Advantages Of Graphene Oxide Research Articles

Removal of malachite green in wastewater and its mechanism by three-dimensional graphene oxide-based aerogels

Malachite green (MG) is a significant water pollutant due to its widespread use and harmful properties, making its effective removal crucial. Graphene oxide (GO) has emerged as a promising material for dye adsorption. Doping GO into cellulose aerogels enhances mechanical properties and prevents GO dissolution. Many reports claim the advantages of GO in adsorption, but challenges remain in understanding and optimizing the adsorption of MG in three-dimensional cellulosic GO (CLGO) aerogels. In this study, three-dimensional CLGO aerogels were prepared using the freeze-drying method. They achieved an MG maximum adsorption capacity of 33.98 mg g−1, and the adsorbent still had 97.04 % adsorption capacity at the seventh adsorption–desorption cycle. The photothermal properties of the CLGO aerogels were also studied, contributing to the development of the zero-liquid discharge (ZLD) post-processing concept. Molecular force field simulations indicated that π-π interaction is the primary force between MG and CLGO aerogels in the absorption process. We believe our research will guide the future optimization of MG specialized absorbent.

In vitro assessments of nanoplexes of polyethylenimine-coated graphene oxide-plasmid through various cancer cell lines and primary mesenchymal stem cells

Efficient gene therapy relies on an efficient gene delivery system. Viral gene delivery approaches excel in transferring and expressing external genes; however, their immunogenicity and difficulty in large-scale production limit their clinical applications. In contrast, nanoparticle-based gene delivery systems have gained increasing attention due to less immunogenicity and more convenience for large-scale production. Nevertheless, their poor transfection efficiency compared to viral systems remains a significant obstacle. In the present study, we investigated the transfection efficiency of our PEI-coated graphene oxides in HEK293T, Calu-3, Calu-6 cell lines, and primary human bone marrow mesenchymal stem cell (MSC). The high surface ratio and good biocompatibility of graphene oxide make it an appealing tool for gene delivery systems. However, the low dispersity of graphene oxide in aqueous environments is the first barrier that needs to be conquered. For this, we enhanced the dispersity and stability of graphene oxide in water by sonicating it for at least 5 hours at a pH of 7. Then, graphene oxide was conjugated with branched PEI (25 kDa) to have a positive charge, enabling it to condense nucleic acids with a naturally negative potential. The physio-chemical characteristics of our synthesized nano-carriers (GO-PEI) were determined by DLS, FT-IR, and AFM. The utilized plasmid in polyplexes contained a GFP gene, allowing us to verify transfection efficiency through fluorescent microscopy and flow cytometry. While GO-PEI carriers were highly efficient in transfecting HEK293T cells, the transfection efficiency in MSCs and Calu-3 cells was notably low. We suppose that the main reason for the low transfection efficiency of GO-PEI in these cells is due to its higher toxicity. Despite this, considering the various advantages of graphene oxide in drug delivery as well as its optical and electrical applications in biomedicine, we propose to functionalize graphene oxide with more biocompatible materials to enhance its potential as a successful gene carrier in these cell types.

Improving the migration resistance against phthalate plasticizer in polyvinyl chloride/graphene oxide composites

AbstractPhthalic plasticizer plays an important role in processing and manufacturing one of the universal polymer materials, poly (vinyl chloride) (PVC), which has been widely applied in every aspect of our lives. However, there still exists the intrinsic problem in migration resistance of phthalic plasticizer in long‐term use. In this work, we take a facile and convenient approach by incorporating commercial graphene oxide (GO) into PVC matrix to prepare polyvinyl chloride/graphene oxide (PVC/GO) composites, forming a sheet structure for improving the migration resistance of phthalic plasticizer. The advantages of GO that has abundant oxygen‐containing groups on its surface, including carboxyl groups at the sheet edges, epoxy groups, and hydroxyl groups on its basal planes. Especially, these oxygen‐containing groups in GO are beneficial to blend with long molecular chain of PVC and the sheet structure of GO can prevent phthalic plasticizer migrating from interior PVC. Addition of GO not only effectively enhanced the mechanical properties of PVC/GO composites but also improve their migration resistance due to the sheet structure. This strategy provides an attractive way to solve the problem of migration of plasticizer with simple incorporation GO into the matrix of PVC, reinforcing the composite properties and broadening its applied fields.

