Reduced Graphene Oxide Loading Research Articles

Glass transition temperature of Agar-Reduced Graphene Oxide (RGO) Composites using 2-D contour mapping of temperature dependent FTIR spectra

In the present work, composites of Reduced Graphene Oxide (RGO) and Agar have been synthesized via the solution cast method and their structural, thermal and dielectric properties are studied. UV–Visible, X Ray Diffraction (XRD), Raman Spectroscopy and Fourier Transform Infrared (FTIR) have been employed for analyzing structural properties of the prepared samples. Analysis of different peaks in XRD and Raman Spectra suggests the interaction of RGO layers with Agar at the molecular level. FTIR spectra indicate that interaction of Agar with RGO occurs through hydrogen bonding linkage. Further, the Glass transition temperature (Tg) of prepared samples has been determined using 2D contour mapping from temperature-dependent FTIR spectra as well as from the Differential Scanning Calorimetry (DSC)technique. Values of Tg obtained from both techniques have been found in close agreement with each other. In addition to that, value of Tg of Agar increases from 72 °C to 80 °C as an effect of 2 wt.% RGO loading indicating the improvement in the thermal behavior of Agar. Moreover, the dielectric behavior of as-prepared composites demonstrate that the dielectric constant of these composites has been increased in comparison to pure Agar.

N-doped reduced graphene oxide loading nano lead oxide as negative additive for enhanced properties of lead-carbon batteries

The use of carbon materials could significantly increase the cycle life of lead-acid batteries (LABs) by inhibiting the irreversible sulfation. However, it will exacerbate hydrogen evolution side reaction at the negative plates, which not only reduce coulombic efficiency, destroy the plate microstructure, but also accelerate moisture loss. Herein, a N-doped reduced graphene oxide/lead oxide nanoparticles(N-rGO/PbO) composite was synthesized by hydrothermal and calcination process. Comparative studies found that the strategy of loading with metal oxide nanoparticles, which with high hydrogen evolution overpotentials (ηH), and N-doped can retard the rate of hydrogen evolution reaction (HER) on composite materials. In addition, the resultant composite can help to promote the uniform distribution of graphene in negative active materials (NAM) and structural stability of the negative plate and enhance the combination between the additive and NAM. Thanks to the superiority of the prepared composite material additives, the high-rate partial-state-of-charge (HRPSoC) life of lead-carbon battery (LCB) containing the composite additive shown a prominent enhancement. Specifically, the simulated micro battery containing 0.50 wt% N-rGO/PbO additive showed the best cycle life (17390 cycles), compared to that with same content rGO additive (7742 cycles) and that without any carbon additive (2777 cycles). What’s more, by adding 0.50 wt% N-rGO/PbO additive, the initial discharge capacity of simulated micro battery could be enhanced from 145.6 to 162.6 mAh g−1 and the rate capability had also been improved. In summary, the N-rGO/PbO composite manifests great potential in lead-carbon batteries for improving HRPSoC cycle life and discharge capacity.

PVDF/RGO based piezoelectric nanocomposite films for enhanced mechanical and dielectric properties

Polymer nanocomposites are dominating today in the global scenario due to their diverse applications. The study involves the investigation of the role of Reduced graphene oxide (RGO) as nanofiller on mechanical and dielectric properties of Polyvinylidene difluoride (PVDF). Flexible piezoelectric thin films of PVDF loaded with RGO nanofillers were synthesized using a solvent casting technique. The crystal structure of neat PVDF and RGO loaded PVDF films were analysed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). Tensile strength and Young’s modulus of polymer nanocomposite films were analysed by performing tensile testing on a universal testing machine (UTM). The results showed an improvement in elastic modulus up to a certain nanofiller percentage (2 wt% RGO). Measurement of dielectric properties of thin films was conducted using an impedance and material analyser (IMA). The dielectric constant of the film increases with increment in RGO loading. Thus, overall increment in piezoelectric properties take place. This nanocomposite can be used for developing flexible and highly sensitive sensors and actuators.

