Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency. Recently, organic light-emitting diodes (OLEDs)have been successfully demonstrated to possess high luminous efficiencies with p-doped graphene anodes. However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics. In this paper, we demonstrate fully solution-processed OLEDs with n-type doped multilayer graphene as the top electrode. The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes. With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process. By contrast, polymer OLEDs are usually built by solution processes, such as spin-coating316In this paper, we demonstrate a method of fabricating an all-solution-processed transparent OLED with graphene film as the top cathode without any vacuum deposition process. In previous reports−3 M. Photoemission spectrum experiments are carried out to examine the n-type doping effect on the graphene films. F). As listed in The work function of pristine graphene film is around 4.4 eVMoreover, to examine the stability of the n-type doping effect, the graphene samples were kept in the glove box for 2 months. As shown in On the other hand, To enhance the electrical properties of graphene as applied in organic devices, we increase the number of graphene layers. Moreover, to maintain the lower work function properties, graphene is n-doped during every transfer process. As shown in 20After demonstration of the capacity of n-type doped graphene as a cathode, the CsF-doped multilayer graphene films are used as the top cathode in solution-processed multilayer OLEDs. To begin with, the transmittance of the device is investigated. As shown in 232628To reveal the n-type doping effect of graphene in electron injection from the cathode, pristine multilayer graphene and CsF-doped multilayer graphene are applied to OLED devices as top cathodes. The current density to voltage (J-V) of the devices is shown in 2 at 13 V, and the maximum current efficiency is 3.1 cd/A at 8.3 mA/cm2. Compared with the typical device with thermally deposited Al as the top cathode, OLEDs with graphene as the top cathode show poorer performance. This can be attributed to poorer contact between the organic layer and the graphene film cathode, resulting in fewer electrons from cathode to organic layer.The current density-voltage-luminance (J-V-L) characteristics and efficiencies of the all-solution blue-light OLEDs fabricated with CsF-doped multilayer graphene as the top cathode are shown in The electroluminescence (EL) spectra of the blue-light transparent OLEDs on the graphene cathode side are shown in the inset of To be a good candidate as a cathode in an organic device, graphene should be n-type doped to reduce the electron injection barriers from cathode to organic layers. A new polymer-free transfer method has been demonstrated to be an efficient way to modify the work function and sheet resistance of graphene, and n-type doped multilayer graphene films obtained using this method can be used as cathodes in OLEDs. Moreover, we have provided a way to produce a transparent OLED with truly all-solution processes, including multilayer graphene as the top electrode. A fully solution-processed transparent blue-light multilayered OLED with n-doped graphene layers used as the top cathode has been produced without any vacuum process. Although the efficiency and brightness of this transparent device may be lower due to the poorer contact between the organic layer and the graphene film cathode. With this transfer method, graphene electrodes can be used in a wide variety of organic optoelectronics with more efficient doping and simple transfer techniques.4)2S2O8) as etchant, and a thin graphite holder with a diameter of 2 cm was then carefully placed at the etchant air boundary, serving as a confinement area for the graphene monolayer on a copper substrate and preventing it from attaching to the edge of the holder. After the copper was etched, the monolayer graphene film was floating on the surface of the solution and the etchant was replaced by a mixture of DI water and IPA solution. After the etchant was totally replaced by the water and IPA, the substrate was placed just below the floating graphene in the solution. The solution was then pulled out with a syringe to lower the graphene onto the substrate. For the n-type doping graphene, a few drops of n-type dopant (CsF or Cs2CO3) were added to the mixture before the extraction of solution. After landing on the substrate, the sample was then heated at 60°C in nitrogen for 10 min to dry the graphene sheets. More details of the experimental setup for the preparation of multilayer graphene films which can be applied to any substrate can be found in our previous report.Single-layer graphene films were synthesized on copper foils by thermal CVD. To form multilayer graphene films, each graphene monolayer was transferred, with or without n-type doping, onto other graphene films. The process of preparation of multilayer graphene films was as follows: A clean Petri dish was filled with 0.1 M ammonium persulphate solution  and X-ray photoemission spectroscopy (XPS) in an ultra-high vacuum (UHV) chamber with a base pressure of 10−10 torr. The photon energies of UPS were 21.2 eV and 40.8 eV for He I and He II respectively, and the resolution was around 0.15 eV.Pristine or doped monolayer graphene film was transferred onto SiOThe solution-processed blue Ph-OLEDs were fabricated based on a phosphorescent emission layer (EML) doped with a blue triplet emitter. These Ph-OLEDs were fabricated on ITO-coated glass substrates with a sheet resistance of 15ω/square. The ITO substrate was UV-ozone treated before fabrication of the device, and the structure of the device was ITO/HAT-CN/VB-FNPD/PVK:Firpic:OXD-7/PFN/n-type doped graphene. A solution of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) (3 mg/ml) was prepared with 2-propanone (acetone) as the solvent, and the solution was spin-coated onto the substrates to form about 5 nm as the hole injection layer (HIL). A thermally polymerized 2,7-disubstituted fluorene-based triaryldiamine (VB-FNPD) was dissolved in chlorobenzene (10 mg/ml) and was spin-coated onto the HAT-CN surface to form a cross-linked hole transport layer (HTL). After that, the blue-light emission layers (EMLs), which consisted of a mixture of poly(N-vinylcarbazole) (PVK), and bis iridium(III) picolinate (FIrpic), were spin-coated onto the VB-FNPD layer from the chlorobenzene solution with a ratio of 9:1, and annealed at 90°C for 30 min to remove the residual solvent. The alcohol/water-soluble polymer, poly (PFN) was incorporated as an electron-injection layer on top of the emitting layer by spin-coating. The PFN solution was first prepared by dissolving PFN in methanol (4 mg/ml). Second, the PFN solution was mixed with water with a volume ratio of 3:1. The mixed solvent was blended with a 0.1% CsF solution at a volume ratio of 8:1, and finally, the blended solution was spin-coated onto the emitting layer to form a 30 nm-thick film. After deposition of the PFN layer, the n-type doping multilayer graphene was transferred onto the PFN layer as the top cathode. After the landing of the multilayer graphene, the OLED was annealed at 80°C for 20 min. All the organic layers were deposited in a glove box except the PFN layer.J-V-L) measurement was carried out immediately in the atmosphere. The J-V and L-V characteristics were simultaneously analyzed by a Keithley 2400 and by photodiodes. The electroluminescence (EL) spectrum was recorded with PR-650 Spectra Colorimeter. The transmittances were measured by V-670 UV-Vis-NIR Spectrophotometer (Jasco Inc.).All measurements were performed at room temperature in ambient air.After fabrication of the device, the current density-voltage-luminance (J.H.C. designed and performed the experiments with data analysis; W.H.L. and J.I.T. helped with the analysis of graphene films. P.C.W., T.A.K. and W.T.C. helped with the device fabrication. S.J.Y. laid out the figures in the text. C.I.W. provided the advice on and coordinated the experiments. J.H.C. and C.I.W. wrote the manuscript.


We report the case of cutaneous sarcoidosis of lichenoid type successfully treated with pimecrolimus. For the first time in the literature, we propose the use of this topical calcineurin inhibitor for the treatment of the cases refractory to common therapy regimens. Lichenoid sarcoidosis is an extremely rare cutaneous manifestation of sarcoidosis, occurring in 1%-2% of all cases and presenting with multiple erythematous or violaceous, slightly scaling maculopapules localized on the trunk, limbs, and face, without systemic involvement. Different therapeutic approaches have been described for the treatment of cutaneous sarcoidosis, but the lesions are often refractory to the common treatments. We described the case of a female patient affected by cutaneous sarcoidosis of lichenoid type successfully treated with topical calcineurin inhibitor Pimecrolimus, never been reported in the literature until now.A 66-year-old woman was referred to our department with a 6-month history of 1-2 mm diameter, violaceous, nonfollicular, infiltrated lichenoid papules with a tendency to group, located on the right knee . The onsShe did not complain of any systemic symptoms or take any kind of drugs. In the past medical history, no relevant diseases were referred, except for a papillary thyroid carcinoma excised 4 years before. General physical examination did not reveal any abnormality or lymphadenopathy. Cutaneous biopsy of one of the lesions revealed mild thinning of the epidermis, and a nonnecrotizing lymphohstiociytic granulomatous infiltrate in the superficial and deep dermis Figures  and 3. NChest X-ray, eye examination, and blood tests, including complete blood count, hepatic and renal functions, serum angiotensin-converting enzyme, blood and urinary calcium, and beta-2-microglobulin, were all normal. A tuberculin reaction was also negative. Clinical and histological findings led to a diagnosis of cutaneous lichenoid sarcoidosis without systemic involvement. As treatment with topical corticosteroids had been ineffective, topical 1% pimecrolimus cream twice daily was prescribed. The patient was followed up monthly and after 6 months of treatment, we noted a nearly complete remission of the lesions on the knee, with no topical and systemic adverse effects referred to by the patient  and no rSarcoidosis is a chronic multisystemic granulomatous disease of unknown etiology, characterized by the formation of noncaseating granulomas in the involved organs. Cutaneous involvement is about 25% and the most common clinical manifestations are maculopapular lesions, whereas lupus pernio is the most characteristic skin lesion.The lichenoid-type lesion is an extremely rare cutaneous manifestation of sarcoidosis and is estimated in 1%-2% of all cases of skin sarcoidosis [Lichenoid lesions have been particularly reported in young children, frequently presenting together with eye and joint complications, but respiratory involvement is usually absent , 4.Diverse therapeutic approaches, including topical, intralesional, and systemic corticosteroids, antimalarials, methotrexate, tetracycline, infliximab, thalidomide, allopurinol, and isotretinoin, have been described in the management of cutaneous sarcoidosis; however, their efficacy varies and adverse effects, like the skin atrophy, sometimes limit their use. In the last decade an increasing interest derived from the use of topical calcineurin inhibitors (TCIs) in the treatment of cutaneous sarcoidosis , 5, 6.Streptomyces tsukubaensis and modulates T-cell-mediated responses by inhibiting calcineurin-dependent dephosphorylation activation of the transcription factor NF-AT [Tacrolimus is a macrolide immunosuppressive agent isolated from or NF-AT .Pimecrolimus is a lipophilic macrolactamic agent isolated from ascomycin; it selectively modulates T-cell-mediated response binding with high affinity to macrophilin-12 and inhibiting calcineurin calcium-dependent phosphatase. These drugs, blocking the production and release of proinflammatory T helper1 cytokines and activation of T lymphocytes, have been successfully used in atopic dermatitis for many years .It is supposed that, in sarcoidosis, granulomas may be caused by a series of factors, including Th1 cell activation by antigen-presenting cells (APC) and their cytokine release (IL2 and interferon-gamma) with a subsequent inflammatory cell recruitment and tissue infiltration; in addition, T lymphocytes and macrophages are responsible for an overproduction of TNF-alpha, amplifying the granulomatous reaction .The ability of tacrolimus to inhibit both hapten-induced production of Th1 cytokines and the production of TNF-alpha by T cells and macrophages constitutes an effective rational for its use in the treatment of sarcoidosis . In the Pimecrolimus has the same actions of tacrolimus but is more selective than tacrolimus in the modulation of immune cells: in fact it acts specifically on T lymphocytes and mast cells with a more antiinflammatory than immunosuppressive action, whereas tacrolimus also downregulates Langerhans cells and basophilic cells .Moreover, pimecrolimus is more lipophilic and binds with higher affinity to structural skin proteins than tacrolimus, having a lower penetration rate in the dermis and a minor systemic biodisponibility .These features allow a better efficacy and tolerability profile than tacrolimus, reducing the possibility of adverse systemic effects .Based on the data in the literature about the use of topical tacrolimus in cutaneous sarcoidosis, we experienced the possibility to use also topical pimecrolimus in the treatment of lichenoid type of cutaneous sarcoidosis, deciding for a long-term treatment of six months for the appearance of relapses with a shorter therapy period, as described in previous cases reported in the literature .The promising results we obtained let us define pimecrolimus as a useful therapeutic option for refractory forms of cutaneous sarcoidosis, besides representing a valuable alternative to tacrolimus for its better efficacy and tolerability profile.


