Showing papers in "Journal of Materials Chemistry in 2009"
TL;DR: In this article, an inverted polymer solar cell geometry comprising a total of five layers was optimized using laboratory scale cells and the operational stability was studied under model atmospheres, where the inverted devices were compared to model devices with a normal geometry where the order of the layers was substrate-ITO-PEDOT:PSS-(active layer)-aluminium.
Abstract: An inverted polymer solar cell geometry comprising a total of five layers was optimized using laboratory scale cells and the operational stability was studied under model atmospheres. The device geometry was substrate-ITO-ZnO-(active layer)-PEDOT:PSS-silver with P3HT-PCBM as the active layer. The inverted devices were compared to model devices with a normal geometry where the order of the layers was substrate-ITO-PEDOT:PSS-(active layer)-aluminium. In both cases illumination was through the substrate which requires that it is transparent. Both device types were optimized to a power conversion efficiency of 2.7% (1000 W m−2, AM1.5G, 72 ± 2 °C). The devices were operated under illumination while being subjected to different atmospheres to identify the dominant modes of degradation. Dry nitrogen (99.999%), dry oxygen (99.5%), humid nitrogen (90 ± 5% relative humidity) and ambient atmosphere (20% oxygen, 20 ± 5% relative humidity) were employed and both device types were found to be stable in a nitrogen atmosphere during the test period of 200 hours. The devices with a normal geometry where an aluminium electrode is employed gave stable operation in dry oxygen but did not give stable device operation in the presence of humidity. The inverted devices behaved oppositely where the less reactive silver electrode gave stable operation in the presence of humidity but poor stability in the presence of oxygen. The inverted model device was then used to develop a new process giving access to fully roll-to-roll (R2R) processed polymer solar cells entirely by solution processing starting from a polyethyleneterephthalate (PET) substrate with a layer of indium-tin-oxide (ITO). All processing was performed in air without vacuum coating steps and modules comprising eight serially connected cells gave power conversion efficiencies as high as 2.1% for the full module with 120 cm2 active area (AM1.5G, 393 W m−2) and up to 2.3% for modules with 4.8 cm2 active area (AM1.5G, 1000 W m−2).
1,237 citations
TL;DR: In this paper, the initiator molecules were covalently bonded to the graphene surface via a diazonium addition and the succeeding atom transfer radical polymerization linked polystyrene chains (82 wt% grafting efficiency).
Abstract: For developing high performance graphene-based nanocomposites, dispersal of graphene nanosheets in polymer hosts and precise interface control are challenging due to their strong interlayer cohesive energy and surface inertia. Here we report an efficient method to functionalize graphene nanosheets. The initiator molecules were covalently bonded to the graphene surface via a diazonium addition and the succeeding atom transfer radical polymerization linked polystyrene chains (82 wt% grafting efficiency) to the graphene nanosheets. The prominent confinement effect arising from nanosheets resulted in a 15 °C increase in the glass transition temperature of polystyrene compared to the pure polymer. The resulting polystyrene nanocomposites with 0.9 wt% graphene nanosheets revealed around 70% and 57% increases in tensile strength and Young's modulus. The protocol is believed to offer possibilities for optimizing the processing properties and interface structure of graphene-polymer nanocomposites.
1,226 citations
TL;DR: In this paper, a superparamagnetic graphene oxide-Fe3O4nanoparticles hybrid was prepared via a simple and effective chemical precipitation method, which was then loaded with doxorubicin hydrochloride (DXR) and the loading capacity was as high as 1.08 mg mg−1.6 wt% by atomic absorption spectrometry.
Abstract: A superparamagnetic graphene oxide –Fe3O4nanoparticles hybrid (GO–Fe3O4) was prepared via a simple and effective chemical precipitation method. The amount of loading of Fe3O4 on GO was estimated as 18.6 wt% by atomic absorption spectrometry. The hybrid was then loaded with doxorubicin hydrochloride (DXR) and the loading capacity was as high as 1.08 mg mg−1. Both of the GO–Fe3O4 hybrids before and after loading with DXR can be dispersed well in aqueous solution. They can congregate under acidic conditions and move regularly under the force of an external magnet. Furthermore, the aggregated hybrid can be redispersed to form a stable suspension under basic conditions. These properties make it a potential candidate for controlled targeted drug delivery and release.
