Showing papers in "Journal of Materials Chemistry in 2005"
TL;DR: In this article, the authors propose a vectorial chemistry approach for the generation of new generations of hybrid materials, which will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.
Abstract: Organic–inorganic hybrid materials do not represent only a creative alternative to design new materials and compounds for academic research, but their improved or unusual features allow the development of innovative industrial applications. Nowadays, most of the hybrid materials that have already entered the market are synthesised and processed by using conventional soft chemistry based routes developed in the eighties. These processes are based on: a) the copolymerisation of functional organosilanes, macromonomers, and metal alkoxides, b) the encapsulation of organic components within sol–gel derived silica or metallic oxides, c) the organic functionalisation of nanofillers, nanoclays or other compounds with lamellar structures, etc. The chemical strategies (self-assembly, nanobuilding block approaches, hybrid MOF (Metal Organic Frameworks), integrative synthesis, coupled processes, bio-inspired strategies, etc.) offered nowadays by academic research allow, through an intelligent tuned coding, the development of a new vectorial chemistry, able to direct the assembling of a large variety of structurally well defined nano-objects into complex hybrid architectures hierarchically organised in terms of structure and functions. Looking to the future, there is no doubt that these new generations of hybrid materials, born from the very fruitful activities in this research field, will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.
2,321 citations
TL;DR: In this article, the industrial applications of poly(3,4-ethylenedioxythiophene) and poly(styrene sulfonic acid) poly(poly(3.4)-ethylenedioitriou glycol (PEDT) are summarized.
Abstract: This article summarises the industrial applications of poly-(3,4-ethylenedioxythiophene)
(PEDT, PEDOT). The basic chemical and physical properties of PEDT are discussed to outline the fundamentals which lead to PEDT as a highly valuable electric and electronic material. PEDT applications are reviewed depending on the two different ways of preparation: in situ polymerisation of the monomer, usually carried out by the user, and applying the prefabricated polymer in the form of its water-based complex with poly(styrene sulfonic acid). Several applications like antistatic coatings, cathodes in capacitors, through-hole plating, OLED's, OFET's, photovoltaics, and electrochromic applications are discussed in detail.
1,343 citations
TL;DR: In this paper, a two-component notation is used to represent the Li2MnO3, LiMO2 and LiM2O4 components, which provide an initial capacity >250 mAh g−1 when discharged between 5 and 2.0 V vs. Li0 and a rechargeable capacity up to 250 mAhg−1 over the same potential window.
Abstract: Recent advances to develop manganese-rich electrodes derived from ‘composite’ structures in which a Li2MnO3
(layered) component is structurally integrated with either a layered LiMO2 component or a spinel LiM2O4 component, in which M is predominantly Mn and Ni, are reviewed. The electrodes, which can be represented in two-component notation as xLi2MnO3·(1 −
x)LiMO2 and xLi2MnO3·(1 −
x)LiM2O4, are activated by lithia (Li2O) and/or lithium removal from the Li2MnO3, LiMO2 and LiM2O4 components. The electrodes provide an initial capacity >250 mAh g−1 when discharged between 5 and 2.0 V vs. Li0 and a rechargeable capacity up to 250 mAh g−1 over the same potential window. Electrochemical charge and discharge reactions are followed on compositional phase diagrams. The data bode well for the development and exploitation of high capacity electrodes for the next generation of lithium-ion batteries.
1,002 citations
TL;DR: In this article, the recent progress of studies on photo-and electroactive amorphous molecular materials, highlighting photochromic amorphus molecular materials and their use in organic EL devices is discussed.
Abstract: A new field of organic materials science that deals with amorphous molecular glasses has been opened up. In addition, amorphous molecular materials have constituted a new class of functional organic materials for use in various applications. This article is focused on the recent progress of studies on photo- and electroactive amorphous molecular materials, highlighting photochromic amorphous molecular materials, amorphous molecular resists, and amorphous molecular materials for use in devices such as organic EL devices. The molecular design concepts, syntheses, reactions, molecular and solid-state properties, functions, and device fabrication and performance are described.
883 citations
TL;DR: In this article, a review summarises the key topics in the field of self-cleaning coatings, concentrating on the materials that have been used in commercial applications and recent research that aims to improve these materials.
