Graphene Oxide Flakes Research Articles

Nanoarchitectonics of hyperbolic paraboloid 2D Graphene Oxide Membranes

AbstractHyperbolic paraboloid surfaces or saddle‐shaped materials can exist in two equilibrium shapes when the saddle shape reverses on itself and, therefore, can be used as structural elements of new stimuli‐responsive and shape‐changing materials. Here we propose a new fast and easy approach to the nanoarchitectonics of graphene oxide nanosheets to form curved interfaces. Our technology involves computer‐aid design, three dimensional (3D) printing, and casting curved templates for the assembly of two‐dimensional (2D) nanosheets. We demonstrate the feasibility of our approach for the nanoarchitectonics of graphene oxide flakes, though it can be expanded to include the whole family of 2D materials. The prepared free‐standing saddle‐shaped graphene oxide membranes show highly ordered nanostructure, typical for flat 2D multilayered materials. We optimize the preparation conditions to construct robust two‐dimensional membranes with nanostructured architecture and controllable thickness and curvature.

Study the electron field emission properties of plasma-based reduction of graphene oxide (GO): An ex-situ plasma approach

Vacuum-based electron emission devices requires fast and low turn-on field processes. Graphene oxide (GO) can be a perfect candidate for field electron emission applications. In this work, we have prepared graphene oxide (GO) via modified Hummer's method and treated it with dense plasma of argon gas (Ar). The surface morphology of the prepared GO reveals the growth of the stacked-layer and large surface area flakes of GO. Raman spectra reveals the high defective growth of GO. The impurities in the GO are due to the incorporation of oxygen moieties. For enhancing the field emission properties, the GO thin films were treated with a dense plasma of Ar gas at 50, 100, 150 and 200 W. Raman spectra strongly indicates the removal of oxygen moieties and formation of defects and vacancies in the sheet of plasma-treated GO. The field emission properties drastically improved in the scenario of plasma-treated GO field emitters. The turn-on and threshold fields were reduced after plasma treatment in comparison with pristine GO field emitters. The reduction in the turn-on and threshold fields is due to the enhancement in the edge effects, protrusion formation and modification in structural properties. The emission current density was drastically enhanced in the 200 W plasma-treated GO field emitters. The emission stability test was performed for a 600 min at 3 V / μ m applied electric field. The stability was enhanced with plasma power and shows the minimum current fluctuation. The field enhancement factor also improved after plasma treatment and for 200 W treated β becomes 3 times the pristine GO. We have also implemented the orthodox emission hypothesis test, which was qualified by the prepared pristine and plasma-treated GO field emitters due to the f e x t r values belonging in the acceptable range. Conclusively, Ar gas plasma-treated GO field emitters can be useful for emission applications in vacuum devices.

The effect of boiling in a thermosyphon on surface tension and contact angle of silica and graphene oxide nanofluids

Thermosyphons are heat transfer devices characterised by high efficiency due to simultaneous phase changes occurring in the evaporation-condensation cycle of working fluid. One of the most promising solutions to enhance their heat transfer capacity of the device is the use of nanofluids – suspensions of particles with at least one dimension below 100 nm. It was determined that nanofluid does not influence the work of thermosyphons condenser section and the focus should be put on the boiling process in the evaporator section. During boiling, nanoparticles tend to deposit on the heater’s surface, what alters characteristics of this surface and near surface hydrodynamics. This changes the appearance of nanofluid, but the precise effect on how the deposition of particles affects the properties of nanofluid is unknown. Changes in surface tension and wettability affect boiling regimes (e.g. reduced surface tension reduces the size of departing bubbles and inhibits geysering), and efficiency of heat transfer through the device. Understanding of those parameters is crucial for the development of appropriate models describing heat transfer in thermosyphon working with nanofluids. The main goal of this study is to determine surface tension and contact angle of nanofluids based on silica nanoparticles and nano-sized graphene oxide flakes before and after the experimental boiling cycle in the thermosyphon. Results show that, in comparison with water, silica nanofluid (2 vol%) is characterised by lower surface tension and contact angles on both analysed surfaces. After-use silica nanofluid exhibited noticeably higher averaged surface tension and smaller contact angles in comparison to the fresh working medium. The change was most likely due to the decreased concentration caused by the deposition of nanoparticles during the thermosyphon operation. Still, the differences between before-use and after-use samples were smaller than the measurement uncertainties. Before-use graphene oxide nanofluid already showed surface tension and contact angle similar to water due to low concentration of graphene flakes (0.1 g/L). Consequently, the properties of after-use graphene oxide fluid were also not much different from water. Additional measurements of surface tension for graphene oxide nanofluid with and without addition of sodium dodecyl sulphate surfactant allowed to differentiate the effects caused by graphene flakes and surfactant. The surfactant reduced the surface tension of the nanofluid, but the change was smaller than in case of surfactant addition to pure water.

