Graphene Oxide-multiwalled Carbon Nanotube Research Articles

Numerical assessment of viscoelastic tetra hybrid nanofluid flow across a stretchable rotatory disk under the Soret and Dufour aspects

PurposeFluid flows through rotatory disks are encountered in industrial and practical engineering processes, such as computer storage devices, gas turbine rotators, rotating machinery, air cleaning machines, etc. The primary purpose of this research is to examine the combined aspects of variable electrical conductivity, thermal radiation, Soret and Dufour effects on a magnetohydrodynamic Maxwell single-walled carbon nanotubes–graphene oxide–multi-walled carbon nanotubes–copper (SWCNT–GO–MWCNT–Cu)/sodium alginate tetra-hybrid nanofluid flow through a stretchable rotatory disk.Design/methodology/approachThe modeled administrative equations of the present flow problem are converted to a non-dimensional system of ordinary differential equations by applying suitable similarity conversion and then solved numerically by implementing the bvp4c method. The impressions of noteworthy dimensionless parameters on velocity, temperature, concentration distributions, Nusselt number, skin friction and Sherwood number are reported via graphs and tables.FindingsThe authors figured out that the developed values of the rotation parameter diminish the temperature but enhance both the radial and angular velocities. Further, the mass and heat transmission rates are better for tetra-hybrid nanofluids than for ternary and hybrid nanofluids.Originality/valueThe present study emphasizes a special type of fluid called the tetra-hybrid nanofluid. The existing literature has not discussed the Maxwell tetra hybrid nanofluid flow through a stretchable rotatory disk with variable electrical conductivity. Besides, the novel aspects of magnetohydrodynamics, thermal radiation, Soret and Dufour effects are also incorporated into the present flow problem.

Aspects of superior photocatalytic dye degradation and adsorption efficiency of reduced graphene oxide multiwalled carbon nanotubes with modified ZnO-Al2O3 nanocomposites

Due to the poor effectiveness of nanomaterials, the elimination of hazardous textile dyes from wastewater is quite challenging. A wide range of low-cost, hybrid, and highly effective nanomaterials have attracted much research for their potential in wastewater treatment. Herein, ZnO-Al2O3 nanoparticles were successfully grafted on reduced graphene oxide/multiwalled carbon nanotubes (ZnO-Al2O3-rGO/MWCNT) via the hydrothermal process. This nanohybrid material has been characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunner Emmet Teller (BET) analysis. ZnO-Al2O3-rGO/MWCNT has degraded 30 ppm Congo red dye to 90% within 1 h, while 20 ppm rose Bengal dye to 80% within 1.5 h. The kinetics of degradation for both these dyes is followed well by the pseudo-first-order model. Furthermore, ZnO-Al2O3-rGO/MWCNT was explored for the adsorption of Sudan III and displayed an outstanding removal capacity (220 mg g−1) compared with bare catalyst ZnO−Al2O3 (72 mg g−1). The sorption of Sudan III dye onto the adsorbent is spontaneous endothermic and follows pseudo−second−order kinetics and Langmuir isotherm models. Experiments using radical trapping have shown that hydroxyl radicals are the principal reactive intermediates in the photoexcitation process. The desorption and regeneration of as−prepared nanocomposite are also assessed.

Investigation on performance of adding manganese dioxide into graphene oxide electrode film

ABSTRACT In this paper, the preparation of electroactive polymers artificial muscle electrode membrane with graphene oxide and manganese dioxide as the main research material to explore the performance of electrode membrane. Using sodium alginate as matrix, manganese dioxide with different mass ratios was compounded with graphene oxide and sodium alginate aqueous solution to prepare electrode films. The effects of manganese dioxide on the morphology and electrochemical properties of electrode films were discussed. From the test results, it can be seen that the scanning electron microscopy results show that the manganese dioxide layer is uniformly compounded on graphene oxide. With the increase of manganese dioxide/graphene oxide mass ratio, the specific capacitance of the electrode film gradually increases and the impedance increases. With the increase of driving voltage, the deflection displacement gradually increases and then shows a downward trend. When the mass ratio of manganese dioxide/graphene oxide is 0.1(# 2), the maximum deflection displacement is 14.1 mm, which is 2.76 times of the minimum deflection displacement of the sample (# 1). The specific capacitance of the electrode film was increased by 1.57 times to 15.62 F · g−1. Finally, the performance difference of graphene oxide electrode film and multi-walled carbon nanotube electrode film on EAP artificial muscle was explored.

