The CC@rGO composite comprises a spherical heterostructure uniformly distributed between graphene sheet layers, preventing stacking the graphene sheet layer. After the introduction of cobalt heterojunction on a graphene substrate, the Co element content increases the reactive sites of the composite and improves its electrochemical properties to some extent. The composite exhibited good cycling performance with an initial discharge capacity of 847.51 mAh/g at 0.5 C and a capacity decay rate of 0.0448% after 500 cycles, which also kept 452.91 mAh/g at 1 C and in the rate test from 3 C back to 0.1 C maintained 993.27 mAh/g. This article provides insight into the design of cathode materials for lithium-sulfur batteries.An interlayer nanocomposite (CC@rGO) consisting of a graphene heterojunction with CoO and Co Lithium-ion batteries have been studied extremely extensively over the past few decades and are used in portable and mobile electronic devices ,2. Howev2-SnS2 [3O4-MnS [3O4-CoP [2-SnS2 nanosheet heterojunctions to determine for the first time the interfacial effect in lithium-sulfur batteries, which improved the diffusion efficiency of ions and significantly accelerated the redox reaction [Various strategies have been proposed to overcome these challenges, including well-designed cathodes, modified separators, and new-developed electrolytes . In the 2-SnS2 , Mn3O4-M[3O4-MnS , and Co3[3O4-CoP . For insreaction . Qin et reaction . Zhang ereaction . Most of9S8 heterojunction composite nanomaterials (CC@rGO). CoSO4, graphene, and chitosan were used as the Co source, carbon source, and supplementary carbon source, respectively. The Co2+ ions were assembled with negatively charged functional groups on graphene oxide through electrostatic adsorption, followed by a hydrothermal-high temperature reduction to generate CoO/Co9S8 heterojunctions uniformly distributed between graphene lamellae. The CC@rGO electrode exhibited excellent cycling stability and rate performance, thanks to graphene’s large surface area and numerous ion-electron transport channels, the built-in accelerating electric field of CoO/Co9S8, and the ability to trap and transform polysulfides. This study provides valuable insights into the potential application of carbon material–metal compound composites in lithium-sulfur battery cathode materials, which may lead to the development of more efficient and sustainable energy storage systems.This study presents a hydrothermal–calcination method for synthesizing rGO-CoO/Co2O2 was added to it to obtain a bright yellow graphene oxide solution. After being cooled, the graphene oxide was left to separate, centrifuged to a pH of 7, and finally freeze-dried, as previously reported by our subject group [Graphene oxide was prepared by modified Hummer’s method. Two grams g scaled graphite powder were added to 250 mL of a mixed acid solution of sulfuric acid-nitric acid (volume 9:2). A total of 12 g of potassium permanganate was added to it and the temperature was increased to 50 °C (40 min), 60 °C (7 h), 90 °C (30 min), and finally, 30 mL of Hct group ,33.9S8/CoO/rGO, abbreviated as CC@rGO) was obtained by calcination at 500 °C for 2 h in the Ar atmosphere. rGO samples were made by the same procedure without the addition of cobalt sulfate and chitosan.A suspension of graphene oxide was prepared , then 2 g of cobalt sulfate and 0.3 g of chitosan were added to 50 mL of deionized water (solution B), and A and B were homogeneously mixed, and transferred to a PTFE-lined reactor, hydrothermally heated at 180 °C for 12 h. The precursor powder was obtained by freeze-drying. The black powder , and binder (PVDF) were ground at 7:2:1 and added to a certain amount of NMP, and stirred for 12 h to make a slurry, coated on carbon-coated aluminum foil, dried at 60 °C for 12 h, and then stamped into a 12 mm × 12 mm circular positive electrode by a press.2 adsorption and desorption experiments .The microscopic morphology of the samples was observed by scanning electron microscopy  as well as elemental analysis . X-ray diffraction analysis  was used to characterize the sample lattice structure in the interval 10°–90° at 5° per minute. Transmission electron microscopy images  were used to obtain the internal microstructure. X-ray photoelectron spectroscopy images were acquired by K-Alpha . To obtain Raman spectra, a Renishaw micro confocal laser Raman spectrometer (633 nm) by HR800  was used. Thermal gravimetric analysis  was used to analyze sample sulfur loading. The specific surface area and pore size distribution before and after modification were analyzed using N3 . Lithium sheets  were used for the negative electrode of the half-cells. Coin cell constant current charge/discharge test was performed in the voltage window range of 1.7–2.8 V. Electrochemical AC impedance (EIS) testing, as well as cyclic voltammetry (CV) testing was performed at the Princeton Electrochemical Workstation , with EIS frequencies ranging from 1 × 10−2 Hz to 106 Hz. Li2S6 adsorption experiments were used to verify the adsorption capacity of the material (0.05 M Li2S6 dissolved in 1:1 DME: DOL).A coin cell (type CR2032) was used for electrochemical testing of the rGO as well as the CC@rGO. A 12 mm × 12 mm circular positive electrode sheet was assembled into a cell in a glove box, and the electrolyte used consisted of 1.0 M LiTFSI -DOL: DME with a 1:1 volume ratio and 2% LiNO2+ combines with the negatively charged oxygen-containing functional group on GO under the effect of electrostatic adsorption, and after the removal of the oxygen-containing functional group by hydrothermal heat, Co2+ fills the oxygen vacancies generated after the removal of the oxygen-containing functional group and achieves the uniform distribution of Co2+ among the graphene sheets. After calcination at 500 °C, CoSO4 was calcined and reduced to CoO and Co9S8 heterogeneous spheres, which were uniformly distributed between the graphene lamellae, forming a typical wrapping structure. Graphene and heterojunction  composites can not only physically limit the dissolution of polysulfides into the electrolyte through the porous structure of graphene, but also trap and transform polysulfides through the heterojunction, inhibiting the shuttle effect that occurs when polysulfides shuttle through the diaphragm to the surface of the lithium sheet and react to cause a decrease in capacity and lifetime.As shown in 9S8@rGO composites, CoSO4/C@GO precursors were prepared by hydrothermal mixing and calcined to generate CoO/Co9S8@rGO composites (labeled as CC@rGO).To prepare CoO/Co9S8, respectively, proving the generation of CoO and Co9S8. rGO exhibits a distinct (002) interface at 26°, which has the amorphous broad peak that is amorphous carbon at 26°. The composites, on the other hand, did not show a clear broad peak at 26°, which indicates a clear amorphization trend of graphene during the carbon thermal reduction process and the disappearance of the broad peak [The compositional analysis of rGO and CC@rGO was carried out using XRD, as shown in oad peak .−1 and 1600 cm−1, corresponding to the D and G peaks [−1 and 1590 cm−1, respectively, which was believed to be due to the addition of heterojunctions that make the material structure vibrate and shift. The double peaks of CC@rGO at 466 cm−1 and 676 cm−1 were considered to be strong interactions between CoO and Co9S8 [D/IG of CC@rGO is reduced from 1.1 to 1.035 and the defects of the material are reduced [Raman spectroscopy was performed for CC@rGO and rGO to measure the disorder of different samples, and the results are shown in  G peaks ,35, respnd Co9S8 ,37. Comp reduced . The add reduced . Meanwhi9S8 have uniformly distributed between graphene lamellar layers as seen in 2+ with oxygen-containing functional groups on graphene during the hydrothermal process.The microstructure and elemental distribution of rGO and CC@rGO were observed by scanning electron microscopy and elemental energy spectroscopy, respectively. As shown in 9S8, respectively  and S2p1/2 (162.8 eV) attributed to metal-S bonds [x-C species [There are also two sets of satellite peaks  in the S2p high-resolution spectrum, with peaks at S2p-S bonds ,43. The 3/2 1.8 eV an species ,44. The 2/g to 46.112 m2/g after compounding the heterojunctions due to the incorporation of heterogeneous spheres with a smaller specific surface area. The pore size , on the other hand, decreased from 8.16 nm to 4.46 nm. The smaller pore size will melt the sulfur-loaded process to encapsulate the sulfur well in the pore channel and maintain sufficient stability. At the same time, during the melting process, due to the good wettability between carbon and sulfur, sulfur will penetrate inward through the capillary of carbon, and when the pore size becomes larger, the capillary force is not enough to let sulfur enter completely. In this way, the small pore size will achieve a better encapsulation of sulfur as well as a better inhibition of polysulfide diffusion. In addition, the small pore size will make the sulfur layer on the material surface thinner, improve the sulfur utilization, and accelerate the electron and ion transfer efficiency; meanwhile, increasing the contact area of the electrolyte will promote the electrolyte to infiltrate the material, reduce the interfacial impedance, and finally reduce the electrochemical