Carbon Dioxide Fixation and Sulfate Sequestration by a Supramolecular Trigonal Bipyramid

The subcomponent self‐assembly of a bent dialdehyde ligand and different cationic and anionic templates led to the formation of two new metallosupramolecular architectures: a Fe^II₄L₆ molecular rectangle was isolated following reaction of the ligand with iron(II) tetrafluoroborate, and a M₅L₆ trigonal bipyramidal structure was constructed from either zinc(II) tetrafluoroborate or cadmium(II) trifluoromethanesulfonate. The spatially constrained arrangement of the three equatorial metal ions in the M₅L₆ structures was found to induce small‐molecule transformations. Atmospheric carbon dioxide was fixed as carbonate and bound to the equatorial metal centers in both the Zn₅L₆ and Cd₅L₆ assemblies, and sulfur dioxide was hydrated and bound as the sulfite dianion in the Zn₅L₆ structure. Subsequent in situ oxidation of the sulfite dianion resulted in a sulfate dianion bound within the supramolecular pocket.     

The Origin of Shape Sensitivity in Palladium‐Catalyzed Suzuki–Miyaura Cross Coupling Reactions

The shape sensitivity of Pd catalysts in Suzuki–Miyaura coupling reactions is studied using nanocrystals enclosed by well‐defined surface facets. The catalytic performance of Pd nanocrystals with cubic, cuboctahedral and octahedral morphologies are compared. Superior catalytic reactivity is observed for Pd NCs with {100} surface facets compared to {111} facets. The origin of the enhanced reactivity associated with a cubic morphology is related to the leaching susceptibility of the nanocrystals. Molecular oxygen plays a key role in facilitating the leaching of Pd atoms from the surface of the nanocrystals. The interaction of O₂ with Pd is itself facet‐dependent, which in turn gives rise to more efficient leaching from {100} facets, compared to {111} facets under the reaction conditions.     

Additive manufacturing for energy storage: Methods,designs and material selection for customizable 3D printed batteries and supercapacitors

Additive manufacturing and 3D printing in particular have the potential to revolutionize existing fabrication processes, where objects with complex structures and shapes can be built with multifunctional material systems. For electrochemical energy storage devices such as batteries and supercapacitors, 3D printing methods allows alternative form factors to be conceived based on the end use application need in mind at the design stage. Additively manufactured energy storage devices require active materials and composites that are printable, and this is influenced by performance requirements and the basic electrochemistry. The interplay between electrochemical response, stability, material type, object complexity and end use application are key to realising 3D printing for electrochemical energy storage. Here, we summarise recent advances and highlight the important role of methods, designs and material selection for energy storage devices made by 3D printing, which is general to the majority of methods in use currently.     

Palladium‐Templated Subcomponent Self‐Assembly of Macrocycles,Catenanes, and Rotaxanes

The reaction of 2,6‐diformylpyridine with diverse amines and Pd^II ions gave rise to a variety of metallosupramolecular species, in which the Pd^II ion is observed to template a tridentate bis(imino)pyridine ligand. These species included a mononuclear complex as well as [2+2] and [3+3] macrocycles. The addition of pyridine‐containing macrocyclic capping ligands allows for topological complexity to arise, thereby enabling the straightforward preparation of structures that include a [2]catenane, a [2]rotaxane, and a doubly threaded [3]rotaxane.     

Edge and terrace structure of CoTPP on Au(1 1 1) investigated by ultra-high vacuum scanning tunnelling microscopy at room temperature

Edge adsorption and terrace molecular domain structures of Cobalt(II) tetraphenylporphyrin (CoTPP) on Au(1 1 1) were investigated using STM at room temperature. Two different terrace domain structures were observed. These two arrangements were found to be enantiomorphous arrangements of the molecular assemblies, where the molecular rows rotate ±16° with respect to the [1 2 1] direction of Au(1 1 1). In both arrangements, most of the CoTPP molecules were imaged as one bright dot with four legs, corresponding to a planar conformation of the macrocycle. A small proportion of the CoTPP molecules appear as two bright dots, corresponding to a saddle shape of the macrocycle. Our results show that most of the saddle-deformed CoTPP molecules are distributed in the vicinity of the bridging sites of the reconstructed gold surface. Besides terrace domains, we found that several edge adsorption structures of CoTPP are also stable enough to be imaged and analysed in detail. Furthermore, the relationship between edge structures and terrace domains was revealed.     

