The composites together with the individual analog of Ag/CNT and Ag/graphene were characterized by means of XRD, TEM-SAED, N2 sorptiometry, Raman, FTIR, UV-Vis, and photoluminescence spectroscopy. These nanomaterials were then tested for the catalytic reduction of 4-nitrophenol (4-NP) to the technologically beneficial 4-aminophenol (4-AP). The Ag2O@Ag@CNT-graphene composite calcined at 400°C has shown fascinating reduction performances for 4-NP either in the dark (k = 0.014 s−1) or under visible light illumination (k = 0.039 s−1) in the presence of 5 mM NaBH4 compared to Ag/CNT (0.0112 s−1) and Ag/graphene (0.010 s−1) catalysts. This was chiefly because Ag2O@Ag@CNT-graphene comprises the highest pore volume (0.49 cm3/g) and involves three types of pores in the margin from 1.8 to 4.0 nm in front of only one modal type of pores for the rest of the catalysts and thus maximizes the adsorptive capacity of the reactants (4-NP and NaBH4). Moreover, the former composite exhibits the highest concentration of the Ag2O component as established by numerous techniques in addition to the cyclic voltammetry, proposing it's facile reaction with 4-NP along with the simultaneous transfer of surface hydrogen and electrons from NaBH4 ions to produce 4-AP. The promotion of the p-n junction evaluated using the Mott-schottky equation on Ag2O@Ag@CNT-graphene assisted by charges separation and surface plasmon resonance bands of Ag and Ag2O are found to be advantageous for 4-NP reduction. The latter composite delivers a specific capacitance of 355 F g−1 at 1.0 A g−1 exceeding those of Ag/CNT (230 F g−1) and Ag/graphene (185 F g−1). The EIS study establishes the high electronic conductivity of the metallic Ag and Ag2O moieties, low internal resistance of CNT-graphene as well as the marked ionic transfer facilitated by the composite porous nature.A simple hydrothermal route assisted by a triblock copolymer was used to synthesize Ag Undeniably, silver nanoparticles have attracted lots of attention in different areas of application; however, the agglomeration and the consequent separation processes prohibit its usage. This can be minimized by affixing the Ag nanoparticles on CNT-graphene composite. Indeed, the functionalized CNT is going to show a p-type transfer that can be converted after graphene incorporation and with the deposited Ag into n-type compensated by the p-type Ag2O formed species. The formation of the p-n junction between oxygen functionalized CNT/Ag2O (as p-type) and Ag/graphene (as n-type) hetero-structure [CNT/Ag2O/Ag/graphene] is expected to enhance the reduction activity based on enhancing the conductivity, electron mobility and lifetime of photo-generated electron-hole pairs. This work inspects the relationships between the photocatalytic activity and structure alterations in view of metal (oxide)–support interaction, average metal size and dispersion, charge transfer, role of surface texturing, and functionalities of Ag2O/Ag/CNT-G on the reduction efficiency of nitrophenols. The supercapacitance performances of the catalysts is estimated and well correlated with the photocatalysts structure as well as their photo-reduction effectiveness.Oxygen-containing CNTs are desirable rather than pristine CNTs since the former are considered as anchoring sites for diverse semiconductors and metal nanoparticles via forming covalent, electrostatic and hydrogen bonds  and 0.5 g of the as-fabricated graphene oxide (according to the modified Hummer method) are dissolved in 10 ml of the synperonic F108 (Triblock copolymer of an average Mn 2800-Sigma Aldrich), formed as a result of dispersing 1 g/100 ml distilled water. To the latter suspension, an aqueous AgNO3 solution (to from 4 wt%Ag) dissolved in 10 ml distilled water was well mixed and kept under stirring for 30 min followed by sonication for another 3.0 h. During the latter sonication process, an addition of NaBH4 (0.1 M) is began till the yellow color is formed. Later on, this suspension is autoclaved at 180°C for 12 h followed by washing, filtering and drying at 100°C for 5 h. This catalyst was finally annealed at 400°C, and to be denoted as 4%Ag/CNT-graphene400. Similarly, the individual analog 4%Ag/CNT400 and 4%Ag/graphene400 catalysts are prepared in a typical way to that mentioned for the hybrid CNT-graphene.0.5 g of the as-obtained multi-walled carbon nanotubes  and mean pore radius (r) were determined from N2 adsorption isotherms measured at 77 K after out-gassing the samples at 473 K for 3 h under a reduced pressure of 10−5 Torr. Diffuse reflectance ultraviolet–visible spectroscopy (UV–vis DRS) of the samples was carried out at room temperature using UV–vis JASCO spectrophotometer (V-570) in the of 200–1,000 nm range using BaSO4 as a standard. The band gap energy (Eg) of the samples is estimated using the equation: αhν = A(hν-Eg)n/2 and determined by finding the intercept of the straight line of the plot of (αhν)1/2 or (αhν)2 against hν for both indirect and direct transitions, respectively  was measured at room temperature using a Philips diffractometer (Model PW-3710). The patterns were progressed with Ni-filtered copper radiation (λ = 1.5418 Å) at 30 kV and10 mA with a scanning speed of 2θ = 5°/min. The Fourier transform infrared (FT-IR) spectra were monitored via a single beam using Thermo scientific Nicolet iS10 instrument thorough which the samples were grounded with KBr (1:100) to form tablets, and to record the measurements in the 4,000–400 cm4. The solution was subjected to a constant stirring. With the addition of NaBH4, the yellow color of the solution was darkened due to the formation of the phenolate ions. The desired amount of catalysts was added (0.025 g); while stirring was continued at room temperature. The dark yellow color of the solution was progressively vanished, demonstrating the reduction of 4-NP. The reaction progress was checked via withdrawing samples from the reaction mixture at normal time intervals. The catalyst/4-NP+NaBH4 suspension was also exposed to the visible light irradiation of a 160 W Hg lamp, to investigate the effect of light on the reduction activity of the catalyst. The conversion of 4-NP to the corresponding amino (4-AP) was checked by UV-Visible spectroscopy (a Perkin Elmer Lamda-900) by measuring the absorption maxima corresponding to the reactant 4-NP as well as the product 4-AP compounds. For the recycling measurement, the used catalyst was separated by filtration and then used without any treatment for further six times under the same conditions. The effect of additives on the catalysts performances toward 4-NP reduction was performed by adding 100 ppm concentration of triethanol amine, isopropyl alcohol, benzoquinone and Na2CO3.To investigate the catalytic reduction of 4-nitrophenols (4-NP), 100 ml of 0.1 mmol aqueous solution of 4-NP was inserted in a 100 ml beaker together with a 12.5 ml of 0.5 M of NaBH2O phase (JCPDS card no. 41-1104) exhibited via the main diffraction plane (111) at 32.8°; beside some others at 2θ = 36.2° and 19.7°, shows an enhancement mostly on the 4% Ag/CNT-graphene400 catalyst. Graphitic peaks due to (002) and (100) planes were only shown on the CNT sample; when compared with the mother CNT-graphene pattern, indicating that the deposition of Ag NP can prevent the stacking of graphene when interconnected with CNT into multilayers , with an average diameter of 7 nm. The HRTEM shows a little deterioration for the CNTs networks as a result of the high calcination temperature. The TEM image of 4%Ag/graphene400 exhibits an agglomeration of Ag nanoparticles of a dimension with 23 nm. The SAED inset-image evidences the presence of lattice fringes with interplanar spacing of 2.47 and 1.40 Å due to (002) and (220) diffraction planes of graphene and Ag nanoparticles, respectively, supporting the results obtained from XRD investigation. The TEM image of the 4%Ag/CNT-graphene400 catalyst shows that graphene coated carbon nanotube and silver nanoparticles of spherical architecture are equally distributed on both of the carbon substrates. The distributed Ag nanoparticles of darker color and of average diameters of 20 nm were seen throughout the image. A lighter color is seen mainly around CNTs to ascribe the presence of the Ag2O phase; in agreement with XRD results, of a mean diameter of 15 nm. The SAED pattern of this sample demonstrates diffraction bright spots at d-spacings 2.51 and 2.04 Å corresponding respectively, to the (002) and (200) planes of graphitic carbons and Ag nanoparticles, respectively.The X-ray diffraction profiles of Ag incorporated graphene, CNT and CNT-graphene catalysts calcined at 400°C were shown in Figure 400 sample (46.8 Å) and thus showed the lowest SBET value (71.4 m2/g) if compared with Ag/CNT400 (412.7 m2/g) and Ag/CNT-graphene400 (365.1 m2/g), depicted in Table 3/g) with a median pore size of 26.9 Å. All the prepared materials exhibited a characteristic Type IV isotherm  compared to 4%Ag/CNT-graphene400 (0.74) whereas 4%Ag/graphene400 retains the ratio of 1.02 similar to that without Ag, pertaining higher graphitization purity and least disturbance. This indeed maximizes the occurred defects in former catalysts comparatively and to comprehend the strong interaction of the Ag nanoparticles within their structures. The 4%Ag/graphene400 sample shows a more diffused and splitted 2D band  with higher wavenumber than those exhibited on the former ones , proposing an extra contribution of the inner double-resonance scattering due to layers of graphene sheets. The appearance of a Raman peak at 594 cm−1 solely on 4%Ag/CNT-graphene400 confirms the existence of Ag-O stretching modes  of the fabricated CNT-graphene, shown as inset in Figure −1 beside peaks at 2,919 and 2,850 cm−1 due to asymmetric and symmetric stretching of the C–H bond; in CH2, and 1,565 cm−1 with 1,451 cm−1 to the aromatic C = C stretching, confirming the hexagonal structure of the graphitic carbons and indeed indicative of the intact structure of CNT and graphene without disruption following the hybridization process  vibration but with a significant decrease in intensity. This catalyst also provokes the evolution of Ag-O moieties as diagnosed via the peak at 560 cm−1. In case of 4%Ag/graphene400, vanishing of the free OH band is attained together with reducing the intensity of all the bands correlated to C = O, C-O, C-OH, and C-O-C functional groups, those suffer blue shifting compared to the Ag free sample to simply comprehend the Ag involvement. The presence of bands at 943, 825, 700, and 615 cm−1 never seen in the hybrid spectrum can be correlated to the involvement of Ag and Ag-O bonds within graphene structure 2 and (hν)  spectra were measured following an excitation at 320 nm  Figure  were 1.5m Figure . All the400, Ag/graphene400 and Ag/CNT-graphene400 electrodes at a scan rate of 100 mV s−1 in the potential window range from −0.4 to 0.5 V in 6.0 M KOH solution. The CV of CNT-graphene400 indicates a cathodic peak at 0.015 V and an anodic one at 0.07 V. Ag incorporation has stimulated shifting both of the peaks into lower potentials elucidating beside its good encapsulation the higher conductivities and ions charge transfer. Conclusively, the CV curves indicate the presence of quasi-capacitance current with an extended potential window in case of the Ag/CNT-G catalyst. This is a good indicative to stability and strong interaction of Ag within CNT-G hybrid than in case of Ag/CNT and Ag/G where the dissolution of Ag is attained at 100 mV  >4%Ag/CNT400 (300 s) >4%Ag/graphene400 (370 s). Accordingly, the calculated kinetics seen as inset in Figure −1>0.0112 s−1 >0.010 s−1. The time dependent ultraviolet-visible spectra of the reaction mixture in the presence of 4%Ag/CNT-graphen400 showed a gradual decrease in the peak intensity (at 400 nm) of 4-nitrophenolate ions with a gradual increase in the peak intensity (at 