Showing papers in "Journal of Materials Chemistry in 2010"
TL;DR: Li-S batteries have received everincreasing attention recently due to their high theoretical specific energy density, which is 3 to 5 times higher than that of Li ion batteries based on intercalation reactions as discussed by the authors.
Abstract: Rechargeable Li–S batteries have received ever-increasing attention recently due to their high theoretical specific energy density, which is 3 to 5 times higher than that of Li ion batteries based on intercalation reactions. Li–S batteries may represent a next-generation energy storage system, particularly for large scale applications. The obstacles to realize this high energy density mainly include high internal resistance, self-discharge and rapid capacity fading on cycling. These challenges can be met to a large degree by designing novel sulfur electrodes with “smart” nanostructures. This highlight provides an overview of major developments of positive electrodes based on this concept.
1,731 citations
TL;DR: Graphene is an emerging carbon material that may soon find practical applications as discussed by the authors, and it is a potential electrode material for electrochemical energy storage, with desirable properties to meet the specific requirements for the design and configuration of advanced supercapacitor devices.
Abstract: Graphene is an emerging carbon material that may soon find practical applications. With its unusual properties, graphene is a potential electrode material for electrochemical energy storage. This article highlights recent research progress in graphene-based materials as supercapacitor electrodes. With a brief description of the working principle of supercapacitors, research progress towards the synthesis and modification of graphene-based materials, including graphene oxide, fullerenes, and carbon nanotubes, is presented. Applications of such materials with desirable properties to meet the specific requirements for the design and configuration of advanced supercapacitor devices are summarized and discussed. Future research trends towards new approaches to the design and synthesis of graphene-based nanostructures and architectures for electrochemical energy storage are proposed.
1,333 citations
TL;DR: A review on the latest developments on graphene, written from the perspective of a chemist, is presented in this article, where the role of chemistry in bringing graphene research to the next level is discussed.
Abstract: A review on the latest developments on graphene, written from the perspective of a chemist, is presented. The role of chemistry in bringing graphene research to the next level is discussed.
1,333 citations
TL;DR: In this paper, a comprehensive review of titania (TiO2)-based semiconductor photocatalysts is presented, including crystal growth, doping, and heterostructuring.
Abstract: Semiconductor photocatalysts have important applications in renewable energy and environment fields. To overcome the serious drawbacks of low efficiency and narrow light-response range in most stable semiconductor photocatalysts, many strategies have been developed in the past decades. This review attempts to provide a comprehensive update and examination of some fundamental issues in titania (TiO2)-based semiconductor photocatalysts, such as crystal growth, doping and heterostructuring. We focus especially on recent progress in exploring new strategies to design TiO2-based photocatalysts with unique structures and properties, elucidating the chemical states and distribution of dopants in doped TiO2, designing and fabricating integrated heterostructure photocatalysts with different charge-carrier transfer pathways, and finally identifying the key factors in determining the photocatalytic efficiency of titania-based photocatalysts.
1,033 citations
TL;DR: In this paper, Nitrogen-doped graphene (N-graphene) is obtained by exposing graphene to nitrogen plasma, and it exhibits much higher electrocatalytic activity toward oxygen reduction and H2O2 reduction than graphene, and much higher durability and selectivity than the widely used expensive Pt for oxygen reduction.
Abstract: Nitrogen-doped graphene (N-graphene) is obtained by exposing graphene to nitrogen plasma. N-graphene exhibits much higher electrocatalytic activity toward oxygen reduction and H2O2 reduction than graphene, and much higher durability and selectivity than the widely-used expensive Pt for oxygen reduction. The excellent electrochemical performance of N-graphene is attributed to nitrogen functional groups and the specific properties of graphene. This indicates that N-graphene is promising for applications in electrochemical energy devices (fuel cells, metal–air batteries) and biosensors.
1,017 citations
TL;DR: A series of titanium dioxide and graphene sheets composites were synthesized with a sol-gel method using tetrabutyl titanate and graphite oxide (GO) as the starting materials.