Nanometer Scale Electrical Characterization of Artificial Mesostructures

In this article, we review advances in experimental techniques for the electrical characterization of artificial mesostructures from nanometer to micrometer size. As the scale of electronic devices is rapidly approaching the 100-nm benchmark, new tools are becoming necessary to study and characterize them. We are also at a point where new tools to fabricate these devices are becoming increasingly relevant. We discuss the various characterization techniques applicable to objects of this scale, with particular emphasis on scanned probe methods.     

Quantitative Acoustic Microscopy for Determination of Properties of Hard Coatings

 For quantitative assessment of the properties of hard coatings there is an increasing demand for testing methods with high reliability of the test results, especially concerning the independence of the method and the comparability between different laboratories. This includes the knowledge about all the factors which influence the test procedure itself, determination of best testing conditions, testing of these conditions in round-robins to get a view of the comparability of results, and formulation of guidelines for standardization. In a European project several test methods for hard coatings on steel were investigated for this purpose and the elastic moduli of the coating and coating thickness were determined non-destructively by means of quantitative acoustic microscopy. This method and the instruments available had not yet been certified in the fields of coatings simply owing to the absence of standardised signal processing, followed by the determination of sound velocities and materials parameter extraction. For this purpose four laboratories carried out investigations and measurements on reference samples and on two types of hard coatings (titanium nitride and C-doped chromium) on M2 tool steel.     

ZrCl4 as an efficient catalyst for a novel one-pot protection/deprotection synthetic methodology

A catalytic quantity of ZrCl 4 (20 mol %) was found to be an efficient catalyst for the one-pot esterification and deprotection of (5 S,6 R)-5,6-diacetoxyoct-7-enoic acid in good yields (44-62%) with a lactone formed as a minor byproduct. ZrCl 4 (10-20 mol %) was also sufficient to deprotect 1,3-dioxalane, bis-TBDMS ethers, and diacetate functional groups in excellent yields of up to 93%. ZrCl 4 (1-10 mol %) also promoted diol protection as the acetonide in 90% yield and acted as a trans-esterification catalyst for a range of esters.     

PHOTOLYSIS OF PHOSPHODIESTER BONDS IN PLASMID DNA BY HIGH INTENSITY UV LASER IRRADIATION

Abstract— The cleavage of phosphodiester bonds in DNA exposed to high intensity UV laser pulses in aerated aqueous solution has been investigated using a krypton fluoride excimer laser (248 nm) and bacterial plasmid DNA. The dependence of strand breakage on fluence and intensity has been studied in detail and shows that the process is non-linear with respect to intensity. The relationship between the quantum yield for strand breakage and intensity shows that the strand breakage reaction involves two-photon excitation of DNA bases. The quantum yield rises with intensity from a lower value of 7 times 10^-5 until a maximum value of 4.5 times 10^-4 is attained at intensities of 10¹¹ W m^-2 and above. This value is approximately fifty-fold higher than the quantum yield for strand breakage induced by exposure to low density UV irradiation (254 nm, 12 W m^-2). DNA sequencing experiments have shown that strand breakage occurs by the specific cleavage of the phosphodiester bond which lies immediately 3' to guanine residues in the DNA, leaving some alkali-labile remnant attached to the terminal phosphate. A mechanism for DNA strand breakage which involves the generation of guanine radical cations is proposed.     

多晶粒银纳米线形变机理对温度依赖性的分子动力学研究

基于大规模分子动力学仿真,研究了包含多个晶粒的柱状银纳米线在不同温度下沿轴向拉伸形变的行为。结果表明,当温度低于200 K时,含较大晶粒的体系中位错滑移是其形变的主要机理,最大应力随温度变化不显著。当环境温度高于200 K时,晶粒的滑动逐渐成为形变的主导因素,这一特征在含更小晶粒的体系内表现更明显。同时最大应力随温度显著降低。基于上述结果,进一步讨论了温度对Hall-Petch关系的影响。