979 citations
TL;DR: In this paper, the authors summarized recent research on and development of semiconductor-based photocatalyst materials that are applicable to environmental remediation and/or chemical synthesis purposes, including the incorporation of noble metal nanoclusters onto the surface of semiconducted particles.
Abstract: This feature article summarizes recent research on and development of semiconductor-based photocatalyst materials that are applicable to environmental remediation and/or chemical synthesis purposes. A wide variety of TiO2 particles and/or films have been studied during the past 30 years because they are the most stable and powerful photocatalysts leading to the degradation of various organic pollutants. The photocatalytic performance of other semiconductor materials such as ZnO, SnO2, WO3, Fe2O3 and CdS has also been intensively investigated. A general limitation in the efficiency of any photocatalytic process is the recombination of the photogenerated charge carriers, i.e., of electrons and holes, following bandgap illumination. Considerable efforts have been made to suppress this recombination and hence to enhance the charge carrier separation and the overall efficiency by means of coupling of different semiconductors with desirable matching of their electronic band structures, or incorporation of noble metal nanoclusters onto the surface of semiconductor photocatalyst particles. Modification of the physicochemical properties, such as particle size, surface area, porosity and/or crystallinity of the semiconductor materials, and optimization of the experimental conditions, such as pH, illumination conditions and/or catalyst loading, during photocatalytic reactions have also been carefully addressed to achieve high reaction rates or yields. To utilize solar energy more efficiently, i.e., to extend the optical absorption of the mostly UV-sensitive photocatalysts into the visible light range, numerous research groups have contributed to the development of novel visible light active photocatalysts. With the application of semiconductors with narrower bandgaps such as CdS, Fe2O3 and WO3 being straightforward choices, doping of wide bandgap semiconductors like TiO2 has been the most popular technique to enhance the catalysts' optical absorption abilities. Research on mixed-oxide-based semiconductor photocatalysts with deliberately modulated band structures has also attracted tremendous attention in the past decade, concentrating on, for example, the generation of H2 and/or O2 from H2O splitting, and the degradation of organic pollutants under visible light irradiation. Both theoretical calculations and experimental results have convincingly shown that the developed materials can serve as highly efficient photocatalysts that are both environmentally and economically significant.
869 citations
TL;DR: In this article, the hierarchical porous NiO nano/micro superstructures were obtained from the precursor by a simple calcination procedure, which achieved a specific capacitance of 710 F g−1 at 1 A g −1 and offered a good capacitance retention of ca. 98% after 2000 continuous charge discharge cycles.
Abstract: We report a practical and efficient strategy for synthesizing hierarchical (meso- and macro-)porous NiO nano/micro spherical superstructures. First, β-Ni(OH)2 microspheres were self-assembled based on the coalescence and Ostwald-ripening mechanisms during refluxing in an alkaline solution with Ni(NH3)x2+ at 97 °C for 1 h under vigorous stirring. Second, hierarchical porous NiO microsphere superstructures were obtained from the precursor by a simple calcination procedure. The resulting superstructures comprised two-dimensional mesoporous NiO petal building blocks. Electrochemical data demonstrated that the hierarchical porous NiO nano/micro superstructures were capable of delivering a specific capacitance of 710 F g−1 at 1 A g−1 and offered a good specific capacitance retention of ca. 98% after 2000 continuous charge-discharge cycles. This indicates that we successfully met key requirements in terms of large specific energy density, high-rate capability and good electrochemical stability. We would expect our superstructures to be good candidates for a low-cost replacement for the state-of-the-art supercapacitor material RuO2.
808 citations
TL;DR: In this article, fluorescent carbon nanoparticles (CNPs) were synthesized by laser irradiation of a suspension of carbon powders in organic solvent and the origin of the luminescence was attributed to carboxylate ligands on the surface of the CNPs.
