Aminated Graphene Oxide Research Articles

Graphene Oxide Surface Modification of Reverse Osmosis (RO) Membrane via Langmuir-Blodgett Technique: Balancing Performance and Antifouling Properties.

The reverse osmosis water treatment process is prone to fouling issues, prompting the exploration of various membrane modification techniques to address this challenge. The primary objective of this study was to develop a precise method for modifying the surface of reverse osmosis membranes to enhance their antifouling properties. The Langmuir-Blodgett technique was employed to transfer aminated graphene oxide films assembled at the air-liquid interface, under specific surface pressure conditions, to the polyamide surface with pre-activated carboxylic groups. The microstructure and distribution of graphene oxide along the modified membrane were characterized using SEM, AFM, and Raman mapping techniques. Modification carried out at the optimal surface pressure value improved the membrane hydrophilicity and reduced the surface roughness, thereby enhancing the antifouling properties against colloidal fouling. The flux recovery ratio after modification increased from 65% to 87%, maintaining high permeability. The modified membranes exhibited superior performance compared to the unmodified membranes during long-term fouling tests. This membrane modification technique can be easily scaled using the roll-to-roll approach and requires minimal consumption of the modifier used.

Membranes Based on Aminated Graphene Oxide with High Selectivity Toward Organic Substances.

In this work, membranes based on graphene oxide, modified with oleylamine, have been prepared by a simple wet chemistry protocol without the use of complex equipment, elevated temperature, and additional reagents. The membrane material was characterized by a set of physicochemical methods: thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The prepared membranes are stable in both aqueous and organic media. The membranes have a high flux for organic substances and do not permeate water at room temperature and atmospheric pressure. The selectivity of the membranes toward organic substances increases with their thickness. The highest flux among the tested organic liquids is registered for methanol. The membranes have high selectivity toward ethanol/1-butanol and acetone/1-butanol pairs, which opens up the possibility of separating actual industrial mixtures. The membrane retains 90% of methylene blue from the alcohol solution. Our work expands the possibilities of using modified GO-based membranes in purification and filtration technologies.

Biomass-Derived Aldehyde and Aminated Graphene Oxide Reinforced Gelatin-Based Composite Films for Biopackaging via a Multipoint Cross-Linking Strategy

Biomass-Derived Aldehyde and Aminated Graphene Oxide Reinforced Gelatin-Based Composite Films for Biopackaging via a Multipoint Cross-Linking Strategy

Comparative toxicological analysis of two pristine carbon nanomaterials (graphene oxide and aminated graphene oxide) and their corresponding degraded forms using human in vitro models

Despite the wide application of graphene-based materials, the information of the toxicity associated to some specific derivatives such as aminated graphene oxide is scarce. Likewise, most of these studies analyse the pristine materials, while the available data regarding the harmful effects of degraded forms is very limited. In this work, the toxicity of graphene oxide (GO), aminated graphene oxide (GO-NH2), and their respective degraded forms (dGO and dGO-NH2) obtained after being submitted to high-intensity sonication was evaluated applying in vitro assays in different models of human exposure. Viability and ROS assays were performed on A549 and HT29 cells, while their skin irritation potential was tested on a reconstructed human epidermis model. The obtained results showed that GO-NH2 and dGO-NH2 substantially decrease cell viability in the lung and gastrointestinal models, being this reduction slightly higher in the cells exposed to the degraded forms. In contrast, this parameter was not affected by GO and dGO which, conversely, showed the ability to induce higher levels of ROS than the pristine and degraded aminated forms. Furthermore, none of the materials is skin irritant. Altogether, these results provide new insights about the potential harmful effects of the selected graphene-based nanomaterials in comparison with their degraded counterparts.

