The experimental results show that the graphene sheets with a low Fermi level and a superior electron mobility accept photo-excited electrons from TiO2 and enable fast electron transportation; while the CuSbS2 quantum dots promote the visible light-absorption of the photoanode. The synergistic effects in this mixed-dimensional (1D–2D–0D) heterostructure photoanode induce a markedly raised photoconversion efficiency of 1.2% at 0.3 V and a photocurrent density of 5.5 mA cm−2 at 0.4 V. Furthermore, the photocurrent density of the mixed-dimensional heterostructure exceeds previously reported TiO2-based photoanodes in neutral media. The improved photoelectrochemical properties are attributed to the synergistic-effect-induced highly organized, mixed-dimensional architectures. It is expected that the mixed-dimensional heterostructure photoanode will be a potential candidate for applications in environmental remediation and energy fields.The growing demands for reproducible and clean sources of power has prompted the exploitation of novel materials for solar-energy conversion; in any case, the improvement of their conversion efficiency remains a big challenge. We report a mixed-dimensional heterostructure to synchronously enhance charge separation and light-absorption of the photoanodes  The growing demands for reproducible and clean sources of power has prompted the exploitation of novel materials for solar-energy conversion; in any case, the improvement of their conversion efficiency remains a big challenge. Meanwhile, TiO2 can only convert less than 5% of the full solar spectrum and this limits the use of solar energy as a primary source of energy because TiO2 is a wide band-gap semiconductor (3.2 eV).7–12Solar energy is regarded as a feasible alternative to fossil fuels because of its promise for addressing environmental remediation and energy conversion. Therefore, the ability to efficiently harness and utilize solar energy is of great importance. Since its use for water photolysis by Fujishima and Honda in 1972, TiO2 including TiO2-tubes, TiO2-rods, TiO2-fibers, TiO2-belts, and TiO2-wires recently have attracted wide interest for photoelectrical applications because of their large surface area for light-absorption, as well as an axial transport of photo-generated carriers with fast transport property.13–18 In addition, forming a Schottky or p–n junctions to realize band structure engineering is another effective approach, which aims to widen the visible light-absorption and hinder from the recombination of electrons and holes to improve the photon-to-energy conversion efficiency.19–21 For example, coupling 1D TiO2 with narrow bandgap zero-dimensional (0D) quantum dots could enhance the photoconductivity by photogating effect. Furthermore, the dangling-bond surfaces of 2D graphene materials offer flexibility in integrating different dimensioned materials into mixed-dimensional heterostructures for next-generation electronic/optoelectronic devices.22 The introduction of two-dimensional (2D) materials such as graphene into the 1D TiO2, will promote the carrier transfer efficiency. The synergistic effect fully exploits the extraordinary electron transport characteristics of 2D graphene and further makes large contribution to the highly promoted photoelectrochemical performance of the mixed-dimensional heterostructures device. It is thus of strategic interest to synthesize the 0D quantum dots/1D TiO2 nanowires/2D graphene  heterostructures with appropriate composition and well-designed structure.23–27 The interface in this mixed-dimensional heterostructure is less constrained due to the absence of the need for lattice matching, resulting in effective interaction.Great efforts have been made including the geometry and band structure engineering to solve these problems. For instance, one-dimensional (1D) TiO28 As a p-type semiconductor with a high light-absorption coefficient (over 105 cm−1 at visible wavelength), copper antimony sulfide quantum dots are made up from environmentally-friendly and earth-abundant elements, the major phase of Cu–Sb–S has a bulk band-gap in the range of 1.0–1.8 eV; this type of non-toxic quantum dots have a high potential for photosensitization of 1D TiO2. Specifically, graphene is widely used in photocatalysis for its unique atomic-thick 2D structure and super physicochemical properties. When combined with 0D the quantum dots/1D TiO2 heterostructure, owe to 2D graphene higher work function which induces photogenerated electron transfer from the conduction band of the semiconductor to graphene. In other word, 2D graphene acts as an electron shuttle.29 To enhance the surface reaction kinetics, introduction of RGO into the 0D quantum dots/1D TiO2 to create mixed-dimensional (0D–1D–2D) heterostructures which provide new reaction pathways to cut down kinetic barriers.Recently, copper antimony sulfide (Cu–Sb–S) quantum dots have gained significant attention in solar cells and photoelectrochemical devices.2 arrays; then, the composite was annealed at 450 °C in an N2 atmosphere for 2 h to improve the adhesion between graphene and TiO2.10 Finally, the 1D TiO2/2D graphene/0D CuSbS2 quantum dots prepared by wet chemical method, followed by annealing at 200 °C for 60 min in argon (Ar) to obtain ternary 1D TiO2/2D graphene/0D CuSbS2 nanocomposites. To increase the interfacial contact between the 1D TiO2 arrays, 2D graphene and the 0D CuSbS2 quantum dots, the graphene sheets were fragmented between the quantum dot/TiO2 heterostructure by tuning the concentration of the spin-coated GO.25 As a consequence, the contact area and interaction between graphene and the other two phases was markedly increased. The experimental results show that the ternary composites exhibited excellent photoelectrochemical properties under solar light irradiation; the peak current reached 6 mA cm−2 and the photo-energy conversion efficiency was 1.2%. Furthermore, the graphene sheets not only reduced the open potential of photocurrent but also improved the stability of the CuSbS2 quantum dots under prolonged irradiation. In a word, it is expected that mixed-dimensional heterostructure photoanode will be a promising candidate for applications in environmental remediation and energy fields.In this work, negative charged graphene oxide (GO) was self-assembled on rutile TiO22.1i) iodide , antimony(iii) chloride , sodium chloride , phosphorus pentoxide , potassium thiosulfate , potassium permanganate , titanium(iv) butoxide (Ti(OBu)4, 99%), N,N′-diphenylthiourea (98%), diphenyl ether (99%), oleylamine , hexane , absolute ethanol , propan-2-ol , acetone , hydrochloric acid , sulfuric acid , hydrogen peroxide , were purchased from Shanghai Chemical Reagents Company without any further treatment. Deionized water was used for all the experiments.The natural graphite powder, 325 mesh, 99.95% was bought from Alfa Aesar. The fluorine-doped tin oxide (FTO) was bought from Zhuhai Kaivo Optoelectronic Technology Co., Ltd. . The copper(2.228 1.5 mM copper(i) iodide and 1.5 mM antimony(iii) chloride were loaded into a 50 ml three-neck flask containing 30 ml oleylamine. The mixture was heated to 100 °C under an Ar atmosphere, and then a clear slight yellow solution would emerge. Afterwards, the temperature of the solution was increased to the target temperatures (150 °C) and 4.5 ml 1 M N,N′-diphenylthiourea dissolved in diphenyl ether was subsequently injected into the mixture as quickly as possible. The solution was cooled to room temperature after 5 min. The mother liquor (1 ml) was added into methanol (3 ml) and centrifuged at 8000 rpm for 3 min. Hexane (4 ml) was used to redisperse the nanocrystals, and the precipitates were separated by centrifugation at 8000 rpm for 3 min. The product was further purified by several precipitation/dispersion cycles.A typical hot-injection method was used for the preparation.2.32/graphene/CuSbS2 composites. The fluorine-doped tin oxide (FTO) substrate (10 mm × 30 mm) was ultrasonically cleaned and then the highly ordered TiO2 nanorod arrays were grown on the FTO substrate via the hydrothermal method. Briefly, 0.45 ml titanium(iv) butoxide (Ti(OBu)4, 99%) and 0.6 g sodium chloride  were added into 30 ml diluted hydrochloric acid . Then, the above precursor (30.45 ml) was transferred into a 100 ml Teflon-lined stainless steel autoclave and for hydrothermal growth at 170 °C for 8 h. The resultant samples (TiO2 nanowire arrays) were rinsed with deionized water and dried at 70 °C in air.via the modified Hummers and Offeman's method,28 the preparation process is given in the ESI.2/GO composites were prepared by spin-coating a GO aqueous solution  onto the TiO2 nanowires array substrate. Then, the composite was annealed at 450 °C in an N2 atmosphere for 2 h to improve the adhesion between graphene and TiO2.Graphene oxide (GO) was prepared 2/graphene composite was immersed in the CuSbS2 quantum dots (3 mg ml−1) for 12 h  heterostructures are shown in 2 arrays were prepared on the FTO substrate, as is shown in 2 arrays is 50–100 nm. The transparent fragmented graphene sheets were overlaid on the prepared 1D TiO2 arrays and made full use of the large gaps in the 1D TiO2 arrays. As a result, a large contact area between 1D TiO2 arrays and the graphene sheets was achieved 2 quantum dots are uniformly distributed on the 1D TiO2 nanowires/2D graphene heterostructures, as shown in 2 quantum dots). The TEM image further shows the morphology of a single rod of the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures 2 quantum dots on the TiO2 