RNR3 and SMF3, containing iron-responsive elements (IRE). Importantly, Sin3 is also recruited to these promoters but only in the presence of functional Cti6. Our findings provide novel insights toward the critical interaction domain in the co-regulator Cti6, which is a component of regulatory complexes that are closely related to chromatin architecture and the epigenetic status of genes that are regulated by pleiotropic co-repressors.Mapping of effective protein domains is a demanding stride to disclose the functional relationship between regulatory complexes. Domain analysis of protein interactions is requisite for understanding the pleiotropic responses of the respective partners. Cti6 is a multifunctional regulator for which we could show recruitment of co-repressors Sin3, Cyc8 and Tup1. However, the responsible core domain tethering Cti6 to these co-repressors is poorly understood. Here, we report the pivotal domain of Cti6 that is indispensable for co-repressor recruitment. We substantiated that amino acids 450–506 of Cti6 bind PAH2 of Sin3. To analyse this Cti6–Sin3 Interaction Domain (CSID) in more detail, selected amino acids within CSID were replaced by alanine. It is revealed that hydrophobic amino acids V467, L481 and L491 L492 L493 are important for Cti6–Sin3 binding. In addition to PAH2 of Sin3, CSID also binds to tetratricopeptide repeats (TPR) of Cyc8. Indeed, we could demonstrate Cti6 recruitment to promoters of genes, such as The online version of this article (10.1007/s00294-020-01109-4) contains supplementary material, which is available to authorized users. In addition, Cti6 is important for iron metabolism in yeast . Importantly, Sin3 was also recruited to these promoters but only in the presence of functional Cti6.Therefore, it was worthy to extend the scope on the regulatory protein Cti6 by characterizing extensively its interaction with both co-repressors and explore additional aspects regarding particular Cti6 target genes. In this report, we show that Cti6 not only interacts directly with both Sin3 and Cyc8/Tup1 co-repressors but also identify precisely the minimal interaction domain responsible for binding of all tested co-repressors. Our in vitro interaction studies showed that amino acids 450–506 of Cti6 bind PAH2 of Sin3 and the same domain mediates the interaction with Cyc8 co-repressor as well. To analyse Cti6–Sin3 interaction domain (CSID) in more detail, selected amino acids within CSID were replaced by alanine. It turned out that hydrophobic amino acids V467, L481 and at least one of the lysines at the positions 491–493 is important for Cti6–Sin3 binding. The results of this work also suggest that repression is not executed entirely via Sin3, but rather CSID is also important for contacting pleiotropic co-repressor Cyc8 via its tetratricopeptide repeats (TPR). Chromatin immunoprecipitation (ChIP) analyses demonstrated Cti6 recruitment to promoters of genes, such as Saccharomyces cerevisiae were used. All of the following strains are haploid. S. cerevisiae strain C13-ABY.S86 lacking four vacuolar proteinases  or gene disruptions . To obtain such isogenic null mutant, disruption plasmid pRAR81 (ΔCTI6::LEU2) was used. Complete genotypes of all strains used are available as supporting online Table 1 (section a). For ChIP analysis, the investigated strains were cultivated under respective repression conditions as described in Puig et al. . The tac promoter controlling GST fusion genes was induced with 1 mM IPTG. Similarly, tetR-dependent gene expression was activated by 0.2 mg/l anhydrotetracycline. Derepression of MET25-dependent gene fusions was achieved by cultivating yeast transformants in the absence of methionine. GST fusion proteins synthesized in E. coli were released by sonication, immobilized on glutathione (GSH) Sepharose and subsequently incubated with yeast or bacterial total protein extracts containing HA fusions. To avoid unspecific interactions, protein extracts were pre-cleared by treatment with GSH Sepharose beads prior to incubation with GST fusions. Details on washing steps at intermediary stringency have been described  while Cti6 domains  were inserted in pGAD-C1 (2 µm GAL4TADLEU2). Double-transformed strains containing both types of fusion plasmids were first selected on medium lacking leucine and tryptophan (-L-T) and subsequently transferred to medium devoid of adenine (-L-T-A).To perform two-hybrid assays, strain PJ69-4A was used  and the absence of any other change in the plasmids obtained .To alter selected residues in the coding region of Cti6, the QuikChange site-directed mutagenesis kit of Stratagene was used. To obtain mutations within CSID, plasmid pRAR47 containing the Cti6 coding region was used. To replace