Iodine-doped graphene oxide is attracting great attention as fuel cell (FC) electrocatalysts with a high activity for the oxygen reduction reaction (ORR). However, most of the reported preparation techniques for iodine-doped graphene (I/rGO) could be transposed into practice as multiple step procedures, a significant disadvantage for scale-up applications. Herein, we describe an effective, eco-friendly, and fast technique for synthesis by a microwave-tuned one-stage technique. Structural and morphological characterizations evidenced the obtaining of nanocomposite sheets, with iodine bonded in the graphene matrix. The ORR performance of I/rGO was electrochemically investigated and the enhancement of the cathodic peak was noted. Based on the noteworthy electrochemical properties for ORR activity, the prepared I/rGO can be considered an encouraging alternative for a more economical electrode for fuel cell fabrication and commercialization. In this perspective, the iodine-based catalysts synthesis can be considered a step forward for the metal-free electrocatalysts development for the oxygen reduction reaction in fuel cells. Iodine-doped graphene oxide is considered to have an increased technological capability as a catalyst for the reduction reaction of oxygen (ORR) in fuel cells. Nowadays, fuel cells (FCs) are thought to be one of the most highly performant electrochemical-based systems that are using fuel (hydrogen) electrochemical reduction to obtain electrical energy, for both mobile and stationary applications. The increased importance of fuel cell utilization for energy production applied in a large number of systems confirms the idea that electricity produced by fuel cells could be considered a rapidly emerging progress in the age of energy, ready for commercialization. One such solution is the proton exchange membrane fuel cell (PEMFC) technology, which definitely has the capability of becoming a sustainable and clean electricity source. PEMFC shows the most promise due to the demonstrated high efficiency and low pollution ,2. Low-tOn the other hand, since graphene’s discovery as another allotrope form of carbon, it has been proven that it has remarkable physical–chemical properties for many electrochemical systems, such as fuel cells, electrolyzers, solar cells, etc. Graphene is known as a single-layered graphite composed of a one-atom-thick carbon sheet constituting a hexagonal lattice structure. Graphene oxide represents the oxidized form of graphene. Graphene oxide (GO) has attracted interest as a suitable route to produce graphene. The presence of different functional groups leads to a hydrophilic behaviour that is strongly influenced by the oxidation level. The GO sheets indicate a good dispersion capacity resulting from a strong electrostatic charge and hydrophilicity. The reduction of GO is a common route to obtain a graphene-like structure. Different chemical, thermal, or photo-thermal reduction methods can be used to prepare rGO structures. Depending on the methods used, the rGO produced can be more or less close to the pure structure of graphene. Reducing agents are either inorganic (sodium borohydride) or organic (phenyl hydrazine hydrate or hydroxylamine) chemical agents. Typically, thermal reduction occurs in an inert atmosphere at high temperatures 300–2000 °C. The photochemical reduction of GO involves a direct laser beam at wavelengths below 390 nm . The proIn order to make graphene active from an electrochemical point of view, it is necessary to change the carbon structure by its functionalization with different types of heteroatoms such as halogens. Currently, the halogen-doped graphene presents high catalytic activity for the ORR reaction ,11,12,13Between halogens, the iodine forms diatomic molecules, where two iodine atoms share a pair of electrons to obtain a stable octet; at high temperatures, these diatomic molecules reversibly dissociate a pair of iodine atoms. Similarly, the iodinated anion, I-, is the strongest reducing agent among the stable halogens, being the lightest oxidized back to the diatomic I2. Iodine is the halogen with the largest atomic radius in the group, it can form partially ionized bonds that can promote charge transfer. The ORR activity can be improved through electrocatalytic efficiency due to iodine doping, facilitated by the formation of load transfer complexes (I3- and I5-) that increase the doping capacity and functionality of the graphene support.To dope the graphene-based materials with iodine atoms is a difficult target that brings a high level of difficulty from a synthesis point of view, since the iodine atomic radius is bigger compared with the carbons’ making it more difficult to transfer the charge from one surface to another. However, the negative ion I3- is formed during the iodine graphene doping process. This will enhance the number of positives in the graphene structure and improve ORR’s functionalized graphene catalytic activity. In this context, it should be noted that during iodine doping bonds are formed between iodine and the graphene matrix that can transport the charge between the halogenated iodine groups.2, the O–O bonds of the adsorbed oxygen are reduced, hence enabling effective transformation to water after reduction and protonation.Furthermore, due to the high potential of the halogen-doped graphene to link OMost of the reported synthesis methods of iodine-doped graphene are multiple step procedures, a significant disadvantage for scale-up applications. Having this target, several works have been developed. Iodine-functionalized graphene nanoplatelets for ORR could be prepared by using sequential steps of ball milling for 24 h. The co-doping of iodine with ammonia on the GO surface was accomplished at a high temperature of over 950 °C. Iodine-doped rGO could be obtained by mixing graphite oxide with PI3 followed by refluxing for 24 h. High-quality I/rGO was reported by using a ball milling time of 48 h and further freeze-drying for 48 h. Iodine-doped graphene was prepared by thermal annealing at temperatures between 500 and 1100 °C. Another method involved a high-efficient heat-pressing technique to obtain I/rGO nanosheets . Our recThe microwave (MW) process has been widely applied in many chemical syntheses; however, this research is the first of its type where it is applied for the iodine doping process together with the reduction of graphene oxide, by using a simpler, more effective, faster, and more economical protocol at atmospheric pressure. Through this paper, a canvas-like structure I/rGO was synthesized starting from the graphene oxide (GO) by involving the MW route under mild conditions. This work emphasizes the capability of I/rGO to work as an ORR electrocatalyst used for fuel cells electrodes development, as a low-cost alternative to the commercial platinum-based catalysts.4, Scharlau, 98%), and the reaction mixture was ultrasonicated (80 Hz) for 10 min. The obtained solution was spilled in the microwave reactor  cylindrical vessels. The single-stage microwave (MW) iodine-doping process parameters, in terms of temperature and reaction time, were optimized for mild conditions: atmospheric pressure, temperature 40–60 °C, power 800 W, and reaction time 15 min. The product was chilled moderately to room temperature. The obtained black solid was separated by ultracentrifugation, and then, alternately, washed using DW and ethanol . Finally, the product was dried by lyophilization.The volatiles from the commercial graphene oxide (GO) powder  were removed by degassing at 110 °C. GO was then was added into demineralized water (DW) and stirred for 15 min. The hydroiodic acid (HI)  was completed and the solution was mixed by 10 min sonication. This compound was further reduced with sodium borohydride  involving the nitrogen adsorption measurements at 77 K. The adsorption–desorption isotherms were obtained in low-pressure nitrogen atmosphere. Prior to the BET analysis, the I/rGO powder humidity was eliminated under vacuum outgassing at 388 K, for 240 min. The pore size distribution and total pore volume were calculated by Barrett–Joyner–Halenda (BJH) method and was applied to evaluate the porous surface of iodine-doped graphene as well as of starting graphene oxide. The mass changes with temperature of the reduced graphene oxide (rGO) and iodine-doped samples (I/rGO), respectively, were studied by thermogravimetric analysis (TGA) using TGA-DSC e NETZCH STA 449 F5 Jupiter system. The TGA measurements were done in air flow, in the temperature domain of 27–1000 °C, heating the sample with a rate of 2 K min−1. In order to prove the iodine doping of the reduced graphene oxide support, ATR-FTIR method was used. The Frontier FT-NIR spectrometer was used for the attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterization. The infrared spectra were recorded in transmittance, in domain of 650–4000 cm−1.X-ray photoelectron spectroscopy (XPS) characterization was done using the X-ray photoelectron spectrometer . XPS spectra were measured using monochromatic Al Kα radiation (1486.7 eV). The qualitative elemental analysis was undertaken by recording the broad spectra, and the identification of the different types of chemical bonds that are formed on the surface was obtained from the high-resolution spectra deconvolution. The PHI-MultiPak software was used for the XPS spectra interpretation. The quantitative elemental analysis in terms of chemical elements atomic concentration was performed by calculating the peak areas by considering the sensitivity factors of the analyzed elements. The yield of iodine was 95 ± 2% based on XPS analysis data of three separately prepared samples. Microstructural investigation and elemental analysis were performed using a Carl Zeiss FEG SEM equipped with an EDX system. The I/rGO powder was transferred for SEM investigation on a double-sticky carbon tape and the surplus was blown with compressed air. The specific surface area of the I/rGO samples was measured by Brunauer–Emmett–Teller (BET) method, using AutosorbIQ (Quantachrome). BET technique is generally consecrated method to estimate the specific surface area (S2 glassy carbon (GC) disk was used as working electrode (WE). A 3 M Ag/AgCl (Metrohm) was used as reference electrode (RE) and a platinum wire as counter electrode (CE). All the measurements were done alkaline electrolyte (0.1 M KOH) that was flushed with oxygen for one hour before each experiment. The pH of our 0.1 M KOH aqueous electrolyte in which KOH salt is dissolved is 13, that means a strong base solution. This electrolyte concentration (pH) is commonly used for the catalysts’ electrochemical properties characterization , and it was chosen according to the most published papers in the domain. The potential presented in this work are versus Ag/AgCl RE. The catalyst aliquot was prepared by stirring overnight 5 mg rGO-based powder together with 240 µL isopropyl alcohol, 10 µL DW, and 20 µL 5 wt.% Nafion® solution. For measurements, 7 µL of catalyst solution was deposited onto GC surface, that was previously polished with alumina and diamond paste, cleaned with demineralized water and dried in air.Oxygen reduction reaction (ORR) of the iridium-doped samples (I/rGO) was measured in comparison with non-doped reduced graphene (rGO). The measurements were carried out in commercial glass cell with three electrodes using a 2273 potentiostat (Princeton Applied Research). A controlled speed OrigaTrod rotating disk electrode (RDE) with 0.196 cmn) transferred during the ORR process, linear sweep voltammograms were recorded with 5 mV/s, between 0.4 V and −0.7 V and at various rotation speeds (ω) (among 250–1000 rpm). Linear sweep voltammetry (LSV) curves for I/rGO were plotted as j, which is the measured current density (mA−1 cm2geo) vs. ω−1/2 (rad s−1)−1/2 and studied following Koutecky–Levich (KL) Equations (1)–(3) [Lj—maximum (limiting) current density required to achieve ORR reaction (A cm−2); kj—kinetics current density (A cm−2); F—Faraday constant (96.485 kCmol−1); A—area of the RDE electrode (0.196 cm2); C0—concentration of oxygen (1.2 × 10−6 mol cm−3) in 0.1 M KOH electrolyte; D0—diffusion coefficient of oxygen in the electrolyte (1.9 × 10−5 cm2 s−1); ν—kinematic viscosity (0.01 cm2 s−1) in 0.1 M KOH; and k—the rate constant (cm s−1) for the electron transfer [In order to calculate the number of electrons ( (1)–(3) ,16,17.. XPS spectroscopy was used to determine the chemical state of iodine forms corresponding to the I/rGO sample.5/2 and I3d3/2) in the 616–635 eV interval. 