After electro-exfoliation, the resulting graphene was premixed with furfuryl alcohol (FA) and an inorganic template (CaCO3 and Na2CO3). Once FA was polymerized to poly (PFA), the mixture was carbonized. Carbon bridges originating in thermally-decomposed PFA joined exfoliated graphene flakes and stabilized the whole sponge-type structure after the nano-template was removed. Gases evolved at the graphite electrode (cathode) played an important role in the process of graphene-flake splitting and accelerated the change of graphite into graphene flakes. Starting graphite materials and graphene sponges were characterized using Raman spectroscopy, SEM, high-resolution transmission electron microscopy (HRTEM), elemental analysis, and low-temperature adsorption of nitrogen to determine their structure, morphology, and chemical composition. The discovered manufacturing protocol had a positive influence on the specific surface area and porosity of the sponges. The SEM and HRTEM studies confirmed a high separation degree of graphite and different agglomeration pathways. Raman spectra were analyzed with particular focus on the intensities of ID and IG peaks; the graphene-type nature of the sponges was confirmed.We demonstrate an accessible and effective technique for exfoliating graphite foil and graphite powder into graphene in a water solution of inorganic salt. In our research, we report an electrochemical cathodic exfoliation in an aqueous solution of Na The intercalation process, as well as gas evolution, may open up graphene sheets, causing their expansion and exfoliation of the graphene layers [Graphene is a two-dimensional layer of carbon atoms which form hexagonal rings based on spdization ,2. A pardization . Unlike dization . Generaldization , graphendization , graphendization . Recentldization . Graphendization . The eledization ,11,12. Edization . To datedization  and typi, NaClO4 ,22,23,24e layers . Exfoliae layers ,11,26. Oe layers ,27. TherThe studies performed on graphene electro-exfoliation thus far have almost exclusively been focused on the graphene flake splitting itself and the chemical alterations of the flakes due to certain electrode reactions. The same studies overlooked the problem of graphene flakes’ secondary adhesion once the dispersing liquid phase (mainly water) was removed. This causes the electro-exfoliation to be a reversible phenomenon, making the outcome benefits (the presence of separate graphene flakes) hardly applicable in practice. No fixation method of split graphene flakes has been proposed so far.2CO3 nanocrystals or CaCO3 nano-powder were used as a hard template. Graphene flakes were obtained by a wet chemistry exfoliation of commercial graphite. The flakes were premixed with a non-specific binder and the hard template and then carbonized at temperatures of 700 to 800 °C under the flow of nitrogen. The addition of a template allowed the surface area to increase up to 287 m2 g−1 for the Na2CO3 template and 333 m2 g−1 in the case of CaCO3, while the surface area of few m2 g−1 was noted for the raw graphite. The wet-chemistry method led to an efficient deglomeration of graphene flakes to double-layered (DLG) and few-layered (FLG) graphene.In the recent study we have successfully elaborated a 3D structuring method for durable fixation of graphene flakes obtained from a commercial graphite by wet-chemistry exfoliation . In situ2SO4). We present the first case of graphene stabilized with a small amount of carbon obtained from poly. The graphene flakes which stabilize in a 3D structure were acquired by electroexfoliating two different graphite precursors: graphite foil and commercial graphite powder. Additionally, we assumed that split flakes can be durably separated from one another by nanoparticles  which can be later removed to release nano-voids, i.e., pores. The influence of process parameters on the characteristics of produced graphene sponges was investigated.Thus, durably fixed graphene flakes can form 3D graphene sponges. These sponges in turn can substitute typical porous carbon-based materials, e.g., activated carbons, in numerous applications exploiting enhanced specific surface area and porosity . In this work, we demonstrate a highly effective electrochemical exfoliation method in aqueous inorganic salt sodium sulfonate , HCl and H3PO4 were of analytical purity grade and were obtained from Sigma Aldrich , POCH  and SS Nano .Extra pure graphite was purchased from Merc. The graphene films/foils 240 μm thick were provided by Sigma Aldrich. Other reagents i.e., Na2SO4 1 M solution), graphite powder was sunk and covered by a porous polymeric membrane/separator to avoid graphite/graphene powder spreading throughout the entire electrolyte volume. The electric circuit was completed by placing a movable polymeric plug containing the second platinum electrode (a mesh), on which ground potential was set (0 V) to enable its cathodic function. The movable plug/electrode provided an additional compressing force which, beside natural sedimentation, caused the graphite particles to be in electric contact with the anode, assuming the whole experimental setup is vertically oriented. The meshed structure of the upper electrode (cathode) was permeable for gases evolved during electro-exfoliation. The electro-exfoliation was performed for an experimentally-verified length of time. After this time passed, the electro-exfoliation was opened and the suspension  was poured into a beaker and subjected to other chemical manipulations. Additional force/weight may generally be placed on the movable plug, though it was not in the current study.Electrochemical exfoliation of extra-pure graphite (Merc) was performed first. Such an electro-exfoliation of a powder creates serious experimental obstacles, since the graphite powder is a loose material with no specific durable shape which could aid holding the mechanical electrode. Therefore, a special electrochemical experimental setup was developed in which the loose powder was electrically charged by temporary contact with a positively charged bottom electrode (platinum plate), as the particles were pulled downwards to the metal surface (sedimentation) by the force of gravity, as depicted in In the second step, we performed the electro-exfoliation of graphite foil (Sigma Aldrich) ca. 3.5 cm × ca. 3.5 cm in size. The foil, since it had a fixed shape, served as an anode once the potential of +10 V was set on it. Thus, the graphite itself played the role of anode while a platinum plate worked as the cathode . Anode and cathode zones were not separated by a membrane in this case b. The sa®HMP2020 power supply) was applied between the platinum and graphite electrodes, and the electrolysis procedure lasted 2 h for graphite powder and 30 min for graphite foil at room temperature. During this process, substances expected to work as a separator of newly exfoliated graphene flakes (denoted later as templates) were added in one of two forms: a nano-powder of CaCO3 (5–40 nm diameter) or a saturated solution of Na2CO3.A direct current (DC) voltage (R&S2CO3 or CaCO3). Furfuryl alcohol was added along with H3PO4  as a potential gluing agent. The resulting graphene–furfuryl alcohol (FA)-template mass was subjected to heat treatment to polymerize PA to poly (1 h at 100 °C), then carbonized in a N2 atmosphere with a heating rate of 10 °C min−1 up to 600 °C. This temperature was maintained for 1 h. The process was carried out in a tubular furnace (Thermolyne F21100). After carbonization, the samples were treated with a concentrated (34%–37%) HCl solution for 20 min (12 mL of acid was used per 1 g of carbon) to remove CaCO3 and Na2CO3. They were then washed with distilled water on a Büchner funnel until the pH of the solution reached 6–7. It was dried again in an electric furnace at 100 °C for 24 h. Further in the text, EG_F_2 and EG_F_1 are used as the denotation of samples obtained from graphite foil with CaCO3 and Na2CO3, respectively. The EG_P_2 and EG_P_1 samples were obtained from graphite powder, using CaCO3 and Na2CO3, respectively.Graphene flakes obtained through electrochemical graphite split were durably separated by the use of an additional agent, i.e., a template (nano-grains of NaBET) and pore structure of graphite samples were examined using the low-temperature nitrogen adsorption method. The relevant isotherms of all samples were measured at −196 °C using an automatic adsorption instrument, ASAP 2010 . Prior to gas adsorption measurements, the carbon materials were outgassed in a vacuum at 200 °C for 2 h. The pore size distribution was derived from adsorption branches by the nonlocalized density functional theory (NLDFT) method. The elemental composition  of the materials was analyzed by means of a combustion elemental analyzer . The morphology of the samples was analyzed using scanning electron microscopy  and high-resolution transmission electron microscopy . The samples were examined using Raman spectroscopy–microscope: Renishaw InVia , laser: Modu-Laser Stellar-REN, Multi-Line (maximum Power 150 mW), camera: Leica DM1300M Infinity 1, lens: Leica, N PLAN L50×/0.5. All spectra were collected at ambient temperatures with a 532 nm excitation wavelength. Atomic force microscopy (AFM) investigations were measured by Scanning Probe Microscope (SPM) produced by Veeco .Structural parameters like the specific surface area , anions (mainly SO42−) absorb on active sites of the graphite electrodes and oxidize to gaseous oxygen. The anions and evolved gas may penetrate into the interstitial space between graphene layers (in powder or foil) and expand the materials to the point of splitting them into less agglomerated forms, like single-layered graphene (SLG) and few-layered graphene (FLG). Gas (mainly oxygen) evolution accelerates the switching rate of graphite to graphene.Graphene flakes can be produced from graphite, either in the form of a foil or a powder electrode, by exfoliation in 1 M Na3CO3  and cetyltrimethylammonium chloride solution (CTAC) was added. After electrochemical exfoliation, the resulting product was ultrasonicated for 30 min, then a Na2CO3 solution at a concentration of about 16.9% was added; the mixture was left on a magnetic stirrer for 1 h, then sonicated again for 1h. The samples were then washed with distilled water on a Büchner funnel. To evaporate the distilled water, the mass was dried in an electric oven at 80 °C for 24 h. In the second method . The current study is based on the separation (addition of nano-templates) and fixation (carbon bridges originating from PFA) of exfoliated flakes. Thus, in the case of these samples, i.e., graphene sponges, structural parameters like surface area and pore structure become measurable. Our study is unique among reports dealing with this problem.BET) are given in 2CO3 or CaCO3. The highest SBET was found for samples obtained with CaCO3 as a separator. Both electro-exfoliation approaches (graphene foil and powder) yielded samples with the highest values of SBET, i.e., EG_F_2 with 121 m2 g−1 and EG_P_2 with 220 m2 g−1. These values were calculated using the regression of data from the original nitrogen adsorption at –196 °C. The same data let us estimate pore size distribution by using the widely accepted nonlocal-density functional theory (NLDFT) model [The results regarding specific surface area (ST) model ,33,34. FThe chemical composition was investigated using CHN combustion elemental analysis and the results are presented in In conclusion, an accessible method was developed and demonstrated for obtaining few-layered graphene directly from graphite by electro-exfoliation and 3D stabilization by means of carbonized PFA as a stabilizer and certain inorganic carbonates as templates. The obtained samples can be treated as porous carbon sponges built of graphene flakes. The study indicates that the presence of carbonized PFA is critical for stabilizing the graphene and improving the surface parameters; the specific surface area increased several times compared to the starting material (graphite). The relatively high graphene purities and excellent stabilization with PFA show both methods to be promising ways of developing porous graphene. The morphological properties include the nanostructure of graphene powder with different sizes, characterized by SEM and HRTEM. The structural properties indicate a high quality for graphene, as determined by Raman spectroscopy. Low-cost and environmentally friendly production of such high-quality graphene is important, not only for future-generation electronics, but also for large-scale applications, such as composite materials, supercapacitors, fuel-cells, and batteries. Any practical application requires upscaling of the electrochemical arrangement and a cost calculation. The economic aspect of electrochemical exfoliation directly points to powdered graphite of high purity since its market prices are definitely much lower than the price of graphene foil. Experimental setup for exfoliation of graphite powder which was tested in the current project can be enlarged as single cell, but also small volume single cells may be used as a cell array. The presented electro-exfoliation approach has one general advantage over typical wet chemistry approaches: the inevitable chemical reagents i.e., electrolytes are common, inexpensive, and relatively easy to utilize. An upscale of the electrochemical cell will be the target of subsequent studies.


