Reduced Graphene Oxide Fe3O4 Research Articles

Magnetization Enhancement of Fe3O4 by Attaching onto Graphene Oxide: An Interfacial Effect

In this paper, we have reported about the enhancement of magnetization and blocking temperature of the Fe3O4-reduced graphene oxide (RGO) nanocomposite, which is formed by embedding Fe3O4 nanoparti...

Clean water generation with switchable dispersion of multifunctional Fe3O4-reduced graphene oxide particles

With the increased need for clean water and decreased supply of fresh water, purification of contaminated water can provide clean water that supplements the fresh water from nature. Physical adsorption, photo-degradation and solar-driven evaporation processes are promising ways to generate clean water with minimum environmental impact. However, different purification process requires different dispersion state of the treating agent to maximize its performance. Herein, we demonstrate that Fe3O4-reduced graphene oxide (MrGO) particles with switchable dispersion can be used as the multifunctional water treating agents to efficiently purify contaminated water through different processes. Under homogenously dispersed nanofluid mode, the MrGO particles have large exposed surface areas and can efficiently remove organic dye pollutants through physical adsorption. The uniform dispersion state also favors high contact efficiency facilitating decontamination of high concentration of organic compounds through solar-driven photocatalytic degradation by the MrGO particles. The excellent magnetic response of MrGO particles not only allows for easy collection of the treating agent from water but also enables assembly of MrGO at the air-water interface with external magnets. Under such interfacial assembled mode, clean water can be distilled out of the contaminated solution with high evaporation efficiency of 74.7% under simulated natural solar radiation. This work demonstrates that dispersion state can be used as another important means to optimize water purification performances.

Design of three-dimensional macroporous reduced graphene oxide–Fe3O4 nanocomposites for the removal of Cr(VI) from wastewater

Three-dimensional macroporous reduced graphene oxide–Fe3O4 nanocomposites (3D macroporous rGO–Fe3O4 nanocomposites) were synthesized through electrostatic self-assembly method. The morphology and structure characteristics of 3D macroporous rGO–Fe3O4 nanocomposites were studied in detail. Then 3D macroporous rGO–Fe3O4 nanocomposites were used as adsorbents for the removal of Cr(VI) from wastewater. The effects of contact time and solution pH on the adsorption properties of 3D macroporous rGO–Fe3O4 nanocomposites were also investigated. Due to the hierarchical porous structure, high surface area and large pore volume, 3D macroporous rGO–Fe3O4 nanocomposite adsorbents exhibited excellent adsorption capability and rapid adsorption rates for Cr(VI) from aqueous solution. The kinetic and isothermal studies suggested that the adsorption process could be best described by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. Moreover, the adsorbents could be separated easily by an external magnetic field for reusability, demonstrating great potential for the treatment of wastewater containing Cr(VI) during practical applications.

Magnetic nanoparticle decorated graphene based electrochemical nanobiosensor for H2O2 sensing using HRP.

To utilize synergetic effect of graphene's higher conductivity and magnetic nanoparticles biocompatibility, an electrochemical nanobiosensor is constructed based on magnetic nanoparticle decorated graphene (MRGO) using Horseradish peroxidase (HRP) for H2O2 sensing. Sensors based on magnetic nanoparticles (MNP) and reduced graphene oxide (RGO) are studied for comparison. MNP, RGO and MRGO were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). XRD studies have confirmed successful synthesis of Fe3O4 MNPs, RGO and MRGO. TEM micrographs revealed uniform decoration of MNPs on graphene. FTIR confirmed the immobilization of HRP on MNP, RGO and MRGO. The MRGO based sensor exhibited higher sensitivity (48.08 μA μM-1 cm-2) compared to MNP (39.08 μA μM-1 cm-2) and RGO (41.08 μA μM-1 cm-2) based biosensors.

