Dispersion Of Reduced Graphene Oxide Research Articles

Reduced graphene oxide-wrapped ZnS-SnS2 heterojunction bimetallic hollow cubic boxes as high-magnification and long lifespan supercapacitor anode materials.

Metal sulfides have attracted extensive attention due to their excellent electrochemical performance. However, issues such as poor conductivity and severe volume expansion during charge and discharge processes affect the applications of sulfides as electrode materials. Here, a combination of coprecipitation and high-temperature sulfidation methods are employed to synthesize a ZnS-SnS2 composite with a hollow cubic structure, which is further composited with reduced graphene oxide (RGO) to form ZnS-SnS2 hollow cubic boxes encapsulated in a conductive framework of reduced graphene oxide (RGO) (denoted as ZnS-SnS2@RGO) for electrode materials. The hollow structure effectively alleviates the pulverization of ZnS-SnS2@RGO caused by volume expansion during charge and discharge processes. The heterogeneous structure formed by ZnS and SnS2 effectively reduces the electron transfer resistance of the material. The use of RGO wrapping enhances the conductivity of the ZnS-SnS2 hollow cubic boxes, and RGO's dispersion effect on the ZnS-SnS2 cubes improves particle agglomeration, further mitigating volume expansion of the material. These results indicate the outstanding electrochemical performance of heterostructural ZnS-SnS2 hollow cubic electrodes encapsulated with reduced graphene oxide as a conductive framework. The fabrication process provides a novel approach for addressing volume expansion and poor conductivity issues in other pseudocapacitive materials.

An experimental and simulation study of RGO effects on mechanical behaviour of structural adhesive and lap shear joints strength

The research investigates the effects of adding Reduced Graphene Oxide (RGO) at various weight fractions (0.25, 0.5, 0.75 and 1 wt%) on mechanical properties of high strength structural adhesive Araldite©️ 2011 and lap shear strength of adhesive joints. For uniform dispersion of RGO across adhesive, an extensive solution mixing technique was carefully carried out for the preparation of RGO/Epoxy combinations. Two types of lap joints: single lap joint (SLJ) and double lap strap joint (DLSJ) were fabricated. The joints were fabricated using Al 5083 as adherends. The adherends were treated with phosphoric acid anodization (PAA) before joining. A comparison of the strength properties was made after tensile testing of the adhesive specimens and lap joints. In the case of adhesive samples, an increase in mechanical properties was observed at lower concentrations. A maximum increase of 9.5% in the tensile strength and 128% in toughness characteristics was observed with the addition of 0.25 wt% RGO. A maximum improvement of 24% for SLJ and 25% for DLSJ was observed at the same filler percentage. Chemical analysis was conducted using Fourier-Transform Infrared Spectroscopy (FTIR), while dispersion analysis was carried out using Ultraviolet–Visible Spectroscopy (UV-VIS-Nir). Digital and Scanning Electron Microscopy (SEM) techniques were utilised in close examination of the fracture surface at high magnification. A finite element analysis based on cohesive zone modelling (CZM) was performed to predict the failure load characteristics of lap joints. Finally, a comparison of strength and fracture behaviour of RGO with GNPs and MWCNTs was critically discused.

Highly stretchable strain sensors based on Marangoni self-assemblies of graphene and its hybrids with other 2D materials

Graphene and other two-dimensional materials (2DMs) have been shown to be promising candidates for the development of flexible and highly-sensitive strain sensors. However, the successful implementation of 2DMs in practical applications is slowed down by complex processing and still low sensitivity. Here, we report on a novel development of strain sensors based on Marangoni self-assemblies of graphene and of its hybrids with other 2DMs that can both withstand very large deformation and exhibit highly sensitive piezoresistive behaviour. By exploiting the Marangoni effect, reference films of self-assembled reduced graphene oxide (RGO) are first optimized, and the electromechanical behaviour has been assessed after deposition onto different elastomers demonstrating the potential of producing strain sensors suitable for different fields of application. Hybrid networks have been then prepared by adding hexagonal boron nitride (hBN) and fluorinated graphene (FGr) to the RGO dispersion. The hybrid integration of 2D materials is demonstrated to become a potential solution to increase substantially the sensitivity of the produced resistive strain sensors without compromising the mechanical integrity of the film. In fact, for large quasi-static deformations, a range of gauge factor values up to 2000 were demonstrated, while retaining a stable performance under cyclic deformations.