2 hybridized C–C bonds certifies the efficaciousness of the graphene oxide matrix reduction. The C–C bonds are dominant since the HI acid reduction occurred, because most of the hydroxyl and epoxy groups were removed. However, some oxygen-containing functional groups still remain in the rGO sheets, which are typical for chemically reduced GO. The elemental composition and iodine bonding types were investigated. As presented in 5/2 (~618.8 eV) and I3d3/2 (~631.3 eV), respectively, suggests the enhancement of the iodine interaction with the graphene oxide matrix. The deconvoluted I3d5/2 peak shows two peaks: first is the 617.96 eV peak of triodide (I3−), and the second is 620.21 eV corresponding to pentaiodide (I5−). These results are the same with the one reported in literature [3− and I5− remained on its surface after the microwave process. According to chemical composition calculated through this method, the iodine concentration of 1.3 wt.% was obtained.As iodine was used as a dopant, its content was very small, 0.13% in the synthesized doped rGO, and the data were collected with noise, but two Gaussian curves were clearly adjusted to the data with FWHM. The noisy XPS deconvoluted spectrum may be due to the high surface sensitivity of XPS, since it has been reported that iodine is a strong p-type dopant for graphene. The XPS signal-to-noise ratio (C-I) is the height of a signal (peak) above a background relative to the noise in the scan/spectrum measured at some point off the peak.The mechanism for the adsorption of iodine molecules on the GO has been studied both theoretically and experimentally to adjust the electronic structure of the GO surface. Theoretically, the adsorption of halogen atoms on GO/rGO was investigated by using a semi local function. It was accepted that an iodine atom can accept 0.5 electrons from the carbon substrate. The doping of the rGO by the physical adsorption is interesting since it can increase the concentration of the carriers without affecting carrier mobility as in the case of chemical adsorbed dopants, where the covalent function can produce crystalline defects and irreversibly alter the electron structure .0 domain in the 0.1 and 0.3 (multipoint model). According to this, the linear high-pressure part is suitable for evaluation of the primary mesopore volume and the external surface area. The secondary mesopore volume (which does not form ordered structures) is calculated as a distinction between the total pore volume and the primary mesoporous volume. The model calculates the maximum amount adsorbed at pressures close to the saturation vapour pressure by converting it to the volume of liquid adsorbed, similar to the evaluation of the micropore volume [With the view to understand the iodine doping impact towards the structure and porosity of graphene oxide support, further investigations are carried out. One of these is gas adsorption that gives an extensive description of the porous materials in comparison with the specific porosity, surface area, and pore size distribution. From the shape of sorption/desorption isotherms obtained during the BET analysis, it is possible to understand the elementary reactions linked to the sorption and desorption of nitrogen and its comportment in spongy-like solid structures. The BET model is based on the multilayer adsorption of gas on the surface of the adsorbent. The BET method determined the specific surface area through the P/Pe volume .2 adsorption/desorption isotherms for both samples correspond to the type IV isotherm according to the specifications from IUPAC. The micropore volume was calculated in the low-pressure region, as the intercept with the adsorbed amount axis represents the volume adsorbed in micropores. It is important to note the excellent linearity starting from the lowest adsorbed amount and also the correlation coefficient R2 very close to one, both indicating a well-defined monolayer and constituting the indicative for the BET data validity.The results calculated using the isotherms for adsorption/desorption are presented in Both adsorption–desorption isotherms present a typical behavior for a mesoporous structure with a uniform pore size distribution, suggesting that the prepared materials have good transport properties among micropores, mesoporous, and macro-porous channels. The calculated specific surfaces and the estimated textural properties for the pore volumes are presented in 0 = 0.02, and a hysteresis loop from P/P0 = 0.45 to P/P0 = 1.0, which is due to the co-existence of both micropores and mesopores. Moreover, it can be noticed that there are little ultra-micropores in the doped graphene material, thus the porous material could provide more active sites and thus improve the redox reactions. The pore size is a critical parameter that affects the basic physicochemical properties and applications of porous doped−graphene, but the preparation of I/rGO with a controllable pore size is still a big challenge. In this paper, the model BJH was applied for the estimation of the pore volume distribution (both for rGO and I/rGO) ) and the pore size and half pore width (nm). The results clearly indicated that a textural change occurred. According to the BJH, most of the pores from the iodine-doped graphene oxide have a size below 5 nm. The doping of iodine into the graphene network provides the modifications of surface area and also for the pore size of the doped material, according to 3 hysteresis loop is correlated with slit-shaped pores, possibly between parallel layers.Herein, iodine−doped graphene presents a vertical uptake under P/P2/g) that is significantly more reduced than that corresponding to rGO (922 m2/g). We can presume that after the iodine inclusion into the graphene framework, the surface area will decrease as an effect of the doping process that favors the tendency and probability of restacking.Iodine-doped graphene has a BET surface area . The calculated pore volumes indicated an open stacking order. The iodination process maintains the sheet-like morphology also observed by SEM microscopy. Perhaps the layers become graphitized and this is reflected in the strongly reduced BET surface area. The pore volumes correspond to open 3D staking of reduced graphene oxide-based powders.A linear relationship between the pore volume and the relative pressure The thermal decomposition curves of the reduced graphene and iodine-doped reduced graphene are presented in −1, respectively. Iodine presence in the I/rGO structure can be noticed from the band at C–I assigned to the C−I stretching vibration.2) in comparison with 1.52 mA/cm2 from 0.383 V of rGO, respectively. Moreover, the I/rGO ORR peak position is shifted with 50 mV to a more positive potential. These findings strongly indicate that the iodine-doped reduced graphene oxide have ORR catalytic activity. The influence of the sweeping towards the I/rGO CV shape and ORR current density is presented in 2 corresponding to 10 mV/s, to 24 mA/cm2 associated with 100 mV/s. This comportment is assigned to the I/rGO surface extensive oxidation with the sweeping rate. The catalytic performance of rGO and I/rGO for the oxygen evolution reaction (ORR) was characterized in alkaline electrolyte (0.1 M KOH) using the cycling voltammetry method (CV) at 50 mV/s . In FiguThe electrochemical activity can be assigned to the ORR mechanism by taking into account the higher electronegativity of iodine (2.66) than carbon (2.55), polarizing carbon atoms and favoring oxygen adsorption as well as the charge transfer.−1 cm2geo) vs. ω−1/2 (rad s−1)−1/2, for various rotation speeds (among 250–1000 rpm) and different potentials (0.4–0.7 V). From the fitted K–L plots, a fair linear relationship at all potentials is noticed, which confirms the electroreduction of iodine. The number of transferred electrons is between 3.41 and 4.09, indicating the preponderance of the four-electron transfer mechanism in the ORR corresponding to the direct reduction of O2 to H2O [n) was calculated to be in the range of 3.41–4.09, suggesting a predominant four-electron O2 reduction in combined two-electron and four-electron pathways of the ORR process [n value is around 3.4, indicating that a hydroperoxide anion HO2− is formed as an intermediate reduction product of the two-electron reduction of O2. The HO2− is reduced into OH− at the electrode at more negative potentials, thus restoring the overall four-electron ORR process. The value of n slightly over 4 towards −0.70 V vs Ag/AgCl suggests a possible another reduction reaction than ORR occurring in the studied catalytic system [In 2 to H2O . The num process ,22. At lc system . In our c system . Accordi3− and I5−) that increase the functionalization capacity of the graphene support. Developing a green chemistry method to prepare I/rGO using MW could be a step forward in obtaining affordable electrodes with ORR activity.This work indicates that starting from a commercially accessible material—graphene oxide—through a specially designed process for chemical synthesis in the microwave field, iodine-doped graphene with specific morphological and structural properties could be obtained. The single-stage microwave (MW) iodine-doping process parameters in terms of temperature and reaction time, were optimized for mild conditions: atmospheric pressure, a temperature of 40–60 °C, a power of 800 W, a reaction time of 15 min, and a doping concentration of 1.3 wt.% was obtained. Cycling voltammetry and rotation disk electrode polarization methods were employed to study the I/rGO electrocatalytic activity with regard to the ORR. The good ORR activity of the I/rGO probe can be explained by the iodine doping of the rGO matrix, promoted by the formation of load transfer complexes (I


Two different modes of improving the strength of the hybrid composite have been followed; one is by the inclusion of graphene at three levels of 0.1, 0.2 and 0.3%, and another by the processing route, squeeze casting technique by compression of the molten hybrid composite slurry before casting. The microstructure and characterisation of the composite material are examined and analysed with the help of XRD, SEM, EDAX and chemical spectroscopy. A microstructure evaluation is employed to justify the homogenous dispersal and the existence of reinforced particles. A tensile test is conducted at room temperature and high temperature environments to assess the tensile strength. The research outcome affirms that a significant improvement in tensile and hardness has been noted in comparison with base alloy. The fracture-morphology results affirm the change in fracture mode from brittle to ductile when the tensile testing environment changes from room temperature to high temperature. Finally, the dispersion strengthening mechanism is validated with an empirical approach.The development of aluminium composite with the inclusion of advanced materials is a continuous research process due to the increasing industrial demand for advanced hybrid materials. To cater for this need, this research work focuses on the development of Al 7075 alloy reinforced with TiB Han Wang et al. [2 reinforced Al 7075 matrix composite, and the authors concluded that the grain size of the composite is smaller than the Al 7075 base alloy. The inhibit property of TiB2 to promote nucleation is the reason for the grain growth. B.P. Sahoo et al. [2 particles infused Al 7075 matrix through experimental and theoretical approach. The research outcome states that nearly 58% of grain size reduction is achieved with the higher content of TiB2 and in turn the noticeable improvement of mechanical properties. Vineet