Multilayer Graphene Oxide Research Articles

Graphene oxide: structure and temperature dependent magnetic characterization

In this report, the temperature dependent magnetic properties of graphene oxide (GO) have been studied. The graphene oxide is prepared by modified Hummer’s method. The formation and structural analysis are carried out using XRD and Raman spectroscopy. Fourier transform infrared spectroscopy (FT-IR) is used to detect the presence of various functional groups. The magnetization curves as a function of the applied magnetic field at temperatures 10, 50, 150, 250 and 350 K has been accomplished. We have observed that ferrimagnetism, paramagnetism in lower temperatures along with ferromagnetism and diamagnetism in higher temperatures exist in the multilayer graphene oxide. The transition of magnetic states of GO with changing temperature is discussed based on average anisotropy energy and coupling interactions. The wrinkled structure and the defects due to the surface functional groups play a significant role in shaping magnetism in GO. The ZFC-FC curves are also analyzed to explore the system further.

Dependence of Structure of Multilayer Graphene Oxide on Degree of Graphitization of Initial Graphite

It was shown that the structure of multilayer graphene oxide (GrO) synthesized by Tour method depends substantially on the degree of graphitization (g) and on the particle size of initial graphite. The obtained GrO was characterized by Raman and infrared spectroscopy, X-ray diffraction, and elemental analysis. The GrO contains carbonyl, carboxyl, and hydroxyl groups as well as C–O–C fragments. The dependence of the O/C molar ratio of GrO on the degree of graphitization of the parent graphite is nonmonotonic with a maximum at g ≈ 90%.

Water and salt dynamics in multilayer graphene oxide (GO) membrane: Role of lateral sheet dimensions

Dependence of salt rejection efficiency and water permeability of layered graphene oxide (GO) membranes on the lateral dimension of constituting sheets are studied through equilibrium molecular dynamic (MD) simulation and experiments. This study suggests that with increasing sheets dimension permeability of the GO membranes decreases but its selectivity increases. The velocity and permeation time of the water molecules while permeating through the membrane are influenced to a greater extent by the pore offset distance (W) of the membranes. More over the larger pore offset distance increases the path length that the water molecules and ions have to traverse for permeating through the layered GO membranes. Based on the simple technique discussed in this work, one can construct GO membranes of required water permeability and salt rejection without the application of any foreign nanomaterials with the GO membrane, which retains the inherent selectivity of the GO membranes. This work also provides the effect of internal structure of GO membrane on the atomistic level details of the solvation shell of ions while they are permeating through the membrane.

Swelling of Thin Graphene Oxide Films Studied by in Situ Neutron Reflectivity

Permeation of multilayered graphene oxide (GO) membranes by polar solvents is known to correlate with their swelling properties and amount of sorbed solvent. However, quantitative estimation of sorption using standard (e.g., gravimetric) methods is technically challenging for few nanometers thick GO membranes/films exposed to solvent vapors. Neutron reflectivity (NR) was used here to evaluate the amount of solvents intercalated into the film which consists of only ∼31.5 layers of GO. Analysis of NR data recorded from the GO film exposed to vapors of polar solvents provides information about change of film thickness due to swelling, amount of intercalated solvent, and selectivity in sorption of solvents from binary mixtures. A quantitative study of GO film sorption was performed for D2O, d-methanol, ethanol, dimethyl sulfoxide (DMSO), acetonitrile, dimethylformamide (DMF), and acetone. Using isotopic contrast, we estimated selectivity in sorption of ethanol/d-methanol mixtures by the GO film. Estimation of...

Unravelling the hydration mechanism in a multi-layered graphene oxide paper by in-situ X-ray scattering

Hydration of a multi-layered graphene oxide (GO) paper in water vapor atmosphere was studied by in-situ X-ray scattering over a wide range of relative humidity (RH). The intercalation of water molecules physically adsorbed between GO layers induces the expansion of the interlayer distance. Two regimes of adsorption are clearly evidenced according to the variation of the interlayer distance as a function of the relative humidity. The expansion of the interlayer distance is limited to ∼1 Å for RH ranging from 6 to 53%, whereas it is ∼3.5 Å for RH 75–100%. The hydration mechanism corresponds to the progressive adsorption of water molecules onto hydrophilic sites at the surface of GO layers in the low-RH regime, then an additional water monolayer is formed in the high-RH regime.

