Objective: The aim of this study was to measure both plasma and cerebrospinal fluid (CSF) TAR DNA-binding protein 43 (TDP-43) and phosphorylated TDP-43 (pTDP-43) levels in sporadic amyotrophic lateral sclerosis (sALS) patients, and to compare them with that of healthy controls. The correlation between plasma or CSF TDP-43/pTDP-43 and clinical indicators of ALS patients was assessed.Methods: Paired plasma and CSF TDP-43/pTDP-43 levels in 69 ALS patients and 59 healthy controls were measured by sandwich ELISA. Time to generalization (TTG), an indicator suggested that the time of symptoms spreading from spinal or bulbar localization to both, was evaluated in all patients screened for mutations in genes associated with ALS.Results: Both of the plasma TDP-43 and pTDP-43 levels were significantly higher in ALS patients than HCs (P < 0.001). The pTDP-43/TDP-43 ratios in plasma were significantly higher in HCs than ALS patients (P < 0.001). The area under the curve (AUC) value was 0.924 for plasma TDP-43 level, with a 91.3% sensitivity and 91.5% specificity. Moreover, the correlation between plasma and CSF TDP-43 was observed in each ALS patient . A correlation between CSF pTDP-43 levels and the ALSFRS-R  was established. A correlation was observed between plasma TDP-43 levels and TTG in ALS patients, which indicated that high levels of plasma TDP-43 correlated with prolonged TTG .Conclusion: The plasma TDP-43 and pTDP-43 levels might play an important role in diagnosis in the future study of ALS. The plasma TDP-43 might differentiate ALS and HC groups based on high sensitivity and specificity, and as an indicator of progression of disease. Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the degeneration of both upper and lower motor neurons, with a median survival of 3–5 years . The patGRN and C9orf72 genes  as compared to the control subjects as assessed by ELISA . Interes72 genes . Junttiln in ALS . Lower T for ALS . Bourbou for ALS . Hosokaw for ALS . In a re for ALS , 16.TARDBP, SOD1, FIG4, FUS, CHMP2B, VCP, ELP3, SETX, HNRNPA1, SPG11, NEFH, VAPB, ANG, OPTN, UBQLN2, SQSTM1, MATR3, ATXN2, PFN1 and DCTN1 genes using multiplex PCR, variants identified in our study had been classified as pathogenic, likely pathogenic, uncertain significance, likely benign, or benign in accordance with Standards and Guidelines for the Interpretation of Sequence Variants: A Joint Consensus Recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology and ClinVar database (http://www.ncbi.nlm.nih.gov/clinvar). Given the potential consequences of gene heterogeneity, nine patients with ALS carrying pathogenic variants were excluded  group comprised of 59 age-matched subjects who initially visited Neurology Clinic and underwent lumbar puncture for the purpose of making the exact diagnosis; however, the final diagnosis were free from neurological diseases.CSF and blood samples were collected at the time of diagnosis in our department for analysis as described previously . All samTotal TDP-43 was determined in plasma and CSF using a commercially available ELISA kit  according to the manufacturer's instructions. The standard provided by the manufacturer consisted of a His-tag recombinant human full-length TDP-43 protein . All the analysis were performed on coded samples by the analyst blinded to the patient data. Results based on duplicates with CV>10% were excluded. Each experiment was repeated at least twice. Plasma and CSF samples were tested undiluted with a single batch of reagents, respectively.pTDP-43 levels in plasma and CSF were measured in duplicate by a commercially available ELISA kit  according to the manufacturer's instructions. In this assay, a biotinylated rabbit polyclonal antibody against TDP-43 phosphorylated at Ser409  was used as a detection antibody. The standard provided by the manufacturer consisted of recombinant human TDP-43 phosphorylated at Ser409. The results were expressed as relative units (plasma or CSF), generated from concentration values normalized to a standard sample loaded on all plates as previously described  were used because of the non-normal distribution and heterogeneity of variance of a majority of the variables and parametric statistics were determined by Spearman's rank correlation coefficient (r). Receiver operating characteristic (ROC) curve analysis was performed for evaluation in the ALS patients; the area under the curve (AUC) was calculated and optimal cut-off values were derived by Youden index. P-values were two-sided, and ≤ 0.05 were considered statistically significant. All analyses were performed using the SPSS for Windows .Median levels and interquartile range (IQR) were used to indicate the central value and range, respectively. The χP < 0.001) (P > 0.05) (P < 0.001) (P < 0.001), but no significant difference was found in CSF (P = 0.409).Sixty nine ALS patients were recruited for this study which comprised 46 males and 23 females with a mean (SD) age of 51.46 (9.42) years. The onset site was classified as spinal onset in 59 patients and as bulbar onset in 10 patients. The median average time from clinical onset to diagnosis was 19.59 months in ALS. The clinical characteristics of all participants are summarized in < 0.001) . There w > 0.05) . In addi< 0.001) . Apart fROC curve analysis was used to differentiate ALS from HC, and the AUC values were 0.924 and 0.588 for plasma and CSF TDP-43 levels, respectively. A cut-off level of 37.58 pg/ml for TDP-43 in plasma generated a sensitivity of 91.30% and specificity of 91.50% . The optP = 0.410, CSF: P = 0.462) and pTDP-43  levels. Moreover, no significant difference was noted between bulbar onset and spinal onset in ALS patients in TDP-43  and pTDP-43  levels  , however, no correlation was found between plasma or CSF pTDP-43 levels and other clinical indicators  levels . Moreove= 0.042) ; Moreovedicators .P = 0.100). Moreover, a correlation was established between plasma TDP-43 levels and TTG , which indicated that high levels of plasma TDP-43 correlated with a long TTG  months. No significant difference was observed between the bulbar onset  and spinal onset  in TTG , the RNA processing protein, was the major component of cytoplasmic inclusions . HoweverLS cases , 24. AppLS cases –27. TDP-LS cases .P = 0.159). Given the limited number of cases, further studies on a larger scale are required to better understand the pathology of ALS subtypes.In this study, we observed a significant increase in the levels of TDP-43 and pTDP-43 in plasma of the ALS group. Moreover, the pTDP-43/TDP-43 ratios in plasma were significantly higher in HCs than ALS, which revealed that plasma TDP-43/pTDP-43 levels and the pTDP-43/TDP-43 ratios in plasma appear to distinguish individuals with ALS from controls. In present study, it is of note that 10 out of 69 ALS patients with apparent decreased levels of CSF pTDP-43 had bulbar signs, and the variability may be due in part to differences between the bulbar-onset and spinal-onset clinical and pathological characteristics of ALS with neurodegeneration , 30, or Previous studies stated that TDP-43 lesions in subpial/subependymal or perivascular localizations had been focused on the TDP-43-linked neurodegeneration, which might account for increased blood or CSF TDP-43 levels through mechanisms remains unclarified . FurtherTARDBP gene in ALS cases, which demonstrated that defects in this gene were sufficient to cause familial ALS and sporadic ALS partially (TARDBP gene (A382T or G348C). They found that the TDP-43 mRNA levels in white blood cells (WBCs) of A382T mutant mice were significantly higher than that of the G348C mutant. The mRNA levels of both apoptosis-related factors (Smn1 and Naip5) correlated with the TDP-43 levels in WBCs and also differed between A382T and G348C, which suggested that each mutation in TARDBP induces distinct RNA metabolism and abnormal RNA metabolism is one of the causes of neuronal cell death in ALS. The study also indicate that different mutation in TARDBP produces varying levels of TDP-43 in WBCs (TARDBP. A previous study described the CSF TDP-43 levels in ALS patients with hexanucleotide repeat expansion (HRE) in the C9orf72 gene, however, no difference in the CSF TDP-43 levels was observed between the C9orf72 expansion carriers and noncarriers in the cohort  2+ < Ca2+. The EDT2+ < Ca2+, and on C9orf72 gene was not evaluated in ALS patients allowing for an extremely low incidence of mutation among Chinese populations in our earlier limited understanding (This is the first study comprising of an Chinese population with screened genetic background of the patient and simultaneous evaluation of the plasma and CSF TDP-43/pTDP-43 levels in ALS patients. The study showed plasma TDP-43 may play an important role in disease diagnosis and as a progression predictor of ALS. However, several caveats should be kept in mind when evaluating our findings. First, the GGGGCC copy number and expansion within the standing . Second,standing , which wThe raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by the Ethics Committee of the Chinese PLA General Hospital. The patients/participants provided their written informed consent to participate in this study.YR: concept, data analysis, experimental studies, and manuscript preparation. XH: design, manuscript editing, and manuscript review. FC: literature search and manuscript editing. ML and HW: data acquisition. FY: data analysis. XS: data analysis and statistical analysis. SC: data acquisition and data analysis. SL: experimental studies and literature search. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Density functional theory was used to investigate the effects of doping alkaline earth metal atoms  on graphene. Electron transfer from the dopant atom to the graphene substrate was observed and was further probed by a combined electron localization function/non-covalent interaction (ELF/NCI) approach. This approach demonstrates that predominantly ionic bonding occurs between the alkaline earth dopants and the substrate, with beryllium doping having a variant characteristic as a consequence of electronegativity equalization attributed to its lower atomic number relative to carbon. The ionic bonding induces spin-polarized electronic structures and lower workfunctions for Mg-, Ca-, and Sr-doped graphene systems as compared to the pristine graphene. However, due to its variant bonding characteristic, Be-doped graphene exhibits non-spin-polarized p-type semiconductor behavior, which is consistent with previous works, and an increase in workfunction relative to pristine graphene. Dirac half-metal-like behavior was predicted for magnesium doped graphene while calcium doped and strontium doped graphene were predicted to have bipolar magnetic semiconductor behavior. These changes in the electronic and magnetic properties of alkaline earth doped graphene may be of importance for spintronic and other electronic device applications. Alkaline earth atom dopants on graphene induce work function tuning and spin polarized electronic properties by ionic bonding. This implies that the substitutional doping of Be atoms on graphene induce a band gap opening on the material, which is attributed to electron localization due to electron transfer from the Be atom to the graphene substrate.Theoretical research for alkaline earth dopants in graphene has had a relatively recent history beginning with studies on beryllium doping in graphenes.3 and sodium-ion batteries.4 In particular, further theoretical development on beryllium–nitrogen co-doped graphene is being pursued in order to determine the feasibility of this material for metal-ion battery chemistries.5 In addition, the adsorption and migration behavior of other alkaline earth metals (particularly Mg and Ca) on pristine and defective graphene have been examined for divalent metal ion battery chemistries.6Be-graphene was further studied for tunability with concentration effects and co-doping with a view towards use as potential anodes for lithium-ion2 storage applications were also explored via theoretical studies.7–9 Doping alkaline earth graphene on divacancy sites9 or on top of the pristine graphene substrate8 were found to induce hydrogen adsorption. For graphene oxides, oxygenous sites on the material were found to be areas where magnesium dopant are likely attached. It was also found that this interaction induces polarization on H2, making adsorption more favorable.7The application of alkaline earth doped graphenes in hydrogen adsorption for H10 and with nitrogen,11 were also investigated for band-gap tuning. Optical properties, such as the optical transparency, for the Be–N co-doped graphene were found to be tunable via this co-doping approach.12 A similar study on the co-doping of magnesium and nitrogen was also conducted by Rafique and colleagues13 where magnetic coupling was found as the main mode of interaction and half-metallic properties were observed. Similar studies on doping AE-atoms on graphene have also been done on boron nitride, a two-dimensional material similar to graphene.14Co-doping beryllium with sulfur3, PH3 and AsH3 molecule adsorption on alkaline earth doped graphenes for sensing applications have been conducted15 using dispersion corrected density functional theory as implemented in Dmol3  ions via changes in observed bright blue (λ ≈ 456 nm) photoluminescence upon exposure to ultraviolet light. This detection was attributed to metal chelation on the carbon quantum dots. This may be causing an electron transfer between Fe3+ and the Mg-CQD, extinguishing the Mg-CQD's photoluminescence. Detection levels of around 50 ppb for Fe3+ were obtained.Magnesium doped carbon quantum dots in the range of 2–8 nanometers in diameter, on the other hand, were synthesized 19,20 these studies sometimes give conflicting results. For instance, while the study by Rafique and their team19 predict for the emergence of magnetic properties for some alkaline-earth doped graphenes and postulated ionic bonding as the source of magnetic properties in alkaline earth doped graphenes, Arsent'ev and colleagues20 do not predict magnetic properties for any alkaline earth dopant and was silent on the possible chemical interactions. Thus, the electronic properties of the alkaline earth doped graphene can still be described and understood better through elucidating the nature of chemical interactions within these materials. As a further example, while previous work on Be-graphenes1,4 indicate a band gap opening, other work indicates possible half-metallic behavior.19 Thus, it may also be possible that the differing computational parameters and details play a role in the discrepancies between the previous theoretical works.These recent studies are indicative of the interest in using alkaline earth group of elements as dopants for various applications. This study hence also intends to contribute to this body of knowledge by theoretically determining the properties induced by doping. While previous theoretical studies have attempted to screen alkaline earth dopants for electronic, optical and magnetic properties,18) or the nature of charge carriers in the material (as in the case of n-type doping in Ca-graphene17), did not directly provide a description of the electronic properties of the material by experimental methods. Further, the experimentally realized atomic-scale structure of these materials have not yet fully examined in detail. Also, while theoretical studies have been conducted on alkaline earth doped graphene, there is still a knowledge gap with respect to how more precisely the interactions induced by alkaline earth dopants on graphene can be described and how it gives rise to electronic and magnetic properties predicted for or observed on the material.In addition, the current experimental studies, while alluding to possible electronic structure-derived properties such as the presence of a band-gap . The larger supercell compared to previous work was chosen in order to minimize dopant–dopant interactions while still being computationally economical and to emphasize the dopant–substrate interaction. This difference in supercell size versus previous studies19,20 may have a significant effect especially when considering the comparability of the results presented in this work. It was also assumed that there is one adsorbate per supercell. The unit cell lattice constant was determined to be 2.470 Å, close to the accepted value of 2.46 Å for graphene. Thus, the 4 × 4 supercell has a lattice dimension of 9.88 Å. This was kept constant while all the atoms in the supercell were allowed to relax. A vacuum spacing of 15 Å was used to minimize spurious interlayer interactions introduced by the periodic boundary conditions assumed by the software.Alkaline earth doped graphene was modeled as a supercell of 4 × 4 unit cells of graphene, implying that each supercell contains 32 atoms. The supercell has one carbon atom substituted with an alkaline earth atom  were used in order to describe electron–ion interactions for all atomic species in the system. The Perdew, Burke and Enzerhof (PBE)24 formulation for the generalized gradient approximation (GGA) was used to account for the energy contributions resulting from quantum effects and electron–electron interaction via exchange correlation. The PAW-PBE pseudopotentials used were those provided by PSLibrary.25 Kinetic energy cutoffs was determined by convergence testing to be 550 eV for the wave function and 5500 eV for the charge density. Results at higher cutoff  agree with those obtained at lower cutoff (550 eV) and thus the results are also verified at that higher cutoff 36 were used to qualitatively evaluate chemical interactions on the materials. The ELF characterizes the localization of electrons by determining the likelihood that an electron can be found near a reference electron of the same spin and at a given point. Thus, ELF37 can be used in order to find areas where electrons tend to be located or localized. This is an important qualitative indicator for bonding behavior, with covalent and ionic bonding being differentiated by where electron localization occurs.38Two qualitative measures of interaction were examined to describe the chemical interactions in AE-graphenes. The electron localization function (ELF)36,39 Hence, the RDG would be necessary in order to evaluate these interactions which are associated with these low electron density areas. This means that the RDG can be used to account for non-covalent  interactions, such electrostatic interactions and steric hindrances on the material.On the other hand, non-covalent interactions tend to be observed at troughs or regions of lowered electron density.40 since it allows for a visualization of interactions at both high electron density zones  and low electron density regions .41,42 This approach thus enables simultaneous and rigorous qualitative examination of the different interactions within a material.This coupled approach using the ELF and the RDG has already been used in previous work to characterize complex organic chemical systems43 and thus provide another picture into the nature of bonding via orbital hybridization within the substance.Density of states (DOS) and band structures were also derived from the DFT calculations in order to further characterize the electronic and magnetic properties observed in the modeled materials. The projected density of states (pDOS) was also used in order to determine hybridization by determining the probability that an electron of a particular orbital and atom occupies a certain energy level3.3.1.44 even when using the 0.4 eV criteria set by Ishii et al.20,45 This configuration will be referred to as out-of-plane doping. Binding and adsorption energies were used to evaluate the energetic feasibility of different alkaline earth dopants in graphene. Monosubstituted alkaline earth dopants were generally found to favor a non-planar doping configuration, with the alkaline earth