Effects of varying the amount of reduced graphene oxide loading on the humidity sensing performance of zinc oxide/reduced graphene oxide nanocomposites on cellulose filter paper

This work presents a nanocomposite-based humidity sensor based on zinc oxide nanostructured powder (ZNP) nanoparticles that achieves a maximum enhancement in the humidity sensing performance at room temperature due to the introduction of different amounts of reduced graphene oxide (rGO) loading from 0.5 wt% to 2.0 wt%. The rGO/ZNP (rZNP) nanocomposite-based humidity sensor was fabricated by using cellulose filter paper as a substrate and clear paper glue as a binder through a facile brush printing method. FESEM, EDS, XRD, HRTEM, XPS, and Raman spectroscopy were employed to investigate the properties of the ZNP and rZNP nanocomposites. The presence of an rZNP nanocomposite with quasi-spherical ZNP nanoparticles that are securely attached and anchored with rGO sheets was confirmed through HRTEM micrographs. Raman spectroscopy analyses confirm and validate the formation of hybrid nanostructures with the presence of distinctive bands related to ZNP and rGO. The presence of oxygen vacancy defects and oxygen-related chemical bonds on the surface of the rZNP nanocomposite, which yields enhanced sensor performance, is revealed by XPS analysis. The rZNP nanocomposite-based humidity sensor with 1.0 wt% rGO loading (rZNP-1.0) had a maximum sensing response of 99.42% and exhibited the highest sensitivity towards humidity changes (172 or 29.2 MΩ/%RH), which was substantially better than the other tested samples.

Effects of Varying the Amount of Reduced Graphene Oxide Loading on the Humidity Sensing Performance of Zinc Oxide/Reduced Graphene Oxide Nanocomposites on Cellulose Filter Paper

Effects of Varying the Amount of Reduced Graphene Oxide Loading on the Humidity Sensing Performance of Zinc Oxide/Reduced Graphene Oxide Nanocomposites on Cellulose Filter Paper

Three-dimensional flexible polyurethane decorated with Ni and reduced graphene oxide for high-sensitive sensing of glucose

Herein, a novel rationally designed nickel/reduced graphene oxide/polyurethane (Ni/RGO/PU) electrode was prepared through multiple immersing-drying processes and electrodeposition methods subsequently, using reduced graphene oxide (RGO) as the support material, nickel (Ni) as the catalyst, and three-dimensional flexible polyurethane sponge as the electrode substrate. The porous structure of the polyurethane sponge provides a larger surface area for the Ni/RGO/PU electrode and creates favorable conditions for the loading of RGO. At the same time, the rough surface of the RGO sheet provides good support for the electrodeposition of Ni, and its excellent conductivity endows a fast electron transmission channel, which is conducive to the rapid adsorption and reaction of glucose on the electrode surface. The results show that the Ni/RGO/PU electrode has excellent electrocatalytic oxidation performance for glucose, and it has superb sensitivities of 20050 μA mM−1 cm−2 with a detection range of 0.01–2.0 mM and 4876 μA mM−1 cm−2 with a detection range of 2.0–4.0 mM for non-enzymatic detection of glucose. Furthermore, the Ni/RGO/PU electrode can successfully detect glucose in fetal bovine serum (FBS). Therefore, the Ni/RGO/PU electrode appears to be a promising candidate for high-sensitivity and sustainable stable non-enzymatic glucose sensors.