Utilizing graphene oxide in cementitious composites: A systematic review

Graphene oxide (GO) is a 2D nanoparticle with dimensions less than 100 nm and acts as nano reinforcement in cementitious composites as a filling, crack-arresting agent, and nuclei for cement hydration. GO can be utilized to improve the microstructure and mechanical properties in a variety of construction and building technology applications. Through a coherent, comprehensive mixed reviewing method, this study seeks to evaluate the research efforts on utilizing GO in cementitious composites and map the research viewpoints from available literature (bibliometric analysis and systematic review). A total of 1437 publications were screened in which 59 articles were selected upon relevancy. Bibliometric mapping is used for keyword occurrence and the tested properties of cementitious composites containing GO. The review finds that the advantage of GO as a reinforcement in cement composite is that it is more effective in controlling crack development and propagation at the nano scale level in contrast to conventional reinforcement. The use of GO in cementitious composites offers many interesting paths and provides a foundation for further optimization in concrete, mortar, engineered cementitious composites, and cement paste. On the other hand, this use has a negative influence on various features of each type of reviewed material. More research is needed to gain a better knowledge of the long-term effects of the mechanical properties and durability of GO-based cementitious composites to promote their wider use in diverse applications in the construction sector.

Preparation of graphene oxide coatings on textured Ti6Al4V by laser micromachining and electrophoretic deposition for improved biocompatibility

Introducing textures and coatings to titanium alloy implant is conducive to improving biocompatibility. In this paper, a two-step scheme comprising laser texturing process followed by electrophoretic deposition stage was investigated to fabricate micron-scale grooves covered with nano-scale graphene oxide (GO) coating precisely and controllably. The effect of multiple-pulse laser ablation on Ti6Al4V alloy (TC4) was analyzed and the correlation between laser parameters and ablation size was built. The normalized pulse overlap was adjusted by changing scanning speed and laser repetition frequency to fabricate well-structured and controllable micro-grooves. Electrophoretic deposition (EPD) of GO was conducted onto micro-grooved TC4 substrate to further improve the biocompatibility. The electrophoretic deposition process was conducted with different graphene oxide concentration and voltages at deposition times from 10 to 25 min. Thereafter, SEM, XRD and Raman test were carried out to analyze the quality and morphology of coatings. In addition, in vitro cellular evaluations and immunofluorescence staining had been used to test the biological properties of the micro-nano structure. The study shows that the micron-scale groove structure and nano-scale GO coating can remain the advantage of groove structure in cell contact guidance, as well as the advantage of GO in biocompatibility, which can promote cell adhesion and proliferation.

Graphene oxide as nano-material in developing sustainable concrete – A brief review

Nanomaterials are the most happening research field in material science. Hydration of cement grains and nano pore filling actions in cement matrix occurring at microscopic levels is greatly benefited by the superior surface area, aspect ratios, size, and greater mechanical characteristics of nano sized materials. Many researchers have used nanoparticles as cementitious materials in concrete. Graphene oxide (GO) is one among many nanomaterials with one of its sides in nano sized measurement and the other two sides are on a bigger scale. One of the advantages of GO over other nanoparticles is that the oxygen functionalities and can be easily dispersed under an aqueous medium. This paper sheds light on brief information about nanotechnology, nanomaterials application in concrete, characterization of GO, and various key researches in the usage of GO in producing concrete of desirable properties. Mainly, GO increases the performance of the resulting cement concrete by creating a strong covalent bond with hydration results like C-S-H. Using polycarboxylate ether and silica fumes the dispersion properties can be effectively improved without forming GO agglomerates. High-Performance cement concrete mixes can be produced by making GO form great bonds with other admixtures.

