Electrolytically tunable graphene “building blocks” for reconfigurable and optically transparent microwave surfaces and absorbers have been designed and fabricated by exploiting Deep Eutectic Solvents (DESs). DESs have been first explored as electrolytic and environmentally friendly media for tuning sheet resistance and Fermi level of graphene together with its microwave response . We consider the tunability of the reconfigurable surfaces in terms of transmittance, absorption and reflectance, respectively, over the X and Ku bands when the gate voltage is varied in the −1.4/+1.4 V range. The numerical simulations and experimental measurements also show the ability of the absorber, in the Salisbury screen configuration, to achieve near perfect absorption with a modulation of about 20%. These results could find applications in several technological fields, ranging from electromagnetic pollution to integrated multi-physical regulation systems, thereby helping the advance of the performance of microwave cloaking systems, stealth windows, frequency selective surfaces, modulators and polarizers. In this framework, one important aspect is related to the ability to manipulate and control reflection, transmission and absorption of microwave radiation in devices that are also optically transparent. In the literature, there are recent examples where attempts are made to achieve microwave absorption in optically transparent structures by means of several configurations based on metamaterials9, metasurfaces10, metallic meshes12, and Salisbury screens13. Recently, the possibility to integrate an optically transparent absorber with an acoustic absorber has also been reported14, leading to a multi-physical regulation system. These devices offer new functionalities, although they share a common limitation: they are “static” and their properties mainly relate to their geometry.The quest for optically transparent microwave devices has increased over the last years. This growing research interest is driven by the opportunity to combine photonic and microwave technologies, thus creating new applications17. Electrolytic gating allows the controlled switching from pristine (high Rs) to doped graphene (low Rs). This opens the possibility (for an optimized configuration) to switch from a microwave transparent window to an absorbing or reflecting one. However, the reported examples of microwave absorbers typically have configurations based on metallic and opaque surfaces. Thus, they are not transparent in the visible range. Moreover, electrolytic gating of graphene typically makes use of ionic liquids 19 which have several drawbacks in terms of cost and toxicity20. This strongly limits their potential applications in commercial devices.Up to now, few reconfigurable examples of microwave absorbers based on electrolyte-gated graphene have been proposed22. They have recently gained increasing attention, in particular in regard to metal-catalysis and organometallics23, energy technology24, electrochemistry25, and nanomaterials growth26, with surprising and unexpected results. In what follows, we demonstrate that DESs represent a valid, low-cost alternative to ionic liquids for realizing a graphene capacitor with a suitable electrochemical window. Specifically, we investigated the hydrophilic ChCl/Gly (1:2 mol/mol) eutectic mixture (melting point −35 °C) as the electrolytic medium. ChCl, also known as vitamin B4, is one of the most widely used ammonium salts extracted from biomass or synthesized from fossil reserves. Thus, it is a very cheap (ca. 2€ kg−1) and biodegradable material, and is produced on the scale of a million metric tonnes per year.In this paper, we take a step forward on the path towards innovative and reconfigurable “optically transparent” graphene-based devices, overcoming both limitations. We propose an optically transparent, flexible and reconfigurable microwave absorber using two main strategies/approaches: (i) an electrolyte-gated graphene capacitor exploiting a Deep Eutectic Solvents (DES) as electrolytic medium and (ii) a “quasi-metal” graphene microwave mirror. In particular, we first propose DESs as electrolytic media for tuning sheet resistance and Fermi level of graphene in order to fully control its microwave response . DESs, which share several physical-chemical properties with traditional ionic liquids , are biodegradable fluids usually made by mixing and gently heating two or three safe and inexpensive components. DES components, often solid compounds at room temperature, are able to interact with each other mainly through hydrogen-bonding interactions, thereby forming eutectic mixtures whose eutectic point temperature is far below those of the individual components. Common mixtures derive from a quaternary ammonium salt  and a neutral hydrogen-bond donor such as glycerol (Gly), urea and natural carboxylic acids. Because of their minimal ecological footprint, in the last few years DESs have been progressively replacing common and toxic volatile organic compounds in several fundamental and applied processes2 that allows the realization of graphene sheets with very low sheet resistance (down to less than 20 ohm/sq)27 that can be implemented as efficient microwave mirror 13.On the other hand, the realization of “quasi-metal” graphene microwave mirror takes advantage of the chemical protocol based on SOClWe thus show that microwave transmittance, reflectance and absorption of the graphene capacitor using the above ChCl-based eutectic mixture can be varied by about 24%, 10% and 15% over the X and Ku bands when an electrochemical window in the −1.4/+1.4 V range is considered. Finally, we numerically and experimentally prove that the DES-gated graphene capacitor can be integrated in a Salisbury screen configuration leading to near perfect absorption with a modulation of about 20%. These results may open the floodgates to unprecedented fully transparent devices for several applications ranging from multi-physics regulation, cloaking, to stealth and other systems.p-doped) and conduction band (n-doped), respectively.Figure The modulation range of graphene electrodes is determined by both graphene structural quality and electrolyte type. The specific electrochemical window of the electrolyte  defines the maximum charge density that can be injected in graphene. On the other side, the quality of graphene electrodes limits the minimum Rs value achievable within the electrochemical windows. We realized an electrolytic capacitor based on double-layer (2L) graphene electrodes. Figure The inset in Fig. D. A VD located at positive or negative voltages is indicative of an intrinsic p- or n-doping state. This intrinsic doping can result from graphene chemical defects and charge transfer from the substrate, the electrolytic medium and charged impurities adsorbed on graphene. The 2L electrode reaches the maximum resistivity value at −0.3 V. When a Vg equal to VD is applied, the Fermi Level is located at the Dirac point, and the material presents the minimum carrier concentration. Then, for Vg > VD or Vg < VD, the material becomes electrically n- or p-doped, respectively, and its Rs decreases. In the exploited electrochemical window (from −1.4 to 1.4 V), the 2L electrode, the Rs modulation range is shifted in the 1700-416 ohm/sq range with a modulation ratio around 4. It is worth noting that the electrochemical window is fixed in the −1.4 to 1.4 V range in order to avoid electrolyte oxidation or reduction at electrode surfaces.The voltage at which the resistivity reaches the maximum value is defined as Dirac voltage, V28.To assess the performance of graphene-base (or G-based) capacitor in the microwave range, we developed a 3D numerical model by means of Comsol-Multiphysics. Figure 20 mode). We set the permittivity and the thickness of the DES equal to 40 and 100 microns, respectively. The contribution of the PET that supports the graphene in the experiments is neglected since it is almost “transparent” in the frequency range of interest.We consider mono-modal propagation in the metallic rectangular waveguide and limit our analysis to the frequency range between 7 GHz and 13 GHz . These results fully confirm that the difference between the front and bottom electrodes is negligible and, hence, the fitted model of Equations 13. Figures 13. Therefore, we determined the absorption A = 1 − R (R = |S11|2) in both cases. Both numerical maps show that the absorption of the Salisbury screen reaches near perfect absorption when Vg = 0 V at about 8 GHz. As Vg increases, the absorption drops down by about 25% (to the detriment of the reflection). Experimental results reported in Fig. Finally, the proposed graphene-based capacitor was used to implement an optically transparent Salisbury screen configuration as sketched in Fig. Maximum absorption of about 97.80% and 99.98% is achieved for the graphene-based and metallic mirrors, respectively. When the absorption higher than 90% is considered, Fig. 28 allows us to extend these concepts to different microwave frequencies and bands.In this paper, we demonstrate the possibility to realize reconfigurable and optically transparent microwave absorbers. This goal was achieved by exploiting highly-doped graphene mirrors operating in the quasi-metallic region and DES-gated graphene capacitors. The combination of these two building blocks allowed us to realize reconfigurable (i) surfaces and (ii) absorbers. Numerical and experimental findings show the ability of these two devices to nearly fully control microwave transmittance, reflectance and absorption of graphene over the X and Ku bands. It is worth highlighting that the independent behaviour of the graphene in the microwave regionTherefore, these results are a mere first step towards innovative and reconfigurable, optically-transparent, graphene-based devices. The flexibility of the proposed surface on flexible substrates could be useful for several applications, such as cloaking and electromagnetic anti-pollution systems, modulators and polarizers. We believe these findings pave the way to conceive a plethora of innovative devices that can simultaneously work in the photonic and microwave domains.6 in the L-S-C-X microwave bands29. This is effectively enough to consider both single and few-layer graphene as an interface with a current sheet J . In turn, the microwave absorption only depends on the Rs of graphene sample rather than their thickness. Therefore, the front and the back electrodes were modelled by two surface currents (J =  σ * E) with different sheet resistance13. In particular, Rs values of both front and back electrodes were fitted by means of an asymmetric double sigmoidal function as follows  graphene sample is around 1 nm-thick that corresponds to ∼λ/100 = 428.32763, A = 1445.88832, xc = −0.19967, w1 = 0.80239 w2 = 0.1112, and w3 = 0.21377.where yg = 0 V. This assumption has been verified in the experimental section (“Results and discussion”).As is evident from Eqs  and 2),,2), it i4 and H2 as precursors. Copper substrate was etched in solution of ammonium persulfate and thermal tape was used for transferring graphene onto corning glass or PET substrates. SOCl2 chemical doping of multilayer-graphene on corning glass was performed in a dry chamber at 105 °C for 60 min (by repeating the same treatment after stacking supplementary graphene layer). Graphene sheet resistance was measured using a four-point contact geometry in the Van der Pauw configuration (5 × 5 mm2).Graphene was grown by chemical vapor deposition methodology on 25 μm thick copper foils at 1000 °C using CHThe eutectic mixture of ChCl/glycerol (1:2 mol/mol) was prepared by heating the corresponding individual components to 60 °C under stirring for 10 min until a clear solution was obtained.2 two-layer graphene foil on 120 µm thick PET foil. Conductive silver paste stripes were used as gate contact (bottom electrode) and source/drain contacts (front electrode). Silicone glue was used to electrically isolate the silver contacts and to seal capacitor. Ag contacts covered with silicone glue  act as spacers between the two graphene electrodes. Source and drain contacts with a broad surface area (width above 4 mm) were used in order to minimize contribution of contact resistance during measurements of graphene resistance. Rs of graphene electrode measured by Van der Pauw four-probe system resulted almost equal to Rs value derived by considering source/drain resistance and relative geometric factors. This attested the negligible contribution of contact resistance. Thus, Rs data of graphene electrode as a function of Vg (−1.4 < Vg < 1.4) were derived by source/drain resistance measurements (VSD = 100 mV).Graphene front and back electrodes consist of 45 * 45 mm


