Showing papers in "Journal of Materials Chemistry in 2006"
TL;DR: In this article, stable aqueous dispersions of polymer-coated graphitic nanoplatelets can be prepared via an exfoliation/in-situ reduction of graphite oxide in the presence of poly(sodium 4-styrenesulfonate).
Abstract: For the first time, stable aqueous dispersions of polymer-coated graphitic nanoplatelets can be prepared via an exfoliation/in-situ reduction of graphite oxide in the presence of poly(sodium 4-styrenesulfonate).
2,493 citations
TL;DR: In this article, the authors describe the use of metal-organic framework (MOF) coordination polymers with regular porosity from the micro to nanopore scale for catalysis and gas processing, as well as a totally novel electrochemical approach for transition metal based MOFs.
Abstract: The generation of metal–organic framework (MOF) coordination polymers enables the tailoring of novel solids with regular porosity from the micro to nanopore scale. Since the discovery of this new family of nanoporous materials and the concept of so called ‘reticular design’, nowadays several hundred different types of MOF are known. The self assembly of metal ions, which act as coordination centres, linked together with a variety of polyatomic organic bridging ligands, results in tailorable nanoporous host materials as robust solids with high thermal and mechanical stability.
Describing examples of different zinc-containing structures, e.g. MOF-2, MOF-5 and IRMOF-8 verified synthesis methods will be given, as well as a totally novel electrochemical approach for transition metal based MOFs will be presented for the first time.
With sufficient amounts of sample now being available, the testing of metal–organic frameworks in fields of catalysis and gas processing is exemplified. Report is given on the catalytic activation of alkynes (formation of methoxypropene from propyne, vinylester synthesis from acetylene). Removal of impurities in natural gas (traces of tetrahydrothiophene in methane), pressure swing separation of rare gases (krypton and xenon) and storage of hydrogen (3.3 wt% at 2.0 MPa/77 K on Cu-BTC-MOF) will underline the prospective future industrial use of metal–organic frameworks in gas processing. Whenever possible, comparison is made to state-of-art applications in order to outline possibilities which might be superior by using MOFs.
2,008 citations
TL;DR: In this article, the authors combined and summarized the experimental findings on this nanomorphology-efficiency relationship and proposed a bicontinuous interpenetrating phase structures within these blend films.
Abstract: Within the different organic photovoltaic devices the conjugated polymer/fullerene bulk heterojunction approach is one of the foci of today's research interest. These devices are highly dependent on the solid state nanoscale morphology of the two components (donor/acceptor) in the photoactive layer. The need for finely phase separated polymer–fullerene blends is expressed by the limited exciton diffusion length present in organic semiconductors. Typical distances that these photo-excitations can travel within a pristine material are around 10–20 nm. In an efficient bulk heterojunction the scale of phase separation is therefore closely related to the respective exciton diffusion lengths of the two materials involved. Once the excitons reach the donor/acceptor interface, the photoinduced charge transfer results in the charge separation. After the charges have been separated they require percolated pathways to the respective charge extracting electrodes in order to supply an external direct current. Thus also an effective charge transport relies on the development of a suitable nanomorphology i.e. bicontinuous interpenetrating phase structures within these blend films. The present feature article combines and summarizes the experimental findings on this nanomorphology–efficiency relationship.
1,390 citations
TL;DR: The new DL_POLY_3 design is discussed, and new features implemented to simulate highly non-equilibrium processes of radiation damage and analyse the structural damage during such processes are discussed.
Abstract: DL_POLY_3 is a general-purpose massively parallel molecular dynamics simulation package embedding a highly efficient set of methods and algorithms such as: Domain Decomposition (DD), Linked Cells (LC), Daresbury Advanced Fourier Transform (DAFT), Trotter derived Velocity Verlet (VV) integration and RATTLE. Written to support academic research, it has a wide range of applications and can run on a wide range of computers; from single processor workstations to multi-processor computers. The code development has placed particular emphasis on the efficient utilization of multi-processor power by optimised memory workload and distribution, which makes it possible to simulate systems of the order of tens of millions of particles and beyond. In this paper we discuss the new DL_POLY_3 design, and report on the performance, capability and scalability. We also discuss new features implemented to simulate highly non-equilibrium processes of radiation damage and analyse the structural damage during such processes.