Conductive Micropatterns Containing Photoinduced In Situ Reduced Graphene Oxide Prepared by Ultraviolet Photolithography

AbstractHerein, one kind of conductive patterned film with high resolution comprised of reduced graphene oxide (RGO) is prepared by the ultraviolet photolithography technique. RGO working as a conductive filler greatly improves the conductivity of films and is formed through the photoinduced in situ reduction of graphene oxide (GO) added to the photoresist of the patterned films. This photoreduction method is very eco‐friendly and efficient with a reduction time of <20 min. Furthermore, the effect of various factors on the conductivity of the films is investigated in detail, and appropriate conditions are selected to optimize the photoreduction of GO to obtain the best conductivity. The maximum conductivity of the fabricated films is 9.90 S cm−1, and micropatterns can reach 0.98 S cm−1. While photoinduced in situ reduction facilitates the dispersion of RGO in the photoresist, the photoresist also serves as an encapsulant to avoid the contact of RGO with oxygen and moisture in the air, which enables the conductive films and micropatterns to have excellent storage stability and suitability for various substrates, especially flexible substrates. Hence, a feasible strategy is offered for the preparation of conductive films and micropatterns with promising prospects in the field of flexible electronic devices.

Effects of TiO2-Modified RGO Composites on the Mechanical and Durability Properties of Ordinary Portland Cement Mortars

Various applications of graphene-based materials in construction are an alternative to improve the properties of ordinary Portland cement (OPC)-based binders. This paper used a titanium dioxide in situ intercalation method to enhance the dispersibility of reduced graphene oxide (RGO) and then explored the effects of the incorporation of the obtained TiO2–RGO composite and RGO on the mechanical and durability-related properties of the OPC-based binders. Experimental results showed that TiO2 was successfully intercalated into the RGO layers and could improve the dispersion of RGO in water or synthesized OPC pore solution significantly, probably due to the greater spacing between each RGO layer. Besides, a proper amount of TiO2-modified RGO composite (0.03 wt % in this study) could elevate the mechanical strengths of OPC mortars, evidenced by a large increment of 24.78% and up to 34.94% in the compressive strength and flexural strength, respectively. The TiO2–RGO composite led to higher flexural-to-compressive strength ratios with the given dosages (0.01–0.05 wt %), implying a higher fractural toughness. Moreover, the resistance of the enhanced OPC-based mortars toward chloride attacks and freeze–thaw cycles was significantly improved. Based on the microstructural analyses including scanning electron microscopy and X-ray diffraction results, it is found that the modified RGO could to some extent promote the hydration of OPC and densify the overall microstructure of bulk specimens, leading to enhanced mechanical and durability properties. Compared to normal RGO, the TiO2–RGO composite was more effective in enhancing the properties of OPC mortars, due in large part to its better dispersion state.

Effect of reduction time of functionalized graphene oxide on the morphology and properties of epoxy composite foams

In this study, N-aminoethylpiperazine (AEP)-functionalized and reduced graphene oxide (RGO) with different structures and properties was prepared by simply tuning the reduction time and then its effect on the rheological, curing and foaming behavior of epoxy resin was carefully investigated using the environment-friendly carbamate as a chemical foaming agent. As the reduction time of RGO increased, the reduction degree of RGO first increased and then levelled off but the grafted AEP was little affected by the reduction time. The addition of RGO undergoing long reduction time improved the viscoelasticity of epoxy/reduced graphene oxide (EP/RGO) composites but weakened the interfacial compatibility of RGO and EP. With increasing the reduction time of RGO, the cell size of EP/RGO composite foams decreased and the cell density increased. However, as compared with pure EP foam, the composite foams containing RGO with lower reduction degree had a larger cell size and a lower density. These results were attributed to the complicated effect of RGO, which not only acted as the heterogeneous nucleating and foaming agent but also affected the viscoelasticity of composites. In addition, as the reduction time of RGO increased, the initial thermal decomposition temperature, storage modulus at room temperature, electrical conductivity, thermal conductivity, and compressive properties of EP/RGO composite foams increased while the glass transition temperature remained unchanged. These results were related not only to the intrinsic properties and dispersion of RGO, but also to the density and cell morphology of the composite foams.