Scaffolds are physical substrates for cell attachments, proliferation, and differentiation, ultimately leading to tissue regeneration. Current literature validates tissue engineering as an emerging tool for bone regeneration. Three-dimensionally printed natural and synthetic biomaterials have been traditionally used for tissue engineering. In recent times, graphene and its derivatives are potentially employed for constructing bone tissue engineering scaffolds because of their osteogenic and regenerative properties. Graphene is a synthetic atomic layer of graphite with SP2 bonded carbon atoms that are arranged in a honeycomb lattice structure. Graphene can be combined with natural and synthetic biomaterials to enhance the osteogenic potential and mechanical strength of tissue engineering scaffolds. The objective of this review is to focus on the most recent studies that attempted to explore the salient features of graphene and its derivatives. Perhaps, a thorough understanding of the material science can potentiate researchers to use this novel substitute to enhance the osteogenic and biological properties of scaffold materials that are routinely used for bone tissue engineering. Tissue engineering utilizes the concept of scaffolding to regenerate the bone defects. The technique for addressing these defects that involves the reconstruction or regeneration of bone always desires a temporary porous scaffold. Bone defects that are caused by trauma, congenital malformations, or due to cancerous lesions can best be therapeutically managed by bone tissue engineering scaffolds. The ultimate aim of modern tissue engineering is to replace the traditional medical procedures involving the repair and regeneration of tissues with three-dimensional scaffolds. These scaffolds have a porous surface that serve as a medium, over which cells can grow rapidly and develop into tissues that are viable. The scaffolds with unique morphology and structural architecture encourage the cells to regenerate bone tissues of extra cellular matrix ,2. IdealThe polymeric scaffolds have excellent biocompatibility and biodegradability, but lack the ability to withstand the forces acting upon. In order to improve their mechanical strength, many researchers have incorporated graphene derivatives within the polymers. Besides enhancing the physical properties, the graphene derivatives also promote cell proliferation and differentiation, owing to their excellent biocompatibility under limited concentrations.Graphene is a single layer of aromatic carbon atoms that are arranged in a two-dimensional lattice ,18. Rese2 bonded carbon atoms arranged in honeycomb lattice structure. Boehm et al. described graphene in 1986 [Graphene is a synthetic atomic layer of graphite with SP in 1986 . In 2004 in 1986 ,22. Grap in 1986 ,26,27,28 in 1986  spans th in 1986  because  in 1986 ,32.Graphene oxide, aids in bone regeneration by enhancing the osteogenic differentiation of progenitor cells. This is accomplished by hydrophobic and electrostatic interactions with the proteins of the microenvironment ,33,34. GVarious biomaterials have been researched as scaffold materials for bone tissue engineering. Biocompatibility, biodegradability, and sufficient mechanical strength to withstand the forces acting upon are the three key factors to be considered for the selection of a scaffold . DependiNatural biomaterials that are used in bone tissue regeneration include proteins like silk, collagen, gelatin, fibrin, fibrinogen, elastin, keratin, actin, and myosin. On the other hand, polysaccharides, such as chitosan, hyaluronic acid, alginate, agarose, cellulose, amylose, dextran, chitin, and glycosaminoglycan’s; and, polynucleotides, like DNA, RNA, chitosan, hyaluronic acid, alginate, and agarose are also being utilized . The afoNishida et al.  coated cAnother study showed that the addition of graphene oxide or reduced graphene oxide to collagen scaffolds increased the tissue compatibility and bioactivity. In vivo studies showed that reduced graphene oxide is more bioactive than graphene oxide when coated on collagen scaffolds . DinescuNair et al.  incorporSynthetic polymers are the commonly used materials for tissue regeneration due to their porosity, quicker degradation time, and superior mechanical strength. They have advantages over natural polymers, like longer shelf-life, cost effectiveness, ability to be tailored to obtain desired shape by milling and printing, can quickly be mass produced under controlled conditions, possess better cell differentiation properties, pore characteristics, and mechanical properties . HoweverPolycaprolactone is a polymer with melting temperature of 60 °C and it is hydrophobic in nature . PolycapPolyvinyl alcohol is another synthetic biodegradable polymer that is soluble in water and hydrophilic in nature. Poly vinyl alcohol (PVA) is used in biomedical application combined with graphene oxide in the form of three-dimensionally printed scaffolds ,66. PolyWei et al.  producedAli et al.  preparedBioactive glass has been widely used in the field of bone tissue engineering because of its ability to form bioactive hydroxyapatite layer, thereby forming a strong bond between implant and the surrounding bone ,75. The Cheng et al.  combinedGraphene, a two-dimensional (2D) nanomaterial has set an enormous trend in research and development in the burgeoning field of biomedical application and bone tissue engineering. Despite their potentiality, very few researchers have attempted to use graphene in human stem cell research. Most of the studies that were done with graphene had focused on increasing the proliferation, adhesion, and growth of stem cells. There has to be a controlled proliferation and differentiation of the stem cells in order to attain successful bone regeneration. This can be achieved with the help of growth factors and osteogenic inducers . Human bLuo et al.  stated tThere are various factors to be considered in designing a scaffold for bone tissue engineering. Although some of the biomaterials that were previously used as a scaffold in clinical trials are available in the commercial market, the methodology and their applications are not always well-balanced. Graphene with its unique properties are potentially validated to be used as bone tissue engineering scaffolds. Research on the contribution of graphene derivatives to bone tissue engineering is still modern, and various studies are ongoing to understand them better. Numerous studies in stem cell research are being conducted in order to explore graphene for its osteogenic potential, and proliferation and differentiation of stem cells. Despite its advantages, graphene derivatives are subjected to few challenges. The toxicity of graphene at higher concentrations and non-biodegradable nature needs further investigations. The interaction of graphene with the biologic cells is yet to be further evaluated in depth. Literature should furnish a wide range of comparative studies in the future, between graphene and the other biomaterials before commercializing them in the market. Concurrently, many in vivo studies involving graphene needs to be tested to understand the exact metabolic pathways in which graphene interacts with the microenvironment and bone tissue regeneration. The success of bone regeneration depends on the proliferation of stem cells. The availability and affordability of graphene derivatives has led to the outcome of many researchers conducting studies to validate the proliferation and differentiation of stem cells by the incorporation of graphene derivatives. A remarkable aspect of graphene derivatives is that their chemical nature seems to act on the proliferation of stem cells, raising the possibility of favoring this process by modifying the chemical configuration. Cell-based bone tissue engineering requires a cell component from the appropriate origin that could be able to repair the target tissues and also a biocompatible material that provides a three-dimensional scaffold for the chosen cells. The ideal combination of cell and scaffold sources varies in relation to the target tissue to be created. Moreover, there have been recent advances in biomaterial synthesis and fabrication tools resulting in the creation of functional and bioactive scaffolds that stimulate different cell functions. Titanium and synthetic biomaterials are used for the reconstruction of lost bone tissues. Titanium is considered as a best suitable material for bone regeneration due to its mechanical strength and biocompatibility. Although titanium helps in better osseointegration, there are chances of development of fibrous tissues, which may lead to failure of implants. To overcome this drawback, graphene can be coated onto the surface of implants to enhance better osseointegration and bone formation. Although graphene enhances the bone formation, the long term success of graphene coated on to the implant surface is yet to be researched. Attempts had been made to use Graphene as a carrier for delivery of BMP-2 for better osseointegration. Nonetheless, the outcomes in clinical application are questionable. Graphene derivatives have been tried along with synthetic biomaterials and titanium for modular endoprosthesis in reconstruction of fractured and resected bone segments. Perhaps, studies are still in the early stages of in vitro analysis and in vivo experiments are yet to be conducted. Prospective in vitro and in vivo studies can be helpful to elucidate the full mechanisms of action of the actual available configurations of graphene-based scaffolds. Indeed, the foreseeable future can take advantage of this carbon material to be used as a promising scaffold for bone tissue engineering.


