Ternary Rotational Polyanion Coupling Enables Fast Li Ion Dynamics in Tetrafluoroborate Ion Doped Antiperovskite Li2OHCl Solid Electrolyte.

Li-rich antiperovskite (LiRAP) hydroxyhalides are emerging as attractive solid electrolyte (SEs) for all-solid-state Li metal batteries (ASSLMBs) due to their low melting point, low cost, and ease of scaling-up. The incorporation of rotational polyanions can reduce the activation energy and thus improve the Li ion conductivity of SEs. Herein, we propose a ternary rotational polyanion coupling strategy to fasten the Li ion conduction in tetrafluoroborate (BF4 -) ion doped LiRAP Li2OHCl. Assisted by first-principles calculation, powder X-ray diffraction, solid-state magnetic resonance and electrochemical impedance spectra, it is confirmed that Li ion transport in BF4 - ion doped Li2OHCl is strongly associated with the rotational coupling among OH-, BF4 - and Li2-O-H octahedrons, which enhances the Li ion conductivity for more than 1.8 times with the activation energy lowering 0.03 eV. This work provides a new perspective to design high-performance superionic conductors with multi-polyanions.

Self-isomerization of nearly planar superatoms formed by actinide embedded gold clusters.

First-principles calculations show a self-isomerization process of the nearly planar superatom, in which the maximum energy difference between different extreme points is below 0.1 eV and a crossing between singlet and triplet states is also involved. Further UV-Vis spectra reveal a correlation between the spectra and structures caused by self-isomerization.

Higher-order Rayleigh-quotient gradient effect on electron correlations.

The incomplete understanding of electron correlation is still profound due to the lack of exact solutions of the Schrödinger equation of many electron systems. In this work, we present the correlation-induced changes in the calculated many-electron systems beyond the standard residual. To locate the minimum of the Rayleigh quotient, each iteration is to seek the lowest eigenpairs in a subspace spanned by the current wave function and its gradient of the Rayleigh-quotient as well as the upcoming higher-order residual. Consequently, as the upcoming errors can be introduced and circumvented with the search in the higher-order residual, a concomitant improved performance in terms of number of iterations, convergence rate, and total elapsed time is very significant. The correlation energy components obtained with the original residual are corrected with the higher-order residual application, satisfying the correlation virial theorem with much improved accuracy. The comparison with the original residual, the higher-order residual significantly improves the electron binding, favoring the localization of electrons' distribution, revealed with the increasing peak of the distribution and correlation function and the reduced interelectron distance and its angle.

Charge Transfer Doping of Carbon Nitride Films through Noncovalent Iodination for Enhanced Photoelectrochemical Performance: Combined Experimental and Computational Insights.

To improve the photoelectrochemical (PEC) performance of photocatalysts, the doping strategy through covalent functionalization is often adopted to adjust material electronic structures. By contrast, this work demonstrates that the noncovalent interaction in the case of iodinated graphitic carbon nitride (g-CN) film can also enhance the PEC performance. Through a facile synthesis method of rapid thermal vapor condensation (RTVC), the prepared iodinated g-CN film shows a significantly improved photocurrent density (38.9 µA cm-2 ), three times that of pure g-CN film (13.0 µA cm-2 ) at 1.23 V versus reversible hydrogen electrode. Computations reveal that the noncovalent attachment of iodine anion (I- ) on g-CN plays a crucial role in modulating the bandgap states and broadening of the visible-light absorption range as well as the charge carrier separation with the photo-induced hole confined to I- and electron to g-CN film. The fully filled valence orbitals (4d10 5s2 5p6 ) of I- determine its noncovalent attachment on the g-CN film and so do the iodine species of I3 - , I5 - , etc. This work offers a favorable synthesis method to achieve efficient doping through noncovalent charge transfer between thin film and certain dopants and provides a useful modification strategy for the establishment of multi-channel transportation of charge carriers in general photocatalysts.

Role of the A-Element in the Structural, Mechanical, and Electronic Properties of Ti3AC2 MAX Phases.