We have little knowledge of how climatic variation  influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change. A core goal of community ecology is to identify the processes that shape community structure, which refers to the richness and composition of species at a specific site and time. Assessing the relative importance of chance (stochastic processes) and ecological rules (deterministic processes) in shaping community structure is central to this goal –5. PhyloWhile some research has examined the factors affecting the structure of tropical communities, much of this research has focused on plants . By comIn recent years, some studies have more explicitly investigated how environmental variation affects the phylogenetic structure of communities. For example, Graham and colleagues , 18 cleaAlthough previous studies have generally found that most mammal communities exhibit a phylogenetic structure that is not statistically different from random, new research has found that the phylogenetic structure of some mammal communities does vary in response to environmental factors. Cardillo  used 102Our knowledge of how climatic variation influences the phylogenetic structure of vertebrate communities and whether these effects are consistent across taxonomic groups is still quite limited. Thus, the goal of this paper is to quantify the phylogenetic structure of mammal communities in Africa and more importantly, to examine how this structure varies in response to the significant climatic variation across the continent. In addition, we test the stress gradient hypothesis , which sIn addition, important biological differences among mammal orders related to their trophic level may have implications for variation in community structure and macroecology across orders –27. For We compiled mammal lists from information on African national parks, game reserves, and protected areas, rather than extracting assumed presence/absence data from species range maps, which often overestimate presences , 32. ForEach locality was recorded with centralized geospatial coordinates . We also associated each site with high-resolution climate data from the WorldClim database , which hMost commonly, community phylogenetic structure has been quantified using two metrics, the net relatedness index (NRI) and the nearest taxon index (NTI) , 40. TheThese metrics were quantified with the PHYLOCOM software package . We usedWe used the mammal supertree presented in Bininda-Emonds et al. , 49 as tWe utilized Kruskal-Wallis tests with Monte Carlo simulation to test for differences in the NRI and NTI values among the three clades of mammals for which we obtained the most data: carnivores, primates, and terrestrial ungulates. We used 9999 randomizations to generate p values. We conducted these analyses using the coin package  for R 5.We used simultaneous autoregressive models (SAR)  to test We calculated NRI and NTI values for our total mammal dataset , as well as for three mammal subsets: primate communities (135), carnivoran communities (199), and ungulate communities (183) that we analyzed separately. At least four species were required in a community for the site to be included in the analysis. In addition, we conducted separate SAR analyses for each of the aforementioned datasets. We used the Spatial Analysis in Macroecology software package  to conduResults for all groupings are presented in These patterns differed when examining finer taxonomic scales individually. At this level of analysis, a greater proportion of communities exhibited a random phylogenetic structure based on the NRI metric. Specifically, 94.8% (128) of primate, 98.0% (195) of carnivoran, and 94.5% (173) of ungulate communities had a random phylogenetic structure. Significant phylogenetic evenness was observed in 3.0% (4) of primate, 0% of carnivoran, and 1.7% (3) of ungulate communities, while phylogenetic clustering accounted for 2.2% (3) of primate, 2.0% (4) of carnivoran, and 3.9% (7) of ungulate communities. In contrast, a lower proportion of communities were phylogenetically random using the NTI metric, especially for carnivores and ungulates. A random phylogenetic structure was found in 95.6% (129) of primate, 93.7% (186) of carnivore, and 89.6% (164) of ungulate communities. A statistically significant degree of phylogenetic evenness was observed for 3.7% (5) of primate, 4.0% (8) of carnivore, and 3.3% (6) of ungulate communities. Phylogenetically clustered patterns were present in 0.7% (1) of primate, 2.5% (5) of carnivore and 7.1% (13) of ungulate communities.The results of our Kruskal-Wallis tests with Monte Carlo simulation yielded a statistically significant difference in NRI values across mammal clades (p = 0.012) . PrimateUsing simultaneous autoregressive models, the phylogenetic structure of mammal communities was significantly predicted by community species richness and climatic variables, though the relationship between these variables and community structure varied across taxonomic scale and across Orders  and species richness on the phylogenetic structure of mammal communities. This supports the idea that African mammal communities have converged on a similar phylogenetic structure when found in similar climatic contexts, even when these communities are found in geographically distinct parts of the continent. In addition, the specific climatic factors influencing community structure varied across mammalian clades, suggesting that differences in the biological traits of these orders plays an important role in their community ecology and evolution, specifically dietary niche. Ungulates are solely primary consumers, whereas other clades, such as carnivorans and primates, comprise species that consume both plant and animal matter , 57, 58.Most individual communities did not exhibit significant phylogenetic structure. This supports prior studies examining mammal community structure in other regions of the world, as well as studies using smaller African datasets , 17, 59.An important assumption of the community phylogenetic framework is the idea that species traits relevant for interspecific competition have strong phylogenetic signal. If this assumption does not hold (e.g. when there are numerous instance of convergent evolution among distantly related species), then competition may actually be stronger between distantly related species, rather than closely related ones. In addition, some traits may exhibit weak phylogenetic signal, being randomly distributed across the phylogeny . If trueSpecies richness was a consistently negative predictor of the net relatedness index (NRI) of communities, i.e. increasingly large communities were associated with more distantly related species. These results are similar to those found in a recent study focused solely on African haplorhine primate communities . One intThe relationship between species richness and community phylogenetic structure may be consistent across a wide array of organisms. This same pattern was found in a recent study by Qian et al.  that exaThe importance of climate for predicting community structure varied across mammalian clades. When all mammals were considered together, temperature seasonality was negatively related to NTI values, indicating that more seasonal sites contained communities with relatively distantly related species. Conversely, mammal communities contained more closely related species in sites with low levels of temperature seasonality. This result suggests that closely related mammal species may be unable to coexist in seasonal habitats due to limited resources, which may have resulted in competitive exclusion in these areas. Alternatively, an evolutionary explanation may be rooted in the idea that taxa inhabiting seasonal habitats may have lower speciation rates than those in regions with higher productivity and climate stability  , 64. In Temperature seasonality was the most consistent predictor of community phylogenetic structure, yet the direction of the relationship differed across orders. Increased temperature seasonality resulted in more phylogenetically even communities across all mammals and within ungulates. Terrestrial ungulate communities were best predicted by environmental variables when using the NTI metric . This supports the idea that ungulate communities may be more affected by environmental factors as primary consumers, compared to primates and carnivorans, which consume both invertebrate and vertebrate prey. The herbivorous ungulates divide their diets into grazers, browsers, and mixed feeders, with browsers also sometimes consuming fruit and mixed feeders usually preferring grass or leaves while eating the other seasonally –67. The In contrast, increased temperature seasonality was related to more phylogenetically clustered carnivoran communities based on both NTI and NRI values. Carnivoran species living in more seasonal habitats may require specific adaptations, which are common in closely related species, to either cope with the seasonal variation in temperature itself, or to manage the challenges in acquiring proper nutrition.Interestingly, there was only a single predictor of NTI variation in primate communities, mean annual precipitation. As precipitation increased, primate communities contained more distantly related species. Primates are typically regarded as forest adapted mammals  and our Explaining the patterns of community phylogenetic structure relies somewhat on the assumption that closely related species have similar biological characteristics  and this similarity declines with increasing phylogenetic distance. In fact, a recent study by Kamilar and Cooper  showed tFinally, our results have important implications for future mammal diversity, especially at the community level. Many of the communities in our dataset are found in the tropics, which are among the most diverse ecosystems in the world. These areas are among the world’s biodiversity hotspots, which are critically important for conservation , 72, andS1 Dataset(XLSX)Click here for additional data file.