Preparation and properties of electrochromic polyimide hybrid materials containing graphene oxide

The aminosylated graphene oxide was synthesized using the compound E3, three anhydrides (3,3′,4,4′ -diphenyl ether tetracarboxylic acid dianhydride, 3,3′,4,4′ -biphenyl tetracarboxylic acid di anhydride and 1,2,4, 5-phenyl tetracarboxylic acid di anhydride) is a series of electrochromic polyimide hybrid materials containing carbazole groups prepared by polypolymerization with aminated graphene oxide (F2). These PIs not only have good solubility and thermal properties,but also the introduction of 0.5 wt% GO increased the contact area between the film and electrolyte ions, which was beneficial to transport and diffusion of ions, thus improving the response speed of the electrochromic materials. Moreover, its excellent tensile properties make it an ideal material for manufacturing flexible devices. In addition, the polyimide hybrid materials exhibit excellent electrochemical and electrochromic properties as well as electrofluorescent properties. Therefore, the new material will be suitable for hole transmission, electrochromic, chemical sensing and other fields.

Enhanced Hydrogen Evolution Performance of Ni−Mo-Based Electrocatalysts in Seawater by Controlling Surface Wettability

Environmental pollution and global warming have become enormous problems all over the world. At the United Nations Climate Change Conference, carbon neutrality was proposed as a way to solve this problem through the Paris Agreement in 2015. To achieve zero net carbon dioxide emissions, research on how to obtain energy from renewable energy resources has been intensively conducted. Among various candidates of renewable chemical fuels, green H2, produced by water electrolysis is considered as one of the promising, next generation chemical fuels.Almost 97% of earth’s water resources exist as seawater. Moreover, seawater has an advantage that it can be used as an electrolyte owing to the various ions, existing naturally. Therefore, one of the ultimate goals in green H2 generation is to directly utilize seawater as the electrolyte source.Although Pt-group materials (PGMs) are well known catalysts in hydrogen evolution reaction (HER) but one of the main challenges for wide commercialization with PGMs is its high cost and scarcity. In order to overcome this issue, research on HER catalysts using non-PGM (NPGM) has been intensively performed. Among various NPGM elements, Ni−Mo has great potential for electrocatalysts in HER owing to its cost effectiveness as well as their high electrocatalytic activities in wide pH range of electrolytes. It is well known that not only the electrocatalytic activity in HER, mainly originating from chemical compositions at the surface, but also the physical surface properties, especially the surface wettability, play an important role to regulate the electrocatalytic performance. The evolved bubbles by the HER form the solid−gas−liquid interfaces, which results in the turn-off of the active sites toward electrochemical reactions until the gas bubbles remove from the electrocatalytic surface. Previous studies reveal that this dynamic, evolutionary behavior of surface active sites by the bubble growth/departure significantly influence the electrocatalytic performance.Herein, we demonstrate the Ni−Mo-based material as the electrocatalyst toward HER in simulated seawater, which is 0.5 M phosphate buffer with 0.6 M NaCl. The electrocatalytic layers are deposited by simple electrodeposition with the aminated graphene oxide (aGO) to form composites (aGO/NiMo). The addition of aGO in Ni−Mo does not influence the electrocatalytic activity in HER, exhibiting nearly the same cyclic voltammograms with pure NiMo. Interestingly, the long-term performance of aGO/NiMo, however, is observed when compared to the pure NiMo. The enhanced durability by chronopotentiometric measurements in the aGO/NiMo is ascribed to the improved surface wettability, originating from added aGO. The images taken by high-speed camera clearly show that the H2 bubbles with smaller sizes at the surface of aGO/NiMo but much larger density than the ones at pure NiMo are observed. These phenomena denotes that the regeneration rate of active sites by bubbles departure from the surface is much higher in the aGO/NiMo than NiMo without aGO, indicating that the aGO is beneficial for improving the surface wettability. The longer residence of H2 bubbles at the pure NiMo increases the actual overpotential applied in the single active site under constant current density, leading to the faster degradation of electrocatalytic activity in HER. The physical properties of surface between aGO/NiMo and NiMo for surface wettability is also supported by surface roughness measurements in atomic force microscope and contact angles. Our study contributes to the fundamental design of the physical properties of electrocatalytic surfaces physical properties, thereby simply improving the electrochemical performance in HER.

