In varicose veins, vascular smooth muscle cells (VSMCs) often shows phenotypic transition and abnormal proliferation and migration. Evidence suggests the FOXC2–Notch pathway may be involved in the pathogenesis of varicose veins. Here, this study aimed to explore the role of long non-coding RNA FOXC2-AS1 (FOXC2 antisense RNA 1) in phenotypic transition, proliferation, and migration of varicose vein-derived VSMCs and to explore whether the FOXC2-Notch pathway was involved in this process.The effect of FOXC2-AS1 on the proliferation and migration of human great saphenous vein smooth muscle cells (SV-SMCs) was analyzed using MTT assay and Transwell migration assay, respectively. The levels of contractile marker SM22α and synthetic marker osteopontin were measured by immunohistochemistry and Western blot to assess the phenotypic transition.The human varicose veins showed thickened intima, media and adventitia layers, increased synthetic VSMCs, as well as upregulated FOXC2-AS1 and FOXC2 expression. In vitro assays showed that FOXC2-AS1 overexpression promoted phenotypic transition, proliferation, and migration of SV-SMCs. However, the effect of FOXC2-AS1 overexpression could be abrogated by both FOXC2 silencing and the Notch signaling inhibitor FLI-06. Furthermore, FOXC2-AS1 overexpression activated the Notch pathway by upregulating FOXC2.FOXC2-AS1 overexpression promotes phenotypic transition, proliferation, and migration of SV-SMCs, at least partially, by activating the FOXC2-Notch pathway. Lower extremity varicose veins are a common disorder of venous dilation and tortuosity, and most varicose veins occur in the great saphenous vein , 2. The The forkhead box C2 (FOXC2) is a transcription factor of the human forkhead family involved in the metabolism of adipose cells, and is closely related to the occurrence and development of blood vessels and lymphatic vessels , 5. NotaLong non-coding RNAs (lncRNAs) have been shown aberrantly expressed in the primary great saphenous varicose veins, suggesting the potential involvement of lncRNAs in the pathogenesis of varicose veins . FOXC2 aIn this study, we first investigated the differences in morphology, VSMCs phenotypic transition, and FOXC2-AS1 expression between the normal veins and varicose veins. Subsequently, we investigated the role of FOXC2-AS1 in regulating phenotypic transition, proliferation, and migration of human great saphenous vein smooth muscle cells (SV-SMCs). Finally, we elucidated whether the mechanisms underlying the FOXC2-AS1-mediated effect was related to the regulation of FOXC2 and Notch signaling pathway.HE staining showed that the thickness of the intima, media, and adventitia of normal veins was normal. However, in the varicose veins, abnormal thickening of the intima was observed, and VSMCs proliferated in the media and adventitia of veins Fig. a. ImmunoThe qRT-PCR results showed that FOXC2-AS1 expression in the varicose veins was significantly higher than that in the normal veins .2O2 to quench endogenous peroxidase activity. Subsequently, the sections were rinsed with distilled water three times and then completely immersed in 0.01 mol/L citrate buffer, heated in a microwave oven, and washed twice with PBS. Following incubation with 5% BSA blocking solution, the sections were incubated with a primary rabbit anti-human SM22α  or rabbit anti-human OPN  at 37 °C for 90 min, followed by the biotin-labeled secondary antibodies at 37 °C for 20 min. The sections were incubated with the streptavidin–biotin–peroxidase complex (SABC) working solution at 37 °C for 20 min and then washed with PBS containing 0.1% TWEEN20. Then samples were stained with diaminobenzidine (DAB), counterstained with hematoxylin, dehydrated, and then embedded in paraffin. The yellowish-brown staining indicates a positive signal. The sections were observed under an Olympus BH-2 light microscope .Immunohistochemistry was used to observe the localization and expression of SM22α and OPN in varicose veins and normal veins. Briefly, the veins sections were dewaxed, hydrated, and then incubated in 3% H−ΔΔCt method and normalized to GAPDH. The primers were as follows: FOXC2-AS1 (forward) 5′-TTCATCGGCTGCGTATTCG-3′, FOXC2-AS1 (reward) 5′-TTGCCTTCTAGTCGCCTCC-3′; FOXC2 (forward) 5′-CGGCCCAGCAGCAAACTTTCC-3′, FOXC2 (reward) 5′-AGAGGCGGCGTGGATCTGTAG-3′; GAPDH (forward) 5′-CGCTGAGTACGTCGTGGAGT-3′, GAPDH (reward) 5′-CGTCAAAGGTGGAGGAGTGG-3′.qRT-PCR was performed to examine the expression of FOXC2-AS1 and FOXC2. Total RNA was extracted from tissues or cells using TRIzol reagent (Invitrogen) and was reverse transcribed into cDNAs using the Reverse Transcription Kit (Takara). The cDNA template was synthesized through qRT-PCR using SYBR Green PCR Kit  by the ABI7900 system (Applied Biosystem). The relative mRNA expression levels were calculated by the 22 in a 25 mL glass culture flask, after which the flask was then inverted to stand upright and cultured at 37 °C. When the tissue block and the bottom of the bottle were observed to be firmly attached, the flask was placed flat, and then the complete medium  was added. After incubation for 12–14 days, the cells are crawled out from the edge of the tissue block, fused, and were routinely digested and passaged. The medium was changed once every 2 days.The human SV-SMCs were isolated from healthy human great saphenous vein. Briefly, the saphenous veins from the patients undergoing cardiac coronary artery bypass grafting surgery were collected and washed with PBS to remove blood. Then the extravascular connective tissues were carefully removed and the adventitia was exfoliated. The blood vessels were cut longitudinally and the inner membranes were bluntly scraped with the scalpel’s knife back. After being digested in 0.25% trypsin–EDTA solution for 5 min, the middle layer of the blood vessel was cut into a tissue block of about 1 mm × l mm × 1 mm in DMEM medium. Subsequently, the tissue block was evenly spread using an elbow pipette at a density of 3–5 pieces/cmThe SV-SMCs of the 3–5th generation were harvested and identified by α-SMA immunofluorescence. Briefly, when the cell confluence reached 75–85%, cells were fixed with 4% paraformaldehyde, permeabilized in 0.3% Triton X-100, and blocked with normal goat serum. Cells were then incubated with primary anti-α-SMA (1:110) overnight at 4 °C, followed by Alexa Fluor 568-labeled secondary antibody (1:60) at 37 °C for 1 h. Then cells were stained with Hoechst 33,342 and observed under a fluorescence microscope.® 2000 (Invitrogen) following the manufacturer’s protocol.To overexpress FOXC2-AS1, the full-length FOXC2-AS1 cDNA fragments were cloned into the pcDNA3.1 plasmid (Invitrogen), generating pcDNA3.1-FOXC2-AS1. An empty pcDNA3.1 vector was used as the control. To knock down FOXC2, FOXC2 siRNA (si-FOXC2) was designed and synthesized by GenePharma . A scramble siRNA was used as negative control (si-Ctrl). The SV-SMCs were transfected with these constructs using LipofectamineTotal protein from veins tissues and SV-SMCs was extracted using RIPA buffer . The protein concentrations were determined by BCA assay. Subsequently, equal protein from cell lysates was separated by 10% SDS-PAGE gels and transferred to PVDF membranes . After blocked with 5% skim milk, the membranes were incubated with the following primary antibodies against SM22α, OPN, FOXC2, Dll4, Notch1, Hey2, and EphrinB2  overnight at 4 °C, followed by the horseradish peroxidase (HRP)-conjugated secondary antibodies  at room temperature for 1 h. The protein was detected with an enhanced chemiluminescence kit  and the band intensity was quantified with Image J 14.0 software. GAPDH served as the loading control.3–5 × 103 cells/well. After 48 h of incubation, 20 μL MTT  was added into each well for 4 h of incubation at 37 °C. Then the medium was replaced with 150 μL DMSO (Sigma) for 10 min. Cellular viability was determined by measuring the optical density (OD) at 490 nm with averages from triplicate wells by an enzyme-labeled analyzer. Cellular viability was normalized to control well.Cell proliferation was analyzed by the MTT assay. Briefly, the SV-SMCs were harvested for 48 h after transfection and then seeded into 96-well plates at a density of 2 × 10Transwell assays were performed to assess cell migration. Briefly, the transfected cells were resuspended in serum-free medium, and 100 μL of the cell suspension was seeded in the upper chamber of Transwell inserts, while 600 μL full-serum medium containing DMEM with 10% FBS was added to lower chambers. After 24 h of incubation, non-migratory cells on the upper chamber of the inserts were scraped off with a cotton swab. Cells cling to the bottom side were fixed with methanol and stained with 0.1% crystal violet. The number of migratory cells was counted in six random fields under a microscope.t-test was used to analyze differences between two groups. One-way ANOVA was used to analyze differences among multiple groups. p < 0.05 was considered to indicate statistically significant.All statistical analyses were performed using SPSS 19.0. The data are presented as the mean ± standard deviation. The unpaired Student’s


E of the neat multimodal-HDPE significantly at the lowest carbon black content.The effect of carbon black (CB) and microwave-induced plasma graphene (g) on the crystallisation kinetics of the multimodal high-density polyethylene was studied under non-isothermal conditions. The non-isothermal crystallisation behaviour of the multimodal-high-density polyethylene (HDPE), containing up to 5 wt.% graphene, was compared with that of neat multimodal-HDPE and its carbon black based nanocomposites. The results suggested that the non-isothermal crystallisation behaviour of polyethylene (PE)-g nanocomposites relied significantly on both the graphene content and the cooling rate. The addition of graphene caused a change in the mechanism of the nucleation and the crystal growth of the multimodal-HDPE, while carbon black was shown to have little effect. Combined Avrami and Ozawa equations were shown to be effective in describing the non-isothermal crystallisation behaviour of the neat multimodal-HDPE and its nanocomposites. The mean activation energy barrier (ΔE), required for the transportation of the molecular chains from the melt state to the growing crystal surface, gradually diminished as the graphene content increased, which is attributable to the nucleating agent effect of graphene platelets. On the contrary, the synergistic effect resulting from the PE-CB nanocomposite decreased the Δ Multimodal high-density polyethylene (HDPE) is an engineered thermoplastic semi-crystalline polymer, which is widely used in films, pressure pipes, bottles, tubes and cables jacketing ,2,3,4,5.3, SiO2, TiO2, BaSO4, on the crystallisation kinetics of HDPE [Graphene has recently emerged as a very promising breakthrough material in the field of polymer nanocomposites and has attracted considerable scientific interest . A large of HDPE ,31,32,33 of HDPE . J. Kim  of HDPE . The mec of HDPE ,34,35,36 of HDPE . Also, a of HDPE . Moreove of HDPE . Polymer crystallisation is a process that essentially involves two consecutive steps, namely the nucleation and growth of the crystal nucleus ,34,35,363. Antioxidants masterbatch containing Irgafos 168 and Irganox 1010 were added to the polymers at 0.5 wt.