dopant sticking out of the graphene substrate. This is consistent with our previous work1,2,15 which may be attributed to differences in computational details and particularly supercell size.AE–C distances was found to increase as the heavier atom is doped, with Be-graphene having the shortest distance and increasing as the atomic number of the dopant atom increases. These bond lengths were found to be longer than the C–C bond length found in pristine graphene. This may be a factor which induces an out-of-plane doping for Be-graphenes. Further, comparing results for Be-graphene with those determined from previous DFT calculations show similar results in terms of AE–C distances predicted. Slight variation in predicted binding energies is observed between the results in this study and previous workThe doping of Be atom on graphene was found to be most stable and lowest in energy. While this stability may be attributed to the low atomic weight (and therefore low atomic radius) of Be atoms as demonstrated by the lowest AE–C distance it shows, it does not explain why Mg was found to be the highest energy (and therefore least stable) dopant atom. This is despite Mg-graphene having the second shortest AE–C bond length. This may imply that factors other than the atomic weight may play a role in determining energetic stability on AE-graphene doping.65,66Comparing the adsorption energy of the alkaline earth dopants with that of adsorbing a carbon atom into the monovacancy shows that the adsorption of carbon into the monovacancy is still more energetically favorable than substituting alkaline earth dopants, or that carbon atoms are preferentially adsorbed in point vacancies over alkaline earth metal atoms. This is consistent with the previously-reported self-healing of defects or self-knitting behavior in graphene.W0) compared to pristine graphene, while the rest of the alkaline earth dopants lower the work function relative to pristine graphene. The heavier alkaline earth atoms were also found to have stronger work function reduction as the atomic weight increases and they have a electrostatic potential barrier attributed to the dopant  due to calcium doping than the 1 eV work function lowering measured in their work. Ca clusters of around 30 nm in size on the graphene surface was observed via atomic force microscopy in their work and a relatively high concentration of Ca atoms was measured for their synthesized doped graphene. On the other hand, this work focused on atomic doping of calcium in graphene. This is an important difference between this work and their work and this may explain the discrepancy in the predicted versus observed work function in the experiment, especially considering there are more complex structures realized in experiment.Results for Ca-graphene have a consistent trend with results by Klain Further, the atomic-level structures were not observed directly for the synthesized samples. However, strong chemical bonding between C and Ca, which was inferred in the experimentally realized synthesized doped graphene through X-ray photoemission spectra. Despite this, this work may help elucidate the contribution on the work function of strong chemical bonding between C and Ca, especially considering that the experimental result does not preclude this possibility. Therefore, it may also be important to investigate further the effect of clusters of alkaline earth elements on workfunction, as well as to further investigate the atomic-level structures in experimentally realized AE-graphene.69 while electron transfer from the dopant to graphene is expected to decrease the work function.17 The beryllium atom has, overall, fewer electrons associated with it than carbon. Thus, it is expected to gain electrons from the carbon atoms in graphene, following chemical potential equalization or electronegativity equalization.70,71 This is despite the tendency for the beryllium atom to transfer electrons to empty its 2s orbital. This effect of the electronegativity equalization is an important consideration to take note of for the interactions on Be-graphene. Conversely, the heavier alkaline earth dopants have absolutely more electrons than carbon even upon the transfer of their outermost s-orbital atoms and thus will tend to donate electrons to graphene.These work function shifts predicted may be caused by the electron transfer from the dopant to the material. Electron transfer from the graphene to the dopant is expected to increase the work function,e− have been observed.This electron transfer is further demonstrated by localized regions of positive and negative charge that emerge from the doping of alkaline earth dopants on graphene, as quantified with Bader charge analysis . This maIn this case, the most salient localized modification in AE-graphenes is the electron deficient, and hence positive charge-dominated region on the AE-dopant atom. These are paired to the negative-charge dominated region on the carbon atoms adjacent to the substrate, as demonstrated in charge difference plots in 15 predicted a negative dopant net charge using Mulliken charge analysis. The trends they predicted for the dopant net charge are also different with the predictions for this work. In contrast, this study, as well as other previous studies1,2 which used Bader charge analysis, predict for a positive charge for the beryllium atom. Thus, this discrepancy may be attributed to this difference in methodology. Further, it had been previously noted that results from Mulliken charge analysis depend strongly on the basis set used,3,72 with smaller basis sets tending to have unrealistic results.It must be noted that for Be-graphene, Luo and colleaguesThe electron localization functions for AE-graphenes  indicateversus electron density.73 This is most apparent near the alkaline-earth dopants, which exhibit high positive charge and therefore, low electron density.It is also interesting to note that for Ca- and Sr-atoms, the shape of the ELF on the dopant atoms are distorted away from a spherical form. This may imply that the electrons on the Ca- and Sr-dopant, respectively, are polarized. This is in consonance with the observation for the respective charge difference plots . It must36 Both repulsive and attractive interactions were demonstrated to be present in AE-graphenes  were also found to play a significant role in AE-graphenes as demonstrated by the reduced density gradient.raphenes . In partraphenes , a blue Red regions, on the other hand, were observed at the bottom of the alkaline-earth dopant. This may indicate steric hindrances or repulsive interactions. This also serves to explain the out-of-plane doping observed for AE-graphenes. This is more pronounced for Ca- and Sr-graphenes due to its larger atomic number. It can also be observed that there are voids or holes in the middle of blue regions for Ca- and Sr-graphenes. It may imply that there is a high enough electron density in that region for the NCI to not be visible given the isosurface level, since the NCI tends to zero in regions of high electron density.The complementary pictures given by the ELF and the RDG qualify the nature of interaction within AE-graphenes. Ionic bonding or electron transfer from the alkaline earth dopant to the graphene substrate was found to be the main mode of interaction for AE-graphenes. The three nearest neighbor carbon atoms primarily receive and share the electrons transferred to the graphene substrate between them. In turn, steric hindrance is caused by the graphene substrate which competes with the ionic bonding and causes out-of-plane doping on AE-graphenes.69 The possibility for covalent bonding to occur on beryllium doping on graphene has also been previously documented.19 This is also consistent with beryllium being expected to have the most similar electronegativity to carbon among all alkaline earth elements.The variation for Be-graphene relative to the other alkaline earth doped graphenes may be attributed to its lower atomic number relative to carbon. Once the beryllium atom transfers its valence electrons to the graphene substrate, it would still have fewer electrons than carbon. This can attract the nearby electron cloud towards it to equalize the chemical potential of all electrons over the material. This may make the interaction appear more covalent since the electron cloud due to the electron transfer from the beryllium dopant is shifted away from the electron accepting carbon atom and pulled back towards the beryllium donor, thereby making the electron cloud less localized on the electron acceptor sites. Thus, the action of electronegativity equalization competes with electron transfer in the ionic bonding observed for Be-graphene. This competition may also explain the work function increase predicted for beryllium doping on graphene, which tends to be a characteristic of electron transfer from a graphene substrate to a dopant atom.In contrast, for magnesium and the heavier alkaline earth atoms, the core electrons would screen the effect of the positive nucleus and repel the electrons from the alkaline earth atom once it has been transferred to the graphene substrate. For instance, the magnesium ion would have a similar electron configuration to neon upon transferring two electrons. This still has more electrons than the carbon atom due to its higher atomic number. The core electrons remaining on magnesium would repel the nearby electron cloud and thus make the bond more localized on the electron acceptor sites. For the heavier alkaline earth atoms, this effect would be more pronounced since they have more core electrons.Therefore, the action caused by electronegativity equalization would reinforce the effect of electron transfer in ionic bonding. This is also evidenced by the existence of regions of low electron density, and hence high RDG between the dopant atom and the adjacent carbon atom; a feature which is absent in Be-graphene. Another effect caused by electronegativity