Showing papers in "Journal of Materials Chemistry in 2012"
TL;DR: In this article, a review of the photo and electron properties of carbon nanodots is presented to provide further insight into their controversial emission origin and to stimulate further research into their potential applications, especially in photocatalysis, energy conversion, optoelectronics, and sensing.
Abstract: Carbon nanodots (C-dots) have generated enormous excitement because of their superiority in water solubility, chemical inertness, low toxicity, ease of functionalization and resistance to photobleaching. In this review, by introducing the synthesis and photo- and electron-properties of C-dots, we hope to provide further insight into their controversial emission origin (particularly the upconverted photoluminescence) and to stimulate further research into their potential applications, especially in photocatalysis, energy conversion, optoelectronics, and sensing.
2,262 citations
TL;DR: In this article, the textural properties and surface chemistry of KOH-activated carbons depend on not only the synthesis parameters, but also different carbon sources employed including fossil/biomass-derived materials, synthetic organic polymers, and various nanostructured carbons (e.g. carbon nanotubes, carbon nanofibers, carbon aerogels, carbide-derived carbons, graphene, etc.).
Abstract: Because of their availability, adjustable microstructure, varieties of forms, and large specific surface area, porous carbon materials are of increasing interest for use in hydrogen storage adsorbents and electrode materials in supercapacitors and lithium–sulfur cells from the viewpoint of social sustainability and environmental friendliness. Therefore, much effort has been made to synthesize and tailor the microstructures of porous carbon materials via various activation procedures (physical and chemical activation). In particular, the chemical activation of various carbon sources using KOH as the activating reagent is very promising because of its lower activation temperature and higher yields, and well-defined micropore size distribution and ultrahigh specific surface area up to 3000 m2 g−1 of the resulting porous carbons. In this feature article, we will cover recent research progress since 2007 on the synthesis of KOH-activated carbons for hydrogen and electrical energy storage (supercapacitors and lithium–sulfur batteries). The textural properties and surface chemistry of KOH-activated carbons depend on not only the synthesis parameters, but also different carbon sources employed including fossil/biomass-derived materials, synthetic organic polymers, and various nanostructured carbons (e.g. carbon nanotubes, carbon nanofibers, carbon aerogels, carbide-derived carbons, graphene, etc.). Following the introduction to KOH activation mechanisms and processing technologies, the characteristics and performance of KOH-activated carbons as well as their relationships are summarized and discussed through the extensive analysis of the literature based on different energy storage systems.
2,046 citations
TL;DR: In this paper, the authors showed that the heating temperature and the presence of sulfur motifs offer a facile chemical pathway for the control of the condensation/polymerization of carbon nitride, and thus adjusting their textural and electronic properties.
Abstract: Converting solar energy into hydrogen gas by water splitting is considered as a long-term solution to address global energy and environmental problems. Great effort has been devoted to the search for abundant systems for the purpose of efficient capture, conversion, and storage of solar energy in a cost-effective manner. To further advance the recently-developed carbon nitride photocatalysis for solar hydrogen generation, thiourea, a sulfur-containing compound, was used as a cheap and easily-available starting material for the synthesis of graphitic carbon nitride semiconductors. The as-prepared photocatalysts were subjected to several characterizations, and the results showed that the heating temperature and the presence of sulfur motifs offer a facile chemical pathway for the control of the condensation/polymerization of carbon nitride, and thus adjusting their textural and electronic properties. Photocatalytic activity experiments demonstrated that the g-C3N4 synthesized from thiourea exhibited a much higher H2 production rate than that of g-C3N4 prepared from dicyanamide or urea, and this activity can be further enhanced by increasing the condensation temperature.
847 citations
TL;DR: A cylindrical piece of Au/graphene hydrogel, 1.08 cm in diameter and 1.28 cm in height, has been synthesized through the self-assembly of Au and graphene sheets under hydrothermal conditions for the first time as mentioned in this paper.