We demonstrate the versatility of graphene etch stops with three-dimensionally integrated nanoelectronics with multiple active layers and nanoelectromechanical devices with performance comparable to the state-of-the-art.Atomically precise fabrication methods are critical for the development of next-generation technologies. For example, in nanoelectronics based on van der Waals heterostructures, where two-dimensional materials are stacked to form devices with nanometer thicknesses, a major challenge is patterning with atomic precision and individually addressing each molecular layer. Here we demonstrate an atomically thin graphene etch stop for patterning van der Waals heterostructures through the selective etch of two-dimensional materials with xenon difluoride gas. Graphene etch stops enable one-step patterning of sophisticated devices from heterostructures by accessing buried layers and forming one-dimensional contacts. Graphene transistors with fluorinated graphene contacts show a room temperature mobility of 40,000 cm 2 gas to pattern graphene based heterostructures with multiple active layers and achieve 1D contacts with low contact resistivity of 80 Ω·µmFabrication methods to pattern thin materials are a critical tool to build molecular scale devices. Here the authors report a selective etching method using XeF Many of the applications for 2D material heterostructure devices demand out-of-plane integration, contacting multiple active layers, and creating interconnects between the different layers5. Examples include 2D material-based integrated circuitry like NAND gates6 or ring oscillator7; devices based on interlayer tunneling like light-emitting diodes (LEDs)8 or tunnel transistors9; and nanoelectromechanical systems (NEMS) like resonators based on atomic membranes10.As next-generation technologies of electronic, photonic, and mechanical devices approach the atomic scale, it is important to develop atomically precise fabrication methods. Among them, etch stops, critical for the vertical integration of nanoelectronic and nanomechanical devices, are created by layering materials with drastically different etch properties and embedded into a structure, allowing for patterning feature sizes, accessing buried layers, or undercutting to create suspended structures. Accordingly, improved fabrication techniques are especially needed in nanoelectronics based on van der Waals (vdW) heterostructures, where two-dimensional (2D) materials are stacked to form electronic devices with nanometer thicknesses14. The current state-of-the-art method is to use edge contacts where heterostructures are etched through to expose the edges of buried layers of graphene encapsulated in insulating hexagonal boron nitride (hBN), and then metals are evaporated onto the edge to make one-dimensional (1D) contacts13. This method has led to a dramatic improvement in the mobility and quality of electronic devices because it allows contact to electronic layers that are fully encapsulated and thus have a minimum of disorder15. However, edge contacts still require careful offsetting of active layer because the etching is not selective so all vertically aligned layers in the heterostructure are exposed simultaneously. A method that combines the superior device behavior of the edge contacts but that simultaneously allows ready patterning of 2D heterostructures from large area continuous sheets and individually addressing of each layer are critical for translating many of the recent demonstrations of this class of devices into scalable technologies.In the current state of the art, the relative ease of assembly of vdW heterostructures, which occurs through the sequential pick-up and stamped release of individual atomic layers, contrasts starkly with the difficulty of patterning and electrically addressing each layer in a heterostructure device. As a result, the majority of studies in this field are performed on monolayers or on heterostructures where each layer has been carefully offset so they are accessible for electrical contacts through direct deposition of metal on top or on the exposed edges of individual 2D layers17. These techniques, which we call GES (graphene etch stops), represent a straightforward method to selectively expose and contact embedded graphene layers within 2D heterostructures. This concept takes advantage of the high chemical selectivity of XeF2, a vapor phase, strong fluorinating agent commonly used as an isotropic etchant for silicon in the microelectromechanical systems (MEMS) industry18. Several 2D materials including hBN and transition metal dichalcogenides, are quickly etched when exposed to XeF220. In contrast, graphene reacts with XeF2 to form fluorographene (FG)24, a wide band-gap semiconducting monolayer22 with composition C4F, in the case that only one side is exposed22. There have been several demonstrations that take advantage of this selectivity to use graphene as an etch mask for shaping MoS216, as a mask to etch underlying silicon27, and to create a sacrificial release layer to suspend graphene membranes on silicon on insulator22. Our innovation has been to apply this etch selectivity to access buried graphene layers embedded within the heterostructures and as masks for patterning the underlying layers. Surprisingly, the embedded contacts, which is composed of FG–metal contacts, lead to room temperature carrier mobilities of 40,000 cm2 V−1 s−1 at carrier density n = 4.0 × 1012 cm−2 and behave as 1D contacts with low contact resistivity of 80 Ω μm, approaching theoretical limits28. This capability enables simple and scalable methods to vertically integrate 2D devices through contacting multiple active layers, interlayer vias, and suspended nanostructures, yet maintains the state-of-the-art performance of fully encapsulated 2D devices.Here we show methods to fabricate nanostructures and access buried interfaces with the precision of a single atomic layer by using graphene as impermeable etch masks and etch stops2. The heterostructure is fabricated by stacking individual materials using established polymer-free, aligned transfer techniques29. Specifically, the heterostructure is composed of two monolayer graphene flakes, set in a cross-alignment and embedded between hBN layers, then placed on top of a Si/SiO2 (285 nm) substrate. The color corresponds with the thickness of the heterostructure. In Fig. 2 (3 Torr for 30 s at room temperature), the exposed hBN is completely etched, while the graphene layers and the hBN underneath them remain. In Supplementary Note 2, WSe2, and black phosphorus (BP).Figure 2. Moreover, Fig. 31 through the chemical modification process32. In Fig. To examine the selectivity and resolution limits of GES, we obtained cross-sectional images of the etched heterostructures with a scanning transmission electron microscope (STEM), as shown in Fig. 2, both grown by chemical vapor deposition (CVD). First, large area continuous graphene was patterned into lines with lithography and oxygen plasma. Two sets of the patterned lines were then sequentially transferred onto large area continuous monolayer WS2 grown by CVD. The second transfer is set perpendicular to the first to form a cross-hatch pattern. After exposure to XeF2, WS2 uncovered by graphene was completely etched, while the region covered by graphene remained under FG  is linear and displayed no hysteresis . Similarly, many device applications of 2D heterostructures that rely out-of-plane transport, like vertical PN junctions35, tunnel junctions9, or light emitters based on 2D materials36 require the same ability to contact vertically aligned layers separately.In addition to offering a simpler fabrication process and state-of-the-art device properties, the selective etch stop also enables capabilities that cannot be easily or scalably realized using other techniques. For example, interlayer vias and independently contacting multiple active layers in vertically aligned heterostructures are critical to integrated circuits like NAND gatesVg = 0 V, equivalent to the in-plane channel resistance of the graphene. The contact resistance is negligibly small compared with the corresponding channel resistances, demonstrating that GES enables efficient, simple, and selective contacts to vertically offset layers to create low resistance interlayer vias, which could be integrated to the complicated devices such as multilayer PCBs or light emitter based on 2D materials.Figure 13  droplet is deposited on a microscope glass slide, then cured overnight at 60 °C. At the same time, poly  (PC) dissolved in chloroform is deposited onto a microscope slide glass. The chloroform is allowed to evaporate in air at room temperature, then the remaining PC film is manually peeled off by hand. The peeled-off PC film is placed onto the PDMS, then the entire structure is baked at 170 °C for 15 min to form conformal contact between PC film and PDMS. The resulting transfer substrate is then fixed to a micromanipulator. In parallel, all 2D flakes used for the vdW heterostructures were separately exfoliated onto the SiO2 (285 nm)/Si substrates with the scotch tape method. The thickness or layer number of each material is separately confirmed using a combination of Raman spectroscopy, atomic force microscopy, and optical microscopy. For the first pick-up, it is necessary to start with an extra thick layer of hBN (~20 nm). The PC/PDMS stamp is placed onto the target hBN flake at 70 °C. To increase adhesion strength between PC and hBN, the temperature is then raised to 130 °C. Then PC/PDMS stamp is gradually lifted up during cooling to 70 °C. This process is then repeated to pick up other 2D flakes subsequently at 90 °C. Each 2D piece must be smaller than the top layer of hBN. After stacking, the stacked heterostructure was transferred onto a clean SiO2/Si substrate by releasing the PC film from the PDMS at a higher temperature above 190 °C. Lastly, the PC film was removed by rinsing the sample in chloroform.To fabricate the heterostructures, we use a 2D material pick-up technique with similar established methods2 etcher (Xactix etching system) was used for the selective etching of 2D materials in pulse mode with PXeF2 = 3 Torr at room temperature. The pulse time for etching, i.e., exposure time was set according to the thickness of top layer of hBN, between 30 s, to 2 min. However, it should be noted that the exposure time is not proportional to etch rate because etching stops at the graphene layer.The XeF2 gas did not affect the ability to remove the poly (methyl methacrylate) (PMMA) used as an e-beam