% for optimum stabilisation during processing. Graphene powder was obtained from FVG Cambridge Nanosystems company , with ≥96% carbon purity, bulk density of 0.0266 g/mL, flake thickness < 1.0 nm with an average lateral size range of 150–500 nm. Carbon Black powder was provided by Orion Engineered Carbons GmbH , with ≥92 cc/100g oil absorption number, ash content of 0.10%, Sulphur content of 0.10%, tint strength of 103%, average primary particle size of 20 nm and a density of 1.7–1.9 g/cm3 at 20 °C.Unstabilised, high density polyethylene powders, produced with Ziegler Natta catalyst via a proprietary Borstar process , melt flow rate of 7.5 g/10 min , Mw = 280 kg/mole, Mn = 8.49 kg/mole and Mw/Mn = 33 and a density of 950 kg/mBoth multimodal-HDPE/graphene (PE-g) and multimodal-HDPE/carbon black (PE-CB) were prepared via melt-intercalation method using Coperion ZSK 18 twin extruder having a screw diameter of 18 mm and a barrel length of 720 mm (L/D = 40). The screw rotation speed was 600 rpm, barrel temperature profile was in the range of 170–240 °C and feed rate was between 1–2 kg/h. For more information, the reader is directed to our previous work [The nanofillers and a dry polyethylene powder were fed separately into the extruder via a spiral flow screw Brabender ISC-CM plus feeder. The nanofillers were fed at 0.1, 0.5, 1, 2 and 5 wt.% loadings. In order to prevent the polymer from degrading, an antioxidant masterbatch was simultaneously added through a side feeder, with the total loading of 0.5 wt.%. The extruded pellets were subsequently compression moulded to about 0.4 mm thickness, following ISO 293 under 5 MPa, at a temperature of 200 °C. This was undertaken via a compression moulding platen press , for an overall programming cycle of 32 min at a heating and cooling rate of 15 °C/min. The specimens were successively conditioned at 23 ± 2 °C and 50 ± 5%, for at least 48 h, prior to being tested. Polarised light microscopy (PLM) analyses were conducted on a ZEISS Axio scope.A1 HAL 100/HBO 100, operated with an AxioCam MRc 5 camera and an AxioVision software. Film samples were sectioned to a thickness of 15 μm, using a fully automated rotary microtome Leica RM2265 . Samples were cooled by DSC at 2.5 °C/min prior to being analysed under the polarised light. ImageJ software was used to calculate the mean particle size of the nanoparticle agglomerates and the %area fraction (200 × 200 µm2) upon the optical light microscopy and transmission electron microscopy (TEM) images. Transmission electron microscopy (TEM) was performed using Hitachi HT7700, at an accelerating voltage of 120 kV. Film samples were cryo-sectioned to a thickness of ~80 nm at −125 °C, using Leica EM UC7/FC7 Cryo-Ultra-microtome.Thermogravimetric analysis (TGA) was carried out with Q500 TGA  with a heating rate of 10 °C/min from room temperature to 1000 °C in a nitrogen atmosphere. High-Resolution (Hi-Res)-Dynamic mode was performed with sensitivity of 2.00 and a resolution of 4 °C. Rheological behaviour of the samples was studied using stress-controlled rotational rheometer (Anton Paar Physica MCR 301 with CTD450 heating unit) at 190 °C under a nitrogen atmosphere. The compression moulded sample, weighing 1.5 g and with measurements of 25 mm in diameter and 1.5 mm in thickness was conditioned at 40 °C for 48 h. The sample was then placed onto a 25 mm parallel plate fixture and trimmed to a thickness of 1.2 mm by slowly lowering the upper plate. The dynamic frequency sweep was conducted from 500 to 0.0154 rad/s at 5% strain. The reason for starting from the maximum frequency was to avoid sample degradation under high temperature and low angular frequency speed. The polydispersity index (PDI) was calculated as follows [G′ is the storage shear modulus, G” is the loss shear modulus, ω is the angular frequency and Differential scanning calorimetry (DSC) was performed in a N2 atmosphere (50 ± 5 mL/min), using approximately 5 mg of the sample, sealed in Al pans with TA Instruments Q2000. The samples were melted at 200 °C, then held for 10 min to eliminate the thermal history and subsequently cooled to 0 °C at cooling rates of 2.5, 5, 10 and 20 °C/min, respectively. The samples were again held at 0 °C for 10 min and subsequently heated to 180 °C at the same cooling rates as the prior cooling rate, in order to obtain the DSC exotherms. Heat flow, as a function of time and temperature, was recorded during both crystallisation and melting processes for consequent data analysis.Tc) was determined from the temperature at maximum heat flow of crystallisation peak. The peak crystallisation temperature (Xc) of the polymers, where ΔHv is the enthalpy of fusion determined from the experiment, ΔHv° is the enthalpy of fusion of the 100% crystalline polymer (ΔHv° = 290 J/g) and fW is the weight fraction of the filler content in HDPE [The following equation:%Xc=ΔHv were around 0.9 µm2 and 0.4 respectively, as shown in 2 and the %area fraction was less than 0.006. The %area fraction and mean particle size were calculated based on TEM and light microscopy analysis and graphene particles of less than 0.05 µm2 or 500 nm were excluded from the calculations. A decrease in the %area fraction means a better distribution and fewer agglomerates. The figure was higher with carbon black as the fused aggregate sizes are commonly bigger than graphene monolayers. As shown from the TEM images in The dispersion and distribution of graphene and carbon black were assessed by TEM and light microscopy, as shown in G′) and loss (G′′) moduli, as well as their frequency dependence [The dispersion and distribution of the nanofillers within the polymer matrix were further investigated by the rheological measurements ,46,47,48pendence ,46,47,48The presence of the nanofillers considerably increased the pseudoplasticity at a low shear rate. At the angular frequency of 0.0154 rad/s, the complex viscosity of the neat multimodal-HDPE increased from 0.19 MPa·s, to 0.34 MPa·s and 0.25 MPa·s at 1 wt.% loading of graphene and carbon black, respectively. Similarly, the loss and storage moduli of the neat polymer increased by a value of ~36% and ~32% with 1 wt.% loading of carbon black and by a value of ~99% and ~78% at 1 wt.% loading of graphene, respectively. The greater amount of storage and loss moduli of the reinforced polymer is attributed to the formation of a strong interfacial bonding between the polymer matrix and the high-modulus nanofillers, which has accordingly reduced the loss tangent, therefore the polymer became more elastic ,28,29,30GC) and crossover angular frequency point (ωC) of the reinforced polymers have shifted to a lower range. The addition of 1 wt.% of graphene decreased the GC and ωC of multimodal-HDPE by a value of 15% and 53%, respectively, while it decreased by a value of 13% and 46% with the 1 wt.% loading of the carbon black. These differences can be attributed to the specific surface area which each nanofiller can offer the polymer matrix through its specific dimensions [ωC to the lower region indicates that the reinforced polymers exhibited higher average molar mass and/or branched (entanglement) molecules [GC to the lower region upon the addition of nanofillers possibly arose also from exposing the neat polymer to a high temperature, under a combination of high shear and elongation forces, for a prolonged period of time. The weight average molar mass (Mw) and z-average molar mass (Mz) of the neat multimodal-HDPE powder decreased from 280 kg/mol and 2099 kg/mol, to 207 kg/mol and 1131 kg/mol, respectively, after being extruded in the conditions described in the experimental section  exhibited broader shape and shifted gradually to a lower temperature. The value of Tc increased from 114.8 °C to 119.8 °C for pristine multimodal-HDPE, when decreasing the cooling rate from 20 to 2.5 °C/min. In general, nucleation at a lower degree of undercooling tends to be sporadic and only a relatively small number of nuclei are obtained during the melt crystallisation [lisation . At highlisation ,11,36,51Hc) decreased where the cooling rate was elevated, as indicated in A rapid decrease in temperature is accompanied by an increase in the viscosity, thereby the transport of material to the growth point becomes more difficult and eventually reduces the growth rate . Hence, Hc at higher cooling rates, can also be attributed to thermal conductivity limitations, as well as lowered annealing effects. At a given cooling rate, Tc of multimodal-HDPE filled with graphene shifted to higher temperatures, as shown in Tc was clearly evident at the lowest graphene content. Afterward, the shift continued to gradually ascend as the concentration of graphene was increased, accompanied by a broadening of the peak  ,55,56,57peak see . For exar matrix . The forr is related to the time (t) and spherulite growth rate (v) through an equation in the form of r = vt, which is valid until the spherulites touch each other [A polarised light microscope was used to examine the spherulitic morphology of the polymers, as shown in ch other ,36,58,59ch other .T) as a function of crystallisation temperature can be calculated using the following equationdH/dT is the enthalpy of crystallisation evolved within an infinitesimal temperature range, T0 is the onset crystallisation temperature, T denotes the arbitrary crystallisation temperature and fT refers to the end temperature of crystallisation [T0 of the multimodal-HDPE filled with graphene shifted significantly to higher temperatures, as shown in T0 was clearly evident even at the lowest graphene content (0.1 wt.%) and continued to increase gradually as the concentration of graphene grew. For example, the value of T0, increased from 120.3 °C to 123.6 °C for PE-CB-1% and to 127.4 °C for PE-g-0.1%, at the cooling rate of 20 °C/min. However, the relative value of T0 remained almost the same for the PE-CB, regardless of the concentration of carbon black.The relative degree of crystallinity  is widely used as an indicator of spherulitic growth rate; the larger the difference, the lower the rate of growth in the spherulites [T0 − Tc) are listed in T0 − Tc) to increase. With a 1wt.% loading, it was increased by 144%, 121%, 105% and 84% at the cooling rate of 2.5, 5, 10, and 20 °C/min, respectively. The value of (T0 − Tc) gradually became larger with increasing graphene content. On the other hand, the relative value of (T0 − Tc) decreased at the lowest content of carbon black, especially at the cooling rate ≥ 10 °C/min and thereafter remained invariable at higher concentrations. These results are in concurrence with the PLM images, that is, the bigger the spherulite radius, the greater the rate of spherulitic growth (r = vt). In non-isothermal crystallisation, the arbitrary crystallisation temperature T is associated with the crystallisation time t through the following equation of the formThe difference between the onset and the peak crystallisation temperatures  extended significantly with the addition of graphene, especially at the cooling rate of ≤10 °C/min. As a further example, in PE-g-1%, the value of t0.5 increased from 0.5, 0.8, 1.2 and 2.1 to 0.8, 1.3, 2.3 and 4.1 min, at the cooling rate of 2.5, 5, 10, 20 °C/min, respectively. The marginal increase in the value of (t − t0.5), indicates that the time-lag occurring as a result of a longer incubation period. On the other hand, a slight decrease in t0.5 and t was generally observed with the addition of carbon black, as shown in t0.5 remained almost saturated when the carbon black content reached 1 wt.