Phthalocyanine molecular nanowires that were prepared using porous alumina as a template: Development in the sample preparation procedure to evaluate electronic properties

We have proposed the synthesis of organic molecular nanowires using porous alumina as a template. We also proposed the use of a magnetic field to control the molecular packing structure in the nanowires. In this paper, we developed the method to evaluate the electronic properties of the nanowire of a phthalocyanine derivative that was synthesized using porous alumina as a template. The developed method facilitates the study in the organic molecular nanowires that were synthesized using templates and helps their use in future electronic devices.     

Environmental dependence of bonding: A challenge for modelling of intermetallics and fusion materials

Bridging the gap between electronic and atomistic levels plays a crucial role in multi-scale modelling of mechanical behaviour of materials. In this review, we summarise a methodology for linking systematically these two levels starting from the first-principles density functional theory and proceeding via the screened tight-binding approximation to development of reliable and transferable many-body interatomic bond-order potentials. We focus our investigations on material properties related to the electron-to-atom ratio. An immediate area of application is studies of the structure and properties of crystal defects in transition metals and intermetallic compounds based on transition metals, where the mixed character of covalent and metallic bonds represents a very challenging issue for understanding mechanical properties at the engineering scale. The need for environmental dependence of bond-order potentials as well as the implication of screening effects on bonding properties of alloys are discussed in connection with modelling of the core structure of dislocations in materials with negative Cauchy pressures and in body-centered cubic (bcc) transition metals. The latter are prime candidates as fusion power-plant materials. We discuss our current work on multiscale modelling, the behaviour of bcc materials under high-energy neutron irradiation, and emphasize the importance of quantum-mechanics in constructing reliable interatomic potentials for large scale molecular dynamic simulations.     

Anharmonic analysis of defective crystals with many-body interactions using symmetry reduction

In this paper we first classify and formulate various types of defects with respect to their symmetries and then show that with this general formulation, one can study the structures and energetics of defects in different crystalline materials effectively. We present all the calculations for the embedded-atom-type potentials but the formulation can, in principle, be applied for any many-body interatomic potential. As examples of defects in crystals with many-body interactions, we study point defects, free surfaces and grain boundaries in fcc Cu and grain boundaries in NiAl. We discuss free surface modelling by relaxing both a semi-infinite lattice and a slab with increasing finite thickness. We demonstrate through several numerical examples that our general framework of anharmonic lattice statics can be used for comparing different interatomic potentials in terms of the structure and energy they predict for a given defect. In the case of fcc Cu, we show how both the structures and energetics of different defects can strongly depend on the choice of potentials.     

Large Magnetoresistance through a Single Molecule due to a Spin-Split Hybridized Orbital

Using organic materials in spintronic devices raises a lot of expectation for future applications due to their flexibility, low cost, long spin lifetime, and easy functionalization. However, the interfacial hybridization and spin polarization between the organic layer and the ferromagnetic electrodes still has to be understood at the molecular scale. Coupling state-of-the-art spin-polarized scanning tunneling spectroscopy and spin-resolved ab initio calculations, we give the first experimental evidence of the spin splitting of a molecular orbital on a single non magnetic C(60) molecule in contact with a magnetic material, namely, the Cr(001) surface. This hybridized molecular state is responsible for an inversion of sign of the tunneling magnetoresistance depending on energy. This result opens the way to spin filtering through molecular orbitals.     

From elastic homogenization to upscaling of non-Newtonian fluid flows in porous media

Upscaling behaviors of heterogeneous microstructures to define macroscopic effective media is of major interest in many areas of computational mechanics, in particular those related to materials and processes engineering. In this paper, we explore the possibility of defining a macroscopic behavior manifold from microscopic calculations, and then use it directly for efficiently performing manifold-based simulations at the macroscopic scale. We consider in this work upscaling of non-Newtonian flows in porous media, and more particularly the ones involving short-fibre suspensions.     

