Graphene Oxide Iron Research Articles

Development of ternary nanoadsorbent composites of graphene oxide, activated carbon, and zero-valent iron nanoparticles for food applications.

In this study, a ternary nanocomposite comprising graphene oxide and carbon loaded with zero‐valent iron nanoparticles was developed as a promising nanoadsorbent, especially for polyphenols available in food industry by‐products. The fabricated nanoadsorbents were characterized in terms of structural, morphological, and chemical attributes. Zero‐valent iron nanoparticles (nZVI) were produced by a modified method leading to the formation of nanoparticles below 50 nm. Also, active carbon was transformed to a needle‐like shape instead of its native shape so that the active surface area was drastically increased which favors the higher adsorption process. Moreover, the space between graphene oxide sheets was enhanced by ultrasonication so that more active carbon and nZVIs could be oriented between these sheets. Finally, the FTIR and Raman data demonstrated the formation of O‐H stretching groups and a D/G value of 0.85 corresponding to the maintenance of a desired structure of the graphene oxide sheets, respectively. To summarize, the developed nanocomposites can be employed as a promising tool for the adsorbance of food and beverage industry by‐products, especially polyphenols.

Synthesis and characterization of hybrid graphene nanocoolant for heat transfer dissipation in microchannel heat sinks

Abstract An attempt is made to examine the effect of hybrid nanocoolant in microchannel heat sink for computer cooling. Two-hybrid coolants with graphene as one of the prime components are synthesized and images of the particles are shown using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Heat transfer properties like thermal conductivity of the hybrid fluid, specific heat, density, and viscosity are evaluated experimentally and theoretically. The heat transfer characteristics are also studied in heat sink channels of micro level in the processors of personal computers. The parameters like internal heat transfer coefficient, thermal resistances and base temperature representing the processor temperature are examined for the applied heater power of 325 W. The coolant dilution was varied in the range of 0.05 vol%, 0.075 vol% and 0.1 vol% and the base temperature is noted. The recorded lowest base temperature is 310.01 K for the concentration of 0.1 vol% graphene-iron oxide (GFO) system for 0.5 mm fin spacing for the graphene-iron oxide hybrid coolant and for graphene oxide–iron oxide (GOFO) hybrid coolant it is 311.24 K for the same operating conditions.

Synthesis of GO-Fe3O4-PANI nanocomposite with excellent NIR absorption property

Photothermal therapy is considered as an alternative to conventional cancer therapy methods, which is a mild practice compared to chemotherapy, radiotherapy, and surgery. The purpose of this study is to synthesize a photosensitizing agent having strong near-infrared (NIR) (˜808 nm) absorption, low cytotoxicity, magnetic properties, and excellent stability. For this purpose, graphene oxide-iron (II,III) oxide-polyaniline (GO-Fe3O4-PANI) was synthesized for the first time towards photothermal application and characterized by UV–vis, FTIR, XRD, TEM, and VSM analyses. The photothermal performance of the nanocomposite was investigated at various concentrations (0.1, 0.05, 0.025 mg/mL) under 1, 1.5, and 2.5 W/cm2 laser power density values. Photothermal conversion efficiency values of the samples were calculated by time constant method and a maximum of 65.80% efficiency was obtained (0.1 g/mL concentration at 1.5 W/cm2 for 5 min). This novel nanocomposite demonstrated superior results among PANI based photosensitizing agents.

Graphene Oxide Functional Nanohybrids with Magnetic Nanoparticles for Improved Vectorization of Doxorubicin to Neuroblastoma Cells.

With the aim to obtain a site-specific doxorubicin (DOX) delivery in neuroblastoma SH-SY5Y cells, we designed an hybrid nanocarrier combining graphene oxide (GO) and magnetic iron oxide nanoparticles (MNPs), acting as core elements, and a curcumin–human serum albumin conjugate as functional coating. The nanohybrid, synthesized by redox reaction between the MNPs@GO system and albumin bioconjugate, consisted of MNPs@GO nanosheets homogeneously coated by the bioconjugate as verified by SEM investigations. Drug release experiments showed a pH-responsive behavior with higher release amounts in acidic (45% at pH 5.0) vs. neutral (28% at pH 7.4) environments. Cell internalization studies proved the presence of nanohybrid inside SH-SY5Y cytoplasm. The improved efficacy obtained in viability assays is given by the synergy of functional coating and MNPs constituting the nanohybrids: while curcumin moieties were able to keep low DOX cytotoxicity levels (at concentrations of 0.44–0.88 µM), the presence of MNPs allowed remote actuation on the nanohybrid by a magnetic field, increasing the dose delivered at the target site.