Abstract: A series of titanium dioxide and graphene sheets (GSs) composites were synthesized with a sol–gel method using tetrabutyl titanate and graphite oxide (GO) as the starting materials. The obtained TiO2/GSs photocatalysts are characterized by X-ray diffraction, N2 adsorption analysis, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated by hydrogen evolution from water photo-splitting under UV-vis illumination. The influence of GSs content and calcinations atmosphere on the photocatalytic activity was also investigated. The results show that both GSs content and the calcinations atmosphere can affect the photocatalytic activity of the obtained composites.
985 citations
TL;DR: The electrochemically reduced graphene oxide (ER-G) has shown promising features for applications in energy storage, biosensors, and electrocatalysis as discussed by the authors, which can be used for energy storage.
Abstract: Graphene oxide is electrochemically reduced which is called electrochemically reduced graphene oxide (ER-G). ER-G is characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The oxygen content is significantly decreased and the sp2 carbon is restored after electrochemical reduction. ER-G exhibits much higher electrochemical capacitance and cycling durability than carbon nanotubes (CNTs) and chemically reduced graphene; the specific capacitance measured with cyclic voltammetry (20 mV s−1) is ∼165, ∼86, and ∼100 F g−1 for ER-G, CNTs, and chemically reduced graphene, respectively. The electrochemical reduction of oxygen and hydrogen peroxide are greatly enhanced on ER-G electrodes as compared with CNTs. ER-G has shown promising features for applications in energy storage, biosensors, and electrocatalysis.
803 citations
TL;DR: Recent progress in the development of AIE-based bio/chemosensors for assays of nuclease and AChE activities, screening of inhibitors, and detection of various analytes including charged biopolymers, ionic species, volatile and explosive organic compounds is summarized.
Abstract: New fluorescent sensors have been developed, utilizing the aggregation-induced emission (AIE) attribute of silole and tetraphenylethene luminogens. In this feature article, we briefly summarize recent progress in the development of AIE-based bio/chemosensors for assays of nuclease and AChE activities, screening of inhibitors, and detection of various analytes including charged biopolymers, ionic species, volatile and explosive organic compounds.
785 citations
TL;DR: The rapidly expanding field of polymer and organic solar cells is reviewed in the context of materials, processes and devices that significantly deviate from the standard approach which involves rigid glass substrates, indium-tinoxide electrodes, spincoated layers of conjugated polymer/fullerene mixtures and evaporated metal electrodes in a flat multilayer geometry as mentioned in this paper.
Abstract: The rapidly expanding field of polymer and organic solar cells is reviewed in the context of materials, processes and devices that significantly deviate from the standard approach which involves rigid glass substrates, indium-tin-oxide electrodes, spincoated layers of conjugated polymer/fullerene mixtures and evaporated metal electrodes in a flat multilayer geometry. It is likely that significant advances can be found by pursuing many of these novel ideas further and the purpose of this review is to highlight these reports and hopefully spark new interest in materials and methods that may be performing less than the current state-of-the-art in their present form but that may have the potential to outperform these pending a larger investment in effort.
762 citations
TL;DR: The progress in the development and understanding of interfacial materials for organic photovoltaics (OPV) is reviewed in this article, where both inorganic and organic interface materials are discussed with respect to their function in the OPV device.
Abstract: The progress in the development and understanding of interfacial materials for organic photovoltaics (OPV) is reviewed. The proper choice of interface materials is a must for highly efficient and stable OPV devices and has become a significant part of the OPV research today. Interface materials are either non-conducting, semiconducting or conducting layers which not only provide selective contacts for carriers of one sort, but can also determine the polarity of OPV devices, affect the open-circuit voltage, and act as optical spacers or protective layers. In this review both inorganic and organic interface materials are discussed with respect to their function in the OPV device.
729 citations
TL;DR: In this article, two alternative strategies for forming CNT-based hierarchical composites are contrasted, the dispersion of CNTs into the composite matrix and their direct attachment onto the primary fibre surface.