1,008 citations
TL;DR: Several polymers have been used to detect nitroaromatic explosives by a variety of transduction schemes as mentioned in this paper, which relies on both electronic and structural interactions between the sensing material and the analyte.
Abstract: Several polymers have been used to detect nitroaromatic explosives by a variety of transduction schemes. Detection relies on both electronic and structural interactions between the sensing material and the analyte. Quenching of luminescent polymers by electron deficient nitroaromatic explosives, such as trinitrotoluene, may be monitored to detect explosives. Resistive sensing using carbon black particles that have been coated with different organic polymers and deposited across metallic leads can also be used to detect nitroaromatic vapors in an electronic nose approach. Frequency changes in surface acoustic wave devices may be monitored to detect nitroaromatics after their adsorption into polymer coatings. Luminescent polymetalloles have recently been investigated for sensing explosives in aqueous-based solutions and for improved visual detection of trace particulates on surfaces.
971 citations
TL;DR: An overview on the recent developments in the field of liquid crystalline bent-core molecules (so-called banana liquid crystals) is given in this article, dealing with general aspects of the systematisation of the mesophases, development of polar order and chirality in this class of LC systems and explaining some general structure-property relationships.
Abstract: An overview on the recent developments in the field of liquid crystalline bent-core molecules (so-called banana liquid crystals) is given. After some basic issues, dealing with general aspects of the systematisation of the mesophases, development of polar order and chirality in this class of LC systems and explaining some general structure–property relationships, we focus on fascinating new developments in this field, such as modulated, undulated and columnar phases, so-called B7 phases, phase biaxiality, ferroelectric and antiferroelectric polar order in smectic and columnar phases, amplification and switching of chirality and the spontaneous formation of superstructural and supramolecular chirality.
753 citations
TL;DR: The considerable efforts devoted to the biomimetic elaboration of mineral structures suggest that they might be the key for future development of improved sol–gel materials for bio-applications.
Abstract: This review is devoted to the most recent developments (2000–2005) of sol–gel materials at the interface with biology. In the context of bioencapsulation in mineral hosts, novel synthetic approaches have been designed, allowing the immobilization of numerous proteins, enzymes and immune molecules as well as poly-saccharides, phospholipids and nucleic acids. These efforts have led to the development of new biosensors and bioreactors. A similar trend was also observed for whole cell encapsulation, survival periods over several weeks now being achieved. This has opened the possibility of designing hybrid hosts for cell-based biosensing and bioproduction, ultimately allowing the development of artificial organs. Indeed, applications of sol–gel processes are not restricted to bioencapsulation, as demonstrated by recent progress in drug release systems and bioactive materials. Finally, the considerable efforts devoted to the biomimetic elaboration of mineral structures suggest that they might be the key for future development of improved sol–gel materials for bio-applications.
722 citations
Journal Article•
TL;DR: This paper discusses how and why wrinkles/buckles form in various materials, and describes several examples from everyday life that demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales.
Abstract: The English-language dictionary defines wrinkles as "small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking". In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (e.g., wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.
670 citations
TL;DR: A two-dimensional network of carbon nanotubes can be regarded as a novel transparent electronic "material" with excellent electrical, optical and mechanical properties as discussed by the authors, which can have a significant impact on a variety of emerging technologies and markets.
Abstract: A two-dimensional network – often referred to as a thin film – of carbon nanotubes can be regarded as a novel transparent electronic “material” with excellent – and tunable – electrical, optical and mechanical properties. The films display high conductivity, high carrier mobility and optical transparency, in addition to flexibility, robustness and environmental resistance. These attributes, coupled with room temperature printing or spraying technology, ensure that the material will have a significant impact on a variety of emerging technologies and markets, ranging from macroelectronics to solid state lighting, organic solar cells and smart fabrics. The performance parameters of the first devices fabricated – smart windows, OLEDs and organic solar cells – indicate that the material is ready for product development
594 citations
TL;DR: Some of the most exciting recent developments in LDH chemistry are discussed, with an emphasis on how we can control their chemistry and how in situ techniques can provide enhanced understanding of the nanoscopic processes involved in intercalation reactions.
