Effect Of Graphene Oxide Sheets Research Articles

Atomistic Modeling of Mechanical Properties and Creep Behavior of Graphene Oxide Reinforced Natural Rubber Composites

AbstractIn the realm of polymer composites, the research of nanoparticles has risen in prominence. Graphene oxide (GO) is one of the best nanofillers in natural rubber (NR). In this work, GO nanosheets are utilized as reinforcement in an NR composite to anticipate mechanical characteristics. The researchers project the effect of GO sheets in NR with varied volume percentages and defective GO sheet reinforcement in NR composites. When the volume percentage of GO sheet in the NR nanocomposite is 4.6% and 7.2%, respectively, the value of Young's modulus rose by 68.8% and 166.2%. GO/NR with a 7.2% volume fraction has the highest ultimate tensile strength as compared with lower volume fractions of GO/NR nanocomposites. An increase of 63.49% in ultimate tensile strength in GO/NR nanocomposites (7.2% vol fraction) is seen as compared with pristine NR. Creep characteristics of NR nanocomposites are also investigated. The results reveal that the addition of GO sheets considerably increases the creep resistance strength of NR nanocomposites. The zone of secondary creep grows narrower as the continuous stress level increases.

Evaluation of the Synergistic Effect of Graphene Oxide Sheets and Co3O4 Wrapped with Vertically Aligned Arrays of Poly (Aniline-Co-Melamine) Nanofibers for Energy Storage Applications.

In the present study, Co3O4 and graphene oxide (GO) are used as reinforcement materials in a copolymer matrix of poly(aniline-co-melamine) to synthesize ternary composites. The nanocomposite was prepared by oxidative in-situ polymerization and used as an electrode material for energy storage. The SEM images revealed the vertically aligned arrays of copolymer nanofibers, which entirely wrapped the GO sheets and Co3O4 nanoparticles. The EDX and mapping analysis confirmed the elemental composition and uniform distribution in the composite. The XRD patterns unveiled composites’ phase purity and crystallinity through characteristic peaks appearing at their respective 2θ values in the XRD spectrum. The FTIR spectrums endorse the successful synthesis of composites, whereas TGA analysis revealed the higher thermal stability of composites. The cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy are employed to elucidate the electrochemical features of electrodes. The ternary composite PMCoG-2 displayed the highest specific capacity of 134.36 C/g with 6 phr of GO, whereas PMCoG-1 and PMCoG-3 exhibited the specific capacities of 100.63 and 118.4 C/g having 3 phr and 12 phr GO at a scan rate of 0.003 V/s, respectively. The best electrochemical performance of PMCoG-2 is credited to the synergistic effect of constituents of the composite material.

Experimental Investigation on the Effect of Graphene Oxide Additive on the Steady-State and Dynamic Shear Properties of PDMS-Based Magnetorheological Elastomer.

Isotropic polydimethylsiloxane (PDMS)-based magnetorheological elastomers (MREs) filled with various contents of graphene oxide (GO) additive were fabricated by the solution blending-casting method in this work. The morphologies of the produced MREs were characterized, and the results indicate that the uniform distribution of GO sheets and carbonyl iron particles (CIPs) becomes difficult with the increase of GO content. The steady-state and dynamic shear properties of the MREs under different magnetic field strengths were evaluated using parallel plate rheometer. It was found that the physical stiffness effect of GO sheets leads to the increase of the zero-field shear modulus with increasing GO content under both the steady-state and dynamic shear loads. The chemical crosslinking density of PDMS matrix decreases with the GO content due to the strong physical crosslinking between GO and the PDMS matrix. Thus, the MREs filled with higher GO content exhibit more fluid-like behavior. Under the dynamic shear load, the absolute MR effect increases with the GO content due to the increased flexibility of the PDMS matrix and the dynamic self-stiffening effect occurring in the physical crosslinking interfaces around GO sheets. The highest relative MR effect was achieved by the MREs filled with 0.1 wt.% GO sheets. Then, the relative MR effect decreases with the further increase of GO content due to the improved zero-field modulus and the increased agglomerations of GO and CIPs. This study shows that the addition of GO sheets is a possible way to prepare new MREs with high MR effect, while simultaneously possessing high zero-field stiffness and load bearing capability.