We report a unique constant phase element (CPE) behavior ( The electrolyte–graphene interface plays a critical role in many promising applications of graphene, such as supercapacitors ,2, biosenterface . Experimnterface  first menterface  and aquenterface ,11,12.These studies have revealed the voltage-dependence of the electrolyte–graphene interfacial capacitance; however, the measurements in most of these studies were performed at fixed frequencies, or within limited frequency ranges, thus failing to display the complexity of the capacitive behavior of the electrolyte–graphene interface. Typically, the liquid–solid interface does not behave as an ideal capacitor but is usually considered as a constant phase element (CPE), with the impedance ( follows :(1)Z=1Q0 reports ,14,15. I reports .In this work, we studied the frequency response of the electrolyte–graphene interface using electrochemical impedance spectroscopy (EIS), and revealed a unique CPE behavior of the electrolyte–graphene interface, showing both The schematic experimental setup in an electrode configuration is shown in The schematic experimental setup in a transistor configuration is depicted in The microscopic images of the graphene electrode and the graphene transistor are shown in the inset of f is the faradaic impedance, and Zw is the Warburg impedance, which is attributed to the diffusion-limited faradaic reaction. The fitting yields a CPE with −9 S·sα and α = 0.89 which corresponds to the capacitive regime with a phase shift of ~−80° in the frequency range of 100–1000 Hz. The results suggest that the electrolyte–-graphene interface behaves as a CPE rather than an ideal capacitor.We first studied the frequency response of the graphene electrode using EIS. −9 S·sα at 2 substrate and the defects in the graphene lattice, which could introduce residual carriers [Using the Randles circuit model, the impedance spectrum of the graphene electrode was analyzed at different gate voltages. To be consistent with the measured results in the transistor mode, in  reports ,8,10. Thcarriers . Howeverf and Zw can be removed leading to a simplified Rs-CPE circuit with the impedance calculated asThe Randles circuit model was shown to be well fitting to the impedance spectrum. However, it might also introduce uncertainties to the fitting result because a quite few fitting parameters were involved, and this could possibly lead to the observed The out-of-phase CQ=2eConsidering the series arrangement of the EDL capacitance  and . The expinset of b. The fi reports ,21. Comp (7) and . The expThe carrier mobility can be extracted based on the Drude model:acitance b. Based 2V−1s−1, for holes and electrons, respectively, and decreases when the carrier density is higher than ~1.5 × 1012 cm−2. The results suggest the transition of the scattering mechanism from the long-range Coulomb scattering  near the Dirac point to the short-range scattering, which is in agreement with the self-consistent theory [The sheet conductivity of graphene was calculated based on the transfer measurement of the electrolyte-gated graphene transistor after evaluating the access resistance shown in t theory . Our rest theory ,24, whicIn summary, we study the unique CPE behavior of the electrolyte–graphene interface with both


The excitement of graphene  has generated numerous procedures for the fabrication of graphene. Here we present a mini-review on a rather less known, but attractive, in situ means to fabricate graphene inside a transmission electron microscope (TEM). This is achieved in a conventional TEM (viz. no sophisticated specimen holders or microscopes are required) and takes advantage of inherent hydrocarbon contamination as a carbon source. Both catalyst free and single atom catalyst approaches are reviewed. An advantage of this technique is that not only can the growth process be imaged in situ, but this can also be achieved with atomic resolution. Moreover, in the future, one can anticipate such approaches enabling the growth of nano-materials with atomic precision. There are numerous routes with which to obtain graphene which include mechanical exfoliation ,3,4,5,6,−9 mbar), a gas molecules mean free path is ca. 40 km! [−7 mbar (HV) and thus while contaminant molecules in the chamber are reduced they are not removed. Moreover, in addition to contamination from the TEM vacuum chamber , the sample itself can introduce additional contamination and moreover, even if not, the sample itself can adsorb contaminants prior to insertion in the TEM. Specimen based contamination is considered the main contributor, in particular, for hydrocarbon contamination [High vacuum (HV) and ultra-high vacuum (UHV) systems by their nature are designed to, in essence, pump-for-nothing, viz. the goal is to have nothing, or at the very least as few as possible atoms and/or molecules. This in practice is hard to achieve as atoms and molecules tend to adsorb or stick to any surface they come in contact with. As one pumps or evacuates a vacuum chamber adsorbed material can desorb. This desorption can be accelerated by heating the surface. However, once material desorbs it has a very high probability of colliding with a chamber wall again as in a vacuum the mean free path of a gas atom/molecule is large. For example, in UHV  and the process becomes more relevant as the irradiating electron energy (Eo) decreases. It also depends on the bond type of the specimen or contaminant. Heating which also arises due to inelastic scattering occurs because electrons have similar mass and thus significant energy can be transferred leading to a local temperature rise. Heating increases with increasing electron current density and varies with the material’s thermal conductivity. Knock-on damage is an elastic scattering event between the irradiating electrons and the sample or contaminant atom nucleus. Since the event is elastic there is no change in the irradiating electrons energy, however, energy is transferred from the irradiating electrons since the electrons are deflected by the atom nucleus and so, to conserve energy and momentum, some energy must be transferred. This is akin to bremsstrahlung radiation, except here, the energy release is not in the form of an X-ray, rather energy transfers as momentum to the atom and can be sufficient to remove the atom itself, hence the term sputtering. The process depends on the incoming electron energy and knock-on damage threshold of the material.In terms of the electron sample interactions (scattering) at the sample, they can be classified into elastic and inelastic events. When an electron from the TEM electron beam undergoes an electrostatic deflection by the Coulomb field of an atom in the sample, this is referred to as elastic scattering. In the case of inelastic scattering, a Coulomb interaction of incoming electrons with electrons surrounding the atoms forming the specimen takes place. These processes are of course important for imaging and diffraction in electron microscopes . They caOf the published data there are two primary approaches to take advantage of (contaminant) hydrocarbon species inside a TEM column as a carbon feedstock for graphene synthesis driven by the electron beam. In the first process no catalyst is required, but can be considered a two-step process where initially carbonaceous material is formed through electron beam induced deposition, and then graphitized with further electron beam irradiation . In the second process, a catalyst  is used to presumably aid cracking (decomposition) of the hydrocarbon and growth of graphene. We first review the case of catalyst free grown graphene and then catalyst assisted growth of graphene. It is also worth pointing out at this stage that all the experiments reviewed here were conducted at room temperature, and calculations show that in all cases the temperature increase due to electron beam irradiation is negligible.2 carbon onions form  [As mentioned above in this graphene fabrication process, two steps are required . In the h other) ,39. The h other) . Howeverh other)  in whichh other) ,42,43.In summary, in this two-step process, amorphous carbon is first deposited by EBID in the STEM mode, and then graphitized through radiolysis reactions by the electron beam in the TEM mode.In the case of catalyst assisted growth of graphene from hydrocarbon contaminants inside a TEM, thus far, all reported cases were conducted at 80 kV in the high resolution TEM (HRTEM) mode. Chronologically, the first reported case was that in which a single Fe atom at a graphene edge would diffuse or move along the edge while under electron irradiation . The difA more recent study by Ta et al, explored Cr atoms at the open edge of graphene layers while under electron beam irradiation (80 kV) . Again tSuch studies are important to better comprehend single atom growth of graphene  and could lead to precision growth of nano-materials at the atomic scale.In this mini review we presented two primary routes in which contaminant molecules, in particular hydrocarbons, present inside a TEM can be used as a carbon source for in situ graphene synthesis driven by electron beam irradiation. Two primary approaches are presented. In the first, a two-step procedure is followed in which hydrocarbon contaminants are decomposed by the electron beam (in STEM mode) to form an amorphous carbon film  over a support. In the second step, the amorphous carbon is transformed to graphene layers parallel to the support surface by an electron beam in the TEM mode. This graphene synthesis procedure does not require a catalyst, while the second approach does, and implements a single metal atom catalyst for the graphitization process. In effect, a single metal atom (Fe or Cr) at an open edge graphene is able incorporate C atoms (growth) as it diffuses along the graphene edge.These studies are important in that they help us understand the growth of graphene at the atomic scale and also pave the way for techniques to study single atom catalysis. Such work can lead to atomically precise growth of 2D materials which could have important implications for the microelectronics industry. Moreover, it is conceivable that such work could be used for lateral hetero 2D materials, for example, stitching graphene into hBN.


Arabidopsis, some introns are longer than 10 kilo base pairs (bp) and others are predicted to be shorter than 10 bp. To identify the shortest intron in the genome, we analyzed the predicted introns in annotated version 10 of the Arabidopsis thaliana genome and found 103 predicted introns that are 30 bp or shorter, which make up only 0.08% of all introns in the genome. However, our own bioinformatics and experimental analyses found no evidence for the existence of these predicted introns. The predicted introns of 30–39 bp, 40–49 bp, and 50–59 bp in length are also rare and constitute only 0.07%, 0.2%, and 0.28% of all introns in the genome, respectively. An analysis of 30 predicted introns 31–59 bp long verified two in this range, both of which were 59 bp long. Thus, this study suggests that there is a limit to how small introns in A. thaliana can be, which is useful for the understanding of the evolution and processing of small introns in plants in general.Most eukaryotic genes contain introns, which are noncoding sequences that are removed during premRNA processing. Introns are usually preserved across evolutionary time. However, the sizes of introns vary greatly. In  Introns are important features of eukaryotic genes. They are usually noncoding sequences in the gene and have to be removed from the premRNA . The bouArabidopsis .The plant materials used in this study were Columbia-0 (Col-0) ecotype Arabidopsis was obtained from the TAIR website . The detailed structure information on individual genes was also searched and checked manually on the TAIR website. Gene expression levels at different developmental stages were checked by looking up the microarray data  and calculated manually one by one.For RT-PCR analysis, mRNA was first reverse transcribed with the RevertAid First Strand cDNA Synthesis Kit . cDNA was amplified with the corresponding primers  online bArabidopsis genome and our previous analysis , some of these 103 very small introns were removed, leaving only 71. The distribution of their lengths is shown in According to the new version of the annotated http://jsp.weigelworld.org/expviz/expviz.jsp; last accessed September 11, 2018). In the beginning, we amplified the genes with relatively high expression levels, then analyzed the genes with a lower expression level and those with expression close to the basal level. A few of the genes had multiple bands  and S28 (AT3G23080.2-4) were proven to be true intron. At 59 bp each, they are the smallest introns found in this study.Although almost all of the very small introns were not confirmed, we found some introns that are also relatively very small. For example, in the analysis of the predicted intron AT1G71280.1-2, we used cDNA sequencing to confirm that the control intron AT1G71280.1-1 is 66 bp  and the Arabidopsis in order to find its smallest introns, and found 103 predicted introns that were 30 bp or smaller in the TAIR10 annotation and 71 in the Araport11 annotation. We narrowed these predicted introns into 48 likely candidates and a further RT-PCR analysis amplified cDNA fragments from 31 genes and genomic DNA fragments from 17 genes. However, we found no evidence that any of these candidates actually were introns. A further analysis of 30 selected introns between 30 bp and 60 bp finally verified two small introns of 59 bp.We analyzed the small introns in the genome of Arabidopsis was sequenced and annotated at very high quality, it is not error free. Arabidopsis is a higher plant and its genome is ∼130 Mb in size, making it one of the smallest reported plant genomes (Arabidopsis, suggesting the genome is still complicated (Although the genome of  genomes . More thplicated . Many ofArabidopsis genome, and this provides some useful insights into the smallest introns in plants as a whole. Introns may retract by DNA deletion, but they are usually preserved during evolution. There is probably a lower limit of the size of introns, but 30 bp seems to be too small. There are several hundreds of predicted introns with sizes from 30 to 60 bp, and these also constitute a very small percentage of the total introns in the genome. The rarity of these predicted introns 30–60 bps long in combination with our results puts doubt on their existence. A further analysis of 30 selected introns in this range only verified two introns of 59 bp, and the true smallest introns in the Arabidopsis genome are probably close to this size. That there are many more introns 60–69 bp than 50–59 bp long (Our data suggest introns of 30 bp or smaller seem to not exist in the  bp long  also supH.G. and W.C. designed the study; W.C., Y.Z., and X.M. carried out the experiments; W.C., Y.Z., X.M., and H.G. analyzed the data; W.C., C.A., and H.G. prepared the manuscript.Supplementary DataClick here for additional data file.


