Improving the ferromagnetism properties of pure carbon-based materials is extremely important for their application in spintronics. Hydrogenation of graphene is an effective way to induce magnetic moment into graphene with the advantage of reversibility. However, little experimental work has been done to prove the effect of hydrogen on the magnetic properties of graphene so far, except for systems containing a large amount of oxygen or plasma-induced vacancy which complicated the magnetic origin. Here we report a facile electrochemical cathodic method to generate hydrogenated multilayer graphene or few-layer graphite using graphite powder as the raw material, and observed hydrogen-induced ferromagnetism in samples annealed at different temperatures. The observed results suggest that ferromagnetism of hydrogenated multilayer graphene can be tuned by high temperature treatment, which is attributed to a changeable relative amount of hydrogen atoms chemisorpted on two different sublattices during thermal treatment. Hydrogenated multilayer graphene was prepared by a facile electrochemical cathodic method and its ferromagnetism was tuned through thermal annealing. One is the requirement of high quality hydrogenated graphene. Magnetic moments induced by methods such as formation of defects and vacancies make the magnetic properties in hydrogenated graphene more complicated.4–7 Introducing a magnetic moment into graphene is easy to operate, but it's difficult for these magnetic moments to couple in a ferromagnetic order. Due to the biparticle nature of the graphene lattice, hydrogen located on the sites of the same sublattice should couple ferromagnetically, otherwise on different sublattice should be non-magnetic or antiferromagnetic,8 basically following the rules obtained from Lieb's theorem.9 However, from the experimental point of view, the hydrogen adsorption process is blind to the graphene lattice, which explained the low magnetism we could obtain regardless of the high defect degree on the graphene surface.10–12 While it is worth mentioning that it is now practically feasible to control the adsorption and desorption of single hydrogen atoms on the surface of graphene with new developments in techniques, such as STM imaging and feedback-controlled lithography,13,14 but these methods can't be extended to industrial scales. It is also suggested theoretically preparing semi-hydrogenated graphene from graphane using physical method, such as applying an external electric field15 or applying pressure on a fluorinated BN sheet supported on a graphane sheet.16 Unfortunately, these methods have not been experimentally demonstrated. Thus, controlling the adsorption of hydrogen atoms on the same sublattice of graphene by macroscopic method still remains a big challenge to achieve high saturation magnetization in carbon-based materials.Hydrogenation of graphene has attracted vast attention recently due to the possibility of tuning its mechanical, electronic, and magnetic properties in a reversible way. For instance, graphene and graphane (fully hydrogenated graphene) have been shown to be diamagnetic, while semi-hydrogenated graphene is predicted to be ferromagnetic.17,18 which reminds us to use hydrogenated multilayer graphene or few-layer graphite instead of few-layer graphene or single layer graphene as sample to tailor the magnetic properties of graphenic materials.Unlike the monolayer graphene, for multilayer graphene or few-layer graphite, theoretical studies show that the typical Bernal stacking of graphite planes effectively breaks sublattice symmetry, making two sublattices inequivalent from each other,19 but this time we use graphite powder as raw material, which is much cheaper compared with highly oriented pyrolytic graphite. By reducing graphite, the sample we achieved is almost free of structural vacancy and any other defects usually caused by oxidation. If these defects also contribute to the magnetic moments, misinterpretation of the results might occur. To that extent, our sample could be a better candidate to study the magnetic properties of hydrogenated multilayer graphene. Then the superconducting quantum interference device (SQUID) is utilized to measure its magnetic properties. The hysteresis loop measurement of the sample shows an obvious ferromagnetism signal at room temperature, more interestingly, our study reveals that the magnetism doesn't decrease when annealed at elevated temperature. Annealing at a certain temperature is helpful to achieve higher magnetism. FTIR, TG-MS results suggest that different desorption rates of hydrogen atoms bonded on different sublattices through thermal annealing process is the main reason.Here we report an electrochemical cathodic method to generate hydrogenated multilayer graphene (few-layer graphite) based on previous work,2.2.16, 99%, powder) was obtained from Sigma-Aldrich and used as received. Propylene carbonate (99.9%) was got from Aladdin.Graphite flake powder (80 mesh) was purchased from Qingdao Graphite Company. Tetrabutylammonium hexafluorophosphate  and a voltage of 30 V was applied for 12 h. After the electrochemical expansion step, the expanded powder was collected, and afterwards thoroughly washed with a mixture of propylene carbonate and ethanol several times by alternating first dissolving and then separation through centrifugation . After the washing step, the product was collected by vacuum filtration.Graphite powder (40 mg) was put in a porous plastic tube with a platinum plate inserted as negative electrode, another platinum plate served as positive electrode. Both electrodes were immersed in propylene carbonate (PC) with tetra-butylammonium hexafluorophosphate (TBAPF2.3−1) using an Evolution and OMNI star equipment. Fourier transform infrared (FTIR) spectra were recorded using a Bruker spectrometer. Room temperature electron paramagnetic resonance (EPR) spectra were recorded using a Bruker A300 X-band (m = 9.4 GHz) spectrometer.X-ray diffraction (XRD) analysis were carried out on an X-ray diffractometer (Ultima IV-185) with Cu Kα radiation. Raman spectra were recorded on a Jobin Yvon LabRAM HR800 micro-Raman spectrometer using a laser excitation of 514 nm at room temperature. X-ray photoelectron spectroscopy (XPS) was performed on ThermoFisher SCIENTIFIC using Al Kα X-ray source. Magnetization measurements were performed using a Quantum Design MPMS XL-5 superconducting quantum interference device (SQUID) magnetometer. The morphologies of the samples were investigated by transmission electron microscopy  and scanning electron microscopy . The magnetic impurity elements  of all the samples were measured by the inductively coupled plasma spectrometry . The thermal gravimetry-mass spectrum (TG-MS) measurements were performed under a flow of argon  serving as supporting electrolyte, the expanded graphite was subsequently washed and then annealed. HG100, HG300, HG500 and HG700 samples were obtained by annealing the expanded graphite at 100 °C, 300 °C, 500 °C, 700 °C respectively.As in our previous research, graphite powder was negatively charged by a relatively high voltage. Trace amounts of water even in aprotic solvents were sufficient as a proton donor to observe hydrogenation of aromatic compounds, therefore no dedicated proton donor is typically required.20 This is also supported by the corresponding SEM images which show the wrinkled porous morphologies. One exception is that for HG100, TEM image appears blurred  is successful, the FT-IR spectra are subsequently employed to identify the presence of chemical bonded hydrogen . For HG3versus the G band is 0.26 in spectra of one typical flake, which is much smaller than the reduced graphene oxide (the ID/IG is much larger than 1).23 Considering the large amount of flake edges and residue chemisorbed hydrogen, which can also induce a D peak, it can be concluded that the amount of defect in the sample after high temperature annealing is very low and the crystal structure is almost perfect.In order to obtain information about the crystal integrity of these flakes, Raman spectra of HG700 is recorded, as shown in the inset of θ = 26.5°, corresponding to the (002) crystal planes of graphite with a layer distance of 3.4 Å.24 For HG100, the XRD pattern (green line) exhibits broad new peaks at 2θ = 20.3° and 24.2°, indicating an interplanar spacing of 4.4 Å and 3.7 Å. The appearance of these two peaks can be attributed to the inserted solvent propylene carbonate and the covalently bounded hydrogen atoms on the surface of the exfoliated multilayer graphene. With the temperature increased to 300 °C, the intensity of the peak at 2θ = 20.3° decreased sharply due to the decomposition and evaporation of solvent. For HG300, HG500, HG700, their XRD patterns exhibit almost the same peaks, a broad peak around 24.2°, and a sharp peak around 26.5°. The former peak originates from the hydrogen atoms covalently bonded on graphene, while the latter peak comes from the crystal structure of graphite, meaning the formation of multilayer graphene with the same stacking order of graphite. Additionally, the amount of hydrogen has no influence on the peak position for HG300, HG500 and HG700 may be due to the curvalete nature of graphene produced by electrochemical method. (Graphene is so curved that hydrogen on the surface doesn't influence the layer distance anymore).X-ray diffraction patterns are displayed in m/z = 28/43/57, which are due to residues of intercalated propylene carbonate. Moreover, the amount of propylene carbonate intercalated into graphite is fairly high, accounting for 35% in weight. In the second region B and the fourth region D, the observed mass loss of about 5.8% and 0.5%, can be attributed to the dehydrogenation of the sample as the mass spectrometric analysis exhibits a peak  for m/z = 2 in these two temperature ranges. The hydrogenation degree calculated reaches almost 80%. It should be mentioned that this value is not so accurate as both hydrogen and fragments of propylene carbonate evolved in the temperature region B. In comparison with other hydrogenated graphene whose dehydrogenation occurs mainly at 500 °C,24,25 our hydrogenated multilayer graphene or few-layer graphite presents two dehydrogenation peaks, a similar observation was also made in the case of hydrogenated graphene on Ni(111),26 they attributed the complex desorption process to different hydrogenation degree. Desorption peak shifts toward lower temperature with higher hydrogenation degree. Besides the high hydrogenation degree, there might be other reasons for this complicated desorption peaks here. Considering the inequality of two sublattices in multilayer graphene (few-layer graphite), the dehydrogenation would occur on two sublattices at different rates.27 As a result, the sample will lose hydrogen from one of the sublattice more easily than from the other one, forming two different desorption peaks.In order to understand the composition change during the process of thermal annealing, thermogravimetric analysis coupled with mass spectrometry (TG-MS) has been applied. For this purpose, the samples were heated from room temperature to 800 °C under a constant flow of argon and the thermally detached parts were analyzed by an EI mass spectrometer. As depicted in 2 hybridized carbon atoms, the secondary peak at 285.1 eV is attributed to sp3 hybridized C atoms or carbon atoms bond to hydrogen,28 the high ratio of sp3 C/sp2 C means the efficient hydrogenation of the multilayer graphene flakes. The efficient hydrogenation also causes the binding energy shift of the sp2 hybridized carbon atoms, from the normal 284.6 eV for HG700 shifts to 284.3 eV for HG300, this new emerged peak corresponding to unhydrogenated carbon atoms next to the C–H bond.29 The third and fourth peak located at 286.4 eV and 289.1 eV are assigned to carbon atoms with –C–O and O PBM data