% and higher. These results are in agreement with the PLM images, that is, the spherulite radius is directly proportional to the rate of spherulitic growth (r = vt). This means that the crystallisation kinetics of PE-CB and PE-g were dominated by the nucleation process. As graphene has a huge surface area, it has introduced a large number of nucleation sites through which the crystallisation initiated and occurred at higher temperatures. The effect of graphene is consistent with most of the results reported in the literature on the effect of nucleating agents upon the behaviour of crystallisation in HDPE, with the exception of the declining rate of the crystallisation [T0 [The magnitude of parameters obtained from hene see c,d. Withlisation . Nonethelisation ,34,47,63lisation . Furtherlisation ,64. F. Ction [T0 ,64. ContCarbon black acting as a nucleating agent in polyethylene has never yet been reported according to the author’s knowledge. Many studies, such as those by S. Song et al. , A. Krum3, SiO2, TiO2 [n is a kinetic constant, m1/ refers to the cooling or heating rate required to achieve a certain relative degree of crystallinity at a unit crystallisation time and a is the ratio of Avrami exponent n to Ozawa exponent m, that is, a = n/m.Using an appropriate model to account for the varying temperatures and cooling rates allows better understanding of the crystallisation kinetics under typical non-isothermal conditions. Various scientists, such as Ziabicki, K. Nakamura et al., Jeziorny, Ozawa, R. M. Patel et al., Dietz, T. Liu et al., have proposed numerous models to describe the non-isothermal crystallisation kinetics of semicrystalline polymers ,22,23,38O2, TiO2 ,28,29,38a can be determined from the intercept and slope of the log φ versus log t plot respectively, as shown in 2 ≥ 0.998, was observed at a given relative degree of crystallinity, indicating that the T. Liu et al. model could aptly describe the non-isothermal crystallisation kinetics of the multimodal-HDPE, PE-g and PE-CB. The kinetic parameter TF as a function of relative degree of crystallinity and the nanofiller content, is shown in a were almost the same. The marginal changes in the values of a, ranged from 1 to 1.3, which also indicates that the combined Avrami-Ozawa equations suitably describes the non-isothermal crystallisation kinetics of the multimodal-HDPE, PE-g and PE-CB, as reported elsewhere [TF values of the neat HDPE and PE-CB were almost the same and increased in a similar pattern across the entire degree of relative crystallinity. A slight decrease in TF was observed when the polyethylene was loaded with ≥1 wt.% carbon black content, which is consistent with the results observed earlier in this study.Parameters lsewhere ,34,35,36TF parameter of PE-CB-1% decreased from 2.8, 7 and 69.5 °C/min to 2.4, 5.8 and 69.2 °C/min at Xt of 10%, 50% and 100%, respectively. This is a confirmation that carbon black did not form a continuous network structure, most probably because of its dimensionality. However, the relative increase in FT was clearly evident even at the lowest graphene content and continued to gradually rise as the concentration of graphene became larger, especially at Xt < 70%. The FT value of the multimodal-HDPE filled with 1 wt.% graphene, increased from 2.8, 7 and 69.5 °C/min to 7.8, 14.1 and 77.1 °C/min at Xt of 10%, 50% and 100%, respectively. This is indicative of a slower crystallisation process compared with the neat HDPE and/or HDPE filled with CB and it is related to the difficulty of crystallisation process to progress further due to the entangled-network structure induced by graphene platelets. These results are consistent with what was observed and discussed earlier in this study. Accordingly, knowledge of the conditions affecting the crystallisation kinetics is crucial for optimising the processing parameters, as this can affect the final properties of the product which includes warpage/shrinkage control, mechanical and optical clarity or an alteration of the cycle time in moulding or extrusion [The xtrusion . In pipextrusion . A replaE) required for the molecular chains to transport from the melt state to the growing crystal surface, in non-isothermal systems, was calculated in this study, using the following H. E. Kissinger equation [R is the universal gas constant. The higher the value of ΔE, the more difficult the transportation of macromolecular chains to the growing surface. These can generally result either from higher viscosity or restriction in the polymer chains as previously discussed in the present study. The activation energies obtained from the slope of the straight-lines in a E of the neat multimodal-HDPE, which was −535 kJ/mol. The value of ΔE decreased gradually to −556, −582, −591, −612 and −705 kJ/mol when increasing the concentration of graphene to 0.1, 0.5, 1, 2, 5 wt.%, respectively. However, the relative value of ΔE decreased significantly to −876 kJ/mol at the lowest carbon black content of 0.1 wt.% and remained almost saturated at higher concentration. In general, the decrease in the activation energy barrier is attributable to the role of the nanoparticles as a nucleating agent. The results indicate that graphene is likely to perform two functions in the multimodal-HDPE matrix. The platelets acted as nucleating agents and accelerated the primary nucleation, which was manifested by the gradual decrease in ΔE and the increase in T0 and Tc. However, the presence of the jammed network structure slowed the diffusion of the polymer chains into the crystalline lattice, thus lowering the overall crystallisation rate, as confirmed by the increase in FT, t0.5 and t. On the other hand, the change in crystallisation kinetics of the multimodal-HDPE, associated with the addition of carbon black, is suggested to be a result of the synergistic effects. This occurs where the longer macromolecular chains and broader MWD accelerated the crystallisation of PE-CB as confirmed from the values of ΔE, t0.5, Tc, FT, as well as rheological results.At a given cooling rate, the relative degree of crystallinity at the peak crystallisation temperature ranges between 11% and 30% for all the polymers. The mean activation energy barrier (Δequation ,36,38,39t0.5 increased significantly with the addition of graphene and continued to increase gradually with an increasing content of graphene. However, the spherulitic growth rate decreased at the lowest graphene content and continued its gradual descent with the increasing amount of graphene content. On the other hand, the non-isothermal crystallisation behaviour of the PE-CB nanocomposites relied on the cooling rate only and the effect of carbon black content as a nucleating agent was found to be marginal, with the exception of the peak crystallisation temperature which increased gradually in concurrence with the carbon black content. At a given cooling rate, the relative onset crystallisation temperature of PE-CB remained almost unchanged with the addition of the carbon black. Also, a slight increase in the spherulitic growth rate accompanied a relative decrease in t0.5 which was observed upon addition of 0.1% carbon black and these remained almost unchanged with further addition.The crystallisation kinetics of the multimodal-HDPE behaved differently with the addition of 0.1 to 5 wt.% carbon black or graphene, under non-isothermal conditions. The non-isothermal crystallisation behaviour of the PE-g nanocomposites relied heavily on both the graphene content and cooling rate. The relative peak crystallisation temperature of PE-g increased with decreasing the cooling rate for a given graphene content and increased gradually with an increase in the concentration of graphene at a given cooling rate. Incorporation of graphene caused a change in the mechanism of nucleation and crystal growth of multimodal-HDPE crystallites, with the effect being more evident at the lowest graphene content. At a given cooling rate, the nucleation initiated at a higher temperature and continued to increase with the graphene content. Similarly, the incubation period as well as the time required to reach 50% of relative crystallinity FT of the multimodal-HDPE filled with 1 wt.% graphene increased from 2.8, 7.0 and 69.5 °C/min to 7.8, 14.1 and 77.1 °C/min at Xt of 10%, 50% and 100%, respectively. However, a slight decrease in FT values was observed when the multimodal-HDPE loaded with ≥1 wt.% carbon black content. Using the H. E. Kissinger equation, the activation barrier energy of the multimodal-HDPE decreased gradually with an increasing the graphene concentration, while it rose by 64% at the lowest carbon black content. However, the value of ΔE remained almost unchanged as the content of carbon black increased. For PE-g, graphene platelets acted as nucleating agents and introduced foreign surfaces, which in turn reduced the barrier activation energy required for the crystallisation. However, the presence of the jammed network structure introduced by graphene platelets retarded the diffusion of the polymer chains into the crystalline lattice and thus slowing the primary crystallisation. Contrastingly, carbon black was shown to have little effect as a heterogeneous nucleating agent on the crystallisation kinetics of multimodal-polyethylene, possibly because of its surface properties.Combined Avrami-Ozawa equations proposed by Liu et al. was found to be effective in describing the non-isothermal crystallisation kinetics of the multimodal-HDPE, PE-CB and PE-g nanocomposites. The cooling rate required to achieve certain degree of crystallinity increased gradually as the graphene content increased. The relative kinetic parameter