Redispersible Reduced Graphene Oxide Prepared in a Gradient Solvent System.

We designed a gradient solvent strategy for the reduction of graphene oxide, matching the hydrophilic properties of graphene oxide (GO) and reduced graphene oxide (RGO), respectively. A third solvent was added dropwise to regulate the hydrophilic variation of the continuous gradient system which maintained the whole reduction process without aggregation, and the obtained RGO dispersions could maintain stability for a long time. The separated RGO solid powder can be directly ultrasonically redispersed in N-methyl-pyrrolidone (NMP) with an average particle size as low as 200 nm. Furthermore, RGO with a high C/O ratio of 13.75 was prepared on the basis of the gradient solvent system. Using different structures of dispersants and polymers as representatives, we employed successive solvent rinsing, thermal solvent extraction, and thermal treatment to study adsorption and desorption. It was found that the above measures differed significantly in the removal of surface sorbates. The selected fatty alcohol polyoxyethylene ether (AEO) series achieved a good balance between the system dispersion and surface adsorbate removal. The conductivity was originally 5236 S m−1, and it increased from 9024 to 18,000 S m−1 after thermal treatment at 300 and 500 °C, respectively.

Synthesis of lysozyme-reduced graphene oxide films for biosensor applications

Graphene-based materials present a high surface area and can present several structural defects or heteroatoms depending on the fabrication method. Such properties facilitate the graphene interaction with biomolecules leading to high electrochemical activity. In this context, we synthesize a high-quality dispersed reduced graphene oxide using Lysozyme as a dispersant (Ly-RGO). In this study, we have investigated the graphite oxidation-reduction fabrication process using X-ray Photoelectron Spectroscopy, X-ray Diffraction, and Raman Spectroscopy. We have used the Ly-RGO to fabricate an electrode on an electrochemical cell in which voltammograms show significant transduction of electrical signals. Finally, cyclic voltammetry and chronoamperometry measurements were performed with human saliva and SARS-CoV-2 RNA samples, to calibrate our biosensor. The results indicate that Ly-RGO has great potential in biosensor devices.

A simple approach to obtaining enhanced mechanical properties of graphene/copper composites with heterogeneous grain structures

Strengthening metal matrix composites by grain refinement and high content of reinforcement usually compromises a dramatic sacrifice of ductility. Here multimodal powder metallurgy is developed to construct heterogeneous grain structures in reduced graphene oxide (RGO) reinforced Cu matrix composites through high temperature oxidation and high energy ball milling for the electrolytic Cu powder followed by spark plasma sintering (SPS) and hot rolling. This process involves the formation of the combined structure of RGO covered with Cu nanoparticles through thermal reduction, which is critical to ensuring the nano-level dispersion of RGO in metal matrix and strong interfacial bonding. Those composites exhibit both high normalized yield stress of up to 3.4 and high uniform tensile strain of 21.8%. The results indicate that the improved strength-ductility synergy may be attributed to the synergistic effects of the RGO and heterogeneous grain structures. This approach could realize macroscopic mixing of powders and nano-level dispersion of reinforcement to manufacture metal matrix composites with heterogeneous grain structures in large-scale productivity, and will help in developing new microstructures for high overall performance.

Influence of aggregation and dispersion of minium nanoparticles decorated reduced graphene oxide platelets and their super-capacitive performances