An electrochemical chiral sensor based on the synergy of chiral ionic liquid and 3D-NGMWCNT for tryptophan enantioselective recognition.

A facile chiral composite (3D-NGMWCNT@(S,S)-CIL) was prepared by integrating three-dimensional N-doped graphene oxide multi-walled carbon nanotubes (3D-NGMWCNT) and chiral ionic liquid ((S,S)-CIL) via electrodeposition. SEM, XRD, XPS, and electrochemical methods were used to characterize this composite and it revealed that the integrated 3D-NGMWCNT@(S,S)-CIL composite showed excellent electrochemical performance. Therefore, a 3D-NGMWCNT@(S,S)-CIL/GCE electrochemical sensor was constructed for enantioselective recognition of Trp enantiomers. The coefficient (IL/ID) of the 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor was 2.26 by differential pulse voltammograms (DPV), revealing that the synthesized 3D-NGMWCNT@(S,S)-CIL had a higher affinity for L-Trp than D-Trp. Moreover, UV-V is spectroscopy and awater contact angle test also proved this result. The 3D-NGMWCNT@(S,S)-CIL/GCE sensor had a detection limit of 0.024μM and 0.055μM, and sensitivity of 62.35μA·mM-1·cm-2 and 30.40μA·mM-1·cm-2 for L-Trp and D-Trp, respectively, with a linear response range of 0.01 to 5mM. In addition, the 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor showed excellent stability, and good reproducibility and was applied to detect L-Trp or D-Trp in real samples. The novel 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor provides an efficient and convenient strategy for chiral enantioselective recognition. Schematic construction of the 3D-NGMWCNT@(S,S)-CIL/GCE chiral electrochemical sensors.

Enhancing Polysulfide Confinement and Electrochemical Kinetics by Amorphous Cobalt Phosphide for Highly Efficient Lithium-Sulfur Batteries.

The application of lithium-sulfur (Li-S) batteries is severely hampered by the shuttle effect and sluggish redox kinetics. Herein, amorphous cobalt phosphide grown on a reduced graphene oxide-multiwalled carbon nanotube (rGO-CNT-CoP(A)) is designed as the sulfur host to conquer the above bottlenecks. The differences between amorphous cobalt phosphide (CoP) and crystalline CoP on the surface adsorption as well as conversion of lithium polysulfides (LiPSs) are investigated by systematical experiments and density-functional theory (DFT) calculations. Specifically, the amorphous CoP not only strengthens the chemical adsorption to LiPSs but also greatly accelerates liquid-phase conversions of LiPSs as well as the nucleation and growth of Li2S. DFT calculation reveals that the amorphous CoP possesses higher binding energies and lower diffusion energy barriers for LiPSs. In addition, the amorphous CoP features reduced energy gap and the increased electronic concentrations of adsorbed LiPSs near Fermi level. These characteristics contribute to the enhanced chemisorption ability and the accelerated redox kinetics. Simultaneously, the prepared S/rGO-CNT-CoP(A) electrode delivers an impressive initial capacity of 872 mAh g-1 at 2 C and 617 mAh g-1 can be obtained after 200 cycles, exhibiting excellent cycling stability. Especially, it achieves outstanding electrochemical performance even under high sulfur loading (5.3 mg cm-2) and lean electrolyte (E/S = 7 μLE mg-1S) conditions. This work exploits the application potential for amorphous materials and contributes to the development of highly efficient Li-S batteries.

Electrochemical Sensor: L-Cysteine Induced Selectivity Enhancement of Electrochemically Reduced Graphene Oxide–Multiwalled Carbon Nanotubes Hybrid for Detection of Lead (Pb2+) Ions

