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The functional groups and physical properties of graphene oxide (GO) are found to be sensitive to and can be controlled by the water content in the reactions when GO samples are prepared at different concentrations of sulfuric acid using a modified Hummers method. GO prepared with 93% sulfuric acid (H2SO4) showed fewer structural defects, less π–π conjugation, and larger interlayer spacing than GO prepared with 99% H2SO4. The intensity ratio of the D-band to the G-band of the Raman spectrum is 0.89 ± 0.01 and 1.02 ± 0.01, corresponding to average interlayer spacing of 0.91 nm and 0.86 nm, respectively. The yield and carbon to oxygen ratio of the GO sheets prepared from different concentrations of H2SO4 are nearly identical. More importantly, compared with GO synthesized with 99% H2SO4, GO prepared with 93% H2SO4 contains more carbon–oxygen single bonds, such as epoxy groups and hydroxyl groups, but fewer carbonyl groups.

A material with a low work function exhibiting field-emission of electrons has long been sought as an ideal point electron source to generate a coherent electron beam with high brightness, long service life, low energy spread, and especially stable emission current. The quality and performance of the electron source are now becoming limiting factors for further improving the spatial resolution and analytical capabilities of the electron microscope. While tungsten (W) is still the only material of choice as a practically usable field emission filament since it was identified more than six decades ago, its electron optical performance remains unsatisfactory, especially the poor emission stability (>5% per hour), rapid current decay (20% in 10 hours), and relatively large energy spread (0.4 eV), even in an extremely high vacuum (10−9 Pa). Herein, we report a LaB6 nanoneedle structure having a sharpened tip apex with a radius of curvature of about 10 nm that is fabricated and finished using a focused ion beam (FIB) and show that it can produce a field emission electron beam meeting the application criteria with a high reduced brightness (1010 A m−2 sr−1 V−1), small energy spread (0.2 eV), and especially high emission stability (

The high-performance silicon (Si) composite electrodes are being widely developed due to their considerable theoretical capacity. Coating with carbon-based materials is an efficient way to solve the common issues of Si-based materials. Currently, most of the reported strategies are complicated, pollutive, or uneconomic, which hamper their practical applications. Herein, a honeycomb-like Si-based composite was prepared to address these issues via a facile and green reduction approach at room temperature. The pre-anchored Si nanoparticles could be packed and interconnected through a three-dimensional graphene network to further enhance the electrochemical properties of the active materials. As an electrode, this composite shows good rate capabilities upon lithium storage and cycling stability. The continued cycling measurement delivers a -0.049% capacity decay rate per cycle within 600 cycles. A direct comparison further exhibits the obviously improved performance between the as-designed Si-based composite and naked Si, suggesting a potential application of this convenient strategy for other high-performance electrode materials.

As an important component of industrial robot, the motion control of rotary flexible joint (RFJ) system is of great significance, especially when the system has unmodeled dynamics or is seriously disturbed. This paper presents an experimental robustness study on a kind data-driven optimal control approach based on an underactuated rotary flexible joint system. The data-driven approach combines the off-policy optimal control algorithm and the popular integral reinforcement learning technique. Through literature review, we find that the key step of the control design lies in that it learns the optimal value function and control policy simultaneously from the input and output (I/O) data. However, the I/O data are often disturbed by the system uncertainty or environmental noise, and then it will indirectly affect the optimal control performance. To investigate the robustness of the data-driven optimal control approach, we artificially set different experimental scenarios and take numerous control experiments on a RFJ experimental setup. The experimental results show that the data-driven optimal control method is quite robust against the system uncertainties in terms of maintaining the stability and delivering satisfactory tracking performance, even when the uncertainty is not a small quantity. In addition, the disturbance originating from environmental noise has certain impact on the controlling of RFJ system, but as long as the noise power is not too large, the control algorithm can converge to a satisfactory result. Finally, we find that the probing signal up has strong influence to this control algorithm, which reminds us to be cautious when selecting the probing signal.

Mid-infrared electro-optic Q-switched lasers with high repetition rates have many vital applications. However, the required voltage of electro-optic Q-switching is proportional to the wavelength leading to the severe piezoelectric ring effect, which limits its developments especially with high repetition rates. Based on the rate equation, this work designs a Langasite (LGS) electro-optic Q-switched laser with high repetition rates at 2 μ m by balancing the gain and loss in the cavity. The driven voltage determines the rotation of the polarization corresponding the loss in the cavity, and the gain depends on the incident pump power and repetition rate. By theoretical calculation, the driven voltage used in the high repetition rates is reduced to be 3.9 kV, which is 45% lower than the quarter-wave voltage. We demonstrated the LGS electro-optic Q-switched 2 μ m laser with a repetition rate of 200 kHz and pulse width of 5.52 ns. To the best of our knowledge, this work presents the highest repetition rate in the electric–optic Q-switched laser at 2 μ m and should be helpful for the design of Q-switched lasers with high repetition rates.

