Understanding Synergistic Catalysis on Cu-Se Dual Atom Sites via Operando X-ray Absorption Spectroscopy in Oxygen Reduction Reaction

The construction and understanding of synergy in well-defined dual-atom active sites is an available avenue to promote multistep tandem catalytic reactions. Herein, we construct a dual-hetero-atom catalyst that comprises adjacent Cu-N₄ and Se-C₃ active sites for efficient oxygen reduction reaction (ORR) activity. Operando X-ray absorption spectroscopy coupled with theoretical calculations provide in-depth insights into this dual-atom synergy mechanism for ORR under realistic device operation conditions. The heteroatom Se modulator can efficiently polarize the charge distribution around symmetrical Cu-N₄ moieties, and serve as synergistic site to facilitate the second oxygen reduction step simultaneously, in which the key OOH*-(Cu₁-N₄) transforms to O*-(Se₁-C₂) intermediate on the dual-atom sites. Therefore, this designed catalyst achieves satisfied alkaline ORR activity with a half-wave potential of 0.905 V vs. RHE and a maximum power density of 206.5 mW cm⁻² in Zn-air battery.     

CO2 Hydroboration: Impact of the Boryl Moieties on the Reactivity of Four Bis(boryl)acetal Compounds toward 2,6-Diisopropylaniline

The hydroboration of CO₂ into bis(boryl)acetal (BBA) compounds is an important transformation, since it enabled to selectively reduce CO₂ by 4e^- and to subsequently use the BBA compounds as C₁ and C_n sources. However, the influence of the nature of the boryl moieties on the reactivity of BBA compounds has not been evaluated so far. In the present study, four BBA compounds – including two new ones – were reacted with 2,6-diisopropylaniline to afford the expected imine. Significant differences in the rate of the reaction from minutes to weeks have been observed depending on the BBA used, showing the importance of the nature of the boryl moieties. Theoretical investigations enabled to propose a mechanism involving the addition of the aniline to the BBA as the rate-determining step and to determine that the steric hindrance of the BBA compounds is the main factor driving the rate of this condensation reaction.     

Study on the ionic conductivity of polyether network polymer electrolytes: effect of the preparation method

In preparing the network polymer electrolytes, two different methods were taken in the incorporation of salt into the polymer network. In one method, the network polyether was dipped into the lithium salt solution with or without plasticizer, and in the other method the network formation was proceeded in the presence of the lithium salt in the reaction medium with or without plasticizer. We designated the former as the network polymer electrolyte (NPE), the latter as the salt added network polycondensate electrolyte (SNPE). For the NPEs, the ionic conductivities increased with decreasing the cross-linking degree, which was mainly attributed to the increase of the free ion fraction with the decrease in the cross-linking degree that was evidenced by ⁷Li NMR relaxation studies. For the NPEs plasticized with MPEG₇, the conductivities increased with increase of the MPEG₇ content, which was largely due to the increase of the mobility of the free ions. The ionic conductivity of the SNPE was higher than that of the NPE, which resulted from the lower microviscosity of the SNPE due to the larger amount of the contained linear polyether and the lower cross-linking degree.     

Magnetic properties of oxalate ligand based molecular materials: NBu4M(II)[Fe(III)(ox)3], Bu4=n-(C4H9)4, M=Co,Cr

The oxalate ligand bridged mixed-metal molecular compounds NBu₄Co(II)[Fe(III)(ox)₃] and NBu₄Cr(II)[Fe(III)(ox)₃] (where NBu₄⁺=tetra-n-butyl ammonium ion, ox²⁻=oxalate ion) are prepared. X-ray powder diffraction profiles are indexed in P6₃ space group to derive unit cell parameters. Their magnetic properties were studied in the temperature range of 5–300 K under different applied magnetic fields in zero-field-cooled as well as field-cooled conditions. The magnetic transition temperatures for these compounds were determined from the temperature dependence of remnant magnetization under a very low field. The compounds are ferrimagnetic in nature and exhibit a disordered structure at temperatures below the magnetic transition temperature.     

On the role of the process zone in dynamic fracture

The evolution of the fracture process zone and its influence on dynamic crack propagation are investigated using a simple constitutive assumption to model the material in the fracture process zone. The mode III problem of anti-plane shear is examined using a finite difference scheme to obtain the full field solution. Unlike the classical approach of determining the steady state solutions for imposed constant speed of crack propagation, here the fracture criterion is imposed along with the formulation of the boundary-initial value problem and the coupled equations are solved numerically to determine the generation and growth of the fracture process zone as well as the crack tip. The results of the simulation indicate that the constitutive behavior of the process zone material (or equivalently the evolution of the process zone itself) plays a key role in determining the dynamics of fast fracture.     

Transformation devices with optical nihility media and reduced realizations

Starting from optical nihility media (ONM), we design several intriguing devices with transformation optics method in two dimensions, such as a wave splitter, a concave lens, a field rotator, a concentrator, and an invisibility cloak. Though the extreme anisotropic property of ONM hinders the fabrication of these devices. We demonstrate that those devices could be effectively realized by simplified materials with Fabry–Pérot resonances (FPs) at discrete frequencies. Moreover, we propose a reduced version of simplified materials with FPs to construct a concentrator and a rotator, which is feasible in experimental fabrications. The simulations of total scattering cross-sections confirm their functionalities.     

Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity

We study the efficiency of modulated external electric pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction.     

Contrasting chiroptical properties of sparteine lactams and thiolactams

The CD spectra of several mono- and dilactams and thiolactams of sparteine were measured with the purpose of clarifying spectra–structure relations. It is shown that the Cotton effects of lactams are predominantly of the opposite sign to those of the corresponding thiolactams. In bichromophoric molecules 7–9 the observed CD spectra are dominated by exciton type interactions.     

基于0级数据的星载大气痕量气体差分吸收光谱仪在轨衰变监测

大气痕量气体差分吸收光谱仪(EM I)是一种紫外可见成像光谱仪,主要用于实现高空间分辨率的全球每日大气痕量气体浓度反演.EM I在轨运行期间,受空间环境影响,元器件性能随时间推移会不断衰变.为有效监测其衰变状况,利用载荷对地各轨0级数据解析出在轨温度,实现长期在轨温度监测;通过计算各轨道星下点黑暗时的暗背景图像噪声的均...     

Aryl group grafted polysilane: novel scintillation solute for high efficiency and environment-friendly scintillator

Journal of Radioanalytical and Nuclear Chemistry - Polysilane is expected to be a highly efficient and environmentally friendly liquid scintillator, for its unique fluorescence performance based on...