Abstract: A cylindrical piece of Au/graphene hydrogel, 1.08 cm in diameter and 1.28 cm in height, has been synthesized through the self-assembly of Au/graphene sheets under hydrothermal conditions for the first time. The hydrogel, containing 2.26 wt% Au, 6.94 wt% graphene, and 90.8 wt% water, exhibited excellent catalytic performance towards the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), which is about 90 times larger than previously reported values for spongy Au nanoparticles and 14 times more than the highest value among the polymer supported Au nanoparticle catalysts. The high catalytic activity arises from the synergistic effect of graphene: (1) the high adsorption ability of graphene towards 4-NP, providing a high concentration of 4-NP near to the Au nanoparticles on graphene; and (2) electron transfer from graphene to Au nanoparticles, facilitating the uptake of electrons by 4-NP molecules.
791 citations
TL;DR: In this paper, boron atoms are doped into graphene frameworks forming borton doped graphene (BG) via a catalyst-free thermal annealing approach in the presence of BORON oxide, which has a flake-like structure with an average thickness of ca. 2 nm.
Abstract: Boron atoms, with strong electron-withdrawing capability, are doped into graphene frameworks forming boron doped graphene (BG) via a catalyst-free thermal annealing approach in the presence of boron oxide. Atomic force microscopic (AFM) and transmission electron microscopic (TEM) characterizations reveal that the as-prepared BG has a flake-like structure with an average thickness of ca. 2 nm. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that boron atoms can be successfully doped into graphene structures with the atomic percentage of 3.2%. Due to its particular structure and unique electronic properties, the resultant BG exhibits excellent electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline electrolytes, similar to the performance of Pt catalysts. In addition, the non-metallic BG catalyst shows long-term stability and good CO tolerance superior to that of Pt-based catalysts. These results demonstrate that the BG, as a promising candidate in advanced electrode materials, may substitute Pt-based nanomaterials as a cathode catalyst for ORR in fuel cells as well as other electrochemical applications similar to the reported nitrogen doped graphene.
755 citations
TL;DR: In this article, a new class of propeller-like luminogenic molecules with aggregation-induced emission (AIE) characteristics has drawn increasing research interest, and tetraphenylethene (TPE) is an archetypal luminogen with a simple molecule structure.
Abstract: Luminescent materials with efficient solid-state emissions are important for the advancement of optoelectronics. Recently, a new class of propeller-like luminogenic molecules with aggregation-induced emission (AIE) characteristics has drawn increasing research interest. Among them, tetraphenylethene (TPE) is an archetypal luminogen with a simple molecule structure but shows a splendid AIE effect. Utilizing TPE as a building block, an effective strategy to create efficient solid-state emitters is developed. In this feature article, we review mainly our recent work on the construction of luminogenic materials from TPE and present their applications in organic light-emitting diodes. The applicability of the synthetic strategy and the utility of the resulting materials are demonstrated.
707 citations
TL;DR: In this paper, a two-dimensional sheet with chiffon-like ripples and a layered structure of graphene oxide modified g-C3N4 with efficient photocatalytic capability under visible light irradiation was fabricated by sonochemical approach.
Abstract: Graphene oxide modified g-C3N4 (GO/g-C3N4) with efficient photocatalytic capability under visible light irradiation was fabricated by sonochemical approach. Transmission electron microscopy images demonstrated that GO was two-dimensional sheets with chiffon-like ripples and the g-C3N4 possessed a layered structure. GO was overlaid on the surface of g-C3N4 in the GO/g-C3N4 hybrids. The UV–vis diffuse reflectance spectra showed that the GO/g-C3N4 hybrid had intense optical absorption in the visible light region. Photoluminescence spectra confirmed that the separation efficiency of photogenerated charge in GO/g-C3N4 was more intensive than pristine g-C3N4, indicating the GO acts as a separation centre and electron acceptor in the GO/g-C3N4 hybrid. The effective photogenerated charge separation efficiency lead to a remarkable improvement in the visible light photocatalysis. The pseudo-first-order kinetic constants of photocatalytic degradation of rhodamine B and 2, 4-dichlorophenol under visible light irradiation with GO/g-C3N4 were 3.80 and 2.08 times as large as that with pristine g-C3N4, respectively. This work indicates that the metal-free GO/g-C3N4 hybrid photocatalyst is a promising material in waste control, and GO could be an excellent material to combine with other semiconductors to make composites.