Lightweight reduced graphene oxide-Fe3O4 nanoparticle composite in the quest for an excellent electromagnetic interference shielding material

This work reports a detailed study of reduced graphene oxide (rGO)-Fe3O4 nanoparticle composite as an excellent electromagnetic (EM) interference shielding material in GHz range. A rGO-Fe3O4 nanoparticle composite was synthesized using a facile, one step, and modified solvothermal method with the reaction of FeCl3, ethylenediamine and graphite oxide powder in the presence of ethylene glycol. Various structural, microstructural and optical characterization tools were used to determine its synthesis and various properties. Dielectric, magnetic and EM shielding parameters were also evaluated to estimate its performance as a shielding material for EM waves. X-ray diffraction patterns have provided information about the structural and crystallographic properties of the as-synthesized material. Scanning electron microscopy micrographs revealed the information regarding the exfoliation of graphite into rGO. Well-dispersed Fe3O4 nanoparticles over the surface of the graphene can easily be seen by employing transmission electron microscopy. For comparison, rGO nanosheets and Fe3O4 nanoparticles have also been synthesized and characterized in a similar fashion. A plot of the dielectric and magnetic characterizations provides some useful information related to various losses and the relaxation process. Shielding effectiveness due to reflection (SER), shielding effectiveness due to absorption (SEA), and total shielding effectiveness (SET) were also plotted against frequency over a broad range (8–12 GHz). A significant change in all parameters (SEA value from 5 dB to 35 dB for Fe3O4 nanoparticles to rGO-Fe3O4 nanoparticle composite) was found. An actual shielding effectiveness (SET) up to 55 dB was found in the rGO-Fe3O4 nanoparticle composite. These graphs give glimpses of how significantly this material shows shielding effectiveness over a broad range of frequency.

Fabrication of Amine-Modified Magnetite-Electrochemically Reduced Graphene Oxide Nanocomposite Modified Glassy Carbon Electrode for Sensitive Dopamine Determination.

Amine-modified magnetite (NH2–Fe3O4)/reduced graphene oxide nanocomposite modified glassy carbon electrodes (NH2–Fe3O4/RGO/GCEs) were developed for the sensitive detection of dopamine (DA). The NH2-Fe3O4/RGO/GCEs were fabricated using a drop-casting method followed by an electrochemical reduction process. The surface morphologies, microstructure and chemical compositions of the NH2–Fe3O4 nanoparticles (NPs), reduced graphene oxide (RGO) sheets and NH2–Fe3O4/RGO nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The electrochemical behaviors of DA on the bare and modified GCEs were investigated in phosphate buffer solution (PBS) by cyclic voltammetry (CV). Compared with bare electrode and RGO/GCE, the oxidation peak current (ipa) on the NH2–Fe3O4/RGO/GCE increase significantly, owing to the synergistic effect between NH2–Fe3O4 NPs and RGO sheets. The oxidation peak currents (ipa) increase linearly with the concentrations of DA in the range of 1 × 10−8 mol/L – 1 × 10−7 mol/L, 1 × 10−7 mol/L – 1 × 10−6 mol/L and 1 × 10−6 mol/L – 1 × 10−5 mol/L. The detection limit is (4.0 ± 0.36) ×10−9 mol/L (S/N = 3). Moreover, the response peak currents of DA were hardly interfered with the coexistence of ascorbic acid (AA) and uric acid (UA). The proposed NH2–Fe3O4/RGO/GCE is successfully applied to the detection of dopamine hydrochloride injections with satisfactory results. Together with low cost, facile operation, good selectivity and high sensitivity, the NH2–Fe3O4/RGO/GCEs have tremendous prospects for the detection of DA in various real samples.

TiO2-based (Fe3O4, SiO2, reduced graphene oxide) magnetically recoverable photocatalysts for imazalil degradation in a synthetic wastewater.