Abstract: Fluorescent carbon nanoparticles (CNPs) were synthesized by laser irradiation of a suspension of carbon powders in organic solvent. The surface modification on the CNPs was fulfilled simultaneously with the formation of the CNPs, and tunable light emission could be generated by selecting appropriate solvents. The origin of the luminescence was attributed to carboxylate ligands on the surface of the CNPs.
804 citations
TL;DR: The layered oxides of vanadium and molybdenum have been studied for close to 40 years as possible cathode materials for lithium batteries or electrochromic systems as mentioned in this paper.
Abstract: The layered oxides of vanadium and molybdenum have been studied for close to 40 years as possible cathode materials for lithium batteries or electrochromic systems. The highly distorted metal octahedra naturally lead to the formation of a wide range of layer structures, which can intercalate lithium levels exceeding 300 Ah/kg. They have found continuing success in medical devices, such as pacemakers, but many challenges remain in their application in long-lived rechargeable devices. Their high-energy storage capability remains an encouragement to researchers to resolve the stability concerns of vanadium dissolution and the tendency of lithium and vanadium to mix changing the crystal structure on cycling the lithium in and out. Nanomorphologies have enabled higher reactivities to be obtained for both vanadium and molybdenum oxides, and with the latter show promise for electrochromic displays.
762 citations
TL;DR: Polydisperse, functionalized, chemically converted graphene (f-CCG) nanosheets, which can be homogeneously distributed into water, ethanol, DMF, DMSO and 3-aminopropyltriethoxysilane (APTS), were obtained via facile covalent functionalization with APTS.
Abstract: Polydisperse, functionalized, chemically converted graphene (f-CCG) nanosheets, which can be homogeneously distributed into water, ethanol, DMF, DMSO and 3-aminopropyltriethoxysilane (APTS), were obtained via facile covalent functionalization with APTS. The resulting f-CCG nanosheets were characterized by FTIR, XPS, TGA, EDX, AFM, SEM, and TEM. Furthermore, the f-CCG nanosheets as reinforcing components were extended into silica monoliths. Compressive tests revealed that the compressive failure strength and the toughness of f-CCG-reinforced APTS monoliths at 0.1 wt% functionalized, chemically converted graphene sheets compared with the neat APTS monolith were greatly improved by 19.9% and 92%, respectively.
699 citations
TL;DR: Graphene is a fascinating new nanocarbon possessing, single-, bi- or few- (≤ ten) layers of carbon atoms forming six-membered rings as mentioned in this paper.
Abstract: Graphene is a fascinating new nanocarbon possessing, single-, bi- or few- (≤ ten) layers of carbon atoms forming six-membered rings. Different types of graphene have been investigated by X-ray diffraction, atomic force microscopy, transmission electron microscopy, scanning tunneling microscopy and Raman spectroscopy. The extraordinary electronic properties of single-and bi-layer graphenes are indeed most unique and unexpected. Other properties of graphene such as gas adsorption characteristics, magnetic and electrochemical properties and the effects of doping by electrons and holes are equally noteworthy. Interestingly, molecular charge-transfer also markedly affects the electronic structure and properties of graphene. Many aspects of graphene are yet to be explored, including synthetic strategies which can yield sufficient quantities of graphene with the desired number of layers.
661 citations
TL;DR: In this paper, the authors introduce the concepts of MRI and MRI contrast agents, and then mainly discuss the synthesis, surface modification, surface functionalization, colloidal stability and biocompatibility of iron oxide particles, followed by their MRI applications.
Abstract: Superparamagnetic iron oxide nanoparticles have received great attention due to their applications as contrast agents for magnetic resonance imaging (MRI). This feature article briefly introduces the concepts of MRI and MRI contrast agents, and then mainly discusses the synthesis, surface modification, surface functionalization, colloidal stability and biocompatibility of iron oxide particles, followed by their MRI applications.