Safranin T- SDS- GO ternary system: A fluorescent pH sensor

Graphene oxide (GO), one of the popular materials in recent years, has been synthesized according to the modified Hummers' method. Stable dispersions of different amounts of negatively charged GO were prepared in aqueous media. The GO/dye composites were prepared in deionized water by a simple method with the positively charged Safranin T compound (SfT), which is known to have strong fluorescence properties. By changing the GO/dye ratio, it was obtained stable composites in aqueous media. It was investigated the interaction of SfT with GO in an aqueous solution under the critical micelle concentration (CMC), at the CMC and above the CMC by adding sodium dodecyl sulfate (SDS). It was clarified the formation of GO-SfT composites by using spectroscopic techniques. In these composites, the effect of GO layers on the SfT’s photophysical properties was examined by absorption and fluorescence spectroscopy techniques. The change in the quenching effect of GO was monitored both adding a stabilizing electrolyte (NaCl) to the media and changing the pH of the medium. The evaluation was on the probability of the GO-SfT-SDS ternary system being a pH sensing biological sensor material. As a result of this study, it was thought that the GO-SfT-SDS system could be functionalized as a fluorescent pH sensor by taking advantage of GO's sensitivity to pH.

Synthesis of Ag nanoparticle supported graphene/multi-walled carbon nanotube based nanohybrids for photodegradation of toxic dyes

Irrespective of the superior surface properties of graphene, research interests are impulsively devoted to synthesizing 1-D carbon nanomaterial-based binary or ternary nanocomposites for potential applications. Nevertheless, an insightful comparison between the properties of graphene oxide (GO) and carbon nanotubes (CNTs) is lacking in the literature. In the present work, quasi-spherical silver nanoparticles (Ag NPs) were anchored on two different carbon nanomaterial/Ag-based photocatalysts, GO/Ag and multiwalled CNT (MWCNT)/Ag via a modified one-pot synthesis approach. The synthesized Ag NPs and photocatalysts were analyzed using XRD, FTIR, FESEM, TEM, and UV-Vis spectroscopy and tested for their photocatalytic efficiency against three different toxic organic dyes, namely rose bengal (RB), methylene blue (MB), and phenol red (PR). During the photocatalytic process, the reactive oxygen species generated via interband transitions from the surface plasmonic resonance of Ag NPs acted synergistically with unique electrostatic interactions by carbon nanomaterials in the GO/Ag-based catalyst to degrade RB, MB, and PR dyes by 92, 87.6, and 81.4%, respectively within 120 min of UV irradiation. Furthermore, temperature dependence and electricity cost consumption were evaluated to establish the specific advantages of GO over its carbon-based counterparts for the purification of wastewater.

Application of sodium dodecyl sulfate intercalated Co[sbnd]Al LDH composite materials (RGO/PDA/SDS-LDH) in membrane separation

Layered double hydroxides (LDHs) is a typical type of anionic clay minerals. In this study, an SDS-LDH with sodium dodecyl sulfate (SDS) intercalation was prepared by the ion exchange method, and the modified SDS-LDH was successfully combined with graphene oxide (GO). In the presence of dopamine, partial reduction of GO to reduced graphene oxide (RGO). RGO/PDA/SDS-LDH (RPS) composite material was prepared successfully and used in the field of membrane separation. The RPS-2 composite membrane combines the advantages of GO and SDS-LDH, which can increase GO flux while maintaining a high rejection rate. The flux was increased from 10.21 L·m−2h−1bar−1 of GO to 79.24 L·m−2h−1bar−1 of RPS-2, and the rejection rate of various dyes was above 97%. The rejection rate of methylene blue (MB) 97.34% was maintained after 10 cycles, and its flux loss rate is only 45.32%. The composite membrane had good stability under different pH conditions, which provides a basis for the practical application of the membrane.