Developing highly selective, economical and stable catalysts for electrochemical converting CO2 into value-added carbon products to mitigate both CO2 emission and energy crisis is still challenging. Here, we report an efficient and robust electrocatalyst for CO2 reduction reaction (CO2RR) by embedding single-atom CoN4 active sites into graphene matrix. These highly dispersed CoN4 sites show an extraordinary CO2RR activity, with a high CO Faradaic efficiency of nearly 95% at −0.76 V (vs. RHE) and remarkable durability. The corresponding overpotential is 0.65 V. Our finding could pave the way for the design of high-efficiency electrocatalyst for CO2RR at the atomic scale.

Searching for viable field-emission structures with a stable emission current, high emission brightness, and low energy spread has always been highly demanded for the development of high-performance electron-optical instrumentation. In this work, a single-crystalline HfC nanowire emitter with an oxycarbide surface is investigated. This new emitter shows an excellent current stability with a fluctuation less than 1%/h, as well as a narrow energy spread and high emission brightness. It exhibits great potentials to be a practical electron source for experimental trials in electron microscopes.

A single hafnium carbide (HfC) nanowire field-induced electron emitter with a sharp tip apex is fabricated by Pt deposition and focused ion beam (FIB) milling. The structure of the electron emitter is characterized by scanning transmission electron microscopy (STEM) and atom probe tomography (APT). The HfC nanowire is single-crystalline with a thin oxide layer on its tip surface. The field emission properties are determined by using both in situ transmission electron microscopy (TEM) and a field-emission probe in a high-vacuum chamber. A high current of 173 nA was obtained at a low extraction voltage of 631 V with an emission gap of 5 mm. The emission current is stable at 60 nA for 100 min with a fluctuation of 0.7%. The deduced work function was 3.1 eV. It is suggested that the implanted Ga ions and the oxide layer induce more downward dipoles that are beneficial for lowering the work function and creating a stable surface. When the low keV FIB processing is applied, it takes within 30 minutes to finish a HfC nanowire emitter, establishing an efficient procedure for the preparation of nanowire emitters. These results provide a controllable and fast production method for the fabrication of single nanowire field-emission point electron sources.

A novel method for producing graphene via enhanced shear exfoliation in a high-pressure fluid has been developed. In the process of exfoliation, graphite flakes, dispersed in a solution of N-methyl-2-pyrrolidone (NMP), were pushed through the exfoliation tube by a high-pressure pump, which produces high shear stresses on the graphite flakes due to the turbulent flow, causing the peeling-off of graphene sheets from the graphite flake. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images show that produced graphene sheets have thicknesses ranging from monolayer to about 12 layers. The results of X-ray photoelectron spectroscopy (XPS) and Raman and infrared (IR) spectroscopy analyses reveal that neither basal-plane defects nor oxides were noticeably introduced to graphene sheets in the process. The graphite solution can be continuously treated in a circular loop. At a pressure of 100 MPa and after 2 h of treatment, exfoliated graphene was obtained with a yield of about 15 ± 0.3%. T...

Carbon nanotubes (CNTs) are an effective spacer to prevent the re-stacking of graphene layers. However, the aggregation of CNTs always reduces the specific surface area of resulting CNT/graphene composites. Meanwhile, different pores always have different contributions to the specific capacitance. In this study, CNT/graphene composites with different porous structures are synthesized by co-reduction of oxidized CNTs and graphene oxide with different mixing ratios. With an optimized CNT content of 20%, the CNT/graphene composite shows 206 F g−1 in 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. It is found that pores larger than twice the size of electrolyte ions can make greater contributions to the specific capacitance.

Unequal electrode capacitance in a symmetric supercapacitor results in an unequal voltage distribution on the two electrodes and the supercapacitor usually cannot utilize the full electrochemical window of electrolyte. In this study, the voltage distribution on the two electrodes of graphene supercapacitor is optimized by an adjustment of electrode mass ratio from 1 to 1.5 and an enlarged energy density of 118 Wh kg−1 is achieved at operating voltage 4.7 V using an ionic liquid electrolyte 1-methyl-1-propylpiperidinium bis (trifluoromethyl sulfonyl) imide (MPPp-TFSI).

The resolution of the electron microscope is now largely limited by the performance of its electron source when various aberrations in the electron imaging system, especially spherical aberrations, are corrected. A nanowire tip could be an ideal point electron source, where electrons are emitted from a small physical area. In this article, we review recent advances in electric-field-induced electron emission using a single nanowire, specifically, single-crystalline lanthanum hexaboride (LaB6) nanowire, compared to the state-of-the-art contemporary tungsten cold-field electron emitter W(310) as well as single atom tip and single-carbon nanotube emitters. Owing to its low work function, improved emission stability, and high emission brightness, the LaB6 nanowire as a cold-field-emission electron source offers a new and exciting opportunity for developing the next generation of electron microscopes.

We report an eco-friendly route for the reduction of graphene oxide (GO) by Azotobacter chroococcum at room temperature. Examinations using X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy indicate the formation of reduced graphene oxide (rGO) with a low degree of agglomeration. Quantitative analyses of electron diffraction data show that the produced rGO consists of single-layer sheets with a random stacking. It is suggested that the GO was reduced directly by the nitrogenase via sequential additions of electrons and protons followed by dehydration. This approach avoids the use of toxic chemical agents and also reduces the agglomeration of rGO.