670 citations
TL;DR: In this article, a critical review of carbon-based nanostructured materials and their composites for use as supercapacitor electrodes is provided, focusing on basic principles of supercapACitors and various factors affecting their performance.
Abstract: This critical review provides an overview of current research on carbon-based nanostructured materials and their composites for use as supercapacitor electrodes. Particular emphasis has been directed towards basic principles of supercapacitors and various factors affecting their performance. The focus of the review is the detailed discussion regarding the performance and stability of carbon-based materials and their composites. Pseudo-active species, such as, conducting polymer/metal oxide have been found to exhibit pseudo-capacitive behavior and carbon-based materials demonstrate electrical double layer capacitance. Carbon-based materials, such as, graphene, carbon nanotubes, and carbon nanofibers, provide high surface area for the deposition of conducting polymer/metal oxide that facilitates the efficient ion diffusion phenomenon and contribute towards higher specific capacitance of the carbon based composite materials with excellent cyclic stability. However, further scope of research still exists from the view point of developing high energy supercapacitor devices in a cost effective and simple way. This review will be of value to researchers and emerging scientists dealing with or interested in carbon chemistry.
655 citations
TL;DR: In this article, the facile fabrication of Ag3PO4, CQDs/Ag3PO 4, Ag/Ag 3PO4 and corresponding complex photocatalysts was reported.
Abstract: In this study, we report the facile fabrication of Ag3PO4, CQDs/Ag3PO4, Ag/Ag3PO4 and CQDs/Ag/Ag3PO4 photocatalysts (CQDs, carbon quantum dots). For CQDs/Ag3PO4 and CQDs/Ag/Ag3PO4, because of the insoluble, photoinduced electron transfer, upconversion luminescence and electron reservoir properties of CQDs, the complex photocatalysts exhibit enhanced photocatalytic activity and structural stability over the photodecomposition of organic compounds (methyl orange) under the irradiation of visible light. Furthermore, the synergistic effect of CQDs and the intense surface plasmon resonance of Ag lead to the highest photocatalytic activity of CQDs/Ag/Ag3PO4 among Ag3PO4 and the corresponding complex photocatalysts. Our results provide an invaluable methodology for designing high-performance photocatalysts based on CQDs and related functional materials, which is promising for catalytic and new energy applications.
654 citations
TL;DR: In this paper, a facile electrochemical method for synthesizing uniform sized graphene quantum dots (GQDs) with a strong yellow emission at 14% quantum yield was presented, which enabled a large-scale production of aqueous GQD solution without the need for polymeric or surfactant stabilizers.
Abstract: We present a facile electrochemical method for synthesizing uniform sized graphene quantum dots (GQDs) with a strong yellow emission at 14% quantum yield. This approach has enabled a large-scale production of aqueous GQD solution without the need for polymeric or surfactant stabilizers. The structure and emission mechanism of the GQDs have been studied by combining extensive characterization techniques, rigorous control experiments and theoretical calculations. We further demonstrate the distinctive advantages of such GQDs for direct and efficient stem cell labeling, opening up great opportunities for their bio-medical applications.
647 citations
TL;DR: In situ sulfur-doped mesoporous g-C3N4 (mpgCNS) was synthesized from a simple organosulfur compound, thiourea, using SiO2 nanoparticles as the hard template as mentioned in this paper.
Abstract: In situ sulfur-doped mesoporous g-C3N4 (mpgCNS) was synthesized from a simple organosulfur compound, thiourea, using SiO2 nanoparticles as the hard template. The resultant product has a high surface area of 128 m2 g−1 and mesopores in the range of 10–20 nm. Based on X-ray photoelectron spectroscopy analysis, the doped sulfur was proposed to substitute carbon in mpgCNS and a downshift of 0.25 eV was resulted in its conduction band. Optical studies indicated that mpgCNS exhibits enhanced and extended light absorbance in the visible light region and a much lower density of defects compared to the native g-C3N4. As a result, mpgCNS has been found to be 30 times more active than the native g-C3N4 for hydrogen evolution from photocatalytic water splitting. A high quantum efficiency of 5.8% at 440 nm was obtained which is among the highest for carbon nitride photocatalysts.