polarization [As shown in rization ,48,49.The composites’ large surface area and thin mesoporous structure will make it easier for the cell’s electrolyte to penetrate the material, which will lower interface impedance, increase charge exchange efficiency, hasten the conversion of sulfur intermediate species, and enhance the cell’s electrochemical performance. As shown in 9S8 heterostructure. It can effectively activate more sulfur-active material while maintaining good cycling stability and promoting the kinetic conversion of polysulfides. The cycling test of CC@rGO using 1C cycling current shows that the first turn discharge capacity is 452.91 mAh/g and the decay rate is 0.0639% after 500 cycles, which further demonstrates the good structural stability and electrical conductivity of the composite material.To characterize the electrochemical performance of the composites with wrapping structure, a series of electrochemical characterizations were performed for the cells assembled with rGO and CC@rGO, respectively. To characterize the electrochemical properties of the composites, CC@rGO and rGO were assembled into CR2032 button cells, respectively. As shown in 9S8 heterojunctions between nonpolar graphene sheets provides abundant polysulfide action sites, effectively suppressing the loss of active material sulfur caused by the “shuttle effect” and reducing the appearance of dead sulfur during the cycling of lithium-sulfur batteries.The rate electrochemical characterization of CC@rGO was performed and the results are shown in 2Sx, 4 ≤ x ≤ 8) and the reduction of soluble polysulfide to insoluble polysulfide  during discharge, respectively [The electrochemical performance of rGO and CC@rGO cells was compared at a scan rate of 0.1 mv/s and a voltage window of 1.7–2.8 V. The two typical reduction peaks  characterized by CC@rGO correspond to the reduction of S to soluble polysulfide  of CC@rGO is reduced from 133 Ω to 88 Ω. The improved tilt of the Warburg curve in the low-frequency region is attributed to the increased conductivity of the composite material after the addition of the heterostructure, which can better perform the adsorption-transformation of polysulfides [The electrical conductivity of the cells assembled from the composites was further tested, and the Nyquist curves were shown in sulfides ; meanwhi2S6 adsorption experiments were carried out to further verify the adsorption capacity of the composites. After 12 h adsorption in 0.05 M Li2S6 solution, the supernatant of CC@rGO on the right side was clarified, while the rGO on the left side still showed a pale yellow color, indicating that CC@rGO has excellent static adsorption ability, which is consistent with the previous characterization results. This indicates that the composites have a better ability to trap polysulfides, which is attributed to the excellent adsorption of polysulfides by metal oxides and the porous structure of graphene, both of which synergistically enhance the performance of the composites.As shown in In 9S8 heterojunction-rGO composites by electrostatic adsorption and calcination. CoO/Co9S8 heterojunction acts as a polysulfide adsorption transformation, while rGO acts as a sulfur-carrying carbon carrier and provides ion and electron transport channels. Due to the wrapping structure, it can play a synergistic-catalytic role well, suppressing the “shuttle effect” of LiPSs and accelerating the electro-kinetic reaction. The results show that the CC@rGO sulfur cathode has good electrochemical performance, good rate performance, and cycling stability at different current densities, and the Coulomb efficiency is always maintained above 97%. Therefore, this electrode material design can provide new insights into the design and development of sulfur carriers for lithium-sulfur battery cathodes.In summary, we propose the preparation of CoO/Co


Migration pattern suggests the more stable dipeptide model bears serine in βL, γD, γL and the alanine in γL and γD configurations. The investigation of side‒chain‒backbone interactions revealed that the most stable conformer, γD–γL, is in the β‒turn region of Ramachandran map; therefore, serine-alanine dipeptide model should be adopted with a β‒turn conformation. Intramolecular hydrogen bonding in β‒turns consideration by QTAIM disclosed γD–γL includes three hydrogen bonds. The computed UV‒Vis spectrum alongside of NBO calculation showed the five main electronic transition bands derived of n → n* of intra‒ligand alanine moiety of dipeptide structure.The conformational analysis of The online version contains supplementary material available at 10.1186/s13065-023-01051-9. The optical purity have key effect on property and should be carefully controlled, i.e. l‒amino acids, in most cases, show a biocompatible identity, but d ‒amino acids may have harmless effects ‒ala‒NHMe [eactions . The proectively , 21. Theectively . Moreoveala‒NHMe  and n‒Acala‒NHMe  tripeptid/l‒alanyl‒d/l‒serine dipeptide have been determined in aqueous solutions by means of potentiometry and calorimetry [2 dipeptide were investigated by the aid of quantum chemical calculations. All peptide bonds of HCO‒ser‒ala‒NH2 dipeptide are in the trans isomeric state, and chiral α‒carbons are in the D enantiomeric state [The thermodynamic properties of protolytic equilibria of orimetry . For theic state .N‒formyl and amine functionalities were attached to the terminus of dipeptides. These moieties safeguard the mimetic of conformational properties of polypeptides and protein segments and simulate the spatial and inductive contacts of those adjacent ser‒ala (sa) amino acid residues.d‒ser‒d‒ala‒NH2 on the Ramachandran map, [ level of theory. However, it is possible that some conformers were lost and less than 243 conformers would be found. Migrations of nonexistent conformers can assist to identification of the relative stabilities and instabilities of the different conformations  and M06‒2x/6‒311 + G  levels of theory in the gas and water solvent. The L and D forms of ser-ala protected dipeptide have been investigated in the previous [The numbering of atomic sequence in the sa‒protected dipeptide was performed under the standardized numbering system , which pprevious , and preβ‒turn is highly variable that can be classified based on the dihedral angles contents of ϕ and ψ of the central residue (Table The backbone (BB) conformation of the ue Table . The devβ‒turn secondary structures exist in types I, II, and III. However, their conformational enantiomers , and VIa1, VIa2, VIb, and VIII types of β‒turns are less common. Conventionally, eight types of β‒turns have been distinguished and those not defined are classified as type IV. The turns comprise n consecutive residues (i to i + n), according to some reports, the distance between α‒carbon of residues symbolized as i and i + n, must be smaller than 7 Å or 7.5 Å [γ‒turns (n = 3), [β‒turns (n = 4), [α‒turns (n = 5) [π‒turns (n = 6) [7), 10 (C10), 13 (C13) and 16 (C16) membered hydrogen bonded (H‒bonded) rings for γ‒, β‒, α‒ and π‒turns, respectively. The term Cn interaction is used when the H‒bond (HB) leads to the formation of a n‒membered ring, include of the donating NH and the accepting CO groups [β‒turn structures, as defined by C.M. Venkatachalam were characterized by a HB between the N‒H and C=O of residues i and i + 3, respectively [n interactions that lead to the formation of a n‒membered ring for n = 5, 7, and 10 were shown in Scheme β‒turn is a multifaceted process driven in part by local torsional preferences, inter‒strand H‒bonding can offer additional stabilization of the turn [Usually, or 7.5 Å , 33. The(n = 3),  β‒turns (n = 4),  α‒turns  (n = 5) , 37 and  (n = 6) , 39. TheO groups . The mosectively , that gethe turn . Anotherthe turn –49, in tthe turn , 48. In The further structural consideration of the studied stable conformers of sa‒protected dipeptide was applied by the UV‒Vis spectrum and Frontier Molecular Orbitals (FMOs) investigations. These complementary results can be used for better understanding of the dipeptide structure.