2D-Mn2C12: An Optimal Electrocatalyst with Nonbonding Multiple Single Centers for CO2-to-CH4 Conversion.

The CO2 reduction reaction (CO2RR) is a promising method that can both mitigate the greenhouse effect and generate valuable chemicals. The 2D-M2C12 with high-density transition metal single atoms is a potential catalyst for various catalytic reactions. Using an effective strategy, we screened 1s-Mn2C12 as the most promising electrocatalyst for the CO2RR in the newly reported 2D-M2C12 family. A low applied potential of -0.17 V was reported for the CO2-to-CH4 conversion. The relative weak adsorption of H atom and H2O in the potential range of -0.2 to -0.8 V, ensures the preferential adsorption of CO2 and the following production of CH4. The different loading amounts of Mn atoms on γ-graphyne (GY) were also investigated. The Mn atoms prefer doping in the nonadjacent triangular pores instead of the adjacent ones due to the repulsive forces between d-orbitals when the Mn loading is less than 32.3 wt % (5Mn). As the Mn concentration further increases, adjacent Mn atoms begin to appear, and the Mn@GY becomes metallic or half-metallic. The presence of four adjacent Mn atoms increases the d-band center of Mn@GY, particularly the dz2 center involved in CO2 adsorption, thereby enhancing the adsorption capacity for CO2. These findings indicate that 1s-Mn2C12 with high Mn atomic loadings is an excellent CO2RR electrocatalyst, and it provides new insights for designing efficient CO2RR electrocatalyst.

Influence of Zr aggregation on Li-ion conductivity of amorphous solid-state electrolyte Li-La-Zr-O.

In our study, we investigated the influence of the local structure of amorphous Li-La-Zr-O (a-LLZO) on Li-ion conductivity using ab initio molecular dynamics (AIMD). A-LLZO has shown promising properties in inhibiting the growth of lithium dendrites, making it a potential candidate for solid electrolytes in all-solid-state lithium batteries. The low Li-ion conductivity of a-LLZO is currently limiting its practical applications. Our findings revealed that the homogeneous distribution of Zr-O polyhedra within the pristine structure of a-LLZO contributes to enhanced Li-ion conductivity. By reducing the interconnections among Zr-O polyhedra, the AIMD-simulated a-LLZO sample achieved a Li-ion conductivity of 5.78 × 10-4 S/cm at room temperature, which is slightly lower than that of cubic LLZO (c-LLZO) with a Li-ion conductivity of 1.63 × 10-3 S/cm. Furthermore, we discovered that Li-ion conductivity can be influenced by adjusting the elemental ratios within a-LLZO. This suggests that fine-tuning the composition of a-LLZO can potentially further enhance its Li-ion conductivity and optimize its performance as a solid electrolyte in lithium batteries.

Chemical Bonding and Activity of Atomically Dispersed Silicon in Two- and Three-Dimensional Materials.

On the basis of the especially tunable electronic property of Si, several kinds of nanomaterials with atomically dispersed Si were constructed and characterized by extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations. The new-type Si(X≡Y)n wide-bandgap semiconductors featuring through-space d-π* hyperconjugation exhibit unique properties in photoelectric conversion, photoconductivity, structural mechanics, etc. The SiC8 siligraphene with the planar tetracoordinate Si (ptSi) has a high lithium-storage capacity and comparably facile surface migration behaviors of both Li and Li+, making it a promising anode material for high-performance Li-ion batteries. The atomically dispersed Si sites of 2D monolayer materials, such as ptSi and three- and four-coordinated Si atoms, generally exhibit remarkable catalytic activity toward CO2 activation with different electron mechanisms, resulting in different scaling relations between the activity and the p-band center. The computational findings enrich the understanding of structural and chemical properties of silicon and open up avenues for developing Si-based functional materials.

[The application of PCR-SSP with the serology in identification and genotyping of ABO ambiguous blood group].