Chak et al. [2O3 through liquid melt deposition followed by hot extrusion and conducted characterization, high temperature tensile and fracture study. They reported that the maintained yield strength up to 150 °C and the fracture analysis revealed the transition failure from brittle to ductile.There are extensive research outcomes and initiations in developing novel metal matrix composites. The recent challenges in the product development to meet the requirement of higher specific strength with minimal weight pave the opportunities for the consistent research in the development of metal matrix composite. In particular, the automobile and aircraft industries mainly focus on and encourage the development of novel metal matrix composite ,2,3,4. T4C) ,6,7,8, o ZrSiO4) , borides2, AlB2)  and nitr2, AlB2)  have rep[3 W/mK) ,12,13, YK) [2/g) ,15,16 reK) [2/g) ,18 statiK) [2/g) . GeneralK) [2/g) . Bi JianK) [2/g)  developeg et al.  investigo et al.  validatek et al.  synthesik et al.  studied k et al.  concludek et al.  carried k et al.  develope2 and graphene. The objective of the present work is to advocate for a dual way of enhancing the mechanical and tribological properties of Al 7075 composite, one way being through the encapsulation of graphene with hard boride particles and another is by achieving porous-free composites through the processing route. Three different levels of graphene content are being followed to compare the effect of graphene inclusion. Additionally, very specific attention has been paid to expose the tensile response of the composite materials at room and high temperature environments. Subsequently, the fracture analysis is also being discussed with the help of micrographs.Numerous research reports that address the improvement of properties of aluminium alloy with the reinforcement of various hard particles are available. However, very scarce research was conducted with the inclusion of graphene on Al 7075 and through the squeeze casting route. In particular, none of the work has been reported with inclusion of TiB2 purchased from Metal mart Coimbatore and the graphene flakes purchased from Shilpa enterprises are used as reinforcements. The mechanical properties of TiB2 and graphene are tabulated in Aluminium 7075 alloy is used as a matrix material and its mechanical properties are depicted in 2 particles and graphene powders with premeasured quantity were preheated to 200 °C to eliminate chemical impurities and moisture. Then, the aluminium alloy was melted to 800 °C in an electric furnace in an open atmosphere. The present work followed constant weight percentage of TiB2 as 10% [2 and graphene in each sample is presented in Initially, the TiB2 as 10% ,28,29 anm, ρrρ and cρ represent the density of matrix, reinforcement and composite, respectively. m, VrV indicate the weight percentage of matrix and reinforcement. Furthermore, the particle size analysis is carried out using CILAS 1064 Liquid setup.The characterization of the developed hybrid composite was carried out in four different ways. Scanning electron microscopy (SEM), chemical spectroscopy (ChemS), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed to study the phase and microstructure. The specimen was cut into the size of 10 mm × 10 mm × 10 mm and subsequently rinsed in acetone followed by polishing through silicon carbide emery sheet. An SEM study was conducted using De-Wintor inverted trinocular metallurgical microscope . The chemical composition and elemental analysis were executed with the help of X-ray Diffraction and chemical spectrometer from Malvern Panalytical . The experimental density of the composite was determined with the help of a densimeter  working under the Archimedes’s principle of displacement. The theoretical density was evaluated with the following relation of the rule of mixture Equation (1), and the percentage of porosity was calculated using the below equation Equation (2).d is the size of the crystallite, k is the shape factor, λ is the wavelength, θ is Bragg angle, and β is the diffraction peak at half-width maximum intensity.The results of XRD were employed to determine the crystallite size and lattice strain. The Sherrer equation, as shown below, was utilized to calculate the crystallite size .(3)d=kλλ is the wavelength, A is constant, θ is Bragg angle, β is the diffraction peak at half-width maximum intensity, and ε is lattice strain.The lattice strain was manipulated by using the following equation, (4)β cosNow the dislocation density can be determined for every specimen by using the following relation ,(5)ρ=3ερ represents dislocation density, ε, bv and d indicate lattice strain, Burgers vector and crystallite size, respectively.In this equation, The tensile test was conducted in two different modes: room temperature and elevated temperature tensile testing. The size of the test specimen was trimmed as per ASTM 638-03 (165 mm length × 19 mm width × 3 mm thickness). The tensile test was carried out at Associated Scientific Engineering works with a range of maximum 5-ton load. Specimens were heated up to 250 °C through an electric furnace to conduct the elevated temperature test.2 was evaluated with the following relation,M is the bending moment in N mm, Y is the distance between the neutral axis to the extreme fibre measured in mm, and I is the moment of inertia of the section calculated in mm4. M is the bending moment, Y is the distance between the neutral axis to the extreme fibre, and I is the moment of inertia of the section.The hardness test was conducted by following ASTM E-10 standard (25 mm × 25 mm × 10 mm) with the help of a micro-Vickers hardness tester , with testing load range of 10 g to 1 kg. As per ASTM D-790 standard, flexural test was carried out in the three-point bending mode. The maximum bending stress in N/mm2 and graphene reinforcement is presented in The deviations between the experimental and theoretical density of the composite with the TiB2 particles and graphene nanoflakes. The inclusion of TiB2 particles is an additional factor for the enhancement of the microstructure by controlling the precipitation mechanism (2 particles. 2. Characterisation and phase identification were conducted with four different methods, namely SEM, EDS, XRD and ChemS. From SEM micrographs, it has been inferred that the homogeneity in the distribution of the two reinforcements exists. The absence of voids and porous microstructure is observed through the micrographs. The compression pressure to the extent of 100 MPa helped to relieve the voids and porosity. The EDS and chemical spectroscopy results confirm the existence of TiBechanism a. Excell2 are in the position to be noticed, whereas the graphene peaks are non-noticeable due to its meagre level of inclusion. The same observation was reported by the researcher [searcher . However2 particles where the weighted mean particle size is observed to be 3.9 µm. The peak for TiB2 particles is narrow and depicts an average value of 3.75 µm.2 and graphene flakes, and the other is by the way of the porous-free squeeze casting processing technique. The phenomenal increment in strength is attributed to the fine-grain structure of the hybrid composite. The noticeable enhancement in grain structure is achieved by the two modes. First, with the addition of TiB2 particles, the composite attains a more refined grain structure with the help of the heterogeneous nucleation capacity of TiB2 to form a dendrite structure [tructure . Second,The empirical prediction reveals that the increased content of graphene increases the dislocation density by resisting the impending dislocation movement. The dislocation density calculated for different proportions of graphene with an empirical approach is given in 2 particles and piling up of dislocation movement into dense dislocation owing to the barrier of graphene particles. The heating of the specimens at high temperatures might cause an increment in the thickness of the oxide layer over the surface of Al particles [The composite specimens were fed into tensile test under an elevated temperature of 250 °C to assess the deformation behaviour in a high-temperature environment. articles . The broIt is evident from the results that the percentage of elongation of all the specimens including the higher content of graphene also records a higher percentage of elongation than the specimens at room temperature. This reflects the thermal softening effect of the hybrid composite due to the high temperature. Moreover, the quick peak in strength followed by the consistent plastic deformation is attributed to the chance of diffusing dislocation density at one point in high temperature and allowing the dislocation to move freely . This phThe investigation of fracture surface at both room temperature and high-temperature composite specimens reveals the change of failure mode with respect to the physical and thermal loading. At room temperature, the mode of failure is in a brittle manner. The plane of failure is at an angle of 90° to the axis of loading with negligible neck formation. This sudden failure is attributed to the stress concentration at the grain boundaries. When the stress value increases, the dislocations are piled up to form dislocation density due to the graphene particle inclusion. Furthermore, the stress value increases, and the stress concentration develops over the grains due to the impediment of dislocations, which initiate a micro void formation. The coalescence of micro void forms the crack, as shown in The dimples in more numbers with shallow depths, as shown in micrograph 2 and graphene justifies the hardness value. The increment in hardness for every fold of increasing graphene content is attributed to the higher number of graphene flakes that resist the indentation due to its high aspect ratio and unique strength. The squeeze casting processing route accelerates the formation of fine-grain structure due to the consistent compaction during solidification. The hardness value is inversely proportional to the grain size advocated by Hall-Petch [ll-Petch ; hence, 2 and graphene on the improvement in flexural strength is represented in The effect of the inclusion of TiB2 and graphene reinforced Al 7075 hybrid composite in the room and at high-temperate environments arrives at the following conclusions.The investigation of the tensile response of squeeze casted TiBThe theoretical and experimental evaluation of the density of the developed composite affirms the negligence void content of 0.2%. The excellent agreement between the theoretical and experimental results of density acknowledges the porous-free nature of the hybrid composite.The characterisation results earned through XRD, SEM and chemical spectroscopy confess the existence of constituent material in the homogenously dispersed state. Moreover, the improved grain structure has also been detected.The room temperature tensile test conducted for the specimens with varying graphene content, including base alloy, reveals the increment in tensile strength for every fold of graphene increment. The higher graphene content of 0.3% records a drastic improvement of 112%, in comparison with the base alloy.Due to the high temperature, the thermal softening effect makes the hybrid material more plastic with a noticeable increment in the percentage of elongation. The reduction in tensile strength and increment in elongation percentage are 18.5% and 28%, respectively.The fracture morphology confirms the change in fracture mode from brittle to ductile, while the tensile examination changes from room temperature to high temperature. The plasticized dimples in SEM micrographs with noticeable length confirms the increment in elongation percentage, and hence the ductile failure is understood.The hardness results proclaim the evident increase in hardness of higher graphene content to the extent of 67.8%, when compared to the base alloy.An improvement of nearly 80% in the flexural strength of the hybrid composite has been reported, in comparison with the Al 7075 alloy, from the flexural strength results.