Fabrication of silver/polyaniline/aminated graphene oxide coated textiles for electromagnetic interference shielding application within the different bands of frequency

The interference and pollution caused by electromagnetic radiation have become serious concerns due to the advancements in telecommunications and electronic technology. Highly efficient electromagnetic interference (EMI) shielding materials are thus urgently needed. The primary purpose of this research is to design silver/polyaniline/aminated graphene oxide based EMI shielding textiles over a wide frequency range to protect humans from harmful electromagnetic radiation. For this, layer by layer strategy was adapted to develop conductive textiles for remarkable EMI shielding performance in a wide range of frequency. Electroless plating of silver was performed on polyaniline-based aminated graphene oxide (AGO) fabric to achieve a multilayered structure. Our shielding effectiveness (SE) findings demonstrate that these modified fabrics provide excellent EMI shielding efficiency across multiple frequency bands, including UHF, L-band, S-band, C-band, and X-band. The modified fabric showed EMI SE greater than 40 dB in all bands of frequency and it is greater than the commercial requirement. Moreover, these fabrics are antibacterial and hydrophobic in nature and the greatest antibacterial activity was exhibited by silver/polyaniline/aminated graphene oxide fabric about 97 % and 99% against E.coli and S. aureus respectively. These modified fabrics have the potential to significantly reduce electromagnetic radiation pollution and protect human life owing to their exceptional EMI shielding properties.

Reverse osmosis membrane functionalized with aminated graphene oxide and polydopamine nanospheres plugging for enhanced NDMA rejection and anti-fouling performance

The use of reverse osmosis (RO) for water reclamation has become an essential part of the water supply owing to the ever-increasing water demand and the utmost performance of the RO membranes. Despite the global RO implementation, its inferior rejection against low molecular weight contaminants of emerging concerns (CECs) (i.e., N-nitrosodimethylamine (NDMA)) and propensity to fouling remain bottle-neck thus affecting process robustness for water reuse. This study aims to enhance both the rejection and antifouling properties of the RO membrane. Herein for the first time, we report RO membrane modification using polydopamine nanospheres (PDAns) followed by aminated-graphene oxide (AGO) deposition as an effective approach to overcome these challenges. The modification of the RO membrane using PDAns-AGO resulted in 89.3 ± 2.7% rejection compared to the pristine RO membrane which demonstrated 69.2 ± 2.1% NDMA rejection. This significant improvement can be ascribed to the plugging and shielding of defective areas (formed during interfacial polymerization) of the polyamide layer through active PDAns and AGO layers and to the added sieving mechanism that arose through narrow channels of the AGO owing to its reduction. Moreover, the in-situ and non-destructive fouling monitoring using optical coherence tomography (OCT) revealed that the PDAns-AGO coating enhanced both the anti-scaling and anti-biofouling characteristics. The improved hydrophilicity and bactericidal effect together with roughness and surface charge suppression synergistically enhanced anti-fouling properties. This study provides a new direction for safe and cost-effective water reuse practices. The membrane with high selectivity against CECs such as NDMA has the potential to eliminate permeate staging using second pass RO and other advanced oxidation processes which are utilized as a tertiary treatment to make reclaimed water suitable for potable/non-potable application.