Objective To investigate the effect of blood group serology and polymerase chain reaction with sequence-specific primers (PCR-SSP) on identification and genotyping of ambiguous ABO blood group. Methods Eighty suspicious ABO blood group samples were identified by serology and polymerase chain reaction with sequence-specific primers (PCR-SSP). The final blood group type and the strategy of the transfusion of each case were determined according to the results of serology and PCR-SSP. Results 40 cases were confirmed to be subtypes, and the remaining 40 cases were normal types with weakened antigens or missing antibodies due to other reasons. The results of molecular genetic blood group typing based on PCR-SSP were 41 cases of subtypes (There were 3 discrepancies between two methods: one was Ael identified by serological methods, while its gene type was O2O2; one was common type O, while its gene type was BO1; one was type A, while its gene type was AB.) and 39 cases of normal ones. Conclusion Genotyping technology combined with serological typing has an important significance in identification of ABO blood groups.

Impact of Prenatal Acetaminophen Exposure for Hippocampal Development Disorder on Mice.

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used as analgesic agents. They have been detected in various environmental matrices. The degradation of environmental contaminants and the long-term adverse effects have become a major public concern. Prenatal exposure to acetaminophen can cause damage to the developing hippocampus. However, the molecular mechanisms behind hippocampal damage following prenatal acetaminophen exposure (PAcE) remain unclear. The present study shows an increased risk of adverse neurodevelopmental outcomes in offspring following exposure to acetaminophen during pregnancy on mice. The results revealed that different doses, timings, and duration of exposure to acetaminophen during pregnancy were associated with dose-dependent changes in the hippocampus of the offspring. Furthermore, exposure to high doses, multiple-treatment courses, and late pregnancy induced pathological changes, such as wrinkling and vacuolation, inhibited hippocampal proliferation and increased apoptosis. In addition, PAcE significantly decreased the expression of genes related to synaptic development in fetal hippocampal neurons and hippocampal astrocyte and microglia were also damaged to varying degrees. The significant reduction either in SOX2, an essential gene in regulating neural progenitor cell proliferation, and reduction of genes related to the SOX2/Notch pathway may suggest that the role of SOX2/Notch pathway in impaired hippocampal development in the offspring due to PAcE. In general, PAcE at high doses, multiple-treatment courses, and mid- and late gestation were associated with neurodevelopmental toxicity to the offspring.

Exploiting the Momentum Distribution in Atomically Confined Plasmonic Fields by Inelastic Scatterings.

The utilization of atomically confined plasmonic fields has revolutionized the imaging technique. According to the fundamental position-momentum uncertainty principle, such a narrow spatial distribution certainly leads to a broad momentum distribution in the fields, which has however been overlooked. Here we propose a novel exploitation for the momentum distribution by adaptively satisfying the conservation law of momentum in inelastic Raman scatterings in periodic systems, providing a unique optical means of directly measuring the whole phonon dispersions. The proposed technique is particularly useful for measuring phonon dispersions of low-dimensional hydrogen-rich materials, which are completely inaccessible via other techniques. The numerical results for a single all-trans polyacetylene chain demonstrate that all phonon dispersion branches can be conclusively measured from their Raman images for the first time. Our findings highlight a unique advantage of the emerging momentum-based nanophotonics and open the door for exploiting highly confined plasmonic fields in another dimension.

Study on the Photocatalytic Properties of Flower-Shaped SnO2.

Using cetyltrimethylammonium bromide (CTAB) as the surfactant from the precursors of SnCl2·2H2O, the flower-shaped nano composite of tin oxide (SnO2) is prepared by the simple eco-friendly hydrothermal method. We can see that the as-prepared SnO2 sample has a rutile phase crystal structure with regular-shaped nanosheets, and the nanosheets were cross-assembled to form nanoflowers. The band gap of the as-prepared SnO2 sample is 2.26 eV, which is close to the calculated energy gap of 2.58 eV based on density functional theory. The sample is used to degrade the organic dye, and this preliminary application study indicates that the as-prepared SnO2 sample has good stability and reusability in the visible light assisted degradation of methyl orange. Through capture experiments, it is determined that electrons and holes play a major role in the degradation process. The reaction mechanism is also analyzed to indicate the internal relationship between the as-prepared SnO2 samples and its photocatalytic properties.