In this work, we have prepared a series of polydimethylsiloxane (PDMS) composites containing various graphene flakes loadings (0.02–2 wt%), and their broadband optical properties are being investigated. We demonstrate the tunability and evolution of transmittance and reflection spectra of the composites in a wide spectral range (0.4–200 μm) as a function of graphene content. Using these data we derive the broadband wavelength-dependent absorption coefficient (α) values. Our results show that α is roughly constant in the visible and IR ranges, and, surprisingly, is approximately one order of magnitude lower in the terahertz regime, suggesting different terahertz radiation scattering mechanism in our composite. Our material could be useful for applications in optical communication, sensing or ultrafast photonics. The outstanding optical, electrical and mechanical properties of graphene flakes12. Examples are as follows: a flexible and/or transparent graphene thin films15; graphene based 3D structures - graphene foam17 or hydrogel20 filled with polymer; multi-stacked sandwiches22; and other nanocarbon/polymer composites24. Remarkably, regardless of the production method, it has been shown that even a small loading of a nanocarbon filler can transfer its extraordinary properties into a composite material. For instance, mechanical and electrochemical reinforcement28 or boost of electrical and thermal transport properties30 that enable increased thermal conductivity34 and stability35, gases impermeability37, increase of electrochemical reactivity and sensing39, or efficient electromagnetic interference shielding41.Literature provides numerous examples of graphene and other nanocarbon material based composites of different architecture and composition, prepared by a variety of methods1 in extremely broadband range. However, how this remarkable feature is transferred into graphene based composite material is still poorly studied and only several works have been written so far. For instance, graphene thin film (10 nm), composed of reduced graphene oxide sheets, deposited on polymer substrate exhibit a transmittance of 70%42. According to Bao et al.43 graphene load as small as 0.7 wt% in pristine polymer (PVAc) causes tenfold rise of the optical absorption of a composite in a UV-NIR range. Ultrathin graphene composite films can serve as an electrode for flexible electronics showing visible light transmittance in the range of 70–95% and can be tuned by graphene flake concentration44. Similar composites can be also applied as optical elements in fibre lasers, e.g. saturable absorbers46 or passive wave guides47.Carbon nanofillers such as graphene flakes offer a possibility of tuning the optical properties of the composite material. This is possible due to graphene’s particularly interesting optical features. It has been shown, for instance, that a single layer of graphene can absorb 2.3% of incident lightIn all above examples the tunability of optical properties is a key factor for progress in the application development. However, in literature the optical transmission/absorption of graphene based composites is investigated only in visible or near infrared range (still only few papers) and no systematic study on how the graphene content influence these properties can be found.In this paper, we demonstrate a systematic study of broadband optical properties of graphene flakes immersed with variable concentration (0.02 to 2 wt%) in PDMS polymer matrix. We show the graphene-content dependent scalability of the absorption, transmission and reflectance properties of the composite in the wavelength range of 0.4–200 µm. For instance, our study shows that less than 0.5% of graphene content is enough to totally block the incoming radiation. Additionally, the experimental transmittance of our samples was compared with a model for stacked graphene multilayer. Finally, we derive broadband absorption coefficient (α) of the composite, that exhibit significantly different behaviour for VIS-IR and THz range, and its values strongly differ from other carbon material.48 or styrene-butadiene rubber50. A specified amount of a few-layer graphene powder (Graphene Supermarket) with average thickness of several nanometers  supplied by Dow Corning Co. as a two-part liquid component kit (base and curing agent), since it is relatively transparent and has no colour, as compared to other commonly used polymer matrixes, i.e. poly methyl-vinyl siloxane rubber51.The impact of the graphene loading level on the optical properties of the composite is already visible with the naked eye, as illustrated in Fig. −1), G (1588 cm−1) and 2D (2680 cm−1) are characteristic for graphene materials, thus are not observed in the pristine PDMS sample. The spectra did not show any changes for different graphene loading . The Raman experiment was conducted using 633 nm excitation wavelength (low power) and 50x objective, at room temperature.To confirm the graphene presence and flakes deployment in the composite, we used Scanning Electron Microscope (Raith) and Raman spectroscope (Renishaw InVia). SEM image in Fig. n is the refractive index, κ is the extinction coefficient, T stands for transmittance, R is reflectance and The optical spectra were obtained using two different instruments depending on the wavelength range. For the VIS-NIR range 420–1700 nm) total reflectance (both specular and diffusive) and transmittance spectra were collected using a PV response analyser (PVE300 Bentham). For NIR-THz range (1.66–200 µm) only the transmittance measurements were conducted using a vacuum Fourier transform infrared spectrometer Bruker IFS-113v. The spectra were collected at the room temperature and ambient pressure (VIS-NIR range) or nitrogen pressure of about 6 mbr in the Bruker spectrometer. We then related obtained transmittance data to absorption coefficient 700 nm toFigure 3 stretch vibrations characteristic for PDMS material47. Intuitively, an addition of given amount of graphene to the composite lowers the transparency almost evenly, without changing the shape of the spectra. This behaviour reflects the property of graphene monolayer which is constant within the optical range24. Thus, we show that our material exhibits a similar feature to mono- or multi-stacked graphene sandwich sample in the UV-IR range.All optical spectra remain relatively flat, except for small peaks around 1.15 µm, which are related to CHet al.42, however our material is much easier to fabricate, requires no substrate. Moreover, it is easier for handling possible application.Clearly, the transmittance depends on the amount of graphene powder used in the process of fabrication. The more graphene is added to the composite, the less light is transmitted through the material. Interestingly, even a composite with the smallest graphene concentration (0.02 wt%) has significantly smaller transmittance (74% of incident light) as compared to the pristine PDMS sample (~94%). The transmittance level of a 0.02 wt% sample is comparable with a 10 nm thick layer of reduced graphene oxide on polymer reported by Wang The drop of the transmittance reaches a saturation point at 0.5 wt% graphene loading, where no light (VIS-NIR) is transmitted by the material, thus making it completely opaque in this range.52. For samples with higher graphene load the reflectance drops below this value, which might be related to a very high absorption level of those samples. This suggests that main contribution to the reflection comes from the polymer matrix, while graphene barely participate in the process or even cause the decrease of the reflection. The reflectance values of our composites are significantly lower than those of bulk graphite53 and approaching the values of mono- to a few layer graphene samples that show reflectance of roughly 1 to 2%2.The optical reflectance level of all studied composites for VIS-NIR range, is kept in 4–8% range see Fig. . On the 55. However, we note that due to the fact that the size of the flakes used in our material is roughly the same size as the wavelength of the incident light in the VIS-NIR spectral range and the non-zero value of absorption of the polymer matrix, radiation primarily scattered in the material would be absorbed before leaving the medium. Thus, it is likely that the mechanism based on internal multiple reflection is negligible. All this provides two conclusions: first, the main mechanism responsible for blocking the light in the studied range is the absorption and secondly, only small fraction of graphene in the material is needed to fully tune its optical properties.Both transmittance and reflectance data are then used to derive the absorption values of our composite for the VIS-NIR spectra range see Fig. . As only47, while the values and their changes depend only on graphene loading. Although there are regions where PDMS transmittance signal is immeasurable, which may be due to relatively high thickness of the composite, we concentrate on “transmittance windows”, where the measurements of the influence of graphene flakes content is possible. In the IR region, again all composites with 0.5 wt% graphene concentration and higher show no measurable transmittance. Remarkably, this is not reproduced in the THz region, (for the wavelengths greater than 44 µm) our material is much more transparent with respect to the graphene content (e.g. sample with 1.5 wt% has ~10% transmittance at 3 T Hz).Next we discuss the transmittance spectra beyond VIS-NIR range, up to terahertz region (1.66–200 µm). Corresponding data are shown Fig. In order to analyse the correlation between graphene loading and broadband transmittance of the fabricated composites in respect to the wavelength, the spectral range was divided into three parts – I: 400–1700 nm; II: 1, 66-6 μm and III: 44–200 μm. For each range a set of wavelengths was selected. Collected values of transmittance were then normalized according to the transmittance of pure PDMS, averaged within their ranges and presented in Table 56. We used this model to fit our data and match the obtained values of transmittance with corresponding number of graphene layer, in order to find a correlation between those two factors . The decrease slope of the transmittance is less steep as compared to first and second stages and values of T(wt%) reach zero only for the composite with 2 wt% load of graphene flakes. This demonstrates that the mechanisms behind the optical transmission of our composites exhibit significantly different behaviour for VIS-IR and THz range.62. In the first and second range the Those differences are even more apparent if we take into account the absorption coefficient  dispersion absorption coefficient63 and requires more thorough study.Calculated 62 are 3 orders of magnitude higher as compared to our materials, similarly if we compare 49 and our composite.Interestingly, it is striking that the values of 43. It appears 0.5 wt% graphene concentration is sufficient to receive a material of almost 100% absorption of incoming radiation with the wavelength between 420 nm and 44 µm, while graphene load of 2 wt% creates a material that is nontransparent in the whole studied spectral range – up to 200 μm.Graphene flakes used as a nanofiller in a polymer composite have direct influence on the material transmittance. Filler concentration as small as 0.02 wt% affects the received material absorption, raising it 30 times compared to the pristine PDMS samples. That influence surpasses other works, which report absorption enhancement by 10 times with 0.07 wt% graphene loadingThe influence graphene loading has on the transmittance of a composite can be compared with transmittance of stacked graphene multilayer. The 0.5 wt% of graphene flakes corresponds to a 90–150 nm thick multilayer graphene, but is much easier and more effective to produce in a form of a PDMS/graphene composite than through multiple delamination, or mechanical exfoliation, thus making the composite more desirable for possible applications.Although the transmittance of pure graphene is known to be independent of wavelength, we show that when graphene is used as a nanofiller in a polymer composite, the transmittance changes as a function of the wavelength change due to different attenuation mechanisms. Calculated absorption coefficients also vary due to the wavelength. This change is most visible in the third spectral range (FIR), where absorption has significantly smaller value – The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.