was replaced with SVG by xgml2pxml:<glyph-data id="z.dbd" format="PBM" resolution="300" x-size="8" y-size="10" xml:space="preserve">00000000000000000000000000000000111111110000000011111111000000000000000000000000</glyph-data><svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="13.200000pt" height="16.000000pt" viewBox="0 0 13.200000 16.000000" preserveAspectRatio="xMidYMid meet"><metadata>Created by potrace 1.16, written by Peter Selinger 2001-2019</metadata><g transform="translate scale" fill="currentColor" stroke="none"><path d="M0 440 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z M0 280 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z"/></g></svg>C–O bond, respectively. Giving the reducing atmosphere where the sample is generated, these remaining oxygen-containing groups probably stemmed from solvent residues. As evidenced in C–O peak decreased gradually, and disappeared after 700 °C thermal treatment. Besides the OC–O peak, the sp3 C/sp2 C ratio also decreased gradually from HG300 to HG700, this is due to the detachment of hydrogen from graphene surface, as evidenced in previous shown TG-MS and FTIR results.To further elucidate the hydrogen contents and functionalities of the electrochemical reduced hydrogenated multilayer graphene, both wide-scan and high-resolution XPS spectra are performed. As shown in M–H curves for all the annealed samples from HG100 to HG700 at 5 K in the field range of −10 kOe < H < +10 kOe. The inset in 10 After subtracting the high field linear background, the saturation magnetic moment (Ms) of these thermal treated samples are calculated to be 0.005 emu g−1 for GH100, 0.01 emu g−1 for GH300, 0.016 emu g−1 for GH500 and 0.007 emu g−1 for GH700, respectively. The magnetization isotherm at 300 K also shows the obvious hysteresis loop for all the samples, meaning the existence of room temperature ferromagnetic state. Compared with 5 K, the Ms at 300 K is slightly smaller (Ms = 0.013 emu g−1 for HG500)  is employed to measure the magnetic properties of the hydrogenated sample treated at different temperatures. r HG500) . While dle HG500 , the meaMs for HG500, in correlation with Lieb's theorem, it can be clearly stated that the hydrogen atoms are more populated on one sublattice than on the other for HG500, although the whole hydrogenation degree is lower than HG300 as suggested by TG-MS and XPS results. This can be explained by the different desorption rates of hydrogen adsorbed on different sublattice.As for the reason of the highest 27 In this case hydrogen atoms on one sublattice become more populated than the other. From TG-MS results, it can be concluded that the first dehydrogenation peak in the range of 250–340 °C mainly comes from hydrogen positioned on the same sublattice, and the larger number difference of hydrogen adsorbed on two sublattices contribute to the higher magnetism in HG-500. The effect of temperature on the magnetic property is briefly shown in When the hydrogenated multilayer graphene (few-layer graphite) is undergoing thermal treatment, the sample will lose H from both sublattices, but at different rates.−1 would give the magnetization of 2.2 × 10−4 emu g−1,32 the magnetic impurities in HG700 are insufficient to give the observed magnetic moment 0.007 emu g−1. Although ICP is rather common, the analyzed amount of magnetic impurities is typically underestimated as not the sample but the components soluble in the standardized nitric acid are detected.33 To further explore the origin of magnetism, we conducted EPR measurement. From the EPR spectra  come from the same source, the magnetic contribution from the possible metallic impurity should be similar for all these samples. So the smaller magnetic moment of HG-700 suggests that metallic impurity should not be the reason of the observed higher ferromagnetism of HG-500. All the above results suggest that magnetism is the intrinsic nature of hydrogenated multilayer graphene.Since the origin of magnetism in pure organic materials has been very controversial, we applied ICP-MS to check the content of possible ferromagnetic impurities in our samples. The total amount of magnetic impurities  is 25.2 ppm for HG-700. Given that Fe impurity content of 1 μg g spectra , we obse4.In summary, we proposed a facile method to generate hydrogenated multilayer graphene or few-layer graphite with rare oxygen-containing group bonded on the lattice due to the reducing atmosphere in the electrochemical process. With few magnetic moments induced by other defects, hydrogen is the main cause of magnetism, thus this sample could be a better candidate to study the magnetism of hydrogenated graphene. Then an easy way was applied to tune the magnetic properties of hydrogenated multilayer graphene by annealing at different temperatures. The influence of temperature on magnetism can be attributed to different desorption energies of hydrogen on two inequivalent sublattices. Moreover, this study may also provide clues for the design of functionalized graphene-based samples with sublattice selectivity by macroscopic method.There are no conflicts to declare.RA-008-C8RA02648C-s001


Mutations in TDP-43, a RNA-binding protein with multiple functions in RNA metabolism, cause amyotrophic lateral sclerosis (ALS), but it is uncertain how defects in RNA biology trigger motor neuron degeneration. TDP-43 is a major constituent of ribonucleoprotein (RNP) granules, phase separated biomolecular condensates that regulate RNA splicing, mRNA transport, and translation. ALS-associated TDP-43 mutations, most of which are found in the low complexity domain, promote aberrant liquid to solid phase transitions and impair the dynamic liquid-like properties and motility of RNP transport granules in neurons. Here, we perform a comparative analysis of ALS-linked mutations and TDP-43 variants in order to identify critical structural elements, aromatic and charged residues that are key determinants of TDP-43 RNP transport and condensate formation in neurons. We find that A315T and Q343R disease-linked mutations and substitutions of aromatic residues within the α-helical domain and LARKS, show the most severe defects in TDP-43 RNP granule transport and impair both anterograde and retrograde motility. F313L and F313-6L/Y substitutions of one or both phenylalanine residues in LARKS suggest the aromatic rings are important for TDP-43 RNP transport. Similarly, W334F/L substitutions of the tryptophan residue in the α-helical domain, impair TDP-43 RNP motility (W334L) or anterograde transport (W334F). We also show that R293A and R293K mutations, which disrupt the only RGG in the LCD, profoundly reduce long-range, directed transport and net velocity of TDP-43 RNP granules. In the disordered regions flanking the α-helical domain, we find that F283Y, F397Y or Y374F substitutions of conserved GF/G and SYS motifs, also impair anterograde and/or retrograde motility, possibly by altering hydrophobicity. Similarly, ALS-linked mutations in disordered regions distant from the α-helical domain also show anterograde transport deficits, consistent with previous findings, but these mutations are less severe than A315T and Q343R. Overall our findings demonstrate that the conserved α-helical domain, phenylalanine residues within LARKS and RGG motif are key determinants of TDP-43 RNP transport, suggesting they may mediate efficient recruitment of motors and adaptor proteins. These results offer a possible mechanism underlying ALS-linked TDP-43 defects in axonal transport and homeostasis. TARDBP), in familial and rare sporadic cases of ALS provided a critical link between TDP-43 genetic variants, pathology, and ALS pathogenesis  is a fatal disease of motor neuron degeneration . Nearly ogenesis . Thus, hn repeats in introns and the 3′UTR of thousands of transcripts, including transcripts important for synaptic and axonal homeostasis , DsRed2-mito (gift from Dr. Thomas Schwarz). To generate different ALS associated TDP-43 mutations and mutations at aromatic and charged residues, site directed mutagenesis was used. Primers used to generate these mutants are given in 2. On the third day in vitro (DIV), 1 µM AraC was added. Neurons (DIV6-9) were co-transfected with DsRed-Mito and eGFP tagged WT TDP-43 or mutant TDP-43 in the ratio of 1:1.5, using lipofectamine 2000 (Invitrogen). HeLa TDP-43 knockout (KO) and KO with TDP-43 rescue cell lines  were cultured in DMEM containing 10% FBS and 1% Glutamax and were transfected using Fugene (4:1 ratio with DNA).Primary cortical neurons were dissociated from E18 Sprague Dawley rat embryos and suspended in Neurobasal medium (Gibco), as described previously . NeuronsLive imaging of primary cortical neurons (DIV7-10) was performed 16 h post-transfection in Hibernate E (Brainbits) supplemented with 2% B27 and 2 mM GlutaMAX, in a temperature-controlled chamber mounted on an inverted NikonTi microscope with apochromat 63x1.49 NA oil-immersion objectives; images were acquired on a Perkin Elmer UltraVIEW VOX spinning disk confocal system equipped with an Ultraview Photokinesis (Perkin Elmer) unit and a C9100-50 EMCCD camera (Hamamatsu) controlled by Volocity software (Perkin Elmer). Axons were identified by morphologic criteria and were imaged at one frame every 2s for 5 min. Fluorescence recovery after photobleaching (FRAP) images were acquired using the 488 nm laser at 1 frame/second for 3–5 s prior to and for 120 s subsequent to photobleaching. The Photokinesis unit was calibrated prior to each experiment, as described .All image processing and analysis was performed using ImageJ/Fiji and/or custom, automated analyses in MATLAB R2018a . For TDP-43 motility, kymographs were prepared in Fiji, and analyzed using custom MATLAB programs  to calcuQuantification of the number of TDP-43 RNP granules in the axon was performed in a semi-automated manner using ImageJ/Fiji software. Briefly, a single time point (t75) image was extracted from each live imaging movie, the axon was straightened and the image was converted to 8 bit. Detection of TDP-43 WT and mutant granules was performed by auto-thresholding with default settings, followed by application of built-in method for local maxima detection (prominence setting of 25). The number of TDP-43 RNP granules thus obtained was divided by the length of the axon in microns; these data are shown as mean ± SEM , withoutThe ConSurf tool  was usedn, the number of neurons or granules per condition; N represents the number of times the experiment was independently repeated.Statistical tests were performed in GraphPad Prism. A Student’s t-test  or Mann-Whitney U test  were used to compare two groups, and one-way analysis of variation with Tukey’s post-hoc test was used to compare multiple groups of normally distributed data. The Kruskal–Wallis test with Dunn’s correction was performed to compare multiple groups of non-normally distributed data. Sample sizes were chosen based on reported data from similar studies in the literature for the neuronal live imaging field. Figure legends state Prior work has shown that the TDP-43 LCD is necessary for heterotypic interactions and assembly into stress granules . The conR2 = 0.76; slope = 0.017 ± 0.002); in contrast, the slope of this correlation is significantly reduced for TDP-43 Δ320-330  and trends lower for A315T (p = 0.06), compared to the slope observed for WT TDP-43  compared to WT (p = 0.05), suggesting RNP granules containing A315T are not completely immotile but instead show defects in long-range, directed motility. A lower motile fraction is also observed with RNP granules containing TDP-43 Q343R mutant  but run lengths and net distance of transport are preserved  data , we founThe collective interaction between associative motifs (“stickers”), such as tyrosine and arginine residues, drive phase separation of many intrinsically disordered proteins. These associative motifs are separated