Superparamagnetic graphene quantum dot as a dual-modality contrast agent for confocal fluorescence microscopy and magnetomotive optical coherence tomography.

A magnetic graphene quantum dot (MGQD) nanoparticle, synthesized by hydrothermally reducing and cutting graphene oxide-iron oxide sheet, was demonstrated to possess the capabilities of simultaneous confocal fluorescence and magnetomotive optical coherence tomography (MMOCT) imaging. This MGQD shows low toxicity, significant tunable blue fluorescence and superparamagnetism, which can thus be used as a dual-modality contrast agent for confocal fluorescence microscopy (CFM) and MMOCT. The feasibility of applying MGQD as a tracer of cells is shown by imaging and visualizing MGQD labeled cells using CFM and our in-house MMOCT. Since MMOCT and CFM can offer anatomical structure and intracellular details, respectively, the MGQD for cell tracking could provide a more comprehensive diagnosis.

Antioxidant efficacy of chitosan/graphene functionalized superparamagnetic iron oxide nanoparticles.

The antioxidant potential of superparamagnetic iron oxide nanoparticles functionalized with chitosan and graphene were examined in the present work. Coprecipitation technique was followed for the synthesis of iron oxide nanoparticles. Graphene-iron oxide nanocomposites were synthesized by mechanical mixing followed by the heat treatment at moderate temperature. The chitosan coated iron oxide nanoparticles were prepared by dispersing nanoparticles in chitosan solution. The nanoparticles/nanocomposites were characterized using XRD, SEM, TEM and HAADF-STEM for phase structure, morphology and elemental analysis. The superparamagnetic behavior of nanoparticles/nanocomposites were confirmed by magnetic measurements using vibrating sample magnetometry. Antioxidant efficacy of these nanoparticles/nanocomposites were investigated in terms of free radical scavenging and reducing potential using an array of in vitro assay system. Ferric reducing antioxidant power (FRAP) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) were used for the antioxidant capacity. The investigation suggests that the graphene improves the antiradical response of iron oxide nanoparticles at higher concentration which is almost comparable to the ascorbic acid used as standard.

Structural and electrical properties of nickel-iron spinel/reduced graphene oxide nanocomposites

Nickel iron spinel/reduced graphene oxide composite material was synthesized by simultaneous hydrothermal treatment of nickel and ferric nitrates and graphene oxide colloidal solution obtained using Hummers method. XRD, SEM, Mossbauer spectroscopy, impedance spectroscopy and low temperature nitrogen adsorption were used for materials characterization. The electrical conductivity mechanisms for pure nickel ferrite, reduced graphene oxide and nickel iron spinel/reduced graphene oxide composite were investigated with the determination of activation energy values. Synchronous hydrothermal synthesis of nickel ferrite and the reduction of graphene oxide allow obtaining novel functional material that consists of oxide nanoparticles spaced by carbon fragments.

Reduced graphene oxide/iron oxide nanohybrid flexible electrodes grown by laser-based technique for energy storage applications

Porous reduced graphene oxide (rGO)/iron oxide nanohybrid thin films were grown through a laser-based technique onto flexible polymer, polydimethylsiloxane substrates. A frequency quadrupled pulsed Nd:YAG laser source (λ = 266 nm, τFWHM ~ 4 ns, υ = 10 Hz) was used for irradiation of dispersions containing the starting nano-materials, graphene oxide (GO) platelets and iron oxide nanoparticles (NPs), to be transferred to the substrates surface. The electrochemical response of the composite layers was investigated by cyclic voltammetry in dark and under UV/visible light illumination, as well as by electrochemical impedance spectroscopy. A comparative study was performed as a function of the nature of the GO base materials, monolayer or multilayer GO platelets, and relative concentration of GO/iron oxide NPs in the dispersions submitted to laser irradiation. The capacitance values of the nanohybrid materials which contain monolayer GO were found to be one order of magnitude higher as compared to their counterparts consisting of multilayer GO and iron oxide NPs. UV–visible light irradiation contributed to the significant enhancement of the electrochemical properties of the electrodes. These results indicate that the nanohybrid thin films are promising candidates as flexible electrodes in micro-supercapacitors and photoelectrochemical devices for simultaneous energy storage and solar energy conversion.

Microstructure and Chemo-Physical Characterizations of Functional Graphene Oxide-Iron Oxide-Silver Ternary Nanocomposite Synthesized by One-Pot Hydrothermal Method.