Unraveling the Catalytic Performance of the Nonprecious Metal Single-Atom-Embedded Graphitic s-Triazine-Based C3N4 for CO2 Hydrogenation.

Graphitic carbon nitride (g-C3N4) is regarded as a promising potent photoelectrocatalyst for CO2 reduction. Here, extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations are performed to systematically explore the structural and electronic properties of nonprecious metal single-atom-embedded graphitic s-triazine-based C3N4 (M@gt-C3N4, M = Mn, Fe, Co, Ni, Cu, and Mo) monolayer materials and their catalytic performances as the single-atom catalysts (SACs) for CO2 hydrogenation to HCOOH, CO, and CH3OH. It is found that the atomically dispersed non-noble metal Mn, Fe, Co, and Mo sites anchored on gt-C3N4 can efficiently activate both H2 and CO2, and their coadsorbed state serves as a precursor to the hydrogenation of CO2 to different C1 products. Among these SACs (M@gt-C3N4, M = Mn, Fe, Co, and Mo), Co@gt-C3N4 was predicted to have the best catalytic performance for CO2 hydrogenation to C1 products, although their mechanistic details are somewhat different. The predicted energy barriers of the rate-determining steps for the conversion of CO2 into HCOOH, CO, and CH3OH on Co@gt-C3N4 are 0.58, 0.67, and 1.19 eV, respectively. The desorption of products is generally energy-demanding, but it can be facilitated remarkably by the subsequent adsorption of H2, which regenerates M@gt-C3N4 for the next catalytic cycle. The present study demonstrates that the catalytic performance of gt-C3N4 can be well regulated by embedding the non-noble metal single atom, and the porous gt-C3N4 is nicely suited for the construction of high-performance single-atom catalysts.

NLRP6 Serves as a Negative Regulator of Neutrophil Recruitment and Function During Streptococcus pneumoniae Infection.

Streptococcus pneumoniae is an invasive pathogen with high morbidity and mortality in the immunocompromised children and elderly. NOD-like receptor family pyrin domain containing 6 (NLRP6) plays an important role in the host innate immune response against pathogen infections. Our previous studies have shown that NLRP6 plays a negative regulatory role in host defense against S. pneumoniae, but the underlying mechanism is still unclear. The further negative regulatory role of NLRP6 in the host was investigated in this study. Our results showed that NLRP6-/- mice in the lung had lower bacterial burdens after S. pneumoniae infection and expressed higher level of tight junction (TJ) protein occludin compared to WT mice, indicating the detrimental role of NLRP6 in the host defense against S. pneumoniae infection. Transcriptome analysis showed that genes related to leukocytes migration and recruitment were differentially expressed between wild-type (WT) and NLRP6 knockout (NLRP6-/-) mice during S. pneumoniae infection. Also, NLRP6-/- mice showed higher expression of chemokines including C-X-C motif chemokine ligand 1 (CXCL1) and 2 (CXCL2) and lower gene expression of complement C3a receptor 1 (C3aR1) and P-selectin glycoprotein ligand-1 (PSGL-1) which are the factors that inhibit the recruitment of neutrophils. Furthermore, NLRP6-/- neutrophils showed increased intracellular bactericidal ability and the formation of neutrophil extracellular traps (NETs) during S. pneumoniae infection. Taken together, our study suggests that NLRP6 is a negative regulator of neutrophil recruitment and function during S. pneumoniae infection. Our study provides a new insight to develop novel strategies to treat invasive pneumococcal infection.

Quantum spin Hall effect in tilted penta silicene and its isoelectronic substitutions.