Abstract: This review summarises the key topics in the field of self-cleaning coatings, concentrating on the materials that have been used in commercial applications and recent research that aims to improve these materials. Hydrophobic and hydrophilic coatings are discussed, and the various mechanisms of self-cleaning are described and related to the material properties of the coatings. Although several multinational companies have released products incorporating self-cleaning coatings, there remains much potential in this field.
861 citations
TL;DR: In this paper, a review deals with the great and imaginative efforts which were devoted to the synthesis of Janus particles in the last fifteen years and a special emphasis is made on scalable techniques and on those which apply to the preparation of the Janus particle in the nanometer range.
Abstract: Because the Roman god Janus was usually represented with two heads placed back to back, the term Janus is used for the description of particles whose surfaces of both hemispheres are different from a chemical point of view. So, they could be used as building blocks for supraparticular assemblies, as dual-functionalized devices, as particular surfactants if one hemisphere is hydrophilic and the other hydrophobic, etc. If they could allow the segregation of negative charges on one hemisphere and positive charges on the other one, they would display a giant dipole moment allowing their remote positioning by rotation in an electric field as a function of field polarity. This review deals with the great and imaginative efforts which were devoted to the synthesis of Janus particles in the last fifteen years. A special emphasis is made on scalable techniques and on those which apply to the preparation of Janus particles in the nanometer range. Specific properties and applications of Janus particles are discussed.
691 citations
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TL;DR: Water-repellency is a property of some materials, either natural or synthetic, which makes water hardly stick to them: drops roll very easily off these solids, and bounce back upon impacting them as discussed by the authors.
Abstract: Water-repellency is a property of some materials, either natural or synthetic, which makes water hardly stick to them: drops roll very easily off these solids, and bounce back upon impacting them. Here we discuss recent advances in this field, which has been particularly lively in recent years. We first examine the physical causes for this effect. Then we discuss the loss of adherence of the drops in such a state, and stress their remarkable dynamic behaviour. We finally suggest several remaining challenges in the field.
659 citations
TL;DR: In this article, a brief overview of organic electroluminescence and electrophosphorescence is provided, and a more detailed consideration of ways in which electron transport in these systems has been enhanced by the incorporation of electron-deficient small molecules and polymers into the devices, either as blends or by covalent attachment of sub-units to the luminophore or as an additional electron-transporting, hole-blocking (ETHB) layer adjacent to the cathode.
Abstract: One of the requirements for efficient organic electroluminescent devices (OLEDs) is balanced charge injection from the two electrodes and efficient transport of both holes and electrons within the luminescent layer in the device structure. Many of the common luminescent conjugated polymers, e.g. derivatives of poly(phenylenevinylene) and poly(fluorene), are predominantly hole transporters (i.e. p-dopable). This article gives a brief overview of organic electroluminescence and electrophosphorescence and provides a more detailed consideration of ways in which electron transport in these systems has been enhanced by the incorporation of electron-deficient (i.e. n-dopable) small molecules and polymers into the devices, either as blends or by covalent attachment of sub-units to the luminophore or as an additional electron-transporting, hole-blocking (ETHB) layer adjacent to the cathode. The chemical structures of these systems are presented and their roles are assessed. Most of these ETHB molecules are electron-deficient aromatic nitrogen-containing heterocycles, e.g. derivatives of 1,3,4-oxadiazole, pyridine, pyrimidine, pyrazine, quinoline, etc. Non-aromatic thiophene-S,S-dioxide derivatives are also discussed. The article is written from an organic chemist's perspective.
599 citations
TL;DR: In this paper, a review of the results of research into replica mesostructures by nanocasting in recent years from the viewpoint of synthesis is presented, and problems that are often encountered in the procedure are discussed with several solutions.
