Graphene Oxide Nanohybrid Research Articles

Highly efficient zinc oxide-reduced graphene oxide nanohybrids for photocatalytic degradation of dye under dark and UV light

In situ growth of zinc oxide (ZnO) nanoparticles (NPs) into self-assembled nanoclusters onto the surface of reduced graphene oxide (RGO) were obtained via a simple soft chemical approach at relatively low temperature (95 °C). A structural transformation of ZnO was observed from NPs to nanoclusters with the variation in concentrations of RGO contents under similar conditions which was clearly seen by TEM micrographs. It was observed that ZnO NPs come closer during nucleation and convert into nanoclusters of size 200–300 nm at the threshold RGO concentration. Furthermore, the effect of structural transformation and role of RGO concentration were evaluated against the degradation of Methylene Blue (MB) under UV as well as without any light source. The results demonstrate that RGO controls the loading and the morphology of ZnO, which improves the degradation performance of nanohybrids without any light source. Furthermore, ZnO-RGO-100 nanohybrid with highest RGO concentration shows excellent degradation behaviour without light irradiation as compared to their individual constituents.

Lanthanum-substituted bimetallic magnetic materials assembled carboxylate-rich graphene oxide nanohybrids as highly efficient adsorbent for perfluorooctanoic acid adsorption from aqueous solutions

Perfluorooctanoic acid (PFOA) is a persistent organic contaminant, and it has recently been recognized as a contaminant in aquatic environments worldwide because of its effects on human health. Herein, we report the synthesis of graphene oxide decorated with highly stable lanthanum-substituted manganese ferrites (LMF) at various concentrations (LMFx%@GO). After the substitution of lanthanum on MF, the surface charge density and the crystalline nature were altered significantly, as supported by the zeta potential, transmission electron and scanning electron microscopy images, and powder X-ray diffraction patterns. Among the concentrations of x = 25, 50, and 75% wt./wt., LMF75%@GO exhibited the highest PFOA removal densities. Electrostatic interaction and hydrogen bonding played vital roles in the adsorption of PFOA, as evidenced by various spectro-analytical techniques, including FTIR, XPS, and TEM-EDX. Several conditions such as contact time, pH, coexisting substances, and quantities of LMF nanoparticles were evaluated to provide information about the PFOA removal process. Moreover, the presence of coexisting pollutants such as anions, cations, and other organic compounds had no remarkable influence on PFOA adsorption using LMF75%@GO nanohybrids. The results suggest that the prepared LMF75%@GO nanohybrids may be a promising candidate for the removal of PFOA from an aqueous environment.

Cationic graphene oxide nanosheets intercalated with polyaniline nanofibers: A promising candidate for simultaneous anticorrosion, antistatic, and antibacterial applications

Development of a coating with simultaneous anticorrosion, antistatic, and antibacterial properties is an important issue which has gained attention from both academic and industrial societies. Multifunctional Polyaniline /cationic reduced graphene oxide (P-RGO+) nanohybrid has been synthesized to induce these properties in waterborne polyurethane (WPU) coatings. The cationic reduced graphene oxide nanosheets (RGO+) were obtained through the in-situ reduction and functionalization with Dimethylformamide (DMF). The cationic reduced graphene oxide nanosheets were intercalated with Polyaniline nanofibers (PANI) to prepare a binary nanohybrid (P-RGO+). This nanohybrid was characterized through the FTIR, XRD, FESEM, and zeta potential techniques and its effect on anticorrosion, antistatic, antibacterial, and mechanical properties of the waterborne polyurethane coatings was studied. The results of Tafel and EIS plots exhibited that the modified coatings have an improved performance in term of protecting steel substrates against corrosion. Moreover, in the presence of the nanohybrid, the electrical surface resistance of the obtained coating reduced to reach 9.8 × 10+6 Ω/sq so that it can be counted as an antistatic coating. Moreover, utilizing P-RGO+ nanohybrid in the WPU dispersion not only improved antibacterial activity against both gram positive and gram negative bacteria but also caused the enhanced mechanical properties of the modified coating compared with the pristine coating.