selected residues against alanine, we used pairs of mutagenic primers introducing a GCA codon instead of the natural codon, flanked by 15–19 nucleotides on both the sides. DNA sequencing was used to confirm the presence of the desired mutant alleles of CTI6 was modified such that it expressed a His-tagged Cti6 without alteration of gene copy number or control region. Tagging was performed by transformation of strain C13-ABY.S86 with a gene-specific modification fragment and selection for resistance against geneticin. The modification fragment was amplified by PCR, using gene-specific primers and plasmid pU6H3HA as a template , FKH11 (SIN3-HIS6-HA3-kanMX) and its isogenic cti6 derivative RAY3 (Δcti6 SIN3-HIS6-HA3-kanMX) grew until mid-log phase and were treated with formaldehyde for 15 min. The cross-linking reaction was subsequently quenched for 5 min by addition of glycine to a final concentration of 125 mM. After lysis, cells were sonicated five times for 30 s to shear chromatin, using a Bandelin Sonoplus UW 70 microtip (35% power). After sonication, lysates were centrifuged for 10 min at 16,000 g to remove insoluble material and incubated for at least 4 h with His-Tag Dynabeads® . After elution of affinity-purified proteins and bound DNA with a buffer containing 300 mM imidazole, cross-linking was reversed by heating to 65 °C overnight. DNA was recovered and analyzed by PCR (29 amplification cycles), using specific primers against promoters of RNR3 (− 400/− 100) and SMF3 (− 350/− 80) or ACT1 gene (+ 841/ + 1165) as a control.Essentially, chromatin immunoprecipitation (ChIP) analysis followed the procedure described by Cobb and van Attikum . ChromosEscherichia coli expression plasmids  encoding various glutathione S-transferase (GST) fusions were constructed. Length variants of coding regions of CTI6 gene were amplified by PCR and fused behind GST. Similarly, HA-tagged length variants of Sin3 representing PAH domains, Cyc8 and Tup1 were expressed in yeast using plasmid p426-MET25HA  has been described , pFK77  and pRAR110  derived from pASK-IBA5  were used. To confirm authenticity of gene fragments obtained by PCR, GST fusions which encode minimal length variants of Cti6 were verified by DNA sequencing . Plasmid names and fused sequences are mentioned in legends of figures and are described in detail in supporting online Table 1 (section b). Gene-specific primers used for PCR amplifications are available as supporting online Table 1 (section c). Plasmid pRAR81 was constructed by established procedures to disrupt the CTI6 gene (Δcti6::LEU2). To construct this plasmid, flanking sequences upstream and downstream of the respective coding regions were amplified by PCR and inserted on both sides of the selection marker, allowing total deletion of the CTI6 reading frame.To perform interaction assays, S. cerevisiae strains, selection for yeast transformants on the respective synthetic media, PCR amplification and β-galactosidase assays have been described  Sepharose. A protein extract from S. cerevisiae (HA-Sin3 full length) was added to this affinity matrix. After intensive washing with increasing stringency, specifically bound protein was eluted by the addition of free GSH.Puig et al.  have pro3-Sin3 could be bound by GST–Cti6 under stringent conditions but not by GST. Thus, Cti6 may execute its function by recruiting the general co-repressor Sin3. As interaction experiments performed with protein extracts from yeast cannot completely rule out indirect interactions mediated by distinct factors, HA3-Sin3 was thereafter also synthesized in E. coli. Since bacterial protein extracts should not contain yeast-specific factors, a direct interaction can be concluded by the use of HA3-Sin3 from E. coli. As is apparent from Fig. E. coli, indicating that interaction between Cti6 and Sin3 occurs directly.As is shown in Fig. We, thus, wished to establish a physical map of interacting domains within Sin3 and Cti6. Sin3 contains four PAH motifs, which have been proposed to mediate various protein–protein interactions  and PAH2 (aa 301–888) were fused with the DNA-binding domain (DBD) of Gal4. Binding domains of Cti6 which have been shown to bind Sin3 in vitro were fused with Gal4 transcriptional-activation domain (TAD). Sin3–Cti6 interactions in vivo should reconstitute a functional Gal4 activator being able to stimulate expression of the 450-506 minimal interaction domain which has displayed in vitro interaction with PAH2 of Sin3 is able to show in vivo binding as well.As is shown in Fig. In contrast to in vitro results, DBD fusions of Sin3  in combination with TAD fusions of Cti6 were unable to mediate growth on medium lacking adenine. Presumably, formation of functional interaction domains in