Pseudomonas aeruginosa for the first time. Efficient and facile one step hydrothermal process adopted in the present work for the synthesis of graphene-tin oxide nanoparticles provides an ideal method for the economic large-scale production of the same. Graphene-tin oxide nanocomposites derived from wood charcoal possess a spherical morphology whereas rod like structures are seen in the case of coconut shell derivatives. An excitation independent fluorescence response is observed in graphene-tin oxide nanohybrids while graphene oxide nanostructures exhibited an excitation dependent behavior. These hydrophilic nanostructures are highly stable and exhibited no sign of luminescence quenching or particle aggregation even after a storage of 30 months. Bactericidal effects of the nanostructures obtained from coconut shell is found to be relatively higher compared to those procured from wood. This variation in antibacterial performance of the samples is directly related to their morphological difference which in turn is heavily influenced by the precursor material used. MIC assay revealed that coconut shell derived graphene-tin oxide composite is able to inhibit the bacterial growth at a lower concentration (250 μg/mL) than the other nanostructures. Nanocomposites synthesized from agro-waste displayed significantly higher antimicrobial activity compared to the precursor and graphene oxide nanostructures thereby making them excellent candidates for various bactericidal applications such as disinfectants, sanitary agents etc.Antibacterial screening of graphene-tin oxide nanocomposites synthesized from carbonized wood and coconut shell is investigated against  One of the biggest challenges in the modern era medicine and sanitation industry is the containment of the evolution and adaptation of various bacterial strains. The consistent improvement in the bacterial resistance towards drugs and other antibiotics has compelled the researchers to look for new antibacterial agents with improved screening7. It is established from the earlier researches that, graphene via its sharp edges can rupture the bacterial cell membranes, thereby making it a promising candidate for bactericidal applications12. Graphenic structures embedded with inorganic nanoparticles are also well known for their antibacterial performance and low cytotoxicity towards the mammalian cells13.Recently, quest for the bulk production of graphene based biocompatible materials has gained momentum owing to their wide range of applications as biosensors, purification membranes, sanitary agents etc16. Even though AgNPs are capable of antimicrobial screening, the studies on the adverse effects of nano-silver particles and Ag+ ions on human cells as well as on the environment poses a serious health concern18. Hence, development of alternative materials with comparable antibacterial performance is the need of the hour. Recently, metal oxides are highly sought after for composite preparations in the field of biomedicine primarily due to their high chemical reactivity making them extremely suitable for nanoparticle formation19. Studies have confirmed that metal oxide nanoparticles considerably decrease the attachment and viability of bacterial agents thereby making them befitting for many antibacterial applications22. Liu et al. reported an increased antimicrobial activity of graphene quantum dot/ZnO nanocomposite under UV photo irradiation due to the enhanced generation of reactive oxygen species (ROS)21.There are many reported studies on various synthesis methods of graphene-silver nanoparticles (AgNPs) and their antimicrobial activity2) is one of the notable metal oxides which possess excellent electrochemical, optical and electronic properties. Recently, Amininezhad et al. reported the inactivation efficiency of tin oxide (SnO2) nanoparticles for gram-negative Escherichia coli and gram-positive Staphylococcus aureus under UV and dark conditions23. Wu et al. investigated the antibacterial activity of graphene-stannous dioxide nanoparticles against Staphylococcus aureus and Pseudomonas aeruginosa (P. aeruginosa) using optical density and plate counting methods12. It was concluded that the presence of SnO2 particles on the graphene framework enhanced the cytotoxicity of the latter because of synergic effect12.Tin oxide  play an important role in regulating the morphology of metal oxide nanoparticles such as SnO2 during the formation of nanocomposite32. Production of graphene nanostructures from materials like graphite and its oxides involves procedures which are either expensive or use hazardous chemicals like hydrazine monohydrate33. Also, the scissoring of large graphene domains into smaller ones is tedious and time consuming34. Barbolina et al. has suggested that the antibacterial mechanism and bacterial viability of graphene oxide heavily depends on the precursor as well as on the methods employed in the production of the same before the antibacterial screening36. Hence, search for an effective precursor that can be developed into a strong antibacterial agent is necessary. In this regard, graphene and metal oxide nanoparticles showcasing relatively high antibacterial properties are worth investigating. However, the quest for a facile