Like endogenous proteins, recombinant foreign proteins produced in human cell lines also need post-translational modifications. However, high and long-term expression of a gene of interest (GOI) presents significant challenges for recombinant protein production in human cells. In this work, the effect of human matrix attachment region elements (MARs), including the β-globin MAR (gMAR), chicken lysozyme MAR (cMAR), and a combination of these two, on the stable expression of GOI was assessed in human HT-1080 cells. After transfection with vectors containing the MAR elements and eGFP, stably HT-1080 cell pools were obtained under selective pressure. eGFP protein expression was analyzed by flow cytometry, while transgene copy number and eGFP mRNA expression levels were determined with qPCR and qRT-PCR technology. We found that MARs could not enhance transfection efficiency, but gMAR could significantly increase eGFP expression in stable HT-1080 cell pools by approximately 2.69-fold. Moreover, gMAR could also increase eGFP expression stability during long-term culture. Lastly, we showed that the effect of the MARs on transgenes was related to the gene copy number. In summary, this study found that MARs could both enhance the transgene expression and stability in HT-1080 cells.

Making use of quasar spectra from LAMOST, in the spectral data around the Mg ii emission lines, research described in this paper has detected 217 Mg ii narrow absorption lines (NALs) with W r λ 2796 ≥ 3 σ w and W r λ 2803 ≥ 2 σ w in a redshift range of 0.4554 ≤ z abs ≤ 2.1110. For quasars observed by both LAMOST and SDSS, we find that 135 Mg ii NALs were obviously observed in the LAMOST spectra, 347 Mg ii NALs were were apparent in the SDSS spectra, and 132 Mg ii NALs were clearly present in both the SDSS and LAMOST spectra. The missed Mg ii NALs are likely ascribed to low signal-to-noise ratios of corresponding spectra. Among the Mg ii NALs obviously observed in SDSS or LAMOST spectra, eight Mg ii NALs were significantly changed with | Δ W r λ 2796 | ≥ 3 σ w in time intervals of Δ MJD/(1 + z em) = 359 – 2819 d.

Mn-Based compounds with high reversible capacities and eco-friendliness are one of the most promising anode materials for lithium ion batteries (LIBs), but their practical applications are still hindered by low rate capability, poor cycling stability, and high cost of production. Herein, we synthesize MnCO3/Mn3O4/reduced graphene oxide (MnCO3/Mn3O4/RGO) ternary composites through a green and facile strategy, which can take full advantage of the raw materials, mitigate pollution effectively, simplify the operating procedure, and shorten the preparation time to realize large-scale preparation. When used as anode materials for LIBs, benefitting from the advantage of their structure and effective synergy among MnCO3, Mn3O4 and graphene, the ternary composites exhibit an excellent cycling stability of 988 mA h g−1 after 200 cycles at 100 mA g−1 and 532 mA h g−1 after 800 cycles at 1 A g−1, which is superior to those of binary MnCO3/RGO and Mn3O4/RGO composites. Analyses using cyclic voltammetry, charge/discharge profiles, and electrochemical impedance spectroscopy reveal improved kinetics in the electrochemical reaction of the MnCO3/Mn3O4/RGO ternary composite with cycling. Furthermore, a systematic study of the potential difference of the redox reaction provides a good explanation for the observed electrochemical performance of the ternary composites.

Hydrazine-reduced graphite oxide and graphene oxide were synthesized to compare their performances as anode materials in lithium-ion batteries and sodium-ion batteries. Reduced graphite oxide inherits the layer structure of graphite, with an average spacing between neighboring layers (d-spacing) of 0.374 nm; this exceeds the d-spacing of graphite (0.335 nm). The larger d-spacing provides wider channels for transporting lithium ions and sodium ions in the material. We showed that reduced graphite oxide as an anode in lithium-ion batteries can reach a specific capacity of 917 mA h g−1, which is about three times of 372 mA h g−1, the value expected for the LiC6 structures on the electrode. This increase is consistent with the wider d-spacing, which enhances lithium intercalation and de-intercalation on the electrodes. The electrochemical performance of the lithium-ion batteries and sodium-ion batteries with reduced graphite oxide anodes show a noticeable improvement compared to those with reduced graphene oxide anodes. This improvement indicates that reduced graphite oxide, with larger interlayer spacing, has fewer defects and is thus more stable. In summary, we found that reduced graphite oxide may be a more favorable form of graphene for the fabrication of electrodes for lithium-ion and sodium-ion batteries and other energy storage devices.

