# Fileset

[GengFX_s41467-024-49270-5.pdf](https://mdr.nims.go.jp/filesets/517efa98-c1fc-483f-9c7b-01cae2b2ecc9/download)

## Creator

Ling Ding, Tianqi Xu, Jiawen Zhang, Jinpeng Ji, Zhaotao Song, Yanan Zhang, Yijun Xu, [Tong Liu](https://orcid.org/0000-0001-7175-8896), Yang Liu, [Zihan Zhang](https://orcid.org/0000-0002-4047-2278), Wenbin Gong, Yunong Wang, [Zhenzhong Shi](https://orcid.org/0000-0001-8033-8041), [Renzhi Ma](https://orcid.org/0000-0001-7126-2006), Jianxin Geng, Huynh Thien Ngo, [Fengxia Geng](https://orcid.org/0000-0001-5557-4165), [Zhongfan Liu](https://orcid.org/0000-0001-5554-1902)

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Covalently bridging graphene edges for improving mechanical and electrical properties of fibers](https://mdr.nims.go.jp/datasets/b8922676-55d4-4298-80db-8ab8273c373b)

## Fulltext

Covalently bridging graphene edges for improving mechanical and electrical properties of fibersArticle https://doi.org/10.1038/s41467-024-49270-5Covalently bridging graphene edges forimproving mechanical and electricalproperties of fibersLing Ding1,9, Tianqi Xu1,2,9, Jiawen Zhang1,2,9, Jinpeng Ji1,9, Zhaotao Song1,2,9,Yanan Zhang1, Yijun Xu3, Tong Liu 3, Yang Liu3, Zihan Zhang4, Wenbin Gong5,Yunong Wang1, Zhenzhong Shi 1, Renzhi Ma4, Jianxin Geng2,6,Huynh Thien Ngo4, Fengxia Geng 1,7 & Zhongfan Liu 7,8Assembling graphene sheets into macroscopic fibers with graphitic layersuniaxially aligned along the fiber axis is of both fundamental and technologicalimportance. However, the optimal performance of graphene-based fibers hasbeen far lower than what is expected based on the properties of individualgraphene. Here we show that both mechanical properties and electrical con-ductivity of graphene-based fibers can be significantly improved if bridges arecreated between graphene edges through covalent conjugating aromaticamide bonds. The improved electrical conductivity is likely due to extendedelectron conjugation over the aromatic amide bridged graphene sheets. Thelarger sheets also result in improvedπ-π stacking, which, alongwith the robustaromatic amide linkage, provides high mechanical strength. In our experi-ments, graphene edges were bridged using the established wet-spinningtechnique in the presence of an aromatic amine linker, which selectively reactsto carboxyl groups at the graphene edge sites. This technique is alreadyindustrial and can be easily upscaled. Our methodology thus paves the way tothe fabrication of high-performance macroscopic graphene fibers underoptimal techno-economic and ecological conditions.Carbon fibers combine light weight with ultra-high mechanicalstrength and are indispensable components in many high-end appli-cations, such as aerospace/aviation industry, civil engineering, andcompetitive sports1–4. The basic structural unit of a carbon fiber at theatomic level is a graphene layer with carbon atoms in a hexagonallattice arrangement, and these sheets are essentially aligned parallel tothe long axis of the fiber3,4. The carbon atoms in such a unit are linkedby strong covalent σ bonds with a strength of 400 kJmol−1, whichimparts a high theoretical fracture strength of 130GPa and a Young’smodulus of 1.0 TPa5,6. Commercially available polyacrylonitrile andmesophase pitch-based carbon fibers are produced by fusion oforganic fragments followedby extremehigh-temperature annealing toachieve graphitization. However, the formed fibers have only smallgraphene units (a few to tens of nanometers) and low-order turbos-tratic stacking. In contrast, mechanical or chemical exfoliation fromgraphite can produce graphene with sizes of the order of tens ofReceived: 1 November 2023Accepted: 23 May 2024Check for updates1College of Energy; School of Physical Science and Technology & Institute for Advanced Study, Soochow University, Suzhou 215006, China. 2BeijingUniversity of Chemical Technology, 100029 Beijing, China. 3Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123,China. 4National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan. 5School of Physics and Energy, Xuzhou University of Technology,Xuzhou, China. 6State Key Laboratory of SeparationMembranes andMembrane Processes; School of Material Science and Engineering, Tiangong University,Tianjin 300387, China. 7Beijing Graphene Institute, 100095Beijing, China. 8Peking University, 100871 Beijing, China. 9These authors contributed equally: LingDing, Tianqi Xu, Jiawen Zhang, Jinpeng Ji, Zhaotao Song. e-mail: gengfx@suda.edu.cnNature Communications |         (2024) 15:4880 11234567890():,;1234567890():,;http://orcid.org/0000-0001-7175-8896http://orcid.org/0000-0001-7175-8896http://orcid.org/0000-0001-7175-8896http://orcid.org/0000-0001-7175-8896http://orcid.org/0000-0001-7175-8896http://orcid.org/0000-0001-8033-8041http://orcid.org/0000-0001-8033-8041http://orcid.org/0000-0001-8033-8041http://orcid.org/0000-0001-8033-8041http://orcid.org/0000-0001-8033-8041http://orcid.org/0000-0001-5557-4165http://orcid.org/0000-0001-5557-4165http://orcid.org/0000-0001-5557-4165http://orcid.org/0000-0001-5557-4165http://orcid.org/0000-0001-5557-4165http://orcid.org/0000-0001-5554-1902http://orcid.org/0000-0001-5554-1902http://orcid.org/0000-0001-5554-1902http://orcid.org/0000-0001-5554-1902http://orcid.org/0000-0001-5554-1902http://crossmark.crossref.org/dialog/?doi=10.1038/s41467-024-49270-5&domain=pdfhttp://crossmark.crossref.org/dialog/?doi=10.1038/s41467-024-49270-5&domain=pdfhttp://crossmark.crossref.org/dialog/?doi=10.1038/s41467-024-49270-5&domain=pdfhttp://crossmark.crossref.org/dialog/?doi=10.1038/s41467-024-49270-5&domain=pdfmailto:gengfx@suda.edu.cnmicrometers, the direct assembly of which is believed to be an effec-tive alternative approach for next-generation high-performance car-bon fibers7–9. The large size of the units also offer the possibility toimprove the electron conductivity of the assembly. Graphene-basedcarbon fibers thus combine light weight, high strength, and excellentelectrical conductivity, and are therefore of great interest as potentiallow cost, light weight substitutes for copper wires in weight sensitiveapplications, such as large military and scientific satellites.Macroscopic graphene fibers have been prepared from two-dimensional graphene oxide (GO) sheets through a solution-basedwet-spinning technology followed by treating them under reducingconditions10. These reports have highlighted the importance of regularalignment of graphene sheets and decreasing structural defects toenhance the mechanical and electrical properties of graphenefibers11–13. The first report estimated the tensile strength of chemicallyreduced GO fibers to be around 200MPa10 and recently a benchmarkvalue of 2.25 GPa was reached by flattening random graphenewrinkles13. Annealing