In this work, a functional graphene oxide-iron oxide-silver (GO-Fe3O4-Ag) ternary nanocomposite was synthesized by using one-pot hydrothermal treatments of mixture solutions of silver nitrate (AgNO3), ferrous chloride tetrahydrate (FeCl2 4H2O), polyvinylpyrrolidone (PVP), graphene oxide (GO), and ammonium hydroxide solution (NH4OH). The systematic effects of synthesis conditions on the microstructure and formation of binary and ternary composite systems were studied. Importantly, high-crystalline GO-Fe3O4-Ag ternary nanomaterials with average sizes of Fe3O4 particles ~16 nm and of Ag particles ~20 nm were obtained at optimized conditions (125 °C, 2.5 mM of AgNO3 and 5 mL of NH4OH). Magnetic analysis indicated that the saturated magnetization value of Fe3O4-Ag binary composite sample (~73.1 emu/g) was improved as compared with pure Fe3O4 nanoparticles (~60.6 emu/g), while this of GO-Fe3O4-Ag ternary composite sample was about 57.3 emu/g. With exhibited advantages of low-cost, high purity and short synthesis time, the hydrothermal-synthesized GO-Fe3O4-Ag ternary nanocomposite can be a promising candidate for advanced environmental catalyst and biomedical applications.

Nanoscale Zero-Valent Iron Decorated on Bentonite/Graphene Oxide for Removal of Copper Ions from Aqueous Solution.

The removal efficiency of Cu(II) in aqueous solution by bentonite, graphene oxide (GO), and nanoscale iron decorated on bentonite (B-nZVI) and nanoscale iron decorated on bentonite/graphene oxide (GO-B-nZVI) was investigated. The results indicated that GO-B-nZVI had the best removal efficiency in different experimental environments (with time, pH, concentration of copper ions, and temperature). For 16 hours, the removal efficiency of copper ions was 82% in GO-B-nZVI, however, it was 71% in B-nZVI, 26% in bentonite, and 18% in GO. Bentonite, GO, B-nZVI, and GO-B-nZVI showed an increased removal efficiency of copper ions with the increase of pH under a certain pH range. The removal efficiency of copper ions by GO-B-nZVI first increased and then fluctuated slightly with the increase of temperature, while B-nZVI and bentonite increased and GO decreased slightly with the increase of temperature. Lorentz-Transmission Electron Microscope (TEM) images showed the nZVI particles of GO-B-nZVI dispersed evenly with diameters ranging from 10 to 86.93 nm. Scanning electron microscope (SEM) images indicated that the nanoscale iron particles were dispersed evenly on bentonite and GO with no obvious agglomeration. The qe,cal (73.37 mg·g−1 and 83.89 mg·g−1) was closer to the experimental value qe,exp according to the pseudo-second-order kinetic model. The qm of B-nZVI and GO-B-nZVI were 130.7 mg·g−1 and 184.5 mg·g−1 according to the Langmuir model.

Sol–gel synthesized BiFeO3–Graphene nanocomposite as efficient electrode for supercapacitor application

In the present work, bismuth iron oxide–graphene composite has been explored as electrode material for electrochemical supercapacitor application. Bismuth iron oxide (BFO) nanoparticles, synthesized by sol–gel process, are mixed with the graphene sheets in a solution. The electrodes are prepared by coating the resulted slurry on stainless steel (SS) substrate, by drop casting process. The morphology and structure of the BFO–graphene composite are characterized by XRD, FIB-SEM, HRTEM and Raman spectroscopy, which show that the nanoparticles with diameter 100–200 nm are randomly distributed on and around the graphene sheets. The composite electrode exhibits significantly enhanced capacitance as compared to BFO. In this structure, the electrons generated by the surface based Faradaic reactions from the BFO nanoparticles can be transported by the graphene nanosheets toward the current collector. The electrochemical characteristic of the electrodes is investigated through cyclic voltammetry and charging/discharging process. The specific capacitance of the electrode measured at 5–100 mV/s was found to be 17–4 mF/cm2 which is comparable to the most commonly used metal oxide based electrode materials. It shows better cycling stability with 95% retention of capacitance after 2000 cycles.