equalization is the potential barrier predicted near the heavier alkaline earth dopant atoms  the ionization of the alkaline metal dopant to a cation by loss of valence electrons and (2) the reception of the valence electrons by the graphene substrate, binding the alkaline metal dopant to the graphene substrate. From the Bader charge analyses  ion-substrate coupling because of weaker electrostatic repulsion or steric effect. Thus, from the perspective of ion-substrate coupling, coupling for Be ions is more energetically favorable than for Sr ions.A similar trend and pattern for interaction was noted by Liu, Merinov and Goddard,via Bader charge analysis and the differing ionization energies for the AE dopants, could probably explain the energetic trend observed.75 The strength of the ion-substrate coupling due to electron transfer is the dominant effect stabilizing Be-graphenes, while Ca- and Sr-graphenes are stabilized by the low ionization energy required to transfer their electrons to the graphene substrate. For Mg-graphene, the two effects compete with none being predominant, that is, the Mg atom transfers electrons to a lower degree but at the same time, this electron transfer requires a higher amount of energy. This causes the relatively more positive binding and adsorption energies for Mg-graphene. This trend may provide a guide for the application of graphene materials for battery technologies based on alkaline earth group atoms as divalent metal ions6 since a balance of adsorption strength is needed for reversible operation in ion batteries.The competition between the strength of ion-substrate coupling, evinced by the degree of electron transfer as computed 3.2.76 and atomic cobalt doped graphene under tension.77 These works attribute the emergence of spin-asymmetry in doped graphene to the electron transfer to the graphene substrate. This may imply that inducing electron transfer or ionic interactions with graphene may render it magnetic, which could explain the emergent ferromagnetism in AE-graphenes. A similar case can be observed with AE-graphenes, particularly also for Rafique and team's work where they explain the interaction between the Mg and N co-dopants in graphene as a magnetic coupling.13An important consequence of the electron transfer and ionic bonding from the alkaline-earth dopant to the graphene substrate is spin-polarization in the electronic structure or the emergence of possible magnetization on AE-graphenes. Magnetization due to electron transfer has been previously observed and predicted for H-grapheneTotal and absolute magnetization values for AE-graphene demonstrate that AE doping on graphene tend to cause ferromagnetic properties on the material . For all78 Similar p-orbital spin polarization (or magnetization) has also been predicted for alkaline-earth carbon compounds exhibiting a rock-salt structure,79 where these compounds were found to have half-metallic properties. Magnetization for these instances were primarily attributed to localization of p orbitals on the carbon component.This spin-polarization on carbon-atoms may imply that Mg-, Ca- and Sr-graphenes provide examples for predicted p-orbital spin polarization.1,2 has no net magnetization. The emergence of magnetization (or the lack thereof), provides a further clue to differences in the exact manner by which the electron transfer occurs on AE-graphenes. For Be-graphenes, the competition between electronegativity equalization and electron transfer may have precluded spin-polarization, while for the other AE-graphenes, the heavily ionic interaction between the AE-dopant and the carbon atoms on the graphene substrate induce magnetization. The presence of this triplet-like ferromagnetic state, as indicated by the total and absolute magnetization .25 The older version of PSLibrary did not treat semicore states for Be, thus, this work also updates the accuracy of our previous work.It must be noted out that in contrast to the previous study by the author's groupet al.1 was done on a larger supercell size of 6 × 6 unit cells. Despite these differences, the band structures predicted by their study and this study are remarkably similar 19 indicated that a half-metallic, and thus spin-polarized electronic properties is predicted for Be-graphene. This may imply that either the supercell size is significant in the predicted band structure, or that the properties of Be-graphene vary at higher doping concentrations . A similar observation on differing supercell sizes accounting for differences in the electronic properties predicted can be made when comparing results between this work and that by Rafique et al., for the other AE-graphenes. In particular, supercell size greatly affects the results of computational studies85–87 since this may affect the significance of dopant–dopant interactions on the simulation and hence the predicted properties.88 Choosing a larger supercell size may emphasize the dopant–substrate interactions by minimizing dopant–dopant interactions.In contrast, previous work by Rafique 1 despite possible increased chemical reactivity due to the highly positive and highly negative sites induced on the material by doping. This is especially considering that electric conductivity is an important aspect to consider when selecting for possible electrocatalysts,89 or sensors.15 Consistent with possible increased chemical reactivity, Ullah and his colleagues has demonstrated the potential of Be-doping on graphene for lithium-ion battery anodes.3 In this work, it was posited that the inclusion of beryllium on graphene makes the graphene material electron deficient, which renders lithium adsorption on the material feasible. This may also imply possible application for beryllium-doped graphenes in this area, not only for lithium-ion batteries but for other batteries where the adsorption of alkali metal ion species is required. Further, application of beryllium as co-dopant5 in order to improve these adsorption-related properties may also be pursued.The presence of the localized states which opened the band-gap as evinced by 3.4.e−), however there is significant spin-polarization observed (μB) of total and absolute magnetization for Mg-graphene, which can be attributed to a triplet pair. Hence, the spin-asymmetry for Mg-graphene can be primarily attributed to the electron transfer induced.Mg-graphene also exhibits electron transfer  and CBM (conduction band minimum) partial charge density for the majority spin Fig. S11b indicatetructure  in Mg-gr92 Further, other two-dimensional materials, such as nickel–carbon–hydrogen and cobalt–carbon–hydrogen metal–organic frameworks also show this “half-metallic Dirac cone” behavior.93 These materials which exhibit a Dirac cone-like feature in only one spin are collectively known as Dirac half-metals (DHMs).94 DHMs are promising for spintronic applications since they combine spin polarization and massless Dirac charge carriers. Further, they “are also capable of generating 100% spin-polarization and massless Dirac fermions, which are expected to perform better than other spintronic materials…”.95 At least one patent has already been applied for with regards to the utilization of DHMs for spintronic applications,96 presumably using manganese trihalides.97 Experimentally, a DHM has already been observed in the form of Mn2CoAl, a Heusler alloy.98 In the case of transition metal-containing DHMs, the magnetism was primarily attributed to the metal atom and their d-orbitals.This p-type Dirac cone-like feature is similar to that observed by Gierz and her team for epitaxial graphene on SiC modified by adsorbed gold atoms.3Ca2 films, where p-orbital magnetization was shown to be primarily responsible for spin asymmetry.99 It is also posited that a wider band gap implies greater stability for the Dirac half-metal behavior, i.e., the Dirac half-metal behavior is kept at a wider range of applied voltages. This may imply that Mg-graphenes, should they be applicable for this application, would be limited to a narrower range of applied voltages, or thus limited to low-power applications. Na2C was also estimated to be a low band gap DHM100 at around 0.7 eV. Other compounds using beryllium and carbon (Be3C2)101 and magnesium and carbon (Mg3C2)102 were also shown to be Dirac half metals. It must be noted that most of these materials have a high concentration of alkali or alkaline earth metals compared to the Mg-graphene system considered in this work. Thus, this electronic structure may be said to emerge from interaction between the alkaline earth atom and carbon and may provide a pathway for developing DHMs if further investigated.In contrast, since there is no atom in Mg-graphene introducing d-orbital states, the magnetism or spin asymmetry is borne by electrons attributed to carbon atoms in the substrate and may be attributed to polarization caused by the electron deficient and hence positive Mg ion. Similar phenomena was also observed in work on CThe projected DOS for Mg-graphene  further On the other hand, the VBM and CBM partial charge density for the minority spin are more strongly localized in the region near the dopant atom and has more overlap Fig. S11c This supvia an applied potential. This is reflected in the higher density of states  electron transfer characteristics with the rest of AE-graphenes. Similar to Mg-graphenes (and in contrast to Be-graphenes), this charge transfer has also induced a triplet state to arise , while Ca- and Sr-graphenes were predicted to be bipolar magnetic semiconductors. These novel electronic properties may prove to be interesting for applications involving magnetic devices and spintronic devices.109 experimental verification and further discovery for these materials will be significant. These in turn will provide for more realistic models derived from experimentally observed structures for further theoretical work and predictions.Hence, it may be worthwhile to further explore magnetism in AE-graphenes, particularly by estimating thermal effects such as the Curie temperature of AE-graphenes. More rigorous computations which may better account for magnetism in materials can be done to verify predictions. More importantly, since Dirac half-metals and bipolar magnetic semiconductors are still developing families of materials,There are no conflicts to declare.RA-011-D0RA08115A-s001RA-011-D0RA08115A-s002