Magnetite (Fe3O4), a core-shell material (SiO2@Fe3O4), and reduced graphene oxide-Fe3O4 (referred as rGO-MN) were used as supports of a specific highly active TiO2 photocatalyst. Thermal treatments at 200 or 450°C, different atmospheres (air or N2), and TiO2:support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO2@Fe3O4 material-or a N2 atmosphere (instead of air) in the thermal treatment-was employed to prepare the TiO2-based catalysts (the magnetic properties being preserved). The materials treated with N2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61mgL-1, i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO2@Fe3O4, an intermediate TiO2:support ratio (1.5), and treated at 200°C under N2 atmosphere (i.e., SiO2@Fe3O4-EST-1.5-200-N2). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53mgL-1), added H2O2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs. Graphical abstract % Imazalil conversion using different magnetic catalysts and comparison with bare TiO2.

Preparation and characterization of reduced graphene oxide/Fe3O4 nanocomposite by a facile in-situ deposition method for glucose biosensor applications

In this work, the reduced graphene oxide-Fe3O4 nanocomposite (rGO/Fe3O4) was prepared by a facile in-situ deposition of Fe3O4 nanoparticles on graphene sheets. The fact that graphene oxide (GO) was completely reduced to graphene by Fe2+ was evidenced by X-ray diffractometer, ultraviolet visible spectrophotometer, Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy. The results showed Fe3O4 nanoparticles were generated uniformly and bonded on the surface of rGO with a particle size of about 50 nm. In addition, the rGO/Fe3O4 nanocomposite showed a good conductivity and was considered as a high volume-surface ratio matrix for the immobilization of glucose oxidase (GOx) on a glassy carbon electrode (GCE). The fabricated rGO/Fe3O4/GOx/GCE exhibited a fast electron transfer and good electrocatalytic activity due to the good electrochemical properties of the rGO/Fe3O4 nanocomposite. These results demonstrated that the rGO/Fe3O4 nanocomposite prepared by in-situ deposition could be applied to high performance biosensor for glucose detection.

Novel in-situ redox synthesis of Fe3O4/rGO composites with superior electrochemical performance for lithium-ion batteries

Coupling transition metal oxides with nanocarbonaceous materials is an effective approach to construct high-efficiency anode materials for lithium-ion batteries (LIBs). In the present study, we demonstrate a novel in-situ redox strategy for facile and cost-effective synthesis of Fe3O4/reduced graphene oxide (Fe3O4/rGO) composites as LIBs anodes. Fe3O4/rGO composites are facilely obtained through redox reaction between highly-oxidized graphene oxide and ferrous salt under basic atmosphere, followed by stabilization treatment ranging from 5 min to 5 h. Well crystallized Fe3O4 nanoparticles with diameters of 10–30 nm are tightly and homogeneously anchored on the flexible graphene substrate. Owing to the distinctive composite nanostructure, including strong integration, homogeneous distribution and surface modification effect, the as-prepared Fe3O4/rGO composites exhibit superior electrochemical lithium-storage performance, especially at high current densities. The Fe3O4/rGO-2h composite delivers a remarkable reversible capacity of 1024 mA h g−1 at the current density of 1000 mA g−1, and retains 584 mA h g−1 at 5000 mA g−1 even after 450 cycles. It is believed that the study will provide a feasible strategy to facilely produce transition metal oxide/carbon composite electrodes with superior electrochemical performance for LIBs.

