Coupling Of Graphene Oxide Research Articles

Efficient abatement of organic pollutants by Fe(III)/Fe(II) cycle activating H2O2 with the assistance of sulfurized manganese-supported graphene

This study develops a novel sulfurized manganese-supported graphene material (S-Mn@GO) designed for promoting Fe(III)/Fe(II) cycling in Fenton treatment. The excellent combination of manganese oxides (MnOx) and graphene oxide (GO), along with subsequent, impart S-Mn@GO with excellent electron transfer capabilities. Selecting Bisphenol A (BPA) as the model compound to evaluate the efficacy of the novel material, the findings indicate that the addition of 0.1 g/L of S-Mn@GO in the Fe(II)/H2O2 system enhanced the removal of BPA from 49.7 % to 98.3 % within 30 min. Results show that the abatement of pollutants in the S-Mn@GO/Fe(II)/H2O2 system was significantly influenced by pH, with the maximum removal efficiency (98.3 %) attained at pH 3.5. And the common coexist substances at environmental concentration levels on pollutant abatement was examined and this system showed excellent tolerance to anions. Quenching experiments and EPR analyses demonstrate that the hydroxyl radicals (HO•) dominates the abatement of BPA and the other reactive species (e.g., FeIVO2+) show negligible contribution. Density Functional Theory (DFT) calculations and other evidences indicate that the rapid cycling of iron species was due to the coupling of GO and manganese/sulfur (Mn/S) species. Moreover, the degradation pathway of BPA was analyzed through DFT calculations and LC-MS detection. Further, cycling experiments and long-term experiments confirm the stability of the material. Herein, using GO-based composite as an accelerator of Fe(III)/Fe(II) cycling provides a new strategy to promote the pollutant degradation in the Fenton process.

Electrophoretically Deposited Multiscale Graphene Oxide/Carbon Nanotube Construct Mediated Interfacial Engineering in Carbon Fiber Epoxy Composites.

Fiber-reinforced polymer composites as a structural material have garnered tremendous interest over the past few decades. In particular, carbon fiber-reinforced epoxy (CFRE) laminates have seen extensive use in the aircraft and aerospace industry. The role of the interface between the matrix and fiber is critical and dictates the overall structural properties of the CFRE laminate. Herein, we attempt to use a commercially viable, green, and facile approach, electrophoretic deposition (EPD), to deposit covalently coupled multiscale graphene oxide (GO)/carbon nanotube (CNT) nanoconstructs onto carbon fiber (CF) fabric. The rationale behind using these hybrid conjugates is to exploit the positive synergistic effect of combining two-dimensional (2D) GO and one-dimensional (1D) CNT nanoparticles, which provide strengthening through different mechanisms resulting in a stronger matrix/fiber interface. The modified laminate with just 0.1 wt % GO/CNT content exhibited an improvement in flexural strength (FS) by 24% and interlaminar shear strength (ILSS) by 30% compared to the neat CFRE. Scanning electron microscope (SEM) micrographs confirmed uniform and homogeneous GO and GO/CNT deposition on CF. Raman, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses validate the successful functionalization of CNT and covalent coupling of GO and CNT. Atomic force microscope (AFM) and contact angle analyses indicate improved interaction between the CF and matrix. The deposition of the GO/CNT nanoconstruct on the CF improved the performance of CFREs owing to enhanced wettability, surface free energy, and surface roughness, leading to increased mechanical interlocking between the epoxy and CF at the interface. Dynamic mechanical analysis showed decreased segmental motion of epoxy chains due to improved interfacial adhesion following modification. Interesting observations were made in SEM fractography, which showed considerably different failure mechanisms in the modified CFREs. Electromagnetic interference (EMI) shielding effectiveness of -45 dB was achieved in the case of the GO/CNT-CFRE system. Electrothermal heating and de-icing performance of the modified system were also explored in this study. This versatile approach can open up new avenues for CFRE modification leading to considerably improved performance.