by “spacers” often containing polar residues, which modulate the material properties of condensates . In contin vitro, with W334 in the conserved α-helical region having the greatest effect  are critical for TDP-43 LLPS t effect . Consistp < 0.01)  . Neitherp = 0.08; p < 0.01, W385F p < 0.05; p = 0.12; None of the W substitutions significantly affected the fraction of anterograde versus retrograde motile tracks, anterograde net velocity, or anterograde run lengths, although W334F and W385F mutants show a trend towards reduced anterograde run length  (p = 0.02), suggesting that a positive charge at this residue is critical for long-range motility and/or interactions with motors/adaptors. Consistent with this notion, RNP granules containing R293A exhibit significantly reduced anterograde net velocity and net transport distance compared to WT  on TDP-43 RNP transport is not known, but the existence of several ALS-associated mutations in the vicinity of R293 and a nonsense mutation (Y374X) that produces a truncated form of TDP-43 (TDP-43 1–373) raise the possibility of a functional role . Conserv< 0.001) . Moreovep < 0.0001) and net velocity (p < 0.05) compared to WT RNP granules . In contrast, Y374T substitution has no effect on any aspect of anterograde motility . These results suggest that RNA binding is important for TDP-43 assembly into RNP condensates . We observed that RRM1/2 mutants exhibit significantly reduced long-range oscillatory motility, similar but more severe than RGG mutants . Comparedensates  and is adensates .p < 0.01; p < 0.05; There are five phenylalanine residues  in IDR1 (274–316) preceding the conserved α-helical region. Of these residues, F283 and F289 form GFG LLPS motifs, while F313 and F316 contribute to a LARKS . We werep < 0.05; p < 0.05; We went on to test whether substitutions of one or both of the highly conserved F313 and F316 residues in the LARKS affect TDP-43 RNP transport  Guenthe. Becausep < 0.01; There are 2 GF/GFG motifs and one FG motif in IDR2 region (346–414) . Since ap < 0.05; p < 0.05; p > 0.01; Disruption of the GF/GFG motifs present in IDR2 with F397Y/L or F401Y/L substitutions does not affect the fraction of motile and oscillatory TDP-43 RNP granules, but there is a small increase in the fraction of stationary F401L RNP granules compared to WT  granules, which regulate post-transcriptional processing of RNA, and mRNA localization and translation . Purifie in vivo . Additio in vivo .Nefl mRNA in the axon   and/or kinesin-2 (KIF3A/B and KAP3), while retrograde transport toward the cell body is driven by cytoplasmic dynein, its activator dynactin, and cargo-specific activating adaptors . Longer 320-340)  and muta320-340) , signifi320-340) . In addi320-340) , suggest320-340) . A non-min vitro  in vitro ].Similarly, substitutions of conserved aromatic residues within the conserved α-helical domain (W334F/L) or LARKS  exhibit defects in TDP-43 RNP granule transport. Anterograde transport appears to be more sensitive to disruptions of these structural elements than retrograde transport, as mutations of either the α-helical domain or LARKS impair anterograde run lengths, net velocity, and/or net distance . In contThe phase separation behavior of TDP-43 depends on net charge of the protein as well as availability of RNA . IncreasRegular spacing of pi-pi, hydrophobic and aromatic residues, and arginine-mediated interactions is critical for TDP-43 phase separation and determining phase dynamics . In agreIn the disordered regions flanking the α-helical domain, we find that F283Y or Y374F substitutions of conserved GFG and SYS motifs, also impair motility, possibly by altering hydrophobicity. Y374F (gain of hydrophobic residue) shows defects in the anterograde and retrograde transport. The possible role of hydrophobic stretches in regulating RNP granule transport is further supported by the F mutants of IDR1 region, though these transport deficits are milder than those seen with Y374T. F283Y and F289Y show defects in net velocity of transport and retrograde transport, respectively .Further studies will be needed to determine whether differences in the motility of TDP-43 WT and mutant RNP granules can be explained by loss of direct and/or indirect association with the motor proteins kinesin 1 and dynein . RecentlTo summarize, this study is the first to compare the functional impact of ALS-linked TDP-43 mutations on RNP transport in neurons and combine this approach with a systematic mutagenesis study to identify conserved structural elements, aromatic and charged residues that are key determinants of TDP-43 RNP granule transport in the axon. We find that disease-linked mutations and substitutions of aromatics within the α-helical domain and LARKS, structural elements important for phase separation and reversible interactions, respectively, display the most severe defects on TDP-43 RNP granule transport. Specifically, we show that the conserved α-helical domain, phenylalanine residues within LARKS and RGG motif are key determinants of TDP-43 RNP transport, suggesting they may mediate efficient recruitment of motors and adaptor proteins. Further studies will be needed to understand whether aberrant phase transitions of TDP-43 disrupt these interactions, leading to ALS-associated defects in axonal transport and homeostasis.


A large number of synthesis techniques including epitaxial growth, liquid phase exfoliation, electrochemical exfoliation, mechanical exfoliation, and chemical vapor deposition are used for the synthesis of graphene. Graphene prepared using different techniques can have a number of benefits and deficiencies depending on its application. This study provides a summary of graphene preparation techniques and critically assesses the use of graphene, its derivates, and composites in environmental applications. These applications include the use of graphene as membrane material for the detoxication and purification of water, active material for gas sensing, heavy metal ions detection, and CO2 conversion. Furthermore, a trend analysis of both synthesis techniques and environmental applications of graphene has been performed by extracting and analyzing Scopus data from the past ten years. Finally, conclusions and outlook are provided to address the residual challenges related to the synthesis of the material and its use for environmental applications. Graphene is fundamentally a two-dimensional material with extraordinary optical, thermal, mechanical, and electrical characteristics. It has a versatile surface chemistry and large surface area. It is a carbon nanomaterial, which comprises sp The scientific community around the globe working on material research is overwhelmed by the research focused on carbon-based nanomaterials, and the emphasis is particularly on the fabrication, characterization, and real-word applications of extremely thin carbon films, where graphene tends be the thinnest and therefore most explored carbon-based nanomaterial ,2,3. Gra2 hybridized carbon atoms organized in a hexagonal lattice [5 cm2V−1s−1), excellent thermal conductivity (3000 WmK−1), good mechanical strength (Young’s modulus of 1 TPa), outstanding chemical stability, exceptionally high surface area (<2600 m2g−1), and excellent optical transparency (97.4% transmittance recorded at 550 nm) [Fundamentally, the graphene structure is an indefinitely extended two-dimensional (2D) sheet composed of sp lattice  as illus 550 nm) ,13,14. T 550 nm) , biomedi 550 nm) , sensors 550 nm) , energy  550 nm) , and env 550 nm) .−1 to $4–5 kg−1 over time, it would be impossible for graphene prepared via CVD to break into this segment of the market [2 vibrations [Applications of graphene depend on numerous factors. Two key parameters are the number of layers and interlayer distance of produced graphene where layer numbers and separation distance can have a substantial impact on its properties and therefore its applications. π–π stocking and strong van der Waals attraction among layers of graphene can result in its layer aggregation. This impacts its properties negatively, e.g., a reduction in its available specific surface area, which results in a reduced number of active sites and sluggish ion diffusion kinetics for a significant number of applications including electrochemical energy storage, catalysis, water decontamination, gas sensing, and other environmental applications. Two main approaches are utilized to address these issues, which can result in improved specific surface area and enhanced accessibility of the porous structure. Firstly, chemical modification can improve the functionalities of graphene layers, and secondly, pore production in graphene or graphene layers and consequentially tuning its morphology can enhance the porous structure and improve graphene suitability for a broad range of applications. An application’s appropriateness regarding graphene also depends on the cost and quality of graphene and graphene-derived nanomaterials since these are the supplementary parameters defining its applicability in different applications and can vary subject to the desired application. For example, high-quality, defect-free graphene manufactured via chemical vapor deposition (CVD) is highly desirable for high-end electronics such as photodetectors, transistors, and large-scale transparent conducting electrodes . Converse market . Therefoe market ,24, wherbrations ,26. FTIRbrations . XPS is brations . The porbrations . 2 [4 [The rapid industrialization and modernization of transport infrastructure and the urbanization of countries have resulted in increased air pollution, with subsequent environmental impacts . This oc2 , CH4 [322 [4 , dyes [32 [4 , pestici2 [4 , and man2 [4 . Release2 [4 . Therefo2 [4 ,37,38,392 [4 . Numerou2 [4 ,42. Lite2 [4 . Similar2 [4 ,45,46. HThis review also discusses, in detail, the advancements, advantages, and disadvantages of some of the most commonly adopted bottom-up synthesis techniques, including CVD and epitaxial growth, and also some of the top-down synthesis methods such as exfoliation  used for the synthesis of graphene. In addition, a number of environmental applications including water purification, gas sensing, metal ion sensing, and adsorption using graphene, GO, rGO, and graphene-based hybrids are comprehensively covered in this review. There are two key graphene synthesis routes, and they can be categorized as (i) top-down and (ii) bottom-up techniques and are schematically represented in Chemical exfoliation is considered an exceedingly efficient and cost-effective top-down synthesis process when compared with other widely used techniques such as epitaxial growth, micromechanical cleavage, and Hummer’s methods. In the chemical exfoliation method, graphene is produced from bulk graphite through exfoliation . By sele2SO4/KMnO4 assisted by ultrasonication. By controlling the reaction parameters, they managed to produce GO and rGO with a minimum number of defects [4 are traditionally used in this technique, which makes it less environmentally friendly. Attention has now been directed toward the use of less harmful chemicals as oxidation agents, and several studies have been conducted using chemical exfoliation with less harmful chemicals utilized as oxidization agents. In a recent study by Betancur et. al, nitric acid (HNO3) and sulphuric acid (H2SO4) were used to start the exfoliation of graphite, followed by the use of an ammonium hydroxide NH4OH solution to complete its exfoliation and partly reduce the resultant graphene samples [−1 are shown in (f), demonstrating the formation of FLG, and (g) displays the statistical analysis, revealing the number of graphene layers and average sheet thickness, which are observed to be less than five [Superior-quality graphene with a minimum number of defects can be produced using this technique, and Gebreegziabher et al. recently reported