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In this work, we disperse Co atomically on three-dimensional networks of N-doped graphene (3DNG) through the impregnation of 3DNG with Co(Ac)2·4H2O solution followed by rapid pyrolysis. The structure, morphology and composition of the as-prepared composite, namely ACo/3DNG, are characterized. The atomically dispersed Co and enriched Co–N species afford the ACo/3DNG with unique catalytic activity for hydrolysis of organophosphorus agents (OPs), and the network structure and super-hydrophobic surface of 3DNG ensures excellent physical adsorption capacity. Thus, ACo/3DNG demonstrates good capability for removal of OPs pesticides from water. [ABSTRACT FROM AUTHOR]

We propose a mode switch based on hybrid-core vertical directional couplers with an embedded graphene electrode to realize the switching function with low power consumption. We designed the device with Norland Optical Adhesive (NOA) material as the guide wave cores and epoxy polymer material as cladding to achieve a thermo-optic switching for the E11, E21 and E12 modes, where monolayer graphene served as electrode heaters. The device, with a length of 21 mm, had extinction ratios (ERs) of 20.5 dB, 10.4 dB and 15.7 dB for the E21, E12 and E11 modes, respectively, over the C-band. The power consumptions of three electric heaters were reduced to only 3.19 mW, 3.09 mW and 2.97 mW, respectively, and the response times were less than 495 µs, 486 µs and 498 µs. Additionally, we applied such a device into a mode division multiplexing (MDM) transmission system to achieve an application of gain equalization of few-mode amplification among guided modes. The differential modal gain (DMG) could be optimized from 5.39 dB to 0.92 dB over the C-band, together with the characteristic of polarization insensitivity. The proposed mode switch can be further developed to switch or manipulate the attenuation of the arbitrary guided mode arising in the few-mode waveguide. [ABSTRACT FROM AUTHOR]

The rareness and weak durability of Pt-based electrocatalysts for oxygen reduction reactions (ORRs) have hindered the large-scale application of fuel cells. Here, we developed an efficient metal-free catalyst consisting of N, S co-doped graphene nanoribbons (N, S-GNR-2s) for ORRs. GNRs were firstly synthesized via the chemical unzipping of carbon nanotubes, and then N, S co-doping was conducted using urea as the primary and sulfourea as the secondary heteroatom sources. The successful incorporation of nitrogen and sulfur was confirmed by elemental mapping analysis as well as X-ray photoelectron spectroscopy. Electrochemical testing revealed that N, S-GNR-2s exhibited an Eonset of 0.89 V, E1/2 of 0.79 V and an average electron transfer number of 3.72, as well as good stability and methanol tolerance. As a result, N, S-GNR-2s displayed better ORR property than either N-GNRs or N, S-GNRs, the control samples prepared with only a primary heteroatom source, strongly clarifying the significance of secondary-heteroatom-doping on enhancing the catalytic activity of carbon-based nanomaterials. [ABSTRACT FROM AUTHOR]

Formation of solid electrolyte interface (SEI) and irreversible electrochemical reactions on the surface of anode during the lithiation/delithiation are considered as the main factors affecting the initial Coulombic efficiency of lithium‐ion battery. In this work, different metal or/and graphene is pre‐electroplated on the surface of graphite powder using a home‐built electrochemical workstation, and the surface states of graphite powder are characterized using FESEM, HRTEM, and TOF‐SIMS. The results show that metal or/and graphene are plated uniformly on the surface of graphite. The electrochemical property of the coin half‐cell using pre‐electroplated graphite as anodes shows that the metal can improve the electron/ion transfer capability of the composites that further suppress the irreversible reactions. The graphene can also control the formation of SEI on the anode, which counteract the considerable consumption of Li ions during the initial lithation/delithiation cycle. [ABSTRACT FROM AUTHOR]

Composites of gold nanoparticles and graphene quantum dots (AuNPs/GQDs) exhibit excellent dispersibility in aqueous solutions. Thus, it is difficult to separate them from wet reaction systems when they are used as catalysts. To resolve this issue, in this study, an AuNPs/GQDs composite was immobilized on silicon dioxide through the hydrothermal method, which involved the formation of an amide bond between the surface GQDs of the AuNPs/GQDs composite and the amino group of the silane. The as-synthesized AuNPs/GQDs/SiO2 composite was found to be suitable for use as a heterogeneous catalyst for the oxidation of veratryl alcohol in water and exhibited catalytic activity comparable to that of bare AuNPs/GQDs as well as better recyclability. [ABSTRACT FROM AUTHOR]