Silicene, a competitive two-dimensional (2D) material for future electronic devices, has attracted intensive attention in condensed matter physics. Utilizing an adaptive genetic algorithm (AGA), we identify a topological allotrope of silicene, named tilted penta (tPenta) silicene. Based on first-principles calculations, the geometric and electronic properties of tPenta silicene and its isoelectronic substitutions (Ge, Sn) are investigated. Our results indicate that tPenta silicene exhibits a semimetallic state with distorted Dirac cones in the absence of spin-orbit coupling (SOC). When SOC is considered, it shows semiconducting behavior with a gap opening of 2.4 meV at the Dirac point. Based on the results of invariant ( = 1) and the helical edge states, we demonstrate that tPenta silicene is a topological insulator. Furthermore, the effect of isoelectronic substitutions on tPenta silicene is studied. Two stoichiometric phases, i.e., tPenta Si0.333Ge0.667 and tPenta Si0.333Sn0.667 are found to retain the geometric framework of tPenta silicene and exhibit high stabilities. Our calculations show that both tPenta Si0.333Ge0.667 and tPenta Si0.333Sn0.667 are QSH insulators with enlarged band gaps of 32.5 meV and 94.3 meV, respectively, at the HSE06 level, offering great potential for practical applications at room temperature.

Charge Compensation Mechanisms and Oxygen Vacancy Formations in LiNi1/3Co1/3Mn1/3O2: First-Principles Calculations.

Charge compensation mechanisms in the delithiation processes of LiNi1/3Co1/3Mn1/3O2 (NCM111) are compared in detail by the first-principles calculations with GGA and GGA+U methods under different U values reported in the literature. The calculations suggested that different sets of U values lead to different charge compensation mechanisms in the delithiation process. Co3+/Co4+ couples were shown to dominate the redox reaction for 1 ≥ x ≥ 2/3 by using the GGA+U 1 method (U 1 = 6.0 3.4 3.9 for Ni, Co, and Mn, respectively). However, by using the GGA+U 2 (U 2 = 6.0 5.5 4.2) method, the results indicated that the redox reaction of Ni2+/Ni3+ took place in the range of 1 ≥ x ≥ 2/3. Therefore, according to our study, experimental charge compensation processes during delithiation are of great importance to evaluate the theoretical calculations. The results also indicated that all the GGA+U i (i = 1, 2, 3) schemes predicted better voltage platforms than the GGA method. The oxygen anionic redox reactions during delithiation are also compared with GGA+U calculations under different U values. The electronic density of states and magnetic moments of transition metals have been employed to illustrate the redox reactions during the lithium extractions in NCM111. We have also investigated the formation energies of an oxygen vacancy in NCM111 under different values of U, which is important in understanding the possible occurrence of oxygen release. The formation energy of an O vacancy is essentially dependent on the experimental conditions. As expected, the decreased temperature and increased oxygen partial pressure can suppress the formation of the oxygen vacancy. The calculations can help improve the stability of the lattice oxygen.

Tunable Electric and Magnetic Properties of Transition Metal@Nx Cy -Graphene Materials by Different Metal and Defect Types.

Transition metal@Nx Cy -graphene (TM@Nx Cy -GR) materials have been widely used as redox reaction catalysts in the field of fuel cells due to their low cost and high performance. In the present work, we systematically investigate the effect of different metal and defect types on the electro-magnetic properties of TM@Nx Cy -GR materials using first principles calculations. Our simulations show that TM@N3 -GR (the minimum defect size) and TM@N7 -GR (the maximum defect size) materials always possess metallic property regardless the metal type. However, doping different TM can regulate the medium defects (TM@N2 C2 -GR-I and TM@N2 C2 -GR-II) among metallicity, half-metallicity and semi-conductivity. In addition, we found that different TM and defect type largely affects the magnetic moment. The spin density and projected density of state calculations show that the net charges of the defect structure are mainly located near the hole, and the magnetic regulation comes from the coupling of TM-d orbital with carbon (nitrogen)-s(p) orbitals. The present study provides abundant valuable information for the TM@Nx Cy -GR materials designs and applicants in the future.

First-Principles Observation of Bonded 2D B4C3 Bilayers.