The demand for high‐performance absorbers in the microwave frequencies, which can reduce undesirable radiation that interferes with electronic system operation, has attracted increasing interest in recent years. However, most devices implemented so far are opaque, limiting their use in optical applications that require high visible transparency. Here, a scheme is demonstrated for microwave absorbers featuring high transparency in the visible range, near‐unity absorption (≈99.5% absorption at 13.75 GHz with 3.6 GHz effective bandwidth) in the Ku‐band, and hence excellent electromagnetic interference shielding performance (≈26 dB). The device is based on an asymmetric Fabry–Pérot cavity, which incorporates a monolayer graphene and a transparent ultrathin (8 nm) doped silver layer as absorber and reflector, and fused silica as the middle dielectric layer. Guided by derived formulism, this asymmetric cavity is demonstrated with microwaves near‐perfectly and exclusively absorbs in the ultrathin graphene film. The peak absorption frequency of the cavity can be readily tuned by simply changing the thickness of the dielectric spacer. The approach provides a viable solution for a new type of microwave absorber with high visible transmittance, paving the way towards applications in the area of optics. For instance, carbon‐based materials including carbon nanotubes, carbon composites, and graphite nanosheets are widely utilized due to their lightweight and efficient microwave absorbing characteristics.In this work, we present a general strategy to design the new type of transparent perfect MA based on asymmetric Fabry–Pérot resonant cavity by employing a multilayer structure in the form of graphene‐dielectric‐ultrathin doped silver (GDS). Here the optically transparent graphene and an ultrathin doped silver (Ag) film function as the microwave absorber and reflector respectively, and fused silica as the dielectric spacer. In addition, by tuning the dielectric spacer thickness to achieve critical coupling in the cavity, we show that this device yields near‐unity (≈99.5%) microwave absorption and remains highly transparent (≈74%) in the visible range, and the relative visible transmittance of the cavity can reach ≈93.5%. Furthermore, by employing the simple building block, an ultrathin planar graphene film, we theoretically and experimentally demonstrate that nearly all the microwave is absorbed in the graphene layer by this transparent MA in contrast to other metamaterials and metasurface absorbers where microwave is mainly absorbed in the tailored metallic components (2D arrays of subwavelength elements).22.1FigureThe microwave absorption by a single graphene layer is very limited. However, with its partially microwave absorbing and reflecting properties, graphene can be an excellent candidate as the top absorbing medium in an asymmetric Fabry–Pérot cavity, where one of the mirrors has significantly higher loss than the other. A schematic view of the proposed visibly‐transparent MA based on cavity resonance is depicted in 2D bands. The 2D band exhibits a single Lorentzian line shape with a full width at half maximum (FWHM) of ≈26 cm−1 located at ≈2686 cm−1 and a higher intensity relative to the G band. In addition, the intensity of D band at ≈1350 cm−1 is below the Raman detection limit, which proves the absence of a significant number of defects. Afterwards, the Fermi energy level of graphene is determined by comparing the G and 2D peak positions we measured, with the characterized correlation from Ref. c = ≈0.3 eV.The designed GDS cavity can be easily fabricated. The synthesis process of the graphene by the typical chemical vapor deposition (CVD) method is shown in Figure S4 in the Supporting Information. Figure The doped Ag and ITO layers were deposited on polyethylene terephthalate (PET) substrate by sputtering. SEM and AFM images of the as‐deposited ITO/Cu‐doped Ag/ITO are shown in Figure 2.2Figuren1, n2, k2, n3, n4, k4, d2, d3), including complex refractive index and thickness of interested layers, are involved in designing the transparent MA in this configuration. The metal thickness is fixed at 8 nm to ensure both microwave reflection and optical transparency. It is convenient to describe the graphene's property using its conductivity (σ) since that this quantity can be modeled or measured directly ranging from radio wave to optical frequencies, and the corresponding refractive index (n) and extinction coefficients (k) can be derived from the conductivity.e is the electron charge, kB is the Boltzmann constant, T is the temperature, ℏ is the reduced Planck constant, ω is the frequency of the incident electromagnetic waves, and Γ is the relaxation time which is assumed to be independent of energy. It is worth nothing that graphene's conductivity strongly depends on the value of its Fermi energy level μc which can be controlled by chemical doping or electrostatic gating.As shown in E(z) is the electric field in the ultrathin graphene film, E0 is the incident electric field, c is the light speed in the vacuum, and f is the frequency of the incident electromagnetic wave. Therefore, the total absorption in the graphene film isWe consider the theoretical condition for perfect microwave absorption in the planar graphene layer by destructive interference through multiple reflections within the GDS cavity. As graphene is the only lossy medium and there is no restriction placed on the metallic substrate in the GDS cavity, so even metal approaching the perfect electric conductor limit can be used. For simplicity, we assume that all the power is consumed by the graphene layer and the bottom reflective layer can provide 100% reflectivity. Here, we adopt an analytical method for the absorber structure studied in the optical regime,d2 ≈ 0.34 nm) is much smaller than the wavelength of the incident microwave (d2 ≪ λ), a sheet of graphene layer minimally changes the electric field profile inside the cavity, and the electric field can maintain its intensity within the monolayer absorber layer, which is also validated by calculating the electric field distribution within the graphene layer at different frequencies . In view of the zero reflection in the critical coupling condition, we can assume thatSince the thickness of monolayer graphene (E(z) = E0 into Equation Atotal = 100%, the sufficient and necessary condition for perfect microwave absorption is obtainedSubstituting πn2κ2d2f/cn1 for normal incidence, revealing that perfect absorption at around 15 GHz can be achieved in the GDS cavity by the graphene film under the condition of μc = 0.3 eV and Γ = 20 ps.The dotted line in the Figure R) and absorption (A = 1−R) of the GDS cavity at interested frequencies. Due to the symmetry of the cavity in the X–Y plane, the device should be independent of polarization at normal incidence. In the following numerical calculations, we only take TE‐polarized incident microwaves into consideration. Figure d3 of 3 mm. It illustrates that the near‐unity absorption of the GDS cavity can be achieved with different Fermi levels in the Region A (black dotted circle), which also shows that the conditions for achieving strong absorption are not very narrow. In addition, the ideal perfect absorption is attained with μc = ≈0.3 eV at near 15 GHz, which is consistent with the predicted result based on Equation d3 varies from 1 to 15 mm, the absorption peak shifts continuously from ≈40 to ≈2.5 GHz.Furthermore, by employing TMM, we can calculate the reflection (d3) and resonant frequency (f0) can be understood by investigating the condition of partial reflected wave for the destructive interference in the Fabry–Pérot configuration, which can be roughly estimated as f0 = c/(4n3d3). However, due to the strong loss in the graphene layer, the reflection phase of partial reflected wave at the air–graphene interface is not equal to π, resulting in a slight resonant peak shifts under the destructive interference condition. Meanwhile, several higher‐order modes start to appear with thicker cavities and higher frequencies, forming several bands on the absorption map. Hence, it is obvious that the peak absorption frequencies can be readily tuned by changing the dielectric thickness of the cavity. Note that at a fixed dielectric thickness , the bandwidth of lower‐order resonances is slightly broader than that of higher‐order modes  and reflection (R) are measured at normal incidence using waveguide configuration, and then used to calculate absorption (A), which is defined as A = 1 − T − R, where R = |S11|2 and T = |S21|2 are obtained from the measured S‐parameters. First, by analyzing the microwave responses of the GDS cavity layers individually, we checked the respective role of each layer. The microwave transmission and reflection of the monolayer graphene on silica substrate and the ITO/Cu‐doped Ag/ITO on PET substrate in the Ku bands are plotted in Figure S6 in the Supporting Information. As predicted, the monolayer graphene is partially reflective and absorptive to the microwaves with averaged ≈25% reflection and ≈45% transmission. On the other hand, besides the high visible transmittance, the ITO/Cu‐doped Ag/ITO layer supports a broadband high microwave reflection, corresponding to only ≈0.3% transmission, which is nearly perfect as a microwave reflection mirror in the cavity.To confirm the microwave absorption performance of the GDS cavity, the microwave transmission  at different frequencies.d3 ranging from 1 to 4 mm. The overall shape, trend and position of the experimental features in Figure Then, we examined the microwave absorption performance of the GDS cavities. The measured microwave reflection and transmission for the GDS cavities with different dielectric thicknesses are shown in d3 = 3 mm) in the Figure d3 = 3 mm, broadband absorption is obtained with the measured absorption of >50% from 8 to 18 GHz, covering the entire X and Ku bands, while all maintaining ultralow microwave transmission through the cavities. In addition, the effective bandwidth is defined as the width of the band with microwave absorption intensity of over 90%. For the GDS cavity at d3 = 3 mm, the measured effective bandwidth is 3.6 GHz, from 12 to 15.6 GHz in Figure d3 = 2.5, 3.5, and 4 mm, the maximal absorption values all exceed 98% at their resonant frequencies, showing excellent microwave absorption performance of the GDS cavities.In addition, with the increase of the dielectric thickness, the location of the absorption peaks gradually red‐shifted to the low frequencies and was able to be tuned across the measured spectrum from 8 to 18 GHz. As characterized by the purple curves d = 3 mm i2.3d3 = 3 mm) at interested wavelengths, are presented in FigureIn order to get a better understanding of the extraordinary microwave absorption by an atomically thin graphene layer, numerical calculations using TMM of the electromagnetic responses,In simple physics, the GDS cavity resembles an asymmetric Fabry–Pérot (FP) cavity comprising of a lossless dielectric core with a partially reflective top layer and back reflector. At resonances, microwave beams reflected from the air/graphene and the silica/metal interfaces form destructive interference, resulting in zero reflection, which accounts for the period absorption peaks in the Figure 2.4FigureThe thickness of such GDS cavity is on the order of several millimeters, which is much larger than the visible wavelengths, so it is hard for the absorbing layer and reflective layer to form an optical cavity in this case due to the incoherent situation. Therefore, the optical transmittance of the GDS cavity can be improved by enhancing the transparency of individual layers or reducing dielectric layers. To characterize the optical property of the GDS cavity, we measured transmittance spectra in the range of 300–1000 nm of the individual layers and GDS cavities with different dielectric thicknesses, as shown in the d3 = 3 mm, we have achieved the near‐unity absorption in the microwave range, and an averaged visible transmittance of 74% (relative to PET substrate) can still be maintained. It is important to note that the transparency of the GDS cavity can be improved by using one single dielectric spacer instead of employing multilayer configuration at the designed thickness, and the visible transmittance of the GDS cavity will be enhanced by eliminating the interface reflection loss up to nearly 87%  could achieve an EMI SE of ≈26 dB, a microwave absorption of ≈99.5% with visible transparency of ≈74% (and can be improved up to >85% by using single layer of silica). With a lower microwave absorption, the GDS cavity with 1‐mm‐thick dielectric spacer shows a visible transmittance of ≈87%. All these values match or outperform most of the reported results shown in the table.3In summary, we have experimentally demonstrated a transparent and near‐unity absorption microwave absorber consisting of graphene, transparent spacer and ultrathin doped Ag based on asymmetric FP cavity. The experimental results are consistent with the theoretical calculations. The physical origin can be explained by the asymmetric FP cavity model. Experimental results show a maximal absorption up to ≈99.5% at 13.75 GHz, an EMI shielding effectiveness of 26 dB with an averaged visible transmittance of 74% (limited by the light reflection from the air/silica interface used in the current experiment). In addition, the GDS cavity is easy to be tuned either by chemical doping or electrostatic gating for the graphene layer or simply altering the cavity thickness. The devised configuration and physical insight opens up a new pathway for transparent microwave absorbing materials and for developing novel microwave optical components.4Graphene Synthesis: The graphene films were grown on 25 µm thick Cu foils  using CVD method at the center of a tube furnace. The foils were subsequently heated to 1000 °C under H2 at 60 Pa for half an hour. Then, the carbon source (CH4) was introduced into the quartz tube for 2 h. After following gas mixtures, we rapidly cooled down the samples to the room temperature (25 °C). The fast cooling rate is critical in suppressing the multiple layers formation of graphene.Graphene Transfer: As‐grown graphene on the Cu foils was transferred by spin‐coating 5 µm thick PMMA on the graphene. After PMMA dried, the sample was immersed into the Marble's etchant (HCl: H2SO4: CuSO4 = 50 mL: 50 mL: 10 g) solvent to etch the Cu foil. After removal, the graphene sample was washed in distilled water and transferred to the 1 mm silica substrate to be used.Film Deposition: Cu‐doped Ag films were fabricated by co‐sputtering of Cu and Ag. The concentration of Cu and Ag was controlled by adjusting the individual sputtering power of the Cu and Ag targets. The calibrated deposition rates for the Cu‐doped Ag film employed in this study are 1.109 and 0.019 nm s−1 for Ag and Cu, respectively, which leads to ≈2% atomic concentration of Cu in the obtained film. The film thickness was controlled by the deposition time. The chamber base pressure was pumped down to about 0.13 mPa before film deposition. During deposition, the Ar gas pressure was 0.6 Pa and the substrate holder was rotated at the speed of 10 rpm.Characterization and Measurements: ITO/Cu‐doped Ag/ITO film thickness of each layer was calculated by the calibrated deposition rates and confirmed by the spectroscopic ellipsometry measurement (J. A. Woollam M‐2000). The morphology of the graphene and ITO/Cu‐doped Ag/ITO films were investigated by SEM (FEI HELIOS Nanolab 600i) and tapping mode AFM (Bruker Dimension FastScan) on fused silica and PET substrates, respectively. The optical transmittance of the films and GDS cavities were measured by a UV‐vis–Infrared spectrophotometer (PerkinElmer Lambda 950) ranging from 300 to 1000 nm with normal incident radiation. The microwave transmission and reflection of the samples was calculated from the measured S‐parameters (S11 and S21) using waveguide methods in the X and Ku bands. Schematic illustration and microwave measurement setup and are shown in the Figure S7 in the Supporting Information.The authors declare no conflict of interest.SupplementaryClick here for additional data file.