The design benefits from the collective excitation of localized surface plasmon resonances of graphene-coated hole array, providing simpler fabrication fellow and more compact structure with respect to graphene-coated spherical nanoparticle array with similar plasmonic behavior. Geometrical parametric study of the reflecting mode shows that the device has lots of degrees of freedom for spectrum tuning and can highly tolerate fabrication imperfections. Moreover, the reflection rate is slightly affected by the dielectric substrate height, which can be tuned to achieve strong absorption by backing it with a metallic mirror. The designed absorber efficiently captures a wide range of obliquely incident transverse electric (TE) and transverse magnetic (TM) waves. Also, the operating frequency of both reflecting and absorbing modes can be tuned after fabrication, thanks to the two-dimensional nature of graphene material. Finally, using vanadium dioxide (VO For instance, the near field enhancement provided by the spherical graphene shells is discussed in the framework of modified Mie Lorenz theory and by extracting equivalent RLC ladder circuit for the resonance behavior of the plasmonic nanoparticles2. Furthermore, graphene oxide wrapped gold nanoparticles are utilized for intracellular Raman imaging and drug delivery3. In other applications, the localized surface plasmon resonances of the graphene wrapped nanoparticles are used to design electromagnetic cloaks and superscatterers5. Moreover, reconfigurable sub-wavelength strong absorbers are proposed by square/hexagonal lattice of graphene shells with spherical morphology8. Graphene hollow spheres have also found applications in supercapacitors, being superior to their planar counterparts9. Also, graphene-coated spherical shells are proposed as a cover for cylindrical wires to reach dual-polarized extinction cross-section enhancement10. Although fabrication of graphene-based spherical geometries is feasible considering current nanofabrication technology11, still, they suffer from complex fabrication fellow. Thus, proposing a geometry with similar optical performance, yet a simpler fabrication process, is helpful for practical usage.Graphene-coated dielectric or metallic spherical nanoparticles has been used in the design of different optical devices respectively due to the localized surface plasmon excitation arising from the charge carriers in the graphene shell and the interplay between plasmons supported by the bulk core and the graphene shell12. Generally, graphene-based structures provide enhanced optical performance with respect to their metallic and high index dielectric counterparts because of being low-loss and supporting highly confined waves13. Thus, the present research aims to investigate the graphene-coated hole arrays as an alternative plasmonic device to metallic hole arrays, benefiting from the exotic properties of graphene material to reach a switchable reflector/absorber performance. Metallic hole arrays support pronounced Fano resonances as interference between light directly transmitted through the holes and light indirectly scattered because of the excitation of localized surface plasmon polaritons, propagating surface plasmon polaritons, or/and waves due to Wood’s anomaly14. A potential application of the metallic nano-hole array is the refractive index sensing for label-free detection15 and can be fabricated by low-cost colloidal sphere lithography16.Previous studies show that extraordinary transmission through arrays of sub-wavelength holes in thin metal films is due to the excitation of surface plasmons17. Also, absorption enhancement in the graphene sheet is obtained by a square lattice of air holes in the high index dielectric18. Moreover, graphene/hBN/graphene multilayer hole array leads to a photonic plasmonic absorption of the electromagnetic wave19. The present paper benefits from the combined use of graphene-based hole arrays and phase change materials to design a reconfigurable switchable reflector/absorber device. Gate tunable feature of graphene material and thermal tunable property of the VO2 material provide two degrees of freedom for the dynamic response achievement20. A switchable absorber/reflector device provides a wide range of applications such as active camouflaging, modulating, electro-optic switching, antenna beam steering, hyper-spectral imaging, and compressive imaging22. The paper is organized as follows. The reflecting mode of the square array of graphene-coated dielectric hole array is investigated by exhibiting the excited localized surface plasmon resonances on graphene shells. Later, by using an optical mirror, the reflecting mode is converted to the absorbing mode and its robust performance in terms of the incident angle of the incoming wave is discussed. Finally, a phase change material is used to switch between these modes.By the use of hole arrays in conjunction with other plasmonic elements or material combinations, the optical performance can be further manipulated. For instance, strong coupling between a nanoparticle dark mode with a high-order metallic hemispherical nano-cavity, bright mode has been exploited for optical field enhancement through Fano resonance excitationIn this section, the design of optical reflector, absorber, and switchable reflector/absorber devices using graphene-coated hole arrays are considered. The performance of all devices relies on the excitation of localized surface plasmon resonances on the spherical shell-shaped graphene holes, where the functionality can be controlled by the substrate.R, embedded in a dielectric medium with the relative permittivity of ε1, as in Fig. p and are drilled on a substrate with the height of h1. Two-dimensional graphene material is wrapped around the sidewalls of the hole as hemispherical shells and it is characterized by its optical parameters, namely, relaxation time τ and chemical potential µc. These parameters essentially manipulate the graphene surface conductivity σ. Note that there are two approaches to simulate the graphene material for optical applications, either to model it with a zero-thickness shell with the surface conductivity calculated by the Kubo formulas or consider it as a very thin dielectric layer with the thickness δ with the equivalent bulk permittivity of ε = 1 + jσ/ωε0δ, where the real part of the permittivity is negative. To avoid three-dimensional fine volumetric meshing due to the contrast between the graphene layer thickness and other dimensions, the former approach is applied in the simulations25. The initial parameters are as follows: R = 100 nm, ε1 = 2, p = 240 nm, h1 = 100 nm, τ = 2 ps, and µc = 1.5 eV. The device is excited from its top side , and chemical methods have been used for wrapping graphene sheets around curved objects36.To understand the origin of high reflection, in Fig. 32. When extracting these results, the distance between the adjacent elements is considered 2R+40 nm in all cases. Moreover, Fig. Once the advantage of the graphene-coated hole array with respect to graphene-coated spherical nano-particle array is discussed, it is illustrative to investigate the optical performance manipulation regarding different parameters. In Fig. 37.In Fig. S parameters38. To this end, the hole array has resided on top of a metal-backed dielectric substrate for transmission blockage and its height is modulated such that a perfect absorption is achieved39. The metal termination is formed by h3 = 20 nm silver layer with the surface conductivity of σs = 6.3 × 107 S/m and it will be replaced by a VO2 layer in the metallic phase in the next section40. For simplicity, the dielectric material is the same as the one used to reside the hole array previously (ε1 = ε2). The final structure is shown in Fig. h2 = 120 nm, perfect absorption is achieved and it is illustrated in Fig. c = 1.2 eV.In this section, the excited localized surface plasmon resonances in the graphene-based hole array are used to design an optical absorber. The absorption rate is calculated from the The sensitivity of the optical absorption to the incident angle of the incoming wave is investigated in Fig. 2 layer with the thickness of 10 nm. Due to the phase transition in VO2, it behaves as a metal with the surface conductivity of 2 × 105 S/m at the temperature of T = 350 K in the metallic phase while behaves as a dielectric with the permittivity of 9 and surface conductivity of 200 S/m in its dielectric phase44. The choice of thickness is to ensure the transmission blockage in the absorbing mode and the substrate height h2 ranges from 260–320 nm. Figure 2 around the same frequency. Importantly, the device has a robust performance against the substrate height.In other to enable switching between the reflecting and absorbing modes, the metallic mirror beneath the proposed absorber is replaced by a VOGraphene-coated hole arrays are a promising candidate for the future optical device design since they support localized surface plasmon resonances similar to the graphene-coated spherical nanoparticle arrays, yet provide simple fabrication fellow. This geometry can be used either in the reflecting or absorbing mode, originating from the fact the reflection rate is not sensitive to the substrate height, thus can be tuned to achieve a high absorption rate. Interestingly, switching between these two modes is also feasible using a phase change material. The proposed geometry has lots of degrees of freedom for spectrum engineering. Importantly, the performance is reconfigurable due to the use of two-dimensional graphene material.45. The absorption rate (A) of the structure is calculated as46:S11 and S12 are the scattering parameters.To investigate the optical performance, numerical simulations are conducted in CST commercial software under unit cell boundary conditions and Floquet port excitation. Graphene material has been opted from the software library


At room temperature, the linearity of the sensor is about 0.98431 and the sensitivity is about 11.41432 Ω/% RH. At 100 °C, the correlation of the sensor is about 0.95046 and the sensitivity is about 1.0145 Ω/% RH; with a response time of only 9 s at ambient humidity from 25% RH to 95% RH, the sensor has very good repeatability and stability.Based on the humidity testing requirements in different environments, this paper investigates the humidity sensitivity of reduced graphene oxide (rGO)-sodium dodecyl sulfate (SDS) composite film humidity sensor. In the experiments, rGO-SDS dispersions with a concentration of 5 mg/mL were prepared, and a microelectromechanical system (MEMS) process was used to prepare the interdigital electrodes. The dispersions were then drop-coated on the interdigital electrodes and dried on a heated plate at 100 °C. The surface characteristics of the rGO-SDS films transferred onto SiO A humidity sensor is a device used to measure changes in humidity in an atmospheric environment. It plays an important role in industrial , environSince 2004, Novoselov, k.s. and Jim. first isolated graphene from graphite using micromechanical methods at the University of Manchester, UK. Graphene is considered one of the most promising materials due to its excellent electrical properties. In recent years, many researchers have modified graphene by reductive oxidation, which can change the properties of graphene so that it can be used to measure humidity , gases , temperaInterdigital electrode (IDE) is one of the most common electrode structures, which has advantages of small size, low energy consumption and low cost. It has been widely used in thin film-type gas sensors and humidity sensors. However, the size of IDE is very important. After reviewing the data, we finalized the style and size of the cross-fingers electrode, the style of IDE is shown in 2 by ultraviolet lithography. In the lithography progress, in order to increase the stickiness between optical resist and SiO2 surface, we coated the Hexamethyldisiloxane (HMDS) adhesion agent on the surface of silicon in a high temperature before lithography. Later, using magnetron sputtering technology, we deposited a metal layer with a thickness of 200 nm on the prepared substrate. In order to remove the excess metal, the deposited metal substrates were subjected to ultrasonic stripping in acetone and alcohol solution for 5 min, respectively. The above is the completion of IDE preparation, as shown in The preparation of the sensor mainly includes the preparation of IDE and moisture-sensitive material. For the IDE, we choose standard MEMS technology. In terms of materials, a single cast silicon wafer with a thickness of 525 μm was used as the substrate. The following steps are the key processes for the preparation of the IDE. First, the silicon wafer is cleaned for 15 min in a strong acid solution, which consists of hydrogen peroxide mixed with concentrated sulfuric acid in a 1:3 volume ratio of hydrogen peroxide to concentrated sulfuric acid, and the strong surface acid solution of the silicon is rinsed with deionized (DI) water. Then it was cleaned for 5 min in a strong alkali solution, which consisted of hydrogen peroxide mixed with ammonium hydroxide and DI water in a 2:1:7 volume ratio of hydrogen peroxide to ammonium hydroxide to DI water, and the strong surface alkali solution of the silicon was rinsed with DI water. The above cleaning steps complete the cleaning of the silicon surface. Second, a layer of silicon dioxide with a thickness of 200 nm is deposited on the cleaned silicon wafer by plasma-enhanced chemical vapor deposition (PECVD) technology. This layer acts as an insulating layer between the metal electrode and the substrate. Third, IDE was formed on the surface of SiOIn the experiment, we used rGO-SDS composite as the moisture-sensitive material. First, we weighed 0.5 g of RGO with purity greater than 99 wt% and 0.05 g of sodium dodecyl sulfonate (SDS) with an electronic balance. SDS as a dispersant can effectively reduce the deposition of rGO. Then, the weighed rGO and SDS were poured into a beaker filled with 100 mL DI water and dispersed in an ultrasonic cleaning machine for 1 h. Finally, a well-mixed rGO-SDS aqueous solution with a concentration of 5 mg/mL was obtained. The process for moisture-sensitive material is shown in Finally, an appropriate amount of rGO-SDS aqueous solution was drawn with a micro-sampling needle, drop-coated on the electrode so that the aqueous solution covered the electrode, and the IDE was placed on a 100 °C constant temperature hot plate to dry to prepare a humidity-sensitive film. The above completes the preparation of the sensor. The physical diagram of the sensor is shown in During the baking process of the rGO-SDS humidity-sensitive film prepared by the drop-coated method, the high-temperature heating solution causes the water to evaporate, leaving the sensitive material attached to the electrode and the surface of the sensitive film wrinkled. In order to characterize the surface morphology of the moisture-sensitive film, the IDE coated with rGO-SDS composite film was observed by scanning electron microscopy (SEM), and the results are shown in −1 is the D peak: indicates the peak of sp3 hybridized defective state C, and 1593 is the G peak indicates the peak of sp2 hybridized graphite C. The ratio of D-band to G-band intensity (ID/IG) is used to quantify the defects present in a particular graphene sample [D/IG = 7.4/8.6 = 0. 