Abstract: Since mesoporous silicates (M41S) were first discovered in the early 1990s, organic–inorganic assembly combined with sol–gel processes by using surfactants as structure-directing agents had been considered to be the major pathway for creating mesoscaled periodic materials. However, unfortunately, many mesostructured materials could not be prepared by the sol–gel process. Nanocasting, using highly ordered mesoporous silica as a template, has brought forward incredible possibilities in preparing novel mesostructured materials, and has led to a great number of ordered nanowire arrays with: a) small diameter (<10 nm); b) large surface areas (up to 2500 m2 g-1) and uniform mesopores (1.5–10 nm); c) tunable 2-D or 3-D mesostructures; d) controlled morphology such as spheres, rods, films, and monoliths; and e) different components including carbon, metals, metal oxides and metal sulfides. We intend to review the results of research into replica mesostructures by nanocasting in recent years from the viewpoint of synthesis. Detailed synthetic processes are described, and problems that are often encountered in the procedure are discussed with several solutions. Many mesostructured replicas are introduced, sorted by their components, including synthetic methods, characteristics of the materials, applications and future challenges. Finally, a simple view of the prospects in this area is provided.
505 citations
TL;DR: In this article, the progress made in the past years and some of the future aspects and challenges are discussed, as well as the potential of using fluorescence in the future. But the implementation of spectroscopic schemes into a useful sensing scheme has been hampered by the lack of appropriate materials including polymers and particles, indicator probes, molecular receptors, carriers, catalysts and fluorescent semiconductor materials.
Abstract: Optical chemical sensors are capable of continuously recording a chemical species and thus have found (and will find) numerous applications in areas such as the chemical industry, in biotechnology and medicine. Among the many optical methods are employed for sensing purposes, fluorescence has attracted particular attention because it is sensitive, has numerous parameters that can serve as an analytical information and knows effects unknown to other spectroscopies. The implementation of spectroscopic schemes into a useful sensing scheme has been hampered though, by the lack of appropriate materials including polymers and particles, indicator probes, molecular receptors, carriers, catalysts and fluorescent semiconductor materials. This article will address the progress made in the past years and some of the futures aspects and challenges.
477 citations
TL;DR: In this article, the incorporation of nanoparticles in the hybrid sol-gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential along with enhancement of the mechanical properties.
Abstract: Sol–gel derived films exhibit a high potential as substitutes for the environmentally unfriendly chromate metal-surface pre-treatment methods. Inorganic sol–gel derived films offer good adhesion between metals and organic paint. However, they cannot provide adequate corrosion protection due to their high crack-forming potential. Introduction of an organic component to an inorganic sol–gel system leads to the formation of thicker, more flexible and functionalized films with enhanced compatibility to different organic top coatings. Incorporation of nanoparticles in the hybrid sol–gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential along with enhancement of the mechanical properties. Furthermore, the incorporation of inorganic nanoparticles can be a way to insert corrosion inhibitors, preparing inhibitor nanoreservoirs for “self-repairing” pre-treatments with controlled release properties.
TL;DR: In this paper, the properties of hybrid O-I materials are dependent on their micro-and nanostructures and on the nature and extent of the interfaces between the OI interfaces.
Abstract: Homogeneously dispersed organic–inorganic hybrid nanocomposites can be obtained by increasing the interfacial interactions between both components via the formation of hydrogen bonds or covalent bonds, by mixing various polymers or via the adequate choice of the inorganic precursors The mechanical response of these advanced functional materials is an issue of paramount importance when industrial applications are targeted Large progress in the understanding of the mechanical properties of O–I hybrids has been gained by testing these materials under different conditions (static and dynamic, low and large deformations up to fracture) and using specific techniques developed for the mechanical characterization of conventional materials such as polymers, glasses or ceramics However, the mechanical properties of hybrid O–I materials are dependent on their micro- and nanostructures and on the nature and extent of the O–I interfaces Consequently, predictable mechanical properties for hybrids still represent a major challenge for hybrid materials science Industrial attraction for hybrid materials has been emphasized by the development of new functional coatings An important issue is the interface between the film and the substrate since strong adhesion can be tailored and ensures that delamination of the film will be limited
TL;DR: Graphite nanoplatelets with thicknesses down to 2-10 nm are synthesized by alkali metal intercalation followed by ethanol exfoliation and microwave drying as mentioned in this paper, which can be achieved either by heating graphite and potassium or caesium at 200 °C, or at room temperature using a sodium-potassium alloy.