This paper presents the synthesis, characterization, and fabrication of a prototype supercapacitor employing lead oxide nanoparticles (Pb3O4 Nps) dispersed reduced graphene oxide (rGO) nanocomposite as electrode material. Novel minium Pb3O4 Nps and the rGO platelets are synthesized using the precipitation method and modified microwave treatment. The various weight percentages of Pb3O4 Nps (1 wt%, 3 wt%, & 5 wt%) are blended with rGO using ultrasonication process followed by stirring process. The prepared nanomaterials are characterized to predict diffraction patterns, molecular vibrations, surface morphology, and elemental composition of Pb3O4 Nps, rGO, and Pb3O4-rGO nanocomposites. The Pb3O4-rGO nanocomposites are coated on the brass substrate and the charge storing characteristics of the electrode systems are evaluated using an electrochemical workstation which displays a remarkable specific capacitance value of 377F/g for Pb3O4-rGO nanocomposite prepared using 3 wt% Pb3O4 Nps coated electrode system at the scan rate of 5 mV/s and displays high retention stability of 95% after 2500 cycles. A prototype is fabricated in a pilot-scale study, where its charge-discharge behavior is demonstrated using a 9 V battery. After charging, a green light-emitting diode is activated for around 11 min while connecting 7 devices in series.

Fabrication Tough and Electrically Conductive Graphene-Based Nanocomposite Gels with Self-Oscillating Performance

Stimulus-responsive polymer gel materials were studied and applied widely in many fields in recent years. However, the poor electrically conductive property and even with poor toughness largely limit their extensive applications in more expanded fields. Herein, we report a novel kind of self-oscillating gels poly(acrylamide-co-acrylic acid-co-Fe(phen)3)/reduced graphene oxide (poly(AM-co-AC-co-Fe(phen)3)/RGO) with excellent electrical conductivity, and compressive strength via an in-situ polymerization accompanied by an ultrasonic assisted method. The dispersed reduced graphene oxide (RGO) improved the conductive and mechanical properties of the prepared materials remarkably. The conductivity of gel reached to 16.88 S·m−1 with the content of 0.34 wt% RGO and the maximum fracture pressure was 4.1 MPa, which is as high as human cartilage. Besides, the prepared gels exhibited the self-oscillating behavior in the Belousov-Zhabotinsky (BZ) solution free of catalyst. Therefore, the prepared materials have potential applications as artificial cartilage and soft electron instrument.

Microstructure evolution and texture tailoring of reduced graphene oxide reinforced Zn scaffold

Zinc (Zn) possesses desirable degradability and favorable biocompatibility, thus being recognized as a promising bone implant material. Nevertheless, the insufficient mechanical performance limits its further clinical application. In this study, reduced graphene oxide (RGO) was used as reinforcement in Zn scaffold fabricated via laser additive manufacturing. Results showed that the homogeneously dispersed RGO simultaneously enhanced the strength and ductility of Zn scaffold. On one hand, the enhanced strength was ascribed to (i) the grain refinement caused by the pinning effect of RGO, (ii) the efficient load shift due to the huge specific surface area of RGO and the favorable interface bonding between RGO and Zn matrix, and (iii) the Orowan strengthening by the homogeneously distributed RGO. On the other hand, the improved ductility was owing to the RGO-induced random orientation of grain with texture index reducing from 20.5 to 7.3, which activated more slip systems and provided more space to accommodate dislocation. Furthermore, the cell test confirmed that RGO promoted cell growth and differentiation. This study demonstrated the great potential of RGO in tailoring the mechanical performance and cell behavior of Zn scaffold for bone repair.

Preparation of a new ionic liquid from cococnut oil for friction-reducing additive for lubricant

A new ionic liquid triethylammonium carboxylate [(C2H5)3NH][RCOO] (where R is fatty acid groups of coconut oil) was synthesized from fatty acid of coconut oil and triethyl amine. Graphene oxide (GO) was synthesized from graphite via modified Hummers method then was reduced to form reduced graphene oxide. The products were characterized and confirmed by FT-IR, XRD and NMR analysis. Friction-reducing additives was prepared from by dispersed reduced graphene oxide in [(C2H5)3NH][RCOO] (0.1%). Friction-reducing properties of materials were measured by GOST P56946-2016 (equivalent to ISO 13500:2008). The results show that using graphene and liquid triethylammonium hydrogen carboxylate lead to increase in the friction-reducing property of based oil in drilling fluid and mixture of them showed highest capacity of increasing the friction-reducing property of drilling fluid.

