Small Charge Research Articles

DFT analysis of the sensitivity of graphene/MoS2 heterostructures toward H2CO

Indoor toxic gases detection is very important for human health, and the use of novel two-dimensional materials to detect or adsorb toxic gases is significant. With these prospects in mind, the potential application of graphene/MoS2 two-dimensional heterostructure as a gas sensor was explored. This study investigated the sucking stability and electronic and magnetic properties of H2CO adsorbed on perfect, vacancy-defected, transition metal (TM)-doped graphene/MoS2 heterostructures through density functional theory analysis. Perfect graphene/MoS2 (GMoS2) exhibited small adsorption energy and low charge transfer, and the TM-doped Mo-vacancy-defected heterostructures exhibited physical adsorption toward H2CO molecules with a shorter desorption time. However, the interaction between H2CO and the substrate changed to chemisorption when TMs (Sc, V, Cr, Mn) were doped with S-vacancy-defected graphene/MoS2. Meanwhile, the density of states of the S-defected heterostructure indicated the hybridization of the d orbitals of the dopants and the p orbital of the H2CO molecule that considerably enhanced the adsorption energy. Furthermore, the asymmetric electron spin distribution of dopants and Mo atoms induced a strong magnetic moment. In summary, this study established an effective approach for H2CO gas detection based on heterostructure.

Investigation of CuxS-based electrode for one-dimensional flexible supercapacitors and its electrochemical performances

In this study, CuxS nanoplates are in-situ synthesized on the surface of copper wire (CW) as active materials (CW@CuxS) for supercapacitor electrodes, in which CW and Na2S are respectively used as copper and sulphur sources. The CW@CuxS electrode exhibits high specific capacitance up to 3.06 F cm−3, good cycling stability with nearly 80% capacitance retention after 5000 cycles, small charge transfer resistance, and low equivalent series resistance. In addition, the CW@CuxS electrode shows excellent flexibility applied to one-dimensional supercapacitors, as indicated by the relative stability of the specific capacitance in different bending states.

Sodium-rich prussian blue analogue coated by poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as superior cathode for sodium-ion batteries

Sodium-ion batteries (SIBs) are a promising alternative to complement costly lithium-ion batteries for grid-scale stationary energy storage systems. However, finding a suitable cathode material has been a challenging process mainly due to the large radius of sodium-ion that hinders the process of intercalation. In our previous work, we have successfully synthesized Prussian blue analogue (PBA) via simple single iron source precipitation and low thermal method. However, it suffered poor electrical conductivity. In this work, the as-prepared PBA (high purity, low vacancy (∼2%), and high sodium-ion content) was then coated with various concentrations of conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS) via simple stirring method to aid the electron route. The coated PBA (PB–P5) demonstrates two-fold enhanced conductivity of 2.04 × 10−5 S cm−1 at 30 °C and 1.18 × 10−4 S cm−1 at 100 °C. XRD peaks of coated PBAs show a slight shifting to higher diffraction angle, indicating the changes from rhombohedral-like to cubic structure. The battery capacity retention has also improved from 73.9% (PB–P0) to 82.87% (PB–P5), on account of having PEDOT-PSS to slow down the side reaction between cathode and electrolyte and eventually improve the cycling stability. Additionally, PB-P5 displays the lowest potential separation in cyclic voltammetry (CV) and small charge transfer resistance, Rct value, in which indicating a better electron transfer and enhanced overall conductivity.

Synergistic effect of Fe (III) doping and MWCNTs integration on the electrochemical performance of nickel sulfide nanoparticles for hybrid supercapacitor applications