Measurements of the Electrical Conductivity of Monolayer Graphene Flakes Using Conductive Atomic Force Microscopy.

The intrinsic electrical conductivity of graphene is one of the key factors affecting the electrical conductance of its assemblies, such as papers, films, powders, and composites. Here, the local electrical conductivity of the individual graphene flakes was investigated using conductive atomic force microscopy (C-AFM). An isolated graphene flake connected to a pre-fabricated electrode was scanned using an electrically biased tip, which generated a current map over the flake area. The current change as a function of the distance between the tip and the electrode was analyzed analytically to estimate the contact resistance as well as the local conductivity of the flake. This method was applied to characterize graphene materials obtained using two representative large-scale synthesis methods. Monolayer graphene flakes synthesized by chemical vapor deposition on copper exhibited an electrical conductivity of 1.46 ± 0.82 × 106 S/m. Reduced graphene oxide (rGO) flakes obtained by thermal annealing of graphene oxide at 300 and 600 °C exhibited electrical conductivities of 2.3 ± 1.0 and 14.6 ± 5.5 S/m, respectively, showing the effect of thermal reduction on the electrical conductivity of rGO flakes. This study demonstrates an alternative method to characterizing the intrinsic electrical conductivity of graphene-based materials, which affords a clear understanding of the local properties of individual graphene flakes.

Synthesis and characterization of graphene oxide flakes for transparent thin films

We have synthesized large scale, thin, transparent graphene oxide (GO) flakes by Hummer’s method and investigated their suitability for fabrication of transparent nanocomposites. The GO flakes were comprehensively characterized by X-ray diffraction, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), Raman spectroscopy and Differential Scanning Calorimetry (DSC). X-ray diffraction displayed the peak of graphene oxide at 9°degree, which is characteristic peak of GO in agreement with the literature results. Scanning Electron Microscopy images revealed that thin, transparent, flake form GO with 14,8 µm lateral size and 0,31µm thickness were synthesized. The comparison with literature results show that for the first time, our group could synthesize large scale, thin and more transparent GO flakes by simple Hummer’s method using simple dispersed graphite. EDX measurements indicate the formation of layered structure with oxygen containing functional groups. The intensity ratio between D and G peaks in the Raman spectra proves that less defective GO flakes have been synthesized. The solution ability of the synthesized material indicate that high quality GO flakes were synthesized, which make them effective soluble material due to oxygen containing groups formed on the graphene plane during synthesis process.DSC results shows that these flakes are thermally stable till 200°C. Due to high solubility properties, large scale and transparency they can be very useful in fabrication of high optical transparent nanocompoties for replacement indium tin oxide transparent conductors in solar panels, biomedical applications and microwave absorbers for electromagnetic interference (EMI) environmental protection.

Folding-induced in-plane birefringence in homeotropically aligned graphene-oxide liquid crystal films formed by solution shear

ABSTRACT Graphene-oxide (GO) has been widely explored as a functional two-dimensional (2D) material. The GO-flakes self-assemble into colossal sheets of 2D aggregates with extreme flexibility and the GO-dispersion in water forms an alternately layered phase with nematic order. Highly ordered supramolecular anisotropic GO films can be fabricated by a hydraulic shear. For a uniform in-plane shear, it is generally known that GO aligns tangential to the shear plane, resulting in homeotropic orientation of the optic axis with no in-plane birefringence. However, it surprisingly results in uniform in-plane birefringence with the optic axis (Δn < 0) aligned perpendicular to the shear direction. The in-plane birefringence originates from the folding deformation of homeotropically aligned GO layers, rather than reorientation of pristine GO flakes. 2D GO aggregates are very large and flexible so that prone to be deformed by external force, rather than reorientation. For the alternately layered GO-LC phase, drying is a directional process so that major compression occurs predominantly along the layer-normal. As a result, both folding width and film thickness are reduced considerably and the folded band protrudes during a drying process. This folding-induced in-plane birefringence of GO-LCs provides useful insights for processing anisotropic 2D materials, beneficial for various electrical, optical, and mechanical applications.