Without compounding with magnetic materials or conductive polymers, Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.Graphene has shown great potential in microwave absorption (MA) owing to its high surface area, low density, tunable electrical conductivity and good chemical stability. To fully realize grapheneʼs MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers (Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth (reflection loss ≤ −10 dB) reaches 5.59 GHz and the minimum reflection loss is up to −42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content (10 wt%) and low density (40–50 mg cmThe online version of this article (10.1007/s40820-017-0179-8) contains supplementary material, which is available to authorized users. Graphene microflowers (Gmfs) for outstanding microwave absorption performance are produced via a three-step protocol.The porous Gmfs show a broad efficient absorption bandwidth of 5.59 GHz with a minimum reflection loss of −42.9 dB, outperforming most graphene-based materials ever reported.−3) of Gmfs are favorable for their practical applications.The mass productivity, low filler content (10%) and low density  of −30 dB. Feng et al. [2O4 with SiO2 and RGO, which exhibited an EAB of 6 GHz and a minimum RL of -43.9 dB. However, no attention has been paid to the microstructure design of individual graphene, which might have a great impact upon the MA performance. Compared with layered structure, folded graphene assemblies with high porosity can induce the multi-reflection loss of microwave [MA materials can be classified into magnetic, dielectric and electric conductive categories according to the absorption mechanisms , 7, 8. Treported –12. In sreported , 14. Amoreported –18. Unforeported  reportedreported –22 reporreported  designedg et al.  coated Zicrowave .2 g−1 and a low density of 40–50 mg cm−3. The maximum EAB reaches 5.59 GHz and the minimum RL is up to -42.9 dB, which is higher than pure graphene fillers and most graphene-based materials in the literature. Moreover, the low filler content (10 wt%) indicates high cost efficiency, benefiting practical applications. The excellent MA ability of Gmfs is attributed to the skeleton microstructure, which can not only promote the attenuation of microwave by multi-reflection between graphene layers, but also favor the formation of conductive network.Herein, we fabricated porous Gmfs powder with high MA performance. Folded graphene sheets assemble together into flower-shaped microparticles, forming a skeleton structure with a high surface area of 230 mhttp://www.gaoxitech.com/). All reagents were purchased from Sinopharm from Chemical Reagent Co., Ltd., and used as received. Commercialized graphene powder (CG) was purchased from Asfour (http://www.asfour.com.tw/).Aqueous suspension of single-layer graphene oxide (GO) with a thickness of 0.8 nm and average lateral sizes of 40–50 μm was commercially available from Gaoxitech  was prepared via a spray-drying procedure. The obtained 4 mg gOne gram of fGO was sealed in a glass pot with the addition of 5 drops of hydrazine. The glass pot was kept in the 80 °C oven for 12 h. The obtained reduced fGO turned from yellow to black. Afterward, the reduced fGO was annealed in the tube furnace. The temperature increased from room temperature to 1300 °C in 160 min and kept under that temperature for 1 h to get Gmfs. The protective gas was nitrogen.CG was annealed in a tube furnace, following the same procedure of fGO.−1 heating rate under nitrogen atmosphere. All samples were heated under 120 °C for 15 min to remove the residual water.The morphologies of the samples were obtained from a Hitachi S4800 field emission scanning electron microscopy (SEM) system. High-resolution transmission electron microscopy (HRTEM) images were collected on a JEM-2010 HRTEM with an accelerating voltage of 120 kV. Nitrogen cryoadsorption was measured on AUTOSORB-IQ-MP . All samples were outgassed under 120 °C for 1 h. Raman spectra were recorded on a Labram HRUV spectrometer operating at 514 nm. X-ray diffraction (XRD) pattern was measured with an X’Pert Pro  diffractometer using monochromatic Cu Kα radiation (λ = 1.5406 Å) at 40 kV. X-ray photoelectron spectroscopy (XPS) studies were carried out using a PHI 5000C ESCA system operated at 14.0 kV. All binding energies were referenced to the C 1s neutral carbon peak at 284.8 eV. Thermogravimetric analyzer  was performed from room temperature to 850 at 10 °C minRL of microwave can be calculated as follows:Zin refers to the normalized input impedance of a metal-backed microwave absorbing layer, μr and εr represent the complex permeability and complex permittivity, respectively, f is the frequency of microwaves, d is the thickness of the absorber and c is the velocity of light in free space.The complex permittivity was tested via a coaxial line method. Gmfs and CG were mixed with paraffin under different filler contents and shaped as cylindrical toroidal specimens with an outer diameter of 7.0 mm, inner diameter of 3.04 mm and thickness of 4.0 mm. The preparation of the composites was conducted by simply mixing melt paraffin and the fillers with a glass stick. The parameters were obtained from the vector network analyzer. The complex permeability was considered to be that of free space since no ferromagnetic materials were involved. The δ ∝ (φ − φc)t [φc is the percolation volume fraction and t is the critical exponent. φc can be obtained by fitting the logδ–φ curves. The further fitting of logδ versus log(φ − φc) gives t. The transformation between φ and weight fraction (w) follows: φ = wρm/(wρm + ρf), where ρm and ρf are the density of matrix and filler, respectively. Here ρm is the density of paraffin (0.9 g cm−3) and ρf is the density of graphene (2.2 g cm−3).The conductivities of all samples were measured on an electrochemical workstation . According to the percolation theory, the electric conductivity follows the power law:  φc)t , where φAs illustrated in Fig. −3  surface area analysis. The absorption/desorption curves and corresponding pore size distributions are shown in Fig. eak Fig. b. The CG−1) and G band (1580 cm−1), respectively [sp3 carbon in graphene, and G band is related to the graphitic sp2 structure. The intensity ratio of the D and G peak is widely used as a metric of disorder in graphene [ID/IG in Gmfs (0.96) demonstrates a more disordered structure compared with CG (ID/IG = 0.14). Such disorder comes from the defects and functional groups left by the reduction in fGO. XRD pattern of Gmfs has one main peak at 26.1°, corresponding to (002) plane . The XPS patterns of Gmfs and CG show little difference, and the element content of CG is similar with that of Gmfs (95.3% carbon and 4.6% oxygen). From the TGA plots, we find that there is negligible weight loss in Gmfs and CG even under 800 °C . Therefore, the chemical compositions of Gmfs and CG are nearly identical, attributing to the 1300 °C treatment on both materials. The reduction in GO recovers the graphitic structure of graphene and increases the electrical conductivity, benefiting the microwave attenuation. The defects in Gmfs enhance the polarization effect, which may increase the MA ability.In order to examine the MA performances of Gmfs, paraffin was selected to make composites for test due to the good processibility and nearly zero reflection loss of microwave. Gmfs can be compounded with paraffin homogeneously without obvious aggregation or precipitation. As shown in Fig. S5a, b, the small crumpled areas in dark color, representing the embedded Gmfs, distribute uniformly on the fracture surface. CG can also form a uniform composite with paraffin, with some graphene flakes stick out from the cross section . Furthermore, paraffin was dissolved by petroleum ether to evaluate the influence of compounding on the structure of filler materials. It is illustrated that Gmfs keep the flowerlike shape with folded surface after paraffin was washed, and CG is still in multilayered structure . Therefore, the influence of compounding on microstructures of the graphene fillers is negligible.ε) was tested via a coaxial line method. Since there are no magnetic materials in Gmfs, CG or paraffin, the permeability can be regarded as 1. The real parts (ε′) and the imaginary parts (ε″) of all samples were obtained in the frequency range of 2–18 GHz. As demonstrated in Figs. ε′ and ε″ decrease with increasing frequency, attributing to the dielectric relaxation [ε′ and ε″ increase with the increment of filler content owing to the enhanced polarization and electric conductivity. However, the introduction of Gmfs results in a lower increment in complex permeability compared with CG. We calculated the average ε′ and ε″ in the frequency range of 8–18 GHz, as summarized in Table ε′ and ε″ of 3 wt% Gmfs/paraffin are in close proximity with those of 3 wt% CG/paraffin. With filling ratio increasing, the ε′ of Gmfs/paraffin becomes significantly lower than CG/paraffin. 8 wt% CG/paraffin shows a ε′ of 6.96 that is even higher than 10 wt% Gmfs/paraffin. The ε″ of Gmfs/paraffin under different filler contents is also lower, except for 8 wt%. For the filler content of 11%, the ε′ and ε″ of Gmfs/paraffin are 7.56 and 5.44, much lower than those of CG/paraffin. The complex permittivity of carbon materials is determined by the graphitization degree and microstructure [ε′ and ε″ of Gmfs can be ascribed to the defective porous structure, which will be further discussed below. It is well known that ε′ represents the storage capability of the incident electric energy, while ε″ influences the dissipation ability based on electromagnetic theory [ε′ and ε″ are low. In contrast, overhigh ε′ and ε″ lead to the mismatch between air and sample interface. Therefore, the complex permittivity must be optimized to obtain best MA performance.The relative complex permittivity  of Gmfs/paraffin and CG/paraffin was compared, as shown in Fig. ε′ and ε″. The enhanced tangent loss with lower complex permittivity can be attributed to the defective porous microstructure of Gmfs. The reduction in fGO leaves functional groups and defects, which improve the polarization and adjust the conductivity, leading to lower ε′ and ε″. The skeleton structure generates high surface area, which favors the formation of conductive network and multi-reflection loss. In consequence, Gmfs feature high tangent loss with rational ε′ and ε″. It is generally accepted that tangent loss represents the capability of converting microwave to other forms of energy. High tangent loss is beneficial for MA, while high values of ε′ and ε″ are harmful for impedance match. The perfect combination of high tangent loss and reasonable complex permittivity in Gmfs/paraffin gives rise to the high EAB and RL values. Based on the transmission line theory, we can calculate the rational range of ε′ and ε″ by setting the thickness as 2 mm [ε′ and ε″ in 13, 15, and 18 GHz, respectively. RL is below -10 dB when ε′ and ε″ under corresponding frequency fall into these circles. The complex permittivities of Gmfs/paraffin are in all three circles, indicating the EAB values are below -10 in 13–18 GHz and the EAB is broader than 5 GHz. For CG/paraffin, the complex permittivities are out of the circles of 13 and 18 GHz, leading to a narrow EAB.In order to reveal the MA mechanism, the tangent loss , high specific surface area (230 m2 g−1) and low filler content (10 wt%) are beneficial to the demands in lightweight and cost reduction. Besides, the facile processing and scalable production of Gmfs are more favorable for practical applications compared with other graphene materials, such as graphene aerogel and graphene composites. Our findings open the way for preparation of high-performance MA materials by rational designing the porous structure.We developed a novel strategy to assemble graphene into a highly porous structure, resembling microflowers. The obtained GO dispersion was spray-dried into fGO, followed by chemical reduction and thermal reduction to obtain Gmfs with skeleton microstructure. The combination of porosity and disorder in Gmf gives rise to a broad EAB of 5.59 GHz with a minimum RL of −42.9 dB, which is much higher than those of CG and most graphene-based materials in the literature. The low density Below is the link to the electronic supplementary material.