The selectivity improvement of Electrochemically reduced Graphene Oxide–Multiwalled Carbon Nanotubes–L-cysteine (ErGO–MWNTs–L-cys) nanocomposite modified Glassy Carbon Electrode (GCE) using drop casting method for electrochemical detection of lead (Pb2+) ions was investigated. Initially, the graphene oxide–Multiwalled Carbon Nanotubes–L-cysteine (GO–MWNTs–L-cys) nanocomposite was synthesized by a facile and cost-effective method at room temperature. The as-prepared, GO–MWNTs–L-cys exhibited good stable aqueous dispersions due to high hydrophilic nature of GO components which led to inhibiting the hydrophobicity of MWNTs. Then, the electrochemical conductivity of ErGO–MWNTs–L-cys nanocomposite modified GCE (ErGO–MWNTs–L-cys/GCE) was improved by the direct electrochemical reduction of GO–MWNTs–L-cys nanocomposite. The GO–MWNTs–L-cys nanocomposites and its individual components were characterized by Attenuated Total Reflection Infrared (ATR-IR), Raman spectroscopy, Atomic Force Microscopy and X-ray diffraction (XRD). The synergistic effect of ErGO–MWNTs–L-cys nanocomposite was confirmed by Cyclic Voltammetry (CV) measurements in [Fe(CN)6]3-/4- redox. Experimental parameters, such as pH, accumulation time and electrochemical reduction degrees, were optimized. Under optimal conditions, the electrochemical performance of modified electrodes towards Pb2+ ions was examined and it exhibited appreciable improvement at the ErGO–MWNTs–L-cys/GCE. In terms of applications, Differential Pulse Anodic Stripping Voltammetry (DPASV) was employed for the determination of Pb2+ ions on ErGO–MWNTs–L-cys/GCE. The calibration plots between anodic current and Pb2+ ions exhibited linear relationship in the range of 0.2–40 μgL-1 with the detection limit calculated to be 0.1 μgL-1 (S/N=3). Finally, the ErGO–MWNTs–L-cys/GCE showed satisfied selectivity and stable results, and the Relative Standard Deviation (RSD) was calculated to be (RSD=2.15%).

Enhancing electrical, mechanical, and thermal properties of polybenzimidazole by 3D carbon nanotube@graphene oxide hybrid

In the present work, comparison of electrical conductivity , mechanical properties and thermal stability of graphene oxide (GO), multi-walled carbon nanotubes (MWCNTs) and GOMWCNT hybrid reinforced polybenzimidazole (PBI) nanocomposites prepared via one-pot in situ polymerization have been carried out. The influences of the nanofillers content and mass ratio of GOMWCNT hybrid on the tensile performances and dc conductivity of nanocomposite films were evaluated. In contrast to single-phase GO and MWCNTs, the incorporation of GOMWCNT (mass ratio of 1:1) hybrid into PBI matrix endows optimum dispersion of GO nanosheets and MWCNTs together with better synergistic enhancing effects on the resultant performances of nanocomposites. Both tensile strength and dc conductivity of the GOMWCNT/PBI (1:1) nanocomposites enhanced remarkably with addition of 0–5 Wt% GOMWCNT, followed by petty improvement at higher filler content. The highest dc conductivity of 2.43 × 10 −5 S/cm was achieved at 10 Wt% loading of GOMWCNT (1:1) in PBI. The dc conductivity was further enhanced to 1.06 × 10 −3 S/cm upon thermal annealing at 400 °C. The tensile strength showed 3-fold increase and the Young's modulus was enhanced by 12-fold with respect to the pure PBI. The reinforcing efficiency of GOMWCNT was predicted using the modified Halpin-Tsai modeling. This work provides a simple method to prepared GOMWCNT/PBI nanocomposite with high electrical conductivity and mechanical properties, which could be explored in potential applications in aerospace structure and aerospace electronics. • Polybenzimidazole nanocomposites reinforced with GO-MWCNT hybrid. • Nanocomposite with excellent dc conductivity, tensile strength and modulus. • Nanocomposite films could be useful for flexible electronic devices.

Characterization of electrodes modified with nanocomposites of cobalt tetraaminophenoxyphthalocyanine, reduced graphene and multi-walled carbon nanotubes

Glassy carbon electrodes or plates were modified with nanocomposites consisting of cobalt tetraaminophenoxyphthalocyanine (CoTAPhPc), reduced graphene oxide nanosheets (rGONs) and multi-walled carbon nanotubes (MWCNTs). The modified electrodes were characterized using cyclic voltammetry, scanning electrochemical microscopy (SECM) and time-of-flight-secondary ion mass spectrometer (TOF-SIMS). The electrocatalytic activity of the modified electrode was tested for detection of L-cysteine. The presence of CoTAPhPc on sequential layers of MWCNT and rGONs resulted in improved detection currents compared to CoTAPhPc alone or when MWCNT/rGONs are mixed in CoTAPhPc–MWCNT/rGONs (mix)–glassy carbon electrode (GCE). CoTAPhPc–MWCNT–GCE (without rGONS) showed higher sensitivity toward l-cysteine as compared to the probes incorporating rGONs with a catalytic rate constant of 4.62 × 104 M−1s−1 and a detection limit of 30 nM. The presence of rGONs improved the stability of the electrode.