Graphene Oxide and Reduced Graphene Oxide Nanoflakes Coated with Glycol Chitosan, Propylene Glycol Alginate, and Polydopamine: Characterization and Cytotoxicity in Human Chondrocytes.

Recently, graphene and its derivatives have been extensively investigated for their interesting properties in many biomedical fields, including tissue engineering and regenerative medicine. Nonetheless, graphene oxide (GO) and reduced GO (rGO) are still under investigation for improving their dispersibility in aqueous solutions and their safety in different cell types. This work explores the interaction of GO and rGO with different polymeric dispersants, such as glycol chitosan (GC), propylene glycol alginate (PGA), and polydopamine (PDA), and their effects on human chondrocytes. GO was synthesized using Hummer’s method, followed by a sonication-assisted liquid-phase exfoliation (LPE) process, drying, and thermal reduction to obtain rGO. The flakes of GO and rGO exhibited an average lateral size of 8.8 ± 4.6 and 18.3 ± 8.5 µm, respectively. Their dispersibility and colloidal stability were investigated in the presence of the polymeric surfactants, resulting in an improvement in the suspension stability in terms of average size and polydispersity index over 1 h, in particular for PDA. Furthermore, cytotoxic effects induced by coated and uncoated GO and rGO on human chondrocytes at different concentrations (12.5, 25, 50 and 100 µg/mL) were assessed through LDH assay. Results showed a concentration-dependent response, and the presence of PGA contributed to statistically decreasing the difference in the LDH activity with respect to the control. These results open the way to a potentially safer use of these nanomaterials in the fields of cartilage tissue engineering and regenerative medicine.

Aquaporin-Incorporated Graphene-Oxide Membrane for Pressurized Desalination with Superior Integrity Enabled by Molecular Recognition.

Aquaporins (AQPs), the natural water channel, have been actively investigated for overcoming the limitations of conventional desalination membranes. An AQP‐based biomimetic high‐pressure desalination membrane is designed by tethering AQP‐carrying red blood cell membrane (RBCM) vesicles onto graphene oxide (GO). RBCMs with AQPs are incorporated into GO based on the molecular recognition between the integrin of RBCM and Arginine‐Glycine‐Aspartate (RGD) ligand on the GO surface. GO is pre‐functionalized with the Glycine‐Arginine‐Glycine‐Aspartate‐Serine peptide to capture RBCMs. RBCMs are inserted between GO flakes through the material‐specific interaction between integrin of RBCM and RGD ligand, thus ensuring sufficient coverage of channels/defects in the GO for the full functioning of the AQPs. The incorporated AQPs are not completely fixed at the GO, as tethering is mediated by the integrin–RGD pair, and suitable AQP flexibility for appropriate functioning is guaranteed without frictional hindrance from the solid substrate. The integrity of the GO–RBCMs binding can provide mechanical strength for enduring high‐pressure reverse‐osmosis conditions for treating large amounts of water. This biomimetic membrane exhibits 99.1% NaCl rejection and a water permeance of 7.83 L m−2 h−1 bar−1 at 8 bar with a 1000‐ppm NaCl feed solution, which surpasses the upper‐bound line of current state‐of‐the‐art membranes.

Effect of graphene oxide flakes size and number of layers on photocatalytic hydrogen production

The present study explored the correlation between the photocatalytic activity toward hydrogen production of the graphene-based materials and graphene oxide (GO) morphology. In this work we applied the technique based on the combination of time-dependent sonication and iterative centrifugation cascades, which were designed to achieve nanosheets size and the number of layers selection. First such obtained GO dispersions were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical spectroscopy. Those combined measurements showed that the intensity of the π-π peak at 230 nm seems to be very sensitive to the number of layers of nanosheets. Next, GO dispersions were used to establish influence of the size and the number of layers of GO flakes on the photocatalytic hydrogen production in the photocatalytic system, containing eosin Y as a sensitizer, triethanolamine as a sacrificial electron donor, and CoSO4 as precatalyst. The H2 production efficiency varied by a factor of 3.7 for GO dispersions sonicated for various amount of time. Interestingly it was found that too long ultrasound treatment had negative impact on the GO enhancement of hydrogen production which was related to the fragmentation of GO flakes. The photocatalytic system produced the highest amount of H2 when graphene oxide occurs as monolayers and efficiency becomes lower with the decrease of GO sheets size. Our results demonstrate the importance of optimizing the size and the number of layers of the GO flakes prior to preparation of GO-based materials.