To the best of our knowledge, such an observation reports the clearest conductance quantization in physically etched graphene nanoconstrictions. The fabrication of such high quality systems and the scalability of the cryo-etching method opens a novel promising possibility of producing more complex truly-ballistic devices based on graphene.We report on a novel implementation of the cryo-etching method, which enabled us to fabricate low-roughness hBN-encapsulated graphene nanoconstrictions with unprecedented control of the structure edges; the typical edge roughness is on the order of a few nanometers. We characterized the system by atomic force microscopy and used the measured parameters of the edge geometry in numerical simulations of the system conductance, which agree quantitatively with our low temperature transport measurements. The quality of our devices is confirmed by the observation of well defined quantized 2 It has been demonstrated that the charge mobility can increase by several orders of magnitude in these structures. However, a fully-tunable electronic confinement of charge carriers in graphene, that has been pursued since its discovery2, is still remaining challenging. It turned out that edge imperfections of graphene based systems are so detrimental for the ballistic charge transport that observations of the quantized conductance even in the simplest nanostructures, such as a nanoconstriction (NC), was problematic.Graphene stands out as one of the most promising 2D materials for electronic applications. Initial problems related to the low charge carrier mobility, which were typical for the first standalone graphene samples, have been successfully resolved. For example, it has been demonstrated that the charge mobility can increase by several orders of magnitude by encapsulating graphene between thin layers of diverse 2D materials, such as hexaboron-nitride (hBN)e2/h or 4e2/h spaced conductance plateaus4, the latter has turned into an arduous technological challenge and yielded less clear evidence of quantized conductance. For example, the first mechanically defined NCs were made of graphene deposited directly onto silicon dioxide wafers5. Conductance steps in those systems appeared to be at least an order of magnitude lower than the conductance quantum 2e2/h7, which could be caused by a plethora of different effects such as the Coulomb blockade, high electron back scattering and localization by disorder or charging effects, or by intrinsically low mobility of carriers. Recently, Tombros et al.8 observed 2e2/h steps of conductance in a high mobility constriction produced by current annealing of suspended graphene flakes. The nanostructure was fabricated by passing high electric current through a suspended graphene flake which was deforming into a NC-like structure. The main limitation of the method is purely technological: accurate control of the dimensions of the graphene NC is difficult to attain and, therefore, such nanostructures are not easily reproducible.Up to now, manifestations of conductance quantization have been observed in nanoscopic channels created by either electrostatic gating or by methods that change the geometry of the sample, such as mechanical or chemical etching. While the former electrostatic approach showed promising results with well defined 29. However, the conductance quatization in such devices based on intercalated graphene was reported to manifest itself in the form of kinks11. Well-defined conductance plateaus could not be observed because of the roughness of the heterostructure’s edges and the planar structure itself (the latter resulting from the intrinsic dielectric behavior of the hBN films). These problems were partially overcome by fabricating NCs from exfoliated graphene on hydrophobic silicon oxide substrates with the use of hexamethyldisilazane (HMDS)13. This method led to a substantial increase of the charge mobility which also remained high for a long period of time (~96 h). Quantized conductance at zero magnetic field was also observed in refs13, but only in the form of kinks, suggesting that the edge definition and roughness control was not sufficiently high. In this contribution we propose a novel cryo-etching method theat enables us to overcome the above mentioned problems and fabricate nanoconstrictions with both very high charge carrier mobility and unprecedented quality of the structure edges.On the other hand, encapsulation of graphene between lattice-matched hBN allowed for the fabrication of reproducible high mobility devices14, and generate samples with a high aspect ratio and cleaning15 in nanometric-size structures16. The extension of the cryo-etching technique to graphene allowed us to create NCs with very low sidewall roughness, as proved by atomic force microscopy (AFM) measurements. AFM micrographs were employed to assess the profile of the sample edges, that were later used as input in numerical simulations. We found an excellent agreement between the measured and calculated electrical conductivity and a good correspondence to the theoretical prediction.In this work we present the fabrication method and characterization of NCs on quasi-2D encapsulated graphene where a cryo-etching technique, commonly applied for bulk three-dimensional materials, has been used to achieve an unprecedented control of the edge-definition. This technique was already successfully implemented in silicon-based devices, where it was possible to control and define low-roughness sidewalls, observe the absence of sidewall scalloping10. To the best of our knowledge, this is the first time that a cryo-etching method is successfully used for the definition of graphene nanostructures.We focus the attention on a hBN/graphene/hBN constriction of a few hundreds of width. The constrictions were defined using the innovative cryo-etching process in graphene-based structures in the third aligned EBL step  is colored in blue. A standard 4–probe configuration to perform the electronic characterization at low-temperatures is sketched in the figure, where a pseudo-dc (13) current of 5 nA was injected/collected from the outer contacts while the voltage drop was measured by an in-phase lock-in preamplifier closer to the constriction (the contacts are colored yellow for clarity). The result of a typical measurement at T = 3.1K is depicted in Fig. e2/h is displayed as a function of the normalized back-gate voltage G = 1/R. In our sample the hole-side region (ΔVg < 0V) is always better resolved than the electron one (ΔVg > 0V), where the ballistic behaviour starts at higher back-gate voltage due to the residual charge density. For this reason, in the main text we restrict our discussion to the hole-side  measured at T = 3.1K (red line) and the conductance obtained from our tight-binding simulations (blue line) with the same edge roughness obtained from the AFM measurements . Figure see Fig. .Figure 3lm is larger than the GNC length L = 206 nm, transport is ballistic. We have estimated from the carrier mobility of our GNC that lm > 1 μm  showing a linear dependence of WkFt is the transmission parameter, being t = 1 for the ideal ballistic transport.In the low-temperature regime, when the elastic mean free path WkF above a threshold value 21, while the experimental conductance increases monotonically because temperature is not low enough to reveal this phenomenon. From the normalized gate voltage ΔVg we can obtain the carrier density n and therefore the Fermi wavenumber n0 ~ 3.3 × 1010 cm−2 experimentally, and accordingly WkF could not be tuned below a threshold value t is estimated from the linear fit of the conductance when t ~ 0.9. This value is close to the fully transmitted carrier regime t = 1, in contrast to the estimation t~0.6 given in ref.10 for a graphene NC with a comparable width W = 230 nm that was not defined by cryo-etching. For the electron-side  and the dimensionless transconductance dG/d(WkF) (blue line) versus WkF are shown in Fig. WkF, corresponding to equally-spaced minima in the transconductance. The quantization of G is also very clear after reverting the direction of the current , where the curves have been horizontally shifted by a factor of 2.5WkF for clarity. The presence of the plateaus is clear and they are noticeably visible below T ~ 10K. They start to smear out at higher temperatures until they are completely washed out at T = 25K. Such a temperature dependence of G can be better studied by inspecting the dimensionless transconductance as presented in Fig. WkF decreases by increasing temperature and finally disappears above T = 15K. A similar threshold temperature for the vanishing of the conductance quantization was very recently found in bilayer graphene constrictions23. This behavior differs markedly from other non-desired effects in diffusive regime, such as localized charge carriers, that disappear at higher temperature or other effects that appear also in ballistic graphene quantum point contacts as Fabry-Pérot oscillations24.A closer inspection of the conductance t~0.9 and the size quantization is clearly manifesting itself as a ladder of several 2e2/h-spaced plateaus of conductance at temperatures up to T = 10K, confirming the high quality of the samples. On the other hand, our fabrication method also proves to be scalable. Nanoconstrictions are the simplest model systems which can be viewed as building blocks for more sophisticated devices. We argue therefore that the proposed cryo-etching technique paves the way for the fabrication of more complex graphene-based