Spinal sarcoidosis is a rare subgroup of neurosarcoidosis. Although most sarcoid lesions develop in the intramedullary compartment, intradural extramedullary (IDEM) spinal sarcoidosis is an extremely rare entity.  We herein report a case of IDEM spinal sarcoidosis mimicking a meningioma. A 32-year-old man presented to the hospital with clumsy hands and was unable to walk without assistance. Magnetic resonance imaging (MRI) of the cervical spine revealed a dural tail sign that is common in meningiomas. The patient underwent gross total resection. The pathological findings consisted with a sarcoid leision of the spinal cord. The patient's myelopathy recovered after surgery.  Physicians should be alert for the possibility of IDEM sarcoidosis mimicking a meningioma in the differential diagnosis of IDEM spinal cord tumors. Sarcoidosis is a systemic disease of unknown etiology characterized by noncaseating giant-cell granulomas affecting all organs. Several case series have detected the nervous system involvement of sarcoidosis in up to 5% of all sarcoidosis cases . FurtherWe herein report a case of IDEM spinal sarcoidosis mimicking a meningioma.A 32-year-old man presented to the hospital with progressive numbness and paresthesia of the right hand, trunk, and both lower limbs. He also complained of clumsy hands and was unable to walk without assistance. His history was significant for systemic sarcoidosis two years earlier. Steroid therapy had not been performed because the systemic sarcoidosis was not active, and he had stopped follow-up.Manual muscle testing was 2/5 in the deltoid, 3/5 in the biceps, 4/5 in the wrist flexors, 5/5 in the wrist extensors, 5/5 in the finger flexors, 4/5 in the finger extensors, 2/5 in the finger abductors, 5/5 in the iliopsoas, 5/5 in the quadriceps, 5/5 in the tibialis anterior, 4/3 in the extensor halluces longus, 5/5 in the gastrocnemius, and 4/5 in the flexor halluces longus. The patient's performance on the 10-second test was slow. Pin prick and temperature sensations were impaired from the T2 dermatome bilaterally. His Japanese Orthopaedic Association (JOA) score for cervical myelopathy, according to the criteria proposed by the association itself, was 3 of 17 points . Laboratory investigations showed normal values for all parameters. Cervical X-ray and computed tomography (CT) showed no apparent abnormalities. MRI of the cervical spine revealed isointensity in the intradural extramedullary on T1-weighted imaging and a low-intense mass at the C3-4 levels on T2-weighted imaging. Following the intravenous administration of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), an intradural extradural mass with a marked gadolinium enhancement and a dural tail sign were observed .The patient underwent laminotomy of the caudal side of the C2, right open door laminoplasty of the C3 to the C4, and laminotomy of the cranial side of the C5. On opening the dura, a firm intradural extramedullary mass was found. The mass was partly adhered to the spinal cord but was not attached to the dura. Of note, the appearance of the actual mass differed from that of a meningioma, as it had been preoperatively suspected to be based on the MRI findings . Gross tAfter the surgery, the patient's myelopathy recovered gradually and he returned to full-time work. Steroid therapy was not performed because the systemic sarcoidosis was not considered to be active. Four years later, his JOA score for cervical myelopathy was shown to be 14 of 17 points, giving a 78% recovery rate. No abnormalities on MRI were noted at that time .Spinal sarcoidosis can occur in intramedullary spaces, intraspinal epidural spaces, intradural extramedullary spaces, and vertebral bodies . Most caIDEM spinal sarcoidosis has been reported to occur usually in the cervical spine. Indeed, in previous reports, the anatomic location of IDEM spinal sarcoidosis was in the cervical spine in eight cases and thoracic spine in two –11. The Although MRI and CT are useful evaluation tools for diagnosing spinal sarcoidosis, the diagnosis of IDEM spinal sarcoidosis is often difficult because of its similarity to spinal cord tumors. In our case, a mass lesion was observed to be isointense on T1-weighted imaging and low intense on T2-weighted imaging. Although meningiomas usually show iso- or high-intensity findings on T2-weighted imaging, approximately 10% of meningiomas show a low intensity on T2-weighted imaging , 13. In The causes of spinal sarcoidosis remain unclear, although Schaller et al. hypothesized that IDEM spinal sarcoidosis represents a very early stage of intramedullary spinal sarcoidosis .Subtotal or total resection of the mass is required for the surgical treatment of IDEM spinal sarcoidosis. Of note, the risk with surgery in cases of IDEM is lower than that in cases of intramedullary lesions because the mass is extramedullary, so several cases of tumor resection have been reported .There is no consensus regarding the pharmacological treatment of neurosarcoidosis. In previous reports of IDEM spinal sarcoidosis, postoperative steroid treatment was performed in seven cases, but not in three others. Regardless of steroid treatment, recurrence was not observed during the follow-up period , 5. HighPhysicians should be alert for the possibility of IDEM sarcoidosis mimicking meningiomas in the differential diagnosis of IDEM spinal cord tumors.


Kainate receptors (KARs) are glutamate-gated ion channels that play fundamental roles in regulating neuronal excitability and network function in the brain. After being cloned in the 1990s, important progress has been made in understanding the mechanisms controlling the molecular and cellular properties of KARs, and the nature and extent of their regulation of wider neuronal activity. However, there have been significant recent advances towards understanding KAR trafficking through the secretory pathway, their precise synaptic positioning, and their roles in synaptic plasticity and disease. Here we provide an overview highlighting these new findings about the mechanisms controlling KARs and how KARs, in turn, regulate other proteins and pathways to influence synaptic function. There are three major subclasses of ionotropic glutamate receptors, kainate receptors (KARs), AMPA receptors and NMDA receptors. KARs are widely distributed throughout the brain and, depending on the cell type in question, they can be localised at pre-, post- and/or extrasynaptic sites. In general, presynaptic KARs modulate both excitatory and inhibitory neurotransmitter release, postsynaptic KARs contribute to excitatory neurotransmission and extrasynaptic KARs play a role in determining neuronal excitability (for reviews of KAR physiology see –4). For (EPSCs) –8. IntriR(EPSCs) , 10.Remarkably, despite their classical ion channel structure, KARs can also signal via a non-canonical G-protein coupled metabotropic cascade . In contOur aim here is to provide an overview of recent advances in understanding the cellular regulation of KARs and their interacting proteins, and how these processes influence KAR-mediated synaptic transmission and plasticity. We highlight what is known, what remains to be established, and outline the future perspectives for KAR research and how it will impact on our understanding of brain function and dysfunction in disease.GRIK1-5 [Since their initial cloning , 19 the GRIK1-5 .KARs are heteromeric assemblies containing four subunits. Each subunit has a large extracellular N-terminal domain (NTD), helical transmembrane domains (TMD) including three membrane spanning domains  and a membrane re-entrant domain (M2), and an intracellular C-terminal domain (CTD). The latter part of the NTD  together with the extracellular loops between M3 and M4 (S2) form the ligand-binding domain (LBD) . RecentlFollowing protein synthesis, the NTDs initiate receptor assembly in the endoplasmic reticulum (ER) by facilitating dimer formation, and the dimerization of two dimers then leads to the formation of tetrameric receptors. Based on affinity for their ligand, KAR subunits have been grouped into low affinity (GluK1-3) and high affinity (GluK4-5) receptors. Studies on recombinant systems have shown that low affinity GluK1-3 subunits can form ion channels as both homomers and heteromers but high affinity GluK4 and GluK5 subunits can only form heteromeric functional ion channels when complexed with the low-affinity subunits , 26, 27.1 and GluK12 [Regions within the N- and C- terminal domains of KAR subunits can undergo alternative RNA splicing. For instance, the extracellular N-terminal domain of GluK1 can produce two variants, GluK1d GluK12 , while td GluK12 , 31. Spld GluK12 –34. C-ted GluK12 –37.In addition to splicing, further diversity arises from varying degrees of RNA editing in GluK1 and GluK2 subunits , 39. For2+ permeability [It is well established that GluK1/GluK2 editing is developmentally controlled through regulation of the enzyme that also catalyses GluK1/2 RNA editing, ADAR2 –44. For eability . Furthereability . Suppreseability . Therefoeability , 50, plaeability  and patheability .The accurate and timely delivery of KARs to specific pre-, post- and extrasynaptic locations is fundamental to many aspects of neuronal function. Most research efforts have focused on the processes of transcription, endocytosis, recycling and degradation . HoBRs, can be translated using both somatic and dendritically localised ribosome patterned rough ER. They then traffic from the ER using dendritic ER exit sites and utilise the somatic Golgi or dendritic Golgi outposts for mature glycosylation [In neurons, mRNAs can be trafficked to distant sites in axons and dendrites for local translation and processing –57. A rasylation , 58–62. sylation . For exasylation .Recently, using the RUSH system, which allows the synchronous release and visualization of cargo proteins trafficking through the secretory pathway , 66, it Although there is a strong base of knowledge about the activity-dependent regulation of KAR endocytosis and recycling , 67–71, As well as interactions with the GluK2 subunit, interactions with GluK5 also determine flux through the secretory pathway. ER retention sequences in the C-terminus of GluK5 facilitate its interaction with the COPI coat complex, driving retrograde Golgi to ER trafficking of KARs, and acting as an ER retrieval mechanism . This inFurther tight control of the ER exit and secretory pathway trafficking of KARs is also provided by post-translational modifications, most notably PKC phosphorylation of GluK2 at residues S846 and S868 , 75, whiThus, far from being a passive process, ER exit of KARs and flux through the secretory pathway is emerging as a major point of regulation in determining the surface expression of KARs under basal and activity-dependent conditions  including phosphorylation , SUMOyla2+ influx-, and CaMKII-dependent plasticity mechanism, which is absent in slices from GluK5−/− mice [−/− slices restored KAR-LTD, expression of a non-phosphorylatable GluK5 did not, demonstrating that direct phosphorylation of GluK5 by CaMKII is required for this form of KAR LTD [LTD of KARs at MF-CA3 synapses is induced by a spike timing-, Ca−/− mice . CaMKII  KAR LTD . Thus, tPKC phosphorylation of GluK2 at S846 and S868 regulates the surface expression of GluK2-containing KARs at several levels. It affects both GluK2 transit through the secretory pathway , 75 and SUMOylation is a post-translational modification that results from the conjugation of a member of the ~ 11kD SUMO family to lysine residues in substrate proteins . GluK2 iOne major functions of protein ubiquitination is to target proteins for lysosomal or proteasomal degradation . A recenKARs are involved in both excitatory and inhibitory neurotransmission, controlling both short and longer-term plasticity. These properties have been extensively reviewed , 11 and 2+–calmodulin complexes and the activation adenylate cyclase and PKA [Presynaptic KARs decrease glutamate release at CA3-CA1 pyramidal cell synapses –112. Int and PKA –115. ThuPostsynaptic KARs at MF-CA3 synapses undergo plastic changes, and exhibit several forms of LTD that can be induced by different stimulation protocols , 87. ChaFurthermore, in cultured neurons, activity-dependent up- or down-regulation of surface KARs can be induced by differential agonist application protocols , 68. KARAMPAR [Recently, a novel form of AMPAR-LTP was discovered at CA3-CA1 synapses that is mediated by activation of postsynaptic KARs (KAR-LTPAMPAR ). DespitAMPAR , 116, acAMPAR , 118, suAMPAR ).