and viable means of production of these graphene nanohybrids with metal oxides is often hindered either by herculean protocols or expensive ways of manufacturing. An economically scalable, large-scale route of production of graphene-metal oxide nanohybrids is quite essential to facilitate their usage in variant applications37.Most often, the precursor material used in the studies reported earlier are either graphene/graphite powder or other relatively expensive materials which are commercially available39. Yadav et al. has recently reported the high antibacterial potential of iron nanoparticles synthesized from Aloe vera against various pathogenic bacteria42. In the current study, we present the synthesis of graphene oxide from the burnt remnants of wood and coconut shell thereby recycling these otherwise waste materials which are rich in activated carbon. A facile and scalable synthesis of graphene oxide nanolayers and nanodots from agro waste materials via a modified Hummers’ method is reported. A simple one step hydrothermal route is adopted for the synthesis of graphene-tin oxide (GTO) nanocomposite. Antibacterial property of the GTO nanocomposites is investigated against P. aeruginosa, one of the highly resilient bacterial strain known to mankind.Use of renewable resources for the synthesis of nanostructures has been gaining limelight in recent yearsGO obtained by a simple, scalable oxidative treatment of wood charcoal (WC) and coconut shell charcoal (CSC) is code named as WC-HS (WC-Hummers’ treated) and CSC-HS (CSC-Hummers’ treated) respectively. The GTO nanocomposites derived from WC-HS and CSC-HS is further coded as WCT and CSCT respectively. The effective inherent reduction of GO to graphene is facilitated by the use of the one-step hydrothermal treatment with tin . Unlike the conventional methods used, absence of hazardous chemical reagents and toxic industrial waste or byproducts during the nanoparticle formation is an added advantage. In addition to this, the adopted method has also achieved the otherwise time-consuming scissoring of large particles into smaller domains.45. With the hydrothermal treatment, XRD profiles are modified with the appearance of the distinctive peaks of SnO2 suggesting the successful incorporation of tin oxide nanoparticles in the graphene network. In GTO composites, the (002) peak corresponding to graphene domain is seen to be overlapping with the diffraction peak of SnO2 from (110) plane. Inherent reduction of graphene oxide during the hydrothermal treatment is apparent from the decreased width along with a slight shift in position of the (002) peak in the composite spectra46. In addition to the graphitic peaks, GTO spectra also features peaks at ~26°, ~33°, ~38°, ~51° and ~64° corresponding to (110), (101), (200), (211) and (112) planes of SnO2 respectively47. From XRD analysis, it is observed that the nanocomposite derived from coconut shell charcoal has distinctively well-defined characteristics in comparison with that obtained from wood charcoal. The presence of oxygen functionalities is also confirmed by Fourier Transform Infrared (FTIR) spectral analysis , C=O (~1590 cm−1) and C-OH (~1200 cm−1) in the oxidized samples. GTO nanocomposites showed the existence of O-H (~3400 cm−1), C=C (~1610 cm−1), C-H (~1187 cm−1), C=O (~1030 cm−1) and Sn-O (~600 cm−1) stretching vibrations substantiating the successful incorporation of SnO2 nanoparticles in the graphene matrix32.X-ray diffractograms of GO and GTO nanocomposites derived from wood charcoal and coconut shell charcoal are given in Fig. −1) and graphitic (G) band (at ~1585 cm−1) in the synthesized material49. Raman analysis of the precursors is given in Supplementary Information Fig. D) to graphitic (IG) band intensity ratio is found to be 0.68, 0.92 and 0.93 for WC, WC-HS and WCT respectively indicating the formation of defects or functional groups in the graphene layers. This ratio is calculated to be 0.69, 0.88 and 0.89 for CSC, CSC-HS and CSCT respectively. The higher value of ID/IG ratio conventionally indicates the effectiveness of the oxidation process which rises the number of defects49. The increased intensity of D band is also attributed to the edge effects present in the graphene network of the sample. From Raman analysis, it is evident that the incorporation of SnO2 nanoparticles has not caused much change in the graphene skeletal network51. It can be concluded that the derived nanomaterials mainly consist of sp2 carbon with some sp3 carbon structures embedded with oxygen functional groups on their surface.Raman spectra of nanocarbon derivatives obtained from carbonized botanical waste materials are presented in Figs 52. Hence, after a relative increase seen in the number of defects via oxidative and hydrothermal treatments, one could expect the rise of antibacterial performance of the respective samples.The defects present in the sample are speculated to increase the ROS formation thereby contributing to an increased antibacterial activity of the sample. Moreover, the presence of edges and other induced defects enhances the available surface area for molecular attachments resulting in an elevated toxicity which aids the bacteriostatic and bactericidal performance of the