Reduced Graphene Oxide Composites Research Articles

Sensitive and selective determination of tryptophan using a glassy carbon electrode modified with nano-CeO2/reduced graphene oxide composite

Nano-CeO2/reduced graphene oxide (RGO) composite were successfully prepared using a simple electrochemical technique. The structure and morphology of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Numerous of CeO2 nanocrystals are found to be wrapped inside uniformly by gossamer like RGO. The electrochemical behaviors of tryptophan (Trp) on the glassy carbon electrode modified with nano-CeO2/RGO (nano-CeO2/RGO/GCE) were investigated by second derivative linear sweep voltammetry (SDLSV) and cyclic voltammetry (CV). It was found that high electrocatalytic activity was exhibited on the modified electrode for Trp oxidation. The peak current increased about 76-fold and the peak potential shifted 88 mV negatively at the nano-CeO2/RGO/GCE compared with that of the bare GCE, demonstrating the synergistic effect of nano-CeO2 and RGO on the electrode surface. The measurement parameters are optimized. Under the optimum conditions, a good linear relationship was observed between Trp oxidation peak current and its concentration in the range of 0.01–10 μM, with a sensitivity of 4.7306 μA μM−1 and the detection limit was obtained as 6.0 nM (S/N = 3) after accumulating at 0 V for 90 s. The developed method also exhibited good reproducibility, stability and anti-interference ability, and has been successfully applied to Trp detection in commercial compound amino acid injections, human serum and human urine samples with recoveries of 98.5%-106.0%.

Corrosion Protection Characteristics of Reduced Graphene Oxide Composites in Microelectronic Devices

This study investigates the effects of the corrosion protection and temperature coefficient of resistivity (TCR) properties of poly-vinyl-alcohol (PVA)/graphene oxide (GO) composites on the zinc substrate and copper (Cu) damascene interconnects. As the PVA content increased, significant amounts of fine wrinkles were observed in the films, and the coating uniformity of the composites also increased. The electrical properties of the composites indicated that the TCR can be improved by optimizing the weight % ratio of PVA/GO. After performing the accelerated corrosion test, the Cu films were lost at the coating interface and at the area without GO coating, but remained at the GO coating bottom area in the SEM and EDX observations. The results shows that corrosion of the Cu interconnects can be prevented by using the composites film and also help solve the resister–capacitor time delay problem.

Optimizing high voltage Na3V2(PO4)2F3 cathode for achieving high rate sodium-ion batteries with long cycle life

Sodium-ion batteries have gained an intense attention as a promising alternate for Li-ion batteries due to their low cost, and abundant availability. To meet high energy density requirements, developing a high voltage cathode with ultra-long cycle life is of great importance. Na3V2(PO4)2F3 (NVPF) features a high working voltage, fast sodium-ion diffusion channels, and small volume change during the cycling process. However, the practical performance of NVPF cathode is currently hindered by poor Na+ ion diffusion at high voltage, low cycle life, and limited rate behavior. Herein, we evaluate the effect of synthesis conditions in sol–gel technique, binders (PVDF, PAI and CMC), and electrolytes (ether, and ester based solvents) to overcome the diffusion limitation in high voltage NVPF cathode. Benefiting from the synergistic effect of CMC binder, and DEGME electrolyte, and reduced graphene oxide composite, NVPF effectively overcome the potential barrier during Na+ ion insertion/extraction at high voltage. NVPF with CMC binder and DEGDME electrolyte displayed a high Na+ ion diffusion kinetics, low cell resistance, and delivered an excellent electrochemical performance. NVPF delivered a high coulombic efficiency (92%), long cycle life (10,000 cycles), and an excellent rate performance (50 C), outperforming the conventional PVDF binder, and carbonate based electrolytes. Furthermore, the full-cell constructed by NVPF cathode, and Na3V2(PO4)3 anode delivered an capacity retention. The current study provides new insights for overcoming the kinetic barrier during sodium ion storage in high voltage cathode that could direct the research development towards high energy sodium-ion batteries.