Combining metallic and ceramic properties, and as precursors for MXenes, MAX phases have attracted extensive attention. In recent years, A-element substitution has been demonstrated as an effective scheme to enrich the MAX family. To explore more possible MAX members, the structural, mechanical, and electronic properties and stabilities of 31 Ti3AC2 (A = Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Os, Ir, Pt, Au, Hg, TI, Pb, Bi, and Po) configurations are investigated in this work. Moreover, the interfacial strength implicating the possibility of exfoliating MAX into MXenes is examined. The A-element plays a crucial role in the lattice parameters and mechanical strength of Ti3AC2, and their variations are well explained by the synergistic effects of d-d and p-d hybridizations between the valence orbitals of Ti and A. Ti3SC2 presents the largest Young's modulus of 360 GPa, which is 6.82% higher than that in the well-studied Ti3SiC2. Ti3SbC2 is a mechanical quasi-isotropic configuration. After checking the mechanical, dynamical, and thermodynamic stability, Ti3AC2 (A = Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Sb, Au, Hg, Pb, TI, and Po) are stable, while Ti3AC2 (A = Fe, Co, Zn, Se, Ru, Rh, Pd, Ag, Te, Ir, Pt, and Bi) are metastable. Compared to Ti3AlC2, Ti3AC2 (A = Ag, Sb, Te, Bi, and Po) exhibit much lower interfacial strength in Ti-A interfaces and larger ratios between the interfacial strengths of neighboring Ti-C and Ti-A interfaces. This implies that these configurations are promising precursors for the synthesis of Ti3C2Tx (Tx denotes surface groups) with a large flake size. All of the configurations are metallic, and Ti3AC2 (A = Fe and Co) are magnetic. Based on the phonon dispersion and electronic structure, these Ti3AC2 configurations might have potential applications in phononic crystals and topological materials.

Spent LiFePO4: An old but vigorous peroxymonosulfate activator for degradation of organic pollutants in water.

Iron-based catalysts have been demonstrated to activate peroxymonosulfate (PMS) to generate reactive radicals, which is however limited by their complex preparation process, high costs and inefficiency for practical applications. Herein we obtain spent LiFePO4 (SLFP), with powerful catalytic capacity by a simple one-step treatment of the retired LiFePO4 cathode material, for PMS activation to decontaminate organic pollutants. Lithium defects and oxygen vacancies in SLFP play critical roles for PMS utilization, further confirmed by density functional theory (DFT) calculations. SLFP materials rapidly adsorb PMS, and the surface PMS is activated by Fe(II) to generate radicals, with •OH playing a major role for the degradation of organics after multi-step reactions. The SLFP/PMS process is finally validated for ability to remove organic contaminants and potential environmental application.

An ultra-sensitive gas sensor based on a two-dimensional manganese porphyrin monolayer.

The development of highly sensitive, low-power consuming, stable and recyclable gas sensing devices at room temperature has become an important solution for environmental safety detection. Utilizing a two-dimensional metalloporphyrin monolayer for gas sensing is appealing due to its large specific surface area and high surface activity. A two-dimensional manganese porphyrin monolayer (2DMnPr) is selected from 2D metalloporphyrins with 3d metal centers due to its semi-metallicity to explore its gas sensing properties. Using first-principles calculations, we systematically investigate the electronic structures and adsorption characteristics of gas molecules with toxicity and greenhouse effect on the surface of 2DMnPr, including H2S, CO, CO2, SO2, NO and NO2. The strength of the interaction and charge transfer between the 2DMnPr surface and the adsorbed molecules have a direct effect on the electronic properties and the sensing properties of the adsorbent surface. The sensing performance of the 2DMnPr adsorbent is evaluated via two observable parameters: work function and electrical conductivity. The work functions of 2DMnPr after the adsorption of CO, SO2, NO and NO2 gas molecules increase by different degrees depending on the charge transfer, and those of the H2S and CO2 cases decrease. In our simulation, adsorption of CO, SO2, NO and NO2 gas molecules affects the electronic properties of 2DMnPr markedly, and current-voltage characteristics within a low bias range uncover the superior sensitivity of the conductivity of the 2DMnPr monolayer to these molecules. Besides, the sensing performance is demonstrated to be stable under strain and at room temperature. The desorption time of a gas is positively related to its adsorption energy. The recovery time of CO is predicted to be short enough to realize sustainable detection at room temperature, and the SO2, NO and NO2 gases can also be desorbed at higher temperatures. These results demonstrate that 2DMnPr enables the sensitive detection of these gases and predict the potential application of 2DMnPr as an ultra-sensitive, low-power, stable and recyclable gas sensor at room temperature.

Epidemiological survey of adult female stress urinary incontinence.