We have designed and synthesized a unique structured graphene/SnO2 composite, where SnO2 nanoparticles are inserted in between interconnected graphene sheets which form hollow spherical multilayers. The hollow spherical multilayered structure provides much flexibility to accommodate the configuration and volume changes of SnO2 in the material. When it is used as an anode material for lithium-ion batteries, such a novel nanostructure can not only provide a stable conductive matrix and suppress the mechanical stress, but also eliminate the need of any binders for constructing electrodes. Electrochemical tests show that the unique graphene/SnO2 composite electrode as designed could exhibit a large reversible capacity over 1000 mA h g−1 and long cycling life with 88% retention after 100 cycles. These results indicate the great potential of the composite for being used as a high performance anode material for lithium-ion batteries.

The dramatically increased demand for electric devices such as electric vehicles and consumer electronics prompted us to explore new ideas in fabricating novel energy storage devices. In this work, we designed, constructed, and studied an asymmetric hybrid lithium-ion capacitor (LIC) by combining an electric double-layer capacitor cathode and a lithium-ion battery anode. Both electrodes were made of a single-wall carbon nanotube and graphene (SG) composite to reduce restacking of the graphene nanosheets, to improve the energy storage capacity, and to improve the electrical conductivity of the electrodes. One of the electrodes was pre-lithiated electrochemically. After pre-lithiation, the lithiated-SG (Li-SG) electrode showed excellent capacity in lithium intercalation and de-intercalation and was used as the anode of the LIC device. The advantage of the hybrid LIC with asymmetric graphene electrodes is that it maximizes the operable voltage between the two electrodes, thus increasing the energy density of the device. The hybrid LIC fabricated in this work exhibited an energy density of 222 W h kg−1 at a power density of 410 W kg−1.

The graphene material prepared by the chemical reduction method usually has oxygenic functional groups in it and such functional groups often result in interactions between the graphene electrode and the electrolyte in supercapacitors. We have examined the existential form of interactions between graphene as the electrode and three kinds of ionic liquid, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMI-TFSI), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF 4 ), and 1-methyl-1-propylpiperidinium bis (trifluoromethyl sulfonyl) imide (MPPp-TFSI), as the electrolyte of a supercapacitor. Mass spectroscopy (MS) and Fourier transform infrared spectroscopy (FT-IR) analyses confirmed that the residual hydroxyl groups in graphene were transferred to EMI + and TFSI − lost oxygen atoms to graphene, while little reaction took place in BF 4 − or MPPp + , during the process of charging. The chemical reactions are suggested to contribute to the device capacitance while it is also one of the reasons for the decreased electrochemical stability window. In this study the highest energy density achieved using the graphene electrode is 169 Wh kg −1 in MPPp-TFSI electrolyte charged to 4.4 V.

Correction for ‘Roles of water in the formation and preparation of graphene oxide’ by Qiang Zhang et al., RSC Adv., 2021, 11, 15808–15816, DOI: 10.1039/D0RA10026A.

Graphene has been widely used as an electrode material for supercapacitors. However, parallelly-stacked graphene layers often result in inefficient ion diffusion and electron transfers that usually reduce the rate capability of a supercapacitor. In this study, reduced graphene oxide (rGO) and poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) composite films were prepared by a solvent evaporation method using PEDOT:PSS as the binder to fix aligned graphene for its good conductivity and strong π-π stacking interactions with the graphene sheets. Analyses using scanning electron microscopy (SEM), nitrogen adsorption-desorption, and small-angle X-ray scattering show that the graphene sheets were well aligned when a magnetic field was applied, though they were oriented randomly without the magnetic field. As a capacitor electrode material, the aligned rGO shows a specific capacitance of 169 F g−1 with a capacitance retention of about 70% at a current density of 50 A g−1 and its cyclic voltammetry (CV) loops maintained a rectangular shape at a voltage scan rate of 2 V s−1. The aligned rGO electrode can help break through the limitations of traditional supercapacitors and increase significantly their charge/discharge rate and power density.

Silicon-based materials with high specific capacities have attracted great attentions as an alternative to graphite anode in lithium-ion batteries. However, the low electrical conductivity and inefficient suppression of volume expansion make it somewhat unsuitable for practical applications. Thence, a rapid self-encapsulating approach was first adopted to construct a conductive and effective carbon protective shell on the surface of layered SiOx-based nanosheets by compositing polyelectrolyte (polyethyleneimine, PEI) with graphene oxide (GO). This designed composite electrode has a compact and robust interfacial structure attributed to chemical integration and electrostatic interactions, which also greatly increased the tap density of the electrode. As an anode material, it delivered a high reversible capacity of 867 mAh g−1 and excellent rate capability. The cycling stability is also retained even after rate performance test, which resulted a −0.033% capacity decay rate for each cycle in 500 cycles.

To improve the lithium storage properties of anode in lithium ion capacitors (LICs), reduced graphene oxide (rGO) decorated with crystallized cobalt borate nanoparticles (Co-B/rGO) was prepared by an in-situ growth method. Microstructural characterizations demonstrate that crystallized Co-B nanoparticles not only act as an effective electron transfer bridge between rGO nanosheets but also provide more active sites for lithium storage. As a result, LIC based on Co-B/rGO anode exhibited stable cycling performance with a capacitance retention of 75% after 2000 cycles at 2000 mA g−1, and high energy and power density. Thus, Co-B/rGO can be a promising anode material for LICs.