Abstract: Layered double hydroxides (LDHs) have a vast number of potential applications in fields as diverse as separation chemistry, polymer additives and catalysis. They are facile and cheap to prepare, and are environmentally friendly. In this paper, some of the most exciting recent developments in LDH chemistry are discussed, with an emphasis on how we can control their chemistry and how in situ techniques can provide enhanced understanding of the nanoscopic processes involved in intercalation reactions.
526 citations
TL;DR: In this paper, the state of the art for hierarchical meso-macroporous inorganic materials and their carbon replicas is reviewed from the viewpoint of synthesis strategies and emerging applications.
Abstract: A great deal of progress has recently been made in the field of ordered porous materials having uniform channel dimensions which can be adjusted over a wide range of length scales. Incorporation of macropores in mesoporous materials combines benefits from both the mesoporous and macroporous structures. Hierarchical materials containing both interconnected macroporous and mesoporous structures have enhanced properties compared with single-sized pore materials due to increased mass transport through the material and maintainance of a specific surface area on the level of fine pore systems. Bimodal mesoporous–macroporous inorganic materials can be prepared by using a self-assembling surfactant or amphiphilic block copolymer species in conjunction with macrotemplates such as colloidal crystals, polymer foams, bio-celluloses, emulsions, inorganic salts and ice crystals, or by macroscopic phase separations. Here, we review the state of the art for hierarchical meso–macroporous inorganic materials and their carbon replicas from the viewpoint of synthesis strategies and emerging applications. Detailed synthetic processes are described, in which the very recently developed spontaneous formation of meso–macroporous (single and binary) metal oxides, metal phosphates and aluminosilicates is specifically addressed. These novel meso–macroporous materials have found a number of applications, including HPLC separation, catalysis, fuel cell electrode materials, biomaterials engineering, controlled drug delivery devices, and membrane reactors, and these are discussed illustratively.
TL;DR: In this paper, an optimal molar Si/Al ratio in the range of 25-50 has been identified for mesoporous ZSM-5 zeolites with preserved structural integrity, and a successive combination of post-treatments, in which desilication is followed by dealumination, enables a decoupled modification of the mesopore and acidic properties.
Abstract: Recent studies have shown that desilication by treatment in alkaline medium is, with respect to other methods, a very suitable and reproducible methodology to obtain mesoporous ZSM-5 zeolites with preserved structural integrity. This feature article analyzes mechanistic and kinetic aspects associated with this post-synthesis treatment. Framework aluminium controls the process of framework silicon extraction and makes desilication selective towards intracrystalline mesopore formation. An optimal molar Si/Al ratio in the range of 25–50 has been identified. At higher Si/Al ratios non-selective and excessive extraction of framework silicon occurs, while minor extraction and limited mesopore formation occurs at lower ratios. The presence of non-framework aluminium species, for example obtained by steam treatment, inhibits mesopore formation by alkaline treatment due to reinsertion of these species into the zeolite framework. Additional kinetic optimization of the physicochemical properties of the hierarchical porous zeolite structures is achieved by variation of time and temperature of the alkaline treatment. A successive combination of post-treatments, in which desilication is followed by dealumination, enables a decoupled modification of the mesoporous and acidic properties, being interesting in catalyst design and optimization. Preliminary work on other zeolite framework types has shown a promising outlook of the alkaline treatment. Development of mesoporous zeolites via desilication should induce a more efficient usage of the zeolite crystal due to an improved accessibility and a facilitated transport to and from the active sites.
TL;DR: In this paper, the authors showed that micrometer-sized and well-defined LDH nanosheets can be readily attained by synthesizing large crystals of LDH-carbonate via homogeneous precipitation and subsequent exfoliation of the nitrate form in formamide.
