and algorithmic design optimization according to given objectives as expressed by target metrics.
Electron-withdrawing Group Modified Carbazolophane Donors for Deep Blue Thermally Activated Delayed Fluorescence OLEDs
Authors: Kumar Gupta Abhishek , Zhang Zhen , Spuling Eduard , Kaczmarek Maria , Wang Yichuan , Hassan Zahid , Samuel Ifor , Braese Stefan , Zysman-Colman Eli
Published: February 2022

We report two blue-emitting thermally activated delayed fluorescence (TADF) compounds employing a substituted carbazolophane (Czp) donor (indolo[2.2]paracyclophane). The compounds CNCzpPhTRZ and CF3CzpPhTRZ show emission maxima of 426 nm and 432 nm, respectively, with high photoluminescence quantum yields (PL) of 73% and 80%, respectively. The singlet-triplet energy gap (EST) of both emitters is 0.22 eV, resulting in long-delayed lifetimes of 132 μs for CNCzpPhTRZ and 158 μs for CF3CzpPhTRZ in PPT as the host matrix. Blue organic light-emitting diodes (OLEDs) showed maximum external quantum efficiencies (EQEs) of 7.4% for CNCzpPhTRZ and 11.6% for CF3CzpPhTRZ with electroluminescence maxima of ca. 460 nm.
Indacenodipyrene Containing Small Molecules and Ladder Polymers
Authors: Uddin Ain , Plunkett Kyle
Published: February 2022

A series of s-indaceno[1,2,3-cd:5,6,7-c'd']dipyrene-containing small molecule and ladder polymers were prepared using a palladium catalyzed arylation reaction. Precursor polymers and their resulting ladder polymers with molecular weights up to 13 kDa were prepared. The rigid, planar materials possessed highest occupied molecular orbital (HOMO) energies of -5.39 to -5.23 eV, lowest unoccupied molecular orbitals (LUMO) energies of -2.42 eV to -2.98 eV, and optical gaps of 1.68 to 2.03 eV. Organic field effect transistors were prepared with derivatives giving hole mobilities up to 2.5 X 10-5 cm2V-1s-1.
Accelerated Prediction of Atomically Precise Cluster Structures Using On-the-fly Machine Learning
Authors: Wang Yunzhe , Liu Shanping , Lile Peter , Norwood Sam , Hernandez Alberto , Manna Sukriti , Mueller Tim
Published: February 2022

The chemical and structural properties of atomically precise nanoclusters are of great interest in numerous applications, but predicting the stable structures of clusters can be computationally expensive. In this work, we present a procedure for rapidly predicting low-energy structures of nanoclusters by combining a genetic algorithm with interatomic potentials actively learned on-the-fly. Applying this approach to aluminum clusters with 21 to 55 atoms, we have identified structures with lower energy than any reported in the literature for 25 out of the 35 sizes. Our benchmarks indicate that the active learning procedure accelerated the average search speed by more than an order of magnitude relative to genetic algorithm searches using only density functional calculations. This work demonstrates a feasible way to systematically discover stable structures for large nanoclusters and provides insights into the transferability of machine-learned interatomic potentials for nanoclusters.
Synthesis and Characterization of Magnesium Vanadates as Potential Mg-ion Cathode Materials Through an Ab Initio Guided Carbothermal Reduction Approach
Authors: Lee Jeongjae , Dey Sunita , Dutton Siân , Grey Clare
Published: February 2022

Many technologically relevant transition metal oxides for advanced energy storage and catalysis feature reduced transition metal (TM) oxides and are often nontrivial to prepare because of the need to control the reducing nature of the atmosphere in which they are synthesized. In this work, we show that an ab initio predictive synthesis strategy can be used to produce multiple gram-scale products of various MgVxOy-type phases (δ-MgV2O5, spinel MgV2O4, and MgVO3) containing V3+ or V4+ relevant for Mg-ion battery cathodes. Characterization of these phases using 25Mg solid-state NMR spectroscopy illustrates the potential of 25Mg NMR for studying reversible magnesiation and local charge distributions. Rotor-Assisted Population Transfer is used as a much needed signal-to-noise enhancement technique. The ab initio guided synthesis approach is seen as a step forward towards a predictive synthesis strategy for targeting specific complex TM oxides with variable oxidation states of technological importance.
Crystal Structure of the Intermediate Na2V2(PO4)3 Phase and Electrochemical Reaction Mechanisms in NaxV2(PO4)3 (1 ≤ x ≤ 4) System
Authors: Park Sunkyu , Wang Ziliang , Deng Zeyu , Moog Iona , Canepa Pieremanuele , Fauth François , Carlier Dany , Croguennec Laurence , Masquelier Christian , Chotard Jean-Noël
Published: February 2022