The thermal transport in 2D materials gains much of the interest, especially when graphene has high thermal conductivity. However, the thermal properties of 2D materials obtained from experiments have large discrepancies. For example, the thermal conductivity of single layer suspended graphene obtained by experiments spans over a large range: 1100–5000 W/m·K. Apart from the different graphene quality in experiments, the thermal characterization methods play an important role in the observed large deviation of experimental data. Here we provide a critical review of the widely used thermal characterization techniques: the optothermal Raman technique and the micro-bridge method. The critical issues in the two methods are carefully revised and discussed in great depth. Furthermore, improvements in Raman-based techniques to investigate the energy transport in 2D materials are discussed.The discovery of graphene and its analog, such as MoS For example, κ of suspended single layer graphene (SLG) ranges from 1100 to 5300 W/m·K [κ of supported graphene drops to hundreds W/m·K, which is also related to the substrate [κ of supported graphene is suppressed due to phonon leakage [κ of suspended and supported graphene by different experimental methods. A large discrepancy among κ can be observed. This discrepancy arises from the characterization methods and the quality of the graphene. The thermal characterization techniques of 2D materials include the optothermal Raman technique [Since the discovery of graphene and other 2D materials such as MoS studied ,2,3,4,5. studied ,7. The t studied ,9. Howevubstrate ,11,12. I leakage ,13. Tablechnique , micro-bechnique ,9, time-echnique  and Johnechnique . In thisechnique .κ of suspended graphene [Tχ) and the Raman shift power coefficient (Pχ) of G peak, the thermal conductivity of graphene can be expressed as κ = Tχ(L/2hW)/Pχ [L, h and W are the distance from the hot spot to the heat sink, thickness of SLG and width of the sample, respectively. The optothermal Raman technique is proven to be powerful and widely used in characterizing the energy transport in 2D materials [The characteristic peaks in Raman spectra of the 2D materials have strong temperature dependence. It is possible to make use of the Raman spectra to characterize the thermal transport in 2D materials ,22,23,24aterials . Advantaaterials . Howeverκ of graphene is the laser power (P) absorbed by the graphene. Usually, two methods are employed to obtain P. One is calculating the absorbed power based on the optical properties [Gα) of SLG is 2.3% [P can be described as P = I0A(1 − exp(−Gδα)), where I0 is the laser intensity on the surface, A is the illuminated area and δ is the thickness of SLG [Gα is easily affected by many factors, such as the wrinkles and the strain [P will affect the accuracy of Pχ, which further introduces uncertainty into the derivation of κ. It is difficult to determine the uncertainty of P. If there is 10% uncertainty in Pχ, 10% uncertainty will be introduced to κ.One important parameter in the deduction of operties . It is we strain . The opte strain , which lκ determination [κ of FLG can be higher than 20% [Another source of uncertainty in the optothermal Raman method is the stress effect in the graphene. During the temperature coefficient calibration, the whole sample is in thermal equilibrium. However, the graphene experiences thermal nonequilibrium in the experiment. This leads to the different stress effects in the graphene during the calibration process and experiment. Thus, the temperature probed by Raman spectroscopy is not precise, which further introduces uncertainty into mination . Apart fmination . Theoretthan 20% .TOT) can be 14.8% higher than that (ZAT) of out-of-plane acoustic (ZA) phonons at the center of the SLG [κ of SLG is increased by 67% [OP) and acoustic (AP) phonons under phonon excitation in 2D materials by constructing steady and nanosecond (ns) inter-phonon branch energy transport states [OP-APT) between OP and AP is reported to be 30% larger than the Raman-probed temperature rise in MoS2 [It is critically important to point out that the Raman optothermal method is based on an assumption that different phonon branches are in thermal equilibrium under the photon excitation. However, Ruan et al., first reported that the phonon branches were in strong thermal nonequilibrium by employing the density functional perturbation theory (DFPT) . For exa the SLG . By usind by 67% . Ruan’s d by 67% . Wang ett states . By deve in MoS2 .2/c-Si structure and discuss what will happen after the laser illumination on the sample. E = E – gE) of the electrons will quickly dissipate to other unexcited electrons and the lattice. Then, the electrons and holes (hot carriers) diffuse and recombine, releasing the energy by scattering with the optical phonons. This leads to a much larger thermal source area than the excitation spot. The specific process is described in detail in the reference [In most research about the energy transport in 2D materials by Raman spectroscopy, the hot carrier diffusion effect is not considered, which is more prominent as the laser spot size is smaller than 0.5 μm . Here, weference . The eleeference . Howeverκ of graphene supported on amorphous SiO2 [sR) of the central beam including both graphene and SiO2 can be expressed as: j,mT  is the temperature rise at the middle point of RT. bR is the thermal resistance of each RT line with the SiO2 beam. By measuring the Rs before and after removing the graphene, κ of graphene is determined. The accuracy of the micro-bridge method is guaranteed only as sR is comparable to bR. As κ of the graphene is low or the length of the graphene/SiO2 beam is longer than tens of μm, sR will be much larger than bR. Thus, the heat conducting into the graphene/SiO2 beam will be very small, which will lead to great uncertainty in the measurement of ΔmT. This will further increase the uncertainty in the determination of κ of graphene. Overall, the micro-bridge method is feasible in principle, but its measurement accuracy is guaranteed when the sample has proper thermal resistance. In addition, it is technically challenging and time consuming to fabricate the whole measurement device.Shi Li et al., first employed the micro-bridge method to measure ous SiO2 . The sch,m+ΔT4,m . Here, Δκ of graphene without or with minimal phonon-edge scattering, Liu et al., first developed the differential transient electrothermal technique (TET) to characterize κ of giant graphene supported by polymethyl methacrylate (PMMA) [V(t)) of the sample is recorded by an oscilloscope. The thermal diffusivity (β) of the whole sample can be obtained by fitting the V(t)~t curve. effκ of the whole sample is calculated as effκ = pβ·ρc. Through simulation, it is found that the interface thermal resistance between graphene and PMMA is negligible in effκ. Thus, effκ can be written as effκ = f. Here, the subscripts p and g indicate PMMA and graphene, respectively. δ is thickness. κ of SLG supported by PMMA was determined to be 365 W/m·K [κ of graphene supported by amorphous SiO2 [The sample size tested by the Raman spectroscopy method and micro-bridge method is at the level of several μm. However, the mean free path (MFP) of phonons in graphene can be as long as hundreds of micrometers , surpasse (PMMA) . The exp65 W/m·K , which ious SiO2 . The abuP), the Raman shift power coefficient (RSC) steady-stateχ = ∂ω/∂P = α·(∂ω/∂T)·f1(κ) is obtained. Here, α is the laser absorption coefficient, ∂ω/∂T is the Raman shift temperature coefficient and κ is the in-plane thermal conductivity. The second energy transport state is the transient-state heating induced by a square wave-modulated CW laser. Similarly, an RSC can be obtained: transientχ = ∂ω/∂P = α·(∂ω/∂T)·f2, where pρc is the volumetric heat capacity of the sample. Since the thermal diffusion lengths in two energy states are different, a normalized RSC parameter can be defined as Θ = transientχ/steady-stateχ = f3 [α and ∂ω/∂T is eliminated. By interpolating the Θ obtained from the experiment into the Θ–κ curve obtained from a 3D numerical simulation of the MoSe2 sample, κ of MoSe2 is determined. The feasibility of the FET-Raman technique has been verified by employing the FET-Raman to determine κ of MoSe2 and the anisotropic thermal conductivities of carbon fibers [In order to resolve the challenges mentioned above in the optothermal Raman technique, various Raman-based techniques, including frequency-domain energy transport state-resolved Raman (FET-Raman) ,36 and e . Thus, tn fibers ,36.mT) consists of the temperature rise of acoustic phonons (ΔAPT) and the temperature difference between optical phonons and acoustic phonons (ΔOAT). ΔmT can be expressed as:Inspired by the theoretical simulation by Ruan et al. ,30,37, WI is the intensity of the absorbed laser at location r. δ (0 < δ < 1) is the portion of the laser energy transfer from optical phonons (OP) to acoustic phonons (AP). ppG is the coupling factor between OP and AP. Furthermore, the Raman intensity weighted temperature rise ΔT¯m|CWI is the laser intensity distribution of the CW laser. OP and AP and the temperature rise of the acoustic phonons, respectively. I0 is the absorbed laser power per unit area, and Lτ is the absorption depth. Before determining the percentages of 2, r0 is the radius of the laser spot. The Raman shift is proportional to the temperature rise caused by unit power; thus, the Raman shift coefficient CWχ can be expressed as [Here, essed as :(3)χCW=AA is a constant. In the experiment, three objective