Exploration on the influence mechanism of heteroatom doped graphene on thermal oxidative stability and decomposition of polypropylene

The inferior thermal oxidative stability of polypropylene (PP) is a limitation for its practical applications. In this study, PP composites filled with heteroatom doped graphene are prepared. Heteroatoms with different electronegativity values, including nitrogen, phosphorus and boron, are successfully doped into the structure of reduced graphene oxide (RGO) through high temperature annealing. Doped RGO is characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. PP/doped graphene composites are acquired by solution blending. The effects of heteroatom doped RGO on thermal oxidative stability and decomposition behavior of PP are investigated by thermogravimetric analysis and thermogravimetric-infrared spectrometry, respectively. The results indicate that doped RGO can significantly improve thermal oxidative stability of PP. Compared with neat PP, the temperature at maximum weight loss rate of PP/N-RGO-2.0, PP/B-RGO-2.0 and PP/P-RGO-2.0 are increased by 112 °C, 141 °C and 122 °C, respectively. Thermal oxidative decomposition mechanism of PP/doped RGO composites is discussed based on the analyses of pyrolysis gaseous products and chemical structures of doped RGO. This work provides a novel exploration for enhancing thermal stability of polymer. This work provides an investigation strategy for in-depth study of enhancement mechanisms of graphene on thermal stability of polymers.

Nano-Zn2SnO4/Reduced Graphene Oxide Composites for enhanced photocatalytic performance

An easy yet viable hydrothermal reaction is demonstrated to prepare ultra-small Zn2SnO4 nanoparticle with ~4.2 nm decorated reduced graphene oxide (RGO) nanocomposites (Zn2SnO4-RGO). The pure phase Zn2SnO4 nanoparticles with ~4.2 nm can be achieved during hydrothermal reaction, meanwhile, these nanoparticles uniformly dispersed on 2D graphene sheet, and graphene oxide was reduced. The photocatalytic performances of the as-prepared Zn2SnO4-RGO nanocomposites with different RGO mass ratio are investigated. The optimum synergetic effect is found when the RGO mass ratio is 7.11%, with the photocurrent and photodegradation efficiency improved by about 300% and 80% on methylene blue (MB), respectively, compared with the pure Zn2SnO4 nanoparticles.

One pot green synthesis of novel rGO@ZnO nanocomposite and fabrication of electrochemical sensor for ascorbic acid using screen-printed electrode

Developing a novel sensor for analysing of ascorbic acid present in food items and nutraceuticals is been very important research topic for materials scientists, medicine and food researchers. In the present work, we demonstrate the detection of an ascorbic acid (AA) by using an electrochemical sensor made from novel rGO@ZnO nanocomposite material. We synthesized a ZnO-nanoparticle-decorated reduced graphene oxide composite (rGO@ZnO) using a one-pot hazard free green-hydrothermal method. Multi characterization techniques like X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and Raman spectroscopy, were precisely used to understand the structure and properties of the rGO@ZnO nanohybrid. Finally, the synthesized rGO@ZnO nanohybrids were utilized to fabricate low cost screen printed electrode (SPE) electrochemical sensor for highly sensitive detection of ascorbic acid (AA). The observed electrochemical sensing results indicate wide linearity from 0.1 mmol to 1.5 mmol with good repeatability and reproducibility. The results confirm that the synthesized novel rGO@ZnO nanohybrids exhibit excellent electrocatalytic activity towards AA with high stability and sensitivity.

Visible-light-driven photocatalytic formation of propylene carbonate using FeNbO4/reduced graphene oxide composites

Photocatalytic cycloaddition of carbon dioxide to propylene oxide was achieved using a series of novel FeNbO4/reduced graphene oxide composites. Three different mass ratios of reduced graphene oxide incorporated FeNbO4 were used, namely, FeNbO4–3% rGO, FeNbO4–5% rGO, and FeNbO4–10% rGO. Prepared photocatalysts were characterized using UV–Visible (UV–Vis) diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) for determination of the specific surface area and porosity. The successful incorporation of reduced graphene oxide into FeNbO4 was further supported with the enhanced photocatalytic performance of these composites, furthermore, FeNbO4–5% rGO exhibited the highest photocatalytic cyclic carbonate formation reaching up to 57% yield. Detailed investigation shows that the prepared composites are promising heterogeneous photocatalysts for the cycloaddition of carbon dioxide under simulated visible light irradiation, their enhanced photocatalytic activities ascribed to the enhanced separation efficiency of photo-generated charge carriers. To the best of our knowledge, this study is the first to report the preparation of FeNbO4/ reduced graphene oxide composites photocatalysts.