Hexagonal boron nitride (h-BN), a well-known dielectric material, may afford the necessary protection. In this research, we demonstrated the van der Waals epitaxy of h-BN nanosheets on mechanically exfoliated graphene by chemical vapor deposition, using borazine as the precursor to h-BN. The h-BN nanosheets had a triangular morphology on a narrow graphene belt but a polygonal morphology on a larger graphene film. The h-BN nanosheets on graphene were highly crystalline, except for various in-plane lattice orientations. Interestingly, the h-BN nanosheets preferred to grow on graphene than on SiO Graphene has attracted global research interests across a wide range of applications ,2. HowevAs an analogue of graphene, h-BN shows a minimal lattice mismatch with graphene of about 1.7%, yet has a wide band gap -8 and loRecently, chemical vapor deposition (CVD) synthesis of h-BN on Ni -16 or Cu3N3H6) could be a promising choice as it would produce BN and hydrogen, which are both environmentally friendly.It has been demonstrated that van der Waals epitaxy by catalyst-free CVD can be a promising route for the growth of topological heterostructures -22. More2/Si and tended to exhibit a triangular morphology when grown on a narrow graphene belt. The h-BN nanosheets grown on graphene were highly crystalline, albeit with various in-plane lattice orientations.In this research, the van der Waals epitaxy of h-BN nanosheets on mechanically exfoliated graphene by catalyst-free low-pressure CVD, using borazine as the precursor to h-BN, was demonstrated. The h-BN nanosheets preferred to grow on graphene rather than on SiO2/Si) wafers by mechanical exfoliation from highly oriented pyrolytic graphite . The h-BN precursor (borazine) was synthesized by the reaction between NaBH4 and (NH4)2SO4 and purified according to our previous reports [2/Si was first annealed for 60 min in an argon/hydrogen flow  of 180 sccm to remove pollutants remaining on the graphene after mechanical exfoliation. During the growth process, borazine, in a homemade bubbler, was introduced to the growth chamber by another Ar flow of 2 sccm, while the Ar/H2 flow remained unchanged. The typical growth time was 5 min, while the pressure was 10 to 100 Pa. After the growth process, the tube was rapidly cooled to room temperature.h-BN nanosheets were synthesized in a fused quartz tube with a diameter of 50 mm. Graphene was transferred onto silicon oxide/silicon .Raman spectroscopy was performed in a Thermo DXR with 532-nm laser excitation . Atomic force microscopy (AFM)  and scanning electron microscopy (SEM)  were used to observe the thickness and morphology of the h-BN nanosheets. X-ray photoelectron spectroscopy (XPS)  was conducted to analyze the chemical composition of the films. The h-BN nanosheets with the graphene substrate were transferred to transmission electron microscopy (TEM) grids for further characterization. Both morphology images and selected area electron diffraction (SAED) patterns of the h-BN nanosheets were obtained by field emission high-resolution transmission electron microscopy (HRTEM)  lattice plane parallel to the surface of the SiO2/Si wafer [Raman spectroscopy provided a useful means of gleaning information about the lattice vibration modes of graphene and h-BN. After being transferred to SiOSi wafer ,2.I2D/IG ratio of graphene was less than 0.5, indicating the multilayer structure of the graphene. Moreover, a weak D peak of graphene at 1,350 cm-1 was observed from the Raman spectra (Figure -1, indicating the E2g vibration mode of h-BN, which was consistent with the reported values [The existence of graphene was shown by Raman spectra in Figure d values ,13-19. Id values  and grapd values ,28, showAccording to previous reports , the gas2/Si, as shown in Figure 2/Si substrate, while the C peak arose from the presence of graphene. The binding energies of B1s and N1s from the XPS spectra were 191.0 and 398.5 eV, respectively, which were in good agreement with reported values [XPS was used to analyze the chemical composition of the h-BN/graphene on the surface of the SiOd values ,19,33,34d values ,36. ThesWe have pointed out the reason for the nucleation of the h-BN on graphene. In fact, the deposition of h-BN nanosheets on graphene was performed as instantaneous nucleation followed by three-dimensional growth in our catalyst-free CVD growth. Similar results of three-dimensional growth in certain situations have been proved by previous reports ,32. As d2/Si, atomic resolution HRTEM was used to study the crystalline structure of the aforementioned h-BN nanosheets on their respective graphene substrates. Figure After the h-BN nanosheets on graphene were transferred to TEM grids after the etching of SiO2/Si, which offered the promise of potential applications for the preparation of graphene/h-BN superlattice structures. The h-BN nanosheets on graphene had a high degree of crystallinity, except for various in-plane lattice orientations. The synthesis of h-BN nanosheets on multilayer graphene has been studied, and h-BN nanosheets on few-layer and even monolayer graphene will be synthesized in future work. This may satisfy certain application requirements for topological heterostructures and graphene-related electronic devices.In summary, we have demonstrated the van der Waals epitaxy of h-BN nanosheets on graphene by catalyst-free CVD, which may maintain the promising electronic characteristics of graphene. The h-BN nanosheets tended to have a triangular morphology on a narrow graphene belt, whereas they had a polygonal morphology on a much larger graphene film. The B/N ratio of the h-BN nanosheets on graphene was 1.01, indicative of an almost stoichiometric composition of h-BN. The h-BN nanosheets preferred to grow on graphene rather than on SiOThe authors declare that they have no competing interests.YS, CZ, BL, and XX designed the experiments, and YS carried out most of the experimental work and material characterizations. CZ and BL synthesized the borazine. YS, CZ, BL, GD, and XX discussed the results, and YS drafted the manuscript. All authors have read and approved the final manuscript.


Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100× wavelength reduction from graphene’s large kinetic inductance. The atomically thin graphene further leads to excellent out-of-plane confinement, and consequently photonic-crystal-slab band structures that closely resemble those of ideal two-dimensional photonic crystals, with broad band gaps even when the slab thickness approaches zero. The overall photonic band structure not only scales with the graphene Fermi level, but more importantly scales to lower frequencies with reduced slab thickness. Just like ideal 2D photonic crystals, graphene-cladded photonic crystal slabs confine light along line defects, forming waveguides with the propagation lengths on the order of tens of lattice constants. The proposed structure opens up the possibility to dramatically reduce the size of terahertz photonic systems by orders of magnitude. During the past two decades, photonic crystals135681113151819submicron periodicity in silicon photonic crystal slabs would be too small to provide a band gap. Additionally, because total internal reflection provides the out-of-plane confinement, only an incomplete band gap is obtained due to the presence of radiation modes that extend into the substrate and superstrate. The size of the in-plane band gap is also significantly reduced from that of a purely 2D crystal, because of the incomplete overlap between the Bloch mode and the slab. Additionally, out-of-plane radiation losses limit the quality factor of point-defect resonatorsUnfortunately, a fundamental limitation of photonic crystal slabs is that their periodicity is proportional to the operating free-space wavelength. This translates to device sizes and mode volumes that are only slightly below the diffraction limit, even when materials with a high refractive index are used. In a silicon photonic crystal slab for instance, the lattice constant defining the in-plane periodicity is generally only about 0.30 to 0.40 times the free space wavelength3One well-known solution for better confinement is to employ a 3D structure that is uniform in the out-of-plane direction and sandwiched between two truncated reflecting boundaries, which are closely spaced such that only the lowest-order mode with a pure polarization is supported . Widely exploited in microwave photonic crystals, this approach has been realized by sandwiching a 2D slab between two metal plates that form a parallel plate waveguide21gated 2D plasmons rather than ungated 2D plasmonsRecently, graphene has emerged as an excellent conductor for the parallel plate geometry at THz frequencies: a quasi-TEM mode is largely confined between two graphene sheets26In this paper, we combine the terahertz graphene parallel plate waveguide and the photonic crystal slab to realize extremely-subwavelength guided Bloch modes with strong out-of-plane confinement. Here two parallel graphene sheets are necessary, and they behave very differently from photonic crystal slabs interfacing with only one graphene sheet41434446We begin this article by introducing the physical configuration and discussing the unique band structure of the graphene photonic crystal slab. We analyse the factors influencing the attenuation of the guided bulk modes. We then discuss the effect that the structure’s thickness and graphene Fermi level have on the size and location of the photonic band gap. Next, we examine the conditions under which the structure exhibits scale invariance that is consistent with all-dielectric photonic crystals. We then discuss the structure’s ability to support modes which are confined to defect waveguides in the bulk crystal. Finally, we conclude by discussing the device’s prospects as a building block for more complex applications.ε = 11.67)ε = 2.25), such as glass or polymer52a) is 300 nm and the slab thickness (g), or equivalently, graphene separation, is 40 nm. The two single layer graphene sheets have identical properties and are characterized by a modified Drude surface conductivity given by3254For concreteness, the structure which we consider is a triangular lattice of silicon rods  corresponds to 10 THz, i.e. a free-space wavelength of 30 μm. In other words, the guided THz photons are comparable in size to an ultraviolet photon. The graphene separation in this case is three orders of magnitude smaller than the free-space wavelength which ensures that higher order parallel-plate-waveguide modes can be neglected. If we take graphene’s resistive losses into account, we observe that these extremely subwavelength modes actually have significant propagation lengths  the modes become very weakly guided. In such index-guided structures this is observed in the band diagram with the bands shifting to higher frequencies and the band gap closing-off (if the dielectric modulation is even strong enough to support a band gap). However, in the graphene-cladded slab, the reduction in slab thickness translates to an increase in the capacitance experienced by the underlying TEM mode, which in turn, shifts the band gap to lower frequencies and enlarges its relative size as shown in g = 0.05a to g = 1.25a, where a = 300 nm. The minimum slab thickness considered in this range is approximately 13 nm. without the graphene cladding will only support weakly guided modes with fields that extend above and below the slab and no photonic band gap , while the second regime corresponds to the lattice constant being much larger than the thickness (the right-most portion of each column). Indeed, this is an expanded picture of our earlier observation and discussion of the band gap’s dependence on slab thickness; now we’re also considering variation of the in-plane lattice constant. To better understand the differences between these two regimes, we plot the electric field magnitude over a plane through the 3D unit cell of two specimens in the bottom row and middle column of in-plane lattice constant, manifested as the horizontal band of the shaded regions in the first row of Among the three slab thicknesses and across the range of in-plane lattice constants, we see the emergence of two distinct regimes. The first regime corresponds to the lattice constant being on nd-order graphene ribbon plasmonnd-order graphene ribbon plasmons. Radiation from the TEM photonic crystal slab modes into the light cone is also suppressed for two reasons: the fields of the slab modes are tightly confined between the graphene sheets .