The Na-superionic-conductor (NASICON) Na3V2(PO4)3 is an important positive electrode material for Na-ion batteries. Here, we investigate the mechanisms of phase transition in NaxV2(PO4)3 (1 ≤ x ≤ 4) upon a non-equilibrium battery cycling. Unlike the widely believed two-phase reaction in Na3V2(PO4)3 – Na1V2(PO4)3 system, we determine a new intermediate Na2V2(PO4)3 phase using operando synchrotron X-ray diffraction. Density functional theory calculations further support the existence of the Na2V2(PO4)3 phase. We propose for the first time two possible crystal structures of Na2V2(PO4)3 analyzed by Rietveld refinement. The two structure models with the space groups P21/c or P2/c for the new intermediate Na2V2(PO4)3 phase show similar unit cell parameters but different atomic arrangements, including a vanadium charge ordering. As the appearance of the intermediate Na2V2(PO4)3 phase is accompanied by symmetry reduction, Na(1) and Na(2) sites split into several positions in Na2V2(PO4)3, in which one of the splitting Na(2) position is found to be a vacancy whereas the Na(1) positions are almost fully filled. The intermediate Na2V2(PO4)3 phase reduces the lattice mismatch between Na3V2(PO4)3 and Na1V2(PO4)3 phases facilitating a fast phase transition. This work paves the way for a better understanding of great rate capabilities of Na3V2(PO4)3.
Polymorphism, Structure, and Nucleation of Cholesterol.H2O at Aqueous Interfaces and in Pathological Media: Revisited from a Computational Perspective
Authors: Shepelenko Margarita , Hirsch Anna , Varsano Neta , Addadi Lia , Leiserowitz Leslie , Kronik Leeor
Published: February 2022

We revisit the important issues of polymorphism, structure, and nucleation of cholesterol monohydrate, using first principles calculations based on dispersion-augmented density functional theory. For the lesser known monoclinic polymorph, we obtain a new, fully extended H-bonded network, comprising the sterol hydroxyl groups and water molecules in a structure akin to that of hexagonal ice. We show that the energy of the monoclinic and triclinic polymorphs is similar, strongly suggesting that kinetic and environmental effects play a significant role in determining polymorph nucleation. Furthermore, we find evidence in support of various O-H…O bonding motifs, in both polymorphs, that may result in structural disorder. We then rationalize what we believe is a single-crystal to single-crystal transformation of the monoclinic form on increased interlayer growth beyond that of a single cholesterol bilayer, interleaved by a water bilayer, and show that the ice-like structure is also relevant to the related cholestanol dihydrate (2H2O) crystal. Finally, we posit a possible role for cholesterol esters in the crystallization of cholesterol.H2O in pathological environments, with a composite of a bilayer of cholesteryl palmitate bound epitaxially as a nucleating agent to the monoclinic form of cholesterol.H2O.
On the Role of Heterojunctions of Core-Shell Heterostructures in Gas Sensing
Authors: Raza Muhammad Hamid , Di Chio Roberto , Movlaee Kaveh , Amsalem Patrick , Koch Norbert , Barsan Nicolae , Neri Giovanni , Pinna Nicola
Published: February 2022

