Iron nanoparticle-containing graphene oxide: synthesis and membrane properties

Three-dimensional (3D) graphene networks are performance boosters for functional nanostructures in energy-related fields. Although tremendous intriguing nanostructures-decorated 3D graphene network...

A study on corrosion behavior of graphene oxide coating produced on stainless steel by electrophoretic deposition

Chemically engineered polyamide 6 (PA6)/graphene oxide (GO) nanocomposites were produced via the functionalization of GO with an amide (CONH2) functional group, in order to produce amide-GO with improved interfacial bonding and dispersion in the host polymer matrix. In situ polymerization of ε-caprolactam was carried out in the presence of amide-GO to create PA6/amide-GO nanocomposites. The nanomaterial (pre- and post-polymerization) and the composites were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and tensile testing. The single-layer nature of GO was attested by TEM. FTIR, XPS, XRD and thermal analysis techniques confirmed the successful amide modification of GO. The expected attachment of PA6 to the surface of GO is demonstrated, along with the reduction of GO during polymerization. Some reduction of GO during the chemical functionalization process was also observed. The thermal stability of the nanocomposites was confirmed, while promotion of α-phase crystallite formation and a molecular weight change of attached PA6 are observed. A linear improvement in stiffness and yield strength was observed as functionalized GO content increased from 0.1 wt% to 0.75 wt%. A levelling off of mechanical properties ensued once the GO content reached 1 wt%, and a decrease was seen at 2 wt%.

The reduction of graphene oxide (GO) thin films deposited on substrates is crucial to achieve a technologically useful supported graphene material. However, the well-known thermal reduction process cannot be used with thermally unstable substrates (e.g., plastics and paper), in addition photo-reduction methods are expensive and only capable of reducing the external surface. Therefore, solid-state chemical reduction techniques could become a convenient approach for the full thickness reduction of the GO layers supported on thermally unstable substrates. Here, a novel experimental procedure for quantitative reduction of GO films on paper by a green and low-cost chemical reductant (L-ascorbic acid, L-aa) is proposed. The possibility to have an effective mass transport of the reductant inside the swelled GO solid (gel-phase) deposit was ensured by spraying a reductant solution on the GO film and allowing it to reflux in a closed microenvironment at 50 °C. The GO conversion degree to reduced graphene oxide (r-GO) was evaluated by Fourier transform infrared spectroscopy (FT-IR) in attenuated total reflectance (ATR) mode and X-ray Diffraction (XRD). In addition, morphology and wettability of GO deposits, before and after reduction, were confirmed by digital USB microscopy, scanning electron microscopy (SEM), and contact angle measurements. According to these structural characterizations, the proposed method allows a bulky reduction of the coating but leaves to a GO layer at the interface, that is essential for a good coating-substrate adhesion and this special characteristic is useful for industrial exploitation of the material.

This study is carried out with the goal of improving the corrosion resistance of aluminum in a saline solution through coating with graphene oxide (GO) and reduced GO (ERGO). The GO layer was applied on an aluminum substrate and then electrochemically reduced by cyclic voltammetry in 0.01 M K2HPO4 solution to form a reduced graphene oxide layer. The surface morphology, structure, and crystallinity of the coated materials were characterized using scanning electron microscope (SEM), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy techniques. To study the electrochemical corrosion behavior of the coated aluminum substrate, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were performed in 3.5 wt% NaCl solution. The results showed that both GO and ERGO films uniformly covered the surface of the aluminum substrates with layered structures. A noteworthy elimination of oxygen-containing functional groups (OFGs) occurred upon the electrochemical reduction of the film, yielding a highly-reduced ERGO layer on the substrate. Furthermore, the electrochemical reduction process significantly increased the thickness of the GO coating. The electrochemical test results exhibited that both GO, and ERGO layers improved the corrosion resistance of the bare aluminum substrate. However, electrochemical reduction of the GO layer had adverse effects on the corrosion barrier properties of the GO coating.