Abstract: Graphite nanoplatelets with thicknesses down to 2–10 nm are synthesized by alkali metal intercalation followed by ethanol exfoliation and microwave drying. Graphite that has already been intercalated and exfoliated with an oxidizing acid is reintercalated with an alkali metal to form a first stage compound, as confirmed by powder X-ray diffraction. This can be achieved either by heating graphite and potassium or caesium at 200 °C, or at room temperature using a sodium–potassium alloy. Reaction of the intercalated graphite with ethanol causes exfoliation of the graphene layers. Microwave radiation aids in drying and results in further separation of the sheets. Thermogravimetric analysis indicates that the graphite nanoplatelets are approximately 150 °C less stable in air than pristine graphite. High aspect ratio graphite nanoplatelets offer promise as reinforcements for high strength carbon–carbon composites.
TL;DR: In this paper, the use of electrospinning in the fabrication of polymeric, ceramic, and composite nanofibers with core-sheath, hollow, or porous structures, as well as the efforts made to improve their morphological homogeneity, functionality, and device performance are highlighted.
Abstract: Recently there has been a great deal of progress in the production of one-dimensional nanostructures with core-sheath structures from a rich variety of materials. Here we highlight the use of electrospinning in the fabrication of polymeric, ceramic, and composite nanofibers with core-sheath, hollow, or porous structures, as well as the efforts made to improve their morphological homogeneity, functionality, and device performance.
TL;DR: The performance of organic field effect transistors (OFETs) is similar to that of amorphous silicon (a-Si : H) devices and they have become one of the most important components of organic electronics as mentioned in this paper.
Abstract: Since organic field-effect transistors (OFETs) were first described in 1987, they have undergone great progress, especially in the last several years. Nowadays, the performance of OFETs is similar to that of amorphous silicon (a-Si : H) devices and they have become one of the most important components of organic electronics. This feature article introduces briefly the operating principles, fabrication techniques of the transistors, and in particular highlights the recent progress, not only including materials and fabrication techniques, but also involving organic single crystal FETs and organic light-emitting FETs, which have been reported recently. Finally, the prospects and problems of OFETs that exist are discussed.
TL;DR: In this paper, an attempt is made to rationalise the various factors and the interconnections to the structure, the texture, and the effects of the nanometre scale, which all contribute to the properties of these materials.
Abstract: Nanostructured CeO2–ZrO2 mixed oxides have attracted great interest in the past 10 years, in particular as redox or oxygen storage promoters in the three-way catalysts. However, it has now became clear that both the chemistry of the simple oxides and the complex metal–CeO2-based oxide interactions can play a critical role in developing novel and highly active materials for a number of processes, ranging from catalysts for H2 production from fuels up to ceramic materials and solid state conductors for fuel cells. Despite the apparent simplicity of these systems, extreme variability of their chemical and textural properties has been observed. An attempt is made here to rationalise the various factors and the inter-connections to the structure, the texture, and the effects of the nanometre scale, which all contribute to the properties of these materials.
TL;DR: The potentialities of EDOT as a building block for the synthesis of functional π-conjugated systems are reviewed in this article, where some recent examples of polymers with specific electrochemical properties and/or a reduced band gap are illustrated.
Abstract: The potentialities offered by EDOT as a building block for the synthesis of functional π-conjugated systems are reviewed. The first part underlines the specific advantages of the EDOT unit for the design of precursors of electrogenerated functional conducting polymers combining high reactivity and low polymerization potential. This topic is illustrated by some recent examples of polymers with specific electrochemical properties and/or a reduced band gap. The second part is focused on the interest of EDOT as a building block for the synthesis of various classes of molecular functional π-conjugated systems. Examples of fluorophores, push–pull chromophores for nonlinear optics and extended π-donors are presented. Emphasis is placed on the optical and crystallographic structure of these compounds, which shows that a major advantage of the EDOT building block lies in an unique combination of strong electron donor properties and self-structuring effects related to intramolecular non-covalent interactions between oxygen and sulfur. Such intramolecular interactions also exert a determining influence on the structure and electronic properties of π-conjugated oligomers incorporating EDOT units which represent some of the more recent uses of the EDOT building block. The structure–property relationships of various classes of EDOT-containing conjugated oligomers are discussed in relation to their potential use as organic semi-conductors. In a brief last section, various synthetic approaches devoted to the chemistry of EDOT itself, or to the modification of its chemical structure, are discussed in relation with possible future research directions.
