Reduced Graphene Oxide Nanosheets Research Articles

Effect of SnS2 concentrations on electrochemical properties of SnS2/RGO nanocomposites synthesized by a one-pot hydrothermal method

Reduced graphene oxide nanosheets (RGO NSs), SnS2 nanoparticles (SnS2 NPs) and SnS2/RGO nanocomposites (SnS2/RGO NCPs) with different SnS2 concentrations (0.5, 0.7 and 2.0 mmol) were synthesized by a one-pot hydrothermal method. XRD results indicated a pure hexagonal phase of SnS2 NPs and all SnS2/RGO NCPs with space group P 6/m. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) revealed nanoplates and quantum dots morphologies of SnS2 anchored on RGO NSs of SnS2/RGO NCPs (0.5 mmol). Dispersive Raman microscopy confirmed the existence of RGO NSs in all SnS2/RGO NCPs samples. Functional groups were verified by Fourier transform infrared spectroscopy (FT-IR). SnS2 content (wt%) in each SnS2/RGO NCPs was determined by thermogravimetric analysis (TGA). Chemical surface of SnS2/RGO NCPs (0.5 mmol) was investigated by X-ray photoelectron spectroscopy (XPS). Pore-size distribution and specific surface area of SnS2 NPs and all SnS2/RGO NCPs were determined using the nitrogen adsorption-desorption isotherm. Electrochemical properties all samples were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) using the three-electrode cell system in 2.0 M KOH aqueous solution. Specific capacitance (Cs) and capacity retention of all SnS2/RGO NCPs electrodes were found to be higher than that of SnS2 NPs electrode, which might be due to the synergistic effects of RGO NSs and SnS2 NPs. Interestingly, the maximum Cs value of 273.54 F g−1 at a current density of 0.3 A g−1 with a good capacity retention of 84.25% after 1000 cycle of charge-discharge test at a current density of 5 A g−1 was obtained in SnS2/RGO NCPs (0.5 mmol).

Ultrastrong Graphene Films via Long-Chain π-Bridging

Summary Converting natural graphite to high-performance graphene films is very attractive due to graphite's abundance. However, this conversion is challenging to do inexpensively and under ambient conditions. One of the major challenges is how to design the interface between adjacent graphene nanosheets to integrate high strength, high toughness, and high conductivity into graphene films. Here, we demonstrate that a long-chain π-π bonding agent can bridge reduced graphene oxide nanosheets into ultrastrong, supertough, and highly conductive graphene films. The strain dependence of Raman frequency shift and molecular dynamics simulations together reveal the strengthening and toughening mechanisms. Additionally, the long-chain π-bridging induces substantial improvement in the graphene nanosheet alignment. The tensile strength and toughness are 1,054 MPa and 36 MJ/m3, surpassing those of reported graphene films. Meanwhile, the electrical conductivity reaches 1,192 S/cm, comparable with high-temperature annealed graphene films. The bioinspired strategy opens an avenue for the assembly of nanoscale building blocks into high-performance films.

One-dimensional architecture with reduced graphene oxide supporting ultrathin MoO2 nanosheets as high performance anodes for lithium-ion batteries

Two-dimensional (2D) materials have been widely studied and used as anode materials for lithium ion batteries (LIBs) because of their high specific surface area and intrinsic mechanical flexibility which could offer numerous active sites and protect effect for LIBs. However, 2D nanosheets are easy to stack and partially lose surface area for Li-ion storage thus greatly affecting their electrochemical performance. Here, we develop a simple strategy to obtain a nanosheets-based one-dimensional structure hybrid by in situ reduction from MoO3 nanorods to MoO2 nanosheets and nanoparticles which are anchored on a 1D reduced graphene oxide skeleton (MoO2-rGO). It was demonstrated that the primary MoO2 nanosheets and nanoparticles are uniformly dispersed on the reduced graphene oxide nanosheets, which are further assembled into a 1D loosened nanostructure. The loosened nanosheets offer more accessible surface area and facilitate transport of electrons and Li-ions. Moreover, MoO2 nanoparticles effectively avoid agglomeration from nanosheets. Results show that MoO2-rGO hybrid demonstrates an enhanced cyclic life, high stability and prominent rate performance when evaluated as anode material for LIBs. The first discharge capacity can reach 1256.4 mAh g−1 and provide a highly reversible capacity of 1003.7 mA h g−1 after 100 cycles at 0.1 A g−1, which makes MoO2-rGO a promising candidate for LIBs. The excellent performance can be attributed to the unique 1D loosened structure consists of MoO2 and conducting rGO nanosheets, which facilitates fast transfer of Li-ion and electron, and the reduced graphene oxide nanosheets acting as a skeleton provide a continuous conductive network and simultaneously strengthen the structural stability.