Fabrication and dielectric performance of RGO-PANI reinforced PVDF/BaTiO3 composite for energy harvesting

Today’s techno savvy world demands smart devices which are light-weight, flexible, and scalable. Functional polymers and their composites are suitable candidates that can fulfill the requirements in flexible device applications. Polyvinylidene fluoride (PVDF) is one kind of functional polymers possessing a large dielectric strength as well as permanent electrical dipole. To improve the dielectric and ferroelectric performance of the PVDF polymer, it can be hybridized with an inorganic/organic inclusion phase, usually ferroelectric ceramic particles or nano-sized low dimensional carbon. In this work, reduced- graphene oxide (RGO) and RGO-PANI were chosen as the inclusion phase (filler). The present work focuses towards enhancing the dielectric and ferroelectric properties of PVDF-BaTiO3 (P/BT) nanocomposites impregnated with RGO and RGO/PANI(Polyaniline) nanofillers. In-situ polymerization method was adapted to fabricate the RGO/PANI nanocomposite and spin coating method for P/BT composites. X-ray diffractograms and FTIR corroborate the presence of ferroelectric phases in P/BT matrix. Wayne Kerr precision impedance analyzer was used in the frequency frame of 1 Hz to 1 MHz and temperature window from 30 °C to 160 °C to study the dielectric properties. The P-E hysteresis loops were obtained using Radiant Ferroelectric Tester at different voltage cycles. The dielectric constant of P/BT matrix with 0.03% RGO loading exhibited the highest dielectric constant 2 × 105. Remarkable increase in the energy density of composites with filler loading was observed. P/BT with 1 wt% loading of RGO-PANI achieved the maximum value of polarization 3.6 µC/cm2 and discharge energy density 0.76 J/cm3 (under the electric field of 170 kV/cm) with 55% efficiency. This contribution provides a potential route to design and fabricate high energy density flexible capacitor for microelectronic devices.

Fabrication of magnesium ferrite microspheres decorated nitrogen-doped reduced graphene oxide hybrid composite toward high-efficiency electromagnetic wave absorption

In this work, magnesium ferrite (MgFe2O4) microspheres decorated nitrogen-doped reduced graphene oxide (NRGO) hybrid composite was fabricated through a solvothermal and hydrothermal two-step method. Results manifested that the three-dimensional netlike structure consisting of MgFe2O4 microspheres and crumpled NRGO was well constructed in the as-synthesized hybrid composite. Significantly, both hybridization with reduced graphene oxide (RGO) and nitrogen doping had few effects on the size of MgFe2O4 microspheres. Furthermore, the influences of hybridization with RGO, nitrogen doping and filler loadings on the electromagnetic absorption properties were carefully examined. It was found that both hybridization with RGO and nitrogen doping were effective strategies to enhance the electromagnetic absorption capacity of MgFe2O4 microspheres. Remarkably, the as-prepared NRGO/MgFe2O4 hybrid composite presented excellent electromagnetic absorption performance, that was the minimum reflection loss of −48.0 dB at 5.2 GHz, and maximum absorption bandwidth of 4.8 GHz under a low filler loading of 25.0 wt% and a small matching thickness of 2.0 mm. In addition, the potential electromagnetic absorption mechanisms were revealed. Therefore, our results could be beneficial to fabricating graphene-based dielectric/magnetic hybrid composites as high-efficiency electromagnetic absorbers.

Effect of filler loading on the shielding of electromagnetic interference of reduced graphene oxide reinforced polypropylene nanocomposites prepared via a twin-screw extruder

Thermoplastic polypropylene (PP) with different loadings (0.5, 1, 3 & 5 wt%) of reduced graphene oxide (RGO) were prepared to design a nanocomposite to shield the electromagnetic interference (EMI) using melt processing technique via a twin-screw extruder. The nanocomposites were characterized by dc conductivity, mechanical, fractography, and electromagnetic shielding applications. Incorporation of RGO significantly affects the mechanical strength of nanocomposites, which helps to rise in the tensile (4.7%) and flexural strength (4%) at maximum (5 wt%) RGO loading compared to pure PP. There has an improvement in the electrical conductivity of nanocomposites with an increase in the filler load. The RGO/PP nanocomposites exhibit the EMI shielding effectiveness (SE) of − 10.2 dB with 2 mm of thickness at 5 wt% of RGO loading. The outcomes showed that the RGO/PP nanocomposites are able to block up to 90% of the EM wave and are a potential candidate for another kind of microwave absorbing material at large-scale manufacturing division.

