bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Devices: Energy Transfer
Authors: Bonacchi Sara , Genovese Damiano , Juris Riccardo , Montalti Marco , Prodi Luca , Rampazzo Enrico , Zaccheroni Nelsi 
Published: February 2012

AbstractDevices are systems able to perform specific functions, which result from the coordinated action of different components. The design of these systems is, hence, based on the identification or the development of the necessary parts, and in their integration in a suitable supramolecular architecture. The main challenge in such a process is undoubtedly synthetic: the control of the mutual interactions between the active moieties, in fact, requires a fine‐tuning of the distance and orientation of the components and, in the case of physically connected donor‐acceptor moieties, of the electronic properties of the interconnecting linkers. Organization through covalent bonding has, in this context, several advantages, and many examples of covalent supramolecular devices have been reported in the last two decades. Besides, the covalent approach led to the design of fascinating and efficient prototypes, that often require the preparation of beautiful but complicated chemical systems, through time‐demanding multistep synthetic paths and that are not suitable for large‐scale production. Many examples of devices derived from a more traditional supramolecular approach based on self‐assembly and host‐guest interactions have also been reported. In this chapter, some relevant examples of both covalent and self‐organizing supramolecular devices based on energy‐transfer (ET) processes are reviewed. The basic principles of ET are also discussed. Recently, the advent of nanomaterials offered to supramolecular chemists new active components and structural platforms suitable for the design of nanometric molecular devices. At the present stage, nanomaterials represent, in fact, an ideal platform to achieve a reasonable degree of spatial organization especially when the integration of a large number of components is required or desired. This approach allows the achievement of complex, extensive devices otherwise not accessible. Moreover, some nanomaterials have unique photophysical properties and can become themselves active nanosized component of the final device. In this chapter, we discuss selected examples of ET‐based supramolecular devices with increasing complexity and size; going from dyads to multicomponent nanostructures.
Clathrate Hydrates
Authors: Alavi Saman , Udachin Konstantin , Ratcliffe Christopher I. , Ripmeester John A. 
Published: February 2012

AbstractClathrate hydrates are arguably the best understood class of supramolecular materials. Extensive experimental work has been carried out over the last 200 years, and theoretical and computational work for the last 50 years. Also, clathrate hydrates have been investigated from an industrial point of view as these materials tend to form blockages in oil and gas pipelines. Finally, clathrate hydrates occur in nature and play a complex and incompletely understood role in the geosphere. This work presents an overview of the structures and properties of clathrate hydrates as supramolecular solids as well as some of the theoretical foundations required to understand these interesting solids formed between water and a variety of guest species.
Coordination Polymers
Authors: Constable Edwin C. 
Published: February 2012

Abstract
This chapter describes the use of metal ions to control the assembly of multifunctional organic molecules to form networks exhibiting one‐, two‐, or three‐dimensional structures. The assembly is based on the concepts of metallosupramolecular chemistry—the matching of ligand donor and spatial properties with the coordination and geometrical requirements of the metal ion. These materials, also termed metal‐organic frameworks (MOFs) or tectonic solids, possess unique extended structures and their ease of synthesis makes them attractive candidates for large‐scale applications. The synthetic strategies and methodologies are reviewed and the present and potential applications of these new materials are discussed in brief.
Functions Based on Dynamic Structural Changes of Coordination Polymers
Authors: Kondo Mitsuru 
Published: February 2012

Abstract

The unique functions of flexible coordination polymers (FCPs) based on the dynamic structural changes are described. Coordination polymers with flexible structures have been classified into four types in this review. Type I shows reversible interconversions between porous and nonporous frameworks in response to removals and reinclusions of guest molecules from/into the channels. FCPs that exhibit Type I structural changes are general. Type II FCPs show reversible switches between the porous and nonporous frameworks depending on the guest molecules. The two‐dimensional coordination polymers that show reversible structural changes in response to the present solvents have been presented as examples of Type II FCPs. Type III FCPs involve the creation of vacant channels for additional guest molecules from nonporous compounds, which is triggered by chemical stimuli. The hydrogen bond‐assembled metal complex has been shown as an example of Tpye III materials. Type IV FCPs have the channel structures that show reversible transformations depending on the physical stimuli. Type III and IV FCPs are rare and unique. Adsorption of EtOH guest molecules induced by the addition of CH
3
OH, which is a smaller guest molecule, is demonstrated. Mechanical trapping of guest molecules in the closed channels induced by physical stimuli is presented as FCPs demonstrating Type IV structural changes.
Assembly of Block Copolymers
Authors: Adams Dave J. , Topham Paul D. 
Published: February 2012