Abstract: A glass carbon (GC) electrode has been modified with horseradish peroxidase (HRP) molecules, which are immobilized on the partially reduced graphene oxide (PCRG). The surface properties of the as-modified electrode are characterized with scanning electron microscopy (SEM), the electrochemical characteristics of the as-modified electrode are studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). We demonstrated that the PCRG can promote the electron transfer between HRP and GC electrode, and the immobilized HRP maintained its catalytic activity of the decomposition of phenol and p-chlorophenol. The GC electrode modified with PCRG immobilized HRP exhibits better electrochemical property over CRG, the modified electrode may find practical application as enzyme-based amperometric sensors used for detections of phenolic molecules or other permanent organic pollutants in water. The method provides a strategy for preparation of a sensitive amperometric sensor for the detection of phenolic compounds and other permanent organic pollutants. [Copyright &y& Elsevier]

Herein, we report the effects of graphene oxides on human fibroblast cells and mice with the aim of investigating graphene oxides' biocompatibility. The graphene oxides were prepared by the modified Hummers method and characterized by high-resolution transmission electron microscope and atomic force microscopy. The human fibroblast cells were cultured with different doses of graphene oxides for day 1 to day 5. Thirty mice divided into three test groups (low, middle, high dose) and one control group were injected with 0.1, 0.25, and 0.4 mg graphene oxides, respectively, and were raised for 1 day, 7 days, and 30 days, respectively. Results showed that the water-soluble graphene oxides were successfully prepared; graphene oxides with dose less than 20 μg/mL did not exhibit toxicity to human fibroblast cells, and the dose of more than 50 μg/mL exhibits obvious cytotoxicity such as decreasing cell adhesion, inducing cell apoptosis, entering into lysosomes, mitochondrion, endoplasm, and cell nucleus. Graphene oxides under low dose (0.1 mg) and middle dose (0.25 mg) did not exhibit obvious toxicity to mice and under high dose (0.4 mg) exhibited chronic toxicity, such as 4/9 mice death and lung granuloma formation, mainly located in lung, liver, spleen, and kidney, almost could not be cleaned by kidney. In conclusion, graphene oxides exhibit dose-dependent toxicity to cells and animals, such as inducing cell apoptosis and lung granuloma formation, and cannot be cleaned by kidney. When graphene oxides are explored for in vivo applications in animal or human body, its biocompatibility must be considered. [ABSTRACT FROM AUTHOR]

A high-selectivity band pass filter with controllable attenuation based on graphene nanoplates is proposed in this paper. Graphene with controllable resistance has a good uniform attenuation effect to electric field intensity. The filter utilizes quarter wavelength stepped impedance resonators and mixed electromagnetic coupling to have compact circuits and high performance. The graphene nanoplates are loaded on the microstrip resonator to reduce the electric field intensity, which results in a flat attenuation in the passband. In addition, the filter has two transmission zeros, which lead to a strong selectivity. Finally, a high-selectivity bandpass filter with controllable attenuation is formed. By changing the bias voltage of graphene, a controllable attenuation of 1.64–11.13 dB can be achieved in the working passband centered at 1.36 GHz. In order to validate the concept, the prototype is fabricated and measured. The measurement results are in good agreement with the simulation results. The proposed high-selectivity bandpass filter with controllable attenuation based on graphene nanoplates has widely potential in reconfigurable wireless communication systems and radar systems due to its high integration and versatility. [ABSTRACT FROM AUTHOR]

We demonstrated that the individual graphene oxide sheets can be readily reduced under a mild condition using l-ascorbic acid (l-AA). This simple approach should find practical applications in large scale production of water soluble graphene. [ABSTRACT FROM AUTHOR]