Optical modulators (OMs) are a key device in modern optical systems. Due to its unique optical properties, graphene has been recently utilized in the fabrication of optical modulators, which promise high performance such as broadband response, high modulation speed, and high modulation depth. In this paper, the latest experimental and theoretical demonstrations of graphene optical modulators (GOMs) with different structures and functions are reviewed. Particularly, the principles of electro-optical and all-optical modulators are illustrated. Additionally, the limitation of GOMs and possible methods to improve performance and practicability are discussed. At last, graphene terahertz modulators (GTMs) are introduced. As one of the key components in photonics systems, an optical modulator is a device used to control the fundamental characteristics of a carrier light propagating in free space or in an optical waveguide upon an external electronics/photonics signal . In ordeAs the prime material for the semiconductor industry, silicon modulators have to be fabricated in large scale to obtain enough modulation depth, due to a relatively weak high-order electro-optical effect. On the other hand, modulators based on germanium and other compounds have problems to be integrated with current complementary metal-oxide-semiconductor (CMOS) techniques. For modulators with resonators, narrow modulation bandwidth limits their development. By contrast, graphene can cover the needs of scale, speed, and techniques. And integration with graphene can help current modulators to improve their performance.Graphene, a single layer of hexagonally packed carbon atoms, was first isolated from graphite via mechanical exfoliation in 2004. For these highly confined two-dimensional crystals, in-plane carbon atoms are connected by strong σ-bonds, while adjacent layers only share weak van de Waals force. The unique crystalline structure endows graphene extraordinary electronic, optical, thermal, and mechanical properties. Graphene is expected to grow into the new silicon in future electronics and photonics. Many proof-of-concept photonics devices based on graphene, including photodetectors ,11, ultr2/(V · s) at room temperature, graphene is considered as one of the fundaments of next-generation ultrafast electronics/photonics devices [πα = 2.293% from visible to infrared wavelengths [α = e2/hc denotes the fine-structure constant [For applications in optical modulators, graphene has its unique advantages as follows: 1) High modulation speed: With a carrier mobility as high as 200,000 cm devices . Ultrafa devices . Thus, t devices ,11, grapelengths , where αconstant , as is s High modconstant , as showconstant ,16. Moreconstant ,20, whicIn this review article, we provide a brief overview of graphene-based optical modulators. Our survey is not intended to cover every single device reported in prior publication, but rather to introduce some typical designs and highlight some recent notable work. Classified by whether electrical elements are involved or not, the principle and paradigms of electro-optical and all-optical graphene optical modulators are elaborated in the ‘Electro-optical graphene optical modulator’ and ‘All-optical grapheme optical modulator’ sections, respectively. In addition, graphene-based material systems for THz wave modulation are discussed in the ‘Graphene terahertz modulator’ section. The article closes with a final conclusion and outlook in the ‘Conclusions’ section.2 hybridization of carbon atoms, graphene has a unique electronic structure in that the conduction band and valence band meet at Dirac points like two cones [Due to the spwo cones ,11. A liα = e2/ħc  [For pristine graphene, electrons can be excited by incident photons with a broad range of energies and only interband transition is permitted Figure a. As a cf light) :1\documeμ (Fermi level EF), which can be controlled by chemical doping or electrical gating. The Kubo formula can be used to describe the dynamic response of graphene, including interband transition and intraband transition [While sufficiently doped, the optical transition of graphene is mainly determined by chemical potential ansition :2\documeμ and the frequency of incident light ω. When μ = 0, no intraband transition will happen. When |μ| < ħ ω/2, (slightly n-doped or p-doped) optical transition is dominated by interband transition. In n- and p-doped (corresponding to positive and negative gating voltage) graphene, the incident photons with energy less than 2EF cannot be absorbed. This is because the electron states in the conduction band are filled up as shown in Figure μ| < ħ ω/2, the intraband transition related to the terahertz range will be dominant [Both interband transition and intraband transition are related to chemical potential dominant -25. At tdominant -28.In earlier theory demonstrations, graphene was treated as an isotropic material ,30. Grap2. Right after the first demonstration, they further improved the modulator by integrating double-layer graphene on the top of a Si waveguide [In 2011, Liu et al. first experimentally demonstrated a GOM by integrating a monolayer graphene sheet on a Si waveguide as shown in Figure aveguide , as is saveguide  and GeSiaveguide .Figure 3With the aim to achieve higher performance, different structures have been developed. High modulation depth not only brings a higher signal quality but also helps to reduce the footprint. Simply increasing the peak-to-peak gate voltage swing can achieve high modulation depth at the expense of increased power consumption. Improving the graphene-light interaction can fundamentally increase the performance. Similar to Liu et al.’s work, Koester and Li simulated a graphene-on-silicon structure  as shown2 and modulation arm length of 27.57 μm in the Mach-Zehnder modulator. And they further reduced the modulation arm length to 16.5 μm [2 was reported recently [By integrating graphene, the performance of current optical modulators can be further enhanced. Hao et al. theoretically demonstrated a Mach-Zehnder modulator with eight-layer graphene embedded , as is s 16.5 μm . Moreove 16.5 μm . The gra 16.5 μm  can be r 16.5 μm . With th 16.5 μm , as is srecently , as is sIn addition, a device integrating both GOMs and a graphene optical photodetector was experimentally demonstrated . Recentlf = 1/2πRC, where R is the total cascade resistance and C is the total capacitance between counter electrodes. These factors can be measured by a network analyzer. The all-optical method is an efficient way to avoid this bottleneck.In theory, the high carrier mobility of graphene will lead to an ultrahigh modulation speed. However, in experimental demonstration, the modulation speed is still limited at approximately 1 GHz ,8 lower The future optical fiber communication system requires a modulator whose operation speed is larger than 100 Ghz . AlthougSaturable absorption is a property of materials where the absorption of light is decreased to a steady level at sufficiently high incident light intensity . This opThe schematic saturable absorption process is shown in Figure 2 substrate, as is shown in Figure Liu et al. firstly experimentally showed all-optical modulation using a graphene-covered microfiber, which is compatible with the optical fiber system . A chemiActually, the all-optical graphene modulator is able to reach ultrafast modulation speed without RC limitation. A practical ultrafast all-optical graphene optical modulator, which is compatible with the current high-speed fiber optical communication system, was fabricated by Li et al. . The strTheoretically, if the intensity of pump light is strong enough , graphene can be totally transparent to carrier light. Thus, the maximum modulation depth is determined by the optical absorption when the pump light is off, which is largely related to the interaction length and position of the graphene sheet. However, in the works above, sufficiently saturable absorption is not achieved and absorption of carrier light is gradually varied with the changes of pump intensity as shown in the inset of Figure In the past decades, terahertz (THz) technology was found to be applied in diverse areas such as astronomy, biology/medicine , communiThe optical conductivity of graphene is determined by interband transition and intraband transition, respectively, mainly for short wavelength (infrared and visible) and long wavelength (terahertz) -25. ThusIn 2012, Sensale-Rodriguez et al. first experimentally demonstrated a GTM enabled only by intraband transitions . Later oFollowing Sensale-Rodriguez et al.’s first demonstration of GTM , Weis etDue to accurate and deep modulation in the THz range, integration with resonators shows a way to cover special needs -77. In gOptical modulators are an important device to the current and future optical systems and still need to be improved. Graphene shows great potential in fabricating broadband and ultrafast optical modulators. Optical transition including interband and intraband transitions in graphene is the main process during absorption. Electro-optical GOMs have been demonstrated while the modulation speed is limited to approximately 1 GHz due to the RC constant. The position of the graphene sheet efficiently influences the light-graphene interaction. Higher modulation depth can be easily achieved by placing graphene close to the maximum of the electric field. Following the first demonstration, many optical modulators enhanced by graphene have been theoretically and experimentally demonstrated. However, higher modulation speed is necessary for current electro-optical GOMs. Driven by saturable absorption, all-optical GOMs show a potential of ultrafast modulation speed due to the ultrafast relaxation time. But direct measurement of ultrafast modulation has not been demonstrated. In the field of terahertz, graphene has a prominent advantage of high modulation depth. Electro-optical and all-optical modulation are both possible. In principle, theoretical simulations go much further than experiment. GOMs with new structures and high performance tend to be demonstrated in the near future.