Efficient removal of aqueous Pb(II) using partially reduced graphene oxide-Fe3O4

Partially reduced graphene oxide-Fe3O4 composite was prepared through in situ co-precipitation and used as an efficient adsorbent for removing Pb(II) from water. The composites were characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectra, Fourier transformation infrared, Raman spectrometer, N2 adsorption–desorption, vibrating sample magnetometer, and zeta potential analyses. The impacts of pH, contact time, adsorbent dosage, temperature, and foreign substances on Pb(II) adsorption performance were investigated. The adsorption mechanism, kinetics, and thermodynamics were analyzed. The results indicate that Fe3O4 is homogeneously anchored inside the thin graphene sheets, with a particle size of 15–20 nm, resulting in a very low remanence and coercivity. The composite shows excellent and efficient adsorption performance toward aqueous Pb(II): adsorption equilibrium was reached in 10 min with the adsorption percent and quantity of 95.77% and 373.14 mgċg−1, respectively, under a condition of pH = 6, adsorbent dosage 250 mgċL−1, and Pb(II) initial concentration 97.68 mgċL−1, with the subsequent magnetic separation taking only 10 s. The adsorption performance is dependent on adsorbent dosage. A lower dosage favors a higher adsorption quantity, implying a strong adsorptive potential for partially reduced graphene oxide-Fe3O4. The adsorption quantity reached 777.28 mgċg−1, given the dosage 100 mgċL−1. The adsorption is monolayer chemisorption, the whole process of which is controlled by chemisorption and liquid film diffusion. In terms of thermodynamics, the adsorption is an exothermic and spontaneous process.

Graphene stirrer with designed movements: Targeting on environmental remediation and supercapacitor applications

Beyond the traditional focus on improvements in mechanical, electronic and absorption properties, controllability, actuation, and dynamic response of monoliths have received increasing attentions for practical applications. However, most of them could only realize simple response to constant conditions (e.g. a stationary magnetic field) while carrying out humdrum motions. By controlling distribution of metal organic framework obtained carbon-enriched Fe3O4 nanoparticles in self-assembly reduced graphene oxide (RGO) monoliths, we could achieve two distinctive RGO–Fe3O4 stirrers that could dynamically respond to the rapidly changing magnetic field while executing designed movements precisely: rotating with lying down posture or standing straight posture. These stirrers can not only be applied in environmental remediation (e.g. suction skimmer), but also be recycled as electrode active materials for supercapacitors after fulfilling their destiny, realizing transformation of trash to treasure, which will inspire other dynamically responsive monoliths for various applications.

Electrophoretic preparation of graphene-iron oxide nanocomposite as an efficient Pt-free counter electrode for dye-sensitized solar cell

Fe3O4-reduced graphene oxide (Fe3O4-RGO) binder-free counter electrode (CE) is prepared by using an easy and low-cost electrophoretic deposition method and controlling the hydrogen evolution process followed by an electrochemical reduction process for dye-sensitized solar cell (DSSC). X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectrometer, Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy (TEM) indicate clearly the formation of Fe3O4-RGO nanocomposite. TEM images show that the Fe3O4 nanoparticles with diameters in the range of 10–30 nm are uniformly deposited on RGO. The layer-by-layer deposition of iron oxide species anchored on graphene nanosheets during the EPD on FTO provides a unique film for DSSC. To evaluate the chemical catalysis and stability of prepared CEs toward I3 − reduction and the interfacial charge transfer properties, Fe3O4-RGO nanocomposite and RGO are characterized by cyclic voltammetry, Tafel polarization, and electrochemical impedance spectroscopy. Under AM 1.5 irradiation (100 mW cm−2), the DSSC based on the Fe3O4-RGO shows a power conversion efficiency of 5.91%, which is comparable with the Pt CE, suggesting that the Fe3O4-RGO nanocomposite is an effective CE material for low-cost DSSC. The proposed approach can prepare a thin film of Fe3O4-RGO at short time with suitable performance in DSSC.

Application of Fe3O4/RGO Nanocomposite as a Sorbent of Pesticides

In the present study, to extract the residue of seven pesticides (diazinon, chlorpyrifos, ethion, permethrine, cypermethrin, fenvalerate RR and fenvalerate SS) from raisin samples, reduced graphene oxide—Fe3O4 magnetic nanocomposite is applied as an adsorbent and then the preconcentrated pesticides were determined by GC–MS. The application of high adsorption capacity magnetic graphene oxide sheets in pesticides solid phase extraction, provides a fast and easy procedure without filtration or centrifugation. The extraction conditions were optimized by analyzing spiked raisin samples (80 ng mL−1). The parameters affecting the performance of the extraction such as nanoparticles concentration, extraction time, solution pH and desorption conditions were investigated using a univariate optimization process. The maximum adsorption was observed within 15 min at pH 7–8 using 0.4 mg mL−1 of adsorbent with the sample ionic strength of 0.02 M NaCl. Limits of detection and quantification were about 14 and 40 µg kg−1, respectively, for all of pesticides. The validated method was successfully applied for the determination of pesticides in raisin samples.