Graphene oxide nanocomposites based room temperature gas sensors: A review

Over the last few decades, various volatile organic compounds (VOCs) have been widely used in the processing of building materials and this practice adversely affected the environment i.e. both indoor and outdoor air quality. A cost-effective solution for detecting a wide range of VOCs by sensing approaches includes chemiresistive, optical and electrochemical techniques. Room temperature (RT) chemiresistive gas sensors are next-generation technologies desirable for self-powered or battery-powered instruments utilized in monitoring emissions that are associated with indoor/outdoor air pollution and industrial processes. In this review, a state-of-the-art overview of chemiresistive gas sensors is provided based on their attractive analytical characteristics such as high sensitivity, selectivity, reproducibility, rapid assay time and low fabrication cost. The review mainly discusses the recent advancement and advantages of graphene oxide (GO) nanocomposites-based chemiresistive gas sensors and various factors affecting their sensing performance at RT. Besides, the sensing mechanisms of GO nanocomposites-based chemiresistive gas sensors derived using metals, transition metal oxides (TMOs) and polymers were discussed. Finally, the challenges and future perspectives of GO nanocomposites-based RT chemiresistive gas sensors are addressed.

Large-scalable graphene oxide films with resistive switching for non-volatile memory applications

In the present work, it is demonstrated for the first time that a simple, specially developed method for graphene oxide (GO) deposition on large areas opens the prospects of GO’s wide application in planar-group technologies for creating different electronic devices including memristor devices for neuromorphic computing systems in the field of large data and artificial intelligence. MOS structures based on synthesized large-area GO films were formed, and their switching characteristics were studied. Current-voltage measurements performed on the MOS capacitors demonstrated forming-less, device’s self-limited current behavior of GO bipolar resistive switching characteristics with the current density of up to 1 A/cm2. Multiple sharp transitions from the high resistance state to low resistance state in the pristine GO film under the DC voltage sweep may indicate formation of multiple conductive filaments that provide stable conductive paths between GO layers. It was found out that in our devices at least two resistive switching mechanisms may occur simultaneously, namely, filament formation and charge trapping/de-trapping, which is great advantages of GO over other materials. The observed effects are interpreted using a model explaining resistive switching in GO associated with the drift of functional groups and its impact on the resulting different sp3 and sp2 domains.