86, IG is greater than ID, indicating that graphene has few lattice defects and low disorder, while the predominance of sp2 hybrid graphite C=C. The G peak appearing near 1593 cm−1 originates from the plane vibration of the first-order E2g phonon, which reflects the symmetry and order of the material; the 2D peak near 2916 cm−1 is a two-phonon resonance Raman peak, whose intensity reflects the stacking degree of graphene. The more layers of graphene, the stronger the sp2 vibration of carbon atoms and the higher the G-peak. Graphite layers below five layers can be determined by Raman spectroscopy, and in particular, the two-dimensional peaks can be used to distinguish single-layer graphene sheets from multilayer graphene sheets. The 2D peaks are about 30 cm−1 wide for single-layer graphene flakes, 50 cm−1 wide for bilayer graphene flakes, and wider for more than three layers, but the difference is not significant. I2D/IG = 2.1/8.6 = 0.244, indicating that the intensity of the 2D peaks is weak, and in general graphene, the intensity of the 2D peaks is greater than that of G.Raman spectroscopy is another effective tool to study carbon nanomaterials . We obsee sample ,35. ID/IAs shown in 2)n bonds. The value 3400 cm−1 corresponds to the characteristic absorption peak of OH, but the peak is very weak, indicating low OH content. The values 2955 and 2869 cm−1 correspond to the stretching vibration of CH bonds, 1589 cm−1 corresponds to the stretching vibration of C=C, 1485 cm−1 corresponds to the bending vibration peak of C-O bonds, and the 950–1250 cm−1 band corresponds to the stretching vibration peak of C-O-C bonds. FTIR shows that the rGO in moisture-sensitive materials is partially reduced, and the material is rich in oxygen functional groups.To study the structure and chemical bonding of moisture-sensitive material, we performed infrared spectroscopy (FTIR), as shown in 2 is the element of the insulating layer.Since FTIR cannot quantitatively characterize each functional group, the content of each functional group cannot be calculated, we performed X-ray photoelectron spectroscopy (XPS) analysis on the moisture-sensitive materials. As shown in 2P. Na is mainly present as Na+.For a detailed analysis of C, O, S and Na elements, we created the xps fine spectra of the corresponding elements, as shown in In order to realize the real-time dynamic testing of the sensor under different humidity and temperatures, a test system was constructed as shown in 2O water molecules by moisture-sensitive materials causes the movement of surface electrons, resulting in changes in their conductivity. rGO contains a large number of oxygen-containing groups, and SDS is a good dispersant with good stability. SDS as a dispersant can improve the water solubility of rGO materials, making rGO disperse uniformly in water [3O+ as a charge carrier. The hydration of H3O+ is very favorable in liquid water, and the hydration reaction of H3O+ occurs in the case of enough adsorbed H2O, H2O + H3O+ → H3O++ H2O, and according to the ion transfer mechanism, energy conservation, so the transfer of H3O+ occurs very easily. As shown by Raman spectroscopy, our prepared rGO-SDS composite film is a multilayer graphite sheet, which is prone to interlayer expansion effects, and the expansion behavior in turn increases the interlayer distance between the rGO-SDS composite film, leading to an increase in film resistance [The principle of humidity sensors is mainly that the adsorption of Hin water . The humin water ,38. At lin water ,40. At hsistance . In addisistance . At highsistance ,44.For the experiments of sensitivity testing, we chose to place the sensor in a closed environment and changed the humidity of the sensor by a humidity controller. In addition, we control the temperature of the sensor with a heating system and select the temperature of the sensor as room temperature, 50, 75 and 100 °C, respectively. When the sensor is selected at a certain temperature environment, the humidity environment of the sensor is changed by the humidity-sensitive controller. The humidity in the environment is 25% RH. When the humidity of the sensor increases from 25% RH to 95% RH and then decreases to 25% RH, the change in the resistance value of the sensor is tested, as shown in In addition, the stable resistance of the sensor under different humidity environments was also selected to fit the pictures of humidity and resistance changes at room temperature, 50, 75 and 100 °C, respectively. In The response time is the time it takes for the sensor signal to rise from zero to a certain percentage of the ventilation equilibrium point. It is usually described by T90. The time required to rise from zero to 50% of the equilibrium signal value is called T50, and the time required to rise from zero to 90% is called T90.Recovery time is a parameter that expresses how quickly the signal returns when the sensor returns from standard gas to zero gas. Commonly used is RT90, which means the time it takes to recover from the sensor ventilated equilibrium state to a 10% signal.In the experiment, three different humidity environments were chosen to test the response recovery time of the sensor. For the sensor response-recovery time tests at different humidity levels, we used a controlled univariate approach, choosing a temperature of 100 °C and humidity levels of 35% RH, 65% RH and 95% RH. For the reaction-recovery time tests at different temperatures, we used a controlled univariate approach with temperatures taken as room temperature, 50 °C, and 100 °C. A humidity of 95% RH was selected for the sensor reaction phase and 25% RH for the recovery phase. For repeated measurement experiments, we chose to place the sensor into the test system and run the humidity from 25% RH to 65% RH for six cycles. Four tests were performed at room temperature, 50, 75 and 100 °C. To test the stability of the sensor, we placed the sensor in the above test setup with the temperature set at 100 °C and humidity at 95% RH, measured the sensor for 10 days, and analyzed the changes in response values and response times over the 10-day period. In order to objectively represent the performance of the rGO-SDS humidity sensor, a comparison In this paper, a humidity sensor was designed and prepared with rGO-SDS composite film as the moisture-sensitive material, and its key structure of interdigital electrode was prepared by a microelectromechanical system (MEMS) process, and the sensor was tested at different temperatures and different humidity levels. The results show that the humidity variation of the sensor is linearly related to the change of resistance in the ambient humidity range of 25–95% RH. At room temperature, the linearity of the sensor is about 0.98431, and the sensitivity is about 11.41432 Ω/% RH; at 100 °C, the correlation of the sensor is about 0.95046, and the sensitivity is about 1.0145 Ω/% RH with short response time and recovery time; its repeatability is good in six consecutive cycles of experiments from 25% RH to 65% RH at room temperature, 50, 75 and 100 °C; at 100 °C, 95% RH test for 10 days, the resistance change and response time remained essentially constant within the error range. Currently, the sensor is directly heated, and subsequently, heated electrodes can be designed between the silicon substrate and the insulating layer to facilitate the operation of the sensor in the constant temperature range.


The paper reports an absorption–transmission multifunctional tunable metamaterial based on graphene. Its pattern graphene layer can achieve broadband absorption, while the frequency selective layer can achieve the transmission of specific band. Furthermore, the absorption and transmission can be controlled by applying voltage to regulate the chemical potential of graphene. The analysis results show that the absorption of the metamaterial is adjustable from 22% to 99% in the 0.72 THz~1.26 THz band and the transmittance is adjustable from 80% to 95% in 2.35 THz. The metamaterial uses UV glue as the dielectric layer and PET  as the flexible substrate, which has good flexibility. Moreover, the metamaterial is insensitive to incident angle and polarization angle, which is beneficial to achieve excellent conformal properties. In recent years, electromagnetic metamaterials have attracted extensive attention because of their many characteristics that natural materials do not have. They can be used to design high-performance devices such as meta-lenses ,2, filteUnfortunately, the above-mentioned absorption–transmission metamaterial absorbers are not tunable, and their performances are fixed once they are manufactured. If the electromagnetic performance needs to be changed, it must be redesigned and processed. Moreover, the operating frequency band of these absorbers is mainly in the microwave frequency band. With the development of radar, communication and detection technology towards high frequency and large bandwidth, microwave metamaterial absorber based on traditional materials can no longer meet the future application requirements, and the absorber in the terahertz band has become a research hotspot and application trend. Graphene is a two-dimensional hexagonal honeycomb structure material composed of single-layer carbon atoms , which hTherefore, we propose a multifunctional tunable THz metamaterial based on graphene. The metamaterial can be regulated by applied voltage, and its electromagnetic properties are insensitive to incident angle and polarization, so it has good conformal properties. Moreover, it uses UV glue as the dielectric layer and PET as the flexible substrate, which has good flexibility. The metamaterial has the functions of THz broadband absorption and narrowband transmission. Through full wave simulation and analysis, the absorbance can be adjusted from 22% to 99% in the range of 0.72 THz~1.26 THz, and the adjustment depth can reach 77%. The transmittance at 2.35 THz is adjustable from 80% to 95%.As shown in e stands for an electron charge, cµ is the chemical potential. df (ε) represents the Fermi–Dirac distribution and can be given by:Bk is Boltzmann’s constant and T is the temperature. cµ of graphene can be determined by the carrier density sn:Fυ ≈ 9.5 × 105 m/s is the Fermi velocity. The carrier density of graphene can be expressed as:Here, −ε0 and dε represent the dielectric constants of air and bias layer, respectively, U is the applied voltage and t is the thickness of the bias layer. According to Equations (3) and (4), the relationship between the applied voltage U and the chemical potential cµ can be obtained as follows:Here, According to the above analysis, we can change the conductivity of graphene by adjusting the applied voltage, and then regulate the electromagnetic properties of graphene metamaterials.T = 300 K, cµ = 0.8 eV, Γ = 2.5 THz, where T is the temperature, cµ is the chemical potential of graphene and Γ is the collision frequency, which is related to the processing technology of graphene. The graphene-based metamaterials’ reflectance and transmission can be acquired by simulating the complex frequency-dependent S parameters, S11 and S21. Then, the calculation formulas of reflectivity R, transmittance T and absorptivity A are as follows:As a two-dimensional nanomaterial, graphene can be set as a thin film described by surface impedance in simulation ,25. In tRABW) of the absorber can be defined as RABW = 2(max − fminf)/(maxf + minf). Therefore, it can be calculated that the relative absorption bandwidth is 55%.In most cases, the electromagnetic wave is not normally incident and the polarization angle will change. In order to realize conformal applications, the electromagnetic properties of metamaterials should be insensitive to incident angle and polarization angle. Therefore, we analyze the absorption and transmission properties of the proposed metamaterial at different incidence angles and different polarization angles. f = 0.97 THz), the real part of the equivalent impedance is 1.03 and the imaginary part is −0.07. Therefore, terahertz wave incident on the metamaterial will hardly be reflected and will eventually be absorbed.Next, in order to explore the broadband absorption mechanism of the designed metamaterial, according to the equivalent medium theory , the equTo further analyze the absorption and transmission mechanism of the proposed multifunctional graphene tunable metamaterial, we simulated the current distribution and the electric field distribution at three key frequency points, as shown in In summary, we proposed an absorption–transmission multifunctional tunable terahertz metamaterial based on graphene. Its patterned graphene layer enables broadband absorption by introducing multiple resonances, while the frequency selective layer enables transmission in specific bands. The metamaterial has the advantage of conformal because it is flexible and insensitive to incident angle and polarization. Furthermore, its absorption and transmission can be controlled by applying voltage to regulate the chemical potential of graphene. The analysis and calculation results show that the absorption of the metamaterial is adjustable from 22% to 99% in the 0.72 THz to 1.26 THz band, and the transmittance is adjustable from 80% to 95% in 2.35 THz band. Therefore, we believe that the excellent properties of this graphene metamaterial will make it have great application prospects in detection, stealth and communication.