Abstract: Exfoliation of layered double hydroxides (LDHs) into single layers provides a new type of nanosheet with ultimate two-dimensional anisotropy and positive charge. In this Highlight article, we briefly review the latest advances in this emerging field. In comparison with the previous studies, we show that micrometer-sized and well-defined LDH nanosheets can be readily attained by synthesizing large crystals of LDH-carbonate via so-called homogeneous precipitation and subsequent exfoliation of the nitrate form in formamide. Some general aspects including the exfoliating process and characterization, a plausible delaminating mechanism, and future challenges, are presented and discussed.
Journal Article•
TL;DR: In this paper, the authors explore recent advances in the design and engineering of materials wholly or principally constructed from peptides, and focus on materials that are able to respond to changes in their environment (pH, ionic strength, temperature, light, oxidation/reduction state, presence of small molecules or the catalytic activity of enzymes) by altering their macromolecular structure.
Abstract: This article explores recent advances in the design and engineering of materials wholly or principally constructed from peptides. We focus on materials that are able to respond to changes in their environment (pH, ionic strength, temperature, light, oxidation/reduction state, presence of small molecules or the catalytic activity of enzymes) by altering their macromolecular structure. Such peptide-based responsive biomaterials have exciting prospects for a variety of biomedical and bionanotechnology applications in drug delivery, bio-sensing and regenerative medicine.
TL;DR: In this article, the authors present several examples of anisotropic noble metal nanocrystals obtained by different methods and the important role of twinning in determining the habit of the final morphology is discussed.
Abstract: Nanotechnology provides the ability to engineer the properties of materials by controlling their size and shape. Among the most interesting nanostructures are anisotropic noble metal nanocrystals such as nanorods and nanowires. Nevertheless, the production of such crystals in a controlled fashion remains as a challenging task, and many available colloidal techniques produce a mixture of morphologies. In cases where high yields of a particular anisotropic structure have been produced, the growth mechanism has been primarily explained in terms of the presence of surfactants or capping agents that regulate the growth of the crystal in a particular direction. However, the growth mechanism should also consider nucleation and kinetics, and not only thermodynamics or physical restrictions imposed by the surface stabilizing agent. In this work, we present several examples of anisotropic noble metal nanocrystals obtained by different methods. Finally, the important role of twinning in determining the habit of the final morphology is discussed.
TL;DR: In this paper, the authors report their recent research progress in this emerging field; their research is concentrated on the exploration of various novel organizing schemes through which interior spaces with architectural design can be created for inorganic nanostructures.
Abstract: One of the major technological challenges in nanoscience and nanotechnology is the self-assembly of tiny nano-building units (e.g., nanokits and nanoparts) into larger (i.e., mesoscale or microscale) organized conformations and geometrical architectures for device applications. To meet the requirements of new applications, an interior space for the nanostructures may be further required. When coupled with chemical functionality of boundary materials, the interior “nanospace” of the nanostructures possesses both aesthetic beauty and scientific attraction. For example, in addition to well studied core–shell nanostructures, there has been increasing research interest in the fabrication of hollow inorganic nanostructures owing to their potential applications in optical, electronic, magnetic, catalytic and sensing devices ranging from photonic crystals to drug-delivery carriers and nanoreactors. In this feature article, we report our recent research progress in this emerging field; our research is concentrated on the exploration of various novel organizing schemes through which interior spaces with architectural design can be created for inorganic nanostructures. These template-free “one-pot” synthetic methods include “oriented attachment”, Ostwald ripening and Kirkendall effect etc. for direct solid evacuation under mild reaction conditions. Future research directions will also be addressed in this article.
Journal Article•
TL;DR: In this paper, the authors argue that most of the difficulties disappear when taking the thixotropy of yield stress fluids into account, and demonstrate an experimental protocol that allows reproducible data to be obtained for the critical stress necessary for flow of these fluids.
Abstract: The yield stress of many yield stress fluids has turned out to be difficult to determine experimentally. This has led to various discussions in the literature about those experimental difficulties, and the usefulness and pertinence of the concept of yield stress fluids. We argue here that most of the difficulties disappear when taking the thixotropy of yield stress fluids into account, and will demonstrate an experimental protocol that allows reproducible data to be obtained for the critical stress necessary for flow of these fluids. As a bonus, we will show that the interplay of yield stress and thixotropy allows one to account for the ubiquitous shear localization observed in these materials. However, due to the thixotropy the yield stress is no longer a material property, since it depends on the (shear) history of the sample.