NIR-light-induced thermoset shape memory polyurethane composites with self-healing and recyclable functionalities

To endow thermoset shape memory polymers with self-healing and recyclable functionalities is highly desirable. In this study, we fabricated Diels-Alder crosslinked polyurethane/functionalized reduced graphene oxide composites (DAPU-FRGOs) through in situ polymerization. The incorporated FRGO with urethane chains could achieve good compatibility with the DAPU matrix, forming physical and chemical crosslinking structures in the composite. And the most effective improvements of mechanical, thermal stability, crystallization-triggered, and photothermal effect were achieved for the DAPU/FRGO2 composite with 2 wt% FRGO. Owing to the outstanding crystallization-induced and photo-thermal effects of FRGO and the thermal reversible behavior of Diels-Alder bonds, the DAPU-FRGO2 composite showed rapid shape memory (<10 s, shape-fixity and recovery ratios were 92.3% and 94.1%, respectively) and self-healing (<120 s, healing efficiencies for tensile strength and elongation at break were 89.3% and 90.4%, respectively) under near-infrared light. Meanwhile, the DAPU-FRGO2 composite exhibited good repeatability of self-healing and shape-memory functionalities, and its shape memory parameters and healing efficiencies were maintained above 92% and 85% after three-cycles, respectively. Further recycling test demonstrated that the mechanical properties of the recycled DAPU-FRGO2 composite could be recovered to more than 82% of the original sample. This work provides a heuristic perspective for designing durable light-responsive thermoset shape memory composite materials.

Highly Oriented β-Bi2O3-decorated Reduced Graphene Oxide Composites for Supercapacitor Electrodes

Highly Oriented β-Bi2O3-decorated Reduced Graphene Oxide Composites for Supercapacitor Electrodes

High electricity generation and COD removal from cattle wastewater in microbial fuel cells with 3D air cathode employed non-precious Cu2O/reduced graphene oxide as cathode catalyst

In this study, we synthesized a non-precious Cu2O decorated reduced graphene oxide composite (Cu2O/rGO) by a facile and direct reduction strategy and evaluated the electricity generation and COD removal performance of MFCs with Cu2O/rGO as cathode catalyst in treating cattle wastewater. The Cu2O/rGO with the mass Cu(Ac)2/GO ratio of 450:50 exhibited the highest catalytic activity by cyclic voltammetry (CV) experiment. The large surface area (363.9 m2 g−1) of Cu2O/rGO with numerous mesoporous exhibited higher exchange current density (12.38 μA cm−2) and lower War-burg impedance (21.82 Ω) comparing with Pt/C (11.99 μA cm−2, 102.10 Ω), and contributed to 4-electron ORR. Notably, the maximum output voltage, power density and coulombic efficiency of MFC with 3D air cathode employed Cu2O/rGO catalyst reached 0.165 V, 1362 mW m−2 and 54.9%, respectively, which were higher than those (0.152 V, 1166 mW m−2 and 53.5%) with 3D air cathode employed Pt/C catalyst in treating cattle wastewater. Moreover, the average COD removal rate of MFC with Cu2O/rGO catalyst reached 71.5%, which were higher than those 69.8% with Pt/C catalyst. Generally, the MFC with 3D air cathode employed non-precious Cu2O/rGO catalyst instead of Pt/C catalysts is a promising method for simultaneous electricity generation and cattle wastewater treatment.

