The Typical Organic Pollutants Health Risk Research Of The Main Source Water In Yellow River Basin

Although the contamination of the organic pollutants had been reported to occur in the Yellow River basin, few studies had been done on the source water contamination and health risk of Yellow River basin. To understand the typical organic pollutant contamination status of the main source water in Yellow River basin, samples were collected from fifty source water points (including reservoir and river) in Yellow River basin. The samples were analyzed for the representative organic pollutants, including Benzene homology, Chlorobenzene compounds, organophosphorous pesticides, and Nitrobenzene compounds, total 17 compounds. It was observed that the concentrations of the 17 compounds in the fifty source waters were all less than the standard limit of Chinese surface water quality standard. In addition, the benzene, toluene, nitrobenzene, p-nitrochlorobenzene, 2,4-dinitrotoluene and 2,4-dinitrochlorobenzene, dichlorvos, demeton, dimethoate methyl parathion, malathion and parathion were more frequently detected in the main source water of Yellow River basin, especially the organophosphorous pesticides, the detection rates of dichlorvos, demeton, methyl parathion, malathion and parathion are all much higher than 90% in the fifty source water points. The results of detection rate of target compounds suggested that the organic pollution had been popular in the source water of the Yellow River basin. The health risk assessment results suggested that the noncarcinogenic risk HQ values of the target compounds were less than one, and the cancer risk values of most source water sites were much less than the 1´10-6, only the sites 23,24,25,26 cancer risk values were much higher than the 1´10-6, which indicated that the heath risk produced by the target compounds in the most source water was in a acceptable level

Out-of-plane polarization and topological magnetic vortices in multiferroic CrPSe3_3

Two-dimensional (2D) multiferroic materials are ideal systems for exploring new coupling mechanisms between different ferroic orders and producing novel quantum phenomena with potential applications. We employed first-principles density functional theory calculations to discover intrinsic ferroelectric and anti-ferroelectric phases of CrPSe$_3$, which show ferromagnetic order and compete with the centrosymmetric phase with an antiferromagnetic order. Our analysis show that the electrical dipoles of such type-I multiferroic phases come from the out-of-plane displacements of phosphorus ions due to the stereochemically active lone pairs. The coupling between polar and magnetic orders creates the opportunity for tunning the magnetic ground state by switching from the centrosymmetric to the ferroelectric phase using an out-of-plane electric field. In ferroelectric and antiferroelectric phases, the combination of easy-plane anisotropy and Dzyaloshinskii-Moriya interactions (DMI) indicate they can host topological magnetic vortices like meron pairs.Comment: 7 pages, 3 figures, and the supplementary materia

Excellent HER and OER Catalyzing Performance of Se-vacancies in Defects-engineering PtSe2: From Simulation to Experiment

Facing with grave climate change and enormous energy demand, catalyzer gets more and more important due to its significant effect on reducing fossil fuels consumption. Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by water splitting are feasible ways to produce clean sustainable energy. Here we systematically explored atomic structures and related STM images of Se defects in PtSe2. The equilibrium fractions of vacancies under variable conditions were detailly predicted. Besides, we found the vacancies are highly kinetic stable, without recovering or aggregation. The Se vacancies in PtSe2 can dramatically enhance the HER performance, comparing with, even better than Pt(111). Beyond, we firstly revealed that PtSe2 monolayer with Se vacancies is also a good OER catalyst. The excellent bipolar catalysis of Se vacancies were further confirmed by experimental measurements. We produced defective PtSe2 by direct selenization of Pt foil at 773 K using a CVD process. Then we observed the HER and OER performance of defective PtSe2 is much highly efficient than Pt foils by a series of measurements. Our work with compelling theoretical and experimental studies indicates PtSe2 with Se defects is an ideal bipolar candidate for HER and OER

Graphene Nucleation on Transition Metal Surface: Structure Transformation and Role of the Metal Step Edge

The nucleation of graphene on a transition metal (TM) surface, either on a terrace or near a step edge, is systematically explored using density functional theory (DFT) calculations and applying the two-dimensional (2D) crystal nucleation theory. Careful optimization of the supported carbon clusters, CN (with size N ranging from 1 to 24), on the Ni(111) surface indicates a ground state structure transformation from a one-dimensional (1D) C chain to a two-dimensional (2D) sp2 C network at N ~ 10-12. Furthermore, the crucial parameters controlling graphene growth on the metal surface, nucleation barrier, nucleus size, and the nucleation rate on a terrace or near a step edge, are calculated. In agreement with numerous experimental observations, our analysis shows that graphene nucleation near a metal step edge is superior to that on a terrace. Based on our analysis, we propose the use of seeded graphene to synthesize high-quality graphene in large area.Comment: 19 pages, 6 figures, accepted in Journal of the American Chemical Societ