TL;DR: The dissolution of high surface area silica with tetralkylammonium hydroxides at concentrations greater than 0.2 M, produces polyanionic cage structures, [R4N+][−OSiO1.5]x.
Abstract: The dissolution of high surface area silica with tetralkylammonium hydroxides at concentrations greater than 0.2 M, produces polyanionic cage structures, [R4N+][−OSiO1.5]x or Qx, where x
= 6, 8 or 10. The value x depends on the type of alkyl or alkanol group. If R = Me or Me3NCH2CH2OH+ group (choline)
x
= 8 is favored. These silicate anions can be functionalized by reaction with chlorosilanes or siloxanes to produce [RSiMe2OSiO1.5]x. The octafunctional molecules are 1.2–1.4 nm in diameter, each functional group occupies a different octant in Cartesian space and as such all functional groups are either orthogonal to or opposite each other. This highly symmetrical structure offers the opportunity to construct multiple kinds of materials one nanometer at a time in one, two or three dimensions. In this review, we discuss methods of synthesizing the polyanionic silicates, their transformation into octafunctional building blocks, “cubes,” and their use in formulating polyfunctional compounds and nanocomposites therefrom. Examples of tailoring global properties by tailoring the chemistries used to link cubes are given.
TL;DR: The studies on enzymes immobilized on ordered mesoporous solids and the need for careful studies in real applications are reviewed and the emerging applications of related biomolecule–mesoporous solid hybrids in other applications are noted.
Abstract: The discovery in the late 1990s of ordered, high surface area silicas with pore sizes of 5 nm and above opened the way to the study of well-defined biomolecule–mesoporous silica hybrids. In particular, it has been possible to immobilize a range of small to medium size enzymes, such as proteases, lipases and peroxidases, via physisorption, encapsulation and tethering on the internal surfaces of the solids. Use has also been made of silicas functionalized for this purpose. In many cases the immobilized enzymes are both active and re-usable. Here we review the studies on enzymes immobilized on ordered mesoporous solids and assess the need for careful studies in real applications. Furthermore, we note the emerging applications of related biomolecule–mesoporous solid hybrids in other applications, such as intracellular drug delivery and transfection technology.
TL;DR: In this paper, organophosphorus acids and their derivatives (salts, esters) are complementary of organosilicon coupling molecules for the preparation of hybrid organic-inorganic materials, by sol-gel processing or surface modification.
Abstract: Organophosphorus acids and their derivatives (salts, esters) are quite complementary of organosilicon coupling molecules for the preparation of hybrid organic–inorganic materials, by sol–gel processing or surface modification. Organosilicon compounds are best suited for the anchoring of organic groups to silicon-containing inorganic matrices or supports, such as silica, silicates, silicon carbide, etc., whereas organophosphorus coupling molecules appear well adapted to matrices or supports based on metals or transition metals: oxides, hydroxides, as well as carbonates and phosphates. The different reactivity of organophosphorus coupling molecules leads to different structures and stabilities of the final hybrid materials and may provide decisive advantages in the sol–gel synthesis of homogeneous hybrids, the preparation of surface monolayers or the selective surface modification of nanopatterned supports.
TL;DR: The concept of free volume is useful for explaining aspects of the chain mobility and permeability of polymers, even though its precise definition is subject to debate as mentioned in this paper, and polymers that trap a large amount of interconnected free volume in the glassy state behave in many respects like microporous materials and potentially find application in membrane separations and heterogeneous catalysis.
Abstract: The concept of free volume is useful for explaining aspects of the chain mobility and permeability of polymers, even though its precise definition is subject to debate. Polymers that trap a large amount of interconnected free volume in the glassy state behave in many respects like microporous materials and potentially find application in membrane separations and heterogeneous catalysis. The development is outlined of a new type of polymer, for which the molecular structure contains sites of contortion (e.g. spiro-centres) within a rigid backbone (e.g. ladder polymer). These polymers of intrinsic microporosity (PIMs) include both insoluble network polymers and soluble non-network polymers that may be processed into membranes or other useful forms. Experimental methods are discussed for elucidating the free volume or micropore distribution, and the behaviour of PIMs is compared with that of the ultrapermeable polymer poly(1-trimethylsilyl-1-propyne).