Graphene oxide (GO) has the ability to absorb certain compounds, and it can be modified with functional groups for different purposes; for instance, iron oxide (IO) nanoparticles can be used to concentrate analyte by a magnet. Recently, many kinds of GO have been developed, such as single-layer GO (SLGO), two-to-four layers of GO (i.e., few-layer GO, FLGO2-4), and four-to-eight layers of GO (i.e., multi-layer GO, MLGO4-8). However, the abilities of these layered GO coated with IO nanoparticles have not been investigated. In this study, we conducted a novel analysis of glimepiride by using layered GO-coated magnetic clusters of IO nanoparticles that were synthesized through a simple and facile emulsion-solvent evaporation method. The methodology is based on (i) enrichment of glimepiride using the layered GO-coated magnetic clusters of IO nanoparticles (IO@SLGO, IO@FLGO2-4, and IO@MLGO4-8), and (ii) rapid determination using magnetic cluster-based surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOFMS). We found that IO@MLGO4-8, the magnetic cluster with the greatest number of GO layers, had the best limit of detection (28.6pmol/μL for glimepiride). The number of GO layers played a significant role in increasing the sensitivity of the SALDI-MS, indicating that the size of GO in the magnetic clusters contributed to the desorption/ionization efficiency. To the best of our knowledge, this is the first study to enrich glimepiride using magnetic clusters of different GO types and to show that the glimepiride in HLB purified urine adsorbed by magnetic clusters can be analyzed by SALDI-TOFMS.

Graphene oxide (GO) and reduced graphene oxide (RGO) presents great potential applications in various fields due to their extraordinary properties. However, to synthesize GO and RGO environmental friendly and inexpensive still is a big challenge for large scale production. Although chemical synthesis method is the easiest, low cost, and large amount production compares to the other methods but there are some disadvantages using chemical such as toxicity, hazardous and corrosive which are harmful to the environment and human health. Therefore, it is recommended to using green reduction agent to replace the chemical agent. This paper presents a summary and discussion of the green reduction of GO to RGO using Oolong Tea extract. It also reviews the characterization of GO and RGO using of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV-Vis).

In this thesis, graphite oxide was synthesized by modified Hummers method and then reduced and surface modified with L-arginine via the microwave method to yield the well-dispersed reduced graphene oxide at first. Secondly, the NaYF4:Yb, Er nanoparticles with near infrared (NIR) upconversion fluorescence imaging property were synthesized, surface coated with silica nanoshells, and then further modified with 3-(triethoxysilyl)propylsuccinic anhydride to generate carboxylic groups on the surface of silica nanoshells. Finally, they were covalently bound on the arginine-modified reduced graphene oxide to form the nanocomposite combining the functions of NIR upconversion fluorescence imaging and photothermal therapy. By transmission electron microscopy (TEM), atomic force microscope (AFM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), Raman spectra, electron spectroscopy for chemical analysis (ESCA), UV/VIS/NIR spectrophometer, and fluorescence spectrophotometer, the products’ morphologies, sizes, crystalline structures, and optical properties were characterized. It was found that the formation of reduced graphene oxide, NaYF4:Yb,Er nanoparticles, and their nanocomposite has been achieved successfully. In addition, by using a HeLa cancer cell line, it was demonstrated this nanocomposite indeed possessed both the functions of NIR photothermal therapy and fluorescence imaging.