TL;DR: Three different classes of ERMs are described, based on supramolecular assemblies, chemically crosslinked gels and (nanoparticle) surfaces, and potential applications in regenerative medicine, diagnostics, and drug delivery are discussed.
Abstract: Enzyme-responsive materials (ERMs) are a new class of smart materials that undergo macroscopic transitions when triggered by selective catalytic actions of enzymes. The use of enzymes as stimuli to trigger mechanical responses in materials opens up a number of possible applications in biology and medicine. Three different classes of ERMs are described, based on supramolecular assemblies, chemically crosslinked gels and (nanoparticle) surfaces. Potential applications in regenerative medicine, diagnostics, and drug delivery are discussed.
TL;DR: The perovskite (La0.75Sr0.25)Cr0.5Mn 0.5O3 (LSCM) is shown to be an effective, redox-stable electrode that can be used for both cathode and anode SOFC operation, to provide a symmetrical fuel cell system with good performance characteristics as mentioned in this paper.
Abstract: The perovskite (La0.75Sr0.25)Cr0.5Mn0.5O3 (LSCM) is shown to be an effective, redox-stable electrode that can be used for both cathode and anode SOFC operation, to provide a symmetrical fuel cell system with good performance characteristics.
TL;DR: In this article, a bi-functional coupling agent, (3-methacryloxypropyl)trimethoxysilane (MPS), was successfully functionalized with a facile neutral solvent method.
Abstract: Alumina nanoparticles were successfully functionalized with a bi-functional coupling agent, (3-methacryloxypropyl)trimethoxysilane (MPS), through a facile neutral solvent method. MPS was found to be covalently bound with the nanoparticles. The linked MPS was polymerized with a vinyl-ester resin monomer through a free radical polymerization. Atomic force microscope phase images showed a uniform distribution of nanoparticles. Microtensile test results revealed the Young's modulus and strength increasing with particle loading. Microscopic examinations revealed the presence of large plastic deformations at the micron scale in the nanocomposites in agreement with the observed strengthening effect of functionalized nanoparticles. Thermo-gravimetric analysis (TGA) did not show any significant change in the thermal degradation of the nanocomposite as compared with the neat resin. The polymer matrix effectively protected the alumina nanoparticles from dissolution in basic and acidic solutions.
TL;DR: In this paper, the T(LIESST) procedure is used to measure the limit temperature above which a photomagnetic effect in a material is erased by warming the material from 10 K at a rate of 0.3 K min−1.
Abstract: The Light-Induced Excited Spin State Trapping (LIESST) effect, encountered in some Spin-Crossover (SCO) complexes, is of major interest for the design of optical switches. Nevertheless, until now any applications have been prohibited, because the lifetimes of the photomagnetic states are long enough only at low temperatures. Hereby we review the recent progress made by using the T(LIESST) procedure, which consists of systematically measuring the limit temperature above which a photomagnetic effect in a material is erased by warming the material from 10 K at a rate of 0.3 K min−1. This method has been today applied to more than sixty SCO compounds and by comparing the various materials a relation between T(LIESST) and thermal spin transition (T1/2) temperatures has been obtained, i.e.T(LIESST) = T0
− 0.3T1/2. The second section reports part of works done to identify the parameters affecting the T0 factor; that is to find a guideline for the rational design of materials with long-lived photomagnetic lifetimes at working room temperature. Finally, we present the procedure used to simulate a T(LIESST) curve and illustrate it using the examples of a mononuclear SCO complex and of a binuclear SCO system displaying antiferromagnetic interactions.
TL;DR: The organic functionalisation method for small detonation diamond agglomerates is reported, which is potentially useful for the synthesis of surface-bound peptides and for the attachment of biologically active building blocks, which could be used in drug delivery and fluorescence marker applications.