Abstract: The introduction of carbon nanotubes (CNTs) into conventional fibre-reinforced polymer composites creates a hierarchical reinforcement structure and can significantly improve composite performance. This paper reviews the progress to date towards the creation of fibre reinforced (hierarchical) nanocomposites and assesses the potential for a new generation of advanced multifunctional materials. Two alternative strategies for forming CNT-based hierarchical composites are contrasted, the dispersion of CNTs into the composite matrix and their direct attachment onto the primary fibre surface. The implications of each approach for composite processing and performance are discussed, along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting hierarchical composites.
TL;DR: In this article, the use of metal and metal oxide-containing inks in the preparation of contacts and interconnects is discussed, as well as the challenges associated with processing these types of inks and ways to successfully obtain the desired features.
Abstract: Printed electronics represent an emerging area of research that promises large markets due to the ability to bypass traditional expensive and inflexible silicon-based electronics to fabricate a variety of devices on flexible substrates using high-throughput printing approaches. This article presents a summary of work to date in the field of printed electronics and the materials chemistry involved. In particular, the focus is upon the use of metal- and metal oxide-containing inks in the preparation of contacts and interconnects. The review discusses the challenges associated with processing these types of inks and ways to successfully obtain the desired features.
TL;DR: In this article, a series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol-water reaction system, and the effects of different starting N : Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated.
Abstract: A series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol–water reaction system. The effects of different starting N : Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated. The photocatalytic activity and stability of the N-doped TiO2 samples were evaluated through using the decomposition of Methylene blue (MB) and Methyl orange (MO) as model reaction under visible light irradiation. Characterization results show that the nitrogen dopant has a significant effect on the crystallite size and optical absorption of TiO2. It was found that the N-doped TiO2 catalysts have enhanced absorption in the visible light region, and exhibit higher activity for photocatalytic degradation of model dyes (e.g. MB and MO). The catalyst with the highest performance was the one prepared using N : Ti molar ratio of 1.0. Electron paramagnetic resonance (EPR) measurement suggests the materials contain Ti 3+ ions, with both the degree of N doping and oxygen vacancies make contributions to the visible light absorption of TON. The presence of superoxide radicals (O u � ) and hydroxyl radicals (OH) on the surface of TON were found to be responsible for MB and MO solution decoloration under visible light. Based on the results of the present study, a visible light induced photocatalytic mechanism has been proposed for N-doped anatase TiO2.
TL;DR: In this article, the authors highlight the recent advances on the chemical synthesis, surface modification and applications of rare earth fluoride nano-/microcrysals, with special emphasis on β-NaY(Gd)F4, F4, Yb3, Er3+ upconversion nanopaticles (UCNPs).
Abstract: This feature article highlights the recent advances on the chemical synthesis, surface modification and applications of rare earth fluoride nano-/microcrysals. In the past decade, great progress in the size and shape control of rare earth fluoride nano-/microcrystals has been made by developing solution phase-based methods such as thermal decomposition, hydro(solvo)thermal reaction, hydrothermal in situ conversion route, and ionic liquids-based synthesis. The main challenge of fluoride nanocrystals for biological applications is that it is hard to obtain ideal nanocrystals with smaller size (sub-50 nm), higher luminescence yield, better dispersity and stability in aqueous solvents, and superior biocompatibility. In order to overcome these shortcomings, a series of strategies of surface modification have been outlined in this review. Finally, we introduce the application of rare earth fluorides, with special emphasis on β-NaY(Gd)F4 : Yb3+, Er3+ upconversion nanopaticles (UCNPs) in biomedical applications including biological labels, multimodal bioimaging, photodynamic therapy and drug delivery.
TL;DR: In this paper, the improvement of the performance of roll-to-roll processed polymer solar cell modules through miniaturization of the device outline is described, and the solar cell module was used to charge a polymer lithium ion battery through a blocking diode.