In this report, Iron (Fe) doped nickel sulfide (NiS) nanoparticles integrated with multi-walled carbon nanotubes (MWCNTs) have been prepared by hydrothermal and ultrasonication approach. X-rays studies of synthesized samples showed the existence of single-phase hexagonal Fe–NiS along MWCNTs with crystallite size of 13.19 nm. SEM images indicated spherical Fe–NiS particles encapsulated by long and thin thread like MWCNTs. Fe–NiS@MWCNTs was drop casted on nickel foam (NF) for the supercapacitor application. Fe–NiS@MWCNTs/NF offered a specific capacity of 662C g−1 at 5 mV s−1 with excellent cyclic stability. Fe–NiS@MWCNTs/NF maintained 70.2% of initial specific capacity at a high scan rate of 100 mV s−1. For impedance studies, a small equivalent series resistance (ESR = 2.30 Ω) and charge transfer resistance (RCT = 3.12 Ω) were observed for Fe–NiS@MWCNTs/NF. The superior electrochemical performance of Fe–NiS@MWCNTs/NF can be accredited to the large surface area and intervened network of Fe–NiS@MWCNTs. Pseudocapacitive Fe–NiS and highly conductive MWCNTs generate synergistic effects that ultimately boost up the specific capacity of Fe–NiS@MWCNTs/NF electrode. The excellent electrochemical performance of proposes Fe–NiS@MWCNTs/NF as effective electroactive material for supercapacitor applications.

Corrosion of X80 steel in the co-existence of sulfate reducing bacteria and permeating hydrogen

PurposeThis study aims to shed light on the corrosion behavior of X80 steel when sulfate-reducing bacteria (SRB) and permeating hydrogen interact.Design/methodology/approachIn this study, electrochemical tests were conducted between 25 and 55 °C, and the surface morphology of the specimen was observed using scanning electron microscopy and three-dimensional photos. The composition of the oxide film was characterized by X-ray photoelectron spectroscopy (XPS).FindingsUnder the condition of 6 MPa simulated natural gas (15% H2), the content of S-containing compounds (FeS and FeSO4) in the corrosion products on the surface of the specimen decreases from 60.8% to 54.4%. This finding indicates that hydrogen permeation inhibits the metabolic processes of SRB in this environment. By comparing the hydrogen-uncharged specimen, it was found that under the condition of 6 MPa simulated natural gas (15% H2) hydrogen charging, the uniform corrosion on the X80 surface was weakened, and the protection of the oxide film on the specimen surface in this environment was better than that without hydrogen charging.Originality/valueTo the best of the authors’ knowledge, most of these existing studies have focused on the effect of hydrogen on the mechanical properties of materials and very little is known about corrosion behavior in the hydrogen environment. In this study, a self-designed small gas phase hydrogen charging device was used to study the X80 surface corrosion behavior in the environment of the H2-doped natural gas pipeline.

General rules and applications for screening high phonon-limited mobility in two-dimensional semiconductors

Two-dimensional (2D) semiconductors with high mobility comparable to three-dimensional (3D) Si or GaAs are still lacking, hindering the development of high-performance 2D devices. In this work, based on the phonon-energy resolved matching function between the electronic band structure and the phonon spectrum recently proposed in our group, we provide some general rules for screening possible high-mobility 2D semiconductors. In general, a 2D semiconductor with high sound velocity, small effective mass, large atomic mass, high-energy optical phonons, small Born effective charge, large effective in-plane dielectric constant, and large effective layer thickness, is likely to have high phonon-limited mobility. Additionally, if the semiconductor has multiple valleys, the mobility-limiting factor due to intervalley scattering can be weak if the valleys are far apart in reciprocal space and have out-of-plane orbitals. Guided by these rules, we have systematically explored the mobility of traditional semiconductors at the 2D limit (2DTSs), which have been theoretically predicted and experimentally realized recently. Seven 2DTSs are found to have mobilities close to or exceeding 1000 $\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Most notably, BSb reaches record-high values of several thousand $\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ at room temperature and the experimentally synthesized 2D AlSb has an electron mobility of 921.9 $\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Using BSb, InN, and AlSb as examples, we reveal that, although the high mobilities of these systems are attributed to different underlying scattering mechanisms, they can all be understood from our proposed general rules. The present work demonstrates that 2DTSs can achieve comparable carrier mobility to 3D, thus opening possible doors to 2D high-performance electronic devices.

