Use of 1-alkyl-3-methylimidazolium l-lactates as both ligand and reaction media for AGET ATRP of acrylonitrile

Chiral ionic liquids, [C₂mim][LLA], [C₄mim][LLA] and [C₆mim][LLA] were firstly applied as both ligand and reaction media for atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) of acrylonitrile (AN) with ascorbic acid (VC) as reducing agent in the presence of air. A small but clear increase of polyacrylonitrile (PAN) isotacticity was observed for AGET ATRP of AN in [C₆mim][LLA] than in [C₆mim][BF₄]. PAN isotacticity markedly increased with the content of [C₆mim][LLA]. Compared with in [C₂mim][LLA] and [C₄mim][LLA], the rate of AGET ATRP of AN in [C₆mim][LLA] was fastest and the polymerization was best controlled. Well-defined PAN with molecular weight at 76,590, relatively narrower distribution at 1.27 and higher isotacticity at 0.37 was successfully prepared in [C₆mim][LLA].     

Molecular Ordering at the Interface Between Liquid Water and Rutile TiO2(110)

The pivotal importance of TiO₂ as a technological material involves most applications in an aqueous environment, but the single‐crystal TiO₂/bulk‐water interfaces are almost completely unexplored, since up to date solid/liquid interfaces are more difficult to access than surfaces in ultrahigh vacuum (UHV). Only a few techniques (as scanning probe microscopy) offer the opportunity to explore these systems under realistic conditions. The rutile TiO₂(110) surface immersed in high‐purity water is studied by in situ scanning tunneling microscopy. The large‐scale surface morphology as obtained after preparation under UHV conditions remains unchanged upon prolonged exposure to bulk water. Moreover, in contrast to UHV, atomically resolved images show a twofold periodicity along the [001] direction, indicative of an ordered structure resulting from the hydration layer. This is consistent with density‐functional theory based molecular dynamics simulations where neighboring interfacial molecules of the first water layer in contact with the bulk liquid form dimers. By contrast, this dimerization is not observed for a single adsorbed water monolayer, i.e., in the absence of bulk water.     

A Fast and Efficient Replacement of CTAB with MUA on the Surface of Gold Nanorods Assisted by a Water‐Immiscible Ionic Liquid

The synthesis and surface modification of gold nanorods (GNRs) is one of the most important and basic issues in nanoscience. Most of the widely investigated GNRs are coated with a cetyltrimethylammonium bromide(CTAB) bilayer. Here, a highly efficient method is proposed to replace CTAB from the surface of GNRs with a bifunctional 11‐mercaptoundecanoic acid in order to decrease the possible toxicity caused by CTAB. This ligand exchange is achieved in a biphasic mixture of an aqueous solution and a water‐immiscible ionic liquid (IL), [BMIM][Tf₂N]. That is, by mixing IL, mercaptoundecanoic acid (MUA)/IL (200 × 10^?3 m ) and a concentrated aqueous solution of GNRs together, followed by vortex stirring for 90 s, CTAB‐capped GNRs with varying aspect ratios can be turned into corresponding MUA‐capped GNRs with the same aspect ratio. Furthermore, the formed MUA‐capped GNRs can be obtained in a large quantity and stored as powders for easy use. The MUA‐capped GNRs with improved biocompatibility and colloidal stability are well suited for further biological functionalization and potential applications. This IL‐assisted ligand exchange can reverse the surface charge, enhance the stability of GNRs, and suppress its cytotoxicity.     

Electrons at the surface of quantum systems

Electrons can be trapped at the surfaces and interfaces of the condensed phases of quantum matter (in particular hydrogen and helium), where they form classical two-dimensional Coulomb systems. Apart from studying the intrinsic properties of these nearly ideal systems, like the transition from an electron gas to a Wigner solid, one can use the electrons also as a sensitive probe to investigate the surface of quantum liquids and solids. The examples presented here include the surface of solid H₂, He films, and the interface between liquid and solid He, where phenomena such as annealing, layering, and crystal growth are studied. In addition, the interaction between the electrons and long-wavelength interfacial modes leads to an electrohydrodynamic instability, which bears interesting similarities with other critical phenomena.     