nanostructures2 nanoparticles. The even distribution of oxygen functional groups on the graphene sheets facilitates the uniform dispersion of SnO2 nanoparticles on the graphene backbone. HRTEM images of WCT show tin oxide nanoparticles with size <3 nm evenly distributed throughout the graphene surface  analysis of WC-HS and WCT are shown in Figs HRTEM images of the chemically oxidized coconut shell charcoal (CSC-HS) is depicted in Fig. 2 nanoparticles on the carbon dots framework has resulted in their effective separation. Tin oxide nanoparticles appear to be stacked in the nanocarbon matrix. The lattice fringe width is found to be 0.33 nm which corresponds to (110) plane of SnO2. Particle size measured from the HRTEM image evidently falls into two categories: carbon dots with size ranging from 5–11 nm and Sn nanorods of length 20–34 nm. Nanorods are particularly believed to be a better shape among the others in combating the infectious bacteria due to their exposed planes and increased reactivity53. Smaller the size of the nanoparticles, higher the surface to volume ratio, which in turn increase the availability of ROS in the sample. ROS plays a pivotal role in enhancing the antibacterial activity by causing membrane damage to the bacterial cells54. SAED pattern clearly shows the high crystallinity of the sample with twinning planes belonging to carbon and tin.HRTEM images of graphene-tin oxide nanocomposite obtained from CSC-HS is depicted in Fig. 55. When WC displayed sheet like carbon domains, CSC possessed relatively smaller polygonal structures. The larger size of the carbon domains present in WC was retained by WC-HS during the oxidative treatments whereas in the case of coconut shell, oxygen group embodiment has resulted in the separation and scissoring of larger particles in to smaller dots. The size and shape of the tin oxide nanostructures adhering to the graphene surface is greatly controlled by the physicochemical traits of GO used in the nanocomposite synthesis32. As a result, post-hydrothermal treatment, spherical SnO2 nanoparticles are observed in WCT whereas rod-shaped structures are formed in CSCT. Thus, from the structural and morphological analysis, it is suggested that the nanoparticle formation and properties are heavily influenced by the precursor characteristics.Comparing WC and CSC derived nanostructures, a difference in morphology is very evident. Considering the fact that the protocol used for the synthesis of both nanocomposites are the same, this variation in morphology of the two can be ascribed to the structural difference in the precursor materials used. The degree of oxidation of nano-systems is known to be greatly influenced by the morphology of the precursor materials2 nanoparticles, a transition of PL characteristics from an excitation dependent to an excitation independent form could be observed. As the excitation changes, the emission intensity was found to be ascending to a maximum at 320 nm and starts decreasing with further increase in the excitation wavelength. The bell curve pattern is still evident in the emission intensities. Absence of the broad satellite peak corresponding to the oxygen functionalities is also noted which supports our claim of a high degree of reduction during the hydrothermal treatment56. A fine tuning of the emission peaks from the carbon core is observed with the incorporation of tin nanoparticles. Both quantum size effect and surface effect could be responsible for this excitation independent behavior showcased by GTO nanocomposite58.Photoluminescence (PL) spectrum of the samples are recorded and compared as a function of excitation wavelength. PL spectrum of GO obtained from WC and CSC is presented in Fig. Nanostructured CSC-HS excited from 280 to 400 nm exhibits a fluorescent dependent behavior with the emission maxima of the carbon core centered at ~310 nm. A broad emission from the functional groups could also be seen at a higher wavelength range. With the incorporation of tin nanoparticles, the fluorescence properties changed altogether. From the PL spectrum of CSCT, it is evident that the change in excitation wavelength has no particular influence on the emission characteristics. The removal of oxygen functional groups could also be noted from the absence of the peaks at higher wavelengths. Both GO and GTO nanostructures obtained from WC and CSC showcases similar pattern of emission intensities with change in excitation wavelengths. So, from the PL analysis of the samples, it is deduced that the nanostructures derived from WC and CSC via Hummers’ treatment show an excitation dependent behavior while with the incorporation of tin nanoparticles, PL response becomes independent of the excitation wavelength. Also, the coconut shell derived GTO nanocomposite manifest a better refined excitation independent PL behavior in comparison with those obtained from wood. The synthesized water-soluble nanostructures are found to be highly stable and showed no sign of aggregation even after a storage period of 30 months. They also retained their fluorescence property without any quenching after such extended period of storage.P. aeruginosa on nutrient agar plates and the zone of inhibition is measured after incubating for 24 