Abstract: The improvement of the performance of roll-to-roll processed polymer solar cell modules through miniaturization of the device outline is described. The devices were prepared using full roll-to-roll processing comprising flexographic printing, slot-die coating and rotary screen printing to create 5 mm wide lines of ZnO, P3HT:[60/70]PCBM, PEDOT:PSS and silver on an ITO-PET substrate. The lines were spaced by 1 mm and the devices were completed by encapsulation using roll-to-roll lamination on both sides using a pressure sensitive adhesive and a multilayered barrier material having a UV-filter with a cut-off at 390 nm, oxygen and water vapor transmission rates of respectively 0.01 cm3 m−2 bar−1 day−1 and 0.04 g m−2 day−1. The final modules comprised 16 serially connected cells. The technical yield was 89% based on the criterion that the Voc had to be larger than 7.2 V. This set of modules gave respectively a voltage, current, fill factor and power conversion efficiency of 8.47 ± 0.41 V, −23.20 ± 4.10 mA, 35.4 ± 2.8% and 1.96 ± 0.34% in the case of modules based on P3HT:[60]PCBM. A total of 1960 modules were prepared for each run and the best power conversion reached was 2.75% for devices based on P3HT:[70]PCBM. The solar cell modules were used to demonstrate the complete manufacture of a small lamp entirely using techniques of flexible electronics. The solar cell module was used to charge a polymer lithium ion battery through a blocking diode. The entire process was fully automated and demonstrates the capacity of polymer solar cells in the context of flexible and printed electronics. Finally a comparison was made between the learning curve for OPV and crystalline silicon solar cells in terms of the cost per watt peak and the cumulative watt peak. OPV as a technology was found to have a significantly steeper learning curve.
TL;DR: Graphene nanoplatelets have been used as a catalyst support for platinum nanoparticles for oxygen reduction reactions in proton exchange membrane fuel cells as mentioned in this paper, and a full cell was constructed with platinum loaded nitrogen doped graphene nanoplatelet and the results have been compared with the results obtained with the conventional chemical reduction technique.
Abstract: Graphene nanoplatelets have been synthesized by thermal exfoliation of graphitic oxide and nitrogen doped graphene nanoplatelets have been obtained by nitrogen plasma treatment. Graphene nanoplatelets and nitrogen doped graphene nanoplatelets have been used as a catalyst support for platinum nanoparticles for oxygen reduction reactions in proton exchange membrane fuel cells. Platinum nanoparticles were dispersed over these support materials using the conventional chemical reduction technique. The morphology and structure of the graphene based powder samples were studied using X-ray diffraction, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A full cell was constructed with platinum loaded nitrogen doped graphene nanoplatelets and the results have been compared with platinum loaded graphene nanoplatelets. A maximum power density of 440 and 390 mW cm−2 has been obtained with platinum loaded nitrogen doped graphene and platinum loaded graphene nanoplatelets as ORR catalysts respectively. Nitrogen plasma treatment created pyrrolic nitrogen defects, which act as good anchoring sites for the deposition of platinum nanoparticles. The improved performance of fuel cells with N-G as catalyst supports can be attributed to the increased electrical conductivity and improved carbon–catalyst binding.
TL;DR: In this article, surface coating of cathode materials has been widely investigated to enhance the life and rate capability of lithium-ion batteries and the surface coating discussed here was divided into three different configurations which are rough coating, core shell structure coating and ultra thin film coating.
Abstract: Surface coating of cathode materials has been widely investigated to enhance the life and rate capability of lithium-ion batteries. The surface coating discussed here was divided into three different configurations which are rough coating, core shell structure coating and ultra thin film coating. The mechanism of surface coating in achieving improved cathode performance and strategies to carry out this surface modification is discussed. An outlook on atomic layer deposition for lithium ion battery is also presented.
TL;DR: In this paper, the authors report the progress of interface engineering in polymer solar cell research, where the multiple functions of the interfacial materials will be discussed, and discuss the energy level alignment at the bulk heterojunction (BHJ) interface, with the aim of providing a better understanding towards the route of high efficiency polymer solar cells.
Abstract: The contact between the polymer active layer and the electrode is one the most critical interfaces in polymer solar cells. In this article, we report the progress of interface engineering in polymer solar cell research, where the multiple functions of the interfacial materials will be discussed. The vertical composition profile in polymer:fullerene blends is an emerging topic, and the interlayer effect on the vertical phase separation and device performance will be highlighted. We also discuss the energy level alignment at the bulk heterojunction (BHJ) interface, with the aim of providing a better understanding towards the route of high efficiency polymer solar cells.