nanowires.The scanning electron microscope (SEM) morphologies of pure 1D TiOachieved . For the2 at 2θ values of 26.578°, 37.768°, 51.755° and 65.740° (JCPDS no. 46-1088) initiated from the FTO substrate, and the diffraction peaks at 2θ values of 27.446°, 36.085°, 54.322° and 62.5° correspond to the (110), (101), (211) and (002) planes of rutile phase of TiO2 arrays, respectively (JCPDS no. 21-1276).13 In the TiO2/CuSbS2 and TiO2/graphene/CuSbS2 composites, the diffraction peaks at 2θ values of 28.47° and 32.09° correspond to the (101) and (201) planes of CuSbS2 quantum dots, respectively, which correspond with the HRTEM results.30 One should note that the rutile phase structure of the TiO2 nanowires shows little change after heat treatment because of its high stability. Additionally, the CuSbS2 quantum dots are stable in the ternary composites, and the graphene sheets exhibited no influence on the CuSbS2 quantum dots.28−1 and 610 cm−1 identify the Eg and A1g vibration modes of rutile TiO2, respectively.26 Two bands located at 1350 cm−1 (D band) and 1595 cm−1 (G band) demonstrate the presence of graphene.31–34 Generally speaking, the G band originates from the first order scattering of the E2g mode, indicating the sp2 hybridized carbon atoms; the D band is assigned to the A1g symmetry vibration of the K-point, revealing the sp3 defects in graphitic structure. Furthermore, the ID/IG ratio is a critical indicator of the defect density or average size of the sp2 domains in graphene.31 The intensity ratio (ID/IG) of graphene oxide (GO) in the TiO2/GO composite was 0.97, the intensity ratio (ID/IG) decreased to 0.80 (TiO2/graphene) after thermal treatment, which indicated the good reduction of graphene oxide. However, the value in the TiO2/graphene/CuSbS2 composites is 0.85, which demonstrated the high surface defect density of the graphene sheets. This phenomena is ascribed to the large contact area between graphene and the CuSbS2 quantum dots, which induce strong interactions and led to the increased ID/IG value.19The Raman spectra are shown in 3.22 arrays exhibit strong absorption in the ultraviolet region and had an absorption edge at ∼410 nm, which corresponded to a band-gap of 3.11 eV. The 1D TiO2/2D graphene composite shows a higher absorption in the visible region than simplex TiO2 arrays, this might be ascribed to the intense visible light-absorption of graphene sheets. However, a red shift of the absorption edge was observed because the sp2 orbit of graphene monished the energy between the Ti (3d) and O (2p) orbits. For the 0D quantum dots/1D TiO2 nanowires/2D graphene  composites, light-absorption ranged from the ultraviolet to the visible.35,36 Significantly, the 0D quantum dots/1D TiO2 nanowires/2D graphene  composites exhibit a more intense absorption in the visible region, this might be ascribed to the large contact area between graphene and the CuSbS2 quantum dots, which promote the synergistic effects on light-absorption.The light-absorption properties of the material is a crucial factor for photoanodes. 2 array exhibited two dominant peaks at 467 nm and 416 nm, these PL signals originate from the charge transfer and band-gap transitions of TiO2 due to oxygen vacancies which trap the electrons.37,38 The PL intensity of the 1D TiO2 nanowires/2D graphene and 1D TiO2 nanowires/0D CuSbS2 decline sharply because of the marriage of the graphene sheets and the fabricate the heterostructure, which observably benefit electron–hole separation.39 Moreover, a further fluorescence decrease was observed for the 0D quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode, this might be attributed to the following: (1) the narrow band gap of the CuSbS2 quantum dots promoted the intense absorption of visible light; the potentials of the conduction band (CB) of CuSbS2 were more positive than TiO2, and the photo-generated electrons transferred to TiO2 because of the potential dissimilarity; (2) the higher work function of the graphene sheets promote the transfer of the photo-generated charge carriers at the interface.The PL behavior originates from the recombination of photoinduced electron–hole pairs. 3.32 arrays exhibit the lowest photoresponse, with a photocurrent density of 1 mA cm−2 at 0.4 V and an onset potential of 0.05 V; the 0D quantum dots/1D TiO2 nanowires exhibited a comparable onset potential, along with an increase in the photocurrent density (2.6 mA cm−2 at 0.4 V) contrast to the pristine TiO2 arrays. This indicates that the CuSbS2 quantum dots were able to improve the photoresponse of the pristine TiO2 arrays, which could be ascribed to its high light-absorption coefficient as well as its narrow band-gap. For the 1D TiO2 nanowires/2D graphene, a reinforced photocurrent density (1.5 mA cm−2 at 0.4 V) and a cathodic shift of the onset potential relative to the pristine TiO2 arrays were observed. For the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode, the onset potential of the sample exhibit a marked negative shift. This indicated that the accumulation of photo-generated carriers at the interface is significantly reduced and could be attributed to the high charge transfer characteristics of the graphene sheets, as well as the large contact area between the graphene and the CuSbS2 quantum dots.40,41 Additionally, the photocurrent density (5.2 mA cm−2 at 0.4 V) increase rapidly alongside the increase of the bias voltage, which was two times higher than that of the 0D quantum dots/1D TiO2 nanowires (under the same bias voltage). Significantly, the photocurrent density is not saturated with increasing bias, this suggest an excellent light response and a high separation of photo-generated carriers in the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures, which is caused by the synergistic effects between graphene and the CuSbS2 quantum dots.η) of each photoanode was calculated based on the current voltage curve as a function of the applied voltage (11J is the photocurrent density (mA cm−2), Plight is the incident light intensity (100 mw cm−2), ERHE is the testing voltage relative to the reversible hydrogen electrode (RHE), ESCE is the testing voltage relative to the SCE, and EΘSCE is the standard electrode potential of saturated calomel electrode (SCE) at 25 °C. The 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode exhibits a highest photoconversion efficiency of 1.2% at 0.3 V, which is observably larger than that of the 1D TiO2 nanowires/2D graphene (0.34%), the 0D quantum dots/1D TiO2 nanowires (0.54%), and pristine TiO2 (0.2%). The PEC property of the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode clearly demonstrated that a synergistic effect is achieved by the integration of 2D graphene and 0D CuSbS2 quantum dots with 1D TiO2 nanowires.The photoconversion efficiency  heterostructures photoanode. The photocurrent density of the TiO2 array is higher than that of 1D TiO2 nanowires/2D graphene; however, the magnitude of the photocurrent density is 20 μA. This is because of the limited use of the solar spectrum by the TiO2 arrays, which led to low light to energy conversion. For 1D TiO2 nanowires/0D CuSbS2 quantum dots, the photocurrent intensity of the heterojunction increase significantly to 147 μA, which indicate that the narrow band-gap CuSbS2 quantum dots could efficiently harness incident solar light. However, the photocurrent density is not stable, after 600 s of illumination the intensity is attenuated to 115 μA. It is important to highlight that the photocurrent density of the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode represent the highest value among these four photoanodes, and the photocurrent rises and falls rapidly with changes between the light-on and light-off states. Although charge relaxation was observed, this phenomenon disappeared gradually with prolonged duration. Additionally, the photocurrent density increased to 287 μA, which indicate that the graphene sheets not only effectively modulated the transport of charge carriers but also improve the stability of the CuSbS2 quantum dots under extended illumination. This can be attributed to the large interfacial contact area between graphene and CuSbS2 quantum dots. To the best of our knowledge, the photocurrent density of the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene mixed-dimensional heterostructures photoanode is highest among other reported TiO2-based photoanodes  heterostructures photoanode has the smallest semicircle diameter among the investigated samples. This indicate a low charge transfer resistance as well as a high electrochemical activity. The main reason for this is that graphene not only promotes the mass transfer process but also improves electron transport, which rapidly increases the carrier concentration. The Bode curves of the samples are fitted from the EIS curves to further study the effects of graphene on carrier modulation, as shown in 2/graphene/CuSbS2 shift markedly to a lower frequency, which reveal a more rapid electron mobility process. In addition, the lifetime of electrons τeff can be extracted via the following equation:42,43Electrochemical impedance spectroscopy (EIS) studies was carried out to investigate charge transport behavior in these photoanodes. Generally, a smaller semicircle diameter in the plot suggests a lower charge transfer resistance. As shown in fmin) of the mid-frequency. In actual calculations, we reverse the minimum frequency (fmin) of Bode plots peak as a function of electron lifetime. The electron lifetime for the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode is 26.5 ms, 1D TiO2 nanowires/0D CuSbS2 quantum dots is 5.1 ms, 1D TiO2 nanowires/2D graphene is 15.9 ms, and for pristine TiO2 is 4.3 ms. The electron lifetime of the novel ternary 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures was the highest among the samples, and it was almost 5 times higher than that of 1D TiO2 nanowires/0D CuSbS2 quantum dots. In this regard, the incorporation of graphene sheets play a vital role in modulating photo-excited carrier transport in the composites.The electron lifetime is only determined by the minimum frequency , 5.57 × 1018 cm−3 (TiO2/graphene), 0.79 × 1018 cm−3 (TiO2/CuSbS2), and 5.08 × 1018 cm−3 (TiO2/graphene/CuSbS2); the results corresponded with the Bode plots, which further demonstrated the strong modulation of the charge carriers by graphene. The highly interconnected and the synergistic effects at 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures contribute to this distinguished photoelectrochemical performance. The flat band potential is obtained by extrapolating the Mott–Schottky plot to 1/C2 = 0 to obtain the intercept. An evident positive shift could be observed after the incorporation of graphene sheets, while a negative shift occurred after the incorporation of CuSbS2 quantum dots. Generally, the positive shift of the flat band potential for TiO2 indicate a decrease in the bending of the band edges, and this could facilitate charge transfer at the electrode/electrolyte interface. The results can be ascribed to the lower Fermi level of graphene, which facilitate the transportation of charge carriers and reduce the band bending between the electrode and the electrolyte interface.The semiconducting properties of the obtained samples were investigated by measuring the Mott–Schottky plots, as shown in 2 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures is proposed and shown in 2 nanowire arrays under illumination. Based on the structure analysis, the band energy difference between these mixed-dimensional induce both electron transfer from the 1D TiO2 nanowire arrays to 2D graphene and hole capture by CuSbS2 quantum dots. There should be a synergistic effect in the composites. This opposite transmission of electrons and holes inhibits the surface recombination of photogenerated charge carriers. The super-fast migration of electrons to the current collector was performed in 2D graphene due to its superior electron mobility, which remarkably suppresses the bulk electron–hole recombination and enhances the charge separation efficiency.29 We thus believe that in our mixed-dimensional heterostructures materials, the highly interconnected and the synergistic effects at different dimensional contribute to this distinguished photoelectrochemical performance. Then, a large number of photogenerated carriers (electrons and holes) are formed due to the quantum effect of the CuSbS2 quantum dots, the average size of CuSbS2 quantum dots (around 6.7 nm) is smaller than their double Debye length of the electrons, which makes the whole quantum dots become the depletion layer, and this distinguishing feature is of high absorption coefficient because of the tiny amount electron injection. Subsequently, the large specific surface area of graphene accelerates mass transfer between the electrode and electrolyte, which prompts the transfer of photogenerated holes to the electrolyte. The synergistic effect fully exploits the extraordinary electron transport characteristics of 2D graphene and further makes large contribution to the highly promoted photoelectrochemical performance of the mixed-dimensional heterostructures device.45 Finally, the photogenerated electrons migrate to the surface of graphene because of its lower Fermi level. Under a certain bias, the electrons collected on the graphene eventually flow to the negative pole through the TiO2 nanowire array under an external electric field.Given the discussion above, a mechanism for the photoelectrochemical mechanism of the novel ternary 0D CuSbS42 quantum dots/1D TiO2 nanowires/2D graphene  heterostructures photoanode was prepared via a simple and economic process where graphene sheets were fragmented between 1D TiO2 nanowires and 0D CuSbS2 quantum dots. The resulting ternary nanocomposites exhibit dramatically enhanced photoelectrochemical properties, including a large photocurrent density and an extended charge carrier lifetime. The enhancement could primarily be attributed to the fragmented graphene sheets; the high work function of the graphene sheets facilitates the migration of the photo-excited charge carriers, and the synergistic effects between graphene and the 0D CuSbS2 quantum dots simultaneously enhances the absorption and conversion of solar energy. The demonstration of such the 0D CuSbS2 quantum dots/1D TiO2 nanowires/2D graphene mixed-dimensional heterostructures proposed here would open up a wide area of opportunities for designing high-performance photoelectrochemical device. This kind of ternary nanocomposites exhibits broad application potential in areas such as CO2 conversion, water splitting, gas sensors, and solar-energy conversion.An innovative ternary 0D CuSbSThe authors declare no conflict of interest.RA-009-C9RA07237C-s001


Graphene is a popular material with outstanding properties due to its single layer. Graphene and its oxide have been put to the test as nano-sized building components for separation membranes with distinctive structures and adjustable physicochemical attributes. Graphene-based membranes have exhibited excellent water and gas purification abilities, which have garnered the spotlight over the past decade. This work aims to examine the most recent science and engineering cutting-edge advances of graphene-based membranes in regard to design, production and use. Additional effort will be directed towards the breakthroughs in synthesizing graphene and its composites to create various forms of membranes, such as nanoporous layers, laminates and graphene-based compounds. Their efficiency in separating and decontaminating water via different techniques such as cross-linking, layer by layer and coating will also be explored. This review intends to offer comprehensive, up-to-date information that will be useful to scientists of multiple disciplines interested in graphene-based membranes. Over the last twenty years, separation via membranes has been deemed as an innovative technology suitable to address massive challenges, such as lack of resources and the environmental impact of human activities . ContrarA membrane is essentially a selective boundary with pores or channels. They are more cost-efficient and effective, and their use is fundamental in eco-friendly technologies . An ideaGraphene and graphene oxide (GO) have demonstrated marked potential in separation processes using membranes, owing to being accessible and because of their strength and notable resistance to various types of solvents . The inc2 hybridization and thicker atomic layers expedite the formulation of ultrathin selective barriers with expected separation capacity [In this context, additional effort has been devoted to comprehending their behavior and exploring the uses of materials based on graphene . Graphencapacity . The intcapacity ,12. The capacity . It shoucapacity ,13.The pristine graphene layer was found to be impenetrable to liquids and gases because of the very small gaps in its structure . GraphenConsidering the issues discussed, graphene-based membranes produced through diverse processes possess specific structures and transport pathways, allowing their application in multiple membrane processes such as water desalination ,19,20, rThis work delves into the most recent (past four years) research findings on the topic of GO-based membranes, going over the vast and scattered literature to obtain and organize the information on the synthesis approaches, the potential challenges related to them and the recorded data on the separation and decontamination efficiency. The novelty of this article is its mission to review the very recent literature and curate up-to-date (and easily comparable) information on the synthesis methods of graphene-based membranes, their applications and efficiency in water purification, bringing attention to the factors affecting the separation/decontamination processes. Appropriate information regarding the pollutants susceptible to each process is further collected and assessed, along with details on the rejection rates achieved.Graphene quantum dots (GQD) is a term used for single or few-layer graphene nanosheets, often during studies of the photoluminescence property. GQDs have generally extremely small size, usually less than ten nm (and an average of five nm), which places them at the lower end of the graphene nanosheets’ range, whose upper end starts at less than 100 nm .The reduction of graphene oxide can be conducted via chemical, thermal, electrochemical and photochemical approaches, resulting in the production of graphene-like materials, such as reduced graphene oxide (rGO) and highly reduced GO (HRG), etc. In spite of the considerable differences between pristine graphene and HRG, they still possess remarkable similarities. Their physicochemical attributes define this step as one of the most significant processes of GO, especially for bulk applications. The attributes of HRG produced via GO-reduction, are highly dependent on the reduction processes .Turbostratic carbon is a 3D sp2-bonded carbon material, with layers whose carbon atoms don’t have a spatial relationship with the atoms