Abstract: Detonation diamond is a promising material for biological applications due to its biocompatibility and fluorescence from lattice defects. Here we report on the organic functionalisation method for small detonation diamond agglomerates. After surface homogenisation by reduction and grafting of a silane linker, amino acids have been coupled to the diamond surface and the formation of a small peptide has been achieved. These novel functionalised diamond materials are potentially useful for the synthesis of surface-bound peptides and for the attachment of biologically active building blocks, which could be used in drug delivery and fluorescence marker applications.
TL;DR: Mesoporous silica SBA-15 was prepared to evaluate its effectiveness as a matrix for the controlled delivery of macrolide-type antibiotics, and two types of material were used to evaluate the delivery.
Abstract: Mesoporous silica SBA-15 was prepared to evaluate its effectiveness as a matrix for the controlled delivery of macrolide-type antibiotics. Two types of material were used to evaluate the delivery: calcined samples and samples functionalized with octyltrimethoxysilane and octadecyltrimethoxysilane. The samples were charged with the macrolide antibiotic erythromycin and the release assays were carried out in vitro. It has been observed that the release rate decreases as the population of hydrophobic –CH2 moieties in the host increases.
TL;DR: In this paper, the bioactivity behavior of mesoporous materials is revisited and strategies to modify their kinetics are proven and discussed, on the basis of the experimental data showing the feasibility of control of their bioactivity kinetics, together with their controlled drug release abilities.
Abstract: The bioactivity behaviour of SBA-15, MCM-48, MCM-41 mesoporous materials, is revisited in this paper. The influence of their different textural and structural properties on apatite formation is outlined and strategies to modify their kinetics are proven and discussed. On the basis of the experimental data showing the feasibility of control of the bioactivity kinetics on mesoporous materials, together with their controlled drug release abilities, new possibilities for tissue engineering developments are proposed.
TL;DR: In this article, in situ X-ray diffraction and Mossbauer spectroscopy were used to monitor the extraction and insertion of Li2FeSiO4 during the first two cycles.
Abstract: The lithium extraction and insertion mechanism in the cathode material Li2FeSiO4 has been monitored by in situ X-ray diffraction and Mossbauer spectroscopy during the first two cycles. The residual amounts of Li2FeSiO4 and LiFeSiO4 in the fully charged and discharged states are 5% and 10%, respectively, on the basis of both Mossbauer spectroscopy and powder XRD studies; this is also in good agreement with the results of electrochemical measurements. The observed lowering of the potential plateau from 3.10 to 2.80 V during the first cycle can be explained by a structural rearrangement in which some of the Li ions (in the 4b site) and Fe ions (in the 2a site) become interchanged.
TL;DR: In this paper, four soluble perylene diimide derivatives (PDIs) have been prepared and their UV-visible and photoluminescence (PL) spectroscopy, cyclic voltammetry (CV) and thermal properties were studied.
Abstract: Four soluble perylene diimide derivatives (PDIs) have been prepared and their UV–visible and photoluminescence (PL) spectroscopy, cyclic voltammetry (CV) and thermal properties were studied. ITO/PEDOT∶PSS/poly(3-hexylthiophene) (P3HT)∶PDIs/LiF/Al photovoltaic devices were fabricated with PDIs as electron accepting and transporting materials. The highest incident photon-to-current conversion efficiency (IPCE) of 19% at 495 nm and the power conversion efficiency (PCE) of 0.18% under AM 1.5 (100 mW cm−2) with a short-circuit current density (JSC) of 1.32 mA cm−2, an open circuit voltage (VOC) of 0.36 V, and a fill factor (FF) of 0.38 have been achieved with 1 ∶ 4 ratio of P3HT
∶
N,N′-di(1-nonadecyl)perylene-3,4,9,10-bis(dicarboximide) (PDI-C9) after annealing at 80 °C for 1 h. 1,7-Bis(N-pyrrolidinyl)-N,N′-dicyclohexyl-3,4,9,10-perylenebis(dicarboximide) (5-PDI), which has the electron donating pyrrolidinyl group, absorbed the long wavelength region to give IPCE onset higher than 750 nm and the pyrrolidinyl group also raised the LUMO level of 5-PDI to render the high VOC (up to 0.71 V) in photovoltaic device.