Bio-capped and green synthesis of ZnO/g-C3N4 nanocomposites and its improved antibiotic and photocatalytic activities: An exceptional approach towards environmental remediation

In this research study, we have synthesized the bio-capped ZnO/g-C3N4 nanocomposites by employing lemon juice (Citrus limon) as a stabilizer and mediator. Fruitfully, lemon juice which contains various acidic functional groups and citric acid has the capability to block the surface of g-C3N4 from chemical reactivity and activated the surface of g-C3N4 for various reactions. Consequently, the agglomeration behavior and controlled shape of g-C3N4 has also been achieved. Our experimental results i.e. XRD, TEM, HRTEM, PL, FS, XPS, and PEC have confirmed that the lemon juice mediated and green g-C3N4 (L-CN) has good performances and remarkable visible light photocatalytic activities as compared to the chemically synthesized g-C3N4 (CN). Furthermore, the small surface area and low charge separation of g-C3N4 is upgraded by coupling with ZnO nanoparticles. It is proved that the coupling of ZnO worked as a facilitator and photoelectron modulator to enhance the charge separation of g-C3N4. Compared to pristine lemon mediated green g-C3N4 (L-CN), the most active sample 5ZnO/L-CN showed ∼5-fold improvement in activities for ciprofloxacin (CIP) and methylene blue (MB) degradation. More specifically, the mineralization process and degradation pathways, and the mineralization process of ciprofloxacin (CIP) and methylene blue (MB) are suggested. Finally, our present novel research work will provide new access to synthesize the eco-friendly and bio-caped green g-C3N4 nanomaterials and their employment for pollutants degradation and environmental purification.

Experimental and Theoretical Evidence of Charge Injection Barrier Control by Small-Molecular Charge Injection Layer and Its Effects on Organic–Inorganic Complementary Inverters

Introducing a contact charge injection layer at the interface between the contact electrode and active materials is considered crucial to obtain efficient charge injection behaviors in thin-film transistors (TFTs). Here, we investigate the effect of a small molecule contact charge injection layer through experimental results and theoretical calculations. We found limited electrical characteristics derived from contact resistance in C8-BTBT TFTs with C8-BTBT as the channel and Au as the electrode. We experimentally demonstrated that the limited electrical characteristics of C8-BTBT TFT can be improved by inserting dinaphtho[2,3-b: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{\prime} $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{\prime} $ </tex-math></inline-formula> -f]thieno [3,2-b] thiophene (DNTT), which has a low contact resistance at the junction with Au, as a charge injection layer. The results of improved contact properties through the DNTT charge injection layer were also consistent with the results of energy structural simulations. Furthermore, we verified the effect of the DNTT charge injection layer at the circuit level through improved noise margin characteristics in the complementary inverter composed of asymmetric charge injection layer TFT (ACIL-TFT) and a-indium gallium zinc oxide (IGZO) TFT.

One-step gas phase sulfided NiFe coating as self-supporting electrode for high efficiency oxygen evolution reaction

The development of cost-effective oxygen evolution reaction (OER) electrocatalytic electrodes is one of the essential means of applying green hydrogen energy. Due to the complex steps in the anodic OER, the high overpotential hinders the kinetics of water splitting. In this paper, the sulfided NiFe coating was innovatively designed as a self-supporting OER electrode by high-velocity oxygen fuel (HVOF) spraying coupled with one-step gas phase sulfuration. The thickness of the NiFe coating is approximately 20 μm. After the sulfuration treatment, the surface of the NiFe coating is remolded into a uniform rock sugar-like structure, and simultaneously forms new NiS and Ni3S4 phases. The sulfided NiFe coating electrode shows relatively low overpotentials of 220 mV and 253 mV at the current density of 10 mA cm−2 and 100 mA cm−2, respectively, and the Tafel slope is as low as 28.6 mV dec−1. The excellent electrocatalytic activity is mainly attributed to the synergistic effect of sulfides, the adsorption of OH− by the Ni3+ in alkaline electrolyte, and the acceleration of O2 separation by the S2− through promoting the cleavage of O–O bonds. In addition, the sulfided NiFe coating electrode also has a small charge transfer resistance, and the potential stability is as high as 98.1% in the 70 h stability test. Therefore, the development of sulfided transition metal coating electrodes can provide a new idea for the large-scale industrialization of water splitting.