New branch on old tree: Green-synthesized RGO/Fe3O4 composite as a photo-Fenton catalyst for rapid decomposition of methylene blue

Abstract We report herein the facile fabrication of reduced graphene oxide (RGO) loaded with Fe3O4 nanocomposites (consisting of gauze-like RGO nanosheets and Fe3O4 nanoparticles) through a simple, low-cost and environmental-friendly procedure that employs a brown alga (Sargassum thunbergii) as the solely reducing agent. The RGO/Fe3O4 nanocomposites could work as novel catalytic materials with magnetic and photo-Fenton catalytic properties. In the presence of Sargassum thunbergii, the spherical-shaped Fe3O4 nanoparticles with an average diameter of 7 nm have uniformly anchored on the RGO nanosheets. The material has displayed excellent performance in terms of dye degradation (methylene blue, MB), showing a 96% degradation rate of MB after 120 min irradiation under almost neutral pH environment, and room temperature conditions. After the reaction, the RGO/Fe3O4 nanocomposite could be easily separated and recycled due to its excellent ferromagnetism and superior stability. Our study provides a strong validation of RGO/Fe3O4 remarkable capacity toward visible-light-driven degradation of organic contaminates.

Theoretical investigation on the magnetization enhancement of Fe3O4-reduced graphene oxide nanoparticle system

We present a theoretical study on the enhancement of magnetization of Fe3O4 nanoparticle system upon addition of reduced graphene oxide (rGO). Experimental data have shown that the magnetization of Fe3O4-rGO nanoparticle system increases with increasing rGO content up to about 5 wt%, but decreases back as the rGO content increases further. We propose that the enhancement is due to spin-flipping of Fe ions at the tetrahedral sites assisted by oxygen vacancies at the Fe3O4 particle boundaries. These oxygen vacancies are induced by the presence of rGO flakes that adsorb oxygen atoms from Fe3O4 particles around them. To understand the enhancement of the magnetization, we construct a tight-binding based model Hamiltonian for the Fe3O4 nanoparticle system with the concentration of oxygen vacancies being controlled by the rGO content. We calculate the magnetization as a function of the applied magnetic field for various values of rGO wt%. We use the method of dynamical mean-field theory and perform the calculations for a room temperature. Our result for rGO wt% dependence of the saturated magnetization shows a very good agreement with the existing experimental data of the Fe3O4-rGO nanoparticle system. This result may confirm that our model already carries the most essential idea needed to explain the above phenomenon of magnetization enhancement.

Theoretical exploration of optical response of Fe3O4-reduced graphene oxide nanoparticle system within dynamical mean-field theory

We theoretically investigate the optical conductivity and its related optical response of Fe3O4-reduced graphene oxide (rGO) nanoparticle system. Experimental data of magnetization of the Fe3O4-rGO nanoparticle system have shown that the saturation magnetization can be enhanced by controlling the rGO content with the maximum enhancement reached at the optimal rGO content of about 5 weight percentage. We hypothesize that the magnetization enhancement is due to spin-flipping of Fe ions at tetrahedral sites induced by oxygen vacancies at the Fe3O4 nanoparticle boundaries. These oxygen vacancies are formed due to adsorption of oxygen atoms by rGO flakes around the Fe3O4 nanoparticle. In this study, we aim to explore the implications of this effect to the optical response of the system as a function of the rGO content. Our model incorporates Hubbard-repulsive interactions between electrons occupying the e g orbitals of Fe3+ and Heisenberg-like interactions between electron spins and spins of Fe3+ ions. We treat the relevant interactions within mean-field and dynamical mean-field approximations. Our results are to be compared with the existing experimental reflectance data of Fe3O4 nanoparticle system.