Thermal stability and dielectric relaxation behavior of in situ prepared poly(vinyl alcohol) (PVA)-reduced graphene oxide (RGO) composites

Poly(vinyl alcohol) (PVA)-reduced graphene oxide (RGO) composite films have been prepared via in situ reduction of graphene oxide (GO) inside PVA matrix. In order to study microstructure and morphology of prepared PVA-RGO composite films, transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, UV-Visible absorption spectroscopy, X-ray diffraction (XRD) technique, and Raman spectroscopy were utilized. Thermogravimetric analysis (TGA) depicts the increase in thermal stability of PVA with increasing loading of RGO. The dielectric properties of composites were explored in frequency range 100 Hz–2.5 MHz which depicts increase in dielectric permittivity and ac conductivity of composite films with increasing RGO loading. The dielectric relaxation behavior and dispersion parameters of composite films were analyzed using Cole-Cole plots using a MATLAB program based on the Havrilak-Negami (HN) model.

Alternately Dipping Method to Prepare Graphene Fiber Electrodes for Ultra-high-Capacitance Fiber Supercapacitors.

SummaryFlexible fiber supercapacitors are promising candidate for power supply of wearable electronics. Fabrication of high-performance fibers is in progress yet challenging. The currently available graphene fibers made from wet-spinning or electro-deposition technologies are far away from practical applications due to their unsatisfactory capacitance. Here we report a facile alternately dipping (AD) method to coat graphene on wire-like substrates. The excellent mechanical properties of the substrate with greatly diverse choices can be carried over to the fiber supercapacitors. Under such guideline, the graphene fiber with a titanium core made by our AD method (AD:Ti@RGO) shows an ultra-high specific capacitance of up to 1,722.1 mF cm−2, which is ∼1,000 times that of wet-spinning- and electro-deposition-fabricated neat graphene fibers and presents the highest specific capacitance to date. With excellent mechanical properties and striking electrochemical performances, the AD:Ti@RGO-based supercapacitors light the path to the next-generation technologies for wearable devices.

Rheological and microstructural characterization of aqueous suspensions of carbon black and reduced graphene oxide

Carbon black is often used as a conductivity enhancer in battery electrodes. Reduced graphene oxide is another conducting material, with a high aspect ratio sheet-like morphology, and offers the possibility of generating a conducting network at loadings that are small compared to carbon black. Suspensions of conducting carbon, active materials and binders are typically coated on current collectors during the formation of electrodes. The rheology of these suspensions is an important indicator of the connectivity of particles in the suspension and impacts the electrical conductivity as well as the thickness of the coated layer. In this work, the rheology and microstructures of aqueous suspensions of para-aminobenzoic acid terminated carbon black (CB) with and without reduced graphene oxide (RGO) were investigated. The CB loading varied between 0.05 wt.% -10 wt.%, while the samples containing RGO had an RGO loading of 0.05 wt.%. The pH of the suspension was varied from 7.5 to 3. The carboxyl groups on the CB surface are deprotonated at pH 7.5, making the particles hydrophilic. Protonation of the carboxylate groups at pH 3 makes the particles partially hydrophobic. Suspensions of CB showed Newtonian behavior at all loadings for pH 7.5, and at loadings below 1.5 wt.% for pH 3. They are shear thinning at loadings between 1.5–10 wt.%. Interestingly, the low shear viscosity is non-monotonic with CB loading, rising up to a CB loading of 7.5 wt.%, and then dropping at 10 wt.%. Cryogenic scanning electron microscopy (SEM) showed CB particles forming aggregates at pH 3 for CB loadings greater than 1.5 wt.%. At pH 3, addition of 0.05 wt.% RGO resulted in a viscosity increase for suspensions containing 0.5 wt.% CB, as the RGO formed connections with CB particles that enhanced network formation. Adding RGO had little effect on suspensions that had 1.5 wt.% CB. The combination of SEM imaging and suspension rheology provides insight into the particle connectivity for the carbon-based materials studied here. These insights will be useful in determining coating conditions for slurries used in rechargeable battery electrodes.