In-situ grown nano silver iodide-graphene oxide-cotton hybrid filter material for dynamic visible light response photocatalysis

A cotton fibers (CFs)-based AgI-decorated graphene oxide (GO) hybrid was designed and fabricated as a glass tube-“just fillable” photocatalytic filtration material for high-efficiency degradation of organic contaminants. It was found that AgI of smaller grain size and β/γ heterolayers can be in-situ grown on GO-modified CFs so that active sites are more exposed and interfacial charge separation becomes more validated. GO coupling plays key roles both in widening optical absorption window to potentiate a green light photoactivity and in promoting charge transfer to improve photocatalysis. The γ-AgI phase is easily reduced after several initial photocatalytic reactions, transforming to a β-AgI-Ag0-GO interface which brings about a subsequent stable photocatalysis. Good photocatalytic degradation efficiency toward toxic and carcinogenic azo dyes was achieved in a dynamic filtration stream under LED excitation. These results indicate feasibility of the simply in-situ grown hybrid as the possible candidate filter material for scalable industrial wastewater treatment applications.

Propagating Surface Plasmon Polaritons Excited at the Graphene Oxide/AgAu Alloy Interface Enhance Nonlinearity

Graphene oxide (GO) contains intrinsic tunable plasmons, leading to highly attractive plasmonic phenomena, besides the GO coupling with metal nanostructures is promising for plasmonics. Herein, a system consisting of an AgAu alloy entangled in a protein network, AgAu@cages, coupled with a GO layer is designed and analyzed. To overcome the challenges posed by the synthesis of the hybrid GO/metal system, the AgAu alloy is grown inside a proteinaceous network. The approach allows control over the alloy size distribution and a close contact with the samples, with positive impact on the plasmonic analysis. The hybrid system reveals a strong dependence on the incident angle and a shorter linewidth as well as a redshift, motivating further investigations to elucidate the phenomenon. Combined experimental and numerical investigations lead to the displaying of the strong coupling that occurs between the plasmons and the molecular cavity of GO, and a coherent amplification of molecular motion. In conclusion, the versatility of GO‐based systems allows the manufacture of plasmonic and optical devices sensitive to a wide range of frequencies, from terahertz to the visible frequencies, with extremely low driving voltage.

A novel approach toward attachment of graphene oxide on copper using electrochemical grafting of an organic interlayer with enhanced corrosion performance

This paper proposes a novel approach for attaching a graphene oxide (GO) film to a Cu substrate using diazonium chemistry. For this purpose, Cu was covalently modified using electrochemical grafting of p-phenylenebis(diazonium) salt (p-PBDS) followed by immersion in a basic GO suspension. The presence of the p-PBDS interlayer facilitated the assembling of GO in a multilayered film instead of a single layer as for the bare Cu substrate. The corrosion performance of the modified Cu was evaluated in 3.5% NaCl aqueous solution using potentiodynamic polarization and electrochemical impedance spectroscopy. The results inferred that the coupling of GO with p-PBDS interlayer protects effectively Cu against corrosion. Due to a low porosity percentage (0.003%), the corrosion current density is decreased by a factor of ∼ 5. It means that the coupling of GO multilayer with p-PBDS considerably prolongs the diffusion pathways for an oxidant toward the substrate. In this way, the polarization resistance of the film was increased by a factor of ∼ 4.5 (to 10.9 kΩ cm2) compared with that of a bare Cu substrate.

Magnetic Graphene Oxide Composite for the Microextraction and Determination of Benzophenones in Water Samples

Magnetite nanoparticles (Fe3O4) functionalized with graphene oxide (GO) have been synthesized through a silanization process of the magnetic nanoparticles with tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane and further coupling of GO. The synthesized nanomaterials have been characterized by several techniques, such as transmission electron microscopy (TEM), and infrared and Raman spectroscopy, which enabled the evaluation of the different steps of the functionalization process. The hybrid nanomaterial has been employed for the extraction of five benzophenones (benzophenone-1, benzophenone-3, 4-hydroxybenzophenone, benzophenone-6 and benzophenone-8) in aqueous samples by dispersive micro-solid phase extraction, combining the magnetic properties of magnetite nanoparticles with the excellent sorption capacity of graphene oxide via hydrophobic interactions with the analytes. The subsequent separation and quantification of the analytes was performed by liquid chromatography with tandem mass spectrometric detection, achieving limits of detection (LODs) in the range 2.5 to 8.2 μg·L−1, with relative standard deviations ranging from 1.3–9.8% and relative recovering in the range 86 to 105%. Positive swimming pool water samples analysed following the developed method revealed the presence of benzophenones in from 14.3 to 39 μg·L−1.

