Computer‐Aided Molecular Design of Environmentally Friendly Solvents for Separation Processes

This review paper presents an optimization technology for the computer‐aided molecular design of environmentally friendly solvents. The approach combines a stochastic optimization method and group contribution methods (GC‐methods) to design solvents with desirable physicochemical and environmental properties. A simulated annealing algorithm is used to investigate feasible molecular structures. The main objective method is adopted to balance the multi‐objective functions. One property is chosen as the main objective function, while the other properties are considered as constraints, and thus, the multi‐objective problem is transformed into a single objective one. The optimal solution is a set of molecules satisfying the formulated target. The properties of each molecule are evaluated through GC‐methods, including pure component properties, mixture properties and environmentally properties. Finally, the proposed methodology is illustrated with several examples of industrial separations.     

Sequence‐Specific Molecular Lithography Towards DNA‐Templated Electronics

Recent advances in the realization of individual molecular‐scale devices [1,2] highlight the integration of individual devices into large‐scale functional circuits as the major challenge. DNA‐programmed assembly is a promising avenue in that direction due to the large amount of information that can be coded into the molecules and the ability to translate that information into physical constructs [3]. Large‐scale DNA‐templated electronics require, however, complex manipulation of double‐stranded DNA (dsDNA) molecules, as well as patterning of the electrical properties instilled to them by, e.g., metallization. To that end, sequence‐specific molecular lithography on single DNA molecules has been developed [4]. This was achieved by harnessing the exquisite homologous recombination process of the RecA protein. Sequence‐specific patterning of the metal coating of DNA molecules, localization of arbitrary labeled molecular objects at any desired dsDNA address without prior modifications, and generation of molecularly accurate stable dsDNA‐dsDNA junctions are demonstrated. The information encoded in the DNA molecules directs the lithographic process in analogy to the masks used in conventional microelectronics. The RecA protein provides the assembling capabilities, as well as the resist function.     

Molecular design of interfacial layers based on conjugated polythiophenes for polymer and hybrid solar cells

In the past two decades, bulk heterojunction organic photovoltaic (OPV) devices have emerged as attractive candidates for solar energy conversion due to their lightweight design and potential for low‐cost, high‐throughput, solution‐phase processability. Interfacial engineering is a proven efficient approach to achieve OPV devices with high power conversion efficiencies. This mini‐review provides an overview of the key structural considerations necessary when undertaking the molecular design of conjugated polyelectrolytes, for application as interfacial layers (ILs). The different roles of ILs are outlined, together with the advantages and disadvantages of competing classes of IL materials. Particular emphasis is placed on the design and synthesis of water‐soluble polythiophene‐based IL materials and the influence of their structural characteristics on their performance as a promising class of IL material. Finally, the challenges and opportunities for polythiophenes as IL materials for OPV devices and other solution‐processed solar cell technologies (e.g. perovskite solar cells) are discussed. © 2017 Society of Chemical Industry     

Initial Molecular Recognition Steps of McjA Precursor during Microcin J25 Lasso Peptide Maturation

Microcin J25 (MccJ25) has emerged as an excellent model to understand the maturation of ribosomal precursor peptides into the entangled lasso fold. MccJ25 biosynthesis relies on the post‐translational modification of the precursor McjA by the ATP‐dependent protease McjB and the lactam synthetase McjC. Here, using NMR spectroscopy, we showed that McjA is an intrinsically disordered protein without detectable conformational preference, which emphasizes the active role of the maturation machinery on the three‐dimensional folding of MccJ25. We further showed that the N‐terminal region of the leader peptide is involved in interaction with both maturation enzymes and identified a predominant interaction of V43–S55 in the core McjA sequence with McjC. Moreover, we demonstrated that residues K23–Q34 in the N‐terminal McjA leader peptide tend to adopt a helical conformation in the presence of membrane mimics, implying a role in directing McjA to the membrane in the vicinity of the lasso synthetase/export machinery. These data provide valuable insights into the initial molecular recognition steps in the MccJ25 maturation process.     