at very high temperatures (>2500 °C) was foundto annihilate atomic defects on graphene sheets and promote theformation of graphitic crystallites11,14, resulting in graphene fibers witha tensile strength of 3.4 GPa and Young’s modulus of 342GPa13. How-ever, using high annealing temperatures is often not desirable fromboth economic and ecological perspectives. Thus, if we want toreplicate the excellent physicochemical properties of graphene inmacroscale graphene fibers, it is of utmost importance to develop newstrategies to prepare high performance graphene fibers, preferably atnear room temperature.Given that previous efforts to align sheets along thefiber axis havemet with some success, the integrated tensile fracture stress as well aselectrical conductivity are predominantly determined by in-planeinter-sheet interactions at the sheet edges. In graphene fibers reportedhitherto, individual graphene sheets are connected mainly in theoverlapping stacking direction throughπ-π bonding (and electrostaticinteractions) with little or no in-plane inter-sheet junctions along thefiber axis7–14, which places an upper limit on themechanical propertiesof the macroscopic graphene fibers formed therefrom. Thus, the keyto translating the excellent properties of individual graphene to themacroscopic scale lies in preventing tensile fracture and in providingelectron conducting pathways, particularly at sheet edges.In this context, we report a simple strategy to create bridges at theedges of individual graphene sheets through covalent conjugation ofan aromatic amide bond, by selectively reacting the carboxyl groups atthe sheet edges with an aromatic amine. Results show that a significantimprovement in both mechanical and electrical conducting perfor-mance can be achieved for the assembly. The design motif andstructural model of the resultant graphene fibers with amide linkagesare shown in Fig. 1a, b. If we consider an amide linkage, it is known thatthe conjugation of the N lone pair with the carbonyl group in amide(–C(=O)NH–) generates a three-center π-system in a rigidly planarconfiguration15. The aromatic amide that bridges the graphene sheetsthus can serve to extend electron conjugation over larger sheet areas.Such links offer three important advantages. First, there is a possibilityto create extended conjugation between the aromatic amide bridgesand the neighboring graphene sheets. Larger linked sheets areexpected to show enhanced π−π interaction, which facilitates orderedstacking of the sheets. Secondly, the extended conjugation can form aπ electron cloud over relatively larger connected areas of grapheneand increase electronmobility across the graphene sheets. Finally, therobust covalent amide –C(=O)NH– bond has a high bond energy closeto that of a C–C bond15, which, along with enhanced π−π interactions,could lead to improved axial stress transfer among the partiallybridged graphene sheets and thereby enhance the mechanical per-formance of the assembly.Results and discussionGraphene fiber assembly from GO sheetsGO sheets were prepared according to a previously reportedmodifiedHummers method16. GO sheets have abundant polar oxygen-Fig. 1 | Edge bridging of graphene sheets with covalent conjugation ofaromatic amide. a Schematic showing the principle of the assembly process. In-plane aromatic amide linkages are generated by the selective reaction of the edgecarboxyl groups of graphene oxide (GO) sheets and aromatic amine, highlightedby the green shading region. GO and acid catalyze the direct amidation.b Fiber constituted by regularly stacked aromatic amide-bridged graphenesheets. Inset: Digital image of two separate films with edge-connected byimmersing in the aqueous coagulant amine; the connected edge transformsto a dark color. The aromatic amide linkage yields extended conjugation andenhanced π-π interaction, which, along with the inherent covalentfeature of the linkage, improves both structural robustness and electricalconductivity.Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 2containing functional groups decorating the basal plane and edges.This leads to negative surface charges and allows stable aqueous dis-persions to be formed. The oxygen-containing functional groups aretypically hydroxyl (C–OH), epoxy (C–O–C), and carboxyl (–C(=O)OH)groups. Atomic force microscopy (AFM) and scanning electronmicroscopy (SEM) (Supplementary Figs. 1, 2) showed that the GOsheets had lateral sizes predominantly in the range of 10–70μm and amean thickness of ~1 nm. This high aspect ratio enabled the formationof a liquid crystalline phase with short-range sheet alignment (Sup-plementary Fig. 3). The presence of oxygen-containing groups wasverified using X-ray photoelectron spectroscopy (XPS) and the C:Oatomic ratio was quantitatively estimated from the survey data to be1.89 (Supplementary Fig. 4).In accordance with the commonly accepted Lerf–Klinowskistructural model17, oxidized GO has hydroxyl (C–OH) and epoxide(C–O–C) groups on the basal ring planes, whereas the sheet edges arepreferentially terminated with carbonyls (C=O) and carboxyl (–C(=O)OH) groups. Carboxyl groups are strong electrophiles and can reactwith nucleophilic amines to form amide linkages15,18. It has also beenshown that the presence of GOor an acid enhances the electrophilicityof the carboxyl group, due to which a direct amidation is enabledwithout the need for an intermediate acyl substitution step19,20. Takinga cue from these previous works, we selected aqueous 1,2,4,5-tetra-aminobenzene tetrahydrochloride as the coagulant during fiber wet-spinning for a direct on-site condensation amidation of carboxylgroups present at GO edges. The details for the reaction mechanismare provided in Supplementary Figs. 5–7. Previous works have usedsimple aliphatic or aromatic diamines as cross-linkers21–24, but it wasfound that in the absence of an acid these amines usually annihilatedsurface oxygen groups onGO, accompanied by the formation of a veryhigh density of vacancy defects25. As a result, the integrated mechan-ical properties of the GO assembly deteriorated (SupplementaryFig. 