β−turn conformers and Frontier Molecular Orbitals investigations by UV–Vis spectrum and NBO considerations of the most stable conformer of dipeptide model were performed. These interesting studies can be presented as the main novelty and differentiation related to the previous reported results by us [In the present research, the new calculations including of the effect of solvent (water) dielectric constant on the stability of ts by us . Moreoven−formyl−d−serine−d−alanine−NH2 was modeled with each residue and protecting group segments were separately for the entirety of the peptide chain numbered. Then, formyl and amide functionalities were attached to the N‒ and C‒terminuses of the dipeptide, respectively for safe guarding the mimetic of steric effects of the neighboring amino acid residues.First, α‒carbon atom of the amino acid subgroups denoted as , , and φ, and ψ dihedral angles specify the BB, while the χ describes the side-chain conformation of the dipeptide. The rotations around φ1, ψ1, φ2, ψ2, and χ were considered most relevant to the shape and stability of sa-protected dipeptide model. The rotation around χ resulted in side-chain conformers that are defined as gauche ( +) (g +), anti (a), and gauche ( −) (g−). Initially, the fully relaxed optimization in the gas phase without any symmetry constraints  was employed at B3LYP [d,p) basis set. M06‒2X is a hybrid meta exchange‒correlation functional and one of the best functioning for studying the organic and biological small molecules [β‒turn conformers. Additionally, the effect of solvent on β − turn structures was calculated using the SCRF keyword with Tomasi’s polarized continuum model  [d−ser−d−ala−NH2 were optimized by restraining the serine residues to the nine conformations, (−) along χ side − chain dihedral angle are present, the multidimensional conformational analysis (MDCA) would lead to the existence of 35 = 243 conformers. In addition, the theoretical electronic transitions (ETs) of vacuous phase of UV‒Vis spectrum of dipeptide optimized geometry were done using time‒dependent DFT (TD‒DFT) calculations. Both of singlet and triplet states were respected; while excitations to triplet excited states were prohibited. Partial atomic charges and Natural bond orbital (NBO) analyses were also computed using B3LYP‒D3/6‒311 + G  level of theory. All computations concerning conformers of serine‒alanine protected dipeptide were carried out by the GAUSSIAN 09 program package, [β − turn structures. The wave functions used in the QTAIM analyses were generated at the B3LYP‒D3/6‒311 + G  and M06‒2X/6‒311 + G  levels of theory. The related calculations were carried out using the AIMAll program [The sa‒protected dipeptide was separated into four units: 1) The N‒terminus protecting group, (2) the D‒ser residue, (3) the D‒ala residue, and (4) the C‒terminus protecting group. A standardized numbering system was separately used into and along the peptide BB to define the numbered dipeptide  , 55. Frepackage,  at 298.1package,  were per program .−1) of different conformations bearing different side‒chain dihedral angles  conformer is more stable than gauche ( −). This is also in agreement with the results that the anti-conformer is the most stable .φ, ψ, and ω, lead to a potential energy hypersurface ). Since in a trans amide bond conformer, the ω torsional angle has a constant value of 180º, the hypersurface E = E  can be simplified to E = E . The calculated results at the B3LYP/6‒311 + G  show that 87 stable conformers were characterized, and the rest changed to the more stable ones. Initial and final optimized conformations , and gauche ( −) side-chain forms) of all 243 possible ones of the sa-protected dipeptide were reported in supplementary information . The three more stable conformers of anti, gauche ( +), and gauche ( −) BB conformers of sa‒protected dipeptide are ((2.95), 4.13(3.14), 4.29(4.29)), (5.91(5.16), 8.22(7.20), 8.27(6.23)) and (0.00(0.00), 2.30(2.13), 4.03(3.88)), respectively. These results confirm the previous section that for the ser and ala residues, the  of the (i + 1)th and (i + 2)th positions. It can result that, 22 cases of the 87 found conformations of For‒d‒ser‒ d‒ala‒NH2 can be categorized as the β − turns. All conformers of β − turns were optimized and verified to be at the minimum energy through vibrational analysis (no imaginary frequency mode). The optimizations of all 22 β − turns structures and frequency calculations were carried out at the B3LYP, B3LYP‒D3 and M06‒2X levels using the standard 6‒311 + G  basis set in gas and solution phases. To study the effect of solvent on the stability of β − turn structures, the quantum mechanical calculations were performed in water using Tomasi’s polarized continuum model at the M06‒2X/6–311 + G  level of theory.β − turns in gas and solution phases at the B3LYP‒D3/6–311 + G  and M06‒2X/6–311 + G  levels of theory, are provided in Table β − turns according to their type, torsional dihedrals  levels of theory in the gas and water phases, was reported in the supplementary information  level of theory are shown in Table As shown in Tables β−turn structures have lesser relative energies and the higher stability. The energy decreasing by a dimensionless factor of 1/ε, (ε is the dielectric constant), is appropriate if the polarized or charged particles are immersed in any medium other than a vacuum. It can be mentioned that a weaker interaction in a polarizable medium  than a vacuum should be formed [μ), are dissolved in polar liquids. The dipole‒dipole interaction between solvent and solute can decrease the relative energies [β−turn structures in the solvent and gas phase is different, which is due to the effect of solvent dielectric coefficient. For example, in the gas phase,β−turn. Increasing the dipole moment of the −1, respectively. Therefore, the However, the results of the solution phase showed that all e formed . Polar menergies . The ordβ − turn structures are stabilized by forming IHBs known as a β−turns are open, which means without any intraturn HB [The aturn HB .ρ value, the more tremendous interaction energy and the positive The theory of QTAIM provides a proper approach to elucidate the intermolecular interactions by considering the total electronic density,s (BCPs) –67. The –1 a.u. along with the negative value of van der Waals and HB interactions, respectively [The high value of eraction . Neverthectively , 67, 69.ectively .HB) of β‒turn structures at the B3LYP‒D3 and M06‒2X levels of theory using the 6‒311 + G  basis set are summarized in Table HB of −1 with distance (r) of 2.07, 2.06, 2.18, and 2.07, 2.09, 2.17 Å at the B3LYP‒D3 and M06‒2X levels of theory, respectively that are in agreement with previous studies, (the NH···OC distance in C10 structures is around 2.10 − 2.20 Å) [β‒turn structures, different types of HBs including A), F), S), A), The topological parameters and IHB energy E 2.20 Å) , 72. The.20 Å , 7HB values [β‒turn conformers in the ranges of 0.014‒0.027 and 0.015‒0.025 a.u. and HB amounts in the range of 2.74‒6.32 and 3.17‒6.25 kcal mol−1 at the B3LYP‒D3 and M06‒2X levels of theory, respectively. The highest and lowest amounts of HB for C7A IHB belonging to the β‒turn secondary structures, respectively. As shown in Table HB are in the ranges of (0.011‒0.036 a.u.), (0.040‒0.121 a.u.),  and (0.013‒0.032 a.u.), (0.048‒0.121 a.u.), , respectively. The residues possessing an HB acceptor and/or donor site potentially lead to a NH → side chain and/or side chain donor → backbone CO HB that are observed concomitantly with backbone − backbone HBs. This is the case for instance with the Ser, His, Asn, and Gln side chains, where an extended locking through multiple bonds occurs between the backbone and the side chain [β‒turns have lowest EHB, whereas, C7F interaction of β‒turn, show the highest one, respectively ,  and ,  at the B3LYP‒D3 and M06‒2X levels of theory, respectively , (in a.u.) at the M06‒2X level of theory for three conventional C7A, C7F, β-turns are shown in Fig. A, HB for these interactions is  kcal mol−1, respectively. Also, the values of V(r) and EHB for C7A, C7F,−1), respectively  level of theory. The computed electronic transitions in vacuo by TD − DFT method show several sharp bands assigned to intra‒charge transfer (CT) in the respected dipeptide.Herein, the electronic study of the most stable conformer of HCO − s and p orbitals. The 49 (HOMO−5), 50 (HOMO−4), 51 (HOMO‒3), and 53 (HOMO‒1) consist primarily of lone pair(s) electrons of atomic orbitals of oxygen atoms of alanine part of sa‒protected dipeptide  and 56 (LUMO + 1) and 58 (LUMO + 3) consist primarily of anti−bonding Rydberg molecular orbitals of hydrogen atoms of alanine moiety of sa‒protected dipeptide . Therefore, it can be said that all of the computed ET bands can be assigned to the n → n* intra−ligand charge transfer (ILCT) transitions  at 164.8, 166.9, 172.7, and 186.2 are attributed to CT of intra transfer of alanine amino acid residue within CT from 49 (HOMO−5), 50 (HOMO−4), 51 (HOMO−3), and 53 (HOMO−1) to 58 (LUMO + 3), respectively. Also, the last one (λ5) at 191.6 nm could be assigned to CT of intra charge transition of alanine amino acid part of dipeptide from 53 (HOMO−1) to 56 (LUMO + 1).However, the computed UV−Vis spectrum of sa‒protected dipeptide indicates several main CTs that five major ones can mention as 164.8, 166.9, 172.7, 186.2 and 191.6 nm see Fig. . The eled−ser−d−ala protected dipeptide was performed using B3LYP/6‒311 + G  calculations in the gas phase. In addition, all β−turn structures were optimized in the gas and solution phases and verified to be at the minimum energy using DFT‒B3LYP‒D3 and M06‒2X levels of theory. Also, the β−turn conformers have been considered at that those same levels of theory by using QTAIM. According to MDCA, the whole 35 = 243 plausible conformers were investigated. The results show that 87 stable conformers were found and 156 ones changed to some different more stable conformations among the found conformations. It can be highlighted that d‒ser‒d‒ala‒NH2 can be categorized as the β−turn structures bearing A complete conformational analysis of the i and i + 3 in β−turns with EHB of 3.62, 3.67, 2.62, and 3.72, 3.52, 2.78 kcal mol−1 at the B3LYP‒D3 and M06‒2X levels of theory, respectively. The β‒turn, is the most stable one that includes three IHBs  and gauche (−) side-chain conformations. Table S2. Classification of β−turn conformers of sa-protected dipeptide according to their type, torsional dihedrals μ) (Debye), at the B3LYP‒D3 and M06‒2X/6‒311+G  levels of theory in the gas and water phases.