nanostructured prototypical devices with truly ballistic transport of high-mobility carriers.In summary, we have proposed a novel implementation of the cryo-etching method, which we used for fabrication of high quality hBN-encapsulated graphene nanoconstrictions. The main advantage of the method is an unprecedented control of the edge definition and reduced roughness. The latter enabled us to fabricate high-mobility graphene nanoconstrictions with well defined, sharp and extraordinarily smooth edges. These systems have been characterized by the standard AFM imaging techniques and then the obtained data were used in large scale transport simulations. Results of such modelling agree very well with our experimental low-temperature measurements and suggest that the transport in the system is almost fully ballistic. In particular, both the predicted and measured values of the transmission parameter are as high as 2, P = 1100 mTorr) for 3 minutes for the exfoliation of large graphene flakes. This treatment was not necessary for hBN exfoliation. Graphite and hBN crystals deposited on the tape were attached to the silicon oxide substrate and subsequently heated to 100 °C for 2 minutes. Finally the tape is gently removed and graphene and hBN flakes are identified by optical microscope then by Raman spectroscopy.The fabrication process started from the exfoliation of graphene and hBN on 290 nm silicon oxide thermally grown on a 4 inch Si wafer. Graphene flakes were obtained from natural graphite crystals  and hBN flakes were obtained from hBN crystals (HQ graphene). Graphite crystals were mechanically exfoliated with Magic Scotch Tape and hBN crystals were exfoliated with Ultron Silicone-Free tape B . Wafers were cleaned previously with acetone followed by 2-propanol. Wafers were treated with a oxygen plasma cleaner process  with output power 100 mW and attenuated down to 10 mW with a spot size of 1 μm. A diffraction grating of 600 g/mm was used to provide a frequency shift resolution of 2 cm−1  polymer (12% in anisole) and spin coated on a PDMS thick layer . PDMS was treated before in a oxygen plasma for 3 minutes . Areas free of impurities and bubbles in the graphene heterostructures were selected by inspecting with Raman spectrometer.hBN/graphene/hBN heterostructures were obtained by dry transfer technique, similar to the one reported by Pizzocchero A bar was defined on the graphene heterostructure with electron beam lithography (EBL), using polymethylmethacrylate (PMMA) as a mask. A standard cleaning process and a rapid thermal annealing was performed at 350 °C in Ar atmosphere for 15 minutes to remove eventual small non-visible bubbles and the PMMA remnant. The next steps were a second EBL for the contacts definition and an evaporation of Cr/Au = 5/45 nm with electron beam evaporator. Finally, a self-aligned EBL was performed to define the nanoconstriction mask. The concentration of PMMA in chlorobenzene used depends on the fabrication step: 4% for the mask of the first etching and contacts definition, 2% for the constriction definition.side contacts is obtained by a dry etching processing in induced coupled plasma (Plasma Pro Cobra 100) with SF6 atmosphere (40 sccm), P = 6 mTorr, P = 75 W at 20 °C. We found a typical etching rate of 2–3 nm/s.The etching for the 6 (10/40 sccm) atmosphere at P = 6 mtorr for 18 s, P = 75 W. The use of cryo temperatures and Ar allows us to obtain GNCs with very low roughness as shown in the SI. Ar gas, instead of the more common O2 gas for a cryoecthing recipe, reduces the possibility of passivation to a minimum. The etching rate of the cryoecthing recipe is 2 nm/s. A polymethylmethacrylate (PMMA) was employed as a mask on this step.Nanoconstrictions were defined by cryo-etching process with a third EBL step, which was performed at −110 °C in a controlled Ar/SF26.The AFM measurements of the graphene NC were performed with a Nanotech AFM instrument controlled by Dulcinea system, operating in contact mode and equipped with silicon cantilevers. The images and line profiles were analyzed by Igor Pro and WSxM softwareπ electrons, i〉 is the atomic orbital of the i-th carbon atom27. The corresponding orbital energy level is set as the origin of energy without losing generality. Here tij stands for the hopping energy parameter between orbitals of the i-th and j-th carbon atoms and has been set to be constant between nearest-neighbor atoms  and zero otherwise. Such approximation provides reliable results near the K and K' points of the Brillouin zone, as already reported in ref.29.The electronic properties of graphene close to Dirac point can be accurately described by a tight-binding Hamiltonian for 31 and electron-electron32 interactions in our calculations, we consider electrons in the fully coherent regime, hence with ballistic motion through the whole device. Combining the quantum transmitting boundary method, based on a finite element approximation33, and an effective transfer matrix method adapted for graphene , the wave function in the whole sample and the transmission coefficient τn(E) for each mode n at an energy E is calculated. These modes, also known as channels or subbands, arise from the transverse quantization due to the lateral confinement at the leads35. According to the Buttiker-Landauer formalism35, at very low temperature the electrical conductance is proportional to the transmission coefficient at the Fermi energy EFn runs over the transverse modes. The factor of 2 accounts for the spin degeneracy whereas the valleys are considered explicitly in our tight-binding calculation of the transmission coefficient τn. As the NC becomes wider, the number of transverse modes for a given energy increases and so does the conductance. But interestingly, we found that the main features are essentially the same provided that the conductance is plotted against WkF, where kF is the Fermi wavenumber and W is the NC width. This has an important practical consequence, namely we can extrapolate results to much larger systems than the ones fabricated experimentally and otherwise computationally very expensive (or even impossible) to simulate.Neglecting electron-phononSuplemen tary infrormation file


Graphene is promising for developing soft and flexible electronic skin. However, technologies for graphene processing is still at an early stage, which limits the applications of graphene in advanced electronics. Laser processing technologies permits mask-free and chemical-free patterning of graphene, revealing the potential for developing graphene-based electronics. In this minireview, we overviewed and summarized the recent progresses of laser enabled graphene-based electronic skins. Two typical strategies, laser reduction of graphene oxide (GO) and laser induced graphene (LIG) on polyimide (PI), have been introduced toward the fabrication of graphene electronic skins. The advancement of laser processing technology would push forward the rapid progress of graphene electronic skin. As an ultrathin carbon material, graphene that features high conductivity, flexibility, transparency, bio-compatibility, and mechanical robustness have revealed great potential for developing soft and flexible electronics, especially, electronic skins  is able to trigger the deoxygenation of GO through the photochemical way  Based on LRGO or LIG, various graphene-based electronic skins have been developed. Taking advantage of the laser direct writing technologies, the properties of graphene-based electronic skin can be tuned by laser power, scanning paths, and scanning speeds. The resulted porous and patterned graphene is helpful for design of graphene-based electronic skin. In this section, we will briefly summarize some typical applications of LRGO and LIG in electronic skins.via laser direct writing technologies, which can detect the wet tip by the distribution of ΔZ/Z0. Moreover, the response and recovery time can be tailored by the OCGs contents of LRGO (Guo et al., An et al. fabricated all-graphene based non-contact moisture-responsive electronic skin matrix (An et al., via single-step and selective laser writing (An et al., An et al. produced LRGO-ZnO composites-based UV detectors Wang et al. fabricated strain sensors based on the self-locked overlapping LRGO sheets (Wang et al., −1 in the range from 0 to 50 kPa (Tian et al., Tian et al. developed graphene-based resistive pressure sensor with a sensitivity of 0.96 kPaTemperature response is another function of skin (Harada et al., Tao et al. reported an LIG-based intelligent artificial throat (Tao et al., Here, we have summarized two promising protocols for preparation and processing of graphene, LRGO and LIG. Taking advantage of the programmable processing manner of laser technologies, mask-free and chemical free patterning of graphene can be realized, revealing great potential for developing graphene-based electronic skins. The processing efficiency of laser fabrication is actually the key of large-scale applications. And the processing efficiency remains to be improved by spatial light modulator. Besides, the further trend of laser fabrication of graphene-based electronic skin can be integrated with various functional devices and/or reducing the device size. We believe that continued efforts in laser fabrication of graphene would push forward the rapid progress of this field and lead to breakthrough in both fundamental investigations and practical applications.All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.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.


