Weight Ratio Of rGO Research Articles

Microstructural and magnetic properties of rGO/MnFe2O4 nanocomposites; relaxation dynamics

In the present investigation, nanocomposite (NC) of reduced graphene oxide (rGO) and manganese ferrite (MnFe2O4) with three different (rGO/MnFe2O4) weight-ratio of rGO have been synthesized using a simple and efficient one-step hydrothermal route. The crystallinity, morphology and magnetic studies were conducted using X-ray diffraction (XRD), confocal Raman imaging and vibrating sample magnetometry (VSM).Detailed ferromagnetic resonance (FMR) studies were performed in the field-sweep mode at different applied frequencies ranging from 5 to 30 GHz using a vector network analyzer (VNA). We have realized a nano-composite layer of rGO/MnFe2O4 NC on top of coplanar waveguide (CPW) transmission lines to perform FMR experiments. The largest ferromagnetic resonance (FMR) absorption of −28 dB was observed for 0.06 g GO doped MnFe2O4 at the 22 GHz frequency. This absorption at FMR is found to be tunable by rGO concentration in manganese ferrite. We have also evaluated various relaxation/damping parameters of the nanocomposites. The experimental values of FMR linewidths were fitted using two micromagnetic models, and hence intrinsic and extrinsic damping parameters were obtained for nanocomposite samples. The damping parameters were observed to influenced by the rGO weight ratio. Therefore the developed nanocomposite can find various applications in the area of microwave monolithic devices and circuits like filters, phase shifters, circulators, etc.

Graphene-mediated organic-inorganic composites with improved hydroxide conductivity and outstanding alkaline stability for anion exchange membranes

A series of composite membranes for application as anion exchange membranes were prepared by introducing various amounts (0.1–5.0 wt%) of reduced graphene oxide (rGO) into chloromethylated poly(arylene ether ketone) (CM-PAEK), followed by quarternization and anionization. CM-PAEK/rGO composite membranes with controlled weight ratios of rGO were fabricated by cost-competitive solution casting method. The field emission scanning electron microscopy (FE-SEM) images of the composite membranes showed that the distribution of rGO was uniform, and the prepared membranes have similar thicknesses confirmed by the cross-sectional image. The composite membranes exhibited enhanced the mechanical strength due to π-π interaction between the aromatic chain of rGO and the polymer backbone, and after the quaternization, hydroxide conduction was improved by hydrogen bonding between rGO and functional ammonium groups. Among the QN-PAEK/rGO membranes with various amounts of rGO, QN-PAEK/rGO 1.0 wt% demonstrated the highest ionic conductivity of 115 mS cm−1, and other composite membranes, which were blended more than that (3 wt% and 5 wt%), showed a decrease in ionic conductivity due to aggregation of inorganic nano fillers. Furthermore, alkaline resistance, mechanical strength, and dimensional stability of composite membranes have been greatly improved due to the introduction of rGO, which demonstrate great potential application as anion exchange membrane for fuel cells.

NiS and graphene as dual cocatalysts for the enhanced photocatalytic H2 production activity of g-C3N4

Up to now, rational design and facile synthesis of photocatalysts with high activity and low cost remain a great challenge. Here, noble-metal-free graphene and NiS co-modified g-C3N4 composite photocatalyst was prepared using an one-step hydrothermal method. The ternary composite displayed enhanced photocatalytic water splitting activity. When the weight ratios of RGO and NiS were 0.25% and 3%, respectively, the highest H2 evolution rate was achieved, which was 21.8-fold that of bulk g-C3N4. The introduction of NiS and RGO dual cocatalysts promoted the separation of photogenerated electron–hole pairs and improved the light absorption of g-C3N4, thus enhancing the photocatalytic activity. This work provides significant guidance for the modification of photocatalytic materials with noble-metal-free cocatalysts to realize high-efficient photocatalytic water splitting for hydrogen generation.

How the Reduced Graphene Oxide Prepared at Different pH Values Affect the Optical Transmittance and the Electrical Properties of Polystrene Latex Films?

