Reduced Graphene Oxide Films Research Articles

A Two-Step Method for the Preparation of Highly Conductive Graphene Film and Its Gas-Sensing Property

In this research, a highly conductive graphene film was synthesized through the chemical reduction of graphene oxide (RGO) nanosheets followed by thermal treatment at 1100℃ (RGO-1100℃) under H2 ambient. The as-prepared graphene films were characterized by using X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, X-ray diffractions, raman spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy and by electrical conductivity measurements. The results showed that the thermal treatment efficiently removed residual oxygen-containing functional groups on the surface of the RGO sheets and simultaneously restored the sp2 carbon networks in the graphene sheets. As a result, the electrical conductivity of RGO-1100℃ (~210 S/cm) film was greatly improved compared with that of RGO (~24 S/cm) and graphene oxide (4.2 × 10–4 S/m) films. In addition, the NO2 gas sensing characteristics of the as-prepared RGO films were studied. The results indicated that RGO films were highly responsive to NO2 at temperature of 200℃.

Effect of microwave irradiation on reduction of graphene oxide films

In this study, the effect of microwave irradiation on reduction of graphene oxide films was investigated.

Synergistic effects of a novel free-standing reduced graphene oxide film and surface coating fibronectin on morphology, adhesion and proliferation of mesenchymal stem cells.

Graphene films have broad use in engineering, energy and biomedical applications. The cost-effective, eco-friendly and easy to scale-up fabrication methods of graphene films are always highly desired. In this work, we develop a novel fabrication method of free-standing reduced graphene oxide (RGO) films by vacuum filtration of graphene oxide aqueous solution through a nanofiber membrane in combination with chemical reduction. Instead of the smooth surface, the generated RGO films have nanoscale patterns transferred from the nanofiber membrane and controlled in a large range by varying the parameters of the electrospinning process. The cellular culture results of the human marrow mesenchymal stem cells (hMSCs) show that the fibronectin modified RGO films could exhibit excellent biocompatibility, which could be attributed to the synergistic effects of the RGO films including both surface morphology and fibronectin modification. The novel fabrication method greatly enhances the fabrication capability and the potential of graphene films for application in cell culture, tissue engineering as well as in other engineering and biomedical applications.

还原石墨烯氧化物-银纳米线柔性复合电极的制备与性能研究

Flexible electrodes with high conductivity and transparence are still great challenges in the fabrication of stretchable optoelectronic devices. In this experiment,we demonstrated a flexible hybrid electrode based on reduced graphene oxide( RGO) and silver nanowires( Ag NW). The RGO was prepared by thermal reduction and hydrazine reduction of graphene oxide to partially remove the oxygen-containing groups and to restore its electrical properties. We employed Ag NW to restore the defects in RGO films,such as grain boundaries and wrinkles,to improve the conductivity of the electrodes. By optimizing the processing conditions,the flexible hybrid electrode exhibited excellent optical and electrical characteristics as well as mechanical flexibility. The optical transmittance and sheet resistance of the hybrid electrode were 62% at 550 nm and 420 Ω / □. The RGO /Ag NW hybrid electrode shows the potential for a wide range of flexible and stretchable optoelectronic device applications.

TiO2 nanotube arrays loaded with reduced graphene oxide films: facile hybridization and promising photocatalytic application

A facile combination of electrodeposition and carbonation techniques was adopted to deposit reduced graphene oxide nanaosheets on TiO2 nanotube arrays. The RGO-TiO2 NTAs demonstrated significantly enhanced photocatalytic activity compared to pristine TiO2 NTAs and annealed TiO2 NTAs.

Electrical and Magnetic Properties of Graphene Films with Ni Nanoparticles

Electrical properties and magnetic properties of graphene oxide and reduced graphene oxide films with addition of Ni nanoparticles were investigated. It is found that reduction of GO by Hydrazine hydrate (HH) and subsequent mixing with Ni NPs yields a higher current (10-5A) compared to the samples where GO is first mixed with Ni NPs and further reduced (10-6A). At the same time, GO sample prepared by addition of Ni NPs to GO with subsequent reduction by HH presents the largest hysteresis with Mr as high as 11.8emu/g. Moreover, mixing of Ni NPs with HH before addition to GO or addition of Ni NPs to already reduced GO yields smaller values of the magnetization. Thus, the optimal procedure to obtain the magnetic response requested for particular application can be chosen.

Rapid production of a bulk of porous mesh reduced graphene oxide films using a naked flame

A simple, rapid, and non-polluting method to produce porous mesh reduced graphene oxide (rGO) films using a naked flame.

Solution-processable reduced graphene oxide films as broadband terahertz wave impedance matching layers

The potential of solution-processable reduced graphene oxide (rGO) films as wave impedance matching layers has been examined in a broad terahertz (THz) spectral bandwidth.

Photoelectric properties of reduced-graphene-oxide film and its photovoltaic application

An efficiency of 3.36% has been achieved for the graphene/silicon solar cell based on low-cost reduced graphene oxide film.