−/− mice lack this novel form of plasticity, indicating an absolute requirement for this subunit in induction of KAR-LTPAMPAR  .ARs while at the same time potentiating extrasynaptic GABAARs, in a process that decreases synaptic inhibitory drive to facilitate synaptic plasticity, while simultaneously protecting against neuronal over-excitation by promoting extrasynaptic inhibition [Moreover, postsynaptic KAR metabotropic signalling depresses synaptic GABAhibition .AR-mediated transmission, KARs separately regulate the potassium-chloride cotransporter KCC2. KCC2 is crucial because it establishes the electrochemical chloride gradient for postsynaptic inhibition through GABAARs [AR-mediated transmission [In addition to this direct effect on GABA GABAARs , 122 and GABAARs ) and epi GABAARs . KCC2 in GABAARs  and GluK GABAARs , which i GABAARs . KCC2 ansmission . In addismission . These fDysregulation of common molecular pathways underlies multiple neurological and neurodegenerative diseases and there is mounting evidence that KAR dysfunction could be one such feature .−/− mice exhibit significantly fewer seizures than wild-type counterparts [−/− mice [KAR dysfunction is particularly closely associated with temporal lobe epilepsy (TLE) , and Gluterparts . TLE is terparts –132 and −/− mice . Consist−/− mice  and gene−/− mice . TogetheIn addition to TLE, both gain  and lossMost recently it has been reported that complete ablation of all KAR subunits results in disrupted corticostriatal function and dramatic obsessive-compulsive-like behaviour with severe self-grooming . TogetheAlthough historically much less studied than AMPARs or NMDARs, there is a currently a renaissance in KAR research fuelled by the realisation that they are multifunctional neuronal modulators that have roles in health and disease far beyond those previously appreciated.To understand how KARs exert these regulatory effects, it is necessary to define how KARs themselves are controlled and how they interact with, and regulate, other proteins and systems. Furthermore, while there is a growing appreciation of the multifaceted roles played by KARs, a number of fundamental questions remain unanswered. For example, while it is widely-accepted that KARs can signal both ionotropically and metabotropically through G-proteins, how this dual signaling occurs, and what determines which ‘mode’ of signaling an individual KAR complex utilizes remains almost entirely unexplored. In addition, while we are beginning to understand the molecular events that control the specific distribution and synaptic localization of KARs, how these mechanisms cooperate to orchestrate the highly selective distribution of KARs in the brain remains an important unanswered question. Finally, although KARs can induce plasticity of AMPARs, exactly how this occurs, how widespread this form of plasticity is in the brain, and whether postsynaptic KARs can direct other forms of bidirectional synaptic plasticity remain unknown.We expect that further studies examining how KAR localisation and signalling at pre- and postsynaptic sites impacts on neuronal function will answer many of these remaining questions, and will transform our understanding of the roles KARs play in development, plasticity and disease.


The anomalous reflection angle covers the range of 10° to 90° with the efficiency higher than 80%, over a broad spectral range from 7 μm–40 μm of infrared spectrum. It reaches above 92% at the center wavelength in the spectral response. By increasing the periodicity of phase gradient, we can expand this frequency band even further without losing efficiency. The compact design of metasurface affords the adjustability of the electrochemical potential level of graphene by means of gating. Additionally, the impact of the number of graphene sheets for the optimum efficiency of the proposed structure is investigated. By adding the secondary graphene metasurface with opposite direction of phase gradient, we demonstrated the tunability of the reflection angle from  Anomalous refraction and reflection of light with these extraordinary surfaces has been utilized in several newly developed devices such as polarimetry, flat lenses, holography, surface plasmon couplers, solar sails, etc8, as the prominent applications of metasurfaces13. As controlling the light propagation in an embedded structure becomes a vital aim, one significant breakthrough for many viable application is to actively manipulate the direction of light, i.e. reflection or refraction by means of external voltage. The rapid progress of improvement and innovative design has become possible for various metasurfaces with the optically exotic graphene20. Graphene and other 2D materials might be one of the best candidates for designing externally controllable metasurfaces. By changing their electrochemical potential level, it is possible to change the optical characteristics (i.e. the surface conductivity) in an extraordinary fashion22.Due to their exotic manner of manipulation of electromagnetic waves, metasurfaces have recently become an essential research topic in the optics and photonics fields26. In this regard, the structures with low quality factors are the center of interests30. Broadband operation and higher efficiency of anomalous reflection are significant factors in realizing flexible metamirrors32. In parallel, trilayer metal-insulator-metal (MIM) metasurfaces with noble metals provide the efficient reflection in the desired direction33. Recently, triangularly shaped plasmonic metallic metasurfaces demonstrated continuous phase gradient configuration35. In an alternative design, magnetically polarized particles have shown an excellent plasmonic metasurface-like behavior with P-polarized electromagnetic waves36.Plasmonic metasurfaces with a phase gradient have the ability to alter and tilt the wavefront of electromagnetic waves27. Besides, cross-polarized metasurfaces do not offer high efficiencies useful for many applications like the solar sails4. Due to the overlapping of Fabry-Perot and the antenna resonances in the spectra of reflection, some metasurfaces act like an absorber metamaterial rather than a mirror, which results in a decrease of the anomalous reflection efficiency39. Efficiency of metamirrors can be easily defined by the power ratio of an anomalously reflected (i.e. reflected in predicted and desired direction) electromagnetic wave to the incident wave. The frequency band of operation is mainly determined by the generalized Snell’s law and the optical properties of materials. An additional influential factor contributing to the anomalous reflection is the near-field interaction of metasurface with the incident electromagnetic wave.In numerous studies, however, metasurfaces that operate at fixed frequencies or in extremely narrow bands suffer low efficiencies in the other frequency bands41. The structure studied here is sensitive to linearly polarized electromagnetic waves. Each graphene ribbon has a specific width, chosen to have a certain plasmon resonance frequency. This provides the strong near-field interaction, and therefore, highly efficient anomalous reflections. Both the periodicity of the phase gradient direction (x-direction) and the periodicity of the polarization direction (y-direction) are considered to design a structure and to investigate the behavior of its reflection accordingly with the assistance of the Finite-difference time-domain (FDTD) method. It is worth mentioning that similar structure with the trapezoid shaped silver plasmonic antennas array operating in the visble light spectrum has been reported by other research group42. However, unlike silver plasmon reflector, the reflection efficiency of our graphene based reflector can have more than 80% for wide wavelength band. Moreover, by leveraging the tunability of the Fermi level of the graphene sheets47, we propose uniquely tunable graphen plasmonic reflector structure in this work.In this paper, infrared multi-layered graphene metasurfaces controllable with bias voltages are designed to achieve exceptional high efficiencies2 with the refractive index of 1.38 is a dielectric layer sandwiched between a graphene multilayer and a metal ground plane. The imaginary part of the refractive index of the MgF2 is negligible in the discussed wavelength band48. The main objective of the dielectric material in our theoretical analysis is to provide a cavity for the metasurface, and the considered material could be replaced with a material with a similar refractive index. The thickness of the dielectric layer is 2.5 μm.The proposed metasurface reflector consists of a multi-sheet graphene layer on top of the dielectric material, followed by the Au ground plane as illustrated in Fig. Px = 20.1 μm and Py = 2.2 μm, with an etched triangle base of We = 2 μm and a length of Le = 20 μm. It is worthy to mention that size of the unit cell is set slightly larger (about 0.1–0.2 um) than the etched triangular hole, to make graphene layers be connected. This design is proposed since the etching of graphene can be more practical than producing triangular graphene islands in the fabrication process. However, the designs based on triangular islands, with specific electrochemical potential level could yield the similar results. In this paper the dimensions of the unit cell and etching dimensions are chosen in order to produce ultra-high efficiency metasurfaces and to make it practical one might need to manipulate the proposed dimensions, due to the fabrication process restrictions.Triangular holes etched through the graphene layer produce the phase gradients required for anomalous reflection. The dimensions of a unit-cell of the metasurfaces reflector are W, and the periodicity, Py of the triangular shape of graphenes (TSGs) in our model has a significant impact on tuning the supported plasmon resonance frequencies. It also affects its Lorentz like phase changes34. Since the width, W of TSG increases in x-direction, the resonance frequencies shift to lower frequencies through the phase