hours. The repeatability of the antibacterial screening of all the samples are also tested for three times. Gram-negative bacterial strain additionally possesses an outer layer of lipopolysaccharides and phospholipids as compared to the gram-positive bacteria and this outermost membrane often acts as a coverage wall for the bacteria thereby rendering it protection from the attack of foreign bodies59. At the end of incubation period of the disc diffusion assay with the synthesized nanomaterials, a clearance zone is seen to be developed around the well indicating the antimicrobial activity of the sample. Absolute alcohol is used as the negative control and antibiotic cephalexin is used as the positive control for the study. Figure The bactericidal test of the synthesized samples (conc. 1 mg/mL) is performed against gram-negative bacteria 60. Sharp edges of the graphene nanosheets also aids in the rupturing of the bacterial cell wall making it forego the cell integrity. A considerable increase in the antimicrobial effects with a relative decrease in size of the particles is also reported61. Hence, the smaller size of nanoparticles formed post-hydrothermal treatment plays a significant role in the enhancement of antibacterial activity of the obtained nanocomposites.The antibacterial screening is observed to be more in the case of GTO nanohybrids comparing to its virgin and GO counterparts. This can be ascribed to the inclusion of tin oxide nanoparticles together with an increase in number of defects in GTO composites causing an increased surface to volume ratio and more oxidative stress in the bacterial cell walls. The oxidative stress induced in the bacterial membrane helps in incapacitating the inherent anti-oxidant defense mechanism of the bacterial cells61. A slight decrease in the observed antibacterial activity of WC-HS points to the earlier reports that the purity of GO depends on the precursor material used and consequently has a direct relation to its antimicrobial effects. The comparatively less surface area of larger GO domains in WC-HS decreases the interaction sites of the nano-system with bacterial surface leading to a diminished antibacterial activity. In comparison with the nanostructures obtained from wood charcoal, those derived from coconut shell manifests a higher antibacterial activity towards P. aeruginosa. CSCT showcases 40.7% higher bactericidal capability when compared to WCT. This is a direct consequence of the morphological difference between the two. Nanostructures synthesized from coconut shell charcoal is found to be smaller in size and possess a superior rod like morphology which contributes in enhancing its microbial activity. The increased surface to volume ratio of CSCT nanoparticles significantly increases the surface area available for interaction with the bacterial membrane leading to a higher bactericidal efficacy. Also, larger particles tend to get adsorbed on the bacterial surface whereas the smaller ones get absorbed in to the bacterial cell resulting in internal damage and alterations in the cell activity62. Hence, CSC nanostructures possessing smaller carbon domains are more effective in eradicating the bacterial strains. The increase in number of defects in the graphene backbone, release of toxic ions in to the bacterial cell and the diminution of surface negative charge after nanocomposite formation might have also benefited the cause13. GTO nanohybrid appears to combine the antibacterial properties of both GO and SnO2 particles, effectively enhancing the antibacterial effect of both the base materials11.Zone of inhibition measured in this study is by far one of the highest reported. Graphene by itself can help in enhancing the antibacterial performance of the nanocarbon by adsorbing to the bacteriaP. aeruginosa is determined by microdilution plate method with resazurin63  implying the efficacy of the coconut shell derived GTO nanocomposite.Minimum inhibitory concentration (MIC) of the synthesized nanostructures against From the disc diffusion assay and MIC analysis of WC and CSC derivatives, it is evident that GTO nanocomposites have better antibacterial efficacy in comparison with the respective precursor and GO counterparts. Zone of inhibition measured in the case of GTO nanocomposite from CSC is comparable to that of the standard antibiotics used. This is in turn corroborated by the low MIC value of CSCT in MIC assay. Thus, GTO nanocomposite derived from coconut shell seems to be promising for various antimicrobial applications.Pseudomonas aeruginosa are 27 ± 1 mm and 38 ± 0.7 mm respectively. This measured antibacterial activity is one of the highest reported of its kind. MIC assay has revealed that CSCT nanocomposite could impede the bacterial growth at lower concentrations than the other synthesized nanostructures. The rod-shaped morphology and well-defined structural characteristics of GTO nanocomposite derived from coconut shell has made them more efficient antimicrobial agents in comparison with WC nanostructures. The effective increase in number of defects as a consequence of the chemical treatments employed has contributed strongly towards the enhancement of antibacterial performance of the nanocomposites. The upgradation of