Mo2C–MoS2 embedded reduced graphene oxide nanohybrid: Epitaxial synthesis of Mo2C to augment the lithium storage properties of MoS2

A striking three-dimensional (3D) MoS2 (MS) nanoflower is synthesized through a lucid two-step process. The 3D MS nanoflower distorts to an extent when embedded in reduced graphene oxide (MS/rGO). MS/rGO is next subjected to controlled thermal annealing under H2 and CH4 to convert some amount of MS to Mo2C (MC). This leads to the formation of a new nanohybrid composed of MC nanosheets attached to MS nanoflowers embedded in a reduced graphene oxide network (M(S+C)/rGO), where MS have vastly exposed stepped edge sites. This epitaxial growth of MC is demonstrated using XRD, HRTEM, XPS and Raman scattering. On evaluation as an anode in lithium ion batteries, M(S+C)/rGO hybrid with lesser active material (MS) exhibits higher specific capacity and delivers better rate capability and cyclic stability compared to MS/rGO.

Co2TiO4/Reduced Graphene Oxide Nanohybrids for Electrochemical Sensing Applications.

For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer–Emmett–Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology.

Electrocatalytic Reduction of Hydrogen Peroxide and Its Non-Enzymatic Electrochemical Detection Using Silver Nanoparticles Anchored on Reduced Graphene Oxide.

Silver-reduced graphene oxide (Ag-rGO) nanohybrid was synthesized by applying a slight modification to the Turkevich method using trisodium citrate as a reducing and stabilizing agent to catalyze the non-enzymatic electrochemical detection of hydrogen peroxide (H₂O₂). Spherical silver nanoparticles (AgNPs) with an average particle size of 2.2 nm surfaced on reduced graphene oxide (rGO) sheets. Cyclic voltammograms (CV) obtained from glassy carbon (GC) electrode coated with Ag-rGO nanohybrid (4 mM) exhibited a peak at an overpotential of -0.52 V, with a larger faradaic current for the reduction of H₂O₂. Using the modified electrode for the linear sweep voltammetry (LSV) detection of H₂O₂, the detection limit and sensitivity were determined to be 4.8 μM (S/N ═ 3) and 0.0262 μA μM-1, respectively. The sensor appeared selective and stable towards H₂O₂ in the presence of possible interference, and it also demonstrated good recoveries of H₂O₂ concentration in real water samples.

Electrochemical Studies of One-Pot Synthesized Tetragonal Hausmannite Manganese Oxide/ Nitrogen-Doped Reduced Graphene Oxide Nanohybrid for Supercapacitor Applications

The increasing consumption of fossils fuel accompanied by related carbon emissions and complex set of issues associated with the generation and use of electricity has raised an urgent need for reliable, renewable and sustainable energy alternatives [1]. Remarkable progress made in nanoscience and nanotechnology brought inspiration for further development of new technologies in electrochemical energy storage. Supercapacitors (SCs) have emerged as a fast-rising class of energy storage technology and have received tremendous attention for potential applications in high-power sources [1,2]. Thus, manipulation of nanostructured materials became an important approach for the improvement of energy storage properties in SCs. Up to now, various synthetic methods have been established to improve the electrode materials for SC applications. Carbon nanomaterials such as carbon nanotubes (CNTs), graphene and graphene oxide (GO) have been widely used and modified to enhance their energy storage performance in SCs. Recently, much interest has been devoted to the doping of carbon materials to improve the performance of SC devices. Manganese oxide-based electrode materials characterized by their high theoretical specific surface area (1370 m2 g-1), high theoretical specific capacitance (1100 to 1300 F g-1), low-cost, abundance and environmentally friendly in nature, have attracted significant interest as active electrode materials for SCs. Although intensive study has been done on the MnO2-based pseudocapacitor, tetragonal hausmannite manganese oxide, Mn3O4, has received limited attention in SCs application [3]. Among various synthetic methods of synthesizing carbon/metal oxides nanohybrids, hydrothermal reduction of metal salts in the presence of carbon material is widely used, due to the simple operation and the low cost. This work present, one-pot synthesis of nitrogen-doped reduced graphene oxide decorated with hausmannite manganese oxide (N-rGO/Mn3O4 nanohybrid) and the study of its electrochemical energy storage performance for supercapacitor application. The microscopic and spectroscopic characterization of N-rGO/Mn3O4 nanohybrid and its precursor materials were acquired using SEM, EDX, Raman and XRD whereas the electrochemical characterization were acquired using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS).

Covalent Functionalization of Graphene Oxide with a Presynthesized Metal-Organic Framework Enables a Highly Stable Electrochemical Sensing.