Reduction of arsenic toxicity in two rice cultivar seedlings by different nanoparticles

In this study, we investigated arsenic uptake and enzymatic activities in rice seedlings after the addition of nanoparticles. Hydroponic experiments were conducted to investigate the effects of different nanomaterials (high-quality graphene oxide, multilayer graphene oxide, 20 nm hydroxyapatite (HA20), 40 nm hydroxyapatite (HA40), nano-Fe3O4 (nFe3O4) and nano-zerovalent iron [nFe]) on the biomass, arsenic uptake, and enzyme activities in seedlings of the rice cultivars T705 and X24. Compared with the control, the addition of different nanomaterials increased seedling growth, with X24 rice growing better than T705 rice. Nanomaterials effectively reduced arsenic uptake in T705 rice seedlings under low and high arsenic concentrations; however, they were only effective at lower arsenic concentrations in X24 seedlings. nFe3O4 and nFe performed better than other nanomaterials in preventing arsenic from being transported to the aboveground parts of the rice seedlings. Different nanomaterials obviously influenced enzyme activities in the T705 seedlings at low arsenic concentrations (≤ 0.8 mg L−1). High-quality and multilayer graphene oxide decreased enzyme activities in the aboveground parts of the T705 seedlings, whereas, HA20 and HA40 increased the enzyme activities. nFe3O4 and nFe also reduced the effect of antioxidants in the aboveground parts of the T705 seedlings. Nanomaterials effectively reduced the arsenic uptake of T705 and X24 rice seedlings at low arsenic concentrations.

Fire retardancy of graphene oxide/wood composite (GOW) prepared by a vacuum-pulse dipping technique

AbstractGraphene oxide/wood (GOW) composite was fabricated by a vacuum-pulse dipping technique, and the resulting composites were characterized by scanning electron microscope (SEM), Raman spectroscopy and thermogravimetric analysis (TGA). As demonstrated, the wood matrix became filled by the dense multilayer graphene oxide (GO) membrane structure, which was formed by the layer-by-layer self-assembly of GO nano-sheets. X-ray diffraction (XRD) revealed that the amorphous GO decreased the composite’s relative degree of crystallinity. Additionally, the filled GO generated improvement in the thermal stability of GOW composites in comparison with that of the natural wood (NW).

Effect of nanomaterials on arsenic volatilization and extraction from flooded soils

Herein, we utilize sequential extraction and high-throughput sequencing to investigate the effects of nanomaterial additives on As volatilization from flooded soils. We reveal that maximum volatilization is achieved in the fourth week and is followed by stabilization. The extent of volatilization decreased in the order of control > nano-zerovalent iron >40-nm hydroxyapatite > nano-Fe3O4 > 20-nm hydroxyapatite > multilayer graphene oxide > high-quality graphene oxide. The most abundant forms of As in soil corresponded to As-Fe and Al oxides. In soil with low levels of As pollution, the contents of these species increased after treatment with graphene oxides but decreased after treatment with other nanomaterials, with an opposite trend observed for soil with high levels of As pollution. The addition of nanomaterials influenced the activity of soil enzymes, e.g., hydroxyapatites affected the activities of urease and alkaline phosphatase, whereas graphene oxides significantly impacted that of peroxidase (P < 0.05). The addition of nanomaterials (which can potentially inhibit microbial growth) affected As levels by influencing the amount of As volatilized from polluted soil. Moreover, As volatilization, enzyme activity, and As speciation were observed to be mutually correlated (e.g., volatilization was negatively correlated to peroxidase activity and the contents of amorphous crystalline hydrous oxides of As-Fe and Al).

Polyelectrolyte–Graphene Oxide Multilayer Composites for Array of Microchambers which are Mechanically Robust and Responsive to NIR Light

Development of composite polymer/graphene oxide (GO) materials attracts significant attention due to their unique properties. In this work, highly ordered arrays of hollow microchambers made of composite polyelectrolyte/GO multilayers (PEGOMs) are successfully fabricated via layer-by-layer assembly on sacrificial or sustainable templates having imprinted patterns of microwells on their surface. Mechanical and optical properties of PEGOMs are studied by nanoindentation and near-infrared (NIR) absorption spectroscopy. Incorporation of three GO layers in between the polyelectrolyte multilayer stacks increases Young's modulus and critical stress of the microchambers by a factor of 5.6 and 2.6, respectively. Optical density of this PEGOM film is found to decrease gradually from 0.14 at λ = 800 nm to 0.06 at λ = 1500 nm. Remote opening of PEGOM microchambers with NIR laser beam is also demonstrated. One of the possible applications of the developed structures includes micropackaging and delivery systems in biological tissues with remote triggering.

