Rational design of Fe/Co-based diatomic catalysts for Li–S batteries by first-principles calculations

Fe/Co-based diatomic catalysts decorated on an N-doped graphene substrate are investigated by first-principles calculations to improve the electrochemical properties of Li–S batteries.Our results demonstrate that Fe CoN8@Gra not only possesses moderate adsorption energies towards Li2Snspecies,but also exhibits superior catalytic activity for both reduction and oxidation reactions of the sulfur cathode.Moreover,the metallic property of the diatomic catalysts can be well maintained after Li2Snadsorption,which could help the sulfur cathode to maintain high conductivity during the whole charge–discharge process.Given these exceptional properties,it is expected that Fe CoN8@Gra could be a promising diatomic catalyst for Li–S batteries and afford insights for further development of advanced Li–S batteries.

Nanoparticle-Decorated Ultrathin La2O3 Nanosheets as an Effcient Electrocatalysis for Oxygen Evolution Reactions

Electrochemical catalysts for oxygen evolution reaction are a critical component for many renewable energy applications. To improve their catalytic kinetics and mass activity are essential for sustainable industrial applications. Here, we report a rare-earth metal-based oxide electrocatalyst comprised of ultrathin amorphous La2O3 nanosheets hybridized with uniform La2O3 nanoparticles(La2O3@NP-NS). Significantly improved OER performance is observed from the nanosheets with a nanometer-scale thickness. The as-synthesized 2.27-nm La2O3@NP-NS exhibits excellent catalytic kinetics with an overpotential of 310 mV at 10 m A cm^-2, a small Tafel slope of 43.1 mV dec^-1, and electrochemical impedance of 38 Ω. More importantly, due to the ultrasmall thickness, its mass activity, and turnover frequency reach as high as 6666.7 A g^-1 and 5.79 s^-1, respectively, at an overpotential of 310 mV. Such a high mass activity is more than three orders of magnitude higher than benchmark OER electrocatalysts, such as IrO2 and RuO2. This work presents a sustainable approach toward the development of highly e cient electrocatalysts with largely reduced mass loading of precious elements.

High-Sensitivity Tunnel Magnetoresistance Sensors Based on Double Indirect and Direct Exchange Coupling Effect

Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level,especially for low operating frequency applications.We investigated the transport properties of tunnel magnetoresistance(TMR)sensors based on the double indirect exchange coupling effect.The TMR ratio of about 150%was obtained in the magnetic tunnel junctions and linear response to an in-plane magnetic field was successfully achieved.A high sensitivity of 1.85%/Oe was achieved due to a designed soft pinned sensing layer of CoFeB/NiFe/Ru/IrMn.Furthermore,the voltage output sensitivity and the noise level of 10.7 mV/V/Oe,10 nT/Hz^(1/2)at 1 Hz and3.3 nT/Hz^(1/2)at 10 Hz were achieved in Full Wheatstone Bridge configuration.This kind of magnetic sensors can be used in the field of smart grid for current detection and sensing.

In vitro study of enhanced photodynamic cancer cell killing effect by nanometer-thick gold nanosheets

Photodynamic therapy(PDT)by near-infrared(NIR)irradiation is a promising technique for treating various cancers.Here,we reported the development of free-standing wafer-scale Au nanosheets(NSs)that exhibited an impressive PDT effect.The Au NSs were synthesized by ionic layer epitaxy at the air-water interface with a uniform thickness in the range from 2 to 8.5 nm.These Au NSs were found very effective in generating singlet oxygen under NIR irradiation.In vitro cellular study showed that the Au NSs had very low cytotoxicity and high PDT efficiency due to their uniform 2D morphology.Au NSs could kill cancer cells after 5 min NIR irradiation with little heat generation.This performance is comparable to using 10 times mass loading of Au nanoparticles(NPs).This work suggests that two-dimensional(2D)Au NSs could be a new type of biocompatible nanomaterial for PDT of cancer with an extraordinary photon conversion and cancer cell killing efficiency.

Effects of different doses of cadmium on secondary metabolites and gene expression in Artemisia annua L.

This study aims to elucidate the underlying molecular mechanisms of artemisinin accumulation induced by cadmium （Cd）. The effects of different Cd concentrations （0, 20, 60, and 120 μmol/L） on the biosynthesis ofArtemisia annua L. were examined. Intermediate and end products were quantified by HPLC-ESI- MS/MS analysis. The expression of key biosynthesis enzymes was also determined by qRT-PCR. The results showed that the application of treatment with 60 and 120 μmol/L Cd for 3 days significantly improved the biosynthesis of artemisinic acid, arteannuin B, and artemisinin. The concentrations of artemisinic acid, arteannuin B, and artemisinin in the 120 llmol/L Cd-treated group were 2.26, 102.08, and 33.63 times higher than those in the control group, respectively. The concentrations of arteannuin B and artemisinin in 60 μmol/L Cd-treated leaves were 61.10 and 26.40 times higher than those in the control group, respectively. The relative expression levels of HMGR, FPS, ADS, CYP71AV1, DBR2, ALDH1, and DXR were up-regulated in the 120 μmol/L Cd-treated group because of increased contents of artemisinic metabolites after 3 days of treatment. Hence, appropriate doses of Cd can increase the concentrations of artemisinic metabolites at a certain time point by up-regulating the relative expression levels of key enzyme genes involved in artemisinin biosynthesis.

Thickness-Dependent Piezoelectric Property from Quasi-Two-Dimensional Zinc Oxide Nanosheets with Unit Cell Resolution

A quantitative understanding of the nanoscale piezoelectric property will unlock many application potentials of the electromechanical coupling phenomenon under quantum confinement.In this work,we present an atomic force microscopy-(AFM-)based approach to the quantification of the nanometer-scale piezoelectric property from single-crystalline zinc oxide nanosheets(NSs)with thicknesses ranging from 1 to 4 nm.By identifying the appropriate driving potential,we minimized the influences from electrostatic interactions and tip-sample coupling,and extrapolated the thickness-dependent piezoelectric coefficient(d_(33)).By averaging the measured d_(33) from NSs with the same number of unit cells in thickness,an intriguing tri-unit-cell relationship was observed.From NSs with 3n unit cell thickness(n=1,2,3),a bulk-like d_(33) at a value of~9 pm/V was obtained,whereas NSs with other thickness showed a~30%higher d_(33) of~12 pm/V.Quantification of d_(33) as a function of ZnO unit cell numbers offers a new experimental discovery toward nanoscale piezoelectricity from nonlayered materials that are piezoelectric in bulk.