resist using normal solvents. For fabrication of the devices in Fig. 2. The top layers of the heterostructure were etched away exposing the contact area of the embedded graphene, which fluorinated during etching  was performed to generate patterns to selectively etch the vdW heterostructures. The exposure to the XeF39. The CVD graphene was then transferred onto a TEM grid. PMMA was spin-coated on the as-grown CVD graphene on a copper foil, followed by etching of copper in ammonium persulfate solution. After rinsing in multiple baths of de-ionized (DI) water, the graphene/PMMA film floating on DI water was scooped with the TEM grid. PMMA film was removed by dipping it in acetone. The cross-section TEM specimens in Fig. In the TEM images of Supplementary Figures STEM images in Fig. 2 substrate were acquired on a Hitachi S-4700 field-emission gun SEM with 2 kV accelerating voltage. The sample is tilted by 45° with respect to the beam direction. False coloring was added after data acquisition.The SEM images in Fig. −1 grating. To minimize damage of graphene by irradiation of the laser, a power of < 5 mW was used with an acquisition of 60 s.Raman measurements in Fig. 2 substrate. We utilized monochromated Al as X-ray sources (Al Kα line: 1486.5 eV) and X-ray power of 12 kV and 3 mA. All measurements were carried out in vacuum (P < 5 × 10−9 mbar).XPS measurement in Supplementary Figure For the temperature-dependent electrical measurements in Fig. Two lasers of different wavelengths were focused on the center of the graphene membrane and used to actuate and detect the mechanical resonance. To actuate the membrane, a 623 nm diode laser was modulated electrically. The reflected light of a second 520 nm laser was monitored through the Si-based avalanche photodetector. The modulation frequency was tuned and monitored using a spectrum analyzer to find the resonance frequency. The measurements were performed in an optical cryostat at < 5 μTorr to reduce damping of the membrane.41 implemented in VASP42 in conjunction with projected augmented wave43. The generalized gradient approximation of Perdew–Burke–Ernzerhof44 was applied to describe the exchange-correlation functional. An energy cutoff of 350 eV was chosen for the plane wave basis and achieves convergence of the total energy of both Pd and Cr and graphene sheet to within 0.01 eV of the total energy. Geometry optimization allowed relaxation until the forces on each atom were < 0.1 eV/Å. A 64-atom supercell of graphene and 7 layers of Pd (111) (or Cr (111)) were used to describe the metal electrode, which is sufficient to recover bulk-like properties in the interior of the slab. Within GGA-PBE, the graphene lattice constant was 2.47 Å, and in our simulations, the Pd metal electrodes are under 3% compressive strain due to lattice mismatch with the graphene membrane. In each supercell, 20 Å of vacuum is included to avoid interaction between adjacent images in the z-direction. A 4 × 8 × 1 mesh was used to sample the system k-space. Furthermore, graphene or fluorinated graphene was introduced on both sides of the metal to maintain symmetry in the supercells and to avoid spurious introduction of electric fields and dipole moments across the supercell.The atomic-scale structure and charge distribution of the interface between metal and FG shown in Fig. Supplementary InformationPeer Review File


In this study, graphene-modified asphalt (GMA) was prepared from SK-70# matrix asphalt and ethylene bis(stearamide) (EBS). Based on the uniform design method, a model was created using Data Processing System (DPS) software and First Optimization (1stOpt) software using the graphene mixing amount, EBS mixing amount, shear rate, shear time, and shear temperature as factors and using the asphalt penetration, softening point, force ductility, SHRP-PG test, and multistress creep recovery data as indices. Calculations and analysis showed that the optimal composition and preparation parameters of GMA are as follows: the graphene proportion is 20‰, the EBS proportion is 1%, the shear rate is 6000 r.p.m., the shear time is 180 min, and the shear temperature is 140 °C. The prepared GMA had a significantly improved softening point, low-temperature fracture energy, antirutting factor, and creep recovery rate, indicating that adding graphene can improve the high- and low-temperature performance of asphalt. The prepared GMA was characterized by X-ray diffraction (XRD). The dispersibility of graphene in asphalt was evaluated by fluorescence microscopy and Image-Pro Plus imaging software. The results show that graphene can exist in asphalt in a stable form, which increases the loose-layered structure of stacked asphalt or gum. The intense adsorption effect of graphene strengthens the ordered structure of asphalt. However, due to its dispersibility characteristics, some graphene exists in asphalt in clustered form. When the graphene-to-dispersant ratio approaches the optimal value, the dispersant changes the form of graphene in asphalt from irregular clusters to regular clusters and from large, distinct clusters to small, indistinct clusters. When dispersant cannot uniformly disperse graphene in asphalt, graphene clusters primarily form medium-sized grains. Huang Gang et al. [Graphene, formed by carbon atoms via sp2 electron orbital hybridization, is a beehive-shaped, two-dimensional carbon nanometer inorganic material with various superior properties. In recent years, graphene has become a focus area of scientific research ,9,10,11.g et al. ,22,23 usg et al.  developeg et al. ,32,33,34Based on the uniform design method and using the asphalt penetration index, softening point, force ductility, SHRP-PG test, and multistress creep recovery test data as indices, this paper employed Data Processing System (DPS) and First Optimization (1stOpt) software to establish a mathematical model to investigate the material composition and preparation parameters of GMA. In addition, a microscopic analysis method and Image-Pro Plus software were applied to evaluate the dispersibility of graphene in asphalt. The matrix asphalt used in this study was SK-70# asphalt (PG64-22). Each index was tested based on the Standard Test Method of Bitumen and Bituminous Mixture for Highway Engineering (JTG E20-2011) by the Chinese Ministry of Communications . The graThe shear processing of the modified asphalt was performed using a BME200L intense shear and mix emulsion machine  from the Shanghai Weikang Machine Manufacturing Co., Ltd., Shanghai, China. The ultrasonic separation of the graphene mixture solution was performed using JP-040 ultrasonic equipment  from the Skymen Cleaning Equipment Shenzhen Co., Ltd., Shenzhen, China. The asphalt penetration index, softening point, and force ductility were measured using an SYD-2801D penetration index tester, an SYD-2806E softening point tester, and an SYD-45DBF ductility/tension tester with temperature and speed regulation from the Shanghai Changji geological instrument Co., Ltd., Shanghai, China. The asphalt rheological performance was tested with a Bohlin DSR I dynamic shear rheometer from the Malvern Panalytical Instrument Co., Ltd., Malvern, UK. The structure characterization of the modified asphalt was performed with a D8-Advance X-ray diffractometer  from the Bruker Corporation, Karlsruhe, Germany. The graphene dispersion in GMA was observed using a DM6 M microscope from the Leica Microsystems Inc. Co., Ltd., Buffalo Grove, IL, USA.The GMA preparation process was as follows: (1) The graphene and EBS were measured using an electric analytical balance  and were placed in a 1000 mL beaker. A total of 350 mL of trichloroethylene was added and mixed with a glass bar to produce a mixed solution. The mixed solution was heated in a constant temperature (80 °C) hot water bath for 15 min. Then, the opening was covered with preservative film. The mixed solution was ultrasonically processed for 2.0 h with a 5-min break every 30 min. (2) First, 350 g of matrix asphalt was prepared. Then, the mixed solution (after ultrasonic processing) was poured into the container filled with 350 g of matrix asphalt. The container opening was sealed with 3–4 layers of preservative film and cultured for 12 h so that the asphalt was completely dissolved in the mixed solution. The trichloroethylene in asphalt was completely removed using a rotary evaporator  with the following parameters: oil bath temperature: 110 °C, rotational speed: 85~90 r.p.m., and evaporation time: 60 min. After the trichloroethylene was removed, the asphalt was poured into a container for the shear test to prepare the GMA with importing nitrogen into the bottom of the container continually. The GMA preparation process is shown in n(qs). “U” represents uniform design; “n” represents n tests; “q” indicates that each factor has q levels; “s” means the table has s columns [Uniform design is an application of the “pseudo-Monte Carlo method” in number theory. Uniform design can select a subset of typical test points from the entire set of test points, ensure the uniform distribution of test points in a test range, and reflect major features of the test system. The uniform design method is widely employed to investigate material composition and demonstrates excellent applicability and accuracy ,37. Ther columns ,39,40. 