vivo is prevented with certain length variants due to failure of correct protein folding. In summary, use of the "two-hybrid" system confirmed in vivo interaction between Cti6 and PAH2 of Sin3.To define the structural principles of Cti6–Sin3 interaction, we looked for an amphipathic pattern of amino acids within a putative α-helix of CSID. Indeed, amino acids 466–493 form such a regular pattern of hydrophobic residues  have been used. To quantify the repression effect of Cti6 in vivo, an effector plasmid was constructed, carrying the DNA-binding domain of the bacterial lexA repressor (lexADBD) together with the Cti6 reading frame. The empty lexA plasmid (pRT-lexA) was used as a control.Cti6 can functionally associate in vivo with the Rpd3–Sin3 complex in If this protein actually acts as a repressor, gene activation should be reduced as a result of co-repressor recruitment (such as Sin3–HDAC), leading to inaccessible chromatin. As shown in Table As shown above, the C-terminus of Cti6 residues 450–506) is able to interact with PAH2 of Sin3 in vitro and in vivo. Within this domain (designated CSID), an amphipathic pattern of hydrophobic amino acids could be identified  were completely defective for interaction with PAH2 of Sin3.Expression plasmids encoding GST fusions of mutagenized Cti6 were synthesized in It can be summarized that leucine residues at amino acid positions 481, 491, 492 and 493 in CSID have a pivotal role in interaction with Sin3. However, it cannot be excluded that a single residue among L491, L492 and L493 is more important for interaction than the remaining leucine residues since all amino acids were replaced simultaneously.GAL2-ADE2 reporter gene which restores growth on adenine-free medium when a functional Gal4 is reconstituted by interaction of the fused proteins. In contrast to the wild-type minimal interaction domain (Cti6450-506), Cti6 variants V467A, L481A and L491A L492A L493A were unable to activate the reporter gene  fused behind DNA-binding domain of Gal4. In the case of Cti6–Sin3 interaction, the resulting hybrid constructs should be able to activate the Gal4-dependent E. coli in the absence of additional yeast proteins  containing HA3-tagged proteins Tup1 protein. As can be seen in Fig. It has been previously reported that Cti6 directly interacts in vivo and in vitro with the co-repressor Cyc8  have been selected as targets for Cti6 regulation. SMF3 is a member of the Nramp family of divalent metal transporter  was employed to monitor directly the occupancy of particular promoters by both regulatory proteins. A growing body of data points to the significant role of Cti6 in iron metabolism  and then Sin3 recruitment to target genes was investigated again. As is apparent from Fig. Δcti6 mutant strain although Sin3 was detected in the presence of an intact copy of Cti6. Thus, Sin3 co-repressor can efficiently be recruited to gene promoters regulated by iron when the Cti6 protein is present.Accordingly, we have first examined the existence of Cti6 at promoters of both target genes under repressive conditions (+ 100 µM Fe +). This is achieved by constructing a strain (RAY1) encoding an epitope-tagged Cti6-HA variant which was subsequently investigated by ChIP analysis. A strain encoding an epitope-tagged variant of Sin3  was kindly provided by F. Kliewe  and Gal4DBD-Sin31–300 (PAH1) could not activate the GAL2-ADE2 reporter gene which can be attributed to problems with protein folding of Sin3 partial domains under in vivo conditions.In this report, we have clearly confirmed that Cti6 directly interacts with the pleiotropic co-repressor Sin3, indicating that the pathway-specific protein Cti6 executes its function by recruiting the general co-repressor Sin3. Data presented here also indicate that a single domain of yeast protein Cti6  is able to interact with the PAH2 of co-repressor Sin3. No interaction has been found within the C-terminus of Sin3 which could be attributed to the fact that the C-terminal region of Sin3 is associated with complex subunits, such as Sap30, Pho23, etc., which render it inaccessible to other proteins. In addition, the recruitment of HDACs is brought about by interactions with regions in which PAH3 and PAH4 are located  has been used to perform a mutational analysis of CSID. While Cti6 interaction with Sin3 appeared to be still functional with a mutated valine (V467A) in vitro (GST pull-down assay), all tested Cti6 variants were defective for the interaction with Sin3 in vivo (two-hybrid assay), indicating that these positions are indispensable for Cti6 binding to Sin3. We suggest that variant V467A may show some residual function which allows interaction in vitro as a result of increased protein amount but is not sufficiently