fluorescence behavior to an excitation independent response after the hydrothermal treatment makes GTO nanocomposite a potential benign candidate for biomedical applications. The nanomaterials synthesized are highly stable and showed no sign of aggregation or photo quenching even after extended storage periods. It can be concluded that, CSC derived GTO nanocomposite holds great promise as an antimicrobial agent in various applications like food packaging, sanitary agent manufacturing, sewage treatments, etc. and needs to be investigated further.In summary, an efficient and easily scalable strategy for the economic large-scale synthesis of water-soluble graphene oxide and graphene-tin oxide nanocomposites from agricultural green carbon wastage is demonstrated. A uniform distribution of tin oxide nanoparticles in the graphene matrix is observed. Morphological difference between WCT and CSCT nanocomposites produced using identical chemical protocol indicates that the initial precursor material used for the graphene oxide synthesis plays a pivotal role in the nanocomposite formation. All the synthesized nanostructures exhibited high antibacterial activity and among them, GTO nanocomposites showcased a marked raise in antibacterial screening. Zone of inhibition exhibited by GTO nanocomposites derived from wood charcoal and coconut shell charcoal against 3 was dispersed in 26 ml of H2SO4. 6 g of KMnO4 was added slowly in steps to the above mixture. The system was kept in an ice bath to prevent overheating. The mixture was stirred for 48 hours in order to facilitate complete oxidation. The reaction was terminated by adding 500 ml 5 °C distilled water and 5 ml 30% H2O2 in order to facilitate the exfoliation of the graphitic domains. The mixture was washed repeatedly with dil. HCl, ethanol and distilled water to get rid of the unoxidized reactants and metal ions. It was further subjected to dialysis for the removal of any leftover acid traces. Once a neutral pH was attained, the samples were sonicated and dried under vacuum to obtain WC-HS (~1.2 g) and CSC-HS (~1.7 g). Third step comprised of a one pot hydrothermal treatment of WC-HS and CSC-HS to obtain GTO nanocomposites and is described as follows. 0.05 g of GO is dissolved in 25 mL ethanol via sonication to ensure the exfoliation of the graphitic domains. At the same time, 2.25 g of SnCl2.2H2O is dissolved in 25 mL ethanol. Both the assortments were then transferred to a beaker and sonicated for 90 minutes to ensure thorough mixing of the two systems. Sn2+ ions get anchored on to the GO sheets during this step. The resultant mixture was heated at 150 °C for 24 hours in a sealed high-pressure Teflon lined autoclave. In this phase, GO undergoes gradual inherent reduction whereas tin nanoparticles get oxidized simultaneously and gets deposited on the graphene surface. The mixture was washed repeatedly with distilled water to eliminate the unwanted chloride ions. The resultant product was then dried in vacuum at 60 °C to obtain GTO nanocomposites WCT (~0.4 g) and CSCT (~1.2 g). The chemicals used were of analytical grade and was purchased from Sigma-Aldrich.The formation of GTO nanocomposites was done in three steps. The remnants obtained after the carbonization of wood (~1 kg for ~320 g WC) and coconut shell (~1 kg for 300 g CSC) were grounded and washed thoroughly as the first step. In the second step, dried samples were subjected to oxidative treatment by using a modified Hummers’ method described as follows. 2 g of the respective precursor along with 2 g of NaNOP. aeruginosa using disc diffusion assay. Sterile Muller-Hinton agar was prepared by autoclaving at 121 °C for about 20 minutes and poured into sterile petri plates under LAF. The plates were allowed to solidify and 100 µL of bacterial suspension P. aeruginosa (0.5 OD) was spread over the nutrient agar using sterile cotton swabs. Thereafter 3 wells (7 mm diameter) were made on the nutrient agar using a sterile cork borer. 0.01 g of the synthesized sample was dissolved in 10 mL of absolute ethanol. 100 µL of this sample was loaded into each well. The plates were then wrapped using a cling film and incubated at 37 °C for 24 hours. Zone of inhibition produced by the nanostructures was then measured using Antibiotic Zonescale supplied by HiMedia Laboratories Pvt. Ltd. Antibiotic cephalexin and clarithromycin (10 μg/disc) were used as positive controls. Negative control was absolute alcohol without any sample. The experiment was performed in triplicate to minimize the experimental errors.Antibacterial studies of the samples were carried out against gram-negative bacterial strain of P. aeruginosa was carried out using 96 well micro-titer plate method63. 100 μL of sterilized Luria Bertani broth was dispensed to each well of the titer plate. 2 mg/mL solution of each sample was prepared in DMSO (Dimethyl Sulfoxide). 