1, X2, X3, X4, X5) were selected to investigate GMA composition and preparation parameters [1 is the shear rate (r.p.m.); X2 is the shear time (min); X3 is the graphene proportion (‰) ; X4 is the EBS proportion (%) (mass fraction of graphene); and X5 is the shear temperature (°C). Each factor has 10 levels, as listed in Five factors with significant impact  and a fluorescence microscope .The penetration index represents the asphalt thickness at the test temperature, which reflects asphalt’s rheological performance to some extent ,43. The The penetration test result in The rheological parameter of graphene asphalt was tested using the Dynamic Shear Rheological test (DSR) proposed by the Strategic Highway Research Project (SHRP) in the United States to characterize viscoelastic energy and evaluate the high- and low-temperature performance and the antifatigue performance of asphalt . The SHRP-PG evaluates the high-temperature performance indices of asphalt cement material. The test reflects two important parameters of asphalt’s viscoelasticity: the complex shear modulus G* and the phase angle δ. The complex shear modulus G* is the ratio of the maximum shear stress and the maximum shear strain in the SHRP-PG classification test. The complex shear modulus G* represents the overall resistance of a material under repeated shear deformation, which includes the elastic modulus G′ and the viscous modulus G″. The elastic modulus is given by G′ = G*cosδ, which reflects the asphalt energy stored and released during shear deformation. The viscous modulus is given by G″ = G*sinδ, which represents the dissipated energy in the form of heat due to internal friction during the asphalt shear process. G*sinδ is defined as the antirutting factor, which represents the capability of asphalt cement material to resist permanent deformation under high temperature ,49. In tRepeated multistress creep recovery tests were performed to further evaluate GMA’s high-temperature stability. The test temperature was based on the SHRP-PG classification test result and the AASHTO T350-14 specification ,52. FirsTo summarize, based on a test of three major indices and the DSR test result, the optimal material composition and parameters for GMA preparation are similar to the design parameters for test groups 7 and 8. In this paper, Data Processing System (DPS) analysis software (Version DPSv17.10) and First Optimization (1stOpt) software (Version 7.0) are employed to calculate the optimal material composition for GMA preparation. DPS is a data processing system that integrates functions such as numeric calculation, statistical analysis, model simulation, drawing, and table generation ,54. 1stO1, fracture energy Y2, softening point Y3, 64 °C antirutting factor Y4, and 0.1 kPa creep recovery rate Y5) are selected to create the regression model for calculation and analysis. During modeling, based on the PRESS statistics after data standardization and a declining trend in the sum of the squared errors, the determinant coefficient R2 is defined as the major criterion to evaluate the regression model’s effectiveness. A larger determinant coefficient indicates better equation fitting. The relationship between the number of latent variables and the determinant coefficient in three regression models calculated by DPS software is given in The interdependency of three force ductility test parameters  in modeling results in multiple colinearity and an unstable calculation result, which impacts the model creation significantly. Therefore, five indices A method for calculating the optimal parameters of GMA and a process to prepare GMA were proposed. For EBS-based GMA, the optimal parameters are as follows: the graphene proportion is 20‰; the EBS proportion is 1%; the high-speed shear rate is 6000 r.p.m.; the shear time is 180 min; the shear temperature is 140 °C. The prepared GMA had a significantly improved softening point, low temperature fracture energy, antirutting factor, and creep recovery rate.(2)The prepared GMA had a softening point of 58.6 °C, a low-temperature ductility force of 168.0 N, low-temperature ductility of 42.54 mm, low-temperature fracture energy of 2099 N·mm, and a 0.1 kPa creep recovery rate of 20.24%. Compared with SK-70# matrix asphalt, the performance of GMA was significantly improved.(3)Graphene can exist in an asphalt medium in a stable form, and some graphene in asphalt is in the form of clusters. When the graphene and dispersant composition is close to the optimal ratio, the dispersant changes the form of graphene in asphalt from irregular clusters to regular clusters and from distinct, large clusters to indistinct, small clusters. When the graphene distribution in asphalt is closer to the ideal situation, graphene asphalt has improved high- and low-temperature performance. When the dispersant cannot distribute graphene evenly in asphalt, the majority of graphene clusters in asphalt are medium-sized.(4)Although EBS is used in this study, graphene is still not distributed evenly in asphalt in the form of flakes but is in the form of small clusters. Methods to ideally disperse or intercalate graphene in asphalt to substantially improve asphalt performance require further investigation.


There are several questionnaires that can evaluate how humans view the relationship they have with their dog. One of those questionnaires is the Monash Dog–Owner Relationship Scale. This questionnaire was originally written for people who speak English. Therefore, it is less useful and also less reliable for people who do not speak English. Since we want the questionnaire to be useful and reliable in more than one language, we wanted to create a reliable translation. The language that we chose for the translation was Dutch. During our translation and reliability study, we found that several of the English questions did not translate well to Dutch. Some words could not be directly translated, and some questions were not interpreted by Dutch-speaking dog owners in the same way that the English questions were interpreted. However, most of the questions were well understood. Therefore, we conclude that a Dutch translation of the Monash Dog–Owner Relationship Scale questionnaire can be used reliably to question Dutch-speaking dog owners after a few adjustments have been made and some questions removed.The Monash Dog–Owner Relationship Scale (MDORS) is a questionnaire that is used to evaluate the perceived relationship between humans and their dog. This questionnaire was originally only formulated and validated in English, which limits its use among non-English speaking individuals. Although a translation could be made, the translation of questionnaires without additional validation often impairs the reliability of that questionnaire. Therefore, the aim of this study was to validate a translation of the MDORS that is suitable for use among native Dutch speakers. To achieve this, a Dutch translation of the MDORS was made and checked for spelling/grammar mistakes, readability, feasibility, and clarity. A test–retest comparison was subsequently performed on the translation together with a calculation of Cronbach’s alpha score and principal component analysis (PCA). Through the PCA, we found that the three-factor model of the original MDORS was also largely present in the Dutch translation. However, deviations were also found, as several questions did not achieve high PCA scores in their original factor. Therefore, we propose that these questions are excluded from the Dutch MDORS.  Over the last few decades, various methods have been proposed to objectively and quantitatively evaluate the relationship between humans and companion animals. Examples of such methods include the Pet Attitude Scale , the PetThe most commonly used concept to quantify human–companion animal relationships seems to be ‘attachment’ ,5. AttacThe discussion about whether humans could be attached to companion animals or not was picked up by Dwyer et al. in their article from 2006 . In thisFor their new quantification method, Dwyer et al.  chose toSince its introduction, the MDORS has been used in multiple studies evaluating the relationship between humans and their canine companions. In some of these studies, the MDORS has been translated to other languages, so it would be applicable to a non-native English public. Examples of such translations include German , SwedishDifferences between an original and translated questionnaire are not an uncommon phenomena . Many quThe absence of validation for translated questionnaires is a serious threat to their reliability, accuracy, and comparability to the original. A questionnaire that is translated but not adjusted or re-validated in a new language may not measure the same constructs as its original counterpart, which would mean that it is technically useless in comparative research. Although it has been used in at least five different languages, to our knowledge, only the Swedish and German translations of the MDORS have been checked for deviations from their original counterpart. However, neither has been fully validated on its own, which still makes whether they measure the same constructs as the original or not questionable. Since we want to stress the importance of validating translated questionnaires, and because there is currently no validated MDORS translation available in Dutch, we aim to develop and validate a Dutch translation of the MDORS questionnaire. If a Dutch translation can be validated, the MDORS can in the future not only be used to reliably evaluate the human–animal relationship between dogs and English-speaking individuals, but also between dogs and Dutch-speaking individuals.We used a multi-step process to test the validity and reliability of a Dutch translation of the MDORS questionnaire. This process consisted of the following steps: translation, expert opinion, subject opinion, and statistical analysis. For the translation step, a Dutch native speaker, who was also fluent in English at an academic level and who had worked with the original MDORS, translated the original English questionnaire to Dutch (version T1). They additionally compared their translation to a separate MDORS translation, which had been used in a previous study (version T2) . A DutchAfter translation, a group of five dog behavior experts who spoke Dutch as their native language and English at an academic level, and were familiar with the original MDORS’s concepts checked the Dutch MDORS for readability , feasibility , clarity , and discrepancies from the original MDORS (only one of the experts had worked on translations before). The experts additionally judged whether they considered each individual question essential to the questionnaire. From the answer to this latter question, a ‘Content Validity ratio’ (CVR)  was calcIn this formula, E stands for the number of experts in the panel that thought the question was essential to the questionnaire, while N stands for the total number of experts in the panel. Calculated scores could range between 1  and –1 .A group of test subjects additionally judged the questions for readability, feasibility, and clarity, in addition to filling out the questionnaire. These individuals were recruited by spreading a recruitment message on various social media platforms. A total of 501 individuals responded to the recruitment message and answered the questionnaire. This group had an average age of 39.62 years (±13.63), a 95% female to 5% male ratio, and lived distributed across the Netherlands. A sample of 88 subjects  were willing to fill out the questionnaire a second time to help test for test–retest reliability via a Pearson coefficient. The intermediate period between both inquiries was two weeks. This period was chosen based on earlier test–retest protocols for questionnaires by Brazier et al. . The construct validity