Fabrication of RGO/Cu composites based on electrostatic adsorption

To address the issues of reduced graphene oxide (RGO) dispersion in copper (Cu) matrix and interface bonding between RGO and Cu, an electrostatic adsorption method with interface transition phase design was employed to prepare the RGO/Cu based composites. Cu-Ti alloy powder was employed to improve the combination by forming carbides at the RGO-Cu interface. It was noted that the mechanical property of 0.3wt.%RGO/Cu-Ti composite was increased by 60% compared with that of the matrix. Strengthening mechanism analysis suggested that the enhancement of the mechanical property was ascribed to the load transfer and second phase strengthening which were from the improved dispersion of RGO and the in-situ formed titanium carbide phase.

Production and characterization of graphene/PVC biocomposite from seashell wastes

Sea shell waste are rich resources which contain calcium and organic materials which could be used as reinforcement in biocomposites due to their abundance and inexpensive. Reduced graphene oxide (RGO) is widely used as bio-filler for composites because of its ease synthesis, large surface area and antibacterial property. Therefore, in this work, PVC (polyvinyl chloride) biocomposites were prepared by reinforcing grinded seashell wastes (SS) into PVC matrix in the presence of RGO as a bio-filler. The biocomposites were produced by colloidal blending method. The structural properties of the biocomposites as a function of SS content were investigated. The biocomposites containing 5, 10, 15 and 20 wt% of SS and 0.1 wt% of RGO filled were fabricated. Compositions (% oxide) of the SS were characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), FTIR spectral analysis, Scanning electron microscopy (SEM) images and EDS mapping analysis. All the analysis results showed that SS distribution in the matrix was better at high reinforcement contents (15 and 20 wt%) compared to low contents (5 and 10% by weight). Since better dispersion of RGO and better interfacial interactions between SS and PVC are important factors in enhancing the properties of biocomposites, this study showed that SS and RGO could be effective, green and potentially cost-efficient alternatives to bio-reinforcement and bio-filler materials.

Study of Reduced Graphene Oxide Dispersions via Electrical Impedance Spectroscopy

The aim of the present work is to study aqueous reduced graphene oxide (rGO) dispersions through the application of Electrical Impedance Spectroscopy. The first step of the production of rGO/cement composites is the production of such dispersions. Six rGO dispersions were produced corresponding to different concentrations of the binder. Ultrasonic energy was applied in all dispersions and their electrical properties are measured through the application of Electrical Impedance Spectroscopy during ultrasonication. The experimental results showed that the appropriate rGO concentration was at 0.15 wt% of the binder, as the dispersion was dense enough for the production of conductive networks, and at sonication energy of 60 kJ, as significant decrease of electrical impedance was noticed.

Enhancement of ultrafast nonlinear optical response of zinc selenide nanoparticle decorated reduced graphene oxide sheets

The synergistic effect of zinc selenide (ZnSe) nanoparticle functionalized into reduced graphene oxide (RGO) sheets on nonlinear optical (NLO) properties has been investigated by single beam z-scan technique. Comprehensive measurements on nonlinear absorption (NLA) as well as nonlinear refraction (NLR) have been performed on RGO, ZnSe, and RGO-ZnSe composites at 630 nm in the femtosecond regime. Both NLA and NLR of RGO-ZnSe show an enhancement in NLO properties compared to pure RGO and ZnSe in an intensity range of 37GW/cm2 to 130GW/cm2. The enhanced optical nonlinearity of RGO-ZnSe may have been caused due to strong interlayer coupling between RGO and ZnSe, as well as the availability of a large number of NLA states in the composite. The interlayer coupling between ZnSe nanoparticles and RGO sheets has been confirmed by transmission electron microscopy, UV-Visible, and photoluminescence spectroscopy. At low input pulse intensity (∼37GW/cm2), saturation absorption dominates, whereas NLA becomes prominent in the higher intensity regime (55GW/cm2–130GW/cm2) for RGO and ZnSe. NLA is the dominant phenomenon for RGO-ZnSe in the whole experimental intensity range. Moreover, it is observed that the dispersion of RGO, ZnSe, and RGO-ZnSe in dimethylformamide exhibits positive NLR. This study indicates an enhancement in nonlinear optical response of the RGO-semiconductor composite, which is very promising for graphene based photonic device applications.