300 nm) of 4-AP. The yellow color of the solution completely fades within 3.5 min reaction time, specifying the over-all conversion of 4-NP to 4-AP. This enhanced activity of the composite CNT-graphene containing Ag is primarily related to increasing the pore volume of this specific catalyst (0.49 cm3/g) and to the presence of three types of pores in the margin from 1.8 to 4.0 nm in front of only one modal type of pores for the rest of the catalysts. This indeed maximizes the adsorptive capability toward the reactants 4-NP and NaBH4 and thus helps the facile reduction-capability. It seems also that the particle size decrement was not the main factor affecting the reduction process since 4%Ag/CNT400 presented the lowest domain (7 nm) and was not the most reactive catalyst. However, the high disperse-ability of the Ag nanoparticles with the appreciable surface area the composite own helps much in improving activity, as TEM and N2 adsorption explores. Exposing the lattice plane (200) on Ag/CNT-graphene400 in front of (220) for rest of the catalysts might advocate higher binding energy between 4-NP and the former plane facilitating the reduction process.To confirm thephotocatalytic activity of the catalysts, a nitrophenol (NP) reduction in the presence of 0.5 mmole NaBHm Figure , showed 400 toward 4-NP reduction under visible light irradiation  for all catalysts in comparison with the Ag free hybrid were determined via the extended linear part of the Mott-Schottky (M-S) plots FB of the samples are −0.018 V, −2.2 V, and −0.05 V for 4% for Ag/CNT-graphene400, 4%Ag/CNT400, 4% Ag/graphene400, respectively in front of 1.4 V (vs. Ag/AgCl) for CNT-graphene400. Thus, the values determined for the CB are −0.22, −2.4, −0.25, and 1.2 V for the above sample sequence (CB ≈ EFB −0.2 V)  was rather larger than 4%Ag/CNT-graphene400 (2.5 × 1018 cm3) under dark condition, manifesting that the depletion of electrons in the latter was faster in favor of Ag2O formation and indeed confirm the p-n interface formation and the role of the latter in achieving high reduction performance.To affirm the latter interface, the flat-band potentials  isopropanol (IPA), and benzoquinone (BQ) were selected as the main scavengers for the holes, (h+), hydroxyl radicals (∙OH), and superoxide radicals  in capturing some electrons (from CNT due to differences in work function) and thus prolonged the distances between electrons and holes to give enough space for facilely perform the reduction process. Rising the activity on the 4%Ag/CNT-graphen400 catalyst might also highlight the necessity of the positively charged Ag2O p-type in stimulating strong interaction with the -NO2 group of 4-NP, through the coulombic interaction forces. In addition, the components of Ag2O can acquire efficient electrons via a transfer process from metallic Ag to efficiently inhibit the recombination of the photo-excited pairs of the latter. Undeniably, few of photo-generated electrons can be captured by the O2 moieties embedded on CNT and graphene surfaces; established via FTIR, to form O2O or OH− to form OH∙ upon light illumination; as scavengers study confirm, those affect the activity via degradation consequences. Accordingly, the marked decrease in the activity during the addition of IPA and BQ is attributed to the abstraction of H+ ions from borohydride to ∙OH and OFor investigating the catalytic mechanism and to unravel the effect of some organics on the reduction consequences of 4-NP, several scavengers were utilized to determine the primary active species responsible for the reduction performances of 4%Ag/CNT-graphen400 catalyst can be proceeded by the diffusion of BH2O@Ag interface is expected. Evidently, lowering the work function of Ag (4.26 eV) than that of CNT-graphene (~4.95 eV) rearranges the charges distribution to be around the CNT-graphene composite and thus enhances the reduction efficacy due to the absorption ability of the composite     , and Ag/manganese dioxide films (225 F g−1 at 2 mVs−1) -activities of the different catalysts, PL results and to the synergistic interaction between Ag2O/Ag/CNT-graphene ternary heterostructure is proposed, as strongly illustrated in Scheme 2O components (p-type) occurs, by exciting electrons (e−) from the VB to the corresponding CB, leaving holes (h+) in the VB. Immediately, the electrons are instantly captured by CNT-graphene to rapidly transferred to the O2 dissolved in the reaction medium or those on the composite surfaces; established via FTIR, to produce superoxide radicals ; emphasized from the scavenger study. Such processes occurred over Ag2O can retard the e−-h+ recombination and indeed prolong their life time to result in an enhanced catalytic performance of the Ag2O/Ag/CNT-graphene heterostructure. Furthermore, the intimate interfacial contact among the hybrid in assembling P-n units in conjunction with their cooperative synergy also contributes to the enhanced (photo)catalytic performance of the ternary hetero-structure.Based on the above methodical exploration, a conceivable photocatalytic mechanism of the Ag2O/Ag/CNT-graphene400 catalyst toward 4-NP reduction was tested via performing 6 successive runs under visible light illumination and without any treatment between the runs. Figure 4 and under illumination. It also dictates the stabilization of both the metal oxide and the NPs via considerable interaction with composite of CNT and graphene preventing them from leaching during the reaction.The durability of the 4%Ag2O@Ag@CNT-graphene has shown fascinating photo-reduction performances for 4-NP with a rate constant of 0.039 s−1 exceeding many in literatures and indicates a magnificent specific capacitance value of 355 F g−1 at 1.0 A g−1. Although this photocatalyst does not reflect the highest number of charge carriers it exposes appreciable amounts of Ag2O (p-type) that played a unique role toward the reactants adsorption and to contribute with the metallic Ag in enhancing the mentioned applications. This study also highlights the synergistic effects prompted by the constructed 3D-like array via 1D CNT (as spacer) and 2D graphene in dispersing Ag2O and Ag nanoparticles. The electronic conductivity of latter moieties, the porous nature of the composite, the p-n junction interface and delaying of e−-h+ recombination together with decreasing the internal resistance are all competes in enhancing the photoreduction and energy storage reactions.The established heterostructure Ag2O@Ag@CNT-graphene catalyst with varied amounts of Ag2O@Ag and compared with the individual analog of Ag/CNT and Ag/graphene. He participate in discussion and writing of this search. MK participate in discussion, writing of this search and preparation of substances under study. AI participate in synthesize of materials and analysis of materials by XRD, TEM, Raman, FTIR, UV-Vis Diffuse reflectance, N2 adsorption beside electrochemical techniques such as cyclic voltammetry (CV), galvanostatic charge-discharge, and impedance spectroscopy (EIS).MM suggest synthesize of AgThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


DMF is one the most commonly-used solvents for preparing graphene nanocomposites. Various processing variables for DMF are being used for the preparation of epoxy/graphene nanocomposites. Whilst the emphasis of all of these reported studies are on the improvements in mechanical, and other properties, of the epoxy/graphene nanocomposites, there is no study investigating how DMF affects the processing and how it is associated with the final properties of the nanocomposites. In this work, different dosages of DMF have been used to prepare nanocomposites. Mechanical testing, X-ray diffraction (XRD), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) have been used to analyze the effectiveness of DMF dosage on the properties of processed nanocomposites. Larger dosages of DMF are not always ideal for dispersing graphene as it promotes reaggregation of graphene during the processing.  Since its discovery in 2004 , graphenEpoxy is a widely used thermoset material due to its superior mechanical properties, thermal stability, solvent resistance, and ease of processing . ApplicaFor epoxy/graphene nanocomposites, graphene can significantly improve the physical and chemical properties of the matrix at extremely low loadings , and thiThe exploration of property enhancements of epoxy/graphene nanocomposites is rapidly advancing. However, in practical terms, graphene is not suitable to disperse in epoxy just by simple mixing, as graphene tends to reaggregate in the matrix due to the strong van der Waals force even after homogenisation. Dispersing them in polymer resin with relatively high viscosity is difficult. Therefore, using solvents as dispersing media has been widely accepted and regarded as the simplest method to distribute isolated graphene homogeneously in the nanocomposite materials.N,N-dimethylformamide (DMF) at 1 g/L, with remarkable improvement in the final properties. Dispersal of graphene in DMF, ethanol, and acetone have even been demonstrated at different concentrations, such as 1 g/2 L, 1 g/3 L, or 1 g/10 L [For example, in some studies ,11,12,131 g/10 L ,33,34,351 g/10 L ,37 repor1 g/10 L ,39,40 re1 g/10 L ,42, THF 1 g/10 L ,44, buta1 g/10 L ,46, acet1 g/10 L ,48, and 1 g/10 L , have al1 g/10 L  using co2/g, the average lateral size and thickness are 4.5 μm and 12 nm, respectively. The epoxy matrix used in this study consists of EPOPHENTM EL5 bisphenol A based liquid epoxy (EP) and EPOPHENTM EHA57 diamine hardener (HD), purchased from Polyfibre UK Ltd.  This epoxy system is a multi-purpose resin offering good all-round properties with the epoxy group content of 4.76–5.25 mol/kg. The viscosities of the liquid epoxy and hardener at room temperature are 12,000–15,000 and 45 cps, respectively. To prepare the epoxy material (EP + HD), 100 parts by weight of liquid epoxy were mixed to 50 parts by weight of hardener. Graphene nanoplates were purchased from Graphene Laboratories Inc.  (product name: AO-3). The graphene nanoplatelets, according to the manufacture’s technical datasheet, have a specific surface area of 80 mFive sets of nanocomposites filled with 0.3 wt % graphene were prepared. One set of samples was prepared as a reference using neat epoxy only, marked as G-0.3. Another four sets were prepared with different dosages of DMF. To understand the relationship among solvent dosage, graphene dispersion state, and the properties of the nanocomposites, 0.3 wt % epoxy/graphene nanocomposites were prepared by using different dosages of DMF. The dosages prepared were 100, 300, 500, and 1500 mL. Graphene (0.45 g) was first dispersed in a specified dosage of DMF  and bath sonicated for 0.5 h. Epoxy monomer was then added to the dispersion and sonicated for another 0.5 h. To remove the DMF solvent, the mixtures were heated to 150 °C with stirring. The mixture with 100 mL of DMF was only heated for 4 h, the mixtures with 300 and 500 mL DMF were heated for 8 h, and the mixture with 1500 mL DMF was heated for 16 h to evaporate the solvent. All mixtures were weighed to ensure full removal of DMF. The mixtures were then cooled to room temperature and the hardener was added with hand stirring for 5 min, followed by 5 min bath sonication. Vacuum degassing was then carried out to remove the entrapped air bubbles. Subsequently, the mixtures were mold-cast and cured at room temperature for 6 h, followed by 6 h post-curing at 80 °C. K1C) according to ASTM D5045. The specimen dimensions were 3 mm × 6 mm × 36 mm with a crack length of 3 mm. The notch was made at the middle of the sample and tapped to sharpen by a razor blade. The K1C was calculated using Equation (1):maxP is the maximum load of the load-displacement curve, f(a/w) is constant related to the sample geometry and was calculated using Equation (2), B is sample thickness (mm), W is sample width (mm), and a is crack length (kept between 0.45 and 0.55 W). The critical strain energy release rate (G1C) was evaluated using Equation (3) where E is the Young's modulus obtained from the tensile tests (MPa), and v is the Poisson's ratio of the polymer, taken to be 0.35.Tensile, three-point bend, and fracture toughness tests were conducted with a universal testing machine , and the crosshead speed was kept at 2 mm/min for all tests. Tensile properties were measured according to ASTMD638 (Type V geometry). The three-point bend test was conducted according to ASTM D790 with specimen dimensions of 3 mm × 12.7 mm × 48 mm. A single-edge-notch three point bending (SEN-TPB) specimen was used to test mode-I fracture toughness (E’) and loss factor tan δ. All tests were conducted by using the temperature sweep method (temperature ramp from 30 to 150 °C at 5 °C/min) at a constant frequency of 1 Hz. Thermogravimetric analysis (TGA) of the nanocomposites was carried out with a TA Instruments Q500 thermal analyzer . The temperature range was from room temperature to 600 °C at a ramp rate of 5 °C/min under N2 atmosphere. The structure of the epoxy/graphene nanocomposites was examined using X-ray diffraction (XRD) carried out with a Siemens D-5000 diffractometer  using a Cu Kα radiation source (λ = 0.15406 nm) with step size of 0.02°. Scanning electron microscopy (SEM) analysis was carried out using a FEI Quanta 200 microscope  to examine the fracture surfaces of nanocomposites. The fractured surfaces were cut from the specimens and a layer of gold was applied using an Emscope sputter coater, model SC500A . For tensile, flexural, fracture, and hardness tests, six specimens were tested for each set of conditions and mean values were then reported.A dynamic mechanical analyzer (DMA)  was used to determine the storage modulus  as a function of temperature for epoxy/graphene nanocomposites. As can be seen from the figure, the storage modulus of G-0.3 is 2.35 GPa. With the increasing dosage of DMF, D-100, D-300, and D-500 samples show increased storage moduli of 2.45, 2.52, and 2.60 GPa respectively. However, with the further increase of the DMF dosage, D-1500 shows a decreased storage modulus with the value of 2.31 GPa. This is the lowest value among all of the samples.gT) characterizes the segmental motion of polymers and was taken as the temperature value at the peak of the tan δ curves, as shown in gT shifted to a higher temperature. This can be ascribed to the fact that the uniformly-dispersed graphene restricted molecular mobility of the epoxy matrix, thus leading to the increased gT values. Among all of these increments, 500 mL DMF-prepared nanocomposites showed the highest gT of 75.57 °C, which is more than 6 °C higher than that of G-0.3 samples, while a 5 °C increment in gT was observed for D-100 and D-300 samples. The reason for this improvement can be explained by the effect of graphene on the cross-linking structure of the nanocomposites. Generally, the cross-linking density means the concentration of cross-linked bonds per volume. As for a typical polymer nanocomposite, the higher the cross-linking density, the stronger the polymer chains bond to each other, therefore leading to a higher gT of the nanocomposites. However, samples prepared with 1500 mL DMF show the lowest gT value of 65.78 °C. The likely reason for this decrease is that graphene, in a liquid matrix, tends to reaggregate over time, especially in a low viscosity medium. As a larger dosage of DMF requires a longer time for complete evaporation, the reaggregation of graphene is more likely to occur. Comparing with the structures of well-dispersed epoxy/graphene nanocomposites, the non-uniformly-dispersed graphene decreased the gT.The glass transition temperature (To summarize the mechanical properties, it has been described in the previous published research that due to the strong van der Waals force on dispersed graphene sheets, graphene tends to reaggregate in liquid matrix with the passage of time ,55,56. FThe fracture surfaces of nanocomposites were examined by SEM and are shown in Finally, XRD was used to characterize the structure of epoxy/graphene nanocomposites. As shown in This graphitic structure could only be caused by the agglomeration of graphene during processing. This result clearly shows that the use of a large dosage of DMF has induced reaggregation of graphene, which leads to the decrements in the properties.In summary, polar solvents, like DMF, are responsible for providing a low-viscosity medium, which is an ideal environment for fullerenes to agglomerate . It is aDMF was used to investigate the effects of solvent dosage on the preparation and properties of epoxy/graphene nanocomposites. This research provides guidelines for the usage of DMF solvents in the preparation of epoxy/graphene nanocomposites, and could also be a reference for other polymer composites where the use of solvents is required in the processing. Mechanical properties, TGA, DMA, SEM, and XRD were tested in this work. The results show that large dosage of solvents are responsible for decreasing the final properties of the nanocomposites. The long processing time, higher temperatures, and low viscosity of solvents are responsible for the promotion of the reagglomeration of graphene. These findings will have profound implications in nanocomposites manufacturing, as large amounts of solvents could be avoided from economic and health and safety perspectives. The processing time could be shortened causing less environmental pollution by reducing the amount evaporated solvents. These results help in optimisation and are having positive implications on the practical processing technology of nanocomposites. However, although the relationship between solvent dosage and the consequent processing of epoxy/graphene nanocomposites has been demonstrated here for the first time, it has not given the critical value for the best condition of dispersibility and processability. Therefore, more work needs to be conducted to fully understand the best usage of solvents.


In addition, the a-Si:H solar cells present notable flexibility whose power conversion efficiencies show little degradation when the solar cells are bent to a radius as small as 14 mm for more than 100 times. The application of this unique flexible substrate can be extended to CuInGaSe and CdTe solar cells and other thin-film devices requiring high-temperature processing.Flexible thin-film solar cells with high weight-specific power density are highly desired in the emerging portable/wearable electronic devices, solar-powered vehicles, etc. The conventional flexible metallic or plastic substrates are encountered either overweight or thermal and mechanical mismatch with deposited films. In this work, we proposed a novel substrate for flexible solar cells based on graphene paper, which possesses the advantages of being lightweight and having a high-temperature tolerance and high mechanical flexibility. Thin-film amorphous silicon ( Mechanically flexible and lightweight thin-film solar cells can be attached to objects with curved surfaces, making them suitable as a source of electricity supply units for portable/wearable electronic devices and unmanned aerial vehicles –5. By co3 vs 7.9 g/cm3 of stainless steel) [−6/K) [Because of the superior thermal stability and coefficient of thermal expansion (CTE), metallic foils are widely used as substrates for flexible solar cells , 15–17. s steel) , 22. How) [−6/K) , 24 and ) [−6/K) , 25. Cel) [−6/K) . Our rec) [−6/K) , 13. HowGraphene, with many unique properties such as high strength and electrical and heat conductivity –30, has a-Si:H) solar cells on smooth graphene papers which were achieved by a filtration method using porous anodic aluminum oxide (AAO) filter. The device depicts a distinct weight-specific power density of 8.31 kW/kg, which is 415 and 4.5 times higher than the previous reports on glass and PI substrates, respectively [a-Si:H is used as the model material in this work with the overall processing temperature below 250 °C, the graphene paper substrates can be extended to other flexible (opto-)electronics, especially suitable for the devices requiring high-temperature processing.As a derivate of graphene, graphene papers have been demonstrated by the solution-phase assembly, electrophoretic deposition, and chemical vapor deposition . The excectively , 38. Mor2·2H2O, and 100 ml deionized water to remove the remaining aluminum substrate and achieve the AAO film supported by PMMA  layer as a spacer layer was then deposited by radio frequency (RF) magnetron sputtering of a 2 wt% AZO ceramic target (99.99% purity) at 250 °C. Subsequently, the n-i-p a-Si:H layers were deposited in a multi-chamber plasma-enhanced chemical vapor deposition (PECVD) system under 250 °C. The n, i and p-type layers were 30-, 280-, and 10-nm thick, respectively. After sputtering an 80-nm indium tin oxide (ITO) thin film, Ag grids were thermally evaporated as the top electrode using a contact mask  curves of thin-film a-Si:H solar cells were carried out under 25 °C using a Xe lamp solar simulator  coupled with an air mass 1.5 global (AM 1.5 G) filter, and the external quantum efficiency (EQE) measurements were characterized by a commercial spectral response system (PV Measurement Inc. QEX10). The thermal stability of the graphene paper substrate was monitored by thermal gravimetry (TG) on a TG instrument (SDTA851 Switzerland-Mettler Toledo) from room temperature up to 1000 °C at a heating rate of 10 K/min. The reliability of solar cells under multiple bending cycles was performed with a home-built automatic bending setup [The surface morphologies were characterized by Hitachi S4800 scanning electron microscope (SEM). All the current density-voltage  as a function of annealing process Fig. c, where a-Si:H solar cells. Its thickness and weight are 53 μm and 5.73 mg, respectively. The device deposited on a rigid glass substrate is also fabricated as a reference. Figure J-V) characteristics of the devices on both GP-3A and glass substrates measured under AM 1.5-G irradiation. A power conversion efficiency (PCE) of 5.86% is obtained on the GP-3A substrate, with an open-circuit voltage (VOC) of 0.87 V, a short circuit current (JSC) of 11.96 mA/cm2, and a fill factor (FF) of 0.57. Compared with the device on glass substrate, the Jsc is improved by 17%, which is further confirmed by EQE measurements  of devices on different substrates. The PW is defined as the ratio of the output power under standard solar irradiation  to the mass of the solar cell per unit area as expressed by following equation:As the thickness of md is the mass of the solar cell per unit area.where the a-Si:H solar cells were successfully fabricated on the patterned PI flexible substrates [a-Si:H solar cells based on GP-3A and the counterpart substrates are summarized in Table Compared with the devices deposited on the glass substrate, the thickness and weight of solar cells on graphene papers are reduced by ~ 20 times and ~ 350 times, respectively. Meanwhile, the power density reaches as high as 8.31 kW/kg, which is 415 times higher than that of its counterpart. In our previous work, bstrates . The GP-J-V curves of the a-Si:H devices after encapsulation. Unfortunately, the energy conversion efficiency of the device was decreased from 5.86 down to 4.14% after the encapsulation. It may be because the copper wire electrodes generate additional contact resistance and slightly damage the device. Thus, elaborate encapsulation strategies would be developed for such GP-based ultra-light devices in future work. After encapsulation, the J-V curves under various bending angles are characterized with a homemade setup [Graphene paper, which possesses superior flexibility, is lightweight, and has high-temperature tolerance, is expected to be an alternative choice for portable device application. Figure de setup . The flede setup , 8, 13. a-Si:H solar cells based on graphene papers were successfully achieved with better photocurrents and comparative energy conversion efficiencies (5.86%) over the counterparts on flat glass substrates. The thickness and weight of solar cells on graphene paper are reduced by ~ 20 and ~ 350 times, respectively. Meanwhile, the power density reaches as high as 8.31 W/g, which is 415 times higher than that of the counterparts. Moreover, the devices based on graphene paper presented an excellent performance with a marginal drop even after 100 bending cycles under 14-mm radius due to ultrathin thickness and excellent mechanical flexibility of graphene paper substrates. Although the work was conducted on a-Si:H material, our proposed scheme can be extended to other material systems that may lead to a new era of flexible optoelectronic devices.In this work, we developed a carbon nanotube-enhanced graphene paper substrate which delivered higher thermal stability, is lightweight, and has excellent mechanical flexibility over traditional flexible substrates. The