Nanoconfined superfluid for highly efficient chemical reactions

Highly efficient chemical reactions are vital for the development of green growth and sustaining industrial society, yet achieving effective flow reactions under mild conditions remains challenging. In a recent research article published in Matter, Pang and colleagues 1 Pang S. Peng D. Hao Y. Song B. Zhang X. Jiang L. Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactions. Matter. 2023; 6: 1173-1187 Abstract Full Text Full Text PDF Scopus (1) Google Scholar achieved a nanoconfined superfluid-based chemical reaction with ∼100% conversion and reaction time of less than 29 s at 22°C using multilayer aminated graphene oxide nanoconfined membranes. These findings highlight the potential for nanoconfined membranes to revolutionize the field of chemical synthesis. Highly efficient chemical reactions are vital for the development of green growth and sustaining industrial society, yet achieving effective flow reactions under mild conditions remains challenging. In a recent research article published in Matter, Pang and colleagues 1 Pang S. Peng D. Hao Y. Song B. Zhang X. Jiang L. Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactions. Matter. 2023; 6: 1173-1187 Abstract Full Text Full Text PDF Scopus (1) Google Scholar achieved a nanoconfined superfluid-based chemical reaction with ∼100% conversion and reaction time of less than 29 s at 22°C using multilayer aminated graphene oxide nanoconfined membranes. These findings highlight the potential for nanoconfined membranes to revolutionize the field of chemical synthesis. Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactionsPang et al.MatterFebruary 13, 2023In BriefIt remains a challenge to achieve effective flow reactions under mild conditions. Here, we report a strategy of regulating interlayer spacing of aminated graphene oxide membranes for efficient Knoevenagel condensation. Through decreasing the interlayer spacing, a flow reaction with ∼100% conversion is achieved at 22°C with a short reaction time (<29 s). This work presents a new strategy for efficient and rapid flow reactions under mild conditions. Full-Text PDF

Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactions

Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactions

Binary Resin-Curing Agent Systems for Fabricating Epoxy and Graphene Oxide-loaded Epoxy Films

In this research, diglycidyl ethers of bisphenol-A (BADGE) and polyethylene glycol (PEGDGE) were binarily cured with a mixture of diamine curing agents including isophorone diamine and polyethylene glycol diamine (PEGDA) in the absence/presence of aminated graphene oxide nanoplatelets (AGNPs, 0.5 wt.%). Four molar ratios of diglycidyl ethers and curing agents were used stoichiometrically in isothermal curing systems. The films prepared from the epoxy networks were entirely strong and pliable. All epoxy thermosets were evaluated using field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and diffuse reflectance-ultraviolet/visible spectroscopy (DR-UV/vis). The absorption coefficients of the epoxy and AGNPs-loaded epoxy materials decreased with increasing the molar ratio of PEGDGE resin and polyethylene glycol diamine curing agent. According to dynamic mechanical analysis no phase heterogeneity occurred in the structure of the prepared thermostats. When the thermoset materials were loaded by AGNPs filler, the peaks associated with alpha relaxations shifted to higher temperatures. Moreover, thermogravimetric analysis demonstrated that the thermal stability of the prepared epoxy thermosets slightly increased after the addition of the nanoplatelets. In addition, the thermal resistance of the prepared thermosets decreased to some extent by increasing the participation rate of monomers containing polyoxyethylene.

Silver electroless plating on aminated graphene oxide-based cotton fabric for electromagnetic interference shielding and bioactivity

The rapid development of electronic and telecommunications technology has made electromagnetic radiation pollution and interference a serious concern. Surrounded by harmful electromagnetic radiation for a long period of time, serious human health consequences like cancer, headaches, nausea, and irregular brain development are expected. Therefore, there is an urgent need for extremely effective electromagnetic interference (EMI) shielding materials to protect human life and the environment. The main objective of this study is to develop high-performance EMI shielding textiles within a broad range of frequency to protect human beings from hazardous radiations. For this, we propose a facile method of silver electroless plating on aminated graphene oxide (NH2-GO) based cotton fabric for remarkable EMI shielding performance within the different bands of frequency namely, UHF band, L band, S band, C band, and X band. The successful formation of silver-plated fabrics was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). EMI shielding performance was evaluated by Vector network analyzer (VNA) having a frequency range from 100 MHz to 13.6 GHz and our results showed that Silver-plated aminated GO-based fabric exhibits 99% shielding within the wide range of frequency bands as amination of GO provides more functional groups for silver electroless plating and maximum shielding effectiveness was about 49 dB at 6.7 GHz with 1.2 mm thickness. Moreover, all modified fabrics exhibit good antibacterial activity, and the highest antibacterial activity was shown by silver/rGO fabric about 99.99%. Thus, the remarkable EMI shielding performance of silver-plated NH2-GO fabrics tends to make significant progress in eliminating electromagnetic radiation pollution from our environment within a broad range of frequency.