641 citations
TL;DR: In this paper, it was shown that carbon dioxide is preferentially adsorbed over methane or nitrogen, and that the concentration of open metal sites plays a major role in the adsorption of methane and carbon dioxide.
Abstract: The metal–organic frameworks M2(dhtp)(H2O)2·8H2O (CPO-27-M, M = Ni, Mg) can be activated to give the empty framework compounds M2(dhtp) with a honeycomb analogous structure containing large micropores of 11–12 A diameter and a high concentration of open metal sites. These sites play a major role in the adsorption of methane and carbon dioxide, which was studied at pressures up to 100 bar and 50 bar, respectively, and various temperatures in the range of 179 to 473 K. Both gases are taken up by the material in significant amounts. The maximum excess adsorption of CO2 observed at 298 K was 51 wt.% for Ni2(dhtp) and 63 wt.% for Mg2(dhtp). A surprisingly large amount of CO2, in the range 25–30 wt.%, was still adsorbed at 473 K. Up to 18 and 22 wt.% methane were adsorbed at 179 K in the nickel and the magnesium compound, respectively. Congruent with this result is the high isosteric heat of adsorption observed, which was found to be in the range 38–43 kJ mol−1 for CO2 and 20–22 kJ mol−1 for CH4, initially. The heat of adsorption decreases significantly after the open metal sites have been occupied, which also is reflected in the shape of the adsorption isotherms. The vacant coordination site at the metal atom also imparts favorable properties in respect to gas separation onto the material. Breakthrough experiments using Ni2(dhtp) and gas mixtures of CO2–N2 and CO2–CH4 demonstrate the ability of the material to separate these gases. It is shown that carbon dioxide is preferentially adsorbed over methane or nitrogen. In the case of CO2–N2, the retention is quantitative within the precision of the detection system.
TL;DR: In this article, a systematic analysis of the particle-based aggregation mechanism of oriented attachment in controllable synthesis of functional inorganic materials is described in particular, with nanoparticles or nanoribbons as primary building units to form 1D, 2D or 3D structures.
Abstract: The latest advances in oriented attachment controlled morphosynthesis and crystal growth of various technically important inorganic materials have been reviewed with the focus on how to generate inorganic micro-/nanostructured materials based on the so-called oriented attachment mechanism. The overview about the basic crystallization principles nowadays falls into two types, i.e., one is the classical crystal growth mode, which is via atom-by-atom additions to an existing nucleus or dissolution of unstable phases and reprecipitation of more stable phases, and the other occurs through particle based aggregation modes involving the process of mesoscopic transformation. The systematic analysis of the particle based aggregation mechanism of oriented attachment in controllable synthesis of functional inorganic materials will be described in particular. Several fashions of attachment are undertaken in the already explored reaction systems, with nanoparticles or nanoribbons as primary building units to form 1D, 2D or 3D structures, and heterostructures. The mechanism of oriented attachment could happen in systems with addition of organic additives or without, demonstrating that organic additives are not the essential factor for this kind of growth mode, which shed new light to intensive understanding of this particular phenomenon. With organic additives, i.e., reactions in organic solvents or in aqueous solution, oriented attachment events can occur too. Current developments in oriented attachment, including the basic principles and potentials with specific examples, indubitably reinforce the understanding of detailed interaction mechanisms between inorganic nanoparticles and their subsequent high order self-assembly mechanism, which are definitely promising for rationally designing various kinds of inorganic materials with ideal hierarchy, controllable length scale, and structures in solution-based systems.
TL;DR: In this paper, the authors summarized several important kinds of novel support materials for PEM fuel cells (including direct methanol fuel cells): nanostructured carbon materials (carbon nanotubes, carbon nanofibers, mesoporous carbon), conductive doped diamonds and nanodiamonds, conductive oxides (tin oxide/indium tin oxide, titanium oxide, tungsten oxide), and carbides (tungsten carbides).