functional in vivo. Although the plant homeodomain (PHD) of Cti6 has an important role for 1-398 (containing only the TPR motifs). In summary, we provide evidence that CSID may be involved in a second pathway of repression acting in parallel to Sin3. Interaction of two co-repressor complexes with a single specific repressor may be the exception but not a general rule, at least in yeast. Besides Cti6, previous reports substantiated that yeast repressor Opi1 being responsible for repression of phospholipid biosynthetic genes contacts Sin3 and Cyc8/Tup1 via a single domain . We hypothesize that Cti6 mediates this repression through recruitment of co-repressors Sin3 and Cyc8-Tup1. In future work, construction of g et al.  demonstrRNR3 and SMF3) have been selected as targets for Cti6 regulation. Both structural genes are playing an important role in iron metabolism , indicating that Sin3 recruitment depends on Cti6. These results are in agreement with data of Puig et al.  catalyzes the rate-limiting step in deoxyribonucleotide synthesis and plays an essential iron-dependent role in DNA replication and repair (Stubbe RNR3 repression is mediated by upstream repression sequences (URS) designated as damage-responsive elements (DREs) that serve as binding sites for the sequence-specific DNA-binding protein Rfx1  inhibiting SMF3 expression by recruiting the pleiotropic co-repressors Sin3 and Cyc8/Tup1. Further work should investigate the possible direct or indirect interaction between Cti6 and Aft2 under both repression and de-repression conditions. Both hypothetical models are summarized in Fig. A related, but slightly different situation may be effective in the case of ession + 0 µM Fe +Supplementary file1 (DOCX 41 kb)Below is the link to the electronic supplementary material.


The described process is a simple, one-step synthesis with little to no side products. The synthesized materials showed an irregular, porous structure, with an average pore size of 3.44–3.61 nm ) and a multi-layer structure and a developed specific surface area at the level of 586–660 m2/g ). On the external surfaces, the occurrence of irregular particles with a size of 0.5 to 10 µm was observed, most probably the effect of doping the graphene structure and the formation of sp3 hybridization defects. The obtained materials show the ability to store electric charge due to the development of the specific surface area. Based on cyclic voltammetry, the tested material showed a capacity of 450–550 mAh/g (charged up to 2.5 V).Doping of graphene and a controlled induction of disturbances in the graphene lattice allows the production of numerous active sites for lithium ions on the surface and edges of graphene nanolayers and improvement of the functionality of the material in lithium-ion batteries (LIBs). This work presents the process of introducing boron and fluorine atoms into the structure of the reduced graphene during hydrothermal reaction with boron fluoride tetrahydrofuran (BF Lithium-ion batteries are the subject of intensive research due to their high potential for applications . Li-ion 6 [−1) [In most cases, Li-ion batteries are made of anode material in the form of graphite (C) and liquid lithium compounds as an electrolyte . Unfort6 [−1) , limited6 [−1) . An impo6 [−1) .2*g−1) [Due to the growing requirements for Li-ion cells, extensive research is carried out on the development of new electrode materials that will ensure higher energy density, high efficiency and a longer cycle life . One of 2*g−1)  and good2*g−1) , which e2*g−1) .Unfortunately, in most cases the analyses are only related to computer simulations. In fact, the non-defected structures of graphene are virtually impossible to produce with the current advancement of synthesis methods and techniques. The vast majority of research on functionalization concerns graphene oxide (GO), and not graphene itself. The presence of oxygen groups in the graphene structure significantly lowers its electrochemical properties .−1) [Meanwhile, the controlled induction of disturbances in the graphene lattice allows for the production of numerous active sites for lithium ions on the surfaces and edges of graphene nanolayers and the improvement of graphene functionality in LIBs . Doping −1) .2 [6, SF4, MoF6 [3 [In recent years, the number of studies and publications on the fluorination of graphene oxide (GO) and reduced graphene oxide (rGO) has increased. One of them is the gas fluorination process with the use of such precursors as F2 , or otheF4, MoF6 . MoreoveF4, MoF6 , photochF4, MoF6  and elecF4, MoF6  fluorinaF4, MoF6 , boron t MoF6 [3  and othe MoF6 [3 .