Graphene oxide-chitosan-silver composite coating on Cu-Ni alloy with enhanced anticorrosive and antibacterial properties suitable for marine applications

We present a novel ternary composite coating consisting of graphene oxide (GO)-chitosan -silver on Cu-Ni Alloy with enhanced anticorrosive and antibacterial properties, produced using inexpensive and industrially scalable electrophoretic deposition (EPD) technique. Electrochemical studies showed a corrosion protection efficiency of ∼99 % and a two order decrease in corrosion current density, with an optimum GO concentration of 0.025 wt% (0.5 g/l of chitosan and 1 mM silver nitrate). The results indicate that the GO retards the diffusion of corrosive ions to the substrate by increasing the detour path and minimizes the electron transport between the electrolyte and metal specimen while chitosan prevents the galvanic coupling of GO with metal surface. The amide linkage between the GO and chitosan matrix gave a good mechanical interlocking, with a crack free compact film. AFM images of composite film surface showed a wrinkled morphology, with an enhanced surface roughness of 56 ± 6 nm. Microbiological analysis revealed an excellent antibacterial activity of the ternary composite, which offer promising applications in marine environment.

Nanostructured Active Media for Volatile Organic Compounds Abatement: the Synergy of Graphene Oxide and Semiconductor Coupling

Among the semiconductor-mediated photoprocesses, gas-phase photocatalytic decomposition of volatile organic compounds represents one of the most valid and feasible options for improving air quality. The present work is meant to show the preparation, characterization, and testing of photocatalytic systems for enhancing the performance of TiO2-based nanostructured membranes, namely, the coupling of semiconductors and addition of cocatalysts. In particular, the use of an additional semiconductor (Ag2CO3) and coupling of graphene oxide have been found to be promising for this purpose. All of the photocatalytic media have been tested in a specifically designed photoreactor with respect to the abatement of acetaldehyde and methanol in the gas phase; the obtained results showed complete degradation of 1600 ppm of acetaldehyde and 600 ppm of methanol in less than 15 and 40 min, respectively. The morphology of the nanostructured membranes and affinity of the catalytic system with the polymeric matrix have been fou...

Cement-Based Materials Containing Graphene Oxide and Polyvinyl Alcohol Fiber: Mechanical Properties, Durability, and Microstructure.

The influence of graphene oxide (GO) and polyvinyl alcohol (PVA) fiber on the mechanical performance, durability, and microstructure of cement-based materials was investigated in this study. The results revealed that compared with a control sample, the mechanical strength and durability of cement-based materials were significantly improved by adding PVA fiber and GO. The compressive and flexural strength at 28 d were increased by 30.2% and 39.3%, respectively. The chloride migration coefficient at 28 d was reduced from 7.3 × 10−12 m2/s to 4.3 × 10−12 m2/s. Under a sulfate corrosion condition for 135 d, the compressive and flexural strength still showed a 13.9% and 12.3% gain, respectively. Furthermore, from the Mercury Intrusion Porosimetry (MIP) test, with the incorporation of GO, the cumulative porosity decreased from more than 0.13 cm3/g to about 0.03 cm3/g, and the proportion of large capillary pores reduced from around 80% to 30% and that of medium capillary pores increased from approximately 20% to 50%. Scanning electron microscope (SEM) images showed a significant amount of hydration products adhering to the surface of PVA fiber in the GO and PVA fiber modified sample. The addition of GO coupling with PVA fiber in cement-based materials could promote hydration of cement, refine the microstructure, and significantly improve mechanical strength and durability.