Multi‐Dimensional Quantum Nanostructures with Polarization Properties for Display Applications

Colloidal semiconductor nanocrystals (NCs), or quantum nanostructures with various dimensions and morphologies, are excellent emerging solution‐processable luminescent materials for display applications. The future of semiconductor NCs in the display market strongly relies on the development of low energy consuming devices. Replacing spherical NCs with multi‐dimensional nanostructures that emit linearly or circularly polarized light with high color purity and brightness, can significantly enhance the performance and efficiency of future display devices. In this review, we highlight some recent advances of colloidal syntheses of multi‐dimensional quantum nanostructures and their implementation as polarized light sources. The most representative examples are quasi‐one‐dimensional (q‐1D) CdSe/CdS dot‐in‐rods with strong linearly polarized emission for liquid crystal display technologies, and two‐dimensional (2D) nanoplatelets with enhanced circular dichroism signals as potential circularly polarized luminescence sources for electroluminescence applications.     

Facile One‐Step Assembly of Bona Fide SUMO Conjugates by Chemoenzymatic Ligation

The post‐translational conjugation of the small ubiquitin‐like modifiers (SUMOs) to target proteins occurs through a complex machinery that involves sequential action of at least three enzymes. SUMOylation performs crucial regulatory functions in several cellular processes. The availability of well‐defined SUMO conjugates is necessary for untangling the mechanism of SUMOylation. However, assembly of homogeneous SUMO conjugates represents a challenge because of the multi‐step synthesis involved and the unwieldiness of the reconstituted biosynthetic systems. Here we describe a simple one‐step chemoenzymatic strategy for conjugating engineered SUMO (eSUMO) proteins to a prefabricated isopeptide‐linked SUMO target peptide. Notably, the eSUMOs were efficiently recognized by the enzymes of the SUMOylation machinery and the SUMO conjugates served as bona fide substrates for DeSUMOylating enzymes.     

Molecular orientation–photoconductivity relationship study of phthalocyanine polymer‐oriented thin films

The molecular orientation–photoconductivity relationships of several kinds of phthalocyanine polymer (PPc)‐oriented thin films have been studied in double‐layered photoreceptor devices, where the charge‐generation layers (CGLs) are phthalocyanine polymer‐oriented thin films and the charge‐transportation layers (CTLs) are composed of hole transporting materials of tetraphenyl benzidine or hydrazone. The oriented thin films containing PPc dispersed in polyvinyl difluoride (PVDF) were prepared by the electric field orientation. The results showed that the photosensitivities of the phthalocyanine polymer (PPcs)‐oriented thin films were higher than those of the unoriented PPcs thin films, and varied with their molecular structures and the molecular stacking in the films. This was thought to be due to the molecular orientation effect, which was demonstrated by the analyses of the polarized fluorescence, DSC, FTIR reflection absorption spectroscopy (FTIR‐RAS), and angle‐dependent XPS. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2331–2339, 2000     

Molecular junctions: from tunneling to function

Thanks to the development of appropriate experimental techniques, molecular devices and their electrical transport properties have recently been the focus of a major research effort. This brief review describes how individual molecules can be contacted with metallic electrodes to form molecular junctions and addresses their basic formation mechanisms. An extension to molecular junctions networks is also discussed. Functionality could be demonstrated in such systems, and examples where conductance modulation using light or chemical stimuli was achieved will be presented.     

Multi‐Component Self‐Assembly of Proteins and Inorganic Particles: From Discrete Structures to Biomimetic Materials

Due to their defined structure, proteins are suitable building blocks for the bottom‐up construction of multi‐component materials. Especially protein containers, with their inherent cavity, can be used to encapsulate synthetic components such as inorganic nanoparticles. This way, multi‐component discrete structures can be assembled. With recent advances in computational protein design, novel protein containers were successfully created, with a high potential for application in biomedicine and materials research. Moreover, engineered protein containers offer a unique building block for the self‐assembly of three‐dimensional materials. They combine the molecular precision of proteins with nanoscale dimensions. Designed interactions lead to novel protein scaffolds. In addition, nanoparticles encapsulated inside the container cavity introduce orthogonal functionality, important for the realization of nanostructured biomimetic materials with emergent properties.     

Towards self‐sterilizing medical devices: controlling infection

Medical devices are an important component of modern medicine. In many cases, medical devices are used to improve the ‘quality of life’ for the patient, and their use is increasing dramatically. At the same time, the emergence of multi‐drug‐resistant bacteria, or ‘super‐bugs’, is a global crisis. At least in part, biomedical devices proliferate the growth of resistant bacteria. This has spurred new research aimed at the development of medical devices that prevent or control bacterial colonization, and this perspective discusses the current efforts in this area. Copyright © 2008 Society of Chemical Industry     

Variations in surface gloss on rubber‐modified thermoplastics: Relation to morphological and rheological behavior

