Gas-Grain Modeling of Interstellar O2

Molecular oxygen (O\begin{document}$ _2 $\end{document}) is essential to human beings on the earth. Although elemental oxygen is rather abundant, O\begin{document}$ _2 $\end{document} is rare in the interstellar medium. It was only detected in two galactic and one extra-galactic region. The inconsistency between observations and theoretical studies is a big challenge for astrochemical models. Here we report a two-phase modeling research of molecular oxygen, using the Nautilus gas-grain code. We apply the isothermal cold dense models in the interstellar medium with two typical sets of initial elemental abundances, as well as the warm-up models with various physical conditions. Under cold dense conditions, we find that the timescales for gas-phase CO, O\begin{document}$ _2 $\end{document} and H\begin{document}$ _2 $\end{document}O to reach peak values are dependent on the hydrogen density and are shortened when hydrogen density increases. In warm-up models, O\begin{document}$ _2 $\end{document} abundances are in good agreement with observations at temperatures rising after 10\begin{document}$ ^5 $\end{document} yr. In both isothermal and warm-up models, the steady-state O\begin{document}$ _2 $\end{document} fractional abundance is independent of the hydrogen density, as long as the temperature is high enough (\begin{document}$ > $\end{document}30 K), at which O\begin{document}$ _2 $\end{document} is prevented from significant depleting onto grain surface. In addition, low density is preferable for the formation of O\begin{document}$ _2 $\end{document}, whether molecular oxygen is under cold conditions or in warm regions.     

超分子高分子化学进展

综述了超分子高分子化学近年来的进展,着重介绍固相聚合和毛杆高分子等方面的最新研究成果及应用展望,对超分子高分子化学的主要研究方法也作了扼要的介绍。     

SO2 Surface Chemistry on Metal Substrates

The surface chemistry, induced by thermal and non-thermal methods, of SO₂ on metal substrates is reviewed. The substrate temperature during dosing is important; regardless of metal, adsorption is dissociative at 300 K and molecular at 100 K. On Ni, Pd, and Pt, molecular adsorption occurs through the S and one O atom, and the molecular plane is perpendicular to the surface. However, on Ag and Cu, adsorption occurs only through the S with the molecular plane perpendicular to the surface. The differences can be attributed to the structure of the metal's molecular orbitals and their interactions with the SO₂ orbitals. Upon heating, SO₂ dissociates on all transition metal surfaces with the exception of Ag, Au, and Cu, where only molecular desorption occurs. On Pt, Fe, and Pd, additional reactions are observed between SO₂ and its dissociation products. The nonthermal reactions induced by photons and electrons for monolayer coverages of SO₂ on Ag (111) are dominated by molecular desorption. Desorption cross sections for 313 nm photons and 50eV electrons were 2.8 × 10^?20 cm² and ?1 × 10^?16 cm², respectively. Nonthermal excitation mechanisms and quenching processes as well as interesting characteristics of SO₂ under irradiation are also reviewed.     

Surface Organometallic Chemistry for Single-site Catalysis and Single-atom Catalysis

Although driven by different research interests, single-site catalysts and single-atom catalysts are both believed to be model systems bridging homogeneous and heterogeneous catalysis. The two concepts are similar but different. In this review, we will first explain the difference between single-atom catalysis and single-site catalysis, in terms of their goals, synthetic methods and coordination structures of corresponding catalysts. Then, we will introduce the surface organometallic chemistry method, a method traditionally used for synthesizing single-site catalyst. We will explain why it might benefit the single-atom catalysis community. At last, the choice of support to accommodate the method for synthesizing single-atom catalysts will be discussed.     

基于表面金属有机化学方法的硅胶表面氧化钛的制备及表征

以普通硅胶为载体, 采用表面金属有机化学合成技术, 通过“一锅”反应制备了硅胶表面金属有机钛化合物, 然后经高温煅烧获得了硅胶表面氧化钛. 采用傅里叶变换红外光谱(FTIR)、 X射线光电子能谱(XPS)、 热重分析(TG-DTA)及原子力显微镜(AFM)对硅胶表面金属有机钛化合物和表面氧化钛进行了结构表征. 结果表明, 高温煅烧过程中, 硅胶表面金属有机钛化合物不仅脱除了有机配体, 并且通氧使其表面“再生”羟基, 确保了钛的四配位形式不变; 氧化钛通过Si—O—Ti键锚定在硅胶表面, 呈分散、 孤立状态分布. 高温煅烧后, 硅胶的骨架结构保持完好.     

The Surface Chemical Bond

Adsorbed particles can be bound chemically to the surface of a solid (chemisorption). Modern variants of electron diffraction and electron spectroscopy now enable us to gain an insight into the nature of such surface chemical bonds, which play a key role in heterogenous catalysis and many other technically important phenomena such as adhesion, lubrication etc. Predominantly localized surface bonds can be compared to the covalent bonds in cluster compounds.     