Abstract
Block copolymers consist of two or more polymer chains covalently linked together. The different blocks can range in compatibility, both within the polymers or between the polymers and the environment. Phase separation between the blocks, as well as between the blocks and solvent, can be used to generate materials with different, yet controlled, nanostructures. In the bulk, phase separation is relatively well understood and related to the segregation strength of the two chemically distinct polymer components. In solution, block copolymers can adopt a range of self‐assembled structures including spherical micelles, wormlike micelles, and vesicles depending on parameters such as the polymer composition, polymer concentration, and solvent choice. This chapter explains how such phase separation comes about in addition to how it can be related to the adopted structures.
Self‐Assembling Fibrillar Networks—Supramolecular Gels
Authors: Smith David K. 
Published: February 2012

Abstract
Self‐assembled fibrillar gels have developed into an important class of supramolecular nanomaterial in which molecular‐scale building blocks hierarchically assemble into nanostructured systems with intriguing macroscopic properties. This chapter provides an overview of supramolecular gels, placing them clearly in a historical context and explaining how they can be investigated experimentally. This chapter then explores how key principles of molecular recognition and self‐assembly can be used to rationalize and predict their behavior. Different classes of gelator are explored in terms of the structures of the molecular‐scale building blocks. Finally, the chapter focuses on the unique features of gel‐phase materials, and the way in which they can be exploited to develop a wide range of new applications—from oil‐spill remediation and artwork conservation to nanoscale electronics and tissue engineering.
Self‐Assembled Polymer Supermolecules as Templates for Nanomaterials
Authors: Nandan Bhanu , Stamm Manfred 
Published: February 2012

AbstractThe current trend of modern high‐tech industries toward minimization and increase of surface/bulk feature density is today dictating the search of novel principles and routes. The top‐down approaches such as conventional lithographic techniques are currently able to achieve feature sizes down toward 100 nm; however, the associated cost of their manufacturing increases rapidly as the process shifts to shorter wavelengths. Therefore, bottom‐up approaches such as self‐assembly by means of a chemical or a physical driving force have attracted considerable interest as an alternative way to build periodic nanostructures with a feature size ranging from a few nanometers up to submicrometers. Self‐assembled polymeric systems, especially, have played an important role as templates for nanofabrication; they offer nanotemplates with different morphologies and tunable sizes, are easily removed after reactions, and could be further modified with different functional groups to enhance the interactions. Among the various self‐assembled polymeric systems, block copolymer (BCP) supramolecular assemblies have received considerable attention because of the inherent processing advantages. These supramolecular assemblies are formed by the noncovalent interactions of one of the blocks of the BCP with a low‐molar‐mass additive. Selective extraction of the additive leads to porous membranes or nano‐objects which could then be used as templates for nanofabrication, leading to a variety of ordered organic/inorganic nanostructures. Moreover, if the low‐molecular‐weight additive has some specific properties (optical, conducting, magnetic, etc.) then it gets incorporated in the polymer system without actually going through some tedious synthetic processes. In this chapter, we present an overview of the recent developments in this area, with a special focus on the use of such materials for fabrication of nanomaterials.
Dynamic Covalent Chemistry
Authors: Gasparini Giulio , Dal Molin Marta , Lovato Andrea , Prins Leonard J. 
Published: February 2012