Metal–Organic Framework‐Based Nanomedicine Platforms for Drug Delivery and Molecular Imaging

Metal–organic frameworks (MOFs), which are a unique class of hybrid porous materials built from metal ions and organic linkers, have attracted significant research interest in recent years. Compared with conventional porous materials, MOFs exhibit a variety of advantages, including a large surface area, a tunable pore size and shape, an adjustable composition and structure, biodegradability, and versatile functionalities, which enable MOFs to perform as promising platforms for drug delivery, molecular imaging, and theranostic applications. In this article, the recent research progress related to nanoscale metal–organic frameworks (NMOFs) is summarized with a focus on synthesis strategies and drug delivery, molecular imaging, and theranostic applications. The future challenges and opportunities of NMOFs are also discussed in the context of translational medical research. More effort is warranted to develop clinically translatable NMOFs for various applications in nanomedicine.     

From the computer to the laboratory: materials discovery and design using first-principles calculations

The development of new technological materials has historically been a difficult and time-consuming task. The traditional role of computation in materials design has been to better understand existing materials. However, an emerging paradigm for accelerated materials discovery is to design new compounds in silico using first-principles calculations, and then perform experiments on the computationally designed candidates. In this paper, we provide a review of ab initio computational materials design, focusing on instances in which a computational approach has been successfully applied to propose new materials of technological interest in the laboratory. Our examples include applications in renewable energy, electronic, magnetic and multiferroic materials, and catalysis, demonstrating that computationally guided materials design is a broadly applicable technique. We then discuss some of the common features and limitations of successful theoretical predictions across fields, examining the different ways in which first-principles calculations can guide the final experimental result. Finally, we present a future outlook in which we expect that new models of computational search, such as high-throughput studies, will play a greater role in guiding materials advancements.     

Tight-binding molecular dynamics for materials simulations

Summary Tight-binding molecular dynamics has recently emerged as a useful method for atomistic simulation of the structural, dynamical and electronic properties of realistic materials. The method incorporates quantum-mechanical calculations into molecular dynamics through an empirical tight-binding Hamiltonian and bridges the gap between ab initio molecular dynamics and simulations using empirical classical potentials. In this paper, we review the accuracy, efficiency, and predictive power of the method and discuss some opportunities and challenges for future development.     

Atomistic calculations and materials informatics: A review

In recent years, there has been a large effort in the materials science community to employ materials informatics to accelerate materials discovery or to develop new understanding of materials behavior. Materials informatics methods utilize machine learning techniques to extract new knowledge or predictive models out of existing materials data. In this review, we discuss major advances in the intersection between data science and atom-scale calculations with a particular focus on studies of solid-state, inorganic materials. The examples discussed in this review cover methods for accelerating the calculation of computationally-expensive properties, identifying promising regions for materials discovery based on existing data, and extracting chemical intuition automatically from datasets. We also identify key issues in this field, such as limited distribution of software necessary to utilize these techniques, and opportunities for areas of research that would help lead to the wider adoption of materials informatics in the atomistic calculations community.     

Base-selective adsorption of nucleosides to pore-engineered nanocarbon, carbon nanocage

Selective molecular recognition is an important subject in supramolecular science as well as in practical applications such as sensing, drug delivery, and biomedical processes. In this research we have investigated adsorption behavior of nucleosides (adenosine, guanosine, and thymidine) onto various porous supports. When compared with mesoporous silica, porous carbons exhibit superior adsorptive performance. We serendipitously observed a pronounced selectivity between purine-base and pyrimidine-base nucleosides by carbon naonocage. These findings are useful for design of materials for applications in adsorption-based separations and as column stationary phases for separation of costly and important biomolecules.     