We also demonstrate that HCl-induced doping is governed by dissolved O2 and pH in accordance with the Nernst equation. The nanoscopic electrochemistry anatomized in this work sets an ambient limit to material properties, which is universal to not only 2D but also other forms of materials.Controlling extra charge carriers is pivotal in manipulating electronic, optical, and magnetic properties of various two-dimensional materials. Nonetheless, the ubiquitous hole doping of two-dimensional materials in the air and acids has been controversial in its mechanistic details. Here we show their common origin is an electrochemical reaction driven by redox couples of oxygen and water molecules. Using real-time photoluminescence imaging of WS Manipulation of charge carriers is promising for tuning electronic, optical and magnetic properties in two-dimensional materials, but mechanistic details are not fully understood. Here, the authors report that ambient redox reactions govern charge transfer doping in graphene and tungsten disulfide. Such chemical modification of the electronic structure allows detection of even a single molecule that adsorbs on graphene in a transistor form5. The charge exchanges can be described by a simple donor–acceptor model by assuming a significant difference in their electron affinities. Despite the apparent simplicity, however, there is a clear lack of understanding in the ubiquitous chemical interactions of 2D materials. The first graphene transistor was reported to be doped with hole carriers originating from unknown chemical entities6. Optical confirmation soon followed this observation, but with no complete mechanistic understanding7. While various acids were exploited to inject hole carriers in graphene, their exchange mechanism is not clear8. All of these underline that the spontaneous charge transfer between 2D materials and the environment is far from being understood, which hampers both fundamental research and application of 2D materials. In this work, we elucidate that the charge exchange is driven by redox couples of oxygen and water molecules, originally proposed for surface conduction of diamonds10, and that the redox reaction is confined within the nanoscopic space between 2D materials and hydrophilic substrates. By exploiting environment-controlled in situ spectromicroscopy, we captured molecular diffusion through the interstitial 2D space and revealed that photoluminescence (PL) of WS2 and lattice vibration of graphene, both as an indicator of charge density, are dictated by oxygen and water contents and their spatiotemporal distribution.Reduction in dimensions has seen many scientific discoveries in various metallic and semiconducting low-dimensional materials during the past four decades. Because of their high fraction of surface atoms, in particular, various material properties of two-dimensional (2D) materials are greatly affected by charge exchange with neighboring chemical entities or environments. When exposed to alkali metals2 (1LWsilica) was mechanically exfoliated onto SiO2/Si substrates (see the “Methods” section) and served as a model 2D system with precise control over gas environments  have substantial binding energy due to dimensionally restricted screening11 and interact with excess charge carriers to form charged excitons or trions (X±) with additional stabilization as depicted in Fig. 1b12. As shown in Fig. silica in the ambient air typically showed two peaks, each originating from excitons (X0 at EX0 = 2.01 eV) and negative trions (X− at EX− = 1.98 eV), the latter of which derived from defect-related native charge carriers12. By assuming that the ionization reactions of excitons into trions are governed by the law of mass action13, their PL intensity ratio (IX−/IX0) serves as a quantitative measure for the density of charge carriers that are modulated by chemical interaction between WS2 and the environments . The concomitant decrease in the total intensity (It = IX− + IX0) is due to the increasing importance of the nonradiative decay channel at higher ne14. Water vapor in the Ar gas, however, reduced ne when judged from a noticeable decrease in IX−/IX0. Exposure to dry or humid O2 led to an even more considerable decrease in the ratio, and thus further depletion of negative carriers. Time-lapse measurements in Fig. 2 atmospheres, which confirmed the molecular origin of the charge modulation. The dissociation energy of the trions (Ediss = EX0 − EX−) showed a strong correlation with the intensity ratio over the entire atmospheric conditions  exhibited a much smaller It and O2 sensitivity than 1LWsilica  of WS2  of 1L graphene/SiO2/Si (1LGsilica) were greatly upshifted and recovered by thermal annealing at 500 and 1000 °C, respectively. Based on the established Raman metrology22 of hole density (nh) and lattice strain (ε) shown in Fig. ωG and ω2D of samples that were treated at various temperatures were translated into nh and ε with high accuracy of ~1 × 1012 cm−2 and ~0.2%, respectively  . As shown in Fig. 2 also exhibited the same sensitivity toward dissolved O2 in water, and the change became more obvious at lower pH  of 2D materials and electrochemical potential  of the redox system as shown in Fig. EF,graphene = −4.57 eV and EF,redox = −5.669 + 0.0592pH − 0.0148 log[p(O2)], reduction of O2 is more favored at lower pH, which leads to increased hole doping of graphene (Supplementary Note 2). On the other hand, the CT is doubly inhibited by a reduction of the reactant and an increase in EF,redox, when the concentration of O2 is decreased. The rate of CT is proportional to the density overlap between occupied states of graphene and empty oxidized states of the redox system, the latter of which is depicted as a Gaussian distribution centered at Eox in Fig. EF,graphene, and can be well described by the Gerischer model  Fig. . Notablyted Fig. . A typic pH Fig. . Eq. 1)2 dissolv2. Redox couples of O2/H2O responsible for the CT reside at the interface of 2D materials and substrates, and their 2D diffusion was captured in real time by wide-field PL imaging. The CT reaction can be turned on and off via controlling O2 or interfacial water serving as a hydration solvent. The CT rate of 2D materials in contact with liquid water can also be tuned by varying the concentration of dissolved protons or O2 as described by the Nernst equation. The presented nanoscopic electrochemistry will pave the way toward efficient control of charge density and the related material properties in 2D, and other low-dimensional materials and devices.In this work, we have shown that the ambient oxygen reduction reaction is behind the long-standing mystery of the spontaneous and activated CT doping in graphene and WS2 (1LWsilica) and graphene (1LGsilica) samples were prepared by mechanically exfoliating bulk crystals  onto SiO2 (285 nm)/Si substrates in the ambient environment. For 1LWBN samples, single layers were first mechanically exfoliated onto polydimethylsiloxane substrates and then dry-transferred onto thin hBN crystals supported on SiO2/Si substrates. To minimize a change in spectroscopic signals induced by optical interference, hBN crystals thinner than 3 nm were selected as substrates. To remove interfacial water in 1LGsilica, we exposed bare substrates briefly to the vapor of diethyl zinc before mechanical exfoliation in a glove box. For thermal activation, samples were annealed at a target temperature for 2 h in a quartz tube furnace that was maintained at a pressure of 3 mTorr.Most of single-layer WS22. Briefly, monochromatic outputs from solid-state lasers operated at 458 and 514 nm were focused onto samples with a spot size of ∼1 μm by using a microscope objective . Backscattered PL and Raman signals were collected with the same objective and guided to a spectrometer equipped with a liquid nitrogen-cooled CCD detector. Overall spectral accuracy was better than 5 and 1 cm−1 for PL and Raman measurements, respectively. To avoid significant photoinduced effects, we maintained the average power of the excitation beam below 6 μW for WS2 and 400 μW for graphene samples.Raman and PL were performed with a homebuilt micro-Raman spectrometer setupFor wide-field PL imaging, the collimated green laser beam was focused at the back-focal plane of the objective with a plano-convex lens  after three-times expansion with a Galilean beam expander. The average power of the wide-field excitation was maintained below 1.5 mW that was illuminated onto an area with a diameter of ~100 μm. PL signals in the range between 1.9 and 2.1 eV mostly contributed to the PL images recorded with the CCD detector.−1) and O2 (5–250 mL min−1). Unless otherwise noted, flow rates for dry gases were 1000 and 250 mL min−1 for Ar and O2, respectively. Relative humidity (RH) inside the gas cell was monitored by a serially connected hygrometer and could be controlled between 5 and 90% by varying the mixing ratio of an additional Ar gas line that passed through a water bubbler  in ambient conditions. The volume of water droplets was maintained in the range of 2.5–3 μL.The hydrophilicity of SiOSupplementary InformationSupplementary Movie 1Supplementary Movie 2Supplementary Movie 3Supplementary Movie 4


