Methane storage in molecular nanostructures

We survey various molecular structures which have been proposed as possible nanocontainers for methane storage. These are molecular structures that have been investigated through either experiments, molecular dynamics simulations or mathematical modelling. Computational simulation and mathematical modelling play an important role in predicting and verifying experimental outcomes, but both have their limitations. Even though recent advances have greatly improved computations, due to the large number of atoms and force field calculations involved, computational simulations can still be time consuming as compared to an instantaneous mathematical modelling approach. On the other hand, underlying an ideal mathematical model, there are many assumptions and approximations, but such modelling often reveals the key physical parameters and optimal configurations. Here, we review methane adsorption for three conventional nanostructures, namely graphite, single and multi-walled carbon nanotubes, and nanotube bundles (including interstitial and groove sites), and we survey methane adsorption in other molecular structures including metal organic frameworks. We also include an examination of minimum binding energies, equilibrium distances, gravimetric and volumetric uptakes, volume available for adsorption, as well as the effects of temperature and pressure on the adsorption of methane onto these molecular structures.     

Li ion battery materials with core-shell nanostructures

Nanomaterials have some disadvantages in application as Li ion battery materials, such as low density, poor electronic conductivity and high risk of surface side reactions. In recent years, materials with core-shell nanostructures, which was initially a common concept in semiconductors, have been introduced to the field of Li ion batteries in order to overcome the disadvantages of nanomaterials, and increase their general performances in Li ion batteries. Many efforts have been made to exploit core-shell Li ion battery materials, including cathode materials, such as lithium transition metal oxides with varied core and shell compositions, and lithium transition metal phosphates with carbon shells; and anode materials, such as metals, alloys, Si and transition metal oxides with carbon shells. More recently, graphene has also been proposed as a shell material. All these core-shell nanostructured materials presented enhanced electrochemical capacity and cyclic stability. In this review, we summarize the preparation, electrochemical performances, and structural stability of core-shell nanostructured materials for lithium ion batteries, and we also discuss the problems and prospects of this kind of materials.     

纳米结构铁氧体磁性材料的制备和应用

铁氧体纳米磁性材料是一类非常重要的无机功能材料,其应用涉及到电子、信息、航天航空、生物医学等领域。综述了纳米结构铁氧体磁性材料化学制备方法的研究进展,分析了相关纳米结构铁氧体磁性材料的制备工艺对磁性能的影响,以及它们的应用,展望了研究和开发纳米结构铁氧体磁性材料的新性能和新技术的应用前景。     

Functional self-assembled DNA nanostructures for molecular recognition

Nucleic acids present a wonderful toolkit of structural motifs for nanoconstruction. Functional DNA nanostructures can enable protein recognition by the use of aptamers attached to a basic core shape formed by DNA self-assembly. Here, we present a facile, programmable strategy for the assembly of discrete aptamer-tagged DNA shapes and nanostructures that can function for molecular recognition and binding in an aqueous environment. These nanostructures, presented here to bind two different protein targets, are easily synthesized in large numbers, and are portable and stable over long periods of time. This construction modality can facilitate on-demand production of libraries of diverse shapes to recognize and bind proteins or catalyze reactions via functional nucleic acid tags.     

Nanoshocks in molecular materials

Nanoshocks are tiny but powerful laser-driven shock waves that can be used to produce large-amplitude compression in molecular materials on the picosecond time scale. When coupled with ultrafast molecular spectroscopy, the molecular response to nanoshocks can be probed in detail. Simple molecular systems (anthracene crystals) are used to characterize the nanoshock pulses. Well-characterized nanoshocks are used to study complex phenomena such as shock-induced chemical reactions, shock-induced orientation of energetic solids, and shock compression of organic polymers and proteins.     

Gravitational drainage of compressible organic materials

A model was developed to simulate drainage of compressible particle suspensions, and study how cake compression and volumetric load influence the process. The input parameters were settling velocity, cake resistance and compressibility. These parameters were found using a new experimental method. Dextran‐MnO₂ particle suspensions were drained as these resemble organic waste slurries with respect to settling and compressibility. It was demonstrated that cake compressibility must be taken into account to obtain adequate simulations. This implies that pressurized filtration resistances cannot be used for drainage simulations. In the filtration step, a distinct increase of dry matter from top to bottom of the cake was observed. During the subsequent consolidation, the cake compressed and a uniform dry matter profile was found. The final dry matter content of the cake increased with feed concentration and volumetric load. The drainage time increased proportionally with feed concentration and, more importantly, proportionally with squared volumetric load. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

生物质炭基材料在有机催化转化中的应用

近年来,生物质因具有富碳可再生、储量丰富、环境友好、价格低廉等特点被作为原料广泛应用于制备生物质炭基材料。本文综述了以生物质为原料衍生炭基材料作为催化剂在有机转化反应中的相关研究进展,重点介绍了杂原子掺杂、金属杂化策略所制备炭基催化材料在液相催化加氢、氧化、偶联等有机转化反应中的催化性能,进而阐明了炭基催化剂与催化活性之间的构效关系。最后,本文总结了生物质炭基催化剂在有机催化反应中的优势,指出了目前生物质衍生炭基催化剂材料合成和有机转化研究领域面临的挑战,并对此领域的未来发展趋势进行了分析与展望。     

Organic materials for organic electronic devices

In recent years, organic electronic devices which use organic materials as an active layer have gained considerable interest as light-emitting devices, energy converting devices and switching devices in many applications. In these organic electronic devices, the organic materials play a key role of managing the device performances and various organic materials have been developed to improve the device performances of organic electronic devices. In this paper, recent developments of organic electronic materials for organic light-emitting diodes and organic solar cells were reviewed.     