Reduced graphene oxide composites and its real-life application potential for in-situ crude oil removal

Crude oil pollution can cause severe and long-term ecological damage and oil cleanup has become a worldwide challenge. Conventional treatment strategies like in-situ burning, manual skimmer and bioremediation were labor-intensive and time-consuming. The high viscosity of crude oil also posed difficulty for traditional absorbents. Herein, to address these limitations, we designed and fabricated a floating absorbent that was comprised of reduced graphene oxide (RGO), melamine sponge (MS), and a 3D-printed mounting platform. Through a facile one-pot hydrothermal method, graphene oxide (GO) was simultaneously reduced to RGO and loaded in MS (RGO-MS). The resulted RGO-MS composites possess desirable hydrophobicity/oleophilicity for oil absorption with a water contact angle of 122°. The effective light-to-heat conversion allowed the RGO-MS composite to absorb approximately 95 times its own weight of crude oil within 12 min under light irradiation. A 3D-printed mounting platform for RGO-MS composites was further fabricated to improve its applicability and allow easy retrieval. Taking advantages of the RGO’s hydrophobicity/oleophilicity and photothermal property, the floating ability of MS, this study demonstrated the real-life applicability of RGO-MS composites for in-situ crude oil cleanup.

Electrochemical sensor for determination of bisphenol A based on MOF-reduced graphene oxide composites coupled with cetyltrimethylammonium bromide signal amplification

A sensitive electrochemical sensor was fabricated for the rapid determination of bisphenol A (BPA) based on cerium-centered metal-organic framework electrochemically reduced graphene oxide composite (Ce-MOF-ERGO) coupled with cetyltrimethylammonium bromide (CTAB) signal amplification. The Ce-MOF-ERGO was synthesized by electrochemical reduction of Ce-MOF-graphene oxide (GO) composite. Under the optimized conditions, the proposed electrochemical sensor exhibited a linear response for BPA in concentration range 3 nM to 10 μM with a detection limit of 1.9 nM. The excellent performance of the proposed sensor was attributed to the high conductivity, large surface area, and catalytic activity of Ce-MOF-ERGO composite. Moreover, the oxidation signals of BPA on Ce-MOF-ERGO-modified electrode were further enhanced significantly after addition of CTAB in electrolyte solution. Based on the dual signal amplification strategy, the sensor exhibited high sensitivity for BPA detection and was successfully applied to detect BPA in real samples with good recoveries.

Facile synthesis of perovskite lanthanum aluminate and its green reduced graphene oxide composite for high performance supercapacitors

A facile simple hydrothermal synthetic route has been developed for the synthesis of perovskite lanthanum aluminate (LaAlO3) and reduced graphene oxide composite (RGO). Green tea extract here is used as reducing agent for conversion of graphene oxide to reduced graphene oxide. The synthesized materials have been characterized for its morphology using, XRD, SEM, EDAX, FTIR and BET techniques. The materials are used as electrode materials for supercapacitor applications. Electron microscopic images indicate RGO sheets are densely attached to surface of LaAlO3 with perforated cage like morphology. A high specific capacitance of 721 F g−1 at a scan rate of 2 mV s−1 was exhibited by RGO/LaAlO3 hybrid structure electrode when compared to pure RGO (531 F g−1) and pure LaAlO3 (105 F g−1) electrodes at the same scan rate using cyclic voltammetry (CV). By using chronopotentiometry (CP), the RGO/LaAlO3 hybrid structure electrode out stretched specific capacitance of 283 F g−1 at a current density of 0.5 A g−1 and able to retain specific capacitance (Csp) of about 157 F g−1 even at very high current density of 20 A g−1. RGO/LaAlO3 composite also possesses an energy density of 57 Wh kg−1 with a maximum power density of 569 W kg−1. RGO/LaAlO3 nanocomposite has also been fabricated for asymmetric supercapacitor device (ASD) system. From the Electrochemical Impedance Spectroscopy (EIS), the RGO/LaAlO3 hybrid structure electrode has shown phase angle close to −90° for frequency up to 0.01 Hz, suggesting that the nanocomposite electrode material approached ideal capacitor behaviour.