Ionic liquid (IL) combined with graphene additives have garnered extensive attention in the field of high-performance lubricating materials. However, the ambiguous mechanism of graphene influencing the load-carrying and anti-wear capacity of ILs needs further study. In this work, friction simulation shows that adding graphene causes friction coefficient to reduce by up to 88% compared with pure ILs, but lubrication performance is lost due to the destruction of graphene under high stress. Meanwhile, multilayer graphene has better friction-reducing performance and friction durability as compared to the monolayer structure, which is attributed to the easy-shear property and the reduction in the percentage of high tensile stress sites in multilayer graphene structure. In addition, it was found that excessively thick ILs film would form a three-body abrasive wear structure with graphene, which accelerated the structural destruction of graphene and caused a decline in its tribological properties. It is believed these findings can be valuable for designing of high-performance lubricating oil for practical engineering. Since the initial report published in 2001 ,5,6,7,8.Recently, extensive effort has been devoted to investigating the tribological properties of composite lubricants based on ILs and graphene. Functionalized multilayer graphene as additives can prominently enhance the anti-wear and friction-reducing ability of IL film under high vacuum, due to the lubrication synergy of ILs and multilayer graphene . Qi et aThe synergistic lubrication mechanism of graphene as additives for ILs has been studied from various aspects of tribochemical reactions and enhancing load-carrying capacity. However, since the scale of graphene as a low-dimensional material has entered the nanoscale, it is difficult to elucidate the microstructure and frictional properties of nano-additives only through experimental studies. Meanwhile, macroscopic experiments cannot observe the synergistic lubrication process as well as the structural changes of additives, and cannot obtain accurate lubrication mechanisms to efficiently guide the optimization of experimental processes. Therefore, the mechanism of graphene molecules as additives affecting tribology behavior of ILs is still unclear. The computer simulation method helps us to gain insight into the friction mechanism from the atomic scale. Hence, it has been widely used to observe the mechanism in tribology field.In this work, a molecular dynamics simulation (MD) approach is used to investigate the synergistic lubrication mechanism based on ILs and graphene. Diamond-like carbon (DLC) is employed as the friction substrate in this research due to its antifriction performance. It was found that their excellent lubrication performance, which has a significant dependence on the application environment, are dementedly influenced by the sp3-to-sp2 ratio . And the3. The IL is consisted of the cation  and the anion  (as shown in 2 carbon (C) atoms arranged in the hexagonal symmetry and H atoms passivating its edge . The open source software OVITO 3.8.0  was usedFn ; the corresponding normal forces, which are 44 nN, 220 nN, and 440 nN, respectively; IL amounts Ni , graphene amounts Ng ; surface roughness R ; and sliding velocity Vy , to investigate the tribology behaviors. The substrate rough surface was obtained by deleting the partial atoms adjacent to friction region according to the following sine function.z is the coordinate of the atoms in the direction of normal stress, R the amplitude of roughness, and y controls the distance between two rough micro-convex bodies. The Ff is calculated by summing the tangential force along the sliding direction of the rigid layer in upper DLC. The molecular average translational kinetic energy formula, Ek = 3kBT/2 [T) of the friction region. The coordination number of C atoms of DLC and graphene was calculated according to a cutoff length of about 1.9 Å, which corresponds to the value of the first minimum of the radial distribution function. The coordination number of C atoms with sp2 and sp3 hybrid states is three and four, respectively. The value of fsp3 was calculated by dividing the number of C atoms with the sp3 hybrid state by the total number of C atoms outside the rigid layer. The binding energy between multilayer graphene was calculated when two graphene sheets completely overlapped. The atomic stress tensor was calculated by multiplying the Voronoi stress tensor by an individual atom’s volume.In the simulation, considerations are given to different factors, such as normal stress = 3kBT/2 , was useFn) and amounts of graphene (Ng) on friction force (Ff). The short period (approximately 5 ps) after the beginning of sliding is defined as the running-in stage. In this stage, Ff is at a large value and then drops rapidly, which is due to the relative sliding of the friction pair required to overcome a large initial resistance. The running-in stage is followed by the stable friction stage. It can be seen from the illustration in Ff is kept at a small value in the whole sliding process in the condition of Fn ≤ 5 GPa. Such a phenomenon can be explained by the fact that the upper and lower layers of DLC are completely separated via composite lubricating film and there is no bonded interaction at the interface which resulted in extremely minute interfacial adhesion. When Fn continues to increase to 10 GPa, Ff increases more rapidly and the Ff at the final state is consistent with that of without graphene. It can be observed that Ng = 2, as shown in Ff increases rapidly at a large distance in the case of high Fn. For the multilayer graphene  between graphene layers. The Be between friction interfaces was calculated, as shown in Be with the upper and lower DLC substrates which makes the graphene move synchronously with the same-side substrate. The weak interlayer Be between graphene leads to the relative movement between the overlapped graphene layers, as shown in Be, which leads to the reduction in friction lubricated by multilayer graphene during the friction simulations. Meanwhile, the low Be between multilayer graphene ensures that the structure is more difficult to rupture [Fn [When the monolayer graphene is present  of C atoms in the graphene layers shown in Ff (Nb) between the graphene layer and the DLC film;, the simultaneously increase in Nb with Be is because of the dangling bonds produced by the bond breaking in the graphene layer and which form the C–C covalent bonds with the C atoms in DLC film across the contact interface. Meanwhile, the large amounts of Nb causes a sufficient adhesion force and thus lead to a remarkable increase in sliding resistant force. This result demonstrates that the good lubrication performance of graphene in low Fn disappeared in high Fn and this is ascribed to the rupture of graphene.In the simulation, it is observed that the layered structure of graphene is ruptured during the sliding process when wn in Ff c increasMultilayer graphene shows a persistent lubrication performance compared to monolayer graphene, which demonstrates that the multilayer graphene structure has better mechanical properties during sliding. In order to figure out the rupture process of the graphene layer, the normal stress state of C atoms in the graphene layer on the sliding plane was calculated during sliding. The local structural evolution of the graphene layer is shown in x–y plane normal stress distribution of C atoms when Fn = 10 GPa. For Ng = 2, we snapshot a piece of graphene with a monolayer structure as a reference, and snapshot a part of the graphene overlapped with multilayer structure in the case of Ng ≥ 4. It can be observed that there are more C atoms subjected to high tensile stress in the monolayer graphene. The distribution of normal stress of C atoms is almost identical for the multilayer structure between Ng = 4 and Ng = 6; most of the C atoms in the graphene layer are subjected to compressive stress and only few atoms are under tensile stress. To quantify this, we plotted the histogram of normal stress of C atoms with different amounts of graphene. The histogram has larger quantity at low-magnitude normal stress and lower quantity at high-magnitude normal stress. It should be noted that the highest frequency of the high-magnitude tensile stress range is in the case of Ng = 2, while the lowest frequency is in the case of Ng = 6. In both cases of Ng = 4 and Ng = 6, the distribution frequency of atomic normal stress is almost identical. This is because all graphene exist in lubricant as overlapping-layer structure in the two cases. The above phenomenon is consistent with the normal stress distribution of C atoms with different layered structure of the graphene, as shown in To further quantitatively investigate the effect of layer structure on rupture behavior of graphene, we performed normal stress sites analysis for different layered graphene structures. Fn and ionic liquids amounts (Ni) on the performance of IL-based lubricants by employing constant graphene amounts (Ng = 4). In the case of small amounts of IL (Ni ≤ 20), the Ff remains at a small value after sliding which is attributed to the separation effect of IL-based lubricants on the DLC friction pairs and low interfacial adhesion between the friction interface. Ni = 10, 20 and 40, we define them as “insufficient”, “appropriate” and “excessive” amounts, respectively. Different Ni represent different thicknesses of the lubricating film. When the Ni ≤ 20 and Fn = 10 GPa, the IL-based lubricants show more persistent lubrication performance with the amounts of IL increasing from insufficient to appropriate; this is because the increase in Ni enhance the dispersion of graphene. On the other hand, in the case of excessive amounts of ILs (Ni = 40), the Ff increases rapidly after sliding a short distance and the increasing rate of Ff is more obvious under higher Fn. The high Ff demonstrates that excessive amounts of ILs may result in the immediate invalidation of the performance of IL-based lubricants.For the three lubrication conditions of Ff at high graphene