Optical transmittance and electrical properties of polystyrene (PS)/reduced graphene oxide (rGO) composites were studied. Photon transmission technique was used to monitor the optical transmittance and two‐/four‐probe methods were used for the electrical conductivity measurements. Two separate experimental sets were prepared. In the first set, the composite films were prepared at equal amounts of PS and rGO where the pH of the solution in which GO was reduced to rGO was changed from about 3 to 10. The second set includes the composite films which were prepared at different weight ratios of rGO which prepared at pH = 10. All of the composite films were annealed under the Infrared lamp and the annealing time was changed from 10 to 30 min to be able to understand the effect of the annealing time. It was observed that increasing annealing time starts the film formation at lower temperatures. Only the void closure stage of the film formation process could be observed for all composite films and increasing amount of rGO decreased the required energy for the void closure stage. POLYM. COMPOS., 40:E1441–E1450, 2019. © 2018 Society of Plastics Engineers

Influence of heating on spectroscopic, mechanical, and thermal properties of reduced graphene oxide-poly(vinyl alcohol) composite films

The spectroscopic, uniaxial tensile, and thermal properties of reduced graphene oxide (rGO)-poly(vinyl) alcohol (PVA) composite films produced by using rGO synthesized using modified Hummer's method with varying weight ratio of rGO up to 10% were investigated by using an uniaxial tensile tester, Fourier Transform Infrared (Ft-IR)/Attenuated Total Reflectance (ATR) spectroscopy, and Differential Scanning Calorimeter (DSC) methods after heating process at different temperatures from room temperature to 200 °C. For unheated composite films, with increasing rGO weight ratio up to 10%, the Young's modulus of rGO-PVA films increased by approximately 2–3 times, conversely the strain at break values decreased greatly by about 40–50%. The heating process led to the significant improvement in the tensile strength and the Young's modulus, and great decrease in extensibility with respect to the unheated samples, e.g., the tensile strength and Young's modulus increased by 3–4 times and 8–10 times, respectively, for the heating temperatures up to 150 °C. With increasing heating temperature, the stress-strain curve of rGO-PVA composite films turned from that of ductile and amorphous polymer to that of more brittle and rigid polymers. With increasing rGO content, the glass transition, the crystallization, and the melting temperatures increased and heating process generally shifted these temperatures to higher values. The great contribution of rGO content and the heating to the improvement of especially mechanical properties of rGO-PVA composite films thanks to the strong intermolecular interactions of rGO nanosheets with the PVA matrix molecules through hydrogen bonding and to the changes in the crystallinity ratio of PVA was shown in detail in the analysis of the spectral results. The relationship between the changes in the mechanical, structural, and thermal properties of the studied composite films was determined by using tensile testing, Ft-IR/ATR, and DSC methods.

Equivalent circuit analysis of Al/rGO-TiO2 metal-semiconductor interface via impedance spectroscopy: Graphene induced improvement in carrier mobility and lifetime

A metal-semiconductor (MS) contact often gives rise to a Schottky barrier junction and is immensely important in electronic devices. Recently, graphene and its nanocomposites have attracted interest for their tremendous potential in schottky barrier diodes (SBDs). To realize a high performance SBD, detail characterization of the MS interface is of utmost importance. In this regard, here we employ impedance spectroscopy (IS) as a simple yet powerful technique for the equivalent circuit analysis and characterization of Al/reduced graphene oxide(rGO)-TiO2 interface. Al/rGO-TiO2 SBDs are fabricated with different weight ratios of rGO (rGO:TiO2 = 0, 1:50, 1: 30, 1:15) in the composite and IS analysis is performed for all the SBDs. Built-in potential, charge carrier density, depletion layer width and barrier height of the diodes are extracted from capacitance-voltage measurements. Moreover, we obtain the charge career lifetime, mobility and diffusion length based on the equivalent circuit model. Current-voltage measurement is also performed and mobility values from IS are further verified by space charge limited current (SCLC) measurements. The best device performance and charge transport properties was exhibited by rGO:TiO2 = 1:15. The carrier mobility increased by almost 2.6 times compared to pure TiO2, while the lifetime and diffusion length improved by 113% and 130% respectively. In short, we demonstrate the equivalent circuit analysis for the investigation of Al/rGO-TiO2 MS interface and successfully implement the IS model to determine charge transport parameters. This study reveals the beneficial impact of graphene on device performance and establish the huge potential of IS technique for characterization of MS devices.