Recent Progress in Metal‐Free Covalent Organic Frameworks as Heterogeneous Catalysts

Covalent organic frameworks (COFs), connecting different organic units into one system through covalent bonds, are crystalline organic porous materials with 2D or 3D networks. Compared with conventional porous materials such as inorganic zeolite, active carbon, and metal‐organic frameworks, COFs are a new type of porous materials with well‐designed pore structure, high surface area, outstanding stability, and easy functionalization at the molecular level, which have attracted extensive attention in various fields, such as energy storage, gas separation, sensing, photoluminescence, proton conduction, magnetic properties, drug delivery, and heterogeneous catalysis. Herein, the recent advances in metal‐free COFs as a versatile platform for heterogeneous catalysis in a wide range of chemical reactions are presented and the synthetic strategy and promising catalytic applications of COF‐based catalysts (including photocatalysis) are summarized. According to the types of catalytic reactions, this review is divided into the following five parts for discussion: achiral organic catalysis, chiral organic conversion, photocatalytic organic reactions, photocatalytic energy conversion (including water splitting and the reduction of carbon dioxide), and photocatalytic pollutant degradation. Furthermore, the remaining challenges and prospects of COFs as heterogeneous catalysts are also presented.     

Orientation-dependent ionization energies and interface dipoles in ordered molecular assemblies

Although an isolated individual molecule clearly has only one ionization potential, multiple values are found for molecules in ordered assemblies. Photoelectron spectroscopy of archetypical pi-conjugated organic compounds on metal substrates combined with first-principles calculations and electrostatic modelling reveal the existence of a surface dipole built into molecular layers. Conceptually different from the surface dipole at metal surfaces, its origin lies in details of the molecular electronic structure and its magnitude depends on the orientation of molecules relative to the surface of an ordered assembly. Suitable pre-patterning of substrates to induce specific molecular orientations in subsequently grown films thus permits adjusting the ionization potential of one molecular species over up to 0.6 eV via control over monolayer morphology. In addition to providing in-depth understanding of this phenomenon, our study offers design guidelines for improved organic-organic heterojunctions, hole- or electron-blocking layers and reduced barriers for charge-carrier injection in organic electronic devices.     

Engineering Homochiral Metal‐Organic Frameworks for Heterogeneous Asymmetric Catalysis and Enantioselective Separation

Owing to the potential applications in technological areas such as gas storage, catalysis, separation, sensing and nonlinear optics, tremendous efforts have been devoted to the development of porous metal‐organic frameworks (MOFs) over the past ten years. Homochiral porous MOFs are particularly attractive candidates as heterogeneous asymmetric catalysts and enantioselective adsorbents and separators for production of optically active organic compounds due to the lack of homochiral inorganic porous materials such as zeolites. In this review, we summarize the recent research progress in homochiral MOF materials, including their synthetic strategy, distinctive structural features and latest advances in asymmetric heterogeneous catalysis and enantioselective separation.     

Determination of the thermal conductivity of foam aluminum

We present calculations and experimental data on determination of the thermal conductivity of porous foam aluminum materials. We analyze the possibility of their use for thermal insulation.     

Organic against inorganic electrodes grown onto polymer substrates for flexible organic electronics applications

One of the most challenging topics in the area of organic electronic devices is the growth of transparent electrodes onto flexible polymeric substrates that will be characterized by enhanced conductivity in combination with high optical transparency. An essential aspect for these materials is their synthesis and/or microstructure which define the transparency, the stability and the interfacial chemistry which in turn determine the performance and stability of the organic electronic devices, such as organic light emitting diodes, organic photovoltaics, etc.In this work, we will discuss the latest advances in the growth of organic (e.g. PEDOT:PSS) and inorganic (e.g. zinc oxide-ZnO, indium tin oxide-ITO) conductive materials and their deposition onto flexible polymeric substrates. We will compare the optical, structural, nano-mechanical and nano-topographical properties of the inorganic and organic materials and we investigate the effect of their structure on their properties and functionality. In the case of the organic conductive materials, we will discuss the effects of PEDOT:PSS weight ratios and the various spin speeds on their optical and electrical properties. Furthermore, in the case of ZnO the growth mechanisms, interface phenomena, crystallinity and optical properties of ZnO thin films grown onto polymer and hybrid (inorganic-organic) flexible substrates will be also discussed.     