Preparation and Characterization of Fluorine-Containing Polybenzoxazole Composite Films including Graphene Oxide as a Reinforcing Material

The fluorine-containing polyhydroxyamide (F-75-PHA) was synthesized by using low-temperature solution polycondensation of 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (BAHHFP, 75 mol%) and 3,3′-dihydroxybenzidine (DHB, 25 mol%) with terephthaloyl chloride (TPC) in N-methyl-2-pyrrolidinone (NMP) without metal salts. The F-75-PBO (polybenzoxazole)/GO (graphene oxide) composite films with different GO contents (0.01, 0.1, and 1.0 wt%, respectively) were prepared by heat-treatment of their precursors (F-75-PHA/GO composite films), and the effects of reinforcing material (GO) on the structural, thermal, and mechanical properties of them were studied systemically. FE-SEM images that the F-75-PBO matrix and GO sheets had a superior hydrogen bonding interaction and formed a three-dimensional (3D) network structure in composite films having a great bendability. FT-IR spectra indicated that the incorporation of GO in composite films could be reacting hydroxyl (−OH) groups on F-75-PHA matrix to carboxyl (−COOH) and/or −OH groups in GO sheets, and thus the O-H stretching peak (23.8 %) for F-75-PHA/GO-0.1 composite film mostly disappeared in comparison with that (100 %) of F-75-PHA film. DSC heating curves revealed that the thermal cyclization temperature (Tc) of the F-75-PHA/GO composite films decreased with an increment of GO content. Interestingly, for F-75-PHA/GO-0.1 composite film, the Tc decreased by up to 254 °C. However, despite the outstanding reinforcing effect of GO sheets, an interesting phenomenon was confirmed that 3D network structure including an excellent hydrogen bonding interaction did not largely influence the mechanical properties of F-75-PBO/GO composite films.

Size effect of graphene oxide sheets on enantioseparation performances in membrane separation

Recently, graphene oxide (GO)-based membranes have been demonstrated to be a potential candidate for gas purification and liquid separation techniques owing to their large surface area, tunable interactive sites, and adjustable interlayer spacing. Notably, GO-based membranes functionalized with chiral selectors have been demonstrated to possess high enantiomer permeability and impressive permeation selectivity toward enantiomeric target guests. However, the influence of the GO sheet size on the separation performance remains unclear. Here, we investigated the effect of the lateral size on the enantioseparation performances by modifying a chiral selector onto GO flakes with different sizes, considering that GO membranes possess an inherently high throughput character. In this work, three GO sheets with mean lateral sizes (~60, 650 and 4100 nm) were prepared, hereafter defined as GO1, GO2, and GO3, respectively. Then, a chemical modification of GO1, GO2 and GO3 with a chiral selector, L-Phenylalanine (L-Phe), yielded the corresponding L-Phe grafted GO sheets, L-Phe-GO1, L-Phe-GO2 and L-Phe-GO3. Finally, L-Phe-GO1, L-Phe-GO2 and L-Phe-GO3 membranes derived from a simple vacuum filtration method were employed to separate D-/L-phenylalanine. Results show that the L-Phe-GO3 based membrane allows for a remarkable chiral separation capacity, having a greatest enantioselectivity among three L-Phe-GO membranes with different lateral GO sizes. Our findings illustrate that the sheet size of GOs plays a dominant role in the enantioselectivity of membrane separation.