TL;DR: In this article, the supermagnetism of NiO and MnO nanoparticles has been characterized by X-ray diffraction and transmission electron microscopy, and it has been shown that NiO exhibits supermagnetic hysteresis below the blocking temperature (TB).
Abstract: Nanoparticles of MnO with average diameters in the 6–14 nm range have been prepared by the decomposition of manganese cupferronate in the presence of TOPO, under solvothermal conditions. Nanoparticles of NiO with average diameters in the 3–24 nm range have been prepared by the decomposition of nickel cupferronate or acetate under solvothermal conditions. The nanoparticles have been characterized by X-ray diffraction and transmission electron microscopy. Both MnO and NiO nanoparticles exhibit supermagnetism, accompanied by magnetic hysteresis below the blocking temperature (TB). The TB increases with the increase in particle size in the case of NiO, and exhibits the reverse trend in the case of MnO.
TL;DR: In this article, the preparation of hybrid polymer/zinc oxide (ZnO) solar cells, in which the metal oxide consists of ZnO columnar structures grown perpendicularly on a flat, dense "backing" layer, as a means to provide a direct and ordered path for photogenerated electrons to the collecting electrode.
Abstract: We focus on the preparation of hybrid polymer/zinc oxide (ZnO) solar cells, in which the metal oxide consists of ZnO columnar structures grown perpendicularly on a flat, dense “backing” layer, as a means to provide a direct and ordered path for photogenerated electrons to the collecting electrode. We used scanning electron microscopy, absorption spectroscopy and photovoltaic device measurements to study the morphology and device performance of the prepared structures. Different solution chemical routes were investigated for the synthesis of the inorganic device components, i.e. the ZnO columnar structures and the “backing” layers, which act as a seed-growth layer for the ZnO rods. The growth of the ZnO rods was dependent on the morphological and structural characteristics of the seed layer and moreover, the seed layer itself was also affected by the synthetic conditions for ZnO rod growth. Different polymers (high hole-mobility MEH-PPV based polymer and P3HT) were compared in these structures and power conversion efficiencies of 0.15 and 0.20% were achieved under 1 Sun illumination, respectively. Results are discussed in terms of the optoelectronic properties of the polymers.
TL;DR: In this article, a highly soluble polycarbazole (PCz) has been synthesized, and used as a donor material with perylene tetracarboxydiimide (PDI) as an acceptor and light harvesting material in bulk-heterojunction solar cells.
Abstract: A highly soluble polycarbazole (PCz) has been synthesized, and used as a donor material with perylene tetracarboxydiimide (PDI) as an acceptor and light harvesting material in bulk-heterojunction solar cells. This donor/acceptor (D/A) pair shows a broad absorption fit within the solar spectrum, and balanced potential levels for charge separation at the D/A interface. The best photovoltaic device exhibits a high external quantum efficiency (EQE) of 16% at 490 nm and a power efficiency of 0.6% under illumination with solar light. The morphology of PCz/PDI films studied by SEM showed the formation of a favorable micro-phase separation, which is important in obtaining high efficiency. Incorporation of poly(3-hexyl)thiophene (P3HT) instead of PCz as donor produced a much lower Voc and thus a lower efficiency in solar cells.
TL;DR: In this article, a review of recent results obtained by studying the low-temperature specific heat of some of the most popular molecule-based materials is presented. And the possibilities of application of such materials for magneto-cooling at low temperatures and the limitations in other temperature ranges are discussed.
Abstract: We critically review recent results obtained by studying the low-temperature specific heat of some of the most popular molecule-based materials. After introducing the experimental techniques and basic theoretical framework needed for heat capacity determination and understanding, we report on the magnetothermal properties of molecular antiferromagnetic wheels. For selected molecular high-spin clusters, particular emphasis is devoted to magnetic quantum tunnelling and coherence as well as collective phenomena as probed by heat capacity experiments. We discuss also the possibilities of application of molecule-based materials for magneto-cooling at low temperatures and the limitations in other temperature ranges. Perspectives for future developments are mentioned as well.