TL;DR: This review will discuss recent advances in important and/or controversial issues concerning ZnO properties and its applications, and areas where further improvements are needed.
Abstract: ZnO is a material which is of great interest for a variety of applications due to its unique properties and the availability of a variety of growth methods resulting in a number of different morphologies and a wide range of material properties of synthesized nanostructures. In this review, we will discuss recent advances in important and/or controversial issues concerning ZnO properties and its applications. We will also discuss areas where further improvements are needed, and in particular discuss the issues related to the environmental stability of ZnO and its implications on reproducibility of measurements and the toxicity of ZnO nanomaterials.
TL;DR: An asymmetric supercapacitor cell with graphitic hollow carbon spheres (GHCS) as the positive electrode and GHCS as the negative electrode can be reversibly charged/discharged at a cell voltage of 2.0 V in a 1.0 mol L−1 Na2SO4 aqueous electrolyte, delivering an energy density of 22.1 Wh kg−1 and a power density of 7.0 kWkg−1.
Abstract: Growing MnO2 nanofibers on graphitic hollow carbon spheres (GHCS) is conducted by refluxing GHCS in a KMnO4 aqueous solution aimed to enhance the electrochemically active surface area of MnO2. The stoichiometric redox reaction between GHCS and MnO4− yields GHCS–MnO2 composites with controllable MnO2 content. It is found that these ultrathin MnO2 nanofibers are vertically grown on the external surface of the GHCS, yielding a composite electrode showing good electron transport, rapid ion penetration, fast and reversible Faradic reaction, and excellent rate performance when used as supercapacitor electrode materials. An asymmetric supercapacitor cell with GHCS–MnO2 as the positive electrode and GHCS as the negative electrode can be reversibly charged/discharged at a cell voltage of 2.0 V in a 1.0 mol L−1 Na2SO4 aqueous electrolyte, delivering an energy density of 22.1 Wh kg−1 and a power density of 7.0 kW kg−1. The asymmetric supercapacitor exhibits an excellent electrochemical cycling stability with 99% initial capacitance and 90% coulombic efficiency remained after 1000 continuous cycles measured using the galvanostatic charge–discharge technique.
TL;DR: The safe preparation and characterization of a new explosive dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) that outperforms all other commonly used explosive materials is detailed in this paper.
Abstract: The safe preparation and characterization (XRD, NMR and vibrational spectroscopy, DSC, mass spectrometry, sensitivities) of a new explosive dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) that outperforms all other commonly used explosive materials is detailed. While much publicized high-performing explosives, such as octanitrocubane and CL-20, have been at the forefront of public awareness, this compound differs in that it is simple and cheap to prepare from commonly available chemicals. TKX-50 expands upon the newly exploited field of tetrazole oxide chemistry to produce a material that not only is easily prepared and exceedingly powerful, but also possesses the required thermal insensitivity, low toxicity, and safety of handling to replace the most commonly used military explosive, RDX (1,3,5-trinitro-1,3,5-triazacyclohexane). In addition, the crystal structures of the intermediates 5,5′-bistetrazole-1,1′-diol dihydrate, 5,5′-bistetrazole-1,1′-diol dimethanolate and dimethylammonium 5,5′-bistetrazole-1,1′-diolate were determined and presented.
TL;DR: In this article, the authors provide an overview of recent research and significant advances reported in the literature, covering from synthesis to properties and to applications especially in energy conversion and storage, such as lithium-ion batteries, solar cells, fuel cells and piezoelectric nanogenerators.