The parameters that promote the formation of surface defects on multi‐phase polymer systems during injection molding are not yet clearly understood. The objective of this work is to establish the influence of composition, particularly the role of rubber, on the rheological properties of such multi‐phase systems and relate that to variations in gloss that appear on the surface of ASA and PC/ASA blends. Analysis of morphology by micro‐thermal analysis (μTA?) in combination with oscillatory rheology, time‐temperature‐superposition (TTS), creep recovery and PVT testing revealed distinct trends of surface gloss with each material's viscoelastic behavior and surface finish. It has been shown that influential properties such as rubber content, particle size and distribution, molecular weight, viscosity ratios and the degree of acrylonitrile mismatching play key roles in each material's rheology, developed morphology and subsequent trends in surface gloss after injection molding.     

分子器件制作方法研究进展

随着现有超大规模集成电路日趋其发展极限,以分子器件作为电子元器件替代品,在世界各国得到高度重视,其发展也日新月异。本文综述了分子器件分类及其制作方法,以此来抛砖引玉,促进我国分子器件的发展。     

Molecular weight variations in perylene‐doped poly(methyl methacrylate) for luminescent solar concentrators

Integrating highly efficient luminescent dyes into poly(methyl methacrylate) matrices with well‐defined parameters, such as degree of polymerization and dispersity, is a key step in the development of emerging technologies such as fiber‐based solar collectors, sensors, contactless coupling devices and integrated light sources. In this work, four perylene‐based fluorescent dyes, perylene from Sigma‐Aldrich, Lumogen F Yellow 083 from BASF, Perylene Orange from TCI and Lumogen F Red 300 from BASF, were polymerized in bulk with methyl methacrylate. The molecular weight distribution was controlled by the ratio between the chain transfer agent and initiator and was measured by size exclusion chromatography. A dopant‐dependent increase in the degree of polymerization, in which the dye causes a drop in the concentration of active growing polymer chains, was observed. Spectroscopic online monitoring of the process in transmission mode confirmed this observation and indicated the formation of stable perylene radicals during the polymerization. Comparative experiments with fluorescent (metal) organic dyes did not show a similar effect. Fitting models for the dye‐dependent molecular weights for Lumogen Yellow and Lumogen Red are proposed. © 2018 Society of Chemical Industry     

Molecular electronics. Synthesis and testing of components

Molecular electronics involves the use of single or small packets of molecules as the fundamental units for computing. While initial targets are the substitution of solid-state wires and devices with molecules, long-range goals involve the development of novel addressable electronic properties from molecules. A comparison of traditional solid-state devices to molecular systems is described. Issues of cost and ease of manufacture are outlined, along with the syntheses and testing of molecular wires and devices.     

From active plasmonic devices to plasmonic molecular electronics

This work is mainly focused on studies combining plasmonic nanostructures and π‐conjugated systems. It describes active molecular plasmonic devices in which π‐conjugated molecules and polymers, grafted on gold nanoparticles, are used to tune the plasmonic properties of metal nanostructures. It also explores two emerging research fields, i.e. plasmonic electrochemistry and plasmonic molecular electronics. In the former, electrochemical reactions are controlled and triggered by plasmons which yield various light‐induced electrochemical reactions at the nanoscale. In the latter, one combines molecular plasmonics and molecular electronics in plasmonic molecular devices. © 2018 Society of Chemical Industry     

Molecular electronic devices based on single-walled carbon nanotube electrodes

As the top-down fabrication techniques for silicon-based electronic materials have reached the scale of molecular lengths, researchers have been investigating nanostructured materials to build electronics from individual molecules. Researchers have directed extensive experimental and theoretical efforts toward building functional optoelectronic devices using individual organic molecules and fabricating metal-molecule junctions. Although this method has many advantages, its limitations lead to large disagreement between experimental and theoretical results. This Account describes a new method to create molecular electronic devices, covalently bridging a gap in a single-walled carbon nanotube (SWNT) with an electrically functional molecule. First, we introduce a molecular-scale gap into a nanotube by precise oxidative cutting through a lithographic mask. Now functionalized with carboxylic acids, the ends of the cleaved carbon nanotubes are reconnected with conjugated diamines to give robust diamides. The molecular electronic devices prepared in this fashion can withstand and respond to large environmental changes based on the functional groups in the molecules. For example, with oligoanilines as the molecular bridge, the conductance of the device is sensitive to pH. Similarly, using diarylethylenes as the bridge provides devices that can reversibly switch between conjugated and nonconjugated states. The molecular bridge can perform the dual task of carrying electrical current and sensing/recognition through biological events such as protein/substrate binding and DNA hybridization. The devices based on DNA can measure the difference in electrical properties of complementary and mismatched strands. A well-matched duplex DNA 15-mer in the gap exhibits a 300-fold lower resistance than a duplex with a GT or CA mismatch. This system provides an ultrasensitive way to detect single-nucleotide polymorphisms at the individual molecule level. Restriction enzymes can cleave certain cDNA strands assembled between the SWNT electrodes; therefore, these strands maintain their native conformation when bridging the ends of the SWNTs. This methodology for creating novel molecular circuits forges both literal and figurative connections between chemistry, physics, materials science, and biology and promises a new generation of integrated multifunctional sensors and devices.     