Graphene Oxide/Elastin Multilayered Membranes for Bone Regeneration

Introduction and objectives: Bone regeneration remains a great challenge due to the complexity of tissue repair. In the past few decades, a common strategy for repairing bone defects is to employ a bone implant1. However, conventional bone substitutes, including metallic materials, bioactive ceramics, and polymers, fail to provide mechanical properties matching those of native bone and biological activity for bone regeneration.Many natural materials have developed superior mechanical properties because of the ordered structure. Nacre, as an example, has an excellent combination of strength and toughness due to its “brick and mortar” layered structure, which consists of highly aligned aragonite platelets connected by organic layers in between the platelets2. Previous works showed that graphene oxide (GO) is an ideal candidate for the “bricks” due to its two-dimensional structure along with the outstanding mechanical strength and modulus3. However, GO-based nacre structures showed in previous works mainly focused on the electronic conductivity or mechanical properties instead of biological properties3-5. As for the choice of “mortar”, it varied from synthetic polymers to natural polymers such as silk fibroin3, chitosan4, and cellulose6. Elastin, as a polymeric extracellular matrix protein, has rarely been explored as the “mortar” phase.In this work, we fabricated multilayered GO/elastin membranes by a facile evaporation approach. GO nanosheets as the “bricks” can provide high modulus and strength to the membrane. Another advantage of GO is that it can promote the osteogenic differentiation of human mesenchymal stem cells, which facilitates bone regeneration. However, the elasticity of the GO membrane is lower than human cortical bone8. So, we select elastin as the “mortar” since it is a natural protein that provides elasticity to connective tissues9. Also, elastin acts as the main apatite nucleator in medial calcification10, which implies that elastin could promote mineralization of the membrane. However, the problem with elastin is weak mechanical strength. By combining GO and elastin, we aim to develop nacre-mimetic membranes with bone-matching mechanical properties and enhanced bioactivity for bone regeneration. R esults and discussions: The microstructure characterization confirmed the resultant membranes possessed a “brick and mortar” layered microstructure (Figure 1a). The prepared membranes had an average thickness ranging from 25 to 30 µm. The addition of elastin improved the stability of the multilayered membranes in water, which is essential for bone regeneration. The addition of elastin increased the tensile strength and Young’s modulus of the membrane (Figure 1b and 1c). However, there was no significant improvement in the tensile strain (Figure 1d). 20 wt% incorporation of elastin membrane showed the maximum tensile strength (90.2 ± 9.6 MPa) and Young’s modulus (13.5 ± 0.4 GPa), which are comparable to those of the human cortical bone8. Immersion tests in simulated body fluid are ongoing to evaluate apatite formation as an indicator of bone-forming ability. Future in vitro studies with mouse bone marrow stem cells could investigate cell viability and osteogenic differentiation on the fabricated membranes. Conclusions: By mimicking the ordered structure of natural nacre, we successfully fabricated multilayered GO/elastin membranes by a simple evaporation method. Incorporation of elastin improved the membrane’s stability in water, tensile strength and Young’s modulus. Among different membrane compositions, 20 wt% elastin addition membrane showed the best mechanical properties. Future simulated body fluid immersion test and cell culture experiments will be performed to investigate the bone regeneration ability of GO/elastin membranes.

Relationship Between Oxygen-Containing Groups and Acidity of Graphene Oxide Supported Mn-Based SCR Catalysts and the Effects on the Catalytic Activity

Graphene oxide (GO) with abundant oxygen-containing groups was chosen as the support for the NH3-SCR catalysts. The as-prepared catalysts were systematically characterized to elucidate the effects of the surface properties and the morphological structure on catalytic activity by Raman, XPS, XRD, SEM, TEM, BET, NH3-TPD, and H2-TPR. It was found that compared with widely researched Graphene (GR), abundant oxygen-containing groups on the surface of GO provided the load sites and further promoted the dispersion of active component, which indicating the much more active sites exposed and further the better catalytic activity shown. Furthermore, the oxygen-containing groups like hydroxyl (-OH) and carboxyl (-COOH) could provide some Bronsted acid sites. After the loading of MnOx, the degree of graphitization of GO increased sharply, indicating the better electron transport and strong chemical interaction between GO and MnOx. Furthermore, the best load amount was found and the acidity was the main reason for the optimalizing performance on Mn-5/GO at low temperature. Besides, not only large specific area, but also outstanding redox performance and high dispersion of active component all contributed to the excellent performance of Mn-5/GO. Over all, this work formulated the advantages of GO worked as the support for SCR catalysts and significantly extended the cognition of GO and the selection basis of supports for the low-temperature NH3-SCR reaction. The abundant oxygen-containing groups on the GO surface promoted the dispersion of the active material (MnOx) and also provided some weak acid sites.

Graphene oxide decorated nanoscale iron sulfide for highly efficient scavenging of hexavalent chromium from aqueous solutions