lenses  are employed to obtain the OP and AP accounts for more than 30% of the temperature rise detected by Raman [OP and AP under photon excitation in graphene paper [OP is found to be 82.1% higher than that of AP under 100× laser heating [Here, by Raman . Zobeirine paper . The Ram heating , which i2 supported by c-Si [psχ = ∂ω/∂P is obtained, which is more affected by the pρc rather than by the hot carrier diffusion coefficient (D) and interface thermal resistance (R). In the steady-state thermal transport, the RSC under 20× and 100× objective lenses are obtained by applying the CW laser. Both CWχ20 under the 20× objective lens and CWχ100 under the 100× objective lens carries the information of D and R. However, CWχ20 is more affected by R, while CWχ100 is more affected by D. Here, the normalized RSC is defined as Θ1 = CWχ20/psχ and Θ2 = CWχ100/psχ. By simulating a 3D heat conduction model in the sample, the RSC contour with R and D as variables is obtained. The cross point of the Θ1 curve and Θ2 curve gives the value of R and D.To consider the hot carrier diffusion effect in the thermal transport in 2D materials, Yuan et al., first developed the ET-Raman to determine the interface thermal resistance and hot carrier diffusion coefficient in MoS by c-Si ,33. The OP-AP thermal nonequilibrium is unclear. Further work can be focused on the OP-AP thermal nonequilibrium in supported 2D materials.In summary, though facing several critical problems, the optothermal Raman technique and micro-bridge method still show suitability and feasibility in energy transport characterization in 2D materials. Much pioneering work about the thermal non-equilibrium in different phonon branches has been reported. However, the physical model and data fitting used in the pioneering work still suffer great uncertainties and make the study rather semi-quantitative. Secondly, past work has studied the thermal nonequilibrium in suspended 2D materials. However, for supported 2D materials, how the interface resistance between 2D material and substrate affects the


Graphene-based materials in the form of fibres, fabrics, films, and composite materials are the most widely investigated research domains because of their remarkable physicochemical and thermomechanical properties. In this era of scientific advancement, graphene has built the foundation of a new horizon of possibilities and received tremendous research focus in several application areas such as aerospace, energy, transportation, healthcare, agriculture, wastewater management, and wearable technology. Although graphene has been found to provide exceptional results in every application field, a massive proportion of research is still underway to configure required parameters to ensure the best possible outcomes from graphene-based materials. Until now, several review articles have been published to summarise the excellence of graphene and its derivatives, which focused mainly on a single application area of graphene. However, no single review is found to comprehensively study most used fabrication processes of graphene-based materials including their diversified and potential application areas. To address this genuine gap and ensure wider support for the upcoming research and investigations of this excellent material, this review aims to provide a snapshot of most used fabrication methods of graphene-based materials in the form of pure and composite fibres, graphene-based composite materials conjugated with polymers, and fibres. This study also provides a clear perspective of large-scale production feasibility and application areas of graphene-based materials in all forms. Since the discovery of graphene and its extraordinary electrical and mechanical potentials, graphene has been studied comprehensively and has become the centre of attraction for research and development ,2,3,4. B2-carbon atoms bonded together in a two-dimensional (2D) honeycomb lattice, and it can be synthesised either by top-down processes, e.g., mechanical/electrochemical/chemical exfoliation of graphite, or bottom-up methods, e.g., chemical vapor deposition and chemical synthesis [2 bonds in the structure and the electron configuration of graphene, it possesses an ultra-high mechanical strength, an electronic band that is tunable, outstanding thermal conductivity, and excellent elasticity [Graphene, the fundamental carbon allotrope, is formed by spynthesis ,13. As synthesis ,13,14. Iynthesis ,16,17,18ynthesis . Althougynthesis ,20. It hynthesis ,22. Besiynthesis ,24. Unliynthesis . Moreoveynthesis ,20. Besiasticity . As a reasticity ,27.Graphene-based materials have been used extensively in so many application areas such as in the field of energy, wearable technologies, agriculture, medical and healthcare, automobile, marine, and aerospace. The need for renewable energy to meet the pollution-related crisis of the current century can be addressed significantly with graphene/polymer composite materials. The solar cells especially, Li-ion batteries, and microbial fuel cells are prominent examples of the application of graphene/polymer composite in renewable and green energy. Additionally, human body temperature, blood pressure, and heartbeat rate can be easily monitored with sensors developed from graphene/polymer composite materials. Moreover, these materials can be used successfully in drug delivery systems, gene therapy, DNA sequencing, tissue engineering, and artificial bones, bioimaging, and potential cancer therapies ,33,34,35Until now, several published review articles have explored the production process, physical and chemical properties, as well as applications of graphene-based materials, which can be used in diversified application areas ,50,51,52The production and use of graphene-based materials are continuously increasing over the last two decades. The number of articles published from 2001 to 2020 on the graphene-based composite materials  and their different production methods are summarised in It is evident that the research interest on the graphene-based materials and their manufacturing techniques is increasing day-by-day. The following describes the most used approaches of the production of graphene-based materials.Graphene fibres can be fabricated using solution spinning techniques such as wet spinning, dry spinning, and dry jet spinning processes. The fabrication of pure graphene fibres using the melt spinning technique is not applicable because of its high temperature at melting point (~4600 °C) . Therefo2SO4, 200 mL) are mixed and stirred continuously overnight. Then potassium permanganate  is added very slowly until the colour of the mixture turns green. Next, de-ionised water  is gradually added, changing the colour of the mixture from green to purple to brown. After that, hydrogen peroxide  solution is added dropwise into the mixture until the colour of the solution turns light yellow. Subsequently, hydrogen chloride  solution  is added into the mixture and stirred for 30–40 min before it is centrifuged for 20~30 min. Finally, the solution is repeatedly washed around 6–7 times with DI water [Before the fabrication of the pure graphene fibres, graphite is required to be converted into graphene oxide (GO). This is because the 2D structure of graphite is made of weaker intermolecular bonding, difficult to reform into a fixed attachment by the direct layer assembling . BesidesDI water ,79. In tide HCl, 0 mL soluDI water . These GThe wet spinning of graphene fibres has been investigated widely because it is an easy process, lower prerequisite of apparatus, and homogeneous dispersibility of GO sheets in the solvents . To prodThe preparation of a suitable dope solution is an important step to assure the optimum spinnability of the GO fibres. Water is mostly used to disperse or dissolve the GO sheet in the production of the GO dope solution. The size of the GO sheets, viscosity, and the concentration of the GO dope solution are also important factors affecting the spinnability of the GO fibres . It has 2, CuSO4, and CaCl2 is reported as a precipitating agent, where the presence of excess metal ions can be removed by the subsequent washing, drying, and thermal treatment of the fibres [Xu and Gao discussed the properties of the LCGO solution by preparing an extensively soluble single-layered GO with a high width/thickness ratio (aspect ratio) . Later, e fibres ,94,95. Fe fibres . As it ie fibres .After the spinning process, the dried graphene fibres go through the chemical reduction processes , or the thermal reduction process . The reduction process aims to remove the oxygen-containing groups from the fibres and repair the lattice defects of the graphene structure (graphitic network), which will eventually increase the electrical conductivity and other functional properties of the fibres ,67,86,96The most commonly used techniques of gPCs fabrications are; solution mixing, melt blending, in situ polymerization, and high shear mixing–calendaring, which are discussed in detail in the following sections . GeneralIt is to be noted that the composite fabrication techniques influence the dispersion of graphene and/or its derivatives in the polymer matrices and will affect the performances of the composite materials . The molSolution mixing is the easiest and the most widely used technique for the large-scale production of graphene/polymer composites. This method is suitable for both thermoplastic and thermoset polymer resins. It usually involves three steps including (i) Dispersion of filler in a suitable solvent, (ii) Incorporation of the polymer, and (iii) Removal of the solvent by distillation or evaporation ,106. As Melt blending is another practical and popular composite fabrication technique, especially for thermoplastic polymer composites. It is eco-friendly, cost-effective, and also worthy of large-scale manufacturing of nanocomposites . This teIn-situ polymerisation is an effective technique ensuring the homogenous dispersion of nano-fillers