Cardiovirus genus of Picornaviridaebecause: i) L protein of both strains is known to disrupt nucleocytoplasmictransport, including transport of polypyrimidine tract binding protein, anRNA-binding protein, ii) motor neurons and oligodendrocytes are targeted in bothTMEV infection and ALS. TDP-43 phosphorylation, cleavage, and cytoplasmicmislocalization to an aggresome were observed in wild type TMEV-infectedcultured cells, with predicted splicing abnormalities. In contrast, cellsinfected with DA and GDVII strains that have L deletion had rare TDP-43mislocalization and no aggresome formation. TDP-43 mislocalization was alsopresent in neural cells of TMEV acutely-infected mice. Of note, TDP-43 wasmislocalized six weeks after DA infection to the cytoplasm of oligodendrocytesand other glial cells in demyelinating lesions of spinal white matter. A recentstudy showed that TDP-43 knock down in oligodendrocytes in mice led todemyelination and death of this neural cell [TDP-43, an RNA-binding protein that is primarily nuclear and important insplicing and RNA metabolism, is mislocalized from the nucleus to the cytoplasmof neural cells in amyotrophic lateral sclerosis (ALS), and contributes todisease. We sought to investigate whether TDP-43 is mislocalized in infectionswith the acute neuronal GDVII strain and the persistent demyelinating DA strainof Theiler’s virus murine encephalomyelitis virus (TMEV), a member of theral cell , suggest TDP-43 is a widely expressed nuclear protein that shuttles between the nucleusand cytoplasm, and regulates many aspects of RNA processing, such as splicing,trafficking, stabilization, and miRNA production. In almost all cases of ALS,neuronal and glial TDP-43 is phosphorylated, cleaved, and mislocalized to thecytoplasm, where it aggregates into stress granules and insoluble inclusionbodies. Although the mechanisms involved in TDP-43 proteinopathy remain unclear,impaired nucleocytoplasmic trafficking is thought to play an important role.Here we investigated whether TDP-43 proteinopathy also occurs during TMEVinfection since TMEV L protein is known to perturb nucleocytoplasmic transport.We found evidence of TDP-43 proteinopathy in both TMEV-infected cultured cells,with predicted splicing abnormalities, as well as in neural and glial cells ofTMEV-infected mice. The findings suggest that TDP-43 may contribute to thepathogenesis of TMEV-induced diseases, including TMEV-induced immune-mediateddemyelination. Trans-activation response (TAR) DNA-binding protein of 43 kDa (TDP-43) is anRNA-binding protein (as well as DNA-binding protein) primarily present in thenucleus and important in RNA processing, mRNA transport/stability, and mRNAtranslation –4. A varCardiovirus genus of Picornaviridae, is knownto disrupt nucleocytoplasmic transport [TDP-43 proteinopathy has been described in a number of diseases in addition to ALS. Since transport , 13, we ransport . TMEV inransport .GDVII sHere we report that TMEV infection of cultured cells causes L-dependentmislocalization of TDP-43, and L-independent cleavage and phosphorylation of TDP-43along with splicing abnormalities. Mislocalization and phosphorylation of TDP-43also occurs in neuronal cells following early TMEV infection of mice, and inoligodendroglia and other glial cells in demyelinated areas 6 weeks after DA virusinfection. These results suggest that TDP-43 mislocalization occurs and presumablycontributes to cellular dysfunction and death in TMEV infections. An important rolefor TDP-43 mislocalization in TMEV-induced demyelinating disease is suggested byrecent findings that TDP-43 binds to mRNAs encoding myelin genes, and that aknockdown of TDP-43 in oligodendrocytes of mice leads to demyelination and the deathof this neural cell .In control mock-infected BHK-21 cells, expression of TDP-43 was primarilyrestricted to the nucleus . FollowiWe questioned whether other RNA-binding proteins were also mislocalized to thecytoplasm in TMEV-infected cells. For this reason, we investigated thelocalization in cells of i) fused in sarcoma (FUS), which like TDP-43 is a causeof familial ALS when mutated, and ii) polypyrimidine tract binding protein(PTB), which is known to be mislocalized in TMEV infections, where it plays arole in TMEV translation , 19. DASince TMEV L protein is known to disrupt nucleocytoplasmic trafficking, weinvestigated TDP-43 localization following infection with mutant TMEV that hadan L deletion. As predicted, DAΔL and GDVIIΔL infection failed to inducemislocalization of TDP-43 in VP1-positive cells , demonstIn order to confirm the cytoplasmic mislocalization of TDP-43 in TMEV-infectedcells, we separated the nucleus and cytoplasm of cultured cells infected withTMEV . The resAs noted above, the juxtanuclear location of TDP-43 seen following TMEV infectionhad a morphology typical of an aggresome. Vimentin surrounded these juxtanuclearstructures , as istAggresomes result from a remodeling of intracellular membranes to generate sitesof virus replication . Fig 3A In order to assess the importance of aggresomes in TMEV infection, we made use ofnocodazole, a microtubule inhibitor that interferes with aggresome formation.BHK-21 cells were exposed to nocodazole , and then infected with DAvirus. Compared to levels obtained with no nocodazole treatment, nocodazole ledto a 10-fold reduction in virus genome at an MOI of 1, and 100-fold reduction atan MOI of 0.25 . AsexpeSGs are mainly composed of stalled translation preinitiation complexes, markerssuch as G3BP1, eIF3A, and TIA1, and RNA-binding proteins including TDP-43. Thesestructures are cytoplasmic non-membranous structures that appear in cellsexposed to various stresses, including virus infections . CertainBorghese and Michiels previousTo determine whether TMEV infection induces cleavage of TDP-43, as in the case ofALS, we carried out Western blots on RIPA-soluble and insoluble (but ureasoluble) fractions extracted from TMEV-infected BHK-21 cell lysates at 8 HPI.Following infection with both wt and TMEVΔL virus, ~35-kDa and ~25-kDa bands aswell as the expected 43-kDa band of full-length TDP-43 were detected in theurea-soluble, but not RIPA-soluble fraction, of BHK-21 cell lysates . These fTDP-43 is known to have an important role in alternative splicing, includingcystic fibrosis transmembrane conductance regulator (CFTR) exon 9 skipping. In ordeIn the case of ALS and ALS/FTD, TDP-43 is depleted in nuclei of neural cells, andmislocalized and phosphorylated in inclusions in the cytoplasm . In ordeDA virus produces a biphasic disease in SJL mice with minimal or subclinicaldisease within the first two weeks post-infection, followed by progressiveparalysis from an inflammatory demyelination that peaks at 6 weekspost-infection. In the acute phase of DA virus infection, VP1-positive neuronsand axons were present in the CA2 region of the hippocampus ; howeverSix weeks after infection with DA virus, the ventral region of the thoracicspinal cord showed perivascular mononuclear cell infiltrates, , demyeliTDP-43 is a ubiquitously expressed RNA-binding protein that predominantly resides inthe nucleus, but shuttles across the nuclear membrane in association with mRNAs. A hallmEnterovirus genus of Picornaviridae, TDP-43 ismislocalized  and cleaved  [As is true of many pathogens, picornaviruses disrupt nucleocytoplasmic traffickingduring infection, leading to cellular dysfunction as well as the redistribution andhijacking of nuclear proteins into the cytoplasm for use during virus replication, 31. Forease 3C) . In CVB3ease 3C) .In ALS, TDP-43 is thought to shuttle into the cytoplasm initially into SGs, and thenremain aggregated in the cytoplasm. In the case of TMEV-infected BHK-21 and L929cells, we detected the normal markers for SGs  in aggresomesrather than SGs. Of note, SGs were present following TMEVΔL infections, suggestingthat L inhibits SG formation, as has been reported by others . The aggMislocalization and phosphorylation of TDP-43 occurred in TMEV-infected culturedcells as well as neuronal and glial cells of TMEV-infected mice. In DA virus-induceddemyelinated regions, TDP-43 and other RNA-binding proteins were mislocalized inglial cells, including oligodendrocytes. The fact that TDP-43 was not present in thecytoplasm following infection with TMEVΔL virus, suggests that L interfered withnucleocytoplasmic transport. TDP-43 mislocalization in neural cells may also beinfluenced by inflammatory stimuli since tumor necrosis factor-α can lead tomislocalization of TDP-43 . In addiThe mislocalization of RNA-binding proteins in TMEV infections may disrupt cellularsplicing and mRNA translation, thereby contributing to neuronal dysfunction anddeath in GDVII and DA early disease as well as oligodendrocyte dysfunction in thelate demyelinating disease of DA-infected mice. Our previous study suggested thepossibility that PTB mislocalization in TMEV-infected neurons played a role inneuronal dysfunction .The delThe study involving the analysis of human subjects was approved by The Universityof Chicago Institutional Review Board for Clinical Research. Informed writtenconsent for an autopsy was obtained from an immediate member of the deceased’sfamily. Animal use was approved by The University of Chicago InstitutionalAnimal Care and Use Committee (IACUC) under the Protocol Number 71772. Animalwork conducted at the University of Chicago complies with all applicableprovisions of the Animal Welfare Act (AWA) and the Public Health Service (PHS)Policy on Humane Care and Use of Laboratory Animals. The PHS Policy incorporatesthe standards in the Guide for the Care and Use of Laboratory Animals and theU.S. Government Principles for the Utilization and Care of Vertebrate AnimalsUsed in Testing, Research and Training and requires euthanasia be conductedaccording to the AVMA Guidelines for the Euthanasia of Animals. The Universityof Chicago Animal Care Program has an approved Assurance with the NationalInstitute of Health (NIH), is registered with the United States Department ofAgriculture (USDA) and is accredited by the Association for Assessment andAccreditation of Laboratory Animal Care International (AAALAC).DA and GDVII viruses were derived from a full-length infectious cDNA clone . DAΔL viInfections were carried out in BHK-21 , L929  orHeLa cells , usually with a multiplicity of infection (MOI) of 10.BHK-21 cells were used for plaque assays and the growth of virus stocks, aspreviously described .For the study of TDP-43 cleavage, cells were treated with 1μM of the proteasomeinhibitor MG-132  for 16hs prior toharvest. For induction of SGs, BHK-21 cells were treated for 45 min with 0.5mMsodium arsenite . In investigations of theaggresome, nocodazole (Sigma Aldrich), a microtubule inhibitor, was solubilizedin DMSO and added at varying concentrations to the culture medium for 1h priorto infection.pDAL and pGDVIIL, which are eukaryotic expression constructs of DA L and GDVII Lrespectively, with myc/His epitope tags at the carboxyl terminus , were trCells on coverslips were harvested 8hs post infection (HPI) or 48hs aftertransfection, fixed in 4% paraformaldehyde for 5 min, and then permeabilizedwith phosphate buffered saline (PBS) with 0.1% Triton X-100 for 20 min at roomtemperature. The coverslips were then incubated overnight at 4°C with primaryantibodies . After rCells were lysed 8 HPI with a radioimmunoprecipitation assay (RIPA) buffercontaining a protease inhibitor and phosphatase inhibitor cocktail . Lysates were centrifuged at 14,000 rpm for 30min at 4°C, and supernatants collected as RIPA buffer-soluble proteins. Thepellets were sonicated and centrifuged twice at 14,000 rpm for 30 min at 4°C toobtain RIPA buffer-insoluble pellets. Pellets were dissolved in urea buffer  and then sonicated again prior to electrophoresis.Ten μg of total protein quantified by a Pierce BCA Protein Assay Kit  was subjected to electrophoresis on 10% SDSpolyacrylamide gels, and then transferred to Amersham Hybond P 0.45 μm PVDFmembrane . The membrane was first blockedwith 5% non-fat skim milk in Tris-buffered saline (TBS) containing 0.05%Tween-20 for 30 min at room temperature, and then incubated for 1h at roomtemperature with a rabbit antibody directed against C-terminal TDP-43  or a mouse monoclonal antibody against TMEV VP1(1:2000), which was previously called GDVII mAb2 [DA RNA was extracted from BHK-21 and HeLa cell homogenates using an RNeasy Plusminikit (Qiagen). A region between nt 1485 and 1684 was amplified using forwardprimer TACTATGGCACCTCTCCTCTTGGA and reverse primer CAGCCGCAAGAACTTTATCCGTTG witha Superscript III Platinum two-step qRT-PCR kit with SYBR green (Invitrogen). Aregion between nt 182 and 721 of the murine β-actin gene, which was used fornormalization and determination of the quality of total mRNA, was amplifiedusing forward primer GTGGGCCGCTCTAGGCACCAA and reverse primerCTCTTTGATGTCACGCACGATTTC. qRT-PCR was conducted on a CFX96 Real-Time System(Bio-Rad). The ΔΔCT method of relative quantitation was used to calculate foldchange of DA with β-actin.In order to assess splicing in TMEV-infected cells, a cystic fibrosistransmembrane conductance regulator (CFTR) minigene construct designed toevaluate CFTR exon 9 splicing  wastraImmunohistochemical studies were performed on autopsied brain specimens of apatient with ALS.TMEV was inoculated intracerebrally in weanling SJL mice , and mice were sacrificed at 1, 2 or 6 weeks post infection (PI). Atthe time of sacrifice, mice were deeply anesthetized and perfused transcardiallyfirst with PBS, and then with 4% paraformaldehyde in 0.1 M phosphate buffer. CNStissues were fixed in 10% buffered formalin and processed into paraffin sections(5 μm thick). Deparaffinized sections were hydrated in ethanol and thenincubated with 0.3% hydrogen peroxide in absolute methanol for 30 min at roomtemperature to inhibit endogenous peroxidase. After rinsing with tap water,sections were washed twice using Tris–HCl with 0.1% Triton X-100 for 5 min, andthen with Tris–HCl for 5 min. Sections were then incubated at 4°C overnight withprimary antibody  diluted Paraffin sections were also used for immunofluorescent staining. Sections weredeparaffinized in xylene, rehydrated through an ethanol gradient, and thenincubated with primary antibody for 1h at room temperature. The followingantibodies were used: mouse monoclonal anti-VP1, rabbit anti-TDP-43, and rabbitanti-2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase) ;rabbit P-value of <0.05 was considered significant. The dataare presented as the mean ± standard deviation (S.D.).Statistical analysis was performed by an unpaired t-test or one-way ANOVA withTukey's multiple comparisons test using GraphPad Prism version 7.0a. AS1 FigImmunofluorescent staining for TDP-43 in BHK-21 cells at 6 and 12 HPI. TDP-43cytoplasmic mislocalization and aggregate formation induced by DA and GDVIIinfection are present by 6 HPI and persists for at least 12 HPI. Scale bars:10 μm.