Abstract

Dynamic covalent chemistry forms the key ingredient for a new approach toward organic synthesis. Dynamic covalent chemistry regards the synthesis of covalent organic molecules under thermodynamic control. It relies on the use of covalent bonds that can be reversibly formed under the experimental conditions. It combines the advantages typically associated with noncovalent synthesis (the formation of molecular structures using noncovalent interactions), such as spontaneous formation, error correction, and proof reading, with the robustness of covalent bonds. For many covalent bonds, experimental conditions under which the reaction occurs reversibly are known, but the majority of systems relies on trans(thio)esterifications and disulfide or imine‐type exchange reactions. These reactions occur rapidly under mild conditions, use readily accessible building blocks, and can be turned off to obtain kinetically inert products. It is illustrated that dynamic covalent chemistry gives a rapid access toward organic structures of nanometer dimensions. Typically, a one‐step, one‐pot synthetic protocol is used, which in some cases also involves multiple dynamic covalent bonds in an orthogonal manner. The fundamental difference with covalent synthesis is that equilibrium reactions are used. This introduces a characteristic property, which is the possibility of the chemical system to adapt to changes in its environment according to Le Châtelier's principle. This concept is referred to as
dynamic combinatorial chemistry
(
DCC
) and has been successfully applied for the preparation of new receptors, guests, sensors, materials, and so forth. Examples, together with the potential and limitations of this approach, are discussed. The final section is dedicated to the systems in which dynamic covalent bonds provide structural stability but intramolecular noncovalent interactions determine the composition of the resulting equilibrium. It is shown that this approach, that is, dynamic covalent capture, is a very sensitive tool for the quantification of weak interactions, for instance, in protein folding or catalysis.
Supramolecular Chemistry of Membranes
Authors: Noble Gavin T. , Mart Robert J. , Liem Kwan Ping , Webb Simon J. 
Published: February 2012

Abstract
Phospholipid bilayer membranes are more than just the delimiting boundaries of cells, they are home to some of the fundamental functions of living organisms, including respiration and photosynthesis. At the core of these complex and remarkably large self‐assembled biological structures is the hydrophobic effect, which causes phospholipids to assemble into bilayers and form closed compartments. Although this elegant process is an area of keen study in its own right, much recent research into the supramolecular chemistry of biomembranes has targeted specific functions, such as signaling, catalysis, or transport. Replicating these cellular processes draws heavily on supramolecular principles and this review describes some of the key works that have progressed supramolecular research into biomembranes, with a focus on those systems developed in phospholipid bilayers. A brief discussion of the fundamental principles that govern biomembrane formation and behavior is provided, which aims to provide background material for researchers in supramolecular chemistry who wish to explore biomembrane chemistry in supramolecular chemistry. Case studies are then introduced to illustrate progress in different aspects of supramolecular membrane chemistry, namely, intramembrane recognition, intermembrane recognition, and reactivity at membranes.
Supramolecular Bioinorganic Chemistry
Authors: Rebilly Jean‐Noël , Reinaud Olivia 
Published: February 2012

Abstract
Metalloenzymes are natural catalysts that carry out various types of reactions including hydrolytic, redox, and others, with impressive turnovers and exquisite selectivity. To achieve this goal, they gather a metal active site and a well‐defined supramolecular environment generated by the protein folding that allows specific spatial preorganization of the substrate and thus high reaction kinetics and selectivities. Traditional chemical models of metalloenzymes (classical coordination complexes), despite being a source of valuable data, miss this fundamental supramolecular aspect. Over the last 30 years, chemists have thus developed several supramolecular strategies to refine them, through the use of molecular receptors or mesoporous matrices to mimic the binding pocket of the enzyme. This field is still in its infancy, but several behaviors observed in natural systems were evidenced by these synthetic supramolecular systems. Each results from supramolecular strategies based on the control of metal site nuclearity, metal/substrate interaction, and the interlocking of host–guest and metal properties. These various approaches constitute tools for the development of new generations of biomimetic coordination systems.
Aptamer Moieties in Biochemical Applications
Authors: Donovan Michael J. , Meng Ling , Gulbakan Basri , Chen Yan , Parekh Parag , Sefah Kwame , Tan Weihong 
Published: February 2012