−1) and the highest efficiency were recorded for the material obtained in the hydrothermal process carried out at the temperature of 150 °C [In his publication, Haoran described the hydrothermal process of producing a hydrogel based on graphene, doped with fluorine atoms. GO was used as the starting material, the source of fluorine was hydrofluoric acid. The mixture was dispersed by ultrasound and then subjected to an elevated temperature  for 24 h. The obtained material was then immersed in deionized water to remove residual acid and then dried at room temperature. Studies have shown that the fluorine content can be easily controlled by the temperature of the process. The XPS and FTIR results mainly indicated the presence of semi-ionic CF bonds that facilitate ion transport, improve electrical conductivity and provide active sites for lithium ions. The highest electric capacitance (227 F * gf 150 °C .0.25)n) which was dispersed in a mixture of H2SO4–H3PO4 (ratio 9:1) acids. Then it was stirred for 2 h at 50 °C. An amount of 18 g of KMnO4 was added to the mixture, and then 10–12 mL of H2O2. The obtained F-GO was subjected to the reduction process by adding four drops of hydrazine monohydrate and heating under a vacuum at 90 °C for 3 h. The material obtained this way showed a specific capacity of 767 mAh * g−1 at a current density of 10 mA * g−1 [Damien and his team conducted and described the process of making the F-GO. The starting material used was a fluorinated graphite polymer  reaction with rGO flake. This will allow understanding of the mechanisms taking place during the doping of graphene with fluorine and to determine the influence of the performed functionalization on its interaction with Li+ ions.This work summarizes the numerical analyses (using molecular modeling in the SCIGRESS v.FJ 2.7 program) and experimental studies of the physical and electrochemical properties of doped (modified) graphene structures in order to determine the type and properties of groups formed as a result of the boron fluoride tetrahydrofuran , respectively, and heating it in a water bath at 100 °C for 24, 48, 72, 96 or 120 h  was dispersed in 100 ml of distilled water using an ultrasonic sonicator . Then, solutions were prepared from the suspension thus obtained by adding 1.5 ml and 3 ml of BFor 120 h . The resThe simulation of phonon vibration spectra of the functionalized graphene was performed as follows. In order to determine the actual functional groups present in the structure of a graphene flake, the appropriate infrared spectra were simulated using the SCIGRESS v.FJ 2.7 software. For this purpose, as a model system of atoms, a graphene structure was created, consisting of 149 carbon atoms and 46 hydrogen atoms, which saturate carbon bonds at the edge of the analyzed graphene flake. Additionally, a defect in the form of a vacancy of one C atom was generated in this structure. This structure represents the actual molecular structure of the flake graphene after the reduction process. Then the created system was optimized in order to achieve the energy minimum. For the obtained energy-optimized structure, molecular modeling was carried out using the semi-empirical method of quantum computing (MOPAC: MO-G PM3), which allowed the identification of the interaction of infrared radiation with characteristic chemical groups.−1 were collected using an Nicolet iS50 Fourier-transform IR spectrometer . Spectra were recorded with the resolution of 2 cm−1 using a high sensitivity MCT-B detector (mercury cadmium telluride). The measurements were performed in a reflection mode with an application of a Sequelle DRIFT accessory working at an angle of incidence equal to 20 degrees. In each case, data from 128 scans were collected to construct a single spectrum.Infrared absorption spectra of the graphene samples in the spectral range 4000 to 400 cmRaman studies were conducted using a Horriba Labram HR (HORIBA Jobin Yvon) micro-Raman spectrometer. Laser power of the 532-nm excitation source (Nd:YAG green laser) was set to 0.3 mW (1%) and 3 mW (10%).The morphology and microstructure of graphene material was characterized using a scanning electron microscope (SEM) Jeol JSM-6610  with an EDS system. The observations were carried out in secondary electron imaging mode (SEI), with an accelerating voltage of 20 kV.2 low temperature adsorption and assumption that nitrogen molecules cover 0.162 nm2 of adsorbent surface. Size and volume of pores between 1.03 nm and 67.5 nm radius were determined using total pore volume (BJH) desorption cumulative volume of pores and BJH desorption average pore radius. During the analysis, ca. 0.1–0.3 g of the samples was placed in a measurement ampoule and degassed for 4 h at 100 °C. Then, the ampoule was attached to the instrument and the adsorption process was carried out