(TIF)Click here for additional data file.S2 FigDouble immunofluorescent staining for pTDP-43 and VP1 in BHK-21 cells at 8HPI. pTDP-43 is present in the cytoplasm of VP1-positive cells infected withDA or GDVII virus. Scale bars: 10 μm.(TIF)Click here for additional data file.S3 Figarrowheads)is present in pDAL- or pGDVIIL-transfected BHK-21, L929, and HeLa cells, Theexpression of L is indicated by Myc positivity. Scale bars: 10 μm.TDP-43 mislocalization and aggregate formation ((TIF)Click here for additional data file.S4 Fig(A) Representative images of immunofluorescence using anti-L antibody. L isexpressed in pDAL- or pGDVIIL-transfected BHK-21 cells (that are detected byMyc staining) and DA-infected BHK-21 cells (that are detected by VP1staining). (B) Intensity of immunofluorescence for L. The Intensity ofimmunofluorescence of L within each cell ) was measured by ImageJ in 20 cells in 5 random fieldsand was then plotted as a dot graph. The intensity of immunofluorescence incells from the three groups is not statistically significant. Scale bars: 10μm.(TIF)Click here for additional data file.S5 FigWestern blotting of nuclear (N) and cytoplasmic (C) fractions ofTMEV-infected BHK-21 cells. The nuclear and cytoplasmic fractions of BHK-21cells were separated by using NE-PER Nuclear and Cytoplasmic ExtractionReagents . In MOCK, DAΔL andGDVIIΔL-infected cells, TDP-43 is predominantly expressed in the nucleus(and transiently may enter the cytoplasm). In contrast, TDP-43 issignificantly mislocalized to the cytoplasm of DA- and GDVII-infected cells.The expression of LaminA/C, a nuclear envelope protein, is primarily in thenuclear fraction, while TMEV VP1 is present in the cytoplasmic fraction.(TIF)Click here for additional data file.S6 Figarrow). Scale bar: 5 μm.HeLa cells infected by DA virus at 12 HPI. Although TDP-43 is slightlymislocalized to the cytoplasm in VP1-positive cells, aggresomes are notobserved in this cell ((TIF)Click here for additional data file.S7 FigBHK-21 cells infected by DA and GDVII virus at 8 HPI. Both TDP-43 and VP1accumulate in the juxtanuclear aggresome. TDP-43 and VP1 are partlyco-localized within the aggresome shown in yellow. Scale bars: 5 μm.(TIF)Click here for additional data file.S8 Fig(A) The amount of DA virus genome at 6 HPI with two different MOIs in HeLacells that had been treated with nocodazole  for 1h priorto infection. The viral genome is only slightly decreased with the 30 μMnocodazole treatment. (B) Plaque assay of DA-infected BHK-21 cells treatedwith nocodazole treatment  shows a similarvirus titer compared to untreated cells.(TIF)Click here for additional data file.S9 Figarrowheads). Scale bars: 10 μm.(A-C) BHK-21 cells treated for 45 minutes with 0.5 mM sodium arsenite, a SGinducer, develop SGs that contain SG markers: G3BP1 (A), eIF3A and TIA1 (B).SG markers in mock-treated cells have homogeneous cytoplasmicimmunostaining. Following sodium arsenite treatment, SG markers are presentin small structures of the typical size of SGs. (C) Following sodiumarsenite treatment, TDP-43 and PTB1 partly move into the cytoplasm and mergewith TIA1 in SGs ((TIF)Click here for additional data file.S10 Figarrows). (C) L929 cells infected by DA virus at 8 HPI.Aggresomes containing G3BP1, eIF3A and TIA1 are observed in VP1-positivecells. Scale bars: 10 μmL929 (A) and HeLa (B) cells infected by DAΔL virus at 8 HPI. SGs containingG3BP1, eIF3A and TIA1 are present in the cytoplasm of VP1-positive cells((TIF)Click here for additional data file.S11 Figarrows) in CA2region two weeks after infection of DA virus. The frequency of TDP-43mislocalization in VP1-positive cells is ~70%, as shown in the graph bar (n= 3). (C) Representative image showing phosphorylation of TDP-43 inVP1-positive CA1 region neuron (arrow) two weeks afterinfection of DA virus. Higher magnification shows skein-like inclusion(arrows) which is immunopositive for pTDP-43(brown) in a VP1-positive cell (pink).The frequency of TDP-43 phosphorylation in VP1-positive cells is ~60%, asshown in the graph bar (n = 3). Scale bars: 10 μm. *P <0.0001. Double immunofluorescence for TDP-43 and VP1 in the hippocampus ofuninfected and TMEV-infected mice. (A) TDP-43 is predominantly localized tothe nucleus of CA1 region neurons in uninfected mice. In contrast, TDP-43 isdepleted in the nucleus, and mislocalized to the cytoplasm of VP1-positiveneurons in CA1 region 1 week after infection with GDVII virus. The frequencyof TDP-43 mislocalization in VP1-positive cells is ~80%, as shown in thegraph bar (n = 3). (B) TDP-43 is depleted in the nucleus and mislocalized tothe cytoplasm in VP1-positive neurons ((TIF)Click here for additional data file.S1 Table(DOCX)Click here for additional data file.S2 Table(DOCX)Click here for additional data file.


Problem posing, the generation of questions by learners, has been shown to be an effective instructional strategy for teaching–learning of complex materials in domains such as mathematics. In this paper, we demonstrate the potential of problem posing in two dimensions. Firstly, we present how problem posing can result in unfolding of knowledge and hence how it can be used as an instructional strategy. Then we present another problem posing-based activity as an assessment tool in an Introductory Programming course (CS1).To explore the potential of problem posing as an instructional strategy, we conducted field studies in the two CS application courses (Data Structures (DS) and Artificial Intelligence (AI)), in which we provided a semi-structured problem posing situation to students. We performed inductive qualitative research and development the questions generated by students using grounded theory-based qualitative data analysis technique. To explore the potential of problem posing as an assessment tool, we conducted a field study in CS1 wherein we employed another problem posing (PP)-based activity in a large class for assessing the learning of computational thinking concepts in an introductory programming course and analysed how performance in traditional assessment tools (quiz score) is related with performance in our non-traditional assessment tool .From the studies in DS and AI courses we found that students pose questions and unfold knowledge using seven strategies — Apply, Organize, Probe, Compare, Connect, Vary, and Implement. From the field study performed in the CS1 course we found that the quality of the problems posed (difficulty level) were mostly aligned to the traditional assessment results in the case of novice learners but not in the case of advanced learners. Problem posing (PP) refers to the generation of a new problem or a question by learners based on the given situation  when they want to clarify any muddy point related to the seed or any previous lecture, and (b) when they want to discover more knowledge related to or based on the contents of the seed instruction. We call this activity of question posing as “think” sub-phase.Share” sub-phase). Students are asked to review others’ questions and ensure that the question is not a repetition of their own question. Two students with similar questions were required to disambiguate the question set by removing one of the two similar questions. Students are not asked to discuss the answers with each other, as this would consume enormous amount of time.After each student has finished posing questions, they are asked to share their questions among each other : All the generated questions are collected, and the teacher answered each question one by one. While answering, the teacher is asked to answer “clarification” type questions first (“Clarify” sub-phase) and then answer “exploratory” type questions (“Explore” sub-phase). By “clarification questions,” we refer to all the questions which require reiteration of the content that has been explicitly been taught in the seed or in any other previous lectures in the course. By “exploratory questions,” we refer to the questions which lead to unfolding or construction of new knowledge. Clarification questions are addressed first because they could be the bottle-neck and pre-requisite for understanding the discussions about exploratory questions. During the “clarify” and “explore” sub-phases, the instructor has the liberty not to answer irrelevant and out-of-scope questions.We did a field study based on this preliminary design in an artificial intelligence (AI) course, and identified the required modifications in the strategy, which led to the revised design of the second DDR cycle.summarization” under phase 3. During the “summarization” sub-phase, the teacher summarizes and organizes all the concepts discussed during the “explore” and “clarify” sub-phases. The summarization is essential in order to enable students to make connections between the concepts discussed for a better learning  for the first DDR cycle was executed in artificial intelligence (AI) course, whereas the field studies  for the second and the third DDR cycles were administered in data structures classes. There were several types of data collected in each field study, but in this paper, the only data that we discuss is the questions generated by students during problem posing phases of field study 1 and field study 2, as the research focused on how much exploration-based learning took place.In the next sections, we discuss the final version of SQDL and the results obtained from the qualitative analysis of the questions.SQDL as a question posing-based teaching–learning strategy that enables students to regulate their learning by posing questions. Students’ pose questions based on the contents of an initial lecture (“Seed”) and determine which content/sub-topics that are conceptually related to the seed have to be taught next. After the last DDR cycle in the current version of SQDL, a single iteration of SQDL consists of three phases: (1) Initial Instruction Phase, (2) PP Phase, (3) Addressal (or next instruction) phase. Phase 2 is comprised of two sub-phases: (2.1) Think and Tag, (2.2) Share and tag. The third phase is comprised of three sub-phases: (3.1) Clarify, (3.2) Explore, (3.3) Summarize.We define In this sub-section we discuss the two implementations of SQDL (field study 1 and field study 2). We delimit our discussion to the collection and analysis of posed questions, with an objective