In this paper, a novel graphene oxide (GO) decorated nanoscale FeS composite (GO/FeS) combining both advantages of GO and FeS was synthesized and tested for the highly efficient scavenging of Cr(VI) from aqueous solutions. The as- synthesized materials were characterized by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectra and X-ray photoelectron spectroscopy (XPS) in detail. The results indicated that FeS nanoparticles were effectively decorated onto the surface of GO through −OH, CO, CO, and O=C–O functional groups, resulting in larger specific surface area and higher reactivity The nanocomposites displayed an enhanced Cr(VI) scavenging capacity, and the acidic conditions favored the Cr(VI) scavenging by GO/FeS. The kinetics of Cr(VI) scavenging on GO/FeS nanoparticles was in accordance with the pseudo-second order kinetic model, suggesting that chemical interaction is mainly responsible for Cr(VI) scavenging on GO/FeS. Furthermore, the Langmuir model fit the best, and qmax, i.e. the maximum scavenging capacity of Cr(VI) obtained from the Langmuir model reached 138.5 mg/g, Surface sorption and reduction were the dominant scavenging mechanisms for Cr(VI) by GO/FeS. The present study demonstrated the promise of GO/FeS as an effective scavenger for the remediation of Cr(VI) in groundwater environment.

Graphene Oxide: A Smart (Starting) Material for Natural Methylxanthines Adsorption and Detection.

Natural methylxanthines, caffeine, theophylline and theobromine, are widespread biologically active alkaloids in human nutrition, found mainly in beverages (coffee, tea, cocoa, energy drinks, etc.). Their detection is thus of extreme importance, and many studies are devoted to this topic. During the last decade, graphene oxide (GO) and reduced graphene oxide (RGO) gained popularity as constituents of sensors (chemical, electrochemical and biosensors) for methylxanthines. The main advantages of GO and RGO with respect to graphene are the easiness and cheapness of synthesis, the notable higher solubility in polar solvents (water, among others), and the higher reactivity towards these targets (mainly due to π–π interactions); one of the main disadvantages is the lower electrical conductivity, especially when using them in electrochemical sensors. Nonetheless, their use in sensors is becoming more and more common, with the obtainment of very good results in terms of selectivity and sensitivity (up to 5.4 × 10−10 mol L−1 and 1.8 × 10−9 mol L−1 for caffeine and theophylline, respectively). Moreover, the ability of GO to protect DNA and RNA from enzymatic digestion renders it one of the best candidates for biosensors based on these nucleic acids. This is an up-to-date review of the use of GO and RGO in sensors.

Selective Chemical Enhancement via Graphene Oxide in Infrared Attenuated Total Reflection Spectroscopy

Graphene oxide (GO) as a readily prepared graphene derivative comprises negatively charged oxygenated functional groups, and a mixture of sp2 and sp3 carbon domains. In comparison with hydrophobic graphene, GO is characterized by superior water dispersibility, and may noncovalently interact with a significantly wider range of molecules. Taking advantage of GO and infrared attenuated total reflection spectroscopy (IR-ATR), an efficient strategy enabling unprecedented absorption signal amplification via chemical enhancement of various molecular species in aqueous environment was demonstrated in this study. The evolution of selectively enhanced molecular fingerprints across the entire mid-infrared spectral range was in situ monitored in real time, while retaining the characteristic molecular IR absorptions, and confirms the utility of GO as a suitable and versatile material in surface-enhanced infrared absorption spectroscopy (SEIRA) scenarios.

Effects of GO and MOF@GO on the permeation and antifouling properties of cellulose acetate ultrafiltration membrane

Cellulose acetate (CA) has been used to prepare ultrafiltration membranes because of its excellent properties, especially its biodegradability. To enhance the performance of the CA membrane, the excellent CA ultrafiltration membrane was synthesized by blending with graphene oxide (GO) and HKUST-1 (a metal–organic framework) @GO through the typical phase inversion process. The effects of the different fillers (GO and HKUST-1@GO) on the membrane properties were investigated. Firstly, the fabricated nanocomposites were analyzed through X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then, the action of the fillers on the membrane morphology, permeability, separation performance, and antifouling properties were studied. Compared with CA/GO membranes, the CA/MOF@GO membranes exhibit higher hydrophilicity and pure water flux. This is because HKUST-1 can fully exploit the structure advantages of GO and prevent the stacking of GO layers, introducing unique properties to the HKUST-1@GO composite. The CA/MOF@GO0.12 membrane has the highest water permeate flux of 183.51 L m−2 h−1 and also exhibits better antifouling performance than the CA membrane, which possesses a flux recovery ratio of 88.13% and a total fouling ratio of 40.32%. Hence, HKUST-1@GO shows potential as a filler in ultrafiltration membranes to improve their performance for water purification applications.