Abstract

Aptamers developed for applications in cancer therapy can improve the efficacy of drug treatment and enhance imaging. Aptamers for these purposes are generated from a process known as SELEX (
s
ystematic
e
volution of
l
igands by
ex
ponential enrichment), or, more precisely when biological cells are used, cell‐based SELEX. Aptamers provide a highly target‐specific means of transporting drugs to cancer cells. Improved imaging is also possible when aptamers are coupled with micelles, nanomaterials, or hydrogels. These aptamer conjugates show great ability as molecular probes in a variety of applications.
Biologically Derived Supramolecular Materials
Authors: Langford Steven J. , Latter Melissa J. , Wilman Bradley E. , Bhosale Sheshanath V. 
Published: February 2012

Abstract
Inspired by nature and its ability to form well‐defined architectures on the nanoscale, this chapter investigates not only examples of hybrid nanostructured materials that utilize the building blocks of nature, such as DNA, biopolymers, and bilayers, but also of biomimicry.
Magnetically Responsive Self‐Assembled Composite Materials
Authors: Nelson Alshakim , Dai Qiu 
Published: February 2012

Abstract
This chapter summarizes the recent advances on the self‐assembled magnetic nanoparticle‐polymer composite materials. This class of composite materials has gained significant attention owing to their unique stimuli‐responsive behavior under internal and external magnetic fields. After a brief introduction of magnetism associated with magnetic materials, we outline the various approaches that have been investigated to synthesize magnetic nanoparticle‐polymer composites with well‐controlled one‐, two‐ and three‐dimensional architectures. This chapter also highlights promising future applications of these composite materials, including magnetic data storage media and nanomedicine (diagnostics, biosensor, and therapeutic agents).
Photochemically Driven Molecular Devices and Machines
Authors: Credi Alberto , Silvi Serena , Venturi Margherita 
Published: February 2012

AbstractLight‐induced processes are the basis of many fundamental natural phenomena as well as of a variety of applications. Since the functions that can arise from the interaction between light and matter depend on the degree of complexity and organization of the receiving “matter,” the research on these processes has progressively moved from molecular to supramolecular (multicomponent) systems, thereby originating the field of supramolecular photochemistry. In this context, several research groups have synthesized and investigated multicomponent chemical systems capable of performing specific light‐induced functions, such as elaboration of information in the form of input/output signals and relative mechanical motions of the molecular components. Systems of this type can be viewed as simple examples of molecular devices and machines. These studies are of interest not only for increasing the basic understanding of photoinduced processes but also for the growth of nanoscience and the development of nanotechnology.
Mesoporous Silica Nanoparticles: Synthesis, Biocompatibility and Drug Delivery
Authors: Tang Fangqiong , Li Linlin , Chen Dong 
Published: February 2012

AbstractIn the past decade, mesoporous silica nanoparticles (MSNs) have attracted more and more attention for their potential biomedical applications. With their tailored mesoporous structure and high surface area, MSNs as drug delivery systems (DDSs) show significant advantages over traditional drug nanocarriers. In this review, we overview the recent progress in the synthesis of MSNs for drug delivery applications. First, we provide an overview of synthesis strategies for fabricating ordered MSNs and hollow/rattle‐type MSNs. Then, the in vitro and in vivo biocompatibility and biotranslocation of MSNs are discussed in relation to their chemophysical properties including particle size, surface properties, shape, and structure. The review also highlights the significant achievements in drug delivery using mesoporous silica nanoparticles and their multifunctional counterparts as drug carriers. In particular, the biological barriers for nano‐based targeted cancer therapy and MSN‐based targeting strategies are discussed. We conclude with our personal perspectives on the directions in which future work in this field might be focused.
A New Fe/V Redox Flow Battery Using a Sulfuric/Chloric Mixed‐Acid Supporting Electrolyte
Authors: Wang Wei , Nie Zimin , Chen Baowei , Chen Feng , Luo Qingtao , Wei Xiaoliang , Xia Guan‐Guang , Skyllas‐Kazacos Maria , Li Liyu , Yang Zhenguo 
Published: February 2012