Synergic effects enhance the catalytic properties of alpha-Ni(OH)2-FeOCPc@rGO composite for oxygen evolution reaction

The effect of size and degree of crystallinity, and the synergic interaction of α-Ni(OH)2 nanoparticles (α-Ni) with reduced graphene oxide (rGO) and octacarboxyphthalocyaninate iron(II) (FeOCPc), on the electrocatalytic activity for the oxygen evolution reaction (OER) are demonstrated using structurally well-defined nanocomposite materials. Larger and crystalline α-Ni@rGO-K nanoparticles (4.7 ± 1.8 nm) generated materials with higher activity than the respective α-Ni(OH)2Na derivatives (1.8 ± 0.3 nm), where the incorporation of rGO improved dramatically the performance. However, an even larger efficiency was achieved when α-Ni@rGO-K was covered up with a controlled amount of FeOCPc, a poor molecular OER catalyst, in this way demonstrating a synergic effect of that macrocycle on the reaction kinetics decreasing further the overpotential of the oxygen evolution reaction. In fact, α-NiFeOCPc@rGO-K was the ternary composite material with best performance, being able to sustain a stable current of 10 mA cm−2 during 8 h of continuous electrolysis at 1.64 V vs RHE, in 1.0 mol dm−3 KOH solution, showing good perspectives as electrode material for OER.

Polymeric iron oxide-graphene nanocomposite as a trace level sensor of vitamin C

The nanocomposite of graphene-iron oxide-polyvinyl alcohol (PIG) was synthesized via simple one-pot hydrothermal method and was used in the modification of pencil graphite electrode for developing an electrochemical sensor. Graphene (G) and iron oxide-graphene (IG) composites were synthesized for providing a comparative study. The structural properties of the prepared PIG were studied through X-Ray diffraction (XRD) technique, whereas the morphological analysis was conducted through field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) study. The chemical states of elements present in the prepared composite were confirmed using X-ray photoelectron spectroscopy (XPS) and the functional groups present in the composite were investigated through Fourier transform infrared (FTIR) spectroscopy. The existence of iron oxide nanoparticles along with PVA polymer in PIG composite enhances the electroactive area (0.073 cm2) and roughness factor (0.186) along with the sensitivity of the material. The square wave voltammetry technique was used for detecting the bio-molecule i.e. vitamin C. At optimized condition, the PIG modified electrode shows a high linear range (40 μM–4100 μM), low limit of detection (0.234 μM) and higher sensitivity (1597.03 μA cm−2 mM−1). The PIG material also provides a good stability towards detection of vitamin C.

Monodisperse Pd nanoparticles assembled on reduced graphene oxide-Fe3O4 nanocomposites as electrocatalysts for borohydride fuel cells

5 nm palladium nanoparticles (Pd NPs) are synthesized and assembled on reduced graphene oxide-iron oxide nanocomposite (rGO-Fe3O4) to be used in oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) studies in alkaline media. The structure and morphology of the resulting Pd/rGO-Fe3O4 hybrid material are evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) analyses. The electrochemical behavior of Pd/rGO-Fe3O4 hybrid material for the ORR and BOR is investigated by voltammetry with rotating disk and rotating ring disk electrode and electrochemical impedance spectroscopy, enabling evaluation of the number of exchanged electrons, Tafel slope, exchange current density and activation energy. The results reveal that ORR at Pd/rGO-Fe3O4 proceeds as a 2-electron process with Tafel slope of 0.133 V dec−1, while BOR proceeds as a 5.6-electron process with Tafel slope of 0.350 V dec−1 and exchange current density of 1.38 mA cm−2. The BOR activation energy was found to be 12.4 kJ mol−1. Overall, this study demonstrates the good efficiency of Pd/rGO-Fe3O4 hybrid material for BOR.

Graphene oxide-metal oxide nanocomposites: fabrication, characterization and removal of cationic rhodamine B dye.

The fabrication and characterization of graphene oxide (GO) nanosheets and their reaction with Fe3O4 and ZrO2 metal oxides to form two nanocomposites, namely graphene oxide–iron oxide (GO–Fe3O4) and graphene oxide–iron oxide–zirconium oxide (GO–Fe3O4@ZrO2), have been examined. The fabricated nanocomposites were examined using different techniques, e.g.transmission electron microscopy, X-ray diffraction, zeta potential measurement and Fourier transform infrared spectroscopy. Compared to GO, the newly fabricated GO–Fe3O4 and GO–Fe3O4@ZrO2 nanocomposites have the advantage of smaller band gaps, which result in increased adsorption capacity and photocatalytic effects. The results also showed the great effect of the examined GO–metal oxide nanocomposites on the decomposition of cationic rhodamine B dye, as indicated by steady-state absorption and fluorescence, time correlated single photon counting and nanosecond laser photolysis techniques. The antibacterial activity of the fabricated GO and GO–metal oxides has been studied against Gram-positive and Gram-negative bacteria.