gradient.It is expected the width, W is given by39,N, P, and μ represent the number of graphene sheets in each ribbon, the width and periodicity related factor, and the electrochemical potential level, respectively.The plasmon resonance frequency of graphene nano-ribbons (GNRs) with fixed 38. In the denominator, the W represents the width of GNRs, which applied to TSG in our model, varies in the y-direction. The effective permittivity of the graphene environment can be calculated from the permittivity of Air (εa) and substrate (εs). We can consider the average value of P is equal to 0.65 for our TSGs, since P = qW/π, where q is the first eigenvalue produced from the mode solution of GNRs37. An additional effective factor of the resonance and phase gradient is μ, where it could be tuned by gating or doping. By increasing the carrier density of the graphene layer, we can blue-shift the resonance frequency. This provides an important degree of freedom in adjusting the phase gradient to a specific frequency band as well as enhancing the reflection efficiency for a specific spectrum. The value of μ is considered to be 250 meV for each graphene sheet. Changing the value of chemical potential does not have an effect in changing the reflection angle. However, by manipulation of μ, we can intensify or diminish the anomalous reflection efficiency and even obscure this behavior. The number of graphene sheets, N, included in Eq.  and the free space wavelength of light are important in determining the angle of reflection. On the other hand, the periodicity in the y-direction (Py) and W determine the operating band where the phase gradient starts and ends.Since ∇Px. As W increases, the wavelength of resonance increases proportionally. Furthermore, increasing the Fermi energy level of the graphene layer blue-shifts the resonance wavelength. Therefore, as the number of graphene sheets increases, the Lorentz like phase change shifts to the longer W side. In the case of having only one graphene layer as shown in the Fig. Px is restricted to shorter W side, so that the phase shift over the unit-cell becomes almost zero, ∇ϕx ≈ 0. In addition, increasing N helps to provide a stronger near-field interaction of light. By increasing the number of the graphene sheets (N) the number of the conducting channels and the total number of the carriers will be increased, which intensifies the plasmonic response of the material, and the plasmon field intensity (i.e. the plasmonic near-field intensity)40. Additionally, it is experimentally proved that multilayer graphene structures provide broader tunability of the Fermi level, comparing to the single layer graphene structure41. In this regard, we purposely chose 20 graphene layers. We examined our proposed structure with different simulation methodologies (1) scaling the conductivity of a single layer graphene up to 20, compared with (2) considering 20 graphene sheets with a spacing of 5 nm to verify the consistency of our results. Figure N on the Lorentz like phase shift along the metasurface.The Fig. λ0 = Px, where we can observe the conversion of propagating waves to surface waves. Figure λ0 = 12 μm and λ0 = 17 μm with reflecting angles of θr = 37°, and θr = 58°, respectively. It shows that the reflection angle increases with wavelength, while the efficiency stays almost the same. The anomalous reflection efficiency for these two cases stays over 85%, which will be discussed in the next section.From the expression of Px, and Py on the overall operating wavelength bandwidth of the TSG metasurface reflector. The cut-off wavelength of anomalous reflection can be analytically predicted by both the surface conductivity of graphene and the generalized Snell’s law, simultaneously. According to Eq.  is determined by the intra-band term of the imaginary part of the conductivity function (The minimum wavelengths limit (Px. The reflection angle covers the broad wavelength band of 7 μm to 20 μm for unit-cell dimensions of Px = 20.1 μm and Py = 2.2 μm. According to Eq. (λL) should red-shift. For instance, the cut-off wavelength for the above unit-cell dimensions is λL = 20.1 μm, and this device is practically operable up to the predicted cut-off wavelength. Additionally, the metasurface with unit-cell of Px = 30.1 μm and Py = 2.2 μm is predicted to have the λL = 30.1 μm, which effectively supports up to λL = 27 μm. The metasurface with the periodicities of Px = 40.1 μm and Py = 2.2 μm supports effectively up to λL = 29 μm, while the predicted maximum cut-off wavelength is 40.1 μm.Figure λ = 14 μm. In other words, this unit-cell can reflect with the angles of 30° to 65° with an efficiency of higher than 80%. In the same regard, the metasurface with longer phase gradient periodicity Px = 30.1 μm supports the wavelength band from 7 μm to 27 μm, while its efficiency stays higher than 80% from 10 μm to 21 μm. The efficiency of this metasurface exceeds 90% at the middle of the operational band. Accordingly, the metasurface with the Px = 40.1 μm, supports the widest wavelength band from 7 μm up to 29 μm, with an efficiency higher than 80% over the wide band of 10 μm to 22 μm. These results exhibit high efficient anomalously reflecting metasurface reflector with flexible choice of wavelengths by choosing the proper physical dimensions of the phase gradient periodicity (Px).As it is shown in the Fig. Py, which is periodicity in y-direction is equal to 2.2 μm. Since the value of W in Eq.  is red-shifted. However, this value could not exceed the predicted cut-off wavelength of Snell’s law . Our simulation results disclosed that by increasing the thickness of the cavity we can reach the higher efficiency in the longer wavelengths at the same time of losing the efficiency in the shorter wavelengths.As it is discussed extensively, the reduction of the efficiency in the longer wavelengths is due to the approaching to the plasmonic cut-off wavelength or the cut-off wavelength supported by the Snell’s law. However, there is a general reduction of the efficiency in the longer wavelength, which is due to the cavity thickness  results in wider spanning range of the reflection angle. For instance, the total spatial range supported by the metasurface with periodicities of μ of graphene sheets, we add a second reflecting metasurface with phase gradient in the opposite direction. Figure h) comparing to the thickness of cavity. Each graphene metasurface is formed from 20 sheets of graphene layer and these two metasurfaces are supported by the same cavity and ground metal plane as shown in the Fig. h is considered to be 50 nm, which is very small comparing to the cavity thickness of 2.5 μm. By implementing the gates inside of the dielectric media or outside of the metasurface or changing the doping level of the graphene sheets, one can change the Fermi level of the graphene phase gradients. By reducing the μ1 to 100 meV, the first phase gradient metasurface loses its functionality and becomes transparent. But due to the second phase gradient metasurface, with μ2 = 250 meV and opposite direction of phase gradients, the reflection angle changes to −θr. This kind of functionality would bring flexibility in controlling the direction of reflectors at any frequency.As it is feasible to manipulate the anomalous reflection by means of changing the μ = 100 meV and also amplified absorption of two metasurfaces with 20 graphene sheets21. In spite of this absorption, 50% efficiency of anomalous reflection still provides better performance than several other metasurface configurations which do not have tunability with external voltage4.However, adding another phase gradient metasurface reduces the efficiency near to 50%. This reduction is due to the strong absorption of the transparent graphene layer with The results also reveal that the polarization of the electromagnetic wave must be perpendicular to the direction of the phase gradient. One can use several phase gradients in different directions in order to have a design supporting anomalous reflection for different polarization directions of the TE waves. This device could be actively controlled with the method illustrated in Fig. λL) of the metasurface is determined by the phase gradient periodicity (Px). In contrast, the minimum cut-off wavelength (λS) is due to the surface conductivity and the surface plasma frequency of the graphene layer. Graphene is an excellent candidate for a tunable metasurface reflector, as the surface conductivity of graphene can be controlled by means of external gating voltage. We found that adjustability of the Fermi level of graphene was not able to change the anomalous reflection direction from a phase gradient metasurface, but can possibly either disable or activate the anomalous reflection operation. Finally, we demonstrated tunability of the reflection angle from θr to −θr by separately controlling the electrochemical potential levels of double phase gradient layers embedded in opposite directions. In this case, one of the phase gradients is disabled by reducing the Fermi level to 100 meV, and the other layer with reverse phase gradient direction is activated by increasing its Fermi level to 250 meV. This novel configuration of the metasurface could be used as a highly efficient, ultra-wideband, electrically tunable metamirror in IR and THz frequency bands in several optical devices and systems.We designed an anomalously reflecting infrared metasurface with exceptional high efficiency and a wide frequency band of operation via triangularly etched multi-sheet graphene layers. Our design achieved the anomalous reflection angle, covering a range of 10° to 90° with an efficiency higher than 80% over a broad spectral range from 7 μm–40 μm. The efficiency of the anomalous reflection exceeds 92% at the center wavelength. In this design, the effective phase gradient is generated from the triangular shape on the graphene layers. This phase gradient and its gradual changes determined the anomalous reflection angles and reflection efficiency in the range of infrared incident wavelength. The maximum cut-off wavelength (In this paper we utilized the Finite-difference time-domain (FDTD) method in order to numerically analyze the anomalous reflection of the electromagnetic waves from the surface of the designed metasurface. Surface conductivity of the graphene sheets for various Fermi-levels in the mid-IR and THz frequency bands are imported to the simulation. Two different simulation approaches were pursued to simulate the plasmonic response of the 20 sheets of the graphene layer realistically; (1) Scaling the conductivity of a single graphene layer to 20, (2) Considering 20 separate sheets of graphene with the 5 nm separation distance between them. The results from both approaches were compared and verified no differences. Both simulation methods confirmed the efficiency and angle of the anomalously reflected light from the metasurface. The complex permittivity function of the gold material for the ground plane reflector is imported from the Johnson and Christy data. The smallest mesh sizes used in the simulation are 100 nm, 80 nm and 2 nm in cubic shape to obtain consistent data. We also verified our simulation results analytically by the numerical method using the equations presented in the context.Supplementary Information