Aniline oligomer-modified graphene for enhanced electrochemical performances

The surface of graphene (Gr) was covalently attached by an aniline oligomer, from the coupling of graphene oxide with aniline tetramer, followed by reduction process. After linked by tetramer aniline, the graphene materials showed remarkably enhanced electrochemical performances. The conductivity of the graphene was increased from 5.8 S cm−1 to 41.7 S cm‒1, under the strong doping effect between Gr and tetramer aniline by means of the π‒π interactions, which was analyzed by FT‒IR, UV–vis and XPS spectra. In addition, the aniline oligomer attached to reduced graphene oxide (AOAG) showed a remarkable energy-storage behavior due to the synergistic effect. The capacitance of AOAGs can be 370 F g−1, while it is 114 F g−1 and 129 F g−1 for graphene oxide and tetramer aniline respectively. Because the covalent bonding between graphene and aniline oligomer can effectively combine the excellent mechanical strength of graphene and the large faradic pseudocapacitance of aniline oligomer, the AOAGs showed quite high charge-discharge cycle stability besides remarkable capacitance. In addition, the ease of electron motion mediated by the covalent bonding in AOAGs supports the sample significant electrochemical catalysis towards nifedipine. Compared with graphene and tetramer aniline, the oxidative current of nifedipine on AOAG showed five-fold increase.

Abstract 24: Graphene Oxide Containing Thermosensitive Hydrogel Improves the Survival of Transplanted Stem Cells in Ischemic Myocardium

Bone marrow derived mesenchymal stem cell (MSC) therapy has the potential to preserve cardiac function and prevent heart failure following a myocardial infarction (MI). However, in our recent studies, long term survival of transplanted stem cells was not detected, which was associated with deterioration of cardiac function. Therefore, strategies to enhance survival of transplanted cells would preserve the benefits of MSCs therapy for heart repair. Recently, graphene oxide (GO) nanosheets are being widely investigated for their ability to promote adherence and homing of transplanted MSCs to the extra cellular matrix in the heart. However, the presence of reactive oxygen functional groups (-OH, -COOH) in the structure of GO increases oxidative stress and activate apoptotic pathways in MSCs, which impairs the benefits of GO based biomaterials. Therefore, to nullify these side effects of GO, we synthesized a novel thermosensitive hydrogel by conjugating GO with chitosan (CS). Our Fourier transformed infrared spectrum (FTIR) analysis revealed an interaction between the oxygen functional groups of GO and amino (-NH2) groups of chitosan. Our data also demonstrate that CS masked the reactive functional groups of GO and prevented GO mediated ROS induction. This novel chitosan-graphene oxide (CS-GO) composite exhibited optimal porosity for cell conjugation and retention. Furthermore, this novel biomaterial was cyto-compatible as it exerted negligible toxicity to encapsulated MSCs. Upon exposure to hypoxic/ischemic environment, we observed a significant increase in apoptosis in MSCs as evidenced by an increase in the Bax/Bcl-xl ratio and caspase 3 activation. However, conjugation of MSCs to CS-GO polymer prevented hypoxia induced apoptosis. Therefore, coupling of GO with chitosan prevented GO mediated oxidative stress and downregulated hypoxia induced apoptosis of MSCs. Therefore, the outcome of this study will provide a novel delivery system for MSCs to the heart and improve their long term survival in the infarcted heart.

In-situ synthesis of graphene oxide/BiOCl heterostructured nanofibers for visible-light photocatalytic investigation

Graphene oxide/BiOCl/polyacrylonitrile (PAN) nanofibers were prepared through a two-step synthesis method and the chemical, structural, morphological, and photocatalytic properties were characterized. Coupling of graphene oxide (GO) and the BiOCl fibers enabled achievement of better photocatalytic performance relative to the pure BiOCl fibers in the degradation of Rhodamine B (RhB) under visible light irradiation. The photocatalytic activity of the graphene oxide/BiOCl/PAN nanofibers was up to 3 times higher than that of the pure BiOCl fibers. Analysis of the mechanism demonstrated that the holes (h+) and electrons (e−) played critical roles in the photocatalytic degradation. Moreover, as-prepared samples were stable under consecutive cycles.