The paper reviews the network of cellular signaling pathways activated by Functional Graphene Nanomaterials (FGN) designed as a platform for multi-targeted therapy or scaffold in tissue engineering. Cells communicate with each other through a molecular device called signalosome. It is a transient co-cluster of signal transducers and transmembrane receptors activated following the binding of transmembrane receptors to extracellular signals. Signalosomes are thus efficient and sensitive signal-responding devices that amplify incoming signals and convert them into robust responses that can be relayed from the plasma membrane to the nucleus or other target sites within the cell. The review describes the state-of-the-art biomedical applications of FGN focusing the attention on the cell/FGN interactions and signalosome activation. Since iThe reduction of GO to G-Red restores the structure and properties of G. In comparison with GO, G-Red is known to have an increased conductivity, and mechanical strength, the fact that makes it a more attractive tool for applications in theranostic nanomedicine. However, the π–π stacking of aromatic rings and van der Waals interactions limit its dispersion in a biological medium and induce aggregation, so only functionalized pristine G or functionalized G-Red can be used in nanomedicine. The chemical functionalization of graphene-based materials  tunes the structural, physical, chemical and electronic properties together with the biological responses . In the literature, the term “Graphene” refers to a broad family of graphene products that include, among others, reduced graphene oxide, graphene oxide, graphene nanoplatelets, etc. They possess a different structure and very diverse physicochemical and mechanical properties that affect the biological responses. In addition, these graphene products, in turn, are not homogeneous materials, rather a mixture with various oxidation states, different lateral sizes, varied number of layers, and different colloidal stability. The lack of standardized ways of reporting the characterization of graphene materials and the presence of traces of impurities  make difficult, sometimes, the reproduction of published biological experiments . In addiTaking in account the impossibility to give a univocal classification to the broad family of graphene products and the presence in literature of comprehensive recent reviews that describe the different aspects of biomedical applications of graphene ,12,13, tIn the last years, the applications of FGN in biomedical fields have prompted great interest and a wide number of compounds have been exploited to convey specific biological properties to graphene materials. Among the different chemical modifications of graphene-based materials, some of them have been designed to generate FGN targeted to mammalian cells , bacteria, yeast, and viruses.The combination of graphene-based materials with polymers has been tailored to synergistically combine the characteristics of both components to obtain multifunctional nanocomposites with a superior performance for biomedical applications . The funEscherichia coli (E. coli); after the recognition and capturing of E. coli by mannose ligands anchored on the platform, the near-infrared (NIR) laser irradiation induced a complete microbial elimination (>99%) ), activated the epidermal growth factor receptor (EGFR) by inducing a transient membrane depolarization and consequent influx of Ca2+ from the extracellular space, leading to an enhanced cellular uptake of the drug-loaded nanoparticles via pinocytosis into tumor cells that over-express EGFR  .,39.38,39The integrity of lysosome compartment is dependent by FGN concentration; no significant effects on the integrity of the lysosomal membrane have been reported at low FGN concentrations (20 μg/mL), while the membrane permeabilization can be affected at high FGN concentrations (100 μg/mL), which can result in cell death via different pathways, including lysosome/mitochondria-dependent apoptosis, lysosome-dependent necrosis, and lysosome-dependent autophagy) . AutophaCombined approaches can be used to monitor the activation of autophagic flux and the autophagosome accumulation induced by graphene exposition. That accumulation can be related to an increased autophagosome synthesis or to decreased autophagosome turnover .The microtubule-associated protein 1A/1B-light chain 3 (LC3) is used as a biological marker to identify autophagy induced by graphene exposition. During autophagy, cytosolic LC3-I is converted to LC3-II and associates to the autophagosomal membrane. Thus, the levels of the LC3II protein, the GFP (green fluorescent protein)-LC3 dot number and the treatment with chemical autophagy inhibitors are employed to determine cellular autophagosome accumulation. In addition, to monitor the autophagic flux activation, the p62 expression levels, normally reduced during the autophagy process, can be evaluated. After the graphene internalization by endocytosis, an increase of LC3II on the autophagosomal membrane corresponds to the accumulation of the p62 protein, indicating the autophagy induction mediated by graphene which does not evolve in the degradation of engulfed contents in the autolysosome vesicles. Further studies should be carried out to clarify why graphene or another type of nanomaterials are sequestrated into lysosomal organelles but not degraded. The consequences of graphene on autophagy are not completely clarified and different effects have been reported. Ji et al. demonstrated that the increased accumulation of autophagosome after GO quantum dots treatment resulted by the block of autophagy flux due to the low degradative activity of lysosomes . In anotThe anticancer drug delivery system induces the initiation of autophagy, which precedes cellular death. In particular, the nuclear translocation of either the LC3 autophagic marker and the chemotherapy drug is stimulated and results in the shut off of the late autophagy events and activation of cell death signals .Deeper studies on the molecular dynamics related to the graphene nanomaterials exposition are still necessary in order to understand whether the graphene endosomal trafficking concludes with lysosomal compartmentalization or involves the recycling of unengulfed materials.Glycyrrhiza glabra) loaded with Dox has been developed (FGN-GA/Dox). From these studies emerged that after internalization, FGN-GA/Dox is transported from the early endosome, gradually maturing into a late endosome and eventually into a lysosome that subsequently transferred mainly to mitochondria due to the targeting properties of FGN-GA. About 82.5% of Dox was delivered into mitochondria and 11.7% of Dox was delivered into the cell nucleus. The FGN-GA/Dox-induced mitochondria-mediated apoptosis (MMA) of cancer cells and exhibited greater antitumor activity compared with Dox·HCl in vitro and in vivo [Recently, particular attention has been devoted to the development of drug delivery strategies targeting subcellular organelles such as mitochondria . Antican in vivo . The nuc in vivo .1O2, at the targeted site of cancerous tissue [The targeted drug delivery strategies have also been investigated to maximize the anticancer effects of photothermal therapy (PTT) or photodynamic therapy (PDT). The basis of these therapeutic strategies is that light is utilized to activate a non-toxic photosensitizer (PS), provoking the formation of heat and highly toxic ROS, mainly singlet oxygen, s tissue . A PS lis tissue .A subcellular targeting for PDT was achieved by the conjugation of GO with integrin αvβ3 monoclonal antibody; after endocytosis, the escape of the nanosystem from lysosomes and the transfer to the mitochondria was observed. The PS  loaded on the nanosystem became in the “on” state into mitochondria performing its effective phototoxicity to kill cells by increasing the MMA .2+ homeostasis [1O2 in aqueous media) and a small diffusion radius (about 0.2 μm for 1O2) in biological system [It was demonstrated that the mitochondrial structure is affected by treatment with GO at low concentrations (<4 μg/mL), resulting in a decline in the membrane potential and the dysregulation of mitochondrial Caeostasis . Considel system , the spal system . From ex1O2. Hence, mitochondrial-specific PDT with in-situ 1O2 burst leads to the decrease of the mitochondrial membrane potential inducing irreversibly tumor cell apoptosis [Recently, in order to optimize the PDT effectiveness and therapeutic efficacy by increasing ROS production directly in mitochondria, a rare-earth doped upconversion nanoparticle (UCNP) was coupled with GQD and a rhodamine derivative  for mitochondrial targeting. The system exploited the properties of UCNP, which can emit UV/VIS light under NIR excitation, and GQD, which can efficiently generate poptosis .Although the mechanism is not clear, the nuclear sub-localization of graphene-based materials has been ascertained in some cases ,53. The The analyses of the literature data suggest that it is hard to predict the exact internalization mechanisms and the subcellular localization of graphene derivatives. Due to having a great diversity of structure, dimension, charge and colloidal stability, the cellular uptake is probably the result of the combination of different endocytotic pathways that might be associated with passive internalization.The studies on the different internalization pathways and the intracellular fate of graphene nanocarriers should be in deep, since they may enlighten the research on organelle-targeting drug delivery systems.The intracellular internalization of graphene-based materials triggers a wide variety of cellular responses mediated by the activation of the intracellular signaling network, which affects the cell environmental ,55,56. TThe modulation of immune response related to graphene exposition was studied in primary murine and immortalized macrophages. Zhou and collaborators  have demA potential branch of cancer gene therapy is represented by immunotherapy approach that stimulates directly the immune response against cancer. Therefore, the evaluation of the impact of the graphene sheets on the cellular environment and the potential modulation of the key components of the immune system could be interesting for a new immunotherapy approach. It has been found that the lateral dimensions of GO can modulate the expression of immune genes encoding for chemokines, cytokines and cytokine receptors. A deep and interesting study by using a genomic approach was conducted by Orecchioni M. et al.  on humanSingle-cell mass cytometry analysis in combination with whole-transcriptomic analysis was performed on purified PBMCs treated with GO and amino GO. The amino functionalization on GO reduced the necrotic events, incremented the CD25 and CD69 expression levels in active T cells, as well as the gene expression for pro-inflammatory cytokines, regulators for an innate and adaptive response. These data suggested the enhanced biocompatibility of GO due to functionalization .Caenorhabditis elegans. In addition, Kang et al. [Current knowledge has demonstrated that the graphene nanostructure triggers an in vitro programmed cell death mechanism in a dose-dependent manner. During earlier events of apoptosis, the translocation of phosphatidylserine occurs from inner to the outer leaflet of the plasmatic membrane. The fluorochrome-labeled Annexin V analysis allows detecting the interaction between Annexin V and the phosphatidylserine exposed on the outer surface, through a flow cytometry assay. Tabish et al. showed that lung cancer cells exposed to a lower concentration of G-Red exhibited late stage of apoptosis, rather than early stages, with a consequent formation of the apoptotic bodies and damage of cell membrane . Insteadg et al.  have demGraphene-based materials have emerged as a subject of enormous scientific interest because of its exceptional properties and they have been proposed for various biomedical applications, such as biosensors, tissue engineering, and drug delivery. However, until now, to the best of our knowledge, no graphene-based materials have progressed to the clinical stage. The main obstacles to this advancement are the non-homogeneous nature of graphene materials and the lack of standardized ways of reporting their characterization. Moreover, along with detailed in vitro characterization of graphene derivatives, more attention should be focused on their evaluation in vivo with respect to inflammatory responses, biocompatibility, and signaling pathways. Thus, the road of graphene in biomedical/pharmaceutical applications seems still very long and winding. However, the enthusiasm of the scientific community is providing a host of very interesting breakthroughs, which place graphene in a pole position in the fields of theranostics and tissue engineering. The present review deals with modified graphene materials in which the structural, physical, chemical, and electronic properties and the biological response  are tuned by organic functionalization and highlights the advances in the investigations of FGN in nanomedicine. The interactions of FGN with cells, the different pathways of cellular uptake and the sub-cellular localization have been dealt. The current knowledge about the intracellular pathway activated by FGN appears still fragmentary and the correlations between the graphene surface functionalization and intracellular signaling network are not yet sufficiently clarified. These aspects should be deeply investigated considering the importance of graphene-based nanomaterials to modulate a cellular microenvironment.