Identification of tagged glycans with a protein nanopore

Structural complexity of glycans derived from the diversities in composition, linage, configuration, and branching considerably complicates structural analysis. Nanopore-based single-molecule sensing offers the potential to elucidate glycan structure and even sequence glycan. However, the small molecular size and low charge density of glycans have restricted direct nanopore detection of glycan. Here we show that glycan sensing can be achieved using a wild-type aerolysin nanopore by introducing a facile glycan derivatization strategy. The glycan molecule can induce impressive current blockages when moving through the nanopore after being connected with an aromatic group-containing tag (plus a carrier group for the neutral glycan). The obtained nanopore data permit the identification of glycan regio- and stereoisomers, glycans with variable monosaccharide numbers, and distinct branched glycans, either independently or with the use of machine learning methods. The presented nanopore sensing strategy for glycans paves the way towards nanopore glycan profiling and potentially sequencing.

MOF-derived crystalline carbon with graphite-like crystal: A high initial coulombic efficiency, low potential and large capacity anode for Na-ion batteries

Carbonaceous materials, such as hard carbon and porous carbon, have gained great attentions as the anode materials for Na-ion batteries (NIBs). However, their defects and disordered structure cause the low initial coulombic efficiency (ICE), high-potential slope region and small charge capacity below 0.5 V. Herein, a structurally stable MOF contained 1,3,5-triazine-2,4,6-triamine moieties, belonging to the tetragonal space group I 4/m, is synthesized. On this basis, MOF-derived crystalline carbon with graphite-like crystal, instead of amorphous porous carbon, can be obtained due to slow pyrolysis of MOF framework along with timely and sufficient reassembly of the pyrolyzed carbon atoms into graphite-like crystal under graphite-induced condition. The graphite-like crystal has a geometrically similar unit cell to graphite crystal but with a magnification ratio of 1.25, yielding proportionally expanded d-spacing of (002) plane (4.2 Å), which enables the reversible Na+ intercalation/de-intercalation. When applied in NIBs, it exhibits a very high ICE of 96.0% and reversible charge capacity of 356.2 mAh g−1, reaching the advanced level of graphite applied in LIBs. More importantly, its charge capacity below 0.5 V can account for 90% of the total charge capacity, which is also the key parameter to effectively increase the energy density of full batteries.

Polyimide and polystyrene‐based activated carbon nanofibers with tubular structure for supercapacitor

AbstractPolyimide (PI) and polystyrene (PS) blend electrospun fibers are prepared by electrospinning method. PI and PS are not completely compatible due to the difference of solubility and surface energy in electrospinning precursor, so PI/PS electrospun fibers have some phase separations along the electric field direction under the high‐voltage electrostatic force. PI with high carbon conversion served as carbon nanofibers, PS with low carbon conversion served as porogenic sacrificial agent, so PI/PS‐based activated carbon nanofibers derived from PI/PS electrospun fibers with well‐controlled opening tubular structure are obtained via thermally induced phase separation process. The morphology and electrochemical performance of activated carbon nanofibers are investigated by structural analysis and electrochemical measurements. The relationships among pores structure, electrolyte character and electrochemical performance of activated carbon fibers are extensively evaluated. Activated carbon nanofibers derived from PI/PS (mass ratio = 1:2) electrospun fibers with nano scale opening tube wall structure show a small charge transfer resistance and the short electric double layers forming time, but also suitable average pore diameter (3.74 nm), high BET specific surface area (952.5 m2 g−1) and average pore volume (0.532 cm3 g−1). Then, a comprehensive electrochemical performance can also be achieved in organic electrolyte: high energy density (31.80 Wh kg−1), good power density (3094.05 W kg−1) and low internal resistance (1.24 Ω). The findings reveal a guideline for the preparation of polymer‐based hierachical porous and opening tubular structure activated carbon nanofibers for electrochemical energy conversion and storage devices.