The correlated effects of filler loading on the curing reaction and mechanical properties of graphene oxide reinforced epoxy nanocomposites

Graphene oxide (GO)/epoxy nanocomposites are prepared by means of the phase extraction method. FTIR and XPS characterizations have confirmed the charge transfer between GO and epoxy that promotes the uniform dispersion and exfoliation of GO. The effects of GO sheets on the curing reaction and interfacial bonding are investigated and correlated with mechanical properties of epoxy nanocomposites. The results show that the GO sheets have a facilitation effect on the curing reaction of epoxy resin, in which the oxygen groups of GO covalently react with epoxy matrix and establish chemical interfacial bonding in epoxy nanocomposites. Therefore, the mechanical properties of nanocomposites are enhanced, showing the highest tensile strength of 88.1 ± 2.5 MPa, flexural strength of 134.2 ± 6.1 MPa and flexural modulus of 3.15 ± 0.11 GPa, respectively. However, GO sheets could simultaneously physically restrict the curing reactivity and reduce the cross-link density in the interface, which results in weakened interfacial property of nanocomposites, especially at high loading. Thus, the reinforcing effect of GO sheets is reduced and the mechanical properties of GO/epoxy nanocomposites decline at relatively higher loading.

Organic Solvent Forward Osmosis of Graphene Oxide-Based Membranes for Enrichment of Target Products

Graphene oxide (GO) membranes with GO sheets of different size were prepared on porous nylon substrates. XRD and FT-IR were employed to explore the size effect of GO sheets on the microstructure of...

Synergistic modification by mercapto hyperbranched polysiloxane and functionalized graphene oxide on the surface of aramid fiber

With the purpose of improving the interfacial properties of aramid fibers reinforced rubber composites and enhancing the tensile strength of aramid fibers simultaneously, mercapto hyperbranched polysiloxane (HPSi) and functionalized graphene oxide (GO) were used to modify the surface of aramid fibers. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and other characterization methods were performed to confirm the process of synergistic modification. Judging from the results of mechanical property tests, it could be acquired that the tensile strength of modified aramid fiber was increased by 16.8%, which could be ascribed to the wrapping effect of GO sheets. The interfacial properties were assessed by the pull-out tests of composites, and the results showed that the maximum pull-out force after synergistic surface modification was increased by 99.3%, which could be mainly related to additive reaction between double bonds and mercapto groups and the promotion of surface energy. More critically, during pull-out test, aramid fiber bundles might bring a part of shear stress into the grafted GO sheets, namely, GO sheets could convert fracture energy into interfacial energy, which would improve interfacial properties dramatically.

Probing the influence of graphene oxide sheets size on the performance of label-free electrochemical biosensors

The integration of graphene materials into electrochemical biosensing platforms has gained significant interest in recent years. Bulk quantities of graphene can be synthesized by oxidation of graphite to graphite oxide and subsequent exfoliation to graphene oxide (GO). However, the size of the resultant GO sheets changes from the parent graphite yielding a polydispersed solution of sizes ranging from a few nanometers to tens of micrometers. Here, we investigate the direct effect of GO sheets sizes on biosensor performance. We separated different GO sheets sizes, and we characterized them via atomic force, scanning electron, Raman and X-ray photoelectron spectroscopies and solid state nuclear magnetic resonance (NMR). As proof of concept, the sensing performance of these GO samples was probed using a well-known ssDNA aptasensor against microcystin-LR toxin and an immunosensor against β-lactoglobulin. The resulting aptasensors and immunosensors are fabricated by using covalent attachment and physical adsorption. We found that the aptasensors fabricated using physical adsorption, the binding signal variation was dramatically increased with increasing the GO sheet size. In contrast, for the aptasensor fabricated using covalent immobilization, the binding signal variation decreased with increasing GO sheet size. However, for the β-lactoglobulin immunosensors, the optimum signals were observed at intermediate GO sheet size. GO sheet size could enhance or inhibit the sensitivity of the graphene-based electrochemical sensors. Our results demonstrate that controlling the size of GO sheets may have a profound impact in specific biosensing applications.

Enhanced interfacial properties of graphene oxide incorporated carbon fiber reinforced epoxy nanocomposite: a systematic thermal properties investigation

In this study influence of the graphene oxide (GO) inclusion on the thermal properties of carbon fiber reinforced polymer (CFRP) hybrid composite is reported. Different wt% content of GO used for development of epoxy matrix and CFRP hybrid composite was prepared using compression moulding process. The nanocomposites were characterized by various techniques viz. DMA, DSC, TMA, and TGA. It is observed that in GO-epoxy resin composites, storage and loss modulus reached maximum for 0.3 wt% of GO. The storage modulus of CFRP hybrid composite is achieved almost double with the addition of 0.3 wt% of GO. The glass transition temperature (Tg) calculated from DMA and TMA of GO incorporated CFRP hybrid composites demonstrated the enhancement in Tg by 4 °C and 12 °C respectively over to CFRP composites at 0.3 wt% GO. This improvement at GO loading is because of constraint effect of GO sheets on the polymer chain mobility in the composite.