A Coordination Chemist's View of Surface Science

Structure, a necessary element for an understanding of chemistry, has not been precisely defined, in molecular detail, for the surface species formed at a solid-gas interface. Dramatic advances in theory, instruments and experimental procedures have now provided the surface scientists with an impressive arsenal of structural and electronic probes. Chemistry in the form of the classic displacement reaction can also provide an insight to the structure of surface compounds. In fact, many of the experimental procedures and systematics of the coordination and organometallic chemist can be effectively utilized in a complementary fashion with surface physics techniques to gain a more definitive picture of chemisorption states and or reactions at a surface.     

Surface Coordination Chemistry: Corrosion Inhibition by Tetranuclear Cluster Formation of Iron with Salicylaldoxime

A tetranuclear iron cluster is the principal component of the purple coatings produced by treating a mild steel surface with a salicylaldoxime corrosion inhibitor. This was shown by comparison of the spectroscopic data with those of the cluster [{Fe(salH)(HsalH)}₄], which was obtained from FeCl₃ and salicylaldoxime (H₂salH) and has a distorted tetrahedral arrangement of Fe^III atoms coordinated by terminal (1−) and bridging (2−) salicylaldoximate ligands (the central core of the cluster is depicted).     

Electrochemistry of Methyl Viologen and Anthraquinonedisulfonate at Diamond and Diamond Powder Electrodes: The Influence of Surface Chemistry

The electrochemical behaviour of methyl viologen and anthraquinonedisulfonate was studied at electrodes produced from differing forms of diamond, including microcrystalline boron doped diamond, boron doped diamond powder and detonation nanodiamond powder. Two types of electrode pretreatment were employed to produce two dissimilar surface terminations: hydrophobic H‐terminated and hydrophilic O‐terminated. In the case of methyl viologen, it was found that the reduced neutral molecule adsorbed on all three electrodes if they were hydrogen terminated, but not if they were oxygen terminated. For anthraquinonedisulfonate, no adsorption was found on the solid diamond electrode, although again significant adsorption was noted on the powder electrodes, provided they were hydrogen terminated. The reasons underlying these observations are discussed in terms of hydrophobic and electrostatic interactions and the electrode morphology. The work provides information into the likely occurrence of adsorption and concomitant electrode fouling, which may be experienced in electroanalytical applications using solid and powdered forms of diamond.     

Preparative Solid State Chemistry: The Present Position

Two types of reaction are distinguished in solid state chemistry: those in which high mobility of the reactants is aimed at (which can be achieved by the use of high temperatures, by the introduction of defects, by the promotion of surface diffusion, or by means of chemical transport phenomena), and those reactions in which the nature of the products is determined by existing structural elements or lattice defects of the reactants. The importance of paying more attention than hitherto to reaction pathways in preparative solid state chemistry is pointed out.     

现代固态有机化学之父——Gerhard M.J.Schmidt

本文主要介绍了GerhardM.J.Schmidt教授的生平、代表性的科研工作及其意义、影响和应用,从中展现出他的优秀品质、治学精神、杰出成就以及影响力。Schmidt教授少年早慧,求学艰辛,天赋独特,痴迷科学,为科学事业奋斗终身,在多个领域都有着卓越的成就,其中以固态有机化学领域最具代表性。他在科研的同时还担任诸多行政职务,为魏茨曼研究所、以色列乃至全世界的科学发展做了许多贡献。     

Preparative Solid-State Chemistry with High-Power CO2 Lasers

The establishment of solid state chemistry as an independent field, which also has had a stimulating effect on material sciences, is a consequence of the experimental skill of chemists. The development of new methods led to an abundance of new compounds, the characteristic properties of which are linked with the solid state. The reaction temperature plays an important role in the synthesis of solid compounds; therefore, it is not surprising that a large number of the newly developed experimental techniques involve methods which can produce high temperatures on the openended temperature scale. Since the development of the CO₂ laser, the solidstate chemist has an excellent heat source available, and with the power available today the range of high temperatures possible has been extended considerably. A way is now open for producing metastable, “entropy-supported” high-temperature compounds and substances with anomalous oxidation states and with macroscopic defects.     

Modeling Surface Engineering: Use of Polymetallic Iron Cages and Computer Graphics To Understand the Mode of Action of a Corrosion Inhibitor

Simple organic molecules can have many functions. The active ingredient in the corrosion inhibitor 3-(4-methylbenzoyl)propionate works because it addresses the metal sites of a surface through carboxylate groups, forms hydrogen bonds with surface hydroxide groups (see picture), and provides excellent surface coverage through efficient packing of substituted aromatic groups.     