Abstract: Catalyst support materials exhibit great influence on the cost, performance, and durability of polymer electrolyte membrane (PEM) fuel cells. This feature article summarizes several important kinds of novel support materials for PEM fuel cells (including direct methanol fuel cells): nanostructured carbon materials (carbon nanotubes, carbon nanofibers, mesoporous carbon), conductive doped diamonds and nanodiamonds, conductive oxides (tin oxide/indium tin oxide, titanium oxide, tungsten oxide), and carbides (tungsten carbides). The advantages and disadvantages, the acting mechanism to promote electrocatalytic performance, and the strategies to improve present catalyst support materials and search for new ones are discussed. This is expected to shed light on future development of catalyst supports for PEM fuel cells.
TL;DR: In this paper, the relationship between material structure and electrode performance is investigated from the viewpoint of graphene. But the understanding of the relationship is still poor due to the complexity of the carbon structures, hindering the development of high performance batteries.
Abstract: Recent progress in the study of graphene has triggered a gold rush for exploiting its possible applications in various areas. Graphene-containing carbonaceous materials have long been selected as electrodes in rechargeable lithium batteries. However, the understanding of the relationship between material structure and electrode performance is still poor due to the complexity of the carbon structures, which hinders the development of high performance batteries. Now it is time to focus on the structure–property relationship of carbonaceous electrodes again, but from the viewpoint of graphene.
TL;DR: In this paper, a general strategy has been demonstrated to achieve optimum electrochemical performance by constructing 3D nanocomposite architecture with the combination of nanosize Sn particles and graphene nanosheets.
Abstract: A general strategy has been demonstrated to achieve optimum electrochemical performance by constructing 3D nanocomposite architecture with the combination of nanosize Sn particles and graphene nanosheets. In the first step, the lithium storage properties of graphene have been investigated by first principles calculations. The results show that lithium can be stably stored on both sides of graphene sheets (LiC3), inducing in a theoretical capacity of 744 mAh/g. In the second step, a synthetic approach has been designed to prepare Sn/graphene nanocomposite with 3D architecture, in which Sn nanoparticles act as a spacer to effectively separate graphene nanosheets. FESEM and TEM analysis revealed the homogeneous distribution of Sn nanoparticles (2–5 nm) in graphene nanosheet matrix. Cyclic voltammetry measurement has proved the highly reversible nature of the reaction between Li+ and Sn/graphene nanocomposite. The 3D nanoarchitecture gives the Sn/graphene nanocomposite electrode an enhanced electrochemical performance. This strategy can be extended to prepare other anode and cathode materials for advanced energy storage and conversion devices such as lithium ion batteries, supercapacitors, and fuel cells.
TL;DR: In this paper, the progress made in the synthesis, characterization and properties of oxide nanosheets, highlighting emerging functionalities in electronic and spin-electronic applications, is reviewed.
Abstract: Two-dimensional (2D) nanosheets obtained via exfoliation of layered compounds have attracted intense research in recent years. In particular, the development of exotic 2D systems such as stable graphene and transition-metal oxide nanosheets has sparked new discoveries in condensed matter physics and nanoelectronics. Here, we review the progress made in the synthesis, characterization and properties of oxide nanosheets, highlighting emerging functionalities in electronic and spin-electronic applications. We also present a perspective on the advantages offered by this class of materials for future nanotechnology.
TL;DR: In this article, a facile and scalable chemical reduction method assisted by microwave irradiation for the synthesis of chemically converted graphene sheets and metal nanoparticles dispersed on the graphene sheets was developed.
Abstract: We have developed a facile and scalable chemical reduction method assisted by microwave irradiation for the synthesis of chemically converted graphene sheets and metal nanoparticles dispersed on the graphene sheets. The method allows rapid chemical reduction of exfoliated graphite oxide (GO) using a variety of reducing agents in either aqueous or organic media. It also allows the simultaneous reduction of GO and a variety of metal salts thus resulting in the dispersion of metallic and bimetallic nanoparticles supported on the large surface area of the thermally stable 2D graphene sheets.
TL;DR: In this article, the authors highlight recent and current advances in developing new synthetic strategies for multifunctional organometallic phosphors, which integrate both luminescent and charge carrier injection/transport functions into the same molecules so that they perform most, if not all, of the necessary functional roles (viz. photoexcitation, charge injection and transport as well as recombination).