Abstract: Metal sulfide nanomaterials have attracted great attention because of their excellent properties and promising applications in electronic, optical and optoelectronic devices. Well-aligned nanostructure arrays on substrates are highly attractive for their enhanced properties and novel applications. The general solution route and thermal evaporation under controlled conditions have been utilized for oriented growth of various metal sulfide nanostructure arrays and demonstrated their applications in energy conversion and storage. The article provides an overview of recent research and significant advances reported in the literature, covering from synthesis to properties and to applications especially in energy conversion and storage, such as lithium-ion batteries, solar cells, fuel cells and piezoelectric nanogenerators.
TL;DR: In this paper, a facile, low cost and high yield method has been developed to prepare single and multi-layer graphene quantum dots (GQDs) from XC-72 carbon black by chemical oxidation.
Abstract: A facile, low cost and high yield method has been developed to prepare single- and multi-layer graphene quantum dots (GQDs) from XC-72 carbon black by chemical oxidation. The single-layer GQDs are demonstrated to be excellent probes for cellular imaging, while the multi-layer GQDs may offer great potential applications in optoelectronic devices.
TL;DR: In this paper, Li7−xLa3Zr2−xTaxO12 (0 ≤ x ≤ 1) was prepared by conventional solid-state reaction and the phase formation and the lithium-ion conductivity were determined using X-ray diffraction (XRD), neutron diffraction and AC impedance.
Abstract: The garnet-related oxides with the general formula Li7−xLa3Zr2−xTaxO12 (0 ≤ x ≤ 1) were prepared by conventional solid-state reaction. X-ray diffraction (XRD), neutron diffraction and AC impedance were used to determine phase formation and the lithium-ion conductivity. The lattice parameter of Li7−xLa3Zr2−xTaxO12 decreased linearly with increasing x. Optimum Li-ion conductivity in the Li-ion garnets Li7−xLa3Zr2−xTaxO12 is found in the range 0.4 ≤ x ≤ 0.6 for samples fired at 1140 °C in an alumina crucible. A room-temperature σLi ≈ 1.0 × 10−3 S cm−1 for x = 0.6 with an activation energy of 0.35 eV in the temperature range of 298–430 K makes this Li-ion solid electrolyte attractive for a new family of Li-ion rechargeable batteries.
TL;DR: Carbon nanotube-graphene hybrid aerogels have been fabricated by supercritical CO2 drying of their hydrogel precursors obtained from heating the aqueous mixtures of graphene oxide and carbon nanotubes with Vitamin C without stirring as discussed by the authors.
Abstract: Carbon nanotube–graphene hybrid aerogels have been fabricated by supercritical CO2 drying of their hydrogel precursors obtained from heating the aqueous mixtures of graphene oxide and carbon nanotubes with Vitamin C without stirring. The resulting hybrid aerogels show very promising performance in water purification including capacitive deionization of light metal salts, removal of organic dyes and enrichment of heavy metal ions.
TL;DR: In this paper, the effects of the electron-deficiency of N-doped graphenes on their application in lithium ion batteries (LIBs), where three different defect models, graphitic, pyridinic, and pyrrolic graphene are used.
Abstract: First-principles calculations are performed to investigate the effects of the electron-deficiency of N-doped graphenes on their application in lithium ion batteries (LIBs), where three different defect models, graphitic, pyridinic, and pyrrolic graphenes are used. First, we investigate adsorption of a single Li atom on various graphenes and explore the change of the electronic properties in order to understand the adsorption mechanism. Then, adsorption of multiple Li atoms is also performed to consider the lithium storage properties of N-doped graphene nanosheets. The results show that the pyridinic graphene is the most suitable for Li storage with a high storage capacity, while the graphitic structure is the weakest of the three types. Moreover, the average potential of Li intercalation in the graphene materials was also calculated, and results indicate that the reversible capacity of the pyridinic structure can reach 1262 mAh g−1, which is higher than the experimental data (1043 mAh g−1). Therefore, we recommend pyridinic graphene in the N-doped structures as anode materials of lithium ion batteries and the corresponding reversible capacity of LIBs would be improved significantly. It is expected that this work could provide helpful information for the design and fabrication of anode materials of LIBs.
TL;DR: In this paper, a combination of high pressure compression molding plus salt-leaching was first proposed to prepare porous graphene/polystyrene composites, and specific shielding effectiveness was as high as 64.4 dB cm3 g−1, the highest value ever reported for polymer based EMI shielding materials at such a low thickness (2.5 mm).