in other nearby layers .Graphene-based materials, which are also mentioned as graphene or graphene-family nanomaterials—refer to a group of 2D materials containing the name ‘‘graphene’’, multilayered materials (less than ten layers) included. They may be chemically modified forms , or materials produced using graphene, its oxide, or other graphene material as a component .Multi-layer graphene (MLG)—a two dimensional material in sheet form, comprising of a limited number (ranging between two and ten) of precisely-defined, stacked layers . They maFew-layer graphene (FLG)—a subgroup of MLG with an average of two to five layers. Examples include graphite nanoplates, nanosheets and nanoflakes; They are two dimensional with ABA or ABCA stacking, whose thickness does not exceed 100 nm .Exfoliated graphite—a multilayer version, produced through partial graphite exfoliation , creating thin multilayer products that maintain the three-dimensional structure of graphite .Graphene nanosheet—a single layer of hexagonally placed, sp2-bonded carbon atoms that is not the main part of a carbon material, but is either free or adhered on an external substrate, whose lateral dimension does not exceed 100 nm ,32.Metal oxides: In order to further improve and expand the applications of graphene, a wide range of metal and metal oxide nanoparticles have been combined with graphene. The CVD method requires the dissolution of carbon in metal surfaces, such as nickel and copper that serve as catalysts and then by cooling the metal to forcing it to separate. Metal and metal oxide nanocompounds are produced by chemically reducing metal precursors such as chloroauric acid, silver nitrate and potassium tetrachloroplatinate, using hydrazine hydrate, amines, and sodium borohydride. The combined effect of graphene and the metal-based materials in these nanocompounds have a new research pathway, including biomedical applications .Polymer Nanocomposites: The binding or loading of metal and metal oxide nanoparticles on graphene for the preparation of graphene-based nanocomposites is commonly achieved in two different ways: post immobilization or in-situ binding. Post immobilization requires combining different graphene nanosheets options and pre-produced nanoparticles. Prior to that, the nanoparticles and/or the surface of graphene sheets are functionalized to improve the ability to process the end results, which greatly improves their solubility and thus offers additional alternatives for the creation of graphene-based compounds. Nevertheless, post immobilization might be affected negatively if the structure of the graphene sheets is not dense enough or if the coverage by the graphene sheets is irregular .Before discussing the actual membranes, the inherent attributes and the creation process of graphene-based components will be summarized, because they heavily impact the preparation process and general efficiency.There is a plethora of articles describing the simple yet perfect structure of graphene, with its atoms placed in a honeycomb-looking lattice , that leThe functional groups that can be found on the surface of component based on graphene offers the potential of formulating bonds with proteins, whereas the structure of pristine graphene allows for hydrophobic π–π interaction to lead any hydrophobic leftovers to the graphene surface . FurtherLi et al. demonstrated that graphene is a very effective additive . Using aThere are two main synthetic pathways, top-down and bottom-up. Graphene can be synthesized via various approaches , such asMechanical exfoliation was the first successful method of producing graphene by consecutive peelings via scotch tape . SeparatThe growth of thin graphene films has proven to be a successful approach for the synthesis of graphene . Xu et aCVD is an effective approach for mass manufacturing of graphene-based membranes. The technique’s advantage is the ability to continuously prepare graphene films using an ever growing list of potential substrates, such as copper, platinum and nickel . The cheThe reduction of GO is a different option for the fabrication of graphene sheets. GO is created according to the Brodie, Staudenmaier and Hummers’ methods . HummersHummer expanded on Brodie’s and Staudenmaier’s approaches, by establishing an oxidation phase for the production of GO  by combiVia reduction, the GO partially reverts to its initial state, but with improved properties, such as better electrical conductivity ,60,61. TLiquid-based exfoliation of graphite is another promising method for manufacturing graphene at a larger scale. It refers to the exfoliation of bulk graphite into thin graphene while being in a liquid medium, excluding the chemical oxidation phase . This apDespite the fact that bottom-up approaches are able to produce single-layer, flawless graphene, they are not currently applicable for large-scale synthesis of graphene and graphene-based materials. As a result, and taking into account the growing demand for the mass production of graphene, top-down solutions have garnered the spotlight. Such methods traditionally require the repeated oxidation and reduction of graphite, which is an inexpensive resource . AdditioNevertheless, there are still some gaps in our knowledge regarding cost-effective top-down synthesis on a large scale, without harming the environment in the process of producing defect-free graphene. The majority of the known synthetic approaches cannot consistently regulate properties such as the size, shape, edge and layer number of the produced graphene, because of the randomness of the exfoliation, growth and assembly steps. In spite of the significant progress in the synthesis of graphene-based inorganic nanomaterials, there are still certain barriers to their large-scale application. For instance, advanced uses of graphene-based metal and metal oxide nanomaterials call for a comprehensive analysis, before understanding the interactions between the surface of graphene and the nanomaterials, since they directly affect the attributes of these resulting composites. This would undoubtedly improve the potential of the produced nanomaterials in various areas, such as biosensors and drug delivery. Multiple techniques have been employed for the synthesis of homogeneously dispersed nanomaterials, using diverse reduction and functionalization approaches. It should be noted however that there are numerous reduction and surfacing materials with adverse impact on their possible uses. It is thus crucial to examine how biocompatible and/or toxic these reductants and surfactants are, to ensure the safety of the produced materials for use in biomedical applications . More spCVD and epitaxial growth are not appropriate for the production of the graphene that is required for the resulting graphene-based nanomaterials, since they typically require large quantities of graphene sheets with a modified surface architecture. Furthermore, mechanical exfoliation via Scotch-tape is a painstaking process and does not usually result in adequate quality graphene monolayers, whereas epitaxial growth requires high-vacuum and a generally high-priced production system. The production of graphene monolayers with large surface areas is now feasible owing to the quite recent advances in chemical vapor deposition techniques; however, the growth of graphene monolayers remains a challenge and appropriate techniques have not yet been fully implemented .Regardless, graphene is an innovative two-dimensional building block for the growth and assembly of metal/metal oxide nanoparticles, and the integration and collaborative effects with graphene significantly improves the performance of the resulting nanocomposite. Graphene-based metal and metal oxide composites with specific or mixed structures have thus great potential for multiple large-scale applications, and they are commercially viable. The regulated production of these nanocomposites, with specified attributes, stops the restacking of graphene nanosheets, but also offers great templates for the creation of three-dimensional porous networks with improved electrical and electronic properties. Additionally, enhancement of the produced quantity will result in the synthesis of nanocompounds, which can be calibrated for numerous possible applications. A multidisciplinary approach should thus be used to establish better protocols for the large-scale synthesis of graphene, and to achieve a higher technological maturity level .Guidelines are required for the creation of graphene-based membranes that offer the optimal transport of water, while still being able to be reused in separation processes. This requires the minimization of the energy barriers upon entering the membrane. Rejection capacity may also be adjusted in a similar manner by ensuring that the inter-sheet spacing only allows a single monolayer of water. To summarize, through the optimization of the process at a molecular level, the viability of graphene oxide as a suitable material for separations  can be maximized .Despite the fact that bottom-up approaches are able to produce single-layer, flawless graphene, they are not currently applicable for mass production of graphene and graphene-based materials. As a result, and taking into account the growing demand for the mass production of graphene, top-down solutions have garnered the spotlight. Such methods traditionally require the repeated oxidation and reduction of graphite, which is an inexpensive resource .Additionally, top-down techniques have become more popular owing to the progress achieved