ZnS@ reduced graphene oxide nanocomposite as an effective sunlight driven photocatalyst for degradation of reactive black 5: A mechanistic approach

Abstract Herein, we report the fabrication of RGO-ZnS nanocomposites by a facile ultrasound assisted hydrothermal process. Three nanocomposites with different weight ratios of RGO namely RGO3-ZnS, RGO5-ZnS and RGO10-ZnS were prepared and characterized by several techniques. The photocatalytic activity of Z nS , the nanocomposites, and P25 was evaluated against Reactive black 5 (RB5) under sunlight irradiation. A high rate constant of 3.05 × 10−2 min−1, the chemical oxygen demand (COD) value of about 10%, and the mineralization efficiency of 90% were obtained within 300 min when RGO3-ZnS was used as a photocatalyst. To elucidate the photocatalytic mechanism of RGO3-ZnS nanocomposite, the reactive oxygen species trapping experiments, photoluminescence, linear sweep voltammetry, and open circuit potential decay measurements were performed. On the basis of the experimental results, the enhanced photocatalytic activities of RGO3-ZnS could be ascribed to the increased dye adsorption, optical absorption and charge carrier generation, efficient separation, and migration of photogenerated charge carriers as well as the decreased recombination probability of electron-hole pairs as a result of introducing of RGO in the nanostructure.

Improved NO2 sensing properties at low temperature using reduced graphene oxide nanosheet–In2O3 heterojunction nanofibers

Pure In2O3 and reduced graphene oxide (rGO)–In2O3 composite nanofibers are prepared by a facile electrospinning technique. Low-temperature gas-sensing properties to NO2 of the produced nanofibers are evaluated. Our results indicate that in comparison with pure In2O3 nanofibers, the rGO–In2O3 heterojunction nanofibers display much better sensing properties in response, selectivity and detection limit to NO2. Moreover, the weight ratios of rGO to In2O3 are used as a parameter to estimate the best gas-sensing properties of rGO–In2O3 nanofibers. Consequently, the heterojunction nanofibers with an optimized amount of rGO (2.2 wt%) exhibit the highest response of 42 to 5 ppm NO2 at the low operating temperature of 50 °C, which is 4.4 times higher than that of pristine In2O3. From our perspective, the enhanced sensing properties of the composite nanofibers can be mainly attributed to the formation of p–n heterojunctions between rGO and In2O3, and ultrahigh specific surface area as well as strong gas adsorption capacity of rGO nanosheets. These excellent gas-sensing properties make the rGO–In2O3 heterojunction nanofibers attractive to application for low-temperature NO2 gas sensors.

Weavable asymmetric carbon nanotube yarn supercapacitor for electronic textiles.

Asymmetric supercapacitors are receiving much research interests due to their wide operating potential window and high energy density. In this study, we report the fabrication of asymmetrically configured yarn based supercapacitor by using liquid-state biscrolling technology. High loading amounts of reduced graphene oxide anode guest (90.1 wt%) and MnO2 cathode guest (70 wt%) materials were successfully embedded into carbon nanotube yarn host electrodes. The resulting asymmetric yarn supercapacitor coated by gel based organic electrolyte (PVDF-HFP-TEA·BF4) exhibited wider potential window (up to 3.5 V) and resulting high energy density (43 μW h cm−2). Moreover, the yarn electrodes were mechanically strong enough to be woven into commercial textiles. The textile supercapacitor exhibited stable electrochemical energy storage performances during dynamically applied deformations.

Immobilization of 2D/2D structured g-C3N4 nanosheet/reduced graphene oxide hybrids on 3D nickel foam and its photocatalytic performance

It is highly desired to immobilize photocatalysts on solid surface for environmental applications. In this work, 2D/2D structured g-C3N4/reduced graphene oxide (rGO) hybrids were successfully immobilized on 3D nickel foam using a facile dip-coating method followed by a hydrazine hydrate reduction process. The g-C3N4/rGO hybrids loaded on nickel foam forms a stable coating with excellent photocatalytic activity for tetracycline and methyl orange degradation under visible light irradiation. The highest photocatalytic activity can be achieved when the weight ratio of rGO to g-C3N4 in hybrids was illustrated as 1:9. Furthermore, this special 2D/2D structured g-C3N4/rGO hybrid coating demonstrated the preferable stability. The effective electrons transfer between g-C3N4 nanosheets and rGO as well as the abundant coupling heterointerfaces may play an important role on the photocatalytic performance of hybrid coating. The formation and photocatalytic mechanisms of g-C3N4/rGO hybrid coating were also proposed in detail.