A fluorescent turn on/off probe for glucose detection based on a boronic acid-capped 1,1′-ferrocenedicarboxylic acid functional graphene oxide

The accurate determination of glucose in the human body is highly desired because excessive ingestion of glucose may lead to obesity, diabetes and other diseases. This work demonstrates a fluorescent probe for sugar detection using the unique affinity of boronates for cis -diols. The fluorescent sensing system is composed of two components: 1) Aminated graphene oxide (GON) decorated with phenylboronic acid (BPA) and 1,1'-ferrocenedicarboxylic acid (FCA) as a fluorescence quencher (FCA–GON–BPA); and 2) fluorophores of a cis -diol modified tetraphenylethylene derivative (TPBD) with aggregation-induced emission (AIE) characteristics as the luminescence. FCA–GON–BPA can selectively bind cis -diol-containing fluorogens, such as TPBD, resulting in fluorescence quenching of the probe system. Upon addition of glucose, a new cyclic boronate ester is formed, resulting in the cis -diol-containing fluorogen dissociating from the quenched system, and TPBD fluorescence is recovered. The probe has an obvious response to the presence of glucose and a low limit of detection (LOD, 4.36 mg/mL). • The fluorophore has the characteristics of aggregation-induced emission. • The reaction platform is graphene oxide with high adsorption surface area. • Glucose preempts binding of fluorophore and quencher to release fluorescence.

Chemically graft aminated GO onto dehydro-fluorinated PVDF for preparation of homogenous DF-PVDF/GO-NH2 ultrafiltration membrane with high permeability and antifouling performance

Blending of hydrophilic nanoparticles into the PVDF ultrafiltration membrane has been proved to be an effective and simple way to improve the hydrophilicity and the anti-fouling performance. However, due to the heterogeneous nature, aggregation or leakage of the hydrophilic nanoparticles usually happened at higher concentration which would further go against for improving the filtration performance. Here, aminated graphene oxide (GO-NH2) and dehydro-fluorination polyvinylidene fluoride (DF-PVDF) were synthesized, and GO-NH2 was chemically grafted on DF-PVDF via Michael addition reaction. The resultant DF-PVDF/GO-NH2 membrane was obtained, and the structure, hydrophilicity, and the antifouling performance of DF-PVDF/GO-NH2 membrane are systematically investigated. As a result, the GO-NH2 grafted membranes (Mg membranes) exhibited uniform and smooth surfaces with numerous visible pores and higher porosity compared to GO co-blending membranes (Mb membranes) and the original PVDF membrane. Besides, the Mg membranes possessed lower water contact angle (48°± 1.0°), higher water flux (355 L/m2 h) and better flux recovery ratio (up to 88%), showing better hydrophilicity and anti-fouling performance together with better mechanical properties. Static adsorption experiment also indicated the better anti-fouling performance of Mg membranes due to the uniformly dispersion of hydrophilic GO and the strong electrostatic repulsion between negatively charged GO and BSA.

The Design of Ternary Composite Polyurethane Membranes with an Enhanced Photocatalytic Degradation Potential for the Removal of Anionic Dyes