CNT-rGO Hydrogel-Integrated Fabric Composite Synthesized via an Interfacial Gelation Process for Wearable Supercapacitor Electrodes.

We demonstrate a flexible and stretchable supercapacitor assembled via straightforward interfacial gelation of reduced graphene oxide (rGO) with carbon nanotube (CNT) on a stretchable fabric surface. The difference between the redox potential of aqueous graphene oxide (GO) dispersion, prepared using a modified Hummers' method, and of a solid Zn plate, which was used as an external stimulus, induces a spontaneous reduction of GO flakes forming porous CNT–rGO hydrogel at the liquid–solid interface. With the aid of Zn, a macroporous and flexible CNT–rGO hydrogel was fabricated on a stretchable fabric platform using a facile fabrication method, and the CNT–rGO fabric composite was assembled into a supercapacitor to demonstrate its feasibility as a wearable electrode. The porous structure of the as-formed CNT–rGO fabric composite allows excellent electrolyte accessibility and ion transport that result in a fast charge/discharge rate up to 100 mV/s and a large areal capacity of 10.13 mF/cm2 at a discharge rate of 0.5 mA (0.1 mA/cm2). The inclusion of one-dimensional CNT as conductive bridges allows an excellent capacity retention of 95.2% after complete folding of the electrode and a capacity retention of 93.3% after 1000 bending cycles. Additional stretching test displayed a high capacity retention of 90.0% even at an applied strain as high as 50%, overcoming previous limitations of brittle graphene-based electrodes. This low-cost, lightweight, easy to synthesize, stretchable supercapacitor holds promise for next-generation wearable electronics and energy storage applications.

Surface Modification of Nanocrystalline LiMn2O4 Using Graphene Oxide Flakes.

In this work, a facile, wet chemical synthesis was utilized to achieve a series of lithium manganese oxide (LiMn2O4, (LMO) with 1–5%wt. graphene oxide (GO) composites. The average crystallite sizes estimated by the Rietveld method of LMO/GO nanocomposites were in the range of 18–27 nm. The electrochemical performance was studied using CR2013 coin-type cell batteries prepared from pristine LMO material and LMO modified with 5%wt. GO. Synthesized materials were tested as positive electrodes for Li-ion batteries in the voltage range between 3.0 and 4.3 V at room temperature. The specific discharge capacity after 100 cycles for LMO and LMO/5%wt. GO were 84 and 83 mAh g−1, respectively. The LMO material modified with 5%wt. of graphene oxide flakes retained more than 91% of its initial specific capacity, as compared with the 86% of pristine LMO material.

Morphology and Chemical Purity of Water Suspension of Graphene Oxide FLAKES Aged for 14 Months in Ambient Conditions. A Preliminary Study.

Graphene and its derivatives have attracted scientists’ interest due to their exceptional properties, making them alluring candidates for multiple applications. However, still little is known about the properties of as-obtained graphene derivatives during long-term storage. The aim of this study was to check whether or not 14 months of storage time impacts graphene oxide flakes’ suspension purity. Complementary micro and nanoscale characterization techniques (SEM, AFM, EDS, FTIR, Raman spectroscopy, and elemental combustion analysis) were implemented for a detailed description of the topography and chemical properties of graphene oxide flakes. The final step was pH evaluation of as-obtained and aged samples. Our findings show that purified flakes sustained their purity over 14 months of storage.

Graphene oxide nanofilm to functionalize bioinert high strength ceramics

This study aimed to join the proven osteogenic properties of graphene oxide (GO) with bioinert zirconia implants. The dip-coating technique allows achieving this goal by forming a thin, homogenous, hydrolytically, and mechanically stable GO film onto silanized ceramic-substrates. SEM, AFM, XPS, and contact angle measurements confirmed the presence, transparency, integrity, and homogenous covering character of the GO film. The GO film is hydrolytically stable since it remained intact after a soaking period of 24 days in double-distilled water (ddH2O) and phosphate buffered saline and resisted a ten-minute sonication treatment for in ddH2O. This strong hydrolytic stability is due to the silanization with 3-amino-propyl-diisopropylethoxy-silane (APDS) enhancing the anchoring of GO flakes onto zirconia surfaces. Besides, the GO film disinfectable in 70% ethanol. Subsequently, we assessed our immobilized GO film as cytocompatible for L929 mouse fibroblast and human mesenchymal stem cells and propitious for the osteogenic differentiation demonstrated by a two times upregulation of the osteogenic transcription factor RunX2. The active hydroxyl and carboxyl groups of the GO film open new perspectives for the functionalization of ceramic implants by immobilization of biological agents, such as growth factors or antibiotics, and thus enhance the osseointegration.