the one-step synthesis of good-quality GO and rGO using chemical exfoliation, where reduced graphene oxide was prepared using H defects . Chemica samples . In anot samples . Hazardo samples . The schhan five .Chemical exfoliation has enormous potential for the synthesis of GO/rGO for wider commercial applications; however, the use of hazardous agents in graphene production and elevated production temperatures make this production process less economical for the large-scale production of graphene, when compared with other widely used techniques. Therefore, this method requires further investigation and research to make it a more viable technique both in terms of environmental friendliness and cost-effectiveness for large-scale production.Mechanical exfoliation includes a number of top-down strategies such as micromechanical cleavage, ball milling, sonication, intercalation, and liquid-mediated exfoliations to produce graphene. The micromechanical cleavage method has been widely used to produce monolayers of the best-quality graphene with lateral dimensions in the µm scale. Novoselov et al. were the first to employ micromechanical cleavage, also known as the Scotch tape technique, to separate few-layer graphene flakes from a piece of HOPG in 2004, earning them the Nobel prize in physics in 2010 ,66. The 2, respectively [−2 is required to remove mono-layer graphene from graphite using mechanical cleaving [Since graphite consists of monolayers of graphene closely stalked by weak van der Waals forces with an interlayer distance and bonding energy of 3.34 A and 2 eV/nmectively , partialcleaving . The pro2 in supercritical condition to produce good-quality FLG, with more than 90% of the produced graphene having less than five layers. This method was found to be scalable, with each batch producing approximately 40 g of graphene, which is an exceptionally high quantity when compared with some of the other state-of-the-art techniques that are being applied presently. The prepared graphene possesses excellent properties such as high electrical conductivity of approximately 3.25 × 105 S−1m on the PVDF substrate. Ball milling has been used as a substitute mechanical technique to synthesize good-quality graphene for industrial-scale production. In this process, shear force is applied laterally to exfoliate graphite into graphene flakes. There are two forces at play, i.e., lateral force and vertical force. Lateral force is highly desirable since it assists in the production of large-sized graphene flakes, whereas vertical force is less attractive since it results in reducing the flake sizes, or in some cases, even makes material completely amorphous. Therefore, it is always endeavored to keep the vertical force to a minimum in order to achieve good-quality, large-sized graphene flakes. Ball milling can be either dry or wet, where the latter can be further divided into two types known as planetary ball milling and stirred-media ball milling and are frequently deployed to produce graphene ,71. Wet −1 in some cases, although different approaches, such as extended sonication time, have recently been trialed to increase graphene concentration [−1 was achieved after an exceptionally long sonication time of 460 h, which resulted in yields of up to 4%wt of monolayers [2SO4 as a solvent produces graphene with the smallest crystallite size, excellent electrical conductivity, the smaller number of defects, and the least interlayer distances [2SO4 at sonication times of 15, 45, and 60 min, respectively, and it is evident that graphene produced in H2SO4 with a sonication time of 45 min is of the best quality, with smooth graphene flakes without any wrinkles. 2SO4 as the solvent has the lowest interlayer distance of 0.3 nm. 2SO4 as the solvent, exhibiting six-fold symmetric diffraction with the hexagonal crystal structure for graphene exfoliated using H2SO4 as an electrolyte, which is the typical crystal structure of graphene [Sonication-assisted liquid-phase exfoliation (LPE) is another mechanical technique where ultrasonication is utilized to extract individual layers of graphene after the successful exfoliation of graphite. Sonication-assisted LPE mainly involves three stages: (i) Graphite dispersion in specific solvent, (ii) sonication, and (iii) centrifugation . This apntration . A studynolayers . Differeistances . Figure graphene .Mechanical exfoliation can be a useful technique for the mass production of graphene; however, this method has its own weaknesses, e.g., it is a low-yield technique, and the production of monolayers is especially very low when mechanical exfoliation is used. Even though a limited number of studies, as discussed above, with higher yield have been successfully conducted when using this technique, these works have been performed at the laboratory scale only. Higher yields are only possible when very long exfoliation times are used, and this is unsustainable both in terms of time and for commercial applications. Furthermore, all mechanical exfoliation techniques suffer from undesirable fragmentation effects resulting in smaller-sized graphene flakes. Mechanical exfoliation can also result in a large amount of unexfoliated graphite requiring centrifugation as an extra step. Reproducibility using mechanical exfoliation is another production issue and requires extra attention. Therefore, graphene production through mechanical exfoliation yet requires an immense amount of research and development (R&D) work to make this technique a commercial success for large-scale development. −1) among graphite layers resulting in the separation of layers [Most recently, the production of graphene through electrochemical exfoliation has turned out to be an effective top-down technique. Advantages of electrochemical exfoliation over other synthesis strategies include a short synthesis duration, a facile production process, low instrumental cost, and the possibility of production and modification of good-quality graphene ,79. Durif layers . A schemf layers . Graphen−1, and these characteristics of prepared graphene are analogous to those obtained by more complicated and energy-intensive techniques such as CVD. The complete synthesis procedure and various characteristics of the graphene produced by this technique are presented in the This method can also provide a cleaner, greener, and environmentally friendlier route to produce good-quality graphene from recycled graphite such as electrodes of spent batteries. Prakoso and co-workers used rods of graphite of spent Zn–C batteries and produced excellent-quality graphene with high transmittance of approximately 89% and low sheet resistance of 1.1 kΩ sqWater electrolysis and the production of oxygen and hydroxyl radicals.The movement of hydroxyl and oxygen radicals and opening of graphite edges.Intercalation of the species of electrolyte and, subsequently, gas formation for the expansion of graphite.Traditionally, graphite exfoliation is performed in an aqueous solution , and the3)4NOH) dissolved in water as an electrolyte, where various distinctive properties of FLG were characterized using a range of methods including Raman spectroscopy, FTIR, XRD, AFM, and UV-Vis analysis, confirming the production of good-quality graphene [Different studies have also been performed using other solutions such as organic electrolytes, e.g., recently, Swapan and co-workers successfully produced multilayer graphene using a pure organic solution of tetramethyleammonium hydroxide . Since silicon has higher vapor pressure than carbon atoms, during high-temperature annealing of the SiC substrate, silicon desorbs first from the substrate surface, leaving a carbon-rich surface behind, followed by the growth of graphene ,90, wher2D/IG) is greater than two in the entire region and is in line with the ratio of monolayer graphene [Although epitaxial growth is considered one of the best methods to produce large-area graphene, the application of an ultra-high vacuum (UHV) makes it extremely challenging to control the thickness of the layers of graphene. Moreover, the high sublimation rate of Si atoms results in creating a large number of defects, especially on C-face of the SiC substrtate, ultimately filling it with carbon. To address the issue of UHV and uncontrolled growth of the graphene layer, Zhao et al. recently adopted a new synthesis strategy to produce good-quality, large-sized graphene under a low-vacuum environment . This megraphene .Even though epitaxial growth has been successfully used to produce excellent-quality graphene with control over the number of layers and flake sizes, this production procedure is highly energy-intensive and difficult to control, particularly at elevated temperatures and Ar pressures, which can be a safety concern. Therefore, this technique requires more R&D work to bring it in line with other techniques. 4 and H2 on metal/dielectric surfaces or through the surface separation of carbon from metal/carbon solutions. There are a number of factors such as the reactor configuration, gas feedstock, gas ratios, partial pressure of gasses, temperature, growth time, and reactor pressure, which govern the type of processes and chemical reactions taking place inside a CVD reactor [CVD is a bottom-up technique and is by far the most adopted procedure to prepare good-quality graphene, with potentially large quantities of monolayer and few-layer graphene. In this method, graphene can be s synthesized by either the deposition of vapors from carbon containing gases such as CH reactor . CVD dep reactor ,98. This reactor ,100, whi reactor .All these methods have their advantages and disadvantages, but it is outside the scope of this paper to cover all these CVD techniques here. One of the effective CVD methods used for the synthesis of graphene is radio frequency plasma-enhanced CVD. (a), whereas inductively coupled plasma systems as shown in (b) can be coupled with an inductive circuit element, which results in high growth rates of graphene [(c) shows the capacitively coupled plasma, which is a simpler setup when compared with other techniques such as ICP, while it is also less energy-intensive; however, this can result in the formation of amorphous layers [The benefit of combining radio frequency with hot filament results in avoiding the annealing step, while graphene is directly deposited on a substrate such as Ni  as showngraphene . Finallys layers . The main shortcomings of this process include toxic gaseous byproducts and the necessity of high operating temperatures 800–1100 °C). These high operating temperatures can be reduced significantly, and reduced temperatures of approximately 550–600 °C have been reported to synthesize graphene with the aid of plasma ,108. Fur0 °C. TheAdvantages and disadvantages including cast, scalability, applicability, environmental concerns, production time scale, quality of produced graphene, and production yields of different high-end synthesis methods for graphene are presented in 2 wafers [2 wafers ., to understand the past trends and future outlook of synthesis strategies of graphene. Graphene was isolated from natural graphite in the early 2000s by mechanical means; however, improvements in production processes over the past two decades have resulted in the development of a wide range of fabrication approaches to produce graphene. Each of these techniques have their own advantages and shortcomings influencing their applications. The authors extracted data from the past ten years from Scopus from a number of different types of publications, specifically research articles, review articles, conference papers, and book chapters on key synthesis techniques, as shown in Figure 16As can be observed from Continuous growth in the number of publications, with more than one-fifth (21%) of these publications in open-access journals, gives an indication of the strong interest in