Outgassing of high temperature-resistant organic polymeric materials

Four polymeric materials, polyphenylene oxide, polyquinoline, acetylene substituted polyimide, and polybenzimidazole, reported to possess high-temperature resistance, were investigated in order. to determine their outgassing characteristics as related to their suitability for high temperature applications in confined structures. The materials were sequentially exposed to 150, 250 and 450°C for 3 h periods and the types and amounts of their outgassed products were determined. The amounts of outgassed- products were small from polyquinoline, acetylene substituted polyimide, and polybenzimidazole. It was concluded that those materials would be suitable for use in applications where high-temperature resistance (up to 450°C) is required, providing that normal ventilation is available. The quantity of outgassed products from polyphenylene oxide was too great to consider that material suitable for shipboard or other confined structure applications requiring high-temperature resistance.     

Rates of molecular vaporization of organic plasticizers

The kinetics of the molecular vaporization process of 21 plasticizers were investigated in detail. By both isothermal and nonisothermal kinetic methods, it was evident that 11 were quite pure single compounds, while 10 were clearly mixtures of compounds. For the single component species internal energies for vaporization and rates of volatilization are listed. The internal energies of vaporization are about one-half or less of values one can estimate from the additive factor method of Small. Thus, solubility parameters based on our experimental values are low by about 30 percent. From this and previous work on linear alkanes, it is concluded that in the molecular vaporization process, the large organic molecules studied evaporate approximately as spheres and hence low values for the energy of vaporization are obtained. Consequently, the difference between our experimental energy and that estimated from solubility parameters is the energy for extending the molecule in a vacuum environment.     

Optical materials based on molecular nanoparticles

A major part of contemporary nanomaterials research is focused on metal and semiconductor nanoparticles, constituted of extended lattices of atoms or ions. Molecular nanoparticles assembled from small molecules through non-covalent interactions are relatively less explored but equally fascinating materials. Their unique and versatile characteristics have attracted considerable attention in recent years, establishing their identity and status as a novel class of nanomaterials. Optical characteristics of molecular nanoparticles capture the essence of their nanoscale features and form the basis of a variety of applications. This review describes the advances made in the field of fabrication of molecular nanoparticles, the wide spectrum of their optical and nonlinear optical characteristics and explorations of the potential applications that exploit their unique optical attributes.     

Selection of barrier materials from molecular structure

A prediction technique for gas permeability from polymer structure has been developed on the basis of a specific free volume diffusion theory. In this theory, the free volume available per unit mass in a polymer structure controls the rate of gas diffusion and, hence, its rate of permeation. The smaller this specific free volume is, the more difficult the gas diffusion and, thus, the better its barrier to gases becomes. Specifically, the theory predicts a linear relationship between log (permeability) and (?1/specific volume). A number of existing polymers covering six orders of magnitude in CO₂ permeability and O₂ permeability were found to follow this correlation. The specific free volume in a polymer was obtained from group contribution calculations. As a result, the gas permeabilities become predictable from the specific volume in a polymer which, in turn, varies with its molecular structure. The advent of this specific free volume theory for gas permeation simplifies greatly the selection of barrier materials for packaging applications. For a given barrier application, a critical specific free volume is first defined from its gas barrier requirement. The polymer structures having specific free volumes smaller than the critical value are then identified. These are the polymers that would have the necessary barrier performance. By this theory, molecular structures, with string polar-to-polar interactions and hydrogen-bonding forces are found to be good barriers to CO₂ and O₂.     

有机化工的基础原料—一四氢呋喃

论述了四氢呋喃的基本性质、合成方法、应用及展望,指出了四氢呋喃是有机化工重要原料。     

含氮杂环类有机发光材料研究进展

含氮杂环类有机材料作为一类性能比较优良的发光材料,越来越受到人们的关注。本文主要介绍了近年来有机含氮杂环类发光材料的最新发展,重点综述了噁二唑环系、吡唑啉衍生物类和咔唑及其衍生物类发光材料的合成和性能。     

有机液体储氢材料的研究进展

氢气是一种清洁、高效的能量,被视为最具发展潜力的清洁能源,其存储和运输是影响氢能大规模应用的关键问题。常用的储氢方法有高压气态储氢、液化储氢、金属合金储氢和有机液体氢化物储氢等,本文综述了其中受到广泛关注的有机液体储氢材料,分析了多种有机液体储氢材料的储氢原理与特点,认为有机液体储氢容量大,可循环使用,更加高效安全。主要介绍了环己烷、甲基环己烷、十氢萘、咔唑和乙基咔唑等,重点对目前的国内外研究现状进行了阐述。根据分析结果,对其发展前景进行了展望,指出如果利用工业上能够大规模获取的化学原料,如萘系多环芳烃,开发高效低成本加氢脱氢催化剂,研究最适宜的加氢与脱氢条件,可大幅降低储氢成本,有利于氢能的大规模应用与发展。