Herein, we aimed to develop a strategy for evaluating the consistency of pharmaceutically important crystallization processes in real time, focusing on two typical cases of polymorphism. Theoretical analysis using a combination of 13C solid-state nuclear magnetic resonance spectroscopy with other polymorphism analysis techniques identified a number of marker signals, the changes of which revealed the presence of two or more structural orientations (lattices and/or molecular conformations) in both cefazolin sodium pentahydrate (α-CEZ-Na) and cephathiamidine (CETD). The proportions of these forms were shown to be batch-dependent and were defined as critical quality attributes (CQAs) to evaluate process consistency. Subsequently, real-time analysis by chemometrics-assisted near-infrared spectroscopy (NIR) was used to obtain useful information corresponding to CQAs. The pretreated spectra of representative samples were transformed by first derivative and vector normalization methods and used to calculate standard deviations at each wavelength and thus detect significant differences. As a result, vibrational responses of H2O, CH3, and CH2 moieties (at 5,280, 4,431, and 4,339 cm−1, respectively) were shown to be sensitive to the CQAs of α-CEZ-Na, which allowed us to establish a highly accurate discrimination model. Moreover, signals of H2O, CONH, and COOH moieties (at 5,211, 5,284, and 5,369 cm−1, respectively) played the same role in the case of CETD, as confirmed by theoretical results. Thus, we established a technique for the rapid evaluation of crystallization process consistency and deepened our understanding of crystallization behavior by using NIR in combination with polymorphism analysis techniques.

Ionic liquids (ILs) with large electrochemical windows up to 4 V have been employed as the electrolyte to boost the energy density of graphene-based supercapacitors. However, due to the larger molecular size, lower conductivity, and higher viscosity of the IL electrolyte, graphene-based supercapacitors in IL electrolyte usually exhibit low rate capability. To make graphene-based electrodes more compatible with the IL electrolyte, we functionalized chemically reduced graphene oxide with the same IL which is also used as the electrolyte. Electrochemical test results show that the relaxation time and charge transfer resistance at electrode-electrolyte interface for IL modified electrode is one third and one fourth of that for the pristine graphene electrode, respectively, indicating the improved compatibility between the IL modified electrode and the electrolyte. Furthermore, the capacitance retention of the IL modified electrode from current density of 0.5 to 20 A g−1 is 85%, which is much higher than that of the pristine electrode (53%).

OBJECTIVES: This study aimed to investigate the safety and therapeutic efficacy of herbal drug, Di Huang Yin Zi (DHYZ), in patients affected by ischemic stroke.METHODS: In this double blind, placebo-controlled study, a total of 100 patients with recent (less than 30 days) ischemic stroke were randomized to receive DHYZ or placebo for 12 weeks. Both groups also received rehabilitation therapy during the study period. As there were 13 dropouts, a total of 45 patients on DHYZ and 42 on placebo were available for analysis. The Fugl-Meyer Assessment (FMA) and Barthel index (BI) were assessed before treatment and at 4-week intervals.RESULTS: We observed that the FMA score and BI were increased, in both groups at week 4, 8 and 12 compared with the baseline. Furthermore, significantly better FMA score was observed in patients treated with DHYZ at week 8 and 12 (both PCONCLUSIONS: DHYZ showed good efficacy, safety and tolerability in patients affected by ischemic stroke. We conclude that DHYZ may be a useful therapeutic option in patients with ischemic stroke.

Carbon nanotube spaced graphene aerogels have been prepared by a hydrothermal method and used for supercapacitor applications. The specific surface area and specific capacitance can be controlled by tuning the amount of added carbon nanotubes. The as-prepared composite aerogels retain the advantage of aerogel structure in providing macropores to ensure electrodes fast wetted by the electrolyte ions and also possess additional mesopores created by the carbon nanotube spacers for more ion adsorption. Benefited from that, the composite aerogels exhibit significantly enhanced supercapacitor properties in both aqueous and ionic liquid electrolyte. Compared with graphene aerogels, the composite aerogels show a 37% larger specific capacitance of 245.5 F g � 1 at a current density of 2.5 A g � 1 and high rate capability of 197.0 F g � 1 at a high current density of 80 A g � 1 in aqueous electrolyte. Moreover, the composite aerogels deliver a 33% larger specific capacitance of 183.3 F g � 1 at 0.5 A g � 1 and a high energy density of 80 Wh kg � 1 when using an ionic liquid (EMIMBF4) as the electrolyte.

The dependence of photocurrent of a typical copper phthalocyanine (CuPc)/C60 device on external negative bias under monochromatic light illumination is reported. With increase of the negative bias, the photocurrent originating from excitons in the CuPc layer is quickly saturated. On the contrary, the photocurrent originating from excitons in C60 layer does not reach saturation but increases continuously with negative bias. This abnormal enhancement shows that the behavior of excitons in C60 layer is completely different from that in the typical donor material CuPc. The triplet exciton–electron interaction in C60 is supposed to cause the photoinduced hole injection enhancement from cathode, resulting in the observed phenomenon. More experiments designed have confirmed this mechanism.