研究生全校公选课“表面物理化学”分类教学改革与实践

为满足学术型和应用型研究生以及交叉学科研究生培养的需要,对我校研究生全校公选课“表面物理化学”进行了教学改革和实践。建立了满足研究生分类培养的课程内容体系,基于不同类型研究生的学习需求和本科基础来组织实施教学和考核,教学中注重教学与科研相结合、理论与实践相统一,使课程适应两类研究生和交叉学科研究生人才培养的需要。。     

The Chemistry of Protactinium

Protactinium exhibits an ambivalent chemical behavior. In non-aqueous solutions and in the solid state, both quadrivalent and quinquevalent protactinium has properties which characterize it as a typical actinide element. On the other hand, investigations in aqueous solution show quinquevalent protactinium to be a homologue of niobium and tantalum. It exhibits – except in hydrofluoric acid solutions – a marked tendency to undergo irreversible hydrolysis and condensation reactions, which leads to the situation that tracer amounts (ca. 10^?12 mole/l) and macroscopic amounts (10^?3–10^?6 mole/l) of protactinium often behave differently. Reduction with strong reducing agents gives aqueous solutions of Pa(IV), the properties of which again correspond in general to those of Th(IV) and show no relation to Nb(IV). Our knowledge of the chemical behavior of this rare radioelement has been advanced, in particular, by the production in 1958–1960 of 100 g of pure protactinium – the largest amount so far – from residues of the British production of uranium.     

含硒表界面化学

硒是人体必需的一种微量元素, 本课题组近年的研究表明含硒化学键具有诸多独特的化学性质. 二硒键具有氧化还原双重响应性, 同时是一类光响应的动态共价键, 能够在可见光辐照下发生可逆的交换反应. 将含硒化学键这些独特的性质与表界面化学相结合可以赋予体系独特的响应行为. 本文综合评述了本课题组近年来在含硒表界面化学领域的研究进展: 采用单分子力谱揭示了含硒化学键相互作用的力学规律; 通过表界面化学实现了二硒键动态平衡的调控; 基于二硒键氧化还原及可见光响应性实现了表界面可逆修饰、 二维材料功能化及层层组装膜材料的制备, 在生物医用、 液体输运等领域具有潜在应用价值.     

基于贻贝仿生化学的分离功能材料

贻贝仿生的表面化学是近年来材料学、化学、生物医学等领域的交叉研究热点。多巴胺可以作为贻贝足丝蛋白(Mfp)超强黏附特性的模型分子,通过复杂的氧化-自聚和组装,形成多种功能的聚多巴胺(PDA)纳米涂层和纳米粒子,在分离膜、吸附材料、生物医用材料、生物黏结剂等领域有着广阔的应用前景。本研究小组近年来持续开展了基于贻贝仿生化学的分离功能材料制备与结构调控的研究工作,率先将多巴胺表面沉积方法应用于多孔分离膜表面的构建与功能化,提出了多巴胺的自聚-沉积过程模型,进而验证了PDA沉积层的纳滤分离特性,建立了一条简单方便的膜表面功能化与纳滤膜制备新途径。本文主要对基于贻贝仿生化学的分离功能材料,特别是分离膜的研究进展进行综述,并对将来的发展趋势进行展望。     

柔性电子学中的表界面化学

柔性电子作为新兴的研究热点, 涉及材料、 化学、 物理等多个基础学科的交叉, 以及在生物医用、 可穿戴设备及人工智能等多个领域的应用. 柔性电子设备的制造加工过程中会用到弹性基底、 导电层、 功能层等多种性质各异的材料, 其互相之间的整合受到它们表面性质和界面结合力的限制; 器件的功能、 可靠性、 对环境的敏感性等也受到了器件表界面性质的影响; 因此, 对材料和器件表界面的处理在柔性电子学中具有重要作用. 本文对柔性电子学中常用的表界面化学过程分为3大类进行介绍: 表面电化学过程, 基于特定化合物反应产生的电流制备电化学传感器, 利用电流/电压控制表面负载化合物; 表面修饰, 通过表面改性提高材料的加工性能, 共价修饰分子层或其它材料赋予器件特殊功能性质或保护层; 不同材料之间的界面连接, 通过共价连接或化学反应辅助的物理交联实现不同材料的结合, 提高柔性器件的稳定性, 实现柔性设备的整合. 对各应用进行总结和举例后, 讨论了存在的问题, 并对未来的发展方向及前景进行了展望.     

The Surface Chemistry of Water on Fe(100): A Density Functional Theory Study

The formation of water by hydrogenation of atomic oxygen is studied using density functional theory. Atomic oxygen preferentially adsorbs at the four‐fold hollow site, the hydroxyl group prefers the bridge site in a tilted configuration, and water is most stable when adsorbed at the top site with the two O? H bonds parallel to the Fe surface. Water formation by the hydrogenation of oxygen is a highly activated process on the Fe(100) surface, with similar activation energies, in the order of 1.1 eV, for the first and second hydrogen additions. A more favourable route for the addition of the second hydrogen atom involves the disproportionation of hydroxyl groups to form water and adsorbed oxygen. Dissociation of the OH is also likely since the activation energy is similar to that for disproportionation of 0.65 eV. Furthermore, the results show that the dissociation of water on Fe(100) is a non‐activated process: 0.16 eV for the zero‐coverage limit and 0.03 eV when surface oxygen is present. Herein, adsorption energies, structures and vibrational frequencies are presented for several adsorption states at 0.25 ML coverage, as well as the potential energy surface for water formation on Fe(100).