100 μL of the sample solution was added to a row of the titer plate and serial dilutions were carried out thereafter. The obtained concentration range was from 1000 to 7.8 μg/mL. 10 µL of bacterial suspension (106 CFU/mL) along with 30 µL of 0.1% of resazurin were added to the sample wells. Antibiotic cephalexin was used as the control. A column of wells dispensed with resazurin was taken as color blank. An adjacent column with both resazurin and bacterial suspension was taken as culture control. The plates were prepared in triplicates and the inoculated plates was incubated at 37 °C for 20 hours.MIC assay of the precursors, GO and GTO nanocomposite against Structural and morphological properties of the samples were studied using various characterization techniques. X-ray diffraction measurements were carried out using a a Bruker AXS D8 Advance X-ray diffractometer. Functional groups were identified using a Shimadzu FT-IR-8400 spectrometer and a RF-5301 PC, Shimadzu fluorescence spectrometer was used to obtain PL spectra of the samples. Raman analysis was carried out using a Horiba LABAM-HR spectrometer at 514 nm. High resolution transmission electron microscope (HRTEM) images of the samples were obtained using a JEM-2100 (JOEL) model system.Supplementary Information


A green and facile method using jet cavitation (JC) was utilized to prepare few layer graphene (FLG) derived from artificial graphite delamination without adding any strong acids and oxidants. The JC method not only provides high quality FLG with high yield but also demonstrate excellent electrochemical performance as anode materials for Li-ion batteries. Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) as well as BET isotherms and XPS are carried out in this study. The results of atomic force microscopy (AFM) further revealed that up to 85% of the prepared FLG were less than 10 layers. This exfoliation process happened mainly due to the cavitation-induced intensive tensile stress acting on the layered materials. Electrochemical measurements demonstrate that graphite anode delivered only 240 mAh/g while FLG anode achieved more than 322 mAh/g at 5C rate test. These results indicate that JC method not only paves the way for cheaper and safer production of graphene but also holds great potential applications in energy-related technology. By down-sizing graphite from micro to nano-scale, namely graphene, the applications would future widen to polymer composites, anode materials for Li-ion batteries, supercapacitors, hydrogen storage materials, adsorbers and catalysts8.Owing to excellent properties of graphene reported so far, such as Young’s modulus (>1060 GPa), electron conductivity (6000 S/cm), thermal conductivity (~3000 W/m K), light and inexpensive10, growth on SiC12, chemical vapor deposition14, molecular beam epitaxy, chemical synthesis18, chemical routes and other methods21. Mass production of graphene or few layer graphene is being hindered by the expensive cost and environmental threat of its conventional synthesis. For example, disadvantages of chemical vapor deposition are high cost and limitation of area. Chemical routes, so called Hummers’ method, suffered from usage of strong acid and oxidants during oxidation processes. A vast amount of waste acids resulted in environmental pollution and problems. Based on these issues, many researchers focus on green process to synthesize graphene or FLG, such as electrochemical exfoliation24, ultrasonicaion process26 and so on. However, many problems, such as low yields and poor quality of as-synthesized FLG still need to overcome.The synthesis of graphene has been carried out by various methods such as exfoliation and cleavage, ultrasonic exfoliation27 and sonication28 to delaminate the graphene or using jet cavitation method and obtained few layer graphene29. Yi et al. showed the feasibility of delamination by JC for unmodified graphite and other layered materials and investigated the influence of feed concentration and processing time on yield and morphology of the product32. Moreover, Yi et al. demonstrated 10 L batch graphene production by a jet cavitation (JC) method and obtained few-layer graphene with low defect concentration29. The processing time, however, was quite long (8 h). Nacken et al. reported an environmentally friendly method for graphene production in large quantities (5 L batches) in processing times <3 h by top-down processing of isostatic and unmodified graphite in an industrial high pressure homogenizer27. According to the above researches, these solvents are organic-based solvents, like NMP, DMF or acetone in the preparation process, even the surfactants including sodium carboxymethyl cellulose (CMC), non-ionic surfactant TWEEN®80 (TW80) or sodium dodecyl sulfate (SDS) are used. In addition, the production of few-layer graphene was got after using centrifuge. In this paper, we propose a green process by using jet cavitation. Here we use an industrial low temperature ultra-high pressure continuous flow cell disrupter (LTHPD) as a delamination device for delamination of graphite suspension continuously by JC method. In this device the graphite suspension is pumped through a nozzle with a defined flow rate to adjust the system pressure. The cavitation and pressure yields a lateral force that induces exfoliation. Through the combination of velocity gradient-induced shear stress, turbulence-induced Reynolds shear stress, and shear effects that emerged from turbulence and flow-induced collisions, a lateral force is generated causing exfoliation. This normal force caused the bulk material to self-exfoliate to single or