The morphology and thickness of the graphene films can be effectively controlled through the adjustment of the ratio of pyrene to CTAB. Furthermore, a high nonlinear refractive index n2 of ~10−12 m2 W−1 is measured from graphene/silica hybrid film, which is six orders of magnitude larger than that of silicon and comparable to the graphene from chemical vapor deposition process.In this work, a novel soft-hard template method towards the direct fabrication of graphene films on silicon/silica substrate is developed via a tri-constituent self-assembly route. Using cetyl trimethyl ammonium bromide (CTAB) as a soft template, silica (SiO In our method, the tri-constituent assembly of pyrene, cetyl trimethyl ammonium bromide (CTAB), and tetramethoxysilane (TMOS) allow the formation of a sandwich-like SiO2/CTAB/pyrene composite within the micelles of CTAB as a soft template and layered SiO2 as a hard template. The sandwich-like films can be further converted to high quantity graphene film with a thickness of ~1 nm and a size of over 5 μm by thermal treatment. Such bottom-up fabrication of graphene film can be operated on any high thermal resistance substrates and the morphology of the synthesized graphene film can be easily adjusted by changing the added amount of PAH precursor. Benefiting from the transparent SiO2 layer, the graphene film within SiO2 shells possesses a high optical transparency (92.2 ~ 93.3%) in the visible light range and large nonlinear refractive index n2 of ~10−12 m2 W−1, which is six orders of magnitude larger than that of siliconComposed of multiple aromatic rings, polycyclic aromatic hydrocarbons (PAHs) can be viewed as nano-scaled fragments of graphene since they all contain a two-dimensional (2D) sp2O was stirred to allow the partially hydrolyzation of TMOS. Then an aqueous solution containing CTAB and pyrene was added2 enable the formation of layers of SiO2 on both sides of the CTAB micelles as hard template. As a result, the tri-constituent self-assembly of pre-hydrolyzed TMOS, CTAB, and pyrene produced a sandwich-like SiO2/CTAB/pyrene composite2 or quartz substrate and thermal treatment of the resulting film at 900 °C in nitrogen flow lead to the formation of graphene films sandwiched in SiO2 shells. The molar ratio of TMOS to CATB is fixed as 4:1 and the ratio of pyrene to CTAB is varied from 0:20, 1:20, 2:20, and 3:20. The self-assembled samples before thermal treatment are denoted as PY-0, PY-1, PY-2, and PY-3, respectively. The derived composite films with graphene sandwiched in SiO2 are named as GS-0, GS-1, GS-2, and GS-3, respectively. The key aspect of our method is simultaneous employment of surfactant CTAB as a soft template and layered SiO2 as a hard template. The micelles of CTAB help the hydrophobic pyrene to form ordered superstructures in aqueous solution. The SiO2 layers provide a flat confinement space to prevent the sublimation or aggregation of pyrene and ensure the formation of a thin graphene layer during the thermal treatment. Moreover, for the application of the produced graphene film in optical devices, the SiO2 shell can further protect the film from scratching or folding. Etching away the SiO2 component with diluted hydrofluoric acid (HF) can release the graphene sheet for structural characterization.The overall synthesis procedures of the graphene film are illustrated in d values of 3.69, 3.76, 3.88, and 3.98 nm, respectively, which exhibit a good linear relationship with the added amount of pyrene. Therefore, the diffractions should correspond to the distances between two neighboring silica layers in the sandwich-like SiO2/CTAB/pyrene composite26d value of ca. 2.6 nm can also be found in all the XRD spectra of the four samples. The variation of the amount of pyrene shows no influence on the 2θ angles of the second-order reflection and the diffractions totally disappear in the XRD spectra of GS-0, GS-1, GS-2 and GS-3, which is thus supposed to be derived from the crystalized CTAB26d-spacings for the (100) reflections of GS-1, GS-2 and GS-3 are calculated as 2.98, 3.17 and 3.27 nm, respectively. Compared with the corresponding samples before thermal treatment, the reduced d values of GS-1, GS-2 and GS-3 should be owing to the shrinkage of the lamellar architectures in the composites.The microstructures of the obtained samples are firstly explored with powder small-angle X-ray diffraction (XRD). In the XRD patterns of PY-0, PY-1, PY-2, and PY-3 , these p−1 can be attributed to the C-H stretching from CTAB and pyrene. In contrast, these peaks are absent in the FTIR spectra of GS-2, indicative of the decomposition of surfactant CTAB and the conversion of pyrene to graphene film after the thermal treatment. Additionally, no peaks from silica can be observed in the FTIR spectra of the graphene after the etching process with HF  and atomic force microscopy (AFM). It is found that the morphology of the graphene sheets show evident dependence on the added amount of pyrene (2 layers. The high-resolution TEM (HRTEM) result of the wrinkled part of this graphene film shows well-resolved lattice structure with a lattice space of ~0.34 nm, which can be assigned to the (002) plane of grapheneIn the Fourier transform infrared (FTIR) spectra of PY-2 , the str with HF , confirm with HF , the crof pyrene  and S3. −1 can be observed for both GS-2 and the graphene from GS-2 after the removal of silica, which correspond to the D and G bands of carbon, respectively31D/IG) of GS-2 and the graphene derived from it are 0.95 and 0.96, respectively, implying both samples have very similar graphitization degrees. Additionally, the 2D peak at ~2700 cm−1 and S3 peak at ~2910 cm−1 of GS-2 are absent in the Raman spectra of the graphene, which might be due to the wrinkled domains and defects in the graphene without the protection of silicaTo evaluate the quality and uniformity of the graphene films, Raman spectra of GS-2 on quartz and the graphene after the removal of silica were further recorded in this work. As shown in 2 substrate and the unique sandwich-like structure of GS-2 enable it to be used in optical devices. Moreover, as shown in optical microscopy image (342 film (GS-0) is about 98%. Since the absorbance of an individual layer of graphene is 2.3%The easy fabrication of graphene on quartz or Si/SiOpy image , the GS-py image , similarn2)2 component in GS-2 has little influence on the Z-scan measurement results  was partially hydrolyzed by a substoichiometric amount of water (0.45 mL) under acidic conditions (pH = 3) for 2 hours at room temperature. Then an aqueous solution containing CTAB (1.14 g) and pyrene was added. The molar ratio of pyrene to CTAB varied from 0:20, 1:20, 2:20, and 3:20. After the mixture was stirred for a few minutes, the homogeneous sol was spin-coating on the quartz and silicon substrates. Subsequently, the films were put in fume cupboard until the total vaporization of the solvent. A heat process  was then required for the further solidification of the composites. Subsequently, thermal treatment of the silica/CTAB/pyrene composites in a nitrogen flow at 900 °C for 2 hours.2/graphene/SiO2 nanocomposites. The silica frameworks were removed by treating the samples with aqueous HF (10%) for 48 hours.To obtain graphene suspension without silica, the sol above mentioned was transferred into dishes. After the heat treatment at 100 °C for 24 hours, the as-made products were scraped from the dishes and ground into fine powders. Thermal trearment was carried out at 900 °C for 2 hours in a nitrogen flow to get the SiOHow to cite this article: Yang, Y. et al. Bottom-up Fabrication of Graphene on Silicon/Silica Substrate via a Facile Soft-hard Template Approach. Sci. Rep.5, 13480; doi: 10.1038/srep13480 (2015).


N-methyldiethanolamine, they were synthesized aqueous dispersions of polyurethane cationomers, from which films were prepared after adding 0–2 wt% graphene. In order to obtain nanocomposites, graphene was previously noncovalent functionalized in tetrahydrofurane in the field of ultrasound. The chemical structure and the morphology of obtained nanocomposites were analyzed by IR spectroscopy, atomic force microscopy (AFM), and differential scanning calorimetry (DSC) microcalorimetry methods. It was found that the presence of graphene results in increased thermal and mechanical strength of received polymer films and contributes to the increase in hydrophobicity of generally hydrophilic coatings prepared from waterborne polyurethane cationomers. Based on received results, possible interactions between graphene and phase structure of polyurethane cationomers were discussed. Relating to the so far described applications of graphene for the modification of polyurethanes, the novelty of this work is the concept of incorporation of graphene particles to polyurethane cationomer chains exclusively through a simple noncovalent functionalization and to investigate the effect of graphene on the properties obtained in this way of thin polyurethane film.In the reaction of 4,4′-methylenebis(phenyl isocyanate), polycaprolactone diol, and  During the past 10 years since the first publication on graphene, a large number of publications regarding the use of the allotropic forms of carbon as a nanofiller in polymer composites were shown . PolymerUnlike graphene, graphene oxide is electrically insulating, which does not allow its application for the production of conducting nanocomposites. So, it is worthwhile to still make new attempts to apply noncovalent methods for graphene modification as a special sonification in organic solvents or in ionic liquids .In recent years, attention is also paid to the possibility of polyurethane material modification by graphene or its functionalized derivatives. New reinforced polyurethane elastomers are being sought in the automotive industry and as varnishes which very useful in the anticorrosive protection of steel and concrete, as well as conducting nanocomposites in electronics –10.In , the autBearing in mind our former achievements concerning the production of waterborne polyurethane cationic dispersion , we madePolyurethane cationomers were synthesized in a four-stage polyaddition process, in a glass stand composed of three-necked flask, heating bowl, mechanical agitator, dropping funnel, thermometer, reflux condenser, and nitrogen supply nozzle. At stage 1, urethane-isocyanate prepolymer was synthesized in the reaction of diisocyanate (B) and polyester (A):3 (6.68 g) of THF was introduced 10 g (0.040 m) MDI, and under agitation after reaching a temperature at about 50 °C, two drops of benzoil chloride (inhibitor) and 8.00 g (0.004 m) PCL were added, and then the reaction was continued for 6 h until complete conversion of the polyester, which is when the concentration of –NCO groups amounted to a maximum of 12.5 wt% (determined by using the well-known acidimetry method using dibutylamine). Initially, after introducing PCL, the concentration of NCO groups in the reaction mixture was 13.61 wt% . Thus, addition of the inhibitor was necessary to limit the side reactions of MDI (present in excess).To 7.5 cm3)) were obtained in the process of sonication at 50 °C for 30 min in ELMASONIC P ultrasonic baths at a frequency of 80 kHz.In the second stage, suspension of graphene in THF was introduced to the resulting mixture of MDI and BAB prepolymer. Appropriate suspensions  in THF  of NMDA (X) and about 0.012 g of DBTL catalyst were introduced to the reaction system, and then the BAB prepolymer extension reaction was continued at 50 °C for a further 30 min, which shows the following reaction:The final content of NCO groups in the resulting mixture no longer exceeded 0.25 wt%. Alkylammonium cations were produced by neutralization of tertiary amino groups. For this purpose, to the reaction mixture, 1.60 g (0.0348 m) of the pure HCOOH was introduced.At stage 4, redistilled water (approximately 36.5 g) with slight amount of NMDA  was added under intensive agitation conditions. That stage was intended not only to produce the water dispersion (38–42 wt%), but cationomer chains with the residual –NCO groups were subjected to extension at the same time in the reaction between groups –NCO and wateror in the reaction between residual groups –NCO and HMDA:The resulting dispersion of waterborne polyurethane was degassed in an ultrasonic field.The reference films were prepared by covering poly(tetrafluoroethylene) (PTFE) or glass plates by the polyurethane cationomer dispersions. Next, the films were placed in a vacuum drier, at 80 °C, over 6 h, and the process of film formation was completed by exposure to ambient air for 10 days. In this way, polymer films containing respectively 0 (PU-0 sample), 0.1 (PU-0.1), 0.5 (PU-0.5), 1 (PU-1), 1.5 (PU-1.5), or 2 wt% (PU-2) of the graphene were received.