This paper reports the covalent functionalization of graphene oxide (GO) by a presynthesized metal-organic framework NH2-MIL-101(Fe) via ultrasonication of the two components. The formation of Fe-O covalent bonding in the NH2-MIL-101(Fe)-GO nanohybrid is clearly evidenced, and the covalent bonding still remains after electrochemical reduction. The morphology and structure of the nanohybrid are characterized via scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. The electrode based on electrochemically reduced NH2-MIL-101(Fe)-GO shows ultrastable and high-sensitive performance in simultaneous electrochemical sensing of three purine metabolic derivatives (uric acid, xanthine, and hypoxanthine); in particular, no signal fading is seen even after running for 120 times. The covalent bonding within the nanohybrid is obviously the key to maintain such a stability.

Erbium-substituted Ni0.4Co0.6Fe2O4 ferrite nanoparticles and their hybrids with reduced graphene oxide as magnetically separable powder photocatalyst

New Ni0.4Co0.6Er0.045Fe1.95O4 spinel ferrite nanoparticles and their hybrids with reduced graphene oxide (rGO) nanohybrids were prepared by simple, low cost surfactant assisted co-precipitation and sonication method respectively. The synthesized materials were characterised by X-ray diffraction (XRD) analysis, Fourier transforms infrared spectroscopy (FTIR), UV–Visible and vibrating sample magnetometeric (VSM) measurements. XRD analysis confirmed the face centered (FCC) spinel ferrites that are further supported by FTIR results. The optical bandgap of nano-crystallites was around 2.66 eV that enable it to be active in both Ultraviolet and Visible spectrum of light. Photocatalytic efficiency was tested for both Ni0.4Co0.6Er0.045Fe1.95O4 ferrite nanoparticles and their graphene based hybrid material using methylene blue as typical organic pollutant as proof of principle. Results showed noticeable photocatalytic degradation up to 31.96% in the case of Ni0.4Co0.6Er0.045Fe1.95O4 nano-crystallites. Furthermore, photocatalytic activity was improved up to 43.1% by graphene based hybrid of Ni0.4Co0.6Er0.045Fe1.95O4 nano-crystallites. This exceptional increase in activity was due to lowering of charge carrier recombination at photocatalyst surface, adsorption of more and more dye molecules by large surface area of graphene and easy transmission of electrons from metal valence band to conduction band.

Interpenetrating polymer network-based nanocomposites reinforced with octadecylamine capped Cu/reduced graphene oxide nanohybrid with hydrophobic, antimicrobial and antistatic attributes.

Designing of mechanically tough elastomeric materials encompassed with intrinsic surface hydrophobicity, antistatic and antimicrobial attributes is in skyrocketing demands, especially to protect the instruments which are submerged in water. Herein, the authors depicted the fabrication of interpenetrating polymer network-based nanocomposites containing different doses of octadecylamine capped Cu/RGO nanohybrid. The structures and morphologies of the synthesized nanohybrid and the fabricated nanocomposites were characterized by using FTIR, XRD, XPS, TGA, FESEM and TEM analyses. Most interestingly the nanocomposites showed good hydrophobicity (static contact angle: 119.2°-129.3°), low surface resistivity (~107 Ω m) and strong antimicrobial activity towards Gram negative (Pseudomonas aeruginosa and Yersinia pestis) and Gram positive (Bacillus cereus) bacterial strains. The fabricated nanocomposites also exhibited antifungal (Candida albicans) activity. In addition, the fabricated nanocomposites showed excellent mechanical properties including high tensile strength (14.03-20.9 MPa), outstanding flexibility (1887-2470%), excellent toughness (249.89-510.1 MJ.m-3), high scratch resistance (>10 kg) and high thermostability (281-288 °C). Therefore, the fabricated nanocomposites can be used as an effective thin film for many advanced applications.

ZnS-Reduced Graphene Oxide Nanohybrid Materials as Photoanodes with Improved Photovoltaic Performance

Solution capable Zinc sulfide-Reduced graphene oxide (ZnS-rGO) nanohybrid composite has been developed by a simple step facile hydrothermal method. During the process GO was reduced into rGO and the different contentment of rGO were uniformly loaded into the ZnO nanoparticles. Hexagonal crystal structure and well spherical shaped individual nanoparticles (40–60 nm) are decorated uniformly on the rGO nanosheet, which is identified through X-ray diffraction and Field emission scanning electron microscope studies. The huge specific area (105.21 m2/g) and pore size (27.24 nm) distribution of ZnS/rGO was observed by N2 absorption–desorption analysis. The sandwich type solar cell was assembled using ZnS/rGO as counter electrode (CE), which delivers a high photocurrent density (16.21 mA/cm2), open-circuit voltage (0.82 V), fill factor (70.1%), and photo conversion efficiency (8.75%). This can be attributed to synergic effect between ZnS and rGO, which induce the effective separation of photo induced electron–hole pairs and transfer ability, simultaneously, prevent the recombination rate electron–hole pairs. The results suggest that this novel hybrid counter electrode can be used as a high performance photovoltaic device application.