of the Dutch MDORS was tested with a principal component analysis (PCA) . We calcA Cronbach’s alpha score was finally calculated for each of the three factors originally found by Dwyer et al.  to deterWe encountered no major issues during the translation process of the English MDORS. Only five disputable points were identified. These points concerned questions number 3, 9, 19, 20, and 28. In question number 3, the translation of the words ‘food treats’ was difficult, as its literal translation ‘voedseltraktaties’ is not commonly used in the Dutch language to describe rewards for dogs. However, no other suitable Dutch translation could be found without the risk of losing the original meaning of the words. Therefore, we chose to use the literal translation in the questionnaire. A similar problem was encountered with question number 9, as an adequate translation for the word ‘groom’ could not be found in Dutch. Therefore, we decided to describe the Dutch term instead of translating the word. The resulting replacement was: ‘het verzorgen van de vacht van de hond’ (to take care of your dog’s coat). After receiving advice from a Dutch language expert, we did not use the word ‘traumatisch’ (traumatic) in question number 19. This word is not commonly used in daily Dutch language, which could cause the misinterpretation of questions in which it is used. Instead, the word ‘moeilijk’ (difficult) was used. In question number 20, the word ‘chore’ was difficult to translate directly to Dutch due to several translation options also being able to mean other words. The word ‘karwei’ was eventually chosen, although this was mistranslated to the word ‘job’ upon back-translation. This is not a common Dutch interpretation of the word, as job is usually translated as either ‘baan’ or ‘werk’. Finally, in question number 28, the back-translations differed from the original English MDORS in context. This is due to the limitation of automated translation, because it can only provide literal translations and cannot fully capture contextual or cultural differences in languages. The product of the translation process can be found in The expert group considered all the questions proposed for the Dutch translation of the MDORS essential for the questionnaire (CVR = 1.0). The readability (0 issues reported), feasibility , and clarity (0 issues reported) of all the questions was additionally deemed sufficient by both the expert and subject group.To test for test–retest reliability, a Pearson coefficient was calculated over the MDORS scores of the 88 subjects who filled out the questionnaire twice. This was done by separately calculating the MDORS score each of the two times the participants filled out the questionnaire. Then, the scores of the first were compared to the scores of the second, which yielded a Pearson coefficient of 0.83. Through the PCA , we founThe questions that study the emotional closeness of owners to their dog (Factor II) are also mostly found in a single question cluster. All but two (questions 18 and 19) had high (over 0.6) component scores, which were additionally oriented in the same direction. The questions that study the perceived cost of dog ownership (Factor III) are also mainly found in a single question cluster. The only exception is question 25, though this is only due to its component score being just below the acceptable level of 0.4 (score 0.37). Similar to the other two question clusters, all the questions are again oriented in the same direction.We calculated Cronbach’s alpha of the Dutch MDORS translation for each of the three factors described by Dwyer et al.  in the oThe conception of the Dutch MDORS was not without some statistical or design issues. A first issue was that some concepts or sentences could not be literally translated to the Dutch language. Therefore, the adjustment of some questions was necessary to make the MDORS applicable to a Dutch population. Cronbach’s alpha for all three factors was additionally calculated to be below 0.7 , which would suggest poor internal consistency. Although we do not have a definite explanation for the low Cronbach’s alpha scores that were found for the Dutch MDORS, we do know that it was not caused by low response numbers, as is sometimes encountered in questionnaires (N = 501) . TherefoFinally, it should be noted that female subjects were overrepresented in this study’s subject group . This is a known phenomenon in voluntary questionnaires ,38,39,40Besides some statistical considerations, the Dutch MDORS translation seems to fit the results that were found by Dwyer et al.  for the Although it is not entirely clear why these questions did not relate fully to the other questions in their original factor, some explanations can be proposed. In Factor I, it should be noted that questions 3 and 8 scored only slightly below the cut-off point . Some other questions of Factor I additionally only scored slightly above the cut-off point (between 0.40–0.45). Therefore, it could be possible that instead of only questions 3 and 8, all the questions belonging to Factor I together are not that related to the rest of the MDORS, and some are only included because of the placement of the cut-off point. This is supported by the percentage of explained variation in the questionnaire associated with Factor I, as it is only 9.58% of the total variation.Regarding Factor II, it appears that question 18 is associated more with the questions placed in Factor I than its original Factor II. This might be because of the concept measured by the question, as it asks owners how often they share secrets with their dog that they do not share with other people. The use of the term often implies frequency, which is perhaps associated more with Factor I as it measures frequency of interaction, rather than Factor II, which measures emotional attachment. Question 19 is also more closely associated with the questions of Factor I than Factor II, although the reasoning behind this association is similarly uncertain. Similar to question 18, the association might be due to the concept addressed by the question, as it asks owners how difficult it would be for them if their dog died. The death of their dog would prevent owners from performing any interactive behaviors with it; therefore it is more closely associated to questions of interaction frequency. Finally, regarding Factor III, it appears that question 25 scores just below the cut-off point (0.4) for any association with this factor. This might be due to the possibility of an open interpretation of this question. The possibility for the open interpretation of this question lies in the use of the word messy, as the word’s exact interpretation may differ between individuals. The downside of open interpretation in MDORS questions has already been studied by Handlin et al.  in theirBesides the exclusion of questions based on our statistical results, we would also like to address two non-statistical points of discussion detected in the original MDORS. The first point is the possibility of bias in the MDORS. In their work from 1996, Zasloff et al.  stated tIn their original MDORS, Dwyer et al.  aimed toIn fact, we advise that no question belonging to Factor I should be counted toward the overall MDORS given how much discussion is possible regarding some of these questions. For example, Handlin et al.  also fouThe second point that we would like to discuss regarding both the original and Dutch MDORS is the use of the social exchange theory. In their original publication, Dwyer et al.  stated tIn conclusion, we found that a translated MDORS can be used to assess dog owner relationships as perceived by the owner among a population of Dutch native-speaking dog owners. However, we advise that questions 18, 19, and 25 of the original MDORS are not used in the Dutch version based on their low PCA scores. Questions 2, 5, and 9 should additionally be removed from Factor I, although the argument to do so is based on logical reasoning rather than statistical analysis. Based on logical reasoning, it would further be advisable to remove the remaining questions of Factor I entirely from the MDORS scale calculation. Questions regarding the positive effects of human–animal relationships may be added to the scoring system instead in order to balance the number of questioned costs and benefits of human–animal interaction, although the further study of these questions is required. The questionnaire resulting from all of these proposed changes can be found in


The obtained responsivity is about two orders of magnitude higher than that of the commercial mid-infrared photodetectors. Our work opens a route towards achieving high-performance optoelectronics operating in the mid-infrared regime.The pursuit of optoelectronic devices operating in the mid-infrared regime is driven by both fundamental interests and envisioned applications ranging from imaging, sensing to communications. Despite continued achievements in traditional semiconductors, notorious obstacles such as the complicated growth processes and cryogenic operation preclude the usage of infrared detectors. As an alternative path towards high-performance photodetectors, hybrid semiconductor/graphene structures have been intensively explored. However, the operation bandwidth of such photodetectors has been limited to visible and near-infrared regimes. Here we demonstrate a mid-infrared hybrid photodetector enabled by coupling graphene with a narrow bandgap semiconductor, Ti 2O3 nanoparticles can enable efficient mid-infrared photodetection. Here, the authors report a graphene-Ti2O3 based hybrid photodetector with high responsivity of ~300 A W-1 up to 10 μm by varying the number of graphene layers and size of Ti2O3 nanoparticles.Coupling graphene with narrow band-gap Ti Practically, long-wavelength infrared (LWIR) detectors are expected to have features of high photon-carrier conversion efficiency, low noise level at room temperature and fast response speed in a broadband wavelength range. It still remains as a challenge to realize high performance LWIR photodetection with the conventional narrow-bandgap semiconductors such as mercury cadmium telluride (HgCdTe) thin films, indium antimonide (InSb) and artificial semiconductor superlattices via inter/intraband transitions4. Recently, significant efforts have been devoted to colloidal quantum dots (CQDs) based photodetectors due to their high absorption efficiency and facile manufacturing processes5. However, CQDs-based photodetectors suffer from limited operation spectral bandwidth because of their