concentration in our research.In previous studies, the decrease in fluidity of graphene caused by sheets aggregation was used to interpret the poor lubrication at high graphene concentration . In ordeFf, as shown in Ni = 10. This loose configuration of lubrication film comprises most of the load acting on the lubricating film loaded by the graphene layer which make the stress on the graphene greater than the theoretical value (Fn = 10 GPa). However, for Ni = 20, this IL-based lubricating film is dense during sliding simulation which makes the stress on graphene closer to the theoretical value. The average normal stress (Sn) value of the C atom in the graphene layer on the z-direction was shown in Fn, the Sn of graphene decreases with the increase in Ni in the sliding process. The increased amounts of IL is responsible for the normal stress on the graphene, which guarantees the stability of the graphene structure.In this work, the normal stress state of C atoms in the graphene was calculated to explain this high Ni = 40), the Ff increases sharply in the initial stage of sliding. Pe) of graphene starts to increase remarkably in the initial stage of sliding. The increase in the Pe of graphene is due to the transition of C atoms from the sp2 hybridized state to sp3 hybridized state which indicates that the regular hexagonal structure of graphene has been ruptured during sliding. And the process of graphene structural rupture is shortened with the increase in stress. Ff. To investigate the mechanism of the invalidation of lubricating performance caused by excess ILs, the stress state of graphene during sliding was calculated, as shown in In the case of excess amounts of IL , the upper and lower surfaces of the DLC can contact directly and form a large number of covalent bonds, as shown in f. Hence, in the case of different roughness, the number of C–C covalent bonds between lubrication interfaces is the leading factor affecting the different Ff.The effect of substrate surface roughness on the lubrication performance of IL-based lubricants were studied under the condition of constant amounts of ILs and graphene layers, as shown in Fn and forms a covalent bond with the substrate which makes graphene have a great adhesion to the substrate, while there is almost no covalent bonds between graphene layers due to the strong van der Waals force, as shown in Ff at a relatively small value during sliding. Ff is still higher in the case of surface roughness than in the case of smooth plane; it indicates that the separation of the graphene layers to DLC pairs and the enhancement of the diffusion performance of compound lubricant weaken the Ff to some extent, but the bonding between DLC substrates still plays a dominant role.The surface roughness will also affect the fluidity of lubricants. The MSD of graphene increases obviously when the surface changes from smooth to roughness, as shown in Vy) on the lubrication performance of IL-based lubricants was studied under the condition of constant Ni and graphene layers, as shown in Ff has a short process of rising and falling at the beginning of sliding which corresponds to the activation of lubricants flow under shear stress, and the amplitude increases with the Vy. At a low sliding speed (Vy = 1 Å/ps), IL-based lubricants can maintain more persistent lubrication performance. The analysis of the bonding between graphene and DLC shows that the amounts of covalent bonds between the interfaces increases significantly with the sliding velocity. This is because high sliding velocity induces the formation of wrinkles in the graphene, which can significantly drop the load-carrying capacity  by almost an order of magnitude [Vy.The effect of sliding velocity (agnitude . TherefoFf in high sliding velocity (Vy ≥ 1.5 Å/ps), the friction results show that the increase in velocity reduces the Ff in the stable stage, which can be explained by the high friction temperature caused by high speed. The failure of lubricant leads to the direct formation of C–C covalent bonds between the upper and lower DLC films and results in mechanical mixing at the contact interface. In this condition, the Ff depends on the composition and structure of the mixing interface. 3C bonding atoms. In the early stage of friction, the decrease in fsp3 corresponds to the sp3–sp2 transitions (graphitization) in the DLC films which is induced by the high temperature in the friction region, as shown in fsp3 is because the sp2-bonded C atoms in graphene bonded with C atoms in DLC films to form the sp3-bonded C atoms during the process of structural damage of the graphene. After the stabilization of fsp3, the fps3 in the case of Vy = 2 Å/ps is lower than that of Vy = 1.5 Å/ps. This is because the high temperature in the friction region caused by high Vy promotes the graphitization of C atoms at the friction interface. It has been demonstrated by many previous studies that high sp2C content can lead to smaller Ff. The graphitization caused by high temperature results in the easy-shear properties and loss of the structural mechanical strength of DLC friction interfaces [Ff in the stable stage.After the stabilization of terfaces , and thuVy, which makes it easier for the graphene to promote the common sliding of IL molecules along the sliding direction, thus enhancing the fluidity of the lubricants. In the initial stage of friction (Time < 1 ps), the flow of lubricant is activated due to the shear stress of the upper DLC film, as shown in Ff to activate the lubricant films at the initial stage of friction. As the velocity of the lubricant molecules reaches a stable level, the fF decreases to a stable value.The increase in speed enhances the fluidity of the IL-based lubricants, as shown in Fn, the lubricating performance of the graphene-added lubricants is superior to that of pure IL lubricants, which is due to the fact that intact graphene prevents direct contact of the friction pairs interface. As the Fn increases, graphene is subjected to high stress to make its structure unstable and C atoms with high chemical activity appear in the graphene. These atoms form covalent bonds with the C atoms in the DLC to rupture the 2D structure of graphene and cause an increase in Ff. The simulation experiments show that the lubricant is ineffective due to the structural destruction of the graphene when Ff is large enough, as evidenced by the comparison of tribological properties with pure ILs at high Fn.Graphene is an excellent IL lubricant additive owing to its high load-carrying capacity and its ability to separate the surface of the friction pairs. At low Fn [Previous experiments have shown that the worse tribological performance of pure ILs lubricants is due to the poor load-carrying capacity in high Fn ,45. For Previous studies have shown that the performance of graphene as additives for IL lubricates is connected with the concentration and the presence of the layered structure of graphene. He et al. found that low concentrations of graphene oxide sheets as additives for lubricants has poor lubricating effects . Saurin Ff, which was ensured by the synergistic effect of graphene and ionic liquids. On one hand, previous research have shown that graphene is easily torn by the frictional substrate [Under all the conditions given in this study, the addition of graphene resulted in a significant reduction in ubstrate , and theubstrate . Graphen(1)Graphene as lubricant additives can improve the lubrication performance of ILs at all given conditions. The reduction reach up to 88%. The improved tribological properties of composite lubricants are attributed to the fact that intact graphene prevents direct contact of the friction pairs interface, but fail under high normal stress due to structure rupture.(2)Multilayer graphene has better friction-reducing performance and better friction durability compared to monolayer structure. The antifriction performance is ascribed to the easy-shear property between the multilayer graphene layers with super-low binding energy, which is 5% of the binding energy between the DLC and the graphene. The friction durability is due to the decrease in the percentage of high tensile stress sites which ensures that the multilayer graphene has a more stable structure in lubrication.(3)Ni. Void space occurring under insufficient Ni in lubrication film makes the Fn acting on graphene higher than the theoretical value, which then makes graphene prone to rupturing under the same theoretical pressure. Over-thick IL film and graphene form a three-body abrasive wear structure with stress concentration in the graphene, and eventually lead to degradation of tribological performance of the compound lubricant.The lubricating performance of the compound lubricating oil is sensitive to (4)Both the rough surface of the substrate and the high sliding speed affects the lubricating properties of the lubricant, which is caused by the excessively concentrated stress in the graphene plane, promoting the bond formations between graphene and DLC substrates. In addition, it is found that graphitization caused by high temperature effectively reduces friction in the stable stage in high speed.(5)The results of this study explain the basic friction mechanism of graphene additives in ionic liquid lubricants, and provide a reference for the development of new fluid lubricants by adjusting the content of graphene, normal stress and the thickness of ionic liquid lubrication film to meet potential applications.In this paper, an atomic configuration comprising two DLC substrates and IL lubricants with graphene additives was constructed to evaluate the tribological behavior of the lubricants using MD simulation. Through the systematical analysis of the evolution of friction interface, dynamic trajectory of the lubricant, and stress state of the additives and friction property, we arrived at the the following conclusions:


A reconfigurable passive device that can manipulate its resonant frequency by controlling its quantum capacitance value without requiring complicated equipment has been experimentally investigated by modifying the Fermi level of large-area graphene using an external electric field. When the total capacitance change, caused by the gate bias in the passive graphene device, was increased to 60% compared to the initial state, a 6% shift in the resonant frequency could be achieved. While the signal characteristics of the graphene antenna are somewhat inferior compared to the conventional metal antenna, simplifying the device structure allowed reconfigurable characteristics to be implemented by using only the gate bias change. Graphene is a monolayer material but acts as an interface for bonding with other materials. Consequently, the primary area of study regarding the constant voltage condition has been the analysis of the resistance change of a device due to the interface charging phenomenon. For radio frequency (RF) applications, the inductance and capacitance of the device greatly affect the operating characteristics. Moreover, unlike metal, most signals applied from the outside would be transmitted, rather than absorbed or reflected, owing to graphene’s thinness  and possibly being due to the frequency dependence of skin depth. This suggests that the material with a thickness in nm is more reactive in the THz region ,2,3.Early studies regarding the RF characteristics of graphene devices primarily focused on applied research, using a high cutoff frequency and the frequency-doubling effect in field-effect transistor (FET)-type active devices ,5,6,7,8.In this work, two dipole antennas integrated on the same plane were fabricated using a four-inch wafer-scale graphene sheet. When graphene was used as an antenna, a 2% level of resonance-frequency modulation was observed, according to the 10% change in capacitance. In addition, when the graphene was used as a ground plane, a 6% level of resonance-frequency modulation was successfully achieved due to the 60% capacitance change achieved via the quantum capacitance of the graphene sheet. For reconfigurable passive devices requiring resonant frequency control ,25, a re2 (300 nm)/Si substrate using a reactive ion-etching process. Subsequently, a 50 nm Pt electrode was deposited inside the trench by using an E-beam evaporation system to form a buried-gate electrode with significant advantages over the other structures in terms of the uniformity of the electric field applied to the channel region. To achieve planarization of the gate electrode, using chemical and mechanical polishing processes, 20 nm of Al2O3 was deposited using an atomic layer deposition (ALD) process and a 300 °C vacuum-annealing process for 1 h. Subsequently, the 4-inch-scale CVD graphene sheets  were transferred using a vacuum-transfer method to ensure a stable and consistent device operation, considering that this method can reduce impurities, such as oxygen and moisture, between the graphene and the substrate [2 plasma, the graphene area was patterned via a photolithography process using a metal hard mask (Au). Finally, the top electrode (Au) was formed using an E-beam evaporation process and wet etching.To create the graphene-antenna device, a 50 nm oxide trench pattern was formed on a SiOubstrate . To prev2O3 gate dielectric was 20 nm (dielectric constant = 6). The antenna itself was simply designed to operate at approximately 660 GHz, with resonance at 10–20 GHz. The ground plane was made of metal and platinum (Pt) to control the Fermi level of the graphene. The spacing between the transmitter and the receiver was alternated between 10 and 150 μm to observe the changes in signal-transmission characteristics. The Fermi level of the graphene could be controlled using the bias applied to the Vg contact shown in A passive device with a transmitter and receiver of two basic dipole antennas integrated on the same plane was fabricated to study the reconfigurable passive device using graphene. Device 1 consisted of 100 μm pitch ground–signal–ground (GSG) pads, as shown in d–Vg (drain current–gate voltage). In a passive device, such as Device 1, a DC current does not flow. Hence, the gate voltage value for accurate Dirac point setting was unknown during the RF measurements. Moreover, Dirac point analysis in graphene devices is possible using C–V measurements instead of Id–Vg measurements. However, reconfiguring the four electrodes into one electrode for correct C–V measurements would be necessary, as two dipole antennas were patterned with graphene during the formation of Device 1. A capacitance measurement was carried out using the top electrode and buried electrode on the same substrate of the antenna device. Consequently, the Fermi level change in the graphene at the S-parameter measurement was set to a point where the Dirac point appeared at a gate voltage of 0 V. In this case, the estimated carrier density existing at the charge neutrality point was 3.1 × 1011cm−2. This value is very important because the quantum capacitance of graphene is generally more clearly observed when it has a lower carrier density than the classical capacitance of the device, and this is the ultimate reason for the tunability of the resonance frequency in these devices [Its characteristics in the RF domain were analyzed using a network analyzer (Agilent 8510C) and a two-port probe system in the 1–40 GHz range. The S-parameters, reflections , and transmissions  were measured using a network analyzer. A constant voltage applied to the ground plane modulated the Fermi level of the graphene. Then, the S-parameters were measured as a function of the Fermi level of the graphene. First, we observed the appearance of signal reflections and transmissions when the spacing between the three antennas physically changed. The Fermi level of the graphene for the graphene antenna was assumed to be at the Dirac point. The observation of the Dirac point, based on the doping condition of graphene devices, can generally be obtained by measuring the I devices .In the case of S12, as shown in The S-parameter measurements of the RF operating characteristics of Device 2 did not exhibit resonance at a specific frequency as they did in Device 1 or in the reference device. For Device 2, analysis was conducted based on the characteristic changes at 4.5 GHz. When the distance between the metal antennas was increased in Device 2, a change in the S-parameter value over the entire frequency range, rather than a resonant frequency shift, was observed. In particular, S12 or S21 showed signal transmission attenuations of more than 15 dB when the distance was increased. Simultaneously, in S11 or S22, the reflection amount increased as the distance between the antennas increased.Next, the RF characteristics were investigated while applying the external bias to the graphene to modulate the Fermi level of the graphene. Using a gate electrode as a ground plane, measurements were made at −5, −3, −1, 0, 1, 3, and 5 V; different polarities were applied to observe the changes in the graphene carrier types in the graphene layer.g increased, the resonant frequency shifted towards the lower frequencies. The frequency shift range was approximately 150 MHz. The change in characteristics due to the Vg was shown in that the degree of the shifting of the resonant frequency was proportional to the absolute value, regardless of the polarity of the Vg, i.e., when the Fermi level of graphene changed via the gate bias, the carrier type and carrier concentration changed based on this value and the polarity of the gate bias. However, as seen from the Id–Vg measurements of the graphene device, the same conductance could be seen even if the absolute value of the gate bias was the same, regardless of the carrier type. Therefore, as shown in As resonance was most apparent when the antenna spacing was at 100 μm, the characteristics based on the gate bias change were observed in the device at that spacing. The results, based on changing the gate bias, did not differ much compared to those obtained when the antenna spacing was changed, as shown in g increased, the signal transmission improved by 3 dB and the reflectance reduced by 1 dB, as shown in Although Device 1 and the graphene RF device exhibited similar resonance characteristics to those of the reference passive device under its operating conditions, their transmittance values were low and their reflectance values were very high, possibly due to the significantly high contact resistance between the graphene and the graphene–metal contact. Therefore, improving the structure of the passive device would be necessary to secure its basic performance while facilitating the movement of resonant frequency by controlling the quantum capacitance of the graphene. The changes in the resonant frequency and measured S-parameter values due to changes in the Fermi levels of graphene, used as a ground plane by the gate bias, were more apparent than those in Device 1. As the VUnder the same conditions, the measured values of Device 1, Device 2, and the reference device were compared to analyze the cause of different signal transmissions and reflection characteristics, as shown in Conversely, in the case of signal transmission , the impedance value of the passive device itself and the space for transmitting the RF signal were important . The RF g was compared, as shown in g could be observed. However, a change in resonant frequency could be seen when the graphene was used. For S11, when Device 1 was exposed to a larger Vg value, an approximately 100 MHz shift towards the lower frequency was observed. However, for Device 2, the resonant frequency increased by approximately 200 MHz. The analysis results of g occurring approximately 1.5 times more, i.e., Device 1 and Device 2 exhibited a resonant frequency change of approximately 200 MHz and 300 MHz, respectively.Consequently, the degree of resonant frequency variation regarding the reflectance and transmittance due to the VIncreasing the carrier concentration of graphene in passive devices improved the RF signal transmission, and the quantum capacitance changes induced a change in the resonant frequency. The capacitance value of each passive device was measured to examine the correlation between the