Natural Biodegradable Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Nanocomposites with Multifunctional Cellulose Nanocrystals/Graphene Oxide Hybrids for High-Performance Food Packaging.

High-performance and useful graphene oxide (GO) and cellulose nanocrystals (CNCs) are easily extracted from natural graphite and cellulose raw materials, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is produced by bacterial fermentation from natural plant corn stalks, etc. In this study, novel ternary nanocomposites consisting of PHBV/cellulose nanocrystal-graphene oxide nanohybrids were prepared via a simple solution casting method. The synergistic effect of CNC with GO nanohybrids obtained by chemical grafting (CNC-GO, covalent bonds) and physical blending (CNC/GO, noncovalent bonds) on the physicochemical properties of PHBV nanocomposites was evaluated and the results compared with a single component nanofiller (CNC or GO) in binary nanocomposites. More interestingly, ternary nanocomposites displayed the highest thermal stability and mechanical properties. Compared to neat PHBV, the tensile strength and elongation to break increased by 170.2 and 52.1%, respectively, and maximum degradation temperature (Tmax) increment by 26.3 °C, were observed for the ternary nanocomposite with 1 wt % covalent bonded CNC-GO. Compared to neat PHBV, binary, and 1:0.5 wt % noncovalent CNC/GO based nanocomposites, the ternary nanocomposites with 1 wt % covalent bonded CNC-GO exhibited excellent barrier properties, good antibacterial activity (antibacterial ratio of 100.0%), reduced barrier properties, and lower migration level for both food simulants. Such a synergistic effect yielded high-performance ternary nanocomposites with great potential for bioactive food packaging materials.

Bimetallic metal-organic frameworks and graphene oxide nano-hybrids for enhanced fire retardant epoxy composites: A novel carbonization mechanism

The fire retarded intumescent epoxy resin (EP) composites were fabricated with the incorporation of bimetallic metal-organic framework (MOF) and graphene oxide (GO) nano-hybrids (MOF@GO) with intumescent fire retardants (IFR). EP/0.5MOF@GO-9.5IFR composite exhibited a 41% decrease in peak heat release rate, 30% decrease in total smoke production compared to reference sample EP/10IFR. According to in-situ morphology observation and X-ray tomography result, we observed such a novel carbonization phenomenon forming an alternately loose and accumulated structure. The further carbonaceous char analysis indicated the formation of a reinforced structure with fewer pores and excellent insulated property. Temperature test revealed that the synergistic effect between MOF@GO and IFR promoted the construction of the insulated carbonaceous char, which can maintain its temperature at around 400 °C, thus providing sufficient time to build up the alternative reinforced char. Besides, the mechanical property of EP composite was also improved with a 11% increase in the tensile strength compared with that of EP/10IFR. In perspective, the observed carbonization phenomenon opens a window for understanding the mechanism for intumescent fire retardants.

Facile Preparation of Cu2O Nanoparticles and Reduced Graphene Oxide Nanocomposite for Electrochemical Sensing of Rhodamine B.

In this paper, the preparation, characterization, and electrochemical application of Cu2O nanoparticles and an electrochemical reduced graphene oxide nanohybrid modified glassy carbon electrode (denoted as Cu2O NPs‒ERGO/GCE) are described. This modified electrode was used as an electrochemical sensor for the catalytic oxidation of rhodamine B (RhB), and it exhibited an excellent electrochemical performance for RhB. The oxidation potential of RhB was decreased greatly, and the sensitivity to detect RhB was improved significantly. Under optimum conditions, a linear dynamic range of 0.01–20.0 μM and a low detection limit of 0.006 μM were obtained with the Cu2O NPs‒ERGO/GCE by using second‒order derivative linear sweep voltammetry. In addition, the selectivity of the prepared modified electrode was analyzed for the determination of RhB. The practical application of this sensor was investigated for the determination of RhB in food samples, and satisfactory results were obtained.