in the area of direct exfoliation of graphite while using different types of solvents without any reducing or stabilizing agents. Graphite-based top-down approaches are thus more financially appropriate for large-scale applications. Nevertheless, there are still some gaps in our knowledge regarding cost-effective top-down synthesis on a large scale, without harming the environment in the process of producing defect-free graphene. The majority of the known synthetic approaches cannot consistently regulate properties such as the size, shape and layer number of the produced graphene, because of the randomness of the exfoliation, growth and assembly steps. In spite of the significant progress in the synthesis of graphene-based inorganic nanomaterials, there are still certain barriers to their large-scale application. For example, advanced uses of graphene-based metal and metal oxide nanomaterials call for a comprehensive analysis, before understanding the interactions between the surface of graphene and the nanomaterials, since they directly affect the attributes of these resulting composites. This would undoubtedly improve the potential of the produced nanomaterials in various areas, such as biosensors and drug delivery. Multiple techniques have been employed for the synthesis of homogeneously dispersed nanomaterials, using diverse reduction and functionalization approaches. It should be noted however that there are numerous reduction and surfacing materials with adverse impact on their possible uses. It is thus crucial to examine how biocompatible and/or toxic these reductants and surfactants are, to ensure the safety of the produced materials for use in biomedical applications Therefore, the graphene-based nanocomposite synthesis primarily revolves around the oxidation and exfoliation of graphite oxide, which is then chemically reduced to create highly reduced graphene oxide or chemically modified graphene .The green reduction of graphene oxide (GO) requires the use of biocompatible components under physiological conditions of temperature and pressure . Most ofSalvadora persica L. roots (miswak) extract. Multiple results have verified that the biomolecules in the roots also functionalize the surface of SP-highly reduced graphene oxide, serving as a capping ligand, stabilizing it in various solvents. This method could offer a better substitute for the large-scale manufacturing of graphene and graphene-based materials for diverse applications such as electronics, nanomedicine, and bionic materials [A previous work by Mujeeb Khan et al. in 2015 described an easy and eco-friendly approach for the bio-reduction of GO using aterials .Abdulhadi H. Al-Marri et al. produced similar results: a green, single-step method for the creation of graphene/silver nanocomposites through the concurrent reduction of both graphene oxide and silver ions, using a plant extract, which functionalizes the surfaces of highly reduced graphene oxide, linking it to the silver nanoparticles. Higher amounts of silver improved the density of silver nanoparticles linked to the highly reduced graphene oxide .The main categories, based on their structure are: (1) porous layers, (2) laminates and (3) compounds that shall be further explored as follows:Porous layers. By limiting the number of defects introduced via physicochemical approaches, uniform nanosized pores can be created on the graphene membrane surface, achieving outstanding selectivity in separation of gases, water desalination, and other applications. Moreover, ultra-thin, porous graphene membranes exhibit much higher permeability than other compounds. The size of the pores is a pivotal factor for use in desalination projects .Their production methods are related to specific types of manufacturing approaches. For example, coating techniques, such as spin-, spray- or dip-coating and membrane casting are widely used for the preparation of membrane layers on the substrates a. Due toAssembled graphene laminates. Laminated membranes based on graphene use GO nanosheets as basic stackable components. There are lot of research works on the subject of the optimal production of laminated membranes with minimum defects and enhanced efficiency. Kim et al.  used a G2. Tsou et al. [2·h.Comparable behavior can also be achieved through a casting process. Akbari et al.  stated tu et al.  examinedGraphene-based composite. GO-modified polymeric membranes have demonstrated enhanced permeability, selectivity, and anti-microbial outcomes . Two mai2/bar/h, and better rejection rates for sodium sulfate (95%), magnesium sulfate (91%), magnesium chloride (62%), and sodium chloride (60%). Zhang et al. [The first method has been tested by various scientists, including Lee et al. , who man sulfate %, magnesPerreault et al.  implemenZhang et al.  developeWater purification through membranes is based on the filtration, the adsorption, the rejection, and the degradation of pollutants. The efficiency of such membranes is evaluated by checking if they are water permeable, using contaminated organic solutions and deionized water. The efficiency of the prepared membrane can be impacted by the concentration of cations, the pore size, spacing between layers, chemistry of the surface, dosage, pressure and other parameters .The various applications such as desalination, rejection of ions, and pollutant removal are depicted in The desalination of seawater guided by a vapor pressure gradient is a relatively new treatment approach. Despite its promising experimental results, the purification of a combination of different pollutants and keeping the temperature stable are significant setbacks that have not yet been addressed . NanofilXu et al.  suggesteRomaniak et al.  created Dong Han Seo et al. proposed a water desalination process via membrane distillation. Graphene films procured from renewable oil achieved notably better water vapor flux retention and rejection rates, and an improved antifouling capacity under a mixture of saline water that contained diverse pollutants ,12.- radicals as indicated in Photocatalysis refers to the process of accelerating a photo-generated electron during catalysis. Recently, Chen et al.  examinedYu et al.  describeMaterials based on graphene play a significant role for the elimination of environmental contaminants via adsorption, which relies on the bonds betwixt the pollutant and the adsorbent surfaces. Its mechanism may be based on adsorption, charge transfer or dipole interactions, electrostatic or dispersion forces, and quadrupole interactions ,111. TheZhan et al.  evaluatePollutant rejection from wastewater through membranes is based on the size of the pores and the interaction between the surface and the ions ,117. GO-Attempts to prevent fouling and swelling have relied on electrokinetic effects, intercalation of ions, physical confinement of organic material molecules, pore size or channel heigh tuning, cross-linking blending with nanocarbons, and reduction of GO. The adjustment of nanochannels and nanowrinkles properties may enhance the rejection rates, because of the existence of extra water transport channels . Yuan etSeunghyun Hong et al. demonstrated the very high charge selectivity for graphene oxide membranes. By estimating the diffusion of a wide range of ions, sizes and charges, they were able to comprehend the corresponding mechanisms and the factors affecting the ionic sieving in GO membranes, namely electrostatic repulsion and the compression of the ionic hydration shell within the membrane’s nanochannels .The pollution of heavy metal ions in water sources and wastewater is an issue of global concern due to their high toxicity even at very low concentrations . The eliVarious approaches have been suggested to eliminate them from water; out of which, membranes based on graphene were deemed to be low cost, effortless and more effective. Wang et al.  demonstrEmerging pollutants such as herbicides, pharmaceuticals and personal care products commonly detected in both potable and waste water, posing a global concern. The inability of traditional approaches of treatment is an important concern for the extraction of these emerging pollutants from wastewater. Graphene-based nanomaterials demonstrated promising potential to eliminate them from wastewater via adsorption, filtration, and photocatalysis .Khalil et al.  producedVarious approaches were established for the manufacturing of GO membranes, such as LbL, vacuum or pressure-assisted, cross linking, intercalation, annealing and coating. Some of the recent works and their findings are summarized in Vacuum/Pressure-Assisted Method. Such techniques are the most frequently used and clear-cut approaches for the mass production of graphene oxide nano-, micro, and ultra-filtration membranes .Cheng et al. used vacuum filtration to fabricate hybrid tungsten disulphide/GO 2D membranes to accomplish fine molecular sieving. The nanochannel size of the tungsten disulphide membrane became smaller and more regular after introducing the GO nanosheets. The hydrated hybrid membrane with 15 wt% GO showed high rejection rate of more than 90% versus dyes and ions. In addition, the nanochannels in the fabricated membrane exhibited strong rigidity under up to 0.5 MPa pressure, while the separation effectiveness slightly changed during 120 h of cross-flow filtration .Sun et al. fabricated new membranes comprising of large-area, high-strength metallurgical graphene, GO, hydrazine and polyamide on porous polysulfone scaffold. The GO layer was created from GO suspensions via vacuum filtration. The effectiveness of the membranes was assessed via forward osmosis tests. The membranes showed promising results in ion blocking (>95%). The results indicated that the manufactured membranes can be useful in treating water .Zhao et al. successfully prepared from GO quantum dots and sheets via a simple vacuum filtration process. The study revealed that the resulting composite displayed improved markedly improved permeability. When more quantum dots were used, the structure was not affected, while the average spacing between layers increased. Furthermore, the intercalation of the quantum dots enhanced the hydrophilicity of the membranes to a degree. More specifically, the permeability of the membranes in all cases was two to four times better without affecting their retention for direct yellow, bovine serum albumin, humic acid, and gold nanoparticles (higher than 99%). This work proves that the homo-structure of zero dimensional GO quantum dots in two-dimensional GO sheets can efficiently enhance the separation performance of GO-based nanofiltration membranes .