TL;DR: Anatase-type TiO2 particles were synthesized by a two-step method consisting of the preparation of a solid precursor through hydrolysis of titanium alkoxide followed by heat treatment at different temperatures under ambient air as discussed by the authors.
Abstract: Anatase TiO2 particles were synthesized by a two-step method consisting of the preparation of a solid precursor through hydrolysis of titanium alkoxide followed by heat treatment at different temperatures under ambient air. This simple method led to a highly porous material with a 200 nm homogenous particle size, while the BET specific surface area and crystallite sizes evolved between 49 m2 g−1 to 223 m2 g−1 and from 17.0 nm to 6.3 nm, respectively. Their electrochemical performances clearly revealed the beneficial influence of the divided texture of anatase-type TiO2 on the reactivity with lithium, namely in terms of reversibility. Furthermore, we showed that the TiO2 texture strongly affects the extent of the solid solution domain. Finally, through a simple chemical titration it was possible to clearly quantify the capacitive/faradaic contributions of the electrochemical reaction.
TL;DR: In this paper, the fungus Fusarium oxysporum was challenged with aqueous anionic complexes SiF62− and TiF 62− respectively and extracellular protein-mediated hydrolysis of the anionic complex results in the facile room temperature synthesis of crystalline titania particles while calcination at 300 °C is required for crystallization of silica.
Abstract: The synthesis of inorganic materials by biological systems is characterized by processes that occur at close to ambient temperatures, pressures and neutral pH. This is exemplified by biosilicification in marine organisms such as diatoms while laboratory-based synthesis of silica involves extreme temperature and pH conditions. We show here that silica and titania particles may be produced by challenging the fungus Fusarium oxysporum with aqueous anionic complexes SiF62− and TiF62− respectively. Extra-cellular protein-mediated hydrolysis of the anionic complexes results in the facile room temperature synthesis of crystalline titania particles while calcination at 300 °C is required for crystallization of silica.
TL;DR: In this article, the results from applying modified silica nanosols to the functionalisation of textiles have been discussed, including textiles with water, oil and soil repellency and with antimicrobial properties.
Abstract: The maintenance and improvement of current properties and the creation of new material properties are the most important reasons for the functionalisation of textiles. The coating of textiles with chemically or physically modified silica sols with particle diameters smaller than 50 nm (“nanosols”) enables the manifold alteration of their physico-mechanical, optical, electrical and biological properties. Thus the protection of textiles against destruction and the creation of new advantageous functions can be realised. Prospective new products to be developed include textiles with water, oil and soil repellency and with antimicrobial properties. This article discusses recent results from applying modified silica nanosols to the functionalisation of textiles.
TL;DR: In this article, a periodic ab initio density functional theory calculation on thin films of ZnO which terminate with the (0001), (000), (100) and (110) surfaces is presented.
Abstract: Many recent studies of ZnO thin film growth have highlighted a propensity for forming c-axis aligned material, with the crystal morphology dominated by the polar {0001} surface. This is illustrated here for ZnO thin films grown by pulsed laser deposition methods, and put to advantage by using such films as templates for aligned growth of ZnO nanorods. Complementary to such experiments, we report results of periodic ab initio density functional theory calculations on thin films of ZnO which terminate with the (0001), (000), (100) and (110) surfaces. Thin (<18 layer) films which terminate with the polar (0001) and (000) surfaces are found to be higher in energy than corresponding films in which these polar surfaces flatten out forming a new ‘graphitic’-like structure in which the Zn and O atoms are coplanar and the dipole is removed. For thinner (<10 layer) slab sizes this coplanar surface is found to be lower in energy than the non-polar (100) and (110) surfaces also. The transition between the lowest energy geometries as the ZnO film thickness increases is investigated, and possible consequences for the growth mechanism discussed.
TL;DR: In this article, a broad overview of organic-inorganic hybrid assemblies based on LDH materials including their synthesis and characterization, and pointing out their potential applications is presented. But the authors focus on the compatibility between the two components, in terms of charge distribution and molecular size for the polymerization process of interleaved molecules.