Antibacterial effects of graphene- and carbon-nanotube-based nanohybrids on Escherichia coli: Implications for treating multidrug-resistant bacteria

Some nanomaterials including Fe0, Ag0, and ZnO are well known for their antibacterial effects. However, very few studies have examined antibacterial effects of nanohybrids. Given that metal oxides, mainly ZnO and TiO2, are known to increase mobility, surface area, and photocatalysis when combined with carbon-based nanomaterials, ZnO- and TiO2-conjugated carbon nanotube and graphene oxide nanohybrids were investigated for their antibacterial effects on Escherichia coli (DH5α, a multidrug-resistant coliform bacterium). Graphene-oxide (GO)-based nanohybrids (ZnO–GO and TiO2–GO) induced increased dispersion compared to carbon-nanotube (CNT)-based nanohybrids (ZnO–CNT and TiO2–CNT). Among the four types of nanohybrids, ZnO-conjugated nanohybrids exhibited a higher antibacterial property, resulting in the antibacterial effect (measured with growth inhibition of cells) in the order ZnO–GO > ZnO–CNT > TiO2–GO > TiO2–CNT. Among four possible antibacterial mechanisms (generation of reactive oxygen species (ROS), physicochemical characteristics, the steric effect, and release of metal ions), a primary mechanism—ROS generation—was identified; whereas, physicochemical characteristics and the steric effect were part of contributing mechanisms. The increasing dispersion of TiO2/ZnO on GO may have contributed to the antibacterial effects due to increasing surface areas. Similarly, significant damages to E. coli cell membranes were found by the GO sheet with its sharp edges. Our results suggest that applying GO-based ZnO or TiO2 could be an effective antibacterial method, especially for the treatment of multidrug-resistant bacteria in the water.

Highly efficient organic dye removal from waters by magnetically recoverable La2O2CO3/ZnFe2O4-reduced graphene oxide nanohybrid

Organic dyes released in the form of textile effluent have caused serious pollution of aqueous environments. Here, we report a reduced graphene oxide (rGO) loaded with La2O2CO3 and ZnFe2O4 (ZF) nanoparticles (LGZF) as a highly efficient adsorbent, which was synthesized through a simple precipitation-hydrothermal method. The LGZF nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, magnetic property, zeta potential, and surface area measurements. The effectiveness of cationic dye sorption on the adsorbent was examined under several experimental variables such as contact time, initial dyes concentrations, solution pH, and solution temperature. A novel magnetic nanohybrid with interlayer crystal structures exhibited an enhanced sorption capacities for methylene blue (MB) and rhodamine B (RhB) from contaminated water in comparison to bare rGO and ZF, in which LGZF with a mass ratio of La to Fe of 1:1 showed the highest adsorption activity. The Langmuir and pseudo-second-order model fully explained experimental adsorption and kinetics data. LGZF displayed maximum adsorption capacity of 201 and 98.4 mg/g for MB and RhB, respectively. The MB and RhB adsorption onto LGZF involved a spontaneous and an endothermic chemisorption through a combination of π–π interaction, electrostatic interaction, surface complexation, and hydrogen bonding. Furthermore, feasibility on the removal of organic dyes and antibiotic in surface water was also evaluated. The enhanced adsorption performance of the LGZF nanohybrid can be attributed to the incorporation of the characteristic La and Zn elements on rGO, which promotes the synergistic effects between rGO, La2O2CO3, and ZF.

Cobalt Diselenide@Reduced graphene oxide based nanohybrid for supercapacitor applications

Cobalt selenide@reduced graphene oxide (CoSe2@rGO) nanohybrid was successfully synthesized by a facile one-pot hydrothermal method and the electrochemical performance of the nanohybrid was evaluated for supercapacitor applications. The CoSe2@rGO nanohybrid show superior electrochemical performance in terms of the specific capacitance (449 F g−1 at 2 mV s−1, 219 F g−1 at 0.5 A g−1) and enhanced cyclic stability (91.3% capacitance retention for 5000 cycles) relative to pure CoSe2 (196 F g−1 at 2 mV s−1, 99 F g−1 at 0.5 A g−1). Such a highly improved specific capacitance found in the CoSe2@rGO nanohybrid electrode is mainly attributed to the nanosized CoSe2 grains with perfect redox property, more electro-active sites induced by synergetic effect at the interface of CoSe2 and rGO, and high specific area of rGO nanosheets. Besides, with the combination of rGO, the electrical conductivity of the CoSe2@rGO nanohybrid is highly enhanced, the ion/electron diffusion path is also reduced leading to faster charge transport during charging/discharging process with an improved cyclic stability.