Small, Thin Graphene Oxide Is Anti-inflammatory Activating Nuclear Factor Erythroid 2-Related Factor 2 via Metabolic Reprogramming.

Graphene oxide (GO), an oxidized form of graphene, has potential applications in biomedical research. However, how GO interacts with biological systems, including the innate immune system, is poorly understood. Here, we elucidate the effects of GO sheets on macrophages, identifying distinctive effects of GO on the inflammatory phenotype. Small, thin (s)-GO dose-dependently inhibited release of interleukin (IL)-1β and IL-6 but not tumor necrosis factor α. NLRP3 inflammasome and caspase-1 activation was not affected. The effect of s-GO was pretranslational, as s-GO blocked Toll-like receptor 4-dependent expression of Il1b and Il6 but not Nlrp3 or Tnf mRNA transcripts. s-GO was internalized by immortalized bone-marrow-derived macrophages, suggesting a potential intracellular action. Uptake of polystyrene beads with similar lateral dimensions and surface charge did not phenocopy the effects of s-GO, suggesting that s-GO-mediated inhibition of interleukin expression was not simply due to particle phagocytosis. RNA-Seq analysis established that s-GO had profound effects on the immunometabolism of the cells, leading to activation of the transcription factor nuclear factor erythroid 2-related factor 2, which inhibited expression of cytokines such as IL-1β and IL-6. Thus, we have identified immunometabolic effects of GO that reveal another dimension to its effects on cells. These findings suggest that s-GO may be used as a valuable tool to generate further insights into inflammatory mechanisms and indicate its potential applications in biomedicine.

Inhibition of carbonation attack in cement-based matrix due to adding graphene oxide

Transport properties of cementitious materials are very important as they effectively influence the durability of these materials. Carbonation rate depends on the ease of carbon dioxide (CO2) movement from outer to internal surfaces. In this study, graphene oxide (GO) was incorporated in cement matrix to improve resistance of cementitious mix against carbon dioxide attack. The results showed very low carbonation depth of cementitious mix with GO (GM), only 8% of carbonation depth of the control cement mixture without GO (CM) after 6 months’ carbonation period. The most notable finding was the limited carbonation depth of GM despite the increasing of exposure to CO2. As carbonation depth increased for CM with time, full carbonation occurred after 24 months. However, GM showed no progress in carbonation front. This significant result can be attributed to interlocking influence of the CO2 molecules. Moisture loss monitoring confirms that GO sheets can act as reservoirs for water (H2O) molecules which limit transport of CO2 towards calcium phases of cement hydration. Physical interlocking was examined through molecule dynamic modelling, Monte Carlo atomistic simulation was conducted to evaluate the effects of GO sheets on carbon dioxide adsorption by cement matrix. The results showed that GO sheets reduce van der Waals adsorption energy of CO2 molecules. In addition, concentration of CO2 molecules around GO sheets was higher than the other porous areas which indicates the capability of these sheets for adsorbing of the gaseous molecule because of their high surface area.

Preparation and characterization of graphene oxide reinforced PVA film with boric acid as crosslinker

ABSTRACTPVA films were prepared through aqueous solution method, and boric acid (BA) as well as graphene oxide (GO) was added to improve the mechanical and thermal properties. It was found that 5 wt % BA could increase the tensile strength threefold (from 23.3 to 67.7 MPa), and the incorporation of 0.2 wt % GO would provide additional percentage growth of 30% (from 67.7 to 88.5 MPa). Moreover, an enhancement of thermal stability of PVA film was found when BA or GO filler was added. The reinforcement mechanisms of both BA and GO were investigated, and a competitive phenomenon that the addition of BA would influence the reinforcement effect of GO sheets was found. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42000.