−2h−1, suggesting that the fabricated membranes have good application potential [Recently Hou et al. created a GO/Methylene Blue (MB) membrane through vacuum filtration, in order to enhance the stability and rejection of dyes. The rejection rate of the GO/MB membrane reached approximately 93% for methyl orange, 99.9% for disperse black 9 and 82% for rhodamine B, whereas the pure water flux was approximately 7.7 Lmotential .The same year Kunimatsu applied vacuum filtration to produce niobate nanosheet (NbN)- GO membranes. The impact of the weight ratio of the nanosheet versus GO on the structure and efficiency were evaluated, finding that the fabricated membranes are more structurally stable in wet conditions and were comparable with GO-rich membranes. NbN55-GO45 particularly exhibits excellent water permeability, practically six times better than the plain niobate one and two times better than a plain GO membrane, without affecting the rejection abilities of anionic dyes and salt .Liu also applied vacuum filtration to manufacture a novel titanium dioxide nanorod inserted in a graphene-based membrane on a cellulose acetate mat. The nanorods extended the spacing between the graphene sheets and thus improved the separation performance of the membranes, achieving a very high flux and very high rejection rates versus dyes, exceeding 99.3 for the examined dyes .Hung studied a series of graphene-modified GO membranes for nanofiltration by pressure-assisted self-assembly. The fabricated membrane exhibited high water flux, salt rejection at approximately 88%, sodium chloride at 91%, magnesium chloride at 97% and magnesium sulphate at 98% .Layer by layer. Layer by layer provides a more accurate regulation of the concentration levels, the deposited film, the monolayer elasticity and the surface state. This technique, able to create nanoscale multilayer films, has thus been at the forefront of the research in various fields .Arenas et al. utilized the technique to produce rGO membranes for desalination purposes and assessed the performance versus sodium and magnesium cations .Slot dye coating. This is a technique that uses GO with reduced viscosity levels, allowing for the production of thin membranes without requiring the GO solution to be pre-treated. The thin wet layer facilitates spontaneous drying, which minimizes the production time needed. Minimal waste of stock solution occurs; thus, this approach could be further examined for membrane production using various materials .Kim et al. also fabricated GO membranes using a slot die coater. The membrane thickness is controllable, according to the quantity of the GO solution and morphology of the substrate. Furthermore, the coating layer and spacing are not affected, as the GO is deoxygenated (dGO). An efficiency test indicates that the manufactured membrane is effective for filtering sub-nanosized dye molecules, with a rejection percentage that reaches 99% for brilliant blue G. The fabricated membrane is stable in the case of cross-flow and high-pressure levels. The process is scalable .Cross-linking methods. Cross-linking has the ability to prevent membrane swelling and dissociation, whereas the resulting membrane is also more structurally stable. Cross-linking refers to both covalent and non-covalent approaches. The covalent option improves the stability and sieving capacity of membranes based on graphene, whereas the non-covalent one assists in the dissolution of the materials .Thakur et al. produced a set of cross-linked laser-induced graphene-poly  LIG−PVA membranes. These membranes demonstrated improved selectivity and permeability and their performance was of the same levels as polymeric ultrafiltration membranes. The fabricated membranes significantly improve the strength of the LIG. Increasing the PVA levels had a positive effect on the rejection rates. The produced membranes were fouling resistant and had good flux recovery ratio .Annealing process. Graphene’s properties can be impacted by either substrate interactions or the processing steps needed to manufacture contacts and devices. Annealing is used when cleaning graphene devices, which might result in doping, defect changes and strain effects . The cleA review conducted by Li et al. verified the applicability of mild annealing for creating partially reduced GO membranes and 2D laminar channels for nanofiltration. The membrane changes were methodically characterized, and results show the process not only made GO membranes more stable but also facilitated the customizable tunable salt rejection of the resulting membranes. Mild annealing rGO membrane (MRGO) accomplished better water permeance and sodium sulfate selectivity .2-Fe3O4, and silver, as well as carbon and titanium dioxide nanotubes.Large molecule intercalation. Due to the high surface area of GO nanosheets, the interlayer electrostatic repulsion may destabilize the GO membranes. To this end, the insertion of large molecules that may intercalate between layers can manage to address the issue and stabilize the structure. This process can also be used to tune the membrane effectiveness by adjusting spacing and enhancing molecular separation . The mosChen et al. created a hierarchical  graphene oxide/covalent organic framework (GO/COF) membrane through the intercalation of COF particles, which possess a hollow structure and nanopores at the almost 2 nm range, as well as multiple functional groups that render it extremely hydrophilic, thus offering additional fast transport nanochannels. The fabricated membrane has outstanding flux at 1 bar and excellent rejection efficiency of dyes. Furthermore, the intercalation of COF is able to considerably reduce the swelling, thus improving membrane stability when exposed to either water or strong acidic/base solutions .Impact of Interlayer Spacing. The spacing between the layers of graphene is approximately 0.34 nm, whereas that of GO is about 0.8 nm . If the Impact of Crosslinking. Crosslinking GO layers, adapting the temperature levels and functionalization, are some of the few factors that can impact the preferred layer spacing. Hung et al. created a GO through treatment with diamine based catalysts . The finStability. The large-scale applications of graphene membranes is a daunting task, requiring the careful preparation of large area porous films, taking into account parameters such as flexibility, ability to handle easily and pore uniformity while designing the process . CleaninIn this work, we explicitly discuss the progress of membranes based on graphene. A large number of research works over the past few years verified that they exhibit outstanding permeability, allowing for very fast and highly-selective transfer of water and thus have very successful wastewater treatment applications through various synthesizing techniques such as the coating, layer by layer, vacuum/pressure-assisted and annealing methods. Nevertheless, there are still certain challenges to address regarding the spacing between layers and the maintenance of the structure in order to be able to exclude small-sized ions. Furthermore, avoiding membrane swelling when dissolved in wet environments is an additional issue that could hinder its usage. Important advancements have been achieved on the separation mechanisms, and various successful liquid separation applications have been highlighted. (a) Their long-term stability is still a significant issue. For large-scale projects, the testing period for their stability ranges between a few hours and a few days, which does not correspond to industrial settings. Thus, the subject needs to be further explored. (b) Secondly, the fabricated membranes must withstand chemical cleaning, since they are required to address fouling. There are still only a few membranes based on graphene that can tolerate such processes. (c) Lastly, it remains difficult to maintain the efficient separation of the membranes in liquids. The spacing of graphene sheets is affected in wet environments.The inability of graphene-based membranes to extract a broad variety of pollutants from wastewater in just one step is an important hindrance that translates to requiring additional exploration to fix the water treatment issue. The diminishing membrane performance owing to fouling is a serious concern that needs to be appropriately addressed. In spite of the technological growth in terms of production methods, the full elimination of defects is crucial before implementations at a larger scale.