Morphology-Dependent Electrochemical Sensing Properties of Iron Oxide-Graphene Oxide Nanohybrids for Dopamine and Uric Acid.

Various morphologies of iron oxide nanoparticles (Fe2O3 NPs), including cubic, thorhombic and discal shapes were synthesized by a facile meta-ion mediated hydrothermal route. To further improve the electrochemical sensing properties, discal Fe2O3 NPs with the highest electrocatalytic activity were coupled with graphene oxide (GO) nanosheets. The surface morphology, microstructures and electrochemical properties of the obtained Fe2O3 NPs and Fe2O3/GO nanohybrids were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. As expected, the electrochemical performances were found to be highly related to morphology. The discal Fe2O3 NPs coupled with GO showed remarkable electrocatalytic activity toward the oxidation of dopamine (DA) and uric acid (UA), due to their excellent synergistic effect. The electrochemical responses of both DA and UA were linear to their concentrations in the ranges of 0.02–10 μM and 10–100 μM, with very low limits of detection (LOD) of 3.2 nM and 2.5 nM for DA and UA, respectively. Moreover, the d-Fe2O3/GO nanohybrids showed good selectivity and reproducibility. The proposed d-Fe2O3/GO/GCE realized the simultaneous detection of DA and UA in human serum and urine samples with satisfactory recoveries.

Zinc oxide incorporated carbon nanotubes or graphene oxide nanohybrids for enhanced sonophotocatalytic degradation of methylene blue dye

Zinc oxide (ZnO) nanocrystallites with different weight ratios are incorporated into carbon nanotubes (ZnO/CNTs) or graphene oxide (ZnO/GO) nanohybrids using ultrasonication/hydrothermal approach. The produced nanohybrids were tested in heterogeneous photocatalytic degradation of methylene blue dye (MB) under visible light illumination and in-situ ultrasonication. The zinc oxide incorporated carbon nanotubes nanohybrid having about 70 wt% of ZnO (ZnO(70)/CNT) showed marked visible light photocatalytic activity enhancement for MB degradation (99%, 0.5 g/L catalyst, 0.015 min−1) compared to the rest of the nanohybrids. The performance of MB degradation using ZnO(70)/CNT nanohybrid was even enhanced during employing the dual sonophotocatalysis approach achieving a rate constant of 0.019 min−1. This arises from the structural advantages at the ZnO(70)/CNT interface by which an improvement in electronic conductivity, facile electron transfer, charge carriers separation and increased oxygen vacancies were thoroughly achieved. This was highly ascertained via the catalysts characterization performed via many physiochemical techniques including XRD, TEM-SAED, FTIR, UV–Vis diffuse reflectance, and electrical conductivity, IPCE, PL and EIS. The scavenger studies of the photocatalytic and sonophotocatalytic processes of the MB degradation using ZnO(70)/CNT illustrate the importance of OH (followed by an electron) and holes (followed by OH), respectively proposing the importance of direct and indirect production of OH; as a strong oxidizing moiety.

SiO2‐covered graphene oxide nanohybrids for in situ preparation of UHMWPE/GO(SiO2) nanocomposites with superior mechanical and tribological properties

ABSTRACTThe modified Hummer technique was used in the preparation of graphene oxide (GO) nanosheets, and then SiO2 decorated GO [GO(SiO2)] nanosheets were synthesized via the sol–gel method. Then, ultrahigh‐molecular‐weight polyethylene (UHMWPE) nanocomposites loaded with 0.5, 1, 1.5, and 2 wt % of GO(SiO2) were prepared using magnesium ethoxide/GO(SiO2)‐supported Ziegler–Natta catalysts via the in situ polymerization. Morphological study of the prepared polymer powders was assessed using field‐emission scanning electron microscopy, which showed that GO(SiO2) nanohybrids have been uniformly dispersed and distributed into the UHMWPE matrix. Also, the neat UHMWPE and its nanocomposites were evaluated with different analyses, including viscosity‐average molecular weight measurement, differential scanning calorimetry, thermogravimetric analysis, tensile test, scratch hardness, and pin‐on‐disk test. The characterization of the UHMWPE nanocomposites indicated that many characterizations, including the mechanical, thermal, and tribological properties of UHMWPE, were significantly improved by incorporation of these new nanosheets in spite of the molecular weight reduction of the polymeric matrix and the improved flowability and processability of the produced nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47796.