in the polymer matrices. This technique facilitates the formation of a strong interaction between the polymer matrix and reinforcement . In this technique, graphene or modified graphene is first mixed and swollen in a monomer solution. Then, these graphene materials are ultrasonically dispersed in the solution and a suitable initiator is added. Finally, the polymerisation process commences either by heat or radiation . The visRoll to roll  milling is also another technique that ensures the homogenous dispersion as well as the high filler contents of polymer matrices to improve composite performances ,139,140.The graphene nanomaterial can be incorporated with the fibre-reinforced polymer composites (FRPCs) by following three methods as described below. In the first method, referred to as the ‘Matrix Modification Method’, graphene is mixed with a suitable polymer and then applied to the reinforcement fibre by either dip coating, hand lay-up, or spray-up techniques. In the second method, known as the ‘Fibre Modification Method’, graphene nanomaterial is directly integrated onto the fibre surfaces via electrophoretic deposition (EPD), chemical vapour deposition (CVD), and chemical grafting techniques. The third method is the combination of the two methods, where graphene can be incorporated with both the fibre and polymer matrix simultaneously to boost the composite properties for the desired end uses .This is the most widely used method to introduce nanomaterials with the polymer composites. The fabrication steps of the gFPCs via the matrix modification method are demonstrated in Graphene nanomaterials can be directly incorporated with the textile preforms including fibre, tow, and fabrics. It has been found that electrophoretic deposition (EPD) and chemical vapour deposition (CVD) methods are the most commonly used techniques to graft graphene and some other nanomaterials including amorphous carbon, carbon nano-fibres, and carbon nanotubes .Electrophoretic deposition (EPD) is a low-cost and practical technique to introduce the graphene nanomaterials onto the surface of the textile preforms ,159. The3)2.6H2O, Fe(NO3)3.9H2O, and Ni(NO3)2·6H2O are used to reduce the temperature of the CVD process and to boost the pyrolysis of the feed gases. These catalysts act as the active sites for depositing graphene film. The annealing process at the elevated temperature causes H2 to dissociate into atomic H, which ultimately leads to the dehydrogenation of hydrocarbon precursors and carbon radicals start to deposit onto the metallic substrate integrated with high-performance fibres [4) concentration plays an important role in the graphene film growing kinetics. Monolayer graphene and multilayer graphene film are found to be deposited onto the metal substrate while using the lower and higher concentration precursors, respectively [2H2 results in less defective graphene [The chemical vapour deposition technique has recently received considerable attention because of the large-scale graphene synthesis with controlled architecture and low defects ,175,176.e fibres ,181. Grae fibres . The CVDe fibres ,183,184.e fibres . Hydrocaectively . Acetylegraphene . Althouggraphene ,189. The2 is used as the connecting agent (3) and functional carboxylic groups (-COOH) are introduced onto the fibre surface. Then, a thin layer of the coupling agent is coated on the carbon fibre surface and finally is treated with modified graphene to be grafted onto the fibre surface. This technique involves some demerits; it is costly, requires multisteps for grafting, uses toxic and corrosive chemicals, damages the fibre surface and deteriorates mechanical properties of fibres, and sometimes it is not possible to remove the chemicals from the fibre surface completely [This is one of the latest techniques to graft graphene or its derivatives onto the surface of the fibres. Chemical grafting is a way of connecting graphene with high-performance fibres such as carbon and aramid fibres by the covalent bonding via a variety of connecting or coupling agents such as hexamethylene diisocyanate (HDI) tri-polymer, poly(amidoamine) (PAMAM) dendrimers ,192,193.ng agent . In thismpletely ,197.Graphene-based materials are found in a wide variety of advanced applications because of their extraordinary structural and functional properties . As a reGraphene-based materials are used in producing renewable energy, which is one of the critical issues of today’s world. Different types of solar cells are produced from graphene to convert solar energy into other forms of energy . For insLi-ion battery (LiB) is another prominently used storage system. However, the anode and cathode materials show low life due to the continuous volume expansion and contraction caused by the lithiation/de-lithiation reaction ,211. Fur−2 and energy density of 37.2 µWh cm−2 have been shown by the graphene fibre fabricated with a titanium core that was prepared using the alternately dipping (AD) technique [2 hybrid supercapacitor demonstrated up to 93% capacitance retention after 1000 cycles, which was a promising outcome to apply in the field of wearable fabric [2 continuous fibres (GTF) are prominent candidates for use in environmental remediation [2 continuous fibres (GTF) have photocatalytic activities under both UV irradiation and visible light irradiation [Graphene-based materials are the subject of huge attraction in the field of wearable technologies. The aim is to assemble fibre-based supercapacitors that are flexible with excellent electrochemical properties. For example, supercapacitors (SCs) are one of the popular examples of wearable storage and conversion devices. SCs are being used in hybrid electric vehicles, energy management, memory backup devices, and industrial power . Differeechnique . In anote fabric . Polyuree fabric . In everediation ,219. Moradiation .Graphene quartz fibre (GQF) are suitable for industrial electronic heaters and real-time biomimetic gas sensor ,235. GasWater contamination with various toxic materials originated from both organic and inorganic sources, for example, industry, agriculture, and household affairs is an alarming topic from the environmental sustainability point of view. Aquatic species are on the verge of extinction due to mass water contamination. Although more than 70% of the Earth’s surface is covered with water, it is becoming increasingly difficult to find clean usable water ,250. TheThe amazing properties of graphene have laid the foundation of a new horizon of possibilities for various applications and the application of graphene/polymer nanocomposites in the biomedical industry is one of them. Since the first report on the use of graphene in the medical field in 2008 ,255, mucBecause of the atomic thickness and extremely high conductivity properties of graphene, it is extensively used in bioimaging materials. Graphene/regenerated silk fibroins (RSFs) composite fibres produced by the wet spinning method have the potential for being used in tissue engineering, biomedical, and biotechnological areas as they have shown significant antimicrobial efficacy against both gram-positive and gram-negative bacteria . Silica At present, the emphasis is on application of lightweight but strong materials in various structural engineering industries, especially in the automotive, aerospace, and marine industries ,277,278.Lightweight, strong, and cost-efficient sports items are made from fibre-reinforced polymer composite materials with multi-functional properties. Nowadays, a wide variety of sports items are made of graphene/polymer nanocomposites among them tennis rackets, helmets, hockey sticks, bicycle frames, skis, and golf clubs ,283,284.In this review, the fabrication methods of graphene-based materials and their potential applications in several fields were discussed. The wet spinning process is one of the most followed methods in the fabrication of pure graphene and composite graphene fibres along with natural and synthetic polymers. These fibres are later reduced with chemical or thermal approaches to make electrically conductive graphene fibres. On the other hand, the composite graphene materials incorporating fibres or thermoplastic and thermosetting polymers are fabricated using the matrix modification process, fibre modification process, or the combination of these two processes. These are the cheap, environmentally friendly, and economically feasible approaches to facilitate the industrial large-scale production of graphene-based composite materials. The fabricated graphene materials and their composites are applied to diverse application areas due to the excellent mechanical properties and functional characteristics of graphene and its derivatives. Sensors, nanocomposites, electrodes for solar cells, medical equipment, different sports items, parts, and frames of automobiles are some examples of the application of graphene-based materials. In addition, these materials are also used in wastewater treatment and water purification systems.Further applications of graphene-based material are expected in nanocomposite industries. Although graphene is currently used in this industry, an excellent understanding of this material is yet to be discovered. Graphene is used in the biomedical and drug-delivery systems; however, focused research is required in the utilisation of all the positive qualities of this remarkable material. This includes investigating the antimicrobial aspects, enhancing biocompatibility, and applying graphene materials to the removal of toxic elements to protect the environment. Apart from these, further research can be carried out to find an optimum and eco-friendly reduction process of graphene that can demonstrate higher electrical conductivity with excellent mechanical properties, which can bring a breakthrough in all application fields. In a nutshell, graphene is a wondrous material in this world that can be tailored in various ways to use in diversified application areas.