Preparation and Performance of Ecofriendly Epoxy/Multilayer Graphene Oxide Composites with Flame-Retardant Functional Groups

This study aimed to prepare ecofriendly flame retardants. Using the –OH and –COOH functional groups of multilayer graphene oxide (GO) for the hydrolytic condensation of tetraethoxysilane (TEOS), TEOS was grafted onto GO to form Si-GO. Subsequently, p-aminophenol (AP) was grafted onto Si-GO to produce Si-GA, forming composite materials with epoxy (EP). The structures and properties of the composite materials were examined with Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and the limiting oxygen index (LOI). In terms of structure, FTIR observed two characteristic peaks of Si-GO, namely Si–O–C and Si-O-Si, indicating that TEOS was successfully grafted onto GO. TGA was used to determine the thermal stability of the epoxy/Si-GA composites; with the increase in Si-GA, the char yield of the materials increased from 15.6 wt % (pure epoxy) to 25 wt % (epoxy/10 wt % Si-GA), indicating that Si-GA effectively enhanced the thermal stability of the epoxy matrix. Lastly, the flame retardant tests determined that the LOI value rose from 19% (pure epoxy) to 26% (epoxy/10 wt % Si-GA), proving that graphene with modified silicon can be used to enhance the flame retardancy of epoxy.

Graphene oxide/Al2O3 membrane with efficient salt rejection for water purification

Abstract To obtain efficient salt rejection in saline solution treatment, an asymmetric graphene oxide/Al2O3 membrane was prepared by a spin-coating process. According to microstructure measurement, the membrane has a multilayer structure and graphene oxide has been tightly coated on the surface of the Al2O3 membrane interlayer homogeneously. During the treatment of different aqueous salt solutions, the permeation flux and salt rejection of the membrane were investigated. The results show the permeation flux of the membrane is about 1.254 L·m−2·h−1·bar−1 and the salt rejection of the membrane reaches 28.66%, 39.24% and 43.52% for 0.01 mol·L−1 NaCl, Cu(NO3)2 and MgSO4, respectively. The mechanism of the salt rejection of the membrane has been explained in this work. All these results indicate the GO/Al2O3 membrane shows great potential in the desalination field.

3D silver nanoparticles with multilayer graphene oxide as a spacer for surface enhanced Raman spectroscopy analysis

We report a three-dimensional (3D) SERS substrate with different numbers of silver nanoparticle (Ag NP) layers using multilayer graphene oxide (GO) as a spacer. The SERS performance of the 3D nanostructure was investigated and it was found that the SERS effect increased as the number of Ag NP layers increased, and showed almost no change for more than four layers. We found that the SERS performance of the 3D nanostructures can be mainly attributed to the topmost hot spots which are closely related to the Ag NP layers in the 3D nanostructure. Furthermore, we explored 3D nanostructures with different Ag NP layers using the finite difference time domain method (FDTD). The 3D SERS substrates also exhibit excellent detection capability. The limit of detection (LOD) was calculated down to 10-15 M for R6G and 10-12 M for CV. In addition, the reproducibility of the 3D SERS substrate was attributed obviously to the increasing number of Ag NP layers. Based on these promising results, the highly sensitive detection of molecules such as malachite green was demonstrated for food safety inspection.

Multi-layer graphene oxide synergistically modified by two coupling agents and its application in reinforced natural rubber composites

Multi-layer graphene oxide (MGO) was co-modified with bis-(P,P-bis-ethylhexyldiphosphato)-ethanediolato titanate triethanolamino chelate solution (NDZ-311w) and bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si-69). Then the co-modified MGO was incorporated into natural rubber (NR) by conventional two-roll mill mixing to prepare MGO/NR composites. The large macromolecule of NDZ-311w is able to efficiently intercalate the layers and increase the interlamellar space of MGO, subsequently resulting in the exfoliation of MGO into thinner sheets with better dispersity. Moreover, the oxygen-containing polar groups of MGO can be largely consumed by Si-69, which enhances the interfacial interaction between MGO and the NR matrix and improves the mechanical properties of the MGO/NR composites. Compared to pure natural rubber, the tensile strength, the stress at 300% strain, and tear resistance of co-modified MGO/NR composites are increased by 26%, 98% and 15%, respectively.

Laser-driven propulsion of multilayer graphene oxide flakes

The laser-driven propulsion of multilayer graphene oxide flakes has been achieved by femtosecond laser irradiation.

Efficient Flame Detection and Early Warning Sensors on Combustible Materials Using Hierarchical Graphene Oxide/Silicone Coatings.

Design and development of smart sensors for rapid flame detection in postcombustion and early fire warning in precombustion situations are critically needed to improve the fire safety of combustible materials in many applications. Herein, we describe the fabrication of hierarchical coatings created by assembling a multilayered graphene oxide (GO)/silicone structure onto different combustible substrate materials. The resulting coatings exhibit distinct temperature-responsive electrical resistance change as efficient early warning sensors for detecting abnormal high environmental temperature, thus enabling fire prevention below the ignition temperature of combustible materials. After encountering a flame attack, we demonstrate extremely rapid flame detection response in 2-3 s and excellent flame self-extinguishing retardancy for the multilayered GO/silicone structure that can be synergistically transformed to a multiscale graphene/nanosilica protection layer. The hierarchical coatings developed are promising for fire prevention and protection applications in various critical fire risk and related perilous circumstances.