Abstract: A combination of high-pressure compression molding plus salt-leaching was first proposed to prepare porous graphene/polystyrene composites. The specific shielding effectiveness of the lightweight composite was as high as 64.4 dB cm3 g−1, the highest value ever reported for polymer based EMI shielding materials at such a low thickness (2.5 mm).
TL;DR: In this paper, the authors presented a systematic investigation on the incorporation of WO3 nanorods and graphene for high-efficiency visible-light-driven photocatalysis and NO2 gas sensing.
Abstract: One-dimensional (1-D) nanostructures are of great importance due to their superior charge transport properties. Anchoring 1-D semiconductor nanomaterials on graphene offers potential advantages in photoelectrochemical and sensing applications. This paper presents a systematic investigation on the incorporation of WO3 nanorods and graphene for high-efficiency visible-light-driven photocatalysis and NO2 gas sensing. This novel composite shows remarkably enhanced performance compared to pure WO3 nanorods for these applications. The high photocatalytic activity of the WO3/graphene nanocomposite is found to be related to the increased adsorption toward chemical species, enhanced light absorption and efficient charge separation and transfer. Meanwhile, the improved conductivity, specific electron transfer and increased gas adsorption also contribute to their superior sensitivity and selectivity to NO2 gas.
TL;DR: In this article, the adsorption of malachite green from aqueous solution on a highly porous metal-organic framework MIL-100(Fe) was studied in view of the adaption isotherm, thermodynamics, kinetics, and regeneration of the sorbent.
Abstract: The adsorption of malachite green from aqueous solution on a highly porous metal–organic framework MIL-100(Fe) was studied in view of the adsorption isotherm, thermodynamics, kinetics, and regeneration of the sorbent. The adsorption isotherms of malachite green on MIL-100(Fe) followed the Freundlich model, and MIL-100(Fe) possessed heterogeneous surface caused by the presence of different functional groups on the surface. The adsorption of malachite green on MIL-100(Fe) is controlled by an entropy effect rather than an enthalpy change, and obeyed a pseudo-second-order kinetics. Analysis of the intraparticle diffusion plots revealed that more than one process affected the adsorption, and film (boundary layer) diffusion controlled the adsorption rate at the beginning. Evidence from zeta potential and X-ray photoelectron spectroscopic data showed that the adsorption of malachite green was also driven by electrostatic attraction and the interaction between the Lewis base –N(CH3)2 in malachite green and the water molecule coordinated metal sites of MIL-100(Fe). MIL-100(Fe) gave much higher adsorption capacity for malachite green than other conventional adsorbents such as activated carbon and natural zeolite. The high adsorption capacity, good solvent stability, and excellent reusability make MIL-100(Fe) attractive for the removal of MG from aqueous solution.
TL;DR: In this paper, a new material, graphene sponge (GS), was developed for water treatment, which was assembled with graphene oxide sheets by hydrothermal treatment with the assistance of thiourea.
Abstract: Seeking highly-efficient, low-cost and robust methods to disinfect and decontaminate water from source to point-of-use is very much in demand. Here, we developed a new material, graphene sponge (GS), for water treatment, which was assembled with graphene oxide sheets by hydrothermal treatment with the assistance of thiourea. These GSs show a tunable pore structure and surface properties, and are mechanically strong. They show high adsorption ability for various water contaminations such as dyes, oils and many other organic solvents. The adsorption capacity of methylene blue and diesel oil in GSs can reach 184 mg g−1 and 129 g g−1, respectively. Moreover, the GSs can be repeatedly used by simple treatment without obvious structure and performance degradation. Additionally, we studied the relationship between the structure and contamination adsorption performance of GSs. It was found that the dye adsorption performance of GSs strongly depends on their surface charge concentration and specific surface area, but the oil adsorption capacity is mainly related to their specific surface area, indicating the different adsorption mechanism. These findings open up many possibilities for the use of graphene in water cleaning, including disinfection, decontamination, re-use, reclamation and desalination.