We have synthesized graphene by reducing carbon dioxide in magnesium and calcium metal flames. The as-prepared graphene has been used as conductive additive to improve the electrical conduction of activated carbon-based supercapacitor electrodes. The graphene/activated carbon composite electrode showed an outstanding specific capacitance of 220 and 180 F g (1) at a current density of 0. 1 A g (1) in 6 M KOH electrolyte when using graphene obtained in magnesium and calcium flames, respectively. (C) 2013 Elsevier B.V. All rights reserved.

Graphene and single-walled carbon nanotube (SWNT) composite aerogel has been prepared by hydrothermal synthesis. The restacking of graphene is effectively reduced by SWNTs inserted in between graphene layers in order to make available more active sites and reactive surface area. Electrochemical experiments show that the graphene–SWNT composite electrode has superior catalytic performance in selective detection of uric acid (UA).

Graphene and single-walled carbon nanotube (CNT) composites are explored as the electrodes for supercapacitors by coating polyaniline (PANI) nano-cones onto the graphene/CNT composite to obtain graphene/CNT–PANI composite electrode. The graphene/CNT–PANI electrode is assembled with a graphene/CNT electrode into an asymmetric pseudocapacitor and a highest energy density of 188 Wh kg−1 and maximum power density of 200 kW kg−1 are achieved. The structure and morphology of the graphene/CNT composite and the PANI nano-cone coatings are characterized by both scanning electron microscopy and transmission electron microscopy. The excellent performance of the assembled supercapacitors is also discussed and it is attributed to (i) effective utilization of the large surface area of the three-dimensional network structure of graphene-based composite, (ii) the presence of CNT in the composite preventing graphene from re-stacking, and (ii) uniform and vertically aligned PANI coating on graphene offering increased electrical conductivity.

We describe a process of co-reduction to reduce dispersed graphene oxide (GO) and single-walled carbon nanotubes (SWNTs) simultaneously for preparation of hybrid electrodes for graphene supercapacitors. The SWNTs are in between the inter-layer space of graphene sheets as a spacer to prevent effectively restacking of graphene that often limits seriously the electrochemical performance of graphene supercapacitors. The SWNTs also act as conductive binders to improve the electrical conduction of the electrode. A high specific capacitance of 261 F g−1 for a single electrode and specific energy density of 123 W h kg−1 measured in the two-electrode configuration have been obtained in ionic liquid (EMI-TFSI).

Organic solar cells suffer from device degradation under various undesirable ambient conditions, which limits their efficiencies and applications a lot. The frequently appeared S-shaped current density–voltage ( J – V ) characteristics just reflect this effect and make its underlying mechanisms even obscurer for experimentalists. By performing device model simulation, we investigate the J – V curves of a organic bulk heterojunction solar cell for different interfacial charge injection conditions. We find the S-shaped kinks appear when both electron and hole injection barriers exceed 0.3 eV, which is attributed to the shortage of dark injection carriers. For the nearly Ohmic contacts, the open circuit voltage is significantly reduced. The quantitative study suggests it arising from the majority carrier accumulation and the induced local field variation at the vicinity of the contacts. S-shaped kink is gradually eliminated with increasing carrier mobilities. Finally, we find the decreasing of fill factor under enhanced light absorption, which results from the drastic bimolecular recombination and thus signifies remarkable internal losses.

Few-layer graphene has been prepared by electrochemical intercalation of graphite cathode using Na + / dimethyl sulfoxide complexes as intercalation agent. By adding thionin acetate salt into the electrolyte, the exfoliated graphite is stabilized and further exfoliated into few-layer graphene. Raman and X-ray photoelectron spectra indicate that the graphene material has lower content of defects and oxygen functional groups compared with that obtained by chemically reducing graphene oxide. The graphene paper produced by filtration shows an electrical conductivity of 380 S m 1 , which is forty times larger than that of the graphene material produced by chemical reduction of thionin-stabilized graphene oxide.

Roles of the buried interface between polymer poly(3-hexylthiophene) (P3HT) layer and indium tin oxide (ITO) on the glass substrate have been characterized by transient photovoltage (TPV). Since P3HT is the hole-transporting material, from intuitiveness, ITO/P3HT contact (IPcontact) tends to be hole extracting. However, in this letter, the negative TPV of ITO/P3HT/Al demonstrates that IPcontact dominates the reversed built in electric field, namely pointing from ITO to Al, and is confirmed to be electron extracting. Meanwhile, an interesting biphasic feature of TPV is demonstrated in a device of ITO/P3HT:[6,6]-phenyl-C61-butyric acid methyl ester/Al. The negative component in biphasic TPV shows that IPcontact is one reason resulting in the leakage current for P3HT based solar cells in normal structures. The theoretical study is conducted, and reveals that the interaction between P3HT and ITO reduces electron barrier by 0.5 eV for IPcontact. Band bending and dipole formation are two possible reasons to reduce the electron barrier. By taking advantage of the electron extraction, IPcontact is employed as a composite cathode in an inverted solar cell by pre-coating a pristine P3HT buffer layer between a blended layer and ITO. The study paves a way to characterize the buried interface in solution processable optoelectronics by observing polarity change of TPV, and to fabricate the simplified inverted organic solar cell employing IPcontact to extract electrons.