8), and such composite membranes were mostly studied in thecontext of separation applications. We have considered other possiblecompeting reactions, for example, electrostatic interaction to form asalt, reaction between carboxyl and hydroxyl to form esters (a recentreport of smart way to self-crosslink GO)26. These reactions, if theyoccur, should beminor (please see Supplementary Fig. 8 for a detaileddiscussion). In the present case, the high H+ concentration ensuredthat the reaction of edge carboxyl groups with the Ar-NH2 to form theamide was predominant. The other groups present on GO have rela-tively lower reactivities at ambient temperature, as experimentallyproven from XPS characterization (Supplementary Fig. 10). It isimportant to note that although the amidation may not go to 100%completion and only a partial bridging of edges is achieved, its pre-sence is expected to increase π-π interactions between larger sheets,thus providing pathways for both electron and stress transfer.The feasibility of the direct amidation to create local amidebridges in GO was experimentally tested by connecting two individualGO films in aqueous 1,2,4,5-tetraaminobenzene tetrahydrochloride.We found that the two films merged at the edges into one larger film.The formation of a chemical connection by the conjugating amidestructure darkened the sample color (digital image shown in inset ofFig. 1b and the amidation process in Supplementary Fig. 11), stronglyindicating increased electron conjugation in the structure. We notehere that the so-connected film showed improvement of tensilestrength from ~200 to 470MPa. Interestingly, immersing the wholefilm in the coagulant led to a dramatic increase in tensile strength to~1000MPa and also in electrical conductivity from 0.2 × 105 to1.0 × 105 Sm−1. Owing to the simplicity of this reaction, we believe thatit can be easily integrated with the industrially scalable wet-spinningprotocol for making fibers.Aqueous GO was made to flow through a confined channel intothe coagulant of aqueous 1,2,4,5-tetraaminobenzene tetra-hydrochloride. Solidification of stable fibers occurred due to thecondensation reaction between the carboxyl groups at the edges ofthe GO sheets and the amine. We note here that no coagulationoccurred when using an aromatic diamine with amino groups on thesame side of the benzene ring, for example, 1,2-diaminobenzenehydrochloride, while also forming an amide bond (SupplementaryFig. 12), whichconfirms the presenceof sheet bridgingby the groups atpara positions in our fiber system. The coagulated GO was chemicallyreduced in a second step to remove in-plane oxygen-related moieties,producing graphene fibers by ordered face-to-face stacking of gra-phene sheets with aromatic amide bridge connections (experimentaldetails in Supplementary Information).The graphene fibers obtained by our method showed a very highmechanical performance with a tensile strength of 3.54 ± 0.25GPa anda Young’s modulus of 340± 32GPa. This is much higher than the bestrecorded values of 2.25GPa and ~180GPa reported so far13. Moreover,the electrical conductivity along the fiber axis was measured to be1.5 × 105 Sm−1 (experimental details on mechanical and electricalproperty measurement are given in the SI), which is one order ofmagnitude higher than that reported for graphene fibers obtained atsimilar temperatures. Hence, our simple strategy is efficient in inte-grating the properties of individual graphene and is promising for theproduction of high-performance macroscopic assemblies.Structural characterization of graphene fibersWe noted that the fibers formed as described above had an unusualbelt-type morphology, although the nozzle was circular. Figure 2ashows a schematic illustrating the possible coagulation mechanism ascompared to the most prevalent solvent exchange mechanism. Typi-cally, solvent exchange between GO dispersed in dimethylformamideand the commonly used precipitation agent ethyl acetate replicatesthe geometry of the confined channel, likely due to rapid solidificationand the absence of constraints among the sheets. Thus, a tubularchannel invariably produces a fiber with a circular cross section andconserves the random alignment of the aqueous dispersion, as con-firmed from previous reports12,13. We also confirmed this from themorphology and microstructure characterization of our own controlsample (Supplementary Figs. 13–15). An ordered assembly of GO into acompact anisotropic flat belt-like structure could only be achieved bymodifying the geometry of the confinement channel using a flatchannel with low height12. When using our selected aromatic amine asthe coagulant,we found that a beltmorphologywithordered assemblycould be spontaneously generated. We have excluded the possibleeffect of a change in surface hydrophilicity after assembly to accountfor the unusual belt morphology (Supplementary Fig. 16). By trackingthe solidification of the GO colloid at the nozzle at the start of coa-gulation, we found that the freshly produced fiber replicates the con-finement geometry, but aflattening of the assembledfiber occurs soonafter contact with the reaction with the coagulant (SupplementaryFig. 17). Thus, a fiber with belt morphology could be obtained evenwhen using a triangular nozzle (Supplementary Fig. 18). Besideschannel geometry, the assembled belt shape was found to be insen-sitive also to nozzle size and GO concentration. It should be noted thata larger diameter of nozzle translates to less constraint on the sheets,and the fiber structure would reflect this intrinsic interaction betweensheets. However, the belt morphology was conserved for all tubularchannels with inner diameters in a test range of 160–1500 μm (Sup-plementary Fig. 19). As mentioned above, varying the GO concentra-tion did not change the belt-shape of the fibers, but it was possible totune the thickness by having different GO concentrations (Supple-mentary Fig. 20). All these results together indicate that the absence ofconstraint from the confining nozzle and the intrinsic edge connectionled to the unusual belt morphology.The unusual belt morphology is indicative of an oriented stackingof sheets. This was confirmed also from scanning electronmicroscopy(SEM) observations; a regular stacking of sheets was observed,Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 3cdirect assembly by solvent exchangeloose, disorderedCircularfiberassembly by selective edge covalent linkageRibbonfiberHighly oriented, ordereda b10 μm10 μmIntensity (arb. units)Azimuthal angle (o)-80 400-40 8019.4 of g hCut linee10 nmdCut line10 nmIntensity (arb. units)Intensity (arb. units)q (Å-1)q (Å-1)01001.01 2 3-3 -2 -1 0 1.5 2.0 2.5 3.0MeridionalEquatorialFiber axis002100100002Fig. 2 | Oriented and compact stacking of planar graphene in theassembled fiber. a Schematic of the process to assemble GO sheets into a mac-roscopic fiber with belt-type morphology with highly oriented and ordered stack-ing structureby selective edge linkage. For comparison, thedisordered assemblyofGO sheets into a fiber with the usually observed circular cross-section is also illu-strated,which replicates the needle geometry due to absenceof constraint. Typicalcross-sectional SEM images of (b) fiber with amide bridges and (c) the control fiber.Representative HR-TEM images for (d) a cross-sectional slice and (e) a transverse-sectional slice of our amide-connected fiber. f Two-dimensional WAXS diffractionpattern of graphene fibers. The equatorial andmeridional scattering directions areindicated by cyan and bronze arrows. Color bar refer to the intensity in arbitraryunits. g The corresponding one-dimensional scattering profile by integratingequatorial and meridional axes of (f, h) azimuthal scan integral curve for the(002) peak.Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 4continuously extending along the longitudinal direction (Supplemen-tary Fig. 21). The good alignment of the sheets within themacroscopicfibers along the fiber axis was further verified by polarized opticalmicroscopy and wide-angle X-ray scattering (WAXS) pattern analysis(Supplementary Figs. 22 and 23). The improvement in ordered stack-ing was also supported by the reduced full width at half maximum ofthe basal reflection in X-ray diffraction (XRD) pattern as compared tothe neat GO fiber. The interlayer spacing of the stacked sheets wasdetermined to be 0.896 nm (Supplementary Fig. 24), which is a typicalvalue for neatGO sheet stacking12,13, implying the near absence of guestmolecules between sheets.The belt morphology and highly aligned structure were wellconserved during the reduction step (Fig. 2b and SupplementaryFigs. 25–27). The control fiber solidified by solvent exchange alsomaintained its circular geometrywith curved and randomalignmentofsheets (Fig. 2c). Scanning transmission electron microscopy in SEM(STEM-in-SEM) characterization of a thin slice of the cross-sectionshowed high alignment and regular stacking of sheets over large areas(>micrometer size) in the fiber with amide linkages (SupplementaryFig. 28), which could account for the obtained belt morphology. Itshould bementioned that external stretching is applied only along theaxial direction and the cross-sectional microstructure is entirelydeterminedby intrinsic interaction between sheets, due towhich somecurved structures are also spotted. A longitudinal thin slice with thelength of ~10μmwas also imaged to gain information on the alignmentand stacking of sheets along the fiber axis direction. Along its wholelength, the fiber showed straight lattice fringes (SupplementaryFig. 29). In contrast, the controlfiber showed an obviously less orderedstructure. Cross-sectional images showed that the sheets are curvedand randomly aligned due to the lack of constraints among curvygraphene sheets. This likely accounts for its circular geometry. In thelongitudinal thin slice, a local alignment of sheets is seen due to thestretching applied along the fiber axis, but misalignment of sheets wasstill obviously observed over large area (Fig. 2c and SupplementaryFigs. 14 and 15). High-resolution TEM was employed to obtain atomic-scale information; example images for cross- and transverse sectionsare displayed, respectively, in Fig. 2d, e (more images in Supplemen-tary Figs. 28 and 29). Although some stacking faults and a few randomwrinkles were observed, large areas of almost straight lattice fringes ingood alignment were seen, indicative of a well-aligned stacking ofgraphene sheets. The distance between the observed straight fringes ismostly 0.337 nm, although at stacking faults, the distances are slightlylarger. The spacing was smaller than that of the control sample(~0.350nm) and close to the stacking distance in an ideal graphitestructure. The small value of the interlamellar distance is a furtherconfirmation of the absence of guest molecules between the stackingsheets and compact stacking. The SAED pattern of the in-plane viewshowed the characteristic planes of the graphene structure (Supple-mentary Fig. 30).XRD and WAXS analyses were performed to provide com-plementary information on thefiber structure. XRDdata showedpeaksrelated with compact sheet stacking and in-plane hexagonal structureof graphene (Supplementary Fig. 31). In the two-dimensional WAXSpattern, signals corresponding to (002) and (100) of graphite structurewere also clearly observed (Fig. 2f, g). The full width at half maximumalong the azimuthal intensity distribution of (002) (denoted as theorientation angle and is usually a measure of the degree of texture),was as small as 19.4° (Fig. 2h), indicating a heavily textured structurewith a high degree of preferential alignment of the basal grapheneplanes. The corresponding orientation factor (f) was estimated to be ashigh as 0.896. The gravimetric density of our graphene fibers mea-sured using the sink-float method was found to be 1.90 g cm−3. Thisdensity is much higher than that those reported for chemicallyreduced graphene oxide fibers (Supplementary Table 1), the density ofwhich are typically below 1.50g cm−311,13,27–32. All the data thus confirmthat our belt-shaped graphene fiber consists of regularly stacked pla-nar graphene sheets with high compactness. We believe that theseattributes originate from the enhanced π-π interaction among thelarger amide-linked graphene sheets, which is a direct consequence ofthe selective condensation reaction of some carboxyl groups at thesheet edges with the aromatic amine.The presence of amide linkages was verified by characterizing theGO fiber with a multitude of spectroscopic techniques. In 13C cross-polarization solid-state nuclear magnetic resonance (NMR) spectrum,a clear signal was observed at the chemical shift of ~150 ppm related tothe amide group (Fig. 3a and Supplementary Fig. 32). Furthermore, thehydroxamic test, which is a straightforward chemical test for the for-mation of amide33, gave positive results (Supplementary Fig. 33). In theXPS C 1s spectrum, an obvious shift of the signal corresponding tocarboxyl to lower energy was seen (Fig. 3b), indicating the transfor-mation of carboxyl to amide. The smaller electronegativity and theinductive effect of N relative to O atoms caused the shift. At the sametime, different from the coagulation in simple amines, no intensityattenuation was observed for the –C-OH/C-O-C signal, confirming thatthe surface groups remained intact and the amine selectively reactedwith the edge carboxyl. Figure 3c depicts the N 1s spectrum. As thedifference in chemical shifts inN 1s is generally small, thedata forfibersproduced with an excess of aromatic amine and for the aliphaticammonium salt are also shown. Higher binding energy values areusually related to partially positively charged N, and the signals fromlower to higher energies could successively be attributed to amino,amide, and protonated amines. Using this assignment, we confirmedthat the majority of N in the best amide fiber was in amide form alongwith minor quantities of unreacted amine. As the edge-to-edge con-nection only needs the reaction of 2 amines on opposite sides of thearomatic tetraamine, themajority amide signal is strongly indicative ofa