at −195 °C.Textural properties of the samples were determined using Micromeritics ASAP 2020 equipment. The total specific surface area (TSSA) analysis was based on the analysis of specific surface area (BET) model of N2 group or the formation of -BH2 groups. Designations of the analyzed graphene systems depending on the place of attachment of -BF2 groups or formation of -BH2 groups are summarized in According to the simulation and optimization of the analyzed graphene structure carried out in the SCIGRESS v.FJ 2.7 program, the C-C bond length is 1.42 Å, while the C-C-C torsion angle in the undefected area is 120°. For such an energetically optimized structure, the system energy simulations were carried out depending on the place of attachment of the -BF3- ion and a model graphene flake composed of 149 carbon atoms and 46 hydrogen atoms with a structural defect in the form of a vacancy of one C atom. The interaction energy of the -BF3- ion as a function of the distance from the surface of the unmodified, defective graphene flake (Gdef.) decreases from 406 to 230 kcal/mol.First, the analysis covered the interaction between the -BF2 group or the formation of -BH2 groups may take place were analyzed. Based on the analysis of the energy values of graphene systems depending on the mentioned parameters, it was determined that the most thermodynamic stable structures are the ones in which, in the reaction of BF3·THF with graphene, -BF2 groups are formed on its surface  and to carbon with hybridization of sp3 or sp2 in the area of graphene defect , and also adatomically  is practically on the same level.Then, the energy values of the most probable systems for which the addition of BF surface . On the 3- ion produces the -BF2 group, there is a growth of negative zones. Additionally, there is a clearly marked tendency to occupy the central zones of the graphene flake by a negative charge. A similar relationship was found by X. Duan, K. O’Donnell [In the areas of graphene where the reaction with the BF’Donnell , who anaThen, for the most thermodynamically stable system  causes the physical interaction of graphene with the lithium cation. The consequence of this phenomenon is the reduction in the system energy as a result of the electrostatic attraction of Li+ by the areas of electrostatic interaction of fluorine. This phenomenon explains why it is possible to achieve a relatively thermodynamically stable physical lithium bond in modified graphene systems—as opposed to unmodified graphene systems. Although the energy of the system decreases as Li+ approaches the graphene surface, the minimum value of the energy of the system is close to 670 kcal/mol compared to Gdef.-Bad-atom-F, whose energy is about 503 kcal/mol.For such assumptions, it was found that the change in the electrostatic potential of the functionalized graphene flake , G (1580 cm−1) and 2D (2698 cm−1)  .3 hybridization-based defects, vacancies, grain boundaries and even edges. It comes from the secondary Raman scattering process involving one iTO phonon and one defect [The D-band corresponds to the disorder of the structure due to the disturbance of the symmetry of the graphene lattice, the presence of spe defect . In the e defect .2 hybridization in a two-dimensional hexagonal lattice. The G applies to all carbon structures with sp2 hybridization, including amorphous carbon, carbon nanotubes, graphite, etc. [On the other hand, the shape and intensity of the G-band result from the vibration of carbon atoms with spte, etc. . It is tte, etc. .The 2D-band comes from the secondary Raman scattering process involving two iTO phonons near the K point . On the 3·THF significantly influenced the changes in individual bands. The G peak was observed at a wavelength of 1566 cm−1; there was a shift towards lower wavenumbers relative to the peak position for the unmodified sample. We observe an increase in its frequency with a reduction in the FWHM . It comes from the fact that the doping of the graphene structure causes the Fermi energy to move away from the Dirac point, and the plasma–phonon coupling effect weakens, which is manifested by an increase in the G phonon energy [The process of rGO functionalization with the use of BFn energy .