Engineering sulfonated polyaniline molecules on reduced graphene oxide nanosheets for high-performance corrosion protective coatings

In this work, we demonstrate engineered sulfonated polyaniline (SPANI) molecules on reduced graphene oxide (rGO) for high-performance water-based corrosion protective coatings. The corrosion protective efficiency of epoxy resin (EP) coatings with 0.5 wt% as-engineered rGO increased from 44.3% to 98.0% compared with that of pure EP. Moreover, Ecorr and phase angle slightly changed with the extension of immersion period. The results suggest that the introduction of rGO anchored with engineered SPANI into EP could retard or defend permeation of the corrosive moieties from the environment, highlighting its great potential for high-performance corrosion protective applications.

Effect of RGO coating on lithium storage performance of monodispersed core–shell MoS2 superspheres

The effect of reduced graphene oxide coating on the electrochemical performance of monodispersed core–shell MoS2 spheres has been presented. The 3D nanoarchitectures constructed with 2D MoS2 and RGO nanosheets can be applied to assemble anodes with highly enhanced capacity in storing lithium. The amount of reduced graphene oxide nanosheets can dramatically affect the electrochemical properties of as-prepared 3D nanoarchitectures. Specifically, the MoS2 anode materials with ~ 7 wt% of reduced graphene oxide exhibit the highest average specific capacity of ~ 1134 mAh g−1 at 100 mA g−1, and it recovers up to 89.2% after performing discharge–charge at 2000 mA g−1. The discharge capacity of the electrode can retain ~ 88.9% of its second discharge capacity after cycling for 100 times at 200 mA g−1 and keep ~ 98.3% of its average Coulombic efficiency after the first cycle. The cells also possess high rate with specific capacity of ~ 739 mAh g−1 even at 1000 mA g−1.

Anchoring effect of the partially reduced graphene oxide doped electrospun carbon nanofibers on their electrochemical performances in vanadium flow battery

In order to improve the wettability and electrochemical activity of electrospun carbon nanofibers, the partially reduced graphene oxide doped electrospun carbon nanofibers have been successfully prepared by introducing graphene oxide into the electrospinning solution with a simple electrospinning and subsequent carbonization process. It is found that some of the partially reduced graphene oxide nanosheets with plenty of wrinkles are embedded between the nanofibers, which directly enhances the physical surface area. Despite the introduced graphene oxide is partially reduced during the carbonization process, the corresponding oxygen content is greatly increased, which results in the improved wettability and further a significant enhancement in the electrochemical surface area. It is worth noting that the electrocatalytic activity is almost unchanged, indicating the improved electrochemical response is attributed to the enhanced electrochemical surface area. Moreover, vanadium flow battery with such composites presents a remarkable improvement in the electrochemical performances such as energy efficiency and discharge capacity, further suggesting that such composites are promising high-efficient electrode materials for vanadium flow battery. Therefore, it is believed that the construction of carbon-based electrode with high electrochemical surface area through the anchoring effect of hydrophilic materials is an effective approach to obtain high-efficient electrode materials for vanadium flow battery.