Reduced graphene oxide-modified biochar electrodes via electrophoretic deposition with high rate capability for supercapacitors

Wood-derived biochar is an attractive material for supercapcitor electrodes due to its natural hierarchical structure. To improve the conductivity of biochar, graphene oxide is electrophoretically deposited, followed by electrochemical reduction. The conductivity can be controlled by either changing the amount of reduced graphene oxide loading by using different concentrations of graphene oxide suspension or by reaching different reduction states by varying the electrochemical reduction potential. The pore structure is also investigated to evaluate the microstructure effect on the material’s capacitive behavior. A specific capacitance of 167 F g−1 is achieved after reduced graphene oxide deposition, which is 4.3 times higher than that of biochar without reduced graphene oxide. The reduced graphene oxide-modified biochar electrodes show a high rate capability retention of approximately 90% with current densities from 0.5 to 3.0 A g−1. Additionally, no degradation is observed after 10,000 charging–recharging cycles under 5.0 A g−1. As the conductivity of raw biochar is low, it has been modified by reduced graphene oxide through electrophoretic deposition and electrochemical reduction. As a result, the conductivity increases approximately 4 times, but the surface area and pore volume decrease because of pore blockage by graphene. Finally, the reduced graphene oxide-modified biochar electrode exhibits specific capacitance 4.3 times higher than that of raw biochar. The rate capability has also been improved due to the enhanced electron transportation.

Enhanced H2S gas-sensing performance of α-Fe2O3 nanofibers by optimizing process conditions and loading with reduced graphene oxide

We systematically investigated the effects of process conditions and reduced graphene oxide (RGO) loading on the H2S gas-sensing performance of the α-Fe2O3 nanofibers (NFs) fabricated via on-chip electrospinning. The annealing temperature and precursor solution contents strongly influenced on the morphology and structure of the α-Fe2O3 NFs that accordingly affected on the gas-sensing performance. The optimum process conditions with the annealing temperature of 600 °C and the precursor solution contents of 11 wt% PVA and 4.0 wt% Fe(NO3)3.9H2O led to the α-Fe2O3 NF sensors having a high response of ∼6.1 at 1 ppm H2S gas. The RGO loading further improved the gas response, increasing the response to 1 ppm H2S gas up to ∼9.2. Also, the RGO-loaded α-Fe2O3 NF sensors enhanced their selectivity and detection limit as compared with pure α-Fe2O3 NF sensors. The enhanced gas-sensing performance was attributed to the presence of nanograins, the increase of surface-to-volume ratio and the formation of potential barriers at nanograin homojunctions and RGO/α-Fe2O3 heterojunctions.

Light absorptive polymeric form-stable composite phase change material for thermal storage

Light absorptive polymeric form-stable composite phase change tablet (RGO-PARB/MA) was prepared by dip-coating myristic acid (MA) tablets into layers of polymer coating solution with reduced graphene oxide (RGO). RGO serves as light absorptive material to harvest sunlight and converts it to thermal energy to be stored in PCM. Ultraviolet (UV)-Visible absorption analysis showed that RGO absorbs UV and visible light at the absorption peak of 255 nm. In this study, a new in-house experimental setup was also developed to quantitatively measure stored heat energy, solar energy conversion, and storage efficiency in the outdoor environment. RGO-PARB/MA tablet with 1.5 wt% RGO loading had the highest amount of stored heat energy which was 48.91% higher than tablet without RGO. The average solar energy conversion and storage efficiency of 1.5 wt% RGO-PARB/MA tablet was about 21%. The melting temperature and latent heat of 1.5 wt% RGO-PARB/MA tablet were 54.79 ± 0.07 °C and 119.91 ± 6.67 J/g, respectively. Thermal cycle test shows that the composite phase change material has good thermal durability, withstanding up to 1000 thermal cycles (2.7 years) with changes in thermal properties less than 2%.