To improve the graphene/copper interfacial bonding and the strength of the copper matrix, Cu–Cr–Mg alloy powder and graphene nanosheets (GNPs) have been used as raw materials in the preparation of a layered graphene/Cu–Cr–Mg composite through high-energy ball-milling and fast hot-pressing sintering. The microstructure of the composite after sintering, as well as the effect of graphene on the mechanical properties and conductivity of the composite, are also studied. The results show that the tensile strength of the composite material reached a value of 349 MPa, which is 46% higher than that of the copper matrix, and the reinforcement efficiency of graphene is as large as 136. Furthermore, the electrical conductivity of the composite material was 81.6% IACS, which is only 0.90% IACS lower than that of the copper matrix. The Cr and Mg elements are found to diffuse to the interface of the graphene/copper composite during sintering, and finely dispersed chromium carbide particles are found to significantly improve the interfacial bonding strength of the composite. Thus, graphene could effectively improve the mechanical properties of the composite while maintaining a high electrical conductivity.  Copper alloys are widely used in electrodes, rail transit, electronic packaging, and electrical contact. The most optimal properties of the copper alloys include high strength while providing excellent electrical and thermal conductivities. The fast development of the mechanical, electronic, and transportation industries has given rise to high expectations of the properties of copper alloys . HoweverHowever, the experimental mechanical properties of graphene/copper composites are usually much lower than the theoretical expectations. This is mainly due to the uneven dispersion of graphene and the weak interfacial bonding between graphene and copper. At present, considerable results have been achieved for the dispersion of graphene in a Cu matrix. In contrast, there are few reports on the optimization of the graphene/copper interface in the composite. The decoration of a graphene surface with metal particles is, at present, a method that can be used to improve the binding within the graphene-copper interface. Since the modified graphene and copper matrix show good chemical affinities, the problem with poor interfacial wettability can be well improved. According to the current reports, Cu, Ni, and Ag can significantly enhance the interfacial binding and mechanical properties of the graphene/Cu composite ,8,9. AnoIn the present study, Cu–Cr–Mg alloy powder and graphene nanosheets were used as raw materials in the preparation of a GNPs/Cu–Cr–Mg composite. The method of high-energy ball-milling was used in this preparation. The problems presented above were then solved by including Cr and Mg elements in the alloy powder. The interfacial bond strength in the composite was improved by the addition of Cr, and the added Mg element did not only play a major role in the solid solution strengthening but also caused segregation in the areas where the Cr element was enriched (to control the size of the carbides).2/g), stearic acid , absolute ethanol , and argon (99.99%). Alloy powder was prepared by gas atomization method using high purity electrolytic copper (99.99%), cast Cu-10Cr (wt.%) intermediate alloy, and cast Cu-10Mg (wt.%) intermediate alloy as raw materials. The resulting powders were sieved, and the powders with average particle size less than 50 μm were collected. The chemical composition of the Cu–Cr–Mg alloy powder is listed in The raw materials that were used in the experiments were a gas-atomized Cu–Cr–Mg alloy powder, graphene nanosheets . Moreover, the density of the composite was measured by using the Archimedes drainage method . The phase composition of the composites was characterized by X-ray diffraction . The electrical conductivity of the composite was tested by using a digital eddy current metal conductometer . Furthermore, field emission scanning electron microscopy  was used to analyze the microscopic morphology of the composite powder, as well as the microstructure and tensile fracture of the composite material. The surface elemental analysis of the prepared composite blocks was carried out by using an electron probe microanalyzer . Moreover, the composite was subjected to room temperature tensile tests by using a universal testing machine  with a strain rate of 1 mm/min.The composite was sintered in fast hot-pressing sintering . Raman spectroscopy  was used to analyze the structure of the GNPs and the composite at different stages by using a light source with a wavelength of 532 nm and a scanning rate in the range of 1000–3000 cmTo understand the microstructure of the sintered GNPs/Cu–Cr–Mg composites, the samples were wire-electrode cut in parallel with the sintering pressing direction. The XRD results of the composite are shown in An EPMA analysis was performed to further study the distribution of graphene and alloying elements in the composite. The EPMA surface scan results can be seen in −1), the G peak (~1580 cm−1), and the 2D peak (~2700 cm−1). The D peak is known as the defect band, and the 2D peak is known as the G0 peak. The D peak has been caused by the vibration of the defects in the graphene plane, or on the edge, which reveals the structural defects in graphene. Moreover, the G peak corresponds to the in-plane vibration of the sp2 hybridized carbon atoms. The intensity ratio of the D-to-G peak can be used to evaluate the defects and quality of graphene [D/IG) to describe the change in graphene defect density, which has also been reported in other studies [D/IG of the pristine GNPs was found to be as small as 0.17, which indicates that the quality of graphene is high. However, the ID/IG of graphene was found to increase to 0.45 after ball-milling, which indicates that the sp2 structure of graphene has been damaged to some extent. The reason is that in the process of high-energy ball-milling, the graphene and ZrO2 balls will collide with each other, causing some damage to the surface and edges of graphene [D/IG value of graphene did slightly increase to 0.55 as a result of sintering. It can, in part, be explained by the plastic deformation that takes place in the powder during the sintering process. On the other hand, Cr in the alloy matrix can react with amorphous carbon at the edge of the graphene during the sintering process, which increases the number of defects in the graphene [The structures of pristine GNPs, as well as the structures of graphene before and after rapid hot-pressing sintering, were analyzed by using Raman spectroscopy. Three characteristic peaks of graphene can be seen in the Raman spectrum in graphene ,20. In a studies ,21. To agraphene . Moreovegraphene ,23,24.The relative density and electrical conductivity of the composites are listed in The conductivity of the Cu–Cr–Mg matrix material was found to have a value of 82.4% IACS. Moreover, the conductivity of the GNPs/Cu–Cr–Mg composite had a value of 81.5% IACS, which is only 0.9% IACS lower than that of the matrix. This decrease in conductivity is small compared with other studies ,8,25. ThThe tensile properties of the GNPs/Cu–Cr–Mg composite are shown in c and σm are the yield strengths of the composite and the matrix, respectively, and Vf is the volume fraction of graphene. The strengthening efficiency (R) of a reinforced phase is an important parameter in the evaluation of the strengthening effect of a reinforced phase in the composite. It is defined as presented in Equation (1) as follows:Furthermore, (1)Flake Cu–Cr–Mg powder was successfully prepared by controlling the parameters of ball-milling. The microstructure of the composite material was also a layered structure, and the directional distribution of graphene was realized. The Cr atoms were found to react with the amorphous carbon at the edge of graphene during the sintering process. Moreover, the Mg atoms were found to limit the size of the carbides by segregating to the surface of the carbide, which effectively improved the binding strength of the graphene/copper interface;(2)D/IG was 0.55, which indicates that the structure of graphene remains intact during the preparation process, and there are few defects;Graphene maintained sharp G peaks and smaller D peaks after ball-milling and sintering. The value of I(3)The tensile strength of the composite reached a value of 349 MPa, which was 46% higher than that of the matrix. Moreover, the enhancement efficiency of graphene was 136. Furthermore, the conductivity of the composite became 81.5% IACS, which was only 1% IACS lower than that of the matrix. This can be attributed to the improvement of the graphene/copper interface by the Cr and Mg elements, as well as the high strength and high conductivity of graphene.By using Cu–Cr–Mg alloy powder and graphene nanosheets as raw materials, a GNPs/Cu–Cr–Mg composite has been prepared by using high-energy ball-milling and fast hot-pressing sintering. The microstructure of the composites, as well as the effect of the alloying elements and graphene on the mechanical properties and electrical conductivity of the composite, have been especially studied. The following results could be made:


Particle shape, size, and concentration were found to be major factors that affected overall biocompatibility of graphene.Graphene-based materials have been shown to have advantageous properties in biomedical and dental applications due to their high mechanical, physiochemical, antibacterial, and stem cell differentiating properties. Although graphene-based materials have displayed appropriate biocompatible properties when used in implant materials for orthopedic applications, little research has been performed to specifically test the biocompatibility of graphene for dental applications. The oral environment, compared to the body, varies greatly and must be considered when evaluating biocompatibility requirements for dental applications. This review will discuss  One such structure that carbon can form is graphene, which is a two-dimensional structure of carbon atoms and one of the strongest materials in existence . Fr. Fr91]. 0.1 w/v% .S. mutans bacteria in vitro and demonstrated good mechanical performance without decreasing adhesive strength. Reduced nano-graphene oxide and graphene nanoplates doped with silver nanoparticles were prepared by another research group, which found that the graphene nanoplates doped with silver nanoparticles displayed good adhesive properties that improves the resin-bonded dentin interface. In addition, cell viability of the adhesive was found to be above 85% -1,3-benzene sulfonate) colorimetric cell proliferation assay using human gingival fibroblasts (HGF-1) to test local biocompatibility up to 6 months periment .Another study was conducted to improve polyetheretherketone (PEEK) nanofillers for bone restoration in orthopedic and orthodontic/dental applications. The researchers created novel surface-porous nanofillers made of PEEK combined with hydroxyapatite (HA) and graphene oxide via a heated injection mold process. The surface morphology, mechanical properties, and cellular responses of the nanofillers were investigated. It was found that the inclusion of the hydroxyapatite and graphene oxide significantly improved the overall cell adhesion and proliferation on the PEEK surface showing notable promise in improving tissue integration of PEEK nanofillers for orthopedic and dental/orthodontic applications . The autFrom these studies, graphene oxide and graphene-based materials are promising as additional filler materials for uses in dental composites and resins in restoratives dentistry and orthodontics. The addition of graphene-based materials as fillers has been shown to provide good mechanical performance in dental composites. Graphene-based materials have also shown enhanced bonding strength in dental adhesives, offer good protection from dentin demineralization in infected teeth, and possess good biocompatibility in such dental applications.in vivo applications, biocompatibility of materials must be assessed. Therefore, the following studies included in vitro biocompatibility tests to further assess graphene's biocompatibility for potential dental applications.Osseointegration and differentiation of stem cells are important factors to consider when creating biomaterials for restorative dental applications and bone tissue engineering applications. Graphene has previously been used in various bone tissue engineering applications to promote cell attachment, proliferation, differentiation, and osteogenesis for dental applications. Graphene-based materials also possess optimal tissue engineering properties by having high surface area, mechanical strength, and ease of functionalization , 103. VaUnderstanding and controlling mesenchymal stem cell (MSC) differentiation mechanisms is an important area of research for tissue engineering. One study investigated the effects of graphene and graphene oxide substrates on osteogenic differentiation of MSCs isolated from adult bone marrow. The chemical interaction between the substrates was investigated to determine molecular insights into proliferation enhancement mechanisms. From the results, higher osteogenic differentiation of MSCs was observed on graphene films in comparison to graphene oxide films. The authors found that the graphene films could preconcentrate osteogenic inducers, dexamethasone and Β-glycerolphosphate, which accelerate differentiation of MSC toward osteogenic differentiation . Graphenμg/ml concentrations and rGO sheets with dimensions of 3.8 ± 0.4 μm at high concentrations of 100 μg/ml displayed high cytotoxic effects after 1 hr of exposure. The likely causes were due to the sharp edges from the graphene and oxidative stress created when interacting with cells. In addition, rGONPs could penetrate into the nucleus of human MSCs and cause genotoxicity at low concentrations around 0.1 to 1 μg/ml after 1 hr.Human MSCs isolated from an infant USB were used to evaluate the concentration and size-dependent cytotoxic and genotoxic effects of graphene sheets and nanoplatelets . Reducedin vivo study was later performed by the same group [in vivo and further investigate the integrin/FAK mechano-transduction pathway that potentially causes osteogenic differentiation  has shown promise in creating graphene films and scaffolds for tissue engineering. Dental pulp stem cells (DPSCs) are commonly used to test the biocompatibility, cell differentiation, and proliferation of graphene incorporated materials using a CVD method for dental applications. DPSCs possess a multi-lineage differentiation potential which allows them to differentiate into odontoblasts that assist in tooth dentin regeneration or osteoblasts which form bone matrices in the tooth . In addime group  to assesntiation . A mesenGraphene has been used in various materials to promote and support the differentiation of human periodontal ligament stem cells (hPDLSCs) as well. Graphene oxide combined with silk fibroin-based scaffolding material was found to promote hPDLSC differentiation into osteoblast-like cells . GO coatin vitro tests using bone mesenchymal stem cells (BMSCs), they found that the cells had good attachment and proliferation on the GO-modified groups compared to control groups. In addition, in vivo studies using rat models of the material found no toxic systemic effects, and the GO-modified scaffold allowed for higher calcium deposition of the BMSCs compared to control groups [Porphyromonas gingivalis bacteria and promoted cell proliferation in embryonic osteoblast MC3T3-E1 cells. They also found that the addition of GO enhanced osteogenic differentiation, in vitro, compared to unmodified composite materials [Polymer substrates and scaffolds are commonly used to promote bone tissue regeneration, and graphene has been incorporated into polymer scaffolds to assist in cell proliferation, differentiation, and osteogenesis. However, most polymer substrates, on their own, possess poor mechanical properties and are hydrophobic, which decreases cell attachment and proliferation. Therefore, graphene is often added into polymer scaffolds to increase hydrophilicity and mechanical, thermal, and electrical properties . A studyl groups . Anotheraterials .in vitro and in vivo. From in vitro tests, they found that the graphene CS/PCL scaffold displayed almost double ALP activity compared to other scaffolds, which indicates early osteoblast differentiation. From in vivo tests, they found that the graphene CS/PCL scaffolds promoted proliferation and osteogenesis of Wharton's jelly MSCs [μm was necessary to promote sufficient bone regeneration and osteoconductivity [Porous polymer scaffolds are used in bone tissue engineering for orthopedic and regenerative tissue engineering in dentistry. Huang et al.  fabricatlly MSCs . A hybrilly MSCs . The poructivity , 120.Collagen is among the main components in soft and hard tissues and is widely distributed throughout bones, tendons, skin, and teeth , 122. Itμg/ml [μg/ml seemed to significantly decrease cell viability, but concentrations below 62.5 μg/ml displayed negligible differences. However, the rGO-modified BCP coating displayed significantly higher new bone formation during in vivo rat studies [Calcium hydroxyapatite (HAP) is another material used in bone tissue engineering due to its excellent biocompatibility and osteoconductivity . Howeverμg/ml . In addiμg/ml . Higher  studies .in vitro cytological examination, researchers found that the composite had good wettability and bond strength that increased cell viability and differentiation potential for bone MSCs. In vivo studies also showed that osseointegration enhancement of the material was observed when implanted into rats [A chitosan HAP composite modified with GO was studied to increase cell adhesion, viability, differentiation, and mineralization in osteogenic properties . From innto rats . In addinto rats . From thGraphene-based materials have been used as coatings for titanium implants. Various layers of graphene oxide have been added to titanium implants and have been shown to increase antibacterial properties, osteogenic cell behavior, and cell proliferation . GO and In general, graphene oxide and reduced graphene oxide materials have displayed relatively good biocompatibility for various bone tissue engineering applications. The addition of graphene oxide has been shown to improve cell attachment, proliferation, and differentiation of DPSCs and hPDLSC in various porous polymer scaffolds and hydroxyapatite composites. It assists in better osseointegration of implants. However, there is still debate over the optimal concentration of GO and rGO in various scaffolds and composites to achieve optimal cell viability and cell attachment. Overall, substrates with graphene-based materials included allow for proper cell adhesion, viability, and proliferation directly related to biocompatible aspects of the overall material .Graphene-based nanoparticles are considered a topic of great interest in the field of dentistry. They are being studied for applications such as dental adhesives, fillings, and tissue engineering. Graphene-based materials have been shown to have promising results as antibacterial agents. Antibacterial and antibiofilm properties for dental implants are crucial since bacterial infections are often the causes for implant failure and integration with the bone. The addition of graphene-based materials in dental composite fillings has offered antibacterial properties to decrease bacterial adsorption onto composite material to prevent further tooth decay. Additionally, graphene nanoparticles have been found to have adequate initial biocompatibility in the mouth when it comes to bone and tissue engineering. They have been shown to possess good osteoblastic differentiation tendencies to increase osseointegration and improve bone tissue development. Increased proliferation and differentiation of stem cells is a major factor in showing graphene's biocompatibility for dental applications.in vitro tests, there is still a lack of long-term cytotoxicity studies of graphene nanoparticles in the body, as well as a lack of understanding as to how easily they can be excreted from the body. Many factors such as particle size, shape, and concentration appear to play a large role in how toxic these nanoparticles can be, and it would seem that the cytotoxicity varies on a case-by-case basis. Standardization of biocompatibility requirements for dental applications is also needed with long-term in vitro and in vivo studies to fully understand the biocompatibility of these nanoparticles and their long-term health effects.Although graphene has been shown to display relatively good biocompatible qualities in various dental applications from