Sonochemical synthesis of perovskite-type barium titanate nanoparticles decorated on reduced graphene oxide nanosheets as an effective electrode material for the rapid determination of ractopamine in meat samples

A simple and facile ultrasound based sonochemical method to incorporate Perovskite-type barium titanate (BaTiO3) nanoparticles inside the layered and reduced graphene oxide sheets (rGOs) is reported. BaTiO3@rGOs nanocomposite was characterized by FESEM, HRTEM, EDX, mapping, XRD, XPS and EIS. The results show that the decoration and also incorporation of BaTiO3 nanoparticles in the multi-layered and ultrasound reduced graphene oxide matrix. Non-enzymatic and differential pulse voltammetric sensor of ractopamine (food toxic) based on the BaTiO3@rGOs nanocomposite modified screen printed carbon electrode is developed. Compared with the original BaTiO3/SPCE and rGOs/SPCE, the BaTiO3@rGOs/SPCE displays excellent current response towards ractopamine and gives linearity in the range of 0.01–527.19 µM ractopamine in neutral phosphate buffer (pH 7.0). The BaTiO3@rGOs nanocomposite modified sensor also exhibits valuable ability of anti-interference to electroactive analytes. Furthermore, the as-prepared BaTiO3 NPs@rGOs/SPCE has been applied to the determination of ractopamine in pork and chicken samples.

Erratum: Targeted delivery of reduced graphene oxide nanosheets using multifunctional ultrasound nanobubbles for visual and enhanced photothermal therapy [Corrigendum

[This corrects the article on p. 7859 in vol. 13, PMID: 30538464.].

Tiny Basic Nickel Carbonate Arrays/Reduced Graphene Oxide Composite for High-Efficiency Supercapacitor Application

3D structure composite made of tiny basic nickel carbonate arrays on the surface of reduced graphene oxide nanosheets (G-NiCH) are prepared by the hydrothermal method. The specific surface area of the G-NiCH composites is twice that of single basic nickel carbonate, which is due to the tiny basic nickel carbonate arrays structure wherein each individual nanoneedle is about 20[Formula: see text]nm in length and 2[Formula: see text]nm in width. The G-NiCH electrodes display high-efficiency electrochemical performance with good specific capacitance (1230[Formula: see text]F[Formula: see text]g[Formula: see text]) and excellent stability (100% capacitance retention after 2000 cycles). This is attributed to the synergistic effect that reduced graphene oxide offer fast electron transmission path and basic nickel carbonate act as high effective active material.

Comparative Study on the Removal of Cationic Dyes Using Different Graphene Oxide Forms

The efficiency of graphene oxide, magnetic graphene oxide, reduced graphene oxide and magnetic reduced graphene oxide nanosheets were examined for the removal of cationic dyes including malachite green (MG), methylene blue (MB) and methyl violet (MV) from water samples. Graphite was used to synthesize graphene oxide (GO) by Hummer method and then magnetized to synthesize magnetic graphene oxide (MGO). Reduced graphene oxide (rGO) was synthesized by chemical method using sodium borohydride (NaBH4) as a reducing agent and then magnetized to synthesize magnetic reduced graphene oxide (MrGO). To characterize the synthesized nanomaterials, Fourier Transform-Infrared spectrophotometry (FT-IR), X-ray diffraction analysis (XRD), vibrating sample magnetometer (VSM) and Transmission electron microscopy (TEM) were used. Different parameters affecting the adsorption capacities including pH of sample solution, contact time and initial concentrations of cationic dyes were investigated and optimized. Based on the obtained results pH of 4, 6, 6 and 5 were considered as the optimum values for GO, MGO, rGO and MrGO adsorbents, respectively at 60 min removal time. Also, two adsorption isotherms including Langmuir and Freundlich were examined for each dye and based on the obtained results, the adsorption of the studied dyes followed by Freundlich isotherm for GO and MGO and their adsorption followed by both Freundlich and Langmuir isotherms for rGO and MrGO adsorbents (R2 ≥ 0.95). Finally, kinetic and thermodynamic adsorption of dyes onto the adsorbents were studied and interpreted.