Robust Sandwiched B/TM/B Structures by Metal Intercalating into Bilayer Borophene Leading to Excellent Hydrogen Evolution Reaction

Bilayer borophene, very recently synthesized on Ag and Cu, possesses extremely flat large surface and excellent conductivity. Besides, the van der Waals gap of bilayer borophene can be intercalated by metal atoms, thereby tailoring the properties of bilayer borophene. Herein, we propose that sandwiched B/TM/B (TM=Co, Ni, Cu, Pd) could be a new 2D formation by transiton metal atoms intercalated into bilayer borophene network, it is quiet robust with both energetic, structural and thermal stability, and exhibits heat resistance of at least 1300 K. Besides, it is novel platform for electrocatalytic hydrogen evolution reaction (HER). The interecalation metal atom serves as single-atomic catalyst, which acting the nonmetal boron layers. Beyond that, the transtion metal is protected by outside boron layers from being corroded by acidic/alkaline solution. B/Cux/B, B/Pdx/B and B/Alx/B with different metal coverage exhibit defect-independent extremely low HER free energy in the range of -0.162 ~ 0.179 eV, -0.134 ~ 0.183 eV and -0.082 ~ 0.086 eV which are comparable to noble metal Pt. Combining excellent conduction, high structural and thermal stability, low resistance to intercalated behaviour, effortless water splitting process, excellent defect-independent catalytic performance, cheapness and abundance of raw materials, free of corrodation, 2D sandwiched B/TM/B (TM=Co, Ni, Cu, Pd) is believed to promising for electrocatalytic HER applications

Sumanene monolayer of pure carbon: a two-dimensional Kagome-analogy lattice with desirable band gap, ultrahigh carrier mobility and strong exciton binding energy

Design and synthesis of novel two-dimensional (2D) materials that possess robust structural stability and unusual physical properties may open up enormous opportunities for device and engineering applications. Herein we propose a 2D sumanene lattice that be regarded as a derivative of the conventional Kagome lattice. Our tight-binding analysis demonstrates sumanene lattice contains two sets of Dirac cones and two sets of flat bands near the Fermi surface, distinctively different from the Kagome lattice. Using first-principles calculations, we theoretically suggest two possible routines for realization of stable 2D sumanene monolayers (named as a phase and b phase), and a-sumanene monolayer can be experimentally synthesized with chemical vapor deposition using C21H12 as a precursor. Small binding energies on Au(111) surface signify the possibility of their peel-off after grown on the noble metal substrate. Importantly, our GW plus Bethe-Salpeter equation calculations demonstrate both monolayers have moderate band gaps (1.94 eV for a) and ultrahigh carrier mobilities (3.4*104 cm2/Vs for a). In particular, a-sumanene monolayer possesses a strong exciton binding energy of 0.73 eV, suggesting potential applications in optics

Stability and superconductivity of freestanding two-dimensional transition metal boridene: M4/3B2

The small atomic mass of boron indicates strong electron-phonon coupling, so it may have a brilliant performance in superconductivity. Recently, a new 2D boride sheet with ordered metal vacancies and surface terminals (Mo4/3B2-x) was realized in experiments (Science 2021, 373, 801). Here, the 2D monolayer freestanding Mo4/3B2is evidenced to be thermodynamically stable. Through electronic structure, phonon spectrum and electron-phonon coupling, monolayer Mo4/3B2 is found to be an intrinsic phonon-mediated superconductor. The superconducting transition temperature (Tc) is determined to be 4.06 K by the McMillian-Allen-Dynes formula. Remarkably, the Tc of monolayer Mo4/3B2 can be increased to 6.78 K with an appropriate biaxial tensile strain (+5%). Moreover, we predict that other transition metal replacing Mo atoms is also stable and retaining the superconductivity. Such as monolayer W4/3B2 is also a superconductor with the Tc of 2.37 K. Our research results enrich the database of 2D monolayer superconductors and boron-related formed materials science