Lead-free double perovskite Cs2AgBiBr6/RGO composite for efficient visible light photocatalytic H2 evolution

Lead halide perovskites have demonstrated great potential in photovoltaic and photocatalytic applications. Despite of their high efficiency, the lead toxicity issue could limit their applications in photocatalysis. Herein, lead-free double perovskite Cs2AgBiBr6 (CABB) combined with reduced graphene oxide (RGO) was facilely synthesized (donated as CABB/RGO) and applied for H2 evolution in saturated HBr aqueous solution. The CABB/RGO composite with optimal RGO loadings exhibited enhanced photocatalytic activity than bare CABB particles, which could be ascribled to the facilitated charge separation and transfer by RGO. As high as 489 μmol g−1 H2 can be produced within 10 h under visible light irradiation (λ ≥ 420 nm, 300 W Xe lamp) using CABB/RGO as photocatalyst. Furthermore, the champion photocatalyst of CABB/2.5%RGO showed high stability for 120 h continuous photocatalytic H2 evolution. This study suggests Cs2AgBiBr6-based perovskite are promising candidate for photocatalytic hydrogen generation.

Effect of the carbon loading on the structural and photocatalytic properties of reduced graphene oxide-TiO2 nanocomposites prepared by hydrothermal synthesis

This work deals with the preparation of reduced graphene oxide (RGO)-TiO2 composites by a one-step hydrothermal treatment. The effect of the RGO loading on both the structural properties and photocatalytic behavior of RGO-TiO2 is deeply addressed herein. The hydrothermal treatment promoted the reduction of graphene oxide, crystallization of TiO2 into anatase, and anchoring of TiO2 nanoparticles on RGO sheets. It was observed that the prepared anatase particles showed sizes below 10nm, whereas the RGO sheets displayed thicknesses smaller than 1nm. The use of RGO at concentrations up to 15wt% greatly increased the specific surface area of RGO-TiO2. It was demonstrated that the combination of RGO and TiO2 gives rise to materials with improved photocatalytic properties and tailored structural properties. The composite with the highest photoactivity was the one containing an RGO loading of 1wt%; this composite displayed a photocatalytic rate constant about 9.5 times higher than that evaluated for pure TiO2. This behavior may be related to the stacking of RGO nanosheets when its concentration is above 1wt%. Moreover, the addition of RGO in excess may prevent the activation of the TiO2 surface by UV light and also decrease the lifetime of the photogenerated electron-hole pairs. Therefore, it appears that 1wt% is the optimal loading of RGO to obtain a close interfacial contact between RGO and TiO2, leading to both an effective activation of TiO2 by UV radiation and an enhanced charge transfer between RGO and TiO2.

Morphology and functional properties of electrospun expanded polystyrene (EPS)/reduced graphene oxide (RGO) nanofiber composite

Conductive polymer nanocomposites are receiving lots of research attention in the field of material science due to their fascinating properties and potentials in many areas of applications. In this work, reduced graphene oxide (RGO); a highly conducting nanofiller was synthesized and incorporated into the matrix of insulating expanded polystyrene (EPS); a recycled polymer, by solution mixing, then electrospun under the effect of optimized processing parameters. A filler loading of between 0.01 and 3 wt% was used at 15% (w/v) concentration of EPS in mixed solvent of DMF and THF to obtain composite nanofibers in submicron range. Analytical tools such as SEM, XRD, FTIR, and RAMAN were used for the investigation of the morphology of the synthesized RGO and electrospun composite nanofibers. Electrical, thermal, and mechanical properties of EPS/RGO composite nanofibers were investigated and compared with that of EPS/Carbon Black composite nanofibers. Keithely 2000 multimeter with four-point probes was used for electrical characterization. A significant drop in resistivity at a very low filler loading of RGO with percolation threshold of 0.7 wt% was recorded for EPS/RGO at conductivity value of 0.132 × 10−4S/m as compared to percolation threshold of 3.0 wt% obtained from EPS/Carbon Black composite nanofibers. A drastic improvement in thermal stability, Young Modulus, and tensile strength were also observed in all the nanocomposites compared with pure electrospun EPS. A sustainable reuse pathway for post-consumer plastic is also hereby presented.