RGO/sAC composites as electrode materials for supercapacitors to enhance electrochemical performance

A compact composite of reduced graphene oxide (RGO) and spherical activated carbon (sAC) was prepared by microwave irradiation reduction using water as the solvent after mixing RGO and sAC and is a promising electrode material for supercapacitors. The removal of the oxygen functional group in RGO and the distinct structure of compact RGO/sAC composites are confirmed by FT–IR, XRD and XPS analyses. The morphology of the composite exhibits homogeneous and thick coating with an RGO nanosheet on the surface of the sAC. This structure has high micropore volume and leads to enhanced electrochemical performance. Based on the specific capacitance from the cyclic voltammetry curves, while the physical mixing compound of RGO/sAC (PM–RGO/sAC) is only 120 F/g at a scan rate of 2 mV/s, the compact RGO/sAC compound (MI–RGO/sAC) is 166 F/g by microwave irradiation, which enhances the specific capacitance by approximately 138% compared to that of the PM–RGO/sAC. Therefore, the composite material of MI–RGO/sAC driven by microwave irradiation can facilitate fast ion transport in supercapacitors and is a good candidate for electrodes.

A flexible and highly pressure-sensitive PDMS sponge based on silver nanoparticles decorated reduced graphene oxide composite

Flexible pressure sensors have a wide range of applications in wearable electronics and human-machine interfacing. A flexible and highly pressure-sensitive sensor was fabricated with silver nanoparticles (Ag NPs) decorated-reduced graphene oxide composites (Ag/rGO) filling into the PDMS sponge. The Ag/rGO composites were synthesized by one-step chemical reduction method that Ag NPs were tightly and uniformly coated on the surface of reduced graphene oxide nanosheets. Then Ag/rGO composites filled PDMS sponge (Ag/rGO-PDMS) was prepared through a dip-drying method as pressure sensitive materials. The Ag NPs coated on the surface of graphene nanosheets improved the conductivity of the Ag/rGO composites and reduced the contact resistance of graphene nanosheets. The graphene nanosheets could enhance the flexible stability and facilitate the electron transport in Ag/rGO-PDMS. The Ag/rGO-PDMS sponge with optimized GO to Ag weight ratio showed maximum pressure sensitivity of 8.86 kPa−1 which enhanced twenty-two times compared with that of pure rGO filled PDMS sponge (0.40 kPa−1). The flexible Ag/rGO-PDMS sponge with high pressure sensitivity could be used for detection of different kinds of mechanical forces (pressing, bending and twisting) and radial artery blood pulses in real-time.

Mesoporous ZnCo2O4/rGO nanocomposites enhancing sodium storage

In this study, mesoporous ZnCo2O4/rGO nanocomposites were favorably synthesized via a simple solvothermal technique. As a prospective anode material for sodium-ion batteries, the resulting ZnCo2O4/rGO-II nanocomposite exhibited superior electrochemical sodium storage performance with predominant specific capacity, favorable cyclability and ascendant rate capability. For example, an outstanding discharge capacity of 210.5 mAh g−1 was delivered at a current density of 200 mA g−1. Notably, the nanocomposite could yield a discharge capacity of 101.7 mAh g−1 at a current density of 1000 mA g−1 after 500 loops, which certifies its superior capacity retention and predominant cycling stability. The boosted performance of the anode materials is due to the mutual synergistic effect resulting from a combination of the mesoporous ZnCo2O4 nanospheres and conducting reduced graphene oxide nanosheets.

Synthesis of Nomega-Nitro-l-arginine methyl ester modified reduced graphene oxide nanosheets and their protective action on experimental preeclampsia in mice

The purpose of this study is to synthesize Nomega-Nitro-L-arginine methyl ester (L-NAME) adsorbed reduced graphene oxide (RGO) sheets and demonstrate their protective impact on the detrimental effect detected in investigational pre-eclampsia, a prerequisite where increase in oxidative stress and decreased Nitric Oxide (NO) production were present. The synthesized graphene sheets were studies by using various characterization techniques. Later, a prerequisite similar to pre-eclampsia has been induced through chronic inhibition of NO fabrication using a 60 mg/kg/day L-NAME, orally in pregnant mice. We observed arterial pressure increase, a decrease of alive fetus toward the end of pregnancy and insulin resistance increase in pregnant L-NAME mice and no much difference was detected in pregnant L-NAME-RGO mice. We also observed an arterial pressure increase in normal L-NAME mice. In this paper, we determined a protective impact of RGO in investigational pre-eclampsia.

Synthesis and characterizations of Ag-decorated graphene oxide nanosheets and their cytotoxicity studies

In this paper, reduced graphene oxide nanosheets decorated with silver nanoparticles (AgNPs/rGO) were prepared by a wet chemical method. In this method, graphene oxide (GO), silver nitrate, and ammonia were used as a precursor. AgNPs/rGO composite was characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared transmission spectroscopy (FTIR), and transmission electron microscopy (TEM). The results show that the spherical silver nanoparticles with average size of about 6–10 nm were distributed on GO sheets. In vitro cytotoxicity of the prepared AgNPs/rGO samples was studied on neuro2A cells and found that the sample eliminates the growth of neuro2A cells up to 50% and Ag nanoparticles reduce the cytotoxicity of the GO sheets.

Reduced graphene oxide nanosheets modified with plasmonic gold-based hybrid nanostructures and with magnetite (Fe3O4) nanoparticles for cyclic voltammetric determination of arsenic(III).

The authors have fabricated reduced graphene oxide nanosheets (rGO) supported with Fe3O4 nanoparticles and Ag/Au hollow nanoshells. The material was placed on a glassy carbon electrode which is shown to enable highly sensitive determination of As(III) which is first preconcentrated from solution at a potential of -0.35V (versus Ag/AgCl) for 100s. The electrode, typically operated at a working potential as low as 0.06V, has a linear response in the 0.1 to 20ppb As(III) concentration range and a 0.01ppb detection limit. The electrochemical sensitivity is 52μAppb-1. The high sensitivity is assumed to be the result of various synergistic effects. The method was applied to ultratrace (0.1ppt) determination of As(III) in real water samples. Graphical abstract The hybrid displays a wide linear response in the 0.1 to 20ppb As(III) concentration range and a 0.01ppb detection limit. The high sensitivity is attributed to various synergistic effects. The method was applied to ultratrace determination of As(III) in real water samples.

RETRACTED ARTICLE: Graphenic nanosheets sandwiched between crystalline cakes of poly(3-hexylthiophene) via simultaneous grafting/crystallization and their applications in active photovoltaic layers

Via simultaneous grafting and crystallization of regioregular poly(3-hexylthiophene) (P3HT) chains onto the reduced graphene oxide nanosheets, the cake-like P3HT crystalline layers sandwiched the nanosheets and sandG-cakeP3HT nano-hybrids were designed. The P3HT grafts directed the P3HT free-chains to vertically assemble onto the rGO-graft-P3HT and reach a flat-on orientation. Further red-shifting and peak intensification were also detected in respective ultraviolet–visible spectra (A0−2 = 491, A0−1 = 552, and A0−0 = 602 nm) and the conductivities of sandG-cakeP3HT nanostructures ranged in 10.13–10.29 S/cm. The bandgap of sandG-cakeP3HT supramolecules [the highest occupied molecular orbital (HOMO) =−5.37 eV, the lowest unoccupied molecular orbital (LUMO) = −3.48 eV] was 1.89 eV. A huge jump in the improvement of photovoltaic characteristics was achieved by newly developed sandG-cakeP3HT nano-hybrids. The P3HT:sandG-cakeP3HT photovoltaic devices led to the characteristics of 9.81 mA/cm2 (short circuit current density), 55% (fill factor), 0.66 V (open circuit voltage) and 3.56% (efficiency). The addition of phenyl-C71-butyric acid methyl ester (PC71BM) also improved the properties to 11.48 mA/cm2, 60%, 0.67 V and 4.61%. The external quantum efficiency measurements verified the influence of developed donor–acceptor nano-hybrids on the photovoltaic characteristics. The maximum peak values of 72–74% were detected at 560 nm for P3HT:sandG-cakeP3HT:PC71BM devices.

Printed Strain Sensors Using Graphene Nanosheets Prepared by Water‐Assisted Liquid Phase Exfoliation

AbstractA novel approach to leverage the extraordinary properties of graphene for designing thin film strain sensors is demonstrated. Graphene nanosheets (GNS) are produced from graphite by a liquid phase exfoliation (LPE) method using water along with N‐methylpyrrolidinone (NMP) as cosolvents. It is found that the water‐NMP solvent system enhances the exfoliation yield and the stability of the GNS dispersion, thereby lowering the number of defects in the GNS basal plane. Both LPE‐based GNS and reduced graphene oxide (RGO) are synthesized for fabricating thin film strain sensors and for comparison purposes. Detailed micro‐Raman, X‐ray photoelectron spectroscopy, and transmission electron microscopy studies indicate that the as‐produced GNS exhibits lower defects than RGO nanosheets. The strain sensing study reveals that strain sensors fabricated using low‐defect GNS exhibit enhanced electrical and electromechanical properties, including higher electrical conductivity, lower noise floor, and more stable electromechanical response as compared to RGO‐based sensors.

High performance polyimide-based composites filled with 2D aluminum oxide coated reduced graphene oxide nanosheets

Two-dimension (2D) graphene-like nanosheets with small thickness and large lateral size attract tremendous attention in the application of high-K materials. In this paper, 2D aluminum oxide coated reduced graphene oxide nanosheet (Al2O3@rGO) were fabricated via bottom-up method in expectation of being a kind of promising dielectric filler. Polyimide (PI) based composites filled by different Al2O3@rGO contents were prepared via in-situ polymerization. The characterization results of the composites indicate that strong filler-matrix bonding contributes to improve the compatibility of Al2O3@rGO in PI. Besides, the orientation of Al2O3@rGO nanosheets in the composites is detected by SAXS and SEM. For the composites, the dielectric behaviors, thermal stabilities and mechanical properties were investigated. The results show that the composites possess high dielectric constant and low dielectric loss. Additionally, the composites have good electrical insulation properties. Furthermore, the enhancements in thermal stabilities and mechanical properties of the composites are also observed attribute to the strong interactions between PI and Al2O3@rGO. Consequently, it is hoped that the composites would be possessing potential applications in flexible dielectric materials owing to its enhanced dielectric constant, thermal stabilities and mechanical performances.

Photodecomposition and adsorption of hazardous organic pollutants by Ce-doped ZnO@Ce-doped TiO2-N/S-dual doped RGO ternary nano-composites photocatalyst for water remediation

In this research, I found that the doping of ZnO@TiO2 core−shell and reduced graphene oxide (RGO) by rare earth cerium ion (Ce4+/Ce3+) and nitrogen (N) and sulfur (S) dual heteroatom is effective way to improve the photocatalytic decomposition of hazardous organic pollutants (phenol, bisphenol and methylene blue (MB)) in the water under visible light irradiation. The 0.1 mol% Ce/ZnO@0.1 mol% Ce/TiO2-N/S/5 wt% RGO, 0.1 mol% Ce/ZnO@0.1 mol% Ce/TiO2-5 wt% RGO, 0.1 mol% Ce/TiO2-N/S/5 wt% RGO, TiO2-N/S/5 wt% RGO and0.1 mol% Ce/ZnO@0.1 mol% Ce/TiO2 ternary and binary nano-composites photocatalyst were synthesised via a simple sol–gel route. Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy (DRS), and Brunauer−Emmett−Teller (BET) analysis were used to characterize the fabricated nano-photocatalyst samples. The N/S/dual-doped RGO nano-sheets were fabrication by a facile hydrothermal route using cysteine as precursor for both N and S heteroatoms. Furthermore, cysteine can simultaneously act as a reducing agent of GO. The 0.1 mol% Ce/ZnO@0.1 mol% Ce/TiO2-N/S/5 wt% RGO exhibited high photodegradation of various hazardous organic pollutants under visible light irradiation.