AbstractA redox flow battery using Fe2+/Fe3+ and V2+/V3+ redox couples in chloric/sulfuric mixed‐acid supporting electrolyte is investigated for potential stationary energy storage applications. The Fe/V redox flow cell using mixed reactant solutions operates within a voltage window of 0.5–1.35 V with a nearly 100% utilization ratio and demonstrates stable cycling over 100 cycles with energy efficiency >80% and no capacity fading at room temperature. A 25% improvement in the discharge energy density of the Fe/V cell is achieved compared with a previously reported Fe/V cell using a pure chloride acid supporting electrolyte. Stable performance is achieved in the temperature range between 0 and 50 °C as well as when using a microporous separator as the membrane. The improved electrochemical performance makes the Fe/V redox flow battery a promising option as a stationary energy storage device to enable renewable integration and stabilization of the electric grid.
Electrospun LiFe1−yMnyPO4/C Nanofiber Composites as Self‐Supporting Cathodes in Li‐Ion Batteries
Authors: von Hagen Robin , Lorrmann Henning , Möller Kai‐Christian , Mathur Sanjay 
Published: February 2012

AbstractLiFe1−yMnyPO4/C nanofiber composites are applied as cathode materials in Li‐ion batteries and their electrochemical properties are explored. Nanofiber meshes are synthesized via electrospinning of commercially available precursors (LiOH·H2O, FeSO4·7H2O, MnSO4·H2O, H3PO4, and polyvinylpyrrolidone). Nanofibers calcined at 850 °C under Ar/H2 (95/5 vol%) atmosphere are directly used as self‐supporting electrodes in Swagelok half cells without the need for any conductive additive or polymer binder. The morphology, phase, and chemical composition of as‐prepared and heat‐treated samples are analyzed by means of X‐ray powder diffraction, thermogravimetric analysis, and electron and scanning microscopy techniques. Brunauer–Emmett–Teller gas adsorption–desorption measurements show a high specific surface area (111m2 g−1) for LiFe0.5Mn0.5PO4. The influence of different Fe/Mn ratios on the morphology, electrical, and electrochemical performances are analyzed.
Cavitation during deformation of polymers on the example of polypropylene
Authors: Pawlak Andrzej 
Published: February 2012

AbstractCavitation during uniaxial deformation of isotactic polypropylene (PP) was studied in samples having different amounts of α and β crystals. It has been shown that deformation is always accompanied by neck formation. Because the very beginning the plastic deformation is accompanied by cavitation. The scale of cavitation, determined with the use of X‐ray scattering and volume measurements increases with an increase of the content of β phase in the examined samples. Cavities change their shape with deformation—at first they are elongated perpendicularly to the direction of stretching, next, at the strain of 1.5, they reorient in the direction of deformation, which is connected with changes in the surrounding lamellar structure. The calculations of Guinier's radius showed that two populations of voids are present in deformed PP samples, characterized by the gyration radii of 5 and 13 nm for small deformations. Estimations based on the volume increase and sizes of cavities indicate that typically more than one cavity are present in amorphous layers adhering to lamella surfaces. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Simple methods influencing on properties of electrospun fibrous mats
Authors: Tomaszewski Waclaw , Swieszkowski Wojciech , Szadkowski Marek , Kudra Michal , Ciechanska Danuta 
Published: February 2012

AbstractIn many cases, potentially good electrospun materials are not satisfactory to the intended uses, but the use of the additional processing allows for an achievement of more suitable properties. Sometimes certain modifications of the spinning solutions are needed to improve its spinning ability and to properly carry out the electrospinning. For example an introducing of ionic and nonionic surfactants as Tebac or Triton X‐100 significantly improved spinning ability of PLA or chitosan solutions. In turn the annealing or the annealing under pressure has enhanced crystallinity, mechanical strength, and an apparent density of raw electrospun fibrous mats from various PLAs, making them more useful. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012