MnO2 Nanowires-Decorated Reduced Graphene Oxide Modified Glassy Carbon Electrode for Sensitive Determination of Bisphenol A

In this paper, MnO2 nanowires-decorated reduced graphene oxide composite (MnO2 NWs-rGO) was synthesized by physical adsorption and controlled potential reduction. Means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and cyclic voltammetry (CV) were used to characterize this material. Glassy carbon electrode (GCE) modified with MnO2 NWs-rGO composite was fabricated by drop-coating method for the sensitive determination of bisphenol A (BPA). Electrochemical behaviors of BPA at the MnO2 NWs-rGO/GCE were studied using CV and chronocoulometry (CC). Experimental results found that MnO2 NWs-rGO/GCE exhibited excellent electrocatalytic activity, sensitivity, stability, and selectivity towards BPA. Under the optimized experimental conditions, quantitative analysis was carried out using the second derivative linear sweep voltammetry (SDLSV), and the MnO2 NWs-rGO/GCE revealed a good linear response to BPA concentration ranging from 0.02–20 μM and 20–100 μM, and the detection limit was 6.0 nM (S/N = 3). This new method possessed some obvious advantages, such as high determination sensitivity, simple preparation process, rapid response and low cost. The sensing performance of MnO2 NWs-rGO/GCE was demonstrated for the detection of BPA in plastic samples, and satisfactory results have been obtained. Therefore, an efficient determination method for monitoring trace levels of BPA was developed.

Polypyrrole modified magnetic reduced graphene oxide composites: synthesis, characterization and application for selective lead adsorption.

To enhance the ability to remove lead from water, polypyrrole modified magnetic Fe3O4/reduced graphene oxide composites (PPy-FG) were prepared via in situ polymerization and employed for the Pb(ii) adsorption. The physicochemical structure and adsorption mechanism of the prepared magnetic PPy-FG were studied via vibrating sample magnetometer, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy. The effects of several factors on Pb(ii) adsorption were evaluated, including pH value, temperature, and competitive ions. Under the optimal conditions (pH 5 and 298 K), the maximum adsorption capacity of PPy-FG was 93.2 mg g−1 giving an improvement of 31% over that of 71 mg g−1 for Fe3O4/reduced graphene oxide (Fe3O4/rGO). Moreover, the experimental data were well fitted with the Langmuir adsorption model and the pseudo-second-order kinetics model, indicating that the adsorption process was mainly a monolayer chemical adsorption. Thermodynamic studies revealed a spontaneous and endothermic adsorption process. The selective adsorption of Pb(ii) by PPy-FG is superior to that of Fe3O4/rGO in the presence of similar metals in the same medium. In addition, the adsorption performance of PPy-FG showed great potential in the remediation of heavy metal contaminated water through using its magnetic properties and excellent affinity for heavy metals.

Mechanism of nicotine degradation and adsorption by a nano-TiO2 engineered reduced graphene oxide composite in light variant conditions

Excellent nicotine degradation was demonstrated by the rGO–TiO2 nanohybrid due to ROS generation under UV irradiation as well as nicotine adsorption on defective carbon rings of the rGO–TiO2 nanohybrid in visible light.

Retraction: Simultaneous sorption and reduction of U(vi) on magnetite-reduced graphene oxide composites investigated by macroscopic, spectroscopic and modeling techniques.

Retraction of ‘Simultaneous sorption and reduction of U(vi) on magnetite–reduced graphene oxide composites investigated by macroscopic, spectroscopic and modeling techniques’ by Wencai Cheng et al., RSC Adv., 2015, 5, 59677–59685, DOI: 10.1039/C5RA10451C.

Enhancement of ultrafast nonlinear optical response of zinc selenide nanoparticle decorated reduced graphene oxide sheets