TL;DR: In this article, the authors reviewed the device structures adopted to achieve high performance solution processed organic light-emitting diodes, the development of solution processable small molecules, and the comparisons of the different nature of the films and devices fabricated by solution-process or vacuum deposition.
Abstract: Organic light-emitting diodes (OLEDs) based on vacuum deposited small molecules have undergone significant progress since the first efficient double-layered OLEDs were reported in 1987 by Tang and Van Slyke. Recently, solution processed small molecular OLEDs are also drawing more and more research attention, as such a technology combines advantages of the facile synthesis of small molecules and the low-cost solution process like polymers. The performance of OLEDs made by solution process is gradually catching up with their vacuum deposited counterparts. This feature article will review the device structures adopted to achieve high performance solution processed OLEDs, the development of solution processable small molecules, and the comparisons of the different nature of the films and devices fabricated by solution-process or by vacuum deposition. Finally, the prospects and remaining problems will be discussed.
TL;DR: In the perovskite structure, B-site and A-site cations adopt different patterns of chemical order as discussed by the authors, and the tendency for A-site cations to order into layers stems from the bond strains that would result at the anion site if A and A′ cations of different sizes were to order with a rock salt arrangement.
Abstract: Although both A- and B-site cations have the same simple cubic topology in the perovskite structure they typically adopt different patterns of chemical order. As a general rule B-site cations order more readily than A-site cations. When cation ordering does occur, rock salt ordering of B/B′ cations is favored in A2BB′X6 perovskites, whereas layered ordering of A/A′ cations is favored in AA′B2X6 and AA′BB′X6 perovskites. The unexpected tendency for A-site cations to order into layers stems from the bond strains that would result at the anion site if A and A′ cations of different size were to order with a rock salt arrangement. The bonding instabilities that are created by layered ordering are generally offset either by anion vacancies or second order Jahn–Teller distortions of a B-site cation. Novel types of A-site cation ordering can be stabilized by a+a+a+ or a+a+c− tilting of the octahedra.
TL;DR: In this article, a stable dispersion of reduced graphene in various organic solvents was achieved via noncovalent functionalization with amine-terminated polymers, which was obtained by chemical reduction of graphene oxide in aqueous media and was vacuum filtered to generate reduced graphene sheets.
Abstract: Stable dispersion of reduced graphene in various organic solvents was achieved via noncovalent functionalization with amine-terminated polymers. An aqueous dispersion of reduced graphene was prepared by chemical reduction of graphene oxide in aqueous media and was vacuum filtered to generate reduced graphene sheets. Good solvents and nonsolvents for the dried reduced graphene were evaluated using a solubility test. To achieve stable dispersion in the evaluated nonsolvents, amine-terminated polystyrene was noncovalently functionalized to the graphene, while graphene sheets were phase transferred via sonication from aqueous phase to the organic nonsolvent phase, including the amine-terminated polymers. Thorough FTIR and Raman spectroscopy investigation verified that the protonated amine terminal group of polystyrene underwent noncovalent functionalization to the carboxylate groups at the graphene surface, providing the high dispersibility in various organic media.
TL;DR: A review with ca. 400 references dealing with the use of mesoporous silica and organically modified silica-based materials for removal of inorganic and organic pollutants from aqueous solutions is provided in this article.
Abstract: A review with ca. 400 references is provided dealing with the use of mesoporous silica and organically-modified silica-based materials for removal of inorganic and organic pollutants from aqueous solutions. After having briefly discussed the interest of functionalized mesoporous silica for environmental remediation purposes, the various synthetic methods to prepare such nanoengineered adsorbents are described. Then, their application to the removal of heavy metal species, toxic anions, radionuclides, and a wide range of organic pollutants is presented in a comprehensive way with the help of extensive tables and some illustrating figures.
TL;DR: In this paper, a planetary mill was used to exfoliate graphite platelets into graphenes in a liquid medium, and irregular shaped single and few-layer graphene sheets (≤3 layers) having a thickness around 0.8-1.8 nm were found from the supernatant.