To investigate the potential protective effect of exogenous recombinant interleukin-22 (rIL-22) on L-arginine-induced acute severe pancreatitis (SAP)-associated lung injury and the possible signaling pathway involved.Balb/c mice were injected intraperitoneally with L-arginine to induce SAP. Recombinant mouse IL-22 was then administered subcutaneously to mice. Serum amylase levels and myeloperoxidase (MPO) activity in the lung tissue were measured after the L-arginine administration. Histopathology of the pancreas and lung was evaluated by hematoxylin and eosin (HE) staining. Expression of B cell lymphoma/leukemia-2 (Bcl-2), Bcl-xL and IL-22RA1 mRNAs in the lung tissue was detected by real-time PCR. Expression and phosphorylation of STAT3 were analyzed by Western blot.Serum amylase levels and MPO activity in the lung tissue in the SAP group were significantly higher than those in the normal control group (P0.05). In addition, the animals in the SAP group showed significant pancreatic and lung injuries. The expression of Bcl-2 and Bcl-xL mRNAs in the SAP group was decreased markedly, while the IL-22RA1 mRNA expression was increased significantly relative to the normal control group (P0.05). Pretreatment with PBS did not significantly affect the serum amylase levels, MPO activity or expression of Bcl-2, Bcl-xL or IL-22RA1 mRNA (P0.05). Moreover, no significant differences in the degrees of pancreatic and lung injuries were observed between the PBS and SAP groups. However, the serum amylase levels and lung tissue MPO activity in the rIL-22 group were significantly lower than those in the SAP group (P0.05), and the injuries in the pancreas and lung were also improved. Compared with the PBS group, rIL-22 stimulated the expression of Bcl-2, Bcl-xL and IL-22RA1 mRNAs in the lung (P0.05). In addition, the ratio of p-STAT3 to STAT3 protein in the rIL-22 group was significantly higher than that in the PBS group (P0.05).Exogenous recombinant IL-22 protects mice against L-arginine-induced SAP-associated lung injury by enhancing the expression of anti-apoptosis genes through the STAT3 signaling pathway.

GdB44Si2 is an excellent thermoelectric material, and nanostructured GdB44Si2 makes it possible to potentially improve its properties further. GdB44Si2 nanowires and nanobelts have been fabricated by chemical vapor deposition and characterized by electron diffraction and high-resolution electron microscopy. These nanostructures are of the YB50 structure and grew in the [010] direction. The nanowires have thickness of less than 100 nm and length of several tens of microns. The nanobelts have thickness of about a few tens of nanometers. Morphological and compositional analyses confirmed that the nanowire growth followed the vapor–liquid–solid mechanism and the nanobelts were formed by a subsequent vapor–solid process of condensation.

We investigate the thermoelectric properties of one-dimensional (1D) graphene antidot arrays by nonequilibrium Greenʼs function method. We show that by introducing antidots to the pristine graphene nanoribbon the thermal conductance can be reduced greatly while keeping the power factor still high, thus leading to an enhanced thermoelectric figure of merit (ZT). Our numerical results indicate that ZT values of 1D antidot graphene arrays can be up to unity, which means the 1D graphene antidot arrays may be promising for thermoelectric applications.

Single-walled carbon nanotubes were deposited on one end of the etched carbon fiber electrodes by an electrophoretic method. The carbon nanotube bundles formed a dense network on the carbon fiber surface. The electrochemical properties of the composite carbon electrodes were studied in the buffered neutral solutions. The results in cyclic voltammetry's characteristic indicate that the electrons on the electrodes transfer very fast. Furthermore, the redox reactions of dopamine (DA) on the composite electrodes show good sensitivity. When the DA concentration was 0.02 mM, the peak current in differential pulse technique reached 1.33 microA after performing the background subtraction. In addition, the simultaneous detection of DA and ascorbic acid (AA) showed that the interference effect was not observed. It was suggested that the carbon composite microelectrodes have potential applications as electrochemical sensors inside a single cell.

Article history: By using the atomistic nonequilibrium Green's function method, we investigate the thermoelectric properties of graphene nanoribbons in the presence of two constrictions (or hexagonal graphene quantum dots). With decreasing widths of the constrictions, the thermal conductance of the nanoribbon can be reduced largely while S 2 Ge (S is the Seebeck coefficient and Ge is the electronic conductance) remains still high as compared with the results of the pristine nanoribbon. Thus, the thermoelectric figure of merit ZT can be enhanced largely. In fact, in the presence of narrowest constrictions the ZT values of the zigzag quantum dots can exceed one at room temperature, while the ZT values of the armchair quantum dots may be close to one, depending on the size of the dot.