Multi‐Relaxation Test to Characterize PE Pipe Performance

A new concept is proposed, which uses results from a multi‐relaxation test to characterize transition of deformation mechanisms in polyethylene (PE) pipes, for plastic deformation from the amorphous phase only to the involvement of the crystalline phase. The former mechanism is believed to lead to brittle fracture, while the latter to ductile fracture. This phenomenon is believed to be related to the transition from ductile to brittle (DB) fracture that has been observed in creep tests of PE pipes by reducing the applied stress below a critical level. This paper presents results from 6 PE pipes of different density and molecular weight distribution. The results suggest that high‐density PE pipes require a higher deformation level for the DB transition than the medium‐density PE pipes. The results also suggest that the trend of change in the critical stress level for the DB transition is close to the trend of change in the hydrostatic design base, but the former takes less than two weeks to complete, while the latter more than 1 year. Therefore, the multi‐relaxation test can be used as an alternative method to characterize PE pipe performance, as a means for preliminary screening or in‐service monitoring of pipe performance.     

Internal Structure of Amorphous Electrospun Nanofiber: Oriented Molecular Chains

The properties of polymeric nanofibers are determined by their internal structure. Although electrospun nanofibers have been widely applied in many fields, their internal structure is still not extensively reported, especially for amorphous nanofibers, which cannot be analyzed by studying the morphology of the crystal lamellar such as the crystalline nanofibers. In this study, the internal structure of electrospun amorphous polycarbonate (PC) nanofibers is investigated. The phase contrast and transmission electron microscopy images show that PC nanofibers exhibit a cylinder‐like structure composed of molecular chains that are highly oriented along the fiber axis. This interesting cylinder‐like internal structure may be the result of evaporation‐induced phase separation in the polymer solution jet and the high strain rate in the electrospinning process. The variation of mechanical properties of PC nanofibers agrees well with the varied internal structure of the nanofibers with different fiber diameters. Due to the high degree of molecular orientation, as‐spun PC nanofibers exhibit superior elastic modulus (6.2 GPa) and strength (780 MPa). The cylinder‐like structure provides an insight into the internal structure of an amorphous electrospun nanofiber, which helps optimize the mechanical performance of amorphous nanofibers and fiber‐based devices.

     

Biologically Relevant Molecular Finite Automata

Bio-Molecular Computing (BMC) has been rapidly evolving as an independent field at the interface between computer science, mathematics, chemistry, and biology. Over the years, numerous architectures of autonomous molecular computing devices have been developed in the lab on the basis of opportunities offered by molecular biology techniques. This account focuses mainly on the realization of programmable DNA-based finite-state automata that can compute autonomously upon mixing all their components in solution.The main advantage of autonomous BMC devices over electronic computers arises from their ability to interact directly with biological systems and even with living organisms without any interface. Indeed, it has been demonstrated that appropriately designed computing machines can produce output signals in the form of a specific biological function via direct interaction with living cells. Additional topics are briefly included to point at interesting opportunities in the field and to describe some of the potential applications and extension of the basic concepts. These include logic evaluators and logic gates that operate in cells, applications in developmental biology, as well as chemical encoding and processing of alphanumeric information.     

Predicting multicomponent adsorption: 50 years of the ideal adsorbed solution theory

Describing multi‐component adsorption is fundamental to using sorption in any chemical separation. 50 years ago, Myers and Prausnitz made a seminal contribution to characterization and prediction of multi‐component adsorption by introducing Ideal Adsorbed Solution Theory (IAST). Here, we give an overview of IAST, highlighting its continued role as a benchmark method in describing adsorption using illustrative examples from a variety of experimental and molecular modeling studies. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2757–2762, 2015