A sensitive amperometric sensor for hydrazine based on Pt nanoparticles-reduced graphene oxide–multi-walled carbon nanotubes composite

ABSTRACTThe platinum nanoparticles-reduced graphene oxide-multi-walled carbon nanotubes composite (PtNPs-rGO-MWCNTs) has been synthesised by one-step chemical co-reduction strategy in ethylene glycol (EG) system using sodium citrate as reducing agent. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), as well as the electrochemical methods have been used for the characterisation of this composite. Benefiting from the large effective surface and good carrier function of rGO-MWCNTs, PtNPs in this nanocomposite have some excellent characteristics such as small particle size, good dispersion, as well as high electrocatalytic activity. Based on this, a new electrochemical sensor for hydrazine has been fabricated using dropping method. Under the optimum conditions, the linear range for the determination of hydrazine by amperometry at 0.20 V (vs. SCE) in phosphate buffer (pH 7.0) is from 2.0 × 10−7 mol L−1 to 2.3 × 10−3 mol L−1. The detection limit and sensitivity is 4.5 × 10−8 mol L−1 (S/N = 3) and 219.7 μA mM−1, respectively. This sensor has some attractive analytical features such as low detection limit, wide linear range, high sensitivity, as well as good stability.

Poly-L-Lysine functionalised MWCNT-rGO nanosheets based 3-d hybrid structure for femtomolar level cholesterol detection using cantilever based sensing platform

In this work we have developed a novel rGO-MWCNT (reduced graphene oxide-multiwalled carbon nanotube) nanocomposite material with Poly-L-Lysine functionalization which can be used for detection of biomolecules with enhanced sensitivity. The reduced GO sheets are found to play a major role as a connector and helps in the assembly of bundles of carbon nanotubes (CNTs) which may sometime play a role of upstanding nanostructures. The overall composite structure is further fully functionalized resulting in an overall high density of amino groups that can be used to capture biomolecules. The sensitivity of the as synthesized film is tested by the oxidation of cholesterol through cholesterol oxidase enzyme that is biochemically immobilized over these composite films. The test for the immobilization density of the novel films are carried out by mounting these films on sensitive thin section static micro/nano-cantilever platforms. The platforms have capability to measure cholesterol traces in blood upto an extent of 100 femto molar through deflection /bending of the cantilevers due to surface reaction. The films developed show a promise of high immobilization density which is further confirmed through fluorescence studies using FITC labeling of functionalized MWCNT-PLL and rGO-PLL films respectively.

Hydrothermal synthesis of three dimensional reduced graphene oxide-multiwalled carbon nanotube hybrids anchored with palladium-cerium oxide nanoparticles for alcohol oxidation reaction

The synergistic effect of 3D carbon support on Pd-based catalyst and its performance toward direct alcohol oxidation reaction is reported here. The surface of 3DrGO-MWCNTs support was modified by loading different amounts (5–20 wt%) of cerium oxide (CeO2) by wet impregnation method. Further, Pd nanoparticles were dispersed over CeO2/3DrGO-MWCNTs nanocomposites by chemical reduction method. The synthesized nanocomposites were characterized by various techniques such as XRD, XRF, SEM, TEM, Raman, and XPS analysis. The electro-oxidation performance and long-term stability of the Pd/CeO2/3DrGO-MWCNTs electro-catalyst were measured by CV, LSV, and CA analysis. The modification of the catalyst's surface by cerium oxide Pd/10CeO2/3DrGO-MWCNTs leads to a higher anodic peak current of about138.43 mA/cm2 and 91.72 mA/cm2 when compared to the Pd/3DrGO-MWCNTs and Pd/C for ethanol and methanol electro-oxidation. In addition, the catalyst showed the highest electro chemical active surface area. The present work demonstrates a possible way to fabricate a nanostructure catalyst to improve the performance of electro-catalytic reactions.