Photocatalysis is an efficient and an eco-friendly way to eliminate organic pollutants from wastewater and filtration media. The major dilemma coupled with conventional membrane technology in wastewater remediation is fouling. In this study, the photocatalytic degradation potential of novel thermoplastic polyurethane (TPU) based NiO on aminated graphene oxide (NH2-GO) nanocomposite membranes was explored. The fabrication of TPU-NiO/NH2-GO membranes was achieved by the phase inversion method and analyzed for their performances. The membranes were effectively characterized in terms of surface morphology, functional group, and crystalline phase identification, using scanning electron microscopy, Fourier transformed infrared spectroscopy, and X-ray diffraction analysis, respectively. The prepared materials were investigated in terms of photocatalytic degradation potential against selected pollutants. Approximately 94% dye removal efficiency was observed under optimized conditions (i.e., reaction time = 180 min, pH 3–4, photocatalyst dose = 80 mg/100 mL, and oxidant dose = 10 mM). The optimized membranes possessed effective pure water flux and excellent dye rejection (approximately 94%) under 4 bar pressure. The nickel leaching in the treated wastewater sample was determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). The obtained data was kinetically analyzed using first- and second-order reaction kinetic models. A first-order kinetic study was suited for the present study. Besides, the proposed membranes provided excellent photocatalytic ability up to six reusability cycles. The combination of TPU and NH2-GO provided effective strength to membranes and the immobilization of NiO nanoparticles improved the photocatalytic behavior.

Novel reusable amine-functionalized cellulose acetate beads impregnated aminated graphene oxide for adsorptive removal of hexavalent chromium ions

In this study, a multi-featured adsorbent was developed for the adsorptive removal of hexavalent chromium (Cr6+) ions. Herein, aminated graphene oxide (GO-NH2) was firstly synthetized and incorporated into cellulose acetate beads (CA) which were followed by surface amine-functionalization process. Varies characterization tools such as FT-IR spectroscopy, SEM, TGA, XRD, BET, XPS and zeta potential were employed to ensure the successful fabrication of GO-NH2@CA-NH2 composite beads. An enhancement in the adsorption performance was attained, while the adsorption equilibrium was closely gotten within only 60 min. Therefore, the adsorption capacity was boosted with increasing GO-NH2 ratio in the beads matrix from 10 to 25%. Furthermore, the adsorption process agreed with Freundlich isotherm model with a supreme adsorption capacity of 410.21 mg/g at pH 2, while data followed the pseudo-second-order kinetic model. Besides, thermodynamic studies denoted that the adsorption process was endothermic, randomness and spontaneous. The composite beads retained better adsorption characteristics for seven sequential cycles with ease of separation. The proposed adsorption of Cr6+ onto GO-NH2@CA-NH2 surface occurred via the electrostatic interactions, reduction process and coordinate–covalent bonds. These findings hypothesize that the fabricated GO-NH2@CA-NH2 beads could be act as easy-separable and reusable adsorbent for efficient adsorption of Cr6+ ions.

Preparation of Polyvinylidene Fluoride Nano-Filtration Membranes Modified with Functionalized Graphene Oxide for Textile Dye Removal.

Water scarcity has become one of the most significant problems globally. Membrane technology has gained considerable attention in water treatment technologies. Polymeric nanocomposite membranes are based on several properties, with enhanced water flux, high hydrophilicity and anti-biofouling behavior, improving the membrane performance, flexibility, cost-effectiveness and excellent separation properties. In this study, aminated graphene oxide (NH2-GO)-based PVDF membranes were fabricated using a phase-inversion method for textile dye removal. These fabricated membranes showed the highest water flux at about 170.2 (J/L.h−1.m−2) and 98.2% BSA rejection. Moreover, these membranes removed about 96.6% and 88.5% of methylene blue and methyl orange, respectively. Aminated graphene oxide-based polyvinylidene fluoride (PVDF) membranes emerge as a good membrane material that enhances the membrane performance.

Fabrication of Multi-functionalized Graphene Oxide Doped Alginate Hybrid Spheres for Enhanced Fluoride Adsorption