Abstract: Organic light-emitting diodes (OLEDs) show great promise of revolutionizing display technologies in the scientific community. One successful approach for improved device efficiency has been to maximize the electron-hole recombination using dopants that emit from the triplet excited state. In this context, heavy transition metal complexes have recently gained tremendous academic and industrial research interest for fabricating highly efficient phosphorescent OLEDs by taking advantage of the 1:3 exciton singlet/triplet ratio predicted by simple spin statistics. Traditional room-temperature phosphorescent dyes are monofunctional materials working only as light-emitting centres but other key issues including charge generation and transport remain to be addressed in the electroluminescence. This Feature Article highlights recent and current advances in developing new synthetic strategies for multifunctional organometallic phosphors, which integrate both luminescent and charge carrier injection/transport functions into the same molecules so that they perform most, if not all, of the necessary functional roles (viz. photoexcitation, charge injection and transport as well as recombination) for achieving high-efficiency devices. Considerable focus is placed on the design concepts towards the tuning capability of charge-transport characteristics and phosphorescence emission colour of this prominent class of metallophosphors. In particular, the latest research endeavor in accomplishing novel triplet emitters with enhanced charge injection/charge transport of both hole and electron carriers is criticially discussed, which can provide good implications regarding their possible routes for future research development in the field.
TL;DR: A green single-step synthesis of iron nanoparticles using tea (Camellia sinensis) polyphenols is described in this article that uses no additional surfactants/polymers as capping or reducing agents.
Abstract: A green single-step synthesis of iron nanoparticles using tea (Camellia sinensis) polyphenols is described that uses no additional surfactants/polymers as capping or reducing agents. The expedient reaction between polyphenols and ferric nitrate occurs within a few minutes at room temperature and is indicated by color changes from pale yellow to dark greenish/black in the formation of iron nanoparticles. The synthesized iron nanoparticles were characterized using transmission electron microscopy (TEM), UV-visible and X-ray diffraction pattern (XRD). The obtained nanoparticles were utilized to catalyze hydrogen peroxide for treatment of organic contamination and results were compared with Fe-EDTA and Fe-EDDS. Bromothymol blue, a commonly deployed pH indicator, is used here as a model contaminant for free radical reactions, due to its stability in the presence of H2O2 and its absorbance in the visible range at pH 6. The concentration of bromothymol blue is conveniently monitored using ultraviolet-visible (UV-Vis) spectroscopy during treatment with iron-catalyzed H2O2. Various concentrations of iron are tested to allow for the determination of initial rate constants for the different iron sources.
TL;DR: In this paper, a review of recent developments in optical high-refractive-index polymers and their typical applications in high-tech fields is presented, including the optical dispersion (Abbe number), birefringence and optical transparency.
Abstract: Rapid developments in advanced photonic devices have led to the increasing exploration of high refractive index (high-n) materials, particularly high-refractive-index polymers (HRIP). High refractive indices have been achieved either by introducing substituents with high molar refractions to make intrinsic HRIPs or by combining high-nnanoparticles with polymer matrixes to make HRIP nanocomposites. For intrinsic HRIPs, aromatic rings, sulfur-containing groups, halogens except fluorine and organometallic moieties are often utilized to increase their refractive indices. However, their upper n limitation is usually below 1.80. Incorporation of high-nnanoparticles into polymers seems to be a more promising strategy to achieve a refractive index higher than 1.80; however, the obtained organic–inorganic hybrid materials sometimes suffer from poor storage stability, higher optical loss and poor processability. Besides the refractive index, optical dispersion (Abbe number), birefringence and optical transparency are often involved in designing HRIPs for practical optical fabrications. Therefore, research of HRIPs is becoming an interdisciplinary subject. This feature article reviews recent developments in optical HRIPs and their typical applications in high-tech fields.
TL;DR: The principal focus of this feature article will be given to light-activated antimicrobial surfaces such as the photocatalyst TiO2 and surfaces with embedded photosensitisers, as well as various antimicrobial techniques being researched to reduce microbial contamination of surfaces.