Heterostructures made from semiconducting metal oxides (SMOX) are fundamental for the development of high-performance gas sensors. Yet, despite the recognition of their importance in real applications, the understanding of the transduction mechanism either related to the heterojunction, or simply to the core and shell materials is still lacking. A better understanding of the sensing response of heterostructured nanomaterials requires the engineering of heterojunctions with well-defined core and shell layers. Here, we introduce a series of prototypes nSMOX-CNT, pSMOX-CNT, and pSMOX-nSMOX-CNT and nSMOX-pSMOX-CNT hierarchical core-shell heterostructures (CSHS) permitting us to directly relate the sensing response to the SMOX shell, or to the p-n heterojunction. The carbon nanotubes are here used as highly conductive substrates permitting to operate the devices at relatively low temperature and are not involved in the sensing response. NiO and SnO2 are selected as representative p- and n-type SMOX, respectively, and the response of a set of samples is studied toward hydrogen considered as model analyte. The n,pSMOX-CNT CSHS exhibit response related to the n,pSMOX-shell layer. On the other hand, the pSMOX-nSMOX-CNT and nSMOX-pSMOX-CNT CSHS show sensing responses, which in certain cases are governed by the heterojunctions between nSMOX and pSMOX and strongly depends on the thickness of the SMOX layers. Due to the fundamental nature of this study, these findings are important for the development of next generation gas sensing devices.
Structure and Biosynthesis of Myxofacyclines: Unique Myxobacterial Polyketides Featuring Varying and Unprecedented Heterocycles
Authors: Popoff Alexander , Hug Joachim , Walesch Sebastian , Garcia Ronald , Keller Lena , Müller Rolf
Published: February 2022

A metabolome-guided screening approach in the novel myxobacterium Corallococcus sp. MCy9072 resulted in the isolation of the unprecedented natural product myxofacycline A featuring a rare isoxazole substructure. Identification and genomic investigation of additional producers alongside targeted gene inactivation experiments and heterologous expression of the corresponding biosynthetic gene cluster in the host Myxococcus xanthus DK1622 confirmed a noncanonical megaenzyme complex as the biosynthetic origin of myxofacycline A. Induced expression of the respective genes led to significantly increased production titers enabling the identification of six further members of the myxofacycline natural product family. Whereas myxofacycline A–D display an isoxazole substructure, myxofacycline E and F intriguingly were found to contain 4 pyrimidinole, a heterocycle unprecedented in natural products. Lastly, myxofacycline G features another rare 1,2 dihydropyrol-3-one moiety. In addition to the full structure elucidation, we report the underlying biosynthetic machinery and present a rationale for the formation of all myxofacyclines. Unexpectedly, an extraordinary polyketide synthase-nonribosomal peptide synthetase hybrid was found to produce all three types of heterocycles in these natural products.
Using Constrained Density Functional Theory to Track Proton Transfers and to Sample Their Associated Free Energy Surface
Authors: Voth Gregory , Li Chenghan
Published: February 2022

The ab initio molecular dynamics (AIMD) and quantum mechanics/molecular mechanics (QM/MM) methods are powerful tools for studying proton solvation, transfer, and transport processes in various environments. However, due to the high computational cost of such methods, achieving sufficient sampling of rare events involving excess proton motion – especially when Grotthuss proton shuttling is involved – usually requires enhanced free energy sampling methods to obtain informative results. Moreover, an appropriate collective variable (CV) that describes the effective position of the net positive charge defect associated with an excess proton is essential for both tracking the trajectory of the defect and for the free energy sampling of the processes associated with the resulting proton transfer and transport. In this work, such a CV is derived from first principles using constrained density functional theory (CDFT). This CV is applicable to a broad array of proton transport and transfer processes.
On the nature of extra-framework aluminum species and improved catalytic properties in steamed zeolites
Authors: Khivantsev Konstantin , Jaegers Nicholas , Kovarik Libor , Kwak Ja-Hun , Derewinski Miroslaw , Szanyi Janos
Published: February 2022