Abstract: Wet ball milling was used to exfoliate graphite platelets into graphenes in a liquid medium. Multi-layered graphite nanosheets with a thickness of 30 to 80 nm were dispersed into N,N-dimethylformamide (DMF) and exfoliated by shear-force-dominated ball milling carried out in a planetary mill. After high-speed centrifugation, irregular shaped single- and few-layer graphene sheets (≤3 layers) having a thickness around 0.8–1.8 nm were found from the supernatant. The graphenes were identified and characterized using transmission and scanning electron microscopy, electron diffraction, atomic force microscopy and Raman spectroscopy. The electrical conductivity of the graphene powder was ∼1.2 × 103 S m−1 at room temperature.
TL;DR: In this article, a review highlights the emerging strategies for polymer membrane modifications using organic and inorganic additives and surface modification to mitigate foulant deposition and biofilm formation in many membrane filtration processes.
Abstract: Biofouling is a critical problem in many membrane filtration processes. This review highlights the emerging strategies for polymer membrane modifications using organic and inorganic additives and surface modification to mitigate foulant deposition and biofilm formation. Constraints and opportunities for future implementation in membrane systems are outlined from the perspectives of water and wastewater treatment applications.
TL;DR: In this paper, a review of the development of RO membranes with improved flux and salt rejection, chlorine tolerance, fouling resistance and thermal stability is presented, focusing on the modification of current polymeric membrane materials, and synthesis and separation performance of new polymer membranes, inorganic membranes, and mixed matrix membranes.
Abstract: Reverse osmosis (RO) desalination is one of the main technologies for producing fresh water from seawater and other saline water sources. The membrane properties greatly affect the water productivity and energy costs in the reverse osmosis desalinatin processes. Recent years have seen significant research efforts devoted to developing high-performance RO membranes. This article reviews recent activities in the development of RO membranes with improved flux and salt rejection, chlorine tolerance, fouling resistance and thermal stability. In particular, this review mainly focuses on the modification of current polymeric membrane materials, and synthesis and separation performance of new polymer membranes, inorganic membranes and mixed matrix membranes.
TL;DR: The development of functionalized graphene (FG) has been growing very fast in the last five years as discussed by the authors, and it seems a suitable time to highlight the recent advances in this field and understand the developing direction of this new member of PNCs.
Abstract: Functionalized graphene (FG) has been considered as one of the next-generation nanofillers for polymer nanocomposites (PNCs) due to its parallel physical properties and cheaper fabricating cost in comparison with carbon nanotubes (CNTs). The development of FG/polymer nanocomposites (FPNs) has been growing very fast in the last five years. It seems to be a suitable time to highlight the recent advances in this field and understand the developing direction of this new member of PNCs. To our best knowledge, this review covers most of the important publications relating to the fabrication, properties and application of FPNs to date.
TL;DR: In this article, a single-layer graphene nanosheets (SLGNs) are prepared by reduction of well-exfoliated graphite oxide aided by a surfactant (sodium dodecylbenzene sulfonate, SDBS) by modulating the concentrations of diazonium compound and monomer during the grafting reaction of the initiator and the succeeding atomic transfer radical polymerization (ATRP).
Abstract: Single-layer graphene nanosheets (SLGNs) are prepared by reduction of well-exfoliated graphite oxide aided by a surfactant (sodium dodecylbenzene sulfonate, SDBS). Grafting density and polystyrene (PS) chain lengths are controlled by modulating the concentrations of diazonium compound and monomer during the grafting reaction of the initiator and the succeeding atomic transfer radical polymerization (ATRP). Atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectra and transmission electron microscopy (TEM) are used to confirm the single-layer structure of graphene sheets, covalent bonding at the interface, and distribution uniformity of grafting PS chains at the SLGN surface. Thermogravimetric analysis (TGA) is performed to assess the control of grafting density and chain length. PS chains grafted on the SLGN surface exhibited remarkably confined relaxation behavior. An increase in the glass transition temperature (Tg) of up to 18 °C is observed for high grafting density, low molecular weight polymer-grafted graphene samples. The low grafting density, high molecular weight sample shows an increase in Tg of ∼9 °C, which is attributed to superior heat conduction efficiency. The measured thermal conductivity for the PS composite film with 2.0 wt% SLGNs increase by a factor of 2.6 compared to that of the pure PS.