In this current study, aminated graphene oxide (AGO) doped on alginate (Alg) matrix offers AGO@Alg hybrid spheres was developed to investigate its potential for retention of fluoride from water. The sophisticated characterization methods likely TGA, SEM, XPS and FTIR studies of AGO@Alg hybrid spheres were attained to recognize its physicochemical properties like thermal stability, morphology, elemental binding energy and functional groups determination. The responsible parameters for fluoride adsorption on AGO@Alg hybrid spheres were optimized under a batch mode to achieve improve defluoridation capacity (DC). The developed AGO@Alg hybrid spheres follow the electrostatic interaction mechanism on fluoride removal. The adsorption isotherms (Langmuir, Temkin, Dubinin–Radushkevich (D–R) and Fruendlich models), kinetics (reaction and diffusion based models) and thermodynamic parameters (ΔS°, ΔG° and ΔH°) were investigated at 303, 313 and 323 K. To minimize the cost-effectiveness of AGO@Alg hybrid spheres the reusability test was carried out. The suitability of AGO@Alg hybrid spheres was also analyzed for the fluoride contaminated field sample taken from fluoride prevalent village.

Nanofluids based on hydrolyzed polyacrylamide and aminated graphene oxide for enhanced oil recovery in different reservoir conditions

Partially hydrolyzed polyacrylamide (HPAM) aqueous fluids in reservoirs produces a significant increase in the produced oil volume. However, the viscosity of these fluids is highly influenced by the temperature and salinity of the medium which is crucial in some reservoir conditions for the oil recovery. Thus, addition of nanomaterials in HPAM solutions to prepare nanofluids has been shown to be a promising alternative to increase viscosity and improve the performance in enhanced oil recovery. In this work, graphene oxide (GO) was prepared using modified Hummers method through the oxidation/exfoliation of expanded graphite while the aminated graphene oxide (GOA-EDA) was prepared using ethylenediamine in an ultrasonic bath. Spectroscopic techniques, elementary and thermogravimetric analyses confirmed the chemical composition of the produced nanomaterials. Images obtained by transmission electron microscope also confirmed the interfacial interactions between GO / GOA-EDA and HPAM. Rheological measurements were performed to determine the nanofluids viscosity as a function of concentration at high temperature (70 °C) under different salinity conditions. The results indicate that the viscosity increases promoted initially by the nanofluids prepared with GOA-EDA were smaller than those obtained by the nanofluids prepared with GO. In particular, the greatest increases in viscosity values occurs in the medium with the highest ionic strength (ηi%μ=0.6>ηi%μ=0.3>ηi%μ=0.1). However, after 90 aging days, nanofluids prepared with GOA-EDA showed better performances reaching gains of up to 146% in viscositiy when compared to the HPAM reference fluids indicating that nanofluids prepared with GOA-EDA are more promising for application in enhanced oil recover.

Graphene Oxide-Modified Aramid Fibers for Reinforcing Epoxy Resin Matrixes

Carboxylated and aminated graphene oxide (CGO and AGO) were first prepared by using carboxyl-terminated aromatic hyperbranched polyester (HBPC) and amino-terminated aromatic hyperbranched polyester (HBPA) noncovalent functionalized GO, respectively. Subsequently, multiscale reinforcing fibers (CGO-PDA-AF and AGO-PDA-AF) were prepared by exploiting the super adhesion of the polydopamine layer (PDA) and its physical adsorption and chemical grafting with the CGO and the AGO. This study examined the tensile strength of the modified aramid fiber (AF) monofilament and the interfacial shear strength (IFSS) between the modified AF monofilament and the EP matrix, and an investigation was conducted on the interfacial enhancement mechanism. As indicated from the results, the AGO exerted a more effective modifying effect than the CGO. The single filament tensile strength and IFSS of the AGO-PDA-AF were the maximum (4.66 GPa and 96.2 MPa), nearly 8.6 and 7.9% higher than those of the CGO-PDA-AF, respectively. The enhancement of the interface performance between the AGO-PDA-AF and the EP was attributed to the introduction of considerable amino active groups in the AGO, thereby forming a stable covalent bond with the epoxy matrix, which significantly improved the interface bonding strength. Moreover, the flexible coating layer formed by the AGO could reduce the stress concentration of the interface through deformation, so the AF could be carried more uniformly. Furthermore, the AGO increased the surface affinities of the AF and improved the mechanical interlocking with the EP matrix.