RuO2 modification of graphene oxide-multiwalled carbon nanotubes as excellent positive electrode for vanadium redox flow battery

Vanadium redox flow batteries (VRFBs) are one of the most appealing candidates for large-scale energy storage, and hence, they have to get more developed to overwhelm commercialization obstacles such as high price of membrane and vanadium electrolyte. In this work, we have synthesized “graphene oxide (GO)-multiwalled carbon nanotubes (MWCNT)-RuO2” as positive electrode material for VRFBs. The mixture of GO and MWCNT was prepared, and then, it was modified with RuO2 nanoparticles. The FE-SEM and XRD were utilized to investigate the morphology and structure of as-prepared electrocatalyst materials. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to look into the electrochemical performance of as-prepared electrocatalyst for vanadium IV/V redox couple reaction. GO-MWCNT-RuO2 reduced the charge transfer resistance from 223.20 Ω (MWCNT) and 186.60 Ω (GO-MWCNT) to 94.25 Ω. The voltammograms showed that peak separation potential was decreased from 605 mV for MWCNT down to 134 mV for GO-MWCNT-RuO2.

Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells

In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide nanowires (TiO2 NWs) and subsequent squeegee method to apply TiO2 NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm2. The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO2 NWs/TiO2 NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually.

Facile fabrication of 3D graphene–multi walled carbon nanotubes network and its use as a platform for natamycin detection

In this work, a three dimensional graphene-multiwalled carbon nanotubes (3DG-MWCNTs) network is successfully fabricated on the surface of glassy carbon electrode (GCE) using pulse potential method (PPM) in a graphene oxide-multi walled carbon nanotubes (GO-MWCNTs) homogeneous dispersion. Scanning electron microscopy (SEM) images and electrochemical experiments confirmed the 3D structure of interpenetrated graphene-MWCNTs network and excellent electrochemical performance. The 3DG-MWCNTs network was presented to develop a sensitive voltammetric sensor for detection of natamycin. Systematic electrochemical tests demonstrate that the 3DG-MWCNTs network modified electrode can effectively increase response to the oxidation of natamycin due to the large accessible surface area as well as its excellent conductivity. Under optimized conditions, the voltammetric sensor showed a linear relationship in the range of 5.0 × 10−8–2.5 × 10−6 mol L−1 and a low detection limit of 1.0 × 10−8 mol L−1. Moreover, the proposed method was also applied for detection of natamycin content in real samples (commercial red wine and beverage).

Improved dielectric behaviour of graphene oxide-multiwalled carbon nanotube nanocomposite

We have prepared graphene oxide (GO)-multiwalled carbon nanotube (MWCNT) composite film through vacuum filtration method. In this work, we carried out the dielectric behaviour of GO-MWCNT composite film in the frequency range of 100 Hz to 1 MHz and temperature range of 30–200 °C. The GO-MWCNT composite film showed significantly higher dielectric constant as 6021 than the GO (5031) which was even very high compared to conventional dielectric materials. The enhancement of dielectric constant is attributed to the strong interaction between sp2 MWCNT fillers and sp3 GO matrix as well as the formation of microcapacitors by highly conductive MWCNT segregated by GO sheets. Furthermore, we found interesting transition between semiconductor to conductor was attained at 165 °C. It is suggested that the temperature dependent transition of electrical properties of GO-MWCNT composite film is closely related with the ion mobility, removal of water molecules and reduction of GO in the composite. The effect of interfacial polarization and relaxation process were studied. The redox peak current has increased significantly for the GO-MWCNT composite electrode than the GO and MWCNT where the highly conducting MWCNT provide the necessary conduction pathways on the electrode surface. These flexible, high dielectric constant nanocomposites are potential flexible dielectric materials for use in high frequency capacitors and in electronic devices.

R-GO/MWCNTs Nanocomposite Film as Electrode Material for Supercapacitor

We synthesized a reduced graphene oxide (r-GO) multi-walled carbon nanotube (MWCNTs) nanocomposite film via layer by layer (LBL) assembly. This structure was prepared by vacuum filtration and heat-treated at a low temperature of 500°C. The morphology of the sample was determined by field emission electron spectroscopy (FE-SEM). The structural detail and the chemical analysis were characterized by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The cyclic voltammetry (CV) curve of r-GO/MWCNTs nanocomposite appeared nearly rectangular in shape. The current density (A/g) was gradually increased by increasing the scan rate of the voltage, as high as a scan rate of 500 mVs-1. At a current density of 10 mAg-1, the specific capacitance of the nanocomposite, estimated by galvanostatic (GA) charge/discharge measurement, is 150 Fg-1. These nanocomposites can be developed for supercapacitor electrodes.