TL;DR: A review of surface plasmon resonance-mediated photocatalysis can be found in this article, where the authors highlight diverse applications of plasmoric photocatalysts in mineralization of organic pollutants, organic synthesis and water splitting.
Abstract: Harvesting abundant and renewable sunlight in energy production and environmental remediation is an emerging research topic. Indeed, research on solar-driven heterogeneous photocatalysis based on surface plasmon resonance has seen rapid growth and potentially opens a technologically promising avenue that can benefit the sustainable development of global energy and the environment. This review briefly summarizes recent advances in the synthesis and photocatalytic properties of plasmonic composites (e.g., hybrid structures) formed by noble metal (e.g., gold, silver) nanoparticles dispersed on a variety of substrates that are composed of metal oxides, silver halides, graphene oxide, among others. Brief introduction of surface plasmon resonance and the synthesis of noble metal-based composites are given, followed by highlighting diverse applications of plasmonic photocatalysts in mineralization of organic pollutants, organic synthesis and water splitting. Insights into surface plasmon resonance-mediated photocatalysis not only impact the basic science of heterogeneous photocatalysis, but generate new concepts guiding practical technologies such as wastewater treatment, air purification, selective oxidation reactions, selective reduction reactions, and solar-to-hydrogen energy conversion in an energy efficient and environmentally benign approach. This review ends with a summary and perspectives.
TL;DR: A brief overview of the recent development of push-pull conjugated polymers and their application in solar cells is provided in this paper, where the relationships between the materials' chemical structures and properties, such as absorption spectra, energy levels, mobilities and photovoltaic behaviors, are also discussed.
Abstract: Bulk-heterojunction polymer solar cells have emerged as an attractive type of cost-effective solar energy–electrical power transforming device. Recently, great progress in the development of new photo-harvesting materials and device optimizations have been achieved in this field, resulting in the significant improvement of the power conversion efficiencies of polymer solar cells from around 1% to higher than 8.0%. The rational design and fine tailoring of the molecular structures of donor polymers significantly contributed to these prominent advances. Among all kinds of donor polymers, push–pull conjugated polymers, which consist of alternating electron-rich and electron-deficient units have been most extensively developed and have dominated the library of donor materials for polymer solar cells, because their intrinsic optical and electronic properties can be readily tuned to the desired situation by controlling the intramolecular charge transfer from donor unit to acceptor unit. This review provides a brief overview of the recent development of push–pull conjugated polymers and their application in solar cells. The relationships between the materials' chemical structures and properties, such as absorption spectra, energy levels, mobilities and photovoltaic behaviors, were also discussed.
TL;DR: In this article, the authors summarize the strategies for chemical modification of graphene, the influence of modification and the applications in various areas, and discuss the challenges associated with the production, processing and performance enhancement.
Abstract: Graphene's unique thermal, electric and mechanical properties originate from its structure, including being single-atom thick, two-dimensional and extensively conjugated. These structural elements endow graphene with advantageous thermal, electric and mechanical properties. However, the application of graphene is challenged by issues of production, storage and processing. Therefore, the stabilization and modification of graphene have attracted extensive interest. In this review we summarize the strategies for chemical modification of graphene, the influence of modification and the applications in various areas. Generally speaking, chemical modification can be achieved via either covalent or non-covalent interactions. Covalent modifications often destroy some of the graphene conjugation system, resulting in compromising some of its properties. Therefore, in this review we focus mainly on the non-covalent modification methodologies, e.g. π–π stacking interactions and van der Waals force, because the non-covalent modifications are believed to preserve the natural structure and properties. We also discuss the challenges associated with the production, processing and performance enhancement. Future perspectives for production of graphene in large size with fewer defects and under milder conditions are discussed along with the manipulation of graphene's electric, mechanical and other properties.
TL;DR: In this paper, Co3O4/Ni(OH)2 composite mesoporous nanosheet networks (NNs) grown on conductive substrates were synthesized by heat treatment.