BACKGROUND: The prevalence of stress urinary incontinence (SUI) in adult female in Taiyuan and what are the related risk factors are not clear. The aim of this study was to provide a basis for exploring the prevention and treatment of SUI in adult female in Taiyuan. METHODS: A voluntary online questionnaire was used to investigate adult female in the community and surrounding townships of Taiyuan. Most of the questionnaires refer to the International Consultation on Incontinence Questionnaire-Female Lower Urinary Tract Symptoms, and adapt to the specific circumstances of the region. Data were analyzed using SPSS software (version 22.0). RESULTS: A total of 4004 eligible questionnaires were obtained. The prevalence of SUI in adult female in Taiyuan was 33.5%. Univariate analysis and multivariate logistic regression analysis showed that place of residence, smoking, body mass index, diet, number of deliveries, mode of delivery, dystocia, menopause, oral contraceptives, urinary tract infection, making the bladder empty faster by pushing down and holding urine were risk factors for adult female stress urinary incontinence in Taiyuan. CONCLUSION: The prevalence of SUI in adult female in Taiyuan was high, and based on risk factors identified in this survey, population-level intervention strategies should be developed for the prevention and treatment of adult female SUI in Taiyuan.

Fragment motion in motor molecules: basic concepts and application to intra-molecular rotations.

The complex motion of atoms inside large molecules can be analyzed by considering translation, rotation, and flexibility of corresponding molecular fragments and by applying classical mechanics based on Pulay forces on the atoms, as in molecular dynamics. We propose a fragment motion analysis that provides a basic qualitative understanding of the motion of the different molecular components. Further, it can help to describe or design simplified fragment motions, e.g. the rotation of a rotator with respect to its stator counterpart in a rotor molecule, despite the higher actual complexity due to flexibility of rotator and stator or due to a variable rotation axis. The formal aspects of the fragment motion analysis are discussed in detail. Its application is illustrated by the rotational motion inside the BTP-BCO molecule and by rotational transitions between cis- and trans-stilbene isomers.

Actinide embedded nearly planar gold superatoms: structural properties and applications in surface-enhanced Raman scattering (SERS).

Planarity is a special property of superatoms, different from atoms. In this work, we predicted a series of nearly planar structures, An@Au6 (An = Ac-1, Th, Pa+1) clusters, using density functional theory (DFT). Calculations of these actinide embedded clusters reveal a 10-electron (1s21p41d4) closed-shell singlet configuration. It is found that all An@Au6 clusters are nearly or purely planar structures with only in-plane two-dimensional occupied superatomic molecular orbitals (SAMOs). In addition, applying them as surface-enhanced Raman scattering (SERS) substrates, the charge-transfer (CT) states at 677 nm (1dmetal-π1*pyridine) can lead to a SERS signal enhancement of 104 for a pyridine-Th@Au6 complex. Our research indicates that actinide embedded nearly planar superatomic clusters have unique optical properties and potential application value.

Repression of miR-217 protects against high glucose-induced podocyte injury and insulin resistance by restoring PTEN-mediated autophagy pathway.

Podocyte damage is the initial hallmark of diabetic nephropathy (DN), leading to the increasing morbidity and mortality in diabetic patients. Recent researches have corroborated the critical roles of miRNAs in the pathological progression of DN. Here, elevation of miR-217 was verified in high glucose (HG)-stimulated podocytes. Moreover, blocking miR-217 expression antagonized HG-induced cell injury by attenuating the adverse role of HG on cell viability and inhibiting ROS levels and cell apoptosis. Simultaneously, miR-217 repression restored HG-disrupted insulin resistance by elevating glucose uptake and nephrin expression, an essential component for insulin-induced glucose uptake. Mechanism assay substantiated the defective autophagy in HG-treated podocytes, which was resumed by miR-217 cessation. Importantly, suppressing autophagy pathway with 3-MA alleviated the protective roles of miR-217 down-regulation in podocyte injury and insulin resistance. Luciferase reporter analysis confirmed that PTEN was a target of miR-217 in podocytes. Additionally, blocking PTEN expression restrained autophagy restoration in miR-217-decreased cells. Furthermore, PTEN down-regulation attenuated the beneficial role of miR-217 suppression in HG-induced injury and insulin resistance. Together, this study manifests that miR-217inhibition can protectively antagonize HG-induced podocyte damage and insulin resistance by restoring the defective autophagy pathway via targeting PTEN, representing a novel and promising therapeutic target against diabetic nephropathy.