−1.The number of defects in the graphene structure, increasing with the progress of the functionalization process, was manifested by an increase in the intensity of the D, D’ and D+G peaks, observed at 1339, 1596 and 2461 cmThe D ’peak becomes visible on the Raman spectrum if the graphene material contains randomly distributed impurities or surface charges. This is due to the fact that the localized vibration modes of contaminants can interact with the extended phonon modes of graphene, which results in the observed division .3 hybridization bonds.The presence of the D peak is related to the disorder and defect of the graphene layer. In the starting material, it is the result of the presence of oxygen functional groups. The functionalization process leads to an increase in the intensity of the D band, which is related to the reactions taking place and the formation of spThe D and D ’bands are created as a result of the photon scattering on iTO phonons from the vicinity of the K point of the Brillouin zone and the iLO from the vicinity of the point Γ Brillouin zone. In order to fulfill the principle of conservation of momentum, the proportion of defects that take over this excess momentum without changing the energy is necessary. Thus, the analysis of the intensity of the D and D’ bands allows the determination of the level of damage to the carbon layer .2 hybridization carbon materials show a strong peak in the range 2500–2800 cm−1 in the Raman spectrum. In combination with the G-band, this spectrum is the Raman signature of graphite materials and is called 2D [−1. In the case of a greater number of layers, the 2D band becomes wider, while the ratio of the intensity of the 2D band to G is lower than one [All types of spalled 2D . The 2D than one .2D/IG ratio for the starting material is 0.62 and for modified samples it ranges from 0.56 to 0.69. The half-width for the rGO before the modification process is 203.6 cm−1, and for successively functionalized materials 127.93 cm−1 (A1), 135.84 cm−1 (A2), 114.73 cm−1 (A3), 123.89 cm−1 (A4), 146.59 cm−1 (A5), which confirms the fact that the tested material consists of more layers.The IBased on the presented data in D/IG).DA/IGA peak intensities read from the Raman spectrum, the level of the defect in the graphene structure can be characterized. The ID/IG intensity ratio for rGO is 0.89, which may indicate that, despite the GO reduction process, some carbon–oxygen bonds still remained in its structure.By analyzing the ratio of the ID/IG ratio increases with the extension of the functionalization time, which may indicate a progressive disturbance of the graphene lattice and an increase in the volume of defects with sp3 hybridization.For the samples subjected to functionalization, the I3 hybridization. Moreover, a large amount of microporosity and narrow gaps between the layered structures can be observed on the surface , total pore volume and average pore size (radius) by measuring low-temperature nitrogen adsorption/desorption. The calculation range of p/p° was 0.05 to 0.3, and the obtained results are presented in −1 (working up to 2.5 V). In practice, the anode materials for lithium-ion cells do not work in the range greater than 1.5 V. In this case, the capacity in this range is less than 300 mAh * g−1, which is less than the value assigned to commercial graphite anodes (max. 372 mAh * g−1).The ability of electric charge storage was determined on the basis of cyclic voltammetry. The material tested showed a capacity between 450 and 550 mAh * g+) indicate reactions of attached functional groups or structures formed with lithium. These peaks repeat in each cycle, which indicates that the reaction is reversible.The peaks visible in the graphs (0.005–0.3 V vs. Li/Li+). The decrease in the capacity associated with the SEI formation is mainly caused by the expansion of the specific surface area of the material after the functionalization process [We also observe a large loss of capacity during the first cycle of operation. This is due to the reaction of some attached functional groups  with lithium during the insertion process (reactions taking place in primary cells) and due to the formation of a solid electrolyte interphase  layer . The decrease in capacity during the first cycle of operation is a result of the reaction of some of the attached functional groups with lithium during the insertion process and the expansion of the specific surface area of the material.The synthesized materials showed a theoretical specific capacity between 450 and 550 mAh * gDue to the fact that the FTIR and Raman analyses showed that, despite the GO reduction process, some carbon–oxygen bonds still remained in its structure, it is necessary to conduct further research in order to eliminate the resulting limitations, taking into account the change of the material reduction mechanism.