Abstract: Driven by the scientific challenges involved in the creation of nanostructures providing access to new materials with unusual properties, the study of hybrid materials based on Layered Double Hydroxides (LDHs) has developed considerably during the last decade. This feature article is intended to give a broad overview of organic–inorganic hybrid assemblies based on LDH materials including their synthesis and characterization, and pointing out their potential applications. The LDH interlayer gap supplies an interesting, constrained environment arising from the anisotropic accommodation of the guest molecule at the nanoscale. Particularly, this article underlines the importance of compatibility between the two components, i.e. the organic and inorganic parts, in terms of charge distribution and molecular size for the polymerization process of interleaved molecules. Exfoliation and staging phenomena are also described. Through several examples of the shape and function of interlayer organic anions, hybrid LDH materials are described for their potential properties in optic devices, as drug delivery systems, and also as nano- and macro-fillers in polymer nanocomposites and cements, respectively. Eventually, LDH hybrid materials merge into even more complex systems for which topical applications are listed.
TL;DR: In this article, the authors synthesize WS2 and MoS2 with a closed cage structure (fullerene-like) that are termed IF phases, which are shown to play a favorable role as solid lubricants under severe conditions.
Abstract: Nanoparticles of WS2 and MoS2 with a closed cage structure (fullerene-like) that are termed IF phases are synthesized in large amounts in a pure form. These nanoparticles were shown to play a favorable role as solid lubricants under severe conditions where fluids are unable to support the heavy load and are squeezed away from the contact area. Various tribological scenarios are presented for these superior solid lubricants, demonstrating the large scale potential for applications of these materials. The mechanism of action of these solid lubricants is briefly discussed. Various other potential applications of IF phases for nanocomposites with high impact resistance; in rechargeable batteries and in optical devices are discussed in short.
TL;DR: In this paper, diacrylate dopants containing azobenzene moieties were blended with liquid crystalline diadrylate hosts and photopolymerized in a twisted configuration, resulting twisted networks were heavily crosslinked with room temperature elastic moduli on the order of 1 GPa.
Abstract: Well-defined gradients in molecular alignment have been used as tools to generate large amplitude, light-induced deformations in stiff polymer networks. These systems are reversible, monolithic and based on a simple one-step self-assembly process. To fabricate the actuators, diacrylate dopants containing azobenzene moieties were blended with liquid crystalline diacrylate hosts and photopolymerized in a twisted configuration. The resulting twisted networks were heavily crosslinked with room temperature elastic moduli on the order of 1 GPa. Regardless of the temperature with respect to the glass transitions, subsequent exposure to UV radiation induced anisotropic expansion/contraction, and simple variations in geometry were used to generate uniaxial bending or helical coiling deformation modes. Because mechanical energy is directly related to elastic modulus, these systems are expected to provide significantly greater work output than contemporary polymer actuator materials.
TL;DR: In this article, the authors discuss the design and different synthetic routes that lead to hybrid thin films that have a periodically organized porosity, the role of the organic functionality and the resulting mesophase, the comparison between one-pot and post-synthesis approaches and the applications domain of this mesostructured hybrid film are described and discussed.
Abstract: This review discussed the design and different synthetic routes that lead to hybrid thin films that have a periodically organised porosity. The mechanism of formation, the role of the organic functionality and the resulting mesophase, the comparison between one-pot and post-synthesis approaches and the applications domain of this mesostructured hybrid film are described and discussed in this article.
TL;DR: In order to conclusively establish the properties of Mn-and Co-doped ZnO, samples with 6% and 2% dopant concentrations have been prepared by the low-temperature decomposition of acetate solid solutions.
Abstract: Following the theoretical predictions of ferromagnetism in Mn- and Co-doped ZnO, several workers reported ferromagnetism in thin films as well as in bulk samples of these materials. While some observe room-temperature ferromagnetism, others find magnetization at low temperatures. Some of the reports, however, cast considerable doubt on the magnetism of Mn- and Co-doped ZnO. In order to conclusively establish the properties of Mn- and Co-doped ZnO, samples with 6% and 2% dopant concentrations have been prepared by the low-temperature decomposition of acetate solid solutions. The samples have been characterized by X-ray diffraction, EDAX and spectroscopic methods to ensure that the dopants are substitutional. All the Mn- and Co-doped ZnO samples (prepared at 400 °C and 500 °C) fail to show ferromagnetism. Instead, their magnetic properties are best described by a Curie–Weiss type behavior. It appears unlikely that these materials would be useful for spintronics, unless additional carriers are introduced by some means.