Abnormal functions of the cell adhesion molecule L1 are linked to several neural diseases. Proteolytic L1 fragments were reported to interact with nuclear and mitochondrial proteins to regulate events in the developing and the adult nervous system. Recently, we identified a 55 kDa L1 fragment (L1-55) that interacts with methyl CpG binding protein 2 (MeCP2) and heterochromatin protein 1 (HP1) via the KDET motif. We now show that L1-55 also interacts with histone H1.4 (HistH1e) via this motif. Moreover, we show that this motif binds to NADH dehydrogenase ubiquinone flavoprotein 2 (NDUFV2), splicing factor proline/glutamine-rich (SFPQ), the non-POU domain containing octamer-binding protein (NonO), paraspeckle component 1 (PSPC1), WD-repeat protein 5 (WDR5), heat shock cognate protein 71 kDa (Hsc70), and synaptotagmin 1 (SYT1). Furthermore, applications of HistH1e, NDUFV2, SFPQ, NonO, PSPC1, WDR5, Hsc70, or SYT1 siRNAs or a cell-penetrating KDET-carrying peptide decrease L1-dependent neurite outgrowth and the survival of cultured neurons. These findings indicate that L1’s KDET motif binds to an unexpectedly large number of molecules that are essential for nervous system-related functions, such as neurite outgrowth and neuronal survival. In summary, L1 interacts with cytoplasmic, nuclear and mitochondrial proteins to regulate development and, in adults, the formation, maintenance, and flexibility of neural functions. The cell adhesion molecule L1 is involved in the regulation of multiple and diverse neural functions, such as proliferation, survival, and migration of neural cells; neuritogenesis, axonal outgrowth, fasciculation, and guidance of axons, as well as myelination and synaptogenesis during nervous system development . InThe beneficial functions of L1 in the nervous system not only depend on homo- and heterophilic interactions , butIn previous studies, we have shown that stimulation of L1 signaling leads to the myelin basic protein-mediated generation of a transmembrane C-terminal fragment of 70 kDa, called L1-70, which plays important roles in neuritogenesis, neuronal migration, and neuronal survival as well as mitochondrial homeostasis ,19,21,25We have shown that the interaction of MeCP2 and HP1 with L1-55 is mediated by the KDET motif in the intracellular domain of L1 (L1-ICD) ,27. BesiTo verify the notion that HistH1e binds to L1-55, immunoprecipitation with HistH1 antibody and cellular subfractions from the brains of wild-type and L1-deficient mice was performed. As a negative control, we used an antibody against NDUFV2, which was shown to co-immunoprecipitate L1-70 but not L1-55 . WesternSince recombinant SFPQ, NonO, PSPC1, and NDUFV2 bind to L1-ICD in ELISA ,28, we pIn the next step, we further analyzed in a cellular context whether the binding of L1 to SFPQ, NonO, PSPC1, WDR5, NDUFV2, Hsc70, SYT1, and HistH1e is mediated via the KDET motif. To this aim, cortical neurons were first incubated with or without the cell-penetrating tat-KDET peptide, then treated with or without function-triggering monoclonal L1 antibody 557, and thereafter subjected to proximity ligation with L1 antibody and an antibody against SFPQ, NonO, PSPC1, WDR5, NDUFV2, Hsc70, SYT1, or HistH1e. The tat-QNQS peptide, which carries a disrupted KDET motif, served as a negative control. As a positive control, proximity ligation with L1 and MeCP2 antibodies was performed. To test whether Nup93 and impβ1 interact with L1 via KDET, proximity ligation with L1 antibody and Nup93 or impβ1 antibody was carried out. Under basal, unstimulated conditions, the numbers of L1/HistH1- and L1/MeCP2-positive dots were reduced by the tat-KDET peptide but not by the tat-QNQS control peptide a. The nuNext, we investigated whether the KDET-mediated interaction of L1 with its binding partners plays a role in L1-dependent neurite outgrowth. Since treatment with L1 antibody 557 increases neurite outgrowth ,21,22, wSince treatment with antibody 557 also protects neurons against hydrogen peroxide-induced oxidative stress ,32, we aTo analyze whether the L1 binding partners HistH1e, NDUFV2, SFPQ, NonO, PSPC1, WDR5, Hsc70, or SYT1, which bind to KDET, are involved in L1-dependent neurite outgrowth, neurite outgrowth was determined after transfection of cortical neurons with siRNA for these KDET-binding proteins. The reduction of HistH1e, NDUFV2, SFPQ, NonO, PSPC1, WDR5, Hsc70, or SYT1 expression had no effect on unstimulated neurons, while reduced HistH1e, NDUFV2, SFPQ, NonO, WDR5, Hsc70, and SYT1 expression, but not reduced PSPC1 expression, inhibited the L1 antibody-promoted neurite outgrowth a. WesterIn this study, we showed that HistH1e, NDUFV2, WDR5, SFPQ, NonO, PSPC1, Hsc70, and SYT1 interact with L1’s KDET motif. L1’s interactions with these and other proteins, namely TOP1, ERα, RXRβ, PPARγ, VDR, and AR, were shown by ELISA and proximity ligation, which detects L1-interacting proteins at a distance of less than 40. Proximity ligation may lead to the identification of the multiplicity of L1’s binding partners. Yet, the predominant goal of the proximity ligation assay was to show that the molecules of interest should be detected in a cellular context as being close to each other. We did not aim at finding new L1 interaction partners.The interaction between L1 and HistH1e was reduced by the γ-secretase inhibitor DAPT. Since the generation of L1-55 by γ-secretase and the interactions of L1-55 with its binding partners MeCP2 and HP1 has been shown to be reduced by DAPT ,27, we cHistH1e interacts with HP1α, HP1β, and HP1γ  and compKDET is present in the L1-ICD sequences of mammalian, amphibian, avian, reptilian, and fish species, suggesting that this motif, being conserved in evolution, plays a crucial role in regulating L1 functions. Here, we show that the KDET motif is essential for the regulation of L1-dependent neural functions, such as neurite outgrowth and neuronal survival. Disturbance of the interaction between L1 and its binding partners via the KDET motif prevents neurite outgrowth and neuronal protection against oxidative stress. Moreover, reduction of NDUFV2, WDR5, SFPQ, NonO, Hsc70, and SYT1 expression, and thus reduction of the level of the interactions between L1 and these KDET-binding proteins, inhibits L1-dependent neurite outgrowth. Of note, the reduction of PSPC1 expression does not affect L1-dependent neurite outgrowth, indicating that KDET-mediated interaction of L1 with PSPC1 is not required for L1-dependent neurite outgrowth.SYT1, which functions as calcium sensors in vesicular trafficking and exocytosis of neurotransmitters and hormones, is involved in the regulation of neurite outgrowth ,36,37 anIn utero suppression of NDUFV2 expression inhibits migration of cortical neurons and impairs the actin and tubulin cytoskeleton in cortical neurons . NDUFV2 WDR5 plays a crucial role in regulating neuronal gene expression and neurite outgrowth and contributes to the development of X chromosome-linked mental retardation .Mutations in HistH1e cause a rare neurodevelopmental disorder known as Rahman syndrome, which is characterized in addition to other symptoms by intellectual disability and autism spectrum disorder .SFPQ is a key regulator of long neuronal gene expression and thus plays an important role in the pathogenesis of amyotrophic lateral sclerosis, frontotemporal lobar degeneration, and autism spectrum disorder, which are often caused by a dysregulation of the expression of long genes . In addiNonO, which forms heterodimers with SFPQ, is associated with an intellectual disability syndrome, including macrocephaly and a thickened corpus callosum .A Hsc70 inhibitor and Hsc70 siRNA have been reported to decrease neurite outgrowth induced by a neuritogenic reagent .Based on these findings, we propose that the concomitant or consecutive interactions of L1 with its binding partners via the KDET motif are not only required for regulating L1-dependent cellular functions, such as neurite outgrowth, but also for regulating nervous system development and functions, such as synaptic plasticity, learning and memory, as well as behavior. It is noteworthy, in this context, that the identified L1 binding partners do not display obvious similarities in function but appear to mostly subserve different functional properties. Our study thus expands the spectrum of L1 activities. It is also noteworthy that different fragments of L1, as exemplified by L1-55 and L1-70 , interacMice were bred and maintained at the Universitätsklinikum Hamburg-Eppendorf at 25 °C on a 12 h light/12 h dark cycle with ad libitum access to food and water. C57BL/6J males and females or L1-deficient males  and wildThe following antibodies were from Santa Cruz Biotechnology : mouse L1 antibody C-2  against the intracellular L1 domain, mouse pan hnRNP A antibody C-6 , mouse HistH1 antibody AE-4 , mouse NDUFV2 antibody F-5 , goat CHL1 antibody C-18 , mouse importin β1 (Karyopherin β1) antibody H-7 , goat TOP1 (Topo I) antibody C-15 , goat SYT (Synaptotagmin 1) antibody N-19 , SFPQ (PSF) antibody H80 , rabbit WDR5 antibody H-36 , rabbit hnRNP A isoform (pan hnRNP A) antibody H-200 , rabbit Nup93 antibody H-300 , rabbit AR (androgen receptor) antibody N-20 , rabbit VDR (vitamin D receptor) antibody C-20 , rabbit RXR (retinoid X receptors) antibody C-20 , and rabbit ER (estrogen receptor) α antibody HC-20 . Rabbit antibodies against PSPC1 , NonO , NDUFV2 , Hsc70  and Histone H1  were from ChromoTek & Proteintech Germany . Rabbit antibodies against PPARγ , MeCP2 , and HP1ɣ  were from Cell Signaling Technology Europe . Rat monoclonal function-stimulating L1 antibody 557 has been described [Production and purification of the recombinant His-tagged intracellular domain of mouse L1  (L1-ICD) and of the mouse close homolog of L1 (CHL1-ICD) have been described ,49.Recombinant His-tagged HP1α  was from Biomol . Recombinant human SFPQ  with His-tag, recombinant human NonO  with His/sumo-tag, recombinant human PRPC1  with His-tag, recombinant full-length human AR (AR-991H) with GST-tag, recombinant human ERα  with GST-tag, recombinant human VDR  with His-tag, recombinant human WD Repeat Domain 5 with His-tag , and recombinant human PPARγ  with His-tag were from BioMart . Recombinant full-length human