The anti-greenhouse gas dimethylsulfide (DMS) is mainly emitted by algae and accounts for more than half of the total natural flux of gaseous sulfur to the atmosphere, strongly reducing the solar radiation and thereby the temperature on Earth. However, the relationship between phytoplankton biomass and DMS emissions is debated and inconclusive. Our study presents field observations from 100 freshwater lakes, in concert with data of global ocean DMS emissions, showing that DMS and algal biomass show a hump-shaped relationship, i.e. DMS emissions to the atmosphere increase up to a pH of about 8.1 but, at higher pH, DMS concentrations decline, likely mainly due to decomposition. Our findings from lake and ocean ecosystems worldwide were corroborated in experimental studies. This novel finding allows assessments of more accurate global patterns of DMS emissions and advances our knowledge on the negative feedback regulation of phytoplankton-driven DMS emissions on climate. Dimethylsulfide (DMS) and its precursor, Dimethylsulphoniopropionate (DMSP), are majorly produced by algae  and also−1 [In recent years, this hypothesis has been debated based on, for example, meteorological evidence ,17. In a−1 , however−1 , negativ−1 ,22, as w−1   where we quantified DMS concentrations, phytoplankton biomass  and various environmental parameters, such as pH, transparency, dissolved oxygen, conductivity and so on. We also collected data of DMS and Chl-a simultaneously from a global sea-surface DMS database  . However, the intercept of DMS was higher in oceans than in lakes, indicating that there may be more sources of DMS at low Chl-a concentration in marine than in freshwater environments.Based on previous studies ,19,24,25−3 ,19, wher−3 [−3 . Hence, −3 [−3 ,23. Our In our study lakes, a strong relationship was found also between DMS concentrations and pH, with a breakpoint at pH = 8.09 ± 0.05 Fig. c. Simila−1 with eight different pH levels ranging from 7 to 10.5 in the laboratory. Accordingly, we found that DMS concentrations decreased when pH increased to >8.0   in coastal regions and it decreased to 1.6–1.7 nM L−1 in the open oceans , we depicted the spatial pattern of DMS concentration in the global oceans by using 14-year 2003–16) averaged monthly composites of MODIS Chl-a data . The res–16 avera studies ,43–46  in the global sea-surface DMS database [−1) rank in the middle of previous estimates (1.5–2.5 nM L−1) (Supplementary Table 3). Thus, the global pattern of DMS concentrations provided here is likely more precise than in previous studies [Based on the hump-shaped relationship  and remote sensing data , the spadatabase  or on emdatabase . However studies ,43–46.In a broader context, our results suggest that, at higher pH, DMS is broken down, leading to a reduced DMS concentration in natural waters. In high productive waters, e.g. mainly in freshwaters and coastal areas of the oceans, high photosynthesis rates may elevate the pH far above 8.1, thus leading to a decline in DMS through pH-driven degradation Fig. . Our resPhaeocystis spp. and coccolithophore Gephyrocapsa oceanica, to pH 8 in the bacterium Ruegeria lacuscaerulensis and Pseudomonas doudoroffii and up to pH 10.5 in a Phaeocystis strain [In addition to enhanced degradation of DMS at high pH, pH changes may also affect phytoplankton that produce DMSP, thereby altering DMS production. A few experimental studies addressing this issue have been performed, although the results are not consistent. For example, when pH declined from 8.3 to 7.49, the algal DMS production declined by ∼50%–60% ,29,41, wAnother widespread role of DMS is its utilization by top predators in biological food webs, specifically among ocean-feeding seabirds when locating crustacean prey, which concentrate at sites with high algal abundances ,48. HencIn brief, the ‘CLAW’ hypothesis proposed an ideal scenario of how biological processes regulate global climate through affecting cloud properties via sulfur-containing aerosols , yet mos2, with a total area of ∼18 800  km2 and a longitude and latitude range of ∼10° × 10° . Water temperature, depth, pH, transparency, dissolved oxygen, conductivity, salinity, turbidity, oxidation-reduction potential and suspended solids were measured in situ by a multi-parameter water-quality sond  and Secchi disk. Physiochemical variables in the water samples, such as total nitrogen, nitrate, nitrite, ammonia, total phosphorus, phosphate, permanganate and Chl-a concentrations, were measured in the laboratory using chemical methods. The water samples for DMS detection were gravity-filtered using a replaceable film needle filter  under the same conditions in the field (a recovery test of DMS through gravity filtration is shown in the Supplementary Note), immediately, and 50 mL of filtered water of each sample were instantly frozen without bubbles and transferred to the laboratory, and then thawed at 4°C before DMS detection. We also collected 426 data sets of surface oceans, including simultaneously detected DMS and Chl-a, from the global database of sea-surface DMS from 20 contributors during 1981 and 2012 . The relationships between environmental parameters and DMS concentration in lakes were analysed .We sampled 246 sites from 100 shallow freshwater lakes in the eastern plain of China during the summers of 2008 and 2009. Surface areas of the lakes ranged from 10.2 to 2933 kmAll DMS samples were detected by Eclipse 4660 Purge and Trap Sample Concentrator  and Gas Chromatography Mass Spectrometry  with a Tenax trap  and an HP-5MS UI column . All parameters and run settings were identical to our previous study .−1. Each solution was prepared before use and the DMS concentrations in the different pH solutions were detected at 0.5, 2.0, 5.0, 10.0 and 24.0 hours after being prepared.Pure DMS standard  was diluted with methanol  as the first DMS stock solution and then diluted with ultrapure water as the second DMS stock solution. To eliminate the possible interferences of biological or chemical factors  on DMS degradation, tris-HCl (pH 7.1–8.9), glycine-NaOH (pH 8.6–10.6) and ultrapure water were used to modulate pH solutions. Then the second DMS stock solution was diluted to the above buffer solutions  with a concentration of 100 ng LP.foveolarum  was obtained from the Freshwater Algae Culture Collection at the Institute of Hydrobiology (a verification experiment of DMS production from P.foveolarum is shown in the Supplementary Note) and cultured with axenic Blue-Green Medium 11 solution . At the beginning, we adjusted the BG11 culture medium to 8-pH levels (pH 7.0–10.25) with tris-HCl and glycine-NaOH, respectively, and then the algae were inoculated in the above mediums. Each treatment had 300 mL algae with ∼1.0 × 106 cells mL−1 and each pH group had three replicates. All groups were cultured in an algal incubator  for 2 days, and then the DMS and pH in each group were detected. Because of buffers and short duration, the pH of each culture medium changed little at the end.Pure E.huxleyi  was obtained from the Center for Collections of Marine Algae at Xiamen University and three replicates were cultured with axenic f/2 Medium  solution for 22 days. DMS and Chl-a were detected every 3 days and pH was detected every day.Pure R2 = 0.34, RMSE = 2.55 ng L−1) in the form of equation (1),We first established an empirical relationship between DMS and Chl-a concentrations in ocean surface water based on measured data at 426 sites from the global sea-surface DMS database . The logy0 = 2.00, a = 0.83, b = 0.35 and x0 = 0.60. Parameter y0 represents a baseline (log-transformed) concentration throughout large areas of low-DMS waters. According to Anderson et al., the model is unable to resolve DMS variability at low log10(Chl-a) [where 0(Chl-a)  and thus0(Chl-a) .We used piecewise linear regression by R version 3.2.5  to confirm the relationship between DMS, Chl-a and pH from field data. SPSS version 20.0 , OriginPro 2015 , Statisticia version 6.0  and ArcGis 10.0  were used to analysis the data and draw the figures.nwaa140_Supplement_FileClick here for additional data file.