few layers through their lateral self-lubricating ability32. This method is simple, scalable and does not require toxic chemicals, graphite oxidation or ultrasound post processing to achieve exfoliation. In this study, we propose a green process by using jet cavitation. Here we use an industrial low temperature ultra-high pressure continuous flow cell disrupter (LTHPD) as a delamination device for delamination of graphite suspension continuously. This method is simple, scalable and does not require toxic chemicals, graphite oxidation or ultrasound post processing to achieve exfoliation.Recently, there were reported in many kinds of literature by using the high pressure homogenizer36. As for applications of graphene anode for Li-ion batteries, Lian et al.37, Jusef et al.38 and Wang et al.39 reported graphene nanosheets synthesized by chemical synthesis demonstrate good electrochemical performances as anodes in lithium-ion cells. However, it suffers from problems of poor electronic conductivity, larger hysteresis and irreversible capacity loss in the first cycle due to structural defects and functional groups in graphene nanosheets resulted from oxidation processes. In addition, Haiyan et al.40 reported the fabrication of anodes for lithium-ion batteries (LIBs) based on graphene nanoflakes. Moreover, the device cycled at 0.5 A/g of current densities present only 200 mAh/g. In 2011, Zhou et al.41 prepared foam-like graphene as an anode for Li-ion batteries. Its capacity at a current density of 0.2 A/g was about only 200 mAh/g.Lithium-ion batteries are among the most widely used energy storage device today. Two-dimensional graphene has drawn much attention because of its admirable properties including conductivity, mechanical strength and high charge carrier mobility which make graphene a suitable electrode material for LIBsTo the best of our knowledge, there are few researches concerning electrochemical behavior and measurements of FLG synthesized from jet cavitation process for Li ion battery. Thus, in this study, we will discuss detail characterizations of FLG in terms of SEM, TEM, BET, AFM as well as Raman and XPS to understand surface morphologies, lateral size, thickness distribution, structural defects, functional groups of as-synthesized FLG. The corresponding electrochemical coin tests, such as C/D tests, cycle life as well as differential capacity plots and AC impedances are carried out.39. In this study, FLG is prepared by JCD without chemical intercalation. Thus, d spacing in 002 plane was closed to 0.34 nm.Figure 43. The average thickness of FLG was 4 nm, which approached 8 layers of graphene (0.5 nm for one layer of graphene) in Fig. 2 adsorption–desorption isotherms of graphene sheets are shown in Fig. 2/g, respectively. FLG demonstrated much larger specific surface area, which indicates that the evidence of graphite exfoliation after our processes.Figure −1, ~1350 cm−1 and ~2700 cm−1 44. The D band is consider the demonstration of the presence of defect and the degree can be estimated by the intensity ratio of the D peak to G peak (ID/IG). The graphite and FLG of intensity ratio of the D peak to G peak (ID/IG) increased from 0.208 to 0.350 through the evolution of ID/IG clearly revealed by comparison of curves. This result demonstrated that defect increased in FLG after exfoliation processes. Furthermore, the oxygen content of graphite and FLG were analysis by XPS is shown in Fig. Raman spectra were analysis so as to examine the defect content of graphite and FLG. Typical spectra for graphite and FLG are shown in Fig. 45. However, graphene is known to have good flexibiltiy compared to graphite. It is believed that graphene will retain the integrity of its shape during rapid lithiation process thus, providing better electrochemical performance. Figure −1 and 369 mAh∙g−1 for graphite and FLG at a current density of 0.1 C (0.035 A/g), corresponding to a coulombic efficiency of 93% and 90, respectively. The reversibility of FLG is comparable to graphite. The solid electrolyte interface (SEI) layer plays an essential role in the reversibility of the capacity. SEI layer is formed by the reaction between graphite and ethylene carbonate (EC) in the electrolyte. It provides kinetic stability to the cell and permits the use of graphite as anode material at the expense of some inevitable irreversible capacity46. Vital properties of energy storage devices such as irreversible capacity loss, cycle life, electrode corrosion, self-discharge rate and safety are highly influenced by the thickness of the SEI layer47. Similar to other literature, as-prepared FLG displayed an irreversible capacity ~0.75 V in the initial cycle attributable to the formation of SEI layer and the reaction of Li+ ions with residual H or O groups in the carbonaceous materials37. Lithium atoms are known to bind quasi-reversibly on the hydrogen terminated edges of graphene. In this study, our few layer graphene is not synthesized by Hummer’s method, namely, reduced graphene oxides. Thus, there is littele functional groups and structural defects in our FLG  and graphene-based (FLG) anode materials for lithium ion battery. During lithiation and de-lithiation, the anode may change its shape51. Rate capability operated