: Novel nanostructured iron oxide-reduced graphene oxide composites were synthesized by a facile one-step hydrothermal method in an ethylene glycol (EG)–water system. Different phases of iron oxides were detected by adjusting fabrication parameters including the EG/H2O ratio, base content and iron ions concentration. Electrochemical propertyof fabricated nanocomposites as anode material was examined in a coin–type cell. The high–rate capacity and cycling stability were found, which is attributed to the improved lithium storage capability due to the application of graphene sheet acting as conductive materials for iron oxide nanoparticles. This study provides a favorable approach for exploring the nanocomposites of metal oxide-graphene anode for lithium ion battery applications. Introduction: Currently,α–Fe2O3 has been considered as a promising candidate for lithium ion batteries due to its much higher theoretical capacity of 1350 mAhg‾1 than that of commercial graphite anode materials and its environmental friendly fabrication methods from low–cost resources [1]. In particular, the use of nanomaterials is an effective path to improve rate capabilities of solid state electrodes in batteries attributed to their relatively small diffusion lengths. Furthermore,graphene, with an excellent electronic conductivity, a high theoretical surface area of 2630 m2/g and superior mechanical properties, is a significantly promising component for high performance electrode materials [2]. In this study, an anode material of iron oxide nanoparticles (mainly α–Fe2O3)–reduced graphene oxide for lithium ion battery has been synthesized and reported. Experimental: FeCl3·6H2O (1.08 g) and NaOH (0.8 g) was dissolved in EG (30 ml) by ultrasonication for 1 hour.Then 10 ml deionized water and 15 mg graphene oxide was added to the mixture under stirring to get a homogeneous solution. The solution was transferred into a 50 ml teflon–lined stainless steel autoclave, sealed and heated at 200oC for 10 hours. The product was collected by centrifuging and washed by ethanol and deionized water alternatively for several times, which was followed by drying at 80oC. Morphologies and phases of synthesized nanocomposites were characterized by scanning electron microscopy (SEM), Raman scattering spectroscopy, X-ray diffraction (XRD), high resolution transmission electron microscopy(TEM). Results: Typical XRD pattern of the products was illustrated in Fig.1 that demonstrated the co–existence of α–Fe2O3 and Fe3O4. Diffraction peaks can be indexed to either the rhombohedral phase of α-Fe2O3 (JCPDS NO.84-0307) or the cubic phase of Fe3O4 (JCPDS NO.65-3107). The characteristic peak of graphene oxide located at 10.4° was not found, confirming the formation of graphene. Fig. 1 also showed the SEM image of fabricated iron oxide nanoparticles that were uniform with the diameter about 50 nm, indicating XRD pattern in good agreement with SEM results. Raman spectra also confirmed that the typical features of reduced graphene oxide with the presence of D band (1348 cm−1) and G band (1598 cm−1).

Synthesis of r-Graphene oxide from GO by reduction using plant extracts as a green reducing agent is nowadays carried out to avoid the impact of toxic, harmful chemicals on the environment. In this context, this present investigation an eco-friendly, non-toxic, and green reducing agents of namely leaf extracts of Artabotrys hexapetalus and Bauhinia tomentosa was used to convert the Graphene oxide (GO) to Reduced Graphene Oxide (RGO). The synthesized GO and RGO were characterized through UV–Visible spectroscopy,Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), 3D optical profilometer, Thermo gravimetric analysis (TGA), and Zeta potential analysis. UV-visible, FT-IR, and XRD results showed the partial removal of oxygen containing groups from the GO and the formation of RGO. Reduction of GO and the formation of RGO was confirmed by the increasing carbon ratio and decreasing oxygen ratio in the results of EDX analysis. SEM results clearly indicated the formation of multiple layers of RGO. Thermal stability of the synthesized RGO was analyzed by Thermo gravimetric study. Surface charge characteristics of GO and RGO were analyzed by zeta potential measurement. All these results confirmed the inexpensive and eco-friendly synthesis of RGO.

Optimization of reduced graphene oxide yield using response surface methodology

We developed a facile method to achieve a homogeneous coating of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) on a graphene oxide (GO) layer with outstanding sheet resistance. We fabricated a transparent bilayer GO/PEDOT:PSS film as a flexible transparent conductive electrode (TCF). GO layer was coated on flexible PET and PI substrate by dip coating. The coated GO layers were modulated by their sizes and post heat treatment. The GO layers were thermally reduced and over coated with a PEDOT:PSS layer. Compared to the values of PEDOT:PSS, the sheet resistance of the bilayer film decreased by 5.2% and cyclic bending durability increased by 47.4%. The synergetic conductive network between the reduced graphene oxide (RGO) layer and the PEDOT:PSS layer resulted in low sheet resistance; the initial network retained under cyclic bending. The bilayer TCF film can be applied to multifunctional electrical devices for which flexibility and high conductivity are necessary.