TL;DR: In this article, a thermally responsive polymer hydrogel network was formed when an yne terminated water-soluble homopolymer was polymerized with a tetrafunctional thiol.
Abstract: Radical mediated thiol-yne polymerization reactions complement the more well-known thiol-ene radical polymerization processes, with the added advantage of increased functionality. In one system studied, the rate constant for the addition of the thiol to the vinyl sulfide created by the initial reaction of the thiol with the alkyne is three times faster than the initial reaction. When hydrocarbon based dialkynes and dithiols were copolymerized, the resulting thiol-alkyne networks containing only hydrocarbon and sulfide linking groups exhibited refractive index values tunable above 1.65, with the refractive index directly related to the sulfur content. The thiol-yne reaction was also found to be useful in functionalizing thiol-terminated polymer chain ends via sequential Michael thiol-ene addition followed by the thiol-yne reaction: the result is the dual functionalization of the polymer chain end. A thermally responsive polymer hydrogel network was formed when an yne terminated water-soluble homopolymer was polymerized with a tetrafunctional thiol.
TL;DR: In this paper, the surface of the PMMA grafted graphene oxide (GPMMA) was characterized by AFM, HRTEM, Raman, FTIR and contact angle.
Abstract: Graphene is a two-dimensional new allotrope of carbon, which is stimulating great curiosity due to its superior mechanical, electrical, thermal and optical properties.
Particularly attractive is the availability of bulk quantities of graphene (G) which can be easily processed by chemical exfoliation, yielding graphene oxide (GO). The resultant oxygenated graphene sheets covered with hydroxyl, epoxy and carboxyl groups offer tremendous opportunities for further functionalization opening plenty of opportunities for the preparation of advanced composite materials.
In this work poly(methyl methacrylate) (PMMA) chains have been grafted from the GO surface via atom transfer radical polymerization (ATRP), yielding a nanocomposite which was soluble in chloroform. The surface of the PMMA grafted GO (GPMMA) was characterized by AFM, HRTEM, Raman, FTIR and contact angle. The interest of these novel nanocomposites lies in their potential to be homogenously dispersed in polymeric dense matrices and to promote good interfacial adhesion, of particular relevance in stress transfer to the fillers. PMMA composite films were prepared using different percentages of GPMMA and pristine GO. Mechanical analysis of the resulting films showed that loadings as low as 1% (w/w) of GPMMA are effective reinforcing agents, yielding tougher films than pure PMMA films and even than composite films of PMMA prepared with GO. In fact, addition of 1% (w/w) of GPMMA fillers led to a significant improvement of the elongation at break, yielding a much more ductile and therefore tougher material. Thermal analysis showed an increase of the thermal stability properties of these films providing evidence that strong interfacial interactions between PMMA and GPMMA are achieved. In addition, AFM analysis, in friction force mode, is demonstrated to be an effective tool to analyse the surface filler distribution on polymer matrices.
TL;DR: In this article, the authors present the current evidence in support of considering some MOFs as semiconductors, including the synthesis of semiconducting MOFs by design and development of applications.
Abstract: The aim of the present feature article is to present the current evidence in support of considering some MOFs as semiconductors. While MOFs and zeolites share common structural properties derived from the microporous crystal structure, zeolites are insulating materials and most of the attempts to exploit them in optoelectronics have met with failure. In contrast, some MOFs may have interesting photochemical properties that derive from the fundamental event of charge separation in electrons and holes upon light absorption. Photoinduced charge separation is the hallmark of a semiconductor that can behave simultaneously as an oxidizing or reducing agent. Considering the novelty of this field, most of the available data about MOFs as semiconductor have been obtained from MOF-5, a case that is complicated due to its low structural stability. Therefore, we point out that further studies showing the semiconducting properties of other MOFs are still welcome. The purpose of this feature article is to trigger intense research in this area including the synthesis of semiconducting MOFs by design and development of applications.