Graphene Inks as Versatile Templates for Printing Tiled Metal Oxide Crystalline Films.

There is great interest in exploiting van der Waals gaps in layered materials as confinement reaction vessels to template the synthesis of new nanosheet structures. The gallery spaces in multilayer graphene oxide, for example, can intercalate hydrated metal ions that assemble into metal oxide films during thermal oxidation of the sacrificial graphene template. This approach offers limited control of structure, however, and does not typically lead to 2D atomic-scale growth of anisotropic platelet crystals, but rather arrays of simple particles directionally sintered into porous sheets. Here, a new graphene-directed assembly route is demonstrated that yields fully dense, space-filling films of tiled metal oxide platelet crystals with tessellated structures. The method relies on colloidal engineering to produce a printable "metallized graphene ink" with accurate control of metal loading, grain size/porosity, composition, and micro/nanomorphologies, and is capable of achieving higher metal-carbon ratio than is possible by intercalation methods. These tiled structures are sufficiently robust to create free standing papers, complex microtextured films, 3D shapes, and metal oxide replicas of natural biotextures.

Insights on the mechanism of water-alcohol separation in multilayer graphene oxide membranes: Entropic versus enthalpic factors

Experimental evidence has shown that graphene oxide (GO) can be impermeable to liquids, vapors and gases, while it allows a fast permeation of water molecules. Theoretical studies to understand the filtration mechanisms come mostly from water desalination, while very few works have been dedicated to alcohol dehydration. In this work, we have investigated the molecular level mechanism underlying the alcohol/water separation inside GO membranes. A series of Molecular Dynamics and Grand-Canonical Monte Carlo simulations were carried out to probe the ethanol/water and methanol/water separation through GO membranes composed of multiple layered graphene-based films with different interlayer distance values and number of oxygen-containing functional groups. Our results show that the size exclusion and membrane affinities are not sufficient to explain the selectivity. Besides that, the favorable water molecular arrangement inside GO 2D-channels forming a robust H-bond network and the fast water permeation are crucial for an effective separation mechanism. In other words, the separation phenomenon is not only governed by membrane affinities (enthalpic mechanisms) but mainly by the geometry and size factors (entropic mechanisms). Our findings are consistent with the available experimental data and contribute to clarify important aspects of the separation behavior of confined alcohol/water in GO membranes.

Mechanical behavior of multilayer GO carbon-fiber cement composites

Graphene oxide (GO) has attracted much attention due to its dispersibility in water, high aspect ratio and excellent mechanical properties. In this study, the mechanical behaviors of multilayer GO carbon-fiber cement composites were experimentally investigated. The experiments of compressive strength and the flexural tensile strength of the composites were performed. For the purpose comparison and explanation, the mechanical properties of GO cement and carbon-fiber cement were also investigated. The results show that the compressive strength of the GO carbon-fiber cement composite with adding 0.06% GO and 1% carbon-fiber was increased by 23.89%, whereas the increment of the flexural tensile strength of the composite was increased by 138.44%. The results were explained with respect to the mechanical behavior of GO cement specimens with incorporating different percentages of GO, and the microstructures of the composites observed by Scanning Electron Microscopy (SEM). The present study not only advanced our understanding of mechanical behaviors of multilayer carbon-fiber cements, but the results can be utilized for civil and transportation structures to improve the performance of the structures.

Studying the fetal bovine serum protein corona associated with single and multilayer graphene oxide nanomaterials

Studying the fetal bovine serum protein corona associated with single and multilayer graphene oxide nanomaterials

Volumetric Capacitance of In-Plane- and Out-of-Plane-Structured Multilayer Graphene Supercapacitors

A graphene electrode with a novel in-plane structure is proposed and successfully adopted for use in supercapacitor applications. The in-plane structure allows electrolyte ions to interact with all the graphene layers in the electrode, thereby maximizing the utilization of the electrochemical surface area. This novel structure contrasts with the conventional out-of-plane stacked structure of such supercapacitors. We herein compare the volumetric capacitances of in-plane- and out-of-planestructured devices with reduced multi-layer graphene oxide films as electrodes. The in-plane-structured device exhibits a capacitance 2.5 times higher (i.e., 327 F cm−3) than that of the out-of-plane-structured device, in addition to an energy density of 11.4 mWh cm−3, which is higher than that of lithium-ion thin-film batteries and is the highest among in-plane-structured ultra-small graphene-based supercapacitors reported to date. Therefore, this study demonstrates the potential of inplane- structured supercapacitors with high volumetric performances as ultra-small energy storage devices. Keywords: In-plane, Electrochemical capacitor, Solid electrolyte, Supercapacitor, Graphene