基于6,13-双氰基并五苯一维滑移堆积微米带状晶体 的双极性电荷传输

Featuring small charge transport scattering, mesoscale size, and easy fabrication, one-dimensional self-assembled micro/nanomaterials (1D-MNMs) based on organic π-conjugated systems can be facilely incorporated into integrated microcircuits. Although tremendous progress has been made in 1D-MNMs based on p- or n-channel organic semiconductors, examples of lD-MNMs based on ambipolar organic semiconductors are scarce. Herein, we achieved a novel 1D-MNM based on 6,13-dicyanopentacene (DCP) with a 1D slipped stacking motif using the physical vapor transport method. The DCP-based 1D-MNM showed outstanding, well-balanced ambipolar charge transport with electron and hole mobilities of up to 0.34 and 0.38 cm2 V−1 s−1, respectively, which are among the best ambipolar transport characteristics of 1D-MNMs. Furthermore, a complementary inverter based on the ambipolar 1D-MNM of DCP was also constructed with a gain of up to 7, indicating potential application in organic logic circuits.

SBETHE: Stopping powers of materials for swift charged particles from the corrected Bethe formula

The Fortran program sbethe calculates the stopping power of materials for swift charged particles with small charges (electrons, muons, protons, their antiparticles, and alphas). The electronic stopping power is computed from the corrected Bethe formula, with the shell correction derived from numerical calculations with the plane-wave Born approximation (PWBA) for atoms, which were based on an independent-electron model with the Dirac–Hartree–Fock–Slater self-consistent potential for the ground-state configuration of the target atom. The density effect correction is evaluated from an empirical optical oscillator strength (OOS) model based on atomic subshell contributions obtained from PWBA calculations. For projectiles heavier than the electron, the Barkas correction is evaluated from the OOS model, and the Lindhard–Sørensen correction is estimated from an accurate parameterization of its numerical values. The calculated electronic stopping power is completely determined by a single empirical parameter, the mean excitation energy or I value of the material. The radiative stopping power for electrons, and positrons, is evaluated by means of Seltzer and Berger's cross section tables for bremsstrahlung emission. The program yields reliable stopping powers and particle ranges for arbitrary materials and projectiles with kinetic energy larger than a certain cutoff value Ecut, which is specific of each projectile kind. The program is accompanied by an extensive database that contains tables of relevant energy-dependent atomic quantities for all the elements from hydrogen to einsteinium. sbethe may be used to generate basic information for dosimetry calculations and Monte Carlo simulations of radiation transport, and as a pedagogical tool. Program summaryProgram title:sbetheCPC Library link to program files:https://doi.org/10.17632/7zw25f428t.1Licensing provisions: CC by NC 3.0Programming language: Fortran 90/95Nature of problem: The program calculates the stopping power of arbitrary materials for swift charged projectiles with small charges. The material is characterized by its chemical composition, mass density, and the empirical I value. The considered projectiles are electrons, positrons, negative muons, antimuons, protons, antiprotons, and alphas, which are described as point particles characterized by their mass and charge. If the actual I value of the material is known, the results from the program are expected to be reliable for projectiles with kinetic energy higher than a value Ecut, of the order of 1 keV for electrons and positrons, 150 keV for muons and antimuons, 0.75 MeV for protons and antiprotons, and 5 MeV for alpha particles.Solution method: The electronic stopping power is calculated by means of a corrected Bethe formula [1], which combines the conventional Bethe logarithm with the following corrections,1) the shell correction obtained from calculations based on the plane-wave Born approximation with the self-consistent Dirac–Hartree–Fock–Slater (DHFS) potential of neutral atoms in their ground-state configuration [2],2) the density effect correction, which accounts for the reduction of the stopping power caused by the dielectric polarization of the medium,3) a parameterization of the Lindhard–Sørensen correction, which generalizes the Bloch correction for relativistic projectiles, and4) the Barkas correction, which accounts for differences between the stopping powers of particles and their antiparticles.The density-effect and the Barkas corrections are calculated from a model of the optical oscillator strength (OOS) of the material, which combines the contributions of inner atomic subshells calculated with the DHFS potential, with a classical oscillator model for the contribution of valence electrons,A simple extrapolation formula is used to extend the calculated electronic stopping power to energies less than Ecut to allow the calculation of particle ranges.For electrons and positrons, the radiative stopping power is calculated from numerical tables prepared by Seltzer and Berger [3].Additional comments including restrictions and unusual features: The calculated stopping power is determined by a single parameter, the mean excitation energy or I value. The program assigns to each material a default I value, derived from the recommendations in the ICRU Report 37, which can be changed by the user. The distribution package includes text files with tables of atomic energy-dependent quantities (subshell optical oscillator strengths, shell corrections, scaled cross sections for bremsstrahlung emission) that are used in the calculations.