Vapour Diffusion Sitting Drop Method to Induce Nucleation of Calcium Phosphate on Exfoliated Graphene and Graphene Oxide Flakes

The preparation of graphene/apatite and graphene oxide/apatite hybrid nanocomposites has recently attracted great attention in the biomaterial community. The sitting drop vapor diffusion technique has been assessed as a preparative method for such nanocomposites in this work. The technique has been employed to induce heterogeneous nucleation and growth of calcium phosphate in the presence of exfoliated graphene and commercial graphene oxide flakes, both labeled with L-Alanine. Exfoliated multilayered graphene flakes were produced by sonication-assisted liquid-phase exfoliation of graphite. In both composites, the apatite nanocrystals displayed similar size and shape, but different labile and B-type carbonation contributions. Graphene and graphene oxide flakes also influenced the carbonation degree of the apatite, which was almost half that measured for the apatite blank, as well as the aggregation state of their composites. In this regard, those composites with graphene oxide formed larger aggregates because of their wider size distribution, with a high-volume percentage of nanosheets (of about 4 nm length). Overall, the method is very useful to prepare small amounts of nanocomposite with high reproducibility.

The relations between wear behavior and basic material properties of graphene‐based materials reinforced ultrahigh molecular weight polyethylene

AbstractThis article aims to investigate the influence of reinforcing graphene oxide (GO) and graphite flakes (GF) fillers into ultrahigh molecular weight polyethylene (UHMWPE) for orthopedic application. These fillers were expected to physically bond to UHMWPE, thus can enhance the subsurface strength, improving the wear behavior of the composites. UHMWPE/GO and UHMWPE/GF composites were prepared at 0.1 and 1.0 wt% by melt‐blending, followed by a compression molding technique. A multidirectional pin‐on‐disc wear test was performed to simulate the kinematic of hip application. Whilst getting exposed in the artificial in‐vivo lubricant bath (30 v/v% diluted bovine serum). Following this, the wear mechanism fostered by each filler (GO and GF) was determined by wear features obtained from the optical microscope and scanning electron microscope (SEM). The crystallinity degree and crystal defect were assessed using x‐ray diffraction (XRD). The mechanical properties of fabricated composites were evaluated by using a universal testing machine and Vickers microhardness. We found that UHMWPE/GO has the lowest specific wear rate due to the improved subsurface strength, as the reduction of a weak adhesive point was observed on the worn surface. Meanwhile, higher GF content (1 wt%) in UHMWPE displayed a lower specific wear rate than neat UHMWPE after completing the 10 km sliding distance attributed to the filler resurfaced, responsible for providing a strong resistance of the shear stress applied upon sliding with the metal counterface. Interestingly, the hardness and tensile strength for both UHMWPE/GO and UHMWPE/GF increased, although the crystallinity percentage was declining compared to neat UHMWPE.

(Nanocarbons Division Best Poster Award - 3rd Place) Reversible Quenching of Graphene Oxide Photoluminescence Under the External Electric Field

With the advent of graphene, there has been an interest in utilizing this material and its derivative, graphene oxide (GO) for novel applications in nanodevices such as bio and gas sensors, solid-state supercapacitors and solar cells. Although GO exhibits lower conductivity and structural stability, it possesses an energy band gap that enables fluorescence emission in the visible/near infrared leading to a plethora of optoelectronic applications. In order to allow fine-tuning of its optical properties in the device geometry, new physical techniques are required that, unlike existing chemical approaches, yield substantial alteration of GO structure. Such a desired new technique is one that is electronically controlled and leads to reversible changes in GO optoelectronic properties. In this work, we for the first time investigate the methods to controllably alter the optical response of GO with the electric field and provide theoretical modeling of the electric field-induced changes. Field-dependent GO emission is studied in bulk GO/polyvinylpyrrolidone films with up to 6% reversible decrease under 1.6 V m−1 electric fields. On an individual flake level, a more substantial over 50% quenching is achieved for select GO flakes in a polymeric matrix between interdigitated microelectrodes subject to two orders of magnitude higher fields. This effect is modeled on a single exciton level by utilizing Wentzel, Kremer, and Brillouin approximation for electron escape from the exciton potential well. In an aqueous suspension at low fields, GO flakes exhibit electrophoretic migration, indicating a degree of charge separation and a possibility of manipulating GO materials on a single-flake level to assemble electric field-controlled microelectronics. As a result of this work, we suggest the potential of varying the optical and electronic properties of GO via the electric field for the advancement and control over its optoelectronic device applications.