Abstract: Co3O4/Ni(OH)2 composite mesoporous nanosheet networks (NNs) grown on conductive substrates were synthesized by heat treatment of Co(OH)2/Ni(OH)2 NNs that were synthesized on Ti substrates by a facile electrochemical deposition route. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and micro-Raman spectroscopy. The above products were directly functionalized as supercapacitor electrodes without using any ancillary materials such as carbon black or binder. Co3O4/Ni(OH)2 composite mesoporous NNs achieved a high specific capacitance (Csp) of 1144 F g−1 at 5 mV s−1 and long-term cyclability. The electrochemical measurements showed Co3O4/Ni(OH)2 composite mesoporous NNs exhibited much better electrochemical performances than single Co3O4 or Ni(OH)2. The binary redox couples of Ni2+/Ni3+ and Co2+/Co3+, nanosheet networks with porous structures, the mesoporous structure within nanosheets, the interconnections among nanosheets, together with the excellent electrical contact with the current collector (substrate) are responsible for the improved electrochemical performances of Co3O4/Ni(OH)2 composite mesoporous NNs. With the ease of large scale fabrication and superior electrochemical characteristics, Co3O4/Ni(OH)2 composite mesoporous NNs grown on Ti substrates will be good candidates for supercapacitor applications.
TL;DR: In this article, the development of functional fullerenes as acceptors, electron selective layers, and morphology stabilizers for bulk heterojunction polymer solar cells is reviewed, and a wide variety of newly developed fullerene-derived molecules have appeared in the past few years and started to show very encouraging photovoltaic performance when they were blended with low bandgap conjugated polymers.
Abstract: Tremendous progress has been made on the design and processing of new active and interfacial materials to enable organic photovoltaics to achieve high power conversion efficiencies of >10%. In this Feature Article the development of functional fullerenes as (1) acceptors, (2) electron selective layers, and (3) morphology stabilizers for bulk heterojunction polymer solar cells is reviewed. In addition to the standard PCBM based acceptors, a wide variety of newly developed fullerene-derived molecules have appeared in the past few years and started to show very encouraging photovoltaic performance when they were blended with low bandgap conjugated polymers. New fullerene derivatives with proper molecular design can also serve as electron selective interfacial materials and morphology stabilizers for the bulk heterojunction layer, which are essential to improve the interfacial property and long term stability of polymer solar cells. Although there still are many challenges ahead before practical polymer solar cells will arrive in the market place, the research in functional fullerenes deserves to have more attention in order to expedite this development process.
TL;DR: A review of existing exfoliation methods and techniques used to produce single-layer materials from graphite precursors can be found in this paper, where a number of methods have been developed, each with advantages and disadvantages.
Abstract: For applications of two-dimensional graphene, commercially viable sources are necessary. Exfoliation from bulk, stacked graphite is the most economical way to achieve large quantities of single layer graphene. A number of methods have been developed to achieve exfoliation of graphite, each with advantages and disadvantages. In this review, we describe current exfoliation methods and techniques used to produce single layer materials from graphite precursors.
TL;DR: In this article, the maximum reflection loss reached −45.1 dB with a thickness of the absorber of only 2.5 mm, and the Debye relaxation processes in graphene/polyaniline nanorod arrays are improved compared to polyanilines nanorods.
Abstract: In the paper, we find that graphene has a strong dielectric loss, but exhibits very weak attenuation properties to electromagnetic waves due to its high conductivity. As polyaniline nanorods are perpendicularly grown on the surface of graphene by an in situ polymerization process, the electromagnetic absorption properties of the nanocomposite are significantly enhanced. The maximum reflection loss reaches −45.1 dB with a thickness of the absorber of only 2.5 mm. Theoretical simulation in terms of the Cole–Cole dispersion law shows that the Debye relaxation processes in graphene/polyaniline nanorod arrays are improved compared to polyaniline nanorods. The enhanced electromagnetic absorption properties are attributed to the unique structural characteristics and the charge transfer between graphene and polyaniline nanorods. Our results demonstrate that the deposition of other dielectric nanostructures on the surface of graphene sheets is an efficient way to fabricate lightweight materials for strong electromagnetic wave absorbents.