Preparation and characterization of graphene oxide/Ag2CO3 photocatalyst and its visible light photocatalytic activity

Graphene oxide (GO) was firstly fabricated from graphite powder by Hummers method. Then a series of GO/Ag2CO3 composite photocatalysts (0.1% GO/Ag2CO3, 0.5%GO/Ag2CO3, 1%GO/Ag2CO3, 4%GO/Ag2CO3) were synthesized by a facile liquid deposition process. The produced products were characterized by powder X-ray diffraction (XRD), N2 physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscope (FT-IR), Raman spectra and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activity of the samples was evaluated by photocatalytic degradation of methyl orange (MO) under visible light irradiation. The influence of GO concentration on the photocatalytic activity of GO/Ag2CO3 was investigated. The results showed that GO can be easily dispersed into Ag2CO3, producing well contacted GO/Ag2CO3 composite. Coupling of trace GO largely enhanced the visible light absorption. Moreover, GO could suppress the growth of Ag2CO3 grain crystals. With optimum GO content (0.5%), the degradation rate of MO is 85.37% after 120min light irradiation, which Exhibits 1.53 times activity of that of pure Ag2CO3. More importantly, a large improvement in stability was obtained over the composite. The increase in photocatalytic activity and stability could be mainly attributed to the coupling of GO which increased the surface area and suppressed the recombination rate of e−/h+ pairs.

Coupling of graphene oxide into titania for purification of gaseous toluene under different operational conditions

Graphene oxide (GO)–titania (TiO2) composite was synthesized using a chemical mixing process and its photocatalytic activity for the degradation of a toxic organic vapor (toluene) under different operational conditions was examined. The as-prepared GO–TiO2 and undoped TiO2 photocatalysts were characterized using SEM, XRD, and UV–VIS–NIR spectra. Moreover, the photocatalytic degradation efficiency of the GO–TiO2 composite was much higher than that of the P25 TiO2, with an average efficiency of the GO–TiO2 composite of 84% and an average efficiency of the TiO2 powder of just 13%. As the air flow rate increased from 1 to 4 L min−1, the average degradation efficiencies of toluene decreased from 86 to 32%. In addition, as the initial concentration increased from 0.1 to 1.0 ppm, the average degradation efficiencies of toluene decreased from 86 to 8%. Overall, the GO–TiO2 composite could be applied effectively for purification of gaseous toluene under optimal operational conditions.

Nuclease Activity and Cytotoxicity Enhancement of the DNA Intercalators via Graphene Oxide

The enhancement of DNA affinity of small molecules usually ensures their high nuclease activities, and may also open a new scope of their applications in biology and medicine. In this work, we demonstrate that the nuclease activity and cytotoxicity of the small DNA intercalators can be dramatically enhanced by single atomic-layered graphene oxide (GO) sheets. Through π–π stacking interaction mainly between GO and the aromatic ligands of intercalators, the conjugates of GO and a small intercalator could be formed. Because of the large planar structure of the GO sheets, the coupling of GO with the small intercalators increased their affinity to DNA. Owing to the formation of conjugates with GO, the binding site of small intercalators to DNA was also changed from a minor groove to a major groove. Notably, GO and small intercalator conjugates exhibited higher cytotoxicity than that of the small intercalator alone. The results open up potential applications of GO for new chemotherapeutic agents that work through DNA intercalation.

Effect of graphene oxide nanomaterial in electroclinic liquid crystals

The collective dielectric relaxation studies have been carried out on the electroclinic liquid crystals (ELCs) doped with 0.1 to 0.2 wt % of graphene oxide (GO) in the frequency range of 20 Hz to 1 MHz. The GO favors for a good quality vertical alignment without any surface treatment of the substrates. The coupling of GO with indium tin oxide (ITO) substrate and ELC materials affects the molecular ordering and supports the ELC molecules to be aligned along the GO attached to the ITO surface in vertical direction. The vertical alignment can be changed to homogeneous by applying a high bias field to the sample and such converted homogeneous cell shows an additional dielectric relaxation peak in the low frequency side of Goldstone mode in SmC∗ phase due to presence of GO whereas in the pure material no such peak was observed. The frequency separation of both peaks (Goldstone mode and an additional peak) increases with temperature and low frequency peak vanishes near transition temperature.