Low Surface Roughness Graphene Oxide Film Reduced with Aluminum Film Deposited by Magnetron Sputtering

Graphene film has wide applications in optoelectronic and photovoltaic devices. A novel and facile method was reported for the reduction of graphene oxide (GO) film by electron transfer and nascent hydrogen produced between aluminum (Al) film deposited by magnetron sputtering and hydrochloric acid (HCl) solution for only 5 min, significantly shorter than by other chemical reduction methods. The thickness of Al film was controlled utilizing a metal detection sensor. The effect of the thickness of Al film and the concentration of HCl solution during the reduction was explored. The optimal thickness of Al film was obtained by UV-Vis spectroscopy and electrical conductivity measurement of reduced GO film. Atomic force microscope images could show the continuous film clearly, which resulted from the overlap of GO flakes, the film had a relatively flat surface morphology, and the surface roughness reduced from 7.68 to 3.13 nm after the Al reduction. The film sheet resistance can be obviously reduced, and it reached 9.38 kΩ/sq with a high transmittance of 80% (at 550 nm). The mechanism of the GO film reduction by electron transfer and nascent hydrogen during the procedure was also proposed and analyzed.

Gold Nanoparticles and Graphene Oxide Flakes Enhance Cancer Cells' Phagocytosis through Granzyme-Perforin-Dependent Biomechanism.

The study aimed to investigate the roles of gold nanoparticles (GNPs) and graphene oxide flakes (GOFs) as phagocytosis enhancers against cancer cells. The nanomaterials were characterized through SEM and UV-VIS absorptions. The GNPs and GOFs increased the macrophages’ phagocytosis ability in engulfing, thereby annihilating the cancer cells in both in vitro and in vivo conditions. The GNPs and GOFs augmented serine protease class apoptotic protein, granzyme, passing through the aquaporin class protein, perforin, with mediated delivery through the cell membrane site for the programmed, calibrated, and conditioned cancer cells killing. Additionally, protease inhibitor 3,4-dichloroisocoumarin (DCI) significantly reduced granzyme and perforin activities of macrophages. The results demonstrated that the GOFs and GNPs increased the activation of phagocytic cells as a promising strategy for controlling cancer cells by augmenting the cell mortality through the granzyme-perforin-dependent mechanism.

Magnetization of Ultraviolet-Reduced Graphene Oxide Flakes in Composites Based on Polystyrene.

This work presents our study results of the magnetization of multilayer UV-reduced graphene oxide (UV-rGO), polymer matrix (polystyrene), and a conjugated composite based on them. The mesoscopic structure of the composites synthesized in this work was studied by such methods as X-ray diffraction, SEM, as well as NMR-, IR- and Raman spectroscopy. The magnetization of the composites under investigation and their components was measured using a vibrating-sample magnetometer. It has been shown that the UV-reduction process leads to the formation of many submicron holes distributed inside rGO flakes, which can create edge defects, causing possibly magnetic order in the graphite samples under investigation on the mesoscopic level. This article provides an alternative explanation for the ferromagnetic hysteresis loop in UV-rGO on the base of superconductivity type-II.

Graphene oxide fibers fuse reversibly

With a quick soak in a solvent bath, researchers can fuse hundreds of graphene oxide (GO) fibers into a thicker cable ( Science 2021, DOI: 10.1126/science.abb6640 ). Another solvent bath then splits the cable back into its original fibers. The advance presents an easy, low-cost way to make strong, graphene-based yarns for electronics and smart materials that change shape when triggered. The yarn can also capture and release particles, which could be useful for pollutant-trapping fabrics and controllable delivery systems. Chao Gao and Zheng Li of Zhejiang University, Yilun Liu of Xi’an Jiaotong University, and their colleagues soak a bundle of hundreds of fibers in water or another solvent for up to 10 min. The fibers, which are made of GO flakes, swell. Flakes in the outer layer of each fiber pack tightly, creating a skin around each fiber. When the researchers remove the bundle from the solvent, surface tension