Graphene is a very promising material for electronics applications. In recent years, its sensitivity to ultraviolet (UV) irradiation has been studied extensively. However, there is no clear answer to the question, which factor has a key influence on the sensitivity of graphene to UV. In order to check the influence of the final substrate on the electrical response, graphene transferred on polymeric and non-polymeric substrate was investigated. To achieve this goal three polymeric and three non-polymeric substrates were tested. The results of the preliminary tests indicated the different character of the reaction on UV irradiation in each of group. To explain the reason of the difference, the complementary studies were done. The samples that were resistant to high temperature were annealed in a vacuum at 500 °C to get rid of water trapped between graphene and the substratum. The samples after annealing reacted less dynamically to UV irradiation. Moreover, the progress of changes in electrical response of the annealed samples had a similar character to the polymeric substrates, with the hydrophobic nature of the surface. These studies clearly prove that the sensitivity of graphene to UV irradiation is influenced by water trapped under the graphene. Due to the fact that 2D materials are only the surface, they are extremely sensitive. Graphene can interact with both the substrate on which it is placed and the surrounding atmosphere. Due to the promising electrical properties of graphene, there have been attempts to use it for the construction of various types of sensors, for example: gas, X-ray [3, NO2, O2,) from graphene [2 substrate [The dynamic technological development observed in recent decades has contributed to increase the efficiency of electronic devices reducing their size. As a result, conducted research on 2D materials has increased. One of the most popular in this group of materials is graphene—single layer of sps, X-ray ,2,3. Anos, X-ray ,5. But tgraphene ,7,8, theubstrate . There aThe authors of this study investigated the reactions of graphene transferred on six different substrates to UV irradiation. The Raman spectroscopy revealed that only the region with monolayer of graphene strongly reacts to UV irradiation. The reaction of multilayer to UV was almost nonvisible. The contact angle measurement pointed that the polymeric substrates are more hydrophobic. The results of the preliminary tests indicated that polymeric materials are less sensitive to UV irradiation, and the character of reaction to UV is different. The complementary studies unambiguously confirm that the water trapped between graphene and substrate has the superior influence on the sensitivity of graphene to UV irradiation.3. Before a graphene transfer, the target substrates were cleaned in acetone, and the gold electrodes were sputtered. The tests were performed on six different substrates belonging to two groups: polymer  (PEN) and poly (tetrafluoroethylene) PTFE and non-polymer (Si/SiO2 (280 nm), Al2O3 and quartz glass). The active surface area of graphene was 3 × 3 mm.High Strength Metallurgical Graphene (HSMG) produced on a bimetallic substrate  was used2 substrate. The power of the laser on the surface of the examined samples was 10 mW and the applied magnification was 100×. All measurements were carried out in ambient conditions and at room temperature.Before UV irradiation a set of tests was done to characterize the substrates as well as the graphene quality after transfer. Water contact angle measurements for all used substrates were performed using the FM40 Easy Drop system with Drop Shape Analysis software (Krüss GmbH). Each measurement was performed on cleaned surfaces such as prepared before transfer. The sample was mounted on the system table, then a 30 μL droplet of deionized water was placed on its surface and contact angle measurement was taken instantly. Graphene quality on different substrates was examined using scanning electron microscope . Raman spectroscopy  with an excited wavelength of 532 nm was used to characterize the graphene before and after irradiation on Si/SiOUV irradiation was carried out at ambient temperature, at atmospheric pressure in air. Samples were irradiated with a UV diode with a wavelength of 270 nm, impulse irradiation at 50% completion time was used. The distance between the UV source and the sample was 3 cm. During the experiment, the resistance changes progress over time was recorded. Comparative measurements of carrier concentration and mobility were determined by measuring the Hall effect in the electrode system according to the Van der Pauw method. The measurements were carried out in a magnetic field with an induction of 400 mT at a sample current of 1 mA.2 contains silane groups and adsorbs water on the surface. On the one hand, this allows for better positioning of graphene on the surface; on the other hand, it traps water between graphene and the substrate [In the wet method of transfer, water is used as a medium positioning graphene on the target substrate. Because of that, substrates’ wettability has a key impact on the quality of the transfer. The polymeric substrates used for the research were characterized by a contact angle exceeding 76°, and the ceramics had the wetting at a similar level. Low contact angle values were noticed for silicon substrates: 46° and 57° .. Previoubstrate ,12. Poly2, quartz glass, kapton and PEN are characterized by a smooth surface. The other two substrates have porosities, but in the case of ceramics, the number of pores is much higher. 2, kapton, PEN and even on Al2O3, are the places where the discontinuities of the graphene layer are present. SEM images do not allow to indicate the cause of graphene’s heterogeneity. Graphene can be mechanically damaged during the transfer process. [To show the state of the substrates surface and the quality of graphene after the transfer, SEM photos were taken. The research reveals that Si/SiOprocess. . Defectsprocess. . The SEM−1) and 2D (~2700 cm−1) peaks are characteristic for graphene Raman spectrum. The G band is the only band coming from a normal first order Raman scattering in graphene [−1 and widens when the amount of graphene layer increases or when defects occur. The ratio of 2D to G peak intensity (I2D/IG) amounts to 4 for pristine graphene and decreases when defects occur [−1) and D’ (~1620 cm−1) bands are activated by single-phonon intervalley and intravalley scattering process. Presence D and D’ peaks on Raman spectrum confirm the defect occurring [The Raman spectroscopy is a very useful method to analyze the quality of graphene. The G ~1585 cm85 cm−1 agraphene ,17. The ts occur ,19. D (~nd D’ ~16 cm−1 ban2D/IG was made (−1—to three (the fitting of this peak is presented in D/IG) (D) was calculated (D/ID’) after UV irradiation, it can be concluded that UV radiation changes the nature of defects. Referring to the values obtained for the graphene monolayer given by A. Eckmann et al.  it can be concluded that UV radiation can cause the formation of sp3 bonds [3-like bonds on the bounder of SiO2 and graphene [To test the graphene quality, Raman map Iwas made . The ratin D/IG)  can be olculated . The calp3 bonds . As it winitial and Rtime are the sensor resistance change within time in response to UV irradiation.The sensitivity of graphene to UV was measured by the change in resistance value. The results obtained for various types of substrates are shown in 2 and PEN are characterized by a completely different UV response: Si/SiO2, 92%; PEN, 23%, while ceramics with high initial resistance exhibit sensitivity at 55%.The tested samples were characterized by different values of initial resistance from approx. 1.6 kΩ to approx. 5.7 kΩ . The reaOn the graph of resistance changes, the relationship between the final substrate and the character of changes in graphene response to UV is clearly visible. Graphene transferred on polymeric substrates is characterized by greater dynamics of reaction and reaches the maximum value of the resistance faster . In the The influence of UV irradiation on the carriers’ concentration and their mobility for all substrates was also examined. For each of the substrates, a decrease of carriers’ concentration was observed with simultaneous increase in their mobility due to irradiation . The gra2, quartz glass and Al2O3) was annealed at 500 °C under 2∙× 10−3 Pa. That allowed to clean the graphene surface and get rid of water trapped between graphene and the substratum. After annealing, the samples were kept under ambient conditions for 24 h. This time was enough to adsorb the water vapor on the graphene. Then the samples were irradiated according to the previously adopted scheme.To check which interactions with graphene are predominant, an additional test was performed. Graphene on substrates that are resistant to high temperatures (Si/SiO2, 2 kΩ; quartz glass, 5.14 kΩ and Al2O3, 50 kΩ. The reason for the increase in resistance may be graphene damage during heating through the release of water. The release of a large amount of water trapped in the pores of the Al2O3 was a very dynamic process and led to a significant damage of graphene. The samples reacted less dynamically to UV irradiation after annealing. There was only a few percent increase in UV resistance. The progress of resistance changes for all tested samples had a similar character to the unheated polymer substrates (2O3 substrate and was the lowest for Si/SiO2.For all tested samples, an increase in resistance after annealing was observed: Si/SiObstrates  (respons2. For the remaining substrates a few percent carrier concentration increase was observed (A decrease of carrier mobility was observed. It may be associated with the increase of amount of defect created in graphene during annealing. Differences were also observed in change of carrier concentration. A slight decrease in concentration after irradiation was observed for Si/SiOobserved .2 exhibit hydrophilic properties, while polymeric substrates and ceramics are hydrophobic. Depending on wettability of the surface, the amount of water enclosed under the graphene surface varies. It is greater for hydrophilic materials and smaller for hydrophobic materials, which results in a difference in the nature of changes in the electrical response. An exception is ceramics, which despite the hydrophobic properties have the ability to accumulate more water in the pores. Because of that, their electrical response is similar to hydrophilic materials. Annealing of the samples allows to get rid of water trapped under graphene, making graphene much less sensitive to UV radiation.The results indicate the relationship between the sensitivity of graphene to UV irradiation and the amount of water trapped under graphene during the transfer. Quartz glass and Si/SiO2O3 is water adsorbed in the pores. The water is not completely removed during the heating. The lowest sensitivity of graphene transferred on Si/SiO2 indicates the almost complete removal of water below the graphene. Trying to explain the nature of phenomena affecting the electrical response of the sensor under the UV irradiation, it can be concluded that the dynamic increase in resistance in the initial phase of irradiation is related to the purification of graphene from water. The drop of resistance observed in the last phase is caused by the interaction of graphene with the substrate. The stabilization stage is a temporary balance between the two above-mentioned processes.The reason for the highest electrical response obtained for AlThe subject of the research was the influence of the final substrate on sensitivity of graphene to UV irradiation. To determine this correlation, the electrical response of graphene was measured. The most important feature that has an influence on sensitivity of graphene to UV is the ability of the substrate to accumulate the water on the surface. The high amount of water adsorbed on the final substrate surface affects both the dynamics of the electrical response of the sensor and the progress of the character of resistance changes. Getting rid of water trapped on the graphene-substrate boundary results in a decrease in the sensitivity of graphene to UV irradiation. Summarizing, the final substrate used in UV sensors should be characterized by hydrophilic properties to provide the appropriate amount of water on the boundary.