at different current rates from 0.1 C to 10 C run for five cycles each  are shown in Fig. 52. An equivalent circuit  formed on the electrode. RCT and CPE2 represent the charge-transfer resistance and the double layer capacitance, respectively, and W1 is the Warburg impedance related to the diffusion of lithium ions into the bulk electrode52. The fitting values from this equivalent circuit are presented in Table S, RSEI and RCT of the graphite electrode are 5.9, 269.9 and 299.9 Ω, respectively, much higher than those of the FLG electrode , which means that both SEI resistance and charge-transfer resistance are significantly reduced in the presence of exfoliation. It is most likely that a more favorable SEI was formed for the FLG electrode than the graphite, which facilitates the lithium ion transfer at the interface between the electrolyte and the electrode. Besides, the thin characteristic was good for the reaction kinetics and diffusion of Li ion53. The Li+ diffusion coefficient can be calculated by the following equation54:R is the gas constant (8.314 J K−1 mol−1), T is the absolute temperature (293.15 K) at room temperature, A is the surface area of the electrode (~1.54 cm2), n is the number of electrons per molecule during oxidization (n = 1), F is Faraday’s constant (96500 C mol−1), and C is the concentration of lithium ions (0.001 mol cm−3). According to the equation  of both graphite and FLG are shown in Fig. ces Fig. 53. Thus,+ intercalation of FLG is faster than that of graphite. The diffusion coefficients of lithium of FLG were increased from 4.39 × 10−11 cm2/s to 2.67 × 10−9 cm2/s. It shows great advantages and is thus proved to be a suitable convenient approach for massive production of graphene. As FLG has been successfully produced by this device and these results indicate that it is potential applications of FLG as anode material for lithium ion battery system.In summary, we develope a method to prepare FLG by JCD. SEM and TEM results indicated that it is transparent and folded, which coincides well with the typical feature of the reported FLG. Beyond the HRTEM and AFM presented in this study, the FLG exhibits thickness of the as-synthesized FLG approaches 10 layers of graphene. Furthermore, the obtained graphene were applied as anode material for lithium ion batteries. During the fast charge and discharge rates (5C), graphite delivered ~239.6 mAh/g while FLG exfoliated in DI water achieved ~322.2 mAh/g, respectively. The FLG presented the lower polarization and the LiThe artificial graphite  was used as feed material for the delamination experiment. All materials were used as supplied without further purification. Deionized water was used for the preparation of all graphite suspensions (10 wt.%). All delamination experiments were carried out in a low temperature ultra-high pressure continuous flow cell disrupter . In this device, the graphite suspension is achieved by high pressure forcing the sample through a small orifice at high speed. At the effect of the shearing, hole and impact, graphite of the sample are crushed; substances of the sample are dispersed and emulsified. And the few layer graphene would be kept the suspension at the crash which operated in circulation cooling device at 14–16 °C circulating water bath. The principle and schematic illustration of JC device are shown in Fig. 2 adsorption by using a Micromeritics TriStar 3000 (USA) analyzer at liquid nitrogen temperature. Spectra were all captured at a resolution of 4 cm−1, and by averaging 10 scans. X-ray photoelectron spectroscopy analysis was performed with a Thermo Scientific K-Alpha using a monochromated Al Kα X-ray source (1486 eV).Raman spectra were obtained with a micro-Raman spectroscopy system; a 532 nm laser was used as the excitation source. Scanning electron microscope (SEM) images were collected by a Hitachi S-4100. Atomic force microscope (AFM) images were captured by a Bruker Dimension Icon. The samples for AFM were prepared by dropping the dispersion directly onto freshly cleaved mica wafer with an injector. Bright-field transmission electron microscope (TEM) and high-resolution TEM (HRTEM) images were taken with a JEM-2100 operating at 200 kV. TEM specimens were made by diluting the suspension in alcohol and pipetting several drops onto holey carbon mesh grid. Brunauer–Emmett–Teller (BET) specific surface area was determined from N6 in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (1:1 in volume ratio). The discharge/charge test were analysed by AcuTech System in the voltage range of 0.01–3.5 V at room temperature. The Cyclic voltammograms (CV) were measured by CH Instruments Analyser CHI 6273E at a scan rate of 0.001 mVs−1 between 0.01 V and 3.5 V, then tested the AC impedance in the frequency range from 1 Hz ~ 100000 Hz in litigation state of 0.001 V.The electrochemical performance of the products were measured by using CR2032 coin cells. The working electrode was composed of 92 wt.% active materials, 3 wt.% KS-6 ), 1 wt.% Super P  and 4 wt.% PVdF, coating on the 10 μm copper foil, then dried at 120 °C for 8 h in vacuum system to remove the residual water. The electrolyte consisted of 1M LiPFSupporting Information


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