Preparation of multiscale graphene oxide‐carbon fabric and its effect on mechanical properties of hierarchical epoxy resin composite

Graphene oxide (GO) was used to modify the surface of carbon fiber layers through electrophoretic deposition, forming a multiscale reinforcement fabric. By adjusting the experimental parameters, the resulting GO‐carbon fabric showed productive and homogenous distribution of thin and less‐agglomerate GO platelets on carbon fiber surface, remarkably enlarging the surface area and roughness of carbon fabric. To investigate the effect of GO sheets on composites, GO‐carbon fabric and carbon fabric‐reinforced hierarchical epoxy resin composites were respectively manufactured. Mechanical tests demonstrated that after introducing GO flakes on carbon fabric, both the flexural strength and interlaminar shear strength of composite had achieved an increase, especially the interlaminar shear strength rising by 34%. Through fractography analysis, it was found that in pure carbon fabric‐reinforced epoxy composite, the fiber/matrix debonding fracture mechanism predominated, while after the GO decoration on carbon fiber surface, the composite featured a stronger interfacial bonding, leading to the enhancement in mechanical properties of hierarchical epoxy resin composite. POLYM. COMPOS., 37:1515–1522, 2016. © 2014 Society of Plastics Engineers

Preparation and characterization of pH- and temperature-responsive nanocomposite double network hydrogels

A methodology is described for the preparation of pH- and temperature-responsive double network (DN) hydrogels with poly(N-isopropylacrylamide) (PNIPAM) as a tightly crosslinked 1st network, polyacrylic acid (PAA) as a loosely crosslinked 2nd network and graphene oxide (GO) as an additive. GO sheets were first prepared via an oxidation reaction and then dispersed in NIPAM aqueous solution via silanization. Free-radical polymerization of NIPAM was carried out at 20°C in a water bath, and then subjected to UV light, leading to the formation of pH- and temperature-responsive PNIPAM/AA/GO DN hydrogels. The effects of GO sheets and AA contents on various physical properties were investigated. Results show that PNIPAM/AA/GO hydrogels undergo a large volumetric change in response to temperature. It also exhibits significantly fast swelling/deswelling compared with conventional PNIPAM hydrogel. Moreover, the PNIPAM/AA/GO hydrogels have a much better mechanical property than the conventional PNIPAM hydrogels.

Computational Investigation on the Effect of Graphene Oxide Sheets as Nanofillers in Poly(vinyl alcohol)/Graphene Oxide Composites

Poly(vinyl alcohol)/graphene oxide (PVA/GO) composites were studied by molecular mechanics and molecular dynamics methods to analyze the effect of GO sheet addition on PVA material. The properties ...

Insight into the effects of graphene oxide sheets on the conformation and activity of glucose oxidase: towards developing a nanomaterial-based protein conformation assay

Protein conformation associates with particular properties of proteins and relates to protein-mediated diseases. Detailed elucidation of secondary and tertiary formation, stability, and the structural and dynamic properties of proteins has been one of the main topics studied in chemistry and biology. In this work, the conformation changes in glucose oxidase (GOx) induced by the graphene oxide (GO) sheets were studied in detail by various spectroscopic techniques including ultraviolet-visible (UV-vis) absorption, fluorescence, and circular dichroism (CD) spectroscopy. The results indicated that GOx underwent substantial conformation changes after assembling on the surface of GO. The interaction of GOx with GO could induce the exposure of the FAD (flavin adenine dinucleotide) moiety to solvent and transfer tryptophan (Trp) residues to a more hydrophobic environment. The calculation from CD spectra showed that GO could induce the conversion of α-helix to β-sheet structures, even unfolding of the protein. These alterations in the conformation of GOx resulted in a significant decrease in the catalytic activity of the enzyme in glucose oxidation. The possible reasons for these conformation changes in GOx are also discussed. This work not only provides insight into the interaction between atomically flat graphitic structures and various biological systems but also creates a framework for analyzing the biosafety of nanomaterials in terms of the biological behavior of biomacromolecules. The results obtained here can direct the further applications of the nanomaterials.