Reduced graphene oxide/Titanium oxide nanocomposite synthesis via microwave-assisted method and supercapacitor behaviors

In this paper, graphene oxide (GO) was firstly synthesized by modification of Hummers method from the literature. Secondly, reduced graphene oxide (rGO)/Titanium oxide (TiO2) nanocomposites were synthesized with different wt/wt % of GO/TiO2 (1:1; 1:2; 1:5 and 1:10) by microwave-assisted method. By treating GO and GO/TiO2 nanocomposites in a microwave oven, reduced graphene oxide (rGO) and rGO/TiO2 materials could be obtained within power of 180 W in 10 min. The weight ratio of rGO and TiO2 was used to obtain the optimum conditions for nanocomposite materials. The rGO/TiO2 nanocomposite active materials were characterized by cyclic voltammetry (CV), Fourier-transform infrared – Attenuated total reflectance (FTIR-ATR), scanning electron microscopy-energy dispersion X-ray (SEM-EDX), thermogravimetry (TGA), differential thermal analyzer (DTA) and electrochemical impedance spectroscopy (EIS) analysis. Thirdly, supercapacitors were fabricated as a symmetric device with two electrode configuration. The device performances were tested by CV, galvanostatic constant current (CC), and EIS measurements. TGA analysis indicated that the thermal stability of the nanocomposites improved from rGO (40% at 892.8 °C) to nanocomposite as the initial feed ratio of [GO]o/[TiO2]o = 1/10 as (94% at 949.3 °C) increased.The result show that the as-prepared symmetrical rGO/TiO2 nanocomposite on the two-electrode system displays very high specific capacitance of 524.02 F/g at 2 mV/s for [GO]o/[TiO2]o = 1/5 with a high energy density of E = 50.07 Wh/kg at 2 mV/s for [GO]o/[TiO2]o = 1/1 and high power density of P = 58.6 kW/kg at a the scan rate 1000 mV/s for [GO]o/[TiO2]o = 1/1. Additionally, the symmetric electrode shows good cycling stability with a retention value of 6.6% for [GO]o/[TiO2]o = 1/1 after 1000 cycles. These good results suggest us that rGO/TiO2 nanocomposite which is obtained by microwave-assisted method has a great potential as an electrode material for supercapacitor applications.The equivalent circuit model of Rs(Cdl(RctW)) was used to explain parameters of solution resistance, double layer capacitance (Cdl), charge transfer resistance (Rct), Warburg impedance (W). Theoretical and experimental values support with each other.

Supersonic cold spraying of titania nanoparticles on reduced graphene oxide for lithium ion battery anodes

Titania (TiO2) nanoparticles were uniformly distributed on and are well attached to reduced graphene oxide (rGO) by supersonic cold spraying. The process facilitated rapid production of lithium ion battery (LIB) anodes. Integration of TiO2 with rGO not only enhanced the conductivity of the anode, but also prevented agglomeration of the titania nanoparticles, which facilitated uniform distribution of the nanoparticles and thus consistently reduced the electron diffusion length. Integration of rGO with TiO2 widened the characteristic voltage range of the resulting rGO-TiO2 composite (0.01–3 V) relative to that of pure TiO2, which enhanced the capacity during the lithiation process. Therefore, the LIB cell exhibited superior performance with long cycle durations even under high current rate. The optimal weight ratio of rGO to TiO2 was found to be 1:1, which produced a retention capacity of 203 mA h g−1 at N = 300 cycle under a current rate of 1 C = 336 mA g−1. Rapid production of rGO/TiO2 nanocomposites via supersonic cold spraying may facilitate commercialization of high-quality LIB cells.

Percolation effect of reduced graphene oxide (rGO) on ammonia sensing of rGO-SnO2 composite based sensor

Reduced graphene oxide (rGO) was added to SnO2 to implement a room temperature chemoresistive ammonia sensor. The percolation effect of rGO on the ammonia sensing properties of SnO2 based sensor was observed. rGO was added physically to SnO2 followed with a magnetic stirring. The sensor using rGO-SnO2 composites exhibited a switch from an n-type semiconductor response behavior to a p-type semiconductor behavior as the rGO content increased from 0.1wt% to 1wt%. The p-type response to ammonia indicated an enhanced sensitivity, better signal stability and faster response/recovery speeds compared to the n-type response. The p-type response can be due to the p-type rGO in the composite and the enhanced room temperature n-type response of SnO2 could be assisted by the added rGO which facilitated the redox reactions of ammonia with oxygen in air. A physical model for prediction of the critical weight ratio of rGO in the composite was developed. The calculated results were reasonably consistent with the experimental ones.

Two-Dimensional Titanium Carbide/RGO Composite for High-Performance Supercapacitors.