Abstract: Environmental surfaces and their role in the epidemiology of hospital-acquired infections (HAIs) have become an area of great scientific interest, particularly in light of the much publicised cases of infections due to methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile in UK hospitals. This feature article sets out to examine the role of surfaces and the inanimate environment in the spread of HAIs, and looks at various antimicrobial techniques being researched to reduce microbial contamination of surfaces. Preventative measures such as coatings which reduce initial microbial adhesion to surfaces will be considered alongside actively antimicrobial measures which inactivate microorganisms already adherent to a surface. The principal focus of this feature article will be given to light-activated antimicrobial surfaces such as the photocatalyst TiO2 and surfaces with embedded photosensitisers. Surfaces which release antimicrobial compounds or metal ions such as silver and copper are also examined, alongside materials which kill microbes upon contact. The widespread research and development of these antimicrobial surfaces is of great importance in maintaining acceptable levels of hygiene in hospitals and will help to fight the spread of HAIs via the contamination of inanimate surfaces in the healthcare environment.
TL;DR: ZnO/CdS core/shell nanowire arrays are fabricated by a two-step chemical solution method for use in semiconductor-sensitized photoelectrochemical cells (PECs) as mentioned in this paper.
Abstract: ZnO/CdS core/shell nanowire heterostructure arrays are fabricated by a two-step chemical solution method for use in semiconductor-sensitized photoelectrochemical cells (PECs). The successive ion layer adsorption and reaction (SILAR) shows a remarkable controllability of CdS shell thickness, which affects visible-light absorption properties and PEC performances of the heterostructures. The cell has a high short-circuit photocurrent density of 7.23 mA/cm2 with a power conversion efficiency of 3.53% under AM 1.5G illumination at 100 mW/cm2. These results demonstrate that the ZnO/CdS core/shell heterostructure nanowire arrays can provide a facile and compatible frame for the potential applications in nanowire-based solar cells.
TL;DR: This review focuses on the chemical reactions that have been used to modify the amino acids in silk proteins, and describes their utility in biomedical applications.
Abstract: Silk proteins belong to a class of unique, high molecular weight, block copolymer-like proteins that have found widespread use in biomaterials and regenerative medicine. The useful features of these proteins, including self-assembly, robust mechanical properties, biocompatibility and biodegradability can be enhanced through a variety of chemical modifications. These modifications provide chemical handles for the attachment of growth factors, cell binding domains and other polymers to silk, expanding the range of cell and tissue engineering applications attainable. This review focuses on the chemical reactions that have been used to modify the amino acids in silk proteins, and describes their utility in biomedical applications.
TL;DR: In recent years, self-assembly has emerged as a powerful tool for the construction of functional nanostructures as discussed by the authors, especially the supramolecular gels derived from low molecular mass compounds.
Abstract: In recent years, self-assembly has emerged as a powerful tool for the construction of functional nanostructures. Myriad applications of these nanoscale architectures, especially the supramolecular gels derived from low molecular mass compounds, in fields such as optoelectronics, light harvesting, organic–inorganic hybrid materials, tissue engineering and regenerative medicine are being envisaged. This review attempts to present a succinct overview of the current state of research on functional nano-scale systems—the design, synthesis and applications of self-assembled nanomaterials “engineered” to carry out precise functions, with an emphasis on supramolecular gel phase materials.
TL;DR: Non-fouling and non-antigenic polymers have been combined with hydrophobic polymers in the design of biocompatible nano-carriers that are expected to exhibit very long circulation times.