of investigating how much exploration-based learning took place.We administered two PP sessions in a seventh semester engineering classroom of 35 students in an AI course. The first phase or the seed instruction phase was of 15 min. The topic covered in the seed lecture of the first AI session was “Comparison of Attributes of Intelligence in Utility based, Goal Based, and Simple Reflex agents”. The learning objective for the first session of the seed instruction was “By the end of the seed instruction student should be able to identify differences between simple-reflex, goal-based, and utility-based agents, with respect to the level and attributes of intelligence”.The topic covered in the seed lecture of the second AI session was “The architecture of learning agents”. Learning objective for this session of the seed instruction was “By the end of the seed instruction student should be able to identify the attributes of intelligence present in the learning agents”. The PP phases in the both sessions continued for 10 min. Students wrote their questions on paper slips and submitted to the TAs. Students were explicitly told about the types (clarification and exploratory) of questions that they could prefer to generate. We collected 25 distinct questions in the first session and 23 distinct questions in the second session.At the end of the AI session, students were asked to write down their feedback to the open-ended question, “How was today’s lecture different, good, and bad from other traditional lectures?” We received responses from 39 students.Similar to the AI session, we administered a PP session in a 4th semester engineering classroom of 60 students in a DS classroom. The instruction phase was executed for 15 min. Topics covered in the seed lecture were “Node Structure” and “Linking two nodes”. The learning objective of the seed instruction was “By the end of the seed instruction, student should be able to define, declare, construct, and access their own nodes and linkages between nodes using Java.” The PP phase continued for 10–15 min. Students were told to write their questions on paper slips, review the questions from their peers to remove the redundant questions, and submit the final question slips to the TAs. After discarding the irrelevant and remaining redundant questions, we were left with a corpus of 56 distinct questions.We have collected a total of 104 student questions from the two PP sessions. We first conducted an in-depth study of these question statements to find out what strategies students use to pose questions in the given semi-structured PP situation. We employed a grounded theory-based inductive qualitative research methodology. After the completion of the analysis, we found the answer to the more refined research question, “How do students use their prior knowledge/experience, and the knowledge from “seed” to generate a new question?” In this paper, we are not reporting the detailed analysis procedures and output, as it has been communicated for publication elsewhere. The result of the analysis was eight PP strategies that explain how students used prior, and the seed knowledge to come up with new questions.We further qualitatively analyzed each question to extract the knowledge type of the prior knowledge used to generate the question, knowledge type of the unfolded knowledge for any question, concept (topic/sub-topic) unfolded by any question.In this paper, we present a descriptive analysis of different PP strategies evident for the question set, the knowledge types of the information requested by the question set, and the amount of knowledge unfolded using PP. The next section contains the analysis results of the study.To analyze the open-ended responses from all students, we performed a content analysis of the text obtained from their feedback notes. We coded each response to answer three questions: (1) What are the advantages of the PP-based SQDL activity? (2) What are the disadvantages of the activity? (3) Reason behind advantage and/or disadvantages?Clarify’, all other seven strategies lead to knowledge unfolding. We are not reporting the analysis procedure, as it has been communicated for publication elsewhere.PP strategies emerged out of grounded theory-based inductive qualitative analysis of 104 questions are described in Table We found a range of topics/sub-topics from the traditional syllabus has been unfolded by the PP activities. The concept map of the concepts unfolded in the DS session is shown in Fig. The grey nodes represent the concepts which were taught in the instruction phase , while the red border around a node denotes that there were some clarification questions generated related to that particular concept. The green nodes show the concepts which were unfolded, i.e., they were not taught to students before. The green node with a dotted border is an unfolded concept which is out of the scope of traditional DS syllabus. The concepts denoted by the yellow nodes are the prior knowledge within the domain which was used during PP.We found that all of the 39 responses suggest that the activity was helpful in learning and creating interest. Students predominantly perceived that the activity was helpful to learning due to the following reasons: (a) The activity helped them to clarify their muddy points and learning basic details. (b) Due to the activity, students came across critical questions. (c) The activity covers all necessary topics. (d) It was better to explore topics more from students point of view. (e) It removed fear and hesitation of participating in the class, and increased active learning. The disadvantage of the activity as perceived by the students was that the activity was very much time-consuming. It would be interesting to study in our future research how much time does the traditional lecture require as compared to the time required by the SQDL approach to cover the same set of topics.RQ1: How can student-generated questions be used to assess the learning of Computer Programming concepts?RQ2: How does the quality of question(s) generated by a student relate to the score achieved by him/her in the traditional assessment?We conducted an in situ field study in the CS101 course. The main objective of the study was to investigate the effect of a 2-week scratch intervention on students’ learning and transitioning to C++. We aided the study with a PP-based nontraditional assessment tool. We designed a PP-based assessment activity, to investigate the learning of computational thinking concepts of introductory programming. The research questions that this study answered were:The PP situation of this activity was completely different than that described in the “After teaching CS1 for 4 weeks using Scratch and C++ as the programming languages, we conducted a traditional assessment in the form of a quiz. In the fifth week, during the lab sessions, each student was asked to generate two practice questions for the coming mid-term exam on which other students could work Fig. . Since PA team of TAs was assigned to talk to students and motivate them to brainstorm and generate questions that may lead to deeper application of the concepts taught in the class. There were 90 students per lab session, and there was one TA per 10 students. TAs were told to intervene whenever they found any student stuck in the activity, or sitting idle for long time, or busy doing some out-of-context work. It was the responsibility of a senior TA to coordinate with junior TAs to manage all the logistics in the lab session.The generated questions were analyzed qualitatively to answer our research questions. We analyzed the questions based on five different qualitative analysis themes, viz., creativity of the problem poser, difficulty of the problem, cognitive level of the problem, problem type, programming concepts Table .Table 4PWe designed qualitative rubrics to define different levels of creativity and difficulty of generated problems. This rubric  scores of the fourth week quiz using stratified attribute tracking diagrams  that they request and hence unfold, we found that students were able to unfold a large number of topics in a single iteration of SQDL. The benefits of PP activity are found to be twofold: (a) potential of addressing muddy points through the generation of clarification questions and (b) knowledge unfolding capability through generation of exploratory questions. As far as the extent of knowledge unfolding is concerned, it was evident that there were large numbers of concepts unfolded during SQDL sessions; still there is no metric to determine what should be called as “adequate” or “acceptable” coverage. This could be an interesting future research objective. The responses of the students to the open-ended feedback question “How was today’s activity helpful?” in the class confirm the above. Some of the responses are given below:SQDL is helpful in student-driven unfolding of course contents which are conceptually related to the seed instruction. However, we do not expect students to ask questions and unfold topics which are conceptually unrelated to the seed concepts. Therefore, in addition to AI and DS, SQDL is suitable for all domains which has a large number of conceptually related topics. The types and distribution PP strategies employed may vary according to the nature of different domains. We believe that there exists potentially interesting research objective to investigate the variations in nature of questions posed across different domains.The second PP situation (PPE activity) was designed to explore the potential of problem posing as an assessment tool. We found that PP can be used to assess the learning of computational thinking concepts by students in the CS1 course. In the PPE activity, students generate questions and they also provide solutions/answers to them. This ensures that the concepts which are required to answer a question are understood by the students. We aggregated all these concepts that emerged from the generated questions and determined the frequency distribution of various concepts learned by the students. It should be noted that we did not assess the learning of any individual student on the topics around which (s)he has not generated questions. Though, PPE can be used to assess the learning of different concepts by the class, as a whole. We also attempted to study the relation of “understanding of programming”  with question quality . We found that for novice learners, the higher the score in the quiz, the lesser was the probability of generating low difficulty question. Interestingly, in the case of advance learners, we found a high probability of generating low difficulty questions by high quiz performers. This shows that the difficulty level can be used to assess the learning of novices, but not of advanced learners. Moreover, it is also possible that in addition to “understanding of programming” the “difficulty level” of the generated question might be affected by other factors. Although the results in the paper show some relation between the traditional assessment scores and PPE-based assessment, we do not claim any statistical correlation.With content analysis of questions for the concepts that any question relates to, PPE can be used in other domains for assessing the conceptual understanding. As far as the difficulty level and other quality parameters are concerned, different domains may need different rubrics for analysis. The use of PPE as an assessment tool shows that different qualitative aspects of questions can reveal a lot about different aspects of learning, and other cognitive and affective parameters. For example, the account of creativity shows how much students are able to relate the concepts to their prior  experiences. More of these aspects are to be identified to make PP useful for assessing a wide range of objectives.