Two-dimensional (2D) B-C compounds possess rich allotropic structures with many applications. Obtaining new 2D B4C3 structures is highly desirable due to the novel applications of three-dimensional (3D) B4C3 in protections. In this work, we proposed a new family of 2D B4C3 from the first-principles calculations. Distinct from previous observations, this family of 2D B4C3 consists of bonded 2D B4C3 bilayers. Six different types of bilayers with distinct bonded structures are found. The phonon spectrum calculations and ab initio molecular dynamics simulations at room temperature demonstrate their dynamic and thermal stabilities. Low formation energies suggest the high possibility of realizing such structures in experiments. Rich electronic structures are found, and the predicted Young's moduli are even higher than those of the previous ones. It is revealed that the unique electronic and mechanical properties are rooted in the bonding structures, indicating the prompting applications of this family of 2D B4C3 materials in photovoltaics, nanoelectronics, and nanomechanics.

Single Mn Atom Anchored on Nitrogen-Doped Graphene as a Highly Efficient Electrocatalyst for Oxygen Reduction Reaction.

Single Mn atom on nitrogen-doped graphene (MnN4 -G) has exhibited good structural stability and high activity for the adsorption and dissociation of an O2 molecule, becoming a promising single-atom catalyst (SAC) candidate for oxygen reduction reaction (ORR). However, the catalytic activity of MnN4 -G for the ORR and the optimal reaction pathway remain obscure. In this work, density-functional theory calculations were employed to comprehensively investigate all the possible pathways and intermediate reactions of the ORR on MnN4 -G. The feasible active sites and the most stable adsorption configurations of the intermediates and transition states during the ORR were identified. Screened from all the possibilities, three optimal four-electron O2 hydrogenation pathways with an ultralow energy barrier of 0.13 eV were discovered that are energetically more favorable than direct O2 dissociation pathways. Analysis of the free energy diagram further verified the thermodynamical feasibility of the three pathways. Thus, MnN4 -G possesses superior ORR activity. This study provides a fundamental understanding of the design of highly efficient SACs for the ORR.

Spin Polarization-Induced Facile Dioxygen Activation in Boron-Doped Graphitic Carbon Nitride.

Dioxygen (O2) activation is a vital step in many oxidation reactions, and a graphitic carbon nitride (g-C3N4) sheet is known as a famous semiconductor catalytic material. Here, we report that the atomic boron (B)-doped g-C3N4 (B/g-C3N4) can be used as a highly efficient catalyst for O2 activation. Our first-principles results show that O2 can be easily chemisorbed at the B site and thus can be highly activated, featured by an elongated O-O bond (∼1.52 Å). Interestingly, the O-O cleavage is almost barrier free at room temperatures, independent of the doping concentration. It is revealed that the B atom can induce considerable spin polarization on B/g-C3N4, which accounts for O2 activation. The doping concentration determines the coupling configuration of net-spin and thus the magnitude of the magnetism. However, the distribution of net-spin at the active site is independent of the doping concentration, giving rise to the doping concentration-independent catalytic capacity. The unique monolayer geometry and the existing multiple active sites may facilitate the adsorption and activation of O2 from two sides, and the newly generated surface oxygen-containing groups can catalyze the oxidation coupling of methane to ethane. The present findings pave a new way to design g-C3N4-based metal-free catalysts for oxidation reactions.

Rational integration of spatial confinement and polysulfide conversion catalysts for high sulfur loading lithium-sulfur batteries.