research work in this field. It is anticipated that this trend will continue for years to come, since various characteristics of graphene, its derivatives, and graphene-based nanomaterials are still being uncovered, resulting in broadening of their application base. In addition, it is presumed that future research will mainly be focused on the cost-effective synthesis of graphene in an environmentally friendly manner to make graphene more desirable for commercial applications. This will shift the synthesis of graphene away from more commonly used traditional methods such as CVD toward improvements in more green and sustainable techniques currently being used and the development of new production processes. Since its discovery, graphene has seen an overwhelming response from scientists working in diverse research areas such as engineering, energy storage/management, medicine, electronics, material science, and many other disciplines. Graphene, graphene oxide, reduced graphene oxides, and its composites have been widely adopted as active materials in a wide range of applications including electrochemical energy-storage devices (EESDs) such as supercapacitors and electrochemical batteries ,117,118.Graphene’s derivatives have evolved and diversified over the past two decades and have resulted in immense progress in their processing and applications. In particular, they have seen recent applications in biomedicine due to their versatility in the synthesis of quantum dots, nanosheets, and nanoparticles where their novel electrical, thermal, optical, mechanical, and magnetic properties make them superior materials for biomedicine applications. The use of graphene in biomedicine includes, but is not limited to, thermal biosensors, biomolecule sensors, drug delivery, tissue engineering, bioimaging, and photothermal and photodynamic therapies ,124,125.Lastly, graphene and it’s derivates and nanocomposites have also been widely used in a wide range of environmental applications such as membranes for the detection and removal of contaminants from wastewater, active materials for gas sensors, carbon storage and conversion, water desalination, electrocatalysis, photocatalysis, and agricultural pollution sensors ,129,130.Gas sensors work on the basic principle of converting gas volume fractions into corresponding electrical signals . Gas senPG is a carbon nanomaterial of single-atom thickness with a 2D structure possessing outstanding properties, making it highly desirable for gas-sensing applications when compared with other 2D materials, especially for the detection and quantification of very low concentrations of gasses, since the surface of PG is highly sensitive, where every single atom is available on a single layer of graphene for adsorption and desorption processes to occur . As disc3 where weak bonding (~20 meV) and inferior charge transfer (~0.027 e) exist between graphene and NH3 [2 as an efficient stabilizer. It was observed that FMNS-derived graphene (G-FMNS) showed excellent sensitivity toward NH3 where FMNS not only provided the perfect active sites for ammonia gas through hydrogen bonding but also assisted in the functionalization of graphene through p-doping (hole rich). This environmentally friendly synthesis strategy can have huge potential of commercialization since it is relatively simple, cost-effective, scalable, and uses biocompatible materials [In certain circumstances, the gas detection ability of graphene is significantly reduced, i.e., in case of NH and NH3 . To redu and NH3 . In a reaterials .GO, which is the derivative of PG, is another exciting material for sensor applications since high-quality GO flakes can be produced easily from graphite and can be reduced to prepare highly conductive rGO. Moreover, the zero or quasi zero bandgap of PG can be an impediment for its application as sensitive layer in devices, although this can be overcome by the use of rGO. There are a number of methods used for the preparation of rGO; however, Hummers’ method is by far the most-adopted one and has evolved considerably over the years to produce high-quality (less defective), high-yield, and larger-sized rGO flakes ,145,146.2 is regarded a valuable renewable source of energy; however, owing to its explosive and flammable nature, it always requires accurate monitoring. Ultrasonic gas sensors commonly based on metal oxides have been employed regularly to monitor H2 since these materials have been shown to be highly efficient for H2 sensing [2. These high-temperature sensors are becoming less desirable for H2 sensing applications because of the danger of explosion and higher energy consumption. Therefore, ultrasonic sensors operating at room temperature were given substantial research considerations, with the very first sensor tested at room temperature in a nitrogen atmosphere, since, due to the reaction of oxygen in air with H2, it was extremely challenging to produce and test high-sensitivity sensors in the air [3 substrate using a platinum catalyzer operating at room temperature. The sensor’s sensitivity was increased by adjusting the deposition parameters of rGO, achieving considerably higher sensitivity at room temperature. This improved room-temperature ultrasonic gas sensor was able to detect exceptionally low concentrations of hydrogen of approximately 5 ppm [2 detection. The sensor displayed a remarkable sensing response of 3.21% for SO2 at a low ppm level of 5 ppm at room temperature, and its sensitivity increased with an increase in SO2 level in ppm [2O3@rGO core-shell film was distributed on the desired substrate by deploying a magnetic field. This core shell film based on 3D γ-Fe2O3@rGO not only eschewed the undesirable coffee-ring effect but also resulted in heteroatoms (p-type) doping, as well as the introduction of surface defects with enhanced gas-sensing performance. The room temperature N2 gas sensor displayed excellent selectivity and superior sensitivity of 3.43 toward 50 ppm of NO2, which was two and half times higher than that of the pure rGO sensor. The sensor’s performance stayed remarkably high even at an extremely low level of N2 of approximately 100 pbb, with a response value of 1.23 [H sensing . However the air ,149. In ly 5 ppm . Similarl in ppm . GO/rGO l in ppm ,154,155.l in ppm ,157. To  of 1.23 . The sen2O3@rGO-based room temperature N2 gas sensor. 3O4 in the shape of uniform-sized nanospheres, whereas in 2O3 hybrid where it can be witnessed that the Fe2O3 sphere remained in shape but was covered in a thin layer of rGO sheets with wrinkled features to produce γ-Fe2O3@rGO core-shell hybrids. Response–recovery curves are recorded in 2 concentration in the range of 100 ppb to 100 ppm, where fast and excellent sensing can be observed, whereas 2, NH3, H2, CO, CH3OH, and N2H4 alongside other superior characteristics of CPs, which are the main reasons for its adoption in gas-sensing applications [2 of this hybrid was three time better than that of PANI, with excellent long-term stability, where an only 18% drop was observed in its performance after constant use for one year [Gas sensors based on conducting polymers (CPs) have also received considerable attention recently because of several advantages such as the ease of synthesis, low/room temperature operability, and stability . Among oications . Howeverications ,162. Karone year . 2 detections and displayed exceptional sensing performances. By using this hybrid composition, excellent sensing operations were achieved with outstanding detection limits of 8ppm at room temperature (20 °C). This was attained by optimizing various parameters with a PEI concentration of 0.01 mg/mL and an RH of 62%. Experimental results revealed that along with the extraordinary sensing performance of rGO, layered N-MXene offered an abundance of active sites for CO2 and water co-adsorption, whereas PEI polymers were suitable for the binding of CO2 molecules, resulting in induced appreciable density variation of charge carriers via proton-conduction behaviour [2 sensing application. To further enhance the detection limits of gas sensors into the ppm range (trace detection), reduce their operational temperatures (lower power consumption), and improve their suitability for use in exceptional situations , composites of graphene with other materials such as CPs and TMOs have been used. In some cases, ternary composites are developed, where graphene hybrids are produced with two other sensing materials simultaneously, where the overall performance can be improved significantly when compared with sensors manufactured using individual sensing materials. In a recent study by Zhou et al., rGO, N-doped MXene (Ti3C2Tx), and polyethyleneimine (PEI) ternary hybrids (rGO/N-MXene/PEI) were used as active materials for COehaviour . Figure 3 due to weaker bonding and inferior charge transfers between these two materials. Moreover, Graphene has a less dense structure and lacks selectivity. Metal oxide-based sensors can only operate at higher temperatures, making them less safe and more energy intensive. CPs such as PANI have their own shortcomings such as the mechanically feeble structure. Therefore, engineering of nanohybrids through hybridization of graphene and its derivatives with nanomaterials including metal oxides, MXene, and conducting polymers can result in superior sensing properties, and these composites exhibit improved sensing performance compared to their individual constituents due to a synergistic effect, also referred to as non-interface-dependent complementary behavior. Therefore, it is believed that the likely direction for future R&D work on graphene-based gas sensors will focus on combining graphene with other functional nanomaterials with improved activity. In addition, theoretical analyses and computational modellings are also obligatory to identify the underlying principles of different interactions taking place between different gases and graphene-based nanomaterials on their surfaces, thereby shifting the research focus from devices to solid–gas interfaces. Graphene and its derivates such as GO and rGO have already demonstrated excellent gas-sensing characteristics when compared with other pristine structures, e.g., carbon nanotubes (CNTs), metal oxides, and conducting polymers, because of their high surface area, tunable electronic/chemical properties, and chemically active surfaces. However, graphene’s sensing-ability is low for certain gases such as NH−1 was achieved with excellent accuracy between 4 and 5% across five consecutive measurements [Organic dyes, heavy metal ions, organic solvents, and oil are some of the main pollutants of water resources . Moreoveurements . 