Surface charging behaviors of electrocatalytic interfaces with partially charged chemisorbates

The surface charge is a key concept in electrochemistry. Mathematically, the surface charge is obtained from a spatial integration of the volume charge along a particular direction. Ambiguities thus arise in choosing the starting and ending points of the integration. As for electrocatalytic interfaces, the presence of chemisorbates further complicates the situation. In this minireview, I adopt a definition of the surface charge within a continuum picture of the electric double layer. I will introduce surface charging behaviors of firstly ordinary electrochemical interfaces and then electrocatalytic interfaces featuring partially charged chemisorbates. Particularly, the origin of nonmonotonic surface charging behaviors of electrocatalytic interfaces is explained using a primitive model. Finally, a brief account of previous studies on the nonmonotonic surface charging behavior is presented, as a subline of the spectacular history of electric double layer.     

Stabilized Nonconforming Mixed Finite Element Method for Linear Elasticity on Rectangular or Cubic Meshes

Based on the primal mixed variational formulation, a stabilized nonconforming mixed finite element method is proposed for the linear elasticity on rectangular and cubic meshes. Two kinds of penalty terms are introduced in the stabilized mixed formulation, which are the jump penalty term for the displacement and the divergence penalty term for the stress. We use the classical nonconforming rectangular and cubic elements for the displacement and the discontinuous piecewise polynomial space for the stress, where the discrete space for stress are carefully chosen to guarantee the well-posedness of discrete formulation. The stabilized mixed method is locking-free. The optimal convergence order is derived in the $L^2$-norm for stress and in the broken $H^1$-norm and $L^2$-norm for displacement. A numerical test is carried out to verify the optimal convergence of the stabilized method.     

Analysis on First-stage Ignition of n-Heptane at Low Temperatures with a Lumped Skeletal Mechanism

Two-stage ignition exists in the low-temperature combustion process of n-heptane and the first-stage ignition also shows a negative temperature coefficient(NTC) phenomenon. To study key reactions and understand chemical principles affecting the first-stage ignition of n-heptane, a lumped skeletal mechanism with 62 species is obtained based on the detailed NUIGMech1.0 mechanism using the directed relation graph method assisted by sensitivity analysis and isomer lumping. The lumped mechanism shows good performance on ignition delay time under wide conditions. The study revealed that the temperature after the first-stage ignition is higher and a larger amount of fuel is consumed at lower initial temperatures. The temperature at the first-stage ignition is relatively insensitive to the initial temperature. Further sensitivity analysis and reaction path analysis carried out based on the lumped mechanism show that the decomposition of RO₂ to produce alkene and HO₂is the most important reaction to inhibit the first-stage ignitions. The chain branching explosion closely related to the first-stage ignition will be terminated when the rate constant for the RO₂ decomposition is larger than that of the isomerization of RO₂ to produce QOOH. The NTC behavior as well as other characteristics of the first-stage ignition can be rationalized from the competition between these two reactions.     

The Bergman kernel for the Vekua equation

The paper extends some well-known results for analytic functions onto solutions of the Vekua equation $\partial \overline{{}_z}W=aW+b\overline{W}$ regarding the existence and construction of the Bergman kernel and of the corresponding Bergman projection operator.     

Electrochromic Detection of Latent Fingermarks on Metal Surface Using 1,1′-Dibenzyl-4,4′-bipyridinium Dichloride

The electrochromic detection of latent fingermarks on polished or unpolished, flat or curved metal surfaces is described using electrochromic material, 1,1’-dibenzyl-4,4’-bipyridinium dichloride. The surface area covered by fingermarks acts as an insulating mask, causing 1,1’-dibenzyl-4,4’-bipyridinium dichloride to change color and produce inversed images of the fingermark. By changing the applied potential, the optical properties of 1,1’-dibenzyl-4,4’-bipyridinium dichloride can be continuously and reversibly adjusted to optimize the visual contrast of fingermarks, so as to realize the detection of latent fingermarks on stainless steel surface. It is demonstrated that the fabricated electrochromic devices can detect the fingermarks on these types of surfaces within twenty seconds at −1.0∼−2.0 V. This work can qualify as a tangible improvement in fingermark detection of the natural fingermarks on the never-cleaned (more than 3 years) and curved surfaces of daily-used container, e. g. cup, and the handle of cleaning tool, mop.     

供/吸电子基团共轭桥联的双BODIPY衍生物的合成及性能

设计合成了4种对称的以不同供/吸电子基团为共轭桥、两端连接meso位苯或噻吩取代的新型氟化硼二吡咯甲川(BODIPY)衍生物;通过1H NMR,13C NMR和MS等手段对其进行了结构表征;并采用紫外吸收光谱、荧光发射光谱及循环伏安(CV)等方法研究了其光电性能.紫外光谱数据表明,BODIPY结构具有明显的特征吸收,中间的桥联基团无论是强供电子的苯并二噻吩(BDT)还是强吸电子的苯并噻二唑(BT)均不能使整个分子产生明显的分子内电子迁移(ICT).另一方面,meso位的取代基可与BODIPY核产生微弱的ICT,且meso位噻吩取代的分子比meso位苯环取代的分子表现出更强的ICT.紫外光谱数据和电化学测试结果表明,meso位噻吩取代的分子比meso位苯环取代的分子具有更低的氧化电位和更窄的能隙.     

聚多联苯2,6-二甲酰对苯二胺的力学性能模拟

设计了一类线型聚多联苯2,6-二甲酰对苯二胺聚合物,并对聚合物分子模型进行了计算机模拟,通过分子力学和力学性质模块的计算得到了聚多联苯2,6-二甲酰对苯二胺的一些力学参数.模拟结果表明,聚多联苯2,6-二甲酰对苯二胺类型芳酰胺聚合物通过自组装可以呈现类倒插蜂窝结构排列,除聚二联苯2,6-二甲酰对苯二胺和聚三联苯2,6-二甲酰对苯二胺以外,该系列聚合物在xy平面内均具有负泊松比.