significant degree of boundary-to-boundary bridging of graphenesheets.To confirm that the amide bridging is present mostly within theplane while π-π interactions hold the fiber together in the stackingdirection, we investigated the stability of GO fibers both in the axialand cross-sectional stacking directions in NMP. NMP, being a gooddispersant of GO, can efficiently break π-π bonds and disintegratesimply stacked GO sheets. As a result, the control fiber prepared bysolvent exchange showed swelling in both cross-sectional and axialdirections and the structure collapsewas confirmed by a total absenceof an XRD signal (Supplementary Fig. 34), which is consistent with aprevious report13. Differently, the amide connected fiber showed ani-sotropic swelling, which only occurred in the stacking direction withnegligible change in the fiber axis direction (Fig. 3d). It is also notedthat the swelling was quite slow. No swelling was observed until after3 h, but thereafter, the swelling continued until beyond 72 h. Thestructural integrity and uniform swelling were confirmed from XRDwhich gave a single expanded spacing of 1.424 nm. The GO surface ishydrophilic due to the rich presence of oxygen-containing groups,which means that water can also break π-π bonds by the indefiniteswelling of the GO assembly. Acid in water can additionally break ionbridges formed through electrostatic attractions and was used as apreliminary test in the selection of an appropriate coagulant (Supple-mentary Figs. 8 and 9). The swelling behavior of our fiber in water andaqueous acid are similar to what observed for NMP, just with longertime (~120 h) and lower swelling degree (0.896–1.280 nm). The goodstability in the lateral direction confirms a high-degree of strong che-mical cross-linking, while the longer time needed to initiate swelling inthe vertical direction could be attributed to the enhanced π-π inter-actions originating from the edge bridging or very low degree ofchemical cross-linking.The swollen fiber in NMP could be further delaminated into acolloid through mechanical shearing. Size analysis of the colloid bylaser diffraction spectroscopy showed obvious increase in sheet sizeArticle https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 5(~20–100μm), and SEM images also showed broken parts of bridgedsheets (Fig. 3e and Supplementary Fig. 35). The successful delamina-tion confirms thatweak interactions arepresent in the vertical stackingdirection, which are mostly π-π or minimal chemical interactions. Theexcellent stability in the lateral direction and the obviously enlargedsheet size even after mechanical shaking indicates the presence ofstrong chemical interactions at edges. Taken together, these results,including the selective swelling limited to the stacking direction eitherin water, acid or NMP, the delamination of interlayer connections, theenlarged sheet size after delamination, along with the almost nochange in the in-plane surface structure, substantiate the conclusionthat the covalent amide linkage bridging is basically at the edges. In thevertical stacking direction, enhanced π-π interactions/very low-degreeof chemical cross-linking is present.Mechanical properties of graphene fibersWhile individual graphene sheets are among the strongest knownmaterials with exceptional tensile strength and Young’s modulus, themechanical tensile behavior of macroscopic fibers consisting ofassembled graphene sheets is dominated by inter-sheet interactions,especially those along the fiber axis. The presence of the covalentaromatic amide connectivity at the edges, together with strong π-πinteractions from the ordered and compact packing of connectedsheets, is expected to enhance the mechanical properties of theassembly. Accordingly, the amide connectedGO fiber showed a tensilestrength of 2.01 ± 0.13GPa, and Young’smodulus of 163 ± 18GPa at thefracture strain of 1.25 ± 0.10% (Supplementary Fig. 36). Chemicalreduction to partially restore sp2 hybridization yielded graphene fiberswith increased tensile strength to 3.54± 0.25GPa and Young’s mod-ulus of 340± 32GPa at the fracture strain of 1.10 ±0.09% (Fig. 4a).These values for GO and graphene fibers are both the highestreported so far. The mechanical strength of our fiber with aromaticamide links is 1.5–1.8 times higher that of the documented best per-formance fiber prepared near room temperature, which has no amideconnection (tensile strength of 2.25 GPa and Young’s modulus of~180GPa13; tensile strength of 1.9 ± 0.1 GPa and Young’s modulus127 ± 24GPa using our GO sheets and experimental set-up). In fact, thestrength value is even higher than that of graphene fibers graphitizedat very high temperatures (tensile strength of 3.40GPa and Young’smodulus of ~342GPa)13, and 1.7 times that of graphitization-annealedgraphene fibers with belt morphology obtained by microfluidicassembly (1.90GPa and Young’s modulus of ~309GPa)12. A detailedcomparison of the performancemetrics of our optimal graphene fiberwith values reported in the literature is presented in Fig. 4b and Sup-plementary Table S2. The significant enhancement in mechanicalbehavior could be due to the optimized inter-sheet junctions at theatomic scale and compact stacking at the microscale, both owing toour proposed assembly protocol.Our results show that the introduction of amide links, even whenpresent in low concentration (due to the low concentration of thecoagulant or low GO oxidation degree), still has a positive effect onthe mechanical performance, when compared to fibers purely solidi-fied by solvent exchange. However, overdose of coagulant or a veryhigh GO oxidation degree adversely affects mechanical performance;the former reduces the edge-to-edge connection and the latter dete-riorates the quality of graphene sheets due to excess –OH/C-O-CFig. 3 | Covalent linking of graphene edges by aromatic amide. a Solid-state 13Ccross-polarization NMR spectrum of the amide-connected GO fiber. b XPS C 1sspectra of freeze-dried GO and the amide-connected GO fiber, (c) N 1s spectrum ofthe optimal amide-connected GO fiber. To label the type of N, data for fibersfabricated with excess of amine and aliphatic ammonium salt are also shown.dOptical images of the amide-connected GO fiber swelling in NMP in the axial andstacking directions; right panel: XRDpatterns of the fibers. The anisotropic swellingand the longer time confirm the presence of selective amide linkages at edges andenhanced π-π interactions. Error bars correspond to the statistical error fromindependent measurements from at least 15 locations. e Sheet size distributioncomparison from laser diffraction measurement of the colloid of delaminatedsheets from the swollen amide-bridged GO fiber and pristine GO.Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 6(Supplementary Figs. 37 and 38). The properties of the control fiberprepared by solvent exchange are almost independent of oxidationdegree due to the absence of linkers. Exclusively large sheets may alsoproduce incomplete patching due to the rough edges of the GO sheetsand steric effects (Supplementary Fig. 39). These results confirm theeffectiveness of in-plane bridging of graphene and the fiber preparedunder optimal conditions of amidation showed the greatestimprovement in mechanical and electrical properties.Electrical properties of graphene fibersThe electrical conductivity of graphene-based materials is heavilyinfluenced by structural imperfections. The high electrical con-ductivity results from the delocalized π-bond in the sp2 hybridizedgraphene sheet. Heterogeneous structures, including functionalgroups, sp3 bonds, and edges have been found to disrupt the sp2hybridized conjugated system and are therefore detrimental to elec-tron transport34. In our fibers, in addition to improving themechanicalstrength, the aromatic amide linkages where present also give rise toextended conjugated system with graphene, enabling improved elec-tron conduction at the sheet edges and increasing the overall electricalconductivity. As a result, our macroscopic graphene fibers fabricatedat near-room temperature achieved a notable electrical conductivity of1.50( ± 0.05) × 105 Sm−1. This electrical conductivity is one order ofmagnitude higher than that of the control fiber with no linker(0.32( ± 0.03) × 105 Sm−1) and previously reported graphene fibersprepared at low temperatures (Supplementary Table 3)11–14,27–32. Theorigin of the high electrical conductivity in aromatic amide-bridgedsamples was revealed from Hall effect measurements on film samples,which showed obvious increase in carrier concentration in the samplewhere aromatic amide bridges were present (Supplementary Fig. 40).These results illustrate the importance of such inter-sheet bridges inimproving electron transport between graphene sheets.With the bridging at edge and improvedπ-π interactions betweenstacking sheets, the electrical conductivity of the obtained graphenefiber is more than one order of magnitude higher than that for poly-acrylonitrile (PAN) based carbon fibers (0.1–1.4 × 105 Sm−1). Inciden-tally, this value is comparable to that of mesophase pitch (MPP)-basedcarbon fibers (the best value of 8.3 × 105 Sm−1), without the need forextreme high-temperature annealing14. Although the mechanicalproperties are still inferior to the benchmark of carbon fibers, thesimultaneous enhancement in tensile strength,modulus, and electricalconductivity of our fiber produced near room temperature highlightsthe importance of controlling graphene sheet assembly and theadvantage of using graphene as the precursor for the fabrication ofhigh-performance fibers.Stress transfer in graphene fibersIn practice, themechanical properties of amacroscopic fiber assemblyare highly dependent on the mechanism of stress transfer amongindividual graphene sheets. Raman spectroscopy is a useful tool toquantitatively observe this effect by measuring the shift in character-istic bands under strain35. As depicted in theRamanspectra (Fig. 4c andSupplementary Fig. 41), a downshift in the graphene G-band wasobserved for our fiber because of the stretching strain on individualsheets. This downshift increased over the entire strain range beforefracture, implying that the external mechanical tensile strain wascontinuously transferred to graphene. In sharp contrast, for the con-trol fiber sample solidified by solvent exchange, increasing stresstransfer only occurred at low strain values (Fig. 4d and SupplementaryFig. 41). A further increase in external strain did not bring about afurther G band shift, indicating that the assembly stopped working asan ensemble and internal fracture occurred. The integrity of ouroptimal fiber under fracture can be attributed to covalent amideconnectivity among sheets at edges in addition to strong π-πFig. 4 | Mechanical properties of aromatic amide-connected graphene fiber.a Typical stress-strain curves of graphene fibers after chemical reduction with andwithout amide linking; dotted lines are replica data. b Comparison of themechanical strength with reported values in the literature. Dependence of thedownshift in the Raman G-band frequency on external loading strain of (c) amide-bridged graphene fiber and (d) control fiber with no linking. e Collective breakagemechanism for amide-connected graphene fiber and the split breakagemechanismfor the control fiber with purely physical non-bonding interactions.Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 7interactions between the stacked graphene faces, as compared to thepurely physical non-bonded interactions in the control fiber sample(schematically shown in Fig. 4e). The concerted stress transfer andhigh strain dependence explains the excellent tensile strength of ourgraphene fibers assembled with aromatic amide linkages.Lastly, we notice that our graphene fibers obtained by chemicalreduction at near room temperature still exhibited a high ID/IG ratio(Supplementary Fig. 42). Considering that FTIR and XPS spectrashowed near to no trace of remnant oxygen-containing groups, thehigh ID can be attributed to remnant defects created during the elim-inationof functional groupsor due to incomplete restorationof the sp2network, both of which may necessitate annealing at high tempera-tures of >1500 °C to repair. Thus, although connecting the individualgraphene sheets with a covalent conjugating linker at sheet edges iseffective in improving the assembly structure and integrated proper-ties, the connection of graphene by edge stitching does not alwayslead to an ideal larger graphene sheet. This could be because ofincomplete patching of the sheets due to irregular sheet edges. Simi-larly, certain local defects and stacking faults could not be completelyavoided due to the low preparation temperature. Thus, clearly there isroom for improvement, both in producing connected defect-free largegraphene sheets and in obtaining perfectly stacked sheets by annihi-lating stacking faults through atomic diffusion during annealing.Whileinfinitely large graphene sheets could be an ideal starting point formaking graphene fibers, in practice, this is difficult to achieve. Oursimple edge connection strategy, even when being far from the idealstructure, significantly influences integrated performances. Thus, ourwork demonstrates efficient edge linking as an alternative to replicatethe ideal properties of graphene in macroscopic assemblies.In conclusion, we developed a strategy to obtain a grapheneassembly of macroscopic fibers with high mechanical strength alongwith excellent