Ti3C2Tx, a 2D titanium carbide in the MXenes family, is obtained from Ti3AlC2 through selective etching of the Al layer. Due to its good conductivity and high volumetric capacitance, Ti3C2Tx is regarded as a promising candidate for supercapacitors. In this paper, the fabrication of Ti3C2Tx/RGO composites with different proportions of Ti3C2Tx and RGO is reported, in which RGO acts as a conductive "bridge" to connect different Ti3C2Tx blocks and a matrix to alleviate the volume change during charge/discharge process. In addition, RGO nanosheets can serve as a second nanoscale current collector and support as well for the electrode. The electrochemical performance of the as-fabricated Ti3C2Tx/RGO electrodes, characterized by CV, GCD, and EIS, are also reported. A highest specific capacitance (Cs) of 154.3 F/g at 2 A/g is obtained at the Ti3C2Tx: RGO weight ratio of 7:1 combined with an outstanding capacity retention (124.7 F/g) after 6000 cycles at 4 A/g.

Oxidation Prevention Properties of Reduced Graphene Oxide Mixed with 1-Octanethiol-Coated Copper Nanopowder Composites

1-Octanethiol-coated Cu nanoparticles were mixed with reduced graphene oxide (rGO) to fabricate Cu nanoinks with enhanced oxidation prevention. Graphene oxide (GO) was synthesized using modified Hummer’s method and rGO was reduced from GO using hydrazine hydrate. Copper nanoinks were fabricated with varying concentrations of rGO (Cu : rGO ratios of 100 : 1, 500 : 1, and 1000 : 1 wt.%). The coating layers on the copper nanoparticles and rGO were observed using transmission electron microscopy and characterized by X-ray photoemission spectroscopy, X-ray diffraction, and Raman spectroscopy. It was observed that surface roughness increased as the concentration of rGO in Cu patterns increased, and an optimized Cu : rGO weight ratio of 1,000 : 1 was established. After sintering, the electrical properties and corrosion resistance of copper patterns both with and without rGO were measured and monitored for 200 days. The copper pattern with rGO (Cu : rGO = 1,000 : 1) was found to maintain its initial resistivity (1.63 × 10−7 Ω·m) for 150 days. Corrosion tests were conducted to confirm the oxidation prohibition of rGO. The resistance polarization(Rp)of the copper pattern was measured to be 1.5 times higher than that of the copper pattern without rGO. Thus, rGO was shown to prevent oxidation and improve the conductivity of copper patterns.

Enhanced field emission properties of a reduced graphene oxide/carbon nanotube hybrid film

A facile vacuum filtration method for the preparation of hybrid films to achieve superior field emission properties from carbon nanotubes (CNTs) using reduced graphene oxide (rGO) as a bi-functional filler has been proposed. In the hybrid films, CNTs serve as electron emitters, while rGO helps to control the density of the CNT-emitters and reduce electrical resistance of the films. Via controlling volumes of CNTs and rGO dispersions, electron field emission properties of the hybrid films can be easily tailored. Higher weight ratio of rGO:CNT results in better electrical properties and the best field emission property is achieved when a rGO:CNT weight ratio of 1:3 is employed. The hybrid film reveals a significant improvement in field emission properties, as compared with the CNT film without adding rGO. Decreases in sheet resistance, turn-on field, and threshold field are attributed to the formation of extended conjugated network between CNTs and rGO in association with the reduction of screening effect through the optimization of density of CNT-emitters. The concept that rGO can be employed to control the density of CNT emitters will be of special interest for field emission enhancement.

Surface-modified reduced graphene oxide electrodes for capacitors by ionic liquids and their electrochemical properties

In this work, reduced graphene oxide (rGO)/ionic liquids (IL) composites with different weight ratios of IL to rGO were synthesized by a simple method. In these composites, IL contributed to the exfoliation of rGO sheets and to the improvement of the electrochemical properties of the resulting composites by enhancing the ion diffusion and charge transport. The structure of the composites was examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The TEM images showed that IL was coated on the surface of rGO in a translucent manner. The electrochemical analysis of the prepared composites was carried out by performing cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). Among the prepared composites, the one with a weight ratio of rGO to IL of 1:7 showed the highest specific capacitance of 147.5Fg−1 at a scan rate of 10mVs−1. In addition, the rate capability and cycle performance of the composites were enhanced compared to pristine rGO. These enhanced properties make the composites suitable as electrode materials for the better performance supercapacitors.