In this paper we report upon the preparation and characterization of electrospun nanofibers of doped polyaniline (PANI)/poly(methyl methacrylate) (PMMA)/amino-functionalized graphene (Am-rGO) by electrospinning technique. The successful functionalization of rGO with amino groups is examined by Fourier transforms infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman microspectrometer. The strong electric field enables the liquid jet to be ejected faster and also contributes to the improved thermal and morphological homogeneity of PANI/PMMA/Am-rGO. This results in a decrease in the average diameter of the produced fibers and shows that these fibers can find promising uses in many applications such as sensors, flexible electronics, etc. Electrospinning is an efficient, relatively simple and low-cost process used to produce continuous nanofibers on a large scale, where the fiber diameter can be adjusted from nanometers to microns by applying a high voltage to a polymer solution from a micro-syringe pump ,2,3,4,5.Polyaniline (PANI) is one of the most conductive polymers, that has been used in many electronic, optical and electrochemical applications, due to its low cost, good environmental stability, redox reversibility, and electrical conductivity ,10. HoweGraphene is a potential nanofiller that can efficiently enhance the mechanical, thermal and electrical properties of polymer-based nanocomposites at a very low loading, useful for various novel applications due to its high thermal conductivity, superior mechanical strength, high specific surface area, excellent mobility of charge carriers and high chemical stability ,20,21. H2–(CH2)2–NH2) was utilized to functionalize graphene surfaces, which produced stitched graphene owing to the presence of two amine (–NH2) functionalities on both sides of the ethylene moiety [Herein, the ethylenediamine  Mw ~ 100,000 g·mol−1, camphor-10-sulfonic acid , N,N dimethylformamide , chloroform , ethylenediamine , were all purchased from Sigma-Aldrich, . Deionized (DI) water was used for all the experiments.Graphene oxide (GO), poly(methyl methacrylate) (PMMA) −1, and kept at 400 °C for 30 min under an argon (Ar) gas flow of 80 mL·min−1; secondly, the temperature was increased from 400 to 650 °C at a rate of 5 °C·min−1, and kept at 650 °C for 30 min under an Ar gas flow of 80 mL·min−1. Finally, the reduced GO samples were naturally cooled to room temperature without argon.Commercial graphene oxide (GO) was reduced by thermal annealing treatment . First, The rGO made in the previous step, where 150 mg of rGO was mixed with 10 mL of EDA, in a vessel under vigorous stirring. The reaction was continued for 24 h under reflux at 80 °C. Afterwards, the aminated-rGO (Am-rGO) was centrifuged at 10,000 rpm for 1 h and was thoroughly washed with deionized water, filtered, and dried in a vacuum oven at 80 °C for 24 h .10 mg of the Am-rGO was dispersed in 2.96 g of DMF by sonication for 1 h. 100 mg of PANI was mixed with 130 mg of HCSA to dope it and dissolving it in 14.78 g of chloroform. The solution was stirred constantly for 6 h and subsequently filtered using Whatman Puradisk PTFE syringe filter  to remove the particulate matter. Then, the Am-rGO solution was mixed with PANI solution and subsequently 85 mg of PMMA (as a carrier polymer) was added to the solution and stirred for 24 h to form the solution for electrospinning see . The PAN−1 resolution. The spectra of the samples were recorded over a wavenumber range of 4000–650 cm−1. Raman microspectrometer and the electron diffraction (SAED) patterns were utilized to investigate the structural changes of GO, rGO, and Am-rGO. Characterization of graphene specimens were performed by Raman microspectrometer with a Renishaw InVia Raman microscope  at an excitation laser wavelength of 514 nm. Raman spectroscopy is a powerful non-destructive tool for studying disorder and defects in crystal structure, it is often used to characterize microstructure of carbon materials. All specimens were deposited on glass slides in powder form without any solvent. For SAED patterns characterization, the graphene specimens were scooped onto a transmission electron microscopy (TEM) copper grid with supporting carbon film  directly. The dispersion characteristics of rGO and Am-rGO were measured by ultraviolet visible (UV–Vis) spectrophotometer at ambient temperature utilizing Infinite 200 PRO  cuvette reader. The chemical composition of the samples were determined by X-ray photoelectron spectroscopic (XPS) analysis using a VG Scientific ESCALAB 3 MK II X-ray photoelectron spectrometer  using an Mg Kα source .In order to ensure the presence of functional groups that should be present from the successful reduction of GO to rGO and functionalization of rGO with amino group, the Fourier transform infrared (FTIR) spectroscopy analysis was undertaken using Perkin Elmer 65 FTIR-ATR instrument . A total of 128 scans were accumulated for signal averaging of each IR spectral measurement with a 4 cm−1.The scanning electron microscope  at an operational voltage of 2 kV was used to study the morphology of electrospun fibers. Fiber diameters were calculated using Image-Pro Plus® software by taking an average of about 300 fibers. To confirm the presence of graphene sheets in the nanofibers of PANI/PMMA/Am-rGO, transmission electron microscopy  was used. For TEM observation, fibers were directly deposited onto a TEM copper grid with supporting carbon film . Thermogravimetric analysis (TGA) was conducted under nitrogen atmosphere using Q5000 TGA  in the temperature range of 20–900 °C, with a heating ramp of 10 °C·min3/DMF (5:1). As shown in 3/DMF in the presence of amino groups  stretching at 1601 cm−1; the C–O (epoxy) stretching at 1040 cm−1 and the C–O (phenolic) stretching at 1213 cm−1 [−1 is ascribed to the skeletal vibration of unoxidized sp2 graphitic domains. After the thermal reduction of GO, the skeletal vibration of sp2 graphitic domain still remains shifts to 1573 cm−1. Besides, some residual presence of bands at 1710, 1150, and 1280 cm−1 were detected providing evidence of the different types of oxygen functionalities in the rGO and their decreases in intensity and others vanished due to thermal reduction [−1; the C–N stretching vibrations at 1180 and 1120 cm−1; and the C=O stretching vibrations of carboxyl group at 1725 cm−1. Furthermore, the Am-rGO has peaks of the C–H stretch of alkyl chain at 2918 and 2854 cm−1; and the C–O stretching in hydroxyl groups at 1015 cm−1. The FTIR spectroscopy results indicate that the chemically functionalized graphene (Am-rGO) was successfully synthesized. Similar results for functionalization of graphene with amino groups have been previously reported in literature [FTIR spectroscopy was performed on GO, rGO and Am-rGO in order to ensure the presence of functional groups that should be present from the successful reduction of GO to rGO and functionalization of rGO with amino groups see a. Differ213 cm−1 ,30. The eduction ,30. In tterature ,30.2 carbon forms system, and it is obtained from the first order Raman scattering [−1 owing to the oxygenation of graphite, which results in the formation of sp3 while, the D band is presented at 1350 cm−1 because of the reduction in size of the sp2 domains by the creation of defects, and distortions during oxidation [−1 and the D band positions remained unchanged at 1350 cm−1, respectively. The G band appears in lower frequency due to the increased number of sp2 carbon atoms following reduction of GO. The intensity ratio of D and G band ID/IG is slightly increased from (0.89) in GO to (0.93) in rGO, demonstrating a decrease in the size of the in-plane sp2 domains after reduction, and can be explained that the thermal redaction creates many new graphitic domains, that are more numerous in number and smaller in size [D/IG intensity ratio (0.97) than the rGO, which is attributed to the formation of the chemical bond between amino groups and basal planes of the rGO. This corresponds to other results reported for functional graphene [Raman spectra was employed to analysis the graphitic structures of of GO, rGO, Am-rGO, as shown in attering ,32, and attering ,32. As exidation . Moreove in size ,34. Whergraphene .2) at 399.7 eV, (C–N–C) at 400.4 eV, and (C–N+–C) at 401.6 eV  at terature .The morphology and microstructure of the GO, rGO and Am-rGO and the electron diffraction (SAED) patterns in the selected area were analyzed by TEM see a–f. The SEM was used to characterize the fabricated PANI/PMMA and PANI/PMMA/Am-rGO nanofibers see a–d. It iTEM was conducted to confirm the presence of the graphene filler in the nanofibers. 2 atmosphere in temperature range between 20 and 900 °C, with a heating ramp of 10 °C·min−1. GO is thermally unstable resulting in three stages of weight loss. In the first stage, a rapid weight loss occurs at about 173 °C, mostly attributed to the removal of the trapped water molecules and epoxy oxygen functional groups. The second stage occurs at 515 °C which can be attributed to the removal of phenolic groups and decomposition of sp3 hybridized carbon atoms located at the defect site of GO. These results were congruent with other studies presented in literature [TGA was performed to observe the thermal stability of the rGO, Am-rGO and electrospun PANI/PMMA and PANI/PMMA/Am-rGO nanofiber mat see a,b, respterature ,37. On tterature ,37. TherIncorporating a small amount of Am-rGO in PANI nanofibers improves its thermal stability. As shown in In this study, Am-rGO was successfully prepared and electrospun nanofibers of PANI/PMMA with amino-functionalized graphene were prepared by a simple electrospinning technique. The FTIR, XPS and Raman spectroscopy analysis confirmed the successful functionalization of the graphene with amino groups, while the TEM observation demonstrated that the addition of amino-functional groups to graphene generated less damage to the graphitic structure of the graphene. SEM micrographs indicated the formation of PANI/PMMA/Am-rGO nanofibers with a diameter ranging between 35 and 133 nm, with a general uniform thickness along the nanofibers. TGA measurements show an improvement of the thermal stability of the PANI in the presence of graphene. In conclusion, the resulting non-woven porous mats with amino-functionalized graphene result in electrospun nanofibers that can be used in future technological applications in various fields.


A properly strained graphene monolayer or bilayer is expected to harbour periodic pseudo-magnetic fields with high symmetry, yet to date, a convincing demonstration of such pseudo-magnetic fields has been lacking, especially for bilayer graphene. Here, we report a definitive experimental proof for the existence of large-area, periodic pseudo-magnetic fields, as manifested by vortex lattices in commensurability with the moiré patterns of low-angle twisted bilayer graphene. The pseudo-magnetic fields are strong enough to confine the massive Dirac electrons into circularly localized pseudo-Landau levels, as observed by scanning tunneling microscopy/spectroscopy, and also corroborated by tight-binding calculations. We further demonstrate that the geometry, amplitude, and periodicity of the pseudo-magnetic fields can be fine-tuned by both the rotation angle and heterostrain. Collectively, the present study substantially enriches twisted bilayer graphene as a powerful enabling platform for exploration of new and exotic physical phenomena, including quantum valley Hall effects and quantum anomalous Hall effects. Precisely strained graphene layers can enable observation of periodic pseudo-magnetic fields with high symmetry. Here, the authors report experimental tuning of large area periodic pseudo-magnetic fields within twisted bilayer graphene and massive Dirac electrons having circularly localized pseudo-Landau levels. In particular, it has been predicted that a non-uniform strain distribution imposed on graphene arising from either external stress2 or interfacial coupling4 can induce a strong gauge potential that in turn can act as a pseudo-magnetic field (PMF) on the Dirac electrons. Indeed, it has been demonstrated experimentally that locally strained graphene in the form of nanobubbles can induce PMFs, as manifested by the emergent pseudo-Landau levels observed using the scanning tunneling microscopy/spectroscopy (STM/S)6. More recently, existence of large-area, spatially distributed PMFs has also been reported for single-layer graphene on a black phosphorus substrate, which provides strain textures due to the mismatched symmetries and lattice constants of the heterostructure7. Separately, intensive theoretical and experimental studies have demonstrated that low-angle twisted bilayer graphene (TBG) can exhibit a variety of exotic phenomena, including superconductivity and quantum phase transitions19. In addition, it has been reported that a small uniaxial heterostrain in low-angle TBG can suppress Dirac cones and lead to the emergence of a zero energy resonance20. In practice, low-angle TBG itself possesses large-scale, natural, and periodic strains due to the incommensurate moiré superstructures21. Such strain has been theoretically studied to significantly affect the electronic properties of the large-scale moiré pattern23. However, yet to date, experimental explorations of such natural and intrinsic strain effects arising from lattice relaxations in the strongly coupled homostructural system, especially the pseudo-magnetic behaviors, are still lacking25.Strain in graphene can be served as an effective tuning parameter in tailoring its exotic properties reflected by different degrees of freedom such as spin and valleyk-space, and can be further tuned, together with the PMFs, by the twist angle and uniaxial heterostrain in the bilayer system. Indeed, the existence of periodic PMFs in such hexagon-structured system provides a possible platform to further explore quantum anomalous Hall effects if a tiny external magnetic field is applied to break the time-reversal symmetry26.In this letter, by combining STM/S experiments and large-scale tight-binding calculations, we study the electronic properties of TBG with extremely small twist angles , the result reproduces the energy peaks that appear in the measured spectra , and their effects on the electronic properties remain to be fully explored.Collectively, the central findings achieved here may have important far-reaching implications. First of all, the existence of PMFs in TBG systems may finally offer testing grounds for observing quantum anomalous Hall effects as originally proposedThe bilayer graphene samples were prepared by chemical vapor deposition on Cu–Ni alloy substrates using 20, and has been shown to reproduce accurately the differential conductance d = 1.42 Å is the nearest carbon-carbon distance, h = 3.349 Å is the interlayer distance, −1, and 34. To reach a precision in energy of 3.5 meV, we have computed 10,000 steps in the continued fraction built in a super-cell of 15 millions of orbitals with periodic boundary conditions.The full tight-binding model by considering Supplementary InformationPeer Review File