S-parameter characteristics and the capacitance changes in the passive device, as shown in g = 0 V. As shown in In this experiment, we changed the resonant frequency in a passive device using graphene. The relationship between the rate of resonant frequency shift and the rate of capacitance change was investigated based on Vg. When graphene was used as an antenna, characteristics similar to those of a passive device using a conventional metal film were observed, suggesting that graphene could be applied as a passive device based on the patterning. However, when a graphene ground plane was used, small-signal RF transmission was compromised and an accurate passive device operation could not be performed. Nonetheless, changes in quantum capacitance and carrier concentration due to graphene Fermi level changes affected the resonant frequency control and signal propagation. For reconfigurable passive devices requiring resonant frequency control, a resonant frequency change rate corresponding to 2.5~9.6% of the capacitance change rate in the passive graphene device was possible. Although these changes are insufficient for the practical application of graphene in reconfigurable passive devices, they indicate the potential to explore and positively contribute to their development.To design a reconfigurable passive device using graphene, we fabricated integrated passive devices with two dipole antennas and analyzed their RF characteristics, aiming to analyze the use of graphene in passive devices and the amount of resonant frequency change possible based on the changes in V


TARDBP, the gene encoding TDP-43, can cause ALS and cluster in the C-terminal prion-like domain (PrLD), where they modulate the liquid condensation and aggregation properties of the protein. TDP-43-positive inclusions are also found in rimmed vacuole myopathies, including sporadic inclusion body myositis, but myopathy-causing TDP-43 variants have not been reported. Using genome-wide linkage analysis and whole exome sequencing in an extended five-generation family with an autosomal dominant rimmed vacuole myopathy, we identified a conclusively linked frameshift mutation in TDP-43 producing a C-terminally altered PrLD (TDP-43p.Trp385IlefsTer10) (maximum multipoint LOD-score 3.61). Patient-derived muscle biopsies showed TDP-43-positive sarcoplasmic inclusions, accumulation of autophagosomes and transcriptomes with abnormally spliced sarcomeric genes (including TTN and NEB) and increased expression of muscle regeneration genes. In vitro phase separation assays demonstrated that TDP-43Trp385IlefsTer10 does not form liquid-like condensates and readily forms solid-like fibrils indicating increased aggregation propensity compared to wild-type TDP-43. In Drosophila TDP-43p.Trp385IlefsTer10 behaved as a partial loss-of-function allele as it was able to rescue the TBPH (fly ortholog of TARDBP) neurodevelopmental lethal null phenotype while showing strongly reduced toxic gain-of-function properties upon overexpression. Accordingly, TDP-43p.Trp385IlefsTer10 showed reduced toxicity in a primary rat neuron disease model. Together, these genetic, pathological, in vitro and in vivo results demonstrate that TDP-43p.Trp385IlefsTer10 is an aggregation-prone partial loss-of-function variant that causes autosomal dominant vacuolar myopathy but not ALS/FTD. Our study genetically links TDP-43 proteinopathy to myodegeneration, and reveals a tissue-specific role of the PrLD in directing pathology.Neuronal TDP-43-positive inclusions are neuropathological hallmark lesions in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Pathogenic missense variants in The online version contains supplementary material available at 10.1007/s00401-023-02565-1. TARDBP, is an evolutionary highly conserved and ubiquitously expressed RNA- and DNA-binding protein . It is iewed in , 44. Theiewed in .TARDBP , even being at equal levels compared to control muscle tissue. These data suggest that accumulations in TDP-43p.Trp385IlefsTer10 muscle tissue are primarily composed of mutant protein, while pTDP-43[Ser409/410]—originating from the wild-type allele—remains at baseline levels in a soluble state.While neuropathological and genetic studies have established the crucial involvement of TDP-43 proteinopathy in the pathogenesis of ALS/FTD and related neurodegenerative disorders , increasopathies . Of intep.Trp385IlefsTer10 clearly differs from the ALS-causing missense variants which are present in an otherwise normal PrLD. Indeed, a major and unexpected finding in this study was the mainly chronic and slowly progressive myopathic clinical manifestation associated to TDP-43p.Trp385IlefsTer10. Although milder neurogenic signs were also present in some patients, ALS and/or FTD phenotypes were never observed. The specific nature of our truncating variant therefore likely holds the key as to how TDP-43p.Trp385IlefsTer10 leads to a muscular rather than a neurodegenerative condition. Interestingly, recent reports have linked a similar truncating TDP-43 variant, TDP-43p.Y374Ter, to a typical ALS phenotype  phosphorylated TDP-43 are maintained in muscle tissue, apparently at the expense of unmodified full-length WT TDP-43 from the normal allele, which could further contribute to a depletion and loss-of-normal function of WT TDP-43. Remarkably, this phenomenon was not observed in fibroblasts, reinforcing the idea that TDP-43 undergoes muscle-specific processing and modification including phosphorylation, thereby providing a possible explanation of the myopathy phenotype associated with TDP-43p.Trp385IlefsTer10. Further evidence for a tissue-specific function of TDP-43 was recently obtained in mouse muscle and neuronal cells showing cell-type-specific differences in TDP-43-mediated pre-mRNA processing [Despite our functional studies suggesting that TDP-43ocessing .p.Trp385IlefsTer10, our transcriptomic analysis of TDP-43p.Trp385IlefsTer10 muscle tissue provided evidence for a nuclear loss-of-function. Through analysis of alternative pre-mRNA processing patterns, a nuclear process TDP-43 is tightly involved in, we identified a number of transcripts affected by AS. Interestingly, the great majority of these AS targets corresponded to muscle-specific structural/contraction-associated proteins. Indeed, 5 out of the top 10 transcripts with the most AS events corresponded to sarcomeric genes, including TTN and NEB, indicating that abnormal nuclear pre-mRNA splicing of functionally important sarcomeric genes could contribute to the pathogenic mechanism of the myopathy in our family.In line with the proposed partial loss-of-function nature of TDP-43TTN and NEB, within sarcoplasmic myo-granules during muscle development/regeneration [p.Trp385IlefsTer10, the attempted and failed regeneration by the muscle fibres would result in an upregulation of myogenic pathways and certain sarcomeric mRNAs, which is supported by the observed upregulation of developmental myosin isoforms [p.Trp385IlefsTer10 resulting in autophagic myodegeneration over time [In mice, TDP-43 has been shown to associate with sarcomeric mRNAs, such as neration , and is neration  showed tisoforms . Furtherver time .Finally, this finding adds TDP-43 to the growing list of RNA-binding proteins as genetic causes of myopathies. Interestingly, similar to TDP-43, frameshift mutations in the PrLDs of HNRNPA2B1 and HNRNPA1 that change the prion-like behaviour of the mutant proteins have been described recently as the genetic cause of myopathies , 29, whep.Trp385IlefsTer10 is in early stages, the findings we report here will help to understand a muscle-specific function for TDP-43 and how it can be related with the development of myopathies. Furthermore, our work points towards a broadening of the disease spectrum of TDP-43 proteinopathies, expanding from pure neurodegenerative to muscular disorders.Although work on TDP-43p.Trp385ilefsTer10 variant was identified. Individuals identified with “m/-“ are affected individuals that have either been genotyped or identified through reconstruction of the pedigree. Individuals that were genotyped are identified with an asterisk(*). Individuals in white are untested but assumed to be unaffected.Figure S2. TEM images and haplotype analysis. a) TEM images of different features of the patient skeletal muscle: i. Intact motoric end-plate without any signs of degeneration; ii. Necrotic muscle fibre with apoptotic bodies (arrows) and abnormal mitochondria (arrowheads); iii. Filamentous material found within the nuclei of the muscular sarcolemma. b) TEM of patient-derived cultured myocytes. i. Presence of multiple vacuolar bodies (arrowheads) and enlarged autophagic compartments (arrow); ii. Close-up of a “zebra” pattern autophagosome containing electron-dense material and “fibre-like” material. c) Haplotype analysis of the members of the family in which the TDP-43p.Trp385IlefsTer10 variant was identified . The 4.7 Mb genomic region shared between all affected individuals (rs10864439-rs10927466) is shown in the red box. The disease haplotype is marked as number 1 (highlighted red). Figure S3. Genome-wide multipoint LOD-scores.Figure S4. IGV view of RNA-seq data in patient muscle tissue. RNA-seq-derived bridged reads spanning the 11 bp deletion in the TARDBP gene on patient muscle samples (red box).Figure S5. Automated microscopy and survival analysis. Rodent primary neurons were dissected, cultured, and transfected with plasmids encoding fluorescent proteins. The cells were then imaged using an automated epifluorescence microscopy platform allowing repeated and chronological visualization of individuals neurons. After 10d of imaging, neurons were identified by customized scripts in python and Fiji (green outline), assigned a unique number (yellow), and their time of death determined based upon the loss of fluorescence, soma rounding, neurite retraction, and/or cellular blebbing (red outline and number). (PDF 28047 kb)Supplementary file1 Figure S1. Expanded pedigree of the TDP-43p.Trp385IlefsTer10 family. Expanded pedigree of the family in which the TDP-43Below is the link to the electronic supplementary material.