Donor/Acceptor Properties of Aromatic Molecules in Complex Metal-Molecule Interfaces.

We present a comparative study, combining density functional theory with scanning tunneling microscopy/spectroscopy, of two aromatic molecules bonded with a variable number of Cu adatom(s) on a Cu(111) surface. The two molecules, 1,3,5-tris(pyridyl)benzene (TPyB) and 1,3,5-tris(4-radical-phenyl)benzene (TPB), possess the same aromatic backbone but bond weakly versus strongly to Cu with different terminal groups, respectively. We find that TPyB and TPB exhibit, respectively, small versus large charge transfers between the surface and the molecule; this contrast results in opposite shifts in the calculated density of states distributions and thus explains the opposite STS peak shifts observed in our experiments. The two molecules exhibit weak donor versus strong acceptor characters. This work provides a fundamental understanding, on a single-molecule level, of the principle that selecting specific functional groups can effectively and intentionally modify the molecular electronic properties in a wider class of molecule-metal interfaces.

Beyond the electrostatic model: the significant roles of orbital interaction and the dispersion effect in aqueous-π systems.

The electrostatic model, which is widely used to explain π-involved interactions, gives an intuitive picture of these intermolecular interactions and has successfully predicted many phenomena in recent decades. Still, this simple model faces problems in certain cases and it has come under fire in previous studies on π-π stacking interactions. Here, employing ab initio calculations, we have identified several counter examples in aqueous-π systems which cannot be explained adequately using the classical electrostatic model, and revealed the underlying reason. We find strong intermolecular orbital interactions in both aqueous-π hydrogen bond and lone-pair-π interactions, and thus extend the previously proposed new model for π-π stacking to aqueous-π systems: while the electrostatic attraction and dispersion effects are the main driving forces pulling the monomers together, Pauli repulsion plays a role in keeping them apart. Interestingly, the molecular orbitals on the concerned monomers exhibit a weak bonding nature at the equilibrium distance.

Tunneling lifetimes of electrons escaping from atoms under a static electric field.

The tunneling lifetime of an electron escaping from an atom is calculated using a projected Green's function method, combining with the radial potential of the atom which is obtained from density functional theory. Results of the calculated electron tunneling lifetimes in model systems such as a quantum dot are shown to be comparable with other theoretical studies. For the first time, we have obtained the tunneling lifetimes of electrons escaping from a series of atoms (He, Ne, Ar, Kr, H, Li, Na, K) under a static electric field. Dependent on both the barrier width/height and the bound strength of the ground state electron, the calculated tunneling lifetime under a static electric field spans from femtosecond level to picosecond level, consistent with the attosecond-level results in experiments using a time-dependent external field.

Bonding reactivity descriptor from conceptual density functional theory and its applications to elucidate bonding formation.

Condensed-to-atom Fukui functions which reflect the atomic reactivity like the tendency susceptible to either nucleophilic or electrophilic attack demonstrate the bonding trend of an atom in a molecule. Accordingly, Fukui functions based concepts, that is, bonding reactivity descriptors which reveal the bonding properties of molecules in the reaction were put forward and then applied to pericyclic and cluster reactions to confirm their effectiveness and reliability. In terms of the results from the bonding descriptors, a covalent bond can readily be predicted between two atoms with large Fukui functions (i.e., one governs nucleophilic attack while the other one governs electrophilic attack, or both of them govern radical attacks) for pericyclic reactions. For SinOm clusters' reactions, the clusters with a low O atom ratio readily form a bond between two Si atoms with big values of their Fukui functions in which they respectively govern nucleophilic and electrophilic attacks or both govern radical attacks. Also, our results from bonding descriptors show that Si-Si bonds can be formed via the radical mechanism between two Si atoms, and formations of Si-O and O-O bonds are possible when the O content is high. These results conform with experimental findings and can help experimentalists design appropriate clusters to synthesize Si nanowires with high yields. The approach established in this work could be generalized and applied to study reactivity properties for other systems.

A new insight into π-π stacking involving remarkable orbital interactions.