relatively large bandgaps7. Alternatively, two-dimensional materials appear to be promising candidates and provide unique properties such as ultrahigh carrier mobility, easy-integrability and broadband light absorption8. Graphene has been successfully demonstrated as a broadband photodetector from visible to the terahertz wavelength regimes14. Unfortunately, the intrinsic low absorption and fast carrier recombination rate of graphene hinder its application in photodetection, and such devices suffer from low responsivity as well as poor detectivity15.High-performance infrared photodetectors that can convert light into electrical signals lead to a wide range of applications ranging from imaging sensors to optical communications17. In such hybrid structures, one type of carrier (either electron or hole) is trapped in the CQD while the other type rapidly circulates in the graphene channel driven by the external source-drain voltage. Similar designs were also employed in the photodetectors with hybrid graphene-TiO218, graphene-ZnO19, graphene-dye20, and graphene-perovskite structures21. However, the operation wavelength of such hybrid photodetectors are limited in the visible and the near-infrared regimes owing to the relatively large intrinsic bandgap of the light absorbers9. Although black phosphorene25 and noble metal dichalcogenides have been recently demonstrated as a near-infrared/mid-infrared semiconductor26, it still remains as a challenge to further improve the performance of photodetectors in terms of photon absorption efficiency, responsivity, and response speed in the important mid-infrared regime.Several pioneering works have been devoted to improving the performance of graphene-based photodetectors through constructing hybrid structures. Ultrahigh optical gain was achieved in hybrid graphene-CQD structures, where graphene serves as the ultrahigh speed carrier transport channel and CQD serves as light absorber with high absorption efficiency2O3) nanoparticles. Ti2O3, a stable semiconductor with extraordinary broadband photoresponse characteristics, has a narrow-band gap of 0.09 eV, corresponding to a cut-off absorption wavelength of 13.3 μm27. The working mechanism is as follows: when the incident light is absorbed by the Ti2O3 nanoparticles, the photo-excited electrons are trapped in the Ti2O3 nanoparticles, while the holes are transferred into the graphene channel, leading to a conspicuous photocurrent measured in a field effect transistor configuration. In addition, we also systematically investigated the photo-generated carrier transfer processes at the interface of graphene and Ti2O3 in this hybrid photodetector. The developed graphene/Ti2O3 photodetector is demonstrated to be capable of operating in both accessible atmospheric windows, the mid-wavelength infrared (MWIR: 3–5 μm) and the LWIR (8–12 μm) regimes. The broadband mid-infrared operation bandwidth, high responsivity and detectivity make the graphene/Ti2O3 a promising candidate for mid-infrared photodetection, providing a novel paradigm for mid-infrared photonics and optoelectronics.Here we demonstrate room-temperature mid-infrared photodetectors with high responsivity, detectivity and high speed, realized by hybridizing graphene with a novel narrow bandgap semiconductor, titanium sesquioxide . Ti2O3 is chosen in this hybrid structure as the light absorber owing to its unique narrow bandgap (0.09 eV) that covers the mid-infrared regime27. Ti2O3 is very different from the well-studied wide bandgap semiconductor TiO2, as shown in Supplementary Figure 2O3, density functional theory (DFT) calculations with a plane-wave basis set were performed. The calculation details are given in the Supplementary Note 2O3 due to its unpaired 3d electrons, which contributes to the states just below the conduction band and forms an upper valence band, as shown in Fig. 2O3 is located between the lower and the upper Hubbard band31, which is estimated to be about 0.09 eV according to the absorption spectrum in Fig. 2 is about 3.3 eV and originated from the separation between O 2p and Ti 3d orbitals. The unique and wide-band light absorption of Ti2O3 as shown in Fig. The schematic diagram of the proposed hybrid graphene/Tiace Fig. , leading2O3 nanoparticles with relatively uniform nanoparticle sizes were prepared by a simple ball milling process followed by ultrasound process and purification in ether solution. Then they were spin-coated on the channel surface of a graphene field effect transistor (FET). As shown in the X-ray diffraction (XRD) pattern in Fig. 2O3 nanoparticles exhibit the corundum phase, which is consistent with the previous reports31. As shown in Fig. 2O3 nanoparticles have an average diameter of ~50–200 nm, characterized by scanning electron microscopy (SEM). Furthermore, high-resolution transmission electron microscopy (HR-TEM) and selected-area electron diffraction (SAED) were performed to characterize the structure of the fabricated Ti2O3 nanoparticles. As shown in Fig. 2O3 lattice. Moreover, the corresponding SAED pattern shown in Fig. 2O3 nanoparticles. The Raman spectrum of the Ti2O3 nanoparticles shows seven active Raman modes . X-ray photoelectron spectroscopy (XPS) was used to characterize the electronic states of Ti and O in the Ti2O3 nanoparticles. As shown in Fig. p3/2 peaks with binding energies of 456.8 and 462.5 eV arise from spin-orbit splitting, corresponding to Ti3+ in Ti2O332. In addition, the peak with a binding energy of 529.6 eV in the O 1s spectrum  from Ti2O3 to graphene in the hybrid structure34. Notably, as fabricated Ti2O3 is a p-type semiconductor36, and our fabricated pristine graphene is also p-type due to the absorbed hydrocarbon molecules or humidity. As a result, the charge transfer in this hybrid structure remains inefficient because of the band misalignment between graphene and Ti2O3, which contributes to the weak shift of the G peak shown in Fig. To examine the interaction between graphene and Ti2O3 to investigate the charge transfer process in the hybrid structure. Figure 2O3 interface39. The 2D peak is derived from a second-order, double-resonant Raman scattering mechanism and its frequency decreases with increasing gate voltage that up-shifts the Fermi level of graphene34. Theoretically, it is proven that with the increase of gate voltage, the G peak which is originated from the coupling between G-phonon lattice vibrations and Dirac fermions should present first blue-shift in the p-type doping regime (Vg < VD) for graphene and then red-shift in the n-type doping regime (Vg > VD) for graphene38. This is contrary to the experimentally observed trend of G peak shown in Fig. 2O3 interface. In the p-type doped regime of graphene (Vg < VD), the gating effect on graphene is the dominant contribution to the red-shifts of both G peak and 2D peak as the charge transfer process is suppressed, as shown in Fig. 2O3 to graphene channel begins to dominate in the n-type doped regime of graphene (Vg > VD) when the Fermi level is upshifted.We thus applied gate voltages to modulate the Fermi level of graphene and align the band structure between graphene and Ti2O3 nanoparticles in the mid-infrared regime and the efficient charge transfer in the hybrid graphene/Ti2O3 structure modulated by proper gate voltage, the mid-infrared photodetection performance of such hybrid photodetectors was demonstrated. The fabrication details of the photodetector can be found in the Id−Vd curves are generally linear and symmetric for small source-drain voltages, indicating ohmic-like electrode contacts. An obvious decrease of channel current is observed with laser irradiation, which is contributed by the photocurrent as shown in Fig. 2O3 structure, which is defined as the absolute value of the source-drain current under the laser illumination subtracted by the dark current, is shown in Fig. p-doped), which is consistent with the inefficient charge transfer due to the band misalignment between graphene and Ti2O3 in the hybrid structure, as shown in Fig. 2O3 into graphene.With the strong optical absorption of the Ti2O3 photodetector shows a broadband photoresponse in the mid-infrared regime as shown in Fig. −1 under a source-drain bias of 2 mV, was achieved with 10 μm laser illumination. This indicates that our hybrid photodetector offers low electrical power consumption. The obtained responsivity here vastly surpasses those in the previous reports on graphene- and other 2D-based mid-infrared photodetectors43, which is about two orders of magnitude higher than that of commercial mid-infrared photodetectors based on MCT, InSb and so on46. Figure 2O3 interface introduced during the device fabrication process47. The device also demonstrated good stability during the on/off measurements, and the performance remains stable after several weeks if the device is properly kept. Furthermore, the hybrid graphene/Ti2O3 photodetector shows versatile photoresponse in a broad spectrum range from 4.5 µm to 10 µm as shown in Fig. The hybrid graphene/Ti2O3 photodetector presents a noteworthy enhancement when the graphene channel increases from monolayer to trilayer as shown in Fig. 2O3 nanoparticles and the graphene layer as explained in Supplementary Figure −1 for hybrid trilayer graphene/Ti2O3 photodetector under 10 µm laser illumination. Another prominent feature of the hybrid photodetector is its high detectivity as obtained from the low noise spectrum as shown in Fig. 48. The detectives, D*, are calculated to be ~2 × 108 cm Hz1/2 W−1, 3 × 108 cm Hz1/2 W−1, and 7 × 108 cm Hz1/2 W−1 for monolayer, bilayer and trilayer graphene according to Supplementary Equation 45. Graphene layer dependent photoresponse properties are shown in Supplementary Note 46. The results here provide hints towards optimizing the 0D-2D hybrid infrared optoelectronic devices.The photoresponse of the hybrid graphene/Ti2O3 nanoparticles on the optoelectronic properties of the hybrid graphene/Ti2O3 structure. As shown in Fig. 2O3 nanoparticles from 200 to 80 nm . Ethanol was added during milling, and the milling speed was fixed at 300 rpm for 48 h. The size distribution of the obtained nanoparticles is shown in the Supplementary Figure Ti2O3 nanoparticles spin-coated on KBr substrate were measured using a Fourier Transform Infrared Spectrometer . The measurements were all performed in the ambient conditions.The absorption spectra of the Ti2 layer. The location and quality of graphene were characterized by optical contrast using an optical microscope and Raman spectroscopy, respectively. Then, graphene-based FETs with the heavily doped silicon substrate as the backgate electrode were fabricated by standard photolithography and e-beam evaporation. Subsequently, the Ti2O3 nanoparticles were dispersed in ethanol solution  and spin-coated (4000 rpm) on the surface of the graphene channel. The devices were then dried in an oven under 100 °C for 12 h.Graphene flakes were mechanically exfoliated from a crystal of highly oriented pyrolytic graphite (HOPG) using adhesive 3M-tape and deposited on a silicon wafer with a 285-nm thermalized SiOThe electrical characteristics were examined by a semiconductor parameter analyzer . The responsivity measurement was performed in a digital deep level transient spectroscopy (BIORAD) system with mid-infrared lasers  to illuminate the whole devices, as shown in Supplementary Figure Supplementary Information