Steamed zeolites have improved catalytic properties for hydrocarbon activation (alkane cracking reaction as well as alkane dehydrogenation). The nature of this practically important phenomenon has remained a mystery for the last six decades and was speculated to be related to increased Bronsted acidity during dealumination. We now prove that during steaming aluminum oxide clusters evolve (due to hydrolysis of Al out of framework positions with the following clustering) in the zeolitic micropores with properties very similar to (nano)facets of hydroxylated transition-alumina surfaces. Bronsted acidity of zeolite does not increase and the total number of Bronsted acid sites decreases during steaming. O5Al(VI)-OH surface sites of alumina clusters dehydroxylate at elevated temperatures to form penta-coordinate Al1O5 sites that are capable of initiating alkane cracking by breaking the first C-H bond very effectively, with the following reaction steps catalyzed by nearby zeolitic Bronsted acid sites. This explains the underlying reason behind the improved alkane cracking and alkane dehydrogenation activity of steamed zeolites: heterolytic C-H bond breaking occurs on penta Al(V)1O5 sites of aluminum oxide clusters confined in zeolitic pores. Furthermore, slightly decreased number of adjacent Al framework sites (due to Al dislodgement from the framework) decreases the coking activity, prolonging catalyst lifetime. Our findings explain the origin of enhanced activity of steamed zeolites at the molecular level and provide the missing understanding of the nature of extra-framework Al species formed in steamed/dealuminated zeolites. Furthermore, our findings suggest that similar La2O3 clusters exist for La-containing zeolites and the origin of their cracking activity promotion should be similar.
Exploration of reduced graphene oxide microparticles as electrocatalytic materials in vanadium redox flow batteries
Authors: Alazmi Amira , Wan Charles , Costa Pedro , Brushett Fikile
Published: February 2022

Augmenting reaction rates on porous carbon electrodes is critical for reducing the cost of all-vanadium redox flow batteries (VRFBs). To this end, reduced graphene oxide (rGO) based carbons hold promise, demonstrating high specific surface area, chemomechanical stability, and electrochemical activity. While initial efforts have shown that rGOs can enhance VRFB performance, the range of unique processing conditions leads to a collection of materials with disparate elemental composition and porous structure, thus obscuring performance-determining characteristics behind redox reactions and frustrating the development of generalizable design principles. Here, we generate rGO electrocatalysts of nearly identical chemical composition but different textures (i.e., surface area and pore structure) by varying the drying step in the graphene synthesis (i.e., vacuum-drying vs. carbon dioxide critical point drying). We apply spectroscopic and electrochemical techniques on the synthesized rGOs, observing a three-fold increase in BET surface area using critical point drying. We subsequently decorate carbon felt electrodes – both pristine and thermally activated – with rGO microparticles via a flow deposition procedure, and evaluate their performance and durability in a VRFB cell. The synthesis approach and findings described in this work inform and complement efforts to advance the material science and engineering of rGO electrocatalysts.
Elucidating Cooperative Luminescence and Cooperative Sensitisation Upconversion of Nonanuclear Lanthanide Complexes in Solution
Authors: Knighton Richard , Soro Lohona , Frances-Soriano Laura , Rodriguez-Rodriguez Aurora , Pilet Guillaume , Lenertz Marc , Platas-Iglesias Carlos , Hildebrandt Niko , Charbonniere Loic
Published: February 2022

Upconversion nanoparticles have led to various breakthrough applications in solar energy conversion, imaging, and biomedicine. One key impediment is the facilitation of such processes at the molecular scale in solution where quenching effects are much more pronounced. In this work we explore, for the first time, molecular solution-state cooperative luminescence (CL) upconversion arising from a Yb excited state and investigate the mechanistic origin behind cooperative sensitisation (CS) upconversion in Yb/ Tb systems. Counterintuitively, the best UC performances were obtained for Yb/Tb ratios close to parity, resulting in the brightest molecular upconversion complexes with an unprecedented quantum yield of 2.8 × 10-6 at a low laser power density of 2.86 W/cm2.
Convolutional Neural Networks for High Throughput Screening of Catalyst Layer Inks for Polymer Electrolyte Fuel Cells
Authors: Eslamibidgoli Mohammad Javad , Tipp Fabian P. , Jistev Jenia , Jankovic Jasna , Eikerling Michael H. , Malek Kourosh
Published: February 2022

The performance of polymer electrolyte fuel cells decisively depends on the structure and processes in membrane electrode assemblies and their components, in particular the catalyst layers. Essential structural building blocks of catalyst layers are formed during processing and application of catalyst inks. Accelerating the structural characterization at the ink stage is thus crucial to expedite further advances in catalyst layer design and fabrication. In this context, deep learning algorithms based on deep convolutional neural networks (ConvNets) can automate the processing of the complex and multi-scale structural features of ink imaging data. This article presents the first application of ConvNets for the high throughput screening of transmission electron microscopy images at the ink stage. Results indicate the importance of model pre-training and employment of data augmentation that works on multiple scales in the training of robust and accurate classification pipelines.