electrical conductivity at room temperature. Ourexperimental protocol involves the selective creation of amide links atthe edges of graphene sheet by condensation reaction with an aro-matic amine, which likely leads to the formation of extended con-jugating structures. The extended conjugation in turn yields enhancedπ-π interaction between the larger bridged sheets, leading to highlyoriented and compact stacking of graphene into an unusual belt-shapemorphology. These effects together improved the mechanical per-formance and electrical conductivity, and furthermore highlight theimportance of controlling inter-sheet interactions in grapheneassembly. Our work thus introduces away to design high-performancemacroscopic graphene fibers, which could also be interesting for theassembly of other 2D materials and for commercial industrial appli-cations related to high-performance structural materials.MethodsMaterialsExpandable graphite (~300μm) was purchased fromNanjing XianfengNano Material Technology Co., Ltd. Hydrochloric acid (HCl)(~12mol L−1), potassium permanganate (KMnO4) (≥99.5%), and sulfuricacid (H2SO4) (~98%) were purchased from Jiangsu Qiangsheng Func-tional Chemical Co., Ltd. Hydrogen peroxide (H2O2) (30%) was pur-chased from Shanghai Lingfeng Chemical Reagent Co., Ltd. Potassiumpersulfate (K2S2O8) and ethanol (≥99.7%) were purchased from Sino-pharm Chemical Reagent Co., Ltd. Phosphorus pentoxide (P2O5) waspurchased from Energy Chemical Co., Ltd. Aqueous hydroiodic acid(HI, 57 wt%) was purchased from Adamas-Beta. 1,2,4,5-tetra-aminobenzene tetrahydrochloride was obtained from Sigma Aldrich.Ultrapure water was collected using a Direct-Q3 ultraviolet (UV)system.Synthesis of aqueous graphene oxideGraphene oxide (GO) sheets for fiber assembly were prepared fromexpandable graphite, following a previously reported modifiedHummers method. Owing to the presence of sulfur- or nitrogen-containing intercalation agents, the expandable graphite underwenttremendous expansionas the temperature of the systemwas increasedup to 1000 °C for 30 s. This expansion allowed the system to reach avery high degree of oxidation during the oxidation step. Next, pre-treatment with a mixture of concentrated H2SO4, K2S2O8, and P2O5 at80 °C and a Hummers oxidation step using H2SO4 and KMnO4 werecarried out successively. The systemwas then diluted and treated with30% H2O2 to reduce the residual permanganate to soluble manganeseions. After separation and thorough washing with HCl and ultrapurewater, the product was collected and dispersed readily in water toproduce aqueous GO.Fabrication of graphene fibersWe used a scalable industrial wet-spinning protocol to obtain GOfibers, followed by chemical reduction to produce high-performancegraphene fibers. The GO spinning solution was extruded through atubular needle (~160μm inner diameter) into a coagulation bath con-taining 1,2,4,5-tetraaminobenzene tetrahydrochloride, mounted on arotating plate. The needle was bent to have it parallel to the rotatingdirection; for large-size needles that could not be easily bent, theneedle was connected to the spinning dope with a flexible hose to fixtheneedle direction. It shouldbenoted that in anaromatic amine theNis less available to be bonded to the proton due to the delocalization ofthe lone pair of electrons into the benzene ring, which means that asubstantial amount of un-ionized Ar-NH2 is present in the solution, asconfirmed by ninhydrin test (Supplementary Fig. 5). Furthermore, onadding GO containing carboxylic acid groups into the system, theprotons have a greater tendency to protonate the oxygen on the car-bonyl group, leaving more un-ionized Ar-NH2.Experimentally, we observed that solidification occurred imme-diately upon contact because of the amidation reaction between theamine group of the coagulant and the carboxyl groups at the graphenesheet edges. The strongly acidic environment prevents salt formationthrough electrostatic interaction. After 5min of immersion in thecoagulation bath and thorough washing with water, black-brown GOgel fibers were obtained. For chemical reduction, the GO fibers weresuspendedonparallel rods and exposed toHI vapor at 90 °C for 12 h orimmersed into aqueousHI at room temperature for 12 h. The graphenefibers were then thoroughly washed alternately withwater and ethanolto remove I-, other soluble polyiodides (I3− or I5−), and I2. The neutral I2and other polyiodides, such as I3− and I5−, show an intense Raman peakat 165 cm−1 36. Our washed samples did not display this peak, implyingthat thewashing procedurewas successful in removing these residues.To prepare control fibers solidified by solvent exchange, GOsheets were first dispersed in N,N-dimethylformamide (DMF) byreplacing water with DMF via three successive centrifugation andwashing cycles. Ethyl acetate was used as the coagulant. All otherexperimental conditions, including the concentration of GO spinningdope, injection rate, rotation speed of the coagulation bath, andconditions of reduction, remained identical.Reporting summaryFurther information on research design is available in the NaturePortfolio Reporting Summary linked to this article.Data availabilityAll data that support the findings of this study are available in themainarticle and Supplementary Information. Source data are provided withthis paper.References1. Jeffries, R. Prospect for carbon fibers. Nature 232, 304–307 (1971).2. Dalton, A. et al. Super-tough carbon-nanotube fibres. Nature 423,703 (2003).Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 83. Chen, S., Qiu, L. & Cheng, H. Carbon-based fibers for advancedelectrochemical energy storage devices. Chem. Rev. 120,2811–2878 (2020).4. Baker, R., Bernardo, C., Figueiredo, J. & Huttinger, K. Carbon fibersfilaments and composites, 169–219 (Springer, 1990).5. Lee, C., Wei, X., Kysar, J. & Hone, J. Measurement of the elasticproperties and intrinsic strength of monolayer graphene. Science321, 385–388 (2008).6. Novoselov, K. et al. A roadmap for graphene. Nature 490,192–200 (2012).7. Fang, B., Chang, D., Xu, Z. & Gao, C. A review on graphene fibers:expectations, advances, and prospects. Adv. Mater. 32,1902664 (2020).8. Li, M. & Lian, J. Microstructure dictating performance: assembly ofgraphene-based macroscopic structures. Acc. Mater. Res. 2,7–20 (2021).9. Xu, T., Zhang, Z. &Qu, L.Graphene-basedfibers: recent advances inpreparation and application. Adv. Mater. 32, 1901979 (2020).10. Xu, Z. & Gao, C. Graphene chiral liquid crystals and macroscopicassembled fibres. Nat. Commun. 2, 571 (2011).11. Xin, G. et al. Highly thermally conductive and mechanically stronggraphene fibers. Science 349, 1083–1087 (2015).12. Xin, G. et al. Microfluidics-enabled orientation and microstructurecontrol of macroscopic graphene fibres. Nat. Nanotech. 