For more than half a century, the phenomenon of π-π stacking has attracted much attention in several research fronts including materials science, chemical synthesis, and even drug design. Despite intense theoretical and experimental exploration, no unified description of the factors contributing to π-π stacking interactions and their weak bonding process has been proposed. In this work, based on calculations of the simplest prototype of π-π stacking, namely the benzene sandwich dimer (together with benzene-phenol, toluene and benzonitrile) using the density functional theory with dispersion correction, previously rarely studied intermolecular orbital interaction is discussed in detail and shown to involve considerable hybridizations of some of the orbitals which make a large contribution to the total interaction energy. We now propose a unified model for the often nebulous π-π stacking process and its analogs: firstly when the two monomers are too far apart, the dispersion effect will play a dominant role in bringing them together, but when they are too close, Pauli repulsion will force them apart. Secondly, at the equilibrium distance, electrostatic interaction, Pauli repulsion, dispersion and intermolecular orbital interaction are all pronounced, with part of the molecular orbitals of the two monomers interacting with each other to form a weak intermolecular bond.

Composition dependent reactivity of titanium oxide clusters.

Based on first-principles calculations of titanium oxide clusters, TinOm (n = 1-4), we reveal the composition dependent reactivity of titanium oxide clusters. Our interesting results include: (1) the reactivity depends on the ratio of O atoms in the clusters, with smaller O ratios associated with higher reactivity; (2) among the different titanium oxide species investigated, the most stable structures are TinO2n, but their reactivities are relatively lower than the clusters with a smaller O atom ratio; moreover, (3) when the O atom ratio is small, the reactivity required to form the Ti-Ti bond is larger than either the Ti-O or O-O bond between two interacting titanium oxide clusters. These results will be useful for designing efficient titanium oxide catalysts, or photocatalysts, in particular, for energy and environmental applications.

Computational prediction of optimal metal ions to induce coordinated polymerization of muscle-like [c2]daisy chains.

Recently, a muscle-like organometallic polymer has been successfully synthesized using Fe(2+) as a linker atom. The polymer exhibits acid-base controllable muscle-like expansion and contraction on the micrometer scale. Further development could be facilitated by revealing the polymerization mechanism and by searching for optimal linker atoms. In this work, we have examined possible equilibrium and intermediate polymer structures, which consist of [c2]daisy chains linked by divalent transition metal ions (Sc(2+), Ti(2+), Fe(2+), Co(2+), Ni(2+) or Zn(2+)) with various hexa-coordination arrangements, based on calculations using density functional theory. We find that the metal linkers in polymers are weaker in acid than in base due to excess positive charges on the polymer, leading to their thermodynamical instability or even decomposition. This can explain the experimental difficulty in improving the degree of polymerization for metal-linked polymers. We also find that the polymers with either Fe(2+) or Co(2+) are the most favorable, with the latter extending 1.4% longer than with the former. Since Fe(2+) has been confirmed experimentally to be a successful linker, Co(2+) would function equally well and thus could be used as an alternative choice for polymerization.

Intramolecular torque, an indicator of the internal rotation direction of rotor molecules and similar systems.

Rotation-inducing torque is ubiquitous in many molecular systems. We present a straightforward theoretical method based on forces acting on atoms and obtained from atomistic quantum mechanics calculations to quickly and qualitatively determine whether a molecule or sub-unit thereof has a tendency to rotate and, if so, around which axis and in which sense: clockwise or counterclockwise. The method also indicates which atoms, if any, are predominant in causing the rotation. Our computational approach can in general efficiently provide insights into the internal rotational degrees of freedom of all molecules and help to theoretically screen or modify them in advance of experiments or to efficiently guide a detailed analysis of their rotational behavior with more extensive computations. As an example, we demonstrate the effectiveness of the approach using a specific light-driven molecular rotary motor which was successfully synthesized and analyzed in prior experiments and simulations.

Efficient emission facilitated by multiple energy level transitions in uniform graphitic carbon nitride films deposited by thermal vapor condensation.

Graphitic carbon nitride (g-CN) films are important components of optoelectronic devices, but current techniques for their production, such as drop casting and spin coating, fail to deliver uniform and pinhole-free g-CN films on solid substrates. Here, versatile, cost-effective, and large-area growth of uniform and pinhole-free g-CN films is achieved by using a thermal vapor condensation method under atmospheric pressure. A comparison of the X-ray diffraction and Fourier transform infrared data with the calculated infrared spectrum confirmed the graphitic build-up of films composed of tri-s-triazine units. These g-CN films possess multiple active energy states including π*, π, and lone-pair states, which facilitate their efficient (6% quantum yield in the solid state) photoluminescence, as confirmed by both experimental measurements and theoretical calculations.