147 research outputs found
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 CrPSe
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, 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
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