Signatures of regular black holes from the quasar continuum spectrum

Regular black holes arising in Einstein gravity coupled to non-linear electrodynamics are worth studying as they can circumvent the r=0 curvature singularity arising in general relativity. In this work we explore the signatures of regular black holes with a Minkowski core from the quasar continuum spectrum. We use thin-disk approximation to derive the theoretical luminosity from the accretion disk and compare it with the optical data of eighty Palomar Green quasars. Our analysis based on error estimators like the chi ^2, the Nash–Sutcliffe efficiency, the index of agreement etc. reveal that optical observations of quasars favor black holes with a small non-linear electrodynamics charge parameter ksimeq 0.15 although the Kerr scenario is allowed within 2-sigma interval. The implications are discussed.

Benzotriazole-based structure in porous organic polymer enhancing O2 activation for high-efficient degradation of tetracycline under visible light

Porous organic polymers (POPs) have emerged as functional materials in photocatalytic degradation of tetracycline (TC) antibiotics but still did not get enough attention on the degradation mechanism and “structure-performance” relationship. It is of great scientific concern to explore the photo-degradation capability of POPs for TC antibiotics under visible light and to reveal their “structure-performance” relationship at the molecular level. Herein, we have constructed a novel benzotriazole-based POP by polymerizing benzotriazole-based structure with melamine. The photo-degradation test results indicate that the POP with benzotriazole-based structure presents an excellent photocatalytic performance with a high TC removal efficiency of 92.12 % and good recyclability. The corresponding pseudo-first-order reaction kinetic constant of benzotriazole-based POP is 6.8 times that of benzene-based one. Such excellent performance of benzotriazole-based POP can be attributed to the physical/chemical property contributions of benzotriazole-based structure to POP, e.g., the narrow energy bandwidth (2.48 eV) for producing more photo-generated electrons/holes, the small charge transfer resistance for circumventing recombination of photo-generated electrons/holes, and the large number of O2− radicals converted from high-activated O2 that produced by the interactions between photocatalyst and O2 under visible light irradiation. This strategy of introducing the benzotriazole-based structure into POP opens new avenues to develop next-generation advanced photocatalysts for removing TC antibiotics from wastewater.

Mechanism of Calcium Permeation in a Glutamate Receptor Ion Channel.

The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are neurotransmitter-activated cation channels ubiquitously expressed in vertebrate brains. The regulation of calcium flux through the channel pore by RNA-editing is linked to synaptic plasticity while excessive calcium influx poses a risk for neurodegeneration. Unfortunately, the molecular mechanisms underlying this key process are mostly unknown. Here, we investigated calcium conduction in calcium-permeable AMPAR using Molecular Dynamics (MD) simulations with recently introduced multisite force-field parameters for Ca2+. Our calculations are consistent with experiment and explain the distinct calcium permeability in different RNA-edited forms of GluA2. For one of the identified metal binding sites, multiscale Quantum Mechanics/Molecular Mechanics (QM/MM) simulations further validated the results from MD and revealed small but reproducible charge transfer between the metal ion and its first solvation shell. In addition, the ion occupancy derived from MD simulations independently reproduced the Ca2+ binding profile in an X-ray structure of an NaK channel mimicking the AMPAR selectivity filter. This integrated study comprising X-ray crystallography, multisite MD, and multiscale QM/MM simulations provides unprecedented insights into Ca2+ permeation mechanisms in AMPARs, and paves the way for studying other biological processes in which Ca2+ plays a pivotal role.