The interfacial characteristic of SiCp/AZ91 magnesium matrix composites fabricated by stir casting

The particle/matrix interfaces in SiCp/AZ91 composite fabricated by stir casting were investigated using transmission electron microscope (TEM) equipped with ultra-thin window energy dispersive X-ray analysis (EDAX) system. Chemical reactions indeed occurred at the interfaces. According to EDAX results, the interfacial reaction products are considered to contain Al₄C₃, MgO, and Mg₂Si phases. The interfaces can be classified into three types (interfaces I, II, and III) according to morphological features of the interfaces: (1) for interface I, interfacial reaction products were in direct contact with the surface of SiCp; (2) for interface II, interfacial reaction products were not in direct contact with the surface of SiCp; (3) for interface III, interfacial reaction products were not observed at the interfaces, i.e., interface III was simply formed by the two surfaces of SiCp and matrix. Mg₁₇Al₁₂ and Al₈Mn₅ precipitate phases heterogeneously nucleated at the particle/matrix interfaces.     

Wrap‐Around Core–Shell Heterostructures of Layered Crystals

Engineered heterostructures create new functionality by integrating dissimilar materials. Combining different 2D crystals naturally produces two distinct classes of heterostructures, vertical van der Waals (vdW) stacks or 2D sheets bonded laterally by covalent line interfaces. When joining thicker layered crystals, the arising structural and topological conflicts can result in more complex geometries. Phase separation during one‐pot synthesis of layered tin chalcogenides spontaneously creates core–shell structures in which large orthorhombic SnS crystals are enclosed in a wrap‐around shell of trigonal SnS₂, forcing the coexistence of parallel vdW layering along with unconventional, orthogonally layered core–shell interfaces. Measurements of the optoelectronic properties establish anisotropic carrier separation near type II core–shell interfaces and extended long‐wavelength light harvesting via spatially indirect interfacial absorption, making multifunctional layered core–shell structures attractive for energy‐conversion applications.     

Vibrational Spectroscopy of Water with High Spatial Resolution

The ability to examine the vibrational spectra of liquids with nanometer spatial resolution will greatly expand the potential to study liquids and liquid interfaces. In fact, the fundamental properties of water, including complexities in its phase diagram, electrochemistry, and bonding due to nanoscale confinement are current research topics. For any liquid, direct investigation of ordered liquid structures, interfacial double layers, and adsorbed species at liquid–solid interfaces are of interest. Here, a novel way of characterizing the vibrational properties of liquid water with high spatial resolution using transmission electron microscopy is reported. By encapsulating water between two sheets of boron nitride, the ability to capture vibrational spectra to quantify the structure of the liquid, its interaction with the liquid‐cell surfaces, and the ability to identify isotopes including H₂O and D₂O using electron energy‐loss spectroscopy is demonstrated. The electron microscope used here, equipped with a high‐energy‐resolution monochromator, is able to record vibrational spectra of liquids and molecules and is sensitive to surface and bulk morphological properties both at the nano‐ and micrometer scales. These results represent an important milestone for liquid and isotope‐labeled materials characterization with high spatial resolution, combining nanoscale imaging with vibrational spectroscopy.     

Volumetric and Isentropic Compressibility Behavior of Ionic Liquid, 1-Propyl-3-Methylimidazolium Bromide in Acetonitrile,Dimethylformamide, and Dimethylsulfoxide at <Emphasis Type="Italic">T</Emphasis> = (288.15 to 308.15) K

Density and speed-of-sound data for 1-propyl-3-methylimidazolium bromide ([C₃mim][Br]) + acetonitrile (MeCN), [C₃mim][Br] + dimethylformamide (DMF), and [C₃mim][Br] + dimethylsulfoxide (DMSO) binary mixtures in the dilute concentration region are reported at T = (288.15 to 308.15) K. From these data, apparent molar volume, isentropic compressibility, excess molar volume, and isentropic compressibility deviation values have been calculated. Negative deviations from the ideal behavior of both molar volume and isentropic compressibility have been observed for all systems investigated in this study. It has been found that deviations from ideal behavior for the [C₃mim][Br] + MeCN system are larger than those for the [C₃mim][Br] + DMF system which, in turn, are larger than those for the [C₃mim][Br] + DMSO system. The results have been interpreted in terms of ion–dipole interactions and structural factors of the ionic liquid and investigated organic solvents.     