−1 at a resolution of 2 cm−1.Infrared spectra of the samples were recorded under vacuum at room temperature using a horizontal attenuated total reflectance (ATR) attachment with ZnSe crystal on a Vertex 70v (Bruker) Fourier transform infrared (FTIR) spectrometer in the range of 4000–550 cm2.Investigation of the topography and heterogeneity relief (PU nanocomposite films were previously freeze-fractured at the temperature of liquid nitrogen) was done by using an atomic force microscope , equipped with the SSS-NCL probe, Super Sharp SiliconTM-SPM-Sensor . Measurements were performed under ambient conditions using the tapping mode atomic force microscopy (AFM) technique. The scans covered the sizes from 1 × 1 to 50 × 50 μmDetermination of phase transition temperatures of polyurethanes was made by differential scanning calorimetry (DSC) using Mettler Toledo 822 differential calorimeter. Samples of 11–17 mg were tested. Each sample was heated and cooled in a temperature range of −80 to 100 °C, at a rate of 10°/min.Thermal gravimetric analysis of the obtained polyurethane foils involved the use of a TGA/DSC1 thermobalance from Mettler Toledo. TG and DTG were derived. The measurements were taken within the temperature range of 25–600 °C, at a constant heating rate of 10°/min, in nitrogen atmosphere. Based on TG thermograms, temperatures corresponding to mass losses of 5, 10, and 50 % were determined.γS were found on the basis of the Owens-Wendt methods. The first one assumes that the surface free energy γS,L may be presented as a sum of two components . Th. ThΘ is p Table  was usedfrom Eq. . The cony Zisman , i.e., bσmax), elongation for maximal σ (εm), tensile strength (σr), elongation for tensile strength (εr), and Young’s modulus (E). It also gives an approximate thickness of the coatings used in the measurements (b).The mechanical strength tests were performed on a testing machine ZWICK type BZ1.0/TH by PN-EN ISO 527–3:1998. Test speed was 100 mm/min, sample width was 10 mm, and gauge length was 50 mm. The following parameters were determined: maximum tensile stress  (M = 2000–8000) and 1,4-butanediol containing 45–77 % hard segment z with dominant crystalline phase therein were characterized by similar IR spectra in the range of the analyzed bands, where in all spectra, a very sharp 3300-cm−1 wave band was visible [The key issue was to obtain a good homogeneity of the films obtained from polyurethane cationomers modified by functionalized graphene only by the noncovalent method. Evidence of new interactions between the graphene and the cationomer chain were explored by analyzing the IR spectra. From FTIR analysis, bands related to amine, asymmetric and symmetric methylene, and carbonyl groups were observed at 3300, 2926, and 2863, 1722, and 1710 cm−1, which may be evidence of the incorporation of the graphene to the noncovalently functionalized PU in the presence of THF. THF as a volatile solvent was removed during drying and seasoning of polymer films. With reference to the above, it is possible to expect that graphene was associated with the polymer matrix, which can in turn be inferred from AFM imaging. It is important that the AFM images were obtained at room temperature immediately after cutting of the sample by a microtome, so they are giving information about the internal structure of material. Already, roughness analysis thus obtained surface made on the basis of the statistical parameters of the sensor height  only from −49.7 to −43.4 °C, while for hard segments, a significant increase of glass temperature (Tg2) from 23.9 to 38.6 °C (as well as an increase in delta Cp) was observed. The higher Tg1 can reflect the changes in long-range segmental mobility in soft segments due to the introduction of graphene. It enhances the rigidity of the soft segments and results in a slight increase in phase transition temperature of PU soft segments. As shown in Table Cp for hard segments increases and, in consequence, the segmental mobility is significantly reduced in samples with graphene, indicating that chain immobilization occurs when they are intercalated between graphene layers. Similar results were observed for PU/organomodified montmorillonite where PU chain mobility was constricted by MMT galleries [As it can be seen from Fig. alleries . This bealleries . In our alleries . For samStiffening of the structure by introducing a graphene clearly resulted in increased heat resistance and mechanical strength of the obtained nanocomposites. With this, the pronounced increase in the thermal resistance—as seen from the TG thermograms shown in Fig. The character of changes of registered curves is presented on Fig. 2, which is a significant value. Lowering of the surface free energy is observed in both values of the dispersion component γSd and—with a much lower value—the polar component γSp. This result is seemingly surprising enough in the light of previous results concerning DSC and AFM analyses, which indicated the presence of additional interactions within the rigid segments. Here, it is necessary to consider that the measurements of contact angles in contrast to the AFM analysis were performed on real coatings and thus they do not characterize the internal structure of the material as the internal surface analysis. It is worth noting that, as presented in [As shown in our earlier studies , the cheented in , a matheented in  indicateTg2 at about 15° in comparison with an unmodified cationomer. Crucial for explaining the homogeneity of morphology of obtained nanocomposites are the results of AFM analyses regarding the interior of the material. The surfaces of the tested samples showed a relatively small increase of roughness with increasing amounts of graphene. However, the surface morphology was complex; an inequality maximum of up to 1 μm and a phase heterogeneity especially in graphene particles were observed. Analysis of phase images indicates that graphene was permanently associated with the polymer matrix. The consequence of the existing heterogeneity of nanocomposite structures was weaker than the expected mechanical properties of the obtained films, although graphene greatly improved the mechanical strength of the modified cationomer coatings, so that its introduction at 0.1 wt% resulted in an increase in Young’s modulus of up to about 400 MPa and a relative elongation of up to 400 %. There was also a distinct improvement in thermal resistance of the obtained composites and a regular increase in the hydrophobicity of the coatings with increasing amounts of graphene, which result in the polar material with average surface free energy of 38 mJ/m2, while the output coating was characterized by an SFE value equal to 45 mJ/m2. In summary, it has been shown that even a relatively simple noncovalent functionalization of graphene may be sufficient for the preparation of polymer films produced from waterborne polyurethane cationomers.It has been shown that the multi-step method of synthesis of the polyurethane cationomer allows already at the stage of synthesis of the isocyanate prepolymer to introduce graphene in the form of a suspension in THF. Advantageous features of graphene for its homogenization in polyurethane mixture were obtained during its noncovalent functionalization in THF—a solvent often used in the preparation of polyurethane ionomers. The possibility of chemical influences of graphene with THF and with rigid segments of chains of synthesized cationomers provides subtle changes in the IR spectra as well as in the AFM and DSC analyses. The influence of graphene on the nature of interactions within the rigid segments indicates the observed increase of


Immunotherapy has become a crucial modality for non-small-cell lung cancer treatment. Recently, two immune checkpoints, PD-1 and PD-L1, have emerged as important targets for immunotherapy. Their antitumor efficacy has been confirmed by in vitro and in vivo studies. But the correlation between PD-1/PD-L1 expression and EGFR expression was controversial and needs more evidences to support the combination of PD-1/PD-L1 inhibitors and tyrosine kinase inhibitors. Lung cancer, the leading cause of cancer-related deaths, has the highest incidence and mortality rates amongst all malignancies worldwide . Lung caAmongst the various types of lung caners, non-small-cell lung cancer (NSCLC) comprises 80% - 85% of all cases and more than 70% are diagnosed as unresectable advanced disease ,5. ThougUp to date, the pivot for curing advanced NSCLC has been the direct inhibition of tumor cell growth by cytotoxic agents or targeted small-molecule inhibitors. However, platinum-based chemotherapy only has a response rate of 20% - 35% and a median OS of 10–12 months, while targeted therapy with tyrosine kinase inhibitors (TKIs) can not prolong OS significantly  and moreGiven that cancers are recognized by human immune system, and under certain circumstances the immune system can obliterate tumors , many clT cells play pivotal effector-like roles in the complicated network of human the immune system. T cells hamper tumor development ,10 but uPD-1, a type 1 transmembrane protein of the Ig superfamily , consistPD-1 has two known ligands, PD-L1 (B7-H1) and PD-L2 (B7-DC), which belong to B7 family ,21. PD-L+ cytotoxic T lymphocyte (CTL) and thus induces apoptosis of tumor-infiltrating T cells [PD-1 and PD-1 L interact with each other and then inhibit expression of multiple transcription factors of T cells such as GATA-3 and T-bet . Besides T cells . Ectopic T cells .