Abstract: Provided the right hydrophilic/hydrophobic balance can be achieved, amphiphilic block copolymers are able to assemble in water into membranes. These membranes can enclose forming spheres with an aqueous core. Such structures, known as polymer vesicles or polymersomes (from the Greek “-some” = “body of”), have sizes that vary from tens to thousands of nanometers. The wholly synthetic nature of block copolymers affords control over parameters such as the molar mass and composition which ultimately determine the structure and properties of the species in solution. By varying the copolymer molecular mass it is possible to adjust the mechanical properties and permeability of the polymersomes, while the synthetic nature of copolymers allows the design of interfaces containing various biochemically-active functional groups. In particular, non-fouling and non-antigenic polymers have been combined with hydrophobic polymers in the design of biocompatible nano-carriers that are expected to exhibit very long circulation times. Stimulus-responsive block copolymers have also been used to exploit the possibility to trigger the disassembly of polymersomes in response to specific external stimuli such as pH, oxidative species, and enzyme degradation. Such bio-inspired ‘bottom-up’ supramolecular design principles offer outstanding advantages in engineering structures at a molecular level, using the same long-studied principles of biological molecules. Thanks to their unique properties, polymersomes have already been reported and studied as delivery systems for both drugs, genes, and image contrast agents as well as nanometer-sized reactors.
TL;DR: In this paper, a variety of Cu2O architectures, evolved from cubes through truncated cubes, cubooctahedrons, truncated octahedral and finally to octahedron, were achieved by simply adjusting the added PVP.
Abstract: In this work, we demonstrate the systematic and delicate geometry control of Cu2O nanocrystals by taking advantage of the selective surface stabilization effect. A variety of Cu2O architectures, evolved from cubes through truncated cubes, cubooctahedrons, truncated octahedrons and finally to octahedrons, were achieved by simply adjusting the added PVP. Based on the understanding of the intrinsic structural features of the cuprite Cu2O and PVP, we elucidated the underlying shape evolution mechanism. The as-prepared products demonstrated a crystallography-dependent adsorption ability with methyl orange (MeO) as the pollutant. With the advantage of a low cost, high yield and straightforward procedure without pre-formed crystals as sacrificial templates, this method may provide a good starting point for the study of shape construction and morphology-dependent properties of other nanocrystals.
TL;DR: In this paper, post-synthesis modification of a MOF by replacing coordinated solvent molecules with highly polar ligands leads to considerable enhancement of CO2/N2 selectivity.
Abstract: Post-synthesis modification of a MOF by replacing coordinated solvent molecules with highly polar ligands leads to considerable enhancement of CO2/N2 selectivity.
TL;DR: The composition of a crosslinked azobenzene liquid-crystalline polymer and a flexible polymer film can provide a variety of simple devices that can walk in one direction like an "inchworm" and move like a "robotic arm" induced by light.
Abstract: The composition of a crosslinked azobenzene liquid-crystalline polymer and a flexible polymer film can provide a variety of simple devices that can walk in one direction like an ‘inchworm’ and move like a ‘robotic arm’ induced by light.
TL;DR: A substantial amount of work has been performed in this area as mentioned in this paper, which summarizes the general design principles and different fabrication approaches of high refractive index (RI) nanocomposites.
Abstract: Organic–inorganic nanocomposites with high refractive index (RI) are typically constructed by integrating high RI inorganic nanoscale building blocks into a processable, transparent organic matrix. These nanocomposites combine the numerous advantages of organic and inorganic components, and have many promising applications in optical design and advanced optoelectronic fabrication. A substantial amount of work has been performed in this area. This Feature article summarizes the general design principles and different fabrication approaches of high RI nanocomposites, and reviews recent research advances and some important optical applications of these nanocomposites.
TL;DR: In this article, a batchmode experiment in NaCl solutions at low voltage (≤2 V) was conducted in a continuously recycling system to investigate the electrosorption performance of graphene.
Abstract: Graphene has been synthesized by the modified Hummers method and used as electrosorptive electrodes for capacitive deionization. Batch-mode experiments in NaCl solutions at low voltage (≤2 V) are conducted in a continuously recycling system to investigate the electrosorption performance of graphene. The results show that the graphene exhibits a high electrosorption capacity of 1.85 mg/g. The ion sorption follows a Freundlich isotherm, indicating monolayer adsorption. And the electrosorption of NaCl onto graphene electrodes is driven by a physisorption process by taking into account the thermodynamic parameters.