NDUFV2  was from OriGene Technologies , recombinant human DNA Topoisomerase-I  was from Biozol , and recombinant full-length human RXRβ (BML-SE127-0050) was from Enzo Life Sciences . Purified bovine histone H1 (14-155) was from Merck . Recombinant human HSC70 with His-tag (SMQ-SPR-106A), human synaptotagmin 1 containing amino acids 136-382 (ABX263211) and full-length human PPARγ  were from Biozol.Synthetic KDET peptide (DSEARPMKDETFGE), QNQS peptide (DSEARPMQNQSFGE), tat-KDET peptide (YGRKKRRQRRRDSEARPMKDETFGE), which comprises the cell-penetrating sequence YGRKKRRQRRR  from the2 and CaCl2  (PBS), treated with blocking solution  for 2  h, washed again with PBS containing 0.005% Tween 20 (PBST), and incubated with increasing concentrations of recombinant His-tagged L1-ICD or CHL1-ICD as ligands for 1 h under gentle agitation. For competition ELISA, 2.5 µM L1-ICD was preincubated for 1 h without or with a 5-fold molar excess of L1 peptides KDET or QNQS. The mixtures were then incubated with substrate-coated recombinant proteins. After washing two times with PBS and three times with PBST, L1 antibody C-2 (1:500) or CHL1 antibody C-18 (1:200) in blocking solution were applied for 1 h, followed by two washes with PBS and three washes with PBST, and incubation with horseradish peroxidase-coupled anti-mouse antibody (diluted 1:2000 in blocking solution) for 1 h. Wells were washed again with PBST, and 1 mg/mL ortho-phenylenediamine dihydrochloride (Thermo Fisher Scientific) was used for the detection of bound L1-ICD or CHL1-ICD. The reaction was terminated by the addition of 25 µL of 2.5 M sulfuric acid. Absorbance was measured at 492  nm with an ELISA reader .For ELISA, 25 µL of 10 or 20  µg/mL recombinant proteins were incubated overnight at 4 °C in 384-well microtiter plates with a high-binding surface . All of the following steps were performed at room temperature. Wells were washed with Dulbecco´s phosphate-buffered saline with MgClg for 15 min. Cells were then diluted in Neurobasal A medium (Thermo Fisher Scientific), supplemented with 2 mM L-glutamine (Thermo Fisher Scientific), 4 nM L-thyroxine (Sigma-Aldrich), 0.1 mg/mL BSA (Sigma-Aldrich), 12.5 μg/mL insulin (Sigma-Aldrich), 30 nM sodium selenite (Sigma-Aldrich), 100 μg/mL transferrin, 0.1 mg/mL streptomycin, and 100 U/mL penicillin (Thermo Fisher Scientific). For the proximity ligation assay, cells were seeded onto poly-L-lysine-coated 12 mm coverslips in a 24-well plate at a density of 2.5 × 105 cells per well. For the determination of neurite outgrowth, cells were seeded at a density of 5 × 104 cells per well of a 48-well plate coated with poly-L-lysine (Sigma-Aldrich). For neuronal survival analysis, cells were seeded at a density of 1.25 × 105 cells per well of a 48-well plate coated with poly-L-lysine.Cerebellar neurons were prepared from the cerebella of 6- to 8-day-old mice. Cerebella were incubated with 10 mg/mL trypsin and 0.5 mg/mL DNase I (Sigma-Aldrich) in Hanks’ balanced salt solution (HBSS) for 15 min at 37 °C, washed with HBSS, mechanically dissociated, and centrifuged at 100× 5 cells per well. For the determination of neurite outgrowth, cells were seeded at a density of 5 × 104 cells or 1 × 106 per well of a 48-well plate coated with poly-L-lysine (Sigma-Aldrich). For Western blot analysis, cells were seeded onto poly-L-lysine-coated 12-well plates at a density of 1.5 × 106 cells per well.For the culturing of cortical neurons, cerebral cortices were dissected from 15.5- to 16.5-day-old embryos and incubated in 0.025% trypsin (Sigma-Aldrich) in HBSS at 37 °C for 30 min. The cortices were then incubated in HBSS containing 1% BSA (Sigma-Aldrich) and 1% trypsin inhibitor  at 37 °C for 5 min. After washing in HBSS, the tissue was mechanically dissociated, and the dissociated cells were cultured in Neurobasal medium (Thermo Fisher Scientific) supplemented with 1% B-27 (Thermo Fisher Scientific), 2 mM L-glutamine (Thermo Fisher Scientific), 100 U/mL penicillin (Thermo Fisher Scientific), and 100 μg/mL streptomycin (Thermo Fisher Scientific). For the proximity ligation assay and immunostaining, cells were seeded onto poly-L-lysine-coated 12 mm coverslips in a 24-well plate at a density of 2.5 × 10To stimulate L1 functions, neurons were treated with 50 µg/mL L1 antibody 557. For DAPT treatment, neurons were treated for 2 h after seeding with 10 µM DAPT in DMSO . Treatment of neurons with 50 µg/mL tat-KDET or tat-QNQS peptide was conducted 30 min after seeding.For transfection of cortical neurons, cortical neurons were seeded onto poly-L-lysine-coated coverslips in 24-well plates (proximity ligation and immunostaining) or onto 12-well plates  and 48-well plates (neurite outgrowth) and maintained for 2 h before transfection with 1 µL (48-well), 2 µL (24-well), or 4 µL (12-well) of 10 µM siRNA and 1-4 µL FuGENE transfection reagent per well. L1 antibody 557 (50 µg/mL) was added to the cultures 24 h after transfection  or 2 h after transfection (neurite outgrowth), and 48 h after transfection, the cells were analyzed for neurite outgrowth and cell survival, or used for immunostaining, Western blot analysis, or proximity ligation assay.https://imagej.nih.gov/ij/index.html; RRID:SCR_003070, 30 March 2022). Numbers of red dots and numbers of DAPI-stained nuclei were determined using ImageJ, and the number of dots per image was divided by the number of nuclei per image to determine the average number of dots per nucleus. The average values were determined from 10 images per condition.Cultures were fixed for 15 min at room temperature in 4% formaldehyde, washed with PBS, and used for immunostaining or subjected to a proximity ligation assay using Duolink PLA products according to the manufacturer’s protocol  with minor modifications. For the proximity ligation assay, cells were incubated with 1% Triton X-100 in PBS for 30 min, washed once with PBS, blocked with Duolink Blocking solution for 30 min, and incubated for 24 h at 4 °C with mouse L1 antibody C-2 and goat or rabbit antibodies against TOP1, SYT, SFPQ, WDR5, hnRNP A isoforms, Nup93, PSPC1, NonO, NDUFV2, HistH1e, ERα, RXR, PPARγ, AR, or VDR, or with rabbit L1 antibody 12399 and mouse antibodies against impβ1 or hnRNP A, all diluted 1:10 in Duolink Antibody Diluent. Cells were washed two times using Duolink Wash Buffer A and incubated with a mixture of secondary antibodies conjugated with oligonucleotides (Duolink PLA Anti-Rabbit or Anti-Goat Probe MINUS and Duolink Anti-Mouse PLA Probe PLUS). The proximity ligation reaction was then performed according to the manufacturer’s protocol using the Duolink In Situ Detection Reagent RED. Thereafter, the coverslips were incubated with 5 µg DAPI/mL in PBS for 15 min, washed twice with PBS, and mounted in Immuno-Mount (Thermo Fisher Scientific). Ten images per condition were taken using an Olympus F1000 confocal microscope and analyzed using ImageJ software .2O2 for 24 h. Live and dead cells were then stained with calcein-AM (ThermoFisher Scientific) and propidium iodide (Sigma-Aldrich) and imaged with a Zeiss AxioObserver.A1 microscope (Carl Zeiss) with a 20× objective (aperture 0.4) and the AxioVision 4.6 software (Carl Zeiss). Live and dead cells were counted in five images (containing 350–400 cells each) from each of three wells per condition and experiment using ImageJ .To determine cell death, neurons were maintained overnight in serum-free medium and then treated with 50 µg/mL L1 antibody 557 and exposed to oxidative stress by the addition of 10 µM HFor the preparation of nuclear and non-nuclear fractions, the Subcellular Protein Fractionation Kit for Tissue (Thermo Fisher Scientific) was used. Fractions in cytoplasmic extraction buffer (CEB) and membrane extraction buffer (CEB) were pooled and taken as a non-nuclear fraction. Fractions in the nuclear extraction buffer were taken as nuclear fraction. Nuclear and non-nuclear fractions were used for immunoprecipitation.TM Protein G, Thermo Fisher Scientific) were washed twice in phosphate-buffered saline (PBS), pH 7.4, incubated in a dilution buffer  for 10 min at 4 °C under rotation. The mouse HistH1 or NDUFV2 antibodies (10 μg per sample) were diluted in dilution buffer. The diluted antibody solutions were incubated with the beads for 1 h at 4 °C under rotation. The beads were washed in dilution buffer for 5 min at 4 °C under rotation. A freshly prepared 13 mg/mL stock solution of dimethyl pimelimidate (DMP) was 1:1 diluted with wash buffer (0.2 M triethanolamine in PBS). After washing the beads in PBS, the diluted DMP solution (pH 8–9) was added to the beads and incubated for 30 min at room temperature (20–24 °C) under rotation. The beads were washed in a wash buffer for 5 min at room temperature under rotation. The beads were then incubated in DMP solution and wash buffer for two further times. Finally, the beads were incubated twice in quenching buffer (50 mM ethanolamine in PBS) for 5 min at room temperature under rotation. After washing, the beads were incubated with brain fractions overnight at 4°C under rotation. The beads were washed twice with lysis buffer and once with PBS. The beads were then boiled for 5 min in the sample buffer .For immunoprecipitation, Protein G magnetic beads (25 μL per sample) . PageRuler™ Plus Prestained Protein Ladder (Thermo Fisher Scientific) was used as a molecular weight marker. Proteins were then transferred to 0.45 μm Protran™ nitrocellulose membranes  and stained with Ponceau S (Thermo Fisher Scientific) to control protein loading. The membranes were then incubated for 1 h in blocking solution   with 0.05% Tween 20 (TBST)) and then incubated overnight with primary antibodies in blocking solution at 4 °C with shaking. After washing five times for 5 min in TBST, the membranes were incubated for 1 h with horseradish peroxidase-conjugated secondary antibodies . Bands were detected using enhanced chemiluminescent solution  and a CCD camera .For Western blot analysis, samples were run on 4–20% Mini-PROTEANp-Values of <0.05, <0.01, <0.001 and <0.0001 were accepted as a significant difference and indicated by *, **, ***, and **** or #, ##, ###, and #### or §, §§, §§§, and §§§§.Analyses were performed using SigmaPlot 14.0. The types of tests are indicated in the legends.