+ T cells into FOXP3+ Tregs [Besides, it was shown that PD-L1 expression plays a critical role in differentiation of regulatory T cells (Tregs) and maintaining their suppressive function . Because3+ Tregs , further3+ Tregs . As well3+ Tregs . It has 3+ Tregs  and Tumo3+ Tregs .In gene level, tumor cells can activate PD-L1 expression of via multiple oncogenic signaling pathways involving IFN-γ/JAK2/IFN , PI3K 3, ALK/STAAltogether, PD-L1/PD-1 interation plays an important role in the reduction of specific T cell apoptosis, inhibition of immune response to tumors, and immune evasion of tumors . The inhGiven that PD-1 is highly expressed on lymphocytes infiltrating human tumors and circulating tumor-specific T cells , and togPD-L1 overexpression on mouse mastocytoma models inhibited tumor-directed T cell cytotoxicity in vitro and furthermore promoted apoptosis of tumor-specific T cells and immune evasion, these effects were neutralized by antibody-mediated blockade of PD-L1 ,31. MoreThe clinical significance for prognosis of PD-L1 expression on tumors is controversial, correlating with inferior outcomes in some studies -47 and s+ T cells in NSCLC suggests a reduced production of various cytokines and T cell proliferation [+ cells are remarkably increased comparing with adjacent lung parenchyma, and PD-L1 expression on NSCLC cells also correlates with poor prognosis and shortened OS [PD-1 overexpression on CD8feration . Abnormaferation -52, and feration ,51. On ttened OS . Hence iTo date, a few antibodies which inhibit the PD-1 pathway by blockade of the PD-1 or PD-L1 have been invented.Nivolumab (BMS-936558) is a fully human IgG4 antibody blocking the PD-1 receptor . ResultsThe most critical clinical data of nivolumab is from a phase Ib dose-escalation study enrolling 269 patients with various advanced solid tumors including NSCLC . A promiIn other studies, nivolumab has also been tested in combination with platinum for first-line NSCLC, with an ORR of 33%, and a grade 3 or 4 AE rate of 49%, and most of AEs were attributable to chemotherapy .In the above trials, patients generally received anti-PD-1 antibody until progression for 1 to 2 years. If study participants achieved a durable response and then subsequently progressed after cessation of therapy, there was an opportunity for rechallenge at the time of progression .Lambrolizumab (MK-3475) is a humanized IgG4 antibody directed against PD-1 . In a phBMS-936559 (previously MDX-1105) is a fully human, PD-L1-specific IgG4 mAb . A phaseIn the clinical trials mentioned above, only a subset of patients responded to PD-1 blockade. And NSCLC is a disease characterized by driver mutation-defined molecular subsets, each with distinct clinicopathologic features and potentials for targeted therapies. Hence, it is appealing to explore the clinicopathological characteristics and molecular associations of NSCLC expressing PD-1 or PD-L1, which might be candidates for anti-PD-1/PD-L1 immunotherapy.As widely known, one of the most commonly mutated oncogenes in NSCLC patients is EGFR, a member of receptor tyrosine kinases superfamily. EGFR binds to extracellular ligands, dimerizes with them and auto-phosphorylate . Then, EEGFR tyrosine kinase inhibitors (TKIs) have been developed for the treatment of advanced NSCLC for years . UnfortuPreliminary results have suggested that PD-L1 expression might be associated with a higher likelihood of response to PD-1 blockade , but relP = 0.006), while PD-L1 positive status was significantly associated with presence of EGFR mutations (P = 0.001). Patients with PD-L1 positive expression had higher sensitivity to EGFR-TKIs, longer time to progression and OS (P = 0.09) than PD-1 negative patients. Mu et al. observed that in stage I NSCLC patients the rate of PD-L1 over-expression was 39.9% (65/163) but there was no significant correlation between PD-L1 expression and EGFR/KRAS/BRAF/ALK expression [The results of the correlation between PD-1/PD-L1 expression and EGFR expression were controversial. Gettinger et al. concluded that EGFR or KRAS mutation status did not correlate with response rate of nivolumab for NSCLC patients . Akbay epression . Similarpression .Conclusively, the mentioned genes, not only EGFR, but also other several genes such as KRAS, BRAF or ALK, can not be satisfactory biomarkers for assessing the effects of blockage of PD-1/PD-L1 pathway based on the results of existing studies.Nowadays, the urgent need-to-be solved problems include the start time point of antibodies using, the duration of administration, the combination with other treatment modalities, the identifying of priority population and the overcoming of antibody resistance .Referring to the combination with other treatment modalities, the distinct molecular and cellular mechanisms whereby CTLA-4 and PD-1 suggest that combined therapeutic strategy of these pathways might be synergistic for cancer immunotherapy. Preclinical models of combined CTLA-4 and PD-1 blockade have shown promising results without a significant increase in toxicity . The cliOne noticeable point is that the therapeutic mechanism of PD-1/PD-L1 targeted therapy is different from chemotherapy and present molecular targeted therapies. Hence, novel assessment criteria for therapeutic effects are needed. We have proposed a preliminary evalation system for the effect of another widely used antitumor immunotherapy, cytokine-induced killer cell therapy , and theFurthermore, the relative contributions of T cells, B cells, NK cells, NKT cells, DCs, and macrophages to the anti-cancer activity of PD-1 blockade should be clarified more deeply, as PD-1 is expressed on all of these types of immune cells.Conclusively, PD-1 and PD-L1 are important checkpoints in tumor development. PD-1/PD-L1 pathway is a promising target for treating NSCLC, and its correlation with EGFR/KRAS mutation needs confirmation by progressive studies.


Turning is a challenging mobility task requiring proper planning, coordination, and postural stability to be executed efficiently. Turn deficits can impair mobility and lead to falls in patients with neurodegenerative disease, such as Parkinson’s disease (PD). It was previously shown that the cranio-caudal sequence involved during a turn  exhibits a signature that can be captured using an inertial system and analyzed through the Kinematics Theory. The so-called cranio-caudal kinematic turn signature (CCKS) metrics derived from this approach could, therefore, be a promising avenue to develop and track markers to measure early mobility deficits.The current study aims at exploring the discriminative validity and sensitivity of CCKS metrics extracted during turning tasks performed by patients with PD.Thirty-one participants (16 asymptomatic older adults (OA): mean age = 69.1 ± 7.5 years old; 15 OA diagnosed with early PD ON and OFF medication, mean age = 65.8 ± 8.4 years old) performed repeated timed up-and–go (TUG) tasks while wearing a portable inertial system. CCKS metrics  were extracted from kinematic data recorded during the turn phase of the TUG tasks. For comparison purposes, common metrics used to analyze the quality of a turn using inertial systems were also calculated over the same trials .p ≤ 0.041) and were sensitive to change in PD medication state (p ≤ 0.033). Common metrics were also able to discriminate between OA and patients (p < 0.014), but they were unable to capture the change in medication state this early in the disease (p ≥ 0.173).All CCKS metrics discriminated between OA and patients (The enhanced sensitivity to change of the proposed CCKS metrics suggests a potential use of these metrics for mobility impairments identification and fluctuation assessment, even in the early stages of the disease. Idiopathic Parkinson’s disease (PD) is a progressive neurodegenerative disease marked by the loss of neurons producing dopamine. Symptoms of PD include tremor, muscle rigidity, postural instability, akinesia (lack of movement), and bradykinesia (slowness of movement) . The abiMobility deficits have been traditionally studied and evaluated in motion laboratory, using advanced equipment such as camera-based optoelectronic devices –13. UsinOver the past decade, wearable inertial systems (IS) have emerged as an alternative to traditional motion-capture system for clinical applications. IS are composed of inertial measurement units (IMU) which include accelerometers, gyroscopes, and magnetometers to measure linear acceleration, angular velocity, and magnetic field, respectively. Nowadays, most IS also include a fusion algorithm which estimates the 3D orientation of the IMU, enabling the capture of motion. Recently, we proposed a measurement approach using measures of trunk and head motions captured with IS to identify cranio-caudal kinematic turn signature (CCKS) metrics . On healAssessment of the turn cranio-caudal kinematic signature refers to the characterization of the axial motion of the head relative to the trunk during the turn. Healthy individuals initiate a turn with the head, followed by the trunk and then the pelvis. The turn cranio-caudal movement can, therefore, be divided into two main phases: (i) the head moves away from the trunk, initiating the turn task; and (ii) the trunk engages into the turn closely followed by the pelvis, closing the gap with the head as the body realigns toward the new desired direction. Assessing the signature of that motion enables identification of different strategies and their related deficits.The proposed cranio-caudal signature analysis is a two-step process, as presented in Figure D: the amplitude of the command sent to the NMS,0: the time of occurrence of the command,tμ: the time delay of the NMS on a logarithmic scale,σ: the response time of the NMS on a logarithmic scale.Mathematical details for the derivation of the different sigma-lognormal parameters as well as further details on the cranio-caudal turn kinematic signature characterization method are available in Lebel et al. .ON medication, and the same patient OFF medication. The present study concentrates on differences in signature patterns to appraise the ability of the approach to discriminate between patients and healthy controls and to determine its sensitivity to change. Specifically, this study focusses on the variation of the maximum head to trunk angle and the amplitude of the NMS commands for both turn phases as these parameters have shown the highest reliability  aged between 55 and 83 years old and 15 OA diagnosed with Parkinson’s disease (PD), aged between 56 and 79 years old] were recruited from the community in collaboration with Quebec Parkinson Network. A description of the sample is available in Table OFF and ON states. OFF state was defined as a minimum delay of 10 h since their last medication (PDoff) while ON state corresponded to a minimum delay of 45 min after medication intake, when motor symptoms disappeared or were greatly reduced (PDon), as confirmed by the patients themselves.Participants performed repeated 10 m timed up-and-go (TUG) trials Figure A while oEach trial was manually segmented using a set of criteria defined in Lebel et al.  to isolaCranio-caudal signature assessment follows the process described in Figure For each participant and condition , the parameters mean was computed over the repeated trials. The maximum relative angle (H2Tmax) and the amplitude of the NMS command for both phases of the turn  were further analyzed to verify their potential to discriminate between populations  using a Wilcoxon–Mann–Whitney test and receiver operating characteristic (ROC) curves. The sensitivity to change of those same parameters was also evaluated , this time using a Wilcoxon signed-rank test. All statistical analysis considered a significance level of 0.05 and were conducted using SPSS . Due to the exploratory nature of the study, no correction for multiple comparison was considered.For comparison purposes, metrics based on raw inertial signals found in the literature, namely the number of steps required to perform the turn, the mean turn velocity, and the max turn velocity, were also computed for each trial. The number of steps is obtained through analysis of the accelerometers signals from the IMUs located on the feet. Briefly, the technique consists in using the norm of the accelerometer signal on which is applied an aggressive high-pass filter to remove most of the signal’s content, leaving only the impacts on the floor. The location of these impacts are then found using a peak detection algorithm. Quality control checks were performed periodically to ensure the accuracy of the results. The mean and max turn velocities correspond to the mean and the max recorded angular velocity of the trunk, in the plane of rotation.p = 0.041]. A similar behavior is also observed with both phase 1 and phase 2 NMS commands , as shown in Figures p = 0.014] while the turn mean and max velocities have shown a significant decrease .The study first aims at verifying the ability of the metrics to discriminate between healthy OA and early PD patients. The distribution of the cranio-caudal parameters value is, therefore, illustrated in Figure 11.9, 21., p = 0.0ON vs OFF medication. Analysis reveal a statistically significant improvement of the H2Tmax (p = 0.033) and the NMS command amplitudes  with medication , as shown in Figure Sensitivity to change of the metrics was then verified, comparing results from patients trials performed A previous study performed by our team had shown the ability of the proposed methodology to capture the turn cranio-caudal signature in asymptomatic elderly . The curThe signal processing technique used in the CCKS approach is partly based on the use of the sigma-lognormal model to provide insights into