In Situ Green Synthesis and Functionalization of Reduced Graphene Oxide on Cellulose Fibers by Cannabis sativa L. Extract

Abstract The last decade has seen an enormous rise in the use of green reducing agents, such as plant extracts, for the chemical synthesis of several materials in view of the limitations of conventional reducing agents, such as their toxicity and instability. This study reports the green reduction and simultaneous functionalization of graphene oxide on cellulose fibers using the aqueous extract from the inflorescences of Cannabis sativa L. The graphene oxide, synthesized using the modified Hummer’s method, was reduced in situ on the cellulose matrix in the presence of the extract at elevated temperatures without external stabilizers in order to functionalize the fibers with reduced graphene oxide (RGO). The cellulose fibers not only acted as a flexible, biodegradable, and cost-effective matrix for the anchorage of RGO but also supported in situ reduction on the fiber surface. Different weight fractions of RGO, from 0.1 to 10 wt %, were used to fabricate RGO/cellulose composites by paper-making technique, which were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The RGO sheets uniformly covered the surface of the cellulose fibers and dispersed well within the fiber matrix. The surface resistivity at 40 V decreased with increasing RGO content from 1.81 × 1011 Ω for 0.1 wt % RGO to 0.15 × 1011 Ω for 10 wt % RGO loading. The presence of air voids between the fibers hindered the physical contact between the RGO layers, thereby preventing the formation of an effective conductive network and significantly affecting the performance of the composites. Likewise, the surface charging capacity of the composites at 40 V dropped from 1.21 × 10−3 ΔmAh for 0.1 wt % RGO to 0.05 × 10−3 ΔmAh for 10 wt % RGO content, indicating a rise in conductivity with RGO loading. These composites show immense potential as sustainable materials for portable energy storage devices, such as capacitors.

Effects of reduced graphene oxide loading on gas-sensing characteristics of flame-made Bi2WO6 nanoparticles

In this study, the effects of reduced graphene oxide (rGO) loading on the gas-sensing characteristics of flame-made Bi2WO6 nanoparticles were systematically investigated. Bi2WO6 nanoparticles produced by flame spray pyrolysis (FSP) were loaded with rGO prepared based on Hummer's method with varying concentrations from 0 to 5 wt%. Characterized results by X-Ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, X-ray photoemission spectroscopy and nitrogen adsorption confirmed the dispersion of rGO sheets within 5–15 nm FSP-made orthorhombic Bi2WO6 nanoparticles. The gas-sensing data measured in dry air demonstrated that the optimal rGO loading level of 2 wt% provided substantial enhancements of H2S response and selectivity. Specifically, the 2 wt% rGO-loaded Bi2WO6 sensor exhibited the highest response of ~29 towards 10 ppm H2S with high selectivity against H2, CH4, NO, NO2, C7H8, CH2O, C8H10, C6H6, C3H6O, CH3OH, C2H5OH, C3H6O2, C3H6O3, C4H8O2, CH3COOH, C4H9COOH and HCOOH at an optimal working temperature of 350 °C. The roles of rGO on gas-sensing behaviors were explained on the basis of p-n heterojunctions between rGO and Bi2WO6. Therefore, the rGO-loaded Bi2WO6 sensor is an attractive candidate for H2S detection.