Electrochemical Determination of Bisphenol A on a Glassy Carbon Electrode Modified with Gold Nanoparticles Loaded on Reduced Graphene Oxide-multi Walled Carbon Nanotubes Composite

Abstract A glassy carbon electrode (GCE) modified with gold nanoparticles loading on the reduced graphene oxide (rGO)-multi-walled carbon nanotubes (MWCNTs) composite film was fabricated by a two-step procedure. Firstly, rGO-MWCNTs composite were prepared by in-situ chemical reduction with hydrazine as a reducing agent. Then, gold nanoparticles (AuNPs) were deposited on the surface of rGO-MWCNTs using simple cyclic voltammetry. This modified electrode was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and electrochemical methods. Furthermore, the electrochemical behavior of bisphenol A (BPA) was also investigated using this modified electrode. The results showed that the modified electrode had high electrochemical activity for the oxidation of BPA. In 0.10 M phosphate buffer (PBS, pH 7.0), the linear range for the determination of BPA with differential pulse voltammetry (DPV) was in the range of 5.0 × 10−9−1.0 × 10−7 M and 1.0 × 10−7−2.0 × 10−5 M. The detection limit was 1.0 × 10−9 M (S/N = 3). The as-prepared modified electrode was successfully used to determine BPA in river water and the shopping receipt samples with recoveries range of 97%–110% and 98%–104%, respectively.

Electrochemical behavior of a Nafion‐membrane‐based solid‐state supercapacitor with a graphene oxide—multiwalled carbon nanotube—polypyrrole nanocomposite

ABSTRACTIn this study, we sprayed a graphene oxide–multiwalled carbon nanotube (GM) suspension in isopropyl alcohol–water onto a Nafion membrane. The electrodeposition of polypyrrole (PPy) was carried out on Nafion to complete the fabrication of a solid‐state symmetric supercapacitor. Nafion 117 membranes are used as electrolyte separators in the preparation of supercapacitors. The characterization of the symmetric supercapacitor was done by X‐ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the symmetric solid‐state supercapacitor were investigated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques in 1M lithium chloride. A specific capacitance of 90.4 mF/cm2 (258.3 F/g1) was obtained for the supercapacitor at a scan rate of 10 mV s−1. Maximum energy and power densities of 10 W h/kg and 6031 W/kg were obtained for the fabricated supercapacitor. In such a symmetric configuration, the highly interconnection networks of GM–PPy provided good structure for the supercapacitor electrode, and the good interaction between PPy and GM provided fast electron‐ and charge‐transportation paths so that a high capacitance was achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44926.

Graphene oxide-multiwalled carbon nanotubes composite as an anode for lithium ion batteries

AbstractNowadays reduced graphene oxide (rGO) is regarded as a highly interesting material which is appropriate for possible applications in electrochemistry, especially in lithium-ion batteries (LIBs). Several methods were proposed for the preparation of rGO-based electrodes, resulting in high-capacity LIBs anodes. However, the mechanism of lithium storage in rGO and related materials is still not well understood. In this work we focused on the proposed mechanism of favorable bonding sites induced by additional functionalities attached to the graphene planes. This mechanism might increase the capacity of electrodes. In order to verify this hypothesis the composite of non-reduced graphene oxide (GO) with multiwalled carbon nanotubes electrodes was fabricated. Electrochemical properties of GO composite anodes were studied in comparison with similarly prepared electrodes based on rGO. This allowed us to estimate the impact of functional groups on the reversible capacity changes. As a result, it was shown that oxygen containing functional groups of GO do not create, in noticeable way, additional active sites for the electrochemical reactions of lithium storage, contrary to what has been postulated previously.

Reduced graphene oxide–multiwalled carbon nanotubes composites as sensing membrane electrodes for DNA detection

Thin films of reduced graphene oxide–multiwalled carbon nanotube (rGO–MWCNT) composites were demonstrated as sensing membrane electrodes for single-stranded DNA (ssDNA) detection. The morphology of the rGO–MWCNT composite thin films was observed via field emission scanning electron microscopy. The GO sheet and MWCNTs were clearly obtained, and the MWCNTs were uniformly distributed on the surface of the GO. The chemical bonding of the rGO–MWCNTs was examined using Fourier transform infrared spectroscopy. The element compositions of carbon, silicon, and oxygen were confirmed via energy-dispersive X-ray spectroscopy and X-ray powder diffraction analysis. The biosensor demonstrated high sensitivity to the ssDNA target with a linear range from 500 to 100 pM. Furthermore, the biosensor demonstrated good selectivity, reproducibility, and long-term stability for DNA detection. Since, the biosensor responded very-well and demonstrated excellent detection capabilities, it is highly recommended to be used in detecting specific biomarkers and other targeted proteins.