Strategically designed reduced graphene oxide based magnetic responsive nanocatalysts for the attenuation of recalcitrant pollutants

The present work attempts to capture the augmentation in the catalytic activity of ferrite (MFe2O4) nanoparticles by employing reduced graphene oxide (RGO) as its solid support that not only provides space for dispersion but also increases the catalytically active sites of nanoferrites. MFe2O4/xRGO (M = Co, Ni and x = 0, 10, 20, 30, 40 wt% GO) were prepared via facile hydrothermal method and their physical characteristics were probed by FT-IR, XRD, FE-SEM, HR-TEM, VSM and BET analysis. Furthermore, the fabricated samples were explored as versatile catalysts for the remediation of hazardous environmental pollutants via oxidation of a cationic dye, an anionic dye and an antibiotic; and reduction of 2-, 3- and 4-nitrophenol. The catalytic behavior of MFe2O4/xRGO was found to be dependent on presence of RGO as solid support as well as on the amount of GO added. The synergistic interaction between dispersed ferrite nanoparticles and RGO sheet was the reason behind the superior catalytic activity of RGO supported nanoferrites in comparison with pure nanoferrites, whereas the increase in specific surface area accounted for augmented activity with increased GO content. High reaction rates were observed even in the absence of light irradiation using MFe2O4/RGO nanocomposites for oxidation reactions. However, for the reduction of nitrophenols, the introduction of RGO resulted in the transformation of inactive CoFe2O4 into highly active catalysts. Also, the usage of just 2 mol% of RGO supported nanoferrites gave astonishing reduction rates. Moreover, the nanocomposites manifested excellent recyclability furthering the humanitarian cause to remove environmental pollutants.

Synthesis and characterisation of a ternary composite of polyaniline, reduced graphene-oxide and chitosan with reduced optical band gap and stable aqueous dispersibility

A ternary composite comprising of p-toluene sulfonic acid doped polyaniline (PANI), chitosan and reduced graphene oxide (RGO) with stable aqueous dispersibility has been synthesised via oxidative polymerisation of aniline in chitosan/RGO dispersion. For comparison; PANI, PANI/chitosan and PANI/RGO composites were also synthesised using the same procedure. FTIR, Raman, XPS, XRD and UV-VIS confirmed the successful synthesis of the PANI and the composites. The aqueous dispersions of the PANI/chitosan and the ternary composites were found to be stable even after more than four months. The stability of the dispersion was attributed to the polycationic nature of the chitosan. The thermogravimetric analysis (TGA) shows an improved thermal stability for the ternary composite compared to PANI, PANI/chitosan and PANI/RGO composites up to about 160 °C. In addition, the electrical conductivity of the ternary composite is around 33 and 2.6 times greater than that of PANI/chitosan composite and PANI, respectively. Interestingly, the analysis of the band gap shows the lowest value of optical band gap of 2.25 eV for the ternary composite compared to PANI, PANI/chitosan and PANI/RGO with 2.50 eV, 2.60 eV and 2.44 eV, respectively. The reduced band gap for the ternary composite might be attributed to the formation of conductive networks throughout the chitosan matrix due to uniform dispersion of RGO in the chitosan matrices as well as the possible grafting of PANI onto chitosan backbone. These observed properties indicate the potential utilisation of the ternary composite in optical, electrical, optoelectronic and many other industrial applications.

Electrochemical exfoliation of graphite in nanofibrillated kenaf cellulose (NFC)/surfactant mixture for the development of conductive paper

The effect of incorporating common dodecyl anionic and cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), dodecylethyldimethylammonium bromide (DDAB), and sodium dodecylsulfate (SDS) in nanocomposites of reduced graphene oxide and nanocellulose are described. The stabilization and electrical properties of the nanocomoposites of reduced graphene oxide (RGO) and nanofibrillated kenaf cellulose (NFC) were characterized using four-point probe electrical conductivity measurements. Raman spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy were used to investigate dispersion morphology and the quality of RGO inside the NFC matrices. Small-angle neutron scattering (SANS) was used to study the aggregation behavior of the aqueous surfactant systems and RGO dispersions. The cationic surfactant DTAB proved to be the best choice for stabilization of RGO in NFC, giving enhanced electrical conductivity five orders of magnitude higher than the neat NFC. The results highlight the effects of hydrophilic surfactant moieties on the structure, stability and properties of RGO/NFC composites.