Assembly of gold nanoparticles on graphene film via electroless deposition: spontaneous reduction of Au3+ ions by graphene film

Electrochemically reduced graphene oxide film catalyzed electroless deposition of gold nanoparticles.

Porous conducting polymer and reduced graphene oxide: preparation, characterization and electrochemical performance

We demonstrated direct deposition a porous conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) nanostructure on reduced graphene oxide (RGO) as high performance electrochemical electrode. The large area RGO film was constructed on substrate through a Langmuir–Blodgett deposition of graphene oxide and a following reductive treatment. The porous PEDOT nanostructure was successively constructed on RGO through an in situ solution polymerization and simple thermal treatment. This porous PEDOT/RGO nanocomposites contained large and highly opened surface area with superior electrochemical activity. A specific capacitance as high as 267 F/g at a current density of 0.5 A/g was achieved. The compared conductive performance between RGO and porous PEDOT resulted in better EIS performance of composite electrode. The stable covering of porous PEDOT on RGO also improved the capacitance retention performance of PEDOT, and the nanocomposites showed excellent capacitance retention rate after 4,000 charge/discharge cycles. The research data revealed that high specific capacitance and good cycling stability can be achieved either by coupling the advantages of carbon materials and conducting polymer.

Annealing induced electrical conduction and band gap variation in thermally reduced graphene oxide films with different sp2/sp3 fraction

Temperature dependent electrical conductivity of as prepared and thermally reduced graphene oxide (GO) thin films was measured in the range 300–520K. As prepared GO films show very low conductivity ∼6.8×10−6S/cm at 300K, which increases slowly till 370K. A sharp increase in conductivity is observed in the temperature range 370–440K, beyond which conductivity is thermally activated with activation energy 0.26eV. Reduced GO films show an increase in conductivity at 300K with increase in reduction temperature. GO films reduced at 400°C exhibit high conductivity ∼40S/cm at 300K, with very low activation energy 0.05eV in the measured temperature range 300–520K. The increase in conductivity after thermal reduction is due to an increase in the ratio sp2/sp3 bonded carbon atoms. The band gap of as prepared GO is 3.20eV and it is decreased by approximately 0.4eV in the case of thermally reduced GO at 400°C in comparison to as prepared GO.

Characterisation of reduced graphene oxide: Effects of reduction variables on electrical conductivity

Abstract Graphene is a useful material because of its excellent electronic and physical properties. Graphene and its derivatives can be used as functional reinforcements in polymers for applications, such as sensors, flexible devices, packaging, and functional nanocomposites. This article focuses on the synthesis, reduction using three different reductants (hydrobromic acid, hydrazine hydrate and hydroiodic acid) and characterisation (using Raman spectroscopy X-ray diffraction and X-ray photoelectron spectroscopy) of reduced graphene oxide in order to systematically maximise its electrical conductivity and identify a structure with physical properties which possesses higher electrical conductivity. Results for reduced graphene oxide film that has been reduced with hydroiodic acid show an electrical conductivity of 103.3 S cm−1 with better flexibility compared to rGOs reduced by hydrobromic acid and hydrazine hydrate.

Investigation of conductivity and catalytic ability at an electrochemically reduced graphene oxide film modified electrode

In this study, we obtained electrochemically reduced graphene oxide (ERGO) film via giving an appropriate negative potential to graphene oxide film on a glassy carbon electrode. The irreversible electrochemical reduction process and the enhancement of conductivity were ascribed to the decrease of oxygen groups of graphene oxide. With reduction potential becoming negatively, the resistance of ERGO declined obviously and the electrocatalytic ability of ERGO film were substantially improved toward probe molecules such as ascorbic acid and K3[Fe(CN)6]. Acid solution contributed to the reduction of graphene oxide and hydrogen ions participated in the electrochemical process. In NaOH solution, two cathodic peaks appeared at −1.40 V and −1.76 V, respectively. It is applicable to obtain ERGO film based on the favorable factors and details. This method is green and fast, and will not result in contamination of the reduced material. In addition, this approach shows promising application in electrochemical sensor field.

Effect of reducing system on capacitive behavior of reduced graphene oxide film: Application for supercapacitor

To determine the best chemical reduction of graphene oxide film with hydriodic acid that gives maximum energy and power density, we studied the effect of two reducing systems, hydriodic acid/water and hydriodic acid/acetic acid, on the morphology and electrochemical features of reduced graphene oxide film. Using acetic acid as solvent results in high electrical conductivity (5195Sm−1), excellent specific capacitance (384Fg−1) and good cyclic stability (about 98% of its initial response after 4000 cycles). Using water as a solvent, results in an ideal capacitive behavior and excellent cyclic stability (about 6% increase of its initial response after 2100 cycles).