To address this limitation, this study introduces a modified transfer process that utilizes a temporary UV-treated SiO2 substrate to adsorb impurities from graphene before transferring it onto the final substrate. Optical microscopy and Raman mapping confirmed the adhesion of impurities to the temporary substrate, leading to a clean graphene/substrate interface. The retransferred graphene shows a reduction in electron–hole asymmetry and sheet resistance compared to conventionally transferred graphene, as confirmed by the transmission line model (TLM) and Hall effect measurements (HEMs). These results indicate that only the substrate effects remain in action in the retransferred graphene, and most of the effects of the impurities are eliminated. Overall, the modified transfer process is a promising method for obtaining high-quality graphene suitable for industrial-scale utilization in electronic devices.Graphene has immense potential as a material for electronic devices owing to its unique electrical properties. However, large-area graphene produced by chemical vapor deposition (CVD) must be transferred from the as-grown copper substrate to an arbitrary substrate for device fabrication. The conventional wet transfer technique, which uses FeCl However, these processes introduce two types of impurities into the graphene layer: polymer residues on the graphene surface and interfacial impurities [The integration of graphene into optoelectronic applications requires a large, homogeneous graphene sheet that is typically produced by chemical vapor deposition (CVD) on metal catalysts such as Cu or Ni, producing diverse outcomes from monolayer to multilayer graphene ,2,3. Forpurities ,7,8,9,10purities .3 as a metal etchant can lead to the formation of complex nanoparticles at the interface between graphene and the substrate. Kraus et al. reported that FeCl3 etching of copper resulted in cubic Fe0.942O nanoparticles under graphene, indicating the presence of uncontrolled phases of iron oxides such as FeO, Fe2O3, Fe3O4, etc. These iron oxides can exhibit n- or p-type behaviors depending on the phase species [The use of FeCl species ,13,14. S species , mechani species , and RCA species . However species .2 substrate to achieve high efficiency in eliminating impurities from the graphene/substrate interlayer. In this technique, the graphene layer is first transferred onto a UV-irradiated hydrophilic substrate, allowing water to intercalate at the interface between the graphene and the substrate. In this process, interfacial impurities are retained on the temporary substrate, and the cleaned graphene can be retransferred to a target substrate without physical damage. Using optical microscopy and Raman spectroscopy, we confirmed that all interfacial impurities in the retransferred graphene were eliminated. Furthermore, we demonstrated significant improvements in electrical measurements using the transmission line model (TLM) and Hall effect measurements (HEMs), such as a reduction in sheet resistance and electron–hole asymmetry in the retransferred graphene. We suggest that this modified wet transfer method can be implemented as an efficient method for obtaining a clean interface during the transfer of all thin films and 2D materials, as well as for devices that are sensitive to interfacial properties [In this study, we introduce a modified wet transfer method that uses a temporary SiOoperties ,20,21,22TM) in a tube-type CVD. The Cu foil was placed inside the CVD chamber and annealed for 1 h with 200 sccm of flowing argon gas, raising the chamber temperature to 980 °C. Subsequently, 80 sccm of hydrogen gas was introduced, and the sample was annealed at the remaining temperature for 1 h. Following annealing, 1.5 sccm of methane gas was introduced to grow graphene for 2 h, resulting in continuous single-layer graphene. Following the growth process, the graphene was rapidly cooled by moving the furnace to the cooling zone.Graphene was grown on commercial copper foils /Si substrates were prepared using various surface treatments, including blowing N2 gas, sonication in deionized (DI) water (40 min), sonication in acetone (20 min) and isopropyl alcohol (20 min), UV treatment (60 s), and annealing at 120 °C for 30 min in high vacuum, to optimize the substrate cleaning conditions for electrical property measurements [Thermally oxidized SiOurements .Raman spectroscopy was performed using a confocal spectrometer  at the CORE Facility Center for Quantum Characterization/Analysis of Two-Dimensional Materials and Heterostructures. The measurements were recorded with a 532 nm laser with 5 mW power and a 100× objective, resulting in a laser spot size of approximately 2 µm.2/Si substrates with pre-deposited Cr/Au (5 nm/30 nm) electrodes. The electrode and graphene channels were defined using laser lithography  with KL5305  as the photoresist and PMMA 950 A6  as the buffer layer.Using the conventional wet transfer method and our modified retransfer method, graphene was transferred onto SiO2 plasma was performed. The Cu foil was etched by floating it on an iron chloride (FeCl3) solution followed by rinsing it with DI water. The general wet transfer process typically involves transferring the PMMA/graphene structure to the final target substrate and removing the PMMA after drying. However, we modified the process by transferring the PMMA/graphene structure onto a temporary SiO2 substrate that had been treated with UV light. Several treatments were tested to determine the highest hydrophilicity for the temporary substrate, among which UV treatment was the most efficient  to the 2D and G peaks (I2D/IG). Compared with the optical microscopy results, the local impurity points and line-shaped graphene folds have high intensities in the ID/IG mapping but low intensities in the I2D/IG mapping. Generally, measuring Raman spectra of graphene on a metal substrate is the most challenging task because the scattering of the metal surface hinders the identification of the distinct peak information of graphene. If graphene is transferred onto a partially metal-containing substrate, that is, onto metal nanoparticles, the background signal increases and shades the graphene spectrum [D/IG and I2D/IG, instead of ID and I2D alone. In general, ID (~1350 cm−1) indicates a defective non-sp2 domain, and some iron oxide phases exhibit a distinct peak near ~1320 cm−1 [D/IG can be used as an index that shows the position of the residual impurities and their structural effects on graphene. I2D/IG is used as an index not only for confirming that the graphene is single-layer, but also for determining the amount of p-doping owing to the increase in the G-peak and decrease in the 2D-peak on p-doped graphene [To check for the invisible quality, we performed Raman analysis of the transferred and retransferred graphene. Raman analysis was conducted by mapping an area of 50 × 50 μmspectrum ,29. To c320 cm−1 . Therefographene .Si) to 1, we could observe changes in both the Raman intensity and intensity ratios. Interestingly, in contrast to the D-peak intensity, which increased due to local defects, the G- and 2D-peak intensities also increased as a result of the impurities. This is explained in We compared the positions, distributions, and electrical effects of the impurities between the two methods. Three points were selected for each Raman mapping result. In the transfer result a, the im−1, 2676.7 cm−1) [To quantitatively analyze the improvement in strain and doping, we used a vector decomposition method based on the quasi-linear change in phonon energy with strain and doping . In this.7 cm−1) . The OX→To determine the strain and doping, we used the Jacobian transformation (Equation (1)) .(1)OX→=D/IG analysis, and are visible in the tensile strain analysis, exhibit n-type doping characteristics, indicating electron donation. This may be attributed to the n-type behavior of certain iron oxide phases [Using Equation (1), we reconstructed Raman mapping images of the disentangled strain and doping of the transferred and retransferred graphene b. Interee phases . Overall2 substrate. Laser lithography was used with a photoresist (PR) and PMMA heterostructure to pattern the electrodes and etch graphene to define the channel dimensions. In general, e-beam lithography is preferred for graphene device fabrication because of its many advantages in fabricating submicropatterns and effective elimination of the PMMA layer. Although laser lithography is faster for fabricating large-scale patterns, an effective cleaning method for PR residues on graphene has not yet been developed. Therefore, we spin-coated PMMA onto the graphene surface and sequentially deposited PR. After developing the desired pattern on the PR, the PMMA and underlying graphene layers were etched using O2 plasma. Subsequently, the remaining PR/PMMA layers were removed using acetone/IPA solvent.The electrical properties of graphene were investigated to confirm the effect of the retransfer process using transmission line model (TLM) devices with a width of 50 μm and a total length of 800 μm. Larger channel dimensions were chosen to avoid sample-to-sample variations due to the impurity size, and the distances between the impurities were at the micro and sub-micro scales. As shown in D-VG curves for the transferred and retransferred graphene devices and their respective channel lengths are presented in e/μh) of transferred graphene FET, which averages 0.76 from 10 devices. In D-VG curve for the retransferred graphene, which showed relatively stable Dirac voltages and drain current levels. This suggests that the interfacial doping effects were significantly reduced, and only the SiO2 substrate effects remained active [2 tends to undergo p-doping. For the retransferred graphene, the ratio between electron and hole mobilities (μe/μh) averaged 0.85.The Id active . GeneralD-VD measurements were performed with VD = 10 mV. The resulting sheet resistance (RS) is shown as a function of channel length in Total = 2Rc + Rs L/W was used to fit the data, where RC is the contact resistance, L is the length, and W is the channel width. We also examined these effects using Hall effect measurements with the van der Pauw method to investigate the electrical properties of the graphene sheet, such as the RS, carrier concentration, and Hall mobility [D/dVG) (Lch/WchVDCox) [2 capacitance is Cox = 11.51 × 10−9 F/cm2. The black and red circles indicate the spread areas of the hole mobilities versus the Dirac voltages for the transferred and retransferred devices, respectively. Comparing the circles, the retransferred sample exhibits a larger improvement than the transferred graphene. We found that the impurities in the graphene–substrate interface consist of p- and n-type dopants with random distributions, resulting in wide spreads in the Dirac voltage and carrier mobilities of the transferred graphene.To examine the changes in the conductance and scattering effect of the TLM devices, Imobility . (See SuchVDCox) , where S2 substrate and UV treatment, our retransfer process enabled the removal of metallic impurities and reduced the interfacial doping effects in graphene. As a result, the retransferred graphene showed significantly improved electrical properties, including reduced sheet resistance and stable electron–hole asymmetry distributions. These findings provide valuable insights for the development of high-performance graphene-based electronic devices, highlighting the importance of interfacial purity in achieving optimal device performance.Our study demonstrated the effectiveness of a modified wet transfer technique for eliminating interfacial impurities in CVD-grown graphene. Using a temporary SiO