Graphene is a nanomaterial with many promising and innovative applications, yet early studies indicate that graphene may pose risks to humans and the environment. According to ideas of responsible research and innovation, all relevant actors should strive to reduce risks related to technological innovations. Through semi-structured interviews, we investigated the idea of graphene as a risk (or not) held by two types of key actors: graphene researchers and innovation advisors at universities, where the latter are facilitating the movement of graphene from the laboratory to the marketplace. The most common idea found is that graphene is not a risk due to, e.g., low toxicity, low amounts produced/used, and its similarity to harmless materials (being “just carbon”). However, some researchers and advisors also say that graphene is a risk, e.g., under certain conditions or due to a lack of risk-related information. We explain the co-existence of these seemingly contradictory ideas through (1) the semantic ambiguity of the word risk and (2) a risk/no-risk rhetoric, where risks are mentioned rhetorically only to be disregarded as manageable or negligible. We suggest that some of the ideas held by the researchers and innovation advisors constitute a challenge to responsible research and innovation regarding graphene. At the same time, we acknowledge the dilemma that the discourse of responsible innovation creates for the actors: denying graphene risks makes them irresponsible due to a lack of risk awareness, while affirming graphene risks makes them irresponsible due to their everyday engagement in graphene development. We therefore recommend more research into what researchers and innovation advisors should do in practice in order to qualify as responsible. In 2010, Andre Geim and Konstantin Novoselov were awarded the Nobel Prize for their “groundbreaking experiments” regarding the carbon-based nanomaterial graphene , high stThe Flagship, launched in 2013, involves more than 150 academic and industrial research groups in 23 countries and is coordinated by Chalmers University of Technology in Gothenburg, Sweden. Given the impact that graphene research “is expected to exert on tomorrow’s technologies and world economy,” among the objectives of the Graphene Flagship are “to build a pathway for the newly accumulated strategic knowledge to impact European industries and society” and “to secure a major role [of the EU] in this ongoing technological revolution” ?”The interviews of the graphene researchers and innovation advisors were transcribed and the material coded into categories in an iterative process. The primary focus was the categorization of the respondents’ main ideas about graphene risks, i.e., the respondents’ risk associations with graphene. By risk association, an actor establishes a connection between something and the notion of risk –47. In oThe notion of risk is multifaceted and has received theoretical interest from a variety of disciplines . Many deIn supposed contrast to this subjective understanding of risk, claims are sometimes made that risk is objective , 53, 54.x is a risk” presuppose a perspective from which some value is at stake. Still, such statements may be motivated by objective reasons, including evidence that human exposure to x can cause cancer  seems to be safe,” “there are no risks with graphene,” “I trust my colleagues who say that there is no risk with graphene,” “it is a safe material,” “graphene is not really a problem in nature,” “we see nothing alarming,” “the consumer has minimal risk,” and “graphene […] is environmentally friendly”. One researcher said:“If we replaced all electronic screens in the world, 2 billion touchscreens per year, there would be 60 kilograms emissions of graphene. This is not much.”This quote suggests that the absence of risk is easily achieved, e.g., by chemical modifications or simply by not (consciously) inserting it into the human body. More specific statements provide graphene’s lack of toxicity as a rationale for its lack of risk: “graphene will not attack cells” and “it is not toxic”. Other claims provide the lack of exposure to graphene as rationale, referring to the presence of safety equipment in labs (masks and fume hoods), the fast excretion of graphene from the body, and graphene being encapsulated in products. Another rationale stated for a lack of risk is the small amounts of manufactured graphene currently existing and anticipated in the future. One researcher said:“Since the 1850s all schoolchildren have used [lead] pencils, they have ingested graphene. Since we learned to make fire we have ingested graphene from the ashes.”Another frequent rationale for graphene not being risky is its similarity to other harmless substances, in particular the graphite carbon in lead pencils. Quotes include “carbon is not dangerous,” “I have no worries touching it, it is like pencils, graphite,” “it does not pollute as it is just carbon,” “regarding risks, graphene should not be that dangerous, it is graphite,” and “graphene is carbon; it is not dangerous for nature”. One researcher said:The basis for this rationale is that the carbon form graphite found in lead pencils and ashes consist of graphene sheets, although separate graphene sheets are considered to be another carbon form  than graphite.“To manufacture graphene you use Scotch tape, it is the same procedure to produce silicon. There is no danger. Not worse than silicon.”A similar rationale is that graphene is not a risk because of its similarity to the presumed harmless material silicon, as exemplified by this quote:“So far we haven’t seen any larger risks, on the contrary, those who are researching the risks […] think that their work is very boring, as they can only publish when they find risks. The toxicologists look for problems and when they can’t find any they can’t publish, so it’s too bad for them – but it’s good, of course that they don’t find anything. So far there are no studies that indicate danger.”The ideas about graphene risk voiced by innovation advisors echoed those of the scientists in many respects. All pointed out that graphene likely poses no risk, in particular due to lack of toxicity: “at the moment it seems that there’s no risk, at least this far we haven’t found any specific risk,” “if it’s handled in a proper way, nothing too worrying has come out,” “one can say that it’s not poisonous, there’s no danger that it is a toxin,” and “no risks that I know of,” “at this time it’s not problematic because we haven’t found anything yet.” One advisor elaborated:This lack of discovered toxicity in graphene by toxicologists was also pointed out by a second advisor. Yet, another advisor said that while there were some doubts about the long-term effects of its use in the human body or with other living creatures, he saw no risks in industrial applications, and that risks had not been discussed—they, the advisors, depended on the common sense of the researchers they worked with, and on the reviews that the research had undergone.“Graphene is a new area and there are no large amounts bought today, and very little is needed. If all mobile phones’ displays were to be covered with graphene, you would only need five kilos or something.”The claim that graphene is not a risk if proper procedures are followed came up. For example, one advisor noted that graphene samples sent within the Graphene Flagship were tracked and that one always has to be careful in handling materials, in the event that they could have a deleterious effect on one’s health. Here too, the small amount of graphene in use was pointed out: “It will be at least ten to fifteen years before graphene will be involved in the large processes.” One advisor said:“[G]raphite has existed all the time – and graphene is basically graphite in many layers, and mixed. People use pencils and children eat the pencils, so you know that it’s probably not supertoxic or anything like that, it’s just carbon.”Like the scientists, some of the advisors pointed out that graphene is simply carbon: “it’s carbon molecules and we have plenty of carbon, “no (risk involved) – we’re talking about carbon atoms, basically” and “graphene oxidizes at 400 degrees, it burns and becomes carbon dioxide.” One advisor explained:Like the scientists, then, these advisors link graphene’s lack of risk to its basis as a common element found throughout nature and currently in common domestic use, such as in pencils.dissimilar to the presumed more dangerous carbon-containing material carbon nanotubes:“You can compare it with the carbon nanotubes. They had some problems a few years back because a few studies appeared which showed that these coal nanotubes weren’t at all beneficial, but rather dangerous, similarly to asbestos […] They are long, and sharp. But graphene doesn’t have that form factor, so to speak.”One advisor brought forward the argument that graphene is not a risk since it is is a risk, or at least that risks cannot be excluded, saying for example that “there must be some dangers with graphene” and that “there are risks with graphene therefore we have protection.” Several mention the lack of knowledge as a rationale for graphene being risky, as shown by these quotes: “[…] risk research is at the beginning, you should not eat it [graphene],” “no one knows if graphene is toxic, some say it is other it isn’t,” “there might be health issues but we don’t know yet,” and “it is not clear how toxic graphene can be.” Some mention as rationales that specific conditions must be fulfilled in order for graphene to constitute a risk, in particular related to exposure probability, saying for example “possibly graphene can be dangerous as nano particles, if you breath them in,” “if you insert graphene into your body it might hurt you,” and “it is important to distinguish between flakes that you can breathe in and powder graphene you do not want to inhale.”Several researchers also expressed that graphene “The risks vary depending on where the material is in the life cycle. In the manufacturing of graphene in tennis rackets there is a risk of inhaling flake at the beginning. […] [W]hat happens when you throw away electronics? This is looked upon at the moment.”