the NMS. Although well known to analyze movement in translation over a single segment, the CCKS is the first application to consider the model on a complex system  as well as on advanced orientation data. The interesting results reported in the original method paper as well as in the current manuscript reveal a potential for the model to be used in this new context. Furthermore, the methodology is based on inertial sensors, a technology that has the major advantage of being portable and relatively low-cost. Hence, the proposed cranio-caudal kinematic signature technique has the potential to be used in the clinic to enhance the accessibility to objective turn mobility assessment. Combined with autonomous activity identification and segmentation algorithms , the tecA limit to this study is the relatively small sample size. However, all patients recruited were in early stages of the disease to avoid extreme motor symptoms related to later stages of the disease. In other words, the CCKS was tested in the most stringent conditions since later stages of the disease would have probably exacerbated the motor deficits in the OFF condition, making it easier for our algorithms to detect them. Nevertheless, further validation of the metrics on a larger sample including a wider spectrum of symptoms is required to enable a clinical understanding of the variations in the metrics. Furthermore, the small sample size combined with the exploratory nature of the study has driven the statistical plan of analysis which does not include a correction for multiple comparison. Indeed, this approach was chosen in order to remain open-minded in the identification of the potential of CCKS metrics and avoid to inflate type-II error . Future The present study reveals a potential for CCKS to assess mobility impairments and medication state at initial stages of the disease. The wearable IS used in this study combined with the sensitivity to change of the CCKS metrics opens the possibility for this technic to be used as markers for disease progression or to assess impact of medication on mobility impairments.Participants gave their informed consent following the procedure approved by the Centre de Recherche de l’Institut Universitaire de Gériatrie de Montreal ethics board.KL developed the algorithm, designed the analysis, and drafted the manuscript. CD conceived the experiment, helped in data interpretation, and reviewed the paper. HN provided significant feedback on the analysis of the study and the manuscript. RP provided feedback on the use of the Sigma-Lognormal model and its interpretation and reviewed the manuscript. PB helped in the conception of the algorithm, the interpretation of the data, and reviewed the analysis and the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Pure graphene in the form of few-layer graphene (FLG) – 1 to 6 layers – is biocompatible and non-cytotoxic. This makes FLG an ideal material to incorporate into dental polymers to increase their strength and durability. It is well known that graphene has high mechanical strength and has been shown to enhance the mechanical, physical and chemical properties of biomaterials. However, for commercial applicability, methods to produce larger than lab-scale quantities of graphene are required. Here, we present a simple method to make large quantities of FLG starting with commercially available multi-layer graphene (MLG). This FLG material was then used to fabricate graphene dental-polymer composites. The resultant graphene-modified composites show that low concentrations of graphene (ca. 0.2 wt %) lead to enhanced performance improvement in physio-mechanical properties – the mean compressive strength increased by 27% and the mean compressive modulus increased by 22%. Herein we report a new, cheap and simple method to make large quantities of few-layer graphene which was then incorporated into a common dental polymer to fabricate graphene-composites which shows very promising mechanical properties. Now that much of the world’s population are living beyond their “threescore years and ten” , that isOne of the main problems facing dental-polymers is that of location. They are situated within the mouth which is an extremely demanding setting – exposure to moisture, high temperatures, and abrasion from toothbrushes plus a variety of foodstuffs all have to be dealt with. These conditions can lead to problems of mechanical failures cancelling out initial clinical success and over time requiring further work for restoration with the associated inconvenience and extra cost. Then there is the issue of biocompatibility to consider.Biocompatibility is a prerequisite for all dental materials. They must be compatible with oral fluids, must not release toxic products into the oral location and must have sufficient strength and durability to be fit for purpose . Most ot−1) provides a useful analysis for assessing the quality and number of layers in graphene materials [For the graphene material it was decided to use commercially available multi-layer graphene (MLG) from Graphit Kropfmühl GmbH (EXGR98350 - batch 08.10.2012). The shape and position of the Raman 2D band  ≈284.6 eV corresponds to C–H, C–C, (CH2)n and C=C bonds that are characteristic of graphite/graphene, ≈286 eV corresponds to C–O–C, ≈288.5 eV corresponds to O–C=O, ≈531.5–532 eV corresponds to C–O and ≈533 eV corresponds to C=O [2 during the heat-treatment. This is in accord with the Raman data which shows a clear “finger-print” for graphene rather than graphene oxide [The XPS analysis  shows ths to C=O . Therefone oxide –15.Six types of FLG-dental polymers were made up; one control plus five with different loadings of graphene. −1) which is indicative of FLG [The Raman spectra of both FLG-dental polymers show a 2D band  solutions containing graphene are shown in There was a progressive significant increase in the dynamic viscosity of the poly(acrylic acid) solutions as the concentration of graphene added to the poly(acrylic acid) solutions was increased. This increase in viscosity with increasing nano-carbon concentration is consistent with that found by other researchers –18. FurtThere was no significant trend in the compressive fracture strength data with increasing concentration of graphene added to the poly(acrylic acid) solutions as shown in For the compressive modulus data, there was no significant trend as the concentration of graphene added to the poly(acrylic acid) solutions was increased as shown in From the results of the mechanical testing it is clear that a small addition of FLG gives a large increase in the FLG-dental polymer fracture strength and compressive modulus. The latter is significant as it shows the capacity of the FLG-dental polymer to withstand loads tending to reduce in size – e.g., biting and chewing. The decrease in these enhanced properties with increasing FLG loading is probably due to aggregation of the FLG in the polymer matrix. Further optimisation tests are ongoing.In summary, we have described herein a new, simple and cheap method to make large quantities of FLG starting with commercially available multi-layer graphene (MLG) and also the incorporation of this graphene into dental polymer composites. We have demonstrated that the fabricated graphene-dental polymer composites have significantly enhanced mechanical properties as compared with the plain dental-polymer material (control group). The mean compressive strength of the graphene-dental polymer showed a 27% increase and the mean compressive modulus showed a 22% increase compared with the control group – this is a significant increase. A recent review  concludeThe multi-layer graphene (MLG) material used in this research was commercially available MLG - EXGR98350 (batch 08.10.2012) supplied by Graphit Kropfmühl GmbH . The MLG material was heated in air at 500 °C for 2 h to give the FLG material.Poly(acrylic acid) powder, 1.0 g, with an average molecular weight of 40000 was mixed with 2.5 mL of distilled water to give a concentration of 40%. Then five concentrations of FLG and these poly(acrylic acid) solutions were made up containing 0.5, 1.0, 2.0, 5.0 or 10.0 mg of FLG (All the poly(acrylic acid) solutions (A–E and control) were hand-mixed with a commercial glass-ionomer (GI) restorative powder  using a powder to liquid mixing ratio of 4:1 (g/g) as recommended by Voco GmbH. In each case 0.188 g of the poly(acrylic acid) solution was pipetted onto one end of a glass slab while 0.75 g of the Ionofil Molar powder was placed onto the opposite end. The GI powder was divided into two halves, the first half was hand-mixed with all the poly(acrylic acid) solution for 20 s using a stainless steel spatula, and then the remaining GI powder was added and mixed for a further 20 s.The viscosity of all the poly(acrylic acid) solutions was measured with a digital viscometer . The poly(acrylic acid) solution was pipetted into the inner chamber of a small sample adaptor attached to the viscometer and a spindle was inserted slowly into the chamber to avoid entrapping air bubbles in the poly(acrylic acid) solution. The spindle was rotated in the poly(acrylic acid) solution at 100 rpm until a constant viscosity reading was obtained and the dynamic viscosity (mPa·s) was recorded. In total, three viscosity measurements were taken for each of the poly(acrylic acid) solutions and the mean dynamic viscosity calculated.The compressive fracture strength was determined by preparing cylindrical specimens of 6.0 ± 0.1 mm height and 4.0 ± 0.1 mm diameter in accordance with ISO 9917-1  using a The mean diameter of each specimen was determined from three measurements taken using a digital micrometer accurate to 10 μm . The compressive fracture strength of each specimen was made by applying a compressive load to the long axis of the specimen at a cross-head speed of 1 mm/min using a tensile testing apparatus . In order to mimic the oral environment, wet filter paper was placed on the flat ends of the specimen prior to testing . The comFf was the load at fracture (N) and r the mean radius of the specimen (mm). The change in stress Δσ (MPa) and strain Δε generated in each specimen during compression testing was quantified using where F was the load (N), r the original mean radius of the specimen (mm), D the deflection undertaken by the specimen during testing (mm) and h the original height of the specimen (mm). Stress/strain plots were derived for each individual specimen and the compressive modulus (the ratio of stress to strain below the fracture limit) was determined by calculating the slope of the initial straight portion of the stress/strain plot prior to fracture [where fracture .p < 0.0001) and Tukey’s post-hoc tests of the compressive fracture strength data identified significant increases for all the groups containing FLG compared with the control group (p = 0.003). For the compressive modulus data, the one-way ANOVA (p = 0.0001) and Tukey’s post hoc tests also identified significant increases for all the groups containing FLG compared with the control group (p = 0.003).All data in The MLG and FLG material was characterized by Raman spectroscopy (Renishaw at 514 nm) and the AFM measurements were performed on a MultiMode V AFM (Veeco) in tapping mode under ambient conditions. RTESP silicon probes (Veeco) were used with a nominal tip radius of 10 nm and nominal spring constant of 40 N/m. Image processing was carried out using the Nanoscope software. The X-ray photoelectron spectroscopy (XPS) measurements were performed on a Theta Probe spectrometer  using monochromatic Al Kα radiation (photon energy of 15 keV with maximum energy resolution of 0.47 eV). High resolution spectra for the core level C 1s and O 1s were recorded in 0.05 eV steps. An electron flood gun was used during the measurements to prevent sample charging. The FLG material was also characterized by TEM, HRTEM (Jeol ARM at 80 kV) and helium ion microscopy . In addition, FLG-polymer A and E were characterized by Raman Spectroscopy (JY T6400 at 514 nm) and SEM .