2SO4 and a lower level of rejection for monovalent salts such as NaCl, along with high dye rejections resulting in low salt removal [2SO4) were produced through premeditated solvation of rGO to attain enhanced desalination. This was achieved through the deposition of an exceptionally thin layer of a solvated rGO microfiltration membrane, and channel sizes were maintained by maintaining a swollen state. This rGO-based membrane resulted in rejecting ∼99% of dye molecules (Direct Red 80-DR 80) whereas almost zero rejection of Na2SO4 and NaCl was detected, making solvated rGO material suitable for nanofiltration membranes for high levels of salt permeance and exceptionally high levels of dye rejection [Commercially used dyes are also very harmful compounds effecting the quality of water resources. Ultrafiltration and nanofiltration membranes with pore sizes smaller than those of dye molecules have drawn enormous interest for dye removal. However, traditional polyamide-based nanofiltration membranes maintain an extremely high level of rejection for divalent salts such as Na removal . On the  removal ,183. Oneejection .3O4/G-AC-800. It was witnessed that 3–8 nm of crystalline iron nanoparticles were encapsulated inside 2–6 layers of graphene sheets. The XRD pattern in 3C, α-Fe, and γ-Fe are shown in 3O4/G-AC-800, and the used Fe3O4/G-AC-800 samples. There are no apparent peaks showing heteroatoms on the surface, since heteroatoms could be removed due to the catalytic graphitization process beyond 800 °C [Despite the excellent adsorption performance of carbonaceous martials such as graphene, the removal of a higher quantity of metal ions efficiently from wastewater is challenging. However, the use of composites based on highly porous nanocarbons and magnetic nanoparticles seems to be a viable solution for this purpose, since both materials can complement each other to improve the overall ability of the removal of contaminants . Bhadurid 800 °C . −2h−1, which resulted in the effective purification of contaminated water with oil. Moreover, this composite membrane demonstrated tremendous stability under a harsh environment, both chemically and physically [−2h−1 with a higher water flux of up to 120 mol m−2h−1, showing very high water/salt selectivity at 4.31 × 103 [2O contact angle of the membrane from 61.9° to 48.8°. Decreases in the reversible fouling and fouling rates of 27.2% and 22.2%, respectively, were observed after the addition of 0.5 wt% BN-GO-Ag to the membrane in reversible fouling resistance and the total fouling rate of the synthesized membrane, respectively. Additionally, the PES membrane with 1 wt% BN-GO-Ag nanocomposites exhibited 77.7% and 88.9% rejection of reactive red 120 and reactive black 5, respectively, which can be credited to the increase in surface negativity of the membrane due to the addition of GO [As discussed above, despite the number of advantageous characteristics of graphene and its derivatives, graphene still struggles to perform efficiently as a membrane as a single material, therefore composites of graphene with other functional nanomaterials such as polymers are an interesting concept. Aromatic polyimides are preferred materials to make hybrids structures with graphene as compared to aliphatic and semi-aromatic polyimides due their nontoxic nature coupled with excellent strength and stability. In a recent study by Zhang et al., a reduced graphene oxide (rGO) and aromatic polyimide (PI) composite (rGO-PI) was synthesized and used as a separation membrane. The substrate of the nanofibrous PI membrane was prepared using a low-temperature polycondensation reaction followed by electrospinning, whereas rGO was produced using a modified Hammer’s method and the entire procedure was performed in a fluorine-free environment. This hybrid membrane attained exceptionally high separation efficiency of over 99% and flux of up to 2040 Lmysically . Advance31 × 103 . Polymer31 × 103 . However31 × 103 . A numbe31 × 103 . A polyeon of GO . Figure on of GO . In summary, graphene with a unique single-atom-thick structure and excellent mechanical and chemical stability has shown some extraordinary permeation characteristics. Graphene membranes can be produced as composites with other materials such as polymers, MXene, or inorganic compounds, and as membranes containing oxygen and nitrogen heteroatoms. However, the synthesis of facile and large-area graphene with controlled layer thickness remains a huge challenge. Another constraint for the use of graphene in membrane applications is the production cost involved to synthesize good-quality graphene. Scalability is another issue that requires attention since larger quantities of active materials are required for membrane applications and is still considered a key hurdle in using graphene for membrane separation applications. Furthermore, graphene production processes are still very complicated. Therefore, further research and development is essential for state-of-the-art membrane production process developments to cost effectively manufacture graphene at a larger scale using simplistic methods. Finally, further investigative work is required to understand the mass transport phenomenon and impact of various parameters such as interlayer spacing, functionalization, and selective defects. This can only be achieved using advanced characterization techniques together with simulation tools. 2+, Cu2+, Pb2+, Ag+, and Cd2+ are released during manufacturing processes and agricultural activities, which can be highly contaminating and are found in abundance in water resources and wastewaters [2 MOF composite was utilized as an electrode material for the detection of multiple heavy metal ions in a real-time study. The solvothermal method was adopted for the in-situ growth of UiO-66-NH2 on graphene surface. The key motive for the synthesis of this composite was to enhance the conductivity of the MOF-based composite since MOF has excellent properties such as structural tuneability, high surface area but are electrically nonconductive materials. TEM, SEM, and XRD were employed to characterize the structure and morphology of GA/MOF composites whereas the porous structure was analyzed using nitrogen adsorption/desorption analysis. 2 with octahedral cubic intergrown morphology. 2 and GA-UiO-66-NH2 composites exhibiting an analogous XRD pattern for both samples confirming the successful integration of UiO-66-NH2 into graphene, where the GA template and matrix, as well as the integrity, of UiO-66-NH2 were not damaged by GA. 2g−1, which will provide a large number of active sites and mass transport channels. As shown in 2-modified GCE for individual analysis, with Cu2+, Pb2+, Hg2+, and Cd2+ over a concentration range of 0.06−3.0 μM, 0.01−4.0 μM, 0.1−3.5 μM, and 0.005−3.0 μM, respectively. These results revealed that the response current of every metal ion was linearly enhanced when boosting target analyte concentrations [Metals ions including Hgtewaters ,194. Thetewaters . Neverthtewaters ,197. A rtrations .2+, Pb2+, and Cu2+ ions, respectively. These are attributed to the exceptionally high surface binding attraction, enhanced electrical conduction path, electron tunnelling, and ion-trapping characteristics along with the extraordinary electrocatalytic activity of rGO/Ala/PANI composites [Even though graphene has prevailed as a wonder material and a potent platform for diversified fields including electrochemical sensing applications, 𝜋–𝜋 stacking and weak interactions can result in restocking/agglomeration of graphene layers resulting in reducing interlayer spacing. This can be addressed through surface functionalization or by producing composites using other nanomaterials such as conducting polymers and metal oxide nanoparticles ,200. In mposites . As discOther most commonly used sensors for heavy metal ions detection include optical sensors. In optical sensors, a change in light beam is measured, which occurs due to the alteration in the intensity of light. This is due to variation in the light optical characteristics, e.g., wavelength, phase, spectral distribution, and polarization. Optical sensors are one of the most versatile tools to detect changes in a wide range of characteristics including pressure, temperature, radiation level, and chemical concentrations. In the past, low-dimensional  materials such as quantum dots, carbon nanowires, gold nanoparticles, and nanotubes had been used intensively in optical sensor applications . However2+) is a heavy metal present in the human body in the range of 1–2 mg, which is an essential part of vitamin B12 that is necessary for the functioning of various body organs including the liver, kidney, heart, and brain. However, an excess of Cobalt (Co2+) in the human body can result in various health complications including higher heart rates, asthma, headaches, and fibrosis in the lungs, consequently requiring accurate monitoring [2+). Thin films were characterized by XPS to confirm the chemical interactions involving Co2+ with existing functional groups on the surface of thin film. These thin-film optical sensors could detect very low concentrations of Co2+ of as low as 0.01 ppm [Cobalt  in the atmosphere and its exponential growth at a disturbing rate, which results in the greenhouse effect [2 concentrations considerably in the past few decades. The extent of CO2 utilization by organic chemicals is somewhat smaller than the CO2 produced through the burning of fossil fuel [2 grasps a large amount of solar heat energy, enacting feasible obstacles for excess heat to leave the upper berth atmosphere, leading to a rise in the global temperature and thereby greenhouse gases in the air, which impact natural life on earth [2. The precise and reliable conversion of CO2 into useful chemicals also helps to minimize CO2 emission and waste gas utilization [2 capture and storage technologies are available commercially, which not only reduce atmospheric CO2 levels, but also store it and allow for their conversion into very useful chemicals as well as organic materials thereafter [2 conversion into different chemicals and organic materials is also crucial for sustainable developments, and therefore CO2 consumption and conversion constitute one of the biggest steps of CO2 recycling. Different strategies have been employed to convert CO2 into organic materials, such as photocatalysis, electrocatalysis, photo-electrocatalysis, etc. [2 has now attracted significant attention from scientist and researchers since it can contribute to the carbon cycle balance and produce different valuable chemicals [2 can be transformed into different useful gases and fuels, such as CO, CH4, CH3OH, and HCOOH, as well as various hydrocarbon-based fuels [2 into useful chemicals such as carbonates, carboxylates, carbamates, etc,. is also desirable [2.One of the main reasons of global warming is the amount of carbon dioxide  have been employed for CO2 conversion; nevertheless, the preparation of homogeneous catalysts has always been a challenge. Furthermore, there are some issues associated with their higher costs, high overpotential, and sensitivity, and these restrict their large-scale commercialization. Therefore, in recent years, heterogeneous catalysts such as carbon-based materials  have been considered promising candidates with excellent activity and low costs for CO2 conversion applications [2 conversion. The structure of graphene consists of different oxygen heteroatoms such as C=O, C=OH, and COOH, which can function as highly active sites for different catalytic reactions such as reduction, oxidation, hydrogen evolution, and coupling. Different functional groups of graphene oxides are typically acid or base sites, which function as promising heterogeneous catalysts for different conversion reactions.Usually, the conversion of COications . Graphen2 into methanol, employing different GOs as the catalysts. Three different GOs were prepared using a revised Hummer’s method by adjusting the oxidant KMnO4 and H3PO4. The SEM micrographs of GO sheets are presented in −1) and D mode (1590 cm−1), respectively. Photocatalytic CO2 reduction was performed at room temperature using a gas flow reactor and a halogen lamp light source, where CO2 was expelled inside, and the methanol concentration was determined through GC-FID in the vapor phase. The methanol formation with the reaction time is plotted in 2 to methanol conversion rate with GO-3 as the catalyst was 0.172 mmol g cat−1 h−1. The photocatalytic CO2 reduction using GO is schematically illustrated in 2 reduction, photogenerated electrons (e−) and holes (h+) travel to the GO surface and function as reducing and oxidizing sites. The reduction potential of e− (donor) in the GO conduction band was −0.79 V (vs. NHE)  and the oxidation potential of h+ (acceptor) in the GO valance band was nearly 4 V . The photogenerated e− and h+ on the GO surface react with adsorbed CO2 and H2O and produce methanol via the reaction shown in 2 reduction as shown in 2 reduction. Gusain et al. [2 into methanol. The bare CuO nanomaterials showed low photocatalytic