The extremely low friction between incommensurate two-dimensional (2D) materials has drawn more attention in the recent years. Structural superlubricity is a fascinating tribological phenomenon that is achieved in 2D heterojunctions despite the aligned or misaligned contacts that occur due to the disappearance of the lateral interactions between two incommensurate contacting surfaces. In this study, using the first-principles method, we report the computational realization of structural superlubricity for graphene/antimonene heterojunctions at the nanoscale. The calculated results clearly demonstrate that structural superlubricity between graphene and antimonene monolayers could be achieved under the misaligned contacts. The structural superlubricity is mainly attributed to lower work of separation, which maintains superlow friction coefficients. Howevformance . Similarformance , therefoThe heterojunctions built from the different 2D materials would help with reducing the exfoliation energy and achieving superlubricity. Indeed, Mandelli and Leven et al. pointed out that graphene/h-BN heterojunctions would be a route to robust superlubricity ,9. They sep) played an important role in obtaining superlow friction coefficient. Structural superlubricity could be achieved under the misaligned contacts. We discussed the unusually tribological behavior to explain what the most important factors for structural superlubricity between graphene and antimonene were.Motivated by our previous work , we usedvdW is set as 0.77  and 1.38 Å  for carbon and antimony, n = 8, and a damping constant of λ = 7.5 × 10−4 is chosen in this work [−5 eV/atom and 0.1 eV/Å. According to the match methods in Refs. [x and y axis. To avoid the interactions between periodic replicas, the vacuum slabs of 20 Å are added along the z axis. The potential energy surfaces (PESs) are sketched by collecting the interlayer interaction energy of the upper graphene monolayer translation over the lower antimonene monolayer for the variable relative lateral positions [All calculations were carried out using the CASTEP code . Based ohis work . During in Refs. ,17, therositions . The chaositions .sepW) [sepW is calculated as follows:A is the interfacial area. The maximum shear force could be calculated by the Equation (2):In our previous work, adhesion between two contact surfaces could be well characterized using the work of separation (Wsep) . Thus, tz axis, where V(z) represents the potential energy with variable interface distances along z axis.Subsequently, we compress the graphene/antimonene heterojunctions in order to investigate the effect of the normal load on the tribological properties. d = 2.25 Å, and as d < 2.25 Å, where the potential energy sharply increases. The derivative of potential energy (Fz) displayed in d < 3.26 Å, Fz corresponds to the attractive force, rather than corresponding to the repulsive force as d < 2.25 Å.The potential energy (PE) curve, with respect to the interface distance d, is plotted in vdWF) is calculated, as shown in NF represents the pressure along z axis. zF, vdWF, and NF.Next, the van der Waals force  is an important physical factor for investigating the tribological properties, we thus calculate three-dimensional (3D) sepW, as plotted in sepW corresponds to a low friction coefficient under the static state [sepW has no concern with interface distance and exhibits small values less than 0.012 J/m2. In order to further understand this phenomenon, the electron density and density of states are calculated subsequently.Because work of separation  are calculated with respect to interface distance d, as shown in on force . The frisepW (about 0.01 J/m2), and the calculated values are less than that in previous work (0.02–0.2 J/m2) [sepW corresponds to a low friction coefficient. Thus, we can conclude that lower sepW should be one important factor for structural superlubricity. On the other hand, the electronic structure and density of states, as shown in In this work, we successfully investigated the tribological properties of graphene/antimonene heterojunctions. We found that structural superlubricity can be achieved between a graphene and antimonene interface. We mainly proceed from three aspects to answer this interesting phenomenon. As shown in .2 J/m2) ,22,23,24d < 2.25 Å, where the potential energy sharply increases and Fz transfers from attractive force to repulsive one. (2) A lower work of separation is found for graphene/antimonene heterojunctions, which play an important role in obtaining structural superlubricity. (3) The strong repulsive interactions and lowest energy barriers could be summarized as two other factors for structural superlubricity. The calculated results exhibit that graphene/antimonene heterojunctions could be an appealing lubricant material. We believe that this work could provide positive guidance for further experimental investigations.In summary, we have successfully probed the unusually tribological behavior of graphene/antimonene heterojunctions using first-principles calculations. We obtained the followed conclusions: (1) As