Reduced graphene oxide (RGO) or graphene as it is commonly referred to is currently the most promising nanomaterial with potential applications. Synthesis of RGO starts with oxidation of graphite to graphene oxide (GO) which is further reduced either by chemical or thermal means. However, chemical reduction of GO to RGO involves the use of toxic chemical reagents which are not environmental friendly. Hence, in this work, low-temperature thermal reduction has been utilized to obtain high-quality RGO from GO effectively at a temperature of only 50 °C. The precursor of RGO which is GO is synthesized by modification of Improved Hummer’s method (Marcano et al. in ACS Nano 4(8):4806–4814, 2010), a non-toxic and non-explosive method of GO production. The highly exothermic reactions in producing GO are controlled by using ice baths with magnetic stirring. The prepared samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscopy and Energy-dispersive X-ray spectroscopy. All four characterizations confirm the efficient oxidation and reduction that has taken place to produce GO and RGO-4. (RGO formed on the 7th day of the reduction process.) XRD peak of GO at 10.46° corresponding to (001) plane indicating an interplanar spacing of 0.80 nm confirms the proper oxidation of graphite to GO. However, after thermal reduction at 50 °C the 2θ peak of GO at 10.46° shifts to 2θ = 24.15° with an interplanar spacing of 0.36 nm that confirms the formation of RGO-4 with retention of most of the sp2 structures by proper reduction of the oxygenated functional groups of GO. The GO produced is hydrophilic in nature due to existence of large number of oxygen-containing functional groups as shown in FTIR analysis. Raman results show that after reduction of GO to RGO-4 at 50 °C, the ID/IG ratio decreased significantly from 1.93 of GO to 1.00 of RGO-4 indicating highly reduced defects density in RGO-4.

3‐Mercaptopropyltrimethoxysilane (MPTMS) modified exfoliated graphene oxide (GO)/nitrile‐butadiene rubber (NBR) nanocomposites were fabricated by latex compounding method. The modification and reduction of GO were simultaneously conducted in situ by a one‐pot design. The reductant, ammonium hydroxide was employed to mildly reduce GO at 78°C. The GO exfoliation, MPTMS modified GO (MGO), and the dispersion of GO sheets in rubber matrix were studied using Wide‐angle X‐ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT‐IR), and transmission electron microscopy (TEM). It is evident that GO sheets are uniformly dispersed in the rubber matrix. The one‐pot design can significantly promote the reduction process and the surface modification of GO, simultaneously. The reduction was confirmed by morphology analysis and FT‐IR analysis of uncured rubber compounds. The mechanical properties of pristine NBR/GO and NBR/MGO nanocomposites were studied within a filler range of 0–2 phr. The NBR/MGO composites exhibited superior mechanical property and higher storage modulus attributing to the stronger interfacial interaction via covalent bonding between MGO and NBR molecules compared with the NBR/GO composites connected by weaker π–π stacking. POLYM. COMPOS., 39:3227–3235, 2018. © 2017 Society of Plastics Engineers

In this study, graphene oxide (GO) was synthesized using the improved Hummers’ method, and reduce graphene oxide (rGO) was synthesized from GO with hydrazine hydrate as reducing agent. Zinc oxide (ZnO) was synthesized from zinc acetate using the precipitation method. Zinc oxide/reduced graphene oxide (ZnO/rGO) composites were synthesized using the ex-situ method. The ZnO/rGO composites with different rGO weight percents (0.05, 0.1, 0.5, 1, and 5 wt%) were used for fabrication of ZnO/rGO anodes. A control anode was fabricated from ZnO (ZnO anode). The band gaps of fabricated anodes were measured using the ultraviolet-visible spectroscopy (UV-vis). The dye-sensitized solar cells (DSSCs) were assembled and investigated by current density-voltage (J-V) curves and electrochemical impedance spectroscopy (EIS). The ZnO/rGO composite with appropriate rGO content was determined to be 1 wt%, with the efficiency of 1.55 %. The Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD) results confirmed wurzite structure of ZnO and the reduction of functional groups of GO to create rGO and ZnO/rGO. The transmission electron microscopy (TEM) showed that the ZnO nanoparticles with size of 10 - 20 nm were evenly distributed on rGO sheets. These results indicated that ZnO/rGO could be the potential material to improve the efficiency of DSSCs.