The synergistic effect of zinc selenide (ZnSe) nanoparticle functionalized into reduced graphene oxide (RGO) sheets on nonlinear optical (NLO) properties has been investigated by single beam z-scan technique. Comprehensive measurements on nonlinear absorption (NLA) as well as nonlinear refraction (NLR) have been performed on RGO, ZnSe, and RGO-ZnSe composites at 630 nm in the femtosecond regime. Both NLA and NLR of RGO-ZnSe show an enhancement in NLO properties compared to pure RGO and ZnSe in an intensity range of 37GW/cm2 to 130GW/cm2. The enhanced optical nonlinearity of RGO-ZnSe may have been caused due to strong interlayer coupling between RGO and ZnSe, as well as the availability of a large number of NLA states in the composite. The interlayer coupling between ZnSe nanoparticles and RGO sheets has been confirmed by transmission electron microscopy, UV-Visible, and photoluminescence spectroscopy. At low input pulse intensity (∼37GW/cm2), saturation absorption dominates, whereas NLA becomes prominent in the higher intensity regime (55GW/cm2–130GW/cm2) for RGO and ZnSe. NLA is the dominant phenomenon for RGO-ZnSe in the whole experimental intensity range. Moreover, it is observed that the dispersion of RGO, ZnSe, and RGO-ZnSe in dimethylformamide exhibits positive NLR. This study indicates an enhancement in nonlinear optical response of the RGO-semiconductor composite, which is very promising for graphene based photonic device applications.

Superior decontamination of toxic organic pollutants under solar light by reduced graphene oxide incorporated tetrapods-like Ag3PO4/MnFe2O4 hierarchical composites

To fabricate an efficient, eco-friendly and stable photocatalyst, the current work describes a demonstration of simple synthesis approach of Ag3PO4/MnFe2O4(x wt%)/reduced graphene oxide composites. Ag3PO4/MnFe2O4 (5 wt%) revealed superior activity for decontamination of dye pollutant. Further, rGO was incorporated with Ag3PO4/MnFe2O4 (5 wt%) to investigate its effect on their overall properties. The resultant composites were characterized by various analytical techniques to confirm their structural and physical-chemical features. FESEM analysis showed that morphology of Ag3PO4 varied significantly from orthorhombic dodecahedrons to tripods and tetrapods with the combinations MnFe2O4 (5 wt%), and MnFe2O4 (5 wt%)+rGO respectively. The photocatalytic decontamination of toxic organic dyes tested against Rhodamine B(RhB) and 4-Nitrophenol. The outstanding performance for decontamination of RhB was observed for Ag3PO4/MnFe2O4(5 wt%)/rGO (~99% in 5 min) with the rate of k = 7.28 × 10−1 min−1. The enhanced activity of Ag3PO4/MnFe2O4(5 wt%)/rGO composites credited to co-catalytic effects of MnFe2O4 and physiochemical properties of rGO which leads to making intimate contact with Ag3PO4 to form heterojunction and rGO served as a medium for charge transfer to prevent their recombination. The incorporation of rGO in Ag3PO4/MnFe2O4 (5 wt%) composite leads to a considerable increase in the photocatalytic activity by offering improved surface area and properties, high electron stability and mobility. Based on experiment results, the photocatalytic enhancement mechanism for organic pollutants degradation was discussed. The recyclability of Ag3PO4/MnFe2O4(5 wt%)/rGO hierarchical composite was evaluated by replicated photocatalytic reaction trials. Overall, the morphological transformation of Ag3PO4/MnFe2O4(5 wt%)/rGO composites played a dynamic role in determining their photocatalytic activity towards the organic industrial dye pollutants.

PVP-assisted laser ablation growth of Ag nanocubes anchored on reduced graphene oxide (rGO) for efficient photocatalytic CO2 reduction

Metallic nanoparticles loaded graphene nanocomposites have been widely studied for various scientific and technological applications. In this study, a facile method was reported to realize a straightforward growth of shape and size-controllable of metallic nanoparticles, and the subsequent hybridization with graphene in solution by strategically coupling wet-chemical route and laser ablation. By mixing graphene oxide (GO) with a tunable concentration level of polyvinylpyrrolidone (PVP) in aqueous solution, Ag nanocubes with a face-centered cubic crystal structure were generated by pulsed laser ablation and then mounted on GO nanosheets with the assistance of PVP. The preferential adsorption of PVP to Ag (100) crystal face led to the production of Ag nanocubes with exposed (100) facet. The result showed that the morphological yield of spherical particles decreased with the increase in PVP concentration. X-ray diffraction (XRD) and UV–visible spectroscopy analyses confirmed that GO was partially reduced. In the reduction of CO2 gas, the photocatalytic conversion rate could achieve 133.1 μmol g−1 h−1 in 6 hrs for cubic Ag-loaded reduced GO composites.