AGET ATRP of acrylonitrile with ionic liquids as reaction medium without any additional ligand

Atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) of acrylonitrile (AN) was carried out for the first time in 1-methylimidazolium acetate ([mim][AT]), 1-methylimidazolium propionate([mim][PT]), and 1-methylimidazolium butyrate ([mim][BT]), respectively. The polymerization was approached by using ascorbic acid (VC) as a reducing agent, ethyl 2-bromoisobutyrate (EBiB) as initiator, only FeBr₃ as catalyst without any additional ligand. Kinetic studies showed that both AGET ATRP of AN in the absence of oxygen and in the presence of air proceeded in a well-controlled manner. Under the same conditions, the polymerization in the presence of air provided rather slower reaction rate and showed better control of molecular weight and its distribution than in the absence of oxygen. The sequence of the apparent polymerization rate constants of AGET ATRP of AN in three ionic liquids was k_app([mim][AT]) > k_app([mim][PT]) > k_app([mim][BT]). The living nature of the polymerization was confirmed by chain end analysis and block copolymerization of methyl methacrylate with polyacrylonitrile as macroinitiator. All the three ionic liquids and FeBr₃ could be recycled and reused and had no effect on the living nature of polymerization.     

Ultra‐Smooth,Chemically Functional Silica Surfaces for Surface Interaction Measurements and Optical/Interferometry‐Based Techniques

The study of interfacial phenomena is central to a range of chemical, physical, optical, and electromagnetic systems such as surface imaging, polymer interactions, friction/wear, and ion‐transport in batteries. Studying intermolecular forces and processes of interfaces at the sub‐nano scale has proven difficult due to limitations in surface preparation methods. Here, we describe a method for fabricating reflective, deformable composite layers that expose an ultra‐smooth silica (SiO₂) surface (RMS roughness < 0.4 nm) with interferometric applications. The robust design allows for cleaning and reusing the same surfaces for over a week of continuous experimentation without degradation. The electric double‐layer forces measured using the composite surfaces are within 10% of the theoretically predicted values. We also demonstrate that standard chemisorption and physisorption procedures on silica can be applied to chemically modify the surfaces; as a demonstration of this, the composite surfaces are successfully modified with octadecyltrichlorosilane (OTS) to study their hydrophobic interactions in water using a surface force apparatus (SFA). These composite surfaces provide a basis for the preparation of a variety of new surfaces, and should be particularly beneficial for the SFA and colloidal probe methods that employ optical/interferometric and electrochemical techniques, enabling characterization of previously unattainable surface and interfacial phenomena.

     

Facile ultrasound-assisted synthesis of ZnO nanorods in an ionic liquid

ZnO nanocrystals have been synthesized by ultrasound-assisted synthesis from Zn(CH₃COO)₂2H₂O and NaOH in the neat room-temperature ionic-liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C₄mim][Tf₂N]. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the formed ZnO nanocrystals are of rod like shape with lengths from 50 to 100 nm and diameters of about 20 nm. X-ray diffraction (XRD) confirms the crystallinity as well as the sample purity. The band gap of the as-prepared ZnO nanorods was estimated to be 3.31 eV from UV–Vis absorption measurements. The photoluminescence spectrum shows the characteristic greenish emission of ZnO at room temperature (λ_max = 563 nm). The ZnO bonding levels have been determined by X-ray photoelectron spectroscopy (XPS). Nitrogen adsorption–desorption measurements show typical samples to have a specific surface area of 49.93 m²/g.     

Dual‐Phase Single‐Ion Pathway Interfaces for Robust Lithium Metal in Working Batteries

The lithium (Li) metal anode is confronted by severe interfacial issues that strongly hinder its practical deployment. The unstable interfaces directly induce unfavorable low cycling efficiency, dendritic Li deposition, and even strong safety concerns. An advanced artificial protective layer with single‐ion pathways holds great promise for enabling a spatially homogeneous ionic and electric field distribution over Li metal surface, therefore well protecting the Li metal anode during long‐term working conditions. Herein, a robust dual‐phase artificial interface is constructed, where not only the single‐ion‐conducting nature, but also high mechanical rigidity and considerable deformability can be fulfilled simultaneously by the rational integration of a garnet Al‐doped Li_6.75La₃Zr_1.75Ta_0.25O₁₂‐based bottom layer and a lithiated Nafion top layer. The as‐constructed artificial solid electrolyte interphase is demonstrated to significantly stabilize the repeated cell charging/discharging process via regulating a facile Li‐ion transport and a compact Li plating behavior, hence contributing to a higher coulombic efficiency and a considerably enhanced cyclability of lithium metal batteries. This work highlights the significance of rational manipulation of the interfacial properties of a working Li metal anode and affords fresh insights into achieving dendrite‐free Li deposition behavior in a working battery.     