Graphene-based materials are promising electrodes for supercapacitors, owing to their unique two-dimensional structure, high surface area, remarkable chemical stability, and electrical conductivity. In this paper, graphene is explored as a platform for energy storage devices by decorating graphenes with flower-like MnO2 nanostructures fabricated by electrodeposition. The as-prepared graphene and MnO2, which were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have been assembled into an asymmetric supercapacitor. The specific capacitance of the graphene electrode reached 245 F/g at a charging current of 1 mA after an electro-activation process. This value is more than 60% larger than the one before electro-activation. The MnO2 nano-flowers which consisted of tiny rods with a thickness of less than 10 nm were coated onto the graphene electrodes by electrodeposition. The specific capacitance after the MnO2 deposition is 328 F/g at the charging current of 1 mA with an energy density of 11.4 Wh/kg and 25.8 kW/kg of power density. This work suggests that our graphene-based electrodes are a promising candidate for the high-performance energy storage devices.

Electron diffraction technique has been developed and refined to establish a systematic procedure to determine the chirality (chiral indices) of each and every shell in a carbon nanotube. We have introduced a zoning scheme to sort the reflection layer lines from the multiple shells of a carbon nanotube. An application of the procedure is demonstrated as an example for an eleven-shell carbon nanotube whose chiral indices of each and every shell were determined unambiguously. The revealed structure of the carbon nanotube suggests that there is no strong correlation among the shells as the nanotube was formed. The limitations of the current method are also discussed.

Annexin B1 (AnxB1) is a calcium-dependent phospholipid binding protein from Taenia solium cysticercus and has been reported to possess anticoagulant activity, to inhibit phospholipase A2, and to regulate membrane transport. Native AnxB1 and its selenomethionyl derivative have been overproduced in Escherichia coli and purified. The results of dynamic light scattering analysis showed that Hepes buffer combined with low concentration salts (NaCl or CaCl2) was beneficial for preventing aggregation and for AnxB1 stabilization in the storage. After the additive screen, crystals have been yielded in the presence of guanidine hydrochloride (Gn-HCl). We determined that a low concentration of Gn-HCl significantly delayed clotting time and increased anticoagulant activity. Analysis of the crystal showed that in the presence of Gn-HCl, AnxB1 crystallizes in orthorhombic space group, which is modified from the cubic space group for crystals grown in the absence of Gn-HCl. A high quality data set (at 1.9 A) has been co...

We have assembled single-wall carbon nanotubes into ultrathin long fibrils using a dielectrophoretic technique and studied the mechanical and electrochemical properties of carbon nanotube fibrils. The diameter of the fibrils can be controlled in the range of 200 nm to 2 mum, and the length can reach as long as 1 cm. The obtained fibrils have a tensile strength of about 65 MPa, electrical conductivity ranging from 80 to 200 S cm(-1), and specific capacitance more than 200 F g(-1). The results indicate that these ultrathin long carbon nanotube fibrils are of great potential for applications as conductive wires and probe electrodes.

We report an experimental measurement of the high tensile modulus of single-walled carbon nanotube (SWNT) bundles and SWNT nano-fibers produced by dielectrophoresis. The average tensile modulus of the SWNT nano-fibers is 265 GPa, much higher than the carbon nanotube fibers spun by other techniques. The tensile modulus increases as the diameter of the fiber decreases due to changes in the dieletrophoretic forces that densify the packing of SWNT bundles. Tensile modulus of 643 � 86 GPa and 443 � 14 GPa were obtained, respectively, from a SWNT bundle of 10 nm diameter and a SWNT nanofiber of diameter 55 nm with a packing density of 69%, respectively. 2009 Published by Elsevier B.V.

Single-crystalline potassium hollandite KTi{sub 8}O{sub 16.5} nanowires were synthesized by the molten salt method at 800 deg. C. Scanning electron microscopy observation shows that the nanowires are with octagonal cross-sections, and combined analyses of transmission electron microscopy and the electron diffraction results show that the terminated planes are angled 90 or 60 degrees to the growth direction, [001] crystallography direction. Ordering of the potassium cations in the tunnels was revealed by electron diffraction. The mechanism of one-dimensional growth of the nanowires was attributed to the oriented attachment mechanism.

Electrical devices based on suspended multi-wall carbon nanotubes were constructed and studied. The chiral structure of each shell in a particular nanotube was determined using nanobeam electron diffraction in a transmission electron microscope. The transport properties of the carbon nanotube were also measured. The nanotube device length was short enough that the transport was nearly ballistic, and multiple subbands contributed to the conductance. Thermal excitation of carriers significantly affected nanotube resistance at room temperature.

A database for preliminary identification and quantification of residual solvents in pharmaceuticals has been established using the parallel dual-column system. Two columns with different polarities, SPB-1 and HP-INNOWAX, connected with a 'Y' splitter, constituted the dual pathways system. Fifty-two solvents were studied according to the guidelines for residual solvents regulated by the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) on this system. Through a single run, preliminary identification and quantification can be performed using the database. An important advantage of the database is that the residual solvents in the pharmaceuticals can be prescreened without using reference organic solvents.