activity as they absorb visible light well and create electron–hole pairs. The electron–hole pairs recombine quickly prior to the photocatalytic reaction because of the lower band gap of CuO, which yielded only 175 μmol g−1 of methanol. Besides, rGO–Cu2O and rGO–CuO composites illustrated enhanced photocatalytic activities as the photogenerated electrons in the conduction band of CuO were effortlessly transported to the rGO network, leading to the slow recombination of charge carries and effective transportation of photo-generated electrons to the catalytic sites of rGO network, which reduce adsorbed CO2 into methanol. The rGO–CuO and rGO–Cu2O composites showed 1228 μmol g−1 and 862 μmol g−1 of methanol, respectively. Similarly, An et al. [2O enhances the photocatalytic activity of the Cu2O/rGO composite six times more compared to pristine Cu2O.Hsu et al.  performen et al.  successfn et al.  proved t2 into different commercially valuable products has been reviewed and has shown to be advantageous owing to its simple operation at ambient temperatures [2 into methanol using electrochemical reduction. Histamine is an electron-rich heterocyclic compound that functionalizes rGO and improved its electrocatalytic activity for the CO2 adsorption. Additionally, the Pt nanoparticles on rGO can offer the essential hydrogen radicals for the reduction process. The 0.1 mol L−1 KNO3 saturated solution with CO2 at pH 2.0 electrolyzed on Pt@His-rGO/GCE at −0.30 (vs. Ag/AgCl) for 16 h produced 2.96 mmol L−1 methanol. The Faradaic efficiency of 37% was obtained for methanol production. Zhang et al. [2 into cyclic carbonate. GOs allowed 97.8% styrene oxide conversion with 97.4% chemo-selectivity to phenylethylene carbonate over the 12 h reaction time. From kinetic and XPS studies, it was proven that GO catalysts with a large number of oxygen heteroatoms deliver higher reaction rates. The performance efficiency was greatly altered with surface characteristics of different GO catalysts for the cycloaddition reaction. N-doped graphene had been popular for the electrochemical reduction of CO2 into different useful chemicals including CO [− [4 [2 adsorption ability. Wu et al. [2 reduction. The SEM images shown in 2 to CO generation on different N-doped graphene and bare graphene free energy diagrams via the lowest-energy-consuming route are presented in 2 reduction and formation of CO, which is outstanding compared to noble metal catalysts such as Au and Ag. The N-doped 3D graphene foam delivered 85% faradaic efficiency at an overpotential value of −0.47 V for CO formation and excellent stability for 5 h.Furthermore, the electrochemical conversion of COeratures . Differeeratures ,228. Zareratures  developeg et al.  also useuding CO , HCOO− [ng CO [− , and CH4CO [− [4 . The pyru et al.  incorpor2 conversion and storge applications, it still requires an immense amount or R&D activity to bring it in line with other heavily used techniques. Even though those techniques are costly, they are proven to work.Although graphene has seen increased used in COTrend analysis was also performed by extracting and analyzing data on the above-discussed applications and comparing them with overall environmental applications of graphene. An upward trend in publications in all four areas of environmental applications of graphene was observed, which validates the growth in the use of graphene in these applications and also in overall environmental applications over the past decade. 2 conversion applications, other nanomaterials are leading and currently being used successfully, which shows the requirements for an immense effort to commercialize graphene for these applications by shifting the results of graphene research on these applications outside laboratory settings and replacing the traditionally used materials with graphene. As with graphene synthesis, a trend analysis of graphene applications, shown in As can been seen from Although immense progress has been made for the use of graphene in environmental applications, it will still be an enormous challenge for years to come to make lab-based research suitable for wider commercial applications. 2 and water produced. Furthermore, graphene has been widely adopted in photocatalysis degradation applications due to its large specific surface area and tunable porous structure, which can provide a large number of active sites for the photocatalytic process to occur. Graphene has mostly been used in the form of composites, providing support to other materials, and acting as a host material to active materials such as metal oxides and semiconductors in the photocatalytic degradation of pollutants [As discussed above, graphene, its derivates, and composites show an adequate capability for different applications such as environmental applications, sensing applications, membrane materials, metal ion detection, and gas sensing/storage. However, there are a number of other environmental applications such as bio/chemo sensors, flexible electronics, bio-culturing, electrocatalysis, and photocatalytic degradation of pollutants in which graphene has shown apt capabilities and performances; however, these cannot be discussed in detail in this review article due to its limited scope and size constraints . Photocallutants . Since iOver the past two decades, efforts have been made to produce high-quality graphene, its derivatives, and composites with an intent to reduce costs and make its production processes simpler. It is anticipated that this trend will continue at a fast pace to develop new synthesis procedures and modify the existing ones, unfolding new and interesting properties of graphene and graphene-based nanomaterials while broadening their applications. A number of production processes have been developed and used, however these synthesis approaches have their own benefits and shortcomings. For instance, chemical vapor deposition has immense potential for commercial-scale applications and is currently the most viable and widely used technique since it results in producing large-sized and high-quality graphene with a controlled number of layers. However, this method still requires the development of an efficient transfer process. Exfoliation methods, whether liquid, chemical, or mechanical, are much simpler, low-cost, and scalable processes to synthesize graphene, not requiring post-production transfer. However, controlling the size and number of layers of graphene flakes is extremely challenging while using exfoliation-based synthesis strategies, and as shown by trend analysis data, exfoliation-based synthesis techniques have seen increased scientific consideration over the past few years. Since the discovery of graphene, the community of material scientists has been facing an immense challenge to cost-effectively produce superior-quality graphene with a controlled number of defects and layers using environmentally friendly processes, since the performance of graphene-based devices greatly depends on these production parameters. It is predicted that applications such as sensing, in which a small quantity of active materials is needed but high-quality graphene is required, will be fulfilled via the chemical vapor deposition method, whereas applications where a higher quantity of material is necessary will be addressed by one of the exfoliation methods. However, with rapid developments in exfoliation-based techniques, it is likely that scientists would be able to modify this synthesis technique to produce substantial quantities of good-quality graphene tailored to a wide range of applications.2 conversion. Each of these applications required finetuning of its different parameters. For example, graphene’s application as an efficient adsorbent requires a high level of porosity, control over the porous structure, and hydrophilic interactions with pollutant ions. Pristine graphene struggles to fulfil all these requirements, whereas its derivatives and composites not only improve its surface area but also enhance its surface chemistry for improved adsorption of pollutant ions. Therefore, the production and use of graphene’s derivatives and hybrids is highly desirable when graphene is used as an adsorbent. Similarly, graphene has seen increased interest in its application in gas sensing, since, by using graphene for gas-sensing applications, a low operational temperature and improved surface activities can be attained. These are some of the fundamental challenges faced by sensing technology used commercially at present. These requirements can be easily achieved with the use of graphene, since graphene and its derivatives retain properties including high surface area and rich surface chemistry. However, this work is still in the transitional stage from laboratory to industry, necessitating immense research efforts for widespread commercialization. It is expected that graphene-based hybrids will be highly useful for a number of environmental applications, particularly gas sensing and carbon dioxide conversion and storage.Graphene has been used in a large number of environmental applications, whereas in this review, we have focused on four of its key applications, i.e., membrane, gas sensing, heavy metal ions detection, and COGraphene has remained one of the most examined materials over the past two decades and its presumed that this will remain the case in the near future, especially in environmental applications. Since graphene was only first isolated at the start of this millennium, it requires more exploration time and scientific efforts to vigorously analyze and evaluate its different characteristics and their impact on its various applications, especially linked to environmental science, as it is still in the early stages of its development. In some cases, the use of graphene in environmental applications is similar to other families of two-dimensional materials such as carbon nanotubes and fullerenes due to their physical and chemical similarities. Therefore, the preference for graphene over other materials in future environmental applications will be based on cost-effectiveness, ease of processability, and environmental consequences. At present, graphene is still more expensive to produce than most commonly used carbon nanomaterials, i.e., activated carbon, but cheaper than single-walled carbon nanotubes; however, its production cost is expected to decrease over time with the scaling up of production processes. Considering the cost/performance of graphene in different applications compared to the traditional materials, its higher production costs could be covered by its higher performance in each application. Likewise, the health and environmental impact of graphene synthesis is expected to decrease over time with the advancements in and utilization of more environmentally friendly production procedures, particularly exfoliation-based techniques.It is exceptionally challenging to predict the exact outlook of graphene applications since it has only been present in the ever-growing commercial market for the past few years. With its fascinating characteristics and progress in industrial-scale production, it is anticipated that the commercialization and industrialization of graphene will grow with time; however, it will be a long journey to gain market capital over other nanomaterials being used in wider applications in general and environment-related applications in particular.We have attempted to provide a comprehensive overview of the most commonly used production processes of graphene and its environmental applications. Trend analysis of both synthesis techniques and environmental applications over the last ten years was also performed, indicating the popularity of synthesis procedures and applications with the most frequent use of graphene, making this study different from previous studies on graphene production routes and applications.