The electronic states of graphene quantum dots (GQDs) can be tuned by varying the lateral size and edge structure, which further influence their optoelectronic properties and the applications. Herein, three kinds of GQDs with different lateral size are prepared by photon‐Fenton reaction and separated through gel column chromatography, and their effects on the photovoltaic performances of inverted organic solar cells based on the poly(3‐hexylthiophene) (P3HT) and poly(3‐hexylthiophene)/(6,6)‐phenyl‐C61 butyric acid methylester (PCBM) blend films are studied systematically. In comparison with P3HT:PCBM cells, the power conversion efficiency of the P3HT:PCBM solar cells containing 0.8% of GQDs‐blue, GQDs‐green, and GQDs‐orange can be increased from 3.06% to 3.54%, 4.43%, and 3.73% with a short‐circuit current density of 10.3, 13.34, and 11.19 mA cm−2. It is illustrated also that the band structures (electronic energy states) tuned mainly by their lateral size of GQDs are the crucial factor to dominate their photovoltaic preferences as additives in conventional P3HT:PCBM solar cells. [ABSTRACT FROM AUTHOR]

A versatile nanoprobe was developed for trypsin quantification with fluorescence resonance energy transfer (FRET). Here, fluorescence graphene quantum dot is utilized as a donor while a well-designed coumarin derivative, CMR2, as an acceptor. Moreover, bovine serum albumin (BSA), as a protein model, is not only served as a linker for the FRET pair, but also a fluorescence enhancer of the quantum dots and CMR2. In the presence of trypsin, the FRET system would be destroyed when the BSA is digested by trypsin. Thus, the emission peak of the donor is regenerated and the ratio of emission peak of donor/emission peak of acceptor increased. By the ratiometric measurement of these two emission peaks, trypsin content could be determined. The detection limit of trypsin was found to be 0.7 μg/mL, which is 0.008-fold of the average trypsin level in acute pancreatitis patient's urine suggesting a high potential for fast and low cost clinical screening. [ABSTRACT FROM AUTHOR]

The capacity and electrochemical kinetics mismatches between cathode and anode are two major obstacles for lithium ion capacitors. In the work, graphene coating and electrochemical prelithiation are used to reinforce the properties of activated carbon and graphitized carbon as cathode and anode. The activated carbon with high specific surface area, and the graphitized carbon with porosity are prepared with anthracite as raw material, then both of them are modified with anthracite-derived graphene. As cathode, activated carbon coated with graphene shows a capacitance of 302 F g−1 with 75% capacitance retention after 10,000 cycles. The anode, graphitized carbon coated with graphene sheets delivers a capacity of 568.1 mAh g−1 at 0.1 A g−1 with 97% capacitance retention after 300 cycles. The LICs assembled with cathode and prelithiated anode show high energy and power densities, 315.1 Wh kg−1 at 300 W kg−1 and 133.3 Wh kg−1 at 15000 W kg−1, and superior cyclic stability, 78% capacity retention after 10,000 cycles. This work illustrates surface graphene coating and prelithiation to balance the capacity and electrochemical kinetics mismatches of electrodes in LICs and blaze an efficient route to convert anthracite to high performance electrodes for LICs and other energy storage systems. [Display omitted] • The anthracite lights the world without emission. • Three carbon-based materials, including activated carbon, graphitized carbon, and graphene, are converted from anthracite. • As cathode, the activated carbon coated with graphene sheets shows an ultrahigh specific capacitance. • As anode, the graphitized carbon coated with graphene sheets delivers a high specific capacity. • The LICs assembled with cathode and pre-lithiated anode show high energy and power densities and superior cyclic stability. [ABSTRACT FROM AUTHOR]

Achieving high specific surface area and ion accessibility in graphene-based electrodes with a high mass loading for supercapacitors poses a significant challenge because strong π-π stacking of graphene sheets often blocks the access of electrolyte ions to active sites. Herein, we report a novel protocol to prepare free-standing laminated graphene/carbon nanofiber films as high areal mass-loading electrodes through a layer-by-layer electrospinning technique. The unique laminated structure of graphene/carbon nanofiber thin films can enhance electrolyte penetration and increase transportations of ions/electrons. The symmetric supercapacitors (SCs) using the as-obtained graphene/carbon nanofiber films as electrodes reach areal specific capacitance of 1536 mF cm−2 at a current density of 1 mA cm−2. Most importantly, the areal energy density of the SCs can reach 0.22 mWh cm−2 at a power density of 1 mW cm−2 with a high areal mass loading of 24 mg cm−2. The exceptional electrochemical properties of the laminated graphene/carbon nanofiber films render them promising materials for electrodes in SCs. [Display omitted] • Laminated graphene/CNFs were prepared via layer-by-layer electrospinning. • The unique laminated structure enhances ions accessibility at high mass loading. • The assembled symmetric supercapacitor exhibits high areal specific capacitance. [ABSTRACT FROM AUTHOR]