“Perhaps there are some hazardous chemicals in the manufacturing process. The problem is that the production will be in India and other countries where they are not as thorough. But this is the same for all electronic products. It is during the production and during the recycling there could be risks. We never talk about risk at work.”Several researchers also say that there are risks related to graphene during production and other product life cycle stages. These are not necessarily related to graphene itself, but possibly to other substances used: “there is a risk with acids that are used in making graphene, but that is easily controlled” and “we use some dangerous chemicals in the process, but they are all approved in the lab.” Two researchers elaborate further:“We haven’t seen any large risks… But at the same time, one can’t yet say that there aren’t any risks because it’s too large an area, there are too many types of material and too many different systems we have to look at, brain cells, intestinal cells, yes, you know, one has to have done so many studies before one can say that something is bad, or good.”Some advisors are also reluctant to conclusively say that graphene is not a risk. The lack of conclusive knowledge about possible risks of graphene is what makes them doubtful, much in the same way as the researchers. They refer to this gap in knowledge in one way or another, while at the same time, maintaining that graphene probably does not constitute a risk:“If a company has a product, they have to class their materials, they have to account whether it contains ‘hazardous materials’ or such. And then they ask if graphene is a dangerous material, of course they ask. And we have to answer, like, ‘a little, well, maybe, maybe a little, or maybe not’… it’s not poisonous, they haven’t been able to prove that it’s toxic… but it’s just this, there is a lot left to do. That’s what one can say. One has to be pretty honest, and say that it’s not poisonous, but there are many studies left to do.”Another advisor points out:“A large flake that is several micrometers in size, for example, probably has completely different health aspects than a flake which is only, say, 10 or 20 nanometers large. So it’s about size, and how they interact with cells, and other things.”Several advisors also adhere to the rationale that graphene constitutes a risk under certain conditions. One advisor points out that although it is composed of carbon atoms, it is not beneficial to inhale. Another notes that difference in health risks are to be expected from different sizes of graphene molecules:Later in the interview, this advisor added that research regarding risks should be carried out in parallel with the development of materials and that it was possible that mistakes might be made with graphene, which is why one has to be careful, carry out evaluations, and be vigilant all the time.“It’s always included in any business plan. One mandatory part of the business plan is having the risk analysis… So it’s just a table that has the description of the risk. The probability of the risk, the severity of the risk if it happens, and the actions to prevent the risk happening. So that’s in it, always. But risk as an element is a really important factor of course… when you think about the risk you have to be thinking about the external ones and the internal ones and the ecological ones and the commercial ones, so... because that’s part of the things that are telling you if this is worth doing, but also telling others that you have at least been thinking about these things. So. It’s just not just a list, it’s important.”One tool that innovation advisors can use to exercise vigilance regarding the possible risks of materials used in new products is the risk assessment carried out routinely when new projects and products are evaluated. In the conversations about risk, four of the six interviewees brought up the importance of these assessments in considering potential problems. One noted:This risk assessment is, then, the currently existing means for detecting human and environmental risks implicated by a future widespread use of graphene. Another advisor noted: “We try to include the concept of sustainability in all our ideas, to think about ‘is this environmentally sustainable?’” He continued, however, to say that it is the economic risks that are the most central in the risk assessment. To consider risk and sustainability “is part of the process,” a third advisor said, but noted that if the researcher presenting the proposal did not know of any risks, it was not followed up. This was echoed by his colleague who claimed that they had not thought about the possible risks of graphene, but rather that they had faith in the researchers’ good judgment considering the reviews their research had undergone. As the risk assessment focuses primarily on commercial risks, and the innovators themselves—together with researchers—are the primary providers of the information used in the assessment, it appears the possibility of detecting novel health and environmental risks in the assessments is limited. The advisors are thus constrained to repeating that to date, no dangers have been discovered and adding that more research is needed.Two ideas expressed by the researchers refer to fundamentally different kinds of risks than the health and environmental risks mentioned above, more related to research and innovation. One said that “the major risk of the graphene is that there is too much money in graphene, other 2D materials are ignored.” The researcher thus suggests that overly high investments in graphene research is hampering important research into other interesting materials and that this is more problematic than any human health- and environmentally related risks. Another researcher said that “the biggest risk is that we will not fulfill the promises around graphene.” This researcher refers to the many promises that graphene brings in terms of innovations see “” sectionis not a risk and that it is a risk. We see two possible reasons for this seemingly contradictory finding: one rhetorical and one semantic. These are explored below.It might seem strange that several researchers and advisors expressed both that graphene As can be seen in Table Considering the semantic explanation, we can first note the conceptual distinction between risk and hazard that is often made in the risk research literature. Hazard then refers to potential loss, while risk refers to exposure to a hazard , 62. “RiHowever useful and clear this theoretical distinction between risk and hazard might be, the word risk has a less narrow and precise meaning in common usage . In factresponsible if they associate graphene with risk, which they partly do. However, the respondents are at the same time irresponsible to associate graphene with risk, since they clearly engage in the then-risky activity of graphene development and innovation on an everyday basis. Demands for responsibility thus also motivate the respondents to dissociate graphene from risk and to downplay risks, which they also do. Given this dilemma-like situation, it is perhaps no wonder that the respondents express a mixed understanding of graphene as a possible risk. Existing research policy on RRI from the European Commission [The semantic explanation does not necessarily point to the respondents being irresponsible from an RRI point of view, but rather to the semantic difficulty  of the risk concept in common language . Howevermmission  providesmmission , 68.Which role should scientists and innovation advisors have in the early anticipation and avoidance of risks?Do scientists and innovation advisors experience a ‘damned if you do, damned if you don’t’ dilemma when it comes to acknowledging technological risks?Can individual-level criteria for RRI be formalized?We therefore recommend further research into how RRI should be approached in practice, in particular what actors such as researchers and innovation advisors should do (or think) to qualify as responsible. Potentially interesting research questions include:Our recommendation is in line with Frankel , who wriWe have found that the main idea held by graphene researchers and innovation advisors is that graphene is not a risk. Rationales provided for this are that graphene is not toxic, that exposure is low, that small amounts are expected to be produced and used, that graphene can be made safe, that graphene is similar to harmless materials , and that graphene is different from hazardous materials such as carbon nanotubes. A less frequent but still common idea is that graphene is a risk. This is motivated by the current lack of risk-related information for graphene, as well as that it can be risky under certain conditions and in different stages during its product life cycle . We suggest that these two seemingly contradictory ideas can be explained through (1) the semantic ambiguity of the word risk, which can denote both actual and potential losses, or (2) a risk/no-risk rhetoric, during which risks are first rhetorically mentioned only to be disregarded as manageable or negligible later. We also note that some researchers mentioned as main risks that the focus on graphene could hamper research and development of other interesting two-dimensional materials, and that the high promises of graphene may not become fulfilled. Given the second explanation, we suggest that some of these ideas held by the graphene researchers and innovation advisors constitute challenges for RRI in the graphene field and for graphene technology. At the same time, we acknowledge that the uncertainty of graphene risks and the RRI discourse put the respondents in a dilemma-like situation. If they deny that graphene is a risk, they become irresponsible because of their lack of risk awareness. If they affirm that graphene is a risk, they also become irresponsible because of the engagement in graphene development that their work constitutes. More research regarding what researchers and innovation advisors should do in practice in order to qualify as responsible is therefore recommended.