B), a mono-vacancy of nitrogen (1 VN), and co-vacancies of boron and nitrogen (VBN) induce, on the structural level: (a) for 1 VB, a contraction n of the B-N bond lengths of ~2.46% and a slight change in the interfacial distance D (~0.096%) with respect to the heterobilayer free of defects (FD) are observed; (b) for 1 VN, a slight contraction of the B-N of bond lengths of ~0.67% and an approach between the h-BN monolayer and the graphene of ~3.83% with respect to the FD heterobilayer are observed; (c) for VBN, it can be seen that the N-N and B-B bond lengths  undergo an increase of ~2.00% and a decrease of ~3.83%, respectively. The calculations of the Löwdin charge for the FD heterobilayer and for those with defects  show that the inclusion of this type of defect induces significant changes in the Löwdin charge redistribution of the neighboring atoms of VB and VN, causing chemically active regions that could favor the interaction of the heterobilayer with external atoms and/or molecules. On the basis of an analysis of the densities of states and the band structures, it is established that the heterobilayer with 1 VB and VBN take on a half-metallic and magnetic behavior. Due to all of these properties, the FD heterobilayer and those with 1 VB, 1 VN, and VBN are candidates for possible adsorbent materials and possible materials that could be used for different spintronic applications.A study is carried out which investigates the effects of the mono-vacancies of boron (VB) and nitrogen (VN) and the co-vacancies of nitrogen (N), and boron (B) on the energetics and the structural, electronic, and magnetic properties of an h-BN/graphene heterobilayer using first-principles calculations within the framework of the density functional theory (DFT). The heterobilayer is modelled using the periodic slab scheme. In the present case, a 4 × 4-(h-BN) monolayer is coupled to a 4 × 4-graphene monolayer, with a mismatch of 1.40%. In this coupling, the surface of interest is the 4 × 4-(h-BN) monolayer; the 4 × 4-graphene only represents the substrate that supports the 4 × 4-(h-BN) monolayer. From the calculations of the energy of formation of the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer, with and without defects, it is established that, in both cases, the heterobilayers are energetically stable, from which it is inferred that these heterobilayers can be grown in the experiment. The formation of a mono-vacancy of boron (1 V Graphene is a semimetal with a zero band gap. Because of its excellent properties and wide range of applications, , graphene has been extensively studied, both theoretically and experimentally. Nevertheless, one of the greatest obstacles to the construction of the new generation of graphene-based micro- and nanoelectronic devices is the absence of a finite band gap. Therefore, opening the band gap in graphene is currently a subject of interest. Enormous efforts have been made in pursuit of this goal, using various techniques; among them can be mentioned: quantum confinement by means of the reduction of its dimension by cutting the graphene into nanoribbons [Graphene was obtained by Novoselov et al.  by meansoribbons  or nanoworibbons , use of oribbons ,6, twistoribbons , doping oribbons ,9,10,11,oribbons , hydrogeoribbons , and grooribbons ,15. In aoribbons ,28,29,30oribbons ,41,42,43oribbons ,51,52,53oribbons ,61,62,63oribbons ,65, and oribbons ,65. Lee oribbons  found thoribbons , using toribbons , using fThe calculations were performed within the framework of density functional theory (DFT) ,70, usinB, 1 VN, and VBN was performed by means of the calculation of the bond energy (bE), the energy of formation (Ef), and the work of adhesion (Wad), respectively. In order to avoid interactions between simultaneous vacancies of boron and nitrogen, a sufficiently large distance of 7.20 Å was used. The energy band diagrams (BD) and the total and projected densities of states (DOSs) for the principal electronic orbitals of the B, N, and C atoms were calculated in the irreducible zone of the first Brillouin zone (1 BZ) with a F) was carried out by means of the Methfessel–Paxton method [The analysis of the energy of the FD 4 × 4-(h-BN)/4 × 4-graphene heterobilayer through those with 1 Vk-points . Finallyn method . All theBNa = 2.5150 Å and the B-N bond length was B-Nl = 1.4521 Å, while the lattice constant for the graphene was graa = 2.4630 Å, and the C-C bond length was C-Cl = 1.4200 Å. All these values are in excellent agreement with the results of previous theoretical [Before beginning the study of the h-BN/graphene heterobilayer with and without a vacancy, we first carried out a complete structural optimization of the isolated h-BN monolayer and the isolated graphene. We found that, for the h-BN monolayer, the lattice constant was oretical ,80,81,82oretical ,84 invesIn order to investigate the effects of the mono-vacancies and co-vacancies of boron and nitrogen on the structural, electronic, and magnetic properties of an h-BN)/graphene heterobilayer, initially, we constructed a 4 × 4-(h-BN)/4 × 4-graphene heterobilayer, which contained 32 atoms of C, 16 atoms of B, and 16 atoms of N.The 4 × 4-(h-BN)/4 × 4-graphene heterobilayer exhibits a mismatch of ~1.4%. In this configuration, three types of vertical stacking are considered: in the first stacking, an atom of B is exactly in the center of the graphene hexagon (B-centered); in the second stacking, an atom of N is exactly in the center of the graphene hexagon (N-centered); and, in the third stacking, the centers of the hexagons of h-BN and the graphene coincide, that is, the B and N atoms are exactly over the C atoms (h-centered), as is shown in bE = −23.920 meV/Å), which corresponds to a distance of interlayer separation D = 3.1180. Hereafter, we refer to the energetically most favorable configuration, that is, the one that has a nitrogen atom exactly in the center of the graphene hexagon. This result is in excellent agreement with the results of the studies by Slotman et al. [In order to determine the energetically most favorable configuration for the three cases under consideration, we calculate the bond energy in the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer. The bond energy  is calculated with the following equation ,77:(1)Ebn et al.  in theirn et al.  and Sachn et al.  in theirIn B) and nitrogen (1 VN), and the co-vacancies and simultaneous vacancies of boron and nitrogen (VBN), in an h-BN/graphene heterobilayer, are established. A schematic representation of these isolated defects is shown in In this subsection, the effects of the mono-vacancies of boron (1 VB-Nl) and the interfacial distance D of the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer with mono-vacancy and co-vacancy after the process of structural relaxation is finished. For 1 VB, we found that there exists a contraction of the B-N bond lengths of ~2.46% with respect to the heterobilayer with no vacancy, while, for 1 VN, there exists a slight contraction in the B-N bond lengths, with the maximum contraction being ~0.67%.BN, it is found that, in both the neighborhood of the B vacancy and in the neighborhood of the N vacancy, there occurs contractions in the B-N bond lengths, with the maximum values being ~3.62% and ~2.22%, respectively.For the VB, the interfacial distance practically does not undergo any change in the discrepancy with respect to the heterobilayer, with no vacancy being ~0.096%, while, for the heterobilayer with 1 VN, the monolayer of h-BN and the graphene undergo a significant approach, since the interfacial distance undergoes a contraction of ~3.83%.In relation to the interfacial distance D, we found that, in the heterobilayer with 1 VB, it is found that the distance N-N  in the heterobilayer free of vacancies, while, for 1 VN, the B-B distance  in the heterobilayer free of vacancies.On the other hand, for 1 VBN covacancy, it is found that the N-N bond lengths ; B, 1 VN, and VBN) and of isolated graphene monolayer, respectively. With the aim of making a more complete study of the energy stability of the heterobilayer with B and N mono-vacancies and co-vacancies, we calculated the energy of formation and the work of adhesion. The energy of formation is defined as the energy needed to create the heterobilayer from its corresponding elemental forms. The energy of formation of the heterobilayer was calculated by means of the following equation ,90,91,92ad = −Efor. The values of the calculations of the bond energy, the energy of formation, and the work of adhesion for the heterobilayer free of defects, with mono-vacancies, and with B and N co-vacancies are shown in Additionally, the work of adhesion was calculated, which is defined as the reversible work required to separate the heterobilayer into two free monolayers. In this case, the work of adhesion is defined as a negative value of the energy of formation ,90, thatB, 1 VN, and co-vacancy VBN, the density of states (DOSs), the band structure (BS), and the distribution of the density electronic charge of Löwdin were calculated. In the calculation of the DOSs and the BS, the Fermi level was chosen as the zero energy.To study the electronic properties of the h-BN/graphene heterobilayer free of vacancies, with 1 VB. The BS , with an N vacancy (1 VN), and with a co-vacancy of nitrogen and boron (VBN). The results are shown in B) in the heterobilayer, there is a slight decrease in the total Löwdin charge in the neighboring atoms of the vacancy  of the boron vacancy.In the same way, in N) is generated in the heterobilayer, there is a slight increase in the total Löwdin charge in the neighbor atoms of the vacancy  is generated in the heterobilayer, a behavior similar to that described for the mono-vacancies B and N is found. For the atoms B6, B10, and B11 (neighbors of the nitrogen vacancy 1 VN), the total Löwdin charge undergoes, on average, an increase of 0.104 e/Bohr3, the average increase in the Löwdin charge  in the orbitals s-B and p-B are 0.087 e/Bohr3 and 0.017 e/Bohr3, respectively, while, in the atoms N3, N4, and N8 (neighbors of 1 VB), the total Löwdin charge undergoes, on average, a decrease of 0.091 e/Bohr3.Finally, it can be seen in 3, while the p-N orbitals of the atoms N3, N4, and N8 experience an average decrease of 0.198 e/Bohr3. These results are coherent with the contour map of The calculation of the Löwdin charge density  shows that the s-N orbitals of atoms N3, N4, and N8 present an average increase of 0.017 e/BohrB, nitrogen vacancy 1 VN, and co-vacancy of boron and nitrogen VBN, are energetically stable. Furthermore, it was found that the inclusion of 1 VB and 1 VN in the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer induces slight structural changes in the distance between the monolayers of 4 × 4-(h-BN) and 4 × 4-graphene and in the bond length  of the neighbor atoms of the 1 VB and 1 VN, respectively.The effects of mono-vacancies and co-vacancies of B and N on the energetics and electronic properties of the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer were investigated using the GGA-PBE-D2 generalized gradient approximation and atomic pseudopotentials. Initially, from the calculations of the energetics, it was established that the heterobilayers’ FD, with boron vacancy 1 VB, 1 VN, and VBN, it was established that this type of point defect generates significant changes in the distribution of the Löwdin charge in the first-neighbor atoms of the VB and VN, respectively; these local zones are converted into chemically active regions that could favor interaction between the surfaces of these heterobilayers with external atoms and/or molecules.From the analysis of the Löwdin charge transfer for the 4 × 4-(h-BN)/4 × 4-grafene heterobilayers’ FD and with 1 VB and 1 VBN in the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer induces, in both cases, a half-metallic and magnetic behavior in this heterobilayer, from which it is inferred that the la 4 × 4-(h-BN)/4 × 4-graphene heterobilayer could be used in spintronic applications.From the analysis of the density of states and the band structure, it was established that the inclusion of 1 V