颗粒型相变储能复合材料

以多孔介质和有机相变物质复合而成颗粒型相变储能复合材料,研究了其相变储能性能、耐久性能以及该复合材料在建筑物综合节能方面的功效。研究结果表明:有机相变物质可渗入多孔介质中从亚微米到数百微米的孔径空间内,占据大部分孔空间,形成的复合材料具有显著的相变储能功能和优良的耐久性能。复合材料的相变储能性能一方面受到有机相变物质在多孔介质中体积含量的影响,另一方面受到多孔介质孔结构骨架的影响。与传统保温隔热材料——膨胀珍珠岩相比,相变储能复合材料具有更强的建筑综合节能功效。      

A magnetic recording simulation program having an improved fit to actual hysteresis loops

In recent years a better understanding of the magnetic recording process has resulted from self-consistent iterative calculations of the magnetization transition induced in the recording medium. One important limitation on these calculations has been the difficulty in fitting realistic hysteresis loops into these calculations. It is not practical to include the actual hysteresis loops, so the practice has been to approximate them by various plausible models. However, none of these models fit the actual loops as closely as would be desired. In this paper, we avoid modelling the major loops, but approximate them using spline interpolation. We demonstrate, by comparison with experimental loops, that the actual loops can be approximated much more closely than with an analytic model. A criterion for deriving the minor loops is given, and we demonstrate a generally better fit of the initial minor loops than that obtained from a model. A self-consistent iterative calculation is made using both an analytic model and the spline approximated loops. We find that the choice of loop model noticeably affects the calculated magnetization distribution and that the spline approximated loops lead to a transition width which more closely matches the width estimated from an experimental single readback pulse. In summary, we demonstrate that good simulation of the hysteresis loops can be significant and discuss a simple approximation technique from which an excellent fit to actual loops can be obtained.     

Steering molecular organization and host-guest interactions using two-dimensional nanoporous coordination systems

Metal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation. The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks. Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C(60) guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions.     

Charge transport physics of conjugated polymer field-effect transistors

Field‐effect transistors based on conjugated polymers are being developed for large‐area electronic applications on flexible substrates, but they also provide a very useful tool to probe the charge transport physics of these complex materials. In this review we discuss recent progress in polymer semiconductor materials, which have brought the performance and mobility of polymer devices to levels comparable to that of small‐molecule organic semiconductors. These new materials have also enabled deeper insight into the charge transport physics of high‐mobility polymer semiconductors gained from experiments with high charge carrier concentration and better molecular‐scale understanding of the electronic structure at the semiconductor/dielectric interface.     

Palladium‐Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions

Oxidation reactions by molecular oxygen (O₂) over palladium (Pd)‐based nanomaterials are a series of processes crucial to the synthesis of fine chemicals. In the past decades, investigations of related catalytic materials have mainly been focused on the synthesis of Pd‐based nanomaterials from the angle of tailoring their surface structures, compositions and supporting materials, in efforts to improve their activities in organic reactions. From the perspective of rational materials design, it is imperative to address the fundamental issues associated with catalyst performance, one of which should be oxygen activation by Pd‐based nanomaterials. Here, the fundamentals that account for the transformation from O₂ to reactive oxygen species over Pd, with a focus on singlet O₂ and its analogue, are introduced. Methods for detecting and differentiating species are also presented to facilitate future fundamental research. Key factors for tuning the oxygen activation efficiencies of catalytic materials are then outlined, and recent developments in Pd‐catalyzed oxygen‐related organic reactions are summarized in alignment with each key factor. To close, we discuss the challenges and opportunities for photocatalysis research at this unique intersection as well as the potential impact on other research fields.