Multifunctional Hybrids Based on 2D Fluorinated Graphene Oxide and Superparamagnetic Iron Oxide Nanoparticles

Carbon-based nanomaterials have garnered a lot of attention in the research of yesteryear. Here this study reports a composite based on fluorinated graphene oxide—a multifunctional subsidiary of graphene; and iron oxide nanoparticles as a contrast agent for magnetic resonance imaging (MRI). Extensive structural and functional characterization is carried out to understand composite behavior toward biotoxicity and its performance as a contrast agent. The electron withdrawing fluorine group decreases the charge transfer to iron oxide increasing the magnetic saturation of the composite thus enhancing the contrast. The interaction of paramagnetic and superparamagnetic systems yields a superior contrast agent for MRI and fluorescent imaging.

Covalent immobilization of peanut β-amylase for producing industrial nano-biocatalysts: A comparative study of kinetics, stability and reusability of the immobilized enzyme

Stability of enzymes is an important parameter for their industrial applicability. Here, we report successful immobilization of β-amylase (bamyl) from peanut (Arachis hypogaea) onto Graphene oxide-carbon nanotube composite (GO-CNT), Graphene oxide nanosheets (GO) and Iron oxide nanoparticles (Fe3O4). The Box-Behnken Design of Response Surface Methodology (RSM) was used which optimized parameters affecting immobilization and gave 90%, 88% and 71% immobilization efficiency, respectively, for the above matrices. β-Amylase immobilization onto GO-CNT (bamyl@GO-CNT) and Fe3O4 (bamyl@Fe3O4), resulted into approximately 70% retention of activity at 65 °C after 100 min of exposure. We used atomic force microscopy (AFM), scanning and transmission electron microscopy (SEM and TEM), Fourier transformed infrared (FT-IR) spectroscopy and fluorescence microscopy for characterization of free and enzyme bound nanostructures (NS). Due to the non-toxic nature of immobilization matrices and simple but elegant immobilization procedure, these may have potential utility as industrial biocatalysts for production of maltose.

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.

Graphene oxide-iron oxide nanocomposite as an inhibitor of Aβ 42 amyloid peptide aggregation

Inhibiting amyloid β (Aβ) aggregation has drawn much attention because it is one of the main reasons for the cause of Alzheimer’s disease (AD). Here we have synthesized a nanocomposite of graphene oxide-iron oxide (GOIO) and demonstrated its ability of modulating Aβ aggregation. The inhibition effects of the GOIO nanocomposite on Aβ aggregates was studied by Thioflavin T fluorescence assay, circular dichroism and transmission electron microscopy, respectively. Furthermore, the cell viability study revealed that the GOIO nanocomposite can reduce the toxicity of Aβ fibrils to neuroblastoma cells. Our results demonstrated that the combination of GO and IO as a nanocomposite material has a potential use for the design new therapeutic agents for the treatment of Alzheimer’s disease.

Lactoferrin modified graphene oxide iron oxide nanocomposite for glioma-targeted drug delivery

Targeting delivery of drugs in a specific manner represents a potential powerful technology in gliomas. Herein, we prepared a multifunctional targeted delivery system based on graphene oxide (GO) that contains a molecular bio-targeting ligand and superparamagnetic iron oxide nanoparticles on the surface of GO for magnetic targeting. Superparamagnetic Fe3O4 nanoparticles was loaded on the surface of GO via chemical precipitation method to form GO@Fe3O4 nanocomposites. Lactoferrin (Lf), an iron-transporting serum glycoprotein that binds to receptors overexpressed at the surface of glioma cells and vascular endothelial cell of the blood brain barrier, was chosen as the targeted ligand to construct the targeted delivery system Lf@GO@Fe3O4 through EDC/NHS chemistry. With the confirmation of TEM, DLS and VSM, the resulting Lf@GO@Fe3O4 had a size distribution of 200–1000nm and exhibited a superparamagnetic behavior. The nano delivery system had a high loading capacity and exhibited a pH-dependent release behavior. Compared with free DOX and DOX@GO@Fe3O4, Lf@GO@Fe3O4@DOX displayed greater intracellular delivery efficiency and stronger cytotoxicity against C6 glioma cells. The results demonstrated the potential utility of Lf conjugated GO@Fe3O4 nanocomposites for therapeutic application in the treatment of gliomas.