Fast Removal of Aqueous Mn(II) Using Partially Reduced Graphene Oxide-Fe3O4†

Fast Removal of Aqueous Mn(II) Using Partially Reduced Graphene Oxide-Fe3O4†

Preparation of Fe3O4/Reduced Graphene Oxide Nanocomposites with Good Dispersibility for Delivery of Paclitaxel

The Fe3O4/reduced graphene oxide (Fe3O4/RGO) nanocomposites with good dispersibility were synthesized for targeted delivery of paclitaxel (PTX). Firstly, the superparamagnetic Fe3O4/functional GO nanocomposites were prepared via hydrothermal method in which GO sheets were modified by surfactant wrapping. The Fe3O4/RGO nanocomposites were successively prepared through the reduction of graphene oxide. The products were investigated by Fourier-transform infrared spectrum, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and vibration sample magnetometry. It was found that spherical Fe3O4 nanoparticles were uniformly anchored over the RGO matrix and the nanocomposites were superparamagnetic with saturation magnetization (Ms) of 9.39 emu/g. Then PTX was loaded onto Fe3O4/RGO nanocomposites, and the drug loading capacity was 67.9%. Cell viability experiments performed on MCF-7 demonstrated that the Fe3O4/RGO-loaded PTX (Fe3O4/RGO/PTX) showed cytotoxicity to MCF-7, whereas the Fe3O4/RGO displayed no obvious cytotoxicity. The above results indicated that Fe3O4/RGO/PTX nanocomposites had potential application in tumor-targeted chemotherapy.

Heat transfer and entropy generation analysis of hybrid graphene/Fe3O4 ferro-nanofluid flow under the influence of a magnetic field

The heat transfer characteristics and entropy generation rate of hybrid graphene-magnetite nanofluids under forced laminar flow that subjected to the permanent magnetic fields were investigated. For this purpose, a nanoscale reduced graphene oxide-Fe3O4 hybrid was synthesized by using graphene oxide, iron salts and tannic acid as the reductant and stabilizer. The thermophysical and magnetic properties of the hybrid nanofluid have been widely characterized and thermal conductivity has shown an enhancement of 11%. The experimental results indicated that the heat transfer enhancement of hybrid magnetite nanofluid compared to the case of distilled was negligible when no magnetic field was applied. Additionally, the heat transfer characteristics have been improved significantly under magnetic field. The outcome of the analysis shows that the total entropy generation rate was reduced up to 41% compared to distilled water. It appears that these magnetic hybrid nanofluids can function as good alternative fluids in the magnetic thermal engineering systems.

Experimental study on heat transfer augmentation of graphene based ferrofluids in presence of magnetic field

The effect of a permanent magnetic field on the heat transfer characteristics of hybrid graphene-magnetite nanofluids (hybrid nanofluid) under forced laminar flow was experimentally investigated. For this purpose, a reduced graphene oxide-Fe3O4 was synthesized by using two-dimensional (2D) graphene oxide, iron salts and tannic acid as the reductant and stabilizer. Graphene sheets acted as the supporting materials to enhance the stability and thermal properties of magnetite nanoparticles. The thermo-physical and magnetic properties of this hybrid nanofluid have been widely characterized and it shows that the thermal conductivity increased up to 11%. The hybrid nanofluid behaves as a Newtonian fluid with liquid like behavior with superparamagnetic properties as was evident from its magnetic saturation value at 45.9emu/g. Moreover, the experimental heat-transfer results indicated that the heat transfer enhancement of the hybrid nanofluid compared to the control fluid (distilled water) was negligible when no magnetic field was applied. Additionally, the convective heat transfer was significantly improved under the influence of a magnetic field with a maximum enhancement of 82% in terms of the convective heat transfer properties of the hybrid nanofluid.