The interface electronic structure of thiol terminated molecules on cobalt and gold surfaces

The bonding strength and interfacial electronic properties of biphenyldimethyldithiol (HS–CH₂–C₆H₄–C₆H₄–CH₂–SH) adsorbed on Au(111) and polycrystalline cobalt are identified from combined photoemission and inverse photoemission. In order to develop a better understanding of the thiol functional group to metal surface interaction, the stable orientation, bonding site, bonding strength and interfacial electronic properties of methylthiol (S–CH₃) adsorbed on Au(111) and Co(0001) have been determined by ab initio density functional calculations. Both experiment and theory suggest that thiol bonding to cobalt surfaces is stronger compared to gold surfaces. The transfer of charge toward the adsorbed sulfur is greater for the thiols on cobalt than on gold.     

Characterisation of Surface Properties,Adsorbates and Functional Groups on Polycrystalline Oxides by Ultraviolet Photoelectron Spectroscopy (UPS)

Ultraviolet photoelectron spectroscopy (UPS), which is known as a powerful technique in the surface science of single crystals, loses much of its analytical potential when applied to rough, non‐ordered complex surfaces of real materials. The paper discusses the question if there are relevant applications of UPS in the analysis of real complex oxide surfaces. It is shown that this technique provides high surface sensitivity combined with chemical sensitivity, which allows to differentiate compounds and adsorbates on surfaces. It is described how UPS contributed to an investigation of depth profiles of the reduction degree in partly reduced V₂O₅. Studies of oxide segregation on mixed‐oxide surfaces (Bi‐Mo‐O, Ca‐Ce‐O) and on titania‐supported oxides (MoO₃, V₂O₅) and of adsorbates and functional groups (H₂O, OH, CO₂) on Ca‐Ce‐O mixed‐oxide surfaces are reported. It is demonstrated that UPS is a highly useful complementary technique in surface‐analytical studies performed with X‐ray photoelectron spectroscopy and Ion scattering spectroscopy. Its application is, however, limited by its high sensitivity to surface charging, which requires to measure spectra at elevated temperatures and excludes wide bandgap insulators.     

Growth of monocrystalline CdS films on mica surfaces through amorphous interfacial layers of silicon monoxide and carbon by chemical transport reactions

The oriented crystallization of CdS through amorphous interfacial layers of silicon monoxide and carbon by the method of chemical transport reactions has been studied. Cleaved mica (muscovite) single crystals were used as substrates. The interfacial layer thicknesses ranged from 70 to 150 Å. The informative ability of the interfacial layers was checked using the method of decoration with anthraquinone. Epitaxial CdS films 3–15 μm thick were obtained on top of the amorphous interfacial layers, with the (0001) CdS plane parallel to the (001) cleavage plane of mica and the direction [10$\text{1}$0]_CdS coinciding with [110]_mica, which corresponds to the orientation of CdS films prepared directly on the mica surface. The structural perfection of CdS films obtained through interfacial silicon monoxide and carbon layers was practically the same as that of films grown on the mica surface with no interfacial layers. For interfacial layer thicknesses exceeding 120 Å for SiO and 100 Å for carbon, the informative properties of the layers vanished and the CdS films were polycrystalline. The suggestion is made that chemical transport reactions leading to oriented crystallization can proceed without direct contact of the reacting components with the surface of the single-crystal substrates.     

Hydrophobic,Electrostatic, and Dynamic Polymer Forces at Silicone Surfaces Modified with Long‐Chain Bolaform Surfactants

Surfactant self‐assembly on surfaces is an effective way to tailor the complex forces at and between hydrophobic‐water interfaces. Here, the range of structures and forces that are possible at surfactant‐adsorbed hydrophobic surfaces are demonstrated: certain long‐chain bolaform surfactants—containing a polydimethylsiloxane (PDMS) mid‐block domain and two cationic α, ω‐quarternary ammonium end‐groups—readily adsorb onto thin PDMS films and form dynamically fluctuating nanostructures. Through measurements with the surface forces apparatus (SFA), it is found that these soft protruding nanostructures display polymer‐like exploration behavior at the PDMS surface and give rise to a long‐ranged, temperature‐ and rate‐dependent attractive bridging force (not due to viscous forces) on approach to a hydrophilic bare mica surface. Coulombic interactions between the cationic surfactant end‐groups and negatively‐charged mica result in a rate‐dependent polymer bridging force during separation as the hydrophobic surfactant mid‐blocks are pulled out from the PDMS interface, yielding strong adhesion energies. Thus, (i) the versatile array of surfactant structures that may form at hydrophobic surfaces is highlighted, (ii) the need to consider the interaction dynamics of such self‐assembled polymer layers is emphasized, and (iii) it is shown that long‐chain surfactants can promote robust adhesion in aqueous solutions.     