Efficiently predicting directional carrier mobilities in organic materials with the Boltzmann transport equation.

Describing charge carrier anisotropy in crystalline organic semiconductors with ab initio methods is challenging because of the weak intermolecular interactions that lead to both localized and delocalized charge transport mechanisms. Small polaron hopping models (localized) are generally used to describe materials with small charge carrier mobilities, while periodic band models (delocalized) are used to describe materials with high charge carrier mobilities. Here, we prove the advantage of applying the constant relaxation time approximation of the Boltzmann transport equation (BTE) to efficiently predict the anisotropic hole mobilities of several unsubstituted (anthracene, tetracene, pentacene, and hexacene) and substituted (2,6-diphenylanthracene, rubrene, and TIPS-pentacene) high-mobility n-acene single crystals. Several density functionals are used to optimize the crystals, and the composite density functional PBEsol0-3c/sol-def2-mSVP predicts the most experimentally similar geometries, adequate indirect bandgaps, and the theoretically consistent n-acene charge transport mobility trend. Similarities between BTE and Marcus mobilities are presented for each crystal. BTE and Marcus charge carrier mobilities computed at the same geometry result in similar mobility trends, differing mostly in materials with more substitutions or structurally complex substituents. By using a reduced number of calculations, BTE is able to predict anisotropic carrier mobilities efficiently and effectively for a range of high-mobility organic semiconductors.

Coordination Tailoring of Epitaxial Perovskite-Derived Iron Oxide Films for Efficient Water Oxidation Electrocatalysis

Cost-effective perovskite oxides have recently offered intriguing promise for electrochemical energy storage and conversion systems. Despite the breadth of previously studied electronic structures and properties, the sluggish kinetics of the oxygen evolution reaction (OER) of perovskite oxides basically restrict their applications in metal–air batteries and electrolytic cells. In this work, we report on a highly efficient OER activity of perovskite-derived SrFeO3−δ (0.0 ≤ δ ≤ 1.0) single-crystal films by selectively tuning the Fe–O coordination structure and film orientation. Our findings show that the facile anionic oxygen-induced topotactic brownmillerite phase of the SrFeO2.5 film possesses superior electrocatalytic performance with a small overpotential and Tafel slope, which is mainly attributed to the peculiar Fe–O coordination framework along with ordered oxygen vacancy channels. Moreover, the low adsorption free energy and small charge transfer resistance could further boost the electrocatalytic OER performance of the (111)-oriented BM-SrFeO2.5 films. This delicate tailoring of the epitaxial SrFeO3−δ films enables the tunable catalytic reaction pathways and concomitantly efficient OER kinetics, which has significant implications for the rational design of cost-effective and high-performance perovskite-based electrocatalysts.

Adduct Ions as Diagnostic Probes of Metallosupramolecular Complexes Using Ion Mobility Mass Spectrometry

Following electrospray ionization, it is common for analytes to enter the gas phase accompanied by a charge-carrying ion, and in most cases, this addition is required to enable detection in the mass spectrometer. These small charge carriers may not be influential in solution but can markedly tune the analyte properties in the gas phase. Therefore, measuring their relative influence on the target molecule can assist our understanding of the structure and stability of the analyte. As the formed adducts are usually distinguishable by their mass, differences in the behavior of the analyte resulting from these added species (e.g., structure, stability, and conformational dynamics) can be easily extracted. Here, we use ion mobility mass spectrometry, supported by density functional theory, to investigate how charge carriers (H+, Na+, K+, and Cs+) as well as water influence the disassembly, stability, and conformational landscape of the homometallic ring [Cr8F8(O2CtBu)16] and the heterometallic rotaxanes [NH2RR'][Cr7MF8(O2CtBu)16], where M = MnII, FeII, CoII, NiII, CuII, ZnII, and CdII. The results yield new insights on their disassembly mechanisms and support previously reported trends in cavity size and transition metal properties, demonstrating the potential of adduct ion studies for characterizing metallosupramolecular complexes in general.