Manganese oxide nanoparticles impregnated graphene oxide aggregates for cadmium and copper remediation

Loading metal oxide nanoparticles (NPs) into porous granular materials with excellent hydraulic characteristics offers a promising option to break the technical barriers of direct application of NPs in scaled-up water decontamination. By taking advantage of graphene oxide (GO) mediating the formation of manganese oxide (MO) nanoparticles at the same time aggregating to form macroporous structure under highly alkaline conditions, we fabricated a novel GO-MO composite (D = ∼160 μm). The intraparticle diffusivity of Cd(II) and Cu(II) onto GO-MO was determined to be 3.17 × 10−9 and 4.67 × 10−9 cm2 s−1, respectively, similar to macroporous resin. The GO-MO showed synergistic sorption capacity for Cd(II) and Cu(II) compared to bulky MO and GO due to the high dispersion of MO NPs (<10 nm) in the aggregated GO matrix and Donnan membrane effect. The GO-MO also had strong sorption selectivity in the presence of Ca(II) and humic acid. HADDF-EDS characterization visually showed that Cu(II) and Cd(II) was selectively adsorbed to MO even in the presence of 50 times higher competing Ca(II) ions, which was quantified as ∼93% of the total adsorbed metal for both Cu(II) and Cd(II) by XPS analysis. Moreover, GO-MO was successfully employed in the column operation with effective treatment volume of ∼1650 and ∼1995 BV for simulated Cd(II)- and Cu(II)-contaminated wastewater, respectively. The exhausted GO-MO can be effectively regenerated using acid-salt binary solution with desorption rate >97%. The results from this study may offer insights to rationally design highly efficient engineered nanocomposites for water purification.

In situ reduction of graphene oxide in the poly (vinyl alcohol) matrix via microwave irradiation

Despite great recent progress, the processing of graphene oxide (GO) sheets in polymers are often one of the most challenging steps in fabricating graphene/polymer nanocomposites. The challenge is how to achieve high levels of dispersion and reduction of GO simultaneously, without any residual reducing agents in the composites. In this work, microwave irradiation is applied as a remote source to in situ reduce GO sheets embedded in the poly (vinyl alcohol) (PVA) matrix, which process maximizes the advantage of GO's solvent processability. The active response of GO to microwave irradiation allows for the uniform and selective heating of GO, leading to a minutes‐quick reduction of GO without physical damage to the polymer matrix. Significant improvements in the mechanical properties, electrical conductivities and glass transition temperatures (Tgs) of GO/PVA nanocomposites are achieved, and possible reasons for the improvements are also discussed. POLYM. COMPOS., 40:170–178, 2019. © 2017 Society of Plastics Engineers

Three-dimensionally stacked Al2O3/graphene oxide for gas barrier applications

We investigated the growth behavior of Al2O3 using atomic layer deposition (ALD) on the surface of chemical vapor deposition (CVD)-grown graphene and graphene oxide (GO). While selective ALD growth was observed on CVD-grown graphene along defective sites, smooth and continuous films were grown on GO without selective growth. Linear growth of Al2O3 on GO was observed without a nucleation region or growth selectivity. This result indicates that the ALD film growth is more suitable for GO because of the abundant and homogeneously distributed reactive sites over its basal plane. By taking advantage of GO as an ideal substrate for the ALD growth of metal oxides, highly aligned, multiple-stacked, three-dimensional Al2O3/GO structures were fabricated, which showed much better effective gas barrier characteristics (1.73 × 10−4 g/m2day) than that exhibited by pristine single Al2O3 thin films of the same thickness.