Hierarchical porosity and high packing density were achieved with the aid of capillary compression in the presence of Fe3O4 nanoparticles. This strategy enables integration of highly wrinkled graphene sheets to form highly compact carbon electrodes with a continuous ion transport network. The generated HWGF exhibited a high packing density of 1.53 g cm−3, a high specific surface area of 383 m2 g−1 and a hierarchically porous structure. The HWGF delivered a high capacitance of 242 F g−1 and 370 F cm−3 at 0.2 A g−1 in 6 M KOH aqueous electrolyte system with excellent rate capability (202 F g−1 and 309 F cm−3 retained at 20 A g−1). The capacity retention rate reached 97% after 10 000 cycles at 1 A g−1. The HWGF-based supercapacitor exhibited a high energy density of 17 W h kg−1 at the power density of 49 W kg−1. Such high capacitive performances could be attributed to the highly dense but porous graphene assemblies composed of highly wrinkled graphene sheets.Highly wrinkled graphene film (HWGF) with high packing density was synthesized by combining an electrostatically self-assembling process, a vacuum filtration-induced film assembling process and capillary compression. Fe A facile strategy was reported to synthesize highly wrinkled graphene film, exhibiting high packing density and excellent capacitive performance. This aggregation decreases their specific surface area and restricts the accessibility of electrolyte ions to their surface, thus leading to a deteriorated performance.3,4Electrochemical capacitors (ECs), also known as supercapacitors, store energy by charging electrical double layers through highly reversible ion adsorption on the surface of high-surface-area electrodes, generally made from porous carbon. Due to their fast charging capability and long life span, supercapacitors are attractive in powering mobile electronics, electric vehicles (EVs) and storing renewable energy for power grids. Graphene is recognized as a promising electrode material for high-performance supercapacitors, due to its flexibility, excellent electrical conductivity, and high theoretical specific surface area  porous graphene architecture, such as highly-crumpled graphene,et al. reported a graphene hydrogel films, with a metastable and adaptive pore structure, can be compressed irreversibly by capillary pressure to increase the packing density through controlled removal of volatile solvent trapped in the gel.22 Volumetric capacitances reached 255.5 F cm−3 in aqueous electrolyte and 261.3 F cm−3 in organic electrolyte at 0.1 A g−1, which were much higher than those of the existing porous carbon materials. The packing density can be increased up to ∼1.33 g cm−3, nearly double that of the traditional activated porous carbon (0.5 to 0.7 g cm−3).27 Tao et al. reported a highly dense but porous graphene-based monolithic carbon with a very high density of 1.58 g cm−3, which is 70% of the theoretical density of graphite (2.2 g cm−3).23 Such graphene assembly was produced by an evaporation-induced drying of a graphene hydrogel and constructed of compactly interlinked nanosheets, exhibiting a volumetric capacitance up to 376 F cm−3 in aqueous electrolyte.Recently, many researches have been focused on highly dense but porous graphene assemblies, opening up new ways to address this challenge. Yang 3O4 nanoparticles. The generated porous yet densely packed HWGF was binder-free and showed robust chemical and mechanical stability. The hierarchical structure facilitates fast ion transport and thus enhanced electrochemical performances were achieved, such as capacitance, cycling stability and rate capability. The high packing density resulted in high volumetric capacitance, facilitating real applications in commercial electrochemical energy storage devices. It should be mentioned that the fabrication process is facile, low-cost and scalable, opening up a new way for the rational design and effective synthesis of highly dense but porous graphene assemblies for high-performance supercapacitors.In this article, we report a low-cost iron oxide hard template strategy to create highly wrinkled graphene film (HWGF) with hierarchical pore structure and high packing density, balancing these two opposing characteristics. Such HWGF can be readily formed by vacuum filtration process and the following heat treatment process with the aid of capillary compression in the presence of Fe28All the chemicals were used in analytical grades without purification. Graphite oxide was synthesized from natural graphite powder by the modified Hummers' method.−1).The prepared graphite oxide was ultrasonically dispersed in deionized water for 1 h to obtain graphene oxide (GO) hydrosol  was added into 100 mL of FeCl3 solution (0.0155 M). Then, the mixed solution was heated up to 80 °C in a water bath and kept at 80 °C for 40 min under magnetic stirring. The obtained Fe(OH)3 colloid solution was cooled to room temperature for further experiment.For preparing Fe(OH)3 colloid solution under magnetic stirring. The volume ratio of GO hydrosol and Fe(OH)3 colloid solution was set as 1 : 2. A flocculent precipitate was formed within a few minutes and a Fe(OH)3@GO hybrid film was obtained by vacuum filtration through a microfiltration devices. Secondly, the Fe(OH)3@GO hybrid film were subjected to heat treatment at 300 °C in a tube-furnace under N2 atmosphere, leading to the formation of Fe3O4@rGO hybrid film. Finally, the Fe3O4@rGO hybrid film was washed by diluted hydrochloric acid to remove Fe3O4 and the HWGF was obtained.The HWGF was prepared by the following processes. First, the prepared GO hydrosol was added dropwise into the prepared Fe(OH)Surface morphologies were characterized by using a JEOL JSM-7001F scanning electron microscope (SEM). Phase was examined by using an X-ray diffractometer  with Cu Kα radiation and a Raman spectroscopy (LabRam HR HORIBA) with 514 nm wavelength laser for detection. Nitrogen adsorption/desorption test was performed at 77 K on a specific surface and porosity analyzer (BELSORP-Mini II). Specific surface area and pore size distribution were calculated by the conventional Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) method, respectively.−1 on a CHI 604 electrochemical workstation . Galvanostatic charge/discharge (GCD) tests were performed between 0.01–1 V at different current densities from 0.2 to 20.0 A g−1 on a Neware 2001 battery test system (Neware Instruments). Electrochemical impedance spectroscopy (EIS) tests were performed at open-circuit potential with amplitude of 5 mV from 100 kHz to 10 mHz.The electrochemical tests were performed in two-electrode supercapacitors, in which a separator, soaked in a 6 M KOH aqueous solution, was sandwiched between two HWGF electrodes. The HWGF electrodes were prepared by pressing the HWGF film onto a nickel foam disk at 20 MPa  and then drying 6 h at 80 °C under vacuum. Cyclic voltammetry (CV) measurements were performed between 0–1 V at different scan rates from 5 to 100 mV s29Cs is the capacitance of single electrode (F g−1), C is the capacitance of double electrode (F g−1), I is the discharge current (A), Δt is the discharge time (s), ΔV is the potential change in discharge (V), m is the mass of the carbon material on single electrodes (g), E is energy density and P is power density.The specific capacitance, energy density and power density of the HWGF electrode was calculated according to the following formula:3 colloid, during which process the Fe(OH)3 colloid particles were electrostatically self-assembled onto the surface of GO sheets. As a result, a flocculent precipitate was produced. As shown in Fig. S1,3 colloid solution ranging from 1 : 1 to 1 : 20. In this paper, the volume ratio of GO hydrosol and Fe(OH)3 colloid solution was set as 1 : 2.As schematically illustrated in 3@GO hybrid film in the following vacuum filtration-induced assembly process. Thirdly, the Fe(OH)3@GO hybrid film is converted to Fe3O4@rGO film via the heat treatment process. Finally, the HWGF, as shown in Fig. S2via the acid washing process. Such HWGF can be highly compressed during the heat treatment process with the aid of capillary compression. Thanks to the presence of Fe3O4 nanoparticles, the HWGF could retain its porous structure in some extent, endowing graphene sheets with highly wrinkled morphology.Secondly, the produced flocculent precipitate substance is self-assembled into Fe(OH)3O4 nanoparticles (NPs) are homogeneously embedded between these nanosheets. Fe3O4 nanoparticles acted as a low cost hard template and show steric hindrance effect, endowing graphene sheets with highly wrinkled morphology. As shown in 3O4 nanoparticles. The HWGF show highly wrinkled yet densely packed morphology, resulted from the joint action of steric hindrance effect of Fe3O4 nanoparticles and the capillary compression during the heat treatment process. As a result, the flexible HWGF exhibited a comparatively high packing density of 1.53 g cm−3, which is calculated based on its areal density (1.84 mg cm−2) and average film thickness (12 μm).As shown by 30 As shown in It has been reported that capillary compression rather than thermal annealing is responsible for the crumpled graphene sheets. The crumpled graphene is also stabilized by plastically deformed ridges, and thus does not unfold or collapse during various types of solution processing or chemical or heating treatments.2O3 NPs shown in side view , (200), (310) and (211) planes of Fe(OH)3 (JCPDS card no. 34-1266). The Fe3O4@rGO hybrid film shows XRD peaks of 30.2, 35.4, 43.2, 57.3 and 62.9°, which are well agreed with (220), (311), (400), (511) and (440) crystal planes of face-centered cubic Fe3O4 (JCPDS standard card no. 86-1354).31 The HWGF shows a broad peak centered at 23.9°, which is the characteristic diffraction peak of graphene sheets. The above mentioned results were also supported by Raman measurements.XRD tests were performed to investigate the phase of Fe(OH)−1 and G band at about 1600 cm−1. The D band corresponds to the structural defects of graphitic domains, whereas the G band is associated with the ordered sp2 bonded carbon.10 The peak intensity ratio of D to G (ID/IG) of the graphite oxide (0.974) is consistent with the reported rations for graphite oxide materials.17 The ID/IG value of the HWGF (1.075) is closed to those of the reported amorphous carbon materials, indicating that the HWGF is mainly composed of amorphous carbon.32 The ratio of D and G band intensities (ID/IG) in HWGF (ID/IG = 1.075) is slightly higher than that in graphite oxide sample (ID/IG = 0.974), which was attributed to the defects created by the removal of oxygen moieties of graphite oxide.33As shown in 34 The HWGF show a high specific surface area of 383 m2 g−1, an average pore size of 27.7 nm and a total pore volume of 0.2652 m3 g−1. As shown in 35As shown in −1, indicating that the capacitance mainly comes from electric double layer capacitance (EDLC). As shown in −1, indicating its small resistance and excellent rate capability.As designed, the HWGF proved to be an ideal electrode material for supercapacitors. As shown in −1 at 0.2 A g−1 and 181 F g−1 at 20 A g−1. Based on its high packing density of 1.53 g cm−3, the volumetric capacitances of the HWGF can reach as high as 370 F cm−3 at 0.2 A g−1 and 309 F cm−3 at 20 A g−1. The capacitance retention rate reaches as high as 70% when the current density increased by 100 times from 0.2 to 20 A g−1, indicating the superior rate capability of the HWGF.The specific capacitance is calculated from the GCD test results. As shown in −1 at a power density of 49 W kg−1 and 12.3 W h kg−1 at 4900 W kg−1. These data are highly comparable to the previously reported graphene based symmetric supercapacitors, such as 3D porous graphene (7.0 W h kg−1 at 500 W kg−1)10 and graphene hydrogel (5.7 W h kg−1 at 30 kW kg−1).36Based on the rate performance shown in −1 to investigate the cycle stability, which is critical for its practical application in supercapacitors. As depicted in 17GCD cycle test was performed at 1 A g3O4 nanoparticles as low-cost and environment friendly hard template. The HWGF show highly wrinkled yet densely packed morphology, resulted from the joint action of steric hindrance effect of Fe3O4 nanoparticles and the capillary compression during the heat treatment process. The generated HWGF exhibited a high packing density of 1.53 g cm−3, a high specific surface area of 383 m2 g−1 and a hierarchically porous structure. The high packing density resulted in high volumetric capacitance, facilitating real applications in commercial electrochemical energy storage devices. The HWGF delivered a high capacitance of 242 F g−1 and 370 F cm−3 at 0.2 A g−1 in 6 M KOH aqueous electrolyte system, with excellent rate capability (202 F g−1 and 309 F cm−3 retained at 20 A g−1) and cycle stability . In brief, the fabrication process is facile, low-cost and scalable, opening up a promising way for the rational design and effective synthesis of highly dense but porous graphene assemblies for compact capacitive energy storage.In summary, highly wrinkled graphene film (HWGF) was synthesized by using FeThere are no conflicts to declare.RA-009-C9RA02132A-s001