Recent Advances in Noble‐Metal‐Free Catalysts for Electrocatalytic Synthesis of Ammonia under Ambient Conditions

Ammonia is an essential chemical for producing fertilizers and energy carriers. However, the industrial Haber–Bosch process causes huge CO₂ emissions and energy waste. As a promising alternative for Haber‐Bosch process, electrochemical synthesis of ammonia has drawn much attention. Catalysts, as a vital part of electrochemical nitrogen reduction reaction (NRR), have developed rapidly in recent years. Compared to noble‐metal catalysts, noble‐metal‐free catalysts possess a low‐cost advantage. In this review, noble‐metal‐free catalysts, including metal‐based materials, metal organic frameworks (MOFs), MXenes, and metal‐free materials, are summarized. In addition, effective design strategies are discussed, along with the main problems and some potential directions of noble‐metal‐free NRR catalysts.     

类锂离子电子碰撞直接和非直接电离速率系数

在库仑-玻恩交换近似及由我们改善了屏蔽常数定义和算法的Z标度类氢模型下,计算了类锂CⅣ、NⅤ和OⅥ离子的内、外壳层电子被入射电子碰撞的直接电离和非直接的激发自电离截面和速率系数。与实验结果比较,对于CⅣ、NⅤ和OⅥ,我们的计算截面值的最大相对误差分别不超过3％、11％和20％,并随入射电子能量的增加误差越来越小。与其它的理论结果相比,随着Z增加,我们计算的速率系数与实验结果符合得更好些。     

Rhodium-catalyzed cross-coupling reaction of arylboronates and diazoesters and tandem alkylation reaction for the synthesis of quaternary α,α-heterodiaryl carboxylic esters

A rhodium-catalyzed one-pot three-component coupling reaction was developed for the synthesis of quaternary α,α-heterodiaryl carboxylic esters. This reaction involves cross-coupling of the arylrhodium(I) complexes with α-aryldiazoacetates to form oxa-π-allylrhodium complexes. With KOtBu and alkyl halides, tandem alkylation of the allyl complex occurs to form a quaternary stereocenter at the carbenic carbon.     

2010年中考物理阅读题的几个特点

新课程标准实施以来,阅读理解题已不再纯粹是语文和英语试卷的常用题型,在物理考试中也频频出现.综观2010年的中考物理阅读题具有以下特点:从试题素材情境的创设上来看,来源广泛,涉及到日常生活、工农业生产、高科技产品的使用、社会的热点、焦点等方方面面;从考查的范围上来看,覆盖了力、热、声、光、电、磁等知识要点,综合性较强,     

Forcing faces in plane bipartite graphs (II)

The concept of forcing faces of a plane bipartite graph was first introduced in Che and Chen (2008) [3] [Z. Che, Z. Chen, Forcing faces in plane bipartite graphs, Discrete Mathematics 308 (2008) 2427–2439], which is a natural generalization of the concept of forcing hexagons of a hexagonal system introduced in Che and Chen (2006) [2] [Z. Che and Z. Chen, Forcing hexagons in hexagonal systems, MATCH Commun. Math. Comput. Chem. 56 (2006) 649–668]. In this paper, we further extend this concept from finite faces to all faces (including the infinite face) as follows: A face $s$ (finite or infinite) of a 2-connected plane bipartite graph $G$ is called a forcing face if the subgraph $G?V\left(s\right)$ obtained by removing all vertices of $s$ together with their incident edges has exactly one perfect matching.For a plane elementary bipartite graph $G$ with more than two vertices, we give three necessary and sufficient conditions for $G$ to have all faces forcing. We also give a new necessary and sufficient condition for a finite face of $G$ to be forcing in terms of bridges in the $Z$-transformation graph $Z\left(G\right)$ of $G$. Moreover, for the graphs $G$ whose faces are all forcing, we obtain a characterization of forcing edges in $G$ by using the notion of $handle$, from which a simple counting formula for the number of forcing edges follows.     

基体匹配–电感耦合等离子体原子发射光谱法测定新型抗菌不锈钢中镓

建立电感耦合等离子体原子发射光谱法测定含镓抗菌不锈钢中镓含量的方法.样品用盐酸和硝酸溶解,在优化的仪器条件下,选择417.206 nm作为分析谱线.采用基体匹配法绘制工作曲线,用以消除基体铁的基体效应;采用铁基体为校准空白,用以消除铁基体的光谱干扰.标准工作溶液中镓光谱强度与基体空白溶液中镓光谱强度之差与镓的质量分数在...     

Plasmonics properties of nano-torus: An FEM method

Nano-torus particles are promising in nano-photonics applications. In this paper, we investigate the plasmonics resonant spectrum of torus and the corresponding horizontal and vertical dimers with the finite element method (FEM) based on strict electromagnetic theory. Compared with sphere, single torus and horizontal dimer under perpendicular polarization are characterized with narrower line width and wider tunability throughout visible and infrared frequencies. These properties make single torus and horizontal dimer suitable for high sensitivity sensing. Furthermore, Purcell factor and local field enhancement of horizontal dimer which are important to high efficient single photon devices are one order of magnitude higher than those of single torus respectively. However, vertical dimer under perpendicular polarization has no above advanced characteristics.     

Porous redox-active Cu2O-SiO2 nanostructured film: Preparation, characterization and application for a label-free amperometric ferritin immunosensor

A novel Cu₂O-SiO₂ nanostructured particle was synthesized by a solution-phase method and was adopted for construction of a label-free amperometric immunosensor. The porous Cu₂O-SiO₂ nanoparticles had good redox electrochemical activity, large surface-to-volume ratio, film-forming ability and high stability. The physical morphology and structure of Cu₂O-SiO₂ nanoparticles were examined by scanning electron microscope (SEM) and transmission electron microscopy (TEM). The chemical component of Cu₂O-SiO₂ was confirmed by X-ray photoelectron spectroscopy (XPS) and auger electron spectra (AES). The electrode modification process was probed by cyclic voltammetry (CV) and the performance of the immunosensor was studied by differential pulse voltammetry (DPV) measurements. To improve the analytical characteristics of the immunosensor, the experimental conditions were optimized. The immunosensor exhibited a good response to ferritin in ranges from 1.0 to 5.0 and 5.0 to 120.0 ng mL⁻¹ with a detection limit of 0.4 ng mL⁻¹. The fabricated immunosensor could make a low-cost, sensitive, quantitative detection of ferritin, and would have a potential application in clinical immunoassays.     

Molecular dynamics simulations of atomic assembly in the process of GaN film growth

Molecular dynamics simulations using a Coulomb–Buckingham potential have been used to investigate the process of wurtzite GaN films growth, including the appearance of films in early stage, regulation of growth, structure of the surface and the dynamic features. The simulations show that the N atoms and Ga atoms are absorbed on the lattice of substrate and take on a distinct sandwich structure. Time evolution of the mean square displacements and diffusion coefficient of the deposited atoms are observed, the results show that the clusters will become stable with the increase of time steps and the atoms reach the initial stable state after 25 ps; N atoms reach the equilibrium positions more quickly than Ga atoms. It is proved by radial distribution function and the ratio of vacancy of every deposited layer that the crystalline characters of the films will become better as the time steps increase and weaker from bottom to top.     

“水窗”波段类Li离子各电离态的电离能

用相对论多组成Ｄｉｒａｃ－Ｆｏｃｋ方法计算了“水窗”波段类Ｌｉ离子各电离态的电离能，这些能量对于优化复合泵浦软Ｘ射线激光机制具有重要意义。