14,168–175 (2019).13. Li, P. et al. Highly crystalline graphene fibers with superior strengthand conductivities byplasticization spinning.Adv. Funct.Mater.30,2006584 (2020).14. Xu, Z. et al. Ultrastiff and strong graphene fibers via full-scalesynergetic defect engineering. Adv. Mater. 28, 6449–6456(2016).15. Clayden, J., Greeves, N. & Warren, S. Organic Chemistry, 2nd ed.,(OUP Oxford, 2012).16. Xu, Z., Sun, H., Zhao, X. &Gao,C. Ultrastrongfibers assembled fromgiant graphene oxide sheets. Adv. Mater. 25, 188–193 (2013).17. Lerf, A., He,H., Forster,M. &Klinowski, J. Structure of graphiteoxiderevisited. J. Phys. Chem. B 102, 4477–4482 (1998).18. Fox, M. & Whitesell, J. Organic Chemistry (Jones and Bartlett pub-lishers, 1994).19. Patel, K.,Gayakwad,E. &Shankarling,G.Grapheneoxide as ametal-free carbocatalyst for direct amide synthesis from carboxylic acidand amine under solvent-free reaction condition. ChemistrySelect5, 8295–8300 (2020).20. Tutorial video at https://www.youtube.com/watch?v=buRFisuSJCM(2014).21. Hung, W. et al. Cross-linking with diamine monomers to preparecomposite graphene oxide-framework membranes with varying d-Spacing. Chem. Mater. 26, 2983–2990 (2014).22. Jia, Z., Wang, Y., Shi, W. &Wang, J. Diamines cross-linked grapheneoxide free-standing membranes for ion dialysis separation. J.Membr. Sci. 520, 139–144 (2016).23. Qian, Y., Zhou, C. & Huang, A. Cross-linking modification with dia-minemonomers to enhance desalination performance of grapheneoxide membranes. Carbon 136, 28–37 (2018).24. Woo, J., Oh, J., Jo, S. & Han, C. Nacre-mimetic graphene oxide/cross-linking agent composite films with superior mechanicalproperties. ACS Nano 13, 4522–4529 (2019).25. Dimiev, A., Alemany, L. & Tour, J. Graphene oxide. origin of acidity,its instability in water, and a new dynamic structural model. ACSNano 7, 576–588 (2013).26. Huang, H., Park, H. & Huang, J. Self-crosslinking of graphene oxidesheets by dehydration. Chem 8, 2432–2441 (2022).27. Chen, L. et al. Toward high performance graphene fibers. Nanos-cale 5, 5809–5815 (2013).28. Hu, X., Xu, Z., Liu, Z. & Gao, C. Liquid crystal self-templatingapproach to ultrastrong and tough biomimic composites. Sci. Rep.3, 2374 (2013).29. Park, H. et al. Dynamic assembly of liquid crystalline grapheneoxide gel fibers for ion transport. Sci. Adv. 4, eaau2104(2018).30. Dong, Z. et al. Facile fabrication of light,flexible andmultifunctionalgraphene fibers. Adv. Mater. 24, 1856–1861 (2012).31. Xiang, C. et al. Graphene nanoribbons as an advancedprecursor formaking carbon fiber. ACS Nano 7, 1628–1637 (2013).32. Xiang, C. et al. Large flake graphene oxide fibers with unconven-tional 100% knot efficiency and highly aligned smallflake grapheneoxide fibers. Adv. Mater. 25, 4592–4597 (2013).33. Soloway, S. & Lipschitz, A. Colorimetric test for amides and nitriles.Anal. Chem. 24, 898–900 (1952).34. Akbari, A. et al. Highly ordered and dense thermally conductivegraphitic films from a graphene oxide/reduced graphene oxidemixture. Matter 2, 1198–1206 (2020).35. Mohiuddin, T. et al. Uniaxial strain in graphene by Raman spectro-scopy: G peak splitting, Gruneisen parameters, and sample orien-tation. Phys. Rev. B 79, 205433 (2009).36. Pei, S., Zhao, J., Du, J., Ren, W. & Cheng, H. Direct reduction ofgraphene oxide films into highly conductive and flexible graphenefilms by hydrohalic acids. Carbon 48, 4466–4474 (2010).AcknowledgementsWe acknowledge financial support from the National Natural ScienceFoundation of China (Grant 52173288). We thank Dr. Mark HermannRümmeli and Yu Liu at our department for discussions. The support fromthe Vacuum Interconnected Nanotech Workstation (Nano-X) of SuzhouInstitute of Nano-tech and Nano-bionics (SINANO), Chinese Academy ofSciences is also acknowledged.Author contributionsF.G. and Z.L. conceived the project and supervised experiments. L.D.,T.X., J.Z., J.J., Z.S. performed materials synthesis and characterizationstudies. Y.X., T.L. helpedwith FIB cutting anddata collectiononSTEM-in-SEM studies. Y.Z., Z.Z., R.M. conducted delamination of the amide-connected fiber and characterization of the delaminated sheets. Y.L.,W.G., H.N., J.G. helped with the reaction design and mechanism analy-sis. Y.W. and Z.S. performed Hall-effect measurements. All authors dis-cussed the results and F.G. organized the paper with input from all co-authors.Competing interestsThe authors declare no competing interests.Additional informationSupplementary information The online version containssupplementary material available athttps://doi.org/10.1038/s41467-024-49270-5.Correspondence and requests for materials should be addressed toFengxia Geng.Peer review information Nature Communications thanks Chao Gao andthe other, anonymous, reviewer(s) for their contribution to the peerreview of this work. A peer review file is available.Reprints and permissions information is available athttp://www.nature.com/reprintsPublisher’s note Springer Nature remains neutral with regard to jur-isdictional claims in published maps and institutional affiliations.Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 9https://www.youtube.com/watch?v=buRFisuSJCMhttps://doi.org/10.1038/s41467-024-49270-5http://www.nature.com/reprintsOpen Access This article is licensed under a Creative CommonsAttribution 4.0 International License, which permits use, sharing,adaptation, distribution and reproduction in any medium or format, aslong as you give appropriate credit to the original author(s) and thesource, provide a link to the Creative Commons licence, and indicate ifchanges were made. The images or other third party material in thisarticle are included in the article’s Creative Commons licence, unlessindicated otherwise in a credit line to the material. If material is notincluded in the article’s Creative Commons licence and your intendeduse is not permitted by statutory regulation or exceeds the permitteduse, you will need to obtain permission directly from the copyrightholder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.© The Author(s) 2024Article https://doi.org/10.1038/s41467-024-49270-5Nature Communications |         (2024) 15:4880 10http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/ Covalently bridging graphene edges for improving mechanical and electrical properties of�fibers Results and discussion Graphene fiber assembly from GO�sheets Structural characterization of graphene�fibers Mechanical properties of graphene�fibers Electrical properties of graphene�fibers Stress transfer in graphene�fibers Methods Materials Synthesis of aqueous graphene�oxide Fabrication of graphene�fibers Reporting summary Data availability References Acknowledgements Author contributions Competing interests Additional information