Behavior of UO<Subscript>2</Subscript> in a room-temperature ionic liquid in the presence of AlCl<Subscript>3</Subscript>

A study was made of interaction between AlCl₃ and room-temperature ionic liquid (RTIL) [C₈H₁₅N₂][N(SO₂CF₃)₂], or BuEtIm-Tf₂N, and of anodic dissolution in RTIL of UO₂ and of a simulated oxide fuel at 297–302 K, depending on the AlCl₃ concentration. It was shown that anodic dissolution of UO₂ pellets and a UO₂-Al mixture in RTIL yields soluble uranium species. Potentiostatic electrolysis of the resulting solutions can yield uranium compounds at the cathode, though with low current efficiencies. The role of AlCl₃ in these processes was suggested. A heterophase reaction between UO₂ and AlCl₃ was studied, depending on the content of AlCl₃ in solution. It was found that the exchange reaction products, soluble uranium species, are accumulated in solution only at the molar ratio AlCl₃/Tf₂N > 1.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 536–539.Original Russian Text Copyright © 2004 by Smolenskii, Bove, Borodina, Bychkov, Osipenko.     

High-performance polymer coatings for carbon steel heat exchanger tubes in geothermal environments

The most critical issue in developing thermal conductive coatings for the interior surfaces of heat exchanger tubes made from mild carbon steel (MCS), which are used in geothermal power plants at temperatures ranging from 110° to 89°C, is the deposition of scales. These scales, induced by the brine, chemically adhere to the coating surfaces. One of the major factors governing the formation of a strong interfacial bond at interfaces between the coatings and scales was the brine-promoted hydrothermal oxidation of the coatings. In seeking coating unsusceptible to hydrothermal oxidation, two semi-crystalline thermoplastic polymers, polyphenylenesulfide (PPS) and polytetrafluoroethylene (PTFE)-blended PPS, were applied as interior surface coatings to the zinc phosphated MCS tubes. The PPS coating surfaces suffered some oxidation caused by their chemical affinity for FeCl₂ in geothermal brine. FeCl₂-promoted oxidation of PPS surfaces not only incorporated more oxygen into them, generating a sulfide sulfone sulfonic acid conformational transformation within the PPS, but also caused the disintegration of PPS, yielding fragmental polychloroaryl compound and ferrous sulfate (FeSO₄) derivatives. The FeSO₄ reaction product formed at the interfaces between the scale and PPS coating was soluble in water, so that the coatings could be easily removed by highly pressurized water. The oxidation of PPS was considerably inhibited by blending PTFE into it, forming coating surface unsusceptible to hydrothermal oxidation reactions with hot brine. The major reason for such inhibition of oxidation was the formation of a chemically inert PTFE layer segregated from the PPS layer at the outermost surface site of the coating. Hence, the scale easily flaked off from the PTFE-blended PPS coating surfaces. This characteristic of surface was similar to that of the stainless steel surfaces. Nevertheless, both PPS and PTFE-blended PPS coatings can be classified as scale-free coatings.     

Modeling organic surfaces with self-assembled monolayers

The interfacial properties of organic materials are of critical importance in many applications, especially the control of wettability, adhesion, tribology, and corrosion. The relationships between the microscopic structure of an organic surface and its macroscopic physical properties are, however, only poorly understood. This short review presents a model system that has the ease of preparation and the structural definition required to provide a firm understanding of interfacial phenomena. Long-chain thiols, HS(CH₂)_nX, adsorb from solution onto gold and form densely packed, oriented monolayers. By varying the terminal functional group, X, of the thiol, organic surfaces can be created having a wide range of structures and properties. More, complex systems can be constructed by coadsorbing two or more thiols with different terminal functional groups or with different chain lengths onto a common gold substrate. By these techniques, controlled degrees of disorder can be introduced into model surfaces. We have used these systems to explore the relationships between the microscopic structure of the monolayers on a molecular and supramolecular scale and their macroscopic properties. Wettability is a macroscopic interfacial property that has proven of particular interest.     

[C_4mim][BF_4]粘度的模拟与实验

为了研究离子液体的粘度特性,以1-丁基-3-甲基咪唑四氟硼酸盐([C4mim][BF4])离子液体为研究对象进行模拟计算与实验测试.基于分子动力学原理,编译了离子液体粘度的模拟计算程序,对[C4mim][BF4]离子液体完成了粘度模拟计算.搭建了粘度测试系统,进行离子液体的粘度测试.通过实验数据与模拟数据的对比,验证了模拟结果的准确性.另外,根据模拟粘度值的拟合曲线,分析了离子液体粘度的变化规律.同时,通过与水粘度的比对研究,阐述了[C4mim][BF4]离子液体的粘度特点.