Spatial confinement is a desirable successful strategy to trap sulfur within its porous host and has been widely applied in lithium-sulfur (Li-S) batteries. However, physical confinement alone is currently not enough to reduce the lithium polysulfide (Li2Sn, 4 ≤n≤ 8, LIPSs) shuttle effect with sluggish LIPS-dissolving kinetics. In this work, we have integrated spatial confinement with a polar catalyst, and designed a three-dimensional (3D) interconnected, Co decorated and N doped porous carbon nanofiber (Co/N-PCNF) network. This Co/N-PCNF film serves as a freestanding host for sulfur trapping, which could effectively facilitate the infiltration of electrolyte and electron transport. In addition, the polar Co species possess strong chemisorption with LIPSs, catalyzing their reaction kinetics as well. As a result of this rational design and integration, the Co/N-PCNF@S cathode with a sulfur loading of 2 mg cm-2 exhibits a high initial discharge capacity of 878 mA h g-1 at 1C, and maintains a discharge capacity of 728 mA h g-1 after 200 cycles. Even with high sulfur loading of 9.33 mg cm-2, the cathode still keeps a stable areal capacity of 7.16 mA h cm-2 at 0.2C after 100 cycles, which is much higher than the current areal capacity (4 mA h cm-2) of commercialized lithium-ion batteries (LIBs). This rational design may provide a new approach for future development of high-density Li-S batteries with high sulfur loading.

Covalent organic framework with high capacity for the lithium ion battery anode: insight into intercalation of Li from first-principles calculations.

Covalent organic frameworks (COFs) generally have high stability, large charge capacity and wide ion diffusion paths, and they may serve as the potential electrode materials for lithium ion batteries. Here we explored the structural, electronic, and lithium-storage properties of the newly synthesized NUS-2 COF material by first-principles calculations. The present results indicate that the micropore environment and the presence of the carbonyl oxygens in the NUS-2 COF can prevent the formation of lithium dimer and the aggregation of lithium bulk, which can improve lithiation efficiency. The predicted maximum theoretical capacity is as high as 742.8 mAh g-1 and the average cell voltage varies from 3.35 V for Li@NUS-2 to 2.04 V for 14Li@NUS-2, suggesting that the NUS-2 COF material should be a quite suitable lithium-storage anode material.

Ultrahigh conductivity of graphene nanoribbons doped with ordered nitrogen.

Graphene is an attractive candidate for developing high conductivity materials (HCMs) owing to an extraordinary charge mobility. While graphene itself is a semi-metal with an inherently low carrier density, and methods used for increasing carrier density normally also cause a marked decrease in charge mobility. Here, we report that ordered nitrogen doping can induce a pronounced increase in carrier density but does not harm the high charge mobility of graphene nanoribbons (GNRs), giving rise to an unprecedented ultrahigh conductivity in the system. Our first-principles calculations for orderly N-doped GNRs (referred to as C5N-GNRs) show that N-doping causes a significant shift-up of the Fermi level (ΔE F), resulting in the presence of multiple partially-filled energy bands (PFEDs) that primarily increase the carrier density of system. Notably, the PFEDs are delocalized well with integral and quantized transmissions, suggesting a negligible effect from N-doping on the charge mobility. Moreover, the PFEDs can cross the E F multiple times as the ribbon widens, causing the conductivity to increase monotonically and reach ultrahigh values (>15G 0) in sub-5 nm wide ribbons with either armchair or zigzag edges. Furthermore, a simple linear relationship between the doing concentration and the ΔE F was obtained, which provides a robust means for controlling the conductivity of C5N-GNRs. Our findings should be useful for understanding the effect of ordered atomic doping on the conductivity of graphene and may open new avenues for realizing graphene-based HCMs.

Tunable Electronic and Magnetic Properties of Graphene-Embedded Transition Metal-N4 Complexes: Insight From First-Principles Calculations.

Motivated by the development of transition-metal-nitrogen-carbon (TM-N-C) materials for catalysts and molecular electronics, we investigated the electronic and magnetic properties of TMN4 -graphene materials with different central atoms (TM=Ti, V, Cr, Mn, Fe, Co, Ni and Cu) and different concentrations. The first-principles results show that a widely tunable magnetic moment in the range from 0 to 4 µB can be obtained in this kind of material by varying the central TM atom, and a regular transition of the electronic property from metallic to half-metallic and to semiconducting characteristics is observed in MnN4 -graphene upon changing the concentration. We find that the peculiar relationship between the electronic characteristics of graphene and its lattice parameters plays a decisive role in determining the electronic and magnetic properties. Our findings are useful for the design of TM-N-C materials for catalysis, spintronics, and molectronics.