Mid-infrared response of reduced graphene oxide and its high-temperature coefficient of resistance

Much effort has been made to study the formation mechanisms of photocurrents in graphene and reduced graphene oxide films under visible and near-infrared light irradiation. A built-in field and photo-thermal electrons have been applied to explain the experiments. However, much less attention has been paid to clarifying the mid-infrared response of reduced graphene oxide films at room temperature. Thus, mid-infrared photoresponse and annealing temperature-dependent resistance experiments were carried out on reduced graphene oxide films. A maximum photocurrent of 75 μA was observed at room temperature, which was dominated by the bolometer effect, where the resistance of the films decreased as the temperature increased after they had absorbed light. The electrons localized in the defect states and the residual oxygen groups were thermally excited into the conduction band, forming a photocurrent. In addition, a temperature increase of 2 °C for the films after light irradiation for 2 minutes was observed using absorption power calculations. This work details a way to use reduced graphene oxide films that contain appropriate defects and residual oxygen groups as bolometer-sensitive materials in the mid-infrared range.

Shewanella-mediated Synthesis of Reduced Graphene Oxide Film for Enhanced Extracellular Electron Transfer†

A novel route was developed to prepare reduced graphene oxide(rGO) films through reduction of graphene oxide(GO) by Shewanella loihica PV-4(S. loihica PV-4) in a single-chamber,three-electrode system. Molecular structures of GO and rGO were characterized by X-ray diffraction and Raman spectroscopy.The results demonstrated that GO film was effectively reduced to rGO by S. loihica PV-4. The obtained rGO film was used as a work electrode to improve the extracllular electron transfer(EET) of S. loihica PV-4. Compared to ITO electrode,the anode current of rGO electrode with a film thickness of 111 nm increased by 13%,and the electric quantity increased by 90%. The Shewanella-mediated reducing method may offer a simple and mild route to prepare electrode material for high performance microbial fuel cell.

Self-assembly of a thin highly reduced graphene oxide film and its high electrocatalytic activity

A thin highly reduced graphene oxide (rGO) film was self-assembled at the dimethyl formamide (DMF)–air interface through evaporation-induced water-assisted thin film formation at the pentane–DMF interface, followed by complete evaporation of pentane. The thin film was transferred onto various solid substrates for film characterization and electrochemical sensing. UV-visible spectrometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemistry techniques were used to characterize the film. An rGO film showing 82.8% of the transmittance at 550 nm corresponds to a few layers of rGO nanosheets. The rGO nanosheets cross-stack with each other, lying approximately in the plane of the film. An rGO film collected on a glassy carbon (GC) electrode exhibited improved electrical conductivity compared to GC, with the electrode charge-transfer resistance (Rct) reduced from 31 Ω to 22 Ω. The as-formed rGO/GC electrode was mechanically very stable, exhibiting significantly enhanced electrocatalytic activity to H2O2 and dopamine. Multiple layers of the rGO films on the GC electrode showed even stronger electrocatalytic activity to dopamine than that of the single rGO film layer. The controllable formation of a stable rGO film on various solid substrates has potential applications for nanoelectronics and sensors/biosensors.

Graphene-based ion rectifier using macroscale geometric asymmetry

Ion rectification is the asymmetrical conduction of ions through a system under different polarities of applied potentials. In this article we report the finding of a novel form of ion rectification in graphene oxide (GO) and reduced graphene oxide (RGO) films which act as an ensemble array of nanochannels. Rectification is imparted by introducing geometric asymmetry in fluidic inlets to the counter-ion selective nanochannels of GO/RGO which creates asymmetry in the enrichment/depletion effects at the macro-/nano-interface. The devices are made simply by cutting a GO or RGO film into a trapezoid and sealing the film within a Polydimethylsiloxane block so that fluid may only enter through one of two inlets. These devices exhibit rectification ratios larger than 20 (in 1 mM NaCl) while operating at modest voltages [−1 V, +1 V].

Fabrication of Electrochemical Reduced Graphene Oxide Films on Glassy Carbon Electrode by Pulsed Potentiostatic Methods and Its Electrochemical Application

AbstractA graphene‐based electrochemical sensing platform for sensitive determination of baicalein was constructed by means of pulsed potentiostatic reduction of graphene oxide (GO) on a glassy carbon electrode (GCE). The resulting electrode (ERGO/GCE) was characterized by cyclic voltammetry (CV) and scanning electron microscopy (SEM). The electrochemical behaviors of baicalein at the ERGO/GCE were investigated in detail by CV, chronoamperometry (CA) and chronocoulometry (CC). The experimental results demonstrated that the ERGO/GCE exhibited excellent response toward the redox of baicalein as evidenced by the significant enhancement of redox peak currents (ip) and the decreased peak‐to‐peak separation (ΔEp) in comparison with a bare GCE. Under the optimum experimental conditions, the reduction peak cureent was proportioanal to the baicalein concentration in the